Researchers from the Laboratory of High Energy Physics at JINR, Tomsk Polytechnic University, and three medical centres from Russia and Germany created a Geant4 model of electron beam mode in a clinical linear accelerator. The methodology used when developing the numerical model of the medical linear accelerator is vendor-independent and readily implementable. In addition, it allows for rapid calculations and can be applied for a variety of purposes, including for the selection of parameters of creating heterogeneous dosimetry phantoms.

A significant number of existing studies focus on developing novel methodologies for dosimetry phantom creation. One of these methods is to produce heterogeneous samples by 3D printing. Numerical simulations are required to select the most appropriate parameters for such products.

In this work, the authors developed a beam-forming system model using a medical linear accelerator as a reference. This model is used to determine simulation parameters and corresponding dose distributions of an electron beam with nominal energies of 6, 12, and 15 MeV in a homogeneous water phantom. These parameters were adapted for maximum agreement between simulated distributions and those experimentally obtained with the clinical linear accelerator.

The beam was simulated using the Geant4 Monte Carlo software. The simulation geometry of the accelerator treatment head includes scattering foil and a flattening filter, which are designed for electron beam broadening. Additionally, the beam-forming system was incorporated to collimate the beam to the required size. A metal applicator was included to reduce the contribution of electron scattering in air. The main simulation parameters were iteratively tuned by comparing simulation results with experimental data.

The simulated percentage depth dose and transverse profiles for electron beams in water phantom are proved to be in good agreement with the experimental data obtained using a cylindrical ionisation chamber. This shows that the methodology employed in the development of the numerical model of the medical linear accelerator is vendor-independent, readily implementable, and suitable for rapid calculations.

The Journal of Instrumentation published the article “Development and verification of a Geant4 model of the electron beam mode in a clinical linear accelerator” in July 2024.