Real Time Data Acquisition for PET Detector Evaluation Based on Dual-Polarity Charge-to-Digital Converter

Positron emission tomography (PET) is an indispensable medical image technology today. An advanced data acquisition system (DAQ) based on dual-polarity charge-to-digital converter (dQDC) for PET detector application was proposed. The DAQ consists of two parts: analog board and digital board. The analog board assembles all analog components in the dQDC scheme while the core of the digital board is a low-cost field programmable gate array (FPGA). In the dQDC implementations, the single-ended voltage-referenced receivers in the FPGA serve as voltage comparators. Under this configuration, two input/output (I/O) pins of the FPGA can be used to perform one-channel charge measurement. Taking advantage of abundant I/O resources in the FPGA, a multi-channel DAQ based on the dQDC scheme can be quickly customized. Totally 128 channels of dQDCs are integrated in the DAQ on the 80×80 mm2 area. To confirm the readout capability of the DAQ, a PET detector was constructed, which consisted of a 15 × 15 array of 1.5 × 1.5 × 20 mm3 LYSO bars coupled with a SiPM detector at one end. The energy resolution of the PET detector ranges from 13.11% to 22.71%. To measure the timing performance of the PET detector, a reference detector was applied. With the DAQ system, experimental results showed that the coincidence timing resolution (CTR) of the two detectors can reach up to 722.9 ps in full width at half maximum (FWHM). This new dQDC scheme is very promising for the low-cost DAQ with hundreds of channels.