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.