ESTRO 2025 - Abstract Book

S3287

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

ESTRO 2025

Conclusion: CMM's commissioning and clinical implementation improved MRgART precision and adaptability at our centre. Robust protocols and clinical flexibility ensure accurate intrafraction motion management, reducing treatment complexity and minimising treatment demands on patients. Future efforts will focus on refining gating thresholds and broadening CMM applications.

Keywords: MRgART, Motion Management, MR-Linac

References: [1] Patel, Imran. (2018). Physics Aspects of Quality Control in Radiotherapy - IPEM Report 81, 2nd edition. [2] Klein EE, Hanley J, Bayouth J, Yin FF, Simon W, Dresser S, Serago C, Aguirre F, Ma L, Arjomandy B, Liu C, Sandin C, Holmes T; Task Group 142, American Association of Physicists in Medicine. Task Group 142 report: quality assurance of medical accelerators. Med Phys. 2009 Sep;36(9):4197-212. doi: 10.1118/1.3190392. PMID: 19810494.

2871

Digital Poster Accuracy of treatment adaptation in an MR-linac Carlos Ferrer 1 , Concepción Huertas 1 , Inmaculada Navarro 2 , Beatriz Moreno 2 , Marcos Martínez 1 , Beatriz Sánchez 2 , Patricia Arroyo 2 , Daniel Camacho 2 , Rocío Gómez 3 , Moisés Sáez 1 1 Medical Physics, La Paz University Hospital, Madrid, Spain. 2 Radiation Oncology, La Paz University Hospital, Madrid, Spain. 3 Applied Physics, Autonomous University of Madrid, Madrid, Spain Purpose/Objective: The workflow on an Elekta Unity MR-linac at the moment the patient is going to receive the radiotherapy session involves the aquisition of a magnetic resonance image (MRI) to obtain the shape and position of the different organs at risk (OAR) as well as for day to day CTV and PTV countouring. After all the structures are recontoured, the adapted plan is calculated on this MRI and approved for treatment if all planification goals are met. The time required for OAR and CTV/PTV contourig can be up to 30 minutes. During this time the internal movement of the OARs and PTVs could cause the dose calculated in the initial MRI image to not correspond to the location and shape of the contoured structures at the time of radiation delivery. In this work, the differences in the volume of the structures and the