Figure 2. (A) Initial 120 s of a dye densitogram (DDG). Vertical line at 32 s indicates mean transit time (MTT), computed as the center of gravity of the first circulation. This is considered as time zero of injection for determining the indocyanine green concentration at injection time (Co). (B) A 15-min semilog plot of a DDG. The clearance slope K (solid line) was computed by linear regression of semilog plot between 2.5 min and 5.5 min after MTT and extrapolated to MTT to compute Co.