Four-layer DOI detector with a relative offset in animal PET system

In order to build an animal PET system with high sensitivity and resolution, we propose a four-layer PET system which provides the DOI (depth of interaction) information. Each crystal layer has a relative offset of half the crystal pitch with each other and uses an identical type of crystals simplifying readout electronics. The proposed system PET system consists of four LYSO (Lu₁₈Y_0.2SiO₅:Ce) or L_0.9GSO (Lu_1.8Gd_0.2 Si_0.4:Ce) crystal layers with a crystal dimension of 1.5times1.5times5.0 mm³. The animal PET system has a diameter of 84 mm with one Hamamatsu H9500 flat panel PMT ring, and can be upgraded to two PMT ring configuration. An estimated efficiency using GATE simulation is ~15% at the center of one detector ring system. We present flood images obtained with a ²²Na radiation source to verify the concepts of the proposed system, and obtained promising results.