Performance study of a PET scanner based on monolithic scintillators for different DoI-dependent methods

One of the technical objectives of the MindView project is developing a brain-dedicated PET insert based on monolithic scintillation crystals. It will be inserted in MRI systems with the purpose to obtain simultaneous PET and MRI brain images. High sensitivity, high image quality performance and accurate detection of the Depth-of-Interaction (DoI) of the 511keV photons are required. We have developed a DoI estimation method, dedicated to monolithic scintillators, allowing continuous DoI estimation and a DoI-dependent algorithm for the estimation of the photon planar impact position, able to improve the single module imaging capabilities. In this work, through experimental measurements, the proposed methods have been used for the estimation of the impact positions within the monolithic crystal block. We have evaluated the PET system performance following the NEMA NU 4-2008 protocol by reconstructing the images using the STIR 3D platform. The results obtained with two different methods, providing discrete and continuous DoI information, are compared with those obtained from an algorithm without DoI capabilities and with the ideal response of the detector. The proposed DoI-dependent imaging methods show clear improvements in the spatial resolution (FWHM) of reconstructed images, allowing to obtain values from 2mm (at the center FoV) to 3mm (at the FoV edges).