MCNP simulation of X-ray beam for a 15 MV medical linear accelerator

Abstract

BackgroundThe application of high-energy medical electron accelerators in the radiotherapy becomes more and more widespread. Study of the radiation source and shielding of high-energy medical electron accelerators has been the focus of attention.PurposeThis study aims to simulate 15 MV X-ray beam of Clinac 23EX medical linear accelerator by using Monte Carlo method.MethodsFirst of all, a fine geometric model of the accelerator head in X-ray mode was constructed according to the material composition and geometric dimensions of the internal parts of the head provided by the manufacturer. Then the Monte Carlo N-Particle Transport Code (MCNP) software was applied to the calculation of the percentage depth dose (PDD) curves and profile curves of the X-ray beam under different irradiation fields. Comparisons of those results with that of measured results at the same conditions in the three-dimensional (3D) water model were performed. In addition, the effects of different components on the X-ray energy spectrum and penetration ability were analyzed.ResultsThe simulation results of the PDD curves and profile curves are in good agreement with the measured results of 3D water tank. The relative deviation of PDD curves is in the range of 0.62% to 1.34%, and the relative deviations of profile curves are between 0.35% and 2.76% in high dose area and 0.48% to 5.86% in low dose area, respectively.ConclusionsIt is confirmed that the detailed model of the accelerator head established in this study is accurate and reliable, hence appliable to the subsequent analysis of various source items. The effects of different components of accelerator on the X-ray energy spectrum and penetration ability provide references for optimizing shielding design and radiotherapy plan.

Keywords

• medical electron accelerator
• x-ray beam
• percent depth dose
• monte carlo