Patient Release Criteria

Welcome to NPC’s special web feature, Patient Release Criteria.

Click CONTINUE below to calculate the dose to other individuals from a patient who was administered a dosage of 131I sodium iodide.  The procedure is described NRC in NUREG-1556, Vol. 9, Ver. 2, 2008.

The Society of Nuclear Medicine (SNM) and the American College of Nuclear Physicians published the “Guide for Diagnostic Nuclear Medicine,” 2004 to provide guidance to the nuclear medicine community for compliance with NRC regulations. Included in that publication is a methodology for the calculation of dose to the members of the public from the release of patients treated with 131I sodium iodide. That calculation methodology is an alternative to that published in NRC documents. (The NPC website uses the methodology described by the NRC.) The basic method of calculating dose in the SNM and the NRC guidance documents is the same. However, there are three assumptions that differ between the two documents.

  1. The NRC makes the assumption that the patient does not void for 8 hours after administration. The SNM assumes the patient voids normally.
  2. The NRC assumes an occupancy factor of 0.75 for the first 8 hours after administration. The SNM assumes the same occupancy factor for the first 8 hours as that used after 8 hours (often 0.25).
  3. The NRC assume no self-shielding from the patient (calculates the dose from an unshielded source). The SNM takes into consideration the shielding provided by the patient for that material not in the thyroid. The NRC methodology is certainly more conservative. The facility using the SNM methodology must assure that the assumptions made by the SNM are valid for the specific case for which they are calculating the dose to the public. A dose calculator which uses the SNM methodology can be found on the RADAR website at Be sure to enter 1 meter for the distance.

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