Patient release criteria after radioactive treatment

Under 10 CFR 35.75, a US licensee may authorise the release from control of a patient (or a patient carrying an implant) containing unsealed byproduct material or brachytherapy sources if the total effective dose equivalent (TEDE) to any other individual from exposure to the released patient is not likely to exceed 5 mSv (0.5 rem). This single numeric threshold, rather than a fixed activity limit for each radionuclide, is what actually governs same-day release after therapies such as iodine-131 for thyroid cancer, lutetium-177 radioligand therapy, or brachytherapy implants, and licensees typically use NRC-provided tables of activities, dose-rate measurements, or patient-specific calculations to demonstrate compliance before discharge.

A second, lower threshold triggers a documentation and counselling obligation rather than a release bar: if the TEDE to any other individual is likely to exceed 1 mSv (0.1 rem), the released individual (or their parent or guardian) must be given written instructions on actions to keep the dose to others as low as reasonably achievable. If a nursing infant or child could receive more than 1 mSv assuming breastfeeding continues uninterrupted, those instructions must also cover guidance on interrupting or discontinuing breastfeeding and the potential consequences of not following that guidance. The licensee must keep a record of the basis for authorising release and, separately, a record of any instructions given to a breastfeeding patient (10 CFR 35.2075).

These thresholds are considerably more permissive than the general public dose limit (1 mSv/year total, under 10 CFR Part 20), reflecting a deliberate policy choice that patients undergoing medically necessary radioactive treatment, and the household members who choose to live with them, accept a higher, time-limited exposure than an uninvolved member of the public would. Facilities commonly apply extra margin above the regulatory minimum (for example, discharging only once a fixed dose-rate-at-one-metre threshold is met) and provide take-home instructions covering distance, time and hygiene precautions for a defined number of days, tailored to the isotope's half-life and the specific therapy given. This entry reflects the regulation as published in the eCFR, checked 2026-09-22; consult the current eCFR text for any amendments.