Level 3: Lacking direct evidence
CT scans provide much more detailed images than plain x-rays but expose patients to much higher doses of radiation. In a cross-sectional retrospective study of 11 CT procedures, researchers estimated the amount of radiation internal organs would be exposed to and calculated the lifetime attributable risk of cancer from each procedure (Arch Intern Med. 2009;169:2078-2086). Analyses, performed by gender and by age groups, found that women had a higher risk than men and that younger patients had a higher risk than older patients. For a 20-year-old woman having a routine chest CT, her lifetime attributable risk of cancer due to radiation from the CT scan was 1 in 390, compared with 1 in 150 for a CT angiogram and 1 in 470 for a routine CT of the abdomen and pelvis. The effective radiation dose for each type of procedure was also reported in terms of an equivalent number of chest x-rays. A multiphase CT of the abdomen and pelvis was equivalent to 442 chest x-rays, and CT angiography was equivalent to 309.