Illustration of a case of left middle cerebral artery (MCA) occlusion with good collateral circulation. CT perfusion Tmax thresholds (left) demonstrates predominantly mild Tmax delay in the left MCA territory (blue) with a Hypoperfusion Intensity Ratio (HIR) of 0, indicating that there is no tissue with a Tmax delay >10 seconds. The CT perfusion image columns (right) demonstrate preserved cerebral blood volume (CBV) in the left hemisphere.

CT= computed tomography, CBF= cerebral blood flow, MTT = mean transit time.


Illustration of a case of left middle cerebral artery (MCA) occlusion with poor collateral circulation. CT perfusion Tmax thresholds (left) demonstrate severe Tmax delay in the left MCA territory (red) with a Hypoperfusion Intensity Ratio (HIR) of 0.8, indicating that a large fraction of the perfusion lesion has a Tmax delay >10 seconds. The CT perfusion image columns (right) demonstrate very low cerebral blood volume (CBV) in the left hemisphere (dark blue).

CT= computed tomography, CBF= cerebral blood flow, MTT = mean transit time.