ESTRO 2025 - Abstract Book

S3460

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Conclusion: A model has been presented to predict the dose rate in pencil beam scanning proton plans. This model reduces the computing requirements making feasible a systematic prospective determination of the dose rate for any plan.

Keywords: Dose rate, pencil beam scanning, proton therapy

References: [1] Meijers, A. et al. Possible association of dose rate and the development of late visual toxicity for patients with intracranial tumours treated with pencil beam scanned proton therapy. Radiat Oncol 19 , 75 (2024). DOI: 10.1186/s13014-024-02464-z

[2] Daartz J. et al. Voxel-wise dose rate calculation in clinical pencil beam scanning proton therapy. Phys. Med. Biol. 69 (2024) 065003. DOI: 10.1088/1361-6560/ad2713

[3] Burguete, J. et al. . Stochastic model for predicting the temporal structure of the plan delivery in a synchrotron based pencil beam scanning proton therapy system. Radiation Physics and Chemistry 226 (2025) 112276. DOI: 10.1016/j.radphyschem.2024.112276

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Digital Poster Machine-learning-based integration of temporal and spectral prompt gamma-ray information for proton range verification Aaron Kieslich 1,2 , Sonja M. Schellhammer 1,2,3 , Alex Zwanenburg 1,4,5 , Toni Kögler 1,2 , Steffen Löck 1,4,6 1 OncoRay—National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology , Helmholtz-Zentrum Dresden – Rossendorf, Dresden, Germany. 2 Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany. 3 Zittau/Görlitz University of Applied Sciences, Faculty of Natural and Environmental Sciences, Zittau, Germany. 4 German Cancer Consortium (DKTK), Partner Site Dresden, German Cancer Research Center (DKFZ), Heidelberg, Germany. 5 National Center for Tumor Diseases Dresden (NCT/UCC), Germany: German Cancer Research Center (DKFZ), Heidelberg, Germany, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany; Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany. 6 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany Purpose/Objective: Precise dose delivery in proton therapy requires accurate proton-beam range verification. Current models for prompt gamma-ray timing (PGT) predict proton beam range shifts based on the temporal information of gamma ray emissions [1]. However, in addition to the temporal information, the energy of the gamma rays is also recorded during PGT, which could contribute to an enhanced performance of these models. Therefore, this study aims to investigate whether integrating correlated temporal and spectral information improves proton range verification. Material/Methods: A cylindrical polymethyl methacrylate (PMMA, i.e. acrylic glass) phantom was irradiated with 162 and 225 MeV proton beams, incorporating air cavities of 0, 5, 10, and 20 mm to simulate anatomical variations. Proton beams were delivered in both static and scanned mode with a time-energy spectrum measured for each proton spot (Figure 1). Scanned spots of repeated irradiations of a single detector were accumulated to mimic the currently envisioned PGT system consisting of eight detector units. Time, energy, energy-band-time (i.e., time features calculated from the time spectra of gamma-rays within energy intervals corresponding to pronounced energy lines in the gamma-ray energy spectrum), higher-order image, and combined feature sets were extracted for each spot.