ESTRO 2025 - Abstract Book

S3504

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

ESTRO 2025

Conclusion: We demonstrated that probabilistic evaluation with an IMPT replanning strategy enables either OAR sparing or target coverage enhancement, effectively advancing personalized treatment planning.

Keywords: IMPT, treatment planning, probabilistic evaluation

References: 1. Korevaar, E. W., Habraken, S. J., Scandurra, D., ... & Langendijk, J. A. (2019). Practical robustness evaluation in radiotherapy–A photon and proton-proof alternative to PTV-based plan evaluation. Radiotherapy and Oncology , 141 , 267-274. 2. Perkó, Z., Van Der Voort, S. R., Van De Water, S., Hartman, C. M., Hoogeman, M., & Lathouwers, D. (2016). Fast and accurate sensitivity analysis of IMPT treatment plans using Polynomial Chaos Expansion. Physics in Medicine & Biology, 61(12), 4646. 3. Lambrecht, M., Eekers, D. B., Alapetite, C., Burnet, N. G., ... & Troost, E. G. (2018). Radiation dose constraints for organs at risk in neuro-oncology; the European Particle Therapy Network consensus. Radiotherapy and Oncology , 128 (1), 26-36.

2462

Poster Discussion Detecting proton range deviations with prompt gamma-ray timing under close-to-clinical conditions Krystsina Makarevich 1,2 , Thyrza Z. Jagt 1,2 , Aaron Kieslich 1,2 , Katja E. Römer 3 , Sonja M. Schellhammer 4 , Joseph A. B. Turko 3 , Konstantin Urban 1,2 , Andreas Wagner 3 , Toni Kögler 1,2 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 Institute of Radiooncology – OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany. 3 Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany. 4 Faculty of Natural and Environmental Sciences, Hochschule Zittau/Görlitz – University of Applied Sciences, Zittau, Germany Purpose/Objective: Prompt gamma-ray timing (PGT) is an in vivo technique for proton treatment verification. Temporal distributions of detected gamma rays provide information on the range of therapeutic particles and enable real-time monitoring of the treatment. This work evaluates PGT's applicability to detect proton range deviations in quasi-clinical scenarios. Material/Methods: A proton therapy dosimetry head phantom (Sun Nuclear) was irradiated with posterior proton pencil beams using an IBA dedicated nozzle (IBA ProteusPlus). A single-layer (162 MeV), 8×8 cm 2 dose plan with clinically realistic spot weights of 0.12 MU (1.4×10 7 protons) was applied to study the performance of PGT. Range shifts (RSs) were artificially created in the phantom by covering the right half of the field with solid water plates of 2, 5, and 7 mm thickness (Fig. 1). The uncovered half of the field acted as a zero RS. For each RS and reference measurement, the same plan was repeated 22 times to obtain a measure of statistical fluctuations. Using the spot-wise accumulated data of 11 random repetitions, we developed a linear prediction model that estimates the introduced RS based on the total number of detected events (Fig. 1). The model was tested using the data of the remaining 11 repetitions, with evaluations performed both on accumulated (11-fold) and individual (single-fold) basis.