Computer-Assisted Analysis of Heterogeneity on B-Mode Imaging Predicts Instability of Asymptomatic Carotid Plaque

Abstract

Background: Computerized assessment of plaque echogenicity by B-mode ultrasonography has demonstrated that the gray-scale median (GSM) pixel intensity of the entire plaque predicts future ischemic stroke in patients with symptomatic carotid stenosis, but not those with asymptomatic stenosis. This study investigated whether plaque heterogeneity (i.e., the distribution of pixel intensities) could predict the instability of asymptomatic plaque. Methods: By comparison with carotid endarterectomy specimens and the GSM values of known tissues on B-mode images, the GSM values for blood, lipid, muscle/fibrous tissue, and calcification were determined. Then we estimated the percent area of each tissue component for 297 asymptomatic plaques causing 40–99% carotid artery stenosis in 250 patients, and monitored the incidence of atherothrombotic cerebral infarction due to carotid stenosis during follow-up. Results: Eight infarcts occurred during a follow-up period of 22 ± 15 months. Plaques in the top tertile for the percent area of lipid-like echogenicity (p < 0.05) and in the lowest tertile for calcification (p = 0.06) showed an association with future infarction according to Kaplan-Meier analysis. This association remained significant after adjustment for the severity of carotid stenosis (hazard ratio 4.4 for lipid-like and 0.24 for calcification-like component, both p < 0.05) according to Cox proportional hazards analysis. Conclusions: The distribution of pixel intensities in carotid plaque on B-mode ultrasonography can be employed to predict instability of asymptomatic plaque and possibly to select patients for interventional procedures. A large-scale investigation will be needed to confirm that estimating the percentage of plaque components relative to the total plaque area can predict ischemic stroke.

Mapeamento ecográfico da bifurcação das artérias carótidas extracranianas para planejamento cirúrgico: diferenças baseadas no gênero do paciente

“…Echography, on the other hand, is a true arteriography of the carotid bifurcation wall, showing the degree of stenosis, plaque extension, the characteristics of the atheromatous plaque, including ulceration, the level of the carotid bifurcation and residual lumen diameters. Studies of echographic characterization have shown that unstable plaques are associated with higher incidence of symptoms on plaque follow-up and at endovascular treatment 19,20 . Cross-sectional ultrasonographic images explain why radiologic luminography may underestimate the degree of stenosis in the presence of elliptic lumens (the majority of cases) 11 or even in cases of overlapping images of the internal and external carotid arteries.…”

Associations of Local Release of Inflammatory Biomarkers during Carotid Artery Stenting with Plaque Echogenicity and Calcification

“…Rus and Niculescu [33] reported 200-fold higher levels of IL-6 in atherosclerotic lesions than in blood. Several studies have shown that echolucent carotid plaques are associated with the risk of ischemic stroke [21,22,23]. Moreover, higher serum levels of IL-6 are associated with lower echogenicity of carotid artery [24].…”

“…Plaque characteristics such as echogenicity and calcification could be important indicators of vascular events. The echolucent plaque in severe carotid stenosis evaluated by plaque echogenicity contains large lipid pools or hemorrhages [20], and could be a predictor of future ischemic cerebrovascular events [21,22,23]. An association was observed between the circulating levels of inflammatory biomarkers, and the echogenicity of carotid plaques [24] and the rate of increase in carotid atherosclerosis [25], thus supporting the critical role of inflammation in plaque vulnerability and plaque progression.…”

Current Strategies and Possible Perspectives of Ultrasonic Risk Stratification of Ischemic Stroke in Internal Carotid Artery Disease

“…In summary, there are a number of studies offering different results and also variable cut-off values for the GSM, thereby underlining the need for a more differentiated approach to assessing plaque stability than the grayscale values alone. One such approach might be the quantitative display of the distribution of the plaque echogenicity pattern, as it was recently described by Hashimoto et al [27].…”