Development of the Quantum-PET Demonstrator

Polarization correlation of annihilation quanta, originating from the quantum mechanical selection rules, may be utilized to improve the signal to noise ratio in Positron Emission Tomography (PET). The initial orthogonality of polarizations of the gammas from para-positronium decay is reflected in the pronounced orthogonality of the azimuthal angles in Comp-ton scattering events and this is successfully measured using single-layer detectors based on adequately segmented scintillator matrices. We developed a demonstrator system to investigate the benefit of using this additional quantum information in PET. The system consists of two pairs of 16 x 16 channel modules. One pair comprises GAGG:Ce scintillators with 3.2 mm segmentation pitch and the other comprises two modules of 2.2 mm segmentation pitch one with GAGG:Ce and the other with LYSO:Ce crystals. The idividual crystals are read out by matching silicon photomultipliers (SiPMs). Dedicated cooling is developed to regulate the SiPM temperature in the desired range and to cool the readout ASICs. The modules are mounted on sliding arms attached to the ring that is a part of mechanical construction, which ensures rotation of the ring and precise positioning of the modules. In this work we report the operational properties of the system obtained in laboratory tests with a point source, including module temperature stability and energy resolution, as well as their basic polarimetric performance.