Caracterização dos espectros de raios X de média energia através do método Monte Carlo

Abstract

This work characterizes the spectra of two X-ray tubes using the Monte Carlo method, specifically, the PENELOPE code. The Monte Carlo method is found in different areas of the exact sciences, being a common resource in medical physics. This method is essentially simple in its approach, achieving a solution of a macroscopic system through the simulation of its microscopic interactions, representing a modeling of nature through direct simulation of the essential dynamics of the system under study. Two medium-energy X-ray tubes were modeled according to the manufacturer’s specifications, and the simulations were divided into two stages due to the computational time. In the first stage, X-ray spectra were obtained right at the tube exit for four qualities of radiation. In the second stage, photon spectra were recorded after modelling the experimental arrangement to obtain the half-value layers (HVLs). An evaluation of the spectra obtained in the second stage was carried out with the spectra from the SpekCalc software, a program that performs the theoretical calculation of spectra under conditions of good geometry, using the t-student statistical test. Mean energy values along with the first and second half-value layer (HVL) of each energy were determined with the respective differences between them. Different discrepancies were found in most cases, and so it is vitally important to consider each situation independently. Finally, secondary electron energy spectra in the second stage of each quality were presented with their respective mean energies, an important parameter considered in the dose deposition of the different experimental geometries that use such qualities. An estimate of the dose impact on Fricke solution of each type of beam is presented at the end of the work to establish a degree of influence of secondary electrons.