Organ doses and associated cancer risks for computed tomography examinations of the thoracic region

The use of computed tomography is increasing rapidly and doses are not negligible especially when medical procedures require more than one scan. The purpose of the present study was to measure doses in an anthropomorphic Rando phantom during a standard and low dose computed tomography protocol of the thorax and to estimate risks of radiation induced cancer for adult patients that undergo multiple computed tomography scans of the thorax. Thermoluminescent and radiophotoluminescent dosimeters were used for dose measurements. Radiation risks of cancer incidence, in the form of lifetime attributable risk, were estimated using the BEIR VII model. For five exposures with the standard protocol mean organ doses were 94 mGy (breast), 85 mGy (stomach), 85 mGy (thyroid), 78 mGy (lung), 52 mGy (liver), and 16 mGy (colon). Associated lifetime attributable risk were found to be up to 0.401 % (401 breast cancers per 100 000 exposed patients) and 0.116 % (116 lung cancers per 100 000 exposed patients) for female and male, respectively. A low dose protocol reduces doses (and risks) by the average factor of 5 and therefore the use of a low dose protocol is recommended whenever it is medicaly justified