Characterization of carotid artery plaques using real-time compound B-mode ultrasound

Relationship between subclavian artery stenosis lesions and posterior circulation infarction: A preliminary study

OBJECTIVE

To investigate the correlation between subclavian steal syndrome and posterior circulation infarction using magnetic resonance imaging.

METHODS

A total of 294 patients diagnosed with subclavian steal syndrome using carotid Doppler ultrasonography were retrospectively included. According to the magnetic resonance imaging results, they were divided into posterior circulation infarction group and non- posterior circulation infarction group. Clinical indicators and carotid Doppler ultrasound parameters of patients were collected, and they were screened to establish a multiple logistic regression model. Receiver operating characteristic curve analysis of the established multiple logistic regression model was performed, and the area under the curve was calculated to evaluate the predictive efficiency of the model.

RESULTS

After statistical analysis of all parameters of the two groups of patients, a total of 10 parameters were included in multiple logistic regression to establish a model. The results showed a correlation between posterior circulation infarction and subclavian artery occlusion, grade III subclavian steal syndrome, gender, vulnerable plaques, National Institutes of Health Stroke Scale score, and age. After the receiver operating characteristic curve analysis of the model, the area under the curve for the multiple logistic regression model was 0.773.

CONCLUSION

The multiparameter composite model based on clinical baseline data and carotid Doppler ultrasonography parameters can effectively predict posterior circulation infarction and offer novel insight for clinical diagnosis.

Development of a Three-Dimensional Carotid Ultrasound Image Segmentation Workflow for Improved Efficiency, Reproducibility and Accuracy in Measuring Vessel Wall and Plaque Volume and Thickness

Automated segmentation of carotid lumen-intima boundary (LIB) and media-adventitia boundary (MAB) by deep convolutional neural networks (CNN) from three-dimensional ultrasound (3DUS) images has made assessment and monitoring of carotid atherosclerosis more efficient than manual segmentation. However, training of CNN still requires manual segmentation of LIB and MAB. Therefore, there is a need to improve the efficiency of manual segmentation and develop strategies to improve segmentation accuracy by the CNN for serial monitoring of carotid atherosclerosis. One strategy to reduce segmentation time is to increase the interslice distance (ISD) between segmented axial slices of a 3DUS image while maintaining the segmentation reliability. We, for the first time, investigated the effect of ISD on the reproducibility of MAB and LIB segmentations. The intra-observer reproducibility of LIB and MAB segmentations at ISDs of 1 mm and 2 mm was not statistically significantly different, whereas the reproducibility at ISD = 3 mm was statistically lower. Therefore, we conclude that segmentation with an ISD of 2 mm provides sufficient reliability for CNN training. We further proposed training the CNN by the baseline images of the entire cohort of patients for automatic segmentation of the follow-up images acquired for the same cohort. We validated that segmentation with this time-based partitioning approach is more accurate than that produced by patient-based partitioning, especially at the carotid bifurcation. This study forms the basis for an efficient, reproducible, and accurate 3DUS workflow for serial monitoring of carotid atherosclerosis useful in risk stratification of cardiovascular events and in evaluating the efficacy of new treatments.

Frailty in relation to the risk of carotid atherosclerosis and cardiovascular events in Chinese community-dwelling older adults: A five-year prospective cohort study

OBJECTIVE

To investigate the frailty, as estimated by accumulated health deficits, in association with the symptomatic carotid atherosclerosis and in relation to five-year cardiovascular (CVD) outcomes.

METHODS

This is a five-year prospective cohort study. Secondary analysis of data from the Beijing Longitudinal Study on Aging. Community-dwelling people aged 55+ years (n = 1257) have been followed between 2009 and 2014, and having carotid ultrasonography examinations with no CVD events at baseline. Frailty was quantified using the deficit accumulation-based frailty index (FI), constructed from 37 health deficits assessed at baseline. The association between the degree of frailty and carotid atherosclerosis was examined using odds ratios (OR) with multivariate logistic regression analyses. Effects of frailty on the probability of five-year cardiovascular events and mortality were evaluated using Cox proportional hazard ratios (HR). The analyses were adjusted for demographics, baseline carotid atherosclerosis status, and CVD risk factors.

RESULTS

The FI showed characteristic properties and was independently associated with the major carotid atherosclerosis symptoms, including carotid artery intima-media thickening (the most frail vs. the least frail: OR = 4.39: 1.98-7.82), carotid plaque (OR = 3.41: 1.28-6.54), and carotid plaque stability (OR = 1.19, 95 % CI: 1.01-3.59). Compared with the least frail, the most frail individuals were more likely to develop a cardiovascular event in five years, including myocardial infarction (HR = 3.38, 95 % CI = 1.84-6.19), stroke (HR = 1.26, 95 % CI = 1.00-5.87), CVD death (HR = 6.33, 95 % CI = 1.69-11.02), and all-cause death (HR = 5.95, 95 % CI = 2.74-8.95).

CONCLUSION

Deficit accumulation was closely associated with carotid atherosclerosis risks and strongly predicted five-year CVD events. The frailty index can be used to help identify older adults at high risks of CVD for improved preventive healthcare.

Quantification of Local Vessel Wall and Plaque Volume Change for Assessment of Effects of Therapies on Carotid Atherosclerosis Based on 3-D Ultrasound Imaging

We developed a new method to measure the voxel-based vessel-wall-plus-plaque volume (VWV). In addition to quantifying local thickness change as in the previously introduced vessel-wall-plus-plaque thickness (VWT) metric, voxel-based VWV further considers the circumferential change associated with vascular remodeling. Three-dimensional ultrasound images were acquired at baseline and 1 y afterward. The vessel wall region was divided into small voxels with the voxel-based VWV change (ΔVVol%) computed by taking the percentage volume difference between corresponding voxels in the baseline and follow-up images. A 3-D carotid atlas was developed to allow visualization of the local thickness and circumferential change patterns in the pomegranate versus the placebo groups. A new patient-based biomarker was obtained by computing the mean ΔVVol% over the entire 3-D map for each patient (ΔVVol%¯). ΔVVol%¯ detected a significant difference between patients randomized to pomegranate juice/extract and placebo groups (p = 0.0002). The number of patients required by ΔVVol%¯ to establish statistical significance was approximately a third of that required by the local VWT biomarker. The increased sensitivity afforded by the proposed biomarker improves the cost-effectiveness of clinical studies evaluating new anti-atherosclerotic treatments.

Effect of evolocumab on the progression of intraplaque neovascularization of the carotid based on contrast-enhanced ultrasonography (EPIC study): A prospective single-arm, open-label study

Background and Purpose: The aim of this study was to explore the effect of half a year of evolocumab plus moderate-intensity statin treatment on carotid intraplaque neovascularization (IPN) and blood lipid levels. Methods: A total of 31 patients with 33 carotid plaques who received evolocumab plus statin treatment were included. Blood lipid levels, B-mode ultrasound and contrast-enhanced ultrasonography (CEUS) at baseline and after half a year of evolocumab plus statin therapy were collected. The area under the curve (AUC) reflected the total amount of acoustic developer entering the plaque or lumen within the 180 s measurement period. The enhanced intensity reflected the peak blood flow intensity during the monitoring period, and the contrast agent area reflected the area of vessels in the plaques. Results: Except for high-density lipoprotein cholesterol (HDL-c), all other lipid indices decreased. Compared with baseline, low-density lipoprotein cholesterol (LDL-c) decreased by approximately 57% (p < 0.001); total cholesterol (TC) decreased by approximately 34% (p < 0.001); small dense low-density lipoprotein (sd-LDL) decreased by approximately 52% (p < 0.001); and HDL-c increased by approximately 20% (p < 0.001). B-mode ultrasonography showed that the length and thickness of the plaque and the hypoechoic area ratio were reduced (p < 0.05). The plaque area, calcified area ratio, and lumen cross-sectional area changed little (p > 0.05). CEUS revealed that the area under the curve of plaque/lumen [AUC (P/L)] decreased from 0.27 ± 0.13 to 0.19 ± 0.11 (p < 0.001). The enhanced intensity ratio of plaque/lumen [intensity ratio (P/L)] decreased from 0.37 ± 0.16 to 0.31 ± 0.14 (p = 0.009). The contrast agent area in plaque/area of plaque decreased from 19.20 ± 13.23 to 12.66 ± 9.59 (p = 0.003). The neovascularization score decreased from 2.64 ± 0.54 to 2.06 ± 0.86 (p < 0.001). Subgroup analysis based on statin duration (<6 months and ≥6 months) showed that there was no significant difference in the AUC (P/L) or intensity ratio (P/L) at baseline or after half a year of evolocumab treatment. Conclusion: This study found that evolocumab combined with moderate-intensity statins significantly improved the blood lipid profile and reduced carotid IPN. Clinical Trial Registration: https://www.clinicaltrials.gov; identifier: NCT04423406.

Five-year outcome of non-shunting and primary closure technique during carotid endarterectomy: a longitudinal cohort study

Objective

The long-term outcomes of primary carotid artery closure after carotid endarterectomy (CEA) have not been sufficiently studied. This prospective study was performed to analyze the 5-year outcomes of the non-shunting and primary arterial repair technique for CEA.

Methods

This study involved 150 patients who underwent CEA with the primary arterial closure technique without arterial shunting and completed 5 years of follow-up.

Results

The patients comprised 107 men and 43 women. The 30-day postoperative course was uneventful in 147 (98.0%) patients; however, cerebrovascular accidents occurred in 3 (2.0%) patients. With respect to the long-term results, most cases of restenosis at 5 years were <50%. Two patients developed asymptomatic total internal carotid artery occlusion. Eleven deaths occurred (mortality rate of 7.3%); one death (0.7%) occurred in the first 30 days.

Conclusion

Primary arteriotomy closure provides very good long-term patency. Routine use of patch closure is unnecessary.

Association between the triglyceride-glucose index and carotid plaque stability in nondiabetic adults

BACKGROUND AND AIMS

The rupture of an unstable atherosclerotic plaque is one of the major causes of thrombosis. However, there was limited evidence on the relationship of triglyceride-glucose (TyG) index, a simple surrogate marker of insulin resistance, with the carotid plaque stability. This study aimed to investigate the association between the TyG index and carotid plaque stability in nondiabetic adults.

METHODS AND RESULTS

The study included 4748 nondiabetic participants from the Asymptomatic Polyvascular Abnormalities Community study. Carotid plaque stability was assessed using ultrasonography. The TyG index was calculated as ln [fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. Logistic regression was used to evaluate the association of the TyG index with carotid plaque stability by calculating odds ratio (OR) and 95% confidence interval (CI). Of the 4748 participants, 1192 (25.11%) participants had stable carotid plaque, and 1247 (26.26%) had unstable carotid plaque. The prevalence of unstable carotid plaque substantially increased with increasing TyG index tertile (P for trend <0.0001). In the fully adjusted model, the OR comparing participants in the highest versus the lowest tertile of the TyG index was 1.31 (95% CI, 1.09-1.57). The optimal cutoff point for the TyG index in case of unstable carotid plaque was 8.56. However, we did not observe a statistically significant association between the TyG index and stable carotid plaque.

CONCLUSIONS

Elevated the TyG index was significantly associated with the prevalence of unstable carotid plaque in nondiabetic adults.

Reduction of TMAO level enhances the stability of carotid atherosclerotic plaque through promoting macrophage M2 polarization and efferocytosis

It has been demonstrated that trimethylamine N-oxide (TMAO) serves as a driver of atherosclerosis, suggesting that reduction of TMAO level might be a potent method to prevent the progression of atherosclerosis. Herein, we explored the role of TMAO in the stability of carotid atherosclerotic plaques and disclosed the underlying mechanisms. The unstable carotid artery plaque models were established in C57/BL6 mice. L-carnitine (LCA) and methimazole (MMI) administration were applied to increase and reduce TMAO levels. Hematoxylin and eosin (H&E) staining, Sirius red, Perl's staining, Masson trichrome staining and immunohistochemical staining with CD68 staining were used for histopathology analysis of the carotid artery plaque. M1 and M2 macrophagocyte markers were assessed by RT-PCR to determine the polarization of RAW264.7 cells. MMI administration for 2 weeks significantly decreased the plaque area, increased the thickness of the fibrous cap and reduced the size of the necrotic lipid cores, whereas 5-week of administration of MMI induced intraplate hemorrhage. LCA treatment further deteriorated the carotid atherosclerotic plaque but with no significant difference. In mechanism, we found that TMAO treatment impaired the M2 polarization and efferocytosis of RAW264.7 cells with no obvious effect on the M1 polarization. In conclusion, the present study demonstrated that TMAO reduction enhanced the stability of carotid atherosclerotic plaque through promoting macrophage M2 polarization and efferocytosis.

Atherosclerotic plaque instability in carotid arteries: miR-200c as a promising biomarker

Early recognition of vulnerable carotid plaques could help in identifying patients at high stroke risk, who may benefit from earlier revascularisation. Nowadays, different biomarkers of plaque instability have been unravelled, among these miRNAs are promising tools for the diagnosis and treatment of atherosclerosis. Inflammation, reactive oxygen species (ROS) and endothelial dysfunction play a key role in unstable plaques genesis. We showed that miR-200c induces endothelial dysfunction, ROS production and a positive mechanism among miR-200c and miR-33a/b, two miRNAs involved in atherosclerosis progression. The goal of the present study was to determine whether miR-200c could be an atherosclerosis biomarker. Carotid plaques of patients that underwent carotid endarterectomy (CEA) were assayed for miR-200c expression. miR-200c was up-regulated in carotid plaques (n=22) and its expression was higher in unstable (n=12) compared with stable (n=10) plaques. miR-200c positively correlated with instability biomarkers (i.e. monocyte chemoattractant protein-1, cicloxigenase-2 (COX2), interleukin 6 (IL6), metalloproteinase (MMP) 1 (MMP1), 9 (MMP9)) and miR-33a/b. Moreover, miR-200c negatively correlated with stability biomarkers (i.e. zinc finger E-box binding homoeobox 1 (ZEB1), endothelial nitric oxide (NO) synthase (eNOS), forkhead boxO1 (FOXO1) and Sirtuin1 (SIRT1)) (stable plaques = 15, unstable plaques = 15). Circulating miR-200c was up-regulated before CEA in 24 patients, correlated with miR-33a/b and decreased 1 day after CEA. Interestingly, 1 month after CEA, circulating miR-200c is low in patients with stable plaques (n=11) and increased to control levels, in patients with unstable plaques (n=13). Further studies are needed to establish whether miR-200c represents a circulating biomarker of plaque instability. Our results show that miR-200c is an atherosclerotic plaque progression biomarker and suggest that it may be clinically useful to identify patients at high embolic risk.

Improved plaque neovascularization following 2-year atorvastatin therapy based on contrast-enhanced ultrasonography: A pilot study

The present study assessed changes in carotid plaque neovascularization following long-term atorvastatin therapy (20 mg/day) using contrast-enhanced ultrasonography (CEUS). In this prospective case series, seven males (mean age, 68±9 years) and three females (mean age, 67±10 years) with a total of 13 carotid plaques underwent standard ultrasonography and CEUS at baseline, as well as after 1 and 2 years of atorvastatin treatment. The same plaques were then examined using real-time CEUS. The results of the enhanced intensity of plaque neovascularization at baseline were compared with results obtained during follow-up to examine the effects of long-term atorvastatin therapy. Standard ultrasonography revealed that 7 of the 13 carotid plaques were uniformly echolucent, whereas 6 carotid plaques were predominantly echolucent. CEUS revealed an enhanced intensity of 10.5±2.1 decibels (dB) prior to treatment, which decreased significantly to 7.3±2.6 dB following 2 years atorvastatin therapy (P<0.001). The ratio of enhanced intensity in the carotid artery lumen to that in the plaque was 3.10±1.10 at baseline and this value significantly increased to 4.96±2.98 following treatment for 2 years (P<0.001). The current pilot study therefore indicates that two-year atorvastatin therapy (20 mg/day) may reduce plaque neovascularization in the Chinese population.

Carotid Artery Plaques, Carotid Intima-Media Thickness, and Risk of Cardiovascular Events and All-Cause Death in Older Adults: A 5-Year Prospective, Community-Based Study

We assessed the effect of asymptomatic carotid atherosclerosis (CAS) on the development of cardiovascular diseases (CVDs) in a community-based population aged ≥55 years in China. A total of 1376 residents underwent CAS assessment by ultrasonography in July 2009. New CVD events, including stroke and coronary heart events, were collected at the follow-up survey at the end of 2014. After adjusting for baseline demographic characteristics and traditional CVD risk factors, the risk of CVD in patients with minimal CAS (mean common carotid artery intima-media thickness [CCA-IMT] ≥1 mm and no plaques), nonstenotic plaques (carotid stenosis <50%), and stenotic plaques (carotid stenosis ≥50%) was 0.8 (hazard ratio [HR]: 0.75, 95% confidence interval [CI]: 0.33-1.69), 2.0 (HR: 2.01, 95% CI: 1.24-3.25), and 3.1 (HR: 3.05, 95% CI: 1.62-5.74) times greater, respectively, than that of patients without CAS (CCA-IMT <1 mm and no plaques). Our findings provide direct evidence of the independent predictive value of the severity of asymptomatic CAS for the development of CVD in older Chinese adults.

Shear Wave Elastography Imaging for the Features of Symptomatic Carotid Plaques: A Feasibility Study

OBJECTIVES

Shear wave elastography (SWE) was performed to evaluate the Young's modulus of carotid plaques in patients presenting with cerebrovascular incidents, to estimate the clinical value and feasibility of this approach.

METHODS

Sixty-one patients (mean age, 65 years; 45 men) underwent common duplex ultrasonic examination and SWE evaluation. The patients were divided into the symptomatic and asymptomatic groups based on the presence of unilateral focal neurological symptoms. Elasticity and echogenicity of the carotid plaque was assessed by Young's modulus and Gray-Weale classification, respectively.

RESULTS

A total of 271 carotid plaques were assessed through duplex ultrasonic examination and SWE imaging. The Bland-Altman test revealed a perfect reproducibility of Young's modulus measurement using SWE. The interframe coefficient of variation was 16% within the 271 plaques. In the 61 representative plaques, significant correlations were found between Gray-Weale classification and mean Young's modulus (r = 0.728, P < .01) when the confounding factors were controlled. The mean Young's modulus of representative plaques in symptomatic group was lower than those in asymptomatic groups (mean Young's modulus: 81 kPa versus 115 kPa; P < .01). Logistic regression combined with receiver operating characteristic analysis suggested increased sensitivity and specificity for the identification of symptomatic carotid plaques when the mean Young's modulus was combined with stenosis rate.

CONCLUSIONS

Shear wave elastography can evaluate the Young's modulus of carotid plaque stably, and could serve as an additional method for the detection of symptomatic carotid plaques, which, in combination with common ultrasound, can promote the efficiency of differentiating symptomatic carotid plaques.

Nakagami-m Parametric Imaging for Atherosclerotic Plaque Characterization Using the Coarse-to-Fine Method

The Nakagami model was used to analyze the statistical differences in ultrasound backscattered signals between different plaque types. To improve image resolution, Nakagami-m parametric imaging using the coarse-to-fine method based on the maximum likelihood estimation (CTF-BOW) was proposed for atherosclerotic plaque characterization. Simulation results confirmed that the CTF-BOW method significantly outperforms the sliding window method in precision, smoothness and resolution. Preliminary in vivo results (n = 45) indicated that the ranges of the m parameters for calcified, mixed and echolucent plaques are, respectively, 0.2852-0.5225, 0.6532-0.8784 and 0.8908-1.4011, with no overlap. Results revealed that the CTF-BOW method significantly improves image resolution without sacrificing accuracy and can distinguish between calcified, mixed and echolucent plaques. Moreover, it was found that the parameter m is related to the composition of the plaque, indicating that Nakagami-m parametric imaging has the potential to characterize plaques.

Lipoprotein-Associated Phospholipase A2 and Risk of Carotid Atherosclerosis and Cardiovascular Events in Community-Based Older Adults in China

We explored the associations between lipoprotein-associated phospholipase A2 (Lp-PLA2) level and carotid atherosclerosis with all phenotypes and cardiovascular disease (CVD) events in Chinese older adults. A total of 1257 adults aged ≥55 years who were free of CVD were enrolled in this cohort study. Lipoprotein-associated phospholipase A2 level was evaluated in 3 categories: Lp-PLA2 < 175, 175≤ Lp-PLA2 < 223, and Lp-PLA2 ≥ 223 ng/mL. The highest level of Lp-PLA2 was independently associated with common carotid artery intima-media thickening (≥1.0 mm; odds ratio [OR]: 1.60, 95% confidence interval [CI]: 1.14-2.26) and carotid plaque (OR: 1.42, 95% CI: 1.01-1.99) in individuals without carotid artery stenosis. At the end of the 5-year follow-up, after adjustment for CVD risk factors and carotid atherosclerosis status, Lp-PLA2 had remained an independent predictor for myocardial infarction (MI; hazard ratio [HR]: 1.90, 95% CI: 1.02-3.55) and CVD death (HR: 1.78, 95% CI: 1.02-3.13). However, no association was found with stroke. Therefore, elevated Lp-PLA2 level in the older adults studied was associated with an increased risk of carotid atherosclerosis and MI and CVD mortality. Lipoprotein-associated phospholipase A2 assessment might be used for MI and CVD death risk prediction.

Semiautomatic quantification of carotid plaque volume with three-dimensional ultrasound imaging

OBJECTIVE

Vessel wall volume (VWV) assessed by three-dimensional duplex ultrasound (3DUS) imaging provides a more comprehensive measure of plaque burden than conventional two-dimensional measures of diameter stenosis. We previously demonstrated that manual outlining of the arterial lumen-intima boundary and outer wall boundary can be performed reliably on images obtained with a commercially available 3D-DUS transducer. Manual segmentation, however, is time consuming (∼45 minutes), limiting its clinical translation. We have developed a semiautomatic algorithm (manual selection of the carotid bifurcation image with subsequent automatic plaque outlining) to outline carotid plaques on 3DUS data sets. In this study, we investigated the accuracy, reproducibility, reliability, and time taken by this algorithm.

METHODS

3DUS data sets from 30 patients with asymptomatic ≥50% carotid stenosis underwent manual outlining of lumen-intima boundary and outer wall boundary to measure VWV. Two observers implemented a semiautomatic segmentation algorithm. The algorithm's accuracy was compared with manual outlining using the Pearson correlation coefficient. The Dice similarity coefficient (DSC) and modified-Hausdorff distance (MHD) were used to quantify the geometric similarity of the outlines. We also compared results after an intermediate stage of the algorithm vs the complete algorithm. Reproducibility and the least amount of detectable change in plaque volume were computed for each method. Intraobserver and interobserver metrics for each method were computed using the intraclass correlation coefficient (ICC), coefficient of variability (CV), minimum detectable change (MDC), and standard error of measurement (SEM) of the VWV.

RESULTS

Plaque volume estimates obtained from the semiautomatic algorithm were accurate compared with manual outlining. The Pearson correlation coefficient was 0.76 (P < .001), and measurements were geometrically similar (DSC, 0.85; MHD, 0.48 mm). The algorithm was more reproducible and reliable and could detect smaller changes in plaque volume on repeat imaging (low interobserver variability: ICC, 0.9; CV, 8.22%; MDC, 5.57%; SEM, 1.45%; DSC, 0.88; MHD, 0.43 mm). Intraobserver variability was even lower (ICC, 0.9; CV, 8%; MDC, 3.62%; SEM, 1.31%; DSC, 0.89; MHD, 0.37 mm). Plaque volume estimates at the intermediate stage of the algorithm matched results from the full algorithm (Pearson correlation coefficient, 0.76; DSC, 0.84; MHD, 0.52 mm). The intermediate approach, however, was less reliable than the full algorithm (interobserver: ICC, 0.81; CV, 11.7%; MDC, 9.58%; SEM, 3.46%; DSC, 0.88; MHD, 0.42 mm; intraobserver: ICC, 0.87; CV, 8.6%; MDC, 4.55%; SEM, 1.64%; DSC, 0.89; MHD, 0.38 mm). The full algorithm required ∼14 minutes to implement. However, a quick (7 minutes) and accurate assessment of VWV can be obtained by running only the intermediate stage of the algorithm, although with a loss in repeatability and reliability.

CONCLUSIONS

We present a unique algorithm to perform semiautomatic quantification of carotid plaque volume using 3DUS imaging. It is quick (mean time, 14 minutes), accurate, repeatable, and implementable in a clinical environment and in longitudinal studies tracking plaque progression. It reliably detects plaque volume changes as low as 4% to 6% with 95% confidence.

Observer performance in characterization of carotid plaque texture and surface characteristics with 3D versus 2D ultrasound

OBJECTIVE

To determine the reproducibility of three-dimensional (3D) ultrasound (US) over two-dimensional (2D) US in characterizing atherosclerotic carotid plaques using inter- and intra-observer agreement metrics.

METHODS

A Total of 51 patients with 105 carotid artery plaques were screened using 3D and 2D US probes attached to the same US scanner. Two independent observers characterized the plaques based on the morphological features namely echotexture, echogenicity and surface characteristics. The scores assigned to each morphological feature were used to determine intra- and inter-observer performance. The level of agreement was measured using Kappa coefficient.

RESULTS

The first observer with 2D US showed fair (k=0.4-0.59) and very strong (k>0.8) with 3D US intra-observer agreements using three morphological features. The second observer indicated moderate strong (k=0.6-0.79) with 2D US and very strong with 3D US (k>0.8) intra-observer performances. Moderate strong (k=0.6-0.79) and very strong (k>0.8) inter-observer agreements were reported with 2D US and 3D US respectively. The results with 2D and 3D US were correlated 62% using only echotexture and 56% using surface morphology coupled with echogenicity. 3D US gave a lower score than 2D 71% of the time (p=0.005) in disagreement cases.

CONCLUSION

High reproducibility in carotid plaque characterization was obtained using 3D US rather than 2D US. Hence, it can be a preferred imaging modality in routine or follow up plaque screening of patients with carotid artery disease.

A User Guide to Compound Imaging

Compound imaging is now available on several high-end ultrasound scanners. It takes different forms and refers to different methods of creating the ultrasound image. The aim of this article is to familiarize the reader with simple background information about how it works, and to provide a clinician's view of how, why and when to use it.

Contemporary carotid imaging: from degree of stenosis to plaque vulnerability

Carotid artery stenosis is a well-established risk factor of ischemic stroke, contributing to up to 10%-20% of strokes or transient ischemic attacks. Many clinical trials over the last 20 years have used measurements of carotid artery stenosis as a means to risk stratify patients. However, with improvements in vascular imaging techniques such as CT angiography and MR angiography, ultrasonography, and PET/CT, it is now possible to risk stratify patients, not just on the degree of carotid artery stenosis but also on how vulnerable the plaque is to rupture, resulting in ischemic stroke. These imaging techniques are ushering in an emerging paradigm shift that allows for risk stratifications based on the presence of imaging features such as intraplaque hemorrhage (IPH), plaque ulceration, plaque neovascularity, fibrous cap thickness, and presence of a lipid-rich necrotic core (LRNC). It is important for the neurosurgeon to be aware of these new imaging techniques that allow for improved patient risk stratification and outcomes. For example, a patient with a low-grade stenosis but an ulcerated plaque may benefit more from a revascularization procedure than a patient with a stable 70% asymptomatic stenosis with a thick fibrous cap. This review summarizes the current state-of-the-art advances in carotid plaque imaging. Currently, MRI is the gold standard in carotid plaque imaging, with its high resolution and high sensitivity for identifying IPH, ulceration, LRNC, and inflammation. However, MRI is limited due to time constraints. CT also allows for high-resolution imaging and can accurately detect ulceration and calcification, but cannot reliably differentiate LRNC from IPH. PET/CT is an effective technique to identify active inflammation within the plaque, but it does not allow for assessment of anatomy, ulceration, IPH, or LRNC. Ultrasonography, with the aid of contrast enhancement, is a cost-effective technique to assess plaque morphology and characteristics, but it is limited in sensitivity and specificity for detecting LRNC, plaque hemorrhage, and ulceration compared with MRI. Also summarized is how these advanced imaging techniques are being used in clinical practice to risk stratify patients with low- and high-grade carotid artery stenosis. For example, identification of IPH on MRI in patients with low-grade carotid artery stenosis is a risk factor for failure of medical therapy, and studies have shown that such patients may fair better with carotid endarterectomy (CEA). MR plaque imaging has also been found to be useful in identifying revascularization candidates who would be better candidates for CEA than carotid artery stenting (CAS), as high intraplaque signal on time of flight imaging is associated with vulnerable plaque and increased rates of adverse events in patients undergoing CAS but not CEA.

Association Between Kidney Dysfunction and Carotid Atherosclerosis in Community-Based Older Adults in China

We investigated the association between kidney dysfunction and carotid atherosclerosis in community-based older adults. This study consisted of 1257 participants, aged 55 years and older and free of cardiovascular disease. Kidney dysfunction was classified as mild, moderate, and severe (estimated glomerular filtration rate, 45-59, 30-44, and <30 mL/min/1.73 m2, respectively). We found that the mean common carotid artery intima–media thickness (CCA-IMT) progressively increased with decrement in kidney function ( P < .001). Even mild kidney dysfunction was significantly associated with CCA-IMT thickening (CCA-IMT ≥1.0 mm; odds ratio [OR] 1.52; 95% confidence interval [CI] 1.16-1.99) compared to normal kidney function. A significantly increased presence of heterogeneous plaque was observed in relation to decreased kidney function ( P for trend = .011), that is, even a mild kidney dysfunction was a potential independent risk factor for heterogeneous plaque (OR 1.43; 95% CI 1.04-1.98). Mild kidney dysfunction may be a predictor of early or accelerated carotid atherosclerosis in older adults.

Sex-associated differences in the modulation of vascular risk in patients with asymptomatic carotid stenosis

In this study, we aimed to identify determinants of the different sex-related stroke risk in subjects with asymptomatic internal carotid artery (ICA) stenosis. In all, 492 women (44.4%) and 617 men (55.6%), with unilateral ⩾ 60% asymptomatic ICA stenosis, were prospectively evaluated with a median follow-up of 37 months (interquartile range, 26 to 43). Vascular risk profile, plaque characteristics, stenosis progression, and common carotid artery intima-media thickness were investigated. Outcome measure was the occurrence of ischemic stroke ipsilateral to ICA stenosis. Myocardial infarction, contralateral stroke and transient ischemic attack were considered as competing events. The incidence rate of ipsilateral stroke over the entire follow-up period was 0.16%: 0.09% (95% confidence interval (CI) 0.05 to 0.15) in women and 0.22% (95% CI 0.17 to 0.29) in men (log-rank test, P<0.001). Stenosis progression significantly influenced the risk of ipsilateral stroke in both men (subhazard ratio, SHR, 8.99) and women (SHR 4.89). Stenosis degree (71% to 90%, SHR 2.35; 91% to 99%, SHR 3.38) and irregular plaque surface (SHR 2.32) were relevant risk factors for ipsilateral stroke only in men. Our findings suggest that characteristics of the stenosis and plaque exert a different effect in modulating vascular risk in the two sexes. Understanding sex differences in cardiovascular disease could help to target sex-specific future therapies.

Abnormal levels of serum anti-elastin antibodies in patients with symptomatic carotid stenosis

BACKGROUND AND OBJECTIVE

A correlation between the levels of antibodies to alpha-elastin (alpha-AEAb) and tropoelastin (tropo-AEAb) and the corresponding peptide concentration is found in human serum in health and disease. Serum elastin peptide and anti-elastin antibodies (AEAb) levels are age-related and vary with the stages of atherosclerotic vascular damage. This study aims to determine if elastin metabolism (assessed by the ratio of tropo-AEAb to alpha-AEAb) differs in patients with symptomatic carotid stenosis versus subjects with asymptomatic stenosis.

PATIENTS AND METHODS

Alpha-AEAb and tropo-AEAb were measured by ELISA in blood sera of 65 patients with ultrasound verified high-grade symptomatic carotid stenosis (resulting in stroke 1-7 days before measurement) compared to 51 patients with asymptomatic stenosis.

RESULTS

Serum anti-alpha-elastin IgG levels are extremely increased in symptomatic versus asymptomatic carotid stenosis. The ratio of tropo-AEAb (reflecting elastin synthesis) to alpha-AEAb (a function of elastin degradation) was 3.7 in symptomatic stenosis versus 14.2 in asymptomatic stenosis (p<0.001).

CONCLUSIONS

There is a significant difference in elastin metabolism in patients with symptomatic carotid stenosis versus asymptomatic stenosis. The ratio of tropo-AEAb to alpha-AEAb as an index of elastin synthesis/degradation proves useful in investigation of atherosclerotic lesions and may represent a new immunologic marker for carotid plaque destabilization.

Ultrasonographic markers of vascular risk in patients with asymptomatic carotid stenosis

Six-hundred twenty-one subjects with unilateral asymptomatic severe internal carotid artery (ICA) stenosis were prospectively evaluated with a median follow-up of 27 months (min=6, max=68). Vascular risk profile, plaque characteristic, stenosis progression, and common carotid artery intima-media thickness (IMT) were investigated in all patients. Outcome measures were occurrence of ischemic stroke ipsilateral to ICA stenosis and vascular death, while myocardial infarction, contralateral strokes, and transient ischemic attack were considered as competing events. A total of 99 subjects (15.9%) suffered from a vascular event. Among them, 39 were strokes ipsilateral to the stenosis (6.3%). Degree of stenosis, stenosis progression, and common carotid artery IMT resulted as independent predictive factors of ipsilateral stroke. Considering a stenosis of 60% to 70% as reference, a degree between 71% and 90% increased the risk by 2.45, while a degree between 91% and 99% increased the risk by 3.26. The progression of stenosis was a strong risk factor (hazard ratio=4.32). Finally, the role of carotid IMT was confirmed as crucial additional measure, with an increased risk by 25% for each 0.1 mm IMT increase. Our data suggest that IMT, stenosis progression and severity should be considered as risk factors for cerebrovascular events in asymptomatic subjects with severe ICA stenosis.

Comparative sonographic appearance of nephroliths and associated acoustic shadowing artifacts in conventional vs. spatial compound imaging

Spatial compound sonography improves visualization of tissue details and allows clearer delineation of structural margins. Improved image clarity is due to reduced speckling artifact; however, other types of acoustic shadowing artifacts may be unchanged or variably altered when conventional and spatial compound sonographic images are compared. Because intrarenal distal shadowing artifacts in conventional sonographic images are oftentimes the first or only evidence that a nephroliths is present, we compared the appearance and associated artifacts of nephroliths examined with both imaging modes. Consensus evaluation by two evaluators confirmed differences in appearance of nephroliths based on imaging mode. Nephroliths with conventional imaging mode were less hyperechoic and had better margin delineation while nephroliths were more hyperechoic and had less distinct margins with spatial compound imaging mode. Distal acoustic shadowing artifacts were present in 43% of spatial compound imaging mode vs. 86% of conventional imaging mode. When present in both imaging modes, intensity of these artifacts was weaker and the distance traveled was shorter in spatial compound imaging mode. Multiple diverging acoustic shadowing artifacts originating from a single source, the nephroliths were occasionally noted in spatial compound but not conventional imaging mode. These results demonstrate that the absence of distal acoustic shadowing cannot be used to exclude the presence of a nephrolith in dogs and cats. Optimal diagnosis of nephroliths, margin delineation, and visualization of the distal renal parenchyma requires paired radiography and sonography, and alternating between sonographic imaging modes is therefore suggested.

Atherosclerotic risk stratification strategy for carotid arteries using texture-based features

Plaques in the carotid artery result in stenosis, which is one of the main causes for stroke. Patients have to be carefully selected for stenosis treatments as they carry some risk. Since patients with symptomatic plaques have greater risk for strokes, an objective classification technique that classifies the plaques into symptomatic and asymptomatic classes is needed. We present a computer aided diagnostic (CAD) based ultrasound characterization methodology (a class of Atheromatic systems) that classifies the patient into symptomatic and asymptomatic classes using two kinds of datasets: (1) plaque regions in ultrasound carotids segmented semi-automatically and (2) far wall gray-scale intima-media thickness (IMT) regions along the common carotid artery segmented automatically. For both kinds of datasets, the protocol consists of estimating texture-based features in frameworks of local binary patterns (LBP) and Law's texture energy (LTE) and applying these features for obtaining the training parameters, which are then used for classification. Our database consists of 150 asymptomatic and 196 symptomatic plaque regions and 342 IMT wall regions. When using the Atheromatic-based system on semiautomatically determined plaque regions, support vector machine (SVM) classifier was adapted with highest accuracy of 83%. The accuracy registered was 89.5% on the far wall gray-scale IMT regions when using SVM, K-nearest neighbor (KNN) or radial basis probabilistic neural network (RBPNN) classifiers. LBP/LTE-based techniques on both kinds of carotid datasets are noninvasive, fast, objective and cost-effective for plaque characterization and, hence, will add more value to the existing carotid plaque diagnostics protocol. We have also proposed an index for each type of datasets: AtheromaticPi, for carotid plaque region, and AtheromaticWi, for IMT carotid wall region, based on the combination of the respective significant features. These indices show a separation between symptomatic and asymptomatic by 4.53 units and 4.42 units, respectively, thereby supporting the texture hypothesis classification.

Noninvasive imaging of carotid arteries in stroke: emerging value of real-time high-resolution sonography in carotid occlusion due to cardiac embolism

OBJECTIVE

Comprehension of the pathophysiologic characteristics of atherosclerosis has focused its attention on the study of dynamic and metabolic processes involving the vessel wall as possible causes of stroke. When compared with conventional radiologic techniques, sonography has the main advantage of being a real-time imaging modality. We report 2 acute stroke cases in which carotid sonography showed some dynamic features that could not be identified with computed tomography (CT) and magnetic resonance angiography (MRA).

METHODS

Carotid sonography with high-resolution probes (9-14 MHz) was compared with CT and MRA findings showing carotid axis occlusion in 2 patients with acute stroke.

RESULTS

In case 1, the internal carotid artery occlusion observed on CT and MRA was interpreted as a dissection on a clinical basis, but sonography showed a mobile embolus originating from the heart in the internal carotid artery. In case 2, the occlusion of the whole carotid axis observed on CT and MRA was instead related to a heart-originating embolus floating in the common carotid artery.

CONCLUSIONS

The evaluation of dynamic aspects of atherosclerosis is fundamental to understanding the pathophysiologic characteristics of stroke. Sonography is fundamental in carotid artery imaging for its possibility of showing dynamic processes that could be misdiagnosed with "static" imaging. The correct identification of the pathophysiologic characteristics of stroke in these cases could have led to different diagnostic and therapeutic algorithms.

Acquisition of 3-D arterial geometries and integration with computational fluid dynamics

A system for acquisition of 3-D arterial ultrasound geometries and integration with computational fluid dynamics (CFD) is described. The 3-D ultrasound is based on freehand B-mode imaging with positional information obtained using an optical tracking system. A processing chain was established, allowing acquisition of cardiac-gated 3-D data and segmentation of arterial geometries using a manual method and a semi-automated method, 3D meshing and CFD. The use of CFD allowed visualization of flow streamlines, 2-D velocity contours and 3-D wall shear stress. Three-dimensional positional accuracy was 0.17-1.8mm, precision was 0.06-0.47mm and volume accuracy was 4.4-15%. Patients with disease and volunteers were scanned, with data collection from one or more of the carotid bifurcation, femoral bifurcation and abdominal aorta. An initial comparison between a manual segmentation method and a semi-automated method suggested some advantages to the semi-automated method, including reduced operator time and the production of smooth surfaces suitable for CFD, but at the expense of over-smoothing in the diseased region. There were considerable difficulties with artefacts and poor image quality, resulting in 3-D geometry data that was unsuitable for CFD. These artefacts were exacerbated in disease, which may mean that future effort, in the integration of 3-D arterial geometry and CFD for clinical use, may best be served using alternative 3-D imaging modalities such as magnetic resonance imaging and computed tomography.

Three-dimensional ultrasound quantification of intensive statin treatment of carotid atherosclerosis

This study was designed to evaluate 3-D ultrasound (3DUS)-derived vessel wall volume (VWV), a 3-D measurement of the carotid artery intima and media, including atherosclerotic plaque, in patients enrolled in a randomized placebo-controlled three-month study of intensive atorvastatin treatment. Thirty-five subjects with carotid stenosis >60% who provided written informed consent and completed a randomized, double-blind, placebo-controlled study were evaluated at baseline and at three months after receiving either 80 mg atorvastatin (16 subjects, nine male, mean age 68+/-8.6 y) or placebo (19 subjects, 15 male, mean age 70+/-9.4 y) daily. 3DUS images were acquired and 3DUS VWV was manually segmented by a single observer. Individual lumen and wall segmentation contours were also used to generate carotid atherosclerosis thickness difference maps by establishing correspondence between points along the vessel wall and lumen segmentation contour surfaces, and digitally subtracting registered baseline and follow-up thickness maps. 3DUS VWV increased by 70+/-140 mm(3) (+4.9+/-10.3%) in the placebo group and decreased by 30+/-110 mm(3) (-1.4+/-7.7%) in the atorvastatin group (p<0.05). Two-dimensional maps generated from the VWV measurements show localized heterogeneity and vessel wall thickness changes for all subjects, mainly in the common carotid artery. Carotid 3DUS VWV is a quantitative measure of atherosclerosis burden including the intima, media and plaque, with sensitivity to detect changes over short periods of time. Quantitative VWV thickness difference maps provide visual evidence of the spatial and temporal dynamics of carotid artery changes.

Real time spatial compound ultrasound in the evaluation of meniscal injuries: a comparison study with conventional ultrasound and MRI

The aim of this study was to compare real time spatial compound ultrasound (RTCS) and conventional ultrasound with MRI in the evaluation of meniscal injuries. Thirty five patients with clinical suspicion of meniscal injury underwent ultrasound of knee alternating between conventional and compound sonography followed by MRI of the knee on a 1.5 T MR system. The images were compared for their quality and ability to detect meniscal tear. Compound ultrasound significantly improved definition of soft tissue planes, reduced speckle and other noise, improved contrast resolution (p value<0.05) with improved confidence in detection of tears in doubtful cases. Interobserver variability was seen only for conventional ultrasound and the sensitivity, specificity, accuracy were 83.3%, 87.5% and 85.7% for the first observer and 80%, 87.5% and 84.3% for second observer. For compound ultrasound it was same for both the observers with sensitivity, specificity and accuracy being 90% each. Although compound ultrasound improves image quality in the evaluation of meniscal injuries the benefit with respect to detection of tears is only marginal. It is a valuable tool for screening the patients before MRI and we recommend that instead of conventional ultrasound, compound ultrasound should be routinely used for sonographic evaluation of meniscal injuries.

Correlation of carotid plaque neovascularization detected by using contrast-enhanced US with clinical symptoms

PURPOSE

To determine the correlation between the degree of plaque enhancement with contrast agent microbubbles and clinical symptoms in patients with carotid atherosclerotic plaque.

MATERIALS AND METHODS

The study was approved by the hospital ethical committee, and informed consent was obtained from all patients. One hundred four patients (83 men: mean age, 64 years +/- 9 [standard deviation]; 21 women: mean age, 61 years +/- 10) with carotid plaques were studied with standard and contrast material-enhanced ultrasonography (US). Contrast enhancement in the plaque was evaluated with visual interpretation and quantitative analysis.

RESULTS

Among the 104 patients, 35 (34%) had transient ischemic attack and/or cerebrovascular ischemic stroke. Plaque enhancement was found in 28 (80%) of 35 symptomatic patients and in 21 (30%) of 69 asymptomatic patients (P < .001). Enhanced intensity in the plaque (13.9 dB +/- 6.4) and the ratio of enhanced intensity in the plaque to that in the lumen of the carotid artery (0.54 +/- 0.23) in symptomatic patients were significantly greater than those in asymptomatic patients (8.8 dB +/- 5.2 [P < .001] and 0.33 +/- 0.19 [P < .001], respectively). Sensitivity and specificity were 74% and 62%, respectively, for enhanced intensity in the plaque (cutoff value, 10.0 dB) and 74% and 75%, respectively, for ratio of enhanced intensity in the plaque to that in the lumen of the carotid artery (cutoff value, 0.46).

CONCLUSION

Symptomatic patients had more intense contrast agent enhancement in the plaque than asymptomatic patients, suggesting that contrast-enhanced carotid US may be used for plaque risk stratification.

Haemodynamics and blood flow measured using ultrasound imaging

Visualization of, and measurements related to, haemodynamic phenomena in arteries may be made using ultrasound systems. Most ultrasound technology relies on simple measurements of blood velocity taken from a single site, such as the peak systolic velocity for assessment of the degree of lumen reduction caused by an arterial stenosis. Real-time two-dimensional (2D) flow field visualization is possible using several methods, such as colour flow, blood flow imaging, and echo particle image velocimetry; these have applications in the examination of the flow field in diseased arteries and in heart chambers. Three-dimensional (3D) and four-dimensional ultrasound systems have been described. These have been used to provide 2D velocity profile data for the estimation of volumetric flow. However, they are limited for haemodynamic evaluation in that they provide only one component of the velocity. The provision of all seven components (three space, three velocity, and one time) is possible using image-guided modelling, in which 3D ultrasound is combined with computational fluid dynamics. This method also allows estimation of turbulence data and of relevant quantities such as the wall shear stress.

Atherosclerosis: contrast-enhanced MR imaging of vessel wall in rabbit model--comparison of gadofosveset and gadopentetate dimeglumine

PURPOSE

To investigate the potential of gadofosveset for contrast material-enhanced magnetic resonance (MR) imaging of plaque in a rabbit model of atherosclerosis.

MATERIALS AND METHODS

All experiments were approved by the animal ethics committee. Thirty-one New Zealand White rabbits were included in one of four study groups: animals with atherosclerosis imaged with gadofosveset (n = 10) or gadopentetate dimeglumine (n = 7) and control animals imaged with gadofosveset (n = 7) or gadopentetate dimeglumine (n = 7). Aortic atherosclerosis was induced through endothelial denudation combined with a cholesterol-enriched diet. Control rabbits underwent a sham surgical procedure and received a regular diet. After 8 weeks, pre- and postcontrast T1-weighted MR images of the aortic vessel wall were acquired. Relative signal enhancement was determined with dedicated software. Statistical analysis was performed by using a generalized linear mixed model. Immunohistochemical staining with CD31 and albumin was used to assess microvessel density and the albumin content of the vascular wall. Group differences were analyzed by using a chi(2) test. Gadofosveset spatial distribution and content within the vessel wall were determined with proton-induced x-ray emission (PIXE) analysis.

RESULTS

Postcontrast signal enhancement was significantly greater for atherosclerotic than for control animals imaged with gadofosveset (P = .022). Gadopentetate dimeglumine could not enable discrimination between normal and atherosclerotic vessel walls (P = .428). PIXE analysis showed higher amounts of gadopentetate dimeglumine than gadofosveset in both atherosclerotic and normal rabbit aortas. Immunohistochemical staining revealed the presence of albumin and increased microvessel density in the vascular walls of atherosclerotic rabbits.

CONCLUSION

These results suggest that gadofosveset can be used to differentiate between atherosclerotic and normal rabbit vessel walls.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/250/3/682/DC1.

Preliminary in vivo atherosclerotic carotid plaque characterization using the accumulated axial strain and relative lateral shift strain indices

In this paper, we explore two parameters or strain indices related to plaque deformation during the cardiac cycle, namely, the maximum accumulated axial strain in plaque and the relative lateral shifts between plaque and vessel wall under in vivo clinical ultrasound imaging conditions for possible identification of vulnerable plaque. These strain indices enable differentiation between calcified and lipidic plaque tissue utilizing a new perspective based on the stiffness and mobility of the plaque. In addition, they also provide the ability to distinguish between softer plaques that undergo large deformations during the cardiac cycle when compared to stiffer plaque tissue. Soft plaques that undergo large deformations over the cardiac cycle are more prone to rupture and to release micro-emboli into the cerebral bloodstream. The ability to identify vulnerable plaque, prone to rupture, would significantly enhance the clinical utility of this method for screening patients. We present preliminary in vivo results obtained from ultrasound radio frequency data collected over 16 atherosclerotic plaque patients before these patients undergo a carotid endarterectomy procedure. Our preliminary in vivo results indicate that the maximum accumulated axial strain over a cardiac cycle and the maximum relative lateral shift or displacement of the plaque are useful strain indices that provide differentiation between soft and calcified plaques.

Sonographic carotid plaque morphologic characteristics and vascular risk factors: results from a population study

OBJECTIVE

The role of vascular risk factors in atherosclerosis development is well established, whereas risk factors involved in determining plaque vulnerability are still a matter of debate. We investigated the vascular risk factor distribution in patients with carotid plaques.

METHODS

We consecutively assessed sonographic plaque morphologic characteristics, the degree of stenosis, and the common carotid artery intima-media thickness (IMT) in 1655 patients. Demographic data, a documented history of symptomatic cerebrovascular disease (CVD), and the presence of vascular risk factors were collected. According to literature, heterogeneous hypoechoic plaques with an irregular surface or ulcerations and those with a severe degree of stenosis (>or=70%) have been considered "complex" plaques at "major" risk of stroke; homogeneous hyperechoic plaques with smooth surface lesions have been considered "simple" plaques at minor risk.

RESULTS

Univariate analysis showed that all vascular risk factors were associated with the presence of carotid atherosclerotic lesions. Multiple logistic regression showed an independent association of hypertension and diabetes with complex plaques, which also had a thicker IMT. A history of CVD was observed more frequently in complex plaques, which had a higher stenosis percentage even after patients with a severe degree of stenosis (>or=70%) and indications for carotid surgery were excluded.

CONCLUSIONS

Hypertension and diabetes are related to a thicker IMT and more severe complex plaques, which may reflect the instability of atherosclerotic process. Because two-thirds of the patients with complex plaques were asymptomatic for CVD, this raises the importance of surveillance sonography to monitor plaque evolution for prevention of symptomatic CVD.

The use of Speckle Reduction Imaging (SRI) Ultrasound in the characterization of carotid artery plaques

BACKGROUND AND PURPOSE

Speckle Reduction Imaging is a new algorithm that improves the image quality of B-mode scanning by reducing the reverberation artifacts. In the present study the value of this method for the characterization of atherosclerotic plaques in the internal carotid artery was investigated.

METHODS

Two hundred and twenty two patients (161 men, 61 women; mean age 73 years) referred for carotid ultrasound evaluation were included in the study. Patients with plaques of the internal carotid artery as identified by conventional B-mode scanning were investigated also with the addition of Speckle Reduction Imaging (SRI) with the use of a 4-11-MHz wide band linear transducer. Plaque morphology was rated according to a standardized protocol by two independent observers.

RESULTS

For the determination of plaque echogenicity, the reproducibility of SRI (kappa=0.83) was higher than that of conventional B-mode ultrasound (kappa=0.68). The interobserver agreement for plaque surface characterization was also higher for SRI (kappa=0.8) than for conventional B-mode (kappa=0.61). At the evaluation of the image quality through a semiquantitative analysis, SRI was rated superior in the plaque texture resolution, plaque borders determination, vessel wall demarcation and fibrous cap depiction. In addition, the level of "speckle" was reduced with the use of SRI.

CONCLUSIONS

SRI is a technique that shows good general agreement with high-resolution B-mode and can be used for the characterization of atherosclerotic plaques in the carotid artery. Furthermore, because this advanced technique allows reduction of ultrasound artifacts, it improves the image quality allowing more precise visualization of plaque morphological details.

Molecular Imaging of Human Thrombus With Novel Abciximab Immunobubbles and Ultrasound

Background and Purpose— Molecular imaging of therapeutic interventions with targeted agents that simultaneously carry drugs or genes for local delivery is appealing. We investigated the ability of a novel microbubble carrier (immunobubble) for abciximab, a glycoprotein IIb/IIIa receptor inhibitor, for ultrasonographic molecular imaging of human clots.

Methods— Human thrombi were incubated with immunobubbles conjugated with abciximab. Control clots were incubated in either saline or with immunobubbles conjugated with nonspecific antibody. We evaluated immunobubble suspensions with variable concentrations of encapsulated gas and measured mean acoustic intensity of the incubated clots. In vivo molecular imaging of human thrombi with abciximab immunobubbles was evaluated in a rat model of carotid artery occlusion.

Results— Mean acoustic intensity was significantly higher for abciximab immunobubbles as compared with control immunobubbles under all conditions tested with maximum difference in intensity at a gas volume of 0.2 μL ( P =0.0013 for mechanical index 0.05, P =0.0001 for mechanical index 0.7). Binding of abciximab immunobubbles to clots in vitro led to enhanced echogenicity dependent on bubble concentration. In vivo ultrasonic detectability of carotid thrombi was significantly higher for clots targeted with abciximab immunobubbles ( P <0.05). Quantification of in vivo contrast enhancement displayed a highly significant increment for abciximab immunobubble-targeted clots compared with nonspecific immunobubble-targeted clots ( P <0.0001) and to native clots ( P <0.0001).

Conclusions— This study demonstrates the feasibility of using a therapeutic agent for selective targeting in vascular imaging. Abciximab immunobubbles improve visualization of human clots both in vitro and in an in vivo model of acute arterial thrombotic occlusion.

ARFI imaging for noninvasive material characterization of atherosclerosis

Cardiovascular disease (CVD) is the leading cause of death in the United States, with 70% of CVD mortalities the result of sequelae of atherosclerosis. An urgent need for enhanced delineation of vulnerable plaques has catalyzed the development of novel atherosclerosis imaging strategies that use X-ray computed tomography, magnetic resonance and ultrasound modalities. As suggested by the pathophysiology of plaque development and progression to vulnerability, insight to the focal material, i.e., mechanical, properties of arterial walls and plaques may enhance atherosclerosis characterization. We present acoustic radiation force impulse (ARFI) ultrasound in application to mechanically characterizing a raised focal atherosclerotic plaque in an iliac artery extracted from a relevant pig model. ARFI results are correlated to matched immunohistochemistry, indicating elastin and collagen composition. In regions of degraded elastin, slower recovery rates from peak ARFI-induced displacements were observed. In regions of collagen deposition, lower ARFI-induced displacements were achieved. This work demonstrates ARFI for characterizing the material nature of an atherosclerotic plaque.

Reliability of 3-D ultrasound measurements of cervical lymph node volume

This study was undertaken to evaluate the reliability of three-dimensional (3-D) ultrasound in measuring cervical lymph node volume. Ultrasound examination of the neck was performed on 15 healthy subjects (eight men and seven women). For each subject, the volume of cervical lymph nodes was measured twice with 3-D ultrasound by two operators, to evaluate the reproducibility of measurements (interoperator variability). 3-D ultrasound measurements of cervical node volume were performed with and without using SonoCT and XRES imaging. Each 3-D data set was reviewed and remeasured by the operators to evaluate the repeatability of measurements (intra-operator variability). Results showed that the reproducibility and repeatability of 3-D ultrasound volumetric measurements of cervical nodes was improved when SonoCT and XRES imaging were used. There was a high repeatability of 3-D ultrasound measurements of cervical node volume (> 90%). A high reproducibility of measurements was found in the posterior triangle nodes (90.3% - 90.9%). When SonoCT and XRES imaging were used with the scanning, there was a high reproducibility for parotid node measurements (87.4%) and a satisfactory level of reproducibility for submental (61.8%), submandibular (69.3%) and upper cervical node (79%) measurements. 3-D ultrasound is a useful and reliable method in measuring cervical lymph node volume. However, further studies to improve the reproducibility of 3-D ultrasound measurements of submental, submandibular and upper cervical node volume are suggested.

The impact of carotid plaque presence and morphology on mortality outcome in cardiological patients

Background

Carotid plaque severity and morphology can affect cardiovascular prognosis.

We evaluate both the importance of echographically assessed carotid artery plaque geometry and morphology as predictors of death in hospitalised cardiological patients.

Methods

541 hospitalised patients admitted in a cardiological division (age = 66 ± 11 years, 411 men), have been studied through ultrasound Duplex carotid scan and successively followed-up for a median of 34 months. Echo evaluation assessed plaque severity and morphology (presence of heterogeneity and profile).

Results

361 patients showed carotid stenosis (67% with <50% stenosis, 18% with 50–69% stenosis, 9% with >70% stenosis, 4% with near occlusion and 2% with total occlusion). During the follow-up period, there were 83 all-cause deaths (15% of the total population). Using Cox's proportional hazard model, age (RR 1.06, 95% CI 1.03–1.09, p = 0.000), ejection fraction > 50% (RR = 0.62, 95% CI 0.4–0.96, p = 0.03), treatment with statins (RR = 0.52, 95% CI 0.29–0.95, p = 0.34) and the presence of a heterogeneous plaque (RR 1.6; 95% CI, 1.2 to 2.14, p = 0.002) were independent predictors of death. Kaplan – Meier survival estimates have shown the best outcome in patients without plaque, intermediate in patients with homogeneous plaques and the worst outcome in patients with heterogeneous plaques (90% vs 79% vs 73%, p = 0.0001).

Conclusion

In hospitalised cardiological patients, carotid plaque presence and morphology assessed by ultrasound are independent predictors of death.