Simulation of a 6 MV Elekta Precise Linac photon beam using GATE/GEANT4

Area of Science:

• Medical Physics
• Computational Physics
• Radiation Oncology

Background:

• The GATE Monte Carlo (MC) platform, initially for PET/SPECT, now includes tools for radiation therapy.
• Accurate simulation of external beam radiotherapy is crucial for treatment planning.

Purpose of the Study:

• To investigate GATE's extension for radiation therapy simulations.
• To propose a general methodology for linear accelerator (Linac) simulations.
• To evaluate a novel multiple source model (MSM) for patient-specific dose calculations.

Main Methods:

• Modeled a 6 MV photon beam from an Elekta Precise Linac using GATE.
• Developed a two-stage simulation: patient-independent phase space (PhS) and patient-dependent MSM.
• Utilized selective bremsstrahlung splitting (SBS) for accelerator head simulation efficiency.
• Validated MSM against full simulations and water phantom measurements.

Main Results:

• MSM accurately calculated depth dose and transverse profiles with 0.8% statistical uncertainty.
• Simulations showed good agreement with measurements (1-2% dose differences).
• Over 90% of points passed the 3%/3 mm gamma index criterion.

Conclusions:

• The proposed MSM is a feasible and accurate method for external radiotherapy simulations using GATE.
• This study highlights GATE's potential for advanced radiotherapy applications.
• The methodology offers efficient and reliable dose calculations for treatment planning.