Scintillator-based Photon Counting Detector: Is it feasible?

By utilizing finely pitched scintillator arrays where the scintillator has high atomic number and density, fast decay time, and high light output, realizing a scintillator-based Photon Counting Detector (PCD) is conceptually feasible. Fabrication of fine-pitched scintillator arrays however, has been the bottleneck for realizing such detectors. Combining the novel scintillator fabrication technique called laser-induced optical barriers (LIOB) where optical barriers can be placed inside a transparent crystal and act as a reflector without removing the material, with laser ablation, we are now able to overcome the obstacles for developing scintillator-based PCD. In this regard, we are developing an LYSO-based PCD where the LYSO crystal is laser pixelated to sub-mm pixels. The scintillator array will be coupled to an application specific integrated circuit (ASIC) where each ASIC pixel has built-in photodiode, amplifiers and 3-4 energy windows and their associated counters. We have simulated light transport for different scenarios where the crystal is pixelated by a combination of LIOB and laser cut techniques, where the 2 mm thick crystal is first pixelated by LIOB to a depth and then the rest is pixelated by the ablation technique. We also simulated the fraction of collected light in the same scintillator pixel by modeling various surface properties of the pixel cuts as well as optical barrier surface roughness and refractive index (RI). Simulation results show that up to ~70% of the scintillation light will be contained in the same pixel when only using the LIOB technique with barrier refractive index of 1.0. These results suggest that laser processed arrays can potentially change the paradigm in PCD development as they can replace the traditional array production and thus allow for scintillator-based PCD development in a more robust and cost-effective manner.