MIRD Pamphlet No. 23: Quantitative SPECT for Patient-Specific 3-Dimensional Dosimetry in Internal Radionuclide Therapy

TLDR

Voxel‑level absorbed‑dose estimation in internal radionuclide therapy is increasingly sought to capture spatial and temporal dose heterogeneity, yet SPECT quantification techniques differ from those used for diagnostic imaging, prompting the development of best‑practice guidance in forthcoming MIRD pamphlets. This report provides an overview of 3‑dimensional SPECT techniques and the requirements for regional and voxel‑level internal dosimetry. The authors emphasize combined SPECT/CT image‑based methods, using CT‑derived anatomy to correct technical factors and enable patient‑specific voxel‑level dosimetry.

Abstract

In internal radionuclide therapy, a growing interest in voxel-level estimates of tissue-absorbed dose has been driven by the desire to report radiobiologic quantities that account for the biologic consequences of both spatial and temporal nonuniformities in these dose estimates. This report presents an overview of 3-dimensional SPECT methods and requirements for internal dosimetry at both regional and voxel levels. Combined SPECT/CT image-based methods are emphasized, because the CT-derived anatomic information allows one to address multiple technical factors that affect SPECT quantification while facilitating the patient-specific voxel-level dosimetry calculation itself. SPECT imaging and reconstruction techniques for quantification in radionuclide therapy are not necessarily the same as those designed to optimize diagnostic imaging quality. The current overview is intended as an introduction to an upcoming series of MIRD pamphlets with detailed radionuclide-specific recommendations intended to provide best-practice SPECT quantification–based guidance for radionuclide dosimetry.