Figure 3
From: Cerebral perfusion metrics calculated directly from a hypoxia-induced step change in deoxyhemoglobin
An illustration of the proposed model. The capillary diagrams show the phases of signal change as the wavefront of the step increase in SaO2 in a population of vessels passes through a voxel to fill all vessels in the voxel with blood containing increased SaO2. The graph shows the net increase in SaO2 within the voxel (red line) and the resulting ΔR2* signal (blue line) as the step change in SaO2 in the population of capillaries reaches the voxel. At dotted line 1 in the graph, the entry phase illustrates the arrival of oxygenated blood (red) displacing the hypoxic blood (blue). Entry is complete in all capillaries at dotted line 2 in the graph and the filling phase is a constant rate of filling with oxygenated blood in all vessels, resulting from a net voxel flow of CBF and a linear decrease in ΔR2* signal. At dotted line 3 in the graph, the linear stage of filling ends and the exit phase is characterized by the slowing of the net rate of increase in SaO2 with ΔR2* signal following a declining exponential pattern reaching an asymptote of zero change at dotted line 4.
