Incorporation of travel and confinement time in the evaluation of nuclear medicine therapy discharge criteria

Abstract

Purpose

A novel method for calculating the dose absorbed by third parties in contact with patients after nuclear medicine treatment is presented. In literature, studies assume a confinement period in which patients have no contacts and whose duration is determined by comparing the dose absorbed after confinement with dose constraints. However, complete isolation is often impractical and the dose during confinement should be considered. Furthermore, dose to third parties should be relevant in case of long return trips and this contribution should also be accounted for.

Method

The calculation model we propose, based on continuous exposure with correction for time and distance, allows evaluation of the above-mentioned dose contributions and can be easily implemented in a spreadsheet. The model was validated against published data under equivalent exposure scenarios and then applied to evaluate additional doses due to travel and restriction period exposures.

Results

Neglecting dose contribution during the confinement period, results are consistent with those published in literature. In this approximation, it is always possible to meet dose constraints, however, if dose during confinement is considered, it may be impossible to comply with the required constraints. Furthermore, long return trips, especially using public transportation, may require postponing travel for several days.

Conclusion

ignoring the dose during the restriction period or long trips can lead to the incorrect conclusion that a constraint is met when it is not. Anyhow, a constraint should be considered as an aid to optimization, and not as a dose limit.