Validation of a Monte Carlo model for multi leaf collimator based electron delivery

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Modeling

Background:

• Conventional electron therapy uses applicators and apertures for beam shaping.
• Photon multi-leaf collimators (pMLC) offer potential for more conformal electron beam shaping.
• Monte Carlo (MC) simulations are crucial for accurate modeling of radiation therapy devices.

Purpose of the Study:

• To develop and validate a MC model of the Varian TrueBeam system.
• To investigate the feasibility of using pMLC for electron collimation.
• To compare pMLC-based electron delivery with conventional applicator-based methods.

Main Methods:

• A Varian TrueBeam MC model was created using TOPAS (Tool for particle simulation).
• Vendor data informed the model of treatment head components and source parameters.
• Calculated doses were compared against ionization chamber and film measurements for various field sizes and energies.

Main Results:

• The MC model demonstrated high agreement with measurements for percentage depth-dose curves (100% gamma pass rate for 2%/1 mm).
• Dose profiles showed excellent agreement for jaw-defined fields (>97% gamma pass rate for 2%/2 mm) and pMLC/applicator fields (98% gamma pass rate for 2%/2 mm).
• Simulations of clinical cases confirmed the utility of pMLC-based electron delivery.

Conclusions:

• A validated MC model for Varian TrueBeam pMLC-based electron delivery was successfully developed.
• MC calculations closely matched experimental data, satisfying stringent gamma criteria.
• The study highlights the clinical potential of pMLC for electron therapy and the role of MC simulations in advancing techniques.