A Novel Concept for PET Scanners Design using Polaroid-based Detectors for Filtering Reflected Optical Photons

The aim of this work is to propose and assess a new detector module for an animal PET scanner, called Polaroid-PET. Polaroid-PET's detector modules consist of monolithic crystals on which a layer of Polaroid sheet is stick on one side to filter unpolarized optical photons. The polaroid sheet filter reflects optical photons and thus enhances the spatial resolution in the detector module based on monolithic scintillator crystals. In the initial step, the GEANT4 Monte Carlo toolkit is used to simulate a detector block consisting of a lutecium-based monolithic crystal (LYSO) with a crystal thickness of 10 mm and semiconductor-based Silicon Photomultipliers. A Polaroid sheet was placed between the crystal and the SiPMs to block unpolarized photons come from the crystal. In the next step, two preclinical PET scanners with and without Polaroid based on 10 detector modules were simulated. The performance of the two detector modules and preclinical PET scanners were assessed by calculating the spatial resolution, and depth of interaction (DOI). The Polaroid-equipped detector module resulted in a better spatial resolution with ~1.05 mm full-width at half maximum (FWHM) compared with the regular detector (~1.3 mm FHWM) for a point source placed in front of the center of the detector's entrance face. Our Polaroid-based PET scanner led to better axial spatial resolution in comparison with the regular small-animal PET scanner for a point source placed at the center of the field-of-view (0.83 mm vs. 1.01 mm FWHM). By filtering reflected unpolarized optical photons, Polaroid-PET was able to achieve improved spatial resolution and sensitivity compared to the original design.