Modelling and validation of a 6 MV compact linear accelerator via Monte Carlo simulation using Geant4 Application for...

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Computational Dosimetry

Background:

• Accurate modeling of linear accelerators (Linacs) is crucial for radiotherapy.
• Technical documentation often lacks critical parameters for Elekta Compact Linac.
• Geant4 Application for Tomographic Emission (GATE) is a powerful tool for radiation therapy simulations.

Purpose of the Study:

• To develop and validate a high-fidelity Geant4 Application for Tomographic Emission (GATE) model of the 6 MV Elekta Compact linear accelerator.
• To precisely calibrate and validate parameters like jaw collimator positioning, electron source energy, flattening filter, and spot size.
• To ensure accurate dosimetry calculations for potential future radiotherapy applications.

Main Methods:

• Simulated the Elekta Compact 6 MV Linac using GATE v.9.1.
• Utilized a 50 cm water phantom and a 100 cm source-to-surface distance.
• Employed Percentage Depth Dose (PDD) and Lateral Dose Profiles for validation.
• Introduced the half-length field difference (FHLD) method for jaw collimator optimization.
• Applied Gamma index analysis for quantitative assessment against measurements.

Main Results:

• Successfully optimized critical Linac Head parameters.
• Achieved high Gamma index acceptance rates: 97.93% (PDD), 100% (Crossplane), and 93.98% (Inplane) at 1%/1 mm criteria.
• Demonstrated excellent agreement between simulated and measured dose profiles.

Conclusions:

• Developed a reliable and highly accurate GATE model for the Elekta Compact Linac.
• The validated model ensures high fidelity in dosimetry calculations.
• This work facilitates future development of novel radiotherapy techniques using this Linac.