Comparator-less PET data acquisition system using single-ended memory interface input receivers of FPGA.

In this study, we propose a linear field-programmable gate array (FPGA)-based charge measurement method by combining a charge-to-time converter (QTC) with a single-ended memory interface (SeMI) input receiver. The QTC automatically converts the input charge into a dual-slope pulse, which has a width proportional to the input charge. Dual-slope pulses are directly digitized by the FPGA input/output (I/O) buffers configured with SeMI input receivers. A proof-of-concept comparator-less QTC/SeMI data acquisition (DAQ) system, consisting of 132 energy and 33 timing channels, was developed and applied to a prototype brain-dedicated positron emission tomography (PET) scanner. The PET scanner consisted of 14 sectors, each containing 2×1 block detectors, and each block detector yielded four energy signals and one timing signal. Because a single QTC/SeMI DAQ system can receive signals from up to eight sectors, two QTC/SeMI DAQ systems connected using high-speed gigabit transceivers were used to acquire data from the PET scanner. All crystals in the PET block detectors, consisting of dual-layer stacked lutetium oxyorthosilicate (LSO) scintillation crystal and silicon photomultiplier arrays, were clearly resolved in the flood maps with an excellent energy resolution. The PET images of hot-rod, cylindrical, and two-dimensional Hoffman brain phantoms were also acquired using the prototype PET scanner and two QTC/SeMI DAQ systems.