Avaliação de dose periférica em um caso de IMRT de cabeça e pescoço utilizando filmes radiocrômicos

Abstract

The objective of this work is to collect and evaluate the peripheral doses in IMRT treatment in the head and neck region with the use of radiochromic films. For this it was necessary to simulate a real IMRT treatment using an anthropomorphic phantom. As dosimeter was used film EBT3 of the company Gafchromic and for irradiation, linear accelerator Varian Clinac 600C / D with beam of 6 MV. Initially the computer tomography of the phantom was imported into the Eclipse ™ software, for the delimitation of volumes and the accomplishment of the radiotherapeutic planning. With the beam properly calibrated, the anthropomorphic phantom was positioned in the isocenter region and the dosimeters were placed in regions of the parotid gland, thyroid, heart and left breast. A total of 5100 MU was applied in a single fraction. Subsequently, it was observed that the highest doses collected were in the parotid, breast and thyroid gland, on average, 11.9, 10.8 and 9.6 cGy, respectively. Although placed in the same cut, the dosimeter in the breast received an average of 1.6 cGy more than the dosimeter in the heart. The parotid and thyroid regions received these dose values because of the proximity of these regions to the target volume of the planning. In heart and breast there was this difference due to the influence of oblique fields in the more lateral dosimeter, that is, in the region of the breast. Regarding the total dose applied, the parotid region received the highest percentage value, being on average 1.7%. Thyroid, heart and breast sites had the following percentages: 1.27%, 1.3% and 1.5%, respectively. It was concluded, therefore, that the radiochromic films were very coherent in the measurements obtained with the IMRT technique and that the doses received at the study sites were relatively low. This is due to the complex configurations of the IMRT and the protection parameters of the structures adjacent to the target, offered by the technique used.