CT perfusion imaging in acute ischemic stroke:: comparison of perfusion maps and conventional CT findings.

To evaluate the findings of acute brain ischemia on different functional maps of cerebral perfusion CT in stroke patients and to compare the results with early ischemic changes on conventional CT. Methods: The baseline CT scans of 45 acute stroke patients were retrospectively evaluated with respect to early CT findings. For each patient the extent of cerebral ischemia as shown on the maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and "time to peak" (TP) was compared and the severity of ischemia was assigned to one of three levels based on the findings of the CBF image. Results: In 75% of all patients conventional CT was performed within 2 hours from symptom onset. 29 of 45 patients showed early signs of ischemia on conventional CT, whereas perfusion CT revealed cerebral ischemia in all patients. Severe ischemia was found in approximately the same rate of incidence in patients with early CT changes (55.2%) and in those with normal findings (43.8%). If the perfusion impairment was judged as mild or moderate the extent of the hypoperfused area was significantly larger on the CBF and TP images than on the CBV map. This was significantly different in patients with severe hypoperfusion where a complete correspondence of the affected area between the three functional maps was found. Discussion: The use of conventional CT for the assessment of stroke in the hyperacute phase is limited. Perfusion CT yields excellent information regarding the severity and extent of ischemia. The use of various perfusion maps helps to differentiate the core of infarction from the ischemic penumbra zone.