Raystation Monte Carlo application: evaluation of electron calculations with entry obliquity.

Abstract

To evaluate the accuracy of Raystation's implementation for Monte Carlo VMC++with electrons at varying angles of incidence for low and medium energy electron beams. Thirty-two profile and percentage depth dose scans were taken at 5° incident angle intervals for 6 and 12MeV and compared to extracted fluences from Raystation calculations using gamma analysis with 2%/2mm criteria. Point dose measurements were compared to calculated doses to determine output accuracy. Electron profile and percentage depth dose curves for both energies show good agreement between 0° and 20° with 29/30 scans above 90% pass rate. Average variation between calculated and measured point doses was -0.73% with all measurements falling within±2% of calculated dose. Raystation's application of VMC++Monte Carlo algorithm provides clinically acceptable accuracy for low and medium energy electron dosimetry at incident angles up to 20° for Varian Clinac iX models.