SU-E-T-324: Multi-Institution Comparison for TrueBeam Commissioning Data and Beam Modeling Verification Using An Anisotropic Analytical Algorithm

Abstract

Purpose: To perform a dosimetric comparison of TrueBeam(TB) commissioning data between UAMS and other institutions; verify the beam modeling accuracy. Methods: Dosimetric data including percentage depth dose (PDD), penumbra, mlc transmission leakage(TL) and dosimetric leaf gap(DLG) for 6MV, 6MV FFF, 10MV and 10MV FFF X-ray beams were compared with two published papers (Chang et.al (Publication #1) and Jan et.al (Publication #2)). The beam modeling accuracy was evaluated by comparing the PDD, absolute point dose and patient dose from Eclipse TPS calculation using AAA algorithm and from measurements. Point dose was measured using calibrated ion chambers of different sizes at different depths, different field sizes for all four energies. Patient IMRT and VMAT doses were verified using PTW Octavius ion chamber and SunNuclear ArcCheck diode array. Results: The comparison of UAMS TB commissioning data with published data shows that the differences for PDDs are within 1% except for 10MV FFF beam, where the maximum difference is within 3% as compared with Publication #2. The differences for penumbra are within 1mm for all four energies. At UAMS, the mlc TL and DLG are 1.21% and 0.45mm for 6MV; 1.02% and 0.348mm for 6MV FFF; 1.39% and 0.545mm for 10MV; and 1.2% and 0.484mm for 10MV FFF beams respectively. These results are in good agreement with those from the other two institutions. For Eclipse beam modeling evaluation, all point dose measurements are within 3% compared with the Eclipse TPS calculation except for the 1.0 cm2 field size, where the maximum difference is 5%. All patient QAs were acceptable with a gamma agreement index score of 95% or higher based on the 3%, 3mm criteria. Conclusion: Commissioning data for the UAMS TB was clinically identical with the published data from two other institutions. The beam modeling verification shows that Eclipse modeling of these four beams is accurate.