Internal exposure in nuclear medicine: application of IAEA criteria to determine the need for internal monitoring

The manipulation of unsealed sources in nuclear medicine poses significant risks of internal exposure to the staff. According to the International Atomic Energy Agency, the radiological protection program should include an evaluation of such risks and an individual monitoring plan, assuring acceptable radiological safety conditions in the workplace. The IAEA Safety Guide RS-G-1.2 recommends that occupational monitoring should be implemented whenever it is likely that committed effective doses from annual intakes of radionuclides would exceed 1 mSv. It also suggests a mathematical criterion to determine the need to implement internal monitoring. This paper presents a simulation of the IAEA criteria applied to commonly used radionuclides in nuclear medicine, taking into consideration usual manipulated activities and handling conditions. It is concluded that the manipulation of 131I for therapy presents the higher risk of internal exposure to the workers, requiring the implementation of an internal monitoring program by the Nuclear Medicine Centers.