Contact restriction time after common nuclear medicine therapies: spreadsheet implementation based on conservative retention function and individual measurements.

The increasing use of new radiopharmaceuticals invites to reconsider some radioprotection issues, such as the contact restriction time that limits the public exposure by nuclear medicine patients. Contact restriction time should be patient specific and conservative, and its assessment made easy for the clinicians. Here a method is proposed, based on conservative estimate of the whole-body retention function and at least one measurement of the patient's dose rate. Recommended values of the retention function are given for eight therapies: 131I (Graves' disease, remnant ablation, patient follow-up, mIBG), 177Lu-PSMA and 177Lu-DOTATATE therapies, 90Y and 166Ho microsphere injection of liver. The patient line source model for scaling dose rate from one distance to another is included in the restriction time calculation. The method is benchmarked against published values and the influence of the dose rate scaling and whole-body retention function illustrated. A spreadsheet is provided, along with the source code, with recommended values for the eight therapies. The recommended values can be changed as well as the dose rate scaling function, other radiopharmaceuticals can be included in the spreadsheet, provided retention functions are defined.&#xD.