Proposal for a PET scanner with 4π formula steradian span

The most frequent Positron Emission Tomography (PET) scanner design is a cylindrical arrangement of detectors with the specimen lying along the axial direction. This distribution doesnot maximize the geometrical sensitivity unless the axial extent becomes much longer than the axial Field of View (FOV), what becomes a very costly solution. The optimal geometry in terms of sensitivity for a PET scanner is a sphere with the specimen located at the center. The state of the art of scintillator crystals and detectors for γ-rays does not facilitate a design with a smooth spherical geometry due to their rigid flat morphology. In this work we propose a PET scanner design of 4 π steradian coverage as a first approximation to the ideal spherical shape. We present here a design for preclinical imaging as a proof of concept, shaped as an icosahedron with scintillators and photodetectors covering its twenty facets. In the simulations the facets are covered by Silicon Photomultipliers (SiPM) arranged in matrices for multiplexing reading, coupled to a monolithic laser-engraved LYSO scintillator crystals with pixels matching the spatial sampling of the SiPM distribution. Preliminary results are based on simulations of sources of known activity distributions. Histograms of lines of response distributions in spherical coordinates as well as sinograms and pseudomichelograms are presented. The results confirm the high-sensitivity, as it is shown on the Noise Equivalent Count curve (NEC), and high spatial resolution of the design due to the dense sampling of the FOV.