Clinical SiPM-Based MRI-Compatible SPECT: Preliminary Characterization

The initial characterization of the first single-photon emission computed tomography (SPECT) insert for simultaneous human brain imaging inside magnetic resonance imaging (MRI) is presented. The instrument features a novel multimini-slit-slat collimator and a static ring of 20 detectors. The scanner architecture is modular and represents the scale-up of a preclinical version whose MRI-compatibility has been already successfully demonstrated. The detectors are based on CsI(Tl) crystals (50 mm ×100 mm × 8 mm) coupled to arrays of silicon photomultipliers and ASIC readout for a total of 1440 channels. The transaxial field of view (FoV) is 20 cm by 9 cm in the axial direction. The experimental results show a sensitivity of 362 cps/MBq, an energy resolution of ~17% (at 140 keV), and a tomographic extrinsic resolution in the transaxial plane of ~8 mm across the whole FoV.