Dosimetry in Targeted Radionuclide Therapy: The Bad Berka Dose Protocol—Practical Experience

Abstract

Aim: Calculating the absorbed dose is important for thedetermination of risk and therapeutic benefit of internal radiationtherapy. Optimal dose estimations require time-consuming andsophisticated methods, which are difficult due to practicalreasons. To make dosimetry available for each of the patients,we developed a specific dosimetry procedure used in dailyclinical routine.Materials and methods: Dosimetry has been performedaccording to the MIRD scheme and adapted to the specialconditions at our department (which we have called as the BadBerka Dose protocol, BBDP): Conjugated planar whole-bodyscintigraphies at 0.5, 3, 24, 48 and 72 hours postinjection areanalyzed by regions of interest with 'HERMES WHOLE-BODYDISPLAYTM and the time-dependent organ and tumor activitiesare determined with Microsoft EXCELTM. The cumulated activityis calculated using the software ORIGIN PRO 8.1GTM and amono- or biexponential fit of the time-activity curves. Meanabsorbed doses are finally estimated using the software OLINDAEXMTM.Results: We found a compromise between the calculationmodel and practical conditions. It has ensured dose estimationin daily clinical routine with a reasonable effort and withinacceptable time. In consequence, the dosimetry methoddeveloped for Bad Berka allows each of our patients to undergodosimetry after therapy using Lu-177-labeled peptides (peptidereceptor radionuclide therapy). Additionally, this approach canbe used for any internal radiotherapy using a gamma-emittingradionuclide.Conclusion: The BBDP is a practicable dosimetric approach,which can be used in daily clinical routine. It not only helps inidentifying patients who would benefit most from the treatment,but also those with unfavorable dosimetry. Additionally, theanalysis of dosimetric data from peptide receptor radionuclidetherapy (PRRNT) could help in predicting possible toxicity.