Lifetime exposure to radiation from imaging investigations

To assess levels of radiation exposure from diagnostic imaging among family practice patients, the degree to which these levels exceed recommended levels, and whether radiation exposure level is associated with a diagnosis of cancer.

Chart abstraction.

Six practices in an academic family medicine centre and 1 family practice in the community.

Two hundred fifty patients between the ages of 45 and 65 years with at least 20 years' information on their charts.

All x-ray procedures, the dates they were performed, the amount of radiation exposure from each procedure based on standard charts, and whether diagnosis of any form of cancer was noted on the chart.

Mean lifetime radiation exposure was 14.94 mSv. No patients had exceeded the lifetime occupational limit of 400 mSv; however, 4.4% of patients had exceeded the annual occupational exposure limit of 20 mSv at some point in their lives. Mean lifetime exposure of those with cancer was found to be significantly higher than exposure of those without cancer. This difference was due to the extra radiation exposure after the cancer was diagnosed; hence a causal relationship was not shown. Mean level of annual radiation exposure from diagnostic imaging has been slowly increasing since the 1960s.

The current lifetime level of radiation to which patients are exposed by diagnostic imaging appears to be far below the maximum recommended level. Some patients do exceed the maximum recommended annual level, but this overexposure is generally warranted due to serious medical illness or injury, and the benefit outweighs the risk. We found no evidence of an association between these low levels of radiation and development of cancer.