ESTRO 2025 - Abstract Book

S2705

Physics - Dose calculation algorithms

ESTRO 2025

Material/Methods: During the update of the Acuros dose calculation algorithm to version 18, the ELM module was introduced. Measurements were performed on the machine for different inter-leaf gaps and integrated into the Treatment Planning System (TPS). In the beam configuration, the profiles, PDDs, and diagonal data measured for the previous version were reintroduced into the new version. After computation, discrepancies between the measurements and the algorithm results were assessed. This model was validated using a configuration created on the TPS, featuring three sliding slits with a 2 mm gap, verified with the EPID. We also compared the various results obtained for electron contamination, the spectrum, the backscatter factor, and the mean radial energy , for a 6 MV photon beam generated by the Varian Clinac iX linear accelerator, equipped with a 120 Millennium MLC, installed at the Radiotherapy Department of Chahid Mahmoudi Hospital in algeria . Results: The results obtained demonstrate a significant difference between the configuration using the new ELM model and the previous one, particularly regarding its impact on the modeling of the secondary source in the Acuros algorithm. For the mean radial energy, the relative discrepancies observed range from 0.2% to 0.9%.