Evaluation of 3D multi-contrast carotid vessel wall MRI: a comparative study

Pathophysiology of carotid atherosclerosis: Calcification, intraplaque haemorrhage and pulse pressure as key players

PURPOSE

Intraplaque haemorrhage (IPH) is a well-known risk factor for faster plaque progression (volume increase); however, its etiology is unclear. We aimed at determining what other local plaque- and systemic factors contribute to plaque progression and to the development and progression of IPH.

METHODS

We examined 98 asymptomatic participants with carotid plaque using serial multi-contrast magnetic resonance imaging. We measured the percent of wall volume (%WV=100 x [wall volume] / [total vessel volume]) and measured IPH and calcification volumes. We used generalized estimating equations-based regression to analyze predictors of %WV change and new IPH while accounting for covariates (sex, age and statin use), and multiple non-independent observations per participant.

RESULTS

Total follow-up was 1.8 ± 0.8 years on average. The presence of IPH (β: 0.6 %/y, p = 0.033) and calcification (β: 1.2 %/y, p = 0.028) were each associated with faster plaque progression. New IPH, detected on a subsequent scan in 4 % of arteries that did not initially have IPH, was associated with larger calcification (odds ratio [OR]: 2.6 per 1-SD increase, p = 0.038) and higher pulse pressure (OR: 2.3 per 1-SD increase, p = 0.016). Larger calcification was associated with greater increases in pulse pressure (β: 1.4 mm Hg/y per 1-SD increase, p = 0.040).

CONCLUSIONS

IPH and calcification are each independently associated with faster plaque progression. The association of carotid calcification to increased pulse pressure and new IPH development suggests a possible mechanism by which calcification drives IPH development and plaque progression.

Systematic Review on Magnetic Resonance Angiography with Vessel Wall Imaging for the Characterization of Symptomatic Carotid Artery Plaque

BACKGROUND

To perform a systematic literature review to assess the usefulness of performing magnetic resonance angiography (MRA) with vessel wall imaging (VWI) sequences for the assessment of symptomatic carotid artery plaques and the identification of risky plaque features predisposing for stroke.

METHODS

We performed a systematic review of the literature pertaining to MRA with VWI techniques in patients with carotid artery disease, focusing on symptomatic patients' plaque features and morphology. Independent reviewers screened and analyzed data extracted from eligible studies, and a modified Newcastle-Ottawa Scale was used to appraise the quality of the design and content of the selected manuscripts to achieve an accurate interpretation.

RESULTS

This review included nineteen peer-reviewed manuscripts, all of them including MRA and VWI assessments of the symptomatic carotid artery plaque. We focused on patients' comorbidities and reviewed plaque features, including intraplaque hemorrhage, a lipid-rich necrotic core, a ruptured fibrous cap, and plaque ulceration.

CONCLUSIONS

MRA with VWI is a useful tool in the evaluation of carotid artery plaques. This imaging technique allows clinicians to identify plaques at risk of causing a neurovascular event. The presence of intraplaque hemorrhage, plaque ulceration, a ruptured fibrous cap, and a lipid-rich necrotic core are associated with neurovascular symptoms. The timely identification of these features could have a positive impact on neurovascular event prevention.

Vessel wall MR imaging of aortic arch, cervical carotid and intracranial arteries in patients with embolic stroke of undetermined source: A narrative review

Despite advancements in multi-modal imaging techniques, a substantial portion of ischemic stroke patients today remain without a diagnosed etiology after conventional workup. Based on existing diagnostic criteria, these ischemic stroke patients are subcategorized into having cryptogenic stroke (CS) or embolic stroke of undetermined source (ESUS). There is growing evidence that in these patients, non-cardiogenic embolic sources, in particular non-stenosing atherosclerotic plaque, may have significant contributory roles in their ischemic strokes. Recent advancements in vessel wall MRI (VW-MRI) have enabled imaging of vessel walls beyond the degree of luminal stenosis, and allows further characterization of atherosclerotic plaque components. Using this imaging technique, we are able to identify potential imaging biomarkers of vulnerable atherosclerotic plaques such as intraplaque hemorrhage, lipid rich necrotic core, and thin or ruptured fibrous caps. This review focuses on the existing evidence on the advantages of utilizing VW-MRI in ischemic stroke patients to identify culprit plaques in key anatomical areas, namely the cervical carotid arteries, intracranial arteries, and the aortic arch. For each anatomical area, the literature on potential imaging biomarkers of vulnerable plaques on VW-MRI as well as the VW-MRI literature in ESUS and CS patients are reviewed. Future directions on further elucidating ESUS and CS by the use of VW-MRI as well as exciting emerging techniques are reviewed.

Associations between carotid atherosclerotic plaque characteristics determined by magnetic resonance imaging and improvement of cognition in patients undergoing carotid endarterectomy

BACKGROUND

To determine the predictive value of carotid plaque characteristics for the improvement of cognition in patients with moderate-to-severe carotid stenosis after carotid endarterectomy (CEA), using vessel wall magnetic resonance imaging (MRI).

METHODS

This was a prospective cohort study. Patients with unilateral, moderate-to-severe carotid stenosis referred to the Peking University Third Hospital for CEA were prospectively recruited and underwent carotid vessel wall MRI within 1 week before CEA. We performed Montreal Cognitive Assessment (MoCA) within 1 week before and 3-4 days after CEA. The morphological and compositional characteristics of carotid plaques on MRI were evaluated. Improvement of cognition was defined as >10% increase of the total MoCA score after CEA compared with baseline. Carotid plaque characteristics were compared between patients with and without cognitive improvement.

RESULTS

In total, 105 patients (91 males; mean age, 65.5±8.4 years) were included. The volume {48.0 [interquartile range (IQR), 21.0 to 91.6] vs. 16.3 (IQR, 8.1 to 53.1) mm3; P=0.005} and cumulative slice [4.0 (IQR, 3.0 to 7.0) vs. 3.0 (IQR, 2.0 to 5.0); P=0.019] of carotid calcification, and maximum percentage of calcification area [13.1% (IQR, 6.0% to 19.8%) vs. 6.2% (IQR, 3.7% to 10.8%); P=0.004] were significantly smaller in participants with cognitive improvement compared to those without. Univariate logistic regression analysis showed that volume [odds ratio (OR) =0.994; 95% confidence interval (CI): 0.989 to 1.000; P=0.043] and cumulative slice (OR =0.823; 95% CI: 0.698 to 0.970; P=0.020) of carotid calcification, and maximum percentage of calcification area (OR =0.949; 95% CI: 0.909 to 0.991; P=0.018) were significantly correlated with cognitive improvement. After adjusting for confounding factors, these associations remained statistically or marginally significant (volume: OR =0.994; 95% CI: 0.988 to 1.000; P=0.057; maximum percentage of calcification area: OR =0.937; 95% CI: 0.890 to 0.987; P=0.014; and cumulative slice: OR =0.791; 95% CI: 0.646 to 0.967; P=0.022). No significant associations were found between other plaque characteristics and cognitive improvement (all P>0.05).

CONCLUSIONS

More than half of the participants with unilateral, moderate-to-severe carotid atherosclerotic stenosis had cognitive improvement. The size of calcification might be an effective indicator of cognitive improvement after CEA.

High-resolution intravascular magnetic resonance imaging of the coronary artery wall at 3.0 Tesla: toward evaluation of atherosclerotic plaque vulnerability

Background

To validate the feasibility of generating high-resolution intravascular 3.0 Tesla (T) magnetic resonance imaging of the coronary artery wall to further plaque imaging.

Methods

A receive-only 0.014-inch diameter magnetic resonance imaging guidewire (MRIG) was manufactured for intravascular imaging within a phantom experiment and the coronary artery wall of the swine. For coronary artery wall imaging, both high-resolution images and conventional resolution images were acquired. A 16-channel commercial surface coil for magnetic resonance imaging was employed for the control group.

Results

For the phantom experiment, the MRIG showed a higher signal-to-noise ratio than the surface coil. The peak signal-to-noise ratio of the MRIG and the surface coil-generated imaging were 213.6 and 19.8, respectively. The signal-to-noise ratio decreased rapidly as the distance from the MRIG increased. For the coronary artery wall experiment, the vessel wall imaging by the MRIG could be identified clearly, whereas the vessel wall imaging by the surface coil was blurred. The average signal-to-noise ratio of the artery wall was 21.1±5.40 by the MRIG compared to 8.4±2.19 by the surface coil, where the resolution was set at 0.2 mm × 0.2 mm × 2 mm. As expected, the high-resolution sequence clearly showed more details than the conventional resolution sequence set at 0.7 mm × 0.7 mm × 2.0 mm. Histological examination showed no evidence of mechanical injuries in the target vessel walls.

Conclusions

The study validated the feasibility of generating magnetic resonance imaging (MRI) at 0.2 mm × 0.2 mm × 2 mm for the coronary artery wall using a 0.014 inch MRIG.

Geometrical characteristics associated with atherosclerotic disease in the basilar artery: a magnetic resonance vessel wall imaging study

Background

Vascular geometry may play an important role in the development of atherosclerosis. This study aimed to investigate the relationships between the geometrical characteristics of basilar artery (BA) and the presence, burden, and distribution of BA plaques using magnetic resonance vessel wall imaging.

Methods

Patients with cerebrovascular symptoms in the posterior circulation were recruited and underwent magnetic resonance imaging. The BA's geometrical characteristics, including actual length, straightened length, tortuosity, lateral basilar artery-vertebral artery (VA) angle, lateral mid-BA angle, and BA convexity, were measured. The presence of plaques, stenosis, and plaque burden, including mean and maximal wall thickness, were evaluated. The BA's cross-sectional vessel wall was divided into 4 quadrants: dorsal, ventral, right, and left quadrant. The distribution of BA plaques was analyzed.

Results

Of 344 recruited patients (mean age: 68.1±11.1 years; 200 males), 100 (29.1%) had BA plaques. Patients with BA plaques had higher tortuosity of the BA (13.6±9.0 vs. 9.7±7.7, P<0.001) compared to those without BA plaques. Multivariate regression analysis showed that tortuosity of the BA was associated with the presence of BA plaques (OR, 1.641; 95% CI, 1.232 to 2.186; P=0.001) and mean wall thickness (β, 0.045; 95% CI, 0.008 to 0.081; P=0.017). The plaque distribution in the left wall and right wall of BA was more frequent in patients with right (P=0.006) and left (P<0.001) convex BA, respectively.

Conclusions

The BA's geometrical characteristics, particularly tortuosity and convexity, are independently associated with the presence, burden, and distribution of plaques in the BA.

Circumferential degree of carotid calcification is associated with new ischemic brain lesions after carotid artery stenting

Background

The relationship between plaque calcification and new ischemic brain lesions after carotid artery stenting (CAS) remains controversial. The purpose of this study was to determine if the circumferential degree of carotid calcification is associated with new ischemic brain lesions on diffusion-weighted imaging (DWI) after CAS.

Methods

A total of 96 patients with carotid stenosis of ≥50% who underwent CAS were enrolled in the study. All patients underwent preoperative carotid computed tomography (CT), and preoperative and postoperative brain MRI. The brain MRI sequences included T1WI, T2WI, T2-fluid-attenuated inversion recovery (FLAIR), and DWI. The location, circumferential degree, volume, percentage volume, maximum density, mean density, Agatston score of carotid calcification, and total plaque volume were assessed and compared between patients with and without new ischemic brain lesions after CAS. Univariate and multivariate analyses were performed to evaluate predictors of new ischemic brain lesions.

Results

All of the 96 patients (67.8±6.8 years of age, 83.3% men) were included in the analysis. New ischemic brain lesions on DWI were observed in 40 patients (41.7%). Patients with new ischemic brain lesions after CAS had a larger circumferential degree of calcification than those without new ischemic brain lesions (P<0.001). There was only a possible trend toward significance for the percentage volume of calcification between the two groups with and without new brain ischemic lesions (P=0.07). No significant differences were found regarding the location (P=0.18), volume (P=0.37), maximum density (P=0.44), mean density (P=0.39), Agatston score (P=0.28), and total plaque volume (P=0.33) of carotid calcification between the DWI+ and DWI- groups. In the multivariate analysis, an increased risk of new ischemic brain lesions was observed in patients with a high score for the circumferential degree of calcification [score 3; odds ratio (OR): 10.7, P<0.001; score 4, OR: 11.7, P=0.038].

Conclusions

The circumferential degree of carotid calcification was associated with new ischemic brain lesions after CAS. CAS should be avoided if possible for carotid stenosis with large circumferential calcified plaques.

Assessment of carotid atherosclerotic plaque using 3D motion-sensitized driven-equilibrium prepared rapid gradient echo: a comparative study

Background

3D motion-sensitized driven-equilibrium prepared rapid gradient echo (MERGE) can characterize carotid atherosclerotic plaque morphology and composition. The present study aimed to evaluate its performance by comparing it with reference images and assessing the inter-reader agreement.

Methods

Eighty-four patients were prospectively recruited and scanned with 3D MERGE. Two trained magnetic resonance imaging (MRI) readers measured and calculated the maximum wall thickness (WT), maximum vessel diameter, total vessel area, lumen area, wall area, normalized wall index, plaque volume, intraplaque hemorrhage (IPH) volume, and calcification volume independently. IPH, calcification, mixed calcification, and ulceration were identified. The intraclass correlation coefficient (ICC) with 95% confidence interval (CI) was used to assess the inter-reader agreement. MERGE performance was assessed in terms of sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, kappa value (κ), and the results of the Bland-Altman analysis and compared with reference images.

Results

MERGE showed excellent inter-reader agreement (All ICCs >0.90). MERGE and simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP) showed excellent agreement in detecting IPH (κ=0.938) and measuring IPH volume (ICC =0.995; 95% CI: 0.991-0.997). MERGE and computed tomography angiography (CTA) showed strong consistency in detecting calcification (κ=0.814) and mixed calcification (κ=0.972), and in measuring calcification volume (ICC =0.996; 95% CI: 0.993-0.997). MERGE and digital subtraction angiography (DSA) showed relatively strong consistency in identifying ulceration (κ=0.737).

Conclusions

MERGE showed excellent performance in identifying and measuring IPH and calcification in carotid atherosclerotic plaques. Therefore, MERGE can be a promising imaging approach in atherosclerotic-vulnerable plaque.

Utility of minimum intensity projection images based on three-dimensional CUBE T1 weighted imaging for evaluating middle cerebral artery stenosis

OBJECTIVE

This study investigated the diagnostic performance of MinIP images based on three-dimensional variable-flip-angle turbo spin echo T₁ weighted imaging (3D CUBE T₁WI) from high-resolution vessel wall magnetic resonance imaging for detecting middle cerebral artery (MCA) stenosis.

METHODS

A total of 63 consecutive patients were included in this study. MinIP images were reconstructed using 3D CUBE T₁WI as the source images. The degree and length of MCA stenosis were measured on MinIP images and were compared with digital subtraction angiography (DSA) as the reference standard.

RESULTS

The intra- and interobserver agreement for both the rate and length of MCA stenosis were excellent for the MinIP images. There was also excellent agreement in the degree of MCA stenosis calculated using MinIP images and DSA. MinIP images had a high sensitivity, specificity for diagnosing MCA stenosis. There was a good correlation between the two methods for measuring the rate and length of MCA stenosis.

CONCLUSION

MinIP images based on 3D CUBE T₁WI are highly consistent with DSA for evaluating the degree and length of MCA stenosis.

ADVANCES IN KNOWLEDGE

MinIP images can be produced as a derivative from vessel wall imaging and implemented as an adjunct to vessel wall imaging without extra acquisition time.

Normalized wall index, intraplaque hemorrhage and ulceration of carotid plaques correlate with the severity of ischemic stroke

BACKGROUND AND AIMS

Carotid atherosclerosis is considered an important cause of ischemic stroke. Tthis study aimed to explore the relationship between plaque features and the severity of stroke, and to identify plaque risk factors for the assessment of the severity of ischemic stroke.

METHODS

Symptomatic patients with carotid atherosclerotic plaques were prospectively recruited and underwent high-resolution vessel wall magnetic resonance imaging (VW-MRI). Two trained MRI readers independently identified intraplaque hemorrhage (IPH), calcification (CA), surface CA, deep CA, and ulceration. They measured and calculated the maximum vessel diameter (Max VD), maximum wall thickness (Max WT), total vessel area, lumen area, normalized wall index (NWI), plaque volume, IPH volume, IPH proportion, CA volume, and CA proportion. Patients were divided into two groups according to their National Institutes of Health Stroke Scale (NIHSS) scores (NIHSS ≤1 vs. NIHSS >1). Clinical characteristics and carotid plaque features were compared using the Mann-Whitney U test or Chi-square test as appropriate. Odds ratio (OR) and corresponding 95% confidence interval (CI) of plaque features to distinguish patients with NIHSS >1 were calculated. Spearman's rank correlations or Pearson correlations were determined for plaque features and NIHSS scores.

RESULTS

Of the 97 included patients, 34 (35.05%) with NIHSS >1 had significantly greater NWI (p < 0.05), larger IPH volume (p < 0.01), and greater IPH proportion (p < 0.01), and higher prevalence of IPH (OR, 5.654; 95%CI, 2.272-14.070; p < 0.01) and ulceration (OR, 2.891; 95%CI, 1.090-7.667; p = 0.033) than patients with NIHSS ≤1. Max WT (r = 0.24, p = 0.018), NWI (r = 0.22, p = 0.032), IPH (r = 0.27, p = 0.007), IPH volume (r = 0.35, p < 0.01), IPH proportion (r = 0.28, p = 0.005), and ulceration (r = 0.35, p < 0.01) had positive correlations with NIHSS scores.

CONCLUSIONS

NWI, IPH, and ulceration of carotid atherosclerotic plaque based on high-resolution VW-MRI may be useful indicators for assessing the severity of ischemic stroke in patients with atherosclerosis. NIHSS score is related to max WT, NWI, IPH, IPH volume, IPH proportion, and ulceration.