Monte Carlo simulation of 6 MV medical electron linear accelerator

Abstract

Objective To analyze the influence of the mean energy and the full-width of half msximum(FWHM)of incident electron beam intensity distilbution(assumed Gaussian distribution)on depth dose curves and off-axis ratios and to derive a most optimal combination of mean energy and FWHM of incident electron beam intensity distribution.Methods The study simulated 6 MV photon beam produced by Varian 600C medical linear accelerator with OMEGA/EGSnrc by matching the relative error of calculated and measured depth dose curves past depth of maximum dose and off-axis ratios at a depth of 10.0 cm in water within 2%.Results The depth dose curves were relatively insensitive to the mean energy past depth of maximum dose and the FWHM of the incident electron beam intensity distribution.Dose profiles were sensitive tO the mean energy and FWHM.The dose profiles horns decreased as the mean energy and tlle FWHM of the ineident electron beam intensity distilbution increased.The calculated value of the depth dose curves matched well with the measured value.The calculated value of the off-axis ratio was consistent with the measured value within the radiation field.However, the maximum errors of individual measurement points in the penumbra region and OUt of the field reached 18.5%.Conclusions In the field.the most optimal combination of mean energy and FWHM of incident electron beam intensitv distribution Can be derived, however,can not be derived out of the field and in the penumbra region. Key words: Linear accelerator; Simulation; Monte Cado simulation; Percentage depth dose; Off-axis ratio