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Jeff Sutherland

Twice the Energy with Half the Stress

CT Scans: High Risk of Cancer

More Cancer Risk Seen in Full-Body CT Scans

By Thomas H. Maugh II and Daniel Costello, Los Angeles Times, 31 Aug 2004

Whole-body CT scans, long controversial because of doubts about their effectiveness in finding hidden disease, can significantly increase the recipient’s risk of developing cancer, according to a study released Monday.

The radiation from a single whole-body scan is equal to that from 100 mammograms and is similar to that received by survivors of the atomic bombings of Hiroshima and Nagasaki, Japan — about 1 1/2 miles from the explosions — according to radiation biologist David J. Brenner of Columbia University.

The radiation from one scan is enough to produce a tumor in every 1,200 people who undergo the procedure, reported Brenner and coauthor Carl D. Elliston of Columbia in the journal Radiology. For those who have annual scans, the risk goes as high as one tumor in every 50 people, they said.

Brenner, D. J. and C. D. Elliston (2004). “Estimated Radiation Risks Potentially Associated with Full-Body CT Screening.” Radiology 232(3): 735-738.

PURPOSE: To estimate the radiation-related cancer mortality risks associated with single or repeated full-body computed tomographic (CT) examinations by using standard radiation risk estimation methods.

MATERIALS AND METHODS: The estimated dose to the lung or stomach from a single full-body CT examination is 14-21 mGy, which corresponds to a dose region for which there is direct evidence of increased cancer mortality in atomic bomb survivors. Total doses for repeated examinations are correspondingly higher. The authors used estimated cancer risks in a U.S. population derived from atomic bomb-associated cancer mortality data, together with calculated organ doses from a full-body CT examination, to estimate the radiation risks associated with single and multiple full-body CT examinations.

RESULTS: A single full-body CT examination in a 45-year-old adult would result in an estimated lifetime attributable cancer mortality risk of around 0.08%, with the 95% credibility limits being a factor of 3.2 in either direction. A 45-year-old adult who plans to undergo annual full-body CT examinations up to age 75 (30 examinations) would accrue an overall estimated lifetime attributable risk of cancer mortality of about 1.9%, with the 95% credibility limits being a factor of 2 in either direction.

CONCLUSION: The authors provide estimates of lifetime cancer mortality risks from both single and annual full-body CT examinations. These risk estimates are needed to assess the utility of full-body CT examinations from both an individual and a public health perspective. (C) RSNA, 2004