Sensores a fibra ótica baseados em redes de Bragg para aplicações em radioterapia

Abstract

The main objective of this dissertation is to evaluate the degradation of sensors based on optical fiber Bragg gratings (FBGs) during irradiation with therapeutic doses in radiotherapy. Two experiments were carried out, the first evaluated the degradation of FBG in real time with fractionated doses over 226 Gy of total accumulated dose, another analysis in this same experiment, using the same technical arrangement, observed the degradation of FBG when inserted in aqueous medium. The second experiment sought to evaluate the loss of transmitted optical power for clinical doses of up to 500 Gy. The irradiations of the first experiment were made in a linear accelerator, while in the second experiment, a Cesium-137 fixed source irradiator was used. The results demonstrate small changes in the sensitivity coefficients of the networks for the different doses and systems. However, this is not enough to make their application as sensors of biomedical variables in radiotherapy environment unfeasible.