Submillimeter Pixelated SPECT Detector Using GAGG:Ce and Light Guide With Optical Barrier Slits

In nuclear medicine imaging systems, intrinsic spatial resolution of the detector is one of the most important performance metrics. In this work, we aim to develop a high-resolution single photon emission computed tomography (SPECT) detector using pixelated Cedoped gadolinium aluminum gallium garnet (GAGG:Ce) scintillators and silicon photomultiplier (SiPM) arrays. Special attention is paid to improving the resolving capability of edge crystals. We propose to place optical barrier (OB) slits onto the light guide that enhances the difference in light distribution for edge crystals. We experimentally optimize OB designs for two scintillator arrays, named as Array-ESR and Array-BaSO4, which uses enhanced specular reflector (ESR) film and barium sulfate (BaSO4) as the reflectors respectively. Both arrays have 31 × 31 0.8 mm × 0.8 mm × 6 mm GAGG:Ce crystals. We introduce the flood map quality (FMQ) parameter to assess the separation of responses of neighboring crystals. The results demonstrate that for Array-ESR, an optimal light guide with two 7° OB slits and two 11° OB slits resolves 92.40 % crystals with an energy resolution of 13.19 ± 0.68%. The FMQ is 1.52 ± 0.38. For Array-BaSO4, the optimal design is a light guide with four 7° OB slits. 98.75 % crystals are resolvable with an energy resolution of 15.33 ± 0.96 % and FMQ parameter of 1.81 ± 0.45. Overall, Array-BaSO4 is more suitable for building SPECT detector for its good crystal resolving performance and fabrication convenience. This study proposes a practical sub-millimeter pixelated SPECT detector design with no detection dead space and compact electronics. It is promising for being used to build largescale detectors for high resolution SPECT systems.