Determination of initial electron parameters by means of Monte Carlo simulations for the Siemens Artiste Linac 6MV photon beam.

Abstract

In this study, we investigated initial electron parameters of Siemens Artiste Linac with 6MV photon beam using the Monte Carlo method. It is essential to define all the characteristics of initial electrons hitting the target, i.e. mean energy and full width of half maximum (FWHM) of the spatial distribution intensity, which is needed to run Monte Carlo simulations. The Monte Carlo is the most accurate method for simulation of radiotherapy treatments. Linac head geometry was modeled using the BEAMnrc code. The phase space files were used as input file to DOSXYZnrc simulation to determine the dose distribution in a water phantom. We obtained percent depth dose curves and the lateral dose profile. All the results were obtained at 100cm of SSD and for a 10×10cm2 field. We concluded that there existed a good conformity between Monte Carlo simulation and measurement data when we used electron mean energy of 6.3MeV and 0.30cm FWHM value as initial parameters. We observed that FWHM values had very little effect on PDD and we found that the electron mean energy and FWHM values affected the lateral dose profile. However, these effects are between tolerance values. The initial parameters especially depend on components of a linac head. The phase space file which was obtained from Monte Carlo Simulation for a linac can be used as calculation of scattering, MLC leakage, to compare dose distribution on patients and in various studies.