a comparison of two pencil beam scanning treatment planning systems for proton therapy

Objective: analytical dose calculation algorithms for eclipse and raystation treatment planning systems (tps), as well as a raystation monte carlo model are compared to corresponding measured point doses. method: the tps were modeled with the same beam data acquired during commissioning. thirty-five typical plans were made with each planning system, 31 without range shifter and four with a 5 cm range shifter. point doses in these planes were compared to measured doses. results: the mean percentage difference for all plans between raystation and eclipse were 1.51 ± 1.99%. the mean percentage difference for all plans between tps models and measured values are -2.06 ± 1.48% for raystation pencil beam (pb), -0.59 ± 1.71% for eclipse and -1.69 ± 1.11% for raystation monte carlo (mc). the distribution for the patient plans were similar for eclipse and raystation mc with a p-value of 0.59 for a two tailed unpaired t-test and significantly different from the raystation pb model with p = 0.0013 between raystation mc and pb. all three models faired markedly better if plans with a 5 cm range shifter were ignored. plan comparisons with a 5 cm range shifter give differences between raystation and eclipse of 3.77 ± 1.82%. the mean percentage difference for 5 cm range shifter plans between tps models and measured values are -3.89 ± 2.79% for raystation pb, -0.25 ± 3.85% for eclipse and 1.55 ± 1.95% for raystation mc. conclusion: both eclipse and raystation pb tps are not always accurate within ±3% for a 5 cm range shifters or for small targets. this was improved with the raystation mc model. the point dose calculations of eclipse, raystation pb, and raystation mc compare within ±3% to measured doses for the other scenarios tested.