Monte Carlo Modeling of the Head of Varian Clinac 2100C Linear Accelerator Operating in 18 MV Utilizing GATE/GEANT4

In this study, the geometry of the head of VARIAN CLINAC 2100C linear accelerator lodged at Blida AntiCancer Centre in Algeria has been modeled using GATE/GEANT4 version 7.2. The model developed contains the majority of the components of the treatment head operating in 18 MV, such as: the target, the primary collimators, the flattening filter, the secondary collimators and the jaws. Using this model, associated with a water phantom of type RFA 200 with dimensions 63.8 cm x 40 cm x 44 cm positioned at a Source-to-Surface-Distance (SSD) of 100 cm, the interactions of the 18 MV radiations in water were simulated. The photon energy spectrum, the Percentage Depth Dose (PDD) and the beam quality specifiers such as D-10 (%), d(max) (cm), d(80)(cm), D-20/D-10 were calculated for field size of 10 cm x 10 cm utilizing the phase space technique. The results obtained in this study are in agreement with those obtained in our previous work using MCNP5 code.