Characterization of fiber radiation dosimeters with different embedded scintillator materials for radiotherapy applications

In-vivo real-time dose rate measurement has attracted much attention in the tumour-treatment field because of the demand for precise delivery of radiotherapy. An optical fiber based dosimeter is presented, which is fabricated by embedding scintillator materials inside the fiber core. Five micron-scale powder based scintillator materials have been identified and their characteristics are compared in this investigation. The dosimeters have been fabricated separately but with exactly the same production process. Their emission spectra have been measured. Furthermore, an evaluation of the dosimeter's performance has been made by analyzing the signal intensity emitted from the scintillation material following transmission through a 25 m length of plastic optical fiber (POF) to a distal MPPC (multi-pixel photon counter) detector. The excellent linearity of the relationship of the signal intensity and the dose rate has been established and simultaneously measured using an ionization chamber (IC) to ensure efficacy of the results. The dependence of the resulting fluorescence signal on water depth of two materials was also obtained and compared with the IC. The investigation clearly shows that currently Gd₂O₂S:Tb is the optimum choice of material for the X-ray optical fiber dosimeter.