State-of-the-Art Imaging of Acute Stroke

Abstract

Stroke is a leading cause of mortality and morbidity in the developed world. The goals of an imaging evaluation for acute stroke are to establish a diagnosis as early as possible and to obtain accurate information about the intracranial vasculature and brain perfusion for guidance in selecting the appropriate therapy. A comprehensive evaluation may be performed with a combination of computed tomography (CT) or magnetic resonance (MR) imaging techniques. Unenhanced CT can be performed quickly, can help identify early signs of stroke, and can help rule out hemorrhage. CT angiography and CT perfusion imaging, respectively, can depict intravascular thrombi and salvageable tissue indicated by a penumbra. These examinations are easy to perform on most helical CT scanners and are increasingly used in stroke imaging protocols to decide whether intervention is necessary. While acute infarcts may be seen early on conventional MR images, diffusion-weighted MR imaging is more sensitive for detection of hyperacute ischemia. Gradient-echo MR sequences can be helpful for detecting a hemorrhage. The status of neck and intracranial vessels can be evaluated with MR angiography, and a mismatch between findings on diffusion and perfusion MR images may be used to predict the presence of a penumbra. The information obtained by combining various imaging techniques may help differentiate patients who do not need intravenous or intraarterial therapy from those who do, and may alter clinical outcomes.

Diffusion tensor imaging of deep gray matter brain structures: Effects of age and iron concentration

“…DWI, while not normally considered as a major dependent variable in research studies, are used clinically as a highly sensitive marker for acute ischemia (Moseley et al, 1990b;Moustafa and Baron, 2007;Srinivasan et al, 2006) and for the evaluation of stroke (Wang et al, 2006). Inspection of DWI, especially in advancing age, reveals a striking conspicuity of the globus pallidus and putamen caused by signal loss in these structures, presumably due to iron accumulation with age.…”

Acute-Onset Migrainous Aura Mimicking Acute Stroke: MR Perfusion Imaging Features

“…10 The patterns of hypoperfusion in acute brain infarction have been described. 11 MR perfusion abnormalities have also been described in other disorders, (eg, seizures, vasospasm following subarachnoid hemorrhage, and severe stenosis of intra-or extracranial vessels). 12,13 MR imaging, nuclear medicine, and CT perfusion studies have demonstrated that migrainous aura may be associated with perfusion abnormalities; however, all articles are limited to a small number of selected patients.…”

Computer-Aided Diagnosis of Hyperacute Stroke with Thrombolysis Decision Support Using a Contralateral Comparative Method of CT Image Analysis

“…CT perfusion is a functional imaging technique that can be used to identify salvageable brain tissue [1,2]. Diffusion-weighted MR imaging can be used for identifying infarcted brain tissue that is irreversibly damaged, whereas perfusion-weighted MR imaging can be used for identifying reversibly injured ischemic brain tissue [3]. Although CT and MR are versatile imaging modalities that are capable of depicting various aspects of acute stroke-associated brain changes, their actual usage at a particular institution depends to a large extent on the availability of equipment and the experience and expertise level of that institution.…”