ESTRO 2025 - Abstract Book

S3462

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

ESTRO 2025

Conclusion: The study shows that integrating spectral information does not noticeably improve the proton range verification accuracy of the current PGT system. Temporal data alone is often sufficient for accurate predictions, offering a potential effective approach for proton range verification, with the potential for clinical applications.

Keywords: proton therapy, prompt gamma-ray timing

References: [1] Schellhammer SM, Wiedkamp J, Löck S, Kögler T. Multivariate statistical modelling to improve particle treatment verification: Implications for prompt gamma-ray timing. Frontiers in Physics. 2022;10:932950. Available from: http://dx.doi.org/10.3389/fphy.2022.932950.

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Digital Poster Assessing the efficiency and dosimetric impact of mini-ridge filters in synchrotron-based PBS proton therapy Zubin R Master, Andrew Wibawa, Clifford Ghee Ann Chua, Calvin Wei Yang Koh, Hong Qi Tan, Kah Seng Lew, Sharon Shuxian Poh, Sung Yong Park Division of Radiation Oncology, National Cancer Centre Singapore, Singapore, Singapore Purpose/Objective: Pencil beam scanning (PBS) proton therapy delivers radiation by scanning a narrow proton beam across the target in the x-y plane, while modulating beam energy to control depth along the z-axis. Target irradiation requires multiple energy layers, each consisting of numerous spots, often generating plans with hundreds to thousands of spots across layers. Treatment time depends on the proton delivery system performance, including dose rate, scanning speed, energy switching, and spot timing. Pristine Bragg peaks, especially at lower energies in synchrotrons, are sharp and narrow, requiring more energy layers for coverage. A mini-ridge filter (MRF) broadens these Bragg peaks, increasing spot size as a secondary effect. This reduces the required energy layers and spots, potentially decreasing treatment time. This study assesses the time-saving benefits and dosimetric impact of MRF in proton therapy with our delivery system. Material/Methods: Five liver cancer cases with shallow tumors were selected where an MRF was expected to provide significant benefits. Two MRF beam models were tested. For each case, treatment plans were generated with and without MRFs and delivered on the proton therapy machine. Plans were compared for delivery time, beam parameters (number of spots and energy layers), dosimetric quality, and interplay effects. Results: Using an MRF reduced spots and energy layers by up to 49.16% and 59.26%, respectively, with beam-on time reduced by up to 37.4% (see figures and table below). Interplay effects were comparable and treatment planning time was faster. However, using MRF caused a slight increase in the dose fall-off (<1 mm), resulting in a minor increase in mean dose to adjacent OARs, primarily the liver (0.46±0.32 Gy), but this was deemed to be clinically insignificant by our physicians.