The Simulation of Linear Accelerator Using BEAMnrc with DOSXYCnrc

Linear accelerator accurate simulation is the prerequisite of Monte Carlo dose calculation algorithm. The study simulated 6MV photon beam produced by Varian 600C medical linear accelerator to derive the mean energy and the full-width half-maximum (FWHM) of incident electron beam intensity distribution (assumed Gaussian distribution) with BEAMnrc and DOSXYZnrc by matching calculated and measured depth dose curves and off-axis ratios at a depth of 10.0cm in water. Depth dose curve is sensitive to the mean energy, insensitive to radial intensity distribution, while off-axis ratio is dramatically affected by mean energy and radial intensity distribution. Depth dose curves and off-axis ratios were performed past the depth of maximum dose within 1.5% of relative error and at 10.0cm depth within 30% of relative error, respectively.