The electronics system for the LBNL positron emission mammography (PEM) camera

We describe the electronics for a high-performance positron emission mammog raphy (PEM) camera. It is based on the electronics for a human brain positr on emission tomography (PET) camera (the Siemens/CTI HRRT), modified to use a detector module that incorporates a photodiode (PD) array. An applicatio n-specified integrated circuit (ASIC) services the photodetector (PD) array , amplifying its signal and identifying the crystal of interaction. Another ASIC services the photomultiplier tube (PMT), measuring its output and pro viding a timing signal. Field-programmable gate arrays (FPGAs) and lookup R AMs are used to apply crystal-by-crystal correction factors and measure the energy deposit and the interaction depth (based on the PD/PMT ratio). Addi tional FPGAs provide event multiplexing, derandomization. coincidence detec tion. and real-time rebinning. Embedded PC/104 microprocessors provide comm unication, real-time control, and configure the system. Extensive use of FP GAs make the overall design extremely flexible, allowing many different fun ctions (or design modifications) to be realized without hardware changes. I ncorporation of extensive onboard diagnostics, implemented in the FPGAs, is required by the very high level of integration and density achieved by thi s system.