Light transport in PET scintillator detectors fabricated using laser induced optical barriers

Laser Induced Optical Barriers (LIOB) is a promising technique for fabrication of high resolution and high sensitivity scintillator detectors for Positron Emission Tomography (PET). With LIOB local changes in refractive index may be introduced inside the bulk of a monolithic crystal by using a tightly focused pulsed laser. One major advantage of LIOB compared to standard mechanical pixelation techniques is the flexibility in patterns that may be created in the crystal to redirect the scintillation light. With the aim of finding the optimal pattern of optical barriers for a single-side readout detector for small animal PET, we are performing simulations to study the light transport within laser-processed crystals. Here we report on results obtained with two 25.4×25.4×20.0 mm³ LYSO:Ce crystals: 1) containing a 1 mm pitch pixel-like pattern throughout the crystal depth, and 2) pixel-like pattern in the top half of the crystal only. The crystal is coupled to an 8×8 photodetector array with 3.2 mm pixel pitch and the light spread functions are analyzed as a function of source location. Results suggest that 1 mm transversal spatial resolution is achievable using the LIOB technique. We further see that depending on the quality of the barrier/crystal interface and the barrier depth within the crystal, some level of DOI information may be obtained from the light response functions when using these simple patterns.