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Figure 11. An example of contrast concentration changes occurring in various tissues during contrast enhancement. The concentration in the capillary plasma can be seen to reach an early peak as the bolus of contrast passes through the tissue vasculature. A second re-circulation peak can also be seen and subsequently there is elevation of the contrast concentration within the plasma which gradually decreases due to renal elimination. The change of concentration of contrast material in the interstitial space can be seen to represent a gradual elevation throughout the time course illustrated here. The amplitude and gradient of that rise will reflect capillary endothelial permeability surface area product and blood flow. The third curve shows the concentration of contrast observed in the tissue as a whole. In this case a small initial peak can be seen due to contrast within blood vessels in the voxel as well as a gradual elevation due to contrast leakage.
