Design of the Time Measurement Circuit, Single Data Frame Sorting, and Packaging Logic of a TOF PET System

Positron Emission Tomography (PET) is an important research direction in the field of nuclear medicine. We designed the Single Processing Unit (SPU) electronics for a brain PET system, which is based on the Time-of-Flight (TOF) PET structure. The SPU electronics are required to achieve a 5%0 energy measurement precision as well as a 50-ps-FWHM time measurement precision. The readout electronics include analog front end amplification, shaping, A/D conversion, and time measurement circuits, as well as digital signal processing logic based on a Field Programmable Logic Gate Array (FPGA). Besides, to relieve the data processing pressure of the Coincidence Process Unit (CPU), we designed a single data frame sorting algorithm based on a token ring structure and swap sorting method. The algorithm guarantees that the single data frames are arranged according to their time information. A data frame packaging algorithm is also implemented to ensure the data frames with the time information within a predetermined period are packaged into data frame packages. We conducted tests on the electronics, and the results showed successful time measurement performance while the single data frame sorting algorithm and the data packaging logic functioned well.