Optimal coincidence time window for ECAT exact HR plus

The effect of various sizes in coincidence time window was investigated on the ECAT Exact HR Plus system. Standard emission and windowed transmission scans were performed using a range coincidence time windows to determine where the maximum in noise equivalent counts (NEC) occurred. Regions of interest (ROI) were also drawn on reconstructed images to compute the statistical variation in images from different time windows. The optimum coincidence time window for simultaneous emission-transmission acquisitions was also determined, based on the generalized NEC of emission sinograms. Results showed that a 10, 14, and 6 ns coincidence time windows provides the highest NEC for standard emission, windowed transmission, and simultaneous scans, respectively. Results based on statistics in ROI, however, suggested the optimal coincidence time windows of 10, 6, and 10 ns for standard emission, windowed transmission, and simultaneous scans, respectively. Improvement of signal to noise (S/N) for different coincidence time windows are negligible for standard emission and windowed transmission scans. For simultaneous emission-transmission data acquisition, a 10 ns coincidence time window may provide an 11% improvement on NEC and 2% improvement on S/N over the default 12 ns window