A depth of interaction detector was designed using three layers of the scintillation pixel array and silicon photomultiplier
through DETECT2000 simulation. The upper and lower layers used diffuse reflectors, and the
middle layer used specular reflectors to distinguish the light signal arising from each layer. The signals obtained
at each layer were characterized by different locations at which photoelectric peaks were formed in the energy
spectrum, which could be analyzed to track the layers in which gamma-rays and scintillation pixels interacted.
Based on the simulation results, the basic experiment was conducted to obtain the energy spectrum. In the
experiment, three photoelectric peaks were identified in the energy spectrum as in the simulation, and the layers
interacted with gamma-rays, and scintillation pixels for each layer were distinguished by analyzing each
photoelectric peak. It is anticipated that by applying the detector design obtained from this study to future
small animal PET operating with MRI, the depth at which gamma-rays and scintillators interact will be measurable,
thus improving the spatial resolution outside the FOV.