Anode position and last dynode timing circuits for dual-layer BGO scintillator with PS-PMT based modular PET detectors

New high spatial resolution positron emission tomography (PET) detectors for small animal and breast imaging have been developed. In these detectors, position-sensitive photomultipliers (R7600-C12) and dual-layer pixelated bismuth germanate (BGO) crystals are employed to detect and localize gamma rays. Modified high-voltage dividers with last dynode readout circuits, front-end anode position, and last dynode timing schemes have been investigated and developed for these detectors. Methods for combining four position-sensitive photomultipliers (PS-PMTs) with simple four (X^-, X⁺, Y^-, and Y⁺) outputs have been developed to further simplify the position processing. The front-end circuits are small so they can be fitted into the detector´s structure. A prototype of two detector modules, each having two PS-PMTs with corresponding electronic circuits, has been built for evaluation. The crystal elements of 10×10 in the proximal layer and 9×9 in the distal can be clearly identified.