ESTRO 2025 - Abstract Book

S3352

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Conclusion: Uncertainties were generally larger for the liver and lung than the heart, and internal position did not correlate well with the external marker. These results indicate that the use of traditional margins with an external surrogate for gating may fail to provide adequate coverage, depending on the target location. This work provides quantitative results that may help guide development of appropriate margins accounting for intrafraction and intra-breath-hold uncertainties.

Keywords: Breath-hold, MRI

4505

Mini-Oral Delivered dose reconstruction for organs with differential motion Björn Eiben 1 , Alex Dunlop 1 , Alison C. Tree 2 , Simeon Nill 1 , Uwe Oelfke 1

1 Joint Department of Physics, The Royal Marsden NHS Foundation Trust and The Institute of Cancer Reserach, London, United Kingdom. 2 Department of Radiotherapy, The Royal Marsden HNS Foundation Trust and The Institute of Cancer Research, London, United Kingdom Purpose/Objective: MR-Linacs (MRL) facilitate time-resolved imaging of the patient during treatment, yet reconstruction and quantification of the motion-including delivered dose to the patients’ anatomy is currently not part of the clinical routine. We designed a prototype workflow that utilises data recorded during the treatment to reconstruct the dose received by the target and adjacent organs at risk whilst allowing for differential motion of such structures.