Development of a modular detector system for C-SPECT

We are developing the detector system of C-SPECT-I, the first generation system of a dedicated Cardiac SPECT platform. For cost-effectiveness, we use medium size single-anode PMTs with NaI(Tl) detector modules to form the body-contouring shape of the C-SPECT detector arc. We have designed and evaluated a test detector module that includes two pixelated NaI(Tl) detector blocks in a common hermetic housing to model a section of the detector arc. Each block is 93×51×10 mm³. Each pixel is 2.75×2.75×10 mm³ with 3mm pitch. We applied black or white epoxy at the edges of the module to investigate the pixel separation and reduction of the edge effect. Seven 2” PMTs in hexagonal pattern in three columns (2-3-2) were used for decoding the pixels. Two PMT configurations were evaluated. Configuration 1: seven standard quantum efficiency (SQE) PMTs. Configuration 2: a mixed array of standard quantum efficiency and high quantum efficiency, HQE, (2_HQE-3_SQE-2_HQE). The HQE/SQE mixed array results in a 14% improvement on the global P/V comparing to that of the SQE array. Using HQE/SQE mixed array improves the average energy resolution from 11.3% to 10.5%. Then we used the mixed array for evaluating different epoxy treatment. Pixels are clearly resolved in the decoding maps except at the very transverse edges of the two blocks. The block with black epoxy treatment performs better in terms of pixel separation at the transverse and axial edges of the block. An average energy resolution of 10.5% and 10.1% was obtained in the blocks with black and white epoxy treatment, respectively.