ABSTRACT. Proper use of medical imaging tools requires knowledge of their associated radiation risks, as well as their possible benefits. The authors assessed physicians’ knowledge of the radiation risks associated with bone scintigraphy (bone scan) during an annual meeting of the Israeli Orthopedic Society. The mortality risk of radiation-induced carcinoma from bone scan was identified correctly by less than 5% of respondents. The most frequent answer (38.4%) was the option that was least correct. Senior orthopedists estimated lower risks than did residents. Overall, respondents grossly underestimated the potential radiation risk from bone scan.

IONIZING RADIATION from occupational exposures is subject to strict international regulations. The regulations, derived from a linear model, (1) set annual occupational exposure limits at 20 mSv (2 rem). (2) Annual ionizing radiation exposure limits for the general public are set at 1 mSv (0.1 rem). Assuming the dose is delivered incrementally, 1 mSv carries a 4/100,000 chance of producing a fatal cancer. A person exposed annually to 1 mSv for 60 yr has a 60 times greater risk for cancer (or 24/10,000). (3)

Regulations limiting exposure to ionizing radiation do not apply to patients undergoing medical evaluation or treatment. The responsibility for deciding whether a patient should undergo radiotherapy is delegated to the physician, who has to compare the benefit of the procedure with the expected risk involved. This judgment requires the physician to have a clear knowledge of the ionizing radiation risks associated with specific imaging techniques. (4)

Physicians usually conceptualize the radiation dose associated with a specific medical imaging test by comparing the test to a standard: the chest radiograph (x-ray). For example, computerized tomography (CT) of the lumbar spine has a radiation dose equivalent to 250 chest x-rays (5 mSv), (5) and bone scintigraphy (bone scan) has a dose equivalent to 200 chest x-rays (4.2 mSv). (6) The authors hypothesized that orthopedists may not be aware of the radiation hazards associated with the imaging tests they commonly use in their practices. To assess their level of knowledge about one of these tests, we administered a short questionnaire on the risks of bone scan at an annual meeting of the Israeli Orthopedic Society.