Purpose: To evaluate the accuracy and performance of DoseCHECK and Mobius as independent plan verification software for the purpose of pre-treatment quality assurance of Varian Ethos adaptive plans.
Methods: DoseCHECK and Mobius were commissioned in accordance with international best practice documents on treatment planning system (TPS) commissioning and quality assurance, including: AAPM TG53, TG119, MPPG5a and IAEA TECDOC1583. All plans were sent to DoseCHECK and Mobius for independent dose calculation, and compared to measurement on the treatment delivery system (TDS). For end-to-end validation, Ethos clinical patient plans (n=50) were generated in the Ethos TPS encompassing a range of clinical sites and techniques (IMRT and VMAT), then sent to DoseCHECK and Mobius for independent dose calculation. Mean dose to the target and overall gamma pass rate were extracted and compared to phantom measurement on the TDS, with plan complexity defined as MU/Gy.
Results: All results for commissioning test plans were within the published tolerances for DoseCHECK and Mobius when compared to the TPS and measurement. Higher degrees of uncertainty were noted for extreme cases, such as small field sizes, build-up region (surface dose) and heterogeneity. All patient plans were validated through measurement and in Mobius and DoseCHECK 3D gamma criteria of 3%/3mm (10% threshold, global normalisation) >95% points passing and mean dose to target difference within 3% was configured to achieve comparable results. The average gamma pass rate for both systems was >95% for all plans tested and mean dose to target difference <1%. In general, plans of higher complexity or significant heterogeneity contained higher uncertainty.
Conclusion: DoseCHECK and Mobius were commissioned and found to be within tolerance of all tests recommended in international best-practice guidelines. Both systems were used to independently verify plan dose calculation for pre-treatment QA of Ethos adaptive plans.
Funding Support, Disclosures, and Conflict of Interest: NSCC has reference site agreements with Varian and SNC.