Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Aug 2002
ReviewB-mode ultrasound and spiral CT for the assessment of carotid atherosclerosis.
More studies on the natural history of carotid artery plaques are needed to predict more reliably which plaque types or features are the most dangerous (see Table 2). Studies on carotid and coronary endarterectomy specimens indicate a dynamic process of rupture, thrombus formation, healing, and remodeling of the plaque. A plaque from a symptomatic patient may not show any signs of plaque rupture if the plaque has healed or evolved since the debut of symptoms. ⋯ This progress is most necessary, considering the very high demands for surrogate endpoints and risk markers in clinical intervention studies. Whether ultrasonic plaque characterization can be implemented in broad general clinical practice, for example, in screening of individuals at high risk of developing atherosclerosis and ischemic events, has to be based upon data from large prospective studies with long-term follow-up. IMT is already used in population screening, as in the ARIC study [9,101].
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The assessment of atherothrombotic plaques by imaging techniques is essential for the in vivo identification of vulnerable plaques. Several invasive and noninvasive imaging techniques are available to assess atherothrombotic disease. The use of some of the available imaging modalities for the study of regression and progression of atherothrombosis are described in more detail in the subsequent articles.
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Atherogenesis is an inflammatory process that begins in childhood. Early detection of atherosclerosis might allow for selection of subjects at risk for future cerebrovascular events at a time when dietary and lifestyle modification may have its greatest impact, and medical intervention may be useful for those who are refractory to such treatment or who are at greater risk for an event. Early detection relies on a knowledge of the distribution of atheroma formation, which can be predicted by understanding the hemodynamic patterns of blood flow. ⋯ In these individuals, understanding atheroma morphology may prove to be of greater utility for assessing stroke risk and determining the appropriate management. Morphologic characterization may also be helpful in monitoring the effect of medical intervention. MRI has proven capable of characterizing the morphologic composition of carotid atheroma, although the clinical implications continue to be investigated.
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Much has been learned about microembolization in the last two decades. The promising blood markers for brain injury will further enhance our future understanding of microembolic events. New surgical techniques, drugs, and devices have substantially reduced microembolization during carotid angioplasty, CEA, and CABG.
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High spatial resolution magnetic resonance imaging (MRI) is one of the most promising modalities for visualizing the carotid atherosclerotic plaque. MR allows direct visualization of the diseased vessel wall, is capable of characterizing plaque morphology, and can potentially monitor progression of the disease. ⋯ Improved imaging techniques are therefore needed to reliably identify the high-risk plaques that lead to cerebrovascular events. This article focuses on the current state-of-the-art in MR carotid atherosclerotic plaque imaging to evaluate plaque morphology and composition.