Author: Eujin Chan, Christopher Colyer, Leon F Dunn, Jonathan Dunning, Michael Grace, Onno Kamst, Alex Livingstone, Thulani Nyathi, Vladimir Sashin, Philip Satory, Hilmar Schachenmayr, Brindha Subramanian, Lindsay J. Tremethick, Luke Webb ๐จโ๐ฌ
Affiliation: GenesisCare ๐
Purpose: The purpose of this work is to outline the methodology and results from the implementation of a 3D recalculation software to replace IMRT/VMAT PSQA measurement across a large, networked radiotherapy provider (71 Linacs, across 43 sites).
Methods: Using the RadCalc (LifeLine Software Inc, Tyler Tx, USA) 3D recalculation, two independent CCC models were developed using average measured data. One for each treatment platform (VersaHD/Monacoยฎ and TrueBeamยฎ/EclipseTM). The models were evaluated in both planning systems using standardised basic plans and geometries as well as comparing model output versus the measured input data. To derive tolerances and test the system, 651 previous IMRT/VMAT treatment plans from both systems were used to statistically derive gamma pass-rate tolerances for clinical use. System stress tests and timing studies were performed to determine whether a single GPU could handle up to 120 - 150 new plans per day from across the country.
Results: The CCC algorithm compares well across all treatment sites independent of planning system used (Monaco / Eclipse) with an average gamma pass-rate of 98.7% ยฑ 0.9 % for 3%/3mm and 97.4% ยฑ 1.5% (1ฯ) for 3%/2 mm when calculating over the entire patient volume. Regions of inhomogeneity and field edge modelling show the largest variation between 3D recalculation and TPS. A single RC server with an ADA 6000 GPU could manage recalculation of up 150 treatment plans per day automatically. Retrospective analysis of 12,100 IMRT/VMAT treatment plans post rollout shows a mean pass rate of 98.5% ยฑ 4.3% for 3%/2mm calculated on the patient volume, and 94.8% ยฑ 8.5% for calculations in the PTV.
Conclusion: RadCalc 3D recalculation is a robust and accurate method to reduce or replace IMRT/VMAT QA measurement when supplemented with additional MLC QA.