Development of a proof-of-principle PET system using multi-time-over-threshold and FPGA without ADC or TDC

The goal of this study was to extend a multi-time-over-threshold (MToT) based multi-channel front-end circuit and field-programmable gate array only data acquisition (DAQ) without analog-to-digital converter or time-to-digital converter for the development of a proof-of-principle positron emission tomography (PET) system. The proposed system was configured with two detector modules, each having a 4 × 2 detector block (128 ch/detector module). The performance of the PET system using a 256-channel analog circuit and a DAQ system was evaluated by measuring energy resolution and time resolution. These values were 20 % and 1.5 ns, respectively. The calculated data packet containing energy, time, and position information was formed into 64-bit single event data package and sent to the host computer using USB 3.0 control interface. Experiment results revealed that the spatial resolution was 2.1 mm at the center and 2.2 mm at 20 mm from the center. The Derenzo Phantom based experiment showed sufficient distinguish for Hod-rod of various radius, confirming the viability of the proposed proof-of-principle system.