Licensee over-reliance on conservatisms in NRC guidance regarding the release of patients treated with 131I

Medical licensees are required to comply with U.S. Nuclear Regulatory Commission (NRC) regulations pertaining to the release of patients administered radioactive material. However, use of the associated NRC guidance expressed in NUREG-1556, Volume 9, is completely optional and has been shown to be overly conservative. Rigid adherence to the guidance recommendations has placed an undue burden on nuclear medicine therapy patients and their families, as well as licensees responsible for ensuring compliance with NRC requirements. More realistic guidance has been published by other responsible professional societies and will be presented in this work. These more realistic calculations allow for higher releasable activity levels than the widely adopted NUREG levels, particularly for thyroid cancer patients. The guidance-suggested releasable activity limit is similar to our calculational result for hyperthyroid patients, 2.1 GBq (57 mCi) compared to 2.3 GBq (62 mCi), but is significantly lower for thyroid cancer patients, 6.6 GBq (179 mCi) vs. 16.9 GBq (457 mCi) using the regulatory definition of the total effective dose equivalent (TEDE). Higher limits are both possible and reasonable, if the permissible extra-regulatory definition of the TEDE is used in which the effective dose equivalent (EDE), rather than the deep-dose equivalent (DDE), is determined. We maintain that professionals evaluating compliance with the NRC requirements for patient release, pursuant to 10 CFR 35.75, should use the procedures presented here and not rely automatically on the NUREG.