Dosimetry for Radiopharmaceutical Therapy: Practical Implementation, From the AJR Special Series on Quantitative Imaging

Radiopharmaceutical therapy (RPT) is advancing rapidly and achieving wider clinical application. However, RPT is not yet optimized in practice, as tumor and normal-organ dose estimates and, in turn, dose-response relationships remain poorly defined. Internal dosimetry is evolving to address such issues, transitioning from the estimation of population-average organ-level or tumor-level doses to individualized patient-specific sub-organ or sub-tumor doses. Derivation of patient-specific doses allows the further development of reliable dose-response relationships for diseased tissues and dose-toxicity relationships for normal tissues. Resources such as commercially available or publicly downloadable software are being increasingly developed to facilitate the use of these emerging methods. This review addresses the determination of patient-specific radiation doses for target tissue and at-risk normal tissues in the setting of RPT. Topics covered include: quantities, units, and radionuclides relevant to RPT; dose prescription algorithms; the steps in the dosimetry workflow; and bioeffects modeling. Implementation of patient-specific dosimetry will be essential for this therapeutic modality's optimization and further clinical expansion.