ESTRO 2025 - Abstract Book

S3597

Physics - Quality assurance and auditing

ESTRO 2025

Conclusion: Inter-center variation in dose accumulation for reirradiation is more impacted by differences in radiobiological dose rescaling than by image registration variation, especially when doses are scaled to account for recovery. These findings stress the need for guidelines for accumulation for reirradiation. Keywords: reirradiation, dose accumulation, radiotherapy References: [1] Andratschke N, Willmann J, Appelt AL, Alyamani N, Balermpas P, Baumert BG, et al. European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making. Lancet Oncol 2022;23:e469–78. https://doi.org/10.1016/S1470-2045(22)00447-8. Digital Poster A compact, correction-less, 3D-printed dosimeter holder for postal reference dosimetry audits Alexis Dimitriadis, Liset de la Fuente, Benjamin Kellogg, Krzysztof Chelminski, Mauro Carrara, Jamema Swamidas Nuclear Sciences and Applications, International Atomic Energy Agency, Vienna, Austria Purpose/Objective: Radiophotoluminescence dosimeters (RPLDs) are increasingly utilized in postal dosimetry audits [1,2] yet current holder designs introduce operational and cost challenges. Existing holders, differ in design to enable measurements in photon or electron beams, require energy-dependent correction factors to account for perturbations, increase the size of postal kits, and can be costly to manufacture. This study presents a novel 3D-printed dosimeter holder designed to accommodate irradiation setups for both photon and electron beam reference dosimetry aiming to eliminate the need for correction factors. Material/Methods: A 3D-printed dosimeter holder was designed using FreeCAD v0.20.2 and printed with Poly-Lactic Acid to accommodate RPLDs encapsulated in waterproof High-Density Poly-Ethylene capsules. The holder is compatible with widely available cylindrical and plane-parallel chamber water tank mounts for photon and electron beam setups. The design supports the cylindrical RPLD at polar ends in an open-ring design, to minimize non-water equivalent material-related perturbations. The holder’s performance was assessed experimentally using a linear accelerator (Varian TrueBeam). Measurements in seven photon (6-18 MV) and eight electron beams (6-22 MeV) were conducted under reference conditions [3] in a water tank with an Exradin W1 scintillator (Standard Imaging, Middleton, WI, USA) and a Razor diode (IBA, Schwarzenbruck, Germany). Holder correction factors (HCFs) were calculated as the ratio of measurements with and without the 3D-printed holder. Results: The RPLD holder design was printed using an Ender-5 Plus 3D-printer (Creality, Shenzhen, China) consuming 7.72 meters of PLA filament, in ~3 hours, weighing ~23 gr. HCFs ranged between 0.999 - 1.001 across all tested beams, with a type-A relative standard uncertainty of 0.1%, confirming negligible perturbations from the holder and thus eliminating the need for correction factors. 1092