Avaliações de altas doses em pequenos campos utilizando filmes radiocrômicos

Abstract

Radiotherapy is a form of treatment to eliminate malignant tumors and inhibit their growth using techniques with increasingly collimated irradiations. These techniques lead to innovations in conformation methodologies, in order to preserve healthy tissues and extinguish tumor tissues. As a motivation for this work, the investigation of the effects of small fields was carried out, for the irradiations in which these effects occur, the analysis of the doses are essential and for this reason they require the study of different energies and different field sizes. Irradiations were carried out in a solid water simulator object through three different photon beams: a cesium-137 source and a Synergy linear particle accelerator from the manufacturer Elekta. The measurements performed showed differences in the dose level of the profile and longitudinal irradiations. The source of cesium-137, because it has less energy, has less penetration compared to the accelerator. It was observed that in the different energies, in relation to longitudinal irradiation, the source of cesium-137 reached the highest dose between 10 and 13 mm, while for a distance of 5 cm in depth, the absorbed dose was 18.7% of the maximum dose. In the cesio-137 source, axial irradiation showed an average relative dose of 94.58% for the X axis and 95.81% for the Y axis. For doses in the energy of 10 MV, the effects of small fields and reduction doses were higher in relation to the energy of 6 MV. For the energies of 6 and 10 MV, the highest doses occurred between 1.1 and 1.2 cm and 2.0 and 2.2 cm, respectively in longitudinal irradiations. The graphs obtained in the results made it possible to analyze the disturbances present in the exposures for the dosimetry of small fields and the impacts on the calculation and analysis on the local dose deposition.