Unenhanced computed tomography

Abstract

The speed, widespread availability, low cost, and accuracy in detecting subarachnoid and intracranial hemorrhage have led conventional computed tomography (CT) scanning to become the first-line diagnostic test for the emergency evaluation of acute stroke [1-6]. Head CT scans can detect ischemic brain regions within 6 h of stroke onset (hyperacute). According to reports by Mohr and Gonz?ez, the introduction of such early detection is comparable to that of conventional T2-weighted magnetic resonance imaging (MRI) [7-12]. For example, based on 68 patients imaged within 4 h of stroke onset,Mohr et al. [11] concluded that CT was equivalent to MRI in its ability to detect the earliest signs of stroke (Table 3.1, Figs. 3.1-3.5). Importantly, the identification of ischemic brain tissue by CT not only defines regions likely to infarct, but also may predict outcome and response to intravenous (i.v.) or intra-arterial (i.a.) thrombolytic therapy [13]. Most commonly, CT is used to exclude parenchymal hemorrhage and significant established infarction.Unenhanced CT findings can additionally, in some settings, help to predict hemorrhagic transformation of already necrotic tissue following arterial reperfusion. Sensitivity values for the CT detection of stroke vary in the literature. These differences are largely caused by the variance in study design and focus, the vascular territory in question, and the generation of CT scanner used. Because control groups without stroke are not commonly included as subjects in published reports, the specificity of CT scanning in stroke detection is not well established [14]. © 2006 Springer-Verlag Berlin Heidelberg.