Seven major categories of physics processes are provided by GEANT4. The following is a list of the standard electromagnetic processes available in Geant4: Photon processes,

Electron/positron processes, Muon processes, Hadron/ion processes, Coulomb scattering processes, Processes order StemRegenin 1 for simulation of polarized electron and gamma beams, Processes for simulation of X-rays and optical protons production by charged particles.[34] Application of the Actors Actors are tools that let to interact with GATE. With the aim of extracting the dosimetric parameters in radiotherapy, the Actors should be used in GATE simulation process.[35] DoseActor and KillActor are used in the calculation of dosimetric parameters and acceleration of the simulation process, respectively. Implementation Stages of Simulation Stage 1: Defining the phase-space, tracking the primary and secondary particles, and recording information about the particles passing through the phase space. At this stage of the simulation, the primary particles were electrons. All the primary and secondary particles passing through the phase space, under the flattening filter, were recorded. KillActor was employed to accelerate the simulation process. As it can be seen in Figure 2, the particles tracking are confined

to regions where they are actually influential on the dosimetric parameters in the water phantom. Figure 2 The view of the particles trajectory, using KillActor Stage 2: Tracking the exit photons of the phase space, calculating dose distributions, and recording the dosimetric parameters. At this stage, the primary particles are the same particles produced in the first phase-space stage. The components of LINAC that are present in the trajectory of particles, from the phase space to the phantom water, include the wedge (in wedge fields) and secondary

collimator. The particles trajectory from the phase space to the water phantom is shown in Figure 3. Figure 3 The trajectory of particles from the phase space and GSK-3 the incident on the opaque water phantom Clustering With the purpose of accelerating the calculations, the cluster computing technique (Condor, platform, version 7.2.4) was utilized, and Condor was used on 9 computers (Intel (R) core (TM), 2 Duo CPU with 2.93 GHz, 2GB RAM). RESULTS The results of this study include the computational and experimental dosimetric parameters. To ensure the accuracy of the simulation results, it is necessary to analyze the correctness of the simulation process. Therefore, prior to calculating the dose distribution in the water phantom, the energy spectrum, the spatial distribution of electron beams, and the implementation of the linear accelerator system were verified.