CT Evaluation of Carotid Plaque Components

Independent of the degree of stenosis, specific features of carotid plaque composition are associated with a high risk of thromboembolic and recurrent stroke. Many lines of evidence show a significant association between the presence of intraplaque hemorrhage and lipid rich necrotic core in carotid plaque independent of vessel stenosis in patients with ipsilateral ischemic infarcts. In fact, up to 17% of ischemic strokes are classified as embolic stroke of undetermined source (ESUS) after a comprehensive diagnostic work-up. A subset of these patients have stroke due to mildly stenotic plaque composed of high-risk non-calcified carotid plaque components that are presently difficult to distinguish by noninvasive conventional imaging tests. Presently first-line imaging of acute stroke patients is computed tomography angiography (CTA) of the head and neck. Although conventional CTA provides information about stenosis, it lacks the ability to distinguish tissue components with similar attenuation curves (e.g., lipid and intraplaque hemorrhage). Thus, invaluable diagnostic information is lost due to limitations of conventional CTA. By contrast, photon-counting/spectral CT is a novel technology that can identify material-specific characteristics and identify plaque components (e.g., iron/hemorrhage, lipid, and calcium) based on the specific behavior of these materials at different photon energy levels. The investigators propose testing the diagnostic performance of this new CT technology to detect different plaque components in subjects who are medically managed by carotid MRI or postprocessing PCCT images using a semi-automated carotid plaque segmentation software. The investigators also propose testing the diagnostic performance of this new CT technology in patients undergoing carotid endarterectomy revascularization surgery as standard of care with carotid MRI and histologic validation of the resected plaque tissue (ground truth). Accurate detection of these high-risk noncalcified plaque components by noninvasive imaging methods would be of great value to identifying a patient population at highest risk for embolic stroke from carotid disease.