Timing improvement by low-pass filtering and linear interpolation for the LabPETTM scanner

Abstract

Digital processing for positron emission tomography (PET) scanners commonly relies on low frequency sampling (≪65 MHz) for reducing power consumption. Timestamps must then be interpolated between samples to achieve adequate time resolution for coincidence detection of annihilation radiation. A low-pass filter based interpolation algorithm adding up to 31 samples between original samples was designed to improve both the energy and timing resolution of the LabPETTM scanner. An energy resolution refinement of ˜2 bits can be achieved with such a technique. The better estimation of triggering threshold leads to a more accurate timestamp generation. Timestamp accuracy was investigated as a function of trigger level (5-50% of maximum value). With the trigger threshold set at 20%, coincidence time resolution of ˜5.0 ns for LYSO-LYSO and ˜9.6 ns for LGSO-LGSO are obtained. A real time implementation of the algorithm was achieved in a Xilinx FPGA.