Development of a SiPM-based Anger camera for INSERT, a new multi-modality SPECT/MRI system for preclinical and clinical imaging

A new multi-modality imaging tool is under development in the framework of the INSERT (INtegrated SPECT/MRI for Enhanced Stratification in Radio-chemoTherapy) project, supported by the European Community. A custom SPECT apparatus, used as an insert for commercially available MRI systems, could enhance the treatment of brain tumors (primarily glioma) by offering more effective and earlier diagnosis with potentially better outcome in survival. In this work we briefly describe the architecture of the gamma-ray photo-detection module with focus on the Silicon PhotoMultiplier (SiPM) detectors and their performance with low-energy gamma-rays (⁵⁷Co - 122 keV). The camera has a 50.40 mm × 51.70 mm photo-detection area, comprising of 144 SiPMs with 36 readout channels, each one composed of four short-circuited SiPMs for an 8 mm × 8 mm active area. We have developed an Anger camera to characterize and qualify the array when coupled to a CsI:Tl scintillator (8 mm thick). We have measured an intrinsic spatial resolution better than 1.35 mm and an energy resolution below 14% using a ⁵⁷Co source, when the tile is cooled down to -17°C to reduce the impact of the dark count rate on the measurements.