MRI in the Evaluation of Cryptogenic Stroke and Embolic Stroke of Undetermined Source.

Cryptogenic stroke refers to a stroke of undetermined etiology. It accounts for approximately one-fifth of ischemic strokes and has a higher prevalence in younger patients. Embolic stroke of undetermined source (ESUS) refers to a subgroup of patients with nonlacunar cryptogenic strokes in whom embolism is the suspected stroke mechanism. Under the classifications of cryptogenic stroke or ESUS, there is wide heterogeneity in possible stroke mechanisms. In the absence of a confirmed stroke etiology, there is no established treatment for secondary prevention of stroke in patients experiencing cryptogenic stroke or ESUS, despite several clinical trials, leaving physicians with a clinical dilemma. Both conventional and advanced MRI techniques are available in clinical practice to identify differentiating features and stroke patterns and to determine or infer the underlying etiologic cause, such as atherosclerotic plaques and cardiogenic or paradoxical embolism due to occult pelvic venous thrombi. The aim of this review is to highlight the diagnostic utility of various MRI techniques in patients with cryptogenic stroke or ESUS. Future trends in technological advancement for promoting the adoption of MRI in such a special clinical application are also discussed.

Detection of Dolichoectasia and Atherosclerosis by Automated MRA Tortuosity Metrics in a Population-Based Study.

BACKGROUND: Intracranial vessel tortuosity is a key component of dolichoectasia and has been associated with atherosclerosis and adverse neurologic outcomes. However, the evaluation of tortuosity is mainly a descriptive assessment. PURPOSE: To compare the performance of three automated tortuosity metrics (angle metric [AM], distance metric [DM], and distance-to-axis metric [DTA]) for detection of dolichoectasia and presence of segment-specific plaques. STUDY TYPE: Observational, cross-sectional metric assessment. POPULATION: 1899 adults from the general population; mean age = 76 years, female = 59%, and black = 29%. FIELD STRENGTH/SEQUENCE: 3-T, three-dimensional (3D) time-of-flight MRA and 3D vessel wall MRI. ASSESSMENT: Tortuosity metrics and mean luminal area were quantified for designated segments of the internal carotid artery, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, and entire length of basilar artery (BA). Qualitative interpretations of BA dolichoectasia were assessed based on Smoker's visual criteria. STATISTICAL TESTS: Descriptive statistics (2-sample t-tests, Pearson chi-square tests) for group comparisons. Receiver operating characteristics area under the curve (AUC) for detection of BA dolichoectasia or segment-specific plaque. Model inputs included 1) tortuosity metrics, 2) mean luminal area, and 3) demographics (age, race, and sex). RESULTS: Qualitative dolichoectasia was identified in 336 (18%) participants, and atherosclerotic plaques were detected in 192 (10%) participants. AM-, DM-, and DTA-calculated tortuosity were good individual discriminators of basilar dolichoectasia (AUCs: 0.76, 0.74, and 0.75, respectively), with model performance improving with the mean lumen area: (AUCs: 0.88, 0.87, and 0.87, respectively). Combined characteristics (tortuosity and mean luminal area) identified plaques with better performance in the anterior (AUCs ranging from 0.66 to 0.78) than posterior (AUCs ranging from 0.54 to 0.65) circulation, with all models improving by the addition of demographics (AUCs ranging from 0.62 to 0.84). DATA CONCLUSION: Quantitative vessel tortuosity metrics yield good diagnostic accuracy for the detection of dolichoectasia. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 2.

Central arterial stiffening and intracranial atherosclerosis: the atherosclerosis risk in communities neurocognitive study (ARIC-NCS): Aortic stiffness & intracranial atherosclerosis.

OBJECTIVES: Previous studies suggest an association between central arterial stiffness (CAS) and intracranial atherosclerotic disease (ICAD) among Asian participants with stroke or hypertension; this association has not been evaluated in United States populations. We assessed the cross-sectional association of CAS with ICAD presence and burden in late-life, and differences in association by age, sex, and race. MATERIALS AND METHODS: We conducted a cross-sectional analysis of 1,285 Atherosclerosis Risk in Communities Study participants [mean age 75 (standard deviation: 5) years, 38 % male, 20  % Black] at Visit 5 (2011-2013). CAS was measured as carotid-femoral pulse wave velocity (cfPWV) using the Omron VP-1000 Plus. ICAD was assessed using high-resolution vessel wall MRI and MR angiography. We evaluated associations of a 1 standard deviation (SD) cfPWV (3.02 m/s) and high vs. non-high cfPWV (≥ 13.57 m/s vs. < 13.57 m/s) with presence of plaques (yes/no) and plaque number (0, 1-2, and >2) using multivariable logistic and ordinal logistic regression models adjusted for covariates. RESULTS: Each one SD greater cfPWV was associated with higher odds of plaque presence (odds ratio (OR)=1.32, 95 % confidence interval (CI): 1.22, 1.43), and an incrementally higher odds of number of plaques (OR 1-2 vs. 0 plaques = 1.21, 95 % CI: 1.10, 1.33; OR >2 vs. 0 plaques = 1.51, 95 % CI: 1.33,1.71). Results suggested differences by race, with greater magnitude associations among Black participants. CONCLUSIONS: CAS was positively associated with ICAD presence and burden; cfPWV may be a useful subclinical vascular measure for identification of individuals who are at high risk for cerebrovascular disease.

Relationship Between Central Artery Stiffness, Brain Arterial Dilation, and White Matter Hyperintensities in Older Adults: The ARIC Study-Brief Report.

[Figure: see text].

Essentials for Interpreting Intracranial Vessel Wall MRI Results: State of the Art.

Intracranial vessel wall (VW) MRI has become widely available in clinical practice, providing multiple uses for evaluation of neurovascular diseases. The Vessel Wall Imaging Study Group of the American Society of Neuroradiology has recently reported expert consensus recommendations for the clinical implementation of this technique. However, the complexity of the neurovascular system and caveats to the technique may challenge its application in clinical practice. The purpose of this article is to review concepts essential for accurate interpretation of intracranial VW MRI results. This knowledge is intended to improve diagnostic confidence and performance in the interpretation of VW MRI scans. © RSNA, 2021 Online supplemental material is available for this article.

Advances in Multimodality Carotid Plaque Imaging: AJR Expert Panel Narrative Review.

Contemporary imaging methods provide detailed visualization of carotid athero-sclerotic plaque, enabling a major evolution of in vivo carotid plaque imaging evaluation. The degree of luminal stenosis in the carotid artery bifurcation, as assessed by ultrasound, has historically served as the primary imaging feature for determining ischemic stroke risk and the potential need for surgery. However, stroke risk may be more strongly driven by the presence of specific characteristics of vulnerable plaque, as visualized on CT and MRI, than by traditional ultrasound-based assessment of luminal narrowing. This review highlights six promising imaging-based plaque characteristics that harbor unique information regarding plaque vulnerability: maximum plaque thickness and volume, calcification, ulceration, intraplaque hemorrhage, lipid-rich necrotic core, and thin or ruptured fibrous cap. Increasing evidence supports the association of these plaque characteristics with risk of ischemic stroke, although these characteristics have varying suitability for clinical implementation. Key aspects of CT and MRI protocols for carotid plaque imaging are also considered. Practical next steps and hurdles are explored for implementing routine imaging assessment of these plaque characteristics in addition to, or even as replacement for, traditional assessment of the degree of vascular stenosis on ultrasound, in the identification of individuals at high risk of ischemic stroke.

Temporal course and implications of intracranial atherosclerotic plaque enhancement on high-resolution vessel wall MRI.

PURPOSE: Little is known about the natural history of intracranial atherosclerotic plaque enhancement and its clinical implications. Our objective was to investigate the value of follow-up high-resolution contrast-enhanced vessel wall MRI (VWMRI) for classifying culprit plaques in patients with intracranial atherosclerotic disease (ICAD). METHODS: Fourteen patients with symptomatic ICAD (50% females; median age 48 years) underwent serial 3T VWMRI. Fifty-five plaques were identified and graded based on the likelihood of having caused the ischemic event (non-culprit, indeterminate, culprit) and degree of enhancement (0, 1, 2) at baseline and follow-up (median follow-up, 140 days). For accuracy analysis, plaque enhancement at baseline and stable or increasing plaque enhancement at follow-up was tested to identify a culprit plaque, and areas under the receiver operating characteristic curves (AUCs) were compared. RESULTS: In 37/55 (67.3%) plaques, enhancement grade remained unchanged. Lack of enhancement was only seen in non-culprit plaques at baseline, and none developed enhancement over time. Enhancement never changed more than one grade. Thirty-seven percent (10/27) of non-culprit plaques that enhanced decreased in enhancement grade at follow-up, but no culprit plaques decreased in enhancement. AUC of baseline and follow-up plaque enhancement combined was significantly larger than AUC of baseline plaque enhancement alone to identify culprit plaques (0.733 vs. 0.567, p = 0.0001). CONCLUSION: Contrast enhancement of ICAD can persist months after the ischemic event. Lack of enhancement at baseline or a decrease in enhancement at follow-up suggests that the plaque is not culprit. Persistent enhancement from baseline to follow-up improves accuracy in identifying culprit plaques.

Carotid Artery Wall Thickness and Incident Cardiovascular Events: A Comparison between US and MRI in the Multi-Ethnic Study of Atherosclerosis (MESA).

Purpose To compare common carotid artery (CCA) wall thickness measured manually by using US and semiautomatically by using MRI, and to examine their associations with incident coronary heart disease and stroke. Materials and Methods This prospective study enrolled 698 participants without a history of clinical cardiovascular disease (CVD) from the Multi-Ethnic Study of Atherosclerosis (MESA) from July 2000 to December 2013 (mean age, 63 years; range, 45 to 84 years; same for men and women). All participants provided written informed consent. CCA wall thickness was measured with US as well as both noncontrast proton-density-weighted and intravenous gadolinium-enhanced MRI. Cox proportional hazards models were used to assess the associations between wall thickness measurements by using US and MRI with CVD outcomes. Results The adjusted hazard ratios for coronary heart disease, stroke, and CVD associated with per standard deviation increase in intima-media thickness were 1.10, 1.08, and 1.14, respectively. The corresponding associations for mean wall thickness measured with proton-density-weighted MRI were 1.32, 1.48, and 1.37, and for mean wall thickness measured with gadolinium-enhanced MRI were 1.27, 1.58, and 1.38. When included simultaneously in the same model, MRI wall thickness, but not intima-media thickness, remained associated with outcomes. Conclusion For individuals without known cardiovascular disease at baseline, wall thickness measurements by using MRI were more consistently associated with incident cardiovascular disease, particularly stroke, than were intima-media thickness by using US. © RSNA, 2018 Online supplemental material is available for this article.

Whole-brain arteriography and venography: Using improved velocity-selective saturation pulse trains.

PURPOSE: To develop velocity-selective (VS) MR angiography (MRA) protocols for arteriography and venography with whole-brain coverage. METHODS: Tissue suppression using velocity-selective saturation (VSS) pulse trains is sensitive to radiofrequency field (B1 +) inhomogeneity. To reduce its sensitivity, we replaced the low-flip-angle hard pulses in the VSS pulse train with optimal composite (OCP) pulses. Additionally, new pulse sequences for arteriography and venography were developed by placing spatially selective inversion pulses with a delay to null signals from either venous or arterial blood. The VS MRA techniques were compared to the time-of-flight (TOF) MRA in six healthy subjects and two patients at 3T. RESULTS: More uniform suppression of stationary tissue was observed when the hard pulses were replaced by OCP pulses in the VSS pulse trains, which improved contrast ratios between blood vessels and tissue background for both arteries (0.87 vs. 0.77) and veins (0.80 vs. 0.59). Both arteriograms and venograms depicted all major cervical and intracranial arteries and veins, respectively. Compared to TOF MRA, VS MRA not only offers larger spatial coverage but also depicts more small vessels. Initial clinical feasibility was shown in two patients with comparisons to TOF protocols. CONCLUSION: Noncontrast-enhanced whole-brain arteriography and venography can be obtained without losing sensitivity to small vessel detection. Magn Reson Med 79:2014-2023, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Patterns and Implications of Intracranial Arterial Remodeling in Stroke Patients.

BACKGROUND AND PURPOSE: Preliminary studies suggest that intracranial arteries are capable of accommodating plaque formation by remodeling. We sought to study the ability and extent of intracranial arteries to remodel using 3-dimensional high-resolution black blood magnetic resonance imaging and investigate its relation to ischemic events. METHODS: Forty-two patients with cerebrovascular ischemic events underwent 3-dimensional time-of-flight magnetic resonance angiography and contrast-enhanced black blood magnetic resonance imaging examinations at 3 T for intracranial atherosclerotic disease. Each plaque was classified by location (eg, posterior versus anterior circulation) and its likelihood to have caused a stroke identified on magnetic resonance imaging (culprit, indeterminate, or nonculprit). Lumen area, outer wall area, and wall area were measured at the lesion and reference sites. Plaque burden was calculated as wall area divided by outer wall area. The arterial remodeling ratio (RR) was calculated as outer wall area at the lesion site divided by outer wall area at the reference site after adjusting for vessel tapering. Arterial remodeling was categorized as positive if RR>1.05, intermediate if 0.95≤RR≤1.05, and negative if RR<0.95. RESULTS: One hundred and thirty-seven plaques were identified in 42 patients (37% [50] posterior and 63% [87] anterior). Compared with anterior circulation plaques, posterior circulation plaques had a larger plaque burden (77.7±15.7 versus 69.0±14.0; P=0.008), higher RR (1.14±0.38 versus 0.95±0.32; P=0.002), and more often exhibited positive remodeling (54.0% versus29.9%; P=0.011). Positive remodeling was marginally associated with downstream stroke presence when adjusted for plaque burden (odds ratio 1.34, 95% confidence interval: 0.99-1.81). CONCLUSIONS: Intracranial arteries remodel in response to plaque formation, and posterior circulation arteries have a greater capacity for positive remodeling and, consequently, may more likely elude angiographic detection. Arterial remodeling may provide insight into stroke risk.

Prevalence of Intracranial Atherosclerotic Stenosis Using High-Resolution Magnetic Resonance Angiography in the General Population: The Atherosclerosis Risk in Communities Study.

BACKGROUND AND PURPOSE: Intracranial atherosclerotic stenosis (ICAS) is a common cause of stroke, but little is known about its epidemiology. We studied the prevalence of ICAS and its association with vascular risk factors using high-resolution magnetic resonance angiography in a US cardiovascular cohort. METHODS: The Atherosclerosis Risk in Communities (ARIC) study recruited participants from 4 US communities from 1987 to 1989. Using stratified sampling, we selected 1980 participants from visit 5 (2011-2013) for high-resolution 3T-magnetic resonance angiography. All images were analyzed in a centralized laboratory, and ICAS was graded as: no stenosis, <50% stenosis, 50% to 69% stenosis, 70% to 99% stenosis, and complete occlusion. We calculated per-vessel and per-person prevalence of ICAS (weighted for n=6538 visit 5 participants) and also estimated the US prevalence. We used multivariable logistic regression to identify variables independently associated with ICAS. RESULTS: Subjects who had an adequate magnetic resonance angiography (n=1765) were aged 67 to 90 years, 41% were men, 70% were white, and 29% were black. ICAS was prevalent in 31% of participants and 9% had ICAS ≥50%. Estimated US prevalence of ICAS ≥50% for 65 to 90 years old was 8% for whites and 12% for blacks. Older age, black race, higher systolic blood pressure, and higher low-density lipoprotein cholesterol levels were associated with increased odds of ICAS, whereas higher levels of high-density lipoprotein cholesterol and use of cholesterol-lowering medications were associated with decreased odds of ICAS. Body mass index and smoking were not associated with ICAS. CONCLUSIONS: The prevalence of ICAS in older adults is high, and it could be a target for primary prevention of stroke and dementia in this population.

MR Imaging Measures of Intracranial Atherosclerosis in a Population-based Study.

Purpose To implement a magnetic resonance (MR) imaging protocol to measure intracranial atherosclerotic disease (ICAD) in a population-based multicenter study and report examination and reader reliability of these MR imaging measurements and descriptive statistics representative of the general population. Materials and Methods This prospective study was approved by the institutional review boards and compliant with HIPAA. Atherosclerosis Risk in Communities (ARIC) study participants (n = 1980) underwent brain MR imaging from 2011 to 2013 at four ARIC sites. Imaging included three-dimensional black-blood MR imaging and time-of-flight MR angiography. One hundred two participants returned for repeat MR imaging to estimate examination and reader variability. Plaque presence according to vessel segment was recorded. Quantitative measurements included lumen size and degree of stenosis, wall and/or plaque thickness, area and volume, and normalized wall index for each vessel segment. Reliability was assessed with percentage agreement, κ statistics, and intraclass correlation coefficients. Results Of the 1980 participants, 1755 (mean age, 77.6 years; 1026 women [59%]; 1234 white [70%]) completed examinations with adequate to excellent image quality. The weighted ICAD prevalence was 34.4% (637 of 1755 participants) and was higher in men than women (38.5% [302 of 729 participants] vs 31.7% [335 of 1026 participants], respectively; P = .012) and in African Americans compared with whites (41.1% [215 of 518 participants] vs 32.4% [422 of 1234 participants], respectively; P = .002). Percentage agreement of plaque identification per participant was 87.0% (interreader estimate), 89.2% (intrareader estimate), and 89.9% (examination estimate). Examination and reader reliability ranged from fair to good (κ, 0.50-0.78) for plaque presence and from good to excellent (intraclass correlation coefficient, 0.69-0.99) for quantitative vessel wall measurements. Conclusion Vessel wall MR imaging is a reliable tool for identifying and measuring ICAD and provided insight into ICAD distribution across a U.S. community-based population. (©) RSNA, 2016 Online supplemental material is available for this article.

Improved cerebrospinal fluid suppression for intracranial vessel wall MRI.

PURPOSE: To develop and assess a three-dimensional (3D) high resolution black blood MRI (BBMRI) method for evaluation of intracranial vessels with improved cerebrospinal fluid (CSF) suppression. MATERIALS AND METHODS: The anti-driven-equilibrium (ADE) pulse was incorporated into a variable flip-angle TSE-based 3D BBMRI to improve CSF suppression. ADE-BBMRI was optimized in 8 participants and compared with BBMRI, with acquired 0.5 mm isotropic resolution and scan time of 5.4 min at 3 Tesla. Contrast-enhanced ADE-BBMRI protocol was implemented in nine patients with intracranial atherosclerosis. Signal and morphological measurements were compared between ADE-BBMRI and BBMRI, as well as pre- and postcontrast ADE-BBMRI. Reliability was assessed by intraclass correlations (ICC). RESULTS: ADE-BBMRI effectively suppressed the surrounding CSF signal of intracranial vessels, with a 36-44% reduction compared with BBMRI. ADE-BBMRI also reduced the overall wall signal by 8-8.5%, but provided a significant improvement in wall-to-CSF contrast-to-noise ratio over BBMRI (middle cerebral artery, 5.93 ± 0.59 versus 3.95 ± 1.67, P < 0.01; basilar artery, 3.8 ± 1.76 versus 1.34 ± 0.54, P = 0.01, respectively). No differences were noted in morphological measurements between ADE-BBMRI and BBMRI (lumen area, 6.35 ± 2.87 versus 6.32 ± 2.84 mm(2) ; wall area, 1.28 ± 0.52 versus 1.27 ± 0.53 mm(2) ; mean wall thickness, 0.93 ± 0.30 versus 0.93 ± 0.32 mm; maximum wall thickness, 1.27 ± 0.33 versus 1.28 ± 0.36 mm, all P > 0.05). Contrast enhanced ADE-BBMRI improved the plaque delineation by the increased wall signal, wall-to-CSF and wall-to-blood contrast-to-noise ratio. ICC ranged from 0.54 to 0.95. CONCLUSION: The 3D ADE-BBMRI provides excellent blood and CSF suppression, and accurate measurements of intracranial vessels at 0.5 mm isotropic resolution in 5 min. Its clinical application may provide insight into stroke risk. J. Magn. Reson. Imaging 2016;44:665-672.

Is carotid intima-media thickness as predictive as other noninvasive techniques for the detection of coronary artery disease?

Carotid intima-media thickness (CIMT) measured by B-mode ultrasound is the most widely used noninvasive imaging method to assess atherosclerosis and cardiovascular risk. CIMT has been consistently associated with coronary artery disease and stroke; however, recent meta-analyses and systematic reviews suggest that its clinical usefulness may be limited because the addition of CIMT to traditional risk factors has not improved the risk prediction of cardiovascular events in the general population. Characterizing the carotid wall by MRI may have greater clinical utility compared with CIMT measurements by ultrasound. Unlike CIMT, MRI measurements of wall thickness include the adventitia and may be sensitive to adventitial thickening that results from vasa vasorum proliferation as a sign of early plaque development. MRI also has the ability to image the entire circumference of the carotid wall, including the outer wall of the carotid bulb where plaque forms in its earliest stage, and identify plaque components such as the lipid core, fibrous cap, and intraplaque hemorrhage that are closely related to plaque vulnerability and cardiovascular risk. Additional research is needed to assess the added prognostic value of MRI measurements of wall and plaque features in risk prediction beyond traditional risk factors.

Carotid bifurcation geometry is an independent predictor of early wall thickening at the carotid bulb.

BACKGROUND AND PURPOSE: Lumen geometry has long been suspected as a risk factor for atherosclerosis by virtue of its influence on blood flow disturbances. Confirmation of this geometric risk hypothesis has, however, proved challenging owing to possible effects of wall thickening on geometry and unproven links between candidate geometric variables and disturbed flow. The purpose of this study was to overcome these challenges. METHODS: The study relied on imaging and risk factor data from progressively refined subsets of the Atherosclerosis Risk in Communities (ARIC) Carotid MRI study. Group 1 (n=467) included only nonstenotic cases having sufficient quality angiography for 3-dimensional analysis. Group 2 (n=346) excluded cases from group 1 having common and internal carotid artery wall thickness above previously identified thresholds for inward remodeling. Group 3 (n=294) excluded cases from group 2 having lumen irregularities and thus was least likely to include lumen geometries influenced by wall thickening. RESULTS: Multiple linear regressions showed that for group 3, bifurcation flare and proximal curvature were independent predictors of internal carotid artery wall thickness, consistent with their previously demonstrated roles in predicting disturbed flow. For the broadest group 1, flare was an independent predictor of internal carotid artery wall thickness but with a sign change in regression coefficient reflecting effects of wall thickening on lumen geometry. CONCLUSIONS: Carotid bifurcation geometry is an independent, albeit weak, predictor of its early wall thickening, but only when assumptions about geometric factors, and the influence of disease on them, are confronted. This highlights pitfalls of previous attempts to confirm geometric risk of atherosclerosis.

Intracranial plaque enhancement in patients with cerebrovascular events on high-spatial-resolution MR images.

PURPOSE: To characterize intracranial plaque inflammation in vivo by using three-dimensional (3D) high-spatial-resolution contrast material-enhanced black-blood (BB) magnetic resonance (MR) imaging and to investigate the relationship between intracranial plaque inflammation and cerebrovascular ischemic events. MATERIALS AND METHODS: The study was approved by the institutional review board and was HIPAA compliant. Twenty-seven patients (19 men; mean age, 56.8 years ± 12.4 [standard deviation]) with cerebrovascular ischemic events (acute stroke, n = 20; subacute stroke, n = 2; chronic stroke, n = 3; transient ischemic attack, n = 2) underwent 3D time-of-flight MR angiography and contrast-enhanced BB 3-T MR imaging for intracranial atherosclerotic disease. Each identified plaque was classified as either culprit (the only or most stenotic lesion upstream from a stroke), probably culprit (not the most stenotic lesion upstream from a stroke), or nonculprit (not within the vascular territory of a stroke). Plaque contrast enhancement was categorized on BB MR images (grade 0, enhancement less than or equal to that of normal arterial walls seen elsewhere; grade 1, enhancement greater than grade 0 but less than that of the pituitary infundibulum; grade 2, enhancement greater than or equal to that of the pituitary infundibulum), and degree of contrast enhancement was calculated. Associations of the likelihood of being a culprit lesion with both plaque contrast enhancement and plaque thickness were estimated with ordinal logistic regression. RESULTS: Seventy-eight plaques were identified in 20 patients with acute stroke (21 [27%] culprit, 12 [15%] probably culprit, and 45 [58%] nonculprit plaques). In these patients, grade 2 contrast enhancement was associated with culprit plaques (odds ratio 34.6; 95% confidence interval: 4.5, 266.5 compared with grade 0) when adjusted for plaque thickness. Grade 0 was observed in only nonculprit plaques. Culprit plaques had a higher degree of contrast enhancement than did nonculprit plaques (25.9% ± 13.4 vs 13.6% ± 12.3, P = .003). CONCLUSION: Contrast enhancement of intracranial atherosclerotic plaque is associated with its likelihood to have caused a recent ischemic event and may serve as a marker of its stability, thereby providing important insight into stroke risk.

Carotid artery plaque morphology and composition in relation to incident cardiovascular events: the Multi-Ethnic Study of Atherosclerosis (MESA).

PURPOSE: To determine if carotid plaque morphology and composition with magnetic resonance (MR) imaging can be used to identify asymptomatic subjects at risk for cardiovascular events. MATERIALS AND METHODS: Institutional review boards at each site approved the study, and all sites were Health Insurance Portability and Accountability Act (HIPAA) compliant. A total of 946 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) were evaluated with MR imaging and ultrasonography (US). MR imaging was used to define carotid plaque composition and remodeling index (wall area divided by the sum of wall area and lumen area), while US was used to assess carotid wall thickness. Incident cardiovascular events, including myocardial infarction, resuscitated cardiac arrest, angina, stroke, and death, were ascertained for an average of 5.5 years. Multivariable Cox proportional hazards models, C statistics, and net reclassification improvement (NRI) for event prediction were determined. RESULTS: Cardiovascular events occurred in 59 (6%) of participants. Carotid IMT as well as MR imaging remodeling index, lipid core, and calcium in the internal carotid artery were significant predictors of events in univariate analysis (P < .001 for all). For traditional risk factors, the C statistic for event prediction was 0.696. For MR imaging remodeling index and lipid core, the C statistic was 0.734 and the NRI was 7.4% and 15.8% for participants with and those without cardiovascular events, respectively (P = .02). The NRI for US IMT in addition to traditional risk factors was not significant. CONCLUSION: The identification of vulnerable plaque characteristics with MR imaging aids in cardiovascular disease prediction and improves the reclassification of baseline cardiovascular risk.

Vessel Wall Imaging Features of Spontaneous Intracranial Carotid Artery Dissection.

BACKGROUND AND OBJECTIVES: Intracranial dissection is an important cause of stroke often with nonspecific angiographic features. Vessel wall imaging (VWI) can detect dissections, but intracranial applications remain unvalidated by pathologic specimens. We sought to determine the ability of VWI to identify the rarely reported spontaneous intracranial carotid dissection (sICD) guided by postmortem validation. METHODS: VWI features of sICD, validated by postmortem specimen analysis in 1 patient, included luminal enhancement within a hypoenhancing outer wall, narrowing the mid to distal ophthalmic (C6) segment, relatively sparing the communicating (C7) segment. VWI examinations were reviewed to identify patients (1) with matching imaging features, (2) no evidence of other vasculopathies (i.e., inflammatory, intracranial atherosclerotic disease [ICAD]), and (3) adequate image quality. These sICD VWI features were compared with those in patients with known ICAD causing similar narrowing of C6 and relative sparing of C7 by a Fisher exact test accounting for multiple samples. RESULTS: Among 407 VWI examinations, 8 patients were identified with 14 sICDs, all women aged 30-56 years, 6 (75%) bilateral. All patients with sICD had risk factors of dissection (e.g., recently postpartum, fibromuscular dysplasia, and hypertension) and 3 (37.5%) had intracranial dissections elsewhere. Seven (87.5%) were diagnosed as moyamoya syndrome on initial angiography. Enhancing lesions varied from thin flap-like defects (n = 6) to thick tissue along the superolateral wall of the internal carotid artery, within the hypoenhancing outer wall. Compared with 10 intracranial carotid plaques in 8 patients with ICAD, sICD demonstrated stronger (84.6% vs 20.0%, p = 0.003-0.025) and more homogeneous (61.5% vs 0.0%, p = 0.005-0.069) enhancement and less positive remodeling (0.0% vs 60.0%, p = 0.004-0.09). T1 hyperintensity was identified in 5 sICDs in 3 patients but not identified in ICAD. Three patients with serial imaging (8- to 39.8-month maximum intervals) revealed little to no changes in stenosis, wall thickening, or enhancement. DISCUSSION: sICD is distinguishable on VWI from ICAD by enhancement characteristics, less positive remodeling, and clinical parameters. These VWI features should raise suspicion especially in young women with risk factors of dissection. Temporal stability and a lack of T1 hyperintensity should not discourage diagnosing sICD.

Association of brain arterial diameters with demographic and anatomical factors in a multi-national pooled analysis of cohort studies.

BACKGROUND AND PURPOSE: Brain arterial diameters are markers of cerebrovascular disease. Demographic and anatomical factors may influence arterial diameters. We hypothesize that age, sex, height, total cranial volume (TCV), and persistent fetal posterior cerebral artery (fPCA) correlate with brain arterial diameters across populations. METHODS: Participants had a time-of-flight MRA from nine international cohorts. Arterial diameters of the cavernous internal carotid arteries (ICA), middle cerebral arteries (MCA), and basilar artery (BA) were measured using LAVA software. Regression models assessed the association between exposures and brain arterial diameters. RESULTS: We included 6,518 participants (mean age: 70 ± 9 years; 41% men). Unilateral fPCA was present in 13.2% and bilateral in 3.2%. Larger ICA, MCA, and BA diameters correlated with older age (Weighted average [WA] per 10 years: 0.18 mm, 0.11 mm, and 0.12 mm), male sex (WA: 0.24 mm, 0.13 mm, and 0.21 mm), and TCV (WA: for one TCV standard deviation: 0.24 mm, 0.29 mm, and 0.18 mm). Unilateral and bilateral fPCAs showed a positive correlation with ICA diameters (WA: 0.39 mm and 0.73 mm) and negative correlation with BA diameters (WA: -0.88 mm and -1.73 mm). Regression models including age, sex, TCV, and fPCA explained on average 15%, 13%, and 25% of the ICA, MCA, and BA diameter interindividual variation, respectively. Using height instead of TCV as a surrogate of head size decreased the R-squared by 3% on average. CONCLUSION: Brain arterial diameters correlated with age, sex, TCV, and fPCA. These factors should be considered when defining abnormal diameter cutoffs across populations.

Carotid Plaque-RADS: A Novel Stroke Risk Classification System.

BACKGROUND: Carotid artery atherosclerosis is highly prevalent in the general population and is a well-established risk factor for acute ischemic stroke. Although the morphological characteristics of vulnerable plaques are well recognized, there is a lack of consensus in reporting and interpreting carotid plaque features. OBJECTIVES: The aim of this paper is to establish a consistent and comprehensive approach for imaging and reporting carotid plaque by introducing the Plaque-RADS (Reporting and Data System) score. METHODS: A panel of experts recognized the necessity to develop a classification system for carotid plaque and its defining characteristics. Using a multimodality analysis approach, the Plaque-RADS categories were established through consensus, drawing on existing published reports. RESULTS: The authors present a universal classification that is applicable to both researchers and clinicians. The Plaque-RADS score offers a morphological assessment in addition to the prevailing quantitative parameter of "stenosis." The Plaque-RADS score spans from grade 1 (indicating complete absence of plaque) to grade 4 (representing complicated plaque). Accompanying visual examples are included to facilitate a clear understanding of the Plaque-RADS categories. CONCLUSIONS: Plaque-RADS is a standardized and reliable system of reporting carotid plaque composition and morphology via different imaging modalities, such as ultrasound, computed tomography, and magnetic resonance imaging. This scoring system has the potential to help in the precise identification of patients who may benefit from exclusive medical intervention and those who require alternative treatments, thereby enhancing patient care. A standardized lexicon and structured reporting promise to enhance communication between radiologists, referring clinicians, and scientists.