Figure 1.

A 78-year-old man with ischemic stroke of unknown onset presented to the emergency department with left hemiplegia. A) Volume rendering CTA (cranio-caudal view) shows occlusion of the right cerebral artery in the M1-M2 segment. B) CTA-SI at level of the basal nuclei with standard window width and center level (W/L) (286/66) is also illustrated. The CTA protocol acquisition occurs at an approximate steady state of contrast in the brain arteries and parenchyma so that the image is predominantly blood volume-weighted. Image review should be performed with narrow window width and center level display settings to maximize gray-white matter differentiation, thereby improving the detection of subtle, hypodense ischemic regions. C) With the same CTA-SI viewed with narrow W/L (38/48), it is possible to better appreciate the hypodense area of ischemic origin in the right cerebral hemisphere attributable to infarct "core" (irreversibly damaged tissue). D) A follow-up unenhanced CT scan clearly delineates the extent of ischemia, corresponding to the region identified with the CTA-SI in Figure 1C. Accurate inspection of CTA-SI with narrow windows enables definition of the ischemic core with the additional advantage of whole brain coverage.