S1725
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
dosimetric accuracy and supports more reliable planning for head-and-neck proton therapy. References: 1. Wong YM, Koh CWY, Lew KS, Chua CGA, Yeap PL, Andrew W, et al. Effects of modern aesthetic dental fillings on proton therapy. Phys Imaging Radiat Oncol. 2024 Jan 1;29. 2. Yamram N, Sanghangthum T, Saikaew P, Phaisangittisakul N, Prayongrat A, Ayuthaya IIN, et al. Simulation of stopping power for therapeutic proton beams in dental amalgam. Health Technol (Berl). 2025 Sep 1;15(5):841–5. Keywords: proton therapy, dose accuracy, dental materials Poster Discussion 2274 Magnetic resonance imaging (MRI)-informed hypoxia-based proton therapy dose escalation for head-and-neck cancer Sebastian Tattenberg 1 , Nils Tanneau 1 , Walid Dandachly 1 , Benjamin Leporq 1 , Charlène Bouyer 2 , Frank Pilleul 1,2 , Vincent Gregoire 1,2 , Marie Claude Biston 1,2 , Olivier Beuf 1 1 INSA-Lyon, Universite Claude Bernard Lyon 1, CNRS, Inserm, CREATIS UMR 5220, U1294, Lyon, France. 2 Radiotherapy, Centre Léon Bérard, Lyon, France
Results: Experimental SPRs of dental materials were 4.51, 3.19, 2.39, 1.43, and 0.97 for amalgam, zirconia, titanium, lithium disilicate, and resin composite, respectively. Significant dose deviations were observed in both SOBP and IMPT plans when the default CT calibration was used. In SOBP analysis, the maximum mean dose differences were 30% for amalgam and 24% for zirconia at a depth of 2 cm. Applying experimental SPR data improved agreement with film measurements. In the CIRS head-phantom IMPT tests, SPR overrides corrected range errors and restored appropriate target coverage. Dose differences between default CT calibration and SPR corrected plans ranged from 20% to 30%, primarily along beam paths traversing these dental materials. Figure 2 illustrates the result for amalgam as an example. Depth-dose profiles along the beam path showed underdose without SPR correction. DVH analysis revealed notable shifts in D95, D98, and the maximum dose for the clinical target volume (CTV) and the oral cavity.
Purpose/Objective: Purpose/Objective: In head-and-neck cancer,
radiotherapy dose escalation is being investigated because hypoxia-induced radioresistance is associated with poorer clinical outcomes.1,2,3 While clinical trials rely on positron emission tomography (PET)-informed hypoxia information, a magnetic resonance imaging (MRI)-informed approach would allow various functional and anatomical maps (with excellent soft tissue contrast) to be extracted from the same scan, without the need for an ionizing radiation dose. This study investigates MRI-informed hypoxia-based dose escalation during proton radiotherapy. Material/Methods: Material/Methods: After approval by the local ethics committee and patients providing informed consent (R201-004–314), 10 head-and-neck cancer patients receiving photon therapy underwent multi-parametric MRI (T2-weighted multi-echo turbo-spin-echo, three- dimensional fast low-angle shot, and work-in-progress motion correction diffusion-weighted imaging). T2 and T2* mapping and intra-voxel incoherent motion (IVIM) modelling were used to generate relative oxygen extraction fraction (rOEF) and slow molecular diffusion coefficient (Dslow) maps based on which clinical target volumes (CTVs) were divided into hypoxic and normoxic sub-volumes, with an example shown in Figure 1.4 Four proton therapy treatment plans were created per patient: conventional intensity-modulated
Conclusion: Dental materials significantly affect proton range and dose-calculation accuracy. Incorporating experimentally measured SPRs into TPS enhances
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