Simulation of the patient-dependent part 6 MV Elekta linac photon beam using GATE

Monte Carlo simulation is widely recognized as an important technique to study the processes physic of particles and their interactions in nuclear medicine and Radiation Therapy. In this task, we take advantage of Geant4 Application for Tomographic Emission (GATE) version 8.2 (OpenGATE Collaboration) to simulate the linear accelerator system. IAEA phase-space files are exploited so as to speed up calculations. The model developed contains the majority of the components of the patient-dependent part using in 6 MV Elekta, such as: Multi-Leaf Collimator (MLC), Tongue and Groove T&G, Rounded leaf Part and finally the Jaws. This model is used, with a homogeneous water phantom with dimensions 50 × 50 × 50 cm
³
, 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 comparisons of our results are performed with measurements in a water tank taking the same dimension and position used in our model. The Percentage Depth Dose (PDD) and transverse profiles, at depth ranging from 1.5 cm to 20 cm, for field size of 10 × 10 cm
²
, are calculated using dose sizes of 5 × 5 × 2 mm
³
and 2 × 5 × 5 mm
³
for PDD and profile measurements, respectively. In addition, the photon energy spectrum, the beam quality such as D
₁₀
(%), d
_ma
(cm), d
₈₀
(cm), TPR
₂₀
/
₁₀
, the two relative differences in dose were derived on ψ
_i
and ψ
_i,max
are calculated, respectively. Finally, the results obtained show a good agreement between the simulation using GATE software and measurements data.