In vitro characterization of atherosclerotic carotid plaque with multidetector computed tomography and histopathological correlation

A Novel Artificial Coronary Plaque to Model Coronary Heart Disease

BACKGROUND

Experimental coronary artery interventions are currently being performed on non-diseased blood vessels in healthy animals. To provide a more realistic pathoanatomical scenario for investigations on novel interventional and surgical therapies, we aimed to fabricate a stenotic lesion, mimicking the morphology and structure of a human atherosclerotic plaque.

METHODS

In an interdisciplinary setting, we engineered a casting mold to create an atherosclerotic plaque with the dimensions to fit in a porcine coronary artery. Oscillatory rheology experiments took place along with long-term stability tests assessed by microscopic examination and weight monitoring. For the implantability in future in vivo setups, we performed a cytotoxicity assessment, inserted the plaque in resected pig hearts, and performed diagnostic imaging to visualize the plaque in its final position.

RESULTS

The most promising composition consists of gelatin, cholesterol, phospholipids, hydroxyapatite, and fine-grained calcium carbonate. It can be inserted in the coronary artery of human-sized pig hearts, producing a local partial stenosis and interacting like the atherosclerotic plaque by stretching and shrinking with the vessel wall and surrounding tissue.

CONCLUSION

This artificial atherosclerotic plaque model works as a simulating tool for future medical testing and could be crucial for further specified research on coronary artery disease and is going to help to provide information about the optimal interventional and surgical care of the disease.

Investigating the relationship between intracranial atherosclerotic plaque remodelling and diabetes using high-resolution vessel wall imaging

BACKGROUND

Intracranial atherosclerosis, a leading cause of stroke, involves arterial plaque formation. This study explores the link between plaque remodelling patterns and diabetes using high-resolution vessel wall imaging (HR-VWI).

AIM

To investigate the factors of intracranial atherosclerotic remodelling patterns and the relationship between intracranial atherosclerotic remodelling and diabetes mellitus using HR-VWI.

METHODS

Ninety-four patients diagnosed with middle cerebral artery or basilar artery atherosclerosis were enrolled. Their basic clinical data were collected, and HR-VWI was performed. The vascular area at the plaque (VAMLN) and normal reference vessel (VAreference) were delineated and measured using image postprocessing software, and the Remodelling index (RI) was calculated. According to the value of the RI, the patients were divided into a positive remodelling (PR) group, intermediate remodelling (IR) group, negative remodelling (NR) group, PR group and non-PR (N-PR) group.

RESULTS

The PR group exhibited a higher prevalence of diabetes and serum cholesterol levels than the IR and NR groups [45.2%, 4.54 (4.16, 5.93) vs 25%, 4.80 ± 1.22 and 16.4%, 4.14 (3.53, 4.75), respectively, P < 0.05]. The diabetes incidence was also significantly greater in the PR group than in the N-PR group (45.2% vs 17.5%, P < 0.05). Furthermore, the PR group displayed elevated serum triglyceride and cholesterol levels compared to the N-PR group [1.64 (1.23, 2.33) and 4.54 (4.16, 5.93) vs 4.54 (4.16, 5.93) and 4.24 (3.53, 4.89), P < 0.05]. Logistic regression analysis revealed diabetes mellitus as an independent influencing factor in plaque-PR [odds ratio (95% confidence interval): 3.718 (1.207-11.454), P < 0.05].

CONCLUSION

HR-VWI can clearly show the morphology and signal characteristics of intracranial vascular walls and plaques. Intracranial atherosclerotic plaques in diabetic patients are more likely to show PR, suggesting poor plaque stability and a greater risk of stroke.

Imaging the Vulnerable Carotid Plaque with CT: Caveats to Consider. Comment on Wang et al. Identification Markers of Carotid Vulnerable Plaques: An Update. Biomolecules 2022, 12, 1192

We read with great interest the review by Wang et al. entitled "Identification Markers of Carotid Vulnerable Plaques: An Update", recently published in Biomolecules [...].

Diagnostic Yield of Neck CT Angiography in Young Adults With Anterior Circulation Ischemic Stroke: A Community Based Study

Background and Purpose

Few community-based studies investigating young adult strokes exist. The aim of this study was to determine the diagnostic yield of head and neck CTA in evaluation of anterior circulation ischemic stroke in young adults.

Materials and Methods

This retrospective review is limited to patients between the ages of 18-50 presenting to the Mayo Clinic Rochester emergency department or referred from smaller institutions in adjacent counties. Patients with posterior circulation infarcts, amaurosis fugax, central retinal artery occlusion or transient ischemic attacks were excluded. The presence of carotid dissection, webs, plaque, or other high-risk lesions were recorded.

Results

A total of 136 patients met inclusion criteria. Mean degree of carotid stenosis ipsilateral to infarct was 14.1%, compared to 6.5% on the contralateral side (p = .006). Ipsilateral mean carotid wall thickness measured .79 mm, compared to contralateral thickness of .80 mm (p = .51). Ipsilateral low-density plaque was observed in 22 patients (16.2%), and 21 patients (15.4%) on the contralateral side (p = .87). Ipsilateral calcified plaque was observed in 37 patients (27.2%), and 29 patients (21.3%) on the contralateral side (p = .31). 20 (14.7%) ipsilateral dissections were noted, compared to 4 (2.9%) contralateral dissections (p = .001). 3 (2.2%) ipsilateral carotid webs were identified, compared to 0 contralateral webs (p = .25).

Conclusion

Carotid dissection was the most common cause of anterior circulation infarct identified on cervical CTA in this population. Carotid webs and atherosclerosis were not common findings.

Carotid Plaque CTA Analysis in Symptomatic Subjects with Bilateral Intraparenchymal Hemorrhage: A Preliminary Analysis

BACKGROUND AND PURPOSE

The presence of IPH is considered the most dangerous feature because it is significantly associated with clinical ipsilateral cerebrovascular events. Our aim was to explore the characterization of plaque with CT in symptomatic subjects with bilateral intraplaque hemorrhage.

MATERIALS AND METHODS

Three-hundred-forty-three consecutive patients with recent anterior circulation ischemic events (<2 weeks) and CT of the carotid arteries (performed within 14 days of the cerebrovascular event) evaluated between June 2012 and September 2017 were analyzed for plaque volume composition to identify all subjects with bilateral intraplaque hemorrhage. Plaque volume was semiautomatically measured, and tissue components were classified according to the attenuation values such as the following: calcified (for values of ≥130 HU), mixed (for values of ≥60 and <130 HU), lipid (for values of ≥25 and <60 HU), and intraplaque hemorrhage (for values of <25 HU). Twenty-one subjects (15 men; mean age, 70 ± 11 years; range, 44-87 years) had bilateral intraplaque hemorrhage and were included in the analysis.

RESULTS

Volume measurement revealed significantly larger plaques on the symptomatic side compared with the asymptomatic one (mean, 28 ± 9 versus 22 ± 8 mm, P = .007). Intraplaque hemorrhage volume and percentage were also significantly higher in the plaque ipsilateral to the cerebrovascular event (P < .001 and < .001, respectively). The volume of other plaque components did not show a statically significant association except for lipid and lipid + intraplaque hemorrhage percentages (23% versus 18% and 11% versus 15%), which were significantly different between the symptomatic and the asymptomatic sides (.016 and .011, respectively). The intraplaque hemorrhage/lipid ratio was higher on the symptomatic side (0.596 versus 0.171, P = .001).

CONCLUSIONS

In patients with bilateral intraplaque hemorrhage and recent ischemic symptoms, the plaque ipsilateral to the symptomatic side has significantly larger volume and a higher percentage of intraplaque hemorrhage compared with the contralateral, asymptomatic side.

Carotid Plaque Characterization with Contrast-Enhanced Ultrasound Imaging and its Histological Validation

Introduction

Better methods are needed to determine the course of intervention in patients with atherosclerosis; therefore, plaque characterization is increasing in importance. Current guidelines suggest that the degree of stenosis and symptoms are the only criteria for the selection of the surgical intervention. However, there remain some challenges. The characterization of plaque morphology may help determine the best course of therapy. Magnetic resonance imaging and computed tomography are current standard techniques to evaluate plaque morphology, but they are expensive and unsuitable for long term surveillance and monitoring.

Objective

In this research, an ultrasound-based methodology for the characterization of carotid plaques is shown. This technique requires the injection of a small volume (approximately 1.5 mL) of contrast agent and the acquisition of postcontrast images. The rationale of this technique is that poorly perfused tissues (such as lipids) show a lower contrast enhancement with respect to highly perfused tissues (such as fibrous and muscular tissue).

Methods

The technique consists of two steps. First, the plaque region is automatically segmented by a completely user-independent algorithm. Then, the portion of the wall corresponding to the plaque is analyzed and color-coded intensity is assigned to a specific tissue. Performance evaluation was performed against histology. Twenty plaque specimens were sent to pathology for reporting. Correlation of the histology report and of the contrast-enhanced ultrasound analysis was performed.

Results

Plaque components that could be effectively identified were thrombi, lipids, fibrous/muscular tissue, and calcium. Overall the errors on 20 plaques between automated classification and histology were: 3.1 ± 1.1% for thrombus, 4.2 ± 1.5% for lipids, 5 ± 3.4% for fibrous/muscular tissue, and 3.2 ± 1.0% for calcium.

Conclusion

Despite the need for further investigation and a quantitative evaluation of the results, this methodology showed encouraging results. This analysis architecture is undergoing validation in a neurology division and is aimed at being used for the follow-up of patients and quantification of drug therapy effects.

Carotid Artery Wall Imaging: Perspective and Guidelines from the ASNR Vessel Wall Imaging Study Group and Expert Consensus Recommendations of the American Society of Neuroradiology

Identification of carotid artery atherosclerosis is conventionally based on measurements of luminal stenosis and surface irregularities using in vivo imaging techniques including sonography, CT and MR angiography, and digital subtraction angiography. However, histopathologic studies demonstrate considerable differences between plaques with identical degrees of stenosis and indicate that certain plaque features are associated with increased risk for ischemic events. The ability to look beyond the lumen using highly developed vessel wall imaging methods to identify plaque vulnerable to disruption has prompted an active debate as to whether a paradigm shift is needed to move away from relying on measurements of luminal stenosis for gauging the risk of ischemic injury. Further evaluation in randomized clinical trials will help to better define the exact role of plaque imaging in clinical decision-making. However, current carotid vessel wall imaging techniques can be informative. The goal of this article is to present the perspective of the ASNR Vessel Wall Imaging Study Group as it relates to the current status of arterial wall imaging in carotid artery disease.

Relationship between Carotid Computed Tomography Dual-Energy and Brain Leukoaraiosis

BACKGROUND

The purpose of this study was to assess if there is a correlation between the carotid computed tomography (CT) Hounsfield unit (HU)-based plaque attenuation values measured using dual-energy CT (DECT) scanner and brain leukoaraiosis (LA).

METHODS

Fifty consecutive patients (34 males, 16 females; mean age, 69 years; age range, 46-84 years) who underwent carotid CT and brain magnetic resonance imaging were included in the study. CT examinations were performed with a DECT scanner, and LA lesion volume quantification was performed using a semiautomated segmentation technique.

RESULTS

We found an inverse statistically significant correlation between the HU-based carotid artery plaque attenuation and the LA lesion volume. Because of the presence of calcified plaques, a second model was calculated at low kiloelectron volt levels from 66 to 100 and 100 kV by taking into consideration the fatty and mixed plaques, and this further led to the associations between HU-based attenuation and LA volume in brain and vascular territories.

CONCLUSIONS

The results of our study suggest that the associations between HU attenuation of the carotid artery plaques (with the exclusion of calcified plaques) and the volume of LA are emphasized at low keV energy levels.

Longitudinal assessment of carotid atherosclerosis after Radiation Therapy using Computed Tomography: A case control Study

OBJECTIVES

To study the carotid artery plaque composition and its volume changes in a group of patients at baseline and 2 years after head and neck radiation therapy treatment (HNXRT).

METHODS

In this retrospective study, 62 patients (41 males; mean age 63 years; range 52-81) who underwent HNXRT and 40 patients (24 males; mean age 65) who underwent surgical resection of neoplasm and did not undergo HNXRT were assessed, with 2-year follow-up. The carotid artery plaque volumes, as well as the volume of the sub-components (fatty-mixed-calcified), were semiautomatically quantified. Mann-Whitney and Wilcoxon tests were used to test the hypothesis.

RESULTS

In the HNXRT group, there was a statistically significant increase in the total volume of the carotid artery plaques (from 533 to 746 mm(3); p = 0.001), in the fatty plaques (103 vs. 202 mm(3); p = 0.001) and mixed plaque component volume (328 vs. 419 mm(3); p = 0.034). A statistically significant variation (from 21.8 % to 27.6 %) in the percentage of the fatty tissue was found.

CONCLUSIONS

Results of this preliminary study suggest that HNXRT promotes increased carotid artery plaque volume, particularly the fatty plaque component.

KEY POINTS

HNXRT increases carotid plaque volume. Plaque volume increase is mainly due to increase.in fatty plaque component. Patients who undergo HNXRT have a progression of carotid artery disease.

An experimental-nonlinear finite element study of a balloon expandable stent inside a realistic stenotic human coronary artery to investigate plaque and arterial wall injury

The stresses induced within plaque tissues and arterial layers during stent expansion inside an atherosclerotic artery can be exceeded from the yield stresses of those tissues and, consequently, lead to plaque or arterial wall rupture. The distribution and magnitude of the stresses in the plaque-artery-stent structure might be distinctly different for different plaque types. In this study, the mechanical properties of six healthy and atherosclerotic human coronary arteries were determined for application in plaque and arterial vulnerability assessment. A nonlinear finite element simulation based on an Ogden material model was established to investigate the effect of plaque types on the stresses induced in the arterial wall during implantation of a balloon expandable coronary stent. The atherosclerotic artery was assumed to consist of a plaque and normal arterial tissues on its outer side. The results indicated a significant influence of plaque types on the maximum stresses induced within the plaque wall and arterial wall during stenting but not when computing maximum stress on the stent. The stress on the stiffest calcified plaque wall was 3.161 MPa, whereas cellular and hypocellular plaques showed relatively less stress on their wall. The highest von Mises stresses within the arterial wall were observed on the hypocellular plaque, whereas the lowest stresses were seen to be located in the calcified and cellular plaques. Although the computed stresses on the arterial wall for the calcified and cellular plaques were not high enough to invoke a rupture, the stress on the hypocellular plaque was relatively higher than that of the strength of the arterial wall. These findings may have implications not only for understanding the stresses induced in plaque and the arterial wall, but also for developing surgeries such as balloon-angioplasty and stenting.

Distribution of calcification in carotid endarterectomy tissues: Comparison of micro-computed tomography imaging with histology

Background:

Calcification in atherosclerotic plaques has been viewed as a marker of plaque stability, but whether calcification accumulates in specific anatomic sites in the carotid artery is unknown. We determined the burden and distribution of calcified plaque in carotid endarterectomy (CEA) tissues.

Methods:

A total of 22 CEA tissues were imaged with high-resolution micro-computed tomography (micro-CT). Total plaque burden and total calcium score using the Agatston method were quantified. The Agatston score (AS) was also normalized for tissue size. Plaque and calcium distribution were analyzed separately for three CEA regions: common segment (CS), bulb segment (BS), and internal/external segments (IES).

Results:

The average CEA tissue length was 40.83 (interquartile range [IQR] 33.31–42.41) mm with total plaque burden of 103.45 (IQR: 78.84–156.81) mm3 and total AS of 38.58 (IQR 11.59–89.97). Total plaque volume was 21.02 (IQR: 14.47–25.42) mm3 in the CS, 37.89 (22.59–48.32) mm3 in the BS, and 54.05 (36.87–74.52) mm3 in the IES. Of the 22 tissues, 15 had no calcium in the CS compared with three in the bulb and two in the IES. Normalized calcified plaque was most prevalent in the BS, the IES and was least prevalent in the CS. The overall correlation of calcification between histology sections and matched micro-CT images was 0.86 ( p<0.001).

Conclusions:

Calcified plaque is heterogeneously distributed in CEA tissues with most in the bulb and IES regions. The amount of calcification in micro-CT slices shows a high correlation with matched histology sections.

Multi-modal CT scanning in the evaluation of cerebrovascular disease patients

Ischemic stroke currently represents one of the leading causes of severe disability and mortality in the Western World. Until now, angiography was the most used imaging technique for the detection of the extra-cranial and intracranial vessel pathology. Currently, however, non-invasive imaging tool like ultrasound (US), magnetic resonance (MR) and computed tomography (CT) have proven capable of offering a detailed analysis of the vascular system. CT in particular represents an advanced system to explore the pathology of carotid arteries and intracranial vessels and also offers tools like CT perfusion (CTP) that provides valuable information of the brain's vascular physiology by increasing the stroke diagnostic. In this review, our purpose is to discuss stroke risk prediction and detection using CT.

A nonlinear finite element simulation of balloon expandable stent for assessment of plaque vulnerability inside a stenotic artery

The stresses induced on plaque wall during stent implantation inside a stenotic artery are associated with plaque rupture. The stresses in the plaque-artery-stent structure appear to be distinctly different for different plaque types in terms of both distribution and magnitude. In this study, a nonlinear finite element simulation was executed to analyze the influence of plaque composition (calcified, cellular, and hypocellular) on plaque, artery layers (intima, media, and adventitia), and stent stresses during implantation of a balloon expandable coronary stent into a stenosed artery. The atherosclerotic artery was assumed to consist of a plaque and normal arterial tissues on its outer side. The results revealed a significant influence of plaque types on the maximum stresses induced within plaque wall and artery layers during stenting, but not when calculating maximum stress on stent. The stress on stiffer calcified plaque wall was in the fracture level (2.21 MPa), whereas cellular and hypocellular plaques play a protective role by displaying less stress on their wall. The highest von Mises stresses were observed on less stiff media layer. The findings of this study suggest a lower risk of arterial vascular injury for calcified plaque, while higher risk of plaque ruptures for cellular and hypocellular plaques.

Accuracy of MDCT for detection and identification of carotid atherosclerotic plaque in a rabbit model

OBJECTIVE

There is a need for a simple, rapid, and repeatable noninvasive imaging method to accurately assess carotid atherosclerotic plaque. The purpose of this study was to explore the utility of MDCT and carotid artery plaque analysis software for detecting and identifying atherosclerotic plaque in a rabbit model of carotid atherosclerosis.

MATERIALS AND METHODS

Plaques from 14 rabbits and cross-sectional carotid artery specimens were detected, stained, and analyzed. Contrast-enhanced MDCT with application of carotid plaque analysis software was performed. Bland-Altman difference plots were used to assess interclass and intraclass consistency in lipid percentage and fibrous percentage on CT images.

RESULTS

A total of 76 of the 158 samples were true positive for plaque. On the basis of histopathologic examination of the samples, the accuracy, sensitivity, and specificity of CT for detecting plaque were 91.8%, 89.4%, and 94.5%, and the accuracy, sensitivity, and specificity of the software for classifying lipid-rich plaques and fibrous plaques were 90.8%, 90.6%, and 90.9%. Repeated measurements by the same physician showed good repeatability, and measurements by two physicians independently showed good correlation.

CONCLUSION

The results showed that MDCT can be used to detect carotid atherosclerotic plaque and that carotid plaque analysis software can be used to measure the content of plaque composition and determine the nature of plaque.

Differences in plaque morphology and correlation of stenosis at the carotid artery bifurcation and the carotid siphon

OBJECTIVE

The purpose of this study was to compare the type of plaque and the degree of stenosis in the carotid artery bifurcation and the carotid siphon to explore potential correlations between these parameters.

MATERIALS AND METHODS

A total of 119 patients (87 men, 32 women; mean age, 69 years) were retrospectively studied using MDCT angiography. Component types of the carotid artery bifurcation and the carotid siphon plaque were defined according to attenuation values, and the volumes of each plaque component were calculated. The degree of stenosis was calculated according to the North American Symptomatic Endarterectomy Trial method. Data were compared using the Wilcoxon signed-rank test, Spearman correlation analysis, and receiver operating characteristic (ROC) analysis.

RESULTS

The results of the Wilcoxon test showed a statistically significant difference (p = 0.0001) between the degree of stenosis at the carotid artery bifurcation and that at the carotid siphon. We observed a statistically significant difference (p = 0.0001) between the total volumes of the carotid artery bifurcation (mean value, 748 mm(3)) and the carotid siphon (mean value, 54 mm(3)) plaque. Moreover, the respective mean percentages of calcified, mixed, and lipid components of plaque were 17%, 56%, and 27% in the carotid artery bifurcation and 73%, 19%, and 8% in the carotid siphon, showing a statistically significant difference (p = 0.001). ROC analysis did not show association between carotid siphon plaque volume and previous cerebrovascular events (Az = 0.562; p = 0.149), whereas the total volume of the carotid artery bifurcation plaque--and, in particular, the volume of the lipid components--showed a statistically significant association (Az = 0.691, and Az = 0.758; p < 0.001).

CONCLUSION

No significant association was found between presence of mixed and fatty components of plaque in the carotid artery bifurcation and presence of similar components in the carotid siphon. The carotid artery bifurcation total plaque volume (and, in particular, carotid artery bifurcation lipid volume) was associated with previous cerebrovascular events, whereas no association with the volume of carotid siphon plaque (and its subcomponents) was found.

A meta analysis and hierarchical classification of HU-based atherosclerotic plaque characterization criteria

Background

Many computed tomography (CT) studies have reported that lipid-rich, presumably rupture-prone atherosclerotic plaques can be characterized according to their Hounsfield Unit (HU) value. However, the published HU-based characterization criteria vary considerably. The present study aims to systematically analyze these values and empirically derive a hierarchical classification of the HU-based criteria which can be referred in clinical situation.

Material and Methods

A systematic search in PubMed and Embase for publications with HU-criteria to characterize lipid-rich and fibrous atherosclerotic plaques resulted in 36 publications, published between 1998 and 2011. The HU-criteria were systematically analyzed based on the characteristics of the reporting study. Significant differences between HU-criteria were checked using Student’s t-test. Subsequently, a hierarchical classification of HU-criteria was developed based on the respective study characteristics.

Results

No correlation was found between HU-criteria and the reported lumen contrast-enhancement. Significant differences were found for HU-criteria when pooled according to the respective study characteristics: examination type, vessel type, CT-vendor, detector-rows, voltage-setting, and collimation-width. The hierarchical classification resulted in 21 and 22 CT attenuation value categories, for lipid-rich and fibrous plaque, respectively. More than 50% of the hierarchically classified HU-criteria were significantly different.

Conclusion

In conclusion, variations in the reported CT attenuation values for lipid-rich and fibrous plaque are so large that generalized values are unreliable for clinical use. The proposed hierarchical classification can be used to determine reference CT attenuation values of lipid-rich and fibrous plaques for the local setting.

Microembolization during carotid artery stenting in patients with high-risk, lipid-rich plaque. A randomized trial of proximal versus distal cerebral protection

OBJECTIVES

The goal of this study was to compare the rate of cerebral microembolization during carotid artery stenting (CAS) with proximal versus distal cerebral protection in patients with high-risk, lipid-rich plaque.

BACKGROUND

Cerebral protection with filters partially reduces the cerebral embolization rate during CAS. Proximal protection has been introduced to further decrease embolization risk.

METHODS

Fifty-three consecutive patients with carotid artery stenosis and lipid-rich plaque were randomized to undergo CAS with proximal protection (MO.MA system, n = 26) or distal protection with a filter (FilterWire EZ, n = 27). Microembolic signals (MES) were assessed by using transcranial Doppler during: 1) lesion wiring; 2) pre-dilation; 3) stent crossing; 4) stent deployment; 5) stent dilation; and 6) device retrieval/deflation. Diffusion-weighted magnetic resonance imaging was conducted before CAS, after 48 h, and after 30 days.

RESULTS

Patients in the MO.MA group had higher percentage diameter stenosis (89 ± 6% vs. 86 ± 5%, p = 0.027) and rate of ulcerated plaque (35% vs. 7.4%; p = 0.019). Compared with use of the FilterWire EZ, MO.MA significantly reduced mean MES counts (p < 0.0001) during lesion crossing (mean 18 [interquartile range (IQR): 11 to 30] vs. 2 [IQR: 0 to 4]), stent crossing (23 [IQR: 11 to 34] vs. 0 [IQR: 0 to 1]), stent deployment (30 [IQR: 9 to 35] vs. 0 [IQR: 0 to 1]), stent dilation (16 [IQR: 8 to 30] vs. 0 [IQR: 0 to 1]), and total MES (93 [IQR: 59 to 136] vs. 16 [IQR: 7 to 36]). The number of patients with MES was higher with the FilterWire EZ versus MO.MA in phases 3 to 5 (100% vs. 27%; p < 0.0001). By multivariate analysis, the type of brain protection was the only independent predictor of total MES number. No significant difference was found in the number of patients with new post-CAS embolic lesion in the MO.MA group (2 of 14, 14%) as compared with the FilterWire EZ group (9 of 21, 42.8%).

CONCLUSIONS

In patients with high-risk, lipid-rich plaque undergoing CAS, MO.MA led to significantly lower microembolization as assessed by using MES counts.

Patient-specific finite element analysis of carotid artery stenting: a focus on vessel modeling

Finite element analysis is nowadays a well-assessed technique to investigate the impact of stenting on vessel wall and, given the rapid progression of both medical imaging techniques and computational methods, the challenge of using the simulation of carotid artery stenting as procedure planning tool to support the clinical practice can be approached. Within this context, the present study investigates the impact of carotid stent apposition on carotid artery anatomy by means of patient-specific finite element analysis. In particular, we focus on the influence of the vessel constitutive model on the prediction of carotid artery wall tensional state of lumen gain and of vessel straightening. For this purpose, we consider, for a given stent design and CA anatomy, two constitutive models for the CA wall, that is, a hyperelastic isotropic versus a fiber-reinforced hyperelastic anisotropic model. Despite both models producing similar patterns with respect to stress distribution, the anisotropic model predicts a higher vessel straightening and a more evident discontinuity of the lumen area near the stent ends as observed in the clinical practice. Although still affected by several simplifications, the present study can be considered as further step toward a realistic simulation of carotid artery stenting.

Computed tomography carotid wall plaque characterization using a combination of discrete wavelet transform and texture features: A pilot study

In 30% of stroke victims, the cause of stroke has been found to be the stenosis caused by plaques in the carotid artery. Early detection of plaque and subsequent classification of the same into symptomatic and asymptomatic can help the clinicians to choose only those patients who are at a higher risk of stroke for risky surgeries and stenosis treatments. Therefore, in this work, we have proposed a non-invasive computer-aided diagnostic technique to classify the detected plaque into the two classes. Computed tomography (CT) images of the carotid artery images were used to extract Local Binary Pattern (LBP) features and wavelet energy features. Significant features were then used to train and test several supervised learning algorithm based classifiers. The Support Vector Machine (SVM) classifier with various kernel configurations was evaluated using LBP and wavelet features. The SVM classifier presented the highest accuracy of 88%, sensitivity of 90.2%, and specificity of 86.5% for radial basis function (RBF) kernel function. The CT images of the carotid artery provide unique 3D images of the artery and plaque that could be used for calculating percentage of stenosis. Our proposed technique enables automatic classification of plaque into asymptomatic and symptomatic with high accuracy, and hence, it can be used for deciding the course of treatment. We have also proposed a single-valued integrated index (Atheromatic Index) using the significant features which can provide a more objective and faster prediction of the class.

Comparison of iodinated contrast media for the assessment of atherosclerotic plaque attenuation values by CT coronary angiography: observations in an ex vivo model

OBJECTIVE

To compare the influence of different iodinated contrast media with several dilutions on plaque attenuation in an ex vivo coronary model studied by multislice CT coronary angiography.

METHODS

In six ex vivo left anterior descending coronary arteries immersed in oil, CT (slices/collimation 64×0.625 mm, temporal resolution 210 ms, pitch 0.2) was performed after intracoronary injection of a saline solution, and solutions of a dimeric isosmolar contrast medium (Iodixanol 320 mgI ml(-1)) and a monomeric high-iodinated contrast medium (Iomeprol 400 mgI ml(-1)) with dilutions of 1/80 (low concentration), 1/50 (medium concentration), 1/40 (high concentration) and 1/20 (very high concentration). Two radiologists drew regions of interest in the lumen and in calcified and non-calcified plaques for each solution. 29 cross-sections with non-calcified plaques and 32 cross-sections with calcified plaques were evaluated.

RESULTS

Both contrast media showed different attenuation values within lumen and plaque (p<0.0001). The correlation between lumen and non-calcified plaque values was good (Iodixanol r=0.793, Iomeprol r=0.647). Clustered medium- and high-concentration solutions showed similar plaque attenuation values, signal-to-noise ratios (SNRs) (non-calcified plaque: medium solution SNR 31.3±15 vs 31.4±20, high solution SNR 39.4±17 vs 37.4±22; calcified plaque: medium solution SNR 305.2±133 vs 298.8±132, high solution SNR 323.9±138 vs 293±123) and derived contrast-to-noise ratios (p>0.05).

CONCLUSION

Differently iodinated contrast media have a similar influence on plaque attenuation profiles.

ADVANCES IN KNOWLEDGE

Since iodine load affects coronary plaque attenuation linearly, different contrast media may be equally employed for coronary atherosclerotic plaque imaging.

Determinants of calcification growth in atherosclerotic carotid arteries; a serial multi-detector CT angiography study

BACKGROUND

Little is known about the natural course of atherosclerotic plaque in the carotid artery bifurcation. This study investigated the growth pattern of calcifications in atherosclerotic carotid arteries and its determinants using serial multi-detector CT angiography (MDCTA).

METHODS

From a cohort of consecutive patients with TIA or ischemic stroke and a baseline MCDTA scan of the carotid arteries, subjects were invited for a follow-up scan after 4-6 years. Calcification volumes were scored semi-automatically on baseline and follow-up scans. Progression of calcification and its determinants were analyzed in two ways: 1. as incidence of newly detectable calcification in patients free of calcification at baseline, using logistic regression analysis; 2. as annual change in calcification volume in all patients, using linear regression analysis.

RESULTS

Two-hundred-twenty-two patients (aged 61.0 ± 9.6 years, follow-up time 4.7 ± 0.8 years) were included. Calcification volumes increased significantly (median 2.9 mm³ at baseline versus 9.4 mm³ at follow-up, p < 0.001). Newly detectable calcification during follow-up was found in 27 out of 67 patients without baseline calcification (40.3%) and was independently associated with age (OR 4.6 per 10 years increase in age, p < 0.001) and hypertension (OR 8.2, p = 0.008). Annual calcification growth was independently associated with age, calcification load, glucose, hypertension, and smoking. Baseline calcification load was the most important risk factor for calcification growth in multivariable analysis.

CONCLUSION

Several modifiable cardiovascular risk factors are associated with carotid calcification growth, however, time and baseline calcification load remain the most important determinants of calcification development.

Association between carotid artery plaque type and cerebral microbleeds

BACKGROUND AND PURPOSE

CMBs have become increasingly recognized with the widespread use of MR imaging techniques that are sensitive to iron deposits. The purpose of this study was to correlate the presence of CMBs and carotid plaque characteristics.

MATERIAL AND METHODS

Seventy consecutive patients (47 men; 23 women; mean age, 65 years) were prospectively analyzed. Carotid arteries were studied using a 16-detector row CT scanner, whereas the brain was explored with an MR imaging 1.5T system. CMBs were studied using a T2*-weighted GRE sequence. CMBs were classified by an ordinal scale and carotid plaques were characterized based on their composition as fatty, mixed, or calcified. Patients were classified as symptomatic and asymptomatic. Chi-square and multiple logistic regression analyses, as well as ROCs, were calculated.

RESULTS

The prevalence of CMBs was 30%. A statistically significant difference in CMB prevalence was observed between symptomatic (46%) and asymptomatic (19%) patients (P value = .0021; OR = 3.7). Correlation analysis demonstrated an association between the number of CMBs and the symptoms (P = .0001). A statistically significant association was observed between the presence of fatty plaque and CMBs (P = .0019).

CONCLUSIONS

The results of this study suggest an association between the presence of carotid artery fatty plaque, symptoms, and CMBs. Moreover, we found that the presence (and entity) of CMBs may represent an indicator of cerebrovascular symptom severity.

Analysis of carotid artery plaque and wall boundaries on CT images by using a semi-automatic method based on level set model

INTRODUCTION

The purpose of this study was to evaluate the potentialities of a semi-automated technique in the detection and measurement of the carotid artery plaque.

METHODS

Twenty-two consecutive patients (18 males, 4 females; mean age 62 years) examined with MDCTA from January 2011 to March 2011 were included in this retrospective study. Carotid arteries are examined with a 16-multi-detector-row CT system, and for each patient, the most diseased carotid was selected. In the first phase, the carotid plaque was identified and one experienced radiologist manually traced the inner and outer boundaries by using polyline and radial distance method (PDM and RDM, respectively). In the second phase, the carotid inner and outer boundaries were traced with an automated algorithm: level-set-method (LSM). Data were compared by using Pearson rho correlation, Bland-Altman, and regression.

RESULTS

A total of 715 slices were analyzed. The mean thickness of the plaque using the reference PDM was 1.86 mm whereas using the LSM-PDM was 1.96 mm; using the reference RDM was 2.06 mm whereas using the LSM-RDM was 2.03 mm. The correlation values between the references, the LSM, the PDM and the RDM were 0.8428, 0.9921, 0.745 and 0.6425. Bland-Altman demonstrated a very good agreement in particular with the RDM method.

CONCLUSION

Results of our study indicate that LSM method can automatically measure the thickness of the plaque and that the best results are obtained with the RDM. Our results suggest that advanced computer-based algorithms can identify and trace the plaque boundaries like an experienced human reader.

Carotid artery plaque classification: does contrast enhancement play a significant role?

BACKGROUND AND PURPOSE

Previous articles have demonstrated that carotid artery plaques may have enhancement after administration of contrast material. The purpose of this study was to evaluate the effect of enhancement in carotid artery classification.

MATERIALS AND METHODS

Three hundred eighty consecutive patients (235 men, 145 women; median age 64, age range 32-87 years) were analyzed using a multidetector row CT scanner. Examinations were performed before and after CM administration. Carotid artery plaques with a attenuation value <60 HU were considered fatty, those from 60-130 HU were considered mixed, and those >130 HU were considered calcified. χ(2) tests, Student t tests, and Cohen analyses were performed.

RESULTS

Before CM administration, we observed 226 calcified, 175 mixed, and 206 fatty plaques; after CM administration, 229 calcified, 213 mixed, and 165 fatty plaques were observed. A statistically significant difference between these 2 groups was observed (P = .016). We found that 19.9% of fatty plaques become mixed (n = 41), whereas 1.7% of the mixed plaques become calcified (n = 3). All calcified plaques remained in the same category. Fatty plaques that changed type showed a larger enhancement compared with those that remained in the same class (P = .001). Cohen analyses showed very good agreement between observers before (κ = 0.834) and after contrast material administration (κ = 0.86).

CONCLUSIONS

The results of this study indicate that the carotid artery plaques (fatty and mixed) significantly change according to whether analysis is performed before or after administration of contrast material.

Advances in noninvasive imaging for evaluating clinical risk and guiding therapy in carotid atherosclerosis

Managing asymptomatic carotid atherosclerosis with a view to preventing ischemic stroke is a challenging task. As the annual risk of stroke in untreated asymptomatic patients on average is less than the risk of surgical intervention, the key question is how to identify those asymptomatic individuals whose risk of stroke is elevated and who would benefit from surgery, while sparing low-risk asymptomatic patients from the risks of surgical intervention. The advent of a multitude of noninvasive carotid imaging techniques offers an opportunity to improve risk stratification in patients and to monitor the response to medical therapies; assessing efficacy at individual and population levels. As part of this, plaque measurement techniques (using ultrasound, computed tomography or MRI) may be employed in monitoring plaque/component regression and progression. Novel imaging applications targeted to plaque characteristics, inflammation and neovascularization, including contrast-enhanced ultrasound and MRI, dynamic contrast-enhanced MRI, and fluorodeoxyglucose-PET, are also being explored. Ultimately, noninvasive imaging and other advances in risk stratification aim to improve and individualize the management of patients with carotid atherosclerosis.

Carotid atherosclerotic plaque progression and change in plaque composition over time: a 5-year follow-up study using serial CT angiography

BACKGROUND AND PURPOSE

Serial in vivo imaging of atherosclerosis is important for understanding plaque progression and is potentially useful in predicting cardiovascular events and monitoring treatment efficacy. This prospective study aims to quantify temporal changes in carotid atherosclerotic plaque volume and plaque composition using MDCTA.

MATERIALS AND METHODS

In 109 patients with TIA or ischemic stroke, serial MDCTA of the carotid arteries was performed after 5.3 ± 0.7 years. The carotid bifurcation was semiautomatically registered for paired baseline follow-up datasets. Outer vessel wall and lumen boundaries were defined using semiautomated segmentation tools. Plaque component volumes were measured using HU thresholds. Annual changes in plaque volume and plaque component proportions were calculated.

RESULTS

One-hundred-ninety-three carotid arteries were analyzed. Plaque volume decreased in 31% and increased in 69% of vessels (range -5.6-10.1%/year). Overall, plaque volume increased 1.2% per year (95% CI, 0.8-1.6, P ≤ .001). Plaque composition changed significantly from BL (fibrous 66.4%, lipid 28.8%, calcifications 4.8%): fibrous tissue decreased by 1.5%, lipid decreased by 1.8%, and calcification increased by 3.3% (P < .001). Intraobserver reproducibility of all volume and proportion measurements was good (ICC 0.78-1.00) and interobserver reproducibility was moderate (ICC 0.76-0.99).

CONCLUSIONS

Changes in carotid plaque burden and plaque composition can be quantified by using serial MDCTA. Plaque burden development is a heterogeneous and slow process.

Carotid artery wall thickness measured using CT: inter- and intraobserver agreement analysis

SUMMARY

The purpose of this work was to compare inter- and intraobserver agreement in the analysis of CAWT by using MDCTA. The CAWT in 35 patients was quantified by 4 observers. Bland-Altman statistics were used to measure the agreement between observers. The results of our study demonstrated that the CAWT measured by using MDCTA shows a good reproducibility between observers by considering inter- and intraobserver agreement.

Carotid plaque enhancement and symptom correlations: an evaluation by using multidetector row CT angiography

BACKGROUND AND PURPOSE

The identification of plaque characteristics that determine its vulnerability is extremely important. The purpose of this work was to evaluate CPE after administration of contrast material and to assess whether there is a statistical association between CPE and cerebrovascular symptoms.

MATERIALS AND METHODS

Ninety-seven consecutive patients (69 men, 28 women; mean age, 62 years; age range, 39-82 years), studied by using an MDCT scanner, were retrospectively analyzed. Examinations were performed before and after administration of contrast medium. Plaque enhancement was analyzed, and the obtained data were compared with the patient's symptoms. Patients were classified as symptomatic (TIA or stroke with a temporal window of 6 months) or asymptomatic according to neurologic assessment and the TOAST criteria. The ROC curve and Az were calculated, and multiple logistic regression analysis was performed.

RESULTS

Thirty-nine patients were excluded because they had calcified plaques (40.2%). CPE was observed in 74% of the remaining 58 patients. A statistically significant difference was observed between symptomatic and asymptomatic patients for the presence of CPE (P = .0013; OR = 7.5). Moreover, we observed that CPE was higher in fatty plaques (P = .035) than in mixed ones and more frequent in the former (P = .0119). The ROC curve demonstrated that a threshold of 15 HU is associated with a specificity and sensitivity of 83.33% and 76.47%, respectively. Multiple logistic regression showed that CPE and symptoms are associated (P = .0315).

CONCLUSIONS

The results of our study suggest that for noncalcified carotid plaques, the presence of CPE is associated with cerebrovascular symptoms. Fatty plaques are more likely to have CPE compared with mixed plaques.

Carotid artery wall thickness and leukoaraiosis: preliminary results using multidetector row CT angiography

BACKGROUND AND PURPOSE

LA is a condition caused by chronic cerebral ischemia and it represents an independent risk for stroke. The purpose of this work was to determine whether CAWT studied by using MDCTA is correlated with LA and its severity.

MATERIALS AND METHODS

Ninety-eight patients ≥60 years of age were retrospectively studied by using multidetector row CT. Supra-aortic vessel analysis and brain CT were performed in the same procedure. In each patient, CAWT was measured with an internal digital caliper, and the presence and severity of LA were assessed. Correlation coefficients by using Spearman statistics and ROC curves were calculated. A P value < .05 was considered statistically significant.

RESULTS

Measurements of the distal common CAWT ranged from 0.5 to 1.53 mm. A correlation between LA and increased CAWT was observed (Pearson correlation, 0.33; P < .001). On the basis of a threshold of 0.9 mm, an important statistical association between increased CAWT and LA (P < .0001) was found. With the same threshold, ROC curve analysis indicated a sensitivity of 55% and a specificity of 75% for LA.

CONCLUSIONS

The results of this study show a statistically significant correlation between increased CAWT and LA (and its severity).

Association between carotid artery plaque ulceration and plaque composition evaluated with multidetector CT angiography

BACKGROUND AND PURPOSE

Symptomatic carotid artery plaque ulceration is associated with distinct plaque components such as a large lipid-rich necrotic core (LR-NC) in ischemic stroke patients with a ≥50% carotid stenosis. We evaluated the associations between carotid artery plaque ulceration and plaque characteristics in ischemic stroke patients with ≥50% stenosis, as well as in those with a low degree of stenosis (0% to 49%).

METHODS

Consecutive patients (n=346) with symptoms in the anterior circulation were evaluated with multidetector CT angiography (MDCTA) for the presence of atherosclerotic plaque, degree of stenosis, and plaque ulceration in the symptomatic carotid artery. Plaque volume and plaque component proportions of LR-NC, fibrous tissue, and calcification were measured. The associations between plaque ulceration and plaque characteristics were analyzed using logistic regression.

RESULTS

Atherosclerotic plaque was present in 185 patients. Plaque ulcerations were present in 38 (21%) patients, of which half had a low degree stenosis (0% to 49%). Plaque volume was significantly larger in ulcerated plaques. After adjustment for age, sex, and degree of stenosis, LR-NC proportion was strongly associated with plaque ulceration (odds ratio, 2.21; 95% CI, 1.49 to 3.27), whereas calcification proportion was inversely associated with plaque ulceration (odds ratio, 0.60; 95% CI, 0.40 to 0.89). These associations remained significant in patients with a low degree stenosis (0% to 49%).

CONCLUSIONS

Plaque volume, degree of stenosis, and LR-NC proportion evaluated noninvasively with MDCTA are associated with carotid artery plaque ulceration, even in patients with a low degree stenosis (0% to 49%). Plaque volume and composition analysis with MDCTA may identify rupture prone plaques and improve risk stratification in ischemic stroke patients.

Carotid artery stenting simulation: from patient-specific images to finite element analysis

The outcome of carotid artery stenting (CAS) depends on a proper selection of patients and devices, requiring dedicated tools able to relate the device features with the target vessel. In the present study, we use finite element analysis to evaluate the performance of three self-expanding stent designs (laser-cut open-cell, laser-cut closed-cell, braided closed-cell) in a carotid artery (CA). We define six stent models considering the three designs in different sizes and configurations (i.e. straight and tapered), evaluating the stress induced in the vessel wall, the lumen gain and the vessel straightening in a patient-specific CA model based on computed angiography tomography (CTA) images. For the considered vascular anatomy and stents, the results suggest that: (i) the laser-cut closed-cell design provides a higher lumen gain; (ii) the impact of the stent configuration and of the stent oversizing is negligible with respect to the lumen gain and relevant with respect to the stress induced in the vessel wall; (iii) stent design, configuration and size have a limited impact on the vessel straightening. The presented numerical model represents a first step towards a quantitative assessment of the relation between a given carotid stent design and a given patient-specific CA anatomy.

Impact of luminal density on plaque classification by CT coronary angiography

Non-invasive coronary CT angiography (CCTA) has the potential to characterize the composition of non-calcified coronary plaques. CT-density values characterized by Hounsfield Units (HU) may classify non-calcified plaques as fibrous or lipid-rich, but the luminal density caused by the applied contrast material influences HU in the plaques in vitro. The influence of luminal density on HU in non-calcified plaques in vivo is unknown. Hence the purpose of this study was to test whether plaque characterization by CCTA in vivo depends on luminal density. Two CCTA-scans using two different contrast protocols were obtained from 14 male patients with coronary artery disease. The two contrast protocols applied resulted in high and low luminal density. Eleven non- calcified and 13 calcified plaques were identified and confirmed by intravascular ultrasound. Luminal attenuation differed with the two contrast protocols; 326[284;367] vs. 118[103;134] HU (P < 0.00001). In non-calcified plaques mean HU-values was lower 48[28;69] vs. 11[-4;25] HU (P = 0.004) with the low density protocol. As a consequence three out of eleven non-calcified plaques (27%) were reclassified from fibrous (high) to lipid rich (low). For calcified plaques a less pronounced but still significant difference in HU-values was found with the low luminal density. 770[622;919] vs. 675[496;855] HU (P = 0.02).

CONCLUSION

Non-calcified plaques can be identified and classified by CCTA. However, the luminal density affects the absolute HU of both non-calcified and calcified plaques. Characterization and classification of non-calcified plaques by absolute CT values therefore requires standardization of contrast protocols.

Characterization of carotid plaque hemorrhage: a CT angiography and MR intraplaque hemorrhage study

BACKGROUND AND PURPOSE

The main objective of this study was to evaluate CT angiographic (CTA) features that are able to predict the presence of intraplaque hemorrhage (IPH) as defined by MR-IPH.

METHODS

One hundred sixty-seven consecutive patients (mean age 69 years, SD 12.8; 58 females) underwent both MR-IPH and CTA within 3 weeks. MR-IPH, the gold standard, was performed at 1.5 T using a neurovascular phased-array coil as a coronal T1-weighted 3-dimensional fat-suppressed acquisition. CTA was performed using a 4-slice or a 64-slice CT machine and evaluated, blinded to MR-IPH findings, for carotid stenosis, plaque density, and plaque ulceration. Plaque density was defined as the mean attenuation of plaque at the site of maximum stenosis and 2 sections above and below. Plaque ulceration was defined as outpouching of contrast into the plaque at least 2 mm deep on any single plane.

RESULTS

Prevalence of IPH increased at higher degrees of carotid stenosis. Mean CT plaque density was higher for plaques with MRI-defined IPH (47 Hounsfield units) compared with without IPH (43 Hounsfield units; P=0.02). However, significant overlap between distributions of plaque densities limited the value of mean plaque density for prediction of IPH. CTA plaque ulceration had high sensitivity (80.0% to 91.4%), specificity (93.0% to 92.3%), positive predictive value (72.0% to 71.8%), and negative predictive value (95.0% to 97.9%) for prediction of IPH. Interobserver agreement for presence/absence of CTA plaque ulceration was excellent (kappa=0.80).

CONCLUSIONS

CTA plaque ulceration, but not mean CTA plaque density, was useful for prediction of IPH as defined by the MR-IPH technique.

Atherosclerotic Plaque Ulceration in the Symptomatic Internal Carotid Artery Is Associated With Nonlacunar Ischemic Stroke

Background and Purpose— Atherosclerotic carotid plaque ulceration is considered a marker of previous plaque rupture and subsequent thromboembolism. It can be accurately detected with multidetector CTA. We hypothesized that atherosclerotic plaque ulceration is associated with nonlacunar ischemic stroke rather than lacunar stroke.

Methods— Prospectively, 750 consecutive patients with transient ischemic attack or ischemic stroke symptoms in the anterior cerebral circulation were evaluated for the presence of atherosclerotic plaque ulceration in the symptomatic carotid artery with multidetector CTA. Patients with stroke attributable to cardiac embolism or other specific etiologies and patients with amaurosis fugax were excluded. Ischemic strokes in the remaining 534 patients were classified as nonlacunar (n=236) or lacunar (n=298) based on clinical symptoms and multidetector CT of the brain. Ulceration was defined as extension of contrast material beyond the vascular lumen into the surrounding plaque.

Results— Plaque ulceration in the symptomatic carotid artery was more common in nonlacunar strokes (n=47; 20%) as compared to lacunar strokes (n=20; 7%; P <0.001). After adjustment for age, gender, cardiovascular risk factors, and degree of stenosis, ulcerations were independently associated with nonlacunar stroke compared to lacunar stroke (odds ratio, 2.70; 95% confidence interval, 1.43–5.09).

Conclusions— Atherosclerotic carotid plaque ulceration is associated with nonlacunar ischemic stroke, independent of the degree of carotid stenosis. These results suggest that nonlacunar stroke and lacunar stroke are caused by different pathophysiological mechanisms.

Segmentation of the outer vessel wall of the common carotid artery in CTA

A novel method is presented for carotid artery vessel wall segmentation in computed tomography angiography (CTA) data. First the carotid lumen is semi-automatically segmented using a level set approach initialized with three seed points. Subsequently, calcium regions located within the vessel wall are automatically detected and classified using multiple features in a GentleBoost framework. Calcium regions segmentation is used to improve localization of the outer vessel wall because it is an easier task than direct outer vessel wall segmentation. In a third step, pixels outside the lumen area are classified as vessel wall or background, using the same GentleBoost framework with a different set of image features. Finally, a 2-D ellipse shape deformable model is fitted to a cost image derived from both the calcium and vessel wall classifications. The method has been validated on a dataset of 60 CTA images. The experimental results show that the accuracy of the method is comparable to the interobserver variability.

Atherosclerotic plaque surface morphology in the carotid bifurcation assessed with multidetector computed tomography angiography

BACKGROUND AND PURPOSE

Complicated (irregular or ulcerated) carotid plaques have proven to be independent predictors of stroke. We analyzed the frequency and location of plaque irregularities in a large cohort of patients with ischemic cerebrovascular disease and the relation with severity of stenosis, cardiovascular risk factors, and symptomatology.

METHODS

Multidetector CT angiography images from 406 patients were evaluated. Plaque surface morphology was classified as smooth, irregular, or ulcerated. The location of the ulceration was defined as proximal or distal to the point of maximum stenosis.

RESULTS

Atherosclerotic plaques with an open lumen were present in 448 carotid arteries; these plaques were classified as: smooth, 276 (62%); irregular, 99 (22%); and ulcerated, 73 (16%). Sixty-two (69%) of the ulcerations were located proximal to the point of maximum luminal stenosis. Complicated plaques were significantly (P<0.001) more common in carotid arteries with stenosis >30% than in those with stenosis <30%. There is an association between complicated plaques and hypercholesterolemia (OR, 3.0) and a trend toward an association with smoking (OR, 1.9). Complicated plaques are more often present in the symptomatic carotid artery than in the contralateral asymptomatic carotid artery; however, this is fully attributed to a significantly higher degree of stenosis in the symptomatic arteries.

CONCLUSIONS

Multidetector CT angiography allows the classification of atherosclerotic carotid plaque surface. Complicated plaques are frequent in atherosclerotic carotid disease, especially with higher stenosis degree. Ulcerations are mostly located in the proximal part of the atherosclerotic plaque. Hypercholesterolemia and smoking are related with the presence of complicated plaques.

Selective deblurring for improved calcification visualization and quantification in carotid CT angiography: validation using micro-CT

Visualization and quantification of small structures with computed tomography (CT) is hampered by the limited spatial resolution of the system. Histogram-based selective deblurring (HiSD) is a deconvolution method that restores small high-density structures, i.e., calcifications, of a CT image, using the high-intensity voxel information of the deconvolved image, while preserving the original hounsfield Units (HUs) in the remaining tissues. In this study, high resolution micro-CT data are used to validate the potential of HiSD to improve calcium visualization and quantification in the carotid arteries on in vivo contrast-enhanced CTA data. The evaluation is performed qualitatively and quantitatively on 15 atherosclerotic plaques obtained from ten different patients. HiSD in combination with vessel segmentation significantly improves calcification visualization and quantification on in vivo contrast-enhanced CT images. Calcification blur is reduced, while avoiding noise amplification and edge-ringing artifacts in the surrounding tissues. Calcification quantification errors are reduced by 23.5% on average.

Intracranial internal carotid artery calcifications: association with vascular risk factors and ischemic cerebrovascular disease

BACKGROUND AND PURPOSE

Atherosclerotic calcifications are present not only in the extracranial carotid bifurcation but also in the intracranial part of the internal carotid artery. We assessed the association between intracranial internal carotid artery calcifications and cardiovascular risk factors in patients with ischemic cerebrovascular disease and the association between calcifications and the presence of this disease.

MATERIALS AND METHODS

Patients undergoing multidetector CT (MDCT) angiography of the carotid arteries for assessment of stenosis degree were included in the study. A semiautomatic custom-made system to quantify calcifications was developed. The associations between the volume of calcifications and cardiovascular risk factors and the type of ischemic cerebrovascular symptoms were assessed with logistic regression.

RESULTS

MDCT angiography was performed in 406 patients (age, 62 +/- 14 years; 242 men). Men had a significantly higher calcification volume (66 mm(3)) than women (33 mm(3)). Calcification volume was positively associated with age in both men and women. Smoking, hypercholesterolemia, and a history of cardiac disease were independently related to the presence of calcifications. A history of cardiac disease and ischemic cerebrovascular disease were independently related to the volume of calcifications. No association was found between calcifications and the presence or type of ischemic cerebrovascular disease in the vascular territory of the intracranial internal carotid artery.

CONCLUSIONS

Calcifications were associated with higher age and male gender. The presence and volume of calcifications were independently associated with cardiovascular risk factors. Calcifications were not related to the presence or type of ischemic cerebrovascular disease.

Vascular resistance in the carotid artery: an in vitro investigation of embolic protection filters

PURPOSE

To assess in vitro performance of four embolic protection filters (EPFs) with a varying mass of injected particles. Evaluation is based on capture efficiency, pressure gradient, flow rate, and vascular resistance.

MATERIALS AND METHODS

A bench-top flow apparatus was used for in vitro testing of four devices (Spider RX, FilterWire EZ, RX Accunet, and Emboshield). A silicone phantom with average human carotid artery dimensions and a 70% symmetric internal carotid artery (ICA) stenosis was used to model the carotid bifurcation. A blood-mimicking solution (glycerol/deionized water) was circulated at the time-averaged mean peak velocity for the common carotid artery. Five and 10 mg of 200- or 300-mum-diameter microspheres were injected into the ICA to evaluate the capture efficiency of the devices. The normalized pressure gradient, flow rate, and vascular resistance in the ICA were calculated from measured values of pressure and flow rate.

RESULTS

The Spider RX captured the most particles (99.9% for 5 mg, 98.4% for 10 mg) and was associated with the slightest increase in pressure gradient (+8%, +15%) for both masses of microspheres injected. The Spider RX and FilterWire EZ were associated with the slightest decreases in flow rate (Spider RX, -1.9% and -12.1%; FilterWire EZ, -3.5% and -8.2%) and the slightest increases in vascular resistance (Spider RX, +10.1% and +33.0%; FilterWire EZ, +20.5% and +32.7%). The device-specific porosity was calculated, and the Spider RX was found to have the greatest at 50.4%; the Emboshield had the lowest at 2.2%.

CONCLUSIONS

The Spider RX and FilterWire EZ had the best overall performances. Design features such as porosity and pore density are important parameters for improving the effectiveness of EPFs. Vascular resistance in the ICA is a flow-derived variable indicative of device performance and affected by the filter design features.