A SiPM-based detection module for SPECT/MRI systems

In the present work we present the development of a Silicon PhotoMultiplier (SiPM)-based detection module for hybrid SPECT/MRI instruments. The module is designed for preclinical SPECT systems for mouse and rat brain imaging, but can also be exploited for clinical SPECT brain scanners. The gamma-ray detection module is designed on the well-established Anger architecture, with a continuous 5 cm χ 5 cm CsI:Tl scintillator read by an array of SiPMs (RGB-HD with 25 μm SPAD cells) from Fondazione Bruno Kessler. The current signals are conveyed to a 36-channel ASIC realized in 0.35 μm CMOS technology and digitized by an external data acquisition system. An operative temperature of 0° C is mandatory to reduce the dark count rate of the SiPM array and to enhance the final performance of the detector in terms of energy and spatial resolution. For this purpose, an MRI-compatible heat sink is realized with a plastic material (Coolpolymer D5506) with a glycol-water mixture as cooling fluid. Gamma-ray measurements with Co-57 (122 keV) have provided an energy resolution better than 14% and an average intrinsic spatial resolution below 1.0 mm.