S1680
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
1 Research in Dosimetric Applications, Belgian Nuclear Research Centre, Mol, Belgium. 2 Department of Radiation Oncology, Maastricht University Medical Centre, Maastricht, Netherlands. 3 Iridium Kankernetwerk, University of Antwerp, Antwerp, Belgium. 4 Department of Chemistry & Biochemistry, Florida State University, Tallahassee, USA Purpose/Objective: Ensuring accurate dose delivery in adaptive radiotherapy (ART) remains a major challenge, particularly in dynamic regions such as the thorax where respiratory motion can induce significant geometric and dosimetric uncertainties. This study aimed to integrate and validate a real-time 2D scintillation-based dosimetry system within a highly realistic 3D-printed anthropomorphic thorax phantom, as developed in the VERIFIED (PIANOFORTE2023-027) project. The objective was to demonstrate accurate, frame-by-frame monitoring of dose delivery during adaptive Volumetric Modulated Arc Therapy (ART- VMAT), providing quantitative feedback for real-time verification and adaptive control. Material/Methods: A flexible scintillating film coupled to a high-sensitivity CMOS scientific camera was integrated into the thoracic surface of a 3D-printed, tissue-equivalent phantom replicating human lung anatomy and motion. The phantom, developed by Maastricht University (UM), includes deformable lung inserts and programmable breathing simulation modules to reproduce respiratory-induced target displacement. The optical system was geometrically and dosimetrically calibrated using ion chamber and film reference measurements following ESTRO-ACROP QA guidelines.During ART-VMAT delivery on a clinical LINAC (ZAS Antwerp), time-resolved 2D scintillation images were acquired at ≥200 fps. Deep learning- based image registration was used to align frames with planned dose maps and to quantify deviations in real time. The acquired images were compared to treatment planning system (TPS) dose distributions via γ-index analysis (3%/2 mm) and dose–response linearity was evaluated up to 15 Gy/min. Results: The system achieved millisecond response times and dose linearity (R² > 0.999) across the clinical dose range. Geometric accuracy in the phantom was maintained within ±0.5 mm under dynamic breathing conditions. Real-time monitoring detected deviations in MLC leaf motion and gantry speed in under 50 ms latency, correlating with intentional TPS perturbations. The γ-index pass rate exceeded 96% (3%/2 mm) under static conditions and 91% during motion. These results confirm the system’s potential for real-time ART-VMAT verification under clinically relevant, dynamic scenarios.
Conclusion: This study introduced a dynamic 3DP anthropomorphic phantom incorporating a
controllable dynamic bladder. More realistic dynamic bladder simulations in this phantom could enable the evaluation of more clinically realistic cases, improving oART workflow quality further. References: 1. Green OL, Henke LE, Hugo GD. Practical clinical workflows for online and offline adaptive radiation therapy. Semin Radiat Oncol. 2019 Jul;29(3):219–27.2. Physics Research Division, Maastro. AMIGOpy (A Medical Image-based Graphical platfOrm – Python). Version 0.3 alpha; 2025. Available from: https://www.amigo-medphys.com/ and https://github.com/PhysicsResearch/AMIGOpy.3. Fedorov A, Beichel R, Kalpathy-Cramer J, Finet J, Fillion- Robin J-C, Pujol S, Bauer C, Jennings D, Fennessy F M, Sonka M, Buatti J, Aylward S R, Miller J V, Pieper S, Kikinis R. 3D Slicer as an Image Computing Platform for the Quantitative Imaging Network. Magn Reson Imaging. 2012 Nov;30(9):1323-41. Keywords: Anthropomorphic dynamic phantom, 3D printing, CBCT Proffered Paper 4103 Real time 2D dosimetry system in a highly realistic anthropomorphic thorax phantom Luana de Freitas Nascimento 1 , Tim Stassen 2 , Frank Verhaegen 2 , Gabriel Paiva Fonseca 2 , Dirk Verellen 3 , Jo Goossens 3 , Tarannuma Ferdous Manny 4 , Sahel Moslemi 4 , Biwu Ma 4
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