Figure 2. The two graphs show the ΔR2* for non-enhancing (control) and enhancing hypoperfused regions before and after arrival time correction (ATC).

In the first graph, due to even a small delay in time-to-peak, the control signal appears to approach baseline faster thus obscuring the phenomenon being measured. However, in the second graph, after the ATC has been applied to the control, it becomes evident that the enhancing region signal is approaching the baseline faster due to the T1 effect of contrast accumulation in the parenchyma.