[Federal Register: June 10, 2005 (Volume 70, Number 111)]
[Rules and Regulations]
[Page 33997-34042]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10jn05-18]
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Part III
Department of Health and Human Services
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Food and Drug Administration
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21 CFR Part 1020
Electronic Products; Performance Standard for Diagnostic X-Ray Systems
and Their Major Components; Final Rule
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
Food and Drug Administration
21 CFR Part 1020
[Docket No. 2001N-0275]
RIN 0910-AC34
Electronic Products; Performance Standard for Diagnostic X-Ray
Systems and Their Major Components
AGENCY: Food and Drug Administration, HHS.
ACTION: Final rule.
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SUMMARY: The Food and Drug Administration (FDA) is issuing a final rule
to amend the Federal performance standard for diagnostic x-ray systems
and their major components (the performance standard). The agency is
taking this action to update the performance standard to account for
changes in technology and use of radiographic and fluoroscopic x-ray
systems and to fully utilize the International System of Units to
describe radiation-related quantities and their units when used in the
performance standard. For clarity and ease of understanding, FDA is
republishing the complete contents, as amended, of three sections of
the performance standard regulations and is amending a fourth section
without republishing it in its entirety. This action is being taken
under the Federal Food, Drug, and Cosmetic Act (the act), as amended by
the Safe Medical Devices Act of 1990 (SMDA).
DATES: This rule is effective June 10, 2006.
FOR FURTHER INFORMATION CONTACT: Thomas B. Shope, Center for Devices
and Radiological Health (HFZ-140), Food and Drug Administration, 9200
Corporate Blvd., Rockville, MD 20850, 301-443-3314, ext. 132.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Background
II. Highlights of the Final Rule
III. Summary and Analysis of Comments and FDA's Responses
A. General Comments
B. Comments on Proposed Changes to Sec. 1020.30
1. Definitions (Sec. 1020.30(b))
2. Information to Be Provided to Users (Sec. 1020.30(h))
3. Beam Quality--Increase in Minimum Half-Value Layer (Sec.
1020.30(m))
4. Aluminum Equivalent of Material Between Patient and Image
Receptor (Sec. 1020.30(n))
5. Modification of Certified Diagnostic X-Ray Components and
Systems (Sec. 1020.30(q))
C. Comments on Proposed Changes to Sec. 1020.31--Radiographic
Equipment
1. Field Limitation and Post Exposure Adjustment of Digital Image
Size
2. Policy Regarding Disabled Positive Beam Limitation Systems
D. Comments on Proposed Changes to Sec. 1020.32--Fluoroscopic
Equipment
1. Testing for Attenuation By the Primary Protective Barrier
2. Field Limitation for Fluoroscopic Systems
3. Air Kerma Rates
4. Minimum Source-Skin Distance
5. Display of Cumulative Irradiation Time
6. Audible Signal of Irradiation Time
7. Last-Image-Hold (LIH) Feature
8. Display of Values of Air Kerma Rate and Cumulative Air Kerma
IV. Additional Revisions of Applicability Statements and Other
Corrections
V. Environmental Impact
VI. Paperwork Reduction Act of 1995
A. Summary
B. Estimate of Burden
VII. Analysis of Impacts
A. Introduction
B. Objective of the Rule
C. Risk Assessment
D. Constraints on the Impact Analysis
E. Baseline Conditions
F. The Amendments
G. Benefits of the Amendments
H. Estimation of Benefits
I. Costs of Implementing the Regulation
1. Costs Associated With Requirements Affecting Equipment Design
2. Costs Associated With Additional Information for Users
3. Costs Associated With Clarifications and Adaptations to New
Technologies
4. FDA Costs Associated With Compliance Activities
5. Total Costs of the Regulation
J. Cost-Effectiveness of the Regulation
K. Small Business Impacts
1. Description of Impact
2. Analysis of Alternatives
3. Ensuring Small Entity Participation in Rulemaking
L. Reporting Requirements and Duplicate Rules
M. Conclusion of the Analysis of Impacts
VIII. Federalism
IX. References
I. Background
The SMDA (Public Law 101-629) transferred the provisions of the
Radiation Control for Health and Safety Act of 1968 (RCHSA) (Public Law
90-602) from title III of the Public Health Service Act (PHS Act) (42
U.S.C. 201 et seq.) to chapter V of the act (21 U.S.C. 301 et seq.).
Under the act, FDA administers an electronic product radiation control
program to protect the public health and safety. As part of that
program, FDA has authority to issue regulations prescribing radiation
safety performance standards for electronic products, including
diagnostic x-ray systems (sections 532 and 534 of the act (21 U.S.C.
360ii(a) and 360kk)).
The purpose of the performance standard for diagnostic x-ray
systems is to improve the public health by reducing exposure to and the
detriment associated with unnecessary ionizing radiation while assuring
the clinical utility of the images produced.
In order for mandatory performance standards to continue to provide
the intended public health protection, the standards must be modified
when appropriate to reflect the changes in technology and product
usage. When the performance standard was originally developed, the only
means of producing a fluoroscopic image was either a screen of
fluorescent material or an x-ray image intensifier tube. Therefore, the
standard was written with these two types of image receptors in mind. A
number of technological developments have been implemented for
radiographic and fluoroscopic x-ray systems, such as solid-state x-ray
imaging (SSXI) and new modes of image recording (e.g., digital
recording to computer memory or other media). These developments have
made the application of the current standard to systems incorporating
these new technologies cumbersome and awkward. FDA is therefore
amending the performance standard for diagnostic x-ray systems and
their major components in Sec. Sec. 1020.30, 1020.31, and 1020.32 (21
CFR 1020.30, 1020.31, and 1020.32) to address the recent changes in
technology. In addition, we are amending Sec. 1030.33(h) (21 CFR
1030.33(h)) to reflect the change in the quantity used to describe
radiation.
These amendments will require that newly-manufactured x-ray systems
include additional features that physicians may use to minimize x-ray
exposures to patients. Advances in technology have made several of
these new features feasible at minimal additional cost.
In the Federal Register of August 15, 1972 (37 FR 16461), FDA
issued a final rule for the performance standard, which became
effective on August 1, 1974. Since then, FDA has made several
amendments to the performance
[[Page 33999]]
standard to incorporate new technology, to clarify misinterpreted
provisions, or to incorporate additional requirements necessary to
provide for adequate radiation safety of diagnostic x-ray systems.
(See, e.g., amendments published on October 7, 1974 (39 FR 36008);
February 25, 1977 (42 FR 10983); September 2, 1977 (42 FR 44230);
November 8, 1977 (42 FR 58167); May 22, 1979 (44 FR 29653); August 24,
1979 (44 FR 49667); November 30, 1979 (44 FR 68822); April 25, 1980 (45
FR 27927); August 31, 1984 (49 FR 34698); May 3, 1993 (58 FR 26386);
May 19, 1994 (59 FR 26402); and July 2, 1999 (64 FR 35924)).
In the Federal Register of December 11, 1997 (62 FR 65235), FDA
issued an advance notice of proposed rulemaking (ANPRM) requesting
comments on the proposed conceptual changes to the performance
standard. The agency received 12 comments from State and local
radiation control agencies, manufacturers, and a manufacturer
organization. FDA considered these comments in developing the proposed
amendments. In addition, the concepts embodied in the amendments were
discussed on April 8, 1997, during a public meeting of the Technical
Electronic Product Radiation Safety Standards Committee (TEPRSSC).
TEPRSSC is a statutory advisory committee that FDA is required to
consult before the agency may prescribe any electronic product
performance standard under the act (21 U.S.C. 360kk(f)(1)(A)). The
proposed amendments themselves were discussed in detail with the
TEPRSSC during a public meeting held on September 23 and 24, 1998. At
that meeting, TEPRSSC approved the content of the proposed amendments
and concurred with their publication for public comment.
FDA proposed the amendments for public comment in the Federal
Register of December 10, 2002 (67 FR 76056). Interested persons were
given until April 9, 2003, to comment on the proposal. FDA received
comments from 12 organizations and individuals in response to the
proposed amendments. These comments were generally supportive of the
proposed changes to the performance standard, although some expressed
concern about specific aspects of some of the proposed amendments.
II. Highlights of the Final Rule
In this final rule, FDA is making a number of changes to the
performance standard for diagnostic x-ray systems and their components,
including the following:
In Sec. 1020.30 of the performance standard, the final
rule makes the following changes:
Adds a number of new definitions to address new technologies and to
further clarify the regulations. One notable amendment to the
definitions is the addition of the terms air kerma and kerma to reflect
a change in the quantity used to describe radiation emissions from
diagnostic x-ray systems (Sec. 1020.30(b));
Requires manufacturers to provide users (e.g., physicians) with
certain information regarding the new features of fluoroscopic systems
in order to better protect their patients from unnecessary x-radiation
exposure (Sec. 1020.30(h));
Requires additional warning label language designed to alert users
and facility administrators to the need to properly maintain and
calibrate their diagnostic x-ray systems (Sec. 1020.30(j)); and
Modifies existing beam quality requirements by increasing the
required minimum half-value layer (HVL) values for radiographic and
fluoroscopic equipment. This increase in HVL values will bring FDA
requirements into agreement with the performance already provided by
systems that are compliant with corresponding international standards.
Therefore, manufacturers currently complying with the international
standards should not be impacted by this change (Sec. 1020.30(m)).
In Sec. 1020.31 of the performance standard, which
addresses radiographic x-ray equipment, the following changes are being
made:
A number of minor, technical corrections to sections applicable to
mammographic x-ray systems that were made necessary by an oversight
that occurred when this performance standard was amended in July 1999
(Sec. 1020.31(f)(3) and (m)).
The provisions in Sec. 1020.32 pertain to fluoroscopic
equipment. Key changes being made to this section of the performance
standard include the following:
Amending the x-ray field limitation and alignment requirements to
promote the addition of features designed to reduce the amount of
radiation falling outside the visible area of the image receptor,
thereby preventing unnecessary patient exposure (Sec. 1020.32(b));
Amending the requirement concerning maximum limits on entrance air
kerma rates (AKR) in order to clarify the circumstances under which the
maximum limits would apply (Sec. 1020.32(d) and (e));
Establishing a minimum source-skin distance requirement for certain
small ``C-arm'' type fluoroscopic systems. FDA traditionally has
granted variances from minimum source-skin distance requirements for
small, portable C-arm systems when such systems were intended only for
the limited use of imaging extremities. The amendment establishes the
conditions under which variances have been granted as part of the
standard and removes the need for manufacturers to continue to request
variances of this type and makes explicit the requirements for these
systems (Sec. 1020.32(g));
Requiring the incorporation of a feature that will continuously
display the last fluoroscopic image taken prior to termination of
exposure (last-image-hold feature). This permits the user to
conveniently view fluoroscopic images without continuously irradiating
the patient (Sec. 1020.32(j)); and
Requiring the incorporation of a feature that will display critical
information to the fluoroscopist regarding patient irradiation,
including the duration, rate (AKR), and amount (cumulative air kerma)
of exposure (Sec. 1020.32(k));
Section 1020.33 addresses computed tomography (CT)
equipment. With regard to CT systems, the final rule makes the
following changes:
Amends the requirements pertaining to beam-on and shutter status
indicators to reflect the change in quantity used to describe x-
radiation from exposure to air kerma. This modification does not alter
the level of radiation protection provided by the existing standard
(Sec. 1020.33(h)).
III. Summary and Analysis of Comments and FDA's Responses
A. General Comments
(Comment 1) FDA received 12 comments on the proposed amendments to
the performance standard, many of which addressed multiple issues. In
general tone and content all 12 individuals or organizations that
commented supported the need for amendments and the approach proposed
by FDA. A number of the comments provided suggestions or critiques
regarding specific aspects of the proposed changes or suggested
additional changes or additions for FDA consideration that were not
part of the FDA proposal. The specific comments and FDA's responses
will be discussed in the following paragraphs for each section of the
performance standard.
Seven of the comments provided general comments that did not
address specific proposed changes. Some of
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them addressed the impact analysis or the estimate of the potential
benefits that would likely result from the amendments. All seven
comments were generally supportive of the changes proposed by FDA. Two
comments suggested that the benefits of the proposed changes would be
greater than estimated by FDA. One comment, from a State agency,
suggested that the patient dose reductions would be greater than
estimated by FDA, based on the State agency's experience with programs
that have improved the information provided to facilities regarding
patient radiation doses. Another comment suggested that the benefit of
any dose reduction resulting from the amendments would greatly exceed
FDA's estimates and criticized FDA for suggesting that the risk from x-
ray radiation is much less than the comment believes it to be. Two of
the comments complimented FDA on its analysis of the potential impact
of the regulation.
(Response) We acknowledge and appreciate the supportive comments.
This rule includes important modifications to the Federal performance
standard for diagnostic x-ray systems to address recent changes in the
technology and usage of radiographic and fluoroscopic x-ray systems.
These modifications will help ensure that the performance standard will
continue to protect and improve the public health by reducing exposure
to unnecessary ionizing radiation while assuring the continued clinical
utility of images produced where these new technologies are in use.
(Comment 2) Two comments questioned the need to apply several of
the requirements to all fluoroscopic x-ray systems, noting that the
benefit of the requirements such as for display of dose information and
a last-image-hold feature would largely result from fluoroscopic
equipment used for interventional procedures. At least five other
comments explicitly supported application of the requirements to all
fluoroscopic systems.
(Response) FDA notes that performance requirements must be tied to
equipment characteristics and not to the potential manner in which the
equipment may be used. Because interventional procedures may be
performed using many types of fluoroscopic equipment, and because the
added costs of the requirements are not expected to be overly
burdensome, FDA has determined that the requirements should apply to
all fluoroscopic equipment as proposed.
(Comment 3) Two comments supported the change in the quantity
proposed for the description of radiation in the standard from exposure
to air kerma. One of these comments was fairly general, while the other
expressed specific support for the approach taken in the proposal that
will maintain all of the various limits on radiation contained in
different requirements of the standard at the same effective level as
in the limits in the current standard where they were expressed using
the quantity roentgen.
(Response) FDA believes that the radiation limits contained in the
existing requirements remain appropriate. Although the change from
exposure to air kerma will result in different numerical values that
may no longer be integer numbers or multiples of 5 or 10 as was
previously the case, the level of radiation protection will effectively
be the same.
(Comment 4) FDA received comments in response to questions posed by
the agency in the preamble of the proposed rule. FDA invited comments
on several questions regarding approaches that could be taken to assure
the radiation safety of fluoroscopic systems through performance
requirements. These questions, which were not associated with specific
proposed amendments, were intended to gather information that might
guide FDA in considering any future modifications to the performance
standard. Among the questions FDA presented for comment was whether
there are any clinical situations that could require entrance AKRs
greater than those currently permitted. FDA also invited comment on
whether limits should be established for the entrance AKR at the
entrance surface of the fluoroscopic image receptor and, if so, how
these limits might be determined and established.
FDA received three comments in response to the questions about
entrance air kerma rates. Two comments recommended that limits should
not be established for the entrance air kerma rate at the entrance
surface of the fluoroscopic image receptor. A third comment suggested
that a mode of operation that would permit momentary imaging with
entrance air kerma rates exceeding current limits should be considered
if limits were to be established for the entrance air kerma rate at the
entrance to the fluoroscopic image receptor. This comment also noted
that any consideration of limits should involve the corresponding
fluoroscopic image quality, and suggested that this is an area for
further consideration by FDA in collaboration with interested parties.
However, these comments did not make specific suggestions for
requirements or provide data or evidence regarding such requirements.
(Response) FDA appreciates these suggestions. Although FDA has
decided not to implement them at this time, FDA will involve interested
parties in discussions about such requirements if modifications such as
these are undertaken in the future.
(Comment 5) Two comments supported the need to modify the
performance standard to address newly-evolving technologies. Although
both comments agreed with FDA's proposed approach, they suggested that
any future efforts to further address new technology with additional
performance requirements, beyond the current proposed changes, would
benefit from additional consultations between FDA and interested or
affected parties. One of these comments suggested that consideration of
further requirements to address additional characteristics of digital
detectors or solid state x-ray imaging devices would benefit from
interactive consultations with professional and scientific
organizations. The other comment suggested that these areas could be
addressed through the International Electrotechnical Commission's (IEC)
standards development process.
(Response) FDA agrees with these suggestions and will encourage and
facilitate such discussions should the future development of additional
amendments be undertaken.
B. Comments on Proposed Changes to Sec. 1020.30
1. Definitions (Sec. 1020.30(b))
As discussed in the preamble to the proposed rule, FDA proposed the
inclusion of a number of new definitions in Sec. 1020.30(b) to address
new technologies and to further clarify the regulations. In addition to
the changes to definitions proposed by FDA, a number of comments
suggested modifications of additional, existing definitions or noted
that new definitions were needed for clarity.
(Comment 6) One comment suggested that the definitions in the
standard be harmonized to the extent possible with those used by the
IEC.
(Response) FDA declines to make this change. The definitions in the
U.S. standard were developed and finalized before the development of
the IEC standards for x-ray equipment. Complete adoption of the IEC
definitions would require FDA to overhaul the entire U.S. standard to
bring it in line with the different structure and approach used in the
IEC standards. In addition, the U.S. standard
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reflects differences in common usage. For example, the IEC standard
uses the term ``radioscopy'' instead of the term ``fluoroscopy'' as
commonly used in the United States. For these reasons, FDA does not
believe that such wholesale revisions are warranted at this time.
(Comment 7) FDA received a comment concerning the definition of
attenuation block that noted that the current size specified is not
large enough to accommodate the large x-ray field sizes used in
conjunction with some current fluoroscopic image receptors that are
significantly larger than earlier image receptors.
(Response) In response to this comment, FDA has modified the
definition to indicate that an attenuation block with dimensions larger
than currently specified is allowed. The new definition reads:
Attenuation block means a block or stack of type 1100 aluminum
alloy or aluminum alloy having equivalent attenuation with
dimensions 20 centimeters or larger by 20 centimeters or larger by
3.8 centimeters. When used, the attenuation block shall be large
enough to intercept the entire x-ray beam.
(Comment 8) One comment suggested the need for clarification of
what the term C-arm fluoroscope means as used in the standard.
(Response) FDA agrees that clarification would be useful and has
included a new definition for this term in the final rule. The new
definition reads:
C-arm fluoroscope means a fluoroscopic x-ray system in which the
image receptor and x-ray tube housing assembly are connected or
coordinated to maintain a spatial relationship. Such a system allows
a change in the direction of the beam axis with respect to the
patient without moving the patient.
Note that this definition will include some systems in which the x-ray
tube and the fluoroscopic imaging assembly are not connected by a C-
shaped mechanical connection. The distinguishing feature of a C-arm
fluoroscope is the capability to change the orientation of the x-ray
beam.
(Comment 9) In the preamble to the proposed rule, FDA noted that
the word ``exposure'' is used in the standard with two different
meanings. One comment suggested adding the second meaning of exposure
to the definition for clarity.
(Response) FDA agrees with this comment. Accordingly, the
definition of exposure is revised to read:
Exposure (X) means the quotient of dQ by dm, where dQ is the
absolute value of the total charge of the ions of one sign produced
in air when all the electrons and positrons liberated or created by
photons in air of mass dm are completely stopped in air; thus X=dQ/
dm, in units of C/kg. Exposure is also used with a second meaning to
refer to the process or condition during which the x-ray tube
produces x-ray radiation.
(Comment 10) One comment suggested that the definition of image
intensifier be modified to add a comparison to a simple fluorescent
screen.
(Response) FDA has concluded that such a change is not warranted.
However, this comment prompted further review of the definition of
fluoroscopy. As a result of this further review, FDA believes the
proposed definition of fluoroscopy should be modified to remove the
description that the images are presented instantaneously to the user.
The word ``instantaneously'' is unnecessarily restrictive and
ambiguous. It could result in confusion in certain situations such as
when some short but finite time is required to process digital images
before displaying them to the user. A further clarification has been
added to note that, whereas ``fluoroscopy'' conforms to common usage in
the United States, it has the same meaning as ``radioscopy'' in the IEC
standards. Therefore, the definition of fluoroscopy is changed to read:
Fluoroscopy means a technique for generating a sequence of x-ray
images and presenting them simultaneously and continuously as
visible images. This term has the same meaning as the term
`radioscopy' in the standards of the International Electrotechnical
Commission.
(Comment 11) One comment suggested that FDA clarify the meaning of
the term ``C-arm gantry'' as used in the proposed definition of
isocenter.
(Response) FDA agrees that clarification of this term would be
useful and has revised the proposed definition of isocenter to read:
Isocenter means the center of the smallest sphere through which
the beam axis passes when the equipment moves through a full range
of rotations about its common center.
(Comment 12) Several comments suggested that FDA clarify the
proposed definition of mode of operation.
(Response) FDA agrees that clarification is needed and has modified
this definition. Mode of operation is defined for the purpose of
assuring that adequate instructions are provided to the user on how to
operate the fluoroscopic system. A mode of operation is intended to
describe the state of system operation in which a set of several
technique factors or other control settings are selected to perform a
specific type of imaging task or procedure. Within a specific mode of
operation, a variety of anatomical or examination-specific technique
selections may be provided, either pre-programmed, under automatic
control, or manually-selected.
(Comment 13) One comment suggested that the proposed definition of
mode of operation would allow wide variations in AKR within a given
mode of operation and that such variations would cause conflict with
several items in Sec. 1020.30(h). The comment suggested that FDA
consider using the definition and information requirements of the IEC
standard IEC 60601-2-43, ``Particular Requirements for the Safety of X-
Ray Equipment for Interventional Radiology'' (Ref. 1).
(Response) FDA disagrees that the proposed definition will conflict
with items of information required by Sec. 1020.30(h). It is true that
specification of a mode of operation does not in itself determine the
AKR produced by the mode, as variations of technique factors or other
controls within a given mode of operation can produce wide variations
in the amount of radiation emitted by the system. Such variation,
however, does not conflict with Sec. 1020.30(h). Proposed Sec.
1020.30(h)(5) would require a description of each mode of operation,
and Sec. 1020.30(h)(6) would require information about the AKR and
cumulative air kerma displays. These sections do not require dose data
for each mode in the information to be provided to users under Sec.
1020.30(h). The IEC standard IEC 60601-2-43 does require providing
certain dose information regarding some of the operating modes for
fluoroscopic systems intended for interventional uses, but this IEC
requirement would not conflict with the proposed changes to the
performance standard.
FDA notes that the definition it is adopting for ``mode of
operation'' differs from the definition used in paragraph 2.107 of the
IEC standard IEC 60601-2-43. The IEC standard defines a mode of
operation for interventional x-ray equipment as ``* * * the technical
state defined by a configuration of several predetermined loading
factors, technique factors or other settings for radioscopy or
radiography, selectable simultaneously by the operation of a single
control.'' FDA does not think it necessary to limit a mode of operation
to system operation selected by operation of a single control. The
definition in this final rule includes methods of system operation that
have specific or unique features or intended purposes about which the
user should be informed in detail. The term mode of operation in this
rule addresses only the information that must be provided to the user
under Sec. 1020.30(h)(5), which requires that users receive complete
instructions regarding the operation and intended function of each mode
of operation.
[[Page 34002]]
FDA does not require information related to the reference AKR for
modes of operation as does the IEC standard. FDA notes that the
required display of AKR will directly inform users regarding actual
entrance AKRs during use. FDA has determined that it is important that
users receive complete descriptions in the user's manual of all the
different modes of operation and their intended purposes or types of
imaging procedures for which they are designed.
The definition of mode of operation has therefore been modified to
read:
Mode of operation means, for fluoroscopic systems, a distinct
method of fluoroscopy or radiography provided by the manufacturer
and selected with a set of several technique factors or other
control settings uniquely associated with the mode. The set of
distinct technique factors and control settings for the mode may be
selected by the operation of a single control. Examples of distinct
modes of operation include normal fluoroscopy (analog or digital),
high-level control fluoroscopy, cineradiography (analog or digital),
digital subtraction angiography, electronic radiography using the
fluoroscopic image receptor, and photospot recording. In a specific
mode of operation, certain system variables affecting air kerma,
AKR, or image quality, such as image magnification, x-ray field
size, pulse rate, pulse duration, number of pulses, SID, or optical
aperture, may be adjustable or may vary; their variation per se does
not comprise a mode of operation different from the one that has
been selected.
(Comment 14) One comment suggested that FDA change the definition
of a solid-state x-ray imaging device to make it less specific and
therefore more likely to accommodate changes in technology.
(Response) FDA agrees. The definition has been modified to read:
Solid-state x-ray imaging device means an assembly, typically in
a rectangular panel configuration, that intercepts x-ray photons and
converts the photon energy into a modulated electronic signal
representative of the x-ray image. The electronic signal is then
used to create an image for display and/or storage.
(Comment 15) One comment suggested that the existing definition of
visible area needs clarification with respect to its use with solid-
state x-ray imaging devices. The comment suggested that the definition
clarify that the visible area can include both active and inactive
elements of the detector when inactive elements are within the outer
borders of the overall area.
(Response) FDA has determined that modification of this definition
is not necessary. FDA notes that the ``area'' cited in this definition
is the overall area defined by the external dimensions of the area over
which photons are detected to form an image. It includes any inactive
elements that might be located between active elements of the image
receptor.
(Comment 16) FDA also received comments suggesting changes to some
of the existing definitions that were not proposed for modification in
the proposed amendments, including the definitions for beam axis,
cradle, pulsed mode, source-image receptor distance (SID), portable x-
ray equipment, and stationary x-ray equipment.
(Response) FDA carefully reviewed the suggestions and has
determined that no changes to these definitions are warranted at this
time. However, as FDA reviewed the comments received regarding proposed
changes to the definitions, it became apparent to the agency that
several additional definitions would be useful to further clarify some
of the terms used in the performance standard. Therefore, FDA has added
new definitions for the terms air kerma rate, cumulative air kerma, and
fluoroscopic irradiation time. These definitions are not intended to
impose any new requirements.
The new definitions read as follows:
Air kerma rate (AKR) means the air kerma per unit time.
Cumulative air kerma means the total air kerma accrued
from the beginning of an examination or procedure and includes all
contributions from fluoroscopic and radiographic irradiation.
Fluoroscopic irradiation time means the cumulative
duration during an examination or procedure of operator-applied
continuous pressure to the device enabling x-ray tube activation in any
fluoroscopic mode of operation.
2. Information to Be Provided to Users (Sec. 1020.30(h))
(Comment 17) Three comments suggested an expansion of the scope of
information required to be provided to users by manufacturers. These
comments suggested that the manufacturer be required to provide: (1) A
full set of system schematics to permit the user or a third party to
troubleshoot electronic problems and perform repairs; (2) system-
specific hardware and software tools to permit a qualified individual
to accomplish quality assurance tests without the need for service
support; or (3) appropriate tools and instructions for their use,
either as part of the system or as required accessories, to permit any
``physics measurements'' needed to assure system performance.
(Response) An expansion of existing information requirements was
not contemplated in the proposed rule. Such requirements could have
significant impact on manufacturers of diagnostic x-ray equipment and
neither should be established without a full opportunity for affected
parties to comment on specific proposals, nor should such requirements
be established without a thorough assessment of the potential benefits
and impacts of such requirements. Therefore, FDA is not incorporating
the suggested requirements into the amendments at this time.
(Comment 18) One comment supported the proposed requirement that
manufacturers provide additional, detailed information regarding the
variety of fluoroscopic system modes of operation. This comment
suggested that manufacturers be required to provide data on the
entrance AKR for each mode of operation and further suggested that such
a requirement could be less costly than the proposed requirement for a
display of air kerma information on fluoroscopic systems. The comment
suggested that users could infer approximate patient doses from such
information with a degree of accuracy comparable to that of the
displayed air kerma information.
(Response) FDA considered the approach described in this comment
when developing the proposal and determined that providing the user
with information on patient doses through data on typical entrance air
kerma rates for each mode of operation was not practical and would not
have the benefits associated with a real-time display of AKR and
cumulative air kerma information. In FDA's opinion, either the entrance
AKR is highly variable within a given mode of operation or there are so
many different modes of operation, which would require separate AKR
data, as to make this approach ineffective in informing physicians
about the doses delivered to a patient in a procedure. For systems with
a number of operating modes, it would be difficult for the user to
remember all of the various entrance AKRs. The real-time display
provides this information on a continuous basis for every patient,
independent of the specific mode selected. For example, interventional
procedures, with their associated long exposure times, may be
undertaken on a variety of types of fluoroscopic systems. It does not
appear feasible to distinguish the type of system that should have the
real-time display from those for which such a display would not be
useful.
The real-time displays are anticipated to have dose-reduction
benefits even in noninterventional procedures. Providing users with
immediate information related to patient doses is expected to have an
impact on use of
[[Page 34003]]
the equipment. In addition, the uncertainty in estimating an individual
patient's specific radiation dose from a reference AKR provided for a
mode of operation is expected, typically, to be much greater than the
uncertainty in the real-time values displayed. This increased
uncertainty is due to the wide variation in AKR possible within a given
mode of operation because of variations in technique factors or other
control factors, patient size and attenuation, and the specific beam
orientations of an individual procedure.
(Comment 19) One comment suggested that the current wording of
Sec. 1020.30(h)(1)(i) be modified to emphasize that the adequate
instructions required by the section be suitably written for physician
operators.
(Response) FDA does not believe that modification of the current
wording is needed. The requirement for adequate instructions embodies
the concept of being adequate for the intended audience. Since
diagnostic x-ray systems are prescription devices, there is a presumed
level of knowledge regarding the use of x-ray equipment on the part of
the users.
(Comment 20) A comment questioned the preamble statement regarding
unique features of equipment that require adequate instructions
regarding radiological safety procedures and the precautions needed
because of these features. FDA noted that any mode of operation that
yields an entrance AKR greater than 88 mGy/min should be considered a
unique mode, and sufficient information should be provided to enable
the user to understand the patient dose implications of using that
mode. The comment questioned whether an 88 mGy/min threshold should be
applied to radiographic modes and further suggested that there be a
requirement that any fluoroscopic mode capable of delivering more than
88 mGy/min be explicitly listed as a mode of operation and that
standardized information regarding entrance AKR be provided for each
such mode.
(Response) FDA disagrees with this comment. As noted in the
preamble of the proposed rule, data regarding the doses from specific
modes of operation are not being required in the information for users.
Rather, the newly-required AKR and cumulative air kerma displays will
be relied on to provide users real-time information on air kerma at the
reference location which can be related to patient dose. Values of the
AKR and cumulative air kerma displayed in real-time do not necessitate
adjustments for particular imaging technique factors or patient size as
would standardized tabulations of AKR information printed as user
information for each mode.
(Comment 21) The same comment also suggested that manufacturers be
required to provide standardized AKR data for fluoroscopic modes of
operation as required in IEC standard IEC 60601-2-43, including
information regarding the AKR for each available frame rate possible
during the normal mode of operation.
(Response) FDA did not accept this suggestion, which is also
addressed in the discussion in the previous paragraphs about the
definition of mode of operation. FDA notes that proposed Sec.
1020.32(k) is being revised as described in the following paragraphs to
clarify the conditions under which the display of AKR is required.
Proposed Sec. 1020.30(h)(5) has been revised to require that
information be provided to users for all modes of operation that
produce images using the fluoroscopic image receptor regarding the
impact of the mode selected on the resulting technique factors. This
includes any mode that produces radiographic images from the
fluoroscopic image receptor.
(Comment 22) One comment suggested several changes to the
performance standard that were not included in the proposed rule. These
suggestions were that in several sections of the performance standard,
where specification of the maximum kilovolts peak (kVp) or a specified
kVp is stated, there should be a specification of the characteristics
of the kV waveform. In particular, the comment suggested that a
waveform having a voltage ripple of less than or equal to 10 percent be
required. One of these sections is 1020.30(h)(2)(i), which requires the
specification of the peak tube potential at which the aluminum
equivalent of the minimum filtration in the beam is determined. The
other is the requirement in Sec. 1020.30(m) for the kVp at which the
minimum HVL values are determined. The comment addresses the
requirement that manufacturers provide information regarding the peak
tube potential at which the aluminum equivalent of the beam filtration
provided by the tube housing assembly or permanently in the beam is
determined. The comment points out the fact that the determination of
the aluminum equivalent is also dependent on the voltage waveform as
well as the peak tube potential.
(Response) FDA will further consider this comment and if it
determines that such a modification to the standard is warranted, a
proposal will be published for public comment. Without specification of
the waveform, uncertainty can be introduced into the specification of
the aluminum equivalence of the filtration because this determination
depends on the voltage waveform and the resulting energy spectrum of
the beam. FDA notes that the IEC standard IEC 60601-1-3 (Ref. 2) that
establishes the minimum HVL requirements for diagnostic x-ray systems
does not specify the voltage waveform as part of the test method for
determining the aluminum equivalence. Rather, the requirement is
specified as a function of the selected operating x-ray tube voltage
over the normal range of use and is therefore dependent on the waveform
of the specific x-ray generator being tested.
When the method for determining HVL was initially established,
there were fewer generator designs and voltage waveforms than there are
currently. It is correct that a complete specification of equivalent
filtration would require a specification of the voltage waveform with
which it was determined, as well as peak tube potential. However, there
are no tolerances or specifications given in the standard regarding the
accuracy with which the filtration equivalent is to be specified. FDA
notes that one might conclude that since no requirements exist in the
standard for the accuracy of the statement regarding filtration
equivalent, it does not need to be so precise as to require description
of or limitation on the waveform used. Note that a similar requirement
exists in 1020.30(h)(4)(ii) for beam-limiting devices.
(Comment 23) One comment strongly supported the consolidation of
instructions for use of the various modes of operation of fluoroscopic
systems into a single section of the user's instructions. The comment
further suggested that the instructions be required to include a
description of all of the controls accessible to the operator at the
normal working position.
(Response) FDA does not believe that such a requirement is
necessary, as FDA expects that any user's instructions will include a
complete description of all controls, including any controls available
at the operator's working position.
(Comment 24) Three comments expressed concern regarding the
requirement in proposed Sec. 1020.30(h)(5) that manufacturers describe
specific clinical procedures or uses for which a specific mode of
operation is designed or intended. The concern expressed was that the
clinical use of the fluoroscopic system should not be limited by any
statements required of the manufacturer
[[Page 34004]]
regarding the purposes of any mode of operation.
(Response) FDA agrees that clinical use of the system should not be
limited to the examples provided by the manufacturer. The manner of use
and the decision to use a particular mode of operation are medical
decisions. In addition, the requirements of the performance standard
apply only to manufacturers and do not impose requirements on the users
of such systems. The requirement at Sec. 1020.30(h)(5)(ii) has been
modified to reflect that a manufacturer's descriptions of particular
clinical procedures exemplifying the use of specific modes of operation
do not limit when or how any mode may be used in actual clinical
practice.
In addition, FDA has revised Sec. 1020.30(h)(5)(i) to further
elaborate the type of information required to be provided to users with
respect to the description of modes of operation. FDA believes it is
important for users to understand the manner in which a given mode of
operation controls the system technique factors and that this
information should be included in the description of the mode of
operation.
(Comment 25) An error in the proposed rule, which was detected by
FDA following publication, was pointed out by one of the comments.
Proposed Sec. 1020.30(h)(6)(i) would have required a statement by the
manufacturer of the maximum deviations of the values of AKR and
cumulative air kerma from their displayed values.
(Response) This requirement should have been removed from the
proposed rule as it was replaced by the requirement in proposed Sec.
1020.32(k)(7) specifying the maximum deviation allowed. Proposed Sec.
1020.30(h)(6)(i) has been removed and Sec. 1020.32(k)(7) has been
revised to be Sec. 1020.32(k)(6). This revision of Sec. 1020.32(k) is
described in section III.D.8 of this document.
(Comment 26) One comment suggested that, in addition to requiring
instructions and schedules for calibrating and maintaining any
instrumentation required for measurement or evaluation of the AKR and
cumulative air kerma, Sec. 1020.30(h)(6)(ii) should also require
manufacturers to provide any hardware or software tools or accessories
necessary to accomplish such calibration or maintenance.
(Response) FDA is not adding such a requirement to the standard at
this time, but will consider it along with the other suggestion
regarding information or equipment features that should be included in
the performance standard.
3. Beam Quality--Increase in Minimum Half-Value Layer (Sec.
1020.30(m))
(Comment 27) One comment objected to the revision of the
requirements for minimum half-value of the x-ray beam in Sec.
1020.30(m)(1) on the grounds that the new minimum requirements for all
systems should not be based on what the comment considered to be state-
of-the-art equipment. The comment suggested a set of reduced minimum
values.
(Response) It appears that the comment misunderstood the basis for
the FDA proposal and the intent of the increased HVL values. Currently,
to comply with paragraph 29.201.5 of the IEC standard IEC 60601-1-3,
all x-ray systems other than mammographic and some dental x-ray systems
must contain total filtration material in the x-ray beam that provides
a quality equivalent filtration (using IEC terminology) of not less
than 2.5 millimeters of aluminum (mm Al). Thus, all currently
manufactured x-ray systems should be manufactured in a manner that
assures this amount of filtration in the beam if compliance with the
IEC standard is claimed. The proposal to increase the HVL requirements
in the FDA standard, which must be expressed as a performance standard
rather than as a design standard for a given thickness of filtration,
is intended to provide HVL values that correspond to those that result
from the use of a filtration corresponding to the 2.5 mm Al required by
the current IEC standard. Therefore, the changes proposed for HVL will
simply bring FDA's requirements into agreement with the performance
provided by systems complying with the IEC standards IEC 60601-1-3 and
IEC 60601-2-43. Manufacturers currently complying with the IEC standard
should experience no impact from this change as all of their production
should already meet the requirement. Therefore, the change suggested by
the comment is not necessary.
FDA notes that several values in table 1 in proposed Sec.
1020.30(m)(1) are being revised in order to fully agree with existing
and proposed IEC standards that address the minimum HVL for diagnostic
x-ray systems. The values of HVL in table 1 in proposed Sec.
1020.30(m)(1) for several tube voltages in the column heading ``II--
Other X-Ray Systems''are being changed. The changes will have no
significant impact on the radiation safety provided by the amendment.
(Comment 28) In conjunction with the proposed revision of the
requirements for the minimum HVL of the x-ray beam, one comment
suggested a 60 kVp lower limit for intraoral dental x-ray systems. The
comment suggested that systems with lower kVp capabilities are not dose
efficient.
(Response) FDA notes that a previous amendment to the performance
standard in 1979 increased the beam quality requirements for x-ray
systems manufactured after December 1, 1980. The increased beam quality
required of these systems was intended to preclude systems from
operating below 70 kVp, while complying with the beam quality
requirements. FDA believes that the modified requirements that became
effective in 1980 limited the ability of dental intraoral x-ray systems
to operate at lower voltages. FDA is not aware of information
indicating that there are significant numbers of newly-manufactured
systems that operate with such low voltage capability. Should FDA
become aware that the current requirements are not effective in
limiting the beam quality of intraoral dental x-ray systems to
appropriate values, future consideration will be given to proposing an
appropriate amendment.
(Comment 29) Two comments suggested that Sec. 1020.30(m)(2)
contain a requirement that the system provide an indication to the user
of the amount of additional filtration that is in the beam at any time
during system use. The comments did not express a preference for the
location for this display, indicating that it could be at the system
control console or at the operator's location. A third comment
supported the addition of Sec. 1020.30(m)(2), noting the impact of the
requirement in reducing patient dose and maintaining image quality.
(Response) FDA agrees that there should be a requirement for a
display of the amount of additional filtration in use because it is
important that the operator of the system be able to easily determine
the added filtration that is currently in use during any procedure. An
active display of this information will assist the operator.
Manufacturers of systems that currently do not provide such a feature
will be required to redesign to implement the capability to select and
add filtration.
Accordingly, FDA has modified proposed Sec. 1020.30(m)(2) to
require an indication of the additional filtration in the beam. FDA has
also clarified the requirement to state that the selection or insertion
of the additional filtration can be either at the option of the user or
automatically accomplished as part of the selected mode of operation.
FDA notes that automatic selection and concurrent modification of the
[[Page 34005]]
technique factors to maintain image quality is the preferred method of
operation. Efficient manual use of additional filtration requires that
the user make appropriate technique changes to preserve optimum image
quality.
FDA notes that, through an oversight, no effective date was
proposed for the new requirement in Sec. 1020.30(m)(2). This new
requirement was intended to become effective, along with all of the
other new requirements, 1 year after the date of publication of the
amendments in the Federal Register. FDA has modified proposed Sec.
1020.30(m)(2) to reflect the effective date.
4. Aluminum Equivalent of Material Between Patient and Image Receptor
(Sec. 1020.30(n))
(Comment 30) One comment noted that the values given in table 2 in
Sec. 1020.30(n) need to be revised as a result of the revision of
Sec. 1020.30(m)(1). According to the comment, if the values of the
maximum aluminum equivalence given in table 2 are not revised to
reflect the increased beam quality required by Sec. 1020.30(m)(1) for
the test voltage of 100 kVp for determining compliance with Sec.
1020.30(n), the current requirements of table 2 in Sec. 1020.30(n)
would in effect require that items between the patient and the image
receptor provide less attenuation than currently required.
(Response) The comment is correct that FDA's proposal was not
intended to reduce the limits on the maximum allowed aluminum
equivalence of materials between the patient and the image receptor.
The comment is also correct that the values in table 2 in Sec.
1020.30(n) were based on the beam qualities associated with the current
values in table 1 in Sec. 1020.30(m)(1), reflecting a beam quality of
2.7 mm of aluminum HVL, and not the beam quality described in the
proposed revision of Sec. 1020.30(n), which is an HVL of 3.6 mm Al at
100 kVp. However, the comment's reference to the values in table 2 in
Sec. 1020.30(n) as HVL values was incorrect, although that does not
invalidate the concern raised by the comment. Therefore, FDA is
revising the values in table 2 in Sec. 1020.30(n) for the maximum
aluminum equivalent of materials between the patient and image receptor
to reflect requirements that are met by current products that comply
with the present standard. These revised limits are consistent with the
maximum limits used in current IEC standard IEC 60601-1-3 (Ref. 2).
This change continues the current requirement for maximum aluminum
equivalence, but has no impact on current products and will not require
changes in design.
5. Modification of Certified Diagnostic X-Ray Components and Systems
(Sec. 1020.30(q))
(Comment 31) Two comments suggested that a party other than the
owner be required to certify the continued compliance of any certified
system that is modified in accordance with Sec. 1020.30(q).
(Response) The current requirement was not proposed for change and
no change is considered necessary by FDA. As discussed in the preamble
to the proposed rule, the requirement in Sec. 1020.30(q)(2) states
that the owner of an x-ray system may modify the system, provided that
the modification does not result in a failure of the system to comply
with an applicable requirement of the performance standard. In
accomplishing such a modification, the owner may employ a third party
with the requisite skills and knowledge to accomplish the modification
in a manner that does not result in noncompliance. As the responsible
party, the owner should assure that any modifications are accomplished
appropriately. This can be done through contractual arrangements with
the party performing the modifications to assure compliance is
maintained or through any other means that satisfies the owner that
compliance has not been compromised by the modification. Section
1020.30(q) does not require that owners themselves perform the
modification, but rather that owners be responsible for assuring the
compliance of the modified system.
(Comment 32) One comment suggested that the party performing the
modification be required to certify and report the modification in a
manner similar to that required of an assembler of a new x-ray system.
Another recommended that the party performing the modification submit a
report as required by subpart B of 21 CFR part 1002 to the owner of the
x-ray system.
(Response) FDA does not see a need for the reporting of such a
modification. The reporting of the assembly of an x-ray system is
required to provide a mechanism for the assembler of the system to
complete the certification that the system has been assembled according
to the manufacturer's instructions and therefore complies with the
standard. The compliance of any modified system can be verified during
a routine inspection by Federal or state authorities. FDA also notes
that the contractual arrangement between the owner and a party engaged
by the owner to perform a modification can be structured to provide the
owner with the necessary assurances that the party performing the
modifications is responsible to the owner for assuring the continued
compliance of the system. FDA concludes that there is no need to
describe these arrangements in the standard beyond the requirement that
the owner be responsible for assuring the continued compliance of any
modifications to its system.
Upon reviewing the comments relating to Sec. 1020.30(q), FDA
decided, on its own initiative, to add a phrase to Sec. 1020.30(q)(2)
that was not described in the proposed rule. This phrase clarifies
where the recorded information regarding an owner-initiated
modification is to be maintained. The phrase specifies that the
information is to be maintained with the system records.
C. Comments on Proposed Changes to Sec. 1020.31--Radiographic
Equipment
1. Field Limitation and Post Exposure Adjustment of Digital Image Size
(Comment 33) One comment suggested a change in the requirement for
beam limitation on radiographic x-ray systems that was not proposed.
This comment recommended that automatic collimation be required for
digital radiographic systems to preclude what it referred to as
``digital masking'' of images obtained with the x-ray beam limiting
device (collimator) adjusted to produce an x-ray field larger than the
sensitive area of the digital image receptor. This comment expressed a
concern about the operation of digital radiographic systems and the
manner in which the x-ray field size is adjusted. Because digital
radiographic systems permit the opportunity for post-exposure image
manipulation, the comment expressed concern that adjustment following
image acquisition of the area imaged or ``image cropping'' might occur,
obscuring the fact that the x-ray field was not adjusted appropriately
and therefore not limited to the clinical area of interest.
(Response) FDA agrees that digital image cropping in lieu of
appropriate x-ray field limitation could be a concern for systems that
produce digital radiographic images with a digital image receptor used
in place of a film/screen cassette, or for fluoroscopic systems when
used to produce a radiographic image via the fluoroscopic image
receptor, analogous to use of a photospot camera for analog images. For
fluoroscopy and radiography using the fluoroscopic imaging assembly,
proposed Sec. 1020.32(b)(4) and (b)(5) require that the x-ray field
not exceed
[[Page 34006]]
the visible area of the image receptor by more than specific
tolerances. These requirements for the fluoroscopic imaging assembly
are intended to prevent imaging with the x-ray field adjusted to a size
greater than the selected visible area of the image receptor. However,
it may not be clear how this requirement applies to radiographic images
at the time of later storage or display.
For radiographic images, obtained directly using a digital
radiographic image receptor, such as a solid-state x-ray imaging
device, or from the fluoroscopic image receptor, the comment raised the
question of whether some control is needed to assure that x-ray fields
are not used when they are larger than necessary for the ultimate size
of the either stored or displayed image.
Neither the current standard nor the proposed amendments address
the issue of post-exposure image cropping of the original image at the
time of image display or image storage. In the case of a radiographic
system, including a purely digital system, the current standard
requires that the x-ray field size not exceed the size of the image
receptor, meaning that portion of the image receptor area that has been
preselected during imaging such as when using a spot-film device.
The comment addresses the concern that the x-ray field might be
larger than necessary to capture the area of clinical interest and that
the individual obtaining the image could ``hide'' this fact by
electronically cropping the digital image for storage and display.
Thus, it would not be possible for someone reviewing the image later to
determine that the image was obtained with an x-ray field size larger
than necessary, resulting in unnecessary patient exposure. The comment
suggests some type of automatic collimation to prevent this
possibility, but does not describe the automatic system envisioned. If
electronic cropping of digital imaging is available post exposure, it
does not appear possible to have an automatic collimation system that
could anticipate how such cropping might be done to the exposure.
FDA notes that the question of electronic image cropping is a
question that requires further exploration and discussion with the
equipment users to determine if a requirement to address this issue is
needed. The agency will review this issue and determine what the
current equipment design and usage practices are. If FDA determines
that a limitation on the ability to crop digital images is warranted
and feasible, it will be addressed in a future proposed amendment.
2. Policy Regarding Disabled Positive Beam Limitation Systems
(Comment 34) One State radiation control agency submitted a comment
expressing disappointment that FDA did not propose an amendment that
would have codified its policy regarding application of the standard to
x-ray systems that are reassembled and that contain positive beam
limitation systems that may have previously been disabled by the owner
of the system.
(Response) FDA did not propose amending the standard to include
this clarification because it is not a performance requirement and the
standard clearly states the performance required of stationary,
general-purpose systems and the obligations of assemblers to install
certified components according to the manufacturer's instructions. The
performance standard originally required that stationary, general-
purpose x-ray systems be equipped with beam limiting devices that
provided positive beam limitation (PBL). The standard was amended in
1993 (58 FR 26386) to remove the requirement that stationary, general-
purpose systems be equipped with a beam limiting device providing PBL
and permitting instead beam limiting device that provides continuous
adjustment of the x-ray field. Questions arose regarding the
performance required of beam limiting devices that were designed and
certified to provide PBL when assembled into x-ray systems that were no
longer required to provide PBL.
The standard requires, in Sec. 1020.30(d), that assemblers of
diagnostic x-ray systems must install certified components according to
the instructions of the component manufacturer when these certified
components are installed in an x-ray system. Thus, the standard
requires that, when an assembler installs a beam limiting device,
including one designed to provide PBL, the beam limiting device must be
installed according to the manufacturer's instructions. That is, the
beam limiting device must be installed such that the PBL system
functions as designed and according to the manufacturer's instructions.
FDA clarified this issue via communications to manufacturers, State
radiation control agencies and others that emphasized the continuing
requirement that any certified component be installed according to the
manufacturer's instructions. Although the installation of a beam
limiting device providing PBL became optional for stationary general-
purpose systems, FDA noted that the requirement to install any
certified component according to manufacturer's instructions remained.
Thus, a PBL system, if installed, must be installed in a manner such
that it functions as designed, even though there is no longer a
requirement that all stationary, general-purpose x-ray systems be
provided with PBL. FDA, therefore, has concluded that the suggested
amendment is not appropriate for a performance standard.
D. Comments on Proposed Changes to Sec. 1020.32--Fluoroscopic
Equipment
1. Testing for Attenuation By the Primary Protective Barrier
(Comment 35) One comment on Sec. 1020.32(a)(2) pointed out
differences between FDA's testing procedures for determining compliance
with the requirements for a primary protective barrier as part of the
fluoroscopic imaging assembly and the testing procedure described in
paragraph 29.207.2 of IEC standard IEC 60601-1-3. The comment noted
that the area of the attenuation block may be insufficient for some
modern fluoroscopic image receptors that accommodate x-ray field sizes
greater that 20 centimeters (cm) by 20 cm.
(Response) FDA acknowledges there may be a need for a larger
attenuation block in some circumstances and, as described previously in
the discussion of changes to definitions in Sec. 1020.30(b), has
modified the definition to accommodate a larger size for the
attenuation block.
(Comment 36) The comment also expressed concern that, because FDA
and IEC compliance testing procedures are different, manufacturers will
need to perform two separate tests in order to meet both standards.
(Response) FDA notes that its performance standard does not require
the manufacturer to determine compliance in any particular way. Section
1020.32(a)(2) describes how FDA will measure compliance. The
manufacturer is free to use any test method that provides assurance
that the product complies and is free to develop a single testing
procedure that would assure compliance with both standards. The comment
is incorrect, therefore, in stating that the manufacturer is required
to perform two different sets of measurements to satisfy both
standards.
FDA also notes that the requirements for the thickness of the
attenuation block and the quantitation of the amount of radiation
transmitted by the protective barrier are different in the performance
standard and the IEC
[[Page 34007]]
standard. The thickness differences most likely arise from the
conversion of linear dimensions in inches (as originally used in the
standard) to centimeters. FDA considers these differences minor and
notes that a manufacturer may develop a single test method that assures
compliance with both requirements.
(Comment 37) The comment also suggested that FDA adopt the complete
wording from the IEC standard related to the attenuation of the primary
beam by the primary protective barrier in lieu of the current FDA
standard.
(Response) FDA does not believe that adoption of the IEC wording
regarding the attenuation of the primary beam by the primary protective
barrier is necessary. Although the two standards employ different
approaches, including different terms, definitions, and organizational
structure, there does not appear to be a significant conflict between
the two standards with regard to this issue.
2. Field Limitation for Fluoroscopic Systems
(Comment 38) One comment opposed proposed Sec. 1020.32(b)(4) and
FDA's intent to promote continuously adjustable, circular field
limitation in all types of fluoroscopic systems. The comment expressed
doubts about the need for such a requirement, especially for systems
designed for extremity imaging only, and was concerned that the
requirement would add to maintenance costs. The comment suggested that
a stricter requirement would be effective only if States modify their
regulations to enforce identical requirements during the useful life of
the equipment.
(Response) The proposal encouraged the provision of circular or
nearly circular collimation for fluoroscopic systems having circular
image receptors, but does not require it. The comment provided no
information about why a collimator providing nearly circular
collimation would be more expensive to maintain than rectangular
collimation. If adopted, the proposed requirement in Sec.
1020.32(b)(4) would apply to affected equipment, regardless of when
inspected or who is performing the inspection. FDA does not understand
the assertion made in the comment that, under State regulations, the
under-framed fluoroscopic field would be enlarged to fill the input
phosphor. Review of the State regulations of the party who submitted
the comment indicates no such requirement. Rather, this State's
regulations require that the x-ray field not exceed the visible area of
the image receptor. There is no requirement that the field be enlarged
to match the size of the image receptor. The State's regulations do not
appear to prohibit an under-framed image. FDA expects that State
regulations will be modified to conform to the Federal standard
because, under section 542 of the act (21 U.S.C. 360ss), States may not
impose different requirements on an aspect of performance of an
electronic product that is addressed by the Federal standard. FDA
acknowledges that the benefit of the requirement will not be as great
for fluoroscopic systems intended for examination of extremities only
as it will be for general-purpose fluoroscopic systems. Nevertheless,
improved collimation for these systems can reduce operator exposures
from scattered radiation and improve image quality. The proposal does
not require circular collimation for equipment designed only for
extremity use. Systems with rectangular collimation will meet the
requirement of this standard. Accordingly, no change to the proposed
requirement was made in response to this comment.
(Comment 39) One comment from a radiology professional organization
stated that the proposed requirements for field limitation and
alignment of fluoroscopic systems were acceptable. Another comment
which specifically addressed Sec. 1020.32(b)(4)(ii)(A) and
(b)(4)(ii)(B) asserted that the clarity of these proposed requirements
would be improved by the addition of the words ``any linear dimension
of'' before the words ``the visible area.''
(Response) FDA agrees with the suggestion to add these words and
has incorporated the change into the final performance standard.
3. Air Kerma Rates
(Comment 40) One comment suggested a change to the wording of
proposed Sec. 1020.32(d)(2)(iii)(B). The comment suggested adding the
phrase ``archive of the'' before the words ``image(s) after termination
of exposure'' to clarify that the presence of a last-image-hold feature
is not sufficient to invoke the exception to the limit on maximum
entrance AKR.
(Response) FDA agrees that suggested language more accurately
reflects the intent of the proposed paragraph. The presence of the
last-image-hold feature, without storage of the images for later
viewing, is not sufficient for the exception to apply. The wording of
proposed Sec. 1020.32(d)(2)(iii)(B) has been modified accordingly.
The agency has also decided to remove the proposed requirement that
the limitation on the maximum AKR apply when images are recorded in
analog format with a videotape or video-disc recorder. The proposed
limitation on maximum AKR cannot be justified solely on the basis of
recording technology used. The display of air kerma information will
directly inform the user of the AKRs delivered by different modes.
Because of the different methods and mechanisms for recording
fluoroscopic images and the differences in the amount of incident
radiation on the image receptor required for different clinical tasks,
there is no consensus on appropriate maximum AKRs during recording of
fluoroscopic images. FDA has concluded that, until such a consensus is
developed, it is not appropriate to establish such limits. Therefore,
the list of exceptions in Sec. 1020.32(d)(2)(iii) specifying when the
limitation on maximum AKR does not apply has been modified to remove
the exclusion of analog recording. Thus, the limit on maximum AKR in
the amended standard does not apply to any mode of operation involving
recording from the fluoroscopic image receptor for fluoroscopic systems
manufactured after the effective date of the amendments.
(Comment 41) One comment supported what it described as the attempt
to establish an upper limit on AKRs during both normal and high-level
control modes of fluoroscopy.
(Response) This comment reflects confusion regarding the proposed
amendments and the revision of Sec. 1020.32(d) and (e). Limits already
exist on AKRs during normal and high-level control fluoroscopy. The
sections are being revised for clarity; the only change is to the
applicability of the exception to the maximum AKR limit to systems
operated in a pulsed mode as described in the following paragraphs.
(Comment 42) One comment noted that the distinction between
recording fluoroscopic images via analog or digital means is not a
reasonable means of differentiating between recording methods that
could have different patient dose implications.
(Response) FDA agrees that this is a legitimate concern. The
limitation on the exception to the maximum AKR limit originally
proposed in Sec. 1020.32(d)(2)(iii)(B) would not be an effective way
to limit AKR as there are now available digital recording products that
could perform the function of previous analog recording devices. The
requirements of current Sec. 1020.32(e)(2)(i) and proposed Sec.
1020.32(d)(2)(iii)(B) were intended to prevent bypassing the limits on
maximum entrance AKRs by the addition of image recording devices to
fluoroscopic systems. Rather than attempting to limit entrance AKRs in
[[Page 34008]]
this manner, FDA has concluded that the display of AKR and cumulative
air kerma will inform operators about the amount of radiation being
delivered during fluoroscopic procedures and that limits during
recording cannot be appropriately justified at this time. FDA has
therefore revised proposed Sec. 1020.32(d)(2)(iii)(B) to remove the
last sentence that would have imposed limits during recording of
fluoroscopic images with an analog format. The standard, as amended,
will not place any limits on AKR during the recording of images from
the fluoroscopic image receptor. Instead, the display of AKR and
cumulative air kerma at the reference location, as required by Sec.
1020.32(k), will be relied on to inform the user regarding radiation
incident on the patient during fluoroscopic procedures.
(Comment 43) One comment noted that the value for the maximum limit
on AKR given in proposed Sec. 1020.32(d)(2)(iii)(C) was expressed as
180 mGy per minute, not 176 mGy per minute, which is twice the rate of
88 mGy per minute as specified for normal fluoroscopy mode.
(Response) FDA agrees with this comment and has revised the limit
to be 176 mGy per minute for consistency.
(Comment 44) One comment suggested that additional information be
provided to permit the AKR at the reference location for the AKR
display to be determined for the maximum permitted AKRs where the
latter are determined at the measurement points specified in Sec.
1020.32(d)(3). The comment also suggested that the measurement point
for mini C-arm systems be specified at the minimum source-skin distance
(SSD), which is, in fact, the measurement point specified in proposed
Sec. 1020.32(d)(3)(iv).
(Response) The requirements in Sec. 1020.32(d) address the limit
on the maximum AKR permitted for fluoroscopic x-ray systems. There is
no requirement that the values obtained for AKR at the compliance
measurement points specified in Sec. 1020.32(d)(3) be provided or
displayed to the user. The comment appears to request that some
comparison be made available to the user regarding the AKR at the
compliance measurement point and the reference location for the AKR
that is displayed according to proposed Sec. 1020.32(k). Providing
information to the user regarding the maximum AKR that could result at
the fluoroscopic reference location could provide additional
information to the user prior to the use of a system. However, as this
information will be displayed in real-time to the user during the use
of the system, FDA does not see the need to add an additional
requirement of the type suggested.
(Comment 45) One comment suggested that additional language be
added to ensure that the entrance AKR limits are met at all times by
systems that permit variation in the source-image receptor distance.
(Response) FDA notes that the current standard already includes
such a requirement and, like all other requirements in Sec. 1020.32,
this requirement applies to all fluoroscopic systems unless there is a
specific exception stated. FDA, therefore, does not believe the
suggested addition is needed.
4. Minimum Source-Skin Distance
(Comment 46) One comment noted the difference in limits on the
minimum source-skin distance permitted in the FDA performance standard
and the limits specified in IEC standard 60601-1-3. The requirements
addressed by the comment are those for fluoroscopic systems not
intended for special surgical applications. Since its inception in
1974, the performance standard has required a minimum source-skin
distance of 38 cm for stationary fluoroscopes. The IEC standard has a
minimum of 30 cm for fluoroscopic systems that are not intended for use
during surgery. The comment suggested a limit of 30 cm for systems
labeled for interventional uses. It was suggested that a minimum of 38
cm for the source-skin distance can limit the manner of clinical use of
C-arm fluoroscopes. The comment also acknowledged the provisions in
both the U.S. performance standard and the IEC standard for a smaller
minimum source-skin distance of 20 cm for systems intended for surgical
applications. The comment noted that, although interventional uses
might be considered surgical applications, the limit of 20 cm for
surgical systems was too short for interventional uses.
(Response) FDA did not propose a change to the minimum source-skin
distance. Furthermore, no other comments suggested that the current
minimum source-skin distance should be modified. FDA will consider the
issue further and, if it determines that the standard should be
modified, the agency will propose the amendment at a future time.
5. Display of Cumulative Irradiation Time
(Comment 47) Six comments expressed very different views on the
requirement to display the cumulative irradiation time at the
fluoroscopist's position, as proposed in Sec. 1020.32(j)(2). Two
comments from manufacturers and one from a State suggested that such
information was not needed at the user's working position and, in fact,
could be confusing to the user. In contrast, comments from two medical
professional associations whose members are users of fluoroscopy
systems, a medical physicist, and a State agency strongly endorsed the
proposed requirements to display the cumulative irradiation time, along
with the AKR and cumulative air kerma, at the user's working position.
(Response) FDA agrees with the comments from the users of
fluoroscopic systems and, accordingly, the final standard retains this
requirement.
(Comment 48) One comment emphasized the importance for the user of
the uniformity and consistency of the display of information and two
comments suggested that FDA require that the units of measurement and
manner of display be specified.
(Response) In response to these comments, FDA has revised Sec.
1020.32(h)(2) to specify the following requirements: The display must
show the irradiation time in minutes and tenths of minutes and such
information must be displayed continuously; updated every 6 seconds,
displayed within 6 seconds of termination of exposure, and displayed
until reset. In addition, as noted in the discussion of Definitions
mentioned previously in the document, FDA has added a definition of
``fluoroscopic irradiation time'' to Sec. 1020.30(b) to further
clarify the meaning of this term.
6. Audible Signal of Irradiation Time
(Comment 49) Five comments addressed the proposed requirement that
an audible signal sound every 5 minutes during fluoroscopy to alert the
fluoroscopist to the passage of irradiation time. Three of these
comments supported the proposed approach of a fixed, 5-minute interval
between audible signals. Two of the comments specifically addressed the
question of whether the interval between audible signals should be
selectable by the user and recommended against such an approach,
suggesting that a variable interval could lead to confusion. One
comment from a manufacturer's association suggested complete
elimination of the audible signal in view of the display of the AKR and
cumulative air kerma to the operator and the potential for the audible
signal to be distracting to the user. However, users of fluoroscopic
systems supported retaining the
[[Page 34009]]
requirement of an audible signal as a feature of the equipment. One
manufacturer commented that the proposed requirement of an audible
signal would lead to a potential conflict with the IEC standard 60601-
2-7, ``Particular Requirements For the Safety of High-Voltage
Generators of Diagnostic X-Ray Generators,'' which contains a
requirement for an audible signal that sounds continuously until reset.
The manufacturer's comment also raised a question regarding the
specification of the interval between reset of the signal and the time
of the next audible signal.
(Response) FDA notes the potential conflict with IEC standard
60601-2-7, and further notes that this requirement for an audible
warning of elapsed fluoroscopic time predates the use of fluoroscopy in
interventional procedures, which often require much more than 5 minutes
of irradiation time. The need to continually reset the 5-minute timer
and the lack of information about the cumulative fluoroscopic time
under those circumstances indicate that the current IEC requirement
should also be revised. FDA will work with the appropriate IEC
committee responsible for the maintenance of IEC 60601-2-7 to encourage
that it be revised to be consistent with the FDA proposal.
(Comment 50) One comment suggested that the audible signal should
be required to be reset manually because a signal of 1-second duration
would likely be ignored.
(Response) In view of the additional requirement for a display of
air kerma information during a procedure, FDA does not think that a
manual reset of the audible signal is needed or that such a requirement
would add significantly to the safety of these systems. The users of
fluoroscopic systems will have both the display of air kerma
information and the periodically recurring audible signal to remind
them of the passage of fluoroscopic irradiation time. Nevertheless, the
standard should not prohibit a manual reset if the user desires such a
feature. Therefore, Sec. 1020.32(j)(2) has been modified to permit, at
the option of the manufacturer, the signal to be automatically
terminated after 1 second or to continue sounding until manually reset.
Manufacturers may provide both options for user selection if they wish.
7. Last-Image-Hold (LIH) Feature
(Comment 51) Six comments supported the proposed requirement for
the LIH feature on fluoroscopic systems. One of these comments
questioned whether the LIH feature was necessary for small, extremity-
only fluoroscopic systems, in view of their low radiation output.
(Response) FDA believes that, even for the small, extremity-only
fluoroscopic systems, the LIH feature can reduce exposure to the
patient and operator. Many of the current extremity-only systems, which
are digital systems, already provide the LIH feature. FDA has
determined that this requirement should apply to all fluoroscopic
systems.
(Comment 52) In response to the proposed requirement that images
that are the result of the LIH display be clearly labeled as LIH
images, two comments stated that there are other conditions during
which confusion might exist regarding whether a displayed image is the
result of concurrent fluoroscopic irradiation or is a display of a
stored image. This could be a concern with systems with more than one
image-display device. A similar concern expressed in the comments was
that, when systems may display stored images, there may be no clear
indication of when the fluoroscopic x-ray tube is activated. These
comments suggested that the standard include additional requirements,
not contained in the proposal, for a visible indication of when
fluoroscopic irradiation is initiated and when irradiation is
occurring. In addition, the comments suggested that the replay of
stored images also be accompanied by a clear indication that the image
is a replay of a stored image and not a live fluoroscopic image.
(Response) FDA agrees it is important that the fluoroscopic system
provide a clear indication of when x-rays are being produced. FDA notes
that Sec. 1020.31(j) requires radiographic systems provide a visual
``beam-on'' indicator whenever x-rays are produced. Such a requirement
was not included in the performance standard applicable to fluoroscopic
systems in the past because the production of the fluoroscopic image
was previously a direct indication of the production of x-rays.
However, with the introduction of LIH features and the serial replay of
stored images, the display of an image on the fluoroscopic display is
not necessarily an indication of x-ray production.
FDA also agrees it is important that users be able to easily
distinguish between display of a previously recorded image(s) and live-
time image. It could be a safety issue if a recorded image were
mistaken for a ``live'' image (or vice versa). However, FDA needs to
further consider whether the requirements suggested by the comments
should be added to the performance standard.
The relevant IEC standard 60601-2-7, ``Particular Requirements for
the Safety of High-Voltage Generators of Diagnostic X-Ray Generators''
(Ref. 3) (see 29.2.102 Indication of Operational States, (b) Loading
state) requires a yellow light on the control panel of the high voltage
generator that indicates the loading state and that there be a means
for connecting a remote indication of the loading state in continuous
mode. This IEC standard also requires that there be a means of
connecting an audible signaling device to indicate the instant of
termination of loading (radiation exposure). However, these IEC
requirements do not address the comment's concern that there be a
requirement for a visual signal visible from anywhere in the room.
The adequacy of the approach taken in the IEC standard is open to
question if, in fact, there is a need for an indication of x-ray
production during fluoroscopy at the user's position. One could ask if
it is sufficient for systems to provide only the means for connecting a
signal device that would be visible in the procedure room or if means
for actually producing such a signal should be required as part of the
system. If only the means for connection is provided, State or local
authorities would have to require that it be used.
The cost of adding such a display would also have to be considered,
although FDA expects that the cost would be minor because the change
would only require adding an indicator if the ``means for connection''
required by the IEC standard is already incorporated in the design.
Manufacturers are encouraged to provide such indicators, and FDA will
urge the development of an appropriate requirement in an IEC standard.
In addition, FDA will consider whether such a feature should be
included in any future amendments to the performance standard that FDA
may develop.
8. Display of Values of Air Kerma Rate and Cumulative Air Kerma
(Comment 53) Eight comments addressed the proposed requirement for
the display of AKR and cumulative air kerma at the fluoroscopist's
working position. None of these comments opposed the proposed
requirement. One of the comments supported the concept, but questioned
whether it is necessary to impose the requirement on small, extremity-
only fluoroscopes. One professional association specifically suggested
that the requirement should apply to all fluoroscopic systems.
[[Page 34010]]
(Response) FDA notes that even small, extremity-only systems can be
used for extended surgical or interventional procedures and that the
radiation output of some of these systems currently is significantly
larger than the output from early versions of these types of systems.
For these reasons, FDA has concluded that the requirement for air kerma
display is appropriate for all fluoroscopic systems.
(Comment 54) Four of the comments raised questions or made
suggestions regarding the technical details and specifics of how the
air kerma information should be described or displayed. One of the
comments referenced the IEC standard 60601-2-43 and the manner of air
kerma display required by that standard, but it incorrectly cited the
requirements of that standard.
(Response) In response to these comments, FDA has modified proposed
Sec. 1020.32(k) to require display of the AKR at the fluoroscopist's
working position when the x-ray tube is activated and the number of
images produced is greater than six images per second. Furthermore, the
value displayed is required to be updated at least once every second.
The value of the cumulative air kerma will be required to be displayed
either within 5 seconds of termination of an exposure, or it can be
displayed continuously and updated at least once every second. The
displayed values of AKR and cumulative air kerma must be clearly
distinguishable from each other. The details of the specific display
means are left to the manufacturer, except that the AKR must be
displayed in units of mGy/min and the cumulative air kerma in mGy.
(Comment 55) A comment from a radiology society suggested that the
cumulative air kerma be displayed continuously at the operator's
position at all times while fluoroscopy is used.
(Response) This comment, from an organization representing users of
fluoroscopic systems, indicates that these users desire a simultaneous
display of both AKR and cumulative air kerma. FDA originally had
envisioned a single display that would alternate between AKR and
cumulative air kerma, depending on the state of the x-ray generator.
However, this physician group indicates a preference for continuous
update and display of the cumulative air kerma. FDA agrees that such a
display is feasible and not likely to add significant costs to meeting
the requirement.
There is a potential advantage to displaying the cumulative air
kerma only at the termination of exposure. This would provide an
incentive to stop or interrupt the exposure to learn or view the
cumulative exposure and thereby perhaps minimize exposure time.
However, during most fluoroscopic procedures, the exposure is
continually interrupted and thus the cumulative air kerma would often
be displayed.
After reviewing the comments received from the radiology society
and others regarding the proposed requirement for the display of AKR
and cumulative air kerma at the fluoroscopist's working position, FDA
has determined that the method of display of cumulative air kerma can
be left to the manufacturer. Either a continuous display of cumulative
air kerma or a display following termination of exposure will provide
the user with the necessary information.
(Comment 56) One comment suggested that a statement be added to
explain that the information displayed would represent the air kerma
measured without scatter.
(Response) FDA notes that this information was contained in the
proposed requirement and is in revised Sec. 1020.32(k)(4).
(Comment 57) One comment suggested that an alternative requirement
was needed for the description of the reference location for
fluoroscopic systems that have variable source-image receptor distance.
(Response) FDA notes that the reference location is specified with
respect to the table or the isocenter for a C-arm system and that,
under Sec. 1020.32(k)(4)(ii), a manufacturer may describe an alternate
reference location if appropriate. Therefore, FDA has concluded that
the addition suggested by this comment is not needed.
(Comment 58) One comment recommended that manufacturers be
permitted to adjust or change the reference location for AKR and
cumulative air kerma to a point specified by the clinical user of the
system.
(Response) This comment appears to suggest that some clinical users
might wish to have the air kerma display indicate the air kerma at
locations other than the location identified by the manufacturer in the
initial design of the system. Users might desire this alternative if
they consider some other point to be more representative of the dose to
the patient. FDA notes that the air kerma at any other location can be
obtained by the use of a multiplicative factor that is the square of
the ratio of distance from the source to the reference location to the
distance from the source to the new location. Such a factor can be
easily calculated. Also, it is permissible for the owner of an x-ray
system to modify (or cause to be modified) the x-ray system as long as
the modification does not cause the system to fail to comply with the
performance standard. Therefore, an owner could request that a system
be modified to display the air kerma at a point different from that
originally specified by the manufacturer, under Sec. 1020.30(q),
provided the user instructions for that specific system are also
appropriately modified to indicate the location of the new reference
location to which the air kerma display is referenced. FDA would
encourage that, for any system so modified, the modification be clearly
posted or labeled so that all users are aware of the modification. Such
a modification would be possible only if the manufacturer's design of
the air kerma display system provides a means by which the calibration
of the air kerma display could be adjusted by a factor to provide the
requested display. FDA does not believe that it is necessary to require
that all systems have such a capability.
(Comment 59) Four comments expressed concern about the tolerance of
25 percent for the deviation of the displayed values of AKR
and cumulative air kerma from the actual values. Several of these
comments asserted that the accuracy of the corresponding display
requirement in IEC standard 60601-2-43 is 50 percent. They
also pointed out that accuracy required of ionization-chamber-based
dose-area-product meters specified by IEC standard IEC 60580 (Ref. 4)
is 25 percent, and that other sources of error would
combine with the basic uncertainties of a measuring instrument such as
a dose-area-product meter to determine the air kerma at the reference
location.
(Response) FDA agrees that the standard should not require accuracy
greater than is technically feasible. FDA discussed this tolerance with
the TEPRSSC advisory committee during a public meeting and members of
the committee expressed the opinion that the display of dose
information should be as accurate as possible to provide a meaningful
indication of the patient dose. These members suggested that an
accuracy of better than 50 percent should be possible.
After considering factors that could contribute to the uncertainty of
the display of AKR and cumulative air kerma, and the importance of
having as accurate an indication as technically feasible, FDA has
concluded that a tolerance of 35 percent is appropriate.
Accordingly,
[[Page 34011]]
proposed Sec. 1020.32(k)(7) has been revised as Sec. 1020.32(k)(6)
and specifies a maximum uncertainty of 35 percent and a
range of AKRs and cumulative air kerma over which this accuracy is to
be met. Manufacturers will need to provide a schedule of maintenance
sufficient to keep the air kerma display values within these
tolerances.
Also, in conjunction with considering the accuracy of the dose
display, FDA noted a need to better describe the conditions under which
compliance would be determined. Therefore, FDA has also included in
Sec. 1020.32(k)(6) a specification that compliance with the accuracy
requirement shall be determined with measurements having an irradiation
time greater than three seconds. This condition is sufficient to allow
for any minimum response times associated with measuring instruments.
IV. Additional Revisions of Applicability Statements and Other
Corrections
In section II.B of the proposed rule (62 FR 76056 at 76059), FDA
described the need to modify the applicability statements in Sec. Sec.
1020.31 and 1020.32 to clearly distinguish between radiographic and
fluoroscopic imaging and to identify the type of equipment to which
each section applies. This clarification was needed in conjunction with
modifying the performance standard to address the new types of image
receptors that have been introduced for fluoroscopy and radiography. As
part of this clarification, definitions of radiography and fluoroscopy
were also proposed.
Although no comments were received on the proposed modifications to
the applicability statements for Sec. Sec. 1020.31 and 1020.32, FDA
has concluded that additional modifications of the applicability
statements for both sections are necessary for clarity. These changes,
which are described in the following paragraphs, are not substantive
changes to the wording of both sections as contained in the proposed
rule.
The proposed rule contained a proposed Sec. 1020.30(a)(1)(i)(F)
that added image receptors that are electrically powered or connected
to the x-ray system, to the list of components to which the performance
standard applies. This addition was proposed because FDA determined
that it was necessary to include new solid-state x-ray imaging devices,
which are being used for both radiography and fluoroscopy, in the list
of components subject to the requirements of the performance standard.
FDA inadvertently failed to discuss the addition of proposed Sec.
1020.30(a)(1)(i)(F) in the preamble to the proposed rule. However, the
application of the performance standard to the new types of image
receptors was extensively discussed in sections II.B and II.C of the
preamble of the proposed rule. Thus, FDA believes that its intention to
apply the standard to these types of x-ray system components was made
clear. No comments were received concerning this addition to Sec.
1020.30(a); therefore, FDA has retained this proposed paragraph in the
final rule.
The application of solid-state x-ray imaging devices as the image
receptors for both radiographic and fluoroscopic x-ray systems requires
additional clarification in the performance standard regarding the
specific requirements that apply to these components and systems
containing them. Previously, the requirements of Sec. 1020.31 for
radiographic systems were understood to apply to systems when x-ray
film was used to obtain static radiographic images. The requirements of
Sec. 1020.32 applied to fluoroscopic x-ray systems, including when the
fluoroscopic image receptor, primarily the x-ray image intensifier
tube, was used to record images such as during cineradiography or when
photospot images were made. With the introduction of solid-state x-ray
imaging devices, we now have the situation where image receptors with
the same or very similar technology may be used in both radiographic
and fluoroscopic x-ray systems. The solid-state x-ray imaging device
used for fluoroscopy may also produce digital radiographic images that
are essentially equivalent to images produced by solid-state x-ray
imaging devices used as the image receptor in digital radiographic x-
ray systems. Such similarities can raise questions about when the
requirements of Sec. Sec. 1020.31 or 1020.32 apply to a system using a
solid-state x-ray imaging device to produce digital images.
To date, this question has not received very much, if any,
discussion in the radiology community. Contrary to the situation
involving x-ray film and intensifying screens in an imaging cassette,
the introduction of solid-state x-ray imaging devices, which are
integral parts of the electronic x-ray system, raises questions as to
what are appropriate performance requirements for these systems. FDA
notes that there has been no consensus developed about how requirements
such as x-ray system linearity, reproducibility, and x-ray field
indication and alignment may need to be modified to appropriately
assure the radiation safety performance of systems using a solid-state
x-ray imaging device. FDA did not specifically raise these issues in
the preamble to the proposed rule.
As discussed previously in section III.A of this document (comment
5), two of the organizations commenting on the proposed rule suggested
that additional action may be needed to determine appropriate
performance requirements for solid-state x-ray imaging devices. FDA
agrees that further investigation and development of consensus on
appropriate requirements for systems using solid-state x-ray imaging
devices is needed and will pursue further discussions and interactions
with the radiology community to better define what these requirements
should be. However, in the meantime, clarification is needed regarding
how the requirements of the current standard apply to systems using new
types of x-ray image receptors. FDA has modified the introductory
applicability statements of Sec. Sec. 1020.31 and 1020.32 to clarify
how these requirements apply to such systems.
In the proposed rule, the applicability statements of Sec. Sec.
1020.31 and 1020.32 were revised to replace the reference to the x-ray
image intensifier tube with a reference to the fluoroscopic image
receptor.
In this final rule, the applicability statements have been further
revised to use the new definitions of radiography and fluoroscopy and
to indicate that, when images are recorded using the fluoroscopic image
receptor, the requirements of Sec. 1020.32, not Sec. 1020.31, will
apply. Thus, if an image receptor is used for fluoroscopic imaging, the
requirements of Sec. 1020.32 apply even when radiographic images are
produced using the fluoroscopic image receptor. When the image receptor
``irrespective of whether it is film-based, computed radiographic, or
solid-state x-ray imaging digital technology'' is used only for
radiographic imaging, the requirements of Sec. 1020.31 will apply. FDA
notes that, if new combination radiographic and fluoroscopic system
designs are developed that use the same image receptor for both
fluoroscopic and all conventional radiographic images, the modified
applicability statements would apply only the requirements of Sec.
1020.32 to these types of systems. FDA recognizes that this particular
application of requirements may not be the optimum approach or the most
appropriate control for systems using new types of image receptors.
However, until a consensus is developed regarding a different approach
or different requirements, FDA has
[[Page 34012]]
concluded that this approach to applying the requirements of Sec. Sec.
1020.31 and 1020.32 is appropriate. FDA will initiate efforts to
develop a consensus in the radiology community regarding the
appropriate requirements that should be applied to systems using solid-
state x-ray imaging devices and, if warranted, propose future revisions
to the performance standard established by this final rule.
FDA also notes that a typographical error regarding the statement
of effective date in the introductory paragraph of Sec. 1020.31 has
been corrected to read November 29, 1984, rather than November 28,
1984. This date was originally established as November 29, 1984 in the
final rule published in the Federal Register of August 31, 1984 (49 FR
34698) but was incorrectly printed as November 28, 1984, in the
revision of the standard published on May 3, 1993 (58 FR 26386).
In addition, there was a typographical error in the text of
proposed Sec. 1020.32(k)(5)(ii), which was intended to describe the
alternate location for the reference location that manufacturers might
choose to designate. This text has been corrected, so that Sec.
1020.32(k)(4)(ii) now reads as intended, ``Alternatively, the reference
location shall be at a point specified by the manufacturer to represent
the location of the intersection of the x-ray beam with the patient's
skin.''
V. Environmental Impact
The agency has determined under 21 CFR 25.30(i) and 25.34(c) that
this action is of a type that does not individually or cumulatively
have a significant effect on the human environment. Therefore, neither
an environmental assessment nor an environmental impact statement is
required.
VI. Paperwork Reduction Act of 1995
A. Summary
This final rule contains information collection provisions that are
subject to review by the Office of Management and Budget (OMB) under
the Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3502). The title,
description, and respondent description of the information collection
provisions are shown in the following paragraphs with an estimate of
the annual reporting burden. Included in the estimate is the time for
reviewing instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing each
collection of information.
FDA received no comments related to the information collection
requirements or the estimate of burden in response to the proposed
rule. FDA, therefore, concludes that readers of the proposed rule
recognized the necessity of the information to be collected, did not
disagree with FDA's estimate of the burden, and had no suggestions of
alternate approaches to accomplishing the goals of the proposal.
Performance Standard for Diagnostic X-Ray Systems and Their Major
Components (21 CFR 1020.30 and 1020.32 Amended)
Description: FDA is amending the performance standard for
diagnostic x-ray systems by establishing, among other things,
requirements for several new equipment features on all new fluoroscopic
x-ray systems. In the current performance standard, Sec. 1020.30(h)
requires that manufacturers provide to purchasers of x-ray equipment,
and to others upon request, manuals or instruction sheets that contain
technical and safety information. This required information is
necessary for all purchasers (users of the equipment) to have in order
to safely operate the equipment. Section 1020.30(h) currently describes
the information that must be provided.
The rule established by this document will add to Sec. 1020.30
paragraphs (h)(5) and (h)(6) describing additional information that
must be included in these manuals or instructions. In addition, Sec.
1020.32(j)(4) specifies additional descriptive information to be
included in the user manuals for fluoroscopic x-ray systems required by
Sec. 1020.30(h). This additional information contains descriptions of
features of the x-ray equipment required by the amendments and
information determined to be appropriate and necessary for safe
operation of the equipment.
Description of Respondents: Manufacturers of fluoroscopic x-ray
systems that introduce fluoroscopic x-ray systems into commerce
following the effective date of these amendments. FDA estimates the
burden of this collection of information as follows:
Table 1.--Estimated Average Annual Reporting Burden for the First
Year\1\
------------------------------------------------------------------------
Annual
No. of Frequency Total Hours Total
21 CFR Section Respondents per Annual per Hours
Respondent Responses Response
------------------------------------------------------------------------
1020.30(h)(5) and 20 10 200 180 36,000
(h)(6) and
1020.32(j)(4)
------------------------------------------------------------------------
\1\ There are no capital costs or operating and maintenance costs
associated with this collection of information.
Table 2.--Estimated Average Annual Reporting Burden for the Second and
Following Year\1\
------------------------------------------------------------------------
Annual
No. of Frequency Total Hours Total
21 CFR Section Respondents per Annual per Hours
Respondent Responses Response
------------------------------------------------------------------------
1020.30(h)(5) and 20 5 100 180 18,000
(h)(6) and
1020.32(j)(4)
------------------------------------------------------------------------
\1\ There are no capital costs or operating and maintenance costs
associated with this collection of information.
B. Estimate of Burden
As described in the assessment of the cost impact of the amendment
(Ref. 5), it is estimated that there are about 20 manufacturers of
fluoroscopic x-ray systems who market in the United States. Each of
these manufacturers is estimated to market about 10 distinct models of
fluoroscopic x-ray systems. Immediately following the effective date of
the amendments, for each model of fluoroscopic x-ray system that
manufacturers continue to market, each manufacturer will have to
supplement the user instructions to include the additional information
required by the amendments.
[[Page 34013]]
Manufacturers already develop, produce, and provide x-ray system
user manuals or instructions containing the information necessary to
operate the systems, as well as the specific information required to be
provided by the existing standard in Sec. 1020.30(h). Therefore, it is
assumed that no significant additional capital, operating, or
maintenance costs will be incurred by the manufacturers in connection
with the provision of the newly required information. The manufacturers
already have procedures and methods for developing and producing the
user's manuals, and the additional information required by the
amendments is expected to only add a few printed pages to these already
extensive manuals or documents.
The burden that will be imposed on manufacturers by the new
requirements for information in the user's manuals will be the effort
required to develop, draft, review, and approve the new information.
The information or data to be contained within the new user
instructions will already be available to the manufacturers from their
design, testing, validation, or other product development documents.
The burden will consist of gathering the relevant information from
these documents and preparing the additional instructions from this
information.
It is estimated that about 3 weeks of professional staff time (120
hours) will be required to gather the required information for a single
model of an x-ray system. It is estimated that an additional 6 weeks
(240 hours) of professional staff time will be required to draft, edit,
design, layout, review, and approve the new portions of the user's
manual or information required by the amendments. Hence, FDA estimates
a total of 360 hours to prepare the new user information that will be
required for each model.
For a given manufacturer, FDA anticipates that every distinct model
of fluoroscopic system will not require a separate development of this
additional information. Because it is thought highly likely that
several models of fluoroscopic x-ray systems from a given manufacturer
will share common design aspects, it is anticipated that similar means
for meeting the requirement for display of exposure time, AKR, and
cumulative air kerma and the requirement for the last-image-hold
feature will exist on multiple models of a single manufacturer's
products. Such common design aspects for multiple models will reduce
the burden on manufacturers to develop new user information. Hence, the
average time required to prepare new user information for all of a
manufacturer's models will be correspondingly reduced. FDA expects that
the average burden will be reduced from 360 hours to about 180 hours
per model, under the assumption that each set of user information for a
given equipment feature design will be applicable to at least two
different models of a manufacturer's fluoroscopic systems. Under this
assumption, the total estimated time for preparing the new user
information that will be required is 36,000 hours, as shown in table 1
in the preamble of this document.
In each succeeding year the burden will be less, as the reporting
requirement will apply only to the new models developed and introduced
by the manufacturers in that specific year. FDA assumes that every 2
years each manufacturer will replace each of its models with a newer
model requiring new user information. The multiple system applicability
of this information is accounted for by also assuming that each new
model only requires 180 hours of effort to develop the required
information. These assumptions result in an estimated burden of 18,000
hours for each of the years following the initial year of applicability
of the amendments, as shown in table 2 of this document. The
information collection burden of the current performance standard at
Sec. Sec. 1020.30 and 1020.32 is approved and reported under an
existing information collection clearance (OMB control number 0190-
0025).
The information collection requirements in this final rule have
been approved under OMB control number 0910-0564. This approval expires
December 31, 2006. An agency may not conduct or sponsor, and a person
is not required to respond to, a collection of information unless it
displays a currently valid OMB control number.
VII. Analysis of Impacts
A. Introduction
FDA has examined the impacts of this final rule under Executive
Order 12866 and the Regulatory Flexibility Act (5 U.S.C. 601-612), and
the Unfunded Mandates Reform Act of 1995 (UMRA) (Public Law 104-4) .
Executive Order 12866 directs agencies to assess all costs and benefits
of available regulatory alternatives and, when regulation is necessary,
to select regulatory approaches that maximize net benefits (including
potential economic, environmental, public health and safety, and other
advantages; distributive impacts; and equity). The agency believes that
this final rule is consistent with the regulatory philosophy and
principles identified in the Executive order. In addition, the final
rule is a significant regulatory action as defined by Executive Order
12866 and, therefore, is subject to review.
The Regulatory Flexibility Act requires agencies to analyze
regulatory options that would minimize any significant impact on small
entities. An analysis of available information suggests that costs to
small entities are likely to be significant, as described in the
following analysis. FDA believes that this regulation will likely have
a significant impact on a substantial number of small entities, and it
conducted an initial regulatory flexibility analysis (IRFA) to ensure
that any such impacts were assessed and to alert any potentially
impacted entities of the opportunity to submit comments. No comments
were received regarding the impact on small entities, and the IRFA
became the final regulatory flexibility analysis without further
revision (see section VII.J of this document).
Section 202(a) of the UMRA requires that agencies prepare a written
statement, which includes an assessment of anticipated costs and
benefits, before proposing any rule that includes any Federal mandate
that may result in an expenditure by State, local, and tribal
governments, in the aggregate, or by the private sector, of $100
million (adjusted annually for inflation) in any one year. The current
threshold after adjustment for inflation is $115 million, using the
most current (2003) Implicit Price Deflator for the Gross Domestic
Product. FDA does not expect this final rule to result in any 1-year
expenditure that would meet or exceed this amount.
The agency has conducted analyses of the final rule, including a
consideration of alternatives, and has determined that the final rule
is consistent with the principles set forth in the Executive order and
in these statutes. The costs and benefits of the rule have been
assessed in two separate analyses that are described in this section of
the document and that were made available for review at the Division of
Dockets Management (HFA-305), Food and Drug Administration, 5630
Fishers Lane, rm. 1061, Rockville, MD 20852. As reviewed in the
following paragraphs, these analyses have an estimated upper limit to
the annual cost of $30.8 million during the first 10 years after the
effective date of the amendments using a 7-percent annual discount rate
and $30.1 million using a 3-percent annual discount rate. The analysis
of benefits projects an average annual amortized pecuniary savings in
the first 10 years after the effective date of at least $320
[[Page 34014]]
million, with an estimated 90 percent confidence interval spanning a
range between $88.3 million and $1.160 billion using a 7-percent annual
discount rate. The same analysis of benefits using a 3-percent annual
discount rate resulted in annualized benefits of $715 million, with a
90-percent confidence interval of between $197.3 million and $2.593
billion. Table 2a of this document shows the annualized costs,
benefits, and net benefits of the final regulation. FDA believes this
analysis of impacts complies with Executive Order 12866 and OMB
Circular A-4, and that the rule is a significant regulatory action as
defined by the Executive order. Because of the preliminary nature of
the initial cost and benefit analyses and estimates, FDA requested
comments on any aspect of their methodologies, assumptions, and
projections in the proposed rule. The only comments received on any
aspect of these analyses were two comments that suggested, for two
different reasons, that FDA had underestimated the benefits that will
result from the amendments. FDA considered these comments and
determined, due to the inherent uncertainty in the benefits cited, that
revision of the estimated benefits analysis is not warranted.
Table 2a.--Summary of Annualized Costs, Benefits, and Net Benefits of the Final Rule
(in millions of dollars)
----------------------------------------------------------------------------------------------------------------
Annualized Range of Annualized Net Annualized
Discount Rate Annualized Costs Benefits Benefits Benefits (Modal)
----------------------------------------------------------------------------------------------------------------
3% Annual discount rate $30.1 $715.6 $197.4 to $2,592.8 $685.5
----------------------------------------------------------------------------------------------------------------
7% Annual discount rate $30.8 $320.3 $88.4 to $1,160.5 $289.5
----------------------------------------------------------------------------------------------------------------
B. Objective of the Rule
The primary objective of the rule is to improve the public health
by reducing exposure to and detriment associated with unnecessary
ionizing radiation from diagnostic x-ray systems, while maintaining the
diagnostic quality of the images. The rule will meet this objective by
requiring features on newly manufactured x-ray systems that physicians
may use to minimize unnecessary or unnecessarily large doses of
radiation that could result in adverse health effects to patients and
health care personnel. Such adverse effects from x-ray exposure can
include acute skin injury and an increased potential for cancer or
genetic damage. The secondary objectives of this rule are to bring the
performance standard up to date with recent and emerging technological
advances in the design of fluoroscopic and radiographic x-ray systems
and to assure appropriate radiation safety for these designs. The
amendments will also align the performance standard with performance
requirements in current international standards that were developed
after the original publication of the performance standard in 1972. In
several instances, the international standards contain more stringent
requirements on aspects of system performance than the current U.S.
performance standard. The changes will ensure that the different safety
standards are harmonized to the extent that systems meeting one
standard will not be in conflict with the other. Such harmonization of
standards lessens the regulatory burdens on manufacturers desiring to
market systems in the global market.
The amendments will require particular x-ray equipment features
reducing unnecessary radiation exposure. FDA believes the amendments
are necessary because the private market may not ensure that these
equipment features will be adopted without a government mandate for
such features. Purchasers in health care organizations may have
insufficient incentive to demand the more expensive x-ray equipment
that will be required by these new amendments because benefits accrue
mainly to patients and health care providers many years in the future.
Patients may not demand this equipment because they lack information
and knowledge about long-term radiation risk and about the highly
technical nature of x-ray equipment. Hence, FDA believes these
amendments are necessary to realize the net benefits described in the
following analysis.
C. Risk Assessment
The risks to health that are addressed by these amendments are the
adverse effects of exposure to ionizing radiation that can result from
procedures utilizing diagnostic x-ray equipment. These adverse effects
are well-known and have been extensively studied and documented. They
are generally categorized into two types-- ``deterministic'' and
``stochastic.'' Deterministic effects are those that occur with
certainty in days or weeks or months following irradiation whose
cumulative dose exceeds a threshold characteristic of the effect. Above
the threshold, the severity of the resulting injury increases as the
radiation dose increases. Examples of such effects are the development
of cataracts in the lens of the eye and skin ``burns.'' Skin is the
tissue that often receives the highest dose from external radiation
sources such as diagnostic or therapeutic x-ray exposure. Depending on
the magnitude of the dose, skin injuries from radiation can range in
severity from reddening of the skin and hair loss to more serious burn-
like effects including localized tissue death that may require skin
grafts for treatment or may result in permanent impairment. Stochastic
effects are those that do not occur with certainty, but if they appear,
they generally appear as leukemia or cancer one or several decades
after the radiation exposure. The probability of the effect occurring
is proportional to the magnitude of the radiation dose in the tissue.
The primary risk associated with radiation is the possibility of
patients developing cancer years after exposure, and the magnitude of
this cancer risk is generally regarded to increase with increasing
radiation dose. Consistent with the conservative approach to risk
assessment described by the National Council on Radiation Protection
and Measurements (Ref. 6), we assume a linear relationship between
cancer risk and dose. The slope of this relationship depends on age at
exposure and on gender. Our benefits analysis presented in section
VII.H of this document is based on linear interpolations of cancer
mortality risk per whole-body equivalent dose derived from table 4-3 of
the fifth report of the Committee on the Biological Effects of Ionizing
Radiations (BEIR) of the National Research Council (Ref. 7). (This
report is commonly known as ``BEIR V'' and henceforth will be
abbreviated that way in this document.) For reasons detailed in section
VII.H of this document, in the estimations of cancer mortality risk
these interpolated values are reduced by
[[Page 34015]]
a dose-rate effectiveness factor (DREF) of 2 for solid cancers (Ref.
8). The values used in our analysis are represented in the following
graph of the excess lifetime probability of death per sievert of whole-
body equivalent dose (figure 1 of this document). Equivalent dose is
determined from the average radiant energy absorbed per mass of tissue
or organ exposed, where this average is multiplied by a dimensionless
radiation weighting factor whose magnitude accounts for the detrimental
biological effectiveness of the type of radiation; the value of the
radiation weighting factor is unity for x rays emitted by the equipment
covered in these regulations (Ref. 13). In the International System of
Units, the unit of measurement of equivalent dose is joule per kilogram
(J/kg) and is given the special name ``sievert'' (Sv) (Ref. 7).
``Whole-body'' means that all of the organs and tissues of the body
receive the same dose.
BILLING CODE 4160-01-S
[[Page 34016]]
[GRAPHIC] [TIFF OMITTED] TR10JN05.000
BILLING CODE 4160-01-C
[[Page 34017]]
Based on Science Panel Report No. 9 (Ref. 8) of the Committee on
Interagency Radiation Research and Policy (CIRRPC) of the Office of
Science Technology and Policy of the Executive Office of the President,
FDA underscores the overarching uncertainty in these projections with
the following statement:
The estimations of radiation-associated cancer deaths were derived
from linear extrapolation of nominal risk estimates for lifetime total
cancer mortality from doses of 0.1 Sv. Other methods of extrapolation
to the low-dose region could yield higher or lower numerical estimates
of cancer deaths. At this time studies of human populations exposed at
low doses are inadequate to demonstrate the actual level of risk. There
is scientific uncertainty about cancer risk in the low-dose region
below the range of epidemiologic observation, and the possibility of no
risk cannot be excluded.
We project that the equipment features that will be required by
three of the amendments will promote the bulk of radiation dose
reduction and hence cancer risk reduction: (1) Displays of irradiation
time, rate, and air kerma values; (2) more filtration of lower-energy
x-rays; and (3) improved geometrical efficiency of the x-ray field
achieved through tighter collimation. We assume that the display
amendment will reduce dose on the order of 16 percent. This assumed
value is one-half of a 32-percent dose reduction observed for several
x-ray modalities in the United Kingdom (UK) between 1985 and 1995. We
assume that one-half of the UK dose reduction was due to technology
improvements alone, whereas the other half stemmed from the quality
assurance use of reference dose levels and patient dose evaluation. The
16-percent dose reduction that we project for the display amendment
thus presumes facility implementation of a quality assurance program
making use of the displayed values. This analysis and other
assumptions--6 percent dose reduction for the filtration amendment, 1
to 3 percent dose reduction for the collimation amendment--are detailed
in Ref. 9. We invited comment on these assumptions in the proposed rule
and received no objections to this approach. One comment suggested,
based on a State's experience, that greater dose reductions would
result from facilitating quality assurance programs by the requirement
for air kerma display. Until recently, the principal radiation
detriment for patients undergoing x-ray procedures was the risk of
inducing cancer and, to a lesser extent, heritable genetic
malformations. Since 1992, however, approximately 80 reports of serious
radiation-induced skin injury associated with fluoroscopically-guided
interventional therapeutic procedures have been published in the
medical literature or reported to FDA. Many of these injuries involved
significant morbidity for the affected patients. FDA's experience with
reports of such adverse events leads the agency to believe that the
number of these injuries is very likely underreported, given the total
number of interventional procedures currently performed. Additionally,
there is the lack of any clearly understood requirement or incentive
for health care facilities to report such injuries. With the advance of
fluoroscopic technology and the proliferating use of interventional
procedures by practitioners not traditionally specializing in the
field, and therefore not completely familiar with dose-sparing
techniques, FDA expects an increasing risk of radiation burns that
warrants the changes to the x-ray equipment performance standard
obtained through the amendments.
D. Constraints on the Impact Analysis
It is FDA's opinion that the amendments will offer public health
benefits that warrant their costs. However, the agency had difficulty
accessing pertinent information from stakeholders to help quantify the
impact of the proposal and alternatives. In view of the limited
information available with which to develop estimates of the costs and
benefits, FDA solicited comments, data, and opinions about whether the
potential health benefits of the amendments would justify their costs.
FDA received only the two limited comments cited previously on this
question and, therefore, has reached a final affirmative determination
as to the appropriateness of the amendments based on the earlier
analyses.
The principal costs associated with the amendments will be the
increased costs to produce equipment that will have the features
required by the amendments. FDA has made an estimate of potential cost.
The cost estimate is based on a number of assumptions designed to
assure that the potential cost is not underestimated. FDA anticipates
that the actual costs of these amendments may be significantly less
than the upper-limit estimate developed. Manufacturers of diagnostic x-
ray systems were urged to provide detailed comments on the anticipated
costs of these amendments that would enable refinement of these cost
estimates. No additional information was received on this topic during
the comment period.
The benefits that are expected to result from these amendments are
reductions in acute skin injuries and radiation-induced cancers. These
benefits will result from two types of changes to the performance
standard that should reduce patient dose and associated radiation
detriment without compromising image quality.
The first type of change involves several new equipment features
that will directly affect the intensity or size of the x-ray field.
These are the requirements addressing x-ray beam quality, x-ray field
limitation, limits on maximum radiation exposure rate, and the minimum
source-skin distance for mini C-arm fluoroscopic systems. Almost all of
the changes that directly affect x-ray field size or intensity will
bring the performance standard requirements into agreement with
existing international voluntary standards. To the extent that these
requirements are included in voluntary standards that have a growing
influence in the international marketplace, the radiological community
has already recognized their benefit and appropriateness. Moreover,
harmonization within a single international framework will eliminate
the need for manufacturers to produce more than one line of products
for a single global marketplace.
The second type of change that will be required by these amendments
involves the information to be provided by the manufacturer or directly
by the system itself that may be utilized by the operator to more
efficiently use the x-ray system and thereby reduce patient dose. These
new features are widely supported and anticipated by many knowledgeable
users of fluoroscopic systems. Similar requirements were recently
included in a new international voluntary standard.
There is a third type of change being made to the standard. These
changes will not have a direct benefit in terms of a reduction in
radiation dose. Rather, they clarify the applicability of the standard,
clarify definitions, and facilitate the application of the standard to
new technology and x-ray system designs.
E. Baseline Conditions
The cost of the amendments to the x-ray equipment performance
standard will be borne primarily by manufacturers of fluoroscopic
systems. The cost for one of the nine amendments will also affect
manufacturers of radiographic equipment and is discussed in detail in
Ref. 5. Therefore, this discussion will focus primarily on fluoroscopy
(i.e., the
[[Page 34018]]
process of obtaining dynamic, real-time images of patient anatomy).
X-ray imaging is used in medicine to obtain diagnostic information
on patient anatomy and disease processes or to visualize the delivery
of therapeutic interventions. X-ray imaging almost always involves a
tradeoff between the quality of the images needed to do the imaging
task and the magnitude of the radiation exposure required to produce
the image. Difficult imaging tasks may require increased radiation
exposure to produce the images unless some significant technological
change provides the needed image quality. Therefore, it is important
that users of x-ray systems have information regarding the radiation
exposures required for the images that are being produced in order to
make the appropriate risk-benefit decisions.
Equipment meeting the new standards in the amendments will provide
image quality and diagnostic information identical to equipment meeting
current standards. Therefore, the clinical usefulness of the images
provided will not change. The amendments will not affect the delivery
of x-ray imaging services because the reasons for performing
procedures, the number of patients having procedures, and the manner in
which procedures are scheduled and conducted would not be changed as a
result of the amendments. In addition, nothing in these amendments will
adversely affect the clinical information or results obtained from
these procedures. These amendments will result in x-ray systems having
features that automatically provide for more efficient use of radiation
or features that provide the physicians using the equipment with
immediate information related to patient dose, thus enabling more
informed and efficient use of radiation. These amendments will provide
physicians using fluoroscopic equipment with the means to actively
monitor the amount of radiation incident on patients and minimize
unnecessary exposure or avoid doses that could result in radiation
injury.
Estimates of the annual numbers of certain fluoroscopic procedures
performed in the United States during the years 1996 or 1997 were
developed, as described in Ref. 9, using data from several sources.
These numbers of specific procedures were used in the estimates of
benefit from the amendments. To keep the estimations relatively simple
and conservative, no attempt was made to project the future growth in
the numbers of procedures suggested by some of the literature (Ref. 9,
note 27, and Ref. 25). FDA estimates that over 3 million
fluoroscopically guided interventional procedures are performed each
year in the United States. These procedures are described as
``interventional procedures'' because they accomplish some form of
therapy for patients, often as an alternative to more invasive and
risky surgical procedures. Interventional procedures may result in
patient radiation doses in some patients that approach or exceed the
threshold doses known to cause adverse health effects. The high doses
occur because physicians utilize the fluoroscopic images throughout the
entire procedure, and such procedures often require exposure times
significantly longer than conventional diagnostic procedures to guide
the therapy.
FDA records indicate that about 12,000 medical diagnostic x-ray
systems are installed in the United States each year. Of these, about
4,200 are fluoroscopic system installations. The amendments will apply
only to those new systems manufactured after the effective date,
therefore affecting the 4,200 new fluoroscopic systems installed
annually and a small fraction of current models of radiographic systems
that do not meet the standard for x-ray beam quality.
In modeling the x-ray equipment market in the United States for the
purpose of developing estimates of the cost of these amendments, FDA
estimates that there are approximately a total of 40 manufacturers of
diagnostic x-ray systems in the United States and half of these (20)
market fluoroscopic systems and radiographic systems. It is assumed
that manufacturers of radiographic systems typically market 20 models
of radiographic systems, while manufacturers of fluoroscopic systems
market 10 different models of fluoroscopic systems. These estimates
were developed by FDA in 2000. These estimates have not been updated
since publication of the proposed rule as the size of the radiographic
and fluoroscopic x-ray equipment is not expected to have changed
significantly in the period since 2000 and in view of the uncertainty
in the original estimates.
F. The Amendments
The changes to the regulations may be considered as nine
significant amendments to the current performance standard for
diagnostic x-ray systems and other minor supporting changes to the
standard. The nine principal amendments may be grouped into three major
impact areas: (1) Amendments requiring changes to equipment design and
performance that would facilitate more efficient use of radiation and
provide means for reducing patient exposure, (2) amendments improving
the use of fluoroscopic systems through enhanced information to users,
and (3) amendments facilitating the application of the standard to new
features and technologies associated with fluoroscopic systems.
Amendments requiring equipment changes include the following:
Changes in x-ray beam quality; provision of a means to add additional
filtration; changes in the x-ray field limitation requirements;
provision of displays of values of irradiation time, AKR, and
cumulative air kerma; the display of the last fluoroscopic image
acquired last-image-hold feature; specification of the minimum source-
skin distance for mini C-arm systems; and changes to the requirement
concerning maximum limits on entrance AKR. Amendments that would result
in improved information for users are those requiring additional
information to be provided in user instruction manuals. Amendments
facilitating the application of the standard to new technologies
include the recognition of SSIX devices, revisions of the applicability
sections, and establishment of additional definitions.
G. Benefits of the Amendments
The amendments will benefit patients by enabling physicians to
reduce fluoroscopic radiation doses and associated detriment and,
hence, to use the radiation more efficiently to achieve medical
objectives. The health benefits of lowering doses are reductions in the
potential for radiation induced cancers and in the numbers of skin
burns associated with higher levels of x-ray exposure during
fluoroscopically-guided therapeutic procedures. FDA believes that the
amendments will not degrade the quality of fluoroscopic images produced
while reducing the radiation doses.
There is widespread agreement in the radiological community that
radiation doses to patients and staff should be kept ``as low as
reasonably achievable'' (ALARA) as a general principle of radiation
protection. The introduction of an increasing variety of new,
fluoroscopically-guided interventional procedures, as alternatives to
more invasive surgical procedures or as totally new therapies, and the
use of a variety of new devices and therapies that are used with
fluoroscopic guidance are resulting in significant increases in the
number of fluoroscopically-guided interventional procedures with long
irradiation times. Thus, the growing number of patients that are
potentially at risk for acute and
[[Page 34019]]
long-term radiation injury makes it important to provide fluoroscopic
systems with features that will assist in reducing the radiation to
patients while continuing to accomplish the medical objectives of the
needed procedures.
The amendments will require that fluoroscopic x-ray systems provide
equipment features that directly enable the user to reduce radiation
doses and maintain them ALARA. Furthermore, the amendments will require
provision of information to the user of the equipment in the form of
additional information in the user's manual or instructions to enable
improved use in a manner that minimizes patient exposures and, by
extension, occupational exposures to medical staff.
There also is widespread agreement that radiation exposures during
fluoroscopy are not optimized. For example, data from the 1991
Nationwide Evaluation of X-Ray Trends (NEXT) surveys of fluoroscopic x-
ray systems used for upper gastrointestinal tract examinations (upper
GI exam) indicate that the mean entrance AKR is typically 5 cGy/min for
an adult patient (Ref. 10). Properly maintained and adjusted
fluoroscopic systems are expected to be able to perform the imaging
tasks associated with the upper GI exam with an entrance AKR of 2 cGy/
min or less (Ref. 11). The NEXT survey data indicate significant room
for improvement in this aspect of fluoroscopic system performance. The
total patient dose could be significantly reduced were the entrance AKR
lowered to what is currently reasonably achievable, and the features
required by the amendments will facilitate this reduction.
The new, required features of last-image-hold and real-time display
of entrance AKR and cumulative entrance air kerma values are intended
to provide fluoroscopists with means to better limit the patient
radiation exposure. The last-image-hold feature will permit
decisionmaking regarding the procedure underway while visualizing the
anatomy without continuing to expose the patient. The air kerma- and
AKR-value displays will provide real-time feedback to the
fluoroscopists and are anticipated to result in improved fluoroscopist
performance to limit radiation dose based on the immediate availability
of information regarding that dose. Realization of the potential dose
reduction benefits will require fluoroscopists to take advantage of
these new features and optimize the way they use fluoroscopic systems.
The potential impact of the change in the beam quality requirement,
which will apply to most radiographic and all fluoroscopic systems, can
be seen from the data on beam quality obtained from FDA's Compliance
Testing Program for the current standard. Between January 1, 1996, and
December 31, 2000, FDA conducted 4,832 tests of beam quality, that is,
measurement of the HVL of the beam for newly-installed x-ray systems.
Of these tests, only 15 systems did not meet the current HVL or beam
quality requirement. If the requirements for HVL contained in these
amendments had been used as the criteria for compliance, only 698
systems or 14.4 percent of the systems tested would have been found not
to have complied. This result suggests that, at a minimum,
approximately 15 percent of recently installed medical x-ray systems
would have their beam quality improved and patient exposures reduced
were the new requirement in place and applicable to them.
Numerous examples are available in the literature that illustrate
the potential reduction in patient dose, while preserving image
quality, that can result from increased x-ray beam filtration.
Reference 12 demonstrates that the addition of 1.5 to 2.0 mm Al as
additional filtration, which is the change required to enable systems
that just meet the current requirement to meet the new HVL requirement,
will result in about a 30-percent reduction in entrance air kerma and
about a 15 percent reduction in the integral dose for the fluoroscopic
examination modeled in the paper at 80 kVp tube potential. Reduction in
entrance skin dose (entrance air kerma) is relevant to reducing the
risk of deterministic injuries to the skin, while a reduction in the
integral dose is directly related to a reduction in the risk of
stochastic effects such as cancer induction. Other authors have
described dose reductions of a similar magnitude from increasing
filtration for radiographic systems.
The requirements in these amendments implement many of the
suggestions and recommendations developed by members of the
radiological community at the 1992 Workshop on Fluoroscopy sponsored by
the American College of Radiology and FDA (Ref. 11). The
recommendations from this workshop stressed the need to provide users
of fluoroscopy with improved features enabling more informed use of
this increasingly complex equipment. In addition, three radiological
professional organizations indicated their opinions to FDA that
radiologists would use the new features to better manage patient
radiation exposure.
H. Estimation of Benefits
Projected benefits are quantified in table 3 of this document in
terms of: (1) Collective dose savings, (2) numbers of lives spared
premature death associated with radiation-induced cancer, (3)
collective years of life spared premature death, (4) numbers of reports
of fluoroscopic skin burns precluded, and (5) pecuniary estimates
associated with the preceding four items. The estimates represent
average annual benefits projected to ramp up during a 10-year interval
in which new fluoroscopic systems conforming to the new rules are
phased into use in the United States. (FDA assumes that 10 years after
the effective date of the new rules all fluoroscopic systems then in
use will conform to those rules and that associated recurring benefits
will continue to accrue at constant rates.) Annual pecuniary estimates
that are averaged over the 10-year ramp-up interval and that are
associated with prevention of cancer incidence, preclusion of premature
mortality, and obviation of cancer treatment are based on the projected
numbers of lives spared premature death. These pecuniary estimates are
valued in current dollars using a 7-percent and, separately, using a 3-
percent discount rate covering the identical 10-year evaluation period
used in the cost analysis. (See section VII.I of this document.) Life
benefits would be realized 20 years following exposure (after a period
of 10 years of cancer latency followed by a period of 10 years of
survival).
Table 3.--Projections of Annual Benefits in the United States
for display, collimation, and filtration rules applied to percutaneous transluminal coronary angioplasty (PTCA),
cardiac catheterization with coronary arteriography or angiography (CA), and upper gastrointestinal fluoroscopy
(UGI) procedures
----------------------------------------------------------------------------------------------------------------
95th
5th Percentile Mode Percentile
----------------------------------------------------------------------------------------------------------------
Average Annual Dose and Life Savings in the First 10 Years After .............. ........... ..............
Effective Date of Rule
----------------------------------------------------------------------------------------------------------------
[[Page 34020]]
Collective dose savings (person-sievert) 3,202 7,231 16,330
----------------------------------------------------------------------------------------------------------------
Number of lives spared premature death from cancer 62 223 808
----------------------------------------------------------------------------------------------------------------
Years of life spared premature death from cancer 1,131 4,094 14,818
----------------------------------------------------------------------------------------------------------------
Number of reported skin burns precluded 0.5 1.1 2.4
----------------------------------------------------------------------------------------------------------------
Average Annual Amortized Pecuniary Savings in the First 10 Years
After Effective Date of Rule 7% Discount Rate
----------------------------------------------------------------------------------------------------------------
Prevention of premature death from cancer ($ millions) 78.61 285.03 1,032.75
----------------------------------------------------------------------------------------------------------------
Obviation of cancer treatment ($ millions) 9.71 35.21 127.56
----------------------------------------------------------------------------------------------------------------
Obviation of radiation burn treatment and loss precluded ($ 0.03 0.07 0.16
millions)\1\
----------------------------------------------------------------------------------------------------------------
Total ($ millions) 88.35 320.31 1,160.00
----------------------------------------------------------------------------------------------------------------
Average Annual Amortized Pecuniary Savings in the First 10 Years
After Effective Date of Rule 3% Discount Rate
----------------------------------------------------------------------------------------------------------------
Prevention of premature death from cancer ($ millions) 178.99 649.02 2,351.60
----------------------------------------------------------------------------------------------------------------
Obviation of cancer treatment ($ millions) 18.34 66.52 241.01
----------------------------------------------------------------------------------------------------------------
Obviation of radiation burn treatment and loss precluded ($ 0.03 0.07 0.16
millions)\1\
----------------------------------------------------------------------------------------------------------------
Total ($ millions) 197.36 715.61 2,592.77
----------------------------------------------------------------------------------------------------------------
\1\ There is no amortization for savings associated with obviation of radiation burn treatment and loss because
the interval for latency, presentation, and treatment of skin injury generally occurs within a year of
radiation exposure.
Columns in table 3 of this document labeled ``Mode,'' ``5th
Percentile,'' and ``95th Percentile'' categorize the results of a
sensitivity analysis performed to account for uncertainties in the
principal variables used to compute the data contained in the rows of
table 3. The columns correspond to the expected (mode) and extremum
values of 90-percent confidence intervals associated with the estimated
benefits. Estimation of these uncertainties is discussed following
descriptions of the row categories in table 3.
Collective dose savings (quantified in units of person-Sv) are the
estimated reductions in radiation dose to the U.S. population projected
to result following implementation of the amended regulations.
Collective dose savings are evaluated in terms of the number of persons
receiving a procedure (Ref. 9, notes 26 and 29, and Ref. 24) multiplied
by the associated effective dose reduction (quantified in units of Sv)
per procedure (Ref. 9, notes 28 and 42). The unit ``person-Sv'' is a
product of the number of persons receiving a procedure and the number
of Sv per procedure, where Sv is the unit of measurement of effective
dose as well as equivalent dose, defined previously. Effective dose is
the weighted sum of equivalent doses in all of the organs; it
represents a level of radiation detriment equal to that for whole-body
irradiation (Ref. 13), and we use it as an approximation of whole-body
equivalent dose. Estimates of effective dose reduction from current
levels that will result from the amendments are 16 percent for the air-
kerma rate and cumulative air-kerma display requirement, 6 percent for
the requirement for increased minimum x-ray filtration, and 1 to 3
percent for the requirement that would improve collimation of the x-ray
field (Ref. 9, notes 9 through 13 and 18 through 25, and Refs. 12 and
15 through 23).
The number of lives spared premature death is the number of
statistical deaths projected to be avoided as a result of the
collective dose savings. It is essentially the product of the estimated
collective dose savings described in the preceding paragraph and the
radiation-associated mortality risk per Sv, represented in figure 1 of
this document, summed for each gender over all ages at exposure. As
illustrated in the Ref. 9 slide entitled ``Annual Life Benefit
Projections in the U.S.,'' age and gender dependences are incorporated
into the estimation of the number of lives spared premature death as
well as into the estimation of collective dose savings and years of
life spared premature death from cancer.
The years of life spared premature death from cancer is a
projection evaluated as the product of the number of lives spared
premature death from cancer and the difference between the actuarial
number of years of life remaining and the 20-year combined interval of
cancer latency and survival.
The number of skin burns precluded is projected as the percentage
dose reduction multiplied by the number of skin burns reported to FDA
annually, which averages approximately 8.6 reports. It is assumed that
the fraction of skin doses exceeding the threshold for skin injury
would be reduced in proportion to the effective-dose reduction
(approximately 25 percent) projected for procedures of PTCA and CA and
that therefore the number of skin burns would be reduced in the same
proportion.
Estimates of average annual amortized pecuniary savings in the
first 10 years after the effective date of the rule are evaluated as
the respective products of two factors: (1) The projected numbers of
lives spared premature death from cancer (with which obviation of
cancer treatment is also associated) and (2) the monetary savings per
single case associated with either prevention of premature death from
cancer or obviation of cancer treatment. Pecuniary savings associated
with obviation of radiation burn treatment and loss are evaluated
simply as the product of the
[[Page 34021]]
projected number of reported skin burns precluded and the estimated
pecuniary savings associated with each case of radiation burn treatment
and loss precluded; although the savings associated with radiation
burns are averaged over the first 10 years after the effective date of
the rule, they are not amortized because the interval for latency,
presentation, and treatment of skin injury generally occurs within a
year of radiation exposure.
Based on an economic model of society's willingness to pay (WTP) a
premium for high-risk jobs, FDA associates a value of $5 million for
each statistical death avoided (Ref. 9, notes 54 through 56 and Refs.
26 through 28).
Savings of $25,000 for preclusion of each cancer treatment are
estimated as follows: According to data of the U.S. National Cancer
Institute (Ref. 9, note 59, and Ref. 29), 75 percent of all cancers are
either stage 1 or 2 at the time of presentation. Per Ref. 9, note 60
(Ref. 30), these cancers have annual treatment costs of $23,000 to
$28,000. In situ cancers are less expensive, and stage 3 and 4 cancers
cost $50,000 to $60,000 annually to treat. (Also see Ref. 9, note 61,
and Ref. 31.) For the FDA analysis, the annual treatment cost is
estimated to be that associated with the modal stage and was estimated
to be $25,000.
Savings of $5,000 for precluding each case of cancer's
psychological impact are estimated as follows: Psychological impact of
dread, anxiety, or depression has long been noted in cancer treatment
research (e.g., see Ref. 9, notes 63 through 65, and Refs. 32 through
34). This literature indicates that symptoms associated with mental
well-being contribute as much as 8 percent to one's overall sense of
health. Of the sense of psychological well-being, depression scales
have shown that worries about personal health account for approximately
one sixth of the 8 percent contribution, where other contributors
include factors associated with family, finances, work, relationships,
etc. Therefore, worries and concerns about personal health contribute
approximately 1.3 percent to one's sense of personal well-being.
Another way to put it is that society's WTP to avoid such worries is
approximately 1.3 percent of overall health costs. The WTP for overall
health is derived from the estimated annual WTP of $5 million to avoid
a statistical death (Ref. 9, notes 54 through 56, and Refs. 26 through
28). This value was derived from blue-collar males of about 30 years of
age whose life expectancy is 41.3 years (adjusted for future expected
bed and nonbed disability per Ref. 9, notes 66 and 67, and Refs. 35 and
36). Amortization of $5 million across 41.3 years at a discount rate of
7 percent implies a WTP of $373,000 per quality adjusted life-year
(QALY). 1.3 percent of this QALY is approximately $5,000 per year for
society's WTP to avoid the sense of psychological dread associated with
concerns about personal health generated by cancer treatments.
Savings of $67,600 for each case of radiation burn treatment and
loss precluded are estimated as follows: Survey data on radiation burns
indicate an average medical treatment cost of $23,000 and an average
work-loss cost of $20,700 (Ref. 9, note 69, and Ref. 37). Costs of pain
and suffering are estimated from an index of the quality of well-being,
where 1.0000 indicates perfect health, 0.0000 death (Ref. 9 notes 63,
66, and 70, and Refs. 32, 35, and 38). Relative functionality is first
based on mobility (ranging from driving a car without help to being in
a special care unit), social activity (ranging from working to needing
help with self-care), and physical activity (ranging from walking
without problems to staying in bed). Each state has been assigned a
relative wellness and is adjusted according to the cause of the state
(e.g., bedridden with a stomach ache versus bedridden with a broken
leg). For the purpose of this analysis, FDA assigns two functional
states to radiation burns: (1) Two weeks of serious debilitation
(relative wellness value 0.3599) and (2) four weeks of functional
distress with some activity (relative wellness value 0.5108). An annual
amortized average value of $373,000 for the societal WTP for a QALY
equals about $7,200 per week for a quality adjusted life week, which
corresponds to the base 1.0000 in the well-being index. The estimate of
the expected WTP to avoid a radiation burn is [2 x $7,200 x (1.0000 -
0.3599)] + [4 x $7,200 x (1.0000 - 0.5108)] = $23,200. Adding this
value to medical treatment and work-loss costs results in a cost per
burn of $67,600.
For the most part, these projections are based on a benefits
analysis (Ref. 9, available at http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.fda.gov/cdrh/radhlth/scifor01f.pdf or http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.fda.gov/cdrh/radhlth/021501_xray.html)
whose domain is intended to be representative but not exhaustive of
prospective savings. To keep the analysis finite and manageable, it is
limited to the three amendments (see sections II.E, II.F, and II.K of
the proposed rule) that would most reduce radiation dose in several of
the most common fluoroscopic procedures. The procedures considered are
those of PTCA, CA, and UGI. There are other very highly-utilized
fluoroscopic procedures, for example, the barium enema examination,
whose dose savings might be of comparable magnitude to those of UGI,
that are not included at all in this analysis. The three amendments
considered would require new fluoroscopic x-ray systems to: (1) Display
the rate, time, and cumulative total of radiation emission; (2)
collimate the x-ray beam more efficiently; and (3) filter out more of
the low energy x-ray photons from the x-ray beam. New requirements for
the source-skin distance for small C-arm fluoroscopes (see section II.J
of the proposed rule) and for provision of the last-image-hold feature
on all fluoroscopic systems (see section II.L of the proposed rule)
will also directly reduce dose, but their dose reductions are expected
to be much smaller than those associated with the preceding changes.
The remaining amendments can be characterized as clarifications of the
applicability of the standard, changes in definitions, corrections of
errors, and other changes that contribute generally to the
effectiveness of implementation of the standard.
Most of the assumptions, rationales, and data sources underlying
the benefit projections are explicitly detailed in Ref. 9 and its
notes. That analysis, however, is incomplete insofar as it refers only
to a single set of point estimates employing the BEIR V mortality risk
estimates, which presume a dose-rate effectiveness factor (DREF) equal
to unity; the DREF is defined as ``a factor by which the effect caused
by a specific dose of radiation changes at low as compared to high dose
rates'' (Ref. 7). For the sensitivity analysis whose results are
tabulated in table 3 of this document, several additional assumptions
are invoked. Among the most important of the underpinnings of the
analysis are the projected percentage dose reductions corresponding to
the three amendments considered and the dependence on the risk
estimates for cancer mortality from BEIR V (Ref. 7). For the former,
FDA assumes a relative uncertainty of a factor of 2 (lower or higher)
to represent the range in projected dose reductions consistent with a
range of confidence of about 90 percent in the findings and assumptions
(Ref. 9).
With respect to the dependence on the BEIR V estimates, FDA follows
two recommendations of the Office of Science and Technology Policy
(OSTP) CIRRPC Science Panel Report No. 9 (Ref. 8) that represent the
Federal consensus position for radiation risk benefit evaluation:
First, we apply a value of 2 as the DREF in the projections of numbers
of solid, non-leukemia cancers. Adopting a DREF value of 2 in
[[Page 34022]]
the analysis nearly halves the Ref. 9 modal point projections of the
numbers of lives and years of life spared premature death from cancer.
A DREF value of 2 implies that diagnostic or interventional fluoroscopy
is a relatively low dose-rate modality. There are ambiguous assessments
of that proposition: Although BEIR V (Ref. 7, pp. 171 and 220)
considers most medical x-ray exposures to correspond to high-dose rates
(for which the DREF is assumed to equal 1 for solid cancers),
International Commission on Radiological Protection (ICRP) Publication
73 (Ref. 13, p. 6) states just as unequivocally that risk factors
reduced by a DREF larger than 1 (i.e., for low dose-rate modalities)
``are appropriate for all diagnostic doses and to most of the doses in
tissues remote from the target tissues in radiotherapy.'' Recognizing
these contrary views of the detrimental biological effectiveness
associated with the rates of delivery of fluoroscopic radiation, we
assume a factor of 2 uncertainty in the DREF to span a 90-percent range
of confidence and incorporate that uncertainty into the sensitivity
analysis. The second recommendation that FDA adopts from CIRPPC Panel
Report No. 9 (Ref. 8) is the interpretation that a factor of 2 relative
uncertainty represents the BEIR V Committee's estimation of the 90-
percent confidence interval for mortality risk estimates (Ref. 7). The
latter value also agrees with that in the recent review of the United
Nations Scientific Committee on the Effects of Atomic Radiation in the
``UNSCEAR 2000 Report'' (Ref. 14).
All of the contributions of relative uncertainty appropriate for
the projections of collective dose savings, lives and years of life
spared premature death associated with radiation-induced cancer,
numbers of reports of fluoroscopic skin burns precluded, and associated
pecuniary estimates are summed in quadrature. For the projected
collective dose savings, the root quadrature sum yields an overall
estimated relative uncertainty of a factor of 2.3 lower and higher than
the modal point estimates of the projected savings. These values
represent, respectively, the 5th and 95th percentile points of a 90
percent confidence interval. For the projected number of lives and
years of life spared premature death, the overall estimated relative
uncertainty is a factor of 3.6 lower and higher spanning a 90 percent
confidence interval. Hence, these factors account for the principal
sources of uncertainty in the projected dose reductions, in DREF, and
in the mortality risk estimates. Applied to the sensitivity analysis,
these relative factors of uncertainty comprise the bounds of
variability within which the true values of table 3 quantities reside,
at a 90-percent confidence level and under the modeling assumptions and
discount rates indicated in preceding paragraphs of this document.
I. Costs of Implementing the Regulation
Costs to manufacturers of fluoroscopic and radiographic systems
will increase due to these proposals. FDA will also experience costs
for increased compliance activities. Some costs represent one-time
expenditures to develop new designs or manufacturing processes to
incorporate the regulatory changes. Other costs are the ongoing costs
of providing improved equipment performance and features with each
installed unit. FDA developed unit cost estimates for each required
activity and multiplied the respective unit cost by the relevant
variables in the affected industry segment. One-time costs are
amortized over the estimated useful life of a fluoroscopy system (10
years) using a 7-percent discount rate. This allows costs to be
analyzed as average annualized costs as well as first-year
expenditures. FDA developed these cost estimates based on its
experience with the industry and its knowledge regarding design and
manufacturing practices of the industry. Initially, gross, upper-bound
estimates were selected to ensure that expected costs were adequately
addressed. The initial assumptions and estimates were posted on FDA's
Web site and circulated to the affected industry for comment in July
2000. FDA received no comments on these initial, upper-bound estimates
and therefore believes that they were generally in line with industry
expectations. Since then, in order to refine the estimates to provide a
more accurate representation of the upper-bound costs of the
amendments, FDA reexamined its estimating assumptions and reduced some
unit cost figures based on the expectation that future economies of
scale would reduce the expense of some required features. This section
presents a brief discussion of the cost estimates. A detailed
description of this analysis is given in Ref. 5.
FDA has no information, indication, or economic presumption on
whether costs estimated to be borne by manufacturers would be passed on
to purchasers. The cost analysis therefore is limited to those parties
who would be directly affected by the adoption of the amendments,
namely, manufacturers and FDA itself. In the proposed rule, FDA
requested information on the costs that would be imposed by these new
requirements that would aid in refining the cost estimates. FDA
received no comments or additional information on these costs.
1. Costs Associated With Requirements Affecting Equipment Design
The agency estimates that approximately one-half (20) of the
manufacturers of x-ray systems will have to make design and
manufacturing changes to comply with the revised beam quality
requirements. It is estimated that a total of 200 x-ray models will be
affected, with a one-time cost of at most $20,000 per model. These
numbers result in an estimated first year expenditure of $4.0 million
to redesign systems to meet the new beam quality requirement.
It will be necessary for manufacturers of fluoroscopic systems
equipped with x-ray tubes with high heat capacity to redesign some
systems to provide a means to add additional beam filtration. FDA
estimates a design cost of $50,000 per model. A total of 100 models are
likely to be affected for a one-time cost of $5.0 million to
fluoroscopic system manufacturers. In addition, each system will cost
more to manufacture because of the increased costs for components to
provide the added feature. The increased cost of this added feature is
estimated at $1,000 per fluoroscopic system. A total of 650
fluoroscopic systems are estimated to be installed annually with high
heat capacity x-ray tubes, resulting in a total of $0.65 million in
increased annual costs.
Modification of x-ray systems to meet the revised requirement for
field limitation will entail either changes in installation and
adjustment procedures or redesign of systems. Each fluoroscopic system
will need either modification in the adjustment procedure for the
collimators (for which new installation and adjustment procedures will
be developed at an estimated one-time cost of $20,000 per model) or
collimators will need to be redesigned at an estimated cost of $50,000
per model. FDA has assumed that half of all fluoroscopic x-ray system
models (5 models each for 20 manufacturers) will need modifications to
meet the new requirement, while the remainder will either meet the new
requirement or could meet it through very minor modifications in the
collimator adjustment procedure. For those system models not meeting
the new requirement, it is assumed that a redesign of the collimator
system is required at a cost of about $50,000 per model, leading to an
upper-bound estimate of the total redesign cost of $5.0 million (20
manufacturers x 5
[[Page 34023]]
models x $50,000). All stationary fluoroscopic systems will most likely
need redesigned collimators that will add an estimated additional
$2,000 per new system due to increased complexity of the collimator. An
annual industry cost increase of $5.0 million accounts for all 2,500
annual installations of systems with these more expensive collimators.
The modification of the requirement limiting the maximum entrance
AKR and removal of the exception to the limit during recording of
images will only affect the adjustment of newly-installed systems
having such recording capability. This requirement is not expected to
impose significant costs.
FDA is requiring that all fluoroscopic systems include displays of
irradiation time, AKR, and cumulative air kerma to assist operators in
keeping track of patient exposures and avoiding overexposures. Each
model of fluoroscopic system will need to be redesigned (at a maximum
estimated cost of $50,000 per model) for an estimated one-time cost of
$10.0 million (200 models x $50,000). Accessory or add-on equipment for
existing fluoroscopic systems that provide similar information are
currently available for an additional cost of over $10,000 per system.
However, FDA expects the average manufacturing cost of including such a
feature as an integral feature of a fluoroscopic system to be less than
$4,000 per system, due to achievable economies of scale and integration
with other system computer capabilities. This assumption produces an
annual cost increase of $16.8 million (4,200 annual installations x
$4,000).
The amendments will require that all newly-manufactured
fluoroscopic systems be provided with LIH capability. FDA expects that
10 fluoroscopic system manufacturers will need to redesign their
systems to include this technology at a maximum cost of $100,000 per
manufacturer. Total one-time design costs will equal $1.0 million for
the industry (10 manufacturers x $100,000). It is estimated that about
half of the new systems installed will already be equipped with this
feature. Thus, about half of the newly-installed systems that currently
do not provide this feature will need it. FDA estimates that the cost
will be an additional $2,000 for each system required to have this
feature. Thus, annual costs will increase by $4.2 million (2,100 annual
systems x $2,000).
The clarification of the requirement for minimum source-skin
distance for small C-arm systems is anticipated to require redesign of
several of these systems. As there are only three manufacturers of
these systems, and the redesign costs are estimated to be no more than
$50,000 per system, the total one-time cost for this change will be
$0.2 million. The average annualized cost of this change will be
negligible.
In summary, total industry costs for compliance with the amendments
in the area of equipment design include onetime costs of $25.2 million.
This total equals an average annualized cost (7-percent discount rate
over 10 years) of $3.6 million. The average annualized cost using a 3-
percent discount rate over 10 years equals $3.0 million. In addition,
annual recurring costs for new equipment features associated with these
provisions are expected to equal $26.7 million.
2. Costs Associated With Additional Information for Users
The amendments will require that additional information be provided
in the user instructions regarding fluoroscopic systems. FDA has
estimated that each model of fluoroscopic system will need a revised
and augmented instruction manual at a cost of less than $5,000 per
model. This is equal to a maximum one-time cost of $1.0 million (200
models of fluoroscopic systems x $5,000) and implies maximum average
annualized costs of $0.14 million (7-percent discount rate) or $0.12
million (3-percent discount rate). In addition, each newly-installed
system will include an improved instruction manual. FDA estimates a
cost of $20 per manual for printing and distribution of the required
additional information. Each of the 4,200 installed fluoroscopy systems
will include a revised manual for an annual cost of approximately $0.1
million.
Related to the requirements for additional information is the
change of the quantity used to describe the radiation produced by the
x-ray system. Because the change to use of the quantity air kerma does
not require any changes or actions on the part of manufacturers or
users, there is no significant cost associated with it.
3. Costs Associated With Clarifications and Adaptations to New
Technologies
The new definitions and clarifications of applicability for the
performance standard do not pose any significant new or additional
costs on manufacturers.
4. FDA Costs Associated With Compliance Activities
FDA costs will increase due to the increased compliance activities
that will result from these regulations. In addition, FDA will
experience implementation costs in developing and publicizing the new
requirements. FDA has estimated that approximately five full-time
equivalent employees (FTEs) will be required to implement the
regulations and conduct training of field inspectors. Using the current
estimate of $117,000 per FTE, the one-time cost of implementation to
FDA is approximately $0.6 million. Amortizing this cost over a 10-year
evaluation period using 7- and 3-percent discount rates results in
average annualized costs of about $0.1 million. Ongoing costs of annual
compliance activities are expected to require about three FTEs, or a
little more than $0.3 million per year.
5. Total Costs of the Regulation
The estimated costs of the amendments identified as having any
significant cost impact are summarized in table 4 of this document. The
costs are identified as nonrecurring costs that must be met initially
or as annual costs associated with continued production of systems
meeting the requirements or additional annual enforcement of the
amendments. The total annualized cost of the regulations (averaged over
10 years using a 7-percent discount rate) equals $30.8 million, of
which $30.4 million will be borne by manufacturers. The annualized
estimate of $30.8 million represents amortization of first year costs
of $53.8 million and expenditures from years 2 through 10 of $27
million annually. If costs are amortized using a 3-percent discount
rate, annualized costs equal $30.1 million. The sections listed in the
left-hand column of table 4 of this document refer to sections of the
proposed rule.
Table 4.--Summary of Costs of Amendments
----------------------------------------------------------------------------------------------------------------
Section of the Proposed Nonrecurring Costs Annual Costs to
Rule Preamble Describing to Manufacturers ($ Nonrecurring Costs Manufacturers ($ Annual Costs to FDA
the Amendment millions) to FDA ($ millions) millions) ($ millions)
----------------------------------------------------------------------------------------------------------------
II.A none 0.0059 none none
----------------------------------------------------------------------------------------------------------------
[[Page 34024]]
II.B none 0.0324 none none
----------------------------------------------------------------------------------------------------------------
II.D 1.0 none 0.084 0.0117
----------------------------------------------------------------------------------------------------------------
II.E 9.0 0.0117 0.650 none
----------------------------------------------------------------------------------------------------------------
II.F 5.0 0.0468 5.0 none
----------------------------------------------------------------------------------------------------------------
II.G, II.H, and II.I none none none none
----------------------------------------------------------------------------------------------------------------
II.J 0.150 0.0234 none none
----------------------------------------------------------------------------------------------------------------
II.K 10.0 0.4680 16.8 0.2340
----------------------------------------------------------------------------------------------------------------
II.L 1.0 0.0234 4.2 none
----------------------------------------------------------------------------------------------------------------
Total 26.150 0.6026 26.734 0.2457
----------------------------------------------------------------------------------------------------------------
Therefore, during the first 10 years after the effective date of
the amendments, using a 7-percent discount rate, the average annual
cost is estimated to be $30.8 million, compared to projected average
annual benefits of $320 million, within a range estimated between $88
million and $1.2 billion. A comparison of costs and benefits using a 3-
percent discount rate results in annualized costs of $30.1 million and
average annual benefits of about $716 million, within an expected range
of $197 million to $2.6 billion.
J. Cost-Effectiveness of the Regulation
We evaluated the cost-effectiveness of the final regulation using
the cost per incidence of cancer avoided due to lower exposure over the
10-year evaluation period. The annual numbers of future-avoided cancers
due to reduced radiation doses are compared to the present values of
the costs for the evaluation period. We used projections of the annual
number of cancer cases that would be avoided due to the final
regulation. The cases that would be avoided because of exposure
reductions during the first year (as improved systems are installed)
are assumed to present themselves after a 10-year latency period. We
expect the overall exposure reduction attributable to this final
regulation to increase by 10 percent each year as currently installed
x-ray systems are replaced by systems meeting the new performance
standards. The most likely estimate for reductions in the number of
premature cancers resulting from reduced unnecessary exposures during
the first compliant year is 66 fewer incidents of cancer. By the 10th
year, the exposure reductions are expected to preclude 664 annual
cancers according to the modal dose-response relationship. Table 5 of
this document shows the annual decrease in cancer incidence expected
for the modal relationship, as well as for the low and high range of
estimated reductions.
Table 5.--Expected Annual Reductions in Cancer Incidences by Year
(Modal, Low, and High Estimates)
------------------------------------------------------------------------
Low Range High Range
Compliance Year Modal Estimate Estimate Estimate
------------------------------------------------------------------------
1 66 18 241
------------------------------------------------------------------------
2 133 37 482
------------------------------------------------------------------------
3 199 55 722
------------------------------------------------------------------------
4 266 73 963
------------------------------------------------------------------------
5 332 92 1,204
------------------------------------------------------------------------
6 399 110 1,445
------------------------------------------------------------------------
7 465 128 1,686
------------------------------------------------------------------------
8 532 147 1,926
------------------------------------------------------------------------
9 598 165 2,167
------------------------------------------------------------------------
10 664 183 2,408
------------------------------------------------------------------------
Although the reductions in cancers would continue beyond the
evaluation period, we have analyzed only through the 10th year.
While the dose reduction attributable to the final regulation
during the first year is expected to avoid 66 future cancers, those
cancers have an assumed latency of 10 years and would not be discovered
until the 11th year. Therefore, while reduced exposures during year 1
are expected to avoid 66 cancers, those avoided cancers would not have
occurred until year 11. Each year's expected number of future avoided
cancers is discounted to arrive at an equivalent number of avoided
cancers during the first year. The present equivalent number of annual
cancers avoided are estimated using both 7- and 3-percent annual
discount rates. These equivalent numbers are shown in table 6 of this
document.
Table 6.--Expected Equivalent Number of Cancers Avoided Discounted to Year 1 Due to Regulation
----------------------------------------------------------------------------------------------------------------
Annual Discount Rate Modal Estimate Low Estimate High Estimate
----------------------------------------------------------------------------------------------------------------
3 Percent 2,217 612 8,034
----------------------------------------------------------------------------------------------------------------
7 Percent 1,173 324 4,252
----------------------------------------------------------------------------------------------------------------
[[Page 34025]]
The present value of the regulatory costs, when divided by the
equivalent number of avoided cancers, will result in the expected cost
per cancer avoided. Annualized costs using a 3-percent discount rate
equaled $30.1 million and result in a present value of $256.8 million
for the evaluation period. Using a 7-percent annual discount rate,
annualized costs of $30.8 million result in a present value of $216.3
million. The cost per avoided cancer is shown in table 7 of this
document.
Table 7.--Regulatory Cost-Effectiveness per Incidence of Cancer Avoided Due to Regulation
----------------------------------------------------------------------------------------------------------------
Annual Discount Rate Modal Estimate Low Estimate High Estimate
----------------------------------------------------------------------------------------------------------------
3 Percent $115,800 $419,600 $32,000
----------------------------------------------------------------------------------------------------------------
7 Percent $184,400 $667,600 $50,900
----------------------------------------------------------------------------------------------------------------
The cost-effectiveness of the final regulation using a 7-percent
discount rate has a modal value of $184,400 within an estimated range
of between $50,900 and $667,600 per cancer avoided. If a 3-percent
annual discount rate is used, the regulation will cost an estimated
$115,800 per avoided cancer within an estimated range of $32,000 to
$419,600.
K. Small Business Impacts
FDA believes that it is likely that the rule will have a
significant impact on a substantial number of small entities and has
conducted an IRFA. This analysis was designed to assess the impact of
the rule on small entities and alert any impacted entities of the
expected impact.
1. Description of Impact
The objective of the regulation is to reduce the likelihood of
adverse events due to unnecessary exposure to radiation during
diagnostic x-ray procedures, primarily fluoroscopic procedures. The
amendments will accomplish this by requiring performance features on
all fluoroscopic x-ray systems that will protect patients and
healthcare personnel while maintaining image quality.
Manufacturers of diagnostic x-ray systems, including fluoroscopy
equipment, are grouped within the North American Industry
Classification System (NAICS) industry code 334517 (Irradiation
Apparatus Manufacturers)\1\. The Small Business Administration (SBA)
classifies as ``small'' any entity with 500 or fewer employees within
this industry. Relatively small numbers of employees typify firms
within this NAICS code group. About one-half of the establishments
within this industry employ fewer than 20 workers, and companies have
an average of 1.2 establishments per company. The manufacturers are
relatively specialized, with about 84 percent of company sales coming
from within the affected industry. In addition, 97 percent of all
shipments of irradiation equipment originate by manufacturers
classified within this industry.
---------------------------------------------------------------------------
\1\ NAICS has replaced the Standard Industrial Classification
(SIC) codes. NAICS Industry Group 334517 (Irradiation Apparatus)
coincides with SIC Group 3844 (X-Ray Apparatus and Tubing).
---------------------------------------------------------------------------
The Manufacturing Industry Series report on Irradiation Apparatus
Manufacturing for NAICS code 334517 from the 1997 Economic Census
indicates 136 companies having 154 establishments for this industry in
the United States. This report also indicates that only 15 of these
establishments have 250 or more employees, with only 5 establishments
having more than 500 employees. Therefore, this industry sector is
predominately composed of firms meeting the SBA description of a
``small entity.'' Of the total value of shipments of $3,797,837,000 for
this industry, 73 percent are from the 15 establishments with 250 or
more employees. Thus, for the purposes of the IRFA, most of the
diagnostic x-ray equipment manufacturing firms that will be affected by
these amendments are small entities.
The impact of the amendments will be similar on manufacturers of
diagnostic x-ray systems, whether or not they are small entities. This
impact is the increased costs to design and manufacture x-ray systems
that meet the new requirements. For those manufacturers that produce
smaller numbers of systems per year, the impact of the cost of system
redesign to meet the new requirements will result in a greater per unit
cost impact than for manufacturers with a high volume of unit sales
over which the development costs may be spread. This may have a
disproportionate impact on the very small firms with a low volume of
sales.
FDA considered whether there were approaches that could be taken to
mitigate this impact on the firms producing the smaller numbers of
systems. FDA, however, identified no feasible way to do this and also
accomplish the needed public health protection. The radiation safety-
related requirements are appropriate for any x-ray system, independent
of the circumstances of the manufacturer. FDA considers it appropriate
for any firm producing x-ray systems to provide the level of radiation
protection that will be afforded by the revised standard. Patients
receiving x-ray examinations or procedures warrant the same degree of
radiation safety regardless of the circumstances of the manufacturer of
the equipment.
2. Analysis of Alternatives
FDA examined and rejected several alternatives to proposing
amendments to the performance standard. One alternative was to take no
actions to modify the standard. This option was rejected because it
would not permit clarification of the manner in which the standard
should be applied to the technological changes occurring with
fluoroscopic x-ray system design and function. This option was also
rejected as failing to meet the public expectation that the federal
performance standard assures adequate radiation-safety performance and
features for radiographic and fluoroscopic x-ray systems. The changes
that have occurred since the standard was developed in the early 1970s
necessitate modification of the standard to reflect current technology
and to recognize the increased radiation hazards posed by new
fluoroscopic techniques and procedures.
The alternative of no action to amend the performance standard was
also rejected because that alternative would continue the current
situation in which the U.S. standard has some performance requirements
that differ from those in several of the standards established by the
IEC for diagnostic x-ray systems. Several IEC radiation-safety
performance requirements are slightly more stringent than those of the
U.S. standard, which has not, to date, reflected a number of changes in
x-ray system technology recognized by the IEC standards. The proposed
amendments will harmonize the U.S. performance standard with several of
[[Page 34026]]
the requirements of the IEC standards where differences currently
exist. Such harmonization will reduce the necessity for manufacturers
to comply with different requirements for products marketed in the
United States versus internationally where the IEC standards are used.
The no-action alternative would continue these discrepancies between
the U.S. and IEC standards.
FDA considered various alternatives for each amendment that would
require new equipment features or, potentially, system redesign. The
assessment of the cost of each proposed amendment (listed in the first
column of table 4 of this document) included consideration of
alternatives to the specific amendment (Ref. 5). For amendments
requiring equipment changes, consideration was given to the following
factors: (1) The options or choices for specific limits or tolerances
when such are imposed; (2) whether the amendment requirement should be
limited to certain types of equipment or applied to all types of
radiographic or fluoroscopic systems; (3) the need, where possible, to
align the U.S. standard with the IEC standards and remove conflicts
among the standards; and (4) whether the requirement could contribute
to improved, safer use of the equipment. FDA concluded that the
amendments are needed to obtain the radiation dose-reduction features
necessary to facilitate safer use of fluoroscopy.
One alternative considered would be to implement only certain of
the proposed amendments and omit others, as a way of reducing the
overall costs of the amendments. FDA rejected this approach as
inappropriate for two reasons. First, it would not result in the
desired harmonization between the U.S. and international standards, one
of the main goals of these amendments. Furthermore, implementing only a
portion of the separate amendments would not result in the anticipated
public health benefits that will result from providing users with the
full range of additional system-performance information and dose-
reduction features.
In the notice of proposed rulemaking (67 FR 76056, December 10,
2002) FDA requested comments on alternatives to these amendments that
would accomplish the needed public health protection and, in
particular, any alternatives that could mitigate the impact on small
businesses. No responses to this request were received.
A portion of the unnecessary radiation exposure resulting from
current fluoroscopic practices might be addressed through the
establishment of controls on the qualifications and training of
physicians permitted to use fluoroscopic systems. Contrary to the
current situation, such requirements could help assure that all
physicians using fluoroscopy were adequately trained regarding
radiation-safety practices, proper fluoroscopic system use, and methods
for maintaining patient doses as low as reasonably achievable. Under
current law FDA does not have the authority to establish such
requirements. To be effective, such a program would have to be
established by States or medical professional societies or
certification bodies. While recognizing that encouragement of such
activities by FDA is worthwhile, reliance on such encouragement alone
will not result in the needed performance improvement of fluoroscopic
x-ray systems.
3. Ensuring Small Entity Participation in Rulemaking
FDA believes it is possible that the new regulations could have a
significant impact on small entities. The impact will occur due to
increased design and production costs for fluoroscopy systems. FDA
solicited comment on the nature of this impact and whether there are
reasonable alternatives that might accomplish the intended public
health goals.
The proposed regulations were available on the Internet at http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.fda.gov
for review by all interested parties. FDA communicated the
proposed regulatory changes to the x-ray equipment manufacturers'
organization as well as to parties that had previously indicated an
interest in amendments to the diagnostic x-ray equipment performance
standard. The proposed amendments were also brought to the attention of
relevant medical professional societies and organizations whose members
are likely to use fluoroscopic x-ray systems.
L. Reporting Requirements and Duplicate Rules
FDA has concluded that the rule imposes new reporting and other
compliance requirements on small businesses. In addition, FDA has
identified no relevant Federal rules that may duplicate, overlap, or
conflict with the rule.
M. Conclusion of the Analysis of Impacts
FDA has examined the impacts of the amendments to the performance
standard. Based on this evaluation, an upper-bound estimate has been
made for average annualized costs amounting to $30.8 million, of which
$30.4 million will be borne by the manufacturers of this equipment. FDA
believes that the reductions in acute and long-term radiation injuries
to patients that will be facilitated by the amendments will appreciably
outweigh the upper-bound costs estimated for compliance with the rules.
Finally, FDA has concluded that it is likely that this proposal will
have a significant impact on a substantial number of small entities.
FDA solicited comment on all aspects of this analysis and all
assumptions used. As noted previously in this document, only two
comments were received that directly addressed the analyses and these
suggested, qualitatively, that FDA had underestimated either the amount
of dose reduction that will result or the benefit of such dose
reduction. These comments, however, do not provide a basis for revising
the estimates of costs and benefits.
VIII. Federalism
This final rule has been reviewed under Executive Order 13132,
Federalism. This Executive order requires that agencies issuing
regulations that have federalism implications follow certain
fundamental federalism principles and provide a federalism impact
statement that: (1) Demonstrates the agency consulted with appropriate
State and local officials before developing the final rule, (2)
summarizes State concerns, (3) provides the agency's position
supporting the need for regulation, and (4) describes the extent to
which the concerns of State and local officials have been met.
Regulations have federalism implications whenever they have a
substantial direct effect on the States, on the relationship between
the National Government and the States, or on the distribution of power
and responsibilities among various levels of government.
The Executive order indicates that, where National standards are
required by Federal statutes, agencies shall consult with appropriate
State and local officials in developing those standards. It also
directs agencies to consult with State and local officials, to the
extent practicable and permitted by law, before issuing any regulation
with federalism implications that preempts State law.
In enacting the provisions of the RCHSA (which were later
transferred from the PHS Act to the act by the SMDA), Congress
recognized that separate State standards alone were insufficient to
achieve the type of consistent and comprehensive protection that was
needed. For this reason, Congress established a National radiation
control program and
[[Page 34027]]
authorized FDA (by delegation of authority from the Secretary of the
Department of Health and Human Services) to develop and administer
Federal performance standards for radiation-emitting electronic
products to more effectively protect the public health and safety (21
U.S.C. 360hh-360ss). To ensure that State standards would not be
inconsistent with Federal performance standards for electronic
products, Congress included explicit preemption language in the act.
Section 542 of the act states the following:
Whenever any standard prescribed pursuant to section 534 with
respect to an aspect of performance of an electronic product is in
effect, no State or political subdivision of a State shall have any
authority either to establish, or to continue in effect, any
standard which is applicable to the same aspect of performance of
such product and which is not identical to the Federal standard.
Nothing in this subchapter shall be construed to prevent the Federal
Government or the government of any State or political subdivision
thereof from establishing a requirement with respect to emission of
radiation from electronic products procured for its own use if such
requirement imposes a more restrictive standard than that required
to comply with the otherwise applicable Federal standard (21 U.S.C.
360ss).
Although States may not establish a performance standard for an
aspect of performance of an electronic product that is not identical to
the Federal standard, State and local governments do have authority to
regulate the use of radiation-emitting electronic products, including
diagnostic x-ray systems. Under this division of responsibility, the
Federal performance standards assure that electronic products
introduced into commerce possess the necessary radiation safety
features. State and local governments, in turn, may prescribe who will
be permitted to purchase or use such products. They may also establish
requirements for facilities using these products in order to assure the
safe function and operation of the products over their useful life.
This division of authority and responsibility has ensured the safe use
of diagnostic x-ray systems since the Federal performance standard was
established in 1972.
FDA has reached out to the States and actively sought their input
throughout the entire process of developing this rule. In December
1997, FDA issued an ANPRM and invited interested parties to express
opinions regarding the need for amendments to the existing performance
standard for diagnostic x-ray products. With the assistance of the
Conference of Radiation Control Program Directors (CRCPD), a
professional association whose membership includes the directors of
State radiation control agencies, the ANPRM was brought to the
attention of all of the State agencies responsible for radiation
control. In response to the ANPRM, FDA received 12 comments, including
comments from three States, one local radiation control agency, and
comments from the CRCPD. In addition, beginning as early as April 1997,
FDA provided opportunities for comment and discussion about the
development of this rule at public meetings of FDA's TEPRSSC committee.
In fact, the TEPRSSC's membership during this period included
representatives of several State or local radiation control programs.
Information regarding the proposed amendments was also posted on the
agency's Internet Web site, and FDA informed the CRCPD of these
postings.
The States also had several opportunities to participate in the
development of this final rule during various CRCPD meetings at which
FDA representatives were in attendance. These meetings include: The May
1998 and April 2001 National meetings, during which FDA made
presentations; the May 2000 National meeting, which provided an
opportunity for discussion about the amendments during the a special
interest session at that meeting; and the May 2004 National meeting,
during which FDA provided an update on the amendments. FDA also
discussed the proposed amendments at two FDA regional meetings with
State radiation control officials held in July and August of 2002.
Finally, the States had an additional opportunity to participate in
the rulemaking process by submitting comments on the proposed rule. FDA
specifically directed a mailing of the proposed rule to State health
officials in order to encourage them to submit comments.
We received no comments from State or local officials regarding the
federalism section of the proposed rule. The two states that commented
on the proposed rule were generally supportive of the rule. The
comments from these States have already been addressed previously in
section III of this document. (See comments 1, 34, and 47.)
FDA believes that this final rule is consistent with the federalism
principles expressed in Executive Order 13132. The rule only preempts
State law to the extent required by statute and only on the limited
aspects of performance of fluoroscopic and radiographic x-ray systems
covered by this rule. In addition, FDA is not aware of any existing
State or local requirements that will be displaced by this rule. The
purpose of this final rule is to amend the Federal performance standard
to account for changes in technology and use of fluoroscopic and
radiographic x-ray systems. FDA believes these amendments are vital to
ensuring the kind of consistent and effective radiation control
protection Congress envisioned when it enacted the radiation control
provisions of the act.
IX. References
The following references have been placed on public display in the
Division of Dockets Management (see the fourth paragraph of section
VII.A of this document) and may be seen by interested persons between 9
a.m. and 4 p.m., Monday through Friday. (FDA has verified the Web site
addresses, but FDA is not responsible for any subsequent changes to the
Web sites after this document publishes in the Federal Register.)
1. International Standard, International Electrotechnical
Commission (IEC) 60601-2-43, ``Medical Electrical Equipment--Part 2-
43: Particular Requirements for the Safety of X-Ray Equipment for
Interventional Procedures,'' edition 1, 2000.
2. International Standard, International Electrotechnical
Commission (IEC) 60601-1-3, ``Medical Electrical Equipment--Part 1:
General Requirements for Safety. 3. Collateral Standard: General
Requirements for Radiation Protection in Diagnostic X-Ray
Equipment,'' 1994.
3. International Standard, International Electrotechnical
Commission (IEC) 60601-2-7, ``Medical Electrical Equipment-Part 2-7:
Particular Requirements for the Safety of High-Voltage Generators of
Diagnostic X-Ray Generators,'' 2d edition, 1998.
4. International Standard, International Electrotechnical
Commission (IEC) 60580, ``Medical Electrical Equipment-Dose Area
Product Meters,'' 2d edition, 2000.
5. ``Assessment of the Impact of the Proposed Amendments to the
Performance Standard for Diagnostic X-Ray Equipment Addressing
Fluoroscopic X-Ray Systems,'' Food and Drug Administration, pp. 1-
28. Also available at http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.fda.gov/cdrh/radhealth/fluoro/amendxrad.pdf
, November 15, 2000.
6. National Council on Radiation Protection and Measurements,
``Evaluation of the Linear-Nonthreshold Dose-Response Model for
Ionizing Radiation,'' NCRP Report 136, Bethesda, MD, June 2001.
7. Upton, A.C. et al., ``Health Effects of Exposure to Low
Levels of Ionizing Radiation: BEIR V,'' Committee on the Biological
Effects of Ionizing Radiations, Board on Radiation Effects Research,
Commission on Life Sciences, National Research Council, National
Academy of Science, National Academy Press, Washington, DC, 1990.
8. Rosenstein, M. et al., Committee on Interagency Radiation
Research and Policy
[[Page 34028]]
Coordination Science Panel Report No. 9, ``Use of BIER V and UNSCEAR
1988 in Radiation Risk Assessment, Lifetime Total Cancer Mortality
Risk Estimates at Low Doses and Low Dose Rates for Low-LET
Radiation,'' (ORAU 92/F-64), OSTP, EOP, Washington, DC, December
1992.
9. Stern, S.H. et al., ``Estimated Benefits of Proposed
Amendments to the FDA Radiation-Safety Standard for Diagnostic X-Ray
Equipment.'' (Poster presented at the 2001 FDA Science Forum,
Washington, DC, February 15-16, 2001.) Also available at http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.fda.gov/cdrh/radhlth/021501_xray.html
.
10. Suleiman, O.H. et al., ``Nationwide Survey of Fluoroscopy:
Radiation Dose and Image Quality,'' Radiology, vol. 203, pp. 471-
476, 1997.
11. Proceedings of the ACR/FDA Workshop on Fluoroscopy,
``Strategies for Improvement in Performance, Radiation Safety and
Control,'' Dulles Hyatt Hotel, Washington, DC, October 16 and 17,
1992, American College of Radiology, Merrifield, VA, 1993.
12. Gagne, R.M., P.W. Quinn, and R.J. Jennings, ``Comparison of
Beam-Hardening and K-Edge Filters for Imaging Barium and Iodine
During Fluoroscopy,'' Medical Physics, vol. 21, pp. 107-121, 1994.
13. Zuur, C. and F. Mettler, ``Radiological Protection and
Safety in Medicine,'' Annals of the ICRP, ICRP Publication 73, vol.
26, No. 2, Pergamon Press, Oxford, UK, 1996.
14. ``Sources and Effects of Ionizing Radiation,'' United
Nations Scientific Committee on the Effects of Atomic Radiation,
UNSCEAR 2000 Report to the General Assembly, with Scientific
Annexes, New York: United Nations, 2000.
15. Rogers A.T. et al., ``The Use of a Dose-Area Product Network
to Facilitate the Establishment of Dose Reference Levels,'' European
Radiation Protection, Education and Training (ERPET), ERPET Course
for Medical Physicists on Establishment of Reference Levels in
Diagnostic Radiology, Passau, Germany, September 13-15, 1999,
Proceedings, EC Directorate General Science, Research and
Development Doc. RTD/0034/20, (BfS-ISH, Oberscheissheim, July 2000),
pp. 255-260.
16. Shrimpton, P.C. et al., A National Survey of Doses to
Patients Undergoing a Selection of Routine X-Ray Examinations in
English Hospitals, NRPB-R200, National Radiological Protection
Board, Chilton, UK, September 1986.
17. Hart, D. et al., Doses to Patients from Medical X-Ray
Examinations in the UK--1995 Review, NRPB-R289, National
Radiological Protection Board, Chilton, UK, July 1996.
18. Kaczmarek, R., Nationwide Evaluation of X-Ray Trends Summary
of 1996 Fluoroscopy Survey, (unpublished draft, November 2000).
19. Laitano, R.F. et al., Energy Distributions and Air Kerma
Rates of ISO and BIPM Reference Filtered X-Radiations, Comitato
Nazionale per la Ricerca e per lo Sviluppo dell'Energia Nucleare e
delle Energie Alternative, p. 29, December 1990.
20. Suleiman, O.H., Development of a Method to Calculate Organ
Doses for the Upper Gastrointestinal Fluoroscopic Examination, Ph.D.
dissertation, Johns Hopkins University School of Hygiene and Public
Health, Baltimore, MD, 1989.
21. Rosenstein, M. et al., Handbook of Selected Tissue Doses for
the Upper Gastrointestinal Fluoroscopic Examination, HHS Publication
FDA 92-8282, U.S. Department of Health and Human Services, Public
Health Service, Food and Drug Administration, Center for Devices and
Radiological Health, Rockville, MD, June 1992.
22. Geleijns, J. et al., ``A Comparison of Patient Dose for
Examinations of the Upper Gastrointestinal Tract at 11 Conventional
and Digital Units in The Netherlands,'' The British Journal of
Radiology, vol. 71, pp. 745-753, July 1998.
23. Stern, S.H. et al., Handbook of Selected Tissue Doses for
Fluoroscopic and Cineangiographic Examination of the Coronary
Arteries (in SI Units), HHS Publication FDA 95-8289, U.S. Department
of Health and Human Services, Public Health Service, Food and Drug
Administration, Center for Devices and Radiological Health,
Rockville, MD, September 1995.
24. Nationwide Inpatient Sample Release 6 for 1997, compiled by
HCUPnet, Healthcare Cost and Utilization Project, Agency for
Healthcare Research and Quality, Rockville, MD, http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.ahrq.gov/data/hcup/
, August 2000.
25. Peterson, E.D. et al., ``Evolving Trends in Interventional
Device Use and Outcomes: Results from the National Cardiovascular
Network Database,'' American Heart Journal, vol. 139, no. 2, pp.
198-207, February 2000.
26. Viscusi, K., Fatal Tradeoffs: Public and Private
Responsibilities for Risk, Oxford University Press, 1992.
27. Fisher, A. et al., ``The Value of Reducing Risks of Death: A
Note on New Evidence,'' The Journal of Policy Analysis and
Management, vol. 8, no. 1, pp. 88-100, 1989.
28. Mudarri, D., Costs and Benefits of Smoking Restrictions: An
Assessment of the Smoke-Free Environment Act of 1993, Environmental
Protection Agency, 1994.
29. U.S. National Cancer Institute, Surveillance, Epidemiology,
and End Results (SEER) Cancer Statistics Review (1973-1994), Annual,
pp. 123-143, 1997.
30. Legoretta, A. et al., ``Cost of Breast Cancer Treatment,''
Archives of Internal Medicine, vol. 156, pp. 2197-2201, 1996.
31. Brown, M. and L. Fintor, ``The Economic Burden of Cancer,''
Cancer Prevention and Control, edited by P. Greenwald et al., Marcel
Dekker Inc., 1995.
32. Kaplan, R. et al., ``Health Status: Types of Validity and
the Index of Well-Being,'' Health Service Research, winter issue,
pp. 478-507, 1976.
33. Radloff, L., ``The CES-D Scale: A Self-Report Depression
Scale for Research in the General Population,'' The Journal of
Applied Psychological Measurement, vol. 1, no. 3, pp. 385-401, 1977.
34. Shrout, P., ``Scaling of Stressful Life Events,'' Stressful
Life Events and Their Contexts, ed. by B.S. Dowrenwend and B.P.
Dowenrend, Rutgers University Press, 1984.
35. Chen, M. et al., ``Social Indicators for Health Planning and
Policy Analysis,'' Policy Sciences, vol. 6, pp. 71-89, 1975.
36. U.S. National Center for Health Statistics, Expectation of
Life and Expected Death by Race, Sex, and Age, Vital Statistics of
the United States, 1995.
37. U.S. Consumer Product Safety Commission, Estimating the Cost
to Society of Consumer Product Injuries, CPSC-C-95-1164, National
Public Services Research Institute, January 1998.
38. Kaplan, R. and J. Bush, ``Health-Related Quality of Life
Measurement for Evaluation Research and Policy Analysis,'' Health
Psychology, vol. 1, no. 1, pp. 61-80, 1982.
List of Subjects in 21 CFR Part 1020
Electronic products, Medical devices, Radiation protection,
Reporting and recordkeeping requirements, Television, X-rays.
0
Therefore, under the Federal Food, Drug, and Cosmetic Act, and under
authority delegated to the Commissioner of Food and Drugs, 21 CFR part
1020 is amended as follows:
PART 1020--PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING
PRODUCTS
0
1. The authority citation for 21 CFR part 1020 continues to read as
follows:
Authority: 21 U.S.C. 351, 352, 360e-360j, 360gg-360ss, 371, 381.
0
2. Revise Sec. 1020.30 to read as follows:
Sec. 1020.30 Diagnostic x-ray systems and their major components.
(a) Applicability. (1) The provisions of this section are
applicable to:
(i) The following components of diagnostic x-ray systems:
(A) Tube housing assemblies, x-ray controls, x-ray high-voltage
generators, x-ray tables, cradles, film changers, vertical cassette
holders mounted in a fixed location and cassette holders with front
panels, and beam-limiting devices manufactured after August 1, 1974.
(B) Fluoroscopic imaging assemblies manufactured after August 1,
1974, and before April 26, 1977, or after June 10, 2006.
(C) Spot-film devices and image intensifiers manufactured after
April 26, 1977.
(D) Cephalometric devices manufactured after February 25, 1978.
(E) Image receptor support devices for mammographic x-ray systems
manufactured after September 5, 1978.
(F) Image receptors that are electrically powered or connected with
the x-ray system manufactured on or after June 10, 2006.
(G) Fluoroscopic air kerma display devices manufactured on or after
June 10, 2006.
(ii) Diagnostic x-ray systems, except computed tomography x-ray
systems, incorporating one or more of such
[[Page 34029]]
components; however, such x-ray systems shall be required to comply
only with those provisions of this section and Sec. Sec. 1020.31 and
1020.32, which relate to the components certified in accordance with
paragraph (c) of this section and installed into the systems.
(iii) Computed tomography (CT) x-ray systems manufactured before
November 29, 1984.
(iv) CT gantries manufactured after September 3, 1985.
(2) The following provisions of this section and Sec. 1020.33 are
applicable to CT x-ray systems manufactured or remanufactured on or
after November 29, 1984:
(i) Section 1020.30(a);
(ii) Section 1020.30(b) ``Technique factors'';
(iii) Section 1020.30(b) ``CT,'' ``Dose,'' ``Scan,'' ``Scan time,''
and ``Tomogram'';
(iv) Section 1020.30(h)(3)(vi) through (h)(3)(viii);
(v) Section 1020.30(n);
(vi) Section 1020.33(a) and (b);
(vii) Section 1020.33(c)(1) as it affects Sec. 1020.33(c)(2); and
(viii) Section 1020.33(c)(2).
(3) The provisions of this section and Sec. 1020.33 in its
entirety, including those provisions in paragraph (a)(2) of this
section, are applicable to CT x-ray systems manufactured or
remanufactured on or after September 3, 1985. The date of manufacture
of the CT system is the date of manufacture of the CT gantry.
(b) Definitions. As used in this section and Sec. Sec. 1020.31,
1020.32, and 1020.33, the following definitions apply:
Accessible surface means the external surface of the enclosure or
housing provided by the manufacturer.
Accessory component means:
(1) A component used with diagnostic x-ray systems, such as a
cradle or film changer, that is not necessary for the compliance of the
system with applicable provisions of this subchapter but which requires
an initial determination of compatibility with the system; or
(2) A component necessary for compliance of the system with
applicable provisions of this subchapter but which may be interchanged
with similar compatible components without affecting the system's
compliance, such as one of a set of interchangeable beam-limiting
devices; or
(3) A component compatible with all x-ray systems with which it may
be used and that does not require compatibility or installation
instructions, such as a tabletop cassette holder.
Air kerma means kerma in air (see definition of Kerma).
Air kerma rate (AKR) means the air kerma per unit time.
Aluminum equivalent means the thickness of aluminum (type 1100
alloy)\1\ affording the same attenuation, under specified conditions,
as the material in question.
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\1\ The nominal chemical composition of type 1100 aluminum alloy
is 99.00 percent minimum aluminum, 0.12 percent copper, as given in
``Aluminum Standards and Data'' (1969). Copies may be obtained from
The Aluminum Association, New York, NY.
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Articulated joint means a joint between two separate sections of a
tabletop which joint provides the capacity for one of the sections to
pivot on the line segment along which the sections join.
Assembler means any person engaged in the business of assembling,
replacing, or installing one or more components into a diagnostic x-ray
system or subsystem. The term includes the owner of an x-ray system or
his or her employee or agent who assembles components into an x-ray
system that is subsequently used to provide professional or commercial
services.
Attenuation block means a block or stack of type 1100 aluminum
alloy, or aluminum alloy having equivalent attenuation, with dimensions
20 centimeters (cm) or larger by 20 cm or larger by 3.8 cm, that is
large enough to intercept the entire x-ray beam.
Automatic exposure control (AEC) means a device which automatically
controls one or more technique factors in order to obtain at a
preselected location(s) a required quantity of radiation.
Automatic exposure rate control (AERC) means a device which
automatically controls one or more technique factors in order to obtain
at a preselected location(s) a required quantity of radiation per unit
time.
Beam axis means a line from the source through the centers of the
x-ray fields.
Beam-limiting device means a device which provides a means to
restrict the dimensions of the x-ray field.
C-arm fluoroscope means a fluoroscopic x-ray system in which the
image receptor and the x-ray tube housing assembly are connected or
coordinated to maintain a spatial relationship. Such a system allows a
change in the direction of the beam axis with respect to the patient
without moving the patient.
Cantilevered tabletop means a tabletop designed such that the
unsupported portion can be extended at least 100 cm beyond the support.
Cassette holder means a device, other than a spot-film device, that
supports and/or fixes the position of an x-ray film cassette during an
x-ray exposure.
Cephalometric device means a device intended for the radiographic
visualization and measurement of the dimensions of the human head.
Coefficient of variation means the ratio of the standard deviation
to the mean value of a population of observations. It is estimated
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR10JN05.001
where:
s = Estimated standard deviation of the population.
X = Mean value of observations in sample.
Xi = ith observation sampled.
n = Number of observations sampled.
Computed tomography (CT) means the production of a tomogram by the
acquisition and computer processing of x-ray transmission data.
Control panel means that part of the x-ray control upon which are
mounted the switches, knobs, pushbuttons, and other hardware necessary
for manually setting the technique factors.
Cooling curve means the graphical relationship between heat units
stored and cooling time.
Cradle means:
(1) A removable device which supports and may restrain a patient
above an x-ray table; or
[[Page 34030]]
(2) A device;
(i) Whose patient support structure is interposed between the
patient and the image receptor during normal use;
(ii) Which is equipped with means for patient restraint; and
(iii) Which is capable of rotation about its long (longitudinal)
axis.
CT gantry means tube housing assemblies, beam-limiting devices,
detectors, and the supporting structures, frames, and covers which hold
and/or enclose these components.
Cumulative air kerma means the total air kerma accrued from the
beginning of an examination or procedure and includes all contributions
from fluoroscopic and radiographic irradiation.
Diagnostic source assembly means the tube housing assembly with a
beam-limiting device attached.
Diagnostic x-ray system means an x-ray system designed for
irradiation of any part of the human body for the purpose of diagnosis
or visualization.
Dose means the absorbed dose as defined by the International
Commission on Radiation Units and Measurements. The absorbed dose, D,
is the quotient of de by dm, where de is the mean energy imparted to
matter of mass dm; thus D=de/dm, in units of J/kg, where the special
name for the unit of absorbed dose is gray (Gy).
Equipment means x-ray equipment.
Exposure (X) means the quotient of dQ by dm where dQ is the
absolute value of the total charge of the ions of one sign produced in
air when all the electrons and positrons liberated or created by
photons in air of mass dm are completely stopped in air; thus X=dQ/dm,
in units of C/kg. A second meaning of exposure is the process or
condition during which the x-ray tube produces x-ray radiation.
Field emission equipment means equipment which uses an x-ray tube
in which electron emission from the cathode is due solely to action of
an electric field.
Fluoroscopic air kerma display device means a device, subsystem, or
component that provides the display of AKR and cumulative air kerma
required by Sec. 1020.32(k). It includes radiation detectors, if any,
electronic and computer components, associated software, and data
displays.
Fluoroscopic imaging assembly means a subsystem in which x-ray
photons produce a set of fluoroscopic images or radiographic images
recorded from the fluoroscopic image receptor. It includes the image
receptor(s), electrical interlocks, if any, and structural material
providing linkage between the image receptor and diagnostic source
assembly.
Fluoroscopic irradiation time means the cumulative duration during
an examination or procedure of operator-applied continuous pressure to
the device, enabling x-ray tube activation in any fluoroscopic mode of
operation.
Fluoroscopy means a technique for generating x-ray images and
presenting them simultaneously and continuously as visible images. This
term has the same meaning as the term ``radioscopy'' in the standards
of the International Electrotechnical Commission.
General purpose radiographic x-ray system means any radiographic x-
ray system which, by design, is not limited to radiographic examination
of specific anatomical regions.
Half-value layer (HVL) means the thickness of specified material
which attenuates the beam of radiation to an extent such that the AKR
is reduced to one-half of its original value. In this definition the
contribution of all scattered radiation, other than any which might be
present initially in the beam concerned, is deemed to be excluded.
Image intensifier means a device, installed in its housing, which
instantaneously converts an x-ray pattern into a corresponding light
image of higher energy density.
Image receptor means any device, such as a fluorescent screen,
radiographic film, x-ray image intensifier tube, solid-state detector,
or gaseous detector, which transforms incident x-ray photons either
into a visible image or into another form which can be made into a
visible image by further transformations. In those cases where means
are provided to preselect a portion of the image receptor, the term
``image receptor'' shall mean the preselected portion of the device.
Image receptor support device means, for mammography x-ray systems,
that part of the system designed to support the image receptor during a
mammographic examination and to provide a primary protective barrier.
Isocenter means the center of the smallest sphere through which the
beam axis passes when the equipment moves through a full range of
rotations about its common center.
Kerma means the quantity as defined by the International Commission
on Radiation Units and Measurements. The kerma, K, is the quotient of
dEtr by dm, where dEtr is the sum of the initial
kinetic energies of all the charged particles liberated by uncharged
particles in a mass dm of material; thus K=dEtr/dm, in units
of J/kg, where the special name for the unit of kerma is gray (Gy).
When the material is air, the quantity is referred to as ``air kerma.''
Last-image-hold (LIH) radiograph means an image obtained either by
retaining one or more fluoroscopic images, which may be temporally
integrated, at the end of a fluoroscopic exposure or by initiating a
separate and distinct radiographic exposure automatically and
immediately in conjunction with termination of the fluoroscopic
exposure.
Lateral fluoroscope means the x-ray tube and image receptor
combination in a biplane system dedicated to the lateral projection. It
consists of the lateral x-ray tube housing assembly and the lateral
image receptor that are fixed in position relative to the table with
the x-ray beam axis parallel to the plane of the table.
Leakage radiation means radiation emanating from the diagnostic
source assembly except for:
(1) The useful beam; and
(2) Radiation produced when the exposure switch or timer is not
activated.
Leakage technique factors means the technique factors associated
with the diagnostic source assembly which are used in measuring leakage
radiation. They are defined as follows:
(1) For diagnostic source assemblies intended for capacitor energy
storage equipment, the maximum-rated peak tube potential and the
maximum-rated number of exposures in an hour for operation at the
maximum-rated peak tube potential with the quantity of charge per
exposure being 10 millicoulombs (or 10 mAs) or the minimum obtainable
from the unit, whichever is larger;
(2) For diagnostic source assemblies intended for field emission
equipment rated for pulsed operation, the maximum-rated peak tube
potential and the maximum-rated number of x-ray pulses in an hour for
operation at the maximum-rated peak tube potential; and
(3) For all other diagnostic source assemblies, the maximum-rated
peak tube potential and the maximum-rated continuous tube current for
the maximum-rated peak tube potential.
Light field means that area of the intersection of the light beam
from the beam-limiting device and one of the set of planes parallel to
and including the plane of the image receptor, whose perimeter is the
locus of points at which the illuminance is one-fourth of the maximum
in the intersection.
Line-voltage regulation means the difference between the no-load
and the load line potentials expressed as a
[[Page 34031]]
percent of the load line potential; that is,
Percent line-voltage regulation = 100(Vn -
Vi)/Vi
where:
Vn = No-load line potential and
Vi = Load line potential.
Maximum line current means the root mean square current in the
supply line of an x-ray machine operating at its maximum rating.
Mode of operation means, for fluoroscopic systems, a distinct
method of fluoroscopy or radiography provided by the manufacturer and
selected with a set of several technique factors or other control
settings uniquely associated with the mode. The set of distinct
technique factors and control settings for the mode may be selected by
the operation of a single control. Examples of distinct modes of
operation include normal fluoroscopy (analog or digital), high-level
control fluoroscopy, cineradiography (analog or digital), digital
subtraction angiography, electronic radiography using the fluoroscopic
image receptor, and photospot recording. In a specific mode of
operation, certain system variables affecting air kerma, AKR, or image
quality, such as image magnification, x-ray field size, pulse rate,
pulse duration, number of pulses, source-image receptor distance (SID),
or optical aperture, may be adjustable or may vary; their variation per
se does not comprise a mode of operation different from the one that
has been selected.
Movable tabletop means a tabletop which, when assembled for use, is
capable of movement with respect to its supporting structure within the
plane of the tabletop.
Non-image-intensified fluoroscopy means fluoroscopy using only a
fluorescent screen.
Peak tube potential means the maximum value of the potential
difference across the x-ray tube during an exposure.
Primary protective barrier means the material, excluding filters,
placed in the useful beam to reduce the radiation exposure for
protection purposes.
Pulsed mode means operation of the x-ray system such that the x-ray
tube current is pulsed by the x-ray control to produce one or more
exposure intervals of duration less than one-half second.
Quick change x-ray tube means an x-ray tube designed for use in its
associated tube housing such that:
(1) The tube cannot be inserted in its housing in a manner that
would result in noncompliance of the system with the requirements of
paragraphs (k) and (m) of this section;
(2) The focal spot position will not cause noncompliance with the
provisions of this section or Sec. 1020.31 or 1020.32;
(3) The shielding within the tube housing cannot be displaced; and
(4) Any removal and subsequent replacement of a beam-limiting
device during reloading of the tube in the tube housing will not result
in noncompliance of the x-ray system with the applicable field
limitation and alignment requirements of Sec. Sec. 1020.31 and
1020.32.
Radiation therapy simulation system means a radiographic or
fluoroscopic x-ray system intended for localizing the volume to be
exposed during radiation therapy and confirming the position and size
of the therapeutic irradiation field.
Radiography means a technique for generating and recording an x-ray
pattern for the purpose of providing the user with an image(s) after
termination of the exposure.
Rated line voltage means the range of potentials, in volts, of the
supply line specified by the manufacturer at which the x-ray machine is
designed to operate.
Rated output current means the maximum allowable load current of
the x-ray high-voltage generator.
Rated output voltage means the allowable peak potential, in volts,
at the output terminals of the x-ray high-voltage generator.
Rating means the operating limits specified by the manufacturer.
Recording means producing a retrievable form of an image resulting
from x-ray photons.
Scan means the complete process of collecting x-ray transmission
data for the production of a tomogram. Data may be collected
simultaneously during a single scan for the production of one or more
tomograms.
Scan time means the period of time between the beginning and end of
x-ray transmission data accumulation for a single scan.
Solid state x-ray imaging device means an assembly, typically in a
rectangular panel configuration, that intercepts x-ray photons and
converts the photon energy into a modulated electronic signal
representative of the x-ray intensity over the area of the imaging
device. The electronic signal is then used to create an image for
display and/or storage.
Source means the focal spot of the x-ray tube.
Source-image receptor distance (SID) means the distance from the
source to the center of the input surface of the image receptor.
Source-skin distance (SSD) means the distance from the source to
the center of the entrant x-ray field in the plane tangent to the
patient skin surface.
Spot-film device means a device intended to transport and/or
position a radiographic image receptor between the x-ray source and
fluoroscopic image receptor. It includes a device intended to hold a
cassette over the input end of the fluoroscopic image receptor for the
purpose of producing a radiograph.
Stationary tabletop means a tabletop which, when assembled for use,
is incapable of movement with respect to its supporting structure
within the plane of the tabletop.
Technique factors means the following conditions of operation:
(1) For capacitor energy storage equipment, peak tube potential in
kilovolts (kV) and quantity of charge in milliampere-seconds (mAs);
(2) For field emission equipment rated for pulsed operation, peak
tube potential in kV and number of x-ray pulses;
(3) For CT equipment designed for pulsed operation, peak tube
potential in kV, scan time in seconds, and either tube current in
milliamperes (mA), x-ray pulse width in seconds, and the number of x-
ray pulses per scan, or the product of the tube current, x-ray pulse
width, and the number of x-ray pulses in mAs;
(4) For CT equipment not designed for pulsed operation, peak tube
potential in kV, and either tube current in mA and scan time in
seconds, or the product of tube current and exposure time in mAs and
the scan time when the scan time and exposure time are equivalent; and
(5) For all other equipment, peak tube potential in kV, and either
tube current in mA and exposure time in seconds, or the product of tube
current and exposure time in mAs.
Tomogram means the depiction of the x-ray attenuation properties of
a section through a body.
Tube means an x-ray tube, unless otherwise specified.
Tube housing assembly means the tube housing with tube installed.
It includes high-voltage and/or filament transformers and other
appropriate elements when they are contained within the tube housing.
Tube rating chart means the set of curves which specify the rated
limits of operation of the tube in terms of the technique factors.
Useful beam means the radiation which passes through the tube
housing port and the aperture of the beam-limiting device when the
exposure switch or timer is activated.
Variable-aperture beam-limiting device means a beam-limiting device
which has the capacity for stepless
[[Page 34032]]
adjustment of the x-ray field size at a given SID.
Visible area means the portion of the input surface of the image
receptor over which incident x-ray photons are producing a visible
image.
X-ray control means a device which controls input power to the x-
ray high-voltage generator and/or the x-ray tube. It includes equipment
such as timers, phototimers, automatic brightness stabilizers, and
similar devices, which control the technique factors of an x-ray
exposure.
X-ray equipment means an x-ray system, subsystem, or component
thereof. Types of x-ray equipment are as follows:
(1) Mobile x-ray equipment means x-ray equipment mounted on a
permanent base with wheels and/or casters for moving while completely
assembled;
(2) Portable x-ray equipment means x-ray equipment designed to be
hand-carried; and
(3) Stationary x-ray equipment means x-ray equipment which is
installed in a fixed location.
X-ray field means that area of the intersection of the useful beam
and any one of the set of planes parallel to and including the plane of
the image receptor, whose perimeter is the locus of points at which the
AKR is one-fourth of the maximum in the intersection.
X-ray high-voltage generator means a device which transforms
electrical energy from the potential supplied by the x-ray control to
the tube operating potential. The device may also include means for
transforming alternating current to direct current, filament
transformers for the x-ray tube(s), high-voltage switches, electrical
protective devices, and other appropriate elements.
X-ray subsystem means any combination of two or more components of
an x-ray system for which there are requirements specified in this
section and Sec. Sec. 1020.31 and 1020.32.
X-ray system means an assemblage of components for the controlled
production of x-rays. It includes minimally an x-ray high-voltage
generator, an x-ray control, a tube housing assembly, a beam-limiting
device, and the necessary supporting structures. Additional components
which function with the system are considered integral parts of the
system.
X-ray table means a patient support device with its patient support
structure (tabletop) interposed between the patient and the image
receptor during radiography and/or fluoroscopy. This includes, but is
not limited to, any stretcher equipped with a radiolucent panel and any
table equipped with a cassette tray (or bucky), cassette tunnel,
fluoroscopic image receptor, or spot-film device beneath the tabletop.
X-ray tube means any electron tube which is designed for the
conversion of electrical energy into x-ray energy.
(c) Manufacturers' responsibility. Manufacturers of products
subject to Sec. Sec. 1020.30 through 1020.33 shall certify that each
of their products meet all applicable requirements when installed into
a diagnostic x-ray system according to instructions. This certification
shall be made under the format specified in Sec. 1010.2 of this
chapter. Manufacturers may certify a combination of two or more
components if they obtain prior authorization in writing from the
Director of the Office of Compliance of the Center for Devices and
Radiological Health (CDRH). Manufacturers shall not be held responsible
for noncompliance of their products if that noncompliance is due solely
to the improper installation or assembly of that product by another
person; however, manufacturers are responsible for providing assembly
instructions adequate to assure compliance of their components with the
applicable provisions of Sec. Sec. 1020.30 through 1020.33.
(d) Assemblers' responsibility. An assembler who installs one or
more components certified as required by paragraph (c) of this section
shall install certified components that are of the type required by
Sec. 1020.31, 1020.32, or 1020.33 and shall assemble, install, adjust,
and test the certified components according to the instructions of
their respective manufacturers. Assemblers shall not be liable for
noncompliance of a certified component if the assembly of that
component was according to the component manufacturer's instruction.
(1) Reports of assembly. All assemblers who install certified
components shall file a report of assembly, except as specified in
paragraph (d)(2) of this section. The report will be construed as the
assembler's certification and identification under Sec. Sec. 1010.2
and 1010.3 of this chapter. The assembler shall affirm in the report
that the manufacturer's instructions were followed in the assembly or
that the certified components as assembled into the system meet all
applicable requirements of Sec. Sec. 1020.30 through 1020.33. All
assembler reports must be on a form prescribed by the Director, CDRH.
Completed reports must be submitted to the Director, the purchaser,
and, where applicable, to the State agency responsible for radiation
protection within 15 days following completion of the assembly.
(2) Exceptions to reporting requirements. Reports of assembly need
not be submitted for any of the following:
(i) Reloaded or replacement tube housing assemblies that are
reinstalled in or newly assembled into an existing x-ray system;
(ii) Certified accessory components that have been identified as
such to CDRH in the report required under Sec. 1002.10 of this
chapter;
(iii) Repaired components, whether or not removed from the system
and reinstalled during the course of repair, provided the original
installation into the system was reported; or
(iv)(A) Components installed temporarily in an x-ray system in
place of components removed temporarily for repair, provided the
temporarily installed component is identified by a tag or label bearing
the following information:
Temporarily Installed Component
This certified component has been assembled, installed, adjusted,
and tested by me according to the instructions provided by the
manufacturer.
Signature
Company Name
Street Address, P.O. Box
City, State, Zip Code
Date of Installation
(B) The replacement of the temporarily installed component by a
component other than the component originally removed for repair shall
be reported as specified in paragraph (d)(1) of this section.
(e) Identification of x-ray components. In addition to the
identification requirements specified in Sec. 1010.3 of this chapter,
manufacturers of components subject to this section and Sec. Sec.
1020.31, 1020.32, and 1020.33, except high-voltage generators contained
within tube housings and beam-limiting devices that are integral parts
of tube housings, shall permanently inscribe or affix thereon the model
number and serial number of the product so that they are legible and
accessible to view. The word ``model'' or ``type'' shall appear as part
of the manufacturer's required identification of certified x-ray
components. Where the certification of a system or subsystem,
consisting of two or more components, has been authorized under
paragraph (c) of this section, a single inscription, tag, or label
bearing the model number and serial number may be used to identify the
product.
(1) Tube housing assemblies. In a similar manner, manufacturers of
tube housing assemblies shall also inscribe or affix thereon the name
of the manufacturer, model number, and serial
[[Page 34033]]
number of the x-ray tube which the tube housing assembly incorporates.
(2) Replacement of tubes. Except as specified in paragraph (e)(3)
of this section, the replacement of an x-ray tube in a previously
manufactured tube housing assembly certified under paragraph (c) of
this section constitutes manufacture of a new tube housing assembly,
and the manufacturer is subject to the provisions of paragraph (e)(1)
of this section. The manufacturer shall remove, cover, or deface any
previously affixed inscriptions, tags, or labels that are no longer
applicable.
(3) Quick-change x-ray tubes. The requirements of paragraph (e)(2)
of this section shall not apply to tube housing assemblies designed and
designated by their original manufacturer to contain quick change x-ray
tubes. The manufacturer of quick-change x-ray tubes shall include with
each replacement tube a label with the tube manufacturer's name, the
model, and serial number of the x-ray tube. The manufacturer of the
tube shall instruct the assembler who installs the new tube to attach
the label to the tube housing assembly and to remove, cover, or deface
the previously affixed inscriptions, tags, or labels that are described
by the tube manufacturer as no longer applicable.
(f) [Reserved]
(g) Information to be provided to assemblers. Manufacturers of
components listed in paragraph (a)(1) of this section shall provide to
assemblers subject to paragraph (d) of this section and, upon request,
to others at a cost not to exceed the cost of publication and
distribution, instructions for assembly, installation, adjustment, and
testing of such components adequate to assure that the products will
comply with applicable provisions of this section and Sec. Sec.
1020.31, 1020.32, and 1020.33, when assembled, installed, adjusted, and
tested as directed. Such instructions shall include specifications of
other components compatible with that to be installed when compliance
of the system or subsystem depends on their compatibility. Such
specifications may describe pertinent physical characteristics of the
components and/or may list by manufacturer model number the components
which are compatible. For x-ray controls and generators manufactured
after May 3, 1994, manufacturers shall provide:
(1) A statement of the rated line voltage and the range of line-
voltage regulation for operation at maximum line current;
(2) A statement of the maximum line current of the x-ray system
based on the maximum input voltage and current characteristics of the
tube housing assembly compatible with rated output voltage and rated
output current characteristics of the x-ray control and associated
high-voltage generator. If the rated input voltage and current
characteristics of the tube housing assembly are not known by the
manufacturer of the x-ray control and associated high-voltage
generator, the manufacturer shall provide information necessary to
allow the assembler to determine the maximum line current for the
particular tube housing assembly(ies);
(3) A statement of the technique factors that constitute the
maximum line current condition described in paragraph (g)(2) of this
section.
(h) Information to be provided to users. Manufacturers of x-ray
equipment shall provide to purchasers and, upon request, to others at a
cost not to exceed the cost of publication and distribution, manuals or
instruction sheets which shall include the following technical and
safety information:
(1) All x-ray equipment. For x-ray equipment to which this section
and Sec. Sec. 1020.31, 1020.32, and 1020.33 are applicable, there
shall be provided:
(i) Adequate instructions concerning any radiological safety
procedures and precautions which may be necessary because of unique
features of the equipment; and
(ii) A schedule of the maintenance necessary to keep the equipment
in compliance with this section and Sec. Sec. 1020.31, 1020.32, and
1020.33.
(2) Tube housing assemblies. For each tube housing assembly, there
shall be provided:
(i) Statements of the leakage technique factors for all
combinations of tube housing assemblies and beam-limiting devices for
which the tube housing assembly manufacturer states compatibility, the
minimum filtration permanently in the useful beam expressed as
millimeters (mm) of aluminum equivalent, and the peak tube potential at
which the aluminum equivalent was obtained;
(ii) Cooling curves for the anode and tube housing; and
(iii) Tube rating charts. If the tube is designed to operate from
different types of x-ray high-voltage generators (such as single-phase
self rectified, single-phase half-wave rectified, single-phase full-
wave rectified, 3-phase 6-pulse, 3-phase 12-pulse, constant potential,
capacitor energy storage) or under modes of operation such as alternate
focal spot sizes or speeds of anode rotation which affect its rating,
specific identification of the difference in ratings shall be noted.
(3) X-ray controls and generators. For the x-ray control and
associated x-ray high-voltage generator, there shall be provided:
(i) A statement of the rated line voltage and the range of line-
voltage regulation for operation at maximum line current;
(ii) A statement of the maximum line current of the x-ray system
based on the maximum input voltage and output current characteristics
of the tube housing assembly compatible with rated output voltage and
rated current characteristics of the x-ray control and associated high-
voltage generator. If the rated input voltage and current
characteristics of the tube housing assembly are not known by the
manufacturer of the x-ray control and associated high-voltage
generator, the manufacturer shall provide necessary information to
allow the purchaser to determine the maximum line current for his
particular tube housing assembly(ies);
(iii) A statement of the technique factors that constitute the
maximum line current condition described in paragraph (h)(3)(ii) of
this section;
(iv) In the case of battery-powered generators, a specification of
the minimum state of charge necessary for proper operation;
(v) Generator rating and duty cycle;
(vi) A statement of the maximum deviation from the preindication
given by labeled technique factor control settings or indicators during
any radiographic or CT exposure where the equipment is connected to a
power supply as described in accordance with this paragraph. In the
case of fixed technique factors, the maximum deviation from the nominal
fixed value of each factor shall be stated;
(vii) A statement of the maximum deviation from the continuous
indication of x-ray tube potential and current during any fluoroscopic
exposure when the equipment is connected to a power supply as described
in accordance with this paragraph; and
(viii) A statement describing the measurement criteria for all
technique factors used in paragraphs (h)(3)(iii), (h)(3)(vi), and
(h)(3)(vii) of this section; for example, the beginning and endpoints
of exposure time measured with respect to a certain percentage of the
voltage waveform.
(4) Beam-limiting device. For each variable-aperture beam-limiting
device, there shall be provided;
(i) Leakage technique factors for all combinations of tube housing
assemblies and beam-limiting devices
[[Page 34034]]
for which the beam-limiting device manufacturer states compatibility;
and
(ii) A statement including the minimum aluminum equivalent of that
part of the device through which the useful beam passes and including
the x-ray tube potential at which the aluminum equivalent was obtained.
When two or more filters are provided as part of the device, the
statement shall include the aluminum equivalent of each filter.
(5) Imaging system information. For x-ray systems manufactured on
or after June 10, 2006, that produce images using the fluoroscopic
image receptor, the following information shall be provided in a
separate, single section of the user's instruction manual or in a
separate manual devoted to this information:
(i) For each mode of operation, a description of the mode and
detailed instructions on how the mode is engaged and disengaged. The
description of the mode shall identify those technique factors and
system controls that are fixed or automatically adjusted by selection
of the mode of operation, including the manner in which the automatic
adjustment is controlled. This information shall include how the
operator can recognize which mode of operation has been selected prior
to initiation of x-ray production.
(ii) For each mode of operation, a descriptive example(s) of any
specific clinical procedure(s) or imaging task(s) for which the mode is
recommended or designed and how each mode should be used. Such
recommendations do not preclude other clinical uses.
(6) Displays of values of AKR and cumulative air kerma. For
fluoroscopic x-ray systems manufactured on or after June 10, 2006, the
following shall be provided:
(i) A schedule of maintenance for any system instrumentation
associated with the display of air kerma information necessary to
maintain the displays of AKR and cumulative air kerma within the limits
of allowed uncertainty specified by Sec. 1020.32(k)(6) and, if the
capability for user calibration of the display is provided, adequate
instructions for such calibration;
(ii) Identification of the distances along the beam axis:
(A) From the focal spot to the isocenter, and
(B) From the focal spot to the reference location to which
displayed values of AKR and cumulative air kerma refer according to
Sec. 1020.32(k)(4);
(iii) A rationale for specification of a reference irradiation
location alternative to 15 cm from the isocenter toward the x-ray
source along the beam axis when such alternative specification is made
according to Sec. 1020.32(k)(4)(ii).
(i) [Reserved]
(j) Warning label. The control panel containing the main power
switch shall bear the warning statement, legible and accessible to
view:
``Warning: This x-ray unit may be dangerous to patient and
operator unless safe exposure factors, operating instructions and
maintenance schedules are observed.''
(k) Leakage radiation from the diagnostic source assembly. The
leakage radiation from the diagnostic source assembly measured at a
distance of 1 meter in any direction from the source shall not exceed
0.88 milligray (mGy) air kerma (vice 100 milliroentgen (mR) exposure)
in 1 hour when the x-ray tube is operated at the leakage technique
factors. If the maximum rated peak tube potential of the tube housing
assembly is greater than the maximum rated peak tube potential for the
diagnostic source assembly, positive means shall be provided to limit
the maximum x-ray tube potential to that of the diagnostic source
assembly. Compliance shall be determined by measurements averaged over
an area of 100 square cm with no linear dimension greater than 20 cm.
(l) Radiation from components other than the diagnostic source
assembly. The radiation emitted by a component other than the
diagnostic source assembly shall not exceed an air kerma of 18 microGy
(vice 2 mR exposure) in 1 hour at 5 cm from any accessible surface of
the component when it is operated in an assembled x-ray system under
any conditions for which it was designed. Compliance shall be
determined by measurements averaged over an area of 100 square cm with
no linear dimension greater than 20 cm.
(m) Beam quality--(1) Half-value layer (HVL). The HVL of the useful
beam for a given x-ray tube potential shall not be less than the
appropriate value shown in table 1 in paragraph (m)(1) of this section
under the heading ``Specified Dental Systems,'' for any dental x-ray
system designed for use with intraoral image receptors and manufactured
after December 1, 1980; under the heading ``I--Other X-Ray Systems,''
for any dental x-ray system designed for use with intraoral image
receptors and manufactured before December 1, 1980, and all other x-ray
systems subject to this section and manufactured before June 10, 2006;
and under the heading ``II--Other X-Ray Systems,'' for all x-ray
systems, except dental x-ray systems designed for use with intraoral
image receptors, subject to this section and manufactured on or after
June 10, 2006. If it is necessary to determine such HVL at an x-ray
tube potential which is not listed in table 1 in paragraph (m)(1) of
this section, linear interpolation or extrapolation may be made.
Positive means\2\ shall be provided to ensure that at least the minimum
filtration needed to achieve the above beam quality requirements is in
the useful beam during each exposure. Table 1 follows:
---------------------------------------------------------------------------
\2\ In the case of a system, which is to be operated with more
than one thickness of filtration, this requirement can be met by a
filter interlocked with the kilovoltage selector which will prevent
x-ray emissions if the minimum required filtration is not in place.
Table 1.
--------------------------------------------------------------------------------------------------------------------------------------------------------
X-Ray Tube Voltage (kilovolt peak) Minimum HVL (mm of aluminum)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Measured Operating Specified Dental I--Other X-Ray II--Other X-Ray
Designed Operating Range Potential Systems\1\ Systems\2\ Systems\3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Below 51 30 1.5 0.3 0.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
40 1.5 0.4 0.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
50 1.5 0.5 0.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
51 to 70 51 1.5 1.2 1.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 34035]]
60 1.5 1.3 1.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
70 1.5 1.5 1.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
Above 70 71 2.1 2.1 2.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
80 2.3 2.3 2.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
90 2.5 2.5 3.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
100 2.7 2.7 3.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
110 3.0 3.0 3.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
120 3.2 3.2 4.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
130 3.5 3.5 4.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
140 3.8 3.8 5.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
150 4.1 4.1 5.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Dental x-ray systems designed for use with intraoral image receptors and manufactured after December 1, 1980.
\2\ Dental x-ray systems designed for use with intraoral image receptors and manufactured before or on December 1, 1980, and all other x-ray systems
subject to this section and manufactured before June 10, 2006.
\3\ All x-ray systems, except dental x-ray systems designed for use with intraoral image receptors, subject to this section and manufactured on or after
June 10, 2006.
(2) Optional filtration. Fluoroscopic systems manufactured on or
after June 10, 2006, incorporating an x-ray tube(s) with a continuous
output of 1 kilowatt or more and an anode heat storage capacity of 1
million heat units or more shall provide the option of adding x-ray
filtration to the diagnostic source assembly in addition to the amount
needed to meet the HVL provisions of Sec. 1020.30(m)(1). The selection
of this additional x-ray filtration shall be either at the option of
the user or automatic as part of the selected mode of operation. A
means of indicating which combination of additional filtration is in
the x-ray beam shall be provided.
(3) Measuring compliance. For capacitor energy storage equipment,
compliance shall be determined with the maximum selectable quantity of
charge per exposure.
(n) Aluminum equivalent of material between patient and image
receptor. Except when used in a CT x-ray system, the aluminum
equivalent of each of the items listed in table 2 in paragraph (n) of
this section, which are used between the patient and image receptor,
may not exceed the indicated limits. Compliance shall be determined by
x-ray measurements made at a potential of 100 kilovolts peak and with
an x-ray beam that has an HVL specified in table 1 in paragraph (m)(1)
of this section for the potential. This requirement applies to front
panel(s) of cassette holders and film changers provided by the
manufacturer for patient support or for prevention of foreign object
intrusions. It does not apply to screens and their associated
mechanical support panels or grids. Table 2 follows:
Table 2.
------------------------------------------------------------------------
Maximum Aluminum
Item Equivalent
(millimeters)
------------------------------------------------------------------------
1. Front panel(s) of cassette holders (total of all) 1.2
------------------------------------------------------------------------
2. Front panel(s) of film changer (total of all) 1.2
------------------------------------------------------------------------
3. Cradle 2.3
------------------------------------------------------------------------
4. Tabletop, stationary, without articulated joints 1.2
------------------------------------------------------------------------
5. Tabletop, movable, without articulated joint(s) 1.7
(including stationary subtop)
------------------------------------------------------------------------
6. Tabletop, with radiolucent panel having one 1.7
articulated joint
------------------------------------------------------------------------
7. Tabletop, with radiolucent panel having two or 2.3
more articulated joints
------------------------------------------------------------------------
8. Tabletop, cantilevered 2.3
------------------------------------------------------------------------
9. Tabletop, radiation therapy simulator 5.0
------------------------------------------------------------------------
[[Page 34036]]
(o) Battery charge indicator. On battery-powered generators, visual
means shall be provided on the control panel to indicate whether the
battery is in a state of charge adequate for proper operation.
(p) [Reserved]
(q) Modification of certified diagnostic x-ray components and
systems. (1) Diagnostic x-ray components and systems certified in
accordance with Sec. 1010.2 of this chapter shall not be modified such
that the component or system fails to comply with any applicable
provision of this chapter unless a variance in accordance with Sec.
1010.4 of this chapter or an exemption under section 534(a)(5) or
538(b) of the Federal Food, Drug, and Cosmetic Act has been granted.
(2) The owner of a diagnostic x-ray system who uses the system in a
professional or commercial capacity may modify the system, provided the
modification does not result in the failure of the system or component
to comply with the applicable requirements of this section or of Sec.
1020.31, 1020.32, or 1020.33. The owner who causes such modification
need not submit the reports required by subpart B of part 1002 of this
chapter, provided the owner records the date and the details of the
modification in the system records and maintains this information, and
provided the modification of the x-ray system does not result in a
failure to comply with Sec. 1020.31, 1020.32, or 1020.33.
0
3. Revise Sec. 1020.31 to read as follows:
Sec. 1020.31 Radiographic equipment.
The provisions of this section apply to equipment for radiography,
except equipment for fluoroscopic imaging or for recording images from
the fluoroscopic image receptor, or computed tomography x-ray systems
manufactured on or after November 29, 1984.
(a) Control and indication of technique factors--(1) Visual
indication. The technique factors to be used during an exposure shall
be indicated before the exposure begins, except when automatic exposure
controls are used, in which case the technique factors which are set
prior to the exposure shall be indicated. On equipment having fixed
technique factors, this requirement may be met by permanent markings.
Indication of technique factors shall be visible from the operator's
position except in the case of spot films made by the fluoroscopist.
(2) Timers. Means shall be provided to terminate the exposure at a
preset time interval, a preset product of current and time, a preset
number of pulses, or a preset radiation exposure to the image receptor.
(i) Except during serial radiography, the operator shall be able to
terminate the exposure at any time during an exposure of greater than
one-half second. Except during panoramic dental radiography,
termination of exposure shall cause automatic resetting of the timer to
its initial setting or to zero. It shall not be possible to make an
exposure when the timer is set to a zero or off position if either
position is provided.
(ii) During serial radiography, the operator shall be able to
terminate the x-ray exposure(s) at any time, but means may be provided
to permit completion of any single exposure of the series in process.
(3) Automatic exposure controls. When an automatic exposure control
is provided:
(i) Indication shall be made on the control panel when this mode of
operation is selected;
(ii) When the x-ray tube potential is equal to or greater than 51
kilovolts peak (kVp), the minimum exposure time for field emission
equipment rated for pulsed operation shall be equal to or less than a
time interval equivalent to two pulses and the minimum exposure time
for all other equipment shall be equal to or less than 1/60 second or a
time interval required to deliver 5 milliampere-seconds (mAs),
whichever is greater;
(iii) Either the product of peak x-ray tube potential, current, and
exposure time shall be limited to not more than 60 kilowatt-seconds
(kWs) per exposure or the product of x-ray tube current and exposure
time shall be limited to not more than 600 mAs per exposure, except
when the x-ray tube potential is less than 51 kVp, in which case the
product of x-ray tube current and exposure time shall be limited to not
more than 2,000 mAs per exposure; and
(iv) A visible signal shall indicate when an exposure has been
terminated at the limits described in paragraph (a)(3)(iii) of this
section, and manual resetting shall be required before further
automatically timed exposures can be made.
(4) Accuracy. Deviation of technique factors from indicated values
shall not exceed the limits given in the information provided in
accordance with Sec. 1020.30(h)(3).
(b) Reproducibility. The following requirements shall apply when
the equipment is operated on an adequate power supply as specified by
the manufacturer in accordance with the requirements of Sec.
1020.30(h)(3):
(1) Coefficient of variation. For any specific combination of
selected technique factors, the estimated coefficient of variation of
the air kerma shall be no greater than 0.05.
(2) Measuring compliance. Determination of compliance shall be
based on 10 consecutive measurements taken within a time period of 1
hour. Equipment manufactured after September 5, 1978, shall be subject
to the additional requirement that all variable controls for technique
factors shall be adjusted to alternate settings and reset to the test
setting after each measurement. The percent line-voltage regulation
shall be determined for each measurement. All values for percent line-
voltage regulation shall be within 1 of the mean value for
all measurements. For equipment having automatic exposure controls,
compliance shall be determined with a sufficient thickness of
attenuating material in the useful beam such that the technique factors
can be adjusted to provide individual exposures of a minimum of 12
pulses on field emission equipment rated for pulsed operation or no
less than one-tenth second per exposure on all other equipment.
(c) Linearity. The following requirements apply when the equipment
is operated on a power supply as specified by the manufacturer in
accordance with the requirements of Sec. 1020.30(h)(3) for any fixed
x-ray tube potential within the range of 40 percent to 100 percent of
the maximum rated.
(1) Equipment having independent selection of x-ray tube current
(mA). The average ratios of air kerma to the indicated milliampere-
seconds product (mGy/mAs) obtained at any two consecutive tube current
settings shall not differ by more than 0.10 times their sum. This is:
|X1 - X2| <= 0.10(X1 + X2);
where X1 and X2 are the average mGy/mAs values
obtained at each of two consecutive mAs selector settings or at two
settings differing by no more than a factor of 2 where the mAs selector
provides continuous selection.
(2) Equipment having selection of x-ray tube current-exposure time
product (mAs). For equipment manufactured after May 3, 1994, the
average ratios of air kerma to the indicated milliampere-seconds
product (mGy/mAs) obtained at any two consecutive mAs selector settings
shall not differ by more than 0.10 times their sum. This is:
|X1 - X2| <= 0.10 (X1 +
X2); where X1 and X2 are the average
mGy/mAs values obtained at each of two consecutive mAs selector
settings or at two settings differing by no more than a factor of 2
where the mAs selector provides continuous selection.
[[Page 34037]]
(3) Measuring compliance. Determination of compliance will be based
on 10 exposures, made within 1 hour, at each of the two settings. These
two settings may include any two focal spot sizes except where one is
equal to or less than 0.45 mm and the other is greater than 0.45 mm.
For purposes of this requirement, focal spot size is the focal spot
size specified by the x-ray tube manufacturer. The percent line-voltage
regulation shall be determined for each measurement. All values for
percent line-voltage regulation at any one combination of technique
factors shall be within 1 of the mean value for all
measurements at these technique factors.
(d) Field limitation and alignment for mobile, portable, and
stationary general purpose x-ray systems. Except when spot-film devices
are in service, mobile, portable, and stationary general purpose
radiographic x-ray systems shall meet the following requirements:
(1) Variable x-ray field limitation. A means for stepless
adjustment of the size of the x-ray field shall be provided. Each
dimension of the minimum field size at an SID of 100 centimeters (cm)
shall be equal to or less than 5 cm.
(2) Visual definition. (i) Means for visually defining the
perimeter of the x-ray field shall be provided. The total misalignment
of the edges of the visually defined field with the respective edges of
the x-ray field along either the length or width of the visually
defined field shall not exceed 2 percent of the distance from the
source to the center of the visually defined field when the surface
upon which it appears is perpendicular to the axis of the x-ray beam.
(ii) When a light localizer is used to define the x-ray field, it
shall provide an average illuminance of not less than 160 lux (15
footcandles) at 100 cm or at the maximum SID, whichever is less. The
average illuminance shall be based on measurements made in the
approximate center of each quadrant of the light field. Radiation
therapy simulation systems are exempt from this requirement.
(iii) The edge of the light field at 100 cm or at the maximum SID,
whichever is less, shall have a contrast ratio, corrected for ambient
lighting, of not less than 4 in the case of beam-limiting devices
designed for use on stationary equipment, and a contrast ratio of not
less than 3 in the case of beam-limiting devices designed for use on
mobile and portable equipment. The contrast ratio is defined as
I1/I2, where I1 is the illuminance 3
mm from the edge of the light field toward the center of the field; and
I2 is the illuminance 3 mm from the edge of the light field
away from the center of the field. Compliance shall be determined with
a measuring aperture of 1 mm.
(e) Field indication and alignment on stationary general purpose x-
ray equipment. Except when spot-film devices are in service, stationary
general purpose x-ray systems shall meet the following requirements in
addition to those prescribed in paragraph (d) of this section:
(1) Means shall be provided to indicate when the axis of the x-ray
beam is perpendicular to the plane of the image receptor, to align the
center of the x-ray field with respect to the center of the image
receptor to within 2 percent of the SID, and to indicate the SID to
within 2 percent;
(2) The beam-limiting device shall numerically indicate the field
size in the plane of the image receptor to which it is adjusted;
(3) Indication of field size dimensions and SIDs shall be specified
in centimeters and/or inches and shall be such that aperture
adjustments result in x-ray field dimensions in the plane of the image
receptor which correspond to those indicated by the beam-limiting
device to within 2 percent of the SID when the beam axis is indicated
to be perpendicular to the plane of the image receptor; and
(4) Compliance measurements will be made at discrete SIDs and image
receptor dimensions in common clinical use (such as SIDs of 100, 150,
and 200 cm and/or 36, 40, 48, and 72 inches and nominal image receptor
dimensions of 13, 18, 24, 30, 35, 40, and 43 cm and/or 5, 7, 8, 9, 10,
11, 12, 14, and 17 inches) or at any other specific dimensions at which
the beam-limiting device or its associated diagnostic x-ray system is
uniquely designed to operate.
(f) Field limitation on radiographic x-ray equipment other than
general purpose radiographic systems--(1) Equipment for use with
intraoral image receptors. Radiographic equipment designed for use with
an intraoral image receptor shall be provided with means to limit the
x-ray beam such that:
(i) If the minimum source-to-skin distance (SSD) is 18 cm or more,
the x-ray field at the minimum SSD shall be containable in a circle
having a diameter of no more than 7 cm; and
(ii) If the minimum SSD is less than 18 cm, the x-ray field at the
minimum SSD shall be containable in a circle having a diameter of no
more than 6 cm.
(2) X-ray systems designed for one image receptor size.
Radiographic equipment designed for only one image receptor size at a
fixed SID shall be provided with means to limit the field at the plane
of the image receptor to dimensions no greater than those of the image
receptor, and to align the center of the x-ray field with the center of
the image receptor to within 2 percent of the SID, or shall be provided
with means to both size and align the x-ray field such that the x-ray
field at the plane of the image receptor does not extend beyond any
edge of the image receptor.
(3) Systems designed for mammography--(i) Radiographic systems
designed only for mammography and general purpose radiography systems,
when special attachments for mammography are in service, manufactured
on or after November 1, 1977, and before September 30, 1999, shall be
provided with means to limit the useful beam such that the x-ray field
at the plane of the image receptor does not extend beyond any edge of
the image receptor at any designated SID except the edge of the image
receptor designed to be adjacent to the chest wall where the x-ray
field may not extend beyond this edge by more than 2 percent of the
SID. This requirement can be met with a system that performs as
prescribed in paragraphs (f)(4)(i), (f)(4)(ii), and (f)(4)(iii) of this
section. When the beam-limiting device and image receptor support
device are designed to be used to immobilize the breast during a
mammographic procedure and the SID may vary, the SID indication
specified in paragraphs (f)(4)(ii) and (f)(4)(iii) of this section
shall be the maximum SID for which the beam-limiting device or aperture
is designed.
(ii) Mammographic beam-limiting devices manufactured on or after
September 30, 1999, shall be provided with a means to limit the useful
beam such that the x-ray field at the plane of the image receptor does
not extend beyond any edge of the image receptor by more than 2 percent
of the SID. This requirement can be met with a system that performs as
prescribed in paragraphs (f)(4)(i), (f)(4)(ii), and (f)(4)(iii) of this
section. For systems that allow changes in the SID, the SID indication
specified in paragraphs (f)(4)(ii) and (f)(4)(iii) of this section
shall be the maximum SID for which the beam-limiting device or aperture
is designed.
(iii) Each image receptor support device manufactured on or after
November 1, 1977, intended for installation on a system designed for
mammography shall have clear and permanent markings to indicate the
maximum image receptor size for which it is designed.
[[Page 34038]]
(4) Other x-ray systems. Radiographic systems not specifically
covered in paragraphs (d), (e), (f)(2), (f)(3), and (h) of this section
and systems covered in paragraph (f)(1) of this section, which are also
designed for use with extraoral image receptors and when used with an
extraoral image receptor, shall be provided with means to limit the x-
ray field in the plane of the image receptor so that such field does
not exceed each dimension of the image receptor by more than 2 percent
of the SID, when the axis of the x-ray beam is perpendicular to the
plane of the image receptor. In addition, means shall be provided to
align the center of the x-ray field with the center of the image
receptor to within 2 percent of the SID, or means shall be provided to
both size and align the x-ray field such that the x-ray field at the
plane of the image receptor does not extend beyond any edge of the
image receptor. These requirements may be met with:
(i) A system which performs in accordance with paragraphs (d) and
(e) of this section; or when alignment means are also provided, may be
met with either;
(ii) An assortment of removable, fixed-aperture, beam-limiting
devices sufficient to meet the requirement for each combination of
image receptor size and SID for which the unit is designed. Each such
device shall have clear and permanent markings to indicate the image
receptor size and SID for which it is designed; or
(iii) A beam-limiting device having multiple fixed apertures
sufficient to meet the requirement for each combination of image
receptor size and SID for which the unit is designed. Permanent,
clearly legible markings shall indicate the image receptor size and SID
for which each aperture is designed and shall indicate which aperture
is in position for use.
(g) Positive beam limitation (PBL). The requirements of this
paragraph shall apply to radiographic systems which contain PBL.
(1) Field size. When a PBL system is provided, it shall prevent x-
ray production when:
(i) Either the length or width of the x-ray field in the plane of
the image receptor differs from the corresponding image receptor
dimension by more than 3 percent of the SID; or
(ii) The sum of the length and width differences as stated in
paragraph (g)(1)(i) of this section without regard to sign exceeds 4
percent of the SID.
(iii) The beam limiting device is at an SID for which PBL is not
designed for sizing.
(2) Conditions for PBL. When provided, the PBL system shall
function as described in paragraph (g)(1) of this section whenever all
the following conditions are met:
(i) The image receptor is inserted into a permanently mounted
cassette holder;
(ii) The image receptor length and width are less than 50 cm;
(iii) The x-ray beam axis is within 3 degrees of
vertical and the SID is 90 cm to 130 cm inclusive; or the x-ray beam
axis is within 3 degrees of horizontal and the SID is 90 cm
to 205 cm inclusive;
(iv) The x-ray beam axis is perpendicular to the plane of the image
receptor to within 3 degrees; and
(v) Neither tomographic nor stereoscopic radiography is being
performed.
(3) Measuring compliance. Compliance with the requirements of
paragraph (g)(1) of this section shall be determined when the equipment
indicates that the beam axis is perpendicular to the plane of the image
receptor and the provisions of paragraph (g)(2) of this section are
met. Compliance shall be determined no sooner than 5 seconds after
insertion of the image receptor.
(4) Operator initiated undersizing. The PBL system shall be capable
of operation such that, at the discretion of the operator, the size of
the field may be made smaller than the size of the image receptor
through stepless adjustment of the field size. Each dimension of the
minimum field size at an SID of 100 cm shall be equal to or less than 5
cm. Return to PBL function as described in paragraph (g)(1) of this
section shall occur automatically upon any change of image receptor
size or SID.
(5) Override of PBL. A capability may be provided for overriding
PBL in case of system failure and for servicing the system. This
override may be for all SIDs and image receptor sizes. A key shall be
required for any override capability that is accessible to the
operator. It shall not be possible to remove the key while PBL is
overridden. Each such key switch or key shall be clearly and durably
labeled as follows:
For X-ray Field Limitation System Failure
The override capability is considered accessible to the operator if
it is referenced in the operator's manual or in other material
intended for the operator or if its location is such that the
operator would consider it part of the operational controls.
(h) Field limitation and alignment for spot-film devices. The
following requirements shall apply to spot-film devices, except when
the spot-film device is provided for use with a radiation therapy
simulation system:
(1) Means shall be provided between the source and the patient for
adjustment of the x-ray field size in the plane of the image receptor
to the size of that portion of the image receptor which has been
selected on the spot-film selector. Such adjustment shall be
accomplished automatically when the x-ray field size in the plane of
the image receptor is greater than the selected portion of the image
receptor. If the x-ray field size is less than the size of the selected
portion of the image receptor, the field size shall not open
automatically to the size of the selected portion of the image receptor
unless the operator has selected that mode of operation.
(2) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall differ from the corresponding
dimensions of the selected portion of the image receptor by more than 3
percent of the SID when adjusted for full coverage of the selected
portion of the image receptor. The sum, without regard to sign, of the
length and width differences shall not exceed 4 percent of the SID. On
spot-film devices manufactured after February 25, 1978, if the angle
between the plane of the image receptor and beam axis is variable,
means shall be provided to indicate when the axis of the x-ray beam is
perpendicular to the plane of the image receptor, and compliance shall
be determined with the beam axis indicated to be perpendicular to the
plane of the image receptor.
(3) The center of the x-ray field in the plane of the image
receptor shall be aligned with the center of the selected portion of
the image receptor to within 2 percent of the SID.
(4) Means shall be provided to reduce the x-ray field size in the
plane of the image receptor to a size smaller than the selected portion
of the image receptor such that:
(i) For spot-film devices used on fixed-SID fluoroscopic systems
which are not required to, and do not provide stepless adjustment of
the x-ray field, the minimum field size, at the greatest SID, does not
exceed 125 square cm; or
(ii) For spot-film devices used on fluoroscopic systems that have a
variable SID and/or stepless adjustment of the field size, the minimum
field size, at the greatest SID, shall be containable in a square of 5
cm by 5 cm.
(5) A capability may be provided for overriding the automatic x-ray
field size adjustment in case of system failure. If it is so provided,
a signal visible at the fluoroscopist's position shall indicate
whenever the automatic x-ray field size adjustment override is engaged.
Each
[[Page 34039]]
such system failure override switch shall be clearly labeled as
follows:
For X-ray Field Limitation System Failure
(i) Source-skin distance--(1) X-ray systems designed for use with
an intraoral image receptor shall be provided with means to limit the
source-skin distance to not less than:
(i) Eighteen cm if operable above 50 kVp; or
(ii) Ten cm if not operable above 50 kVp.
(2) Mobile and portable x-ray systems other than dental shall be
provided with means to limit the source-skin distance to not less than
30 cm.
(j) Beam-on indicators. The x-ray control shall provide visual
indication whenever x-rays are produced. In addition, a signal audible
to the operator shall indicate that the exposure has terminated.
(k) Multiple tubes. Where two or more radiographic tubes are
controlled by one exposure switch, the tube or tubes which have been
selected shall be clearly indicated before initiation of the exposure.
This indication shall be both on the x-ray control and at or near the
tube housing assembly which has been selected.
(l) Radiation from capacitor energy storage equipment. Radiation
emitted from the x-ray tube shall not exceed:
(1) An air kerma of 0.26 microGy (vice 0.03 mR exposure) in 1
minute at 5 cm from any accessible surface of the diagnostic source
assembly, with the beam-limiting device fully open, the system fully
charged, and the exposure switch, timer, or any discharge mechanism not
activated. Compliance shall be determined by measurements averaged over
an area of 100 square cm, with no linear dimension greater than 20 cm;
and
(2) An air kerma of 0.88 mGy (vice 100 mR exposure) in 1 hour at
100 cm from the x-ray source, with the beam-limiting device fully open,
when the system is discharged through the x-ray tube either manually or
automatically by use of a discharge switch or deactivation of the input
power. Compliance shall be determined by measurements of the maximum
air kerma per discharge multiplied by the total number of discharges in
1 hour (duty cycle). The measurements shall be averaged over an area of
100 square cm with no linear dimension greater than 20 cm.
(m) Primary protective barrier for mammography x-ray systems--(1)
For x-ray systems manufactured after September 5, 1978, and before
September 30, 1999, which are designed only for mammography, the
transmission of the primary beam through any image receptor support
provided with the system shall be limited such that the air kerma 5 cm
from any accessible surface beyond the plane of the image receptor
supporting device does not exceed 0.88 microGy (vice 0.1 mR exposure)
for each activation of the tube.
(2) For mammographic x-ray systems manufactured on or after
September 30, 1999:
(i) At any SID where exposures can be made, the image receptor
support device shall provide a primary protective barrier that
intercepts the cross section of the useful beam along every direction
except at the chest wall edge.
(ii) The x-ray system shall not permit exposure unless the
appropriate barrier is in place to intercept the useful beam as
required in paragraph (m)(2)(i) of this section.
(iii) The transmission of the useful beam through the primary
protective barrier shall be limited such that the air kerma 5 cm from
any accessible surface beyond the plane of the primary protective
barrier does not exceed 0.88 microGy (vice 0.1 mR exposure) for each
activation of the tube.
(3) Compliance with the requirements of paragraphs (m)(1) and
(m)(2)(iii) of this section for transmission shall be determined with
the x-ray system operated at the minimum SID for which it is designed,
at the maximum rated peak tube potential, at the maximum rated product
of x-ray tube current and exposure time (mAs) for the maximum rated
peak tube potential, and by measurements averaged over an area of 100
square cm with no linear dimension greater than 20 cm. The sensitive
volume of the radiation measuring instrument shall not be positioned
beyond the edge of the primary protective barrier along the chest wall
side.
0
4. Revise Sec. 1020.32 to read as follows:
Sec. 1020.32 Fluoroscopic equipment.
The provisions of this section apply to equipment for fluoroscopic
imaging or for recording images from the fluoroscopic image receptor,
except computed tomography x-ray systems manufactured on or after
November 29, 1984.
(a) Primary protective barrier--(1) Limitation of useful beam. The
fluoroscopic imaging assembly shall be provided with a primary
protective barrier which intercepts the entire cross section of the
useful beam at any SID. The x-ray tube used for fluoroscopy shall not
produce x-rays unless the barrier is in position to intercept the
entire useful beam. The AKR due to transmission through the barrier
with the attenuation block in the useful beam combined with radiation
from the fluoroscopic image receptor shall not exceed 3.34 x
10-3 percent of the entrance AKR, at a distance of 10 cm
from any accessible surface of the fluoroscopic imaging assembly beyond
the plane of the image receptor. Radiation therapy simulation systems
shall be exempt from this requirement provided the systems are intended
only for remote control operation and the manufacturer sets forth
instructions for assemblers with respect to control location as part of
the information required in Sec. 1020.30(g). Additionally, the
manufacturer shall provide to users, under Sec. 1020.30(h)(1)(i),
precautions concerning the importance of remote control operation.
(2) Measuring compliance. The AKR shall be measured in accordance
with paragraph (d) of this section. The AKR due to transmission through
the primary barrier combined with radiation from the fluoroscopic image
receptor shall be determined by measurements averaged over an area of
100 square cm with no linear dimension greater than 20 cm. If the
source is below the tabletop, the measurement shall be made with the
input surface of the fluoroscopic imaging assembly positioned 30 cm
above the tabletop. If the source is above the tabletop and the SID is
variable, the measurement shall be made with the end of the beam-
limiting device or spacer as close to the tabletop as it can be placed,
provided that it shall not be closer than 30 cm. Movable grids and
compression devices shall be removed from the useful beam during the
measurement. For all measurements, the attenuation block shall be
positioned in the useful beam 10 cm from the point of measurement of
entrance AKR and between this point and the input surface of the
fluoroscopic imaging assembly.
(b) Field limitation--(1) Angulation. For fluoroscopic equipment
manufactured after February 25, 1978, when the angle between the image
receptor and the beam axis of the x-ray beam is variable, means shall
be provided to indicate when the axis of the x-ray beam is
perpendicular to the plane of the image receptor. Compliance with
paragraphs (b)(4) and (b)(5) of this section shall be determined with
the beam axis indicated to be perpendicular to the plane of the image
receptor.
(2) Further means for limitation. Means shall be provided to permit
further limitation of the x-ray field to sizes smaller than the limits
of paragraphs (b)(4) and (b)(5). Beam-limiting devices manufactured
after May 22, 1979, and incorporated in equipment with a variable SID
and/or
[[Page 34040]]
the capability of a visible area of greater than 300 square cm, shall
be provided with means for stepless adjustment of the x-ray field.
Equipment with a fixed SID and the capability of a visible area of no
greater than 300 square cm shall be provided with either stepless
adjustment of the x-ray field or with a means to further limit the x-
ray field size at the plane of the image receptor to 125 square cm or
less. Stepless adjustment shall, at the greatest SID, provide
continuous field sizes from the maximum obtainable to a field size
containable in a square of 5 cm by 5 cm. This paragraph does not apply
to non-image-intensified fluoroscopy.
(3) Non-image-intensified fluoroscopy. The x-ray field produced by
non-image-intensified fluoroscopic equipment shall not extend beyond
the entire visible area of the image receptor. Means shall be provided
for stepless adjustment of field size. The minimum field size, at the
greatest SID, shall be containable in a square of 5 cm by 5 cm.
(4) Fluoroscopy and radiography using the fluoroscopic imaging
assembly with inherently circular image receptors. (i) For fluoroscopic
equipment manufactured before June 10, 2006, other than radiation
therapy simulation systems, the following applies:
(A) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall exceed that of the visible area of
the image receptor by more than 3 percent of the SID. The sum of the
excess length and the excess width shall be no greater than 4 percent
of the SID.
(B) For rectangular x-ray fields used with circular image
receptors, the error in alignment shall be determined along the length
and width dimensions of the x-ray field which pass through the center
of the visible area of the image receptor.
(ii) For fluoroscopic equipment manufactured on or after June 10,
2006, other than radiation therapy simulation systems, the maximum area
of the x-ray field in the plane of the image receptor shall conform
with one of the following requirements:
(A) When any linear dimension of the visible area of the image
receptor measured through the center of the visible area is less than
or equal to 34 cm in any direction, at least 80 percent of the area of
the x-ray field overlaps the visible area of the image receptor, or
(B) When any linear dimension of the visible area of the image
receptor measured through the center of the visible area is greater
than 34 cm in any direction, the x-ray field measured along the
direction of greatest misalignment with the visible area of the image
receptor does not extend beyond the edge of the visible area of the
image receptor by more than 2 cm.
(5) Fluoroscopy and radiography using the fluoroscopic imaging
assembly with inherently rectangular image receptors. For x-ray systems
manufactured on or after June 10, 2006, the following applies:
(i) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall exceed that of the visible area of
the image receptor by more than 3 percent of the SID. The sum of the
excess length and the excess width shall be no greater than 4 percent
of the SID.
(ii) The error in alignment shall be determined along the length
and width dimensions of the x-ray field which pass through the center
of the visible area of the image receptor.
(6) Override capability. If the fluoroscopic x-ray field size is
adjusted automatically as the SID or image receptor size is changed, a
capability may be provided for overriding the automatic adjustment in
case of system failure. If it is so provided, a signal visible at the
fluoroscopist's position shall indicate whenever the automatic field
adjustment is overridden. Each such system failure override switch
shall be clearly labeled as follows:
For X-ray Field Limitation System Failure
(c) Activation of tube. X-ray production in the fluoroscopic mode
shall be controlled by a device which requires continuous pressure by
the operator for the entire time of any exposure. When recording serial
radiographic images from the fluoroscopic image receptor, the operator
shall be able to terminate the x-ray exposure(s) at any time, but means
may be provided to permit completion of any single exposure of the
series in process.
(d) Air kerma rates. For fluoroscopic equipment, the following
requirements apply:
(1) Fluoroscopic equipment manufactured before May 19, 1995--(i)
Equipment provided with automatic exposure rate control (AERC) shall
not be operable at any combination of tube potential and current that
will result in an AKR in excess of 88 mGy per minute (vice 10 R/min
exposure rate) at the measurement point specified in Sec.
1020.32(d)(3), except as specified in Sec. 1020.32(d)(1)(v).
(ii) Equipment provided without AERC shall not be operable at any
combination of tube potential and current that will result in an AKR in
excess of 44 mGy per minute (vice 5 R/min exposure rate) at the
measurement point specified in Sec. 1020.32(d)(3), except as specified
in Sec. 1020.32(d)(1)(v).
(iii) Equipment provided with both an AERC mode and a manual mode
shall not be operable at any combination of tube potential and current
that will result in an AKR in excess of 88 mGy per minute (vice 10 R/
min exposure rate) in either mode at the measurement point specified in
Sec. 1020.32(d)(3), except as specified in Sec. 1020.32(d)(1)(v).
(iv) Equipment may be modified in accordance with Sec. 1020.30(q)
to comply with Sec. 1020.32(d)(2). When the equipment is modified, it
shall bear a label indicating the date of the modification and the
statement:
Modified to comply with 21 CFR 1020.32(h)(2).
(v) Exceptions:
(A) During recording of fluoroscopic images, or
(B) When a mode of operation has an optional high-level control, in
which case that mode shall not be operable at any combination of tube
potential and current that will result in an AKR in excess of the rates
specified in Sec. 1020.32(d)(1)(i), (d)(1)(ii), or (d)(1)(iii) at the
measurement point specified in Sec. 1020.32(d)(3), unless the high-
level control is activated. Special means of activation of high-level
controls shall be required. The high-level control shall be operable
only when continuous manual activation is provided by the operator. A
continuous signal audible to the fluoroscopist shall indicate that the
high-level control is being employed.
(2) Fluoroscopic equipment manufactured on or after May 19, 1995--
(i) Shall be equipped with AERC if operable at any combination of tube
potential and current that results in an AKR greater than 44 mGy per
minute (vice 5 R/min exposure rate) at the measurement point specified
in Sec. 1020.32(d)(3). Provision for manual selection of technique
factors may be provided.
(ii) Shall not be operable at any combination of tube potential and
current that will result in an AKR in excess of 88 mGy per minute (vice
10 R/min exposure rate) at the measurement point specified in Sec.
1020.32(d)(3), except as specified in Sec. 1020.32(d)(2)(iii):
(iii) Exceptions:
(A) For equipment manufactured prior to June 10, 2006, during the
recording of images from a fluoroscopic image receptor using
photographic film or a video camera when the x-ray source is operated
in a pulsed mode.
(B) For equipment manufactured on or after June 10, 2006, during
the recording of images from the fluoroscopic image receptor for the
purpose of providing the user with a recorded image(s) after
termination of
[[Page 34041]]
the exposure. Such recording does not include images resulting from a
last-image-hold feature that are not recorded.
(C) When a mode of operation has an optional high-level control and
the control is activated, in which case the equipment shall not be
operable at any combination of tube potential and current that will
result in an AKR in excess of 176 mGy per minute (vice 20 R/min
exposure rate) at the measurement point specified in Sec.
1020.32(d)(3). Special means of activation of high-level controls shall
be required. The high-level control shall be operable only when
continuous manual activation is provided by the operator. A continuous
signal audible to the fluoroscopist shall indicate that the high-level
control is being employed.
(3) Measuring compliance. Compliance with paragraph (d) of this
section shall be determined as follows:
(i) If the source is below the x-ray table, the AKR shall be
measured at 1 cm above the tabletop or cradle.
(ii) If the source is above the x-ray table, the AKR shall be
measured at 30 cm above the tabletop with the end of the beam-limiting
device or spacer positioned as closely as possible to the point of
measurement.
(iii) In a C-arm type of fluoroscope, the AKR shall be measured at
30 cm from the input surface of the fluoroscopic imaging assembly, with
the source positioned at any available SID, provided that the end of
the beam-limiting device or spacer is no closer than 30 cm from the
input surface of the fluoroscopic imaging assembly.
(iv) In a C-arm type of fluoroscope having an SID less than 45 cm,
the AKR shall be measured at the minimum SSD.
(v) In a lateral type of fluoroscope, the air kerma rate shall be
measured at a point 15 cm from the centerline of the x-ray table and in
the direction of the x-ray source with the end of the beam-limiting
device or spacer positioned as closely as possible to the point of
measurement. If the tabletop is movable, it shall be positioned as
closely as possible to the lateral x-ray source, with the end of the
beam-limiting device or spacer no closer than 15 cm to the centerline
of the x-ray table.
(4) Exemptions. Fluoroscopic radiation therapy simulation systems
are exempt from the requirements set forth in paragraph (d) of this
section.
(e) [Reserved]
(f) Indication of potential and current. During fluoroscopy and
cinefluorography, x-ray tube potential and current shall be
continuously indicated. Deviation of x-ray tube potential and current
from the indicated values shall not exceed the maximum deviation as
stated by the manufacturer in accordance with Sec. 1020.30(h)(3).
(g) Source-skin distance. (1) Means shall be provided to limit the
source-skin distance to not less than 38 cm on stationary fluoroscopes
and to not less than 30 cm on mobile and portable fluoroscopes. In
addition, for fluoroscopes intended for specific surgical application
that would be prohibited at the source-skin distances specified in this
paragraph, provisions may be made for operation at shorter source-skin
distances but in no case less than 20 cm. When provided, the
manufacturer must set forth precautions with respect to the optional
means of spacing, in addition to other information as required in Sec.
1020.30(h).
(2) For stationary, mobile, or portable C-arm fluoroscopic systems
manufactured on or after June 10, 2006, having a maximum source-image
receptor distance of less than 45 cm, means shall be provided to limit
the source-skin distance to not less than 19 cm. Such systems shall be
labeled for extremity use only. In addition, for those systems intended
for specific surgical application that would be prohibited at the
source-skin distances specified in this paragraph, provisions may be
made for operation at shorter source-skin distances but in no case less
than 10 cm. When provided, the manufacturer must set forth precautions
with respect to the optional means of spacing, in addition to other
information as required in Sec. 1020.30(h).
(h) Fluoroscopic irradiation time, display, and signal. (1)(i)
Fluoroscopic equipment manufactured before June 10, 2006, shall be
provided with means to preset the cumulative irradiation time of the
fluoroscopic tube. The maximum cumulative time of the timing device
shall not exceed 5 minutes without resetting. A signal audible to the
fluoroscopist shall indicate the completion of any preset cumulative
irradiation-time. Such signal shall continue to sound while x-rays are
produced until the timing device is reset. Fluoroscopic equipment may
be modified in accordance with Sec. 1020.30(q) to comply with the
requirements of Sec. 1020.32(h)(2). When the equipment is modified, it
shall bear a label indicating the statement:
Modified to comply with 21 CFR 1020.32(h)(2).
(ii) As an alternative to the requirements of this paragraph,
radiation therapy simulation systems may be provided with a means to
indicate the total cumulative exposure time during which x-rays were
produced, and which is capable of being reset between x-ray
examinations.
(2) For x-ray controls manufactured on or after June 10, 2006,
there shall be provided for each fluoroscopic tube:
(i) A display of the fluoroscopic irradiation time at the
fluoroscopist's working position. This display shall function
independently of the audible signal described in Sec.
1020.32(h)(2)(ii). The following requirements apply:
(A) When the x-ray tube is activated, the fluoroscopic irradiation
time in minutes and tenths of minutes shall be continuously displayed
and updated at least once every 6 seconds.
(B) The fluoroscopic irradiation time shall also be displayed
within 6 seconds of termination of an exposure and remain displayed
until reset.
(C) Means shall be provided to reset the display to zero prior to
the beginning of a new examination or procedure.
(ii) A signal audible to the fluoroscopist shall sound for each
passage of 5 minutes of fluoroscopic irradiation time during an
examination or procedure. The signal shall sound until manually reset
or, if automatically reset, for at least 2 second.
(i) Mobile and portable fluoroscopes. In addition to the other
requirements of this section, mobile and portable fluoroscopes shall
provide an image receptor incorporating more than a simple fluorescent
screen.
(j) Display of last-image-hold (LIH). Fluoroscopic equipment
manufactured on or after June 10, 2006, shall be equipped with means to
display LIH image following termination of the fluoroscopic exposure.
(1) For an LIH image obtained by retaining pretermination
fluoroscopic images, if the number of images and method of combining
images are selectable by the user, the selection shall be indicated
prior to initiation of the fluoroscopic exposure.
(2) For an LIH image obtained by initiating a separate
radiographic-like exposure at the termination of fluoroscopic imaging,
the techniques factors for the LIH image shall be selectable prior to
the fluoroscopic exposure, and the combination selected shall be
indicated prior to initiation of the fluoroscopic exposure.
(3) Means shall be provided to clearly indicate to the user whether
a displayed image is the LIH radiograph or fluoroscopy. Display of the
LIH radiograph shall be replaced by the fluoroscopic image concurrently
with re-initiation of fluoroscopic exposure, unless separate displays
are provided for the LIH radiograph and fluoroscopic images.
[[Page 34042]]
(4) The predetermined or selectable options for producing the LIH
radiograph shall be described in the information required by Sec.
1020.30(h). The information shall include a description of any
technique factors applicable for the selected option and the impact of
the selectable options on image characteristics and the magnitude of
radiation emissions.
(k) Displays of values of AKR and cumulative air kerma.
Fluoroscopic equipment manufactured on or after June 10, 2006, shall
display at the fluoroscopist's working position the AKR and cumulative
air kerma. The following requirements apply for each x-ray tube used
during an examination or procedure:
(1) When the x-ray tube is activated and the number of images
produced per unit time is greater than six images per second, the AKR
in mGy/min shall be continuously displayed and updated at least once
every second.
(2) The cumulative air kerma in units of mGy shall be displayed
either within 5 seconds of termination of an exposure or displayed
continuously and updated at least once every 5 seconds.
(3) The display of the AKR shall be clearly distinguishable from
the display of the cumulative air kerma.
(4) The AKR and cumulative air kerma shall represent the value for
conditions of free-in-air irradiation at one of the following reference
locations specified according to the type of fluoroscope. The reference
location shall be identified and described specifically in the
information provided to users according to Sec. 1020.30(h)(6)(iii).
(i) For fluoroscopes with x-ray source below the x-ray table, x-ray
source above the table, or of lateral type, the reference locations
shall be the respective locations specified in Sec. 1020.32(d)(3)(i),
(d)(3)(ii), or (d)(3)(v) for measuring compliance with air-kerma rate
limits.
(ii) For C-arm fluoroscopes, the reference location shall be 15 cm
from the isocenter toward the x-ray source along the beam axis.
Alternatively, the reference location shall be at a point specified by
the manufacturer to represent the location of the intersection of the
x-ray beam with the patient's skin.
(5) Means shall be provided to reset to zero the display of
cumulative air kerma prior to the commencement of a new examination or
procedure.
(6) The displayed AKR and cumulative air kerma shall not deviate
from the actual values by more than 35 percent over the
range of 6 mGy/min and 100 mGy to the maximum indication of AKR and
cumulative air kerma, respectively. Compliance shall be determined with
an irradiation time greater than 3 seconds.
0
5. Amend Sec. 1020.33 by revising paragraph (h)(2) to read as follows:
Sec. 1020.33 Computed tomography (CT) equipment.
* * * * *
(h) * * *
(2) For systems that allow high voltage to be applied to the x-ray
tube continuously and that control the emission of x-ray with a
shutter, the radiation emitted may not exceed 0.88 milligray (vice 100
milliroentgen exposure) in 1 hour at any point 5 cm outside the
external surface of the housing of the scanning mechanism when the
shutter is closed. Compliance shall be determined by measurements
average over an area of 100 square cm with no linear dimension greater
than 20 cm.
* * * * *
Dated: May 31, 2005.
Jeffrey Shuren,
Assistant Commissioner for Policy.
[FR Doc. 05-11480 Filed 6-7-05; 10:51 am]
BILLING CODE 4160-01-S