some medical imaging facilities are promoting a new use of computed
tomography (CT), also called computerized axial tomography (CAT)
scanning. This use is referred to as whole-body CT scanning or whole-body
CT screening, and it is marketed as a preventive or proactive healthcare
measure to healthy individuals who have no symptoms or suspicion
of disease. At this time the FDA knows of no data demonstrating
that whole-body CT screening is effective in detecting any particular
disease early enough for the disease to be managed, treated, or
cured and advantageously spare a person at least some of the detriment
associated with serious illness or premature death. Any such
presumed benefit of whole-body CT screening is currently uncertain,
and such benefit may not be great enough to offset the potential
harms such screening could cause.
Public health agencies and national medical and professional societies-the
College of Radiology, the American
College of Cardiology / American Heart Association, the
Association of Physicists in Medicine, the Health
Physics Society, the Agency for Healthcare Research
and Quality's U.S.
Preventive Services Task Force, and the American
Medical Association - do not recommend CT screening.
CT is a diagnostic imaging procedure that
uses x rays to obtain cross-sectional images of the body. Since
its introduction and rapid adoption into medicine in the mid-1970s,
CT has become recognized as a valuable medical tool for the diagnosis
of disease, trauma, or abnormality and for planning, guiding, and
Important information regarding whole-body CT screening:
- Such screening provides uncertain
benefit with potential for some risk - The most likely
outcomes of CT screening of a healthy person with no symptoms
of illness are:
- Normal findings or
- Suspicious findings requiring follow-up tests
Normal findings carry the possibility of inaccuracy and false
reassurance. For suspicious findings, follow-up may involve
simple, non-invasive testing. It may also involve invasive procedures
associated with surgical risks of anesthesia, bleeding, infection,
scarring, or it may entail additional radiological exams, associated
with radiation risk and the potential risk of allergic reaction
to injected contrast material. In any case, it is unlikely that
CT screening will benefit an individual lacking signs or symptoms
of disease by detecting a serious disease early enough to treat
it and alter the outcome significantly.
- Radiation Dose - CT screening
subjects the individual screened to radiation exposure from x
rays. The dose a patient receives during
a typical CT procedure is generally much larger than the radiation
doses associated with most conventional x-ray imaging procedures.
The principal risk associated with the radiation dose resulting
to a person from a CT procedure is the small possibility of developing
a radiation-induced cancer some time later in that person's life.
For a patient with a medical need, the benefit of a diagnostic
or therapeutic CT procedure recommended by a physician normally
far exceeds the small cancer risk associated with a CT procedure.
For a person without symptoms, CT screening is unlikely to discover
serious disease, and the potential harm to the individual may
be greater than the presumed benefit.
- Scientific Studies - There are no data demonstrating
that whole-body CT screening of individuals without symptoms
provides a greater probability of benefit than harm. Nor is there
any scientific study known to be underway to develop such data.
Although there are several ongoing
investigational studies of the effectiveness of using CT to
screen people, the studies are focused on high-risk groups for
specific diseases (e.g., cigarette smokers for lung cancer). In
such studies only a limited portion of the body is irradiated,
not the whole body, and only screening for a specific type of
disease is being evaluated, rather than screening for just anything
that might be found anywhere in the body.
- No Food and Drug Administration
(FDA) Approval of CT for Screening - Statements by CT
imaging facilities that imply FDA "approval," "clearance,"
or "certification" of CT for screening procedures misrepresent
the actual situation. FDA has never approved or cleared or certified
any CT system specifically for use in screening (i.e., of individuals
without symptoms), because no manufacturer has ever demonstrated
to the FDA that their CT scanner is effective for screening for
any disease or condition.
- Pediatric Use - Radiation exposure is a concern
in both adults and children. However, children are more sensitive
to radiation than adults and have a longer life expectancy. Using
the same exposure parameters on a child as used on an adult may
result in larger doses to the child. There is no need for these
larger doses to children, and CT settings can be adjusted to reduce
dose significantly while maintaining diagnostic image quality.
The National Cancer Institute and The Society for Pediatric Radiology
developed a brochure, Radiation
Risks and Pediatric Computed Tomography: A Guide for Health Care
Providers, and the FDA issued a Public Health Notification,
Radiation Risk from Computed Tomography for Pediatric and Small
Adult Patients, that discuss the value of CT and the
importance of minimizing the radiation dose, especially in children.
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