Clinical implementation of a PRIMO Monte Carlo-based dose verification and quality assurance model for stereotactic body radiotherapy (SBRT) treatment plans of the lung

Natural The validation and clinical implementation of the PRIMO Monte Carlo (MC) model of Clinac®iX Linear accelerator as an independent dose verification and quality assurance (QA) tool for the SBRT lung treatment plans.

An independent MC based dose verification was performed for ten volumetric modulated arc therapy (VMAT) SBRT treatment plans.The plans generated in the Varian Eclipse treatment planning system (TPS) were recalculated with a PRIMO MC system for identical beam parameters.The log file-based QA was performed by comparing the TPS dose against the dose reconstructed from machine log files and the results were cross-verified with the Mobius3D® verification system. The dose-volume histogram (DVH) based plan comparison and 3D global gamma analysis were carried out. The statistical significance of the differences was tested with the Wilcoxon signed-rank test with a significance level of P < 0.05.

No statistically significant differences were observed in PTV and organs at risk (OARs) DVH parameters except for the PTVmax dose for both TPS vs PRIMO independent dose check and TPS vs PRIMO dynalog based QA. The 3D gamma analysis results show a minimum pass rate of 95% between TPS and PRIMO. Mobius3D® results showed a slightly higher percentage variation in the mean dose to PTV and OARs and a slightly lower gamma pass than TPS vs PRIMO results.

This study showed that a validated MC model of PRIMO could be used as an effective tool for independent dose verification and machine log-files-based quality assurance of VMAT SBRT plans.