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

Aim: Calculating the absorbed dose is important for the determination of risk and therapeutic benefit of internal radiation therapy. Optimal dose estimations require time-consuming and sophisticated methods, which are difficult due to practical reasons. To make dosimetry available for each of the patients, we developed a specific dosimetry procedure used in daily clinical routine. Materials and methods: Dosimetry has been performed according to the MIRD scheme and adapted to the special conditions at our department (which we have called as the Bad Berka Dose protocol, BBDP): Conjugated planar whole-body scintigraphies at 0.5, 3, 24, 48 and 72 hours postinjection are analyzed by regions of interest with 'HERMES WHOLE-BODY DISPLAYTM and the time-dependent organ and tumor activities are determined with Microsoft EXCELTM. The cumulated activity is calculated using the software ORIGIN PRO 8.1GTM and a monoor biexponential fit of the time-activity curves. Mean absorbed doses are finally estimated using the software OLINDA EXMTM. Results: We found a compromise between the calculation model and practical conditions. It has ensured dose estimation in daily clinical routine with a reasonable effort and within acceptable time. In consequence, the dosimetry method developed for Bad Berka allows each of our patients to undergo dosimetry after therapy using Lu-177-labeled peptides (peptide receptor radionuclide therapy). Additionally, this approach can be used for any internal radiotherapy using a gamma-emitting radionuclide. Conclusion: The BBDP is a practicable dosimetric approach, which can be used in daily clinical routine. It not only helps in identifying patients who would benefit most from the treatment, but also those with unfavorable dosimetry. Additionally, the analysis of dosimetric data from peptide receptor radionuclide therapy (PRRNT) could help in predicting possible toxicity.