Modelamento de um acelerador linear Varian 600 C/D para estudo dosimétrico usando método de Monte Carlo

Abstract

Based on the high availability of low energy linear accelerators in Brazil and with the goal of developing a reliable tool for dose distribution calculations in radiotherapy; this research aims to validate a linear accelerator head model using MCNP Monte Carlo code. The Varian600 C/D linear accelerator installed at the Hospital São João de is taken as reference. The main components of the linear accelerator head were simulated based on detailed information of the manufacturer. In order to calculate dose distribution, a water phantom with dimensions of 30 x 30 x 30 cm3 was simulated and placed at 100 cm of source-surfacedistance. A monoenergetic electron beam of 6,3 MeV was considered as a source. The number of primary particles used in the simulation was 108. A Phase-Space Surface was used to scoring the photon spectrum below the tungsten target. Others two were placed in the model in order to reduce computational time and improve statistical accuracy. In orderto validate the developed model, the X-ray spectrum generated by bremsstrahlung was calculated and analyzed. Furthermore, the results of percentage depth doses and beam profiles calculations were compared with available measurements. The MCNP calculations results were compared to measurement showing good agreement between them. The comparison between MCNP calculations and measurement of PDD showed reasonable coherence at build-up region. The results were in an acceptable interval of confidence at the flat region of beam profiles comparison for three different field sizes. In this work, we compared MCNP calculations to experimental data in order to validate the developed LINAC head model. The results showed a good agreement according to the recommended criteria. The developed model was validated as an accurate tool for LINAC quality control procedures.