ESTRO 2025 - Abstract Book

S3212

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

ESTRO 2025

Keywords: STAR, motion estimation, ITV margin creation

References: [1] Blanck O, Buergy D, Vens M, Eidinger L, Zaman A, Krug D, et al. Radiosurgery for ventricular tachycardia: preclinical and clinical evidence and study design for a German multi-center multi-platform feasibility trial (RAVENTA). Clin Res Cardiol 2020;109:1319–32. https://doi.org/10.1007/s00392-020-01650-9. [2] Mayinger M, Boda-Heggemann J, Mehrhof F, Krug D, Hohmann S, Xie J, et al. Quality assurance process within the RAdiosurgery for VENtricular TAchycardia (RAVENTA) trial for the fusion of electroanatomical mapping and radiotherapy planning imaging data in cardiac radioablation. Physics and Imaging in Radiation Oncology 2023;25:100406. https://doi.org/10.1016/j.phro.2022.12.003.

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Digital Poster Intrafraction deviation in non-coplanar single-fraction intracranial radiosurgery treatments Vanessa Filipa da Silva Mendes, Lili Huang, Johannes Muecke, Claus Belka, Christopher Kurz, Guillaume Landry, Michael Reiner, Stefanie Corradini Radiation Oncology, University Hospital of LMU Munich, Munich, Germany Purpose/Objective: The delivery of non-coplanar cranial stereotactic radiosurgery (SRS) treatments involves a challenging workflow as the correct position of the patient needs to be guaranteed throughout the whole session. Real-time and continuous image guidance, as well as the possibility to reposition the patient, are important for SRS, being intrafractional X-ray imaging a crucial modality for this. The aim of this study was to assess intrafractional position errors before delivering stereotactic noncoplanar treatments, where patient displacements are detected by stereoscopic x-ray imaging acquired after each new couch rotation. We analysed both retrospective patient data and phantom acquisitions. Material/Methods: Intrafractional X-ray data of 39 stereotactic single-fraction SRS treatments for intracranial lesions were collected. All patients were immobilised with a double layer mask, positioned and monitored using ExacTrac Dynamic (Brainlab AG, Germany) and HexaPOD evo RT System (Elekta AB, Sweden). A total of 172 stereoscopic X-rays were acquired and the first measured error after each couch rotation was evaluated. To distinguish the magnitude of displacements caused by the couch rotation from real patient motion, a similar study with an anthropomorphic head phantom, containing an implanted ball bearing (Brainlab AG) was performed. Stereoscopic X-rays were acquired for 7 equidistant couch rotations in two scenarios: one with no weight on the couch and a second with 80kg evenly distributed. This experiment was performed 5 times (35 measurements each). Results: The included patients needed to be repositioned 74 times (43%) after couch rotations, due to at least one degree of freedom out of tolerance (deviation ≥0.5mm/0.5°). Most translations exceeding the tolerance were observed in the lateral (17%) and yaw (24%) directions. 97% of all deviations were below 1mm/1°.