Accuracy and uniqueness of three in vivo measurements of atherosclerotic carotid plaque morphology with black blood MRI

Abstract

High-resolution MRI provides unique information about morphology of atherosclerotic carotid plaque. In this study, the accuracy and precision of measurements of carotid plaque burden and lumen narrowing were determined for in vivo black blood MRI assessment with respect to ex vivo MRI in a group of 37 atherosclerosis patients who underwent carotid endarterectomy (CEA). Three different plaque measures were compared between paired in vivo and ex vivo MR images: maximum wall area (MWA), minimum lumen area (mLA), and wall volume (WV Carotid atherosclerosis is one of the main causes of stroke (1). Traditionally, the degree of lumen stenosis has been used as a marker for high-risk plaques that may cause thromboembolic events. Clinically, X-ray (conventional angiography), CT, MR angiography, and ultrasound are used to determine lumen stenosis. Although these techniques have been shown to accurately assess the severity of lumen narrowing, they do not provide as much information as MRI regarding the internal composition of the plaque (2). Furthermore, MRI provides high contrast between the vessel wall and surrounding tissues, enabling measurement of plaque burden. Because both plaque composition and burden are believed to be closely associated with plaque vulnerability (3), MRI is emerging as a valuable tool for evaluating atherosclerosis.The significance of measuring plaque burden in addition to lumen stenosis arises because a vessel may go through compensatory remodeling where the buildup of plaque leads to outward expansion of the vessel (4). This outward expansion may proceed independently from lumen narrowing, making plaque burden a complementary measurement to lumen stenosis. In order to use plaque burden as an additional risk factor, a method for accurately measuring burden must be established. For this purpose, flow suppressed (black blood) MRI is a strong candidate because it can visualize the artery lumen and provide detailed information about the artery wall (2). In a recent study, Yuan et al. (5) showed that, based on a group of 14 patients, the in vivo measurement of maximum wall area strongly correlates to the same measurement on excised plaque specimens, where ex vivo images were used as a gold standard. However, this study did not address the relationship of maximum wall area and lumen narrowing. The accuracy of vessel wall area measurement was not established either.The goals of this study were to 1) determine the accuracy and precision of quantitative measurements of vessel wall size using a high-resolution black blood MRI technique on the human carotid artery with respect to ex vivo data, and 2) study the association between these measurements and lumen stenosis. Analyses comparing three key vessel wall size measurements between in vivo and ex vivo MRI scans were carried out. These parameters were vessel wall volume (WV), maximum wall area (MWA), and minimum lumen area (mLA). Measurements obtained from plaque specimens removed intact during surgery were used as the gold standard for the in vivo measure...

Relationship Between Arterial Stiffness and Subclinical Aortic Atherosclerosis

“…With software approved for beta testing by the Food and Drug Administration, 10,11 the lumen and outer wall boundary of the abdominal aorta were identified and manually traced in each slice on both the T2 and PDW image. 12 For all but 14 of the cases, the tracing resulting from the T2-weighted scan was used for subsequent analysis. In 14 cases, the outer boundary or luminal surface could not be accurately identified in Ͼ25% of its circumference.…”

Predictors of carotid atherosclerotic plaque progression as measured by noninvasive magnetic resonance imaging

“…A number of studies have shown that MRI can accurately quantify vessel wall dimensions of atherosclerotic arteries in vivo (4), with measurement errors ranging from 4-6% for the lumen and wall, and 3.3% for total vessel area measurement (5,6). Thus, MRI provides a promising tool to study plaque progression and the remodeling process of atherosclerosis in humans in a non-invasive fashion.…”

Quantitative Evaluation of Carotid Plaque Composition by In Vivo MRI

“…In addition, morphological information about the status of the fibrous cap 12 and the American Heart Association (AHA) lesion type 13 can be obtained noninvasively. Moreover, the tomographic orientation of MRI enables the full cross-sectional view of the vessel wall, which can be measured accurately 14 and reproducibly. 15 It has been demonstrated that ex vivo MRI of endarterectomy specimen is able to identify 16 and quantify 17,18 plaque components with high diagnostic accuracy.…”