Ye Qiao

Intracranial arterial wall imaging using three-dimensional high isotropic resolution black blood MRI at 3.0 Tesla.

To develop a high isotropic‐resolution sequence to evaluate intracranial vessels at 3.0 Tesla (T).

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 plaque neovascularization and hemorrhage detected by MR imaging are associated with recent cerebrovascular ischemic events.

BACKGROUND AND PURPOSE: Pathologic studies suggest that neovascularization and hemorrhage are important features of plaque vulnerability for disruption. Our aim was to determine the associations of these features in carotid plaques with previous cerebrovascular ischemic events by using high-resolution CE-MRI. MATERIALS AND METHODS: Forty-seven patients (36 men; mean age 72.5 ± 10 years) underwent CE-MRI and MRA examinations for carotid plaque at 3T. IPH presence was recorded. Neovascularity was categorized by the degree of adventitial enhancement (0, absent; 1, <50%; 2, ≥50%). Reader variability was assessed by using weighted κ. Associations with events were determined by using multivariable logistic regression. RESULTS: Intra- and inter-reader agreement for grading adventitial enhancement were good to excellent. IPH was present in 49% of patients and was associated with events (P = .03). Patients grouped by categories 0, 1, and 2 adventitial enhancement had increasing frequencies of events (14% category 0, 48% category 1, 65% category 2; P = .02). Events were associated with IPH (OR, 10.18; 95% CI, 1.42–72.21) and adventitial enhancement (compared with category 0: OR, 14.90, 95% CI, 0.98–225.93 for category 1; OR, 51.17, 95% CI, 3.4–469.8 for category 2) after controlling for age, sex, cardiovascular risk factors, wall thickness, and stenosis. Stenosis was not associated with events. CONCLUSIONS: Adventitial enhancement and IPH are independently associated with previous events and may provide important insight into stroke risk not achievable by stenosis.

Identification of Intraplaque Hemorrhage on MR Angiography Images: A Comparison of Contrast-Enhanced Mask and Time-of- Flight Techniques

BACKGROUND AND PURPOSE: MRA is widely used to measure carotid narrowing. Standard CE- and TOF-MRA techniques use highly T1-weighted gradient-echo sequences that can detect T1 short blood products, so they have the potential to identify IPH, an indicator of plaque rupture. We sought to determine the accuracy and reliability of these MRA sequences to detect IPH. MATERIALS AND METHODS: 3D TOF and CE carotid MRA scans were obtained at 3T on 15 patients (age range, 58–86 years; 13 men) scheduled for CEA. The source images from the precontrast (mask) CE-MRA and the TOF sequences were reviewed by 2 independent readers for IPH presence (identified as hyperintense signal intensity compared with adjacent muscle). CEA specimens were stained with antibody against glycophorin A and Mallory stain to detect IPH and were correlated with MR images. RESULTS: Nine of 15 CEA specimens (61 of 144 MR images) contained IPH confirmed by histology. Compared with TOF, CE-MRA mask demonstrated greater sensitivity, specificity, PPV, and NPV for IPH detection. The accuracy for correctly identifying IPH by using CE-MRA mask images and TOF images was 94% and 84%, respectively. Inter- and intraobserver agreement for IPH detection was excellent by mask images (κ = 0.91 and κ = 0.94, respectively) and TOF images (κ = 0.77 and κ = 0.84, respectively). CONCLUSIONS: CE-MRA mask images are highly accurate and reliable for identifying IPH, more so than the TOF sequence, and can potentially provide valuable information about risk for rupture.

Intracranial Vessel Wall MRI: Principles and Expert Consensus Recommendations of the American Society of Neuroradiology

SUMMARY: Intracranial vessel wall MR imaging is an adjunct to conventional angiographic imaging with CTA, MRA, or DSA. The technique has multiple potential uses in the context of ischemic stroke and intracranial hemorrhage. There remain gaps in our understanding of intracranial vessel wall MR imaging findings and research is ongoing, but the technique is already used on a clinical basis at many centers. This article, on behalf of the Vessel Wall Imaging Study Group of the American Society of Neuroradiology, provides expert consensus recommendations for current clinical practice.

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.

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.

Comparison of carotid plaque ulcer detection using contrast-enhanced and time-of-flight MRA techniques.

BACKGROUND AND PURPOSE: Ulceration in carotid plaque is a risk indicator for ischemic stroke. Our aim was to compare plaque ulcer detection by standard TOF and CE-MRA techniques and to identify factors that influence its detection. MATERIALS AND METHODS: Carotid MR imaging scans were acquired on 2066 participants in the ARIC study. We studied the 600 thickest plaques. TOF-MRA, CE-MRA, and black-blood MR images were analyzed together to define ulcer presence (plaque surface niche ≥2 mm in depth). Sixty ulcerated arteries were detected. These arteries were randomly assigned, along with 40 nonulcerated plaques from the remaining 540, for evaluation of ulcer presence by 2 neuroradiologists. Associations between ulcer detection and ulcer characteristics, including orientation, location, and size, were determined and explored by CFD modeling. RESULTS: One CE-MRA and 3 TOF-MRAs were noninterpretable and excluded. Of 71 ulcers in 56 arteries, readers detected an average of 39 (55%) on both TOF-MRA and CE-MRA, 26.5 (37.5%) only on CE-MRA, and 1 (1.5%) only on TOF-MRA, missing 4.5 (6%) ulcers by both methods. Ulcer detection by TOF-MRA was associated with its orientation (distally pointing versus perpendicular: OR = 5.57 [95% CI, 1.08–28.65]; proximally pointing versus perpendicular: OR = 0.21 [95% CI, 0.14–0.29]); location relative to point of maximum stenosis (distal versus isolevel: OR = 5.17 [95% CI, 2.10–12.70]); and neck-to-depth ratio (OR = 1.96 [95% CI, 1.11–3.45]) after controlling for stenosis and ulcer volume. CONCLUSIONS: CE-MRA detects more ulcers than TOF-MRA in carotid plaques. Missed ulcers on TOF-MRA are influenced by ulcer orientation, location relative to point of maximum stenosis, and neck-to-depth ratio.

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.