Avaliação do movimento respiratório em radioterapia utilizando simulação Monte Carlo

Abstract

The aim of the study was to evaluate respiratory motion, which is one of the major sources of error in all radiotherapy techniques but is particularly critical in techniques such as the corporal stereotactic radiotherapy, which applies high doses in a few fractions. The Monte Carlo method is today one of the most powerful tools in dose evaluation in radiotherapy. In this work, the Respiratory Gated Radiotherapy technique was evaluated to verify the magnitude of the movement, and the only free code based on the Monte Carlo method, appropriate to this situation, was used, the GATE. The methodology consisted of using a phantom that simulates the respiratory movement, the Eclipse planning system and the GATE code. The data were analysed by comparing the results of the dose profiles using the gamma index with criteria of 3% / 3mm.The experimental measurements were performed using radiochromic films with the phantom static, in motion and with the phantom in motion and the triggering of the beam. For the simulation with Monte Carlo method, the Novalis Classic accelerator head was simulated generating a phase space dependent on the patient, which was used in the simulations. The results demonstrate that even simple and regular movements of the breath can lead to a decrease in the plateau of the dose profile by approximately 1 cm. The simulations with the static and moving phantom show that the analysed points are approved with indices greater than 92%, demonstrating the ability of the GATE code in the simulation of respiratory movement.