S1632
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
Digital Poster Highlight 914 Scintillation Quenching in Conventional and Ultra- High Dose Rate Proton Beams Nassim Tavakoli 1,2 , Cloé Giguère 3,4 , Uwe Titt 4 , Luc Beaulieu 3,5 , Sam Beddar 4,6 , Ramin Abolfath 2,4 1 Department of Medical Physics, Columbia University, New York, USA. 2 Department of Physics and Astronomy, Howard University, Washington, DC, USA. 3 Département de Physique, de Génie Physique et d’Optique et Centre de Recherche sur le Cancer, Université Laval, Québec, Canada. 4 Department of Radiation Physics and Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA. 5 Département de Radio-Oncologie et Axe Oncologie du CRCHU de Québec, Université Laval, Québec, Canada. 6 UTHealth Houston Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, USA Purpose/Objective: Clinical implementation of FLASH proton therapy demands the development of accurate and traceable dosimeters to ensure patient safety. Plastic scintillation dosimeters (PSDs), with their water equivalence, high temporal resolution, and dose-rate independence, could become the reference dosimeters for FLASH dosimetry, but their response suffers from ionization quenching around the Bragg peak curve in proton and other heavy-ion beams. This work presents experimental data fitted with a first- principles quantum mechanical framework that models the scintillation quenching phenomenon at FLASH ultra-high dose rates (UHDRs). Our approach demonstrates how spatial and temporal particle clustering in dense ionization tracks further decreases scintillation yield by channeling energy into non- radiative pathways, such as vibrational phonon modes, compared to conventional dose rates (CDRs). Material/Methods: Through experimental measurements at MD Anderson’s FLASH-capable proton beamline using a 5- channel PSD, we characterized the response of 4 plastic scintillators under both CDR and UHDR irradiation conditions. A quantum model based on a stochastic master equation formalism was fitted to the data, yielding effective decay rates as polynomial functions of a modified LET parameter accounting for inter-track correlations. Results: Multi-scale fitting of our theoretical model to experimental data revealed distinct parameter sets that quantify enhanced non-radiative decay contributions under FLASH conditions, with excellent agreement ( 𝑅 2 ≥ 0.94) across all fits. We identified a continuous transition between 2 physical regimes– intra-track and inter-track dominant interactions– as a
Figure 2: Top: Stamp used to induce abdominal deformation in the phantom shown bellow; Bottom: corresponding dose for the adapted and the reference plan. Conclusion: TAM-ARa provides a reproducible, multimodal platform for E2E validation of ART workflows. A comprehensive evaluation on the Varian Ethos system demonstrated realistic anatomy and motion, with accurate dose delivery across deformation scenarios, confirming its suitability for adaptive workflow verification and QA. References: Dona Lemus OM et al. Adaptive radiotherapy: next- generation radiotherapy. Cancers. 2024;16(6):1206.Liu H et al. CBCT-based online adaptive radiotherapy: current trend and future direction. Radiat Oncol. 2023;18:144.Dohm O et al. Definition and quality requirements for stereotactic radiotherapy. Strahlenther Onkol. 2022;198(3):235–246.Mamalui- Hunter M et al. Technological quality requirements for stereotactic radiotherapy. Strahlenther Onkol. 2024;200(4):301–313.Bakhtiari Moghaddam A et al. A dynamic anthropomorphic phantom for end-to-end testing in image- and surface-guided adaptive radiotherapy. Med Phys. 2025;52(11):e70107 Keywords: Adaptive, End-to-End, Anthropomorphic Phantom
Made with FlippingBook - Share PDF online