S1631
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
References: 1) Hayyan, M. et al., Chem. Rev.2016, 116 (5), 3029– 3085. 2) Baldacchino, G. et al., Radiat. Res.1998, 149 (2), 128–33. Keywords: ROS production, FLASH irradiation, Radiolysis Digital Poster Highlight 793 End-to-End testing of Ethos adaptive workflow with an anthropomorphic phantom Anahita B Moghaddam 1,2 , Raquel F Augusto 1,3 , Patrick Darremont 1,3 , Armin Runz 1,3 , Gernot Echner 1,3 , Wibke Johnen 1,3 , Peter Haering 1,3 , Clemens Lang 1,3 , Mona Lifferth 1,3 , Abdallah Qubala 4,5 , Oliver Jäkel 1,3 , Christian Karger 1,3 1 Division of Medical Physics in Radiation Oncology,, German Cancer Research Center (DKFZ), Heidelberg, Germany. 2 Faculty of Medicine, University of Heidelberg, Heidelberg, Germany. 3 Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany. 4 Heidelberg Ion Beam Therapy Center (HIT), University Hospital Heidelberg, Heidelberg, Germany. 5 Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Purpose/Objective: Online adaptive radiotherapy workflows enable daily treatment plan adaptation based on the patient’s anatomy at the time of treatment, improving target coverage and sparing of organs at risk. To ensure their clinical reliability, these adaptive workflows need to be thoroughly tested under realistic conditions [1,2]. Anthropomorphic phantoms capable of reproducing realistic patient motion and multimodal image contrast, while allowing for dose measurement, are essential tools for end-to-end (E2E) testing of online adaptive radiotherapy (ART), as they ensure the safety, accuracy, and reproducibility of the treatment workflow [3-5]. The Thoracic Anthropomorphic Phantom with Motion for Adaptive Radiotherapy (TAM-ARa) was developed to support this quality assurance (QA) process. Material/Methods: An anthropomorphic phantom incorporating anatomically realistic internal organs and bone structures within a flexible matrix was developed to simulate physiologic elastic deformation in the thoracic and abdominal regions (figure 1). The lungs and stomach were filled with air, and abdominal displacement was introduced using spiked-surface stamps connected to a rigid lower-abdominal frame.
Figure 1: Left: 3D model of the TAM-Ara phantom, including internal organs and fixed frame for stamp attachment; Right: photo of TAM-ARa phantom.Tissue- equivalent materials were selected to reproduce realistic anatomy and multimodal image contrast in CT and 3T MRI. The online adaptive workflow was executed on a Varian Ethos system, employing Adapt to Position (dose recalculation) and Adapt to Shape (re-optimization) modes, with independent verification via secondary dose calculation (Mobius 3D-Adapt). E2E tests with the TAM-ARa phantom were conducted under four scenarios: static reference, homogeneous deformation, spiked deformation, and lung-volume variation. Dosimetric validation was performed using a Semiflex ionization chamber (type 31010, PTW, Freiburg, Germany) positioned in the hepatic target region. Results: The phantom provided realistic CT and MRI contrast (maximum deviation 22%). Anatomical variations were successfully reproduced using the stamps (figure 2), with efficient setup and dosimeter exchange. Across all four adaptive delivery scenarios, the measured dose deviated by less than 3% from the reference plan within each scenario, confirming excellent accuracy of the online adaptive workflow.
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