Benchmarking the gamma pass score using ArcCHECK for routine dosimetric QA of VMAT plans

A minimum expected gamma (gamma) pass rate for VMAT plan verification using ArcCHECK was established based on the RTTQA, TG119 test cases and 10 clinical plans with varying levels of complexity. The impact of the 'Measurement Uncertainty' parameter as available in the ArcCHECK software on gamma pass rate was studied for both global and local gamma analysis. Our results show that excluding measurement uncertainty adds tighter tolerance in local gamma comparison. From the verification of our benchmark cases we established minimum expected gamma pass rates of 85% and 88% for 2%/2mm global and 3%/3mm local tolerance criteria.