S1983
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Mobius3D to local clinical conditions. Material/Methods:
Measurements and calculations were performed using four Varian TrueBeam linear accelerators (two HD- MLC, two Millennium MLC). Verification plans were recalculated in Mobius3D for DLG correction factors of − 1, 0, and +1. Regression analysis was used to determine optimal DLG values for each energy (6X, 6FFF, 10FFF). Validation was carried out using the Mobius Verification Phantom™ with a PinPoint ionization chamber, comparing measured doses with Eclipse TPS and Mobius3D results. Additionally, 87 clinical IMRT/VMAT plans were recalculated in Mobius3D using default, varied, and optimized DLGs under both Autodetection and SRS (1 mm grid) configurations. Results: A strong linear dependence was observed between DLG correction factor and percentage dose deviation (R ² > 0.96) (Fig. 1).Optimal DLG values were determined as 0.55 mm (6X), 0.70 mm (6FFF), and − 1.00 mm (10FFF). Phantom measurements using the Mobius Verification Phantom™ confirmed agreement between Mobius3D, Eclipse TPS, and ion-chamber readings within 1–3%.Clinical validation across 87 plans demonstrated high gamma pass rates (> 95% for 5%/3 mm) and improved DVH consistency with optimized DLGs.Point dose comparison between
Conclusion: Parameter-specific doses resolve the ambiguity in biologically weighted dose due to dose-grid discretization for structures with different biological parameters. The approach is utilized in clinical versions of RayStation for BNCT RBE-weighted dose
Eclipse and Mobius3D showed systematic improvement after DLG optimization (Fig. 2).
and is forthcoming for EQD2 evaluation. Keywords: DVH, EQD2, dose-statistics
Digital Poster 4195
Optymalizacja i walidacja kliniczna ustawień Dosimetric Leaf Gap (DLG) w Mobius3D na potrzeby zapewnienia jakości specyficznej dla pacjenta Jan Konieczek 1 , Joanna Kaminska 2 , Monika Dami ę cka 1 , Micha ł Posiewnik 2 1 Department of Oncology and Radiotherapy, University Clinical Center, Gda ń sk, Poland. 2 Department of Oncology and Radiotherapy, Medical University, Gda ń sk, Poland Purpose/Objective: Independent dose verification is a key component of radiotherapy quality assurance (QA). The accuracy of Mobius3D—a commercial secondary dose verification system—strongly depends on proper configuration of the Dosimetric Leaf Gap (DLG) parameter. The aim of this study was to optimize and clinically validate DLG settings for different photon beam energies to adapt
Figure 1. DLG correction factor (CF) versus percentage difference for 6X, 6FFF, and 10FFF photon energies, showing strong linear correlation (R ² > 0.96).
Figure 2. Boxplots of point dose difference [%] between Mobius3D and Eclipse TPS for 6X, 6FFF, and 10FFF beams using the Mobius Verification Phantom™. Conclusion: Energy-specific optimization of DLG significantly improves Mobius3D dose calculation accuracy and
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