Evaluation and benchmarking of EGSnrc code in the simulation of 18 MV photon beam produced by Siemens Oncor® linear accelerator

Introdution: The aim of this study was to evaluate and benchmark EGSnrc code in the simulation of 18 MV photon beam produced by Siemens Oncor® linear accelerator.
This study was conducted in a comparative and simulation based on experience method. The Beamnrc code was used to model the accelerator head and generate phase space files. The phase space files were obtained with the following parameters: field size of 10×10 , the energy of 14 Mev up to 14.8 Mev, and Full Width at Hall of Maximun of 0.12 cm. The phase space files were then used as input to the Dosexyznrc code to do dosimetry in the homogeneous water phantom with 50×50×50 size. Then, the output of DOSXYZnrc code, 3ddose files were used to obtain depth-dose curves and dose profile curves. Finally, Simulations were compared with experimental data by using gamma index.
The energy tuning procedure have shown that the optimum energy and FWHM for the simulation model, were 14 Mev, 14.2 Mev , 14.4 Mev and 0.12 cm, respectively. The gamma index values, for depth-dose curves and dose-profile curve, were obtained less than 1.

In this study, Monte Carlo model of Oncor® linac treatment head was simulated and the results have shown that the optimum nominal energy and FWHM were 14 Mev, 14.2 Mev, 14.4 Mev and 0.12 cm, respectively.