Carotid Plaque Morphology and Ischemic Vascular Brain Disease on MRI

Differences in distribution and features of carotid and middle cerebral artery plaque in patients with pial infarction and perforating artery infarction: A 3D vessel wall imaging study

PURPOSE

Atherosclerotic plaques of carotid artery (CA) and middle cerebral artery (MCA) are important causes of acute ischemic stroke (AIS). This study was designed to jointly assess the plaque distribution and features of CA and MCA in AIS patients with pial infarction (PI) and perforating artery infarction (PAI), and to investigate the associations between plaque characteristics and ischemic infarction patterns.

METHODS

Imaging data of sixty-five patients from a cross-sectional study were reviewed. All the patients had acute infarction in the MCA territory on diffusion weighted imaging (DWI) and underwent CA and MCA vessel wall imaging (VWI). The CA and MCA plaque presence and high-risk features on the ipsilateral side of infarction were analyzed. The brain infarction lesions were divided into PI group vs. non-PI group, and PAI group vs. non-PAI group. Different plaque distribution types and plaque features were compared in each two groups, and their associations were investigated using binary logistic regression.

RESULTS

Sixty-five patients (mean age, 54.6 ± 10.1 years; 61 men) were included. The CA high-risk plaque (OR: 5.683 [1.409-22.929], P = 0.015) and MCA plaque presence (OR: 3.949 [1.397-11.162], P = 0.010) were significantly associated with PI. MCA plaques that involved the orifice of the perforating arteries were significantly associated with PAI (OR: 15.167 [1.851-124.257], P = 0.011).

CONCLUSION

CA and MCA plaques show distinct distribution and high-risk features in patients with PI and PAI. Combined intracranial and extracranial arteries imaging should be considered for the evaluation of the symptomatic ischemic patients.

Patients with Carotid Intraplaque Hemorrhage Have Higher Incidence of Cerebral Microbleeds

AIMS

Carotid intraplaque hemorrhage (IPH) is considered a marker of plaque vulnerability. Cerebral microbleeds (CMBs) are recognized on magnetic resonance imaging (MRI) in patients with cerebrovascular disease. Any connection between carotid IPH and CMBs remains scantly investigated. This study aimed to determine whether the histologic evidence of carotid IPH is related to CMBs.

METHODS

We retrospectively enrolled 101 consecutive patients undergoing carotid endarterectomy with symptomatic (ischemic stroke, TIA, and amaurosis fugax) or asymptomatic ipsilateral carotid artery disease. The presence and the extent (%) of IPH were identified on carotid plaques stained with Movat Pentachrome. CMBs were localized on T2*-weighted gradient-recalled echo or susceptibility-weighted imaging sequence on brain MRI before surgery. The degree of carotid stenosis was measured by neck CTA.

RESULTS

IPH was identified in 57 (56.4%) patients, and CMBs were found in 24 (23.7%) patients. CMBs were more commonly observed in patients with carotid IPH compared to those without [19 (33.3%) vs 5 (11.4%); p=0.010]. The carotid IPH extent was significantly higher in patients with CMBs than in those without [9.0 % (2.8-27.1%) vs 0.9% (0.0-13.9%); p=0.004] and was associated with the number of CMBs (p=0.004). Logistic regression analysis demonstrated an independent association between carotid IPH extent and the presence of CMBs [OR 1.051 (95% CI 1.012-1.090); p=0.009]. Additionally, patients with CMBs had a lower degree of ipsilateral carotid stenosis compared to those without [40% (35-65%) vs 70% (50-80%); p=0.049].

CONCLUSIONS

CMBs may be potential markers of the ongoing process of carotid IPH, especially in those with nonobstructive plaques.

Association between high-risk extracranial carotid plaque and covert brain infarctions and cerebral microbleeds

PURPOSE

Covert brain infarctions (CBIs) and cerebral microbleeds (CMBs) represent subclinical sequelae of ischemic and hemorrhagic cerebral small vessel disease, respectively. In addition to thromboembolic stroke, carotid atherosclerosis has been associated with downstream vascular brain injury, including inflammation and small vessel disease. The specific plaque features responsible for this are unknown. We aimed to determine the association of specific vulnerable carotid plaque features to CBIs and CMBs to better understand the relation of large and small vessel disease in a single-center retrospective observational study.

METHODS

Intraplaque hemorrhage (IPH) and plaque ulceration were recorded on carotid MRA and total, cortical, and lacunar CBIs and CMBs were recorded on brain MR in 349 patients (698 carotid arteries). Multivariable Poisson regression was performed to relate plaque features to CBIs and CMBs. Within-subject analysis in those with unilateral IPH and ulceration was performed with Poisson regression.

RESULTS

Both IPH and plaque ulceration were associated with total CBI (prevalence ratios (PR) 3.33, 95% CI: 2.16-5.15 and 1.91, 95% CI: 1.21-3.00, respectively), after adjusting for stenosis, demographic, and vascular risk factors. In subjects with unilateral IPH, PR was 2.83, 95% CI: 1.76-4.55, for CBI in the ipsilateral hemisphere after adjusting for stenosis. Among those with unilateral ulceration, PR was 1.82, 95% CI: 1.18-2.81, for total CBI ipsilateral to ulceration after adjusting for stenosis. No statistically significant association was seen with CMBs.

CONCLUSION

Both IPH and plaque ulceration are associated with total, cortical, and lacunar type CBIs but not CMBs suggesting that advanced atherosclerosis contributes predominantly to ischemic markers of subclinical vascular injury.

Carotid Plaque Composition and the Importance of Non-Invasive in Imaging Stroke Prevention

Luminal stenosis has been the standard feature for the current management strategies in patients with atherosclerotic carotid disease. Histological and imaging studies show considerable differences between plaques with identical degrees of stenosis. They indicate that specific plaque characteristics like Intraplaque hemorrhage, Lipid Rich Necrotic Core, Plaque Inflammation, Thickness and Ulceration are responsible for the increased risk of ischemic events. Intraplaque hemorrhage is defined by the accumulation of blood components within the plaque, Lipid Rich Necrotic Core is composed of macrophages loaded with lipid, Plaque Inflammation is defined as the process of atherosclerosis itself and Plaque thickness and Ulceration are defined as morphological features. Advances in imaging methods like Magnetic Resonance Imaging, Ultrasound, Computed Tomography and Positron Emission Tomography have enabled a more detailed characterization of the plaque, and its vulnerability is linked to these characteristics, changing the management of these patients based only on the degree of plaque stenosis. Studies like Rotterdam, ARIC, PARISK, CAPIAS and BIOVASC were essential to evaluate and prove the relevance of these characteristics with cerebrovascular symptoms. A better approach for the prevention of stroke is needed. This review summarizes the more frequent carotid plaque features and the available validation from recent studies with the latest evidence.

Emerging Feature Extraction Techniques for Machine Learning-Based Classification of Carotid Artery Ultrasound Images

Plaque deposits in the carotid artery are the major cause of stroke and atherosclerosis. Ultrasound imaging is used as an early indicator of disease progression. Classification of the images to identify plaque presence and intima-media thickness (IMT) by machine learning algorithms requires features extracted from the images. A total of 361 images were used for feature extraction, which will assist in further classification of the carotid artery. This study presents the extraction of 65 features, which constitute of shape, texture, histogram, correlogram, and morphology features. Principal component analysis (PCA)-based feature selection is performed, and the 22 most significant features, which will improve the classification accuracy, are selected. Naive Bayes algorithm and dynamic learning vector quantization (DLVQ)-based machine learning classifications are performed with the extracted and selected features, and analysis is performed.

Cerebral Small Vessel Disease Burden Related to Carotid Intraplaque Hemorrhage Serves as an Imaging Marker for Clinical Symptoms in Carotid Stenosis

Objectives: In patients with carotid stenosis, to investigate the relationship between carotid intraplaque hemorrhage (IPH) and total burden of cerebral small vessel disease (CSVD) and preliminarily explore whether the total CSVD burden as an imaging marker can distinguish the severity of clinical symptoms. Methods: A total of 108 patients (the mean age was 66 ± 7 years, and 85.2% were male) with unilateral carotid stenosis ≥50% underwent brain MRI and high-resolution MRI for carotid plaque characterization. The total burden of CSVD was calculated by accumulating one point according to the presence or severity of each of the four MRI markers: white matter hyperintensities, lacunes, perivascular spaces, and cerebral microbleeds. Recent clinical symptoms including transient ischemic attack, amaurosis fugax, and ischemic stroke were recorded. The association between intraplaque hemorrhage (IPH) and total CSVD burden was examined adjusted for other risk factors. The symmetry of CSVD burdens between the ipsilateral and contralateral hemispheres of IPH was tested. Imaging features (CSVD score, IPH, degree of stenosis, and completeness of the circle of Willis) were correlated with clinical symptoms by Kruskal-Wallis H test, Chi-square test, and Fisher's exact test. Results: Multivariable logistic regression analysis showed that IPH (OR = 2.98, 95% CI [1.39, 6.40], p = 0.005) was independently associated with a higher CSVD score. The presence of unilateral IPH was associated with the inter-hemispheric CSVD score difference (p = 0.004). Patients with stroke had a higher ipsilateral CSVD score than asymptomatic patients (p = 0.004) and those with transient ischemic attack/amaurosis fugax (p = 0.008). The statistical difference was marginally significant between symptoms and IPH (p = 0.057). No statistical difference was found between the symptoms and degree of stenosis and the completeness of the circle of Willis (p > 0.05). Conclusions: Carotid IPH is associated with an elevated total burden of CSVD in patients with carotid stenosis. Compared with the degree of stenosis, primary collaterals, and IPH, the total CSVD score might be a more effective imaging marker linked with clinical symptoms.

Added value of femoral artery atherosclerosis for determining severity of white matter lesion by carotid atherosclerosis: a magnetic resonance imaging study

BACKGROUND

Previous studies reported that single vascular atherosclerosis was an effective indicator for white matter lesions (WMLs).

PURPOSE

To investigate the added value of femoral atherosclerosis for determining severity of WMLs by carotid atherosclerosis using three-dimensional vessel wall magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Elderly individuals without cardiovascular symptoms within the previous six months were recruited. The plaque features of carotid and femoral arteries were evaluated and compared between individuals with WML score ≤ 3 and those with WML score > 3. Logistic regression and receiver operating characteristic (ROC) analyses were used to determine the value of plaque features in discriminating WMLs with score > 3.

RESULTS

In total, 112 individuals (49 men, mean age 72.0±5.6 years) were included. Participants with a WML score > 3 showed a significantly greater carotid wall area and femoral artery stenosis and higher incidence of carotid calcification and femoral artery calcification and lipid-rich necrotic cores (LRNC) compared to those with a WML score ≤ 3 (all P < 0.05). Carotid artery calcification and femoral artery calcification, LRNC, and stenosis were found to be significantly associated with severe WMLs before and after adjustment for clinical factors (odds ratio 1.51-3.79, all P < 0.05). ROC analysis showed, in discriminating severe WMLs, the area under the curve increased from 0.615 to 0.754 after combining femoral artery LRNC and stenosis with carotid calcification compared to the carotid calcification alone.

CONCLUSION

Characteristics of femoral artery atherosclerosis determined by vessel wall MRI have added value for carotid atherosclerosis in determining the severity of WMLs.

Cardiovascular risk scoring and magnetic resonance imaging detected subclinical cerebrovascular disease

Aims 

Cardiovascular risk factors are used for risk stratification in primary prevention. We sought to determine if simple cardiac risk scores are associated with magnetic resonance imaging (MRI)-detected subclinical cerebrovascular disease including carotid wall volume (CWV), carotid intraplaque haemorrhage (IPH), and silent brain infarction (SBI).

Methods and results

A total of 7594 adults with no history of cardiovascular disease (CVD) underwent risk factor assessment and a non-contrast enhanced MRI of the carotid arteries and brain using a standardized protocol in a population-based cohort recruited between 2014 and 2018. The non-lab-based INTERHEART risk score (IHRS) was calculated in all participants; the Framingham Risk Score was calculated in a subset who provided blood samples (n = 3889). The association between these risk scores and MRI measures of CWV, carotid IPH, and SBI was determined. The mean age of the cohort was 58 (8.9) years, 55% were women. Each 5-point increase (∼1 SD) in the IHRS was associated with a 9 mm³ increase in CWV, adjusted for sex (P < 0.0001), a 23% increase in IPH [95% confidence interval (CI) 9–38%], and a 32% (95% CI 20–45%) increase in SBI. These associations were consistent for lacunar and non-lacunar brain infarction. The Framingham Risk Score was also significantly associated with CWV, IPH, and SBI. CWV was additive and independent to the risk scores in its association with IPH and SBI.

Conclusion 

Simple cardiovascular risk scores are significantly associated with the presence of MRI-detected subclinical cerebrovascular disease, including CWV, IPH, and SBI in an adult population without known clinical CVD.

Machine Learning Quantitation of Cardiovascular and Cerebrovascular Disease: A Systematic Review of Clinical Applications

Research into machine learning (ML) for clinical vascular analysis, such as those useful for stroke and coronary artery disease, varies greatly between imaging modalities and vascular regions. Limited accessibility to large diverse patient imaging datasets, as well as a lack of transparency in specific methods, are obstacles to further development. This paper reviews the current status of quantitative vascular ML, identifying advantages and disadvantages common to all imaging modalities. Literature from the past 8 years was systematically collected from MEDLINE^® and Scopus database searches in January 2021. Papers satisfying all search criteria, including a minimum of 50 patients, were further analysed and extracted of relevant data, for a total of 47 publications. Current ML image segmentation, disease risk prediction, and pathology quantitation methods have shown sensitivities and specificities over 70%, compared to expert manual analysis or invasive quantitation. Despite this, inconsistencies in methodology and the reporting of results have prevented inter-model comparison, impeding the identification of approaches with the greatest potential. The clinical potential of this technology has been well demonstrated in Computed Tomography of coronary artery disease, but remains practically limited in other modalities and body regions, particularly due to a lack of routine invasive reference measurements and patient datasets.

Correlation of Cerebral White Matter Lesions with Carotid Intraplaque Neovascularization assessed by Contrast-enhanced Ultrasound

PURPOSE

Carotid atherosclerotic plaque is closely associated with cerebral white matter lesions (WMLs), while intraplaque neovascularization (IPN) contributes significantly to arterial remodeling and plaque vulnerability. In this study, we aim to evaluate the correlation of carotid IPN with cerebral WMLs.

METHODS

The presence of IPN and WMLs were assessed by contrast-enhanced ultrasound (CEUS) and MRI respectively. IPN was evaluated utilizing semi-quantification visual grading scale and WMLs was divided according to Fazekas grading scale. We investigated the baseline data, Fazekas grades, and IPN grades among 269 participants. We explored the influences of each variable on Fazekas grades using ordinal logistic regression and evaluated the relationship between IPN grades and WMLs Fazekas grades.

RESULTS

Increased age (OR: 1.06, P<0.001), hypertension (OR: 2.17, P=0.002), cerebral infarction (OR: 1.74, P=0.046), and elevated carotid IPN grading were significantly associated with aggravated Fazekas grades (grade 2 or 3). To be specific, people having grade 3, 2, and 1 carotid IPN were 25.84 (P<0.001), 10.64 (P<0.001), and 5.96 (P=0.010) times as likely to have elevated Fazekas grades compared with those who having grade 0 carotid IPN.

CONCLUSION

Increased carotid IPN is independently correlated with aggravated cerebral WMLs.

Gadolinium Enhancement of the Aneurysm Wall in Extracranial Carotid Artery Aneurysms

BACKGROUND AND PURPOSE

The natural history and optimal treatment of extracranial carotid artery aneurysms are unknown. Gadolinium enhancement of the aneurysm wall may reflect aneurysm wall inflammation and instability. In this study, we investigated the feasibility of extracranial carotid artery aneurysm wall imaging and explored a potential relationship of aneurysm wall enhancement with aneurysm growth and the presence of (silent) brain infarcts and white matter lesions.

MATERIALS AND METHODS

Fourteen conservatively treated patients with 15 asymptomatic extracranial carotid artery aneurysms underwent gadolinium-enhanced 3T MR imaging at 2 time points with a 12-month interval. Primary outcome was growth of the aneurysm sac (≥2.0 mm); secondary outcomes were the presence of (silent) brain infarcts and white matter lesions at baseline and follow-up. MR images were reviewed by 2 independent observers, and inter- and intraobserver reproducibility was assessed.

RESULTS

Seven (50%) patients were men; the median age was 55 years (range, 40-69 years). Eleven extracranial carotid artery aneurysms (73%) were saccular (median size, 11 mm; range, 5.0-38.5 mm), and 4 were fusiform (median size, 21.5 mm; range, 10.0-40.0 mm). Eleven of 15 aneurysms (73%) exhibited gadolinium enhancement at baseline. Four aneurysms (27%) showed growth at follow-up imaging, 2 gadolinium-positive (+) and 2 gadolinium-negative (-) (P = .245). Three patients (21%) had ipsilateral brain infarcts at baseline; 1 of them showed a new silent brain infarct at follow-up imaging (gadolinium+). Nine patients (64%) showed bilateral white matter lesions at baseline. In 3 patients, increased white matter lesion severity was observed at follow-up (2 gadolinium+). All observations showed excellent inter- and intraobserver reproducibility.

CONCLUSIONS

In this explorative study, we demonstrated that extracranial carotid artery aneurysm wall imaging was feasible. Future well-powered studies are needed to investigate whether extracranial carotid artery aneurysm gadolinium enhancement predicts aneurysm growth and thromboembolic complications.

Serum insulin levels are associated with vulnerable plaque components in the carotid artery: the Rotterdam Study

BACKGROUND

To investigate the association between fasting serum insulin and glucose levels with atherosclerotic plaque composition in the carotid artery. Impaired insulin and glucose levels are implicated in the etiology of cardiovascular disease; however, their influence on the formation and composition of atherosclerotic plaque remains unclear.

METHODS

In 1740 participants (mean age 72.9 years, 46% women, 14.4% diabetes mellitus) from the population-based Rotterdam Study, we performed carotid MRI to evaluate the presence of calcification, lipid core, and intraplaque hemorrhage in carotid atherosclerosis. All participants also underwent blood sampling to obtain information on serum insulin and glucose levels. Using logistic regression models, we assessed the association of serum insulin and glucose levels (per s.d. and in tertiles) with the different plaque components, while adjusting for sex, age, intima-media thickness, and cardiovascular risk factors.

RESULTS

Serum insulin levels were associated with the presence of intraplaque hemorrhage (adjusted odds ratio (OR): 1.42 (95% CI: 1.12-1.7)) We found no association with the presence of calcification or lipid core. Sensitivity analyses restricted to individuals without diabetes mellitus yielded similar results. No associations were found between serum glucose levels and any of the plaque components.

CONCLUSIONS

Serum insulin levels are associated with the presence of vulnerable components of carotid plaque, specifically with intraplaque hemorrhage. These findings suggest a complex role for serum insulin in the pathophysiology of carotid atherosclerosis and in plaque vulnerability.

Cortical Cerebral Microinfarcts on 3T Magnetic Resonance Imaging in Patients With Carotid Artery Stenosis

Background and Purpose- Carotid artery stenosis is common in the elderly and contributes to cognitive impairment and dementia. Cortical cerebral microinfarcts (CMIs) play an important role in vascular cognitive impairment and dementia. We aimed to investigate the association between CMIs on 3T magnetic resonance imaging and clinical and radiological features, including plaque morphology, and cognitive function in patients with carotid stenosis. Methods- Eighty-nine patients with >30% carotid stenosis on ultrasound were prospectively enrolled, and underwent brain and carotid artery magnetic resonance imaging. CMIs were rated according to predetermined criteria based on 3D-double inversion recovery and fluid-attenuated inversion recovery images. Results- CMIs were identified in 26 patients (29%; median number 0, range 0-9). Poisson regression models adjusted for age and sex revealed that CMIs were associated with intraplaque hemorrhage (rate ratio, 1.95; 95% CI, 1.26-3.18), lacunar infarcts (rate ratio, 1.54; 95% CI, 1.00-2.44), and cortical infarcts (rate ratio, 3.22; 95% CI, 2.20-5.00). These associations were also observed in asymptomatic patients (n=64). Of 81 patients with unilateral carotid stenosis, the prevalence and number of CMIs were significantly higher in the hemisphere ipsilateral to the carotid stenosis than in the contralateral hemisphere ( P=0.005 and P<0.001, respectively). The presence of CMIs was associated with poor cognitive function. Conclusions- Our results indicate that vulnerable carotid plaque increases the risk of CMIs and subsequent cognitive impairment. Carotid atherosclerosis could be a potential therapeutic target for cognitive impairment.

Magnetic Resonance Imaging Identified Brain Ischaemia in Symptomatic Patients Undergoing Carotid Endarterectomy Is Related to Histologically Apparent Intraplaque Haemorrhage

OBJECTIVE

Intraplaque haemorrhage (IPH) has been independently associated with a higher risk of future ipsilateral stroke in patients with carotid artery stenosis. Evaluation of plaque characteristics may contribute to risk assessment of recurrent (silent) cerebrovascular events in order to prioritise patients for timing of treatment. It is unknown if patients showing histologically apparent IPH also have increased risk of silent ischaemic brain lesions in the waiting period between index event and revascularisation.

METHODS

A retrospective analysis was performed based on prospectively collected data of patients included simultaneously in the magnetic resonance imaging (MRI) substudy of the International Carotid Stenting Study and Athero-Express biobank. Patients randomised for carotid endarterectomy (CEA) underwent surgery between 2003 and 2008. Brain MRI was performed one to seven days prior to CEA. Plaques were histologically examined for presence of IPH. The primary outcome parameter was presence of silent ipsilateral brain ischaemia on magnetic resonance diffusion weighted imaging (MR-DWI) appearing hypo or isointense on apparent diffusion coefficient.

RESULTS

Fifty-three patients with symptomatic carotid stenosis meeting the study criteria were identified, of which 13 showed one or more recent ipsilateral DWI lesion on pre-operative scan. The median time between latest ipsilateral neurological event and revascularisation was 45 days (range 6-200) in DWI negative patients vs. 34 days (range 6-74, p = .16) in DWI positive patients. IPH was present in 24/40 (60.0%) DWI negative patients vs. 12/13 (92.3%) DWI positive patients (OR 8.00; 95% CI 0.95-67.7, p = .06). Multivariable logistic regression analysis correcting for age and type of index event revealed that IPH was independently associated with DWI lesions in the waiting period till surgery (OR 10.8; 95% CI 1.17-99.9, p = .04).

CONCLUSION

Symptomatic patients with ipsilateral carotid stenosis and silent brain ischaemia on pre-operative MR-DWI, more often showed pathological evidence of IPH compared with those without ischaemic lesions. This identifies carotid IPH as a marker for patients at risk of silent brain ischaemia and possibly for future stroke and other arterial disease complications. Such patients may be more likely to benefit from CEA than those without evidence of ipsilateral carotid IPH.