Contrast carotid ultrasound for the detection of unstable plaques with neoangiogenesis: a pilot study

Contrast-Enhanced Ultrasound Feasibility in Assessing Carotid Plaque Vulnerability-Narrative Review

The risk assessment for carotid atherosclerotic lesions involves not only determining the degree of stenosis but also plaque morphology and its composition. Recently, carotid contrast-enhanced ultrasound (CEUS) has gained importance for evaluating vulnerable plaques. This review explores CEUS's utility in detecting carotid plaque surface irregularities and ulcerations as well as intraplaque neovascularization and its alignment with histology. Initial indications suggest that CEUS might have the potential to anticipate cerebrovascular incidents. Nevertheless, there is a need for extensive, multicenter prospective studies that explore the relationships between CEUS observations and patient clinical outcomes in cases of carotid atherosclerotic disease.

Assessment of plaque vulnerability in carotid atherosclerotic plaques using contrast-enhanced ultrasound

Background

Atherosclerotic carotid plaques are one of the most important causes of stroke. Apart from the severity of stenosis, there are certain plaque characteristics such as neovascularization and, surface ulceration which makes a plaque vulnerable. This study was performed to study the plaque characteristics using contrast-enhanced ultrasound (CEUS) and evaluate their association with presence of ischemic cerebrovascular symptoms in these patients.

Methods

This study included patients presenting at a tertiary care center, having carotid plaques causing >60% stenosis. CEUS was performed for assessment of intraplaque neovascularity and plaque surface characteristics. These plaque features were then evaluated for their association with presence of ischemic cerebrovascular symptoms in patients.

Results

Sixty plaques were studied in 50 patients. Thirty-two plaques were associated with ischemic cerebrovascular symptoms. On CEUS, intraplaque neovascularization was seen in 38 of the 60 plaques studied (63.3%). There was statistically significant association of intraplaque neovascularity and plaque surface characteristics with presence of ischemic cerebrovascular symptoms.

Conclusion

CEUS allows better characterization of plaque surface characteristics and also depicts plaque neovascularization, which helps in determining the plaque vulnerability. It should be used as an adjunct to ultrasound and doppler assessment of carotid plaques.

On vasa vasorum: A history of advances in understanding the vessels of vessels

The vasa vasorum are a vital microvascular network supporting the outer wall of larger blood vessels. Although these dynamic microvessels have been studied for centuries, the importance and impact of their functions in vascular health and disease are not yet fully realized. There is now rich knowledge regarding what local progenitor cell populations comprise and cohabitate with the vasa vasorum and how they might contribute to physiological and pathological changes in the network or its expansion via angiogenesis or vasculogenesis. Evidence of whether vasa vasorum remodeling incites or governs disease progression or is a consequence of cardiovascular pathologies remains limited. Recent advances in vasa vasorum imaging for understanding cardiovascular disease severity and pathophysiology open the door for theranostic opportunities. Approaches that strive to control angiogenesis and vasculogenesis potentiate mitigation of vasa vasorum-mediated contributions to cardiovascular diseases and emerging diseases involving the microcirculation.

Urinary Proteomics Identifying Novel Biomarkers for the Diagnosis and Phenotyping of Carotid Artery Stenosis

Background: Carotid artery stenosis (CAS) is caused by the formation of atherosclerotic plaques inside the arterial wall and accounts for 20–30% of all strokes. The development of an early, noninvasive diagnostic method and the identification of high-risk patients for ischemic stroke is essential to the management of CAS in clinical practice.

Methods: We used the data-independent acquisition (DIA) technique to conduct a urinary proteomic study in patients with CAS and healthy controls. We identified the potential diagnosis and risk stratification biomarkers of CAS. And Ingenuity pathway analysis was used for functional annotation of differentially expressed proteins (DEPs). Furthermore, receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic values of DEPs.

Results: A total of 194 DEPs were identified between CAS patients and healthy controls by DIA quantification. The bioinformatics analysis showed that these DEPs were correlated with the pathogenesis of CAS. We further identified 32 DEPs in symptomatic CAS compared to asymptomatic CAS, and biological function analysis revealed that these proteins are mainly related to immune/inflammatory pathways. Finally, a biomarker panel of six proteins (ACP2, PLD3, HLA-C, GGH, CALML3, and IL2RB) exhibited potential diagnostic value in CAS and good discriminative power for differentiating symptomatic and asymptomatic CAS with high sensitivity and specificity.

Conclusions: Our study identified novel potential urinary biomarkers for noninvasive early screening and risk stratification of CAS.

Role of CEUS in Vascular Pathology

In recent years, the implementation of contrast-enhanced ultrasound (CEUS) in clinical practice has opened new horizons in the arterial pathologies research field, since this technique is able to supply new sets of data that can be crucial in patient management. The main applications of CEUS in the arterial system are the detection, characterization, and follow-up of carotid plaques and endoleaks after EVAR. Other situations in which CEUS was demonstrated to be a useful tool are large vessel vasculitis, dissections, and untreated aneurysms. In carotid atherosclerosis CEUS is not only able to acquire quantitative data about stenosis but also to perform a qualitative assessment of the plaque. The most important plaque features that CEUS is able to depict are ulceration, neovascularization, and the presence of inflammatory infiltrates. All of these factors contribute to plaque vulnerability. Thus, CEUS is crucial in order to allow better risk stratification and management of patients. In follow-up after EVAR, CEUS shows sensitivity and specificity values similar to CTA while ensuring several advantages, such as lower cost and the absence of ionizing radiation and nephrotoxic agents. Moreover, CEUS is able to offer real-time evaluation of endoleaks and thus is a useful tool in cases that are ambiguous on CTA. Most limitations are patient-related and are the same as in all other ultrasound techniques, such as high BMI and meteorism.

Carotid intraplaque neovascularisation as a predictive factor for future vascular events in patients with mild and moderate carotid stenosis: an observational prospective study

Background:

Intraplaque neovascularisation (IPN) increases the vulnerability of plaques, which makes them more likely to rupture and increases the risk of vascular events. However, it is unclear whether IPN can predict future vascular events (stroke recurrence and cardiovascular events). Previous studies on IPN have focused on patients with severe stenosis but overlooked patients with mild and moderate stenosis. This study aimed to investigate whether IPN assessed by contrast-enhanced ultrasonography (CEUS) in patients with mild and moderate degrees of stenosis is associated with future vascular events.

Methods:

One hundred and twenty-one patients participated in this study. 76 patients who met the inclusion and exclusion criteria were included in the final dataset of the study. IPN was graded from 0 to 2 according to the extent of the microbubbles assessed using CEUS. The degree of carotid stenosis was graded as mild, moderate, or severe. We recorded future vascular events during the follow-up. Univariate and multivariate logistic regression analyses were used to evaluate risk factors for future vascular events.

Results:

After a follow-up period of 30 ± 6 months, 30 patients (39.5%) experienced subsequent vascular events. Compared with the ‘non-recurrent’ group, the ‘recurrent’ group showed a higher proportion of grade 2 neovascularisation (p < 0.05), and it was an independent predictor of subsequent vascular events (odds ratio 6.066, 95% confidence interval 1.565–23.512, p < 0.05). Furthermore, in patients with mild and moderate stenosis, future vascular events occurred in an unexpectedly high proportion (up to 42.9%). In the ‘recurrent’ group, 55% of patients with mild and moderate stenosis had grade 2 neovascularisation.

Conclusion:

IPN by CEUS was an independent predictor of future vascular events in patients with recent ischemic stroke, and the high proportion of neovascularisation in patients with mild and moderate stenosis requires more attention.

Vascularized Carotid Atherosclerotic Plaque Models for the Validation of Novel Methods of Quantifying Intraplaque Neovascularization

BACKGROUND

Intraplaque neovascularization (IPN) in advanced lesions of the carotid artery has been linked to plaque progression and risk of rupture. Quantitative measurement of IPN may provide a more powerful tool for the detection of such "vulnerable" plaque than the current visual scoring method. The aim of this study was to develop a phantom platform of a neovascularized atherosclerotic plaque within a carotid artery to assess new methods of quantifying IPN.

METHODS

Ninety-two synthetic plaque models with various IPN architectures representing different ranges of IPN scoring were created and assessed using contrast-enhanced ultrasound. Intraplaque neovascularization volume was calculated from contrast infiltration in B mode. The plaque models were used to develop a testing platform for IPN quantification. A neovascularized enhancement ratio (NER) was calculated using commercially available software. The plaque model NERs were then compared to human plaque NERs (n = 42) to assess score relationship. Parametric mapping of dynamic intensity over time was used to differentiate IPN from calcified plaque regions.

RESULTS

A positive correlation between NER and IPN volume (rho = 0.45; P < .0001) was found in the plaque models. Enhancement of certain plaque model types showed that they resembled human plaques, with visual grade scores of 0 (NER mean difference = 1.05 ± SE 2.45; P = .67), 1 (NER mean difference = 0.22 ± SE 3.26; P = .95), and 2 (NER mean difference = -0.84 ± SE 3.33; P = .80). An optimal cutoff for NER (0.355) identified grade 2 human plaques with a sensitivity of 95% and specificity of 91%.

CONCLUSIONS

We developed a carotid artery model of neovascularized plaque and established a quantitative method for IPN using commercially available technology. We also developed an analysis method to quantify IPN in calcified plaques. This novel tool has the potential to improve clinical identification of vulnerable plaques, providing objective measures of IPN for cardiovascular risk assessment.

Carotid Atherosclerosis, Ultrasound and Lipoproteins

Carotid artery plaques are considered a measure of atherosclerosis and are associated with an increased risk of atherosclerotic cardiovascular disease, particularly ischemic strokes. Monitoring of patients with an elevated risk of stroke is critical in developing better prevention strategies. Non-invasive imaging allows us to directly see atherosclerosis in vessels and many features that are related to plaque vulnerability. A large body of evidence has demonstrated a strong correlation between some lipid parameters and carotid atherosclerosis. In this article, we review the relationship between lipids and atherosclerosis with a focus on carotid ultrasound, the most common method to estimate atherosclerotic load.

Carotid Intraplaque Neovascularization on Contrast-Enhanced Ultrasound Correlates with Cardiovascular Events and Poor Prognosis: A Systematic Review and Meta-analysis

The goal of this meta-analysis is to investigate whether carotid intraplaque neovascularization (IPN) on contrast-enhanced ultrasound (CEUS) correlates with past cardiovascular events (CVEs) and prognosis. The present meta-analysis included 22 studies involving 3232 patients. The pooled analysis revealed that the presence of IPN was significantly associated with a higher incidence of future CVEs (pooled relative risk = 3.28, 95% confidence interval [CI]: 2.28-4.73) and a lower event-free probability (pooled hazard ratio = 2.51, 95% CI: 1.48-4.27). The presence of IPN was significantly associated with higher rates of past cardiac events (odds ratio = 4.25, 95% CI: 2.48-7.29) and past cerebrovascular accidents (odds ratio = 4.83, 95% CI: 2.66-8.78). Our results suggest that carotid IPN on CEUS significantly correlates with past cardiac events and cerebrovascular accidents and can predict future CVEs. Carotid CEUS is useful in CVE risk stratification.

CT imaging features of carotid artery plaque vulnerability

Despite steady advances in medical care, cardiovascular disease remains one of the main causes of death and long-term morbidity worldwide. Up to 30% of strokes are associated with the presence of carotid atherosclerotic plaques. While the degree of stenosis has long been recognized as the main guiding factor in risk stratification and therapeutical decisions, recent evidence suggests that features of unstable, or ‘vulnerable’, plaques offer better prognostication capabilities. This paradigmatic shift has motivated researchers to explore the potentialities of non-invasive diagnostic tools to image not only the lumen, but also the vascular wall and the structural characteristics of the plaque. The present review will offer a panoramic on the imaging modalities currently available to characterize carotid atherosclerotic plaques and, in particular, it will focus on the increasingly important role covered by multidetector computed tomographic angiography.

Contrast-enhanced ultrasound (CEUS) in the diagnostic evaluation of popliteal artery aneurysms, a single-center study

BACKGROUND

Popliteal artery aneurysms (PAA) are the most common peripheral artery aneurysms. Most common cause is arteriosclerosis. Acute thromboembolic limb ischemia and rupture of the PAA depict severe complications. Diagnostic tools for identifying PAAs are (Doppler) ultrasound, CT/MR angiography and DSA.

PURPOSE

The aim of the present retrospective single-center study is to assess the application and safety of CEUS for assessing untreated and treated PAAs.

MATERIALS AND METHODS

13 patients were included in this study on whom CEUS was performed between 2007-2016. CEUS examinations were performed and interpreted by an experienced single radiologist (EFSUMB Level 3).

RESULTS

CEUS allowed for the detection of PAAs in all cases. CEUS allowed for detection of partial thrombosis of PAA in 7/8 of untreated patients, proper exclusion of PAA upon femoro-popliteal bypass in 3 patients, incomplete exclusion of PAA upon femoro-popliteal bypass in 1 patient and ruling out of in-stent stenosis in 1 patient.

CONCLUSION

CEUS is a useful and safe tool for in real-time evaluation of PAAs in the pre-/post-treatment status. In addition to conventional (Doppler) ultrasound and as an alternative tool to more elaborate imaging modalities, CEUS might be integrated in the future diagnostic work-up and follow-up of PAA patients.

Single-center study: dynamic contrast-enhanced ultrasound in the diagnostic assessment of carotid body tumors

Background

Carotid body tumors (CBTs) depict the most common paraganglioma of the head and neck that can metastasize in up to 15% of cases. They develop either sporadically or hereditarily and may produce catecholamines ("functioning CBTs") resulting in associated symptoms like headache, palpitations or flush. Non-functioning CBTs usually present as slowly and often tender growing mass which may affect adjacent cranial nerves. CBTs can be visualized by ultrasound, CT, MRI or angiography. Pre-surgical interventional embolization, surgical resection and radiation therapy are therapeutical options. The aim of this retrospective single-center study is to assess the safe and real-time evaluation of CBTs by contrast-enhanced ultrasound (CEUS).

Methods

Ten patients with CBT were included in this study on whom CEUS was performed between 2007-2018 (mean age: 62 years). In 6/10 patients, results were confirmed by MRI, 4/12 patients underwent subsequent angiography. CEUS was performed and interpreted by a single consultant radiologist with experience since 2000 (EFSUMB level 3). VueBox^® software was used for standardized perfusion quantification.

Results

CEUS allowed to detect all CBTs and visualize intratumoral microcirculation. Perfusion quantification was performed in 6/10 cases. CBTs showed significantly reduced peak-enhancement (PE), reduced wash-in perfusion index (WiPI) and significantly elevated time to peak (TTP) compared to common carotid arteries (CCA).

Conclusions

CEUS is a useful and safe tool for identifying CBTs and evaluating intratumoral microperfusion at high spatial and temporal resolutions in real-time. In addition to conventional ultrasound, CT, MRI and digital substraction angiography (DSA), CEUS may be implemented in the future diagnostic work-up and follow-up of CBT patients.

Contrast imaging ultrasound for the detection and characterization of carotid vulnerable plaque

Not only the degree of luminal narrowing but also the plaque morphology and composition play an important role in risk stratification of carotid atherosclerotic lesions. During the last few years, carotid contrast-enhanced ultrasound (CEUS) has emerged as a valuable imaging tool to assess such vulnerable carotid plaques. This review article discussed the use of CEUS for the detection of carotid plaque irregularities and ulcerations as well as the quantification of intraplaque neovascularization and its correlation with histology and inflammatory biomarkers. Apart from evaluating for markers of vulnerable carotid plaques, CEUS enhancement is directly associated with past cerebrovascular events. More importantly, preliminary evidence has shown that CEUS could be used to predict future cerebrovascular and cardiovascular events. Despite the progress in CEUS imaging for carotid atherosclerotic disease, past studies still suffer from the retrospective nature, small sample size, and a lack of matched, well controlled prospective studies. In the future, large multi-center prospective studies addressing the relationship between CEUS findings and patient clinical outcomes in carotid atherosclerotic disease are warranted.

Contrast enhanced ultrasound of carotid plaque in acute ischemic stroke (CUSCAS study)

INTRODUCTION

Carotid atherosclerosis represents 8 to 15% of ischemic strokes in relation to the concept of "vulnerable" plaque. Contrast enhanced ultrasound (CEUS) can detect moving microbubbles within the plaque corresponding to neovessels that constitute "precursors" of vulnerable plaque and intraplaque hemorrhage. CEUS was not studied specifically in acute ischemic strokes. The aim of this study is to analyse the prevalence of CEUS carotid plaque ipsilateral at the ischemic stroke as well as the main characteristics of contrast-plaques.

METHOD

A single-centre prospective pilot study involving 33 consecutive patients with a stroke ≤10 days, diagnosed by an MRI with positive diffusion sequence and having a carotid plaque thickness ≥2.5mm with low or heterogeneous echogenicity, located in the ipsilateral carotid territory at the stroke. Plaque echogenicity was done by visual analysis and by measurement of the gray scale median (GSM). A transcranial Doppler monitoring was carried out in search of HITS. The contrast ultrasound was performed after 2.5 cc IV injection of SonoVue®. A video clip was recorded after injection which was used for interpretation by visual analysis in 3 grades, provided by two independent expert readers.

RESULTS

The population consisted of 10 women and 23 men aged 73 on average. The topography of strokes in the carotid territory was located on the right in 11 (33%) cases and on the left in 22 (67%) cases. Seventeen patients had carotid stenosis between 0 and 49% according to the Nascet method and 16 patients had stenosis of 50 to 99%. The visual characterisation of the plaques had echolucent dominance (Type 1-2) in 18 cases and echogenic dominance (Type 3-4a) in 15 cases. Cardiovascular risk factors were common with no difference by sex. The inter-observer agreement of plaque enhancement was moderate in first reading (k=0.48) and excellent at consensus (k=0.91). Only one disagreement was found. Contrast agent enhancement of carotid plaque was observed in 11/32 patients, representing a prevalence of 34.4% - CI95% [17.9-50.9]. Variables associated with contrast plaque included the absence of antiplatelet drug (63.6% vs. 23.8%, P=0.05) and the presence of a regular edge on the plaque (91% vs. 48%, P=0.04). There was no difference in contrast enhancement for stenosis>or<50% in diameter and neither for the type of plaque.

CONCLUSION

In a consecutive cohort of 33 patients, the prevalence of CEUS from an ipsilateral carotid plaque to a recent acute ischemic stroke was 34.4%. There was a statistically significant association between the contrast enhancement of the plaque and the absence of antiplatelet drug (P=0.05) and also the presence of a regular edge on the plaque (P=0.04). There was no correlation between plaque contrast and clinical and biological characteristics of patients or the presence of HITS.

Contrast-Enhanced Ultrasound to Assess Carotid Intraplaque Neovascularization

Contrast-enhanced ultrasound (CEUS) is increasingly being used to identify patients with carotid plaques that are vulnerable to rupture, so-called vulnerable atherosclerotic plaques, by assessment of intraplaque neovascularization. A complete overview of the strengths and limitations of carotid CEUS is currently not available. The aim of this systematic review was to provide a complete overview of existing publications on the role of CEUS in assessment of carotid intraplaque neovascularization. The systematic review of the literature yielded 52 studies including a total of 4660 patients (mean age: 66 y, 71% male) who underwent CEUS for the assessment of intraplaque neovascularization. The majority of the patients (76%) were asymptomatic and had no history of transient ischemic attack (TIA) or stroke. The assessment of intraplaque neovascularization was mostly performed using a visual scoring system; several studies used time-intensity curves or dedicated quantification software to optimize analysis. In 17 studies CEUS was performed in patients before carotid surgery (endarterectomy), allowing a comparison of pre-operative CEUS findings with histologic analysis of the tissue sample that is removed from the carotid artery. In a total of 576 patients, the CEUS findings were compared with histopathological analysis of the plaque after surgery. In 16 of the 17 studies, contrast enhancement was found to correlate with the presence and degree of intraplaque neovascularization on histology. Plaques with a larger amount of contrast enhancement had significantly increased density of microvessels in the corresponding region on histology. In conclusion, CEUS is a readily available imaging modality for the assessment of patients with carotid atherosclerosis, providing information on atherosclerotic plaques, such as ulceration and intraplaque neovascularization, which may be clinically relevant. The ultimate clinical goal is the early identification of carotid atherosclerosis to start early preventive therapy and prevent clinical complications such as TIA and stroke.

Carotid Plaque Neovascularization Detected With Superb Microvascular Imaging Ultrasound Without Using Contrast Media

Background and Purpose- A significant proportion of ischemic strokes are caused by emboli from unstable carotid artery plaques with intraplaque neovascularization (IPN) as a key feature of plaque instability. IPN is not detectable with conventional Doppler ultrasound. Contrast-enhanced ultrasound (CEUS) can visualize IPN, but its use is limited in clinical practice because it requires an intravenous injection of contrast. Superb microvascular imaging (SMI) without contrast uses an algorithm to remove clutter and motion wall artifacts while preserving low-velocity blood flow signals, enabling visualization of IPN. Our aim was to assess the feasibility of SMI for the detection of IPN. Methods- Thirty-one patients with >50% carotid stenosis were included: 22 patients were symptomatic and 9 asymptomatic. All patients underwent conventional carotid ultrasound, CEUS, SMI, and blood tests. CEUS and SMI findings were compared and correlated to histological plaque assessments after endarterectomy. Results- There was significant positive correlation between an IPN visual 5-level classification of SMI and a semiquantitative analysis of CEUS (P<0.001, r=0.911). Plaques with higher SMI grades had higher numbers of neovessels quantified at histology (P=0.041, r=0.460). Hypoechoic plaques had higher grades of IPN on both CEUS and SMI (P<0.001). Higher visual IPN counts on SMI were associated with (1) increased areas of inflammation (P=0.043, r=0.457), (2) combined rank scores of granulation tissue, inflammation and lipids (P=0.02, r=0.494) at histology, and (3) higher peak-intensity values on quantitative CEUS (P=0.042, r=0.514). Conclusions- SMI ultrasound can detect neovascularization with accuracy comparable to CEUS, suggesting SMI to be a promising noninvasive alternative to CEUS for the assessment of carotid plaque stability.

General principles and overview of vascular contrast-enhanced ultrasonography

Ultrasonography (US) is the first-line modality for the evaluation of vascular pathology. Although well-established for many diseases, US has inherent limitations that can occasionally hinder an accurate diagnosis. The value of US was improved by the introduction of microbubbles as ultrasonographic contrast agents (UCAs) and the emergence of contrast-enhanced ultrasonography (CEUS), following the introduction of second-generation UCAs and the emergence of modern contrast-specific techniques. CEUS offers valuable information about vascular disease, both on a macrovascular and a microvascular level, with well-established applications for carotid disease, post-interventional follow-up of abdominal aortic aneurysms, and the assessment of portal vein thrombosis. The purpose of this review is to discuss the principles of CEUS and to present an overview of its vascular applications.

An Ultrasonographic Multiparametric Carotid Plaque Risk Index Associated with Cerebrovascular Symptomatology: A Study Comparing Color Doppler Imaging and Contrast-Enhanced Ultrasonography

BACKGROUND AND PURPOSE

Various ultrasonographic features of carortid plaques have been associated with the occurence of stroke, highlighting the need for multi-parametric assessment of plaque's vulnerability. Our aim was to compare ultrasonographic multiparametric indices using color Doppler imaging and contrast-enhanced sonography between symptomatic and asymptomatic carotid plaques.

MATERIALS AND METHODS

This was a cross-sectional observational study recruiting 54 patients (72.2% male; median age, 61 years) undergoing sonography and contrast-enhanced sonography. Patients were included if a moderately or severely stenotic internal carotid artery plaque was detected, with the plaque being considered symptomatic if it was ipsilateral to a stroke occuring within the last 6 months. A vulnerability index, previously described by Kanber et al, combined the degree of stenosis, gray-scale median, and a quantitative measure of surface irregularities (surface irregularity index) derived from color Doppler imaging and contrast-enhanced ultrasonography, resulting in 2 vulnerability indices, depending on the surface irregularity index used. Mann-Whitney U and t tests were used to compare variables between groups, and receiver operating characteristic curves were used to compare diagnostic accuracy.

RESULTS

Sixty-two plaques were analyzed (50% symptomatic), with a mean degree of stenosis of 68.9%. Symptomatic plaques had a significantly higher degree of stenosis (mean, 74.7% versus 63.1%; P < .001), a lower gray-scale median (13 versus 38; P = .001), and a higher Kanber vulnerability index based both on color Doppler imaging (median, 61.4 versus 16.5; P < .001) and contrast-enhanced ultrasonography (median, 88.6 versus 25.2; P < .001). The area under the curve for the detection of symptomatic plaques was 0.772 for the degree of stenosis alone, 0.783 for the vulnerability index-color Doppler imaging, and 0.802 for the vulnerability index-contrast-enhanced ultrasonography, though no statistical significance was achieved.

CONCLUSIONS

Symptomatic plaques had a higher degree of stenosis, lower gray-scale median values, and higher values of the Kanber vulnerability index using both color Doppler imaging and contrast-enhanced ultrasonography for plaque surface delineation.

Carotid artery imaging: The study of intra-plaque vascularization and hemorrhage in the era of the "vulnerable" plaque

Intraplaque hemorrhage (IPH) is one of the main factors involved in atherosclerotic plaque (AP) instability. Its recognition is crucial for the correct staging and management of patients with carotid artery plaques to limit ischemic stroke. Imaging plays a crucial role in identifying IPH, even if the great variability of intraplaque vascularization and the limitations of our current imaging technologies make it difficult. The intent of this review is to give a general overview of the main features of intraplaque vascularization and IPH on Ultrasound (US), Computed Tomography (CT), Magnetic Resonance (MR) and Nuclear Medicine, and a brief description on the future prospectives.

Carotid Ultrasound

Doppler ultrasound (US) is the primary noninvasive imaging modality for detecting, grading, and monitoring extracranial internal carotid artery (ICA) stenosis, which is a well-established surrogate marker for stroke risk. In addition, Doppler US is the primary imaging modality for surveillance of patients following carotid intervention with endarterectomy or stent placement. This article reviews the pathophysiology and epidemiology of stroke, technique for performing a carotid US examination, normal findings, and diagnostic US criteria for evaluating carotid plaque, grading stenosis in the native ICA and following intervention, as well as waveform analysis of the carotid arteries.

Medial Hypoxia and Adventitial Vasa Vasorum Remodeling in Human Ascending Aortic Aneurysm

Human ascending aortic aneurysms characteristically exhibit cystic medial degeneration of the aortic wall encompassing elastin degeneration, proteoglycan accumulation and smooth muscle cell loss. Most studies have focused on the aortic media and there is a limited understanding of the importance of the adventitial layer in the setting of human aneurysmal disease. We recently demonstrated that the adventitial ECM contains key angiogenic factors that are downregulated in aneurysmal aortic specimens. In this study, we investigated the adventitial microvascular network (vasa vasorum) of aneurysmal aortic specimens of different etiology and hypothesized that the vasa vasorum is disrupted in patients with ascending aortic aneurysm. Morphometric analyses of hematoxylin and eosin-stained human aortic cross-sections revealed evidence of vasa vasorum remodeling in aneurysmal specimens, including reduced density of vessels, increased lumen area and thickening of smooth muscle actin-positive layers. These alterations were inconsistently observed in specimens of bicuspid aortic valve (BAV)-associated aortopathy, while vasa vasorum remodeling was typically observed in aneurysms arising in patients with the morphologically normal tricuspid aortic valve (TAV). Gene expression of hypoxia-inducible factor 1α and its downstream targets, metallothionein 1A and the pro-angiogenic factor vascular endothelial growth factor, were down-regulated in the adventitia of aneurysmal specimens when compared with non-aneurysmal specimens, while the level of the anti-angiogenic factor thrombospondin-1 was elevated. Immunodetection of glucose transporter 1 (GLUT1), a marker of chronic tissue hypoxia, was minimal in non-aneurysmal medial specimens, and locally accumulated within regions of elastin degeneration, particularly in TAV-associated aneurysms. Quantification of GLUT1 revealed elevated levels in the aortic media of TAV-associated aneurysms when compared to non-aneurysmal counterparts. We detected evidence of chronic inflammation as infiltration of lymphoplasmacytic cells in aneurysmal specimens, with a higher prevalence of lymphoplasmacytic infiltrates in aneurysmal specimens from patients with TAV compared to that of patients with BAV. These data highlight differences in vasa vasorum remodeling and associated medial chronic hypoxia markers between aneurysms of different etiology. These aberrations could contribute to malnourishment of the aortic media and could conceivably participate in the pathogenesis of thoracic aortic aneurysm.

[Imaging of neoangiogenesis of internal carotid artery's atherosclerotic plaque by contrast-enhanced sonography and histological examination]

Previously, atherosclerosis was considered a disease accompanied exclusively by lipids accumulation. At present time success of fundamental and experimental science confirmed that atherosclerotic process is also associated with neovascularization and prolonged inflammatory response at all stages of atherogenesis from initial manifestations to thrombotic complications. The cause of atherosclerotic plaque instability is neovascularization, which is accompanied by intra-plaque hemorrhage and damage. Complications of carotid arteries atherosclerosis are strokes and transient ischemic attacks. The use of a wide range of diagnostic and pathohistological techniques is required for assessing this pathology. The most promising diagnostic technique is Contrast Enhanced Ultrasonography (CEUS) which allows to assess neovascularization degree in atherosclerotic plaque through the injection of a contrast agents.

Computational imaging of aortic vasa vasorum and neovascularization in rabbits using contrast-enhanced intravascular ultrasound: Association with histological analysis

OBJECTIVE

Neoangiogenesis is pathophysiologically related to atherosclerotic plaque growth and vulnerability. We examined the in vivo performance of a computational method using contrast-enhanced intravascular ultrasound (CE-IVUS) to detect and quantify aortic wall neovascularization in rabbits. We also compared these findings with histological data.

METHODS

Nine rabbits were fed with a hyperlipidemic diet. IVUS image sequences were continuously recorded before and after the injection of a contrast agent. Mean enhancement of intensity of a region of interest (MEIR) was calculated using differential imaging algorithm. The percent difference of MEIR before and after the injection of microbubbles (d_MEIR) was used as an index of the density of plaque or/and adventitial neovascularization. Aortic segments were excised for histological analysis.

RESULTS

CE-IVUS and histological analysis were performed in 11 arterial segments. MEIR was significantly increased (~20%) after microbubble injection (from 8.1±0.9 to 9.7±1.8, p=0.016). Segments with increased VV/neovessels in the tunica adventitia (histological scores 2 and 3) had significantly higher d_MEIR compared with segments with low presence of VV/neovessels (score 1); 40.5±22.9 vs. 8±14.6, p=0.024, respectively.

CONCLUSION

It is possible to detect VV or neovessels in vivo using computational analysis of CE-IVUS images, which is in agreement with histological data. These findings may have critical implications on vulnerable plaque assessment and risk stratification.

The inter-observer agreement in the assessment of carotid plaque neovascularization by contrast-enhanced ultrasonography: The impact of plaque thickness

BACKGROUND

The interobserver agreement in the assessment of the grade of carotid plaque neovascularization by contrast-enhanced ultrasonography is poorly established.

METHOD

We examined 140 carotid plaques in 66 patients (all patients had bilateral plaques, and 8 patients had 2 plaques on one side). We performed conventional and contrast-enhanced ultrasonography to analyze the presence of carotid plaque neovascularization, which was graded by two independent observers whose interobserver agreement (κ) was evaluated according to the thickness of carotid plaque.

RESULTS

For all carotid plaques, the mean κ was 0.689 (95% confidence interval 0.604-0.774). It was 0.689 (0.569-0.808), 0.637 (0.487-0.787), and 0.740 (0.585-0.896), respectively for carotid plaques with maximal thickness <2 mm, from 2 mm to 3 mm, and >3 mm.

CONCLUSION

The interobserver agreement for assessing carotid plaque neovascularization by using contrast-enhanced ultrasonography is substantial and acceptable for research purposes, regardless of the maximal thickness of the plaque.

Non-invasive imaging techniques and assessment of carotid vasa vasorum neovascularization: Promises and pitfalls

Carotid adventitia vasa vasorum neovascularization (VVn) is associated with the initial stages of arteriosclerosis and with the formation of unstable plaque. However, techniques to accurately quantify that neovascularization in a standard, fast, non-invasive, and efficient way are still lacking. The development of such techniques holds the promise of enabling wide, inexpensive, and safe screening programs that could stratify patients and help in personalized preventive cardiovascular medicine. In this paper, we review the recent scientific literature pertaining to imaging techniques that could set the stage for the development of standard methods for quantitative assessment of atherosclerotic plaque and carotid VVn. We present and discuss the alternative imaging techniques being used in clinical practice and we review the computational developments that are contributing to speed up image analysis and interpretation. We conclude that one of the greatest upcoming challenges will be the use of machine learning techniques to develop automated methods that assist in the interpretation of images to stratify patients according to their risk.

Evaluation of Intraplaque Neovascularization Using Superb Microvascular Imaging and Contrast-Enhanced Ultrasonography

BACKGROUND

Several studies have shown a linkage between intraplaque neovascularization (IPN) and plaque instability. Although contrast-enhanced ultrasonography (CEUS) may help visualize IPN in the carotid artery, its benefits are limited in Japan, where there is no health insurance coverage for contrast agents in medical imaging. Superb microvascular imaging (SMI), however, enables the depiction of low-velocity blood flow. The current study compares the diagnostic accuracy of SMI and CEUS in the evaluation of IPN.

METHODS

The SMI and CEUS video images were transferred to a workstation and then analyzed to determine whether intraplaque blood flow signals were detected with SMI and whether plaques were contrast-enhanced with carotid artery CEUS. The images generated were independently interpreted by 2 radiologic technologists and 1 neurologist.

RESULTS

Intraplaque enhancement was observed in 19 patients using CEUS while intraplaque blood flow signals were observed in 12 patients using SMI. A 100% specificity was recorded for SMI (all 12 patients with SMI-detected intraplaque blood flow showed contrast-enhanced plaques), while its sensitivity was 63% (8 of the 15 patients with no SMI-detected intraplaque blood flow showed contrast-enhanced plaques on CEUS).

CONCLUSIONS

The results of this study show that patients with SMI-detected blood flow will tend to have plaque enhancement using CEUS. This suggests that SMI, as a simpler, safer, and noninvasive technique, can facilitate the visualization of carotid artery IPN without the use of a contrast agent, as well as in the clinical evaluation of plaque instability.

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.

[Contribution of contrast enhanced ultrasonography in the characterization of carotid lesions]

Harmonic mode ultrasound with injection of a contrast enhancement agent allows visualization of mobile microbubbles in the carotid plaque corresponding to neovessels secondary to an inflammation or hypoxia. These neovessels could be considered "precursor" markers of the vulnerable plaque. The aim of this work was to give an update on ultrasound contrast imaging acquisition in the exploration of carotid artery both for atheromatous lesions and for large vessel vasculitis. A precise description of the material to be used, the image acquisition methodology and the environmental conditions is discussed, emphasizing the pitfalls to be avoided as well as proper image interpretation. Microbubbles in a plaque are significantly associated with an increase in cardiovascular events (infarction and acute coronary syndrome) and ipsilateral cerebral ischemic events. Wall irregularities, microfissures and ulcer plaque detection are facilitated by the use of contrast compared to the CT scan. No studies have yet validated contrast enhanced ultrasound in the exploration of asymptomatic carotid stenosis. Contrast enhanced ultrasound also allows to detect vasculitis of the large vessels active phases by the presence of microbubbles in the carotid wall thickening and to monitor the regression under appropriate medical treatment. Future validation studies or even registries are needed to allow better use of this tool in everyday clinical practice.

Contrast-Enhanced Ultrasound Imaging Quantification of Adventitial Vasa Vasorum in a Rabbit Model of Varying Degrees of Atherosclerosis

This study used an atherosclerotic rabbit model to investigate the feasibility of quantifying adventitial vasa vasorum (VV) via contrast-enhanced ultrasound (CEUS) imaging to identify early atherosclerosis. Recent evidence has linked adventitial VV with atherosclerotic plaque progression and vulnerability. A growth in VV density has been detected preceding intimal thickening and even endothelial dysfunction. In our study, carotid atherosclerosis rabbit models were used, and animals underwent CEUS imaging at the end of the atherosclerotic induction period. Normalized maximal video-intensity enhancement (MVE) was calculated to quantify VV density. After CEUS imaging, animals were euthanized, and their carotids were processed for histopathological analysis following staining for CD31 and VEGF. Adventitial normalized MVE increased as atherosclerosis progressed (p < 0.001), and normalized MVE also progressed, demonstrating a linear correlation with histological findings (r = 0.634, p < 0.001 for VEGF-positive; r = 0.538, p < 0.001 for CD31-positive). Thus, we histologically validated that CEUS imaging can be used to quantify the development of adventitial VV associated with atherosclerosis progression. This method can be used for monitoring the VV to detect early atherosclerosis.

Differential Intensity Projection for Visualisation and Quantification of Plaque Neovascularisation in Contrast-Enhanced Ultrasound Images of Carotid Arteries

Studies have reported that intraplaque neovascularisation (IPN) is closely correlated with plaque vulnerability. In this study, a new image processing approach, differential intensity projection (DIP), was developed to visualise and quantify IPN in contrast-enhanced non-linear ultrasound image sequences of carotid arteries. DIP used the difference between the local temporal maximum and the local temporal average signals to identify bubbles against tissue non-linear artefact and noise. The total absolute and relative areas occupied by bubbles within each plaque were calculated to quantify IPN. In vitro measurements on a laboratory phantom were made, followed by in vivo measurements in which 24 contrast-enhanced non-linear ultrasound image sequences of carotid arteries from 48 patients were selected and motion corrected. The results using DIP were compared with those obtained by maximum intensity projection (MIP) and visual assessment. The results indicated that DIP can significantly reduce non-linear propagation tissue artefacts and is much more specific in detecting bubble signals than MIP, being able to reveal microbubble signals that are buried in tissue artefacts in the corresponding MIP image. A good correlation was found between microvascular area (MVA) (r = 0.83, p < 0.001)/microvascular density (r = 0.77, p < 0.001) obtained using DIP and the corresponding expert visual grades, comparing favourably to r = 0.26 and 0.23 obtained using MIP on the same data. In conclusion, the proposed method exhibits great potential in quantification of IPN in contrast-enhanced ultrasound images of carotid arteries.

Contrast-enhanced ultrasound of the carotid system: a review of the current literature

Carotid disease is a major current health problem accounting for a significant part of stroke patients. Ultrasound with colour Doppler and spectral analysis is the primary imaging technique used for screening and diagnostic evaluation of the extracranial part of carotid arteries offering identification and grading of carotid disease. However, inherent limitations of this technique include flow-related artefacts like Doppler angle dependence and aliasing artefact which may sometimes hinder complete assessment of a stenotic part of the vessel, potentially failing to address clinically significant differential diagnosis issues. The intravenous use of microbubbles as an US contrast agent has been introduced for the supplementation of conventional technique. The value of contrast-enhanced ultrasound (CEUS) has been investigated in the evaluation of carotid disease leading to promising results. CEUS provides improved flow visualization free of artefacts and detailed plaque surface delineation, thus being able to accurately grade stenosis, identify carotid plaque ulcerations, differentiate occlusion from highly stenotic plaques and identify carotid dissection. Furthermore, microbubbles can be used to identify and grade intraplaque neovascularization, carotid wall inflammation in patients with arteritis, follow-up patients after carotid intervention and assist interventional procedures reducing the need for nephrotoxic contrast agents. The purpose of this review is to present and discuss the current literature regarding the various uses of CEUS in carotid arteries.

Atherosclerotic Carotid Plaques: Multimodality Imaging with Contrast-enhanced Ultrasound, Computed Tomography, and Magnetic Resonance Imaging

Introduction

The imaging of carotid plaques has undergone a paradigm shift increasing importance being given to plaque characterization. Patients with "vulnerable" plaques are more prone to develop future neurovascular events.

Purpose

The purpose of this study is to analyze the role of multimodality imaging techniques in the assessment of carotid atherosclerotic plaques.

Materials and Methods

Twenty-six patients were prospectively enrolled in the study. Patients underwent multidetector computed tomography (CT) angiography, ultrasound, contrast-enhanced ultrasound, and high-resolution magnetic resonance imaging (MRI) of the carotid arteries with special emphasis on the carotid bifurcation.

Results

The mean age of patients was 65.41 years. Twenty-one were males. Plaque neovascularization was seen in 10 of the 18 plaques studied (55.56%). Based on the predominant components of the plaque, plaques were characterized as lipid (3), lipid with recent hemorrhage (1), fibrous (7), fibrofatty (4), fibrofatty with some hemorrhagic components (3), and recent hemorrhage (2).

Conclusions

Together, contrast-enhanced ultrasound, CT, and MRI provide complete information about the plaque characteristics.

Increased Vascularization in the Vulnerable Upstream Regions of Both Early and Advanced Human Carotid Atherosclerosis

BACKGROUND

Vascularization of atherosclerotic plaques has been linked to plaque vulnerability. The aim of this study was to test if the vascularization was increased in upstream regions of early atherosclerotic carotid plaques and also to test if the same pattern of vascularization was seen in complicated, symptomatic plaques.

METHODS

We enrolled 45 subjects with early atherosclerotic lesions for contrast enhanced ultrasound and evaluated the percentage of plaque area in a longitudinal ultrasound section which contained contrast agent. Contrast-agent uptake was evaluated in both the upstream and downstream regions of the plaque. We also collected carotid endarterectomy specimens from 56 subjects and upstream and downstream regions were localized using magnetic resonance angiography and analyzed using histopathology and immunohistochemistry.

RESULTS

Vascularization was increased in the upstream regions of early carotid plaques compared with downstream regions (30% vs. 23%, p = 0.033). Vascularization was also increased in the upstream regions of advanced atherosclerotic lesions compared with downstream regions (4.6 vs. 1.4 vessels/mm2, p = 0.001) and was associated with intra-plaque hemorrhage and inflammation.

CONCLUSIONS

Vascularization is increased in the upstream regions of both early and advanced plaques and is in advanced lesions mainly driven by inflammation.

Evaluation of the thrombus of abdominal aortic aneurysms using contrast enhanced ultrasound - preliminary results

It is hypothesized that the degree of vascularization of the thrombus may have a significant impact on the rupture of aortic aneurysms. The presence of neovascularization of the vessel wall and mural thrombus has been confirmed only in histopathological studies. However, no non-invasive imaging technique of qualitative assessment of thrombus and neovascularization has been implemented so far. Contrast-enhanced ultrasound (CEUS) has been proposed as a feasible and minimally invasive technique for in vivo visualization of neovascularization in the evaluation of tumors and atherosclerotic plaques. The aim of this study was the evaluation of mural thrombus and AAAs wall with CEUS. CEUS was performed in a group of seventeen patients with AAAs. The mural thrombus enhancement was recognized in 12 cases, yet no significant correlation between the degree of contrast enhancement and AAAs diameter, thrombus width, and thrombus echogenicity was found. We observed a rise in AAAs thrombus heterogeneity with the increase in the aneurysm diameter (r = 0.62, p = 0.017). In conclusion CEUS can visualize small channels within AAAs thrombus, which could be a result of an ongoing angiogenesis. There is a need for further research to find out whether the degree of vascularization of the thrombus may have a significant impact on the rupture of aneurysms.

Analysis of Carotid color ultrasonography and high sensitive C-reactive protein in patients with atherosclerotic cerebral infarction

Objectives:

To detect the correlation between high-sensitivity-CRP, carotid plaque, neurological function and intima–media thickness, and help physicians in the diagnosis of atherosclerotic cerebral infarction.

Methods:

A total of 96 patients with the first onset of atherosclerotic cerebral infarction were included in the study from July 2013 to May 2015. The test of high-sensitivity-CRP, examination of carotid color ultrasonography and neurological function evaluation were carried out for all the participants.

Results:

Ninety-six patients were divided into carotid plaque group and non-plaque group according to the existence of a carotid plaque after carotid artery ultrasonography. The carotid plaque group was further subdivided into stable plaque and unstable plaque subgroups according to plaque characteristics. The age in two subgroups was significantly higher than the non-plaque group (p<0.05). The unstable plaque subgroup presented with the highest values in intima–media thickness and high-sensitivity-CRP level, followed by stable plaque subgroup and non-plaque group (p<0.05). With the nervous damage scale increase, the level of high-sensitivity-CRP increase significantly (p<0.05). In addition, there was significant correlation between NIHSS score and high-sensitivity-CRP in patients with atherosclerotic cerebral infarction (p<0.05).

Conclusion:

The level of high-sensitivity-CRP and intima–media thickness is closely associated with the development of carotid plaque, and high-sensitivity-CRP can be regarded as a high sensitive index in deciding the risk and prognosis of atherosclerotic cerebral infarction.

Assessment of the vulnerable carotid atherosclerotic plaque using contrast-enhanced ultrasonography

Carotid atherosclerosis represents a primary cause for cerebrovascular ischemic events and its contemporary management includes surgical revascularization for moderate to severe symptomatic stenoses. However, the role of invasive therapy seems to be questioned lately for asymptomatic cases. Numerous reports have suggested that the presence of neovessels within the atherosclerotic plaque remains a significant vulnerability factor and over the last decade imaging modalities have been used to identify intraplaque neovascularization in an attempt to risk-stratify patients and offer management guidance. Contrast-enhanced ultrasonography of the carotid artery is a relatively novel diagnostic tool that exploits resonated ultrasound waves from circulating microbubbles. This property permits vascular visualization by producing superior angiography-like images, and allows the identification of vasa vasorum and intraplaque microvessels. Moreover, plaque neovascularization has been associated with plaque vulnerability and ischemic symptoms lately as well. At the same time, attempts have been made to quantify contrast-enhanced ultrasonography signal using sophisticated software packages and algorithms, and to correlate it with intraplaque microvascular density. The aim of this review was to collect all recent data on the characteristics, performance, and prognostic role of contrast-enhanced ultrasonography regarding carotid stenosis management, and to produce useful conclusions for clinical practice.

Diagnostic vascular ultrasonography with the help of color Doppler and contrast-enhanced ultrasonography

The use of ultrasonography and especially of contrast-enhanced ultrasonography (CEUS) in the diagnosis of vascular pathologies before and after interventions has significantly increased over the past years due to the broader availability of modern ultrasound systems with CEUS capabilities and more trained user experience in this imaging modality. For the preinterventional and postinterventional work-up of carotid diseases, duplex ultrasound as well as CEUS have been established as the standard-of-care examination procedures for diagnosis, evaluation, and follow-up. In addition to its use for carotid arterial diseases, ultrasonography has also become the primary modality for the screening of vascular pathologies. This review describes the most common pathologies found in ultrasonography of the carotid arteries, the abdominal aorta, and the femoral arteries.

Detection of Carotid Atherosclerotic Plaque Neovascularization Using Contrast Enhanced Ultrasound: A Systematic Review and Meta-Analysis of Diagnostic Accuracy Studies

BACKGROUND

Intraplaque neovascularization is considered an important indicator of plaque vulnerability. Contrast-enhanced ultrasound (CEUS) of carotid arteries improves imaging of carotid intima-media thickness and permits real-time visualization of neovascularization of the atherosclerotic plaque. The authors conducted a systematic review and meta-analysis to evaluate the accuracy of CEUS-detected carotid atherosclerotic plaque.

METHODS

A systematic search was performed to identify studies published in the MEDLINE, Embase, Scopus, and Web of Science databases from 2004 to June 2015. Studies evaluating the accuracy of quantitative analysis and qualitative analysis (visual interpretation) for the diagnosis of intraplaque neovascularization compared with histologic specimens and/or clinical diagnosis of symptomatic plaque were included. Parameters evaluated were plaque quantitative CEUS intensity and the visual grading of plaque CEUS. A random-effects meta-analysis was used to pool the likelihood ratios (LRs), diagnostic odds ratios, and summary receiver operating characteristic curves. Corresponding areas under the curves were calculated.

RESULTS

The literature search identified 203 studies, 20 of which were selected for systematic review; the final meta-analysis included seven studies. For qualitative CEUS, pooled sensitivity was 0.80 (95% CI, 0.72-0.87), pooled specificity was 0.83 (95% CI, 0.76-0.89), the pooled positive LR was 3.22 (95% CI, 1.67-6.18), the pooled negative LR was 0.24 (95% CI, 0.09-0.64), the pooled diagnostic odds ratio was 15.57 (95% CI, 4.94-49.03), and area under the curve was 0.894. For quantitative CEUS, pooled sensitivity was 0.77 (95% CI, 0.71-0.83), pooled specificity was 0.68 (95% CI, 0.62-0.73), the pooled positive LR was 2.34 (95% CI, 1.69-3.23), the pooled negative LR was 0.34 (95% CI, 0.25-0.47), the pooled diagnostic odds ratio was 7.06 (95% CI, 3.6-13.82), and area under the curve was 0.888.

CONCLUSIONS

CEUS is a promising noninvasive diagnostic modality for detecting intraplaque neovascularization. Standardization of quantitative analysis and visual grading classification is needed to increase reliability and reduce technical heterogeneity.

Quest for the Vulnerable Atheroma: Carotid Stenosis and Diametric Strain--A Feasibility Study

The Bernoulli effect may result in eruption of a vulnerable carotid atheroma, causing a stroke. We measured electrocardiography (ECG)-registered QRS intra-stenotic blood velocity and atheroma strain dynamics in carotid artery walls using ultrasonic tissue Doppler methods, providing displacement and time resolutions of 0.1 μm and 3.7 ms. Of 22 arteries, 1 had a peak systolic velocity (PSV) >280 cm/s, 4 had PSVs between 165 and 280 cm/s and 17 had PSVs <165 cm/s. Eight arteries with PSVs <65 cm/s and 4 of 9 with PSVs between 65 and 165 cm/s had normal systolic diametric expansion (0% and 7%) and corresponding systolic wall thinning. The remaining 10 arteries had abnormal systolic strain dynamics, 2 with diametric reduction (>-0.05 mm), 2 with extreme wall expansion (>0.1 mm), 2 with extreme wall thinning (>-0.1 mm) and 4 with combinations. Decreases in systolic diameter and/or extreme systolic arterial wall thickening may indicate imminent atheroma rupture.

The Use of Contrast-enhanced Ultrasonography for Imaging of Carotid Atherosclerotic Plaques: Current Evidence, Future Directions

Contrast-enhanced ultrasonography (CEUS) is a rapidly evolving modality for imaging carotid artery disease and systemic atherosclerosis. CEUS coupled with diagnostic ultrasonography predicts the degree of carotid artery stenosis and is comparable with computed tomography and magnetic resonance angiography. This article reviews the literature on the evolving role of CEUS for the identification and characterization of carotid plaques with an emphasis on detection of intra-plaque neovascularization and related high-risk morphologic features notably present in symptomatic patients. CEUS carotid imaging may play a prominent additive role in risk stratifying patients and serve as a powerful tool for monitoring therapeutic interventions.

Spatio-temporal Quantification of Carotid Plaque Neovascularization on Contrast Enhanced Ultrasound: Correlation with Visual Grading and Histopathology

OBJECTIVE/BACKGROUND

To evaluate whether carotid intraplaque neovascularization (IPN) can be accurately assessed by two types of quantitative analysis on contrast enhanced ultrasound (CEUS), the time intensity curve analysis and the analysis of contrast agent spatial distributions, and whether the quantitative analysis correlates with semiquantitative visual interpretation and histopathology.

METHODS

Forty-four plaques in 34 patients were included for CEUS examination. A three point score system (absent, moderate, and extensive) was used for semiquantitative grading of IPN. Eight spatial quantitative parameters were derived, including the IPN area ratio in plaque (AR) and the AR in plaque core (AR13). Two temporal quantitative parameters were obtained, namely the enhanced intensity in plaque (EI) and the enhanced intensity ratio (EIR). Histopathology with CD34 staining for quantification of microvessel density (MVD) was performed on 12 plaques excised by carotid endarterectomy.

RESULTS

Both spatial and temporal parameters were correlated with MVD on histology (AR: r = .854; AR13: r = .858; EI: r = .767; EIR: r = .750 [p < .01]), as well as with semiquantitative grading (p < .01). Five mutually independent factors were condensed from 10 interrelated parameters by using factor analysis, and they significantly predicted MVD with an radj value as high as .932 (p = .01).

CONCLUSION

Both spatial and temporal analysis on CEUS can accurately assess IPN. Combining them provides better IPN assessment and may be useful for plaque vulnerability evaluation and risk stratification.