A GENERALIZED ALGORITHM FOR DETERMINING THE TIME OF RELEASE AND THE DURATION OF POST-RELEASE RADIATION PRECAUTIONS FOLLOWING RADIONUCLIDE THERAPY

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Abstract
The Nuclear Regulatory Commission has recently amended its regulation concerning patients who have received therapeutic amounts of radioactivity. The amended regulation allows patient release based on a total effective dose equivalent (TEDE) limit of 5 mSv (500 mrem) instead of the activity administered or retained [1,110 MBq (30 mCi)] or the dose rate [0.05 mSv h−1 (5 mrem h−1) at 1 m]. Record-keeping and written post-release radiation safety precautions are required, however. A general algorithm, combining patient-specific kinetics and dose rate measurements, has been developed to systematically determine the actual duration of post-release radiation precautions as well as the time of release post-treatment. This algorithm is based on the maximum permissible effective dose equivalents (MPEDEs) of the respective cohorts exposed, 5 mSv (500 mrem) to non-pregnant adult family members and 1 mSv (100 mrem) to pregnant women, children, and members of the general public. Operational equations to determine the times post-radionuclide treatment of release from medical confinement, of not working, of avoiding pregnant women and children, of limiting holding of children, and of sleeping partners not sleeping together have been derived and illustrated with a hypothetical example. TEDE-based release criteria should be less restrictive than the previous activity-based or dose rate-based release criteria. However, post-release radiation precautions may be more intrusive and longer in duration than those to which most practitioners have grown accustomed. Up to now, however, the duration (typically 1–2 d) of advised post-release precautions had not been rigorously derived from MPEDEs and were generally inappropriately short. Even so, dose-based release criteria should prove more cost-effective overall than hospitalization of patients commonly imposed by activity-based and dose rate-based release criteria.