Introduction: For fractionated radionuclide therapy protocols that involve large activities administered within short periods of time, there is a lack of guidance concerning how patient release calculations should be performed.
Objectives: Present a solution for estimating the effective dose of individuals exposed to a patient undergoing fractionated radionuclide therapy; this is intended to be used for iterative determination of patient release instructions.
Methods: The effective dose of an individual in the vicinity of a patient is described by a piecewise function that is integrated over periods of time that are defined by several variables relevant to clinical planning of fractionated radionuclide therapy protocols. This solution is compared to a simpler calculation that treats all administrations as identical events.
Results: For the two compared methodologies, their equivalence for estimating effective dose depends on several variables. However, for protocols where the elimination time of the radionuclide is far smaller than the time between administrations, both methodologies produce essentially equal results.
Conclusion: The author recommends using the presented solution for iterative determination of patient release instructions if a simpler approach generates release instructions that are overly restrictive. Doing so will allow for less strict release instructions because the dose mitigation from repeated adherence to release instructions after each fraction, in addition to potential inpatient time after each fraction, will be taken into account. Lastly, a spreadsheet that incorporates the presented solution has been made freely available for download.