Comprehensive imaging of ischemic stroke with multisection CT

Identification by CT scan of ischemic stroke patients with high risk of brain death

The identification of patients with high risk of evolution to brain death is one of the more important tasks of transplant coordination teams. Although most of pool of potential donors come from the group of patients who suffer a head injury or hemorrhagic stroke, the procurement of organs from brain-dead patients suffering an ischemic stroke as the cause of brain damage must also be considered. The main objective of this study was to investigate the radiological signs that in the CT scan of admission to a neurological ICU are more frequently associated with progression to brain death. We studied the CT scans of 15 brain-dead patients after an ischemic stroke versus the scans of 15 recovered patients admitted to ICU with the same diagnosis. The radiological signs included: insular ribbon sign, hyperintensities inside the big arteries of the base of the skull, hemispheric hypodensities, midline shift, and compression of the cerebrospinal fluid spaces. There were two signs significantly associated with brain death: midline shifts and the compression of the ambiens cistern. It may be concluded that analysis of the CT scan at admission of patients with an ischemic stroke in the ICU can predict the risk of evolution to brain death.

Imaging of acute stroke: state of the art

The high incidence of stroke, plus its fatal or debilitating outcome, has prompted tremendous advances over the last two decades on both diagnostic and therapeutic fronts. Multiple randomized trials have proven the utility of thrombolytic agents with rejuvenation of the role of diagnostic imaging. State of the art imaging (mainly computed tomography and magnetic resonance imaging) is crucial for patient selection (eg, excluding intracranial hemorrhage), diagnosis of stroke and prediction of prognosis. Here, we discuss the anatomic and physiologic changes due to an ischemic insult as manifested by modern imaging techniques, including diffusion and perfusion imaging, as well as demonstration of vascular disease by cross sectional angiography supplemented by three dimensional postprocessing. The main target of management is "Penumbra", or salvageable tissue, which is primarily dependent upon the expediency of the whole process, better expressed by the phrase "Time is Brain".

Imagerie des accidents vasculaires cerebraux en urgence

Over the last 25 years, advances in neuroimaging have significantly changed the evaluation and management of acute stroke syndromes. In the seventies, computed tomography (CT) could differentiate between ischemic and hemorrhagic stroke. Magnetic resonance imaging (MRI) is nowadays the imaging modality of choice in the initial assessment of acute stroke. MRI images can better discriminate acute, subacute and chronic infarcts, differentiate venous from arterial infarcts, detect arterial dissection, stenosis or occlusion. Diffusion-weighted images are highly sensitive and specific to acute infarction and the combination with perfusion technique is suitable to define potentially reversible ischemia (area of cerebral "mismatch" which is thought to represent the so-called ischemic penumbra). This penumbra is a potential therapeutic target of valuable interest for the treating physician.

Perfusion CT and angio CT in the assessment of acute stroke

In order to evaluate the clinical utility of non-enhanced CT with perfusion and angio CT in the assessment of acute ischaemic stroke, 42 patients with symptoms of acute stroke were examined within the first 6 h from onset of symptoms with non-enhanced CT (NECT), perfusion CT (PCT) and CT angiography (CTA). Maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were analysed visually, and after drawing regions of interest (ROIs) in the territory of anterior, middle and posterior cerebral arteries, maximum-intensity projection and volume-rendering images of the cervical and cerebral vessels were created. All patients underwent a control CT or MR examination 24-48 h after the initial examination. Twenty-nine patients developed an area of infarction at control examinations. Significant perfusion abnormalities were found in 27 cases, whilst in two patients the perfusion studies were considered to be normal. All the cases with perfusion abnormalities showed arterial stenoses or occlusions on angio CT. Small infarctions at levels other than the ones selected for perfusion CT, and arteriosclerotic changes, were observed in the two cases with no perfusion abnormalities. In conclusion, combining non-enhanced CT with PCT and CTA is a simple and a very valuable tool in the initial assessment of acute stroke.

Advances in Multidetector Computed Tomography

The improvement in multidetector computed tomography has had a tremendous impact on neuroimaging. Some of these strides include imaging in the setting of acute stroke with the advent of perfusion computed tomography, and studying intracranial aneurysms and, to some extent, carotid artery disease. The purpose of this article is to review these applications as they were outlined at the "Advances in Multidetector CT" meeting held in Washington, DC, September 13-14, 2003.

CT Angiography of Intracranial Aneurysms: A Focus on Postprocessing

Computed tomographic (CT) angiography is a well-known tool for detection of intracranial aneurysms and the planning of therapeutic intervention. Despite a wealth of existing studies and an increase in image quality due to use of multisection CT and increasingly sophisticated postprocessing tools such as direct volume rendering, CT angiography has still not replaced digital subtraction angiography as the standard of reference for detection of intracranial aneurysms. One reason may be that CT angiography is still not a uniformly standardized method, particularly with regard to image postprocessing. Several methods for two- and three-dimensional visualization can be used: multiplanar reformation, maximum intensity projection, shaded surface display, and direct volume rendering. Pitfalls of CT angiography include lack of visibility of small arteries, difficulty differentiating the infundibular dilatation at the origin of an artery from an aneurysm, the kissing vessel artifact, demonstration of venous structures that can simulate aneurysms, inability to identify thrombosis and calcification on three-dimensional images, and beam hardening artifacts produced by aneurysm clips. Finally, an algorithm for the safe and useful application of CT angiography in patients with subarachnoid hemorrhage has been developed, which takes into account the varying quality of equipment and software at different imaging centers.

Cerebral Angiography in the Assessment of Acute Cerebral Ischemia: Guidelines and Recommendations

Catheter-based cerebral angiography remains an essential tool for evaluating patients with acute cerebral ischemia. Noninvasive vascular imaging techniques have yet to achieve the accuracy and wide availability necessary for this purpose. Angiography is rarely indicated when patients present within the short 3-hour time window for treatment with intravenous alteplase. For the many patients who present later in their course, however, angiography is useful for the accurate evaluation of the cerebral vasculature. In addition, angiography serves as the foundation for the endovascular therapies that may be performed to treat acute ischemic stroke beyond the 3-hour time window.