Validation of Monte Carlo simulation of 6 MeV photon beam produced by Varian Clinac 2100 linear accelerator using BEAMnrc code and DOSXYZnrc code

The Monte Carlo model for the photon-beam output from the Varian Clinac 2100 linear accelerator was validated to compare the calculated to measured PDD and beam dose profiles. The Monte Carlo calculation method is considered to be the most accurate method for dose calculation in radiotherapy. The objective of this study is to build a Monte Carlo geometry of Varian Clinac 2100 linear accelerator as realistically as possible. The Monte Carlo codes used in this work were the BEAMnrc code to simulate the photon beam and the DOSXYZnrc code to examine the absorbed dose in the water phantom. We have calculated percentage depth dose (PDD) and beam profiles of the 6 MeV photon beam for the 6 × 6, 10 × 10, and 15 × 15 cm field sizes. We have used the gamma index technique for the quantitative evaluation to compare the measured and calculated distributions. Good agreement was found between calculated PDD and beam profile compared to measured data. The comparison was evaluated using the gamma index method and the criteria were 3% for dose difference and 3 mm for distance to agreement. The gamma index acceptance rate was more than 97% of both distribution comparisons PDDs and dose profiles, and our results were more developed and accurate. The Varian Clinac 2100 linear accelerator was accurately modeled using Monte Carlo codes: BEAMnrc and DOSXYZnrc codes package.