ESTRO 2025 - Abstract Book

S2624

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Conclusion: EPIgray demonstrated good repeatability and generally acceptable accuracy across most clinical scenarios. However, its performance was less accurate for small fields and low-density tissues, such as the lung. Further research is recommended to explore these limitations and enhance its suitability for routine in-vivo dosimetry.

Keywords: in-vivo EPID-based dosimetry

References: Dogan N, Mijnheer BJ, Padgett K, et al. AAPM Task Group Report 307: use of EPIDs for patient-specific IMRT and VMAT QA. Med Phys. 2023; 50(8): e865-e903

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Digital Poster Application of ESTRO commissioning protocol to a commercial solution for secondary check and EPID-based in vivo dosimetry: a multicenter study Elisabetta Cagni 1 , Cinzia Mordacchini 2 , Salvatore Pittera 3 , Andrea Bruschi 4 , Marco Pio Petrillo 5 , Ayman El Ouati 5 , Serenella Russo 4 1 Medical Physics Unit, Department of Advanced Technology, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy. 2 Medical Physics Unit, ASST dei Sette Laghi, Varese, Italy. 3 Medical Physics Unit, Grande Ospedale Metropilitano, Reggio Calabria, Italy. 4 Medical Physics Unit, Azienda USL Toscana Centro, Florence, Italy. 5 Physics Department, Università di Modena e Reggio Emilia, Modena, Italy Purpose/Objective: To evaluate a commercial software for secondary check and in vivo dosimetry (IVD) before the clinical use. A practical framework for testing electronic portal imaging detector (EPID) based IVD systems recently published by the dedicated ESTRO working group [1] has been adopted. Material/Methods: This work has been conducted by an RadCalc Italian User Consortium (RIUC) working group created in 2024, for supporting the implementation and standardizing the use of several modules offered by a commercial solution (RadCalc, LAP, USA), related to independent secondary plan check, including independent dose calculation (both Monte Carlo (MC) and Collapsed Cone (CC)) and EPID in vivo dosimetry (EPID IVD) implementation. Four national centers participated in this study, the characteristics of each institute (treatment planning systems (TPS), linear accelerator (Linac), EPID dosimetry systems) are reported in Table 1. The performed tests included a set of square irradiation fields (from 2cmx2cm to 20cmx20cm) in homogeneous water-equivalent slab phantoms, SLABthick (30 cm thick) and SLABthin (10 cm thick), as well in an inhomogeneous water-equivalent slab phantom, 18 cm solid water slab phantom with 2cm air inhomogeneity (2cmAirGap) and 26 cm solid water slab phantom with 5 cm air inhomogeneity (5cmAirGap). For all the tests, the percentage dose difference at isocenter (DD%) and a gamma 3D analysis (global normalisation, 3%/2mm, 30% threshold at isocenter dose) between the TPS and secondary check were considered.