Monte Carlo Simulations for Small Electron Field Size Irradiation

Fricke Xylenol Gel (FXG) is a chemical dosimeter based on swine skin gelatin, Xylenol Orange (XO) and ferrous sulphate. When irradiated with ionizing radiation, absorbed dose distributions and profiles can be inferred through spectrophotometric techniques due to the [Fe⁺³-XO] complex absorbencies, which are field size and post irradiation time dependent. Although these two dependencies have already been experimentally considered in literature, theoretical models have not been extensively explored. In this work, a Monte Carlo Method (MCM) simulation was proposed in order to assess electron beam profiles for: variable field size and post irradiation time. The proposed simulational model describes the above processes, in a similar way when FXG samples are irradiated with megavoltage electrons, i.e., transition from Gaussian-like profiles to step functions (small to large fields, respectively) and Gaussian time dependent curves for diffusion effects (Fokker-Planck theory), indicating that this transition is primarily controlled by the beam geometric factors and the radiation random nature.