MDCT diagnosis of acute ischemic stroke: considerations on image quality and clinical value

Introduction
In cases of suspected acute ischemic stroke, the diagnostic workup increasingly involves advanced neuroimaging methods [ 1]. While noncontrast CT provides structural information about the brain parenchyma and can rule out intracranial hemorrhage, contrast-enhanced imaging studies also provide functional information about blood flow in the vessels and tissues. In particular, angiography is used to determine the site of vascular occlusion, while perfusion studies can reveal an area of hypoperfused but still viable parenchyma, called tissue at risk or ischemic penumbra. The information provided by these multimodality examinations has important implications on treatment decisions, especially considering the availability of new thrombolytic therapies.
Cerebrovascular imaging studies can be done using either CT or magnetic resonance imaging (MRI), although CT is more readily available in emergency settings [ 2]. In the study of perfusion, for both CT and MRI there are several different imaging protocols that allow the measurement of different perfusion parameters (reviewed in [ 3]). This article highlights recent advances in cerebrovascular image quality in CT angiography and dynamic perfusion CT, and then examines the ongoing debate on the appropriate use of these imaging studies in clinical practice.