Dosimetry Investigation and Evaluation for Removing Flattening Filter Configuration of Linac: Monte Carlo Study

The objective of this study is to build a Monte Carlo geometry of Varian Clinac 2100 linear accelerator as realistically as possible and then to investigate the removing of flattening filter impact on dosimetry for a high radiotherapy efficiency. Monte Carlo codes used in this work were BEAMnrc code to simulate photons beam and DOSXYZnrc code to examinate absorbed dose in water phantom. PDDs and beam profiles were calculated for 6 × 6 cm2 and 10 × 10 cm2 field sizes. Good agreement was found between calculated PDD and beam profile compared to measurements. Gamma index acceptance rate was more than 98% of both distribution comparisons PDDs and dose profiles and our results were more developed and accurate. Varian Clinac 2100 linear accelerator was accurately modeled using Monte Carlo codes: BEAMnrc, DOSXYZnrc and BEAMDP codes package. Varian Clinac 2100 with removing flattening filer could increase the dose by a gain was approximately 80% for 6 × 6 cm2 field size and it was approximately 110% for 10 × 10 cm2 at the build-up dose region but for all depth in water phantom, the dose of without FF configuration of linac was increased by more than 40% of dose of with FF configuration of linac.