Diffusion, Negative enhancement integral, Mean time to enhance from dynamic susceptibility contrast perfusion imaging, and PASL perfusion imaging in a patient with a proximal right MCA occlusion. Diffusion restriction is seen the right basal ganglia and insular cortex (arrowhead, A). The diffusion restriction corresponds to decreases in blood volume (blue areas) (arrowhead, B) seen on the negative enhancement integral. The mean time to enhance shows a much larger region of at risk tissue (green area)(arrows, C) surrounding the core infarct. PASL shows a similar region of hypoperfusion (arrows) corresponding to the defect on the mean time to enhance map. (D) PASL perfusion imaging cannot distinguish small perfusion differences below 20 mL/100g/min so infarction looks similar to at risk tissue. In these low flow situations, the PASL perfusion defect is comparable to the mean time to enhance rather than reflecting true CBF.