S1701
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
and delivered on an Elekta linear accelerator under five conditions: static, gated (with and without beam- on delay), deep-inspiration breath-hold (DIBH), and free breathing. Dose distributions were measured with Gafchromic EBT4 films placed in the tumor plane. Results: Reproducible respiratory tumor motion was achieved using the clinical ventilator, with a displacement of 0.41 mm per mbar input pressure. Measurements using inspiratory gating with and without delay, as well as DIBH showed similar dose distributions to the ideal static case (9.63% of the film irradiated area exhibited a relative signal intensity ≥ 90% of the signal maximum for all four cases). This demonstrates a significant improvement over free breathing irradiation, where the area with a relative signal intensity ≥ 90% covered 18.32% of the irradiated film. Conclusion: This study demonstrated that the setup allows rapid and efficient implementation of motion-managed irradiation tests using the TAM-ARa phantom. Gating and DIBH effectively reduced motion induced dose degradation. The future work will investigate higher target motion amplitudes and irregular breathing patterns to further assess robustness under realistic clinical conditions. References: 1Samuel Wilcox, Zhefeng Huang, Jay Shah, Xiaofeng Yang, and Yue Chen. Respiration-induced organ motion compensation: a review. Annals of Biomedical Engineering, 53(2): 271–283, 2025. 2Abdallah Qubala, Jehad Shafee, Thomas Tessonnier, Julian Horn, Marcus Winter, Jakob Naumann, and Oliver J¨akel. Characteristics of breathing-adapted gating using surface guidance for use in particle therapy: a phantom-based end-to-end test from ct simulation to dose delivery. Journal of Applied Clinical Medical Physics, 25(1):e14249, 2024. 3Vania Batista, Juergen Meyer, Malin Kügele, and Hania Al-Hallaq. doi: https://doi.org/10.101 Keywords: Gating, Dynamic Anthropomorphic Phantom, E2E, SGRT Patient-specific Monte Carlo simulations of fast neutron and prompt gamma ray detection for in- vivo proton beam range verification Sander Blørstad Thu 1 , Anna Milde Bekkevoll 2,1 , Camilla Hanquist Stokkevåg 2,1 , Hunter Nathaniel Ratliff 3 , Ilker Meric 3 , Toni Kögler 4,5 , Kristian Smeland Ytre-Hauge 1 1 Department of Physics and Technology, University of Bergen, Bergen, Norway. 2 The Cancer Clinic, Haukeland University Hospital, Bergen, Norway. 3 Department of Computer Science, Electrical Engineering and Mathematical Sciences, Western Digital Poster Highlight 5083
Norway University of Applied Sciences, Bergen, Norway. 4 OncoRay–National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden – Rossendorf, Dresden, Germany. 5 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology OncoRay, Dresden, Germany Purpose/Objective: While proton therapy offers advantages in terms of physical dose sparing, it is sensitive to proton beam range uncertainties caused by deviations such as organ motion, patient positioning, and conversion between CT Hounsfield unit and stopping power ratio. One route to reduce range uncertainties is through range verification by the detection and imaging of secondary particles like fast neutrons (FNs) and prompt gamma rays (PGs). In this study we present in- silico predictions of PG and FN detection with a compact scintillation detector to reconstruct individual proton beam ranges from PG and FN emission distributions. Material/Methods: First, a novel detector design consisting of multiple individual scintillator bars grouped in alternately oriented layers was modelled in the FLUKA Monte Carlo software. Proton treatment plans and patient CT geometries were then implemented for four patients with respective tumor sites brain, head-and-neck (HNC), prostate and lung (Figure 1). Ten spots centrally positioned within one treatment field per patient were chosen and simulated with patient geometry using 1x109 primary protons each. Information about all interactions occurring in the scintillator bars was recorded during simulation. The number of detected PG- and FN events were counted based on events with triple coincidence Compton interactions, and double coincidence (n,p) scatters, which were necessary to reconstruct the emission distributions. All interactions in an event were required to occur in different scintillator bars and to deposit at least 10 keV for PGs and 200 keV for FNs, respectively.
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