A data acquisition sub-system for distributed, digital, computational, APD-based, bimodal PET/CT architecture for small animal imaging

The integration of a positron emission tomography (PET) scanner and a computed tomography (CT) scanner using the same detection system is a real challenge. The goal of the proposed PET/CT scanner design is to achieve high-speed data acquisition with a coincidence time window smaller than 10 ns and less than 1 mm spatial resolution in both PET and CT imaging using the same PET detectors and electronics. Events can be processed at high count-rate, based on a distributed computational architecture mounted directly within the PET ring. To satisfy these new technological requirements, a modular data acquisition sub-system (DASS) was designed, capable of handling up to 64 individual PET/CT detector channels. The DASS is based on off-the-shelf 8-bit, 100-MHz, high-speed free running analog-to-digital converters (ADC) and digital signal processing running on field programmable gate arrays (FPGA). The core of the processing units consists of four Xilinx Spartan-III FPGAs that can hold up to 16 individual channels each. The modular printed circuit board (PCB) has twelve copper layers, allowing separate ground and power planes to be implemented. The PCB outline allows various configurations in a multi-ring stacking geometry to realize 3-D scanners.