Characterization of scintillating materials in use for brachytherapy fiber based dosimeters

This paper reports the characterization of two scintillating materials in powder form, Gadox and YVO embedded in a light-activated resin, used in a probe developed for oncological brachytherapy in-vivo dosimetry. The materials were characterized in terms of internal absorption, scintillation decay time, and light yield. The measurement of the optical characteristics highlighted a significant internal absorption at the scintillation light wavelength, with values of 6.5 dB/mm for Gadox and 14.1 dB/mm for YVO. Measurements of the characteristics scintillation time and of the light yield were performed with a novel method based on single photon counting, profiting from the long decay time of the materials under study. Measurements have been complemented by a two-step simulation with Geant4 to study the energy deposition followed by a ZEMAX OpticStudio (R) ray tracing to estimate the light collection effi-ciency. The decay time for scintillating materials were measured to be r?????????????????????????????? = (458 & PLUSMN; 3 & PLUSMN; 3) mu s and rYVO = (451 & PLUSMN; 8 & PLUSMN; 3) irs and the estimated values of the light yield are (7.1 & PLUSMN; 0.5) x 104 photon/MeV for Gadox and (4.8 & PLUSMN; 0.5) x 104 photon/MeV for YVO.