Commissioning and validation of the Elekta One GPUMCD algorithm for an Elekta VersaHD linear accelerator

The purpose of this work was to commission and validate GPUMCD, a GPU-accelerated Monte Carlo dose calculation engine for c-arm Elekta linear accelerators (linac). This algorithm was recently released for clinical implementation in the Elekta One Treatment Planning System (v6.2.3, EOP).

A GPUMCD beam model was generated for all photon energies of a VersaHD linac (6X, 6FFF, 10X, 10FFF, 18X). A validated version of the Monaco Commissioning Utility was used to compare calculated percent depth dose (PDD) profiles as well as lateral profiles for open fields against measurements. An adapted MPPG 5.b methodology was used to verify point-doses and 3D dose distributions in homogeneous and heterogeneous media using the ArcCheck, solid water, the CIRS ZEUS phantom, and the IROC HN and spine phantoms.

The average agreement between measured and calculated PDDs and beam profiles using a local 2% dose difference (DD) in the high dose region for fields greater than 5 × 5 cm² was 98.4% ± 2.3% for all energies. Using a 2% DD and 2 mm distance-to-agreement (DTA) gamma criteria for all fields using a 5% dose threshold yielded an agreement of 99.9% ± 0.5%. For open fields, GPUMCD reduced the calculation time by 93% as compared to X-ray voxel Monte Carlo (XVMC) using the same hardware. All MPPG 5.b. recommended testing was within the suggested tolerance limits. All plan measurements passed at the recommended gamma criteria. GPUMCD heterogeneity agreement and point dose measurements were found to agree within 3%.

The GPUMCD algorithm in EOP was successfully tested and commissioned for clinical use for the VersaHD linac.