Initial test and results of an AwakeAnimalPET system

We have developed AwakeSPECT, a small animal SPECT/CT system for imaging the live mouse brain using an optical motion tracking system. The system successfully has been used in mouse brain studies without the need of anesthesia. As an extension of this technology we have built a prototype Awake Animal PET system by using the motion tracking system and modular PET detectors. The system consists of a commercial motion tracking system that utilizes four CCD cameras equipped with near infra-red (NIR) strobes and retro-reflective markers, and a modular PET system with 8 detector modules. The motion tracking system measures six degrees of freedom (x, y, z, roll, pitch, and yaw) of then moving target at 60 frames per second. The PET system uses a 32 channel flash ADC system developed at Thomas Jefferson National Accelerator Facility. Each PET detector module is built with a Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT) optically coupled to a 48 x 48 pixelated 1 mm pitch LYSO scintillator array. Custom built PSPMT read-out electronics were built that uses Anger-logic to provide four channel output per detector module. Geometrical calibration was performed using Na-22 point source phantom using the same method used for AwakeSPECT. Initial proof-ofprinciple tests were performed using a foam mouse phantom with three IR reflectors and an embedded Na-22 point source. During the PET scan, the foam mouse was moved/rotated by hand motion. Image reconstruction with motion compensation resulted in good point image reconstruction.