Design of a PET/MRI DOI Detector Consisting of a Quasi-Block Scintillator and a Dual-Sided Readout Photosensor with MLPE in a High Magnetic Field

The spatial resolution of small animal positron emission tomography/magnetic resonance imaging (PET/MRI) detectors for operating in a high magnetic field, which use very small and thin scintillation pixels, is degraded at the periphery of the field of view (FOV). To solve this problem, we designed a detector that measures the depth of interaction (DOI) when gamma rays, a form of electromagnetic radiation, interact with scintillation pixels. The detector consists of four layers of quasi-block scintillators with photosensors with no signal distortion in a magnetic field at both ends of each layer, and the location of scintillation events was determined using a lookup table and maximum likelihood position estimation (MLPE). DETECT2000 simulation was performed to evaluate the performance of the designed detector. A lookup table was created using the light signals collected from the photosensors, and the location was determined by comparing it with new signals with reference to the MLPE. As a result, the discrimination accuracy was excellent at 92.0%. The application of this detector to small animal PET/MRI is expected to deliver outstanding spatial resolution.