Magnetic resonance imaging of carotid plaques: current status and clinical perspectives

The relationship between fibrous cap status or plaque surface morphology and intraplaque hemorrhage volume over time: The PARISK Study

BACKGROUND

Carotid intraplaque hemorrhage (IPH) is a strong predictor of stroke, but factors contributing to IPH development are incompletely understood. Therefore, we investigate the longitudinal relationship between a thin/ruptured fibrous cap (TRFC)/disrupted plaque surface and IPH volume.

METHODS

116 ischemic TIA/stroke patients with ipsilateral carotid plaques underwent baseline and two-year follow-up MRI. IPH and fibrous cap status (thick versus TRFC) on MRI and disruption of the plaque surface (smooth versus fissure/ulceration) on CTA were assessed.

RESULTS

In the TRFC and disrupted plaque surface groups, the median IPH volume (tended) to decrease during follow-up (baseline: 97.3 IQR: [3.2-193.3] mm3 versus follow-up: 29.7 [0.0-115.1] mm3, p = 0.09, and baseline: 25.1 [0.0-166.2] mm3 versus follow-up: 11.2 [0.0-68.3] mm3, p = 0.04, respectively). In the group with a thick fibrous cap/smooth plaque surface, the median IPH volumes were zero at baseline and follow-up. The risk of IPH progression was higher in the TRFC/disrupted plaque groups (risk ratio (RR): 2.9 and 2.0, respectively) than in patients with a thick fibrous cap/smooth plaque surface.

CONCLUSION

TIA/stroke patients with a TRFC/disrupted plaque showed a net decrease in IPH volume over time, indicating plaque healing in some patients, but patients with a TRFC/disrupted plaque are still at increased risk for IPH progression.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01208025.

Combining artificial intelligence assisted image segmentation and ultrasound based radiomics for the prediction of carotid plaque stability

PURPOSE

Utilizing artificial intelligence (AI) technology for the segmentation of plaques on ultrasound images to evaluate the stability of carotid artery plaques and analyze its diagnostic accuracy in differentiating vulnerable plaques from stable ones.

METHODS

A retrospective study was conducted on 202 patients with ischemic stroke, who were divided into vulnerable plaque group (85 cases) and stable plaque group (117 cases) based on the results of carotid color Doppler ultrasound examination. From the vulnerable plaque group, 63 cases were randomly selected as the modeling group and 22 cases as the validation group; similarly, from the stable plaque group, 87 cases were randomly selected as the modeling group and 30 cases as the validation group. Based on the ultrasound images of the modeling group, plaques were segmented using artificial intelligence technology, and 1414 radiomics features were extracted. These features were then subjected to dimensionality reduction and feature selection using the least absolute shrinkage and selection operator (LASSO) method. Subsequently, a Support Vector Machine (SVM) model was constructed and validated using the selected features. The sensitivity, specificity, and Area Under the Curve (AUC) of the model were evaluated through the analysis of the receiver operating characteristic (ROC) curve.

RESULTS

A total of 43 radiomics feature parameters were selected by the LASSO method. The training group for the SVM model had an AUC of 89.42% (95% CI: 80.74-98.10%), sensitivity of 79.84%, and specificity of 93.10%, while the validation group had an AUC of 82.73% (95% CI: 71.64-93.81%), sensitivity of 81.82%, and specificity of 80.00%.

CONCLUSION

The use of artificial intelligence technology for the segmentation of plaques in ultrasound images, coupled with the analysis of radiomics models, can efficiently distinguish the stability of carotid artery plaques, providing a diagnostic basis for the clinical prediction of ischemic stroke.

CLINICAL TRIAL NUMBER

Not applicable.

Benefits of prophylactic carotid revascularization in patients with asymptomatic carotid artery stenosis undergoing coronary artery bypass surgery: A narrative review

Patients undergoing coronary artery bypass grafting (CABG) are at increased risk of perioperative stroke. Carotid atherosclerosis has been identified as an independent risk factor for stroke during and in the early postoperative period of cardiac surgery. However, the pathogenesis of peri-CABG stroke is multifactorial and frequently involves other noncarotid causes, such as cardiac emboli and aortic atheroma. Therefore, routine population-wide screening of carotid stenosis is not recommended, but target screening of patients at high risk of carotid-related perioperative stroke can have benefits. Carotid duplex sonography is recommended as an initial screening tool. Elimination of carotid stenosis before cardiac surgery is indicated in patients in whom carotid atherosclerosis is suspected to be the primary contributor to perioperative stroke. In patients with advanced carotid atherosclerosis, an individualized revascularization approach, including simultaneous or staged procedures, is advocated. The prevailing consensus is that synchronous surgery is safer than staged procedures. Carotid artery stenting represents a less invasive alternative, but its role in high-risk patients requires further investigation. In conclusion, the risk of perioperative stroke in patients undergoing CABG involves different factors, and carotid artery stenosis is involved in its pathogenesis only in some patients. Therefore, individualized approaches and careful consideration of patient risk factors are essential in determining the need for carotid screening and revascularization before CABG.

Differentiation of Atherosclerotic Carotid Plaque Components With Dual-Energy Computed Tomography

OBJECTIVES

Carotid plaque vulnerability is a strong predictor of recurrent ipsilateral stroke, but differentiation of plaque components using conventional computed tomography (CT) is suboptimal. The aim of our study was to evaluate the ability of dual-energy CT (DECT) to characterize atherosclerotic carotid plaque components based on the effective atomic number and effective electron density using magnetic resonance imaging (MRI) and, where possible, histology as the reference standard.

MATERIALS AND METHODS

Patients with recent cerebral ischemia and a ≥2-mm carotid plaque underwent computed tomography angiography and MRI. A subgroup underwent carotid endarterectomy. Trained observers delineated plaque components on histology or MRI, independent of computed tomography angiography. DECT was coregistered with MRI and/or histology. Intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), fibrous tissue, and calcifications were delineated on DECT, and ρeff and Zeff values were determined in the derivation cohort (n = 55). Spatial separation of these components was evaluated in a ρeff-Zeff-cluster plot. Ranges that optimally differentiate plaque features were determined. For validation, plaque components were quantified in the validation cohort (n = 29) using these ρeff-Zeff ranges and literature-based Hounsfield unit (HU) ranges and correlated to MRI volumes.

RESULTS

Eighty-four participants (68 ± 8 years; 55 male) were evaluated. In the derivation cohort, plaque components were well separated on the cluster plot, resulting in the following ranges: IPH:ρeff < 1.15, Zeff < 7.5, LRNC:ρeff < 1.15, Zeff:7.5-8.75, fibrous tissue:ρeff < 1.15, Zeff > 8.75, and calcifications: ρeff > 1.15, Zeff > 0. In the validation cohort, significant correlations were found between ρeff-Zeff-based and MRI plaque volumes for fibrous tissue (r = 0.69, P < 0.001), LRNC (r = 0.94, P < 0.001), IPH (r = 0.35, P = 0.03), and calcifications (r = 0.70, P < 0.001). Lower correlations were found between HU-based and MRI plaque volumes for fibrous tissue (r = 0.40, P = 0.02), LRNC (r = 0.86, P < 0.001), and calcifications (r = 0.47, P = 0.005), with no correlation for IPH (r = 0.02, P = 0.45).

CONCLUSIONS

We determined ρeff-Zeff ranges for plaque assessment. ρeff-Zeff-based volumes showed strong-to-very strong correlations with MRI for LRNC, fibrous tissue, and calcifications and a weak correlation for IPH. ρeff-Zeff-based volumes demonstrated superior agreement with MRI for all plaque components compared with HU-based volumes, highlighting the potential of DECT for the identification of patients with vulnerable plaques.

Advancements in risk stratification and management strategies in primary cardiovascular prevention

Atherosclerotic cardiovascular disease (ASCVD) remains a leading cause of morbidity and mortality worldwide, highlighting the urgent need for advancements in risk assessment and management strategies. Although significant progress has been made recently, identifying and managing apparently healthy individuals at a higher risk of developing atherosclerosis and those with subclinical atherosclerosis still poses significant challenges. Traditional risk assessment tools have limitations in accurately predicting future events and fail to encompass the complexity of the atherosclerosis trajectory. In this review, we describe novel approaches in biomarkers, genetics, advanced imaging techniques, and artificial intelligence that have emerged to address this gap. Moreover, polygenic risk scores and imaging modalities such as coronary artery calcium scoring, and coronary computed tomography angiography offer promising avenues for enhancing primary cardiovascular risk stratification and personalised intervention strategies. On the other hand, interventions aiming against atherosclerosis development or promoting plaque regression have gained attention in primary ASCVD prevention. Therefore, the potential role of drugs like statins, ezetimibe, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, omega-3 fatty acids, antihypertensive agents, as well as glucose-lowering and anti-inflammatory drugs are also discussed. Since findings regarding the efficacy of these interventions vary, further research is still required to elucidate their mechanisms of action, optimize treatment regimens, and determine their long-term effects on ASCVD outcomes. In conclusion, advancements in strategies addressing atherosclerosis prevention and plaque regression present promising avenues for enhancing primary ASCVD prevention through personalised approaches tailored to individual risk profiles. Nevertheless, ongoing research efforts are imperative to refine these strategies further and maximise their effectiveness in safeguarding cardiovascular health.

Association Between Calculated Small Dense Low-Density Lipoprotein Cholesterol (sdLDL-C) and Soft Carotid Plaques on CT Angiogram of the Head and Neck

BACKGROUND

Cerebrovascular accident (CVA), also commonly known as stroke, is an acute condition characterized by jeopardized perfusion of the brain tissue. Atherosclerosis is a common converging point for the various risk factors for CVA. It is a chronic, evolving condition of the vessel wall characterized by peculiar lesions known as atheromas. Low-density lipoprotein cholesterol (LDL-C) has been one of the established and traditional risk factors for the development of plaques in atherosclerosis. Small dense LDL-C (sdLDL-C) is a subclass of LDL-C that is considered more atherogenic, and its role in atherosclerotic plaque formation has been very well established. Hence, in this study, we aimed to find the association between calculated sdLDL-C and atherosclerotic carotid plaque (including various plaque characteristics).

MATERIALS AND METHODS

This retrospective cross-sectional study was conducted at Sri Ramachandra Medical College and Research Institute between December 2022 and December 2023 after getting ethics approval from the Institutional Ethics Committee. Patients who underwent CT angiogram (312) were included in the study, and their lipid profile data were collected from the Laboratory Information System. Participants were divided into groups depending on the presence or absence of carotid plaque, the characteristics of the plaque, and the narrowing caused by the plaque. sdLDL-C was calculated using Sampson formula from the lipid parameters in these groups. Statistical analysis was done using SPSS Statistics version 16.0 (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.). A p-value of <0.05 was considered significant.

RESULTS

sdLDL-C was significantly higher in the plaque group (37.25 ± 13.69 mg/dL) when compared to the group without plaques on CT angiogram (34.09 ± 11.64 mg/dL) (p<0.05), wherein the LDL-C wasn't significantly different between the two groups. sdLDL-C was also elevated in the soft plaque sub-group (39.46 ± 13.63 mg/dL) when compared to the calcific plaque sub-group (35.41 ± 13.05 mg/dL), which was statistically significant (p<0.05).

CONCLUSION

sdLDL-C is associated with atherosclerotic carotid plaques, especially the soft plaques on CT angiogram, which are considered to be vulnerable plaques. Thus, calculated sdLDL-C can be utilized as a cost-effective tool to assess plaque vulnerability and monitor hypolipidemic treatment in addition to LDL-C.

Signal intensity and volume of carotid intraplaque hemorrhage on magnetic resonance imaging and the risk of ipsilateral cerebrovascular events: The Plaque At RISK (PARISK) study

BACKGROUND

The Plaque At RISK (PARISK) study demonstrated that patients with a carotid plaque with intraplaque hemorrhage (IPH) have an increased risk of recurrent ipsilateral ischemic cerebrovascular events. It was previously reported that symptomatic carotid plaques with IPH showed higher IPH signal intensity ratios (SIR) and larger IPH volumes than asymptomatic plaques. We explored whether IPH SIR and IPH volume are associated with future ipsilateral ischemic cerebrovascular events beyond the presence of IPH.

METHODS

Transient ischemic attack and ischemic stroke patients with mild-to-moderate carotid stenosis and an ipsilateral IPH-positive carotid plaque (n = 89) from the PARISK study were included. The clinical endpoint was a new ipsilateral ischemic cerebrovascular event during 5 years of follow-up, while the imaging-based endpoint was a new ipsilateral brain infarct on brain magnetic resonance imaging (MRI) after 2 years (n = 69). Trained observers delineated IPH, a hyperintense region compared to surrounding muscle tissue on hyper T1-weighted magnetic resonance images. The IPH SIR was the maximal signal intensity in the IPH region divided by the mean signal intensity of adjacent muscle tissue. The associations between IPH SIR or volume and the clinical and imaging-based endpoint were investigated using Cox proportional hazard models and logistic regression, respectively.

RESULTS

During 5.1 (interquartile range: 3.1-5.6) years of follow-up, 21 ipsilateral cerebrovascular ischemic events were identified. Twelve new ipsilateral brain infarcts were identified on the 2-year neuro MRI. There was no association for IPH SIR or IPH volume with the clinical endpoint (hazard ratio (HR): 0.89 [95% confidence interval: 0.67-1.10] and HR: 0.91 [0.69-1.19] per 100-µL increase, respectively) nor with the imaging-based endpoint (odds ratio (OR): 1.04 [0.75-1.45] and OR: 1.21 [0.87-1.68] per 100-µL increase, respectively).

CONCLUSION

IPH SIR and IPH volume were not associated with future ipsilateral ischemic cerebrovascular events. Therefore, quantitative assessment of IPH of SIR and volume does not seem to provide additional value beyond the presence of IPH for stroke risk assessment.

TRIAL REGISTRATION

The PARISK study was registered on ClinicalTrials.gov with ID NCT01208025 on September 21, 2010 (https://clinicaltrials.gov/study/NCT01208025).

Robustness and classification capabilities of MRI radiomic features in identifying carotid plaque vulnerability

OBJECTIVES

To assess how radiomic features may be combined with plaque morphological and compositional features identified by multi-contrast MRI to improve upon conventional risk assessment models in determining culprit carotid artery lesions.

METHODS

Fifty-five patients (mean age: 62.6; 35 males) with bilateral carotid stenosis who experienced transient ischaemic attack (TIA) or stroke were included from the CARE-II multi-centre carotid imaging trial (ClinicalTrials.gov Identifier: NCT02017756). They underwent MRI within 2 weeks of the event. Classification capability in distinguishing culprit lesions was assessed by machine learning. Repeatability and reproducibility of the results were investigated by assessing the robustness of the radiomic features.

RESULTS

Radiomics combined with a relatively conventional plaque morphological and compositional metric-based model provided incremental value over a conventional model alone (area under curve [AUC], 0.819 ± 0.002 vs 0.689 ± 0.019, respectively, P = .014). The radiomic model alone also provided value over the conventional model (AUC, 0.805 ± 0.003 vs 0.689 ± 0.019, respectively, P = .031). T2-weighted imaging-based radiomic features had consistently higher robustness and classification capabilities compared with T1-weighted images. Higher-dimensional radiomic features outperformed first-order features. Grey Level Co-occurrence Matrix, Grey Level Dependence Matrix, and Grey Level Size Zone Matrix sub-types were particularly useful in identifying textures which could detect vulnerable lesions.

CONCLUSIONS

The combination of MRI-based radiomic features and lesion morphological and compositional parameters provided added value to the reference-standard risk assessment for carotid atherosclerosis. This may improve future risk stratification for individuals at risk of major adverse ischaemic cerebrovascular events.

ADVANCES IN KNOWLEDGE

The clinical relevance of this work is that it addresses the need for a more comprehensive method of risk assessment for patients at risk of ischaemic stroke, beyond conventional stenosis measurement. This paper shows that in the case of carotid stroke, high-dimensional radiomics features can improve classification capabilities compared with stenosis measurement alone.

Advancements in non-invasive imaging of atherosclerosis: Future perspectives

Atherosclerosis is a chronic inflammatory disease characterized by the buildup of plaques in arterial walls, leading to cardiovascular diseases and high morbidity and mortality rates worldwide. Non-invasive imaging techniques play a crucial role in evaluating patients with suspected or established atherosclerosis. However, there is a growing body of evidence suggesting the need to visualize the underlying processes of plaque progression and rupture to enhance risk stratification. This review explores recent advancements in non-invasive assessment of atherosclerosis, focusing on computed tomography, magnetic resonance imaging, and nuclear imaging. These advancements provide valuable insights into the assessment and management of atherosclerosis, potentially leading to better risk stratification and improved patient outcomes.

Association between Antiplatelet Therapy and Changes in Intraplaque Hemorrhage in Patients with Mild to Moderate Symptomatic Carotid Stenosis: A Longitudinal MRI Study

INTRODUCTION

Carotid atherosclerotic intraplaque hemorrhage (IPH) predicts stroke. Patients with a history of stroke are treated with antiplatelet agents to prevent secondary cardiovascular events. A positive association between previous antiplatelet use and IPH was reported in a cross-sectional analysis. We investigated the changes in IPH over 2 years in patients who recently started versus those with continued antiplatelet use.

METHODS

In the Plaque at Risk (PARISK) study, symptomatic patients with <70% ipsilateral carotid stenosis underwent carotid plaque magnetic resonance imaging (MRI) at the baseline and after 2 years to determine IPH presence and volume. Participants were categorized into new users (starting antiplatelet therapy following the index event) and continued users (previous use of antiplatelet therapy before the index event). The association between previous antiplatelet therapy and the presence of IPH at baseline MRI was investigated using multivariable logistic regression analysis. The IPH volume change over a period of 2 years, defined as the difference in volume between follow-up and baseline, was investigated in each group with a Wilcoxon signed-rank test. The IPH volume change was categorized as progression, regression, or no change. Using multivariable logistic regression, we investigated the association between new antiplatelet use and (1) newly developed ipsilateral or contralateral IPH and (2) IPH volume progression.

RESULTS

A total of 108 patients underwent carotid MRI at the baseline and follow-up. At the baseline, previous antiplatelet therapy was associated with any IPH (OR = 5.6, 95% CI: 1.3-23.1; p = 0.02). Ipsilateral IPH volume did not change significantly during the 2 years in patients who continued receiving antiplatelet agents (86.4 mm3 [18.2-235.9] vs. 59.3 mm3 [11.4-260.3]; p = 0.6) nor in the new antiplatelet users (n = 31) (61.5 mm3 [0.0-166.9] vs. 27.7 mm3 [9.5-106.4]; p = 0.4). Similar results of a nonsignificant change in contralateral IPH volume during those 2 years were observed in both groups (p > 0.05). No significant associations were found between new antiplatelet use and newly developed IPH at 2 years (odds ratio [OR] = 1.0, 95% CI: 0.1-7.4) or the progression of IPH (ipsilateral: OR = 2.4, 95% CI: 0.3-19.1; contralateral: OR = 0.3, 95% CI: 0.01-8.5).

CONCLUSION

Although the baseline association between IPH and previous antiplatelet therapy was confirmed in this larger cohort, the new onset of antiplatelet therapy after transient ischemic attack/stroke was not associated with the newly developed IPH or progression of IPH volume over the subsequent 2 years.

Application of mask images of contrast-enhanced MR angiography to detect carotid intraplaque hemorrhage in patients with moderate to severe symptomatic and asymptomatic carotid stenosis

PURPOSE

Carotid intraplaque hemorrhage (IPH) on MRI predicts stroke. Magnetization-prepared rapid acquisition gradient (MP-RAGE) is widely used to detect IPH. CE-MRA is used routinely to assess stenosis. Initial studies indicated that IPH can be identified on mask images of CE-MRA, while Time-of-Flight (TOF) images were reported to have high specificity but lower sensitivity. We investigated the diagnostic accuracy of detecting IPH on mask images of CE-MRA and TOF.

METHODS

Thirty-six patients with ≥ 50% stenosis enrolled in the ongoing 2nd European Carotid Surgery Trial underwent carotid MRI. A 5-point quality score was used. Inter-observer agreement between two independent readers was determined. The sensitivity and specificity of IPH detection on mask MRA and TOF were calculated with MP-RAGE as a reference standard.

RESULTS

Of the 36 patients included in the current analysis, 66/72 carotid arteries could be scored. The inter-observer agreements for identifying IPH on MP-RAGE, mask, and TOF were outstanding (κ: 0.93, 0.96, and 0.85). The image quality of mask (1.42 ± 0.66) and TOF (2.42 ± 0.66) was significantly lower than MP-RAGE (3.47 ± 0.61). When T1w images were used to delineate the outer carotid wall, very high specificities (>95%) of IPH detection on mask and TOF images were found, while the sensitivity was high for mask images (>81%) and poor for TOF (50-60%). Without these images, the specificity was still high (>97%), while the sensitivity reduced to 62-71%.

CONCLUSION

Despite the lower image quality, routinely acquired mask images from CE-MRA, but not TOF, can be used as an alternative to MP-RAGE images to visualize IPH.

Quantification of carotid plaque composition with a multi-contrast atherosclerosis characterization (MATCH) MRI sequence

Background and purpose

Carotid atherosclerotic plaques with a large lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), and a thin or ruptured fibrous cap are associated with increased stroke risk. Multi-sequence MRI can be used to quantify carotid atherosclerotic plaque composition. Yet, its clinical implementation is hampered by long scan times and image misregistration. Multi-contrast atherosclerosis characterization (MATCH) overcomes these limitations. This study aims to compare the quantification of plaque composition with MATCH and multi-sequence MRI.

Methods

MATCH and multi-sequence MRI were used to image 54 carotid arteries of 27 symptomatic patients with ≥2 mm carotid plaque on a 3.0 T MRI scanner. The following sequence parameters for MATCH were used: repetition time/echo time (TR/TE), 10.1/4.35 ms; field of view, 160 mm × 160 mm × 2 mm; matrix size, 256 × 256; acquired in-plane resolution, 0.63 mm2× 0.63 mm2; number of slices, 18; and flip angles, 8°, 5°, and 10°. Multi-sequence MRI (black-blood pre- and post-contrast T1-weighted, time of flight, and magnetization prepared rapid acquisition gradient echo; acquired in-plane resolution: 0.63 mm2 × 0.63 mm2) was acquired according to consensus recommendations, and image quality was scored (5-point scale). The interobserver agreement in plaque composition quantification was assessed by the intraclass correlation coefficient (ICC). The sensitivity and specificity of MATCH in identifying plaque composition were calculated using multi-sequence MRI as a reference standard.

Results

A significantly lower image quality of MATCH compared to that of multi-sequence MRI was observed (p < 0.05). The scan time for MATCH was shorter (7 vs. 40 min). Interobserver agreement in quantifying plaque composition on MATCH images was good to excellent (ICC ≥ 0.77) except for the total volume of calcifications and fibrous tissue that showed moderate agreement (ICC ≥ 0.61). The sensitivity and specificity of detecting plaque components on MATCH were ≥89% and ≥91% for IPH, ≥81% and 85% for LRNC, and ≥71% and ≥32% for calcifications, respectively. Overall, good-to-excellent agreement (ICC ≥ 0.76) of quantifying plaque components on MATCH with multi-sequence MRI as the reference standard was observed except for calcifications (ICC = 0.37-0.38) and fibrous tissue (ICC = 0.59-0.70).

Discussion and conclusion

MATCH images can be used to quantify plaque components such as LRNC and IPH but not for calcifications. Although MATCH images showed a lower mean image quality score, short scan time and inherent co-registration are significant advantages.

Biliverdin Reductase B Is a Plasma Biomarker for Intraplaque Hemorrhage and a Predictor of Ischemic Stroke in Patients with Symptomatic Carotid Atherosclerosis

BACKGROUND

Intraplaque hemorrhage (IPH) is a hallmark of atherosclerotic plaque instability. Biliverdin reductase B (BLVRB) is enriched in plasma and plaques from patients with symptomatic carotid atherosclerosis and functionally associated with IPH.

OBJECTIVE

We explored the biomarker potential of plasma BLVRB through (1) its correlation with IPH in carotid plaques assessed by magnetic resonance imaging (MRI), and with recurrent ischemic stroke, and (2) its use for monitoring pharmacotherapy targeting IPH in a preclinical setting.

METHODS

Plasma BLVRB levels were measured in patients with symptomatic carotid atherosclerosis from the PARISK study (n = 177, 5 year follow-up) with and without IPH as indicated by MRI. Plasma BLVRB levels were also measured in a mouse vein graft model of IPH at baseline and following antiangiogenic therapy targeting vascular endothelial growth factor receptor 2 (VEGFR-2).

RESULTS

Plasma BLVRB levels were significantly higher in patients with IPH (737.32 ± 693.21 vs. 520.94 ± 499.43 mean fluorescent intensity (MFI), p = 0.033), but had no association with baseline clinical and biological parameters. Plasma BLVRB levels were also significantly higher in patients who developed recurrent ischemic stroke (1099.34 ± 928.49 vs. 582.07 ± 545.34 MFI, HR = 1.600, CI [1.092-2.344]; p = 0.016). Plasma BLVRB levels were significantly reduced following prevention of IPH by anti-VEGFR-2 therapy in mouse vein grafts (1189 ± 258.73 vs. 1752 ± 366.84 MFI; p = 0.004).

CONCLUSIONS

Plasma BLVRB was associated with IPH and increased risk of recurrent ischemic stroke in patients with symptomatic low- to moderate-grade carotid stenosis, indicating the capacity to monitor the efficacy of IPH-preventive pharmacotherapy in an animal model. Together, these results suggest the utility of plasma BLVRB as a biomarker for atherosclerotic plaque instability.

Pearls and Pitfalls of Carotid Artery Imaging: Ultrasound, Computed Tomography Angiography, and MR Imaging

Stroke represents a major cause of morbidity and mortality worldwide with carotid atherosclerosis responsible for a large proportion of ischemic strokes. Given the high burden of the disease , early diagnosis and optimal secondary prevention are essential elements in clinical practice. For a long time, the degree of stenosis had been considered the parameter to judge the severity of carotid atherosclerosis. Over the last 30 years, literature has shifted attention from stenosis to structural characteristics of atherosclerotic lesion, eventually leading to the "vulnerable plaque" model. These "vulnerable plaques" frequently demonstrate high-risk imaging features that can be assessed by various non-invasive imaging modalities.

Analysis of carotid vulnerable plaque MRI high-risk features and clinical risk factors associated with concomitant acute cerebral infarction

BACKGROUND

This study aimed to investigate the correlation between the high-risk characteristics of high-resolution MRI carotid vulnerable plaques and the clinical risk factors and concomitant acute cerebral infarction (ACI).

METHODS

Forty-five patients diagnosed with a single vulnerable carotid plaque by MRI were divided into two groups based on whether they had ipsilateral ACI. The clinical risk factors and the observation values or frequency of occurrence of high-risk MRI phenotypes of plaque volume, LRNC, IPH and ulcer were statistically compared between the two groups.

RESULTS

A total of 45 vulnerable carotid artery plaques were found in 45 patients, 23 patients with ACI and 22 patients without ACI. There were no significant differences in age, sex, smoking, serum TC, TG and LDL between the two groups (all P > 0.05), but the ACI group had significantly more patients with hypertension (P < 0.05) and the without ACI group coronary heart disease (P < 0.05). The volume of vulnerable carotid plaque in the group with ACI (1004.19 ± 663.57 mm3) was significantly larger than that in the group without ACI (487.21 ± 238.64 mm3) (P < 0.05). The phenotype of vulnerable carotid artery plaque was 13 cases of LRNC, 8 cases of LRNC + IPH, 5 cases of LRNC + Ulcer, and 19 cases of LRNC + IPH + Ulcer. There was no significant difference in this distribution between the two groups (all P > 0.05) with the exception of LRNC + IPH + Ulcer. The 14 cases of LRNC + IPH + LRNC + IPH + Ulcer (60.87%) in the group with ACI and was significantly greater than the 5 (22.73%) in patients without ACI (P < 0.05).

CONCLUSION

It is preliminarily thought that hypertension is the main clinical risk factor for vulnerable carotid plaques with ACI and the combination of plaque volume with vulnerable carotid plaque and LRNC + IPH + Ulcer is a high-risk factor for complicated ACI. It has high clinical therapeutic value due to the accurate diagnosis of responsible vessels and plaques with high-resolution MRI.

Detecting vulnerable carotid plaque and its component characteristics: Progress in related imaging techniques

Carotid atherosclerotic plaque rupture and thrombosis are independent risk factors for acute ischemic cerebrovascular disease. Timely identification of vulnerable plaque can help prevent stroke and provide evidence for clinical treatment. Advanced invasive and non-invasive imaging modalities such as computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy can be employed to image and classify carotid atherosclerotic plaques to provide clinically relevant predictors used for patient risk stratification. This study compares existing clinical imaging methods, and the advantages and limitations of different imaging techniques for identifying vulnerable carotid plaque are reviewed to effectively prevent and treat cerebrovascular diseases.

Vessel wall MR imaging in neuroradiology

Vessel wall MR imaging (VW-MRI) has been introduced into clinical practice and applied to a variety of diseases, and its usefulness has been reported. High-resolution VW-MRI is essential in the diagnostic workup and provides more information than other routine MR imaging protocols. VW-MRI is useful in assessing lesion location, morphology, and severity. Additional information, such as vessel wall enhancement, which is useful in the differential diagnosis of atherosclerotic disease and vasculitis could be assessed by this special imaging technique. This review describes the VW-MRI technique and its clinical applications in arterial disease, venous disease, vasculitis, and leptomeningeal disease.

Development of Molecular Magnetic Resonance Imaging Tools for Longitudinal Tracking of Carotid Atherosclerotic Disease Using Fast Imaging with Steady-State Precession

Identification of patients with high-risk asymptomatic carotid plaques remains a challenging but essential step in stroke prevention. Current selection criteria for intervention in carotid disease are still determined by symptomatology and degree of luminal stenosis. This strategy has been less effective in identifying the high-risk asymptomatic individual patients. Inflammation is the key factor that drives plaque instability causing clinical sequelae. Currently, there is no imaging tool in routine clinical practice to assess the inflammatory status within atherosclerotic plaques. Herein we describe the development of a novel molecular magnetic resonance imaging (MRI) strategy to interrogate plaque inflammation, and hence its vulnerability in vivo, using dual-targeted iron particle-based probes and fast imaging with steady-state precession (FISP) sequence, adding further prognostic information to luminal stenosis alone. A periarterial cuff was used to generate high-risk plaques at specific timepoints and location of the carotid artery in an apolipoprotein-E-deficient mouse model. Using this platform, we demonstrated that in vivo dual-targeted iron particles with enhanced FISP can (i) target and characterise high-risk vulnerable plaques and (ii) quantitatively report and track the inflammatory activity within carotid plaques longitudinally. This molecular imaging tool may permit (i) accurate monitoring of the risk of carotid plaques and (ii) timely identification of high-risk asymptomatic patients for prophylactic carotid intervention, achieving early stroke prevention.

Correlation of the characteristics of symptomatic intracranial atherosclerotic plaques with stroke types and risk of stroke recurrence: a cohort study

Background

Symptomatic intracranial atherosclerotic stenosis (sICAS) patients had a higher risk of stroke recurrence, and the risk of acute ischemic stroke (AIS) was higher than transient ischemic attack (TIA). Therefore, it is important to explore the risk factors associated with sICAS clinical subtypes and the risk of stroke recurrence. The purpose of this study was to investigate the association between intracranial arterial culprit plaque characteristics with sICAS clinical subtypes and the risk of stroke recurrence.

Methods

A total of 206 patients with sICAS were included. Baseline demographic data and relevant serologic indices were collected from all participants. All participants were assessed by high-resolution vessel wall imaging (HR-VWI) for culprit vessel and culprit plaque characteristics. The follow-up method was outpatient or telephone follow-up. Associated factors for sICAS clinical subtypes were analyzed by binary logistic regression. Cox proportional hazard regression analysis were used to analysis the independent risk factors for recurrent stroke.

Results

In this group, there were 154 patients with AIS, 52 patients with TIA, 124 patients with anterior circulation ischemic symptom (ACiS), and 82 patients with posterior circulation ischemic symptom (PCiS). Male gender [odds ratio (OR) =5.575, 95% confidence interval (CI): 2.120 to 14.658], history of previous statin use (OR =0.309, 95% CI: 0.113 to 0.843) and serum apolipoprotein A/B values (OR =0.363, 95% CI: 0.139 to 0.948) were associated factors for AIS. A total of 24 patients (11.7%) experienced stroke recurrence during the 1-year follow-up period. Hyperintensity on T1 weighted imaging (T1WI) in the culprit plaque [hazard ratio (HR) =3.798, 95% CI: 1.433 to 10.062] was an independent risk factor for stroke recurrence. The incidence of significant enhancement (62.2% vs. 39.5%, χ²=9.681, P=0.002), positive remodeling (69.5% vs. 52.4%, χ²=5.661, P=0.020), and hyperintensity on T1WI (42.7% vs. 22.6%, χ²=16.472, P=0.003) was higher in the posterior circulation than in the anterior circulation.

Conclusions

The characteristics of intracranial arterial culprit plaques were independent risk factors for recurrent stroke, and there were differences in the plaque characteristics of anterior and posterior circulation. Early HR-VWI examination for sICAS patients is of great significance for patient risk stratification and personalized management.

Current advances in the imaging of atherosclerotic vulnerable plaque using nanoparticles

Vulnerable atherosclerotic plaques of the artery wall that pose a significant risk of cardio-cerebral vascular accidents remain the global leading cause of morbidity and mortality. Thus, early delineation of vulnerable atherosclerotic plaques is of clinical importance for prevention and treatment. The currently available imaging technologies mainly focus on the structural assessment of the vascular wall. Unfortunately, several disadvantages in these strategies limit the improvement in imaging effect. Nanoparticle technology is a novel diagnostic strategy for targeting and imaging pathological biomarkers. New functionalized nanoparticles that detect hallmarks of vulnerable plaques are promising for advance further control of this critical illness. The review aims to address the current opportunities and challenges for the use of nanoparticle technology in imagining vulnerable plaques.

Imaging Approaches to the Diagnosis of Vascular Diseases

PURPOSE OF REVIEW

Vascular imaging is a complex field including numerous modalities and imaging markers. This review is focused on important and recent findings in atherosclerotic carotid artery plaque imaging with an emphasis on developments in magnetic resonance imaging (MRI) and computed tomography (CT).

RECENT FINDINGS

Recent evidence shows that carotid plaque characteristics and not only established measures of carotid plaque burden and stenosis are associated independently with cardiovascular outcomes. On carotid MRI, the presence of a lipid-rich necrotic core (LRNC) has been associated with incident cardiovascular disease (CVD) events independent of wall thickness, a traditional measure of plaque burden. On carotid MRI, intraplaque hemorrhage (IPH) presence has been identified as an independent predictor of stroke. The presence of a fissured carotid fibrous cap has been associated with contrast enhancement on CT angiography imaging. Carotid artery plaque characteristics have been associated with incident CVD events, and advanced plaque imaging techniques may gain additional prominence in the clinical treatment decision process.

Emerging Role of Carotid MRI for Personalized Ischemic Stroke Risk Prediction in Patients With Carotid Artery Stenosis

Rupture of a vulnerable carotid plaque is an important cause of ischemic stroke. Prediction models can support medical decision-making by estimating individual probabilities of future events, while magnetic resonance imaging (MRI) can provide detailed information on plaque vulnerability. In this review, prediction models for medium to long-term (>90 days) prediction of recurrent ischemic stroke among patients on best medical treatment for carotid stenosis are evaluated, and the emerging role of MRI of the carotid plaque for personalized ischemic stroke prediction is discussed. A systematic search identified two models; the European Carotid Surgery Trial (ECST) medical model, and the Symptomatic Carotid Atheroma Inflammation Lumen stenosis (SCAIL) score. We critically appraised these models by means of criteria derived from the CHARMS (CHecklist for critical Appraisal and data extraction for systematic Reviews of prediction Modeling Studies) and PROBAST (Prediction model Risk Of Bias ASsessment Tool). We found both models to be at high risk of bias. The ECST model, the most widely used model, was derived from data of large but relatively old trials (1980s and 1990s), not reflecting lower risks of ischemic stroke resulting from improvements in drug treatment (e.g., statins and anti-platelet therapy). The SCAIL model, based on the degree of stenosis and positron emission tomography/computed tomography (PET/CT)-based plaque inflammation, was derived and externally validated in limited samples. Clinical implementation of the SCAIL model can be challenging due to high costs and low accessibility of PET/CT. MRI is a more readily available, lower-cost modality that has been extensively validated to visualize all the hallmarks of plaque vulnerability. The MRI methods to identify the different plaque features are described. Intraplaque hemorrhage (IPH), a lipid-rich necrotic core (LRNC), and a thin or ruptured fibrous cap (TRFC) on MRI have shown to strongly predict stroke in meta-analyses. To improve personalized risk prediction, carotid plaque features should be included in prediction models. Prediction of stroke in patients with carotid stenosis needs modernization, and carotid MRI has potential in providing strong predictors for that goal.

Effects of Combined Vitamin K2 and Vitamin D3 Supplementation on Na[18F]F PET/MRI in Patients with Carotid Artery Disease: The INTRICATE Rationale and Trial Design

INTRICATE is a prospective double-blind placebo-controlled feasibility study, assessing the influence of combined vitamin K2 and vitamin D3 supplementation on micro-calcification in carotid artery disease as imaged by hybrid Sodium [¹⁸F]Fluoride (Na[¹⁸F]F) positron emission tomography (PET)/ magnetic resonance imaging (MRI). Arterial calcification is an actively regulated process and results from the imbalance between calcification promoting and inhibiting factors. Considering the recent advancements in medical imaging, ultrasound (US), PET/MRI, and computed tomography (CT) can be used for the selection and stratification of patients with atherosclerosis. Fifty-two subjects with asymptomatic carotid artery disease on at least one side of the neck will be included in the study. At baseline, an Na[¹⁸F]F PET/MRI and CT examination will be performed. Afterwards, subjects will be randomized (1:1) to a vitamin K (400 µg MK-7/day) and vitamin D3 (80 µg/day) or to placebo. At the 3-month follow-up, subjects will undergo a second Na[¹⁸F]F PET/MRI and CT scan. The primary endpoint is the change in Na[¹⁸F]F PET/MRI (baseline vs. after 3 months) in the treatment group as compared to the placebo arm. Secondary endpoints are changes in plaque composition and in blood-biomarkers. The INTRICATE trial bears the potential to open novel avenues for future large scale randomized controlled trials to intervene in the plaque development and micro-calcification progression.

Potential Role of Melatonin as an Adjuvant for Atherosclerotic Carotid Arterial Stenosis

Carotid artery stenosis (CAS) is an atherosclerotic disease characterized by a narrowing of the artery lumen and a high risk of ischemic stroke. Risk factors of atherosclerosis, including smoking, hypertension, hyperglycemia, hyperlipidemia, aging, and disrupted circadian rhythm, may potentiate atherosclerosis in the carotid artery and further reduce the arterial lumen. Ischemic stroke due to severe CAS and cerebral ischemic/reperfusion (I/R) injury after the revascularization of CAS also adversely affect clinical outcomes. Melatonin is a pluripotent agent with potent anti-inflammatory, anti-oxidative, and neuroprotective properties. Although there is a shortage of direct clinical evidence demonstrating the benefits of melatonin in CAS patients, previous studies have shown that melatonin may be beneficial for patients with CAS in terms of reducing endothelial damage, stabilizing arterial plaque, mitigating the harm from CAS-related ischemic stroke and cerebral I/R injury, and alleviating the adverse effects of the related risk factors. Additional pre-clinical and clinical are required to confirm this speculation.

Sodium [18F]Fluoride PET Can Efficiently Monitor In Vivo Atherosclerotic Plaque Calcification Progression and Treatment

Given the high sensitivity and specificity of sodium [¹⁸F]Fluoride (Na[¹⁸F]F) for vascular calcifications and positive emerging data of vitamin K on vascular health, the aim of this study is to assess the ability of Na[¹⁸F]F to monitor therapy and disease progression in a unitary atherosclerotic mouse model. ApoE^−/− mice were placed on a Western-type diet for 12-weeks and then split into four groups. The early stage atherosclerosis group received a chow diet for an additional 12-weeks, while the advanced atherosclerosis group continued the Western-type diet. The Menaquinone-7 (MK-7) and Warfarin groups received MK-7 or Warfarin supplementation during the additional 12-weeks, respectively. Control wild type mice were fed a chow diet for 24-weeks. All of the mice were scanned with Na[¹⁸F]F using a small animal positron emission tomography (PET)/computed tomography (CT). The Warfarin group presented spotty calcifications on the CT in the proximal aorta. All of the spots corresponded to dense mineralisations on the von Kossa staining. After the control, the MK-7 group had the lowest Na[¹⁸F]F uptake. The advanced and Warfarin groups presented the highest uptake in the aortic arch and left ventricle. The advanced stage group did not develop spotty calcifications, however Na[¹⁸F]F uptake was still observed, suggesting the presence of micro-calcifications. In a newly applied mouse model, developing spotty calcifications on CT exclusively in the proximal aorta, Na[¹⁸F]F seems to efficiently monitor plaque progression and the beneficial effects of vitamin K on cardiovascular disease.

Stroke Prevention After Cryptogenic Stroke

PURPOSE OF REVIEW

Cryptogenic stroke represents a heterogenous but clinically important collection of stroke etiologies for which our understanding continues to grow. Here, we review our current knowledge and most recent recommendations on secondary prevention for common causes of cryptogenic stroke including paroxysmal atrial fibrillation, atrial cardiopathy, patent foramen ovale, and substenotic atherosclerotic disease as well as the under-recognized mechanisms of occult malignancy, heart failure, and, most recently, infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

RECENT FINDINGS

The results from recent observational studies and randomized clinical trials have provided greater insight into the causal relationship and attributable risk of these suspected etiologies and have identified potential strategies to reduce the rates of recurrence. However, further clinical trials are needed to confirm the benefits of specific stroke prevention strategies, including the patient populations most likely to benefit from anticoagulation. There is ongoing research aimed at both reducing the proportion of ischemic strokes classified as cryptogenic and resolving much of the clinical equipoise that still exists. The results of these studies have the potential to provide us with a better understanding of these occult mechanisms and allow for more targeted interventions.