Implementation of Photonic Crystals into Davis LUT module for GATE simulation.

The performance of Positron Emission Tomography (PET) detectors has been constrained by the photodetector collection of optical photons emitted in the scintillator, which was limited to photons reaching the exit surface with an angle larger than the critical angle. Photonic Crystals (PhCs) are periodic nanostructures with sizes comparable to the optical photons' wavelengths, which can break through the critical angle limit. Thorough experimental investigation of PhCs effect on optical harvest in scintillator detectors is complex and costly. Simulation can overcome these challenges. Mainstream software such as GATE does not support PhCs simulation. Here, we generalize the GATE optical model by incorporating the PhCs optical model into the LUT Davis model. We can model the performance of advanced scintillator detectors via the generalized LUT Davis model. The scintillator and PhCs materials tested in this work were lutetium oxyorthosilicate and titanium dioxide, respectively. Scintillators with a cross-section of 3×3 mm or 10×10 mm and a thickness varying from 9 mm to 18 mm with a step size of 3 mm were modeled with a PhCs interface to the photodetector. Among the 4 tested PhCs configurations, the best optical photon harvest was improved by 62.4% compared to traditional coupling with variable results between PhCs structures. The energy resolution only slightly improved. We thus investigated the angular distribution of collected optical photons, which can guide the optimization of photodetectors' detection efficiency at specific angles.