Inter-Scan Reproducibility of Carotid Plaque Volume Measurements by 3-D Ultrasound

Validation and Reproducibility of Total Plaque Thickness in Carotid and Femoral Arteries Using Ultrasound

OBJECTIVE

Plaque burden quantification by ultrasound improves cardiovascular (CV) risk prediction. However, measuring total plaque volume (TPV) with 3-D ultrasound, the current gold standard, is time consuming. In the present study we investigated the reproducibility of weighted total plaque thickness (wTPT) measured by 2-D ultrasound and its correlation with TPV.

METHODS

Participants in an ongoing study of subclinical atherosclerosis and CV risk with no known atherosclerotic CV disease but who were found to have one or more plaques in carotid or femoral arteries by 2-D ultrasound were included. A total of 34 women and 26 men (mean age: 59.4 y, standard deviation: 8.7) underwent primary 2-D and 3-D ultrasound examinations. Participants then underwent a 2-D ultrasound examination by another radiologist blinded to the first radiologist's findings. Finally, all participants underwent a follow-up 2-D ultrasound by the first radiologist.

RESULTS

Comparison of wTPT measurements between the 2-D studies revealed no significant difference (mean difference: 0.29 mm, 95% confidence interval [CI]: -0.48 to 1.17). Inter-observer and intra-observer analyses revealed intraclass correlation coefficients of 0.97 (95% CI: 0.96-0.98) and 1.0 (95% CI: 0.99-1.00), respectively. wTPT correlated with TPV (Spearman's ρ = 0.98, 95% CI: 0.96-0.99). Elapsed time for assessing wTPT was less than that for TPV (mean difference: 36.1 min, 95% CI: 26.0-46.3).

CONCLUSION

wTPT had high reproducibility and correlation with TPV while requiring substantially less time. Future studies addressing the role of wTPT in predicting CV disease are needed.

Reliability of tomographic 3D ultrasound in measuring internal carotid artery plaque volume

BACKGROUND

Tomographic 3D ultrasound (t3DUS) is a promise imaging technique for quantifying carotid plaque through measuring the degree of stenosis and plaque volume. Carotid plaque volume (CPV) could add benefit in predicting the potential risk of stroke.

PURPOSE

To assess the reproducibility and accuracy of t3DUS for measuring CPV within the internal carotid artery in patients undergoing carotid endarterectomy.

MATERIAL AND METHODS

t3DUS was used to obtain CPV in vivo from 25 symptomatic patients prior to surgery. Ex vivo CPV from the carotid endarterectomy specimen was then measured using a validated saline displacement method as a reference standard. CPV for each patient was measured twice using both methods (total n = 50 per technique). Intraclass correlation coefficient (ICC) and Bland-Altman plot were used to establish bias and limit of agreement between CPV measurements.

RESULTS

There was an excellent agreement between t3DUS and reference test with respect to measuring CPV with an ICC value of 0.98 (95% confidence interval = 0.97-0.99, P < 0.001). Bias in measurements was 0.02 ± 0.11 cm3 (95% limit of agreement = -0.19 to 0.25). Intra-observer agreement of t3DUS CPV measurements was excellent with an ICC value of 0.95 (95% confidence interval = 0.92-0.97, P < 0.001). Bias in measurements was 0.004 ± 0.07 cm3 (95% limit of agreement = -0.14 to 0.15).

CONCLUSION

t3DUS is a reproducible imaging method and showed excellent agreement with the reference standard with respect to measuring CPV. These findings suggest that t3DUS has the potential to be a valuable non-invasive tool for assessing carotid plaque burden and predicting the risk of stroke.

Feasibility and Accuracy of Measuring Carotid Plaque Volume (Burden) With Contrast-Enhanced Tomographic 3D Ultrasound and Ultrasound Image Fusion

BACKGROUND

Stenosis severity has been the indication for carotid endarterectomy (CEA) for 4 decades, but the annual stroke risk in asymptomatic carotid stenosis >70% is under 2%. Atherosclerotic volume has emerged as a risk factor for future stroke, but needs to be measured noninvasively. Tomographic ultrasound (tUS) is a novel technology that assembles 3D images in seconds. We evaluated accuracy of measuring Carotid Plaque Volume (CPV) with tUS in patients undergoing CEA.

METHOD

Consecutive patients were imaged immediately before CEA by tUS and contrast-enhanced tUS (CEtUS). CPV was measured using tUS, CEtUS, and a fused images incorporating both tUS and CEtUS by trained vascular scientists. Precise volume of the endarterectomy specimen was measured using Archimedes technique.

RESULTS

Mean ± sd (range) CPV in 129 endarterectomy specimens was 0.75 ± 0.43 cm³ (0.10-2.47 cm³). Mean ± sd CPV measured by tUS (n = 114) was 0.87 ± 0.51 cm³, CEtUS (n = 104) was 0.75 ± 0.45 cm³ and with fusion (n = 95) was 0.83 ± 0.49 cm³. Differences between specimen volume and CPV measured by tUS (0.13 ± 0.24 cm³), CEtUS (-0.01 ± 0.21 cm³) or fusion (-0.08 ± 0.20) were clinically insignificant. Intra-/interobserver differences were minimal.

CONCLUSIONS

tUS accurately measures CPV with excellent intra-/interobserver agreement. CEtUS improves accuracy if precise CPV measurement is needed for research but tUS alone would be sufficient for population screening.

Differences in Carotid Artery Geometry and Flow Caused by Body Postural Changes and Physical Exercise

Different body postures and physical exercises may lead to changes in arterial geometry and hemodynamics, which may be associated with the distribution of atherosclerosis lesions. This study was aimed at investigating potential geometric and hemodynamic changes of the carotid bifurcation in different body postures and after high-intensity interval training (HIIT) workouts. Three-dimensional vascular ultrasound (3DVUS) and Doppler ultrasound images were acquired for 21 healthy participants (aged 29 ± 6 y, 14 men and 7 women) in different body postures (sitting and three sleeping postures [supine, left lateral and right lateral]) and after physical exercises. The common carotid artery (CCA) and internal carotid artery (ICA) diameters of the left carotid artery were found to increase significantly from supine to left lateral (both p <0.05). CCA diameters (p < 0.05) and ICA/CCA diameter ratio (p < 0.01) of the left carotid artery changed significantly from supine to sitting. Significant differences in CCA peak systolic velocity (CCA PSV, p < 0.001), CCA end-diastolic velocity (CCA EDV, p < 0.001), CCA pulsatility index (CCA PI, p < 0.001) and maximum velocity-based wall shear stress at the CCA (WSS_(max) at the CCA, p < 0.001) were identified in different postures. After physical exercises, significant increases were observed in the CCA diameter (p < 0.001), CCA PSV (p < 0.001), ICA PSV (p < 0.05), WSS_(max) at the CCA (p < 0.001) and WSS_(max) at the ICA (p < 0.05), as were significantly lower values of the CCA EDV (p < 0.01) and ICA/CCA PSV ratio (p < 0.05). Side-to-side differences were also detected in different postural change scenarios and after physical exercise; more significant differences were found to occur only in the left-sided carotid artery. Significant differences were identified under postural change and after physical exercise among healthy adults, suggesting that daily activity has an effect on the carotid bifurcation. These changes may be associated with formation and development of carotid atherosclerosis. Moreover, these side differences might be severe for patients and worth further attention in clinical practice.

New 3-Dimensional Volumetric Ultrasound Method for Accurate Quantification of Atherosclerotic Plaque Volume

BACKGROUND

Carotid and femoral plaque burden is a recognized biomarker of cardiovascular disease risk. A new electronic-sweep 3-dimensional (3D)-matrix transducer method can improve the functionality and image quality of vascular ultrasound atherosclerosis imaging.

OBJECTIVES

This study aimed to validate this method for plaque volume measurement in early and intermediate-advanced plaques in the carotid and femoral territories.

METHODS

Plaque volumes were measured ex vivo in pig carotid and femoral artery specimens by 3-dimensional vascular ultrasound (3DVUS) using a 3D-matrix (electronic-sweep) transducer and its associated 3D plaque quantification software, and were compared with gold-standard histology. To test the clinical feasibility and accuracy of the 3D-matrix transducer, an experiment was conducted in intermediate-high risk individuals with carotid and femoral atherosclerosis. The results were compared with those obtained using the previously validated mechanical-sweep 3D transducer and established 2-dimensional (2D)-based plaque quantification software.

RESULTS

In the ex vivo study, the authors assessed 19 atherosclerotic plaques (plaque volume, 0.76 µL-56.30 μL), finding strong agreement between measurements with the 3D-matrix transducer and the histological gold-standard (intraclass correlation coefficient [ICC]: 0.992; [95% CI: 0.978-0.997]). In the clinical analysis of 20 patients (mean age 74.6 ± 4.45 years; 40% men), the authors found 64 (36 carotid and 28 femoral) of 80 scanned territories with atherosclerosis (measured atherosclerotic volume, 10 μL-859 μL). There was strong agreement between measurements made from electronic-sweep and mechanical-sweep 3DVUS transducers (ICC: 0.997 [95% CI: 0.995-0.998]). Agreement was also high between plaque volumes estimated by the 2D and 3D plaque quantification software applications (ICC: 0.999 [95% CI: 0.998-0.999]). Analysis time was significantly shorter with the 3D plaque quantification software than with the 2D multislice approach with a mean time reduction of 46%.

CONCLUSIONS

3DVUS using new matrix transducer technology, together with improved 3D plaque quantification software, simplifies the accurate volume measurement of early (small) and intermediate-advanced plaques located in carotid and femoral arteries.

Echolucent carotid plaques becomes more echogenic over time - a 3D ultrasound study

OBJECTIVES

We aimed to detect changes in carotid artery atherosclerotic plaque volume and echogenicity over time in patients with an acute thromboembolic event and in patients with chronic atherosclerotic disease, both treated with statin, using a novel 3D ultrasound system.

METHODS

We included two cohorts of patients; 70 patients, naïve to statin treatment, admitted with acute, first-time myocardial infarction (aMI) and 69 patients who had been on statin treatment for a minimum of 6-months with chronic peripheral arterial disease (cPAD). 3D ultrasound examination was performed at baseline and after 3- and 12-months. Plaque volume was quantified in 3D ultrasound plaque acquisitions and echogenicity was assessed using gray-scale median (GSM) and normalized with adventitia as reference.

RESULTS

The aMI group had darker plaques than the cPAD group at baseline (mean GSM: 60.98, standard deviation (SD): 24.09 vs 71.75, SD: 21.55; P=0.006), 3-months (63.64, SD: 20.47 vs 73.44, SD: 20.46; P=0.006) and at 12-months follow-up (59.25, SD: 18.07 vs 71.02, SD: 22.31; P=0.004). The differences were not significant after adjusting for traditional risk factors. Dividing both groups by the median GSM, the darkest half of the aMI group's had an increase in GSM mainly within the first 3-months (10.49, CI95%: 2.45 - 18.53; P=0.012) and hereafter remained unchanged at 12-months follow-up (-0.53, CI95%: -7.28 - 6.22, P=0.875). In the darkest cPAD group GSM also increased within 3-months (8.14, CI95%: 1.85 - 14.32, P=0.012) and hereafter stabilised till 12-months (-2.54, CI95%: -9.62 - 4.53, P=0.475). Plaque volume did not change in the aMI group from baseline (median: 55.41mm³, interquartile range (IQR): 24.24 - 84.31) to 12-months (58.67mm³, IQR: 31.81 - 93.51) (P=0.220) whereas there was a small decrease in the cPAD group from baseline (71.63mm³, IQR: 40.12 - 135.61) to 12-months (67.73mm³, IQR: 31.00 - 122.38) (P=0.026).

CONCLUSION

Assessed with the novel 3D matrix ultrasound system echolucent carotid plaque had increasing GSM within a 3-months period, indicating stabilization of the more vulnerable plaques in aMI and cPAD patients. Plaque volume decreased over 12-months follow-up in long-term statin treated patient with cPAD, but not during the first 12 months statin therapy in patients with aMI.

Three-dimensional ultrasound for carotid vessel wall volume measurement

Objectives:

The intima–media thickness (IMT) of the carotid artery can now be detected on a three-dimensional (3D) plane. The 3D vessel wall volume (VWV) more accurately represents vascular conditions. Through 3D ultrasound, we established a standardized method for carotid VWV measurement.

Materials and Methods:

A total of thirty patients without stroke or cardiovascular disease who received carotid duplex sonography were retrospectively reviewed. Gray-scale 3D images from the distal common carotid artery (CCA) to internal carotid artery on both sides were acquired using a single-sweep 3D transducer and analyzed offline by using the vascular plaque quantification function of the Philips QLAB software. Then, the 3D IMT(QLAB intima–media thickness [QIMT]), total plaque volume (TPV), and VWV were measured by a neurologist and a technician, and the interobserver variability was assessed.

Results:

The mean two-dimensional (2D) carotid IMT was 0.65 ± 0.12 mm. The mean QIMT, TPV, and VWV measured by observer 1 were 0.68 ± 0.18 mm, 26 ± 12 mm³, and 94 ± 10 mm³, respectively. The Bland–Altman plot of the mean differences between the QIMT, TPV, and VWV values measured by observers 1 and 2 showed that those of observer 2 were within two standard deviations of those of observer 1. Intraclass correlation coefficients (ICCs) indicated strong correlations in QIMT (ICC = 0.76), TPV (ICC = 0.85), and VWV (ICC = 0.90; P < 0.001) between observers 1 and 2. Both 2D IMT and 3D QIMT exhibited a positive linear correlation with age.

Conclusion:

This study established a standardized VWV measurement through 3D ultrasound. Reasonable interobserver differences were obtained within a 95% limit of agreement and high reliability (ICC = 0.90). The VWV 1 cm from the CCA bifurcation was quantified with a mean value of 94.2 mm³. Further studies on the 3D ultrasound quantification of carotid arteries are warranted.

Carotid plaque inflammatory activity assessed by 2-[18F]FDG-PET imaging decrease after a neurological thromboembolic event

Background

Atherosclerotic plaque vulnerability is comprised by plaque composition driven by inflammatory activity and these features can be depicted with 3D ultrasound and 2-[18F]FDG-PET, respectively. The study investigated timely changes in carotid artery plaque inflammation and morphology after a thromboembolic event with PET/CT and novel ultrasound volumetric grayscale median (GSM) readings. Patients with a single hemisphere-specific neurological symptom and the presence of an ipsilateral carotid artery atherosclerotic plaque were prospectively included to both 2-[18F]FDG PET/CT and 3D ultrasound scans of the plaque immediately after their event and again three months later. On PET/CT images the maximum standardized uptake value (SUV_max) was measured and the volumetric ultrasound acquisitions were analyzed using a semiautomated software measuring GSM values.

Results

Baseline scans were performed by a mean of 7 days (range 2–14) after the symptom and again after 98 days (range 91–176). For the entire group (n = 14), we found a decrease in average SUV_max from baseline to follow-up of − 0.18 (95% confidence interval: − 0.34 to − 0.02, P = 0.034). GSM did not increase significantly over time (mean change: + 2.21, 95% confidence interval: − 17.02 to 21.44, P = 0.808).

Conclusion

A decrease in culprit lesion 2-[18F]FDG-uptake 3 months after an event indicates a decrease in inflammatory activity, suggesting that carotid plaque stabilization over time. 3D ultrasound morphological quantitative differences in GSM were not detectable after 3 months.

Patients with Unstable Atherosclerosis Have More Echolucent Carotid Plaques Compared with Stable Atherosclerotic Patients: A 3-D Ultrasound Study

Using a novel 3-D ultrasound system, we aimed to determine differences in carotid plaque size and echogenicity in two atherosclerotic groups. Seventy patients admitted with acute myocardial infarction (aMI) and 69 patients known with chronic peripheral arterial disease (cPAD) were included. The cPAD group had larger plaque volumes (median: 70.24 mm³, interquartile range [40.12-135.61] vs. 55.41 mm³ [4.24-84.31], p = 0.004), thicker plaques (2.45 mm [1.85-3.25] vs. 1.99 mm [1.55 - 2.64], p = 0.005) and higher gray-scale medians (GSMs) (mean: 71.75, standard deviation: 21.55 vs. 60.99 [24.09], p = 0.006) than the aMI group. After adjustment for traditional risk factors, the difference persisted for thickness and volume. The difference in GSM persisted after adjustment for volume only. Patients with stable atherosclerotic disease had larger and brighter carotid plaques compared with unstable atherosclerotic patients. 3-D ultrasound may prove useful in identifying thromboembolic risk.

The Role of Carotid and Femoral Plaque Burden in the Diagnosis of Coronary Artery Disease

PURPOSE OF REVIEW

With limitations of cardiovascular disease risk stratification by traditional risk factors, the role of noninvasive imaging techniques, such as vascular ultrasound, has emerged as a prominent utility for decision-making in coronary artery disease. A review of current guidelines and contemporary approaches for carotid and femoral plaque assessment is needed to better inform the diagnosis, management, and treatment of atherosclerosis in clinical practice.

RECENT FINDINGS

The recent consensus-based guidelines for carotid plaque assessment in coronary artery disease have been established, supported by some outcomes-based research. Currently, there is a gap of evidence on the use of femoral ultrasound to detect atherosclerosis, as well as predict adverse cardiovascular outcomes. The quantification and characterization of individualized plaque burden are important to stratify risk in asymptomatic or symptomatic atherosclerosis patients. Standardized quantification guidelines, supported by further outcomes-based research, are required to assess disease severity and progression.

Recommendations for the Assessment of Carotid Arterial Plaque by Ultrasound for the Characterization of Atherosclerosis and Evaluation of Cardiovascular Risk: From the American Society of Echocardiography

Atherosclerotic plaque detection by carotid ultrasound provides cardiovascular disease risk stratification. The advantages and disadvantages of two-dimensional (2D) and three-dimensional (3D) ultrasound methods for carotid arterial plaque quantification are reviewed. Advanced and emerging methods of carotid arterial plaque activity and composition analysis by ultrasound are considered. Recommendations for the standardization of focused 2D and 3D carotid arterial plaque ultrasound image acquisition and measurement for the purpose of cardiovascular disease stratification are formulated. Potential clinical application towards cardiovascular risk stratification of recommended focused carotid arterial plaque quantification approaches are summarized.

Non-invasive ultrasound-based imaging of atherosclerosis

Early detection of vascular damage in atherosclerosis and accurate assessment of cardiovascular risk factors are the basis for appropriate treatment strategies in cardiovascular medicine. The current review focuses on non-invasive ultrasound-based methods for imaging of atherosclerosis. Endothelial dysfunction is an accepted early manifestation of atherosclerosis. The most widely used technique to study endothelial function is non-invasive, flow-mediated dilation of the brachial artery under high-resolution ultrasound imaging. Although an increased intima-media thickness value is associated with future cardiovascular events in several large population studies, systematic use is not recommended in clinical practice for risk assessment of individual persons. Carotid plaque analysis with grey-scale median, 3-D ultrasound or contrast-enhanced ultrasound are promising techniques for further scientific work in prevention and therapy of generalized atherosclerosis.