S1700
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
nodes(B+LNF)) were contoured by a radiation oncologist. Two European RT photon institutions created treatment plans for each target, using the same dose prescription and energy (6X) but different techniques (Table 1). Treatment plans were delivered on a Varian Truebeam with Millennium 120 MLC and on Elekta Versa HD. Fetal doses were measured at two points corresponding to the fetal head and body using radiophotoluminescent (RPL) glass dosimeters. For the WB plan (hybrid technique), additional 2D dose mapping was performed with EBT3 Gafchromic films placed in two transversal planes (cranial and caudal) inside the fetus. Results: RPL measurements range between 12 and 22 mGy for WB plans, 0.88 and 1 mGy for BB plans and 22 and 37 mGy for B+LNF plans (Table 1). Doses in fetal head and body differ by at most few mGy for the same plan. EBT3 film measurements for WB plan show a dose distribution without considerable gradients within the fetus. Average doses are 19.6 and 8.8 mGy in cranial and caudal planes with a maximum fetal dose below 40 mGy. Film and RPL measurements in representative positions are in good agreement.
radiotherapy." Journal of applied clinical medical physics 25.2 (2024): e14240.[2] ICRP, 2000. Pregnancy and Medical Radiation. ICRP Publication 84. Ann. ICRP 30 (1). Keywords: fetal dose, breast radiotherapy
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E2E Evaluation of a Surface-Guided Gating Workflow with a Dynamic Anthropomorphic Phantom Anahita Bakhtiari Moghaddam 1,2 , Patrick Darremont 1,2 , Raquel Figueiredo Augusto 1,2 , Florian Stieler 3 , Armin Runz 1,2 , Wibke Johnen 1,2 , Peter Häring 1,2 , Christian P. Karger 1,2 1 Division of Medical Physics in Radiation Oncology, DKFZ, Heidelberg, Germany. 2 National Center for Radiation Research in Oncology (NCRO), HIRO, Heidelberg, Germany. 3 Department of Radiation Oncology of the University Medical Center Mannheim, University of Heidelberg, Heidelberg, Germany Purpose/Objective: Respiratory motion presents a significant challenge in image guided radiation therapy (IGRT), especially for thoracic and abdominal treatments1. Various motion management techniques such as breath hold, abdominal compression, and respiratory gating are clinically available to mitigate motion related uncertainties and improve treatment accuracy2. Surface guided radiation therapy (SGRT) further enables non invasive, markerless tracking of patient motion throughout imaging and beam delivery3. Before clinical application, these approaches and their integration into IGRT workflows must be comprehensively evaluated under controlled and reproducible conditions. Dynamic anthropomorphic phantoms enable realistic end-to-end (E2E) validation of motion management and gating strategies. In this study, a dynamic thoracic phantom was used to evaluate different motion management techniques under clinically relevant conditions. Material/Methods: The thoracic anthropomorphic phantom TAM-ARa, containing a liver tumor and anatomically realistic bone and soft tissue structures within a flexible matrix, was used to evaluate motion managed radiotherapy. Respiratory motion was generated via a clinical ventilator (Elisa 500 MRI, Löwenstein Medical, Germany) using a periodic signal (positive end expiratory pressure = 5 mbar, rate = 10 breaths per second, peak inspiratory pressure = 28 mbar) during 4DCT acquisition. Five CT images with different ventilator input pressures were acquired to create a calibration curve for the tumor motion. Additionally, a 5 Gy treatment plan was created on the planning CT
Conclusion: Results from the initial measurements for TENA-II indicate that the total fetal doses received during these treatments are below the 100 mGy threshold, which is considered safe according to ICRP recommendations [2]. Measurements are currently ongoing across several photon and proton centers, using different techniques and gestational stages. This ongoing research will provide evidence for safe use of RT during pregnancy and enhance our understanding of its potential impacts on fetal exposure. References: [1] Kopačin, Vjekoslav, et al. "Development and validation of the low ‑ cost pregnant female physical phantom for fetal dosimetry in MV photon
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