Acute stroke services have been installed in most hospitals in the industrialized world, and dealing with hyperacute stroke has become one of the most frequently performed tasks of the on-call radiologist. Imaging plays a key role in current guidelines for thrombolysis, and knowledge of classic early ischemic signs or depiction of hemorrhage at nonenhanced computed tomography (CT) is necessary (although not sufficient) for a satisfactory imaging study. A modern CT examination must also include perfusion CT and CT angiography. Perfusion CT delineates the ischemic tissue (penumbra) by showing increased mean transit time with decreased cerebral blood flow (CBF) and normal or increased cerebral blood volume (CBV), whereas infarcted tissue manifests with markedly decreased CBF and decreased CBV. CT angiography can depict the occlusion site, help grade collateral blood flow, and help characterize carotid atherosclerotic disease. A complete CT study (nonenhanced CT, perfusion CT, and CT angiography) may be performed and analyzed rapidly and easily by general radiologists using a simple standardized protocol and may even facilitate diagnosis by less experienced radiologists in affected patients.
(c) RSNA, 2008.