System electronics for the MiCES small animal PET scanner

The final electronics system for the micro crystal element scanner (MiCES) small animal positron emission tomograph is described. Groups of four position-sensitive photomultiplier tubes (PSPMTs) are connected to an adapter board which provides four output signals from each PSPMT. The adapter board outputs are routed to an analog processing board which contains application specific integrated circuits (ASIC) for signal amplification, base line restoration, and time to digital conversion. The amplified signals are continuously digitized and the data routed to field programmable gate arrays (FPGA). Each analog board is configured into two independent channels, each channel processing the data from two PSPMTs. The digital data is routed to a digital board that includes a microprocessor and a 1394a (FireWire) bus controller. The MiCES uses 18 board sets to process signals from 72 PSPMTs. In addition, a coincidence controller imposes a rough coincidence window on the data. Finally, a motion controller drives the gantry table and the rotation motors. All of the electronics with the exception of the motion controller, power supplies, and host computer rotate with the detector array. The low speed signal and power buses are connected to the electronics via a slip ring. The 1394a bus is connected to the host computer via a rotating optical coupler and 1394a copper to optical converters.