Abstract
Silicon photomultiplier (SiPM) coupled scintillation detectors, are considered as promising tools for basic design of imaging instrumentation for the next generation PET, PET/MRI, SPECT and autoradiography scanners. The precise technical knowledge is inadequate, and still some challenges need to be addressed in order to successfully implement the SiPM technology in high resolution PET systems. Firstly, the advantages of SiPM pixel array 1:1 coupled crystal detector were obvious, and has minimized the position resolution errors of charge sharing in multiplexing circuits. However, in the system level, too many electronic channels have perplexed with complications, such as complex, messy electronics or dedicated ASIC chips. Multiplexing circuits were usually used to lower the complexity and cost of electronics, which has resulted in gradual deterioration of the performances of the detectors. Secondly, the light guide has become a necessity in high-resolution preclinical PET detectors. For a complete SiPM detector block, the light yield of outermost two rows/columns crystals were blurred due to the edge effects. In order to avoid this edge deterioration effect, crystal array size was reduced than that of the SiPM array in many PET detectors. The PET system built by these detectors had big gaps between the detector modules, which has largely affected the quality of reconstructed images. In order to solve these key problems, the Trans-PET basic detection module (BDM) II was designed and implemented in this study. This module was a flexible, easy to upgrade, simple, box geometry, small animal PET scanner. A better balance could be achieved by this detector, while reducing the electronic channels, and could simultaneously enhance the position resolution and time performance. A specially customized semi-cutting light guide had been designed, which could be optically multiplexed and diffused to optimize the effect of edge deterioration, so that both the outermost and inner crystals could be clearly distinguished. Specifically, in this PET module, two type crystal arrays with different crystal size had been designed, 13× 13 crystal array with 1.89 mm width and 18× 18 crystal array with 1.2 mm width, based on the same 6× 6 SiPM array and frond-end electronics. The total area of 6× 6 SiPM was 25.0× 25.0 mm2, which was similar to Hamamatsu PSPMT R8900. The area of the SiPM array was slightly smaller than the size of the crystal array, in order to reduce the gap of the PET system built by this detector. The purpose of this study was to evaluate the performance of this detector module, including position profile quality, energy resolution, timing resolution in different operating environment. Based on this detector module, PET scanners can easily be designed with different shapes such as, quadrilaterals, hexagonals, octagonals, dodecagonals, twenty-four-sides, and other shapes.