Evaluation of computed tomography angiography plaque thickness measurements in high-grade carotid artery stenosis

Prevalence of non-stenotic vulnerable carotid plaques in embolic stroke of undetermined source

INTRODUCTION

The latest research in ischaemic stroke pathogenesis is directed to unveil what is inside embolic stroke of undetermined source (ESUS). Whether vulnerable non stenotic carotid plaques (NSTEPS), i.e. atherosclerotic lesions in carotid arteries determining a stenosis lower than 50%, may represent a cause of stroke in ESUS is a matter of debate. We aimed to study the prevalence of NSTEPS in an ESUS population.

PATIENTS AND METHODS

We retrospectively identified a consecutive ESUS population admitted to the Stroke-Unit of Careggi Hospital, Italy from 2019 to 2022. Characteristics of atherosclerotic plaques (thickness, ulceration, hypodensity) and their location (ipsilateral versus contralateral to the stroke) were studied on carotid CT angiography (CTA). Follow-up data were recorded up to 24 months after stroke.

RESULTS

We identified 57 ESUS patients with unilateral ischaemic lesions studied with CTA; 53 (93%) had an ipsilateral carotid plaque, 81% contralateral, (p = 0.754) and 74% both. Plaques ipsilateral to stroke were ≥ 3 mm thick in 15 (28%) patients; hypodense in 14 (26%) and ulcerated in 5 (9%). The frequency of hypodensity was higher in ipsilateral compared to contralateral plaques (26% vs. 13%, p = 0.039) and ulceration was around four times more frequent, although not statistically significant (9% vs. 2%, p = 0.219). At follow-up, six patients had stroke recurrence (11%), 2 of them were in the same vascular territory of the former.

DISCUSSION AND CONCLUSIONS

Our data suggest that plaques ipsilateral to stroke seem to be more frequently vulnerable and consequently more prone to embolization. Prospective data are needed to clarify the causal role of NSTEPS in ESUS.

Nonstenotic carotid artery plaques on computed tomography angiography in embolic stroke of undetermined source

This study aims to evaluate the role of <50% stenotic cervical carotid artery plaques in embolic stroke of undetermined source (ESUS), focusing on plaque characteristics in symptomatic versus asymptomatic carotid arteries (contralateral). In this cross-sectional observational study, 81 patients who met the diagnostic criteria for ESUS and underwent were retrospectively analyzed. Carotid plaques causing <50% stenosis were examined, noting features such as plaque thickness, degree of luminal stenosis, irregularity, ulceration, calcification, and hypodensity. These characteristics were compared between the ipsilateral and contralateral carotid arteries. The study involved 33 men and 48 women, with plaques ≥3mm thick significantly more common in the ipsilateral carotid arteries (P < .05). Notable features such as plaque ulceration, irregularity, noncalcified plaque, and hypodensity were significantly more frequent ipsilaterally (P < .05). Of the plaque patients, 54.3% (44/81) were on the ipsilateral side, compared to 29.6% (24/81) on the contralateral side (P = .0024). Our findings underscore the potential significance of non-stenotic carotid plaques in ESUS. These plaques, especially those with certain high-risk characteristics, are more prevalent ipsilaterally and should be considered in clinical evaluations and treatment of ESUS.

Using machine learning to predict carotid artery symptoms from CT angiography: A radiomics and deep learning approach

Purpose

To assess radiomics and deep learning (DL) methods in identifying symptomatic Carotid Artery Disease (CAD) from carotid CT angiography (CTA) images. We further compare the performance of these novel methods to the conventional calcium score.

Methods

Carotid CT angiography (CTA) images from symptomatic patients (ischaemic stroke/transient ischaemic attack within the last 3 months) and asymptomatic patients were analysed. Carotid arteries were classified into culprit, non-culprit and asymptomatic. The calcium score was assessed using the Agatston method. 93 radiomic features were extracted from regions-of-interest drawn on 14 consecutive CTA slices. For DL, convolutional neural networks (CNNs) with and without transfer learning were trained directly on CTA slices. Predictive performance was assessed over 5-fold cross validated AUC scores. SHAP and GRAD-CAM algorithms were used for explainability.

Results

132 carotid arteries were analysed (41 culprit, 41 non-culprit, and 50 asymptomatic). For asymptomatic vs symptomatic arteries, radiomics attained a mean AUC of 0.96(± 0.02), followed by DL 0.86(± 0.06) and then calcium 0.79(± 0.08). For culprit vs non-culprit arteries, radiomics achieved a mean AUC of 0.75(± 0.09), followed by DL 0.67(± 0.10) and then calcium 0.60(± 0.02). For multi-class classification, the mean AUCs were 0.95(± 0.07), 0.79(± 0.05), and 0.71(± 0.07) for radiomics, DL and calcium, respectively. Explainability revealed consistent patterns in the most important radiomic features.

Conclusions

Our study highlights the potential of novel image analysis techniques in extracting quantitative information beyond calcification in the identification of CAD. Though further work is required, the transition of these novel techniques into clinical practice may eventually facilitate better stroke risk stratification.

Usefulness of cone-beam computed tomography to predict residual stenosis after carotid artery stenting

OBJECTIVES

The long-term durability of carotid artery stenting (CAS) may be determined by various factors; however, residual stenosis is a known risk factor for in-stent restenosis. The authors of this article utilized cone-beam computed tomography (CBCT) in angiosuite to investigate plaque features affecting the character and quality of stent expansion after CAS.

METHODS

Forty-two CAS cases with both pre- and post-CAS CBCT evaluations were included in this retrospective analysis. Five features derived from pre-CAS images were tested: (1) eccentricity, (2) overballoon, (3) maximum plaque thickness, (4) calcification barrier, and (5) stenotic degree. For post-CAS CBCT, stent configuration was assessed if the stent was expanded and oval or round in shape as well as outward or inward in orientation. Variables were tested if they were associated with oval expansion, outward expansion, and 20% residual stenosis after CAS.

RESULTS

Oval or outward expansion is directly related to residual stenosis. The oval expansion was associated with maximum plaque thickness, and outward expansion was associated with the presence of a calcification barrier. Variables related to > 20% residual stenosis were the maximum plaque thickness, calcification barrier, and pre-CAS stenotic degree.

CONCLUSIONS

CBCT for carotid stenosis may provide valuable information about plaque features, especially calcification features that may interfere with the angioplasty effect, as well as the characteristics and quality of stent expansion. Residual stenosis > 20% was associated with calcification barrier, maximum plaque thickness, and pre-CAS stenotic degree.

Increased Serum CRP-Albumin Ratio is Independently Associated With In-Stent Restenosis After Carotid Artery Stenting

Atherosclerotic stenosis of the carotid artery contributes significantly to ischemic strokes. This study investigates the correlation between the C-reactive protein (CRP) to albumin ratio (CAR) and in-stent restenosis (ISR) in patients (n = 529) undergoing carotid artery stenting. Patients were categorized based on ISR occurrence. Cox regression analyses were performed to identify independent predictors of ISR. The ISR rate was 10.3%. Laboratory analysis revealed higher levels of uric acid, CRP, and CAR in the ISR group. Cox regression identified CAR as an independent predictor of ISR (Hazard ratio (HR): 1.13, 95% CI: 1.03-1.24, P = .01), along with diabetes and smoking. A CAR cut-off of 0.28 predicted ISR with 93% sensitivity and 89% specificity (Area under the curve (AUC): 0.945, 95% CI: 0.923-0.963, P < .001). This study establishes a significant association between CAR and ISR in carotid artery stenting patients. The inflammatory response, indicated by CAR, emerges as a crucial factor in ISR development. The study contributes valuable insights into predicting and preventing ISR, emphasizing the potential of CAR as a prognostic biomarker. This easily accessible and cost-effective biomarker could enhance ISR prediction and guide preventive strategies for high-risk patients.

Systematic review and meta-analysis of the diagnostic value of computed tomography angiography for severe internal carotid artery stenosis

BACKGROUND

Due to the increasing incidence of ischaemic cerebrovascular diseases, the accurate assessment of internal carotid artery (ICA) stenosis is crucial for the development of treatment plans. This systematic review and meta-analysis aimed to evaluate the diagnostic value of computed tomography angiography (CTA) for severe ICAstenosis, thereby providing support for clinical decision-making and promoting diagnostic updates.

METHODS

The PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Database, VIP Database for Chinese Technical Periodicals (VIP), and Chinese Biomedical Literature (CBM) electronic databases were searched from inception to March 21, 2024, to identify publicly available research literature on the use of CTA to diagnose severe ICA stenosis. Literature screening, data extraction, and quality assessment were conducted based on the inclusion and exclusion criteria as well as the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) standards. Data analysis was performed using Stata 17.0 and Meta-Disc 1.4 software. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio of the included studies were calculated using Stata 17.0 software, and forest plots and summary receiver operating characteristic (SROC) curves were generated. The area under the curve (AUC) was calculated, and funnel plots were constructed to assess publication bias.

RESULTS

A total of 16 studies with 2368 vascular segments were included. The meta-analysis revealed that the combined sensitivity and specificity of CTA for severe ICA stenosis were 0.93 (95% CI: 0.88 ~ 0.96) and 0.99 (95% CI: 0.96 ~ 1.00), respectively. The combined positive likelihood ratio and negative likelihood ratio were 92.0 (95% CI: 24.2 ~ 349.6) and 0.07 (95% CI: 0.04 ~ 0.13), respectively. The diagnostic odds ratio was 1302 (95% CI: 257 ~ 6606), and the AUC of the SROC curve was 0.98. The Deeks funnel plot suggested no publication bias among the included studies.

CONCLUSION

CTA demonstrated high sensitivity and specificity for diagnosing severe ICA stenosis. Therefore, this study provided important evidence for the accurate diagnosis and treatment of severe ICA stenosis. However, there was considerable heterogeneity among the included studies, thus indicating the need for additional high-quality prospective studies to confirm the clinical applicability of CTA.

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.

Clinical Application of Dark-blood Imaging in Head and Neck CT Angiography: Effect on Image Quality and Plaque Visibility

RATIONALE AND OBJECTIVES

The aim of this study was to explore the potential of a newly developed dark-blood imaging technique to improve image quality and plaque visibility in head and neck computed tomography (CT) angiography.

MATERIALS AND METHODS

Patients who underwent triphasic head and neck CT angiography scans from August 2021 to March 2023 were retrospectively enrolled (mean age 67.23 ± 10.81 [SD] years, range 43-85 years, 64.7% male). The CT protocol consists of pre-contrast, arterial and delayed phases. Dark-blood images were postprocessed with the contrast-enhancement boost (CE-boost) technique. The quantitative assessment involved evaluating the CT value, image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of calcified plaque and non-calcified plaque. The plaque CNR relative to the vessel lumen (CNRplaque-lumen), vessel wall (CNRplaque-wall), and adjacent muscle (CNRplaque-muscle) was respectively calculated. Two experienced radiologists independently evaluated the CT images (5, best; 1, worst) by four characteristics including calcified plaque visibility, non-calcified plaque visibility, diagnostic confidence, and overall image quality. Inter-rater variability was also evaluated. The artery stenosis rate and plaque burden on dark-blood images were measured and compared with arterial phases. The intraclass correlation coefficient (ICC) was used for consistency analysis. The diagnostic accuracy of dark-blood images for the stenosis rate was evaluated by the area under the curve (AUC).

RESULTS

A total of 43 patients with 54 calcified plaques and 34 non-calcified plaques were assessed in this study. When compared with pre-contrast and delayed phase, dark-blood images yielded significantly higher CNRplaque-lumen and CNRplaque-muscle of calcified (219.79 ± 159.20 and 181.23 ± 112.12, respectively) and non-calcified (30.30 ± 29.11 and 6.28 ± 4.75, respectively) plaques (all p < 0.001). Calcified plaque SNR of dark-blood showed equal or slightly lower than other phases (p > 0.05 or p = 0.02). A major increase was observed in the non-calcified plaque SNR of dark-blood compared to the arterial phase (5.56 ± 3.71 vs. 4.23 ± 3.56, p = 0.02), although there were no apparent differences compared to pre-contrast and delayed phases (p > 0.05). In subjective analyzes, the calcified plaque visibility (4.99 ± 0.07), non-calcified plaque visibility (4.62 ± 0.48), overall image quality (4.81 ± 0.34), and diagnostic confidence (4.74 ± 0.36) in dark-blood images dominated the highest scores (p < 0.001). The subjective scores of radiologists exhibited good consistency (all kappa value>0.7). The dark-blood image and the arterial phase image exhibited good consistency in identifying the stenosis rate (p < 0.001). In the evaluation of plaque burden, the interobserver agreement for dark-blood images was higher compared to arterial phase images (ICC = 0.870 vs. 0.729).

CONCLUSIONS

Compared to conventional triphasic head and neck CT angiography, the CE-boost derived dark-blood imaging demonstrated a significant improvement in image quality and visibility for both calcified and non-calcified plaque assessment.

CIRSE Standards of Practice on Carotid Artery Stenting

BACKGROUND

Carotid artery stenting has been used effectively to treat internal carotid artery stenosis since 1989 (Mathias et al. in World J Surg. 25(3):328-34, 2001), with refined and expanded techniques and tools presently delivering outstanding results in percutaneous endoluminal treatment of carotid artery stenosis.

PURPOSE

This CIRSE Standards of Practice document is directed at interventional radiologists and details the guidelines for carotid artery stenting, as well as the different implementation techniques. In addition to updating all previously published material on the different clinical indications, it will provide all technical details reflective of European practice for carotid artery stenting. CIRSE Standards of Practice documents do not aim to implement a standard of clinical patient care, but rather to provide a realistic strategy and best practices for the execution of this procedure.

METHODS

The writing group, which was established by the CIRSE Standards of Practice Committee, consisted of five clinicians with internationally recognised expertise in carotid artery stenting procedures. The writing group reviewed existing literature on carotid artery stenting procedures, performing a pragmatic evidence search using PubMed to select relevant publications in the English language from 2006 to 2022.

RESULTS

Carotid artery stenting has an established role in the management of internal carotid artery stenosis; this Standards of Practice document provides up-to-date recommendations for its safe performance.

Radiomics Signatures of Carotid Plaque on Computed Tomography Angiography : An Approach to Identify Symptomatic Plaques

PURPOSE

To develop and validate a combined model incorporating conventional clinical and imaging characteristics and radiomics signatures based on head and neck computed tomography angiography (CTA) to assess plaque vulnerability.

METHODS

We retrospectively analyzed 167 patients with carotid atherosclerosis who underwent head and neck CTA and brain magnetic resonance imaging (MRI) within 1 month. Clinical risk factors and conventional plaque characteristics were evaluated, and radiomic features were extracted from the carotid plaques. The conventional, radiomics and combined models were developed using fivefold cross-validation. Model performance was evaluated using receiver operating characteristic (ROC), calibration, and decision curve analyses.

RESULTS

Patients were divided into symptomatic (n = 70) and asymptomatic (n = 97) groups based on MRI results. Homocysteine (odds ratio, OR 1.057; 95% confidence interval, CI 1.001-1.116), plaque ulceration (OR 6.106; 95% CI 1.933-19.287), and carotid rim sign (OR 3.285; 95% CI 1.203-8.969) were independently associated with symptomatic status and were used to construct the conventional model and s radiomic features were retained to establish the radiomics model. Radiomics scores incorporated with conventional characteristics were used to establish the combined model. The area under the ROC curve (AUC) of the combined model was 0.832, which outperformed the conventional (AUC = 0.767) and radiomics (AUC = 0.797) models. Calibration and decision curves analysis showed that the combined model was clinically useful.

CONCLUSION

Radiomics signatures of carotid plaque on CTA can well predict plaque vulnerability, which may provide additional value to identify high-risk patients and improve outcomes.

Identification of vulnerable carotid plaque with CT-based radiomics nomogram

AIM

To develop and validate a radiomics nomogram for identifying high-risk carotid plaques on computed tomography (CT) angiography (CTA).

MATERIALS AND METHODS

A total of 280 patients with symptomatic (n=131) and asymptomatic (n=139) carotid plaques were divided into a training set (n=135), validation set (n=58), and external test set (n=87). Radiomic features were extracted from CTA images. A radiomics model was constructed based on selected features and a radiomics score (rad-score) was calculated. A clinical factor model was constructed by demographics and CT findings. A radiomics nomogram combining independent clinical factors and the rad-score was constructed. The diagnostic performance of three models was evaluated and validated by region of characteristic curves.

RESULTS

Calcification and maximum plaque thickness were the independent clinical factors. Twenty-four features were used to build the radiomics signature. In the validation set, the nomogram (area under the curve [AUC], 0.977; 95% CI, 0.899-0.999) performed better (p=0.017 and p=0.031) than the clinical factor model (AUC, 0.862; 95% CI, 0.746-0.938) and radiomics signature (AUC, 0.944; 95% CI, 0.850-0.987). In external test set, the nomogram (AUC, 0.952; 95% CI, 0.884-0.987) and radiomics signature (AUC, 0.932; 95% CI, 0.857-0.975) showed better discrimination capability (p=0.002 and p=0.037) than clinical factor model (AUC, 0.818; 95% CI, 0.721-0.892).

CONCLUSION

The CT-based nomogram showed satisfactory performance in identification of high-risk plaques in carotid arteries, and it may serve as a potential non-invasive tool to identify carotid plaque vulnerability and risk stratification.

HViT: Hybrid vision inspired transformer for the assessment of carotid artery plaque by addressing the cross-modality domain adaptation problem in MRI

BACKGROUND

Medical image classification is crucial for accurate and efficient diagnosis, and deep learning frameworks have shown significant potential in this area. When a general learning deep model is directly deployed to a new dataset with heterogeneous features, the effect of domain shifts is usually ignored, which degrades the performance of deep learning models and leads to inaccurate predictions.

PURPOSE

This study aims to propose a framework that utilized the cross-modality domain adaptation and accurately diagnose and classify MRI scans and domain knowledge into stable and vulnerable plaque categories by a modified Vision Transformer (ViT) model for the classification of MRI scans and transformer model for domain knowledge classification.

METHODS

This study proposes a Hybrid Vision Inspired Transformer (HViT) framework that employs a convolutional layer for image pre-processing and normalization and a 3D convolutional layer to enable ViT to classify 3D images. Our proposed HViT framework introduces a slim design with a multi-branch network and channel attention, improving patch embedding extraction and information learning. Auxiliary losses target shallow features, linking them with deeper ones, enhancing information gain, and model generalization. Furthermore, replacing the MLP Head with RNN enables better backpropagation for improved performance. Moreover, we utilized a modified transformer model with LSTM positional encoding and Golve word vector to classify domain knowledge. By using ensemble learning techniques, specifically stacking ensemble learning with hard and soft prediction, we combine the predictive power of both models to address the cross-modality domain adaptation problem and improve overall performance.

RESULTS

The proposed framework achieved an accuracy of 94.32% for carotid artery plaque classification into stable and vulnerable plaque by addressing the cross-modality domain adaptation problem and improving overall performance.

CONCLUSION

The model was further evaluated using an independent dataset acquired from different hardware protocols. The results demonstrate that the proposed deep learning model significantly improves the generalization ability across different MRI scans acquired from different hardware protocols without requiring additional calibration data.

Association Between Spotty Calcification in Nonstenosing Extracranial Carotid Artery Plaque and Ipsilateral Ischemic Stroke

Background Small spotty calcifications in the coronary arteries are associated with an increased risk of myocardial infarction. We examined the association between spotty calcifications near the carotid bifurcations and ipsilateral ischemic stroke in patients with <50% luminal stenosis of the extracranial carotid arteries. Methods and Results We used data from the CAESAR (Cornell Acute Stroke Academic Registry), a prospective registry of all patients with acute ischemic stroke admitted to our institution. We included patients who met criteria for cryptogenic stroke and underwent computed tomography angiography and brain magnetic resonance imaging. Patients with extracranial carotid artery stenosis ≥50% and patients with posterior or bilateral anterior circulation infarcts were excluded. We examined the carotid bifurcations for spotty calcifications, defined as ≥1 contiguous regions of luminal calcification ≤3 mm along the long axis of the vessel. We also measured low-density plaque and maximum plaque thickness. The eligible cohort consisted of 117 patients with a mean age of 66.7±1.65 years with a median National Institute of Health Stroke Scale stroke at the time of arrival of 6 (range, 3-13). The number of spotty calcifications present within a low-density plaque was significantly associated with ipsilateral infarction (0.3±0.8 versus 0.1±0.4, P=0.02). Maximum plaque thickness was also significantly associated with ipsilateral infarction (1.4 mm ±1.5 versus 1.0 mm ±1.1, P=0.004). Conclusions Spotty calcifications associated with low-density plaque and maximum plaque thickness were associated with ipsilateral ischemic stroke in patients with nonstenotic carotid atherosclerosis, suggesting a role as imaging markers of high-risk plaque.

Carotid Plaque Diagnosis With 3-Dimensional Computed Tomography Angiography: A Comparison With Magnetic Resonance Imaging-Based Plaque Diagnosis

OBJECTIVE

Although a qualitative diagnosis of plaque causing carotid stenosis has been attempted with carotid computed tomography angiography (CaCTA), no clear findings have been reported. We examined the correlation between the plaque CT values and plaque images obtained by magnetic resonance imaging to derive a qualitative diagnosis of the plaque using CaCTA.

METHODS

Preoperative CaCTA images acquired from patients stented for carotid stenosis were retrospectively analyzed with respect to magnetization-prepared rapid acquisition with gradient echo and time-of-flight magnetic resonance angiography data. Carotid plaques in the stenosed region were quantified in terms of CT density and the plaque/muscle ratio (magnetization-prepared rapid acquisition with gradient echo), and correlations between these 2 features were determined. Plaques were classified as stable or unstable based on the plaque/muscle ratio, with the smallest plaque/muscle ratio observed among plaques positive for intraplaque hemorrhage set as the cutoff value (1.76).

RESULTS

A total of 165 patients (179 plaques) were included. Perioperative complications included minor stroke (n = 3), major stroke (n = 1, fatal), and hyperperfusion (n = 2). The correlation between CT density and the plaque/muscle ratio was nonlinear (P = 0.0139) and negative (P < 0.0001). The cutoff point (1.76) corresponded to a CT density of 83 HU, supporting this value as a standard reference for plaque stability.

CONCLUSIONS

Computed tomography density exhibits a nonlinear (P = 0.0139) and highly negative correlation (P < 0.0001) with the plaque/muscle ratio. Our results demonstrate that plaque characteristics can be meaningfully diagnosed based on CaCTA image data.

Non-stenosing carotid artery plaques in embolic stroke of undetermined source: a retrospective analysis

BACKGROUND

We aim to identify the association between high-risk carotid plaques and their laterality to stroke in ESUS patient population. We also discuss recurrent stroke events and their laterality to the index stroke.

METHODS

This was a retrospective study. We reviewed data for patients with ESUS between June 20, 2016, and June 20, 2021. Using computed tomography angiography, we analyzed plaque features that are associated with ESUS, and then, we identified the recurrent stroke events and characterized lateralization to the index stroke.

RESULTS

Out of 1779 patients with cryptogenic ischemic stroke, we included 152 patients who met the criteria for ESUS. High-risk plaque features were found more often ipsilateral to the stroke side when compared contralaterally: plaque ulceration (19.08% vs 5.26%, p < .0001), plaque thickness > 3 mm (19.08% vs 7.24%, p = 0.001), and plaque length > 1 cm (13.16% vs 5.92%, p = 0.0218). There was also a significant difference in plaque component in which both components (soft and calcified) and only soft plaques were more prevalent ipsilaterally (42.76% vs 23.68% and 17.76% vs 9.21%, respectively, p < .0001). Of the 152 patients, 17 patients were found to have a recurrent stroke event, and 47% (n = 8) had an ipsilateral stroke to the index event. Moreover, stroke was bilateral in 41% of the patients (n = 7), and contralateral in 12% (n = 2).

CONCLUSION

High-risk plaque features studied here were more prevalent ipsilaterally to the stroke side in ESUS than contralaterally. Multicenter studies are needed to form precise prediction models and scoring systems to help guide treatment, i.e., choice of medical therapy and/or revascularization.

Studying plaque characteristics in extracranial carotid artery disease using CT angiography - Risk predictors beyond luminal stenosis

OBJECTIVES

Carotid atherosclerosis accounts for around 20 % of ischemic strokes. Literature on CT angiography [CTA] to study plaque morphology is limited. We studied plaque characteristics of extracranial carotid arteries using CTA to ascertain the high risk features beyond luminal stenosis.

MATERIALS AND METHODS

Retrospective study design, where patients with carotid territory ischemia who underwent CTA from January 2011 till December 2015 were recruited from medical records. CT images were reviewed for plaque characteristics like attenuation, ulceration, plaque thickness and presence of intraluminal thrombus [ILT] along with percentage stenosis.

RESULTS

114 patients with 201 carotids [102 symptomatic and 99 asymptomatic] were reviewed. Mixed density plaques [p = 0.05], ulceration [p = 0.001], ILT [p = 0.004] and higher soft plaque thickness [p < 0.001] were significantly associated with symptomatic carotids whereas calcified plaques were seen in asymptomatic carotids [p = 0.005]. Plaque characteristics were comparable in symptomatic patients with moderate[50-69 %] and severe[70-99 %] stenosis. Multivariate analysis showed that increased soft plaque thickness remained significantly associated with symptomatic carotid. A cut-off value for soft plaque thickness of 2.75 mm could predict symptomatic carotid disease with a sensitivity of 85.2 % and specificity of 68.0 % [Youden's index]. An increase in soft plaque thickness of 4.0 mm significantly predicts change from asymptomatic to symptomatic carotid [p < 0.05].

CONCLUSIONS

Of the studied CTA plaque characteristics, soft plaque thickness is an independent predictor of symptomatic disease irrespective of the percentage stenosis. Soft plaque thickness over 2.75 mm and smallest detectable change[4 mm] are new measures to help ascertain the risk of ischemic events in carotid atherosclerotic disease.

Prediction of Carotid In-Stent Restenosis by Computed Tomography Angiography Carotid Plaque-Based Radiomics

In-stent restenosis (ISR) after carotid artery stenting (CAS) critically influences long-term CAS benefits and safety. The study was aimed at screening preoperative ISR-predictive features and developing predictive models. Thus, we retrospectively analyzed clinical and imaging data of 221 patients who underwent pre-CAS carotid computed tomography angiography (CTA) and whose digital subtraction angiography data for verifying ISR presence were available. Carotid plaque characteristics determined using CTA were used to build a traditional model. Backward elimination (likelihood ratio) was used for the radiomics model. Furthermore, a combined model was built using the traditional and radiomics features. Five-fold cross-validation was used to evaluate the accuracy of the trained classifier and stability of the selected features. Follow-up angiography showed ISR in 30 patients. Carotid plaque length and thickness were independently associated with ISR (multivariate analysis); regarding the conventional model, the area under the curve (AUC) was 0.84 and 0.82 in the training and validation cohorts, respectively. The corresponding AUC values for the radiomics-based model were 0.87 and 0.82, and those for the optimal combined model were 0.88 and 0.83. Plaque length and thickness could independently predict post-CAS ISR, and the combination of radiomics and plaque features afforded the best predictive performance.

Evaluation of non-stenotic carotid atherosclerotic plaques with combined FDG-PET imaging and CT angiography in patients with ischemic stroke of unknown origin

OBJECTIVES

Non-stenotic plaques are an underestimated cause of ischemic stroke. Imaging aspects of high-risk carotid plaques can be identified on CT angiography (CTA) and 18F-fluoro-deoxyglucose positron emission tomography (FDG-PET) imaging. We evaluated in patients with cryptogenic ischemic stroke the usefulness of FDG-PET-CTA.

METHODS

44 patients imaged with CTA and FDG-PET were identified retrospectively. Morphological features were identified on CTA. Intensity of FDG uptake in carotid arteries was quantified on PET.

RESULTS

Patients were imaged 7 ± 8 days after stroke. 44 non-stenotic plaques with increased 18F-FDG uptake were identified in the carotid artery ipsilateral to stroke and 7 contralateral. Most-diseased-segment TBR on FDG-PET was higher in artery ipsilateral vs. contralateral to stroke (2.24 ± 0.80 vs. 1.84 ± 0.50; p < .05). In the carotid region with high FDG uptake, prevalence of hypodense plaques and extent of hypodensity on CTA were higher in artery ipsilateral vs. contralateral to stroke (41% vs. 11%; 0.72 ± 1.2 mm2 vs. 0.13 ± 0.43 mm2; p < .05).

CONCLUSIONS

In patients with ischemic stroke of unknown origin and non-stenotic plaques, we found an increased prevalence of high-risk plaques features ipsilateral vs. contralateral to stroke on FDG-PET-CTA imaging suggesting a causal role for these plaques.

Carotid artery web with fetal posterior cerebral artery variant masquerading as recurrent ipsilateral cryptogenic ischaemic strokes

A 31-year-old woman was referred to vascular surgeons with the history of recurrent ischaemic strokes in two cerebral artery territories over a span of 1 year. On investigation, she was found to have a right internal carotid artery web, with thrombus and a fetal right posterior cerebral artery (PCA), which explained the ischaemic strokes in right middle cerebral and PCA territory. The rare association of these two infrequent entities makes the case a singular one in the medical literature. Successful surgical excision was done after multidisciplinary teamwork. The carotid web was excised as part of carotid artery endarterectomy and repaired with great saphenous vein patch angioplasty. The patient made a good recovery.

Prevalence and characteristics of atherosclerotic plaque: Left compared with right arteries and anterior compared with posterior circulation stroke

PURPOSE

To evaluate atherosclerotic plaque prevalence and characteristics between left and right cervicocephalic arteries and between anterior and posterior circulation stroke (ACS and PCS).

METHODS

This retrospective study included 284 patients with acute ischemic stroke (199 ACS and 85 PCS) involving large-artery atherosclerosis or small-artery occlusion. We assessed atherosclerotic plaque prevalence and characteristics (plaque type, plaque surface morphology, plaque distribution, location of calcified nodules and plaque thickness) in each segment and their comparisons between left and right arteries and between ACS and PCS.

RESULTS

The left subclavian artery (L-SA), common carotid artery (L-CCA) and intracranial vertebral artery (L-IVA) had significantly higher prevalence of atherosclerotic plaque than the right (R) corresponding arteries (70.1% versus 59.5%, P = 0.008), (48.1% versus 28.9%, P < 0.001), (23.9% versus 16%, P = 0.018), respectively. L-SA had a higher prevalence of mixed plaque (non-calcified > calcified) (19.6% versus 16.4%) and noncalcified plaque (51.9% versus 31.7%), and a lower prevalence of calcified plaque (8.9% versus 23.3%) and mixed plaque (calcified > non-calcified) (19.6% versus 28.6%) than R-SA, P < 0.001. The distribution of plaque type in the SA and extracranial vertebral artery (EVA) were significantly different between ACS and PCS. The soft plaque thickness of SA in PCS was significantly greater than that in ACS (3.85 ± 1.27 versus 3.51 ± 1.04, P = 0.032).

CONCLUSIONS

Atherosclerotic plaque prevalence and characteristics vary in different segments, sides and between ACS and PCS. These differences should be noted during plaque diagnosis.

Extracranial Vascular Disease: Carotid Stenosis and Plaque Imaging

Carotid atherosclerosis is an important contributor to ischemic stroke. When imaging carotid atherosclerosis, it is essential to describe both the degree of luminal stenosis and specific plaque characteristics because both are risk factors for cerebrovascular ischemia. Carotid atherosclerosis can be accurately assessed using multiple imaging techniques, including ultrasonography, computed tomography angiography, and magnetic resonance angiography. By understanding the underlying histopathology, the specific plaque characteristics on each of these imaging modalities can be appreciated. This article briefly describes some of the most commonly encountered plaque features, including plaque calcification, intraplaque hemorrhage, lipid-rich necrotic core, and plaque ulceration.

Assessing robustness of carotid artery CT angiography radiomics in the identification of culprit lesions in cerebrovascular events

Radiomics, quantitative feature extraction from radiological images, can improve disease diagnosis and prognostication. However, radiomic features are susceptible to image acquisition and segmentation variability. Ideally, only features robust to these variations would be incorporated into predictive models, for good generalisability. We extracted 93 radiomic features from carotid artery computed tomography angiograms of 41 patients with cerebrovascular events. We tested feature robustness to region-of-interest perturbations, image pre-processing settings and quantisation methods using both single- and multi-slice approaches. We assessed the ability of the most robust features to identify culprit and non-culprit arteries using several machine learning algorithms and report the average area under the curve (AUC) from five-fold cross validation. Multi-slice features were superior to single for producing robust radiomic features (67 vs. 61). The optimal image quantisation method used bin widths of 25 or 30. Incorporating our top 10 non-redundant robust radiomics features into ElasticNet achieved an AUC of 0.73 and accuracy of 69% (compared to carotid calcification alone [AUC: 0.44, accuracy: 46%]). Our results provide key information for introducing carotid CT radiomics into clinical practice. If validated prospectively, our robust carotid radiomic set could improve stroke prediction and target therapies to those at highest risk.

Semiautomated carotid artery plaque composition: are intraplaque CT imaging features associated with cardiovascular risk factors?

BACKGROUND

Little remains known about the connection between cardiovascular (CV) risk factors and carotid plaque morphologies. This study set out to assess for any such associations.

MATERIALS AND METHODS

A retrospective review was completed of consecutive patients that had CTA neck imaging prior to CEA. Body mass index (BMI), tobacco and/or alcohol use, and history of diabetes and/or hypertension were collected from patients' medical records. Lab values were dichotomized based on values: total cholesterol < 200 or ≥ 200; low-density lipoprotein (LDL) < 130 or ≥ 130, high-density lipoprotein < 35 or ≥ 35, and triglycerides < 200 or ≥ 200. A semiautomated analysis of CTA images computed maximum stenosis, intraplaque volumes of intraplaque hemorrhage, lipid-rich necrotic core (LRNC), and matrix, and intraplaque volume and proportional plaque makeup of calcifications of each carotid plaque.

RESULTS

Of 87 included patients, 54 (62.1%) were male. Mean age was 70.1 years old. Both diabetes and hypertension were associated with greater intraplaque calcification volume (p = 0.0009 and p = 0.01, respectively), and greater proportion of calcification within a plaque (p = 0.004 and p = 0.01, respectively). Higher BMI was associated with greater intraplaque volume of LRNC (p=0.02) and matrix (0.0007). Elevated total cholesterol was associated with both larger intraplaque calcification volume (p = 0.04) and greater proportion of calcification within a plaque (p = 0.01); elevated LDL was associated with greater intraplaque calcification volume (p = 0.005).

CONCLUSION

Multiple CV risk factors are associated with morphological differences in carotid artery plaques. Dysregulation of both total cholesterol and LDL and higher BMI are associated with higher volumes of intraplaque LRNC, a marker of plaque vulnerability.

CT imaging features of carotid artery plaque vulnerability

Despite steady advances in medical care, cardiovascular disease remains one of the main causes of death and long-term morbidity worldwide. Up to 30% of strokes are associated with the presence of carotid atherosclerotic plaques. While the degree of stenosis has long been recognized as the main guiding factor in risk stratification and therapeutical decisions, recent evidence suggests that features of unstable, or ‘vulnerable’, plaques offer better prognostication capabilities. This paradigmatic shift has motivated researchers to explore the potentialities of non-invasive diagnostic tools to image not only the lumen, but also the vascular wall and the structural characteristics of the plaque. The present review will offer a panoramic on the imaging modalities currently available to characterize carotid atherosclerotic plaques and, in particular, it will focus on the increasingly important role covered by multidetector computed tomographic angiography.

Carotid Vessel Wall Imaging on CTA

Vessel wall imaging has been increasingly used to characterize plaque beyond luminal narrowing to identify patients who may be at the highest risk of cerebrovascular ischemia. Although detailed plaque information can be obtained from many imaging modalities, CTA is particularly appealing for carotid plaque imaging due to its relatively low cost, wide availability, operator independence, and ability to discern high-risk features. The present Review Article describes the current understanding of plaque characteristics on CTA by describing commonly encountered plaque features, including calcified and soft plaque, surface irregularities, neovascularization, and inflammation. The goal of this Review Article was to provide a more robust understanding of clinically relevant plaque features detectable on routine CTA of the carotid arteries.

Associations Between Features of Nonstenosing Carotid Plaque on Computed Tomographic Angiography and Ischemic Stroke Subtypes

Background

Thromboembolism from nonstenosing carotid plaques may be an underrecognized cause of embolic strokes of undetermined source (ESUS). We evaluated the association between features of nonstenosing atherosclerotic plaque on computed tomographic angiography and ESUS.

Methods and Results

We identified consecutive acute ischemic stroke patients from 2011 to 2015 who had unilateral anterior territory infarction on brain magnetic resonance imaging and a neck computed tomographic angiography. We included ESUS cases and as controls, cardioembolic strokes. Patients with ≥50% internal carotid artery atherosclerotic stenosis ipsilateral to the stroke were excluded from this analysis. Reviewers blinded to infarct location and stroke cause retrospectively evaluated computed tomographic angiography studies for specific plaque features including thickness of the total, soft, and calcified plaque; presence of ulceration; and perivascular fat attenuation. Paired t tests and McNemar's test for paired data were used to compare plaque features ipsilateral versus contralateral to the side of infarction. Ninety‐one patients with ESUS or cardioembolic stroke were included in this study. Total plaque thickness was greater on the infarcted side (2.1±2.0 mm) than the contralateral side (1.2±1.5 mm) (P=0.006) among ESUS cases, but not among cardioembolic cases (1.9±1.6 mm versus 1.8±1.6 mm) (P=0.32).

Conclusions

Among ESUS cases, total plaque thickness was greater ipsilateral to the side of infarction than on the contralateral, stroke‐free side. No such side‐to‐side differences were apparent in cardioembolic strokes. Our findings suggest that nonstenosing large‐artery atherosclerotic plaques represent one underlying mechanism of ESUS.

Semiautomated Characterization of Carotid Artery Plaque Features From Computed Tomography Angiography to Predict Atherosclerotic Cardiovascular Disease Risk Score

PURPOSE

To investigate whether selected carotid computed tomography angiography (CTA) quantitative features can predict 10-year atherosclerotic cardiovascular disease (ASCVD) risk scores.

METHODS

One hundred seventeen patients with calculated ASCVD risk scores were considered. A semiautomated imaging analysis software was used to segment and quantify plaque features. Eighty patients were randomly selected to build models using 14 imaging variables and the calculated ASCVD risk score as the end point (continuous and binarized). The remaining 37 patients were used as the test set to generate predicted ASCVD scores. The predicted and observed ASCVD risk scores were compared to assess properties of the predictive model.

RESULTS

Nine of 14 CTA imaging variables were included in a model that considered the plaque features in a continuous fashion (model 1) and 6 in a model that considered the plaque features dichotomized (model 2). The predicted ASCVD risk scores were 18.87% ± 13.26% and 18.39% ± 11.6%, respectively. There were strong correlations between the observed ASCVD and the predicted ASCVDs, with r = 0.736 for model 1 and r = 0.657 for model 2. The mean biases between observed ASCVD and predicted ASCVDs were -1.954% ± 10.88% and -1.466% ± 12.04%, respectively.

CONCLUSIONS

Selected quantitative imaging carotid features extracted from the semiautomated carotid artery analysis can predict the ASCVD risk scores.

The Growing Field of Imaging of Atherosclerosis in Peripheral Arteries

In the past decades, peripheral arteries have represented a model for the comprehension of atherosclerosis as well as for the development of new diagnostic imaging modalities and therapeutic strategies. Peripheral arteries may represent a window to study atherosclerosis. Pathology has prominently contributed to move the clinical and research attention from the arterial lumen stenosis and angiography to morphological and functional imaging techniques. Evidence from large and prospective cohort or randomized controlled studies is still modest. Nevertheless, several emerging imaging investigations represent a potential tool for a comprehensive "in vivo" evaluation of the entire natural history of peripheral atherosclerosis. This constitutes a demanding assignment, as it would be desirable to obtain both single-lesion focused and extensive arterial system views to achieve the most accurate prognostic information. Our narrative review rests upon the fundamental pathological evidence, summarizing the rapidly growing field of imaging of atherosclerosis in peripheral arteries and presenting a selection of both currently available and emerging imaging techniques.

Computed tomography scan based prediction of the vulnerable carotid plaque

BACKGROUND

Primary to validate a commercial semi-automated computed tomography angiography (CTA) -software for vulnerable plaque detection compared to histology of carotid endarterectomy (CEA) specimens and secondary validating calcifications scores by in vivo CTA with ex vivo non-contrast enhanced computed tomography (NCCT).

METHODS

From January 2014 to October 2016 53 patients were included retrospectively, using a cross-sectional design. All patients underwent both CTA and CEA. Sixteen patients had their CEA specimen NCCT scanned. The semi-automated CTA software analyzed carotid stenosis using different HU values defining plaque components. The predictive values of CTA based detection of vulnerable plaques were calculated. Quantification of calcifications on CTA using region of interest (ROI)-function and mathematical equations was done manually, and validated by NCCT of the CEA specimen.

RESULTS

The semi-automated CTA software had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 89.1% (95% CI, 73.6% - 96.4%), 31.3% (95% CI, 12.1% - 58.5%), 75% (95% CI, 59.3% - 86.2%) and 55.6% (95% CI, 22.6% - 84.6%). Strong correlation between in vivo CTA and ex vivo NCCT in quantification of calcification was observed, but CTA systematically underestimated calcificationsscore (CALS) with increasing calcification.

CONCLUSION

The CTA-software cannot be used in risk assessment of patients, due to poor specificity and NPV. The correlation between in vivo CTA and ex vivo NCCT was strong, proposing it to be used in both scientifically and clinical settings, but studies with larger sample sizes are needed.

Noninvasive Vascular Modulography Method for Imaging the Local Elasticity of Atherosclerotic Plaques: Simulation and In Vitro Vessel Phantom Study

Mechanical and morphological characterization of atherosclerotic lesions in carotid arteries remains an essential step for the evaluation of rupture prone plaques and the prevention of strokes. In this paper, we propose a noninvasive vascular imaging modulography (NIV-iMod) method, which is capable of reconstructing a heterogeneous Young's modulus distribution of a carotid plaque from the Von Mises strain elastogram. Elastograms were computed with noninvasive ultrasound images using the Lagrangian speckle model estimator and a dynamic segmentation-optimization procedure to highlight mechanical heterogeneities. This methodology, based on continuum mechanics, was validated in silico with finite-element model strain fields and ultrasound simulations, and in vitro with polyvinyl alcohol cryogel phantoms based on magnetic resonance imaging geometries of carotid plaques. In silico, our results show that the NiV-iMod method: 1) successfully detected and quantified necrotic core inclusions with high positive predictive value (PPV) and sensitivity value (SV) of 81±10% and 91±6%; 2) quantified Young's moduli of necrotic cores, fibrous tissues, and calcium inclusions with mean values of 32±23, 515±30, and 3160±218 kPa (ground true values are 10, 600, and 5000 kPa); and 3) overestimated the cap thickness by . In vitro, the PPV and SV for detecting soft inclusions were 60±21% and 88±9%, and Young's modulus mean values of mimicking lipid, fibrosis, and calcium were 34±19, 193±14, and 649±118 kPa (ground true values are 25±3, 182±21, and 757±87 kPa).

Association between Carotid Plaque Features on CTA and Cerebrovascular Ischemia: A Systematic Review and Meta-Analysis

BACKGROUND

CTA is a widely available imaging examination that may allow the evaluation of high-risk carotid plaque features.

PURPOSE

Our aim was to evaluate the association between specific carotid plaque features on CTA and ipsilateral cerebrovascular ischemia.

DATA SOURCES

We performed a systematic review of Ovid MEDLINE, Ovid Embase, Scopus, and the Cochrane Library from inception to March 2016 for articles that evaluated the relationship between CTA-detected carotid plaque features and ischemic events, defined as ipsilateral ischemic stroke or transient ischemic attack.

STUDY SELECTION

Sixteen studies were ultimately included after screening 12,557.

DATA ANALYSIS

Two readers recorded data from each study and assessed the study quality with all disagreements resolved by a third reader. A random-effects OR was used to evaluate the association between cerebrovascular ischemia and each of the evaluated plaque features.

DATA SYNTHESIS

We found significant positive relationships with cerebrovascular ischemia for the presence of soft plaque (OR, 2.9; 95% CI, 1.4-6.0), plaque ulceration (OR, 2.2; 95% CI, 1.4-3.4), and increased common carotid artery wall thickness (OR, 6.2; 95% CI, 2.5-15.6). We found a significant negative relationship between calcified plaque and ipsilateral ischemia (OR, 0.5; 95% CI, 0.4-0.7).

LIMITATIONS

We found heterogeneity in the existing literature secondary to lack of standardized plaque features and clinical definitions.

CONCLUSIONS

Soft plaque, plaque ulceration, and increased common carotid artery wall thickness on CTA are associated with ipsilateral cerebrovascular ischemia, while calcified plaque is negatively associated with downstream ischemic events.

Presence, Characteristics, and Prognostic Associations of Carotid Plaque Among People Living With HIV

BACKGROUND

Data from broad populations have established associations between incidental carotid plaque and vascular events. Among people living with HIV (PLWHIV), the risk of vascular events is increased; however, whether incidental carotid plaque is increased and there is an association between incidental carotid plaque, plaque characteristics, and vascular events among PLWHIV is unclear.

METHODS AND RESULTS

Data from the multi-institutional Research Patient Data Registry were used. Presence and characteristics (high-risk plaque, including spotty calcification and low attenuation) of carotid plaque by computerized tomography among PLWHIV without known vascular disease were described. Data were compared with uninfected controls similar in age, sex, and cardiovascular risk factors, including diabetes mellitus, hyperlipidemia, and cigarette smoking to cases. Primary outcome was an atherosclerotic cardiovascular disease event, and secondary outcome was ischemic stroke. Cohort consisted of 209 PLWHIV (45±10 years, 72% male) and 168 controls. Using computerized tomography, PLWHIV without vascular disease had higher rates of any carotid plaque (34% versus 25%; P=0.04), noncalcified (18% versus 5%; P<0.001) and high-risk plaque (25% versus 16%; P=0.03). Over a follow-up of 3 years, 19 atherosclerotic cardiovascular disease events (9 strokes) occurred. Carotid plaque was independently associated with a 3-fold increase in atherosclerotic cardiovascular disease events among PLWHIV (hazard ratio, 2.91; confidence interval, 1.10-7.7, P=0.03) and a 4-fold increased risk of stroke (hazard ratio, 4.43; confidence interval, 1.17-16.70; P=0.02); high-risk plaque was associated with a 3-fold increased risk of atherosclerotic cardiovascular disease events and a 4-fold increased risk of stroke.

CONCLUSIONS

There is an increase in incidental carotid plaque, noncalcified plaque, and high-risk plaque among PLWHIV, and the presence and characteristics of carotid plaque are associated with subsequent vascular events.

Investigation of 3D reduced field of view carotid atherosclerotic plaque imaging

To investigate the feasibility of using CUBE based reduced field of view imaging in atherosclerotic plaque imaging. Twenty-four patients were enrolled in this prospective study (13 males, 11 females, age 63±10). All patients underwent MRI exams consisting of 3D TOF, MPRAGE, iMSDE, DANTE, full FOV and reduced FOV CUBE imaging; 18 patients under went contrast enhanced imaging. The resulting images from different imaging sequences were assessed in terms of blood suppression, SNR, motion artifacts and vascular clarity. Reduced field of view CUBE outperformed MPRAGE, iMSDE and full FOV CUBE in blood suppression (P<0.05); outperformed MPRAGE, iMSDE and DANTE in SNR(P<005); outperformed MPRAGE and iMSDE in motion artifacts (P<005); outperformed MPRAGE and iMSDE in vascular clarity (P<0.05). The identifications of hemorrhage and calcification components were consistent between full FOV CUBE and reduced FOV CUBE (P<0.05). Overall, CUBE combined with reduced field of view imaging would be a promising method in atherosclerotic plaque imaging.

Carotid Plaque Morphology and Ischemic Vascular Brain Disease on MRI

BACKGROUND AND PURPOSE

Vulnerable carotid plaque components are reported to increase the risk of cerebrovascular events. Yet, the relation between plaque composition and subclinical ischemic brain disease is not known. We studied, in the general population, the association between carotid atherosclerotic plaque characteristics and ischemic brain disease on MR imaging.

MATERIALS AND METHODS

From the population-based Rotterdam Study, 951 participants underwent both carotid MR imaging and brain MR imaging. The presence of intraplaque hemorrhage, lipid core, and calcification and measures of plaque size was assessed in both carotid arteries. The presence of plaque characteristics in relation to lacunar and cortical infarcts and white matter lesion volume was investigated and adjusted for cardiovascular risk factors. Stratified analyses were conducted to explore effect modification by sex. Additional analyses were conducted per carotid artery in relation to vascular brain disease in the ipsilateral hemisphere.

RESULTS

Carotid intraplaque hemorrhage was significantly associated with the presence of cortical infarcts (OR, 1.9; 95% confidence interval, 1.1-3.3). None of the plaque characteristics were related to the presence of lacunar infarcts. Calcification was the only characteristic that was associated with higher white matter lesion volume. There was no significant interaction by sex.

CONCLUSIONS

The presence of carotid intraplaque hemorrhage on MR imaging is independently associated with MR imaging-defined cortical infarcts, but not with lacunar infarcts. Plaque calcification, but not vulnerable plaque components, is related to white matter lesion volume.

Carotid Bulb Webs as a Cause of "Cryptogenic" Ischemic Stroke

BACKGROUND AND PURPOSE

Carotid webs are intraluminal shelf-like filling defects at the carotid bulb with recently recognized implications in patients with recurrent ischemic stroke. We sought to determine whether carotid webs are an under-recognized cause of "cryptogenic" ischemic stroke and to estimate their prevalence in the general population.

MATERIALS AND METHODS

A retrospective review of neck CTA studies in young patients with cryptogenic stroke over the past 6 years (n = 33) was performed to determine the prevalence of carotid webs compared with a control group of patients who received neck CTA studies for reasons other than ischemic stroke (n = 63).

RESULTS

The prevalence of carotid webs in the cryptogenic stroke population was 21.2% (95% CI, 8.9%-38.9%). Patients with symptomatic carotid webs had a mean age of 38.9 years (range, 30-48 years) and were mostly African American (86%) and women (86%). In contrast, only 1.6% (95% CI, 0%-8.5%) of patients in the control group demonstrated a web. Our findings demonstrate a statistically significant association between carotid webs and ischemic stroke (OR = 16.7; 95% CI, 2.78-320.3; P = .01).

CONCLUSIONS

Carotid webs exhibit a strong association with ischemic stroke, and their presence should be suspected in patients lacking other risk factors, particularly African American women.

WALL SHEAR STRESS AND OSCILLATORY SHEAR INDEX DISTRIBUTION IN CAROTID ARTERY WITH VARYING DEGREE OF STENOSIS: A HEMODYNAMIC STUDY

A significant proportion of cerebral stroke is a consequence of the arterial stenotic plaque rupture causing local thrombosis or distal embolization. The formation and subsequent rupture of the plaque depends on wall shear stress (WSS) and oscillatory shear index (OSI). The purpose of the present study was to understand the effect of hemodynamics on the spatial and temporal variations of WSS and OSI using realistic models with varying degree of carotid artery stenosis (DOS). Multiple CT volumes were obtained from subjects in the carotid bifurcation zone and the 3D models were generated. A finite volume-based computational fluid dynamics (CFD) method was utilized to understand the hemodynamics in pulsatile flow conditions. It was observed that high stenosis models occupied a large value of normalized WSS in the internal carotid artery (ICA) whereas they had smaller values of normalized WSS in the common carotid artery (CCA). For clinical use, the authors recommend using the spatial average value of oscillatory shear rather than the maximum value for an accurate knowledge about the severity of stenosis. The resultant vorticity changes the direction of spin after the bifurcation zone. Additionally, we propose the use of limiting streamlines as a novel and convenient method to identify the disturbed flow regions that are prone to atherogenesis.

Prevalence and distribution of calcified nodules in carotid arteries in correlation with clinical symptoms

PURPOSE

Calcified nodules ("CN") are responsible for up to 5% of coronary-infarcts and, therefore, classified as minor criteria of "vulnerable" atherosclerotic plaque. We sought to evaluate prevalence and distribution of CN in carotid arteries in correlation with clinical symptoms.

METHODS

178 consecutive patients with unilateral ischemic stroke and carotid plaques ≥2 mm by duplex ultrasound underwent a carotid-black-blood-3T-MRI with fat-saturated pre- and post-contrast T1w-, PDw-, T2w- and TOF images using dedicated surface-coils. CN were defined as distinct calcification with an irregular, protruding, and convex luminal surface. Prevalence of CN was determined in common carotid artery ("CCA") and internal carotid artery ("ICA") in consensus by two reviewers blinded to clinical information.

RESULTS

Thirty seven CN in 28 arteries of 26 patients were identified. Prevalence of CN in CCA compared to ICA was slightly higher (59 vs. 41%), but nearly similar in 66 arteries with ≥30% compared to 290 arteries with <30% stenosis (9.1 vs. 7.6%) and in the artery ipsilateral versus contralateral to stroke (7.9 vs. 7.9%; P values n.s.). Prevalence of CN was significantly higher in 40 symptomatic arteries with ≥30% stenosis compared to asymptomatic 26 arteries (15.6 vs. 0%; P = 0.04). There was a significantly higher prevalence of hypercholesterolemia and hypertension in patients with CN (57.7 vs. 36.0 and 88.5 vs. 66.7%; P values <0.05).

CONCLUSION

CN were found in 7.9% of arteries with carotid-plaques ≥2 mm by duplex-ultrasound; prevalence was significantly higher in symptomatic arteries with ≥30% stenosis compared to asymptomatic with <30% stenosis, suggesting that CN play a role in pathogenesis of ischemic stroke in a small subset of patients.

Carotid artery web and ischemic stroke: A case-control study

OBJECTIVE

To determine whether there is an association between carotid artery web and ischemic stroke.

METHODS

This was a single-center, age- and sex-matched, case-control study. Cases were consecutive patients with anterior circulation ischemic stroke of undetermined etiology (Trial of Org 10172 in Acute Stroke Treatment [TOAST] classification). Controls were consecutive patients with cerebral aneurysms, arteriovenous malformations, or primary intracerebral hemorrhages. Additional inclusion criteria were age <60 years and CT angiography of the neck. Two neuroradiologists diagnosed webs according to previously published criteria. One neuroradiologist also assessed for nonstenotic atherosclerotic plaque (carotid wall thickness ≥3 mm or intramural calcification). We used conditional logistic regression to estimate the odds ratio between carotid web and ischemic stroke and its 95% confidence interval.

RESULTS

Fifty-three of 62 cases (85%) were matched by age (within 1 year) and by sex to 102 controls. There was a carotid web in 4 of 53 cases (9.4%) vs 1 of 102 controls (1.0%, odds ratio = 8.0, 95% confidence interval = 1.2-67, p = 0.032). There was no significant difference in the prevalence of nonstenotic carotid atherosclerotic plaque between the case and control groups. There was agreement on diagnosis of web for 163 of 164 patients (99%) and 7 of 8 webs (88%), and the Cohen κ for interobserver agreement was 0.93.

CONCLUSIONS

There is an association between carotid artery web and ischemic stroke in patients who lack an alternative cause of stroke. Carotid web may be an underappreciated risk factor for stroke.

High Extent of Intracranial Carotid Artery Calcification Is Associated with Downstream Microemboli in Stroke Patients

BACKGROUND

Intracranial arterial calcification (ICAC) is frequently detected on head computed tomography and has been found to be associated with ischemic stroke by recent clinical studies.

AIMS

Based on a hospital-based study, we aimed to compare the occurrence of cerebral microembolic signals (MES) among stroke patients with different degrees of ICAC, which may indicate the potential mechanisms linking ICAC and ischemic stroke in intracranial atherosclerosis patients.

METHODS

This is a post-hoc analysis of our previous clinical study in 2005-2007, recruiting consecutive ischemic stroke patients with middle cerebral artery territory infarctions and good temporal window for MES monitoring. The degrees of ICAC in the Circle of Willis, especially calcification in the ipsilateral intracranial internal carotid artery (iICA), were evaluated both qualitatively and quantitatively on unenhanced head computed tomography.

RESULTS

Among the 68 recruited patients, MES was detected in 26 patients (38.24%). The overall degree of ICAC in the Circle of Willis was similar between patients with and without MES. For calcification in ipsilateral iICA, the presence of MES was more frequent in the high extent group (widest arc of calcification ≥90°) than in the low extent group (54.2% versus 29.5%, P = .046). Logistic regression found that a high extent ipsilateral iICA calcification was an independent risk factor of MES (odds ratio: 3.134; 95% confidence interval, 1.029-9.543; P = .044).

CONCLUSIONS

MES is frequently detected in patients with a high extent of ipsilateral iICA calcification, which suggests that a high extent of iICA calcification indicates artery vulnerability and accounts for the occurrence of microemboli in the corresponding artery.

Nonstenotic carotid plaque on CT angiography in patients with cryptogenic stroke

OBJECTIVE

To determine whether large (≥3 mm thick) but nonstenotic (<50%) carotid artery atherosclerotic plaque predominantly occurs ipsilateral rather than contralateral to cryptogenic stroke.

METHODS

This was a cross-sectional observational study. Using a stroke registry, we identified consecutive patients with anterior circulation embolic stroke of undetermined source (ESUS). Using CT angiography, we measured carotid plaque size (thickness, mm) and carotid artery stenosis (North American Symptomatic Carotid Endarterectomy Trial method) for each patient. We dichotomized plaque size at several predefined thresholds and calculated the frequency of plaque size above each threshold ipsilateral vs contralateral to stroke.

RESULTS

We included 85 patients with ESUS. Plaque with thickness ≥5 mm was present ipsilateral to stroke in 11% of patients, and contralateral in 1% (9/85 vs 1/85; p = 0.008). Plaque with thickness ≥4 mm was present ipsilateral to stroke in 19% of patients, and contralateral in 5% (16/85 vs 4/85; p = 0.002). Plaque with thickness ≥3 mm was present ipsilateral to stroke in 35% of patients, and contralateral in 15% (30/85 vs 13/85; p = 0.001). There was no difference in percentage stenosis ipsilateral vs contralateral to stroke (p = 0.98), and weak correlation between plaque size and stenosis (R(2) = 0.26, p < 0.001).

CONCLUSIONS

Large but nonstenotic carotid artery plaque is considerably more common ipsilateral than contralateral to cryptogenic stroke, suggesting that nonstenotic plaque is an underrecognized cause of stroke. We measured plaque size using CT angiography, a method that could be easily implemented in clinical practice.

A Review on Carotid Ultrasound Atherosclerotic Tissue Characterization and Stroke Risk Stratification in Machine Learning Framework

Cardiovascular diseases (including stroke and heart attack) are identified as the leading cause of death in today's world. However, very little is understood about the arterial mechanics of plaque buildup, arterial fibrous cap rupture, and the role of abnormalities of the vasa vasorum. Recently, ultrasonic echogenicity characteristics and morphological characterization of carotid plaque types have been shown to have clinical utility in classification of stroke risks. Furthermore, this characterization supports aggressive and intensive medical therapy as well as procedures, including endarterectomy and stenting. This is the first state-of-the-art review to provide a comprehensive understanding of the field of ultrasonic vascular morphology tissue characterization. This paper presents fundamental and advanced ultrasonic tissue characterization and feature extraction methods for analyzing plaque. Additionally, the paper shows how the risk stratification is achieved using machine learning paradigms. More advanced methods need to be developed which can segment the carotid artery walls into multiple regions such as the bulb region and areas both proximal and distal to the bulb. Furthermore, multimodality imaging is needed for validation of such advanced methods for stroke and cardiovascular risk stratification.

Plaque morphology (the PLAC Scale) on CT angiography: predicting long-term anatomical success of primary carotid stenting

OBJECT

Carotid angioplasty and stenting has emerged as an alternative to carotid endarterectomy for the treatment of atherosclerotic carotid stenosis. Primary carotid stenting, performed using self-expanding stents alone without deliberate use of embolic protection devices and balloon angioplasty, has been shown to be effective and faster, cheaper, and potentially safer than conventional techniques. However, the long-term morphological results of this technique have not been established. The aim of this study was to determine whether preprocedural carotid plaque imaging at the site of maximal stenosis by using CT angiography (CTA) could predict the long-term morphological outcome of primary carotid stenting.

METHODS

One hundred eighty-one patients were treated over an 11-year period. Preprocedural CTA was performed in 102 of these. A morphological scale (the Predicting Long-term outcome with Angioplasty of the Carotid artery [PLAC] Scale), with grades from 0 to 4 and A or B, was used to evaluate the circumferential degree of plaque calcification, and the presence or absence of soft plaque. All patients were followed using duplex carotid ultrasound and plain radiographs. Satisfactory morphological outcome was defined as a peak systolic velocity < 120 cm/s and internal carotid artery/common carotid artery ratio < 1.4.

RESULTS

The average follow-up duration was 29.7 months (median 24.5 months, range 0.3–87 months). Univariate logistic regression demonstrated that a low calcification grade (p < 0.001), less thick calcification (p < 0.001), and moderate amounts of soft plaque (p < 0.001) are factors that are highly associated with good long-term outcome. Multivariate analyses confirmed that these factors are independent of each other in predicting outcome.

CONCLUSIONS

The long-term morphological outcome of primary carotid stenting was predicted with considerable accuracy by using a straightforward CTA carotid plaque grading scale.

Improving imaging to optimize screening strategies for carotid artery stenosis

Carotid stenosis is a major risk factor for ischemic stroke. Recently, the United States Preventive Services Task Force issued a recommendation against screening for carotid stenosis in the general population. There is the potential for efficient risk-stratifying or staged screening approaches that identify individuals at highest risk for carotid stenosis and stroke, but these tools have yet to be proven effective in external validation studies. In this paper, we review how medical imaging can be used to detect carotid stenosis and highlight several areas that could be improved to identify potentially efficient screening strategies for carotid stenosis.

Atherosclerotic Plaque Analysis: A Pilot Study to Assess a Novel Tool to Predict Outcome Following Lower Limb Endovascular Intervention

INTRODUCTION

Atherosclerotic plaque analysis using computed tomography angiography (CTA) has been found to be accurate and reproducible in the coronary and carotid arteries. The aim of our study was to assess the utility of this technique in predicting outcome following lower limb endovascular interventions.

METHODS

Pre-procedural CTA was retrospectively analysed in 50 patients who had undergone femoropopliteal (F-P) angioplasty (and/or stenting). Plaque analysis was performed using TeraRecon workstation by two observers blinded to the long-term outcome. Using the Hounsfield units (HU) scale atherosclerotic plaque composition was subdivided into volumes of soft (-100-100 HU) fibrocalcific (101-300 HU) or calcified (300-1000 HU) components. The relationship between plaque composition, clinical and procedural variables, and the study end points (vessel patency, binary restenosis rate, and Amputation-Free Survival [AFS]) were assessed using multivariate analysis.

RESULTS

The technical success rate of the endovascular procedure was 98%, with 48% of patients receiving F-P stents. The AFS was 90%, primary patency 84%, assisted primary patency 88%, and binary restenosis 44% all at 1 year. A significantly greater total volume of calcified plaque (1.1 [.01-3.2] cm(3) vs. .11 [0-1.86] cm(3), p < .001) was found in patients developing restenosis (>50%) compared with those who did not. Patients with a calcified plaque volume greater than 1.1 cm(3) had a significantly worse AFS than those with a volume less than 1.1 cm(3) (p = .0038). Multivariate analysis showed that the percentage calcified plaque (p = .003, HR 11.4, 95% CI 1.45-37.29) was an independent predictor of binary restenosis at 12 months, and that absolute volume of calcified plaque (p = .001, HR 3.56, 95% CI 1.64-7.7) was independently associated with AFS.

CONCLUSIONS

The burden of calcified plaque, but not soft or fibrocalcific plaque is related to restenosis, reintervention, and AFS. Computed tomography plaque analysis may form an important non-invasive tool for risk stratification in patients undergoing F-P endovascular procedures.

Moving beyond luminal stenosis: imaging strategies for stroke prevention in asymptomatic carotid stenosis

BACKGROUND

With progressive improvements in medical therapy and resultant reductions in stroke risk, luminal stenosis criteria are no longer adequate to inform decisions to pursue surgical revascularization in patients with asymptomatic carotid artery stenosis.

SUMMARY

In this evidence-based review, we discuss the imaging-based risk stratification strategies that take into account factors beyond luminal stenosis measurements, including cerebral hemodynamics and plaque composition. The existing literature lends support to the use of certain imaging tests in patients with asymptomatic carotid stenosis including cerebrovascular reserve testing, MRI of plaque composition, ultrasound of plaque echolucency, and transcranial Doppler evaluation for microemboli. The highest quality evidence thus far in the literature includes only systematic reviews and meta-analyses of cohort studies with no randomized trials having yet been performed to show how these newer imaging biomarkers could be used to inform treatment decisions in asymptomatic carotid stenosis. Beyond the need for randomized trials, there are additional important steps needed to improve the relevance of evidence supporting risk assessment strategies. Imaging studies evaluating the risk of stroke in carotid disease should clearly define asymptomatic versus symptomatic disease, use uniform definitions of clearly defined outcome measures such as ipsilateral stroke, ensure that imaging interpretations are performed in a manner blinded to treatments and other risk factors, and include cohorts which are on modern intensive medical therapy. Such studies of risk stratification for asymptomatic carotid stenosis will be most valuable if they can integrate multiple high-risk features (including clinical risk factors) into a multi-factorial risk assessment strategy in a manner that is relatively simple to implement and generalizable across a wide range of practice settings. Key Messages: Together, modern imaging strategies allow for a more mechanistic assessment of stroke risk in carotid disease compared to luminal stenosis measurements alone, which, with further validation in randomized controlled trials, may improve current efforts at stroke prevention in asymptomatic carotid stenosis.

Detection of Symptomatic Carotid Plaque Using Source Data from MR and CT Angiography: A Correlative Study

BACKGROUND

Carotid plaque MRI has been a useful method to characterize vulnerable atherosclerotic plaque elements. Recent investigations have suggested that source images from CT angiography (CTA) and MR angiography (MRA) can identify the simple high-risk features of symptom-producing carotid artery plaque. We studied the correlation and relative diagnostic accuracies of CTA and MRA source images in detecting symptomatic carotid artery plaque.

METHODS

Subjects were eligible if they had carotid stenosis between 50 and 99% and had MRA and CTA exams performed within 10 days of one another. We measured the soft (non-calcified) plaque and hard (calcified) plaque thickness on CTA axial source images and intraplaque high-intensity signal (IHIS) on 3D-time-of-flight MRA source images in subjects. We assessed whether a correlation existed between increasing CTA soft plaque thicknesses and the presence of MRA IHIS using the Student's t-test. We calculated the differences in sensitivity and specificity measures of CTA and MRA source-imaging data with the occurrence of recent ipsilateral stroke or transient ischemic attack (TIA) as the reference standard. We also performed logistic regression analyses to evaluate the predictive strength of plaque showing both IHIS and increased CTA soft plaque thickness in predicting symptomatic disease status.

RESULTS

Of 1994 screened patients, 48 arteries met the final inclusion criteria with MRA and CTA performed within 10 days of one another. The mean and median time between CTA and MRA exams were 2.0 days and 1 day, respectively. A total of 34 of 48 stenotic vessels (70.8%) were responsible for giving rise to ipsilateral stroke or TIA. CTA mean soft plaque thickness was significantly greater (4.47 vs. 2.30 mm, p < 0.0001) in patients with MRA-defined IHIS, while CTA hard plaque thickness was significantly greater (2.09 vs. 1.16 mm, p = 0.0134) in patients without MRA evidence of IHIS. CTA soft plaque thickness measurements were more sensitive than MRA IHIS (91.2 vs. 67.6%, p = 0.011) in detecting symptomatic plaque, while differences in specificity were not significantly different (p = 0.1573). In the subset of patients with both IHIS on MRA and plaque thickness >2.4 mm on CTA, the odds ratio of detecting symptomatic plaque, corrected for stenosis severity, was 45.3 (p < 0.0005).

CONCLUSIONS

Unprocessed source images from CTA and MRA, which are routinely evaluated for clinical studies demonstrate the highly correlated presence of IHIS and increasing soft plaque thickness. In particular, plaque that shows high-risk features on both MRA and CTA are very strongly associated with symptom-producing carotid plaque. With further validation, such techniques are promising practical methods of extracting risk information from routine neck angiographic imaging.

CT angiographic features of symptom-producing plaque in moderate-grade carotid artery stenosis

BACKGROUND AND PURPOSE

Emerging evidence indicates that plaque imaging can improve stroke risk stratification in patients with carotid artery atherosclerosis. We studied the association between soft and hard (calcified) plaque thickness measurements on CTA and symptomatic disease status (ipsilateral stroke or TIA) in patients with moderate-grade carotid artery stenosis.

MATERIALS AND METHODS

We measured soft-plaque and hard-plaque thickness on CTA axial source images in each carotid artery plaque in subjects with NASCET 50%-69% ICA stenosis. We used logistic regression and receiver operating characteristic analyses to assess the strength of the association between thickness measurements and prior stroke or TIA.

RESULTS

Twenty of 72 vessels studied (27.7%) had ischemic symptoms ipsilateral to the side of moderate-grade carotid stenosis. Each 1-mm increase in soft plaque resulted in a 3.7 times greater odds of a prior ipsilateral ischemic event (95% CI, 1.9-7.2). Conversely, for each 1-mm increase in hard plaque, the odds of being symptomatic decreased by approximately 80% (OR, 0.22; 95% CI, 0.10%-0.48%). Receiver operating characteristic analysis showed an area under the curve of 0.88 by using soft-plaque thickness measurements to discriminate between asymptomatic and symptomatic plaques. Sensitivity and specificity were optimized by using a maximum soft-plaque thickness of 2.2 mm, which provided a sensitivity of 85% and a specificity of 83%.

CONCLUSIONS

Simple CTA plaque-thickness measurements might differentiate symptomatic and asymptomatic moderate-grade carotid artery plaque. With further prospective validation, CTA plaque measures could function as an easily implementable tool for risk stratification in carotid artery disease.