ESTRO 2025 - Abstract Book

S2583

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Conclusion: These findings suggest that the previously observed nonlinear effects are likely attributable to electrometer limitations which was not designed for FLASH, rather than intrinsic properties of the W2 scintillator. This study supports the use of the W2-scintillator for accurate dose measurement in UHDR radiation therapy.

Keywords: FLASH, UHDR, SCINTILLATION

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Digital Poster Commissioning and Performance Assessment of the AQURE Mobile Accelerator for Intraoperative Radiotherapy Tomasz Piotrowski 1,2,3 , Adam Ryczkowski 2 , Bartosz Pawałowski 2 , Marta Kruszyna-Mochalska 2,1 1 Electroradiology, University of Medical Sciences, Poznań, Poland. 2 Medical Physics, Greater Poland Cancer Centre, Poznań, Poland. 3 Biomedical Physics, Adam Mickiewicz University, Poznań, Poland Purpose/Objective: The AQURE is a newly developed mobile linear accelerator for intraoperative electron radiotherapy (IOERT). This study evaluates, documents, and compares the dosimetric characteristics measured during the commissioning of the machine at our centre. Material/Methods: The AQURE was tested at electron energies of 4, 6, 9, and 12 MeV, with applicators of cylindrical shape ranging from 4 to 10 cm in diameter. Two sets of measurements were conducted: (a) using a microDiamond detector in a BeamScan water phantom to evaluate depth dose distributions, flatness and symmetry of dose profiles, as well as output constancy and linearity, and (b) using a Farmer ionization chamber in a solid water phantom to assess output variation with gantry angle. The results were compared with data from other IOERT accelerators and analyzed according to current scientific recommendations and regulatory standards. Results: The measured parameters were consistent with the recommended ranges. The profiles and depth dose distributions were in close agreement with data from other IOERT systems, with any observed differences attributed to the specific technical features of the AQURE that influence the final dose distribution. Analysis of the mean and most probable energy values indicated that the electron beams used in IOERT cannot be considered strictly mono-energetic. We recommend further investigating the energy spectrum for each mobile IOERT accelerator before clinical application. Table. The worst value of dosimetric parameters obtained during our measurements (Worst OBS) compared with the limit values of acceptable discrepancy according to American (AAPM [1]), Italian (ISS [2]), and Polish (PSMP [3]) recommendations and legal regulations in the authors' country (RMZ [4]).