Erlangen 2026 – scientific programme

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ST: Fachverband Strahlen- und Medizinphysik

ST 4: DPG meets DGMP: Dosimetry in Nuclear Medicine

ST 4.3: Invited Talk

Wednesday, March 18, 2026, 17:15–17:45, KH 01.013

Dosimetry in Targeted Radionuclide Therapy: Challenges, Concepts, and Perspectives — •Johannes Tran-Gia — Universitätsklinikum Würzburg

Targeted radionuclide therapy (TRT) has emerged as a rapidly expanding modality in nuclear medicine, driven by highly effective β- and α-emitting radiopharmaceuticals. Unlike external beam radiation therapy (EBRT), where radiation dose delivery can be planned and verified with high spatial and temporal precision, TRT involves internally distributed, time-dependent radiation exposure from radiopharmaceuticals whose biodistribution and kinetics vary substantially between patients. Consequently, dosimetry in TRT poses distinct physical and methodological challenges, including limited imaging sensitivity and spatial resolution, complex decay schemes, and the need for quantitative SPECT or PET imaging over multiple time points.

This talk introduces the principles of dosimetry in TRT and highlights key differences compared to EBRT from a physics perspective. Current clinical practice, which largely relies on fixed administered activities, is discussed in the context of historical and technical constraints. At the same time, growing evidence for absorbed dose*effect relationships for tumor response and normal-tissue toxicity motivates a shift toward dosimetry-guided treatment planning and verification. Recent advances in quantitative imaging, standardization, and computational methods offer promising pathways toward routine patient-specific dosimetry. The talk concludes with an outlook on how these developments may enable individualized and optimized TRT.

Keywords: targeted radionuclide therapy; internal radiation dosimetry; quantitative nuclear medicine imaging; absorbed dose estimation; absorbed dose–effect relationships