Monte Carlo evaluation of particle interactions within the patient-dependent part of Elekta 6 MV photon beam applying IAEA phase space data.

Background: This work aims to provide a simulated method to be used by designers of medical accelerators and in clinical centers to manage and minimize particles' interaction in the patient-dependent part of a 6 MV X-Ray Beam generated by the Elekta linear accelerator system, based on the latest GATE software version 9.0 Monte Carlo simulation, IAEA phase space data, and the last version of "Slurm" computing cluster.

Materials And Methods: The experimental results are obtained using the Elekta 6 MV accelerator. The simulation MC developed includes the majority of the patient-dependent segments, such as Multi-Leaf Collimator (MLC), Tongue and Groove T&G, Rounded leaf Part, including the Jaws (XY). This model is used, with a simulated Iba Blue Phantom 2 homogeneous water phantom with dimensions 480 × 480 × 410 mm, positioned at a Source-to-Surface-Distance (SSD) of 100 cm, all of the interactions of the mega voltage 6 MV radiations in water are simulated. The IAEA phase space (PS) provided by the International Atomic Energy Agency database and cluster computing (Slurm HPC-MARWAN, CNRST, Morocco) are employed to reduce our simulation time.

Results: The results confirm that there are many interactions in all areas and the patient-dependent part's internal structures. Thus, electrons and positrons participation appear in the generated field previously designed to be an X-ray beam. Besides, to validate our implementation geometry, the PDD's and transverse profiles, at a depth ranging from 1.5 to 20 cm, for a field size of 10 × 10 cm, the beam quality such as , (cm), (cm), , the two relative differences in dose were derived on and are calculated, respectively. Additionally, gamma index formalism for 2%/2 mm criteria is used. Once and for all, we typically take a good agreement between simulation MC GATE 9.0 and the experiment data with an error less than 2%/2 mm.

Conclusions: In the field of X-ray photons, a significant contribution of electrons and positrons has been found. This contribution could be enough to be essential or affect the delivered dose. A good agreement of 98% between this new approach of simulation MC GATE 9.0 software based on IAEA phase space and experimental dose distributions is observed regarding the validation tests used in this task.