Each symbol represents the average density of seven rats in every instance of image taking. There was no significant difference statistically between groups C and PE at time zero (white arrows). The distribution of the symbols can apply to a quadratic function graph, and so the peak density can be determined. The peak density of group PE was significantly lower than that of group C (109 ± 10 versus 137 ± 11, p < 0.001), indicating a decrease in vascular volume in the peripheral area in PE. When compared at 1.7 s after initial infusion (black arrows), the density of group PE was also significantly lower than that of group C (97 ± 10 versus 129 ± 11, p < 0.001).