WG13 – Dosimetry in nuclear medicine

Lara Struelens
Belgian Center for Nuclear Research (SCK CEN)
Email: lara [dot] struelens [at] sckcen [dot] be (lara[dot]struelens[at]sckcen[dot]be)

Peter Covens
Vrije Universiteit Brussel
Email: peter [dot] covens [at] vub [dot] be (peter[dot]covens[at]vub[dot]be)
 

The WG13 has:

• 20 full members,
• approx. 20 corresponding members and
• approx. 20 observers.

Liaisons

The WG13 has four liaisons from EANM - Silvano Gnesin (Dosimetry) and Elena Prieto (Radiation Protection), SIG-FRID - Manuel Bardiès and ICRP - Augusto Giussani.

Task Group leader: Lara Struelens (SCK CEN, Belgium)

The growing use of nuclear medicine and the diversity of new radiopharmaceuticals, stimulate the need for a more comprehensive re-evaluation of the radiological risk for caregivers and general public coming into proximity of nuclear medicine patients. The objective of this task is to develop a more comprehensive dose calculation approach by using the most recent advancements in computational dosimetry, such as Monte Carlo simulations, realistic flexible human phantoms, and time activity distribution curves from the most recent biokinetic models. In addition to caregiver and general public dose assessment, this new dose calculation framework is particularly important for modelling some of the most concerning close contact exposure situations, such as an adult holding/comforting a child, or a mother breastfeeding her child.

Task Group leader: Vladimir Spielmann (BfS, Germany)

This task will focus on pharmacokinetic model techniques, uncertainty evaluation and sensitivity analysis. Based on available clinical data and predefined goals, individual (PK), population-based (PopPK), pharmacodynamic (PD), physiologically based (PBPK), or combined pharmacokinetic–pharmacodynamic (PK–PD) models may be developed or used in this task.

The absorbed dose to patients from administered radiopharmaceuticals is usually calculated according to the generalized scheme recommended by the MIRD and ICRP. In these calculations, mathematical models for time-dependent activity curves in organs and tissues (pharmacokinetic models) and mathematical and digital representations of the human body (voxel phantoms) are first evaluated. Because of uncertainties in the image acquisition chain and variability among patients, the image-based pharmacokinetic models and the reference human phantoms used for estimating absorbed doses in patients are subject to significant sources of uncertainty.

In this task, general methods and programs will be developed and used to assess the uncertainty of time-activity curves (TACs), time-integrated activity coefficients (TIACs), and from that resulting organ absorbed doses in patients undergoing diagnostic procedures and treatments. Furthermore, a global, variance-based sensitivity analysis approach will be applied to identify the most important model parameters in the PK and dose calculation chain. 

Task Group leader: Weibo Li (BfS, Germany)

This task group aims to explore and advance the use of artificial intelligence (AI) across the nuclear medicine workflow, with a focus on pharmacokinetic (PK) modelling, theranostic applications, and patient‑specific dosimetry. As a first step, we are preparing a EURADOS review on “AI Applications in Nuclear Medicine Dosimetry and Radiopharmaceutical Therapy.”

The review will provide an overview of the current state of AI‑based methods, highlight existing gaps and limitations, and identify opportunities where AI could meaningfully support or enhance the clinical and research workflow. Building on these insights, the task group will investigate how AI approaches can be evaluated, compared, and integrated into PK modelling, theranostic decision‑making, and dosimetric calculations.

In addition to these core activities, the task group will support other WG13 tasks by identifying and providing AI‑based methods that can be benchmarked against conventional or emerging approaches relevant to each task’s focus area. This will promote harmonised evaluation strategies and help ensure that AI solutions are assessed within the broader context of WG13’s objectives.

Task Group leader: Astrid Delker (LMU, Germany)

This task focuses on current practices, clinical needs, and open research challenges in clinical molecular radiotherapy dosimetry. The aim is to assess the level of harmonization and standardization across centers and to identify priorities for further methodological development and clinical implementation.

Therefore, the first task is the execution and evaluation of a multi-center survey addressing:

• Imaging protocols and methodologies 
• Dosimetry methodologies (software tools, segmentation approaches, dose calculation methods, corrections, and uncertainty reporting)
• Clinical implementation aspects 

Based on the survey results, the task aims to:

• Define clinical requirements and open research topics in clinical dosimetry
• Identify gaps in current practice and opportunities for improved standardization
• Foster collaboration with other professional organizations (e.g. EANM, EFOMP)

Currently, the task focuses on ¹⁷⁷Lu-PSMA therapy and initiated comparative evaluations of partial volume correction methods for ¹⁷⁷Lu dosimetry, including factor-based, image-based, and AI-based approaches using synthetic data, phantoms, and comparison exercises. Overall, TG5 serves as a platform to connect clinical practice with dosimetric research, supporting the translation of dosimetry methods into routine clinical workflows.

Task Group leader: Philipp Ritt (FAU Erlangen-Nürnberg, Germany)

This task will utilize advanced dosimetric techniques, leveraging in-vitro and in-vivo imaging technologies, to evaluate absorbed doses at the sub-tissue and sub-organ levels, such as in the kidneys and bone marrow. The initial sub-task will involve an intercomparison exercise using a semi-artificial autoradiography dataset. This approach will allow all participants to work with realistic, voxelized data and also facilitate a better understanding of potential errors and variability in small-scale dosimetry.

The task group comprises scientists from various European hospitals and research organizations and is open to welcoming interested newcomers.

Task Group leaders: Lara Struelens (SCK CEN, Belgium) / Siria Medici (CHUV, Switzerland)

This task addresses dosimetric evaluation of radiopharmaceutical extravasations occurring during nuclear medicine procedures. Although extravasations are not uncommon, there is currently no harmonised guidance on when and how to perform dosimetry, how to interpret dose estimates, or how dosimetric results should support patient management and communication.

In collaboration with EANM, a review is ongoing of the existing literature and recommendations, gather expert opinion, and assess the different dosimetric approaches proposed for extravasation scenarios. 

While EANM focuses on progressing toward pragmatic, proportionate, and harmonised guidance for the management of extravasation cases - supporting risk assessment, patient management workflows, and 
clinical communication - EURADOS will contribute its dosimetric expertise by critically assessing and comparing the various dosimetric approaches currently in use. This includes methods ranging from average dose models to more advanced voxel‑based techniques, with particular attention to the impact of modelling assumptions, quantitative imaging biases, and tissue radiosensitivity on the resulting absorbed dose estimates.