Occupational radiation monitoring at a large medical center in Japan.

Occupational radiation dose monitoring is a method of ensuring that radiation levels are within the regulatory limits. Our objective in this study was to evaluate the radiation doses experienced by personnel at a radiology facility between 2001 and 2010. Overall, 2418 annual dose records for workers who were categorized into four occupational groups were analyzed. The groups included: (1) radiologists, (2) radiologic technologists, (3) nurses, and (4) other workers, who belong to other hospital departments, but who participate partially in some radiologic procedures. The dose distribution was found to be skewed, with 76 % of personnel having received no measurable doses and almost 2 % having received doses of more than 2 mSv. The weighted-average annual doses ranged from 0.13 to 0.57, 0.9 to 2.12, 0.01 to 0.19, and 0.01 to 0.09 mSv for the radiologists, radiologic technologists, nurses, and the other workers, respectively. The radiologic technologists received the highest radiation exposure among the four groups. It was found that the average annual doses were decreasing over time for the radiologists, radiologic technologists, and others, whereas they were increasing for the nurses. Nurses play an important role in assisting radiologists and patients during various radiologic procedures, which might have increased their average annual dose. During the 10-year period of this study, there was no incidence of a dose exceeding the annual dose limit of 20 mSv. Furthermore, there was no detectable neutron exposure.