Development of Two-Layer Depth-of-Interaction Detector for Small Animal Positron Emission Tomography(PET)/Magnetic Resonance Imaging (MRI) through Photoelectric Peak Analysis

A depth of interaction (DOI) detector was developed to improve the spatial resolution of positron emission tomography (PET) systems with magnetic resonance imaging (MRI) for small animals. The detector uses a silicon-based optical sensor that is not affected by magnetic fields and can be used in MRI systems. The design includes a two-layer scintillation pixel array with different reflectors for each layer such that the intensity and peak area of the signal detected by the optical sensor differs for each layer. A spectrum of the photoelectric peaks as a function of the energy was constructed by irradiating the scintillator block with Na-22 gamma radiation of 511 keV and by collecting the light generated by the silicon photomultiplier (SiPM) optical sensor. By analyzing the areas of the two photoelectric peaks separately, the DOI layer could be identified. The use of this detector is expected to enable excellent spatial resolution to be achieved in all areas of the field of view, and to produce images with excellent quality.