Monte Carlo Simulation of a Linear Accelerator and Electron Beam Parameters Used in Radiotherapy

In recent decades, several Monte Carlo codes have been introduced for research and medical applications. These methods provide both accurate and detailed calculation of particle transport from linear accelerators. The main drawback of Monte Carlo techniques is the extremely long computing time that is required in order to obtain a dose distribution with good statistical accuracy. In this study, the MCNP-4C Monte Carlo code was used to simulate the electron beams generated by a Neptun 10 PC linear accelerator. The depth dose curves and related parameters to depth dose and beam profiles were calculated for 6, 8 and 10 MeV electron beams with different field sizes and these data were compared with the corresponding measured values. The actual dosimetry was performed by employing a Welhofer-Scanditronix dose scanning system, semiconductor detectors and ionization chambers. The result showed good agreement (better than 2%) between calculated and measured depth doses and lateral dose profiles for all energies in different field sizes. Also good agreements were achieved between calculated and measured related electron beam parameters such as E0, Rq, Rp and R50. The simulated model of the linac developed in this study is capable of computing electron beam data in a water phantom for different field sizes and the resulting data can be used to predict the dose distributions in other complex geometries.