Characterization of the Detection Module of the INSERT SPECT/MRI Clinical System

Within the vast panorama of multimodal systems for clinical diagnosis, PET/MRI has been receiving significant attention. In parallel, new technological solutions have been paving the way to simultaneous SPECT/MRI systems, whose development has been so far delayed due to the challenging compatibility between MRI, gamma-ray detectors, and collimators. This paper presents an silicon photomultiplier (SiPM)-based Anger camera designed for preclinical and clinical SPECT static inserts for standard MR scanners. The gamma-ray detector is based on a continuous CsI(Tl) scintillator readout by arrays of SiPMs and custom ASICs. The design has been adapted to fit with the limited space conditions (23 mm thickness), but also considering mutual compatibility issues. Despite these constraints and thanks to the adoption of an iterative statistical event estimation method simply requiring a flood image, the detector maintains state-of-the-art performance in terms of intrinsic spatial resolution (1.0 mm FWHM within the usable field of view) and an energy resolution below 14% FWHM at 140 keV. The experimental studies here performed show that the camera, designed to operate at 0 degrees C to reduce the dark current of SiPMs, can operate up to 10 degrees C without significant worsening of imaging performance.