Performance comparison of two compact multiplexed readouts with SensL's SPMArray4 for high-resolution detector module
The purpose of this study was to investigate a compact readout for silicon photomultiplier (SiPM) array in the development of high-resolution imaging detector to reduce the readout channels while maximizing the detectors performance. The detector module was composed of a LYSO scintillation crystal array and a SensL's SPMArray4. The crystal array was coupled to the SiPM array with a 2mm-thick silicone pad to improve the light sharing among the SiPM array elements. Three LYSO crystal arrays of 4x4, 8x8 and 12x12 crystal elements with pixel sizes of 3.2, 1.6 and 1.0 mm were investigated in this study. Two compact multiplexed readouts based on the light sharing principle have been developed to reduce the detectors readout channels from 16 to 4 outputs while achieving a maximized performance in its spatial resolution. One is based on a conventional charge division method which was utilized with a discretized positioning circuit (DPC). The other is based on a novel two-stage charge division which was utilized with a symmetric charge division circuit to divide the charges from 16 SiPM elements into a 4-row and 4-column resistive network and then used a subtractive readout circuit to further reduce the readout channels from 8 to 4 outputs. The performance of the detector module with two compact multiplexed readouts was evaluated with LYSO arrays with different crystal sizes using a 137Cs point source. The preliminary results show that both compact multiplexed readouts can provide very good spatial resolution with good uniformity and resolve up to 1mm pixel elements of LYSO arrays. The compact readout based on the two-stage charge division with subtractive resistive-readout shows a slightly better improvement in the crystal identification while reducing the non-linearity of the flood image as compared to the DPC readout. In conclusion, both compact multiplexed readouts are effective approaches for the development of high-resolution detector module for compact micro-PET.