Evaluation of candidate template beam models for a matched TrueBeam treatment delivery system

PURPOSE: To explore candidate RayStation beam models to serve as a class‐specific template for a TrueBeam treatment delivery system. METHODS: Established validation techniques were used to evaluate three photon beam models: a clinically optimized model from the authors’ institution, the built‐in RayStation template, and a hybrid consisting of the RayStation template except substituting average MLC parameter values from a recent IROC survey. Comparisons were made for output factors, dose profiles from open fields, as well as representative VMAT test plans. RESULTS: For jaw‐defined output factors, each beam model was within 1.6% of expected published values. Similarly, the majority (57–66%) of jaw‐defined dose curves from each model had a gamma pass rate >95% (2% / 3 mm, 20% threshold) when compared to TrueBeam representative beam data. For dose curves from MPPG 5.a MLC‐defined fields, average gamma pass rates (1% / 1 mm, 20% threshold) were 92.9%, 85.1%, and 86.0% for the clinical, template, and hybrid models, respectively. For VMAT test plans measured with a diode array detector, median dose differences were 0.6%, 1.3%, and 1.1% for the clinical, template, and hybrid models, respectively. For in‐phantom ionization chamber measurements with the same VMAT test plans, the average percent difference was −0.3%, −1.4%, and −1.0% for the clinical, template, and hybrid models, respectively. CONCLUSION: Beam model templates taken from the vendor and aggregate results within the community were both reasonable starting points, but neither approach was as optimal as a clinically tuned model, the latter producing better agreement with all validation measurements. Given these results, the clinically optimized model represents a better candidate as a consensus template. This can benefit the community by reducing commissioning time and improving dose calculation accuracy for matched TrueBeam treatment delivery systems.