Addressing Light Distribution Truncation and 3D Impact Positioning in PET: Edgeless Approach

Research in the field of small animal Positron Emission Tomography (PET) imaging is currently driven by improving both spatial resolution and sensitivity.We already constructed an edgeless PET system based on a single scintillator annulus that enables Depth of Interaction (DOI) capabilities. Including accurate DOI information plays an important role in small aperture scanners, since it is essential for retrieving a homogeneous spatial resolution across the scanner Field of View (FOV). Our previous system, named Zero prototype, was based on a single LYSO piece with inner cylindrical face but ten outer planar facets to allow for easy photodetector coupling. However, this design results in some undesired internal reflections. To mitigate the impact of these reflection in the estimation of the photon interaction coordinates within the scintillator, we present an upgraded version based on a single LYSO piece with both inner and outer faces following a cylindrical geometry.Monte Carlo simulations have been performed using nuclear and optical tracking. An improvement on the light distribution (LD) profiles was observed. We have calculated a spatial resolution of 0.8 mm at the center of the FOV (cFOV) that remains almost constant along the radial direction. A sensitivity of 12% was found at the system cFOV for a 50% energy window. The reconstructed image quality (IQ) phantom shows the capabilities of this novel approach to resolve all rods of the phantom.