Fig. 4

Coefficient of variation (COV) in the phantom background compartment of both, P1 and P2 reconstructions at different acquisition times, in graphs with a standard scale and b log-log scale. A power-law fit resulted in COV = 208 T^−0.446. The coefficient of determination r² equals 0.99, which indicates a good fit. Three additional non-overlapping reconstructions were included for five acquisition times (240, 140, 100, 30, and 10 s/bed) to obtain a measure of error