Technique Factor Selection and Display

Questions Key Words/Related Topics

Citation:

900.12(b)(9)(i),(ii),(iii): Technique factor selection and display.

(i) Manual selection of milliampere seconds (mAs) or at least one of its component parts (milliampere (mA) and/or time) shall be available.

(ii) The technique factors (peak tube potential in kilovolt (kV) and either tube current in mA and exposure time in seconds or the product of tube current and exposure time in mAs) to be used during an exposure shall be indicated before the exposure begins, except when automatic exposure controls (AEC) are used, in which case the technique factors that are set prior to the exposure shall be indicated.

(iii) Following the AEC mode use, the system shall indicate the actual kilovoltage peak (kVp) and mAs used during the exposure. The mAs may he displayed as mA and time.

Discussion:

Question 1: Would an x-ray unit with both a manual mode and an automatic exposure control mode assure that the mAs selection requirement is met?

Question 2: When used in manual mode a facility's x-ray unit displays kVp, mA, and time before the exposure. When in AEC mode, the display usually changes from the preset indications after the exposure. Does this meet the requirement?

Question 3: Are there any specific requirements for the mechanism of the display required by 900.12(b)(9)(iii)?

Question 4: If only the preset kVp is displayed by the unit when used in the AEC mode, is it necessary for a "preset" indication of mA and/or mAs to be indicated prior to the exposure?

Question 1: Would an x-ray unit with both a manual mode and an automatic exposure control mode assure that the mAs selection requirement is met?

Yes. If the system has a manual mode, then the selection of the mAs or a component part (mA or time) will be available to the operator. A properly functioning manual mode would ensure that the requirement is satisfied.

Question 2: When used in manual mode a facility’s x-ray unit displays kVp, mA, and time before the exposure. When in AEC mode, the display usually changes from the preset indications after the exposure. Does this meet the requirement?

Yes.

Question 3: Are there any specific requirements for the mechanism of the display required by 900.12(b)(9)(iii)?

No. Under a separate FDA performance standard, the Diagnostic X-ray Performance Standard, the display must be clear, legible, and visible to the operator at the unit or the operator control location. The actual mechanism can be achieved in any manner that provides the required information in an unambiguous fashion.

Question 4: If only the preset kVp is displayed by the unit when used in the AEC mode, is it necessary for a "preset" indication of mA and/or mAs to be indicated prior to the exposure?

Any technique factor that is set prior to exposure in the AEC mode must be indicated. However, the indication need not be by digital display or dial. With units where the kVp is the only factor under direct control of the operator, the corresponding preset mA or mAs may be set automatically by the unit and may not be normally visible on the control panel. However, these corresponding values should be available from the manufacturer, if standard for the model, or from the installer, if they can be set to meet the needs of the facility. If these values are given on a label attached to the control panel or on the technique chart, the unit will be in compliance with this requirement.

Key Words:

Equipment

Technique Factors

Kilovoltage Peak

Automatic Exposure Control (AEC)

Related Topics:

Automatic Exposure Control (AEC)

Automatic Exposure Control (AEC) Annual Quality Control Test

Kilovoltage Peak Annual Quality Control Test