Vulnerable plaque: Detection of agreement between multi-detector-row CT angiography and US-ECD

In vitro analysis of carotid lesions using a preliminary microwave sensor to detect vulnerable plaques: Correlation with histology, Duplex ultrasound examination, and computed tomography scanner: The Imaging and Microwave Phenotyping Assessment of Carotid stenosis Threat (IMPACT) study

Objective

Progress in best medical treatment have made identification of best candidates for carotid surgery more difficult. New diagnostic modalities could be helpful in this perspective. Microwaves (MWs) can quantify dielectric properties (complex relative permittivity) of biological tissues and MW technology has emerged as a promising field of research for distinguishing abnormal tissues from healthy ones. We here evaluated the ability of a dedicated MW sensor developed in our laboratory to identify vulnerable carotid lesions.

Methods

We included 50 carotid lesions in this study. The plaques were analyzed and classified preoperatively by ultrasound (US) examination, computed tomography angiography and tested postoperatively using a MW sensor. Histopathological analysis was used as a gold standard to separate vulnerable plaques (VPs) from nonvulnerable plaques (NVPs).

Results

VPs were more frequently types 2 or 3 plaques (on US examination), had a greater proportion of low (<60 Hounsfield unit) and moderate (60-130 Hounsfield unit) attenuation components (computed tomography angiography) and displayed higher dielectric constant values (MW) than NVPs, which had an opposite profile. NVPs were more frequently asymptomatic plaques compared with VPs (P = .035). Multivariate analysis showed that US examination and MW identified VPs with a sensitivity of 77% and a specificity of 76% (cutoff value, -0.045; area under the curve, 0.848; P < .0001).

Conclusions

We found that the presence of types 2 to 3 (on US examination) and high dielectric constant plaques in vitro was highly indicative of a VP based on histological analysis. Further studies are needed to determine the potential of MW to identify the most dangerous asymptomatic carotid lesions.

Imaging diagnosis and research progress of carotid plaque vulnerability

Ischemic stroke (IS) exhibits a high disability rate, mortality, and recurrence rate, imposing a serious threat to human survival and health. Its occurrence is affected by various factors. Although the previous research has demonstrated that the occurrence of IS is mainly associated with lumen stenosis caused by carotid atherosclerotic plaque (AP), recent studies have revealed that many patients will still suffer from IS even with mild carotid artery lumen stenosis. Blood supply disturbance causes 10% of IS to the corresponding cerebral blood supply area caused by carotid vulnerable plaque. Thrombus blockage of distal branch vessels caused by rupture of vulnerable carotid plaque is the main cause of ischemic stroke. Therefore, how to accurately evaluate vulnerable plaque and intervene as soon as possible is a problem that needs to be solved in clinic. The vulnerability of plaque is determined by its internal components, including thin and incomplete fibrous cap, necrotic lipid core, intra-plaque hemorrhage, intra-plaque neovascularization, and ulcerative plaque formation. The development of imaging technology enables the routine detection of AP vulnerability. By analyzing the pathological changes, characteristics, and formation mechanism of carotid plaque vulnerability, this article aims to explore the modern imaging methods which can be used to identify plaque composition and plaque vulnerability to provide a reference basis for disease diagnosis and differential diagnosis.

Multinational Survey of Current Practice from Imaging to Treatment of Atherosclerotic Carotid Stenosis

BACKGROUND

In the last 20-30 years, there have been many advances in imaging and therapeutic strategies for symptomatic and asymptomatic individuals with carotid artery stenosis. Our aim was to examine contemporary multinational practice standards.

METHODS

Departmental Review Board approval for this study was obtained, and 3 authors prepared the 44 multiple choice survey questions. Endorsement was obtained by the European Society of Neuroradiology, American Society of Functional Neuroradiology, and African Academy of Neurology. A link to the online questionnaire was sent to their respective members and members of the Faculty Advocating Collaborative and Thoughtful Carotid Artery Treatments (FACTCATS). The questionnaire was open from May 16 to July 16, 2019.

RESULTS

The responses from 223 respondents from 46 countries were included in the analyses including 65.9% from academic university hospitals. Neuroradiologists/radiologists comprised 68.2% of respondents, followed by neurologists (15%) and vascular surgeons (12.9%). In symptomatic patients, half (50.4%) the respondents answered that the first exam they used to evaluate carotid bifurcation was ultrasound, followed by computed tomography angiography (CTA, 41.6%) and then magnetic resonance imaging (MRI 8%). In asymptomatic patients, the first exam used to evaluate carotid bifurcation was ultrasound in 88.8% of respondents, CTA in 7%, and MRA in 4.2%. The percent stenosis upon which carotid endarterectomy or stenting was recommended was reduced in the presence of imaging evidence of "vulnerable plaque features" by 66.7% respondents for symptomatic patients and 34.2% for asymptomatic patients with a smaller subset of respondents even offering procedural intervention to patients with <50% symptomatic or asymptomatic stenosis.

CONCLUSIONS

We found heterogeneity in current practices of carotid stenosis imaging and management in this worldwide survey with many respondents including vulnerable plaque imaging into their decision analysis despite the lack of proven benefit from clinical trials. This study highlights the need for new clinical trials using vulnerable plaque imaging to select high-risk patients despite maximal medical therapy who may benefit from procedural intervention.

Association of Serum Lipoprotein-Associated Phospholipase A2 and A379V Gene Polymorphisms with Carotid Plaques

Objective: Lipoprotein-associated phospholipase A2 (LP-PLA2) is closely related to the development of atherosclerosis. The A379V gene polymorphism, located in exon 11 of the PLA2G7 gene, can affect LP-PLA2 levels and the inflammatory response. However, the association between the A379V polymorphism and formation of carotid plaques is unclear. Materials and Methods: A total of 516 ischemic stroke patients were classified according to carotid intima-media thickness as measured by ultrasound into the plaque group (n = 375, including 258 and 117 cases having vulnerable and stable plaques, respectively) and the nonplaque group (n = 141). The LP-PLA2 gene A379V polymorphism was determined by DNA sequencing, and Lp-PLA2 serum protein levels were determined simultaneously. Results: The serum Lp-PLA2 levels (p < 0.0005), CT+TT genotype frequency (odds ratio [OR]: 1.730, 95% confidence interval [CI]: 1.114-2.686, p = 0.014), and T allele frequency (OR: 1.592, 95% CI: 1.082-2.342, p = 0.018) in the plaque group were significantly higher than those in the nonplaque group. Lp-PLA2 serum levels in the vulnerable plaque subgroup were significantly higher than those in the stable plaque subgroup (p = 0.003). However, there were no significant differences in the frequency of the A379V polymorphism between the vulnerable and stable plaque subgroups. For all subjects, Lp-PLA2 serum levels for patients having a CC genotype were significantly lower than those for patients having a CT (p = 0.003), TT (p = 0.014), or CC+TT genotype (p = 0.001). Logistic regression showed that the Lp-PLA2 level was a risk factor for carotid plaque formation (OR: 1.024, 95% CI: 1.011-1.030, p = 0.001), but the A379V gene polymorphism was not (OR: 1.037, 95% CI: 0.357-3.012, p = 0.947). Conclusion: The A379V gene polymorphism might be associated with serum Lp-PLA2 levels and carotid plaque formation, but not with plaque vulnerability in a Chinese Han population. Serum Lp-PLA2 level was shown to be a risk factor for carotid plaque formation.

Carotid plaque composition by CT angiography in asymptomatic subjects: a head-to-head comparison to ultrasound

OBJECTIVES

To describe carotid plaque composition by computed tomography angiography (CTA) in asymptomatic subjects and to compare this to carotid plaque assessment by ultrasound, coronary plaques by coronary CTA, and inflammatory biomarkers in plasma.

METHODS

Middle-aged asymptomatic men, n = 43, without known cardiovascular disease and diabetes were included. Plaques in coronary and carotid arteries were evaluated using CTA. Total plaque volumes and plaque composition were assessed by a validated plaque analysis software. The 60% centile cut point was used to divide the population into low or high carotid total plaque volumes. The occurrence of carotid plaques and intima-media thickness (IMT) was estimated by ultrasound.

RESULTS

Carotid plaque by ultrasound was undiagnosed in 13 of 28 participants (46%) compared to CTA. Participants having carotid plaques by ultrasound had significantly higher absolute volumes of all CTA-defined carotid plaque subtypes and a higher fraction of calcified plaque. A high carotid total plaque volume was independently associated with age (adjusted odds ratio (OR) 1.41 [95% confidence interval (CI) 1.14-1.74], p = 0.001), IMT (adjusted OR 2.26 [95% CI 1.10-4.65], p = 0.03), and D-dimer (adjusted OR 8.86 [95% CI 1.26-62.37], p = 0.03). All coronary plaque features were significantly higher in participants with a high carotid total plaque volume.

CONCLUSION

The occurrence of carotid plaques in asymptomatic individuals is underestimated by ultrasound compared to plaque assessment by CTA. Carotid plaque composition by CTA is different in individuals with and without carotid plaques by ultrasound.

KEY POINTS

• The occurrence of carotid plaques by ultrasound was underestimated in 46% of participants who had plaques by carotid CTA. • Participants with carotid plaques by ultrasound had higher volumes of all plaque subtypes and a higher calcified plaque component as determined by carotid CTA compared to participants without carotid plaques by ultrasound. • A high carotid total plaque volume was independently associated with age, intima-media thickness, and D-dimer.

Imaging of the ulcerated carotid atherosclerotic plaque: a review of the literature

Abstract

Carotid atherosclerotic disease constitutes a major modern health problem whose diagnosis primarily relies on imaging. Grading of stenosis has been long used as the main factor for risk stratification and guiding of management. Nevertheless, increasing evidence has shown that additional plaque characteristics such as plaque composition and surface morphology play an important role in the occurrence of symptoms, justifying the term “vulnerable plaque”. Carotid plaque surface characteristics either in the form of surface irregularities or ulceration represent an important factor of vulnerability and are associated with the occurrence of neurologic symptoms. The delineation of the carotid plaque surface can be performed with virtually all imaging modalities including ultrasound, contrast-enhanced ultrasound, multi-detector computed tomography angiography, magnetic resonance angiography and the traditional reference method of angiography. These techniques have shown varying levels of diagnostic accuracy for the identification of ulcerated carotid plaques or plaque surface irregularities. As a consequence and given its high clinical significance, radiologists should be familiar with the various aspects of this entity, including its definition, classification, imaging findings on different imaging modalities and associations. The purpose of this review is to present the current literature regarding carotid plaque ulcerations and present illustrative images of ulcerated carotid plaques.

Teaching Points

• Plaque surface and ulceration represent risk factors for stroke in carotid disease.

• Characterisation of the plaque surface and ulcerations can be performed with every modality.

• US is the first-line modality for carotid disease and identification of ulcerations.

• The administration of microbubbles increases US accuracy for diagnosis of carotid ulceration.

• MDCTA and MRA are valuable for diagnosing ulceration and evaluating plaque composition.

The Accuracy of Noninvasive Imaging Techniques in Diagnosis of Carotid Plaque Morphology

BACKGROUND

The stroke is leading cause of death and severe disability worldwide. Atherosclerosis is responsible for over 30% of all ischemic strokes. It has been recently discovered that plaque morphology may help predict the clinical behavior of carotid atherosclerosis and determine the risk of stroke. The noninvasive imaging techniques have been developed to evaluate the vascular wall in an attempt to identify "vulnerable plaques".

AIM

The purpose is to investigate the diagnostic accuracy of ultrasound, multidetector computed tomography and magnetic resonance imaging in the identification of plaque components associated with plaque vulnerability.

MATERIAL AND METHODS

One hundred patients were admitted for carotid endarterectomy for high grade carotid stenosis. We defined the diagnostic value of B-mode ultrasound of carotid plaque in a half, and the accuracy of multidetector computed tomography and magnetic resonance imaging, in the other group, for detection of unstable carotid plaque. The reference standard was histology.

RESULTS

Sensitivity of ultrasound, multidetector computed tomography and magnetic resonance imaging is 94%, 83% and 100%, and the specificity is 93%, 73% and 89% for detection of unstable carotid plaque.

CONCLUSION

The ultrasound has high accuracy for diagnostics of carotid plaque morphology, magnetic resonance imaging has high potential for tissue differentiation and multidetector computed tomography determines precisely degree of stenosis and presence of ulceration and calcifications. The three noninvasive imaging modalities are complementary for optimal evaluation of the morphology of carotid plaque. This will help to determine the risk of stroke and to decide on the best treatment - carotid endarterectomy or carotid stenting.

The role of imaging in acute ischemic stroke

Neuroimaging has expanded beyond its traditional diagnostic role and become a critical tool in the evaluation and management of stroke. The objectives of imaging include prompt accurate diagnosis, treatment triage, prognosis prediction, and secondary preventative precautions. While capitalizing on the latest treatment options and expanding upon the "time is brain" doctrine, the ultimate goal of imaging is to maximize the number of treated patients and improve the outcome of one the most costly and morbid disease. A broad overview of comprehensive multimodal stroke imaging is presented here to affirm its utilization.

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.

Imaging of the carotid artery vulnerable plaque

Atherosclerosis involving the carotid arteries has a high prevalence in the population worldwide. This condition is significant because accidents of the carotid artery plaque are associated with the development of cerebrovascular events. For this reason, carotid atherosclerotic disease needs to be diagnosed and those determinants that are associated to an increased risk of stroke need to be identified. The degree of stenosis typically has been considered the parameter of choice to determine the therapeutical approach, but several recently published investigations have demonstrated that the degree of luminal stenosis is only an indirect indicator of the atherosclerotic process and that direct assessment of the plaque structure and composition may be key to predict the development of future cerebrovascular ischemic events. The concept of "vulnerable plaque" was born, referring to those plaque's parameters that concur to the instability of the plaque making it more prone to the rupture and distal embolization. The purpose of this review is to describe the imaging characteristics of "vulnerable carotid plaques."

CTA for screening of complicated atherosclerotic carotid plaque--American Heart Association type VI lesions as defined by MRI

BACKGROUND AND PURPOSE

High-resolution carotid MR imaging can accurately identify complicated American Heart Association lesion type VI plaques, which are characterized by thrombus, hemorrhage, or a ruptured fibrous cap. The purpose of this study is to evaluate whether CTA can be used as screening tool to predict the presence or absence of American Heart Association lesion type VI plaques as defined by high-resolution MR imaging.

METHODS

Fifty-one patients with suspected ischemic stroke or TIA with carotid CTA and carotid MR imaging performed within 14 days of the event/admission from April 2008 to December 2010 were reviewed. Vessels with stents or occlusion were excluded (n = 2). Each carotid artery was assigned an American Heart Association lesion type classification by MR imaging. The maximum wall thickness, maximum soft plaque component thickness, maximum calcified component thickness, and its attenuation (if the soft plaque component thickness was >2 mm) were obtained from the CTA.

RESULTS

The maximum soft plaque component thickness proved the best discriminating factor to predict a complicated plaque by MR imaging, with a receiver operating characteristic area under the curve of 0.89. The optimal sensitivity and specificity for detection of complicated plaque by MR imaging was achieved with a soft plaque component thickness threshold of 4.4 mm (sensitivity, 0.65; specificity, 0.94; positive predictive value, 0.75; and negative predictive value, 0.9). No complicated plaque had a soft tissue plaque thickness <2.2 mm (negative predictive value, 1) and no simple (noncomplicated) plaque had a thickness >5.6 mm (positive predictive value, 1).

CONCLUSIONS

Maximum soft plaque component thickness as measured by carotid CTA is a reliable indicator of a complicated plaque, with a threshold of 2.2 mm representing little to no probability of a complicated American Heart Association lesion type VI plaque.

First in vivo application of microwave radiometry in human carotids: a new noninvasive method for detection of local inflammatory activation

OBJECTIVES

This study investigated whether temperature differences: 1) can be measured in vivo noninvasively by microwave radiometry (MR); and 2) are associated with ultrasound and histological findings.

BACKGROUND

Studies of human carotid artery samples showed increased heat production. MR allows in vivo noninvasive measurement of internal temperature of tissues.

METHODS

Thirty-four patients undergoing carotid endarterectomy underwent screening of carotid atherosclerosis by ultrasound and MR. Healthy volunteers were enrolled as a control group. During ultrasound study, plaque texture, plaque surface, and plaque echogenicity were analyzed. Temperature difference (ΔT) was assigned as maximal minus minimum temperature. Association of thermographic with ultrasound and histological findings was performed.

RESULTS

ΔT was higher in atherosclerotic carotid arteries compared with the carotid arteries of controls (p < 0.01). Fatty plaques had higher ΔT compared with mixed and calcified (p < 0.01) plaques. Plaques with ulcerated surface had higher ΔT compared with plaques with irregular and regular surface (p < 0.01). Heterogeneous plaques had higher ΔT compared with homogenous (p < 0.01). Specimens with thin fibrous cap and intense expression of CD3, CD68, and vascular endothelial growth factor (VEGF) had higher ΔT compared with specimens with thick cap and low expression of CD3, CD68, and VEGF (p < 0.01).

CONCLUSIONS

MR provides in vivo noninvasive temperature measurements of carotid plaques, reflecting plaque inflammatory activation.