Computed tomography scan hazard.

Computed tomography (CT) exposes patients to higher levels of radiation than most doctors realize, according to a review article in the New England Journal of Medicine. In CT (also known as CAT) scans, a computer integrates X-rays taken from different angles to form a detailed cross section picture. Radiation dosage varies with the organ being scanned, the size of the patient, and the scanner being used. (The 64-slice scanner emits more radiation.)ACT scan of the abdomen exposes patients to 10 mSv of radiation, 500 times the radiation produced during a single chest X-ray. Studies of radiation workers in the nuclear industry and of Japanese survivors of atomic-bomb blasts show a significant increase in cancer risk among people who receive between 5 and 150 mSv.

Most practitioners and patients are unaware of CT's risks. In the NEJM review article, Columbia University researchers David J. Brenner and Eric J. Hall report that about 75% of surveyed radiologists and emergency room physicians "significantly underestimated the radiation dose from a "CT scan" (Radiology, 2004; 231: 393-8). When disease symptoms are present, CT scans often help determine a diagnosis. However, too many people without any symptoms at all undergo CT screening "just in case." Even the FDA discourages this growing practice of CT screening: "... the FDA has never approved CT for screening any part of the body for any specific disease, let alone for screening the whole body when there are no specific symptoms of disease at all." Another concern is the growing use of CT scans to diagnose appendicitis in children. Children are more sensitive to radiation than adults. Ultrasonography, for the most part, is just as accurate as CT but does not cause radiation damage.

Brenner and Hall suggest three ways to lessen CT radiation exposure. First, newer scanners have an automatic exposure-control option that helps reduce radiation dose to patients. Brenner and Hall also suggest using magnetic resonance imaging (MRI) or ultrasonography whenever possible. (CT is the most accurate diagnostic technology for some conditions.) Finally, Brenner and Hall recommend prescribing CT only when symptoms and a lack of diagnostic alternatives justify its use. They write, "... if it is true that about one-third of all CT scans are not justified by medical need, and it appears to be likely, perhaps 20 million adults and, crucially, more than one million children per year in the United States are being irradiated unnecessarily."

Brenner DJ, Hall EJ. Computed tomography--an increasing source of radiation exposure. The New England Journal of Medicine. November 29, 2007; 357(22): 2277-2284. Available at: www.nejm.org. Accessed October 5, 2008.

Ozner M. Avoiding the radiation dangers of cardiac CAT scans. Life Extension. March 2008: 51-59.

US Food and Drug Administration. Whole body scanning using computed tomography (CT) April 17, 2002 (last update). Available at: www.fda.gov/cdrh/ct/screening.html.Accessed October 5,2008.