  Small animal Positron Emission Tomography (PET) is dedicated to small animal
imaging. Animals used in experiments, such as rats and monkeys, are often much
smaller than human bodies, which requires higher position and energy precision
of the PET imaging system. Besides, Flexibility, high efficiency are also the
major demands of a practical PET system. These requires a high-quality analog
front-end and a digital signal processing logic with high efficiency and
compatibility of multiple data processing modes. The digital signal processing
logic of the small animal PET system presented in this paper implements
32-channel signal processing in a single Xilinx Artix-7 family of
Field-Programmable Gate Array (FPGA). The logic is designed to support three
online modes which are regular package mode, flood map and energy spectrum
histogram. Several functions are integrated, including two-dimensional (2D) raw
position calculation, crystal identification, events filtering, etc. Besides, a
series of online corrections are also integrated, such as photon peak
correction to 511 keV and timing offset correction with crystal granularity. A
Gigabit Ethernet interface is utilized for data transfer, Look-Up Tables (LUTs)
configuration and commands issuing. The pipe-line logic processes the signals
at 125 MHz with a rate of 1,000,000 events/s. A series of initial tests are
conducted. The results indicate that the digital processing logic achieves the
expectations.
