S1686
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
Digital Poster 4459 A new scintillator-based dosimetry system for real- time UHDR electron beam monitoring Behzad Shirmardi 1 , Spencer Gunn 1 , Philip von Voigts- Rhetz 2 , Marc Swallyee 3 , Stéphane SIMON 4 , sebastien Penninckx 4 1 BrightComSol GmbH, BrightComSol GmbH, Vienna, Austria. 2 IntraOp Medical Corporation, IntraOp Medical Corporation, Munich, Germany. 3 IntraOp Medical Corporation, IntraOp Medical Corporation, Brussels, Belgium. 4 Radiation Oncology, Institut Jules Bordet,, Bruseels, Belgium Purpose/Objective: Existing dosimetry systems for electron FLASH radiotherapy are challenged with the stringent requirements for real-time and 2D monitoring of ultra- high dose rate (UHDR) beams. There is a need to develop a dosimetry solution specifically designed for UHDR applications(1). Scintillator-based dosimeters have demonstrated promising potential for real-time monitoring of electron UHDR beams, making them strong candidates for future system development (2). The goal of this study was to monitor UHDR electron beam parameters in real-time using the BrightEye (3) dosimetry system. Monitored parameters included the number of pulses, total dose, dose/pulse, flatness, and symmetry. A key objective is to evaluate the linearity of the scintillation light response against the deposited dose. Material/Methods: Radiation source: IntraOp Mobetron with FLASH-IQ (4) electron LINAC capable of delivering 6MeV and 9MeV UHDR beams, equipped with two beam current transformers (BCTs) (5). The BrightEye dosimetry system includes a BrightLeaf scintillator (6), a Fast machine vision camera (BOA1936-400cc), and image processing software. Gafchromic film (model EPT-XD, Ashland) (7) was used as a reference to calibrate the BrightEye and live-measured total dose, flatness, and symmetry of the beam. Results: Following initial calibration of the scintillation light response against BCT and Gafchromic film, the BrightEye successfully monitored the total Dose, Dose/pulse, and eliminated the 24-hour waiting period required for Gafchromic dosimetry. The thin film scintillator introduced a beam disturbance of up to 5 % and demonstrated the readability of individual pulses ranging from 1 to 50 pulses. No brightness light leakages (crosstalk) to subsequent frames were observed, even at a PRF of 120Hz pulse repetition frequency, confirming the scintillator's low afterglow. Conclusion: This study is the first report on the capability of the BrightEye system for real-time beam monitoring of
electron UHDR beams. This system could be a potential alternative for in-line beam monitoring of the
UHDR LINAC. References:
1. De Freitas, N. L. & Gasparini, A. Review of real-time 2D dosimetry in external radiotherapy: Advancements and techniques. Radiat. Measure. 180, 107344 (2025)2. Verdi Vanreusel et al.Characterization and ex vivo application of flexible 2D scintillating coatings in ultra- high dose rate electron beams for FLASH radiotherapy https://doi.org/10.48550/arXiv.2504.158243. https://www.brightcomsol.com/general-7-34. https://intraop.com/flash-radiotherapy-electrons/5. https://www.bergoz.com/products/acct/6. https://www.brightcomsol.com/general-7-17. https://www.ashland.com/industries/medical/radiothe rapy-films/ebtxd Keywords: Scintillator, Dosimetry, FLASH, UHDR, Digital Poster 4526 Calculation of field output factors for intraoperative radiotherapy equipment with solid- state detectors and ionisation chambers. Diana Andrés, Raúl Pascual, Iago Mosquera, Constantino Fernández, César Quilis, Cristina Camacho Radiophysics and Radiation Protection, Hospital Clínico Universitario de Valencia, Valencia, Spain Purpose/Objective: Correct evaluation of output factors in intraoperative radiotherapy accelerators is essential, as they are used in the direct calculation of the monitor units to be delivered in treatment. In this study, the OFs for different configurations of the LIAC HWL (Sordina) were characterised using a solid-state detector and an ionisation chamber, and the measurements were compared with the MC model provided by the manufacturer to determine the most suitable detectors for characterising this equipment. Material/Methods: The OFs were measured for electron energies of 6, 8, 10, and 12 MeV for all applicators with a 0° bevel. A PTW 60019 microDiamond detector and a PTW31022 PinPoint 3D camera were used in a water phantom. The saturation correction factors (ksat) for the PinPoint were calculated according to Laitano's method [1], measuring only the applicators with diameters of 3 and 10 cm for the four energies and obtaining a regression line of ksat versus pulse charge. Results: It can be seen that, despite the small separation between PinPoint electrodes, the ksat values are not negligible, requiring correction of the collected charge
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