Pilot tests of a PET insert based on monolithic crystals in a 7T MR

We designed a novel PET insert based on monolithic LYSO crystals. From our first evaluation, we can conclude that sub-millimeter detector spatial resolution, combined with accurate photon DOI determination, make it possible to acquire high resolution reconstructed images. This enables us to combine simultaneously high resolution and sensitivity PET with high field preclinical MRI to extract simultaneously complex data capable to provide both anatomical and molecular information and to dynamically follow non-invasively animal models of different pathologies with no compromise in performance of each imaging modality. Each detector head (8 in total) mounts a 50×50×10 mm
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LYSO block coupled to a high density array of SiPMs. The readout used on each detector returns the X and Y projections of the scintillation light distribution. The PET geometry defines an axial and transaxial FOV of 46 mm (1 ring system) and 80 mm, respectively. The PET is surrounded of carbon fiber to avoid RF field interferences into the PET electronics without generating eddy currents affecting the MRI integrity. Current results show a PET resolution nearing 750 um (using Derenzo-like phantoms) simultaneously working with the MRI. In-vivo pilot tests of the PET insert system at the KU-Leuven (Belgium) inside a 7 T Bruker MRI equipped with a BGA 20S-HP gradient coil have shown the capability of both PET and MRI to simultaneously work providing high resolution PET and MRI images.