Characterization of scintillating materials in use for brachytherapy fiber based dosimeters

This paper reports the characterization of two scintillatingmaterials in powder form, Gadox and YVO embedded in a light-activated resin, used in a probe developed for oncological brachytherapy in-vivo dosimetry. Thematerialswere characterized in terms of internal absorption, scintillationdecay time, and lightyield. The measurementof the optical characteristics highlighted a significant internal absorptionat the scintillation light wavelength, with values of 6.5dB/mm for Gadox and 14.1dB/mm for YVO. Measurements of the characteristics scintillation time and of the light yieldwere performedwith a novel method based on single photon counting, profiting from the long decay time of thematerials under study. Measurements have been complemented by a two-step simulation with Geant 4 to study the energy deposition followed by a ZEMAX OpticStudio® ray tracing to estimate the light collection efficiency. The decay time for scintillating materials were measured tobe 𝜏𝐺𝑎𝑑𝑜𝑥 =(458 ±3 ±3) μs and 𝜏𝑌𝑉𝑂=(451 ±8 ±3)𝜇 s and the estimated values of the light yield are(7.1±0.5)×104 photon/MeV for Gadox and (4.8 ±0.5)×104 photon/MeV for YVO.