Two studies appearing in the Dec. 14/28 issue of Archives of Internal Medicine have concluded that radiation doses from commonly performed CT scans are higher than previously believed and may be the cause of tens of thousands of future cancer cases.
In the first study, "Radiation Dose Associated With Common Computed Tomography Examinations and the Associated Lifetime Attributable Risk of Cancer," researchers at the University of California at San Francisco studied more than 1,000 patients undergoing 11 common types of CT scans and found that radiation dosage and associated cancer risks varied widely between different types of scans. Routine head CT scans typically had the lowest radiation doses while multiphase abdomen and pelvis scans had the highest. Researchers also found that the average radiation dose for the same CT procedure had a thirteenfold variation depending on who performed the scan and the facility where it was done.
Cancer risks resulting from CT scans varied by type of procedure and each patient's age and sex, researchers found. About one in 270 women and one in 600 men undergoing CT heart scans at age 40 will develop cancer as a result, for example.
National Cancer Institute researchers conducting the second study, "Projected Cancer Risks from Computed Tomographic Scans Performed in the United States in 2007," estimated that about 29,000 people will develop cancer as a result of CT scans performed during 2007. About one-third of those cases will occur in people who received the scan between the ages of 35 and 54, researchers said.