MO‐E‐342‐03: Radionuclide Therapy and Dosimetry in Nuclear Medicine

Advances in our understanding of the molecular biology of cancer and other diseases have identified molecules and signaling pathways that we can now visualize, in vivo , for diagnosis, staging, and to identify optimal therapy and monitor patient response to therapy. These advances have also helped identify targets for targeted radionuclide therapy, making it possible to target radiation at the cellular and molecular level. Planning for this treatment approach is similar, in principle, to external beam radiotherapy treatment planning, but substantially different in practice. Dosimetry for systemic or locoregional administration of a therapeutic radiopharmaceutical requires an understanding of its biodistribution and pharmacokinetics, this must be coupled with a methodology for translating total number of radionuclide disintegration in a particular anatomical volume to the absorbed dose to the volume. Advances in imaging and computing technology over the past 20 to 30 years have fostered corresponding advances in the implementation of the basic radionuclide dosimetry scheme outlined above. Dosimetry in nuclear medicine is evolving from a standard anatomical model‐based calculation that provides mean absorbed dose over a target organ volume to a calculation that provides the spatial distribution of absorbed dose over the individual patient target and organ geometry and that also incorporates radiobiological modeling as a step towards assessing the biological consequences of the dose distribution. The evolution of nuclear medicine dosimetry as well as recently approved and emerging radionuclide‐based therapeutics will be reviewed.