Vessel Wall Magnetic Resonance Research Articles

Advancements in imaging of intracranial atherosclerotic disease: beyond the arterial lumen to the vessel wall.

Intracranial atherosclerotic disease (ICAD) significantly increases the risk of ischemic stroke. It involves the accumulation of plaque within arterial wallsandnarrowing or blockage of blood vessel lumens. Accurate imaging is crucial for the diagnosis and management of ICAD at both acute and chronic stages. However, imaging the small, tortuous intracranial arterial walls amidstcomplex structures is challenging. Clinicians have employed diverse approaches to improve imaging quality, with a particular emphasis on optimizing the acquisition ofimages using newtechniques, enhancing spatial and temporal resolution of images, and refining post-processing techniques. ICAD imaging has evolved from depicting lumen stenosis to assessing blood flow reserve and identifying plaque components. Advanced techniques such as fractional flowreserve (FFR), high-resolution vessel wall magnetic resonance (VW-MR), optical coherence tomography (OCT), and radial wall strain (RWS) now allow direct visualization offlow impairment, vulnerable plaques, and blood flow strainto plaque, aiding in the selection of high-risk strokepatients for intervention. This article reviews the progression of imaging modalities from lumen stenosis to vessel wall pathology and compares their diagnostic value forrisk stratification in ICAD patients.

Vulnerable carotid plaque characteristics on magnetic resonance vessel wall imaging: potential predictors for hemodynamic instability during carotid artery stenting.

This cross-sectional study sought to explore the possible risk factors assessed with magnetic resonance (MR) vessel wall imaging for hemodynamic instability (HI) during carotid artery stenting (CAS). Patients with carotid stenosis who were referred for CAS from January 2017 to December 2019 were recruited and underwent carotid MR vessel wall imaging. The vulnerable plaque features, including lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), fibrous cap rupture, and plaque morphology, were evaluated. The HI was defined as a drop of systolic blood pressure (SBP) of ≥30 mmHg or the lowest SBP measurement of <90 mmHg after stent implantation. The carotid plaque characteristics were compared between the HI and non-HI groups. The association between carotid plaque characteristics and HI was analyzed. A total of 56 participants (mean age 68.7±8.3 years; 44 males) were recruited. Patients in the HI group (n=26, 46%) had a significantly greater wall area [median 43.2 (IQR, 34.9-50.5) vs. 35.9 (IQR, 32.3-39.4) mm2; P=0.008], total vessel area (79.7±17.2 vs. 69.9±17.3 mm2; P=0.03), prevalence of IPH (62% vs. 30%; P=0.02), prevalence of vulnerable plaque (77% vs. 43%; P=0.01), and volume of LRNC [median 344.7 (IQR, 155.1-665.7) vs. 103.1 (IQR, 53.9-162.9) mm3; P=0.001] in carotid plaque compared to those in non-HI group (n=30, 54%). Carotid LRNC volume (OR =1.005, 95% CI: 1.001-1.009; P=0.01) and presence of vulnerable plaque (OR =4.038, 95% CI: 0.955-17.070; P=0.06) were significantly and marginally associated with HI, respectively. Carotid plaque burden and vulnerable plaque features, particularly a larger LRNC, might be effective predictors for HI during the CAS procedure.

Automated morphologic analysis of intracranial and extracranial arteries using convolutional neural networks.

To develop an automated method for 3D magnetic resonance (MR) vessel wall image analysis to facilitate morphologic quantification of intra- and extracranial arteries, including vessel centerline tracking, vessel straightening and reformation, vessel wall segmentation based on convoluted neural networks (CNNs), and morphological measurement. MR vessel wall images acquired using DANTE-SPACE sequences and corresponding time-of-flight-MRA images of 67 subjects (including 47 healthy volunteers and 20 patients with atherosclerosis) were included in this study. The centerline of the vessel was firstly extracted from the MRA images and copyed to the 3D MR vessel wall images through the registration relationship between the MRA images and the MR vessel wall images to extract, straighten, and reconstruct interested vessel segments into 2D slices. Then a complete CNN-based Unet-like method was used to automatically segment the vessel wall to obtain quantitative morphological measurements such as maximum wall thicknesses and normalized wall index (NWI). The proposed automatic segmentation network was trained and validated with 11,735 slices and tested on 2517 slices. The method showed satisfactory agreement with manual segmentation method. The Dice coefficients of intracranial arteries were 0.90 for lumen and 0.78 for vessel wall, while the Dice coefficients of extracranial arteries were 0.90 for lumen and 0.82 for vessel wall. The maximum wall thickness and NWI obtained from the proposed automatic method were slightly larger than those obtained from the manual method for both intra- and extracranial arteries. However, there was no significant difference of the quantitative measurements between the two methods (p > 0.05). In addition, the automatically measured NWI of plaque slice was significantly larger than that of normal slice. We propose an automatic analysis method of MR vessel wall images, which can realize automatic segmentation of intra- and extracranial vessel wall. It is expected to facilitate large-scale arterial vessel wall morphological quantification. We have proposed an automatic method for analysis of intra- and extracranial MR vessel wall images simultaneously based on CNN, which can facilitate large-scale quantitative analyses of vessel walls.

Vessel wall imaging: a promising enhancement in the management of inflammatory intracranial vasculopathy

This scientific commentary refers to 'Vessel wall magnetic resonance and arterial spin labelling imaging in the management of presumed inflammatory intracranial arterial vasculopathy', by Benjamin et al. (https://doi.org/10.1093/braincomms/fcac157).

Slice-based and time-specific hemodynamic measurements discriminate carotid artery vulnerable atherosclerotic plaques

Background and objectiveHemodynamic patterns play key roles in progression of carotid vulnerable plaques. However, most of previous studies utilized maximum or averaged value of hemodynamic measurements which is not an ideal representative of hemodynamic patterns. This study aimed to investigate the association of slice-based and time-specific hemodynamic measurements with carotid vulnerable plaque using magnetic resonance (MR) vessel wall imaging and histology. MethodsThirty-two patients (mean age: 63.9±8.1 years; 25 males) with carotid atherosclerotic stenosis (≥50% stenosis) referred to carotid endarterectomy were recruited and underwent MR vessel wall imaging. Carotid plaque burden was evaluated on MR images and vulnerable plaque features including calcification, lipid-rich necrotic core, and intra-plaque hemorrhage (IPH) were identified by histology. The slice-based and time-specific hemodynamic measurements were extracted from computational fluid dynamics simulation of 3D carotid arterial model. Correlation coefficients between hemodynamic measurements and carotid plaque features were calculated and the logistic regressions with generalized estimating equation (GEE) were conducted. The value in discriminating carotid vulnerable plaque features was determined by receiver-operating-characteristic analysis. ResultsOf 102 MR-histology matched slices from 32 patients, time-averaged wall shear stress (TAWSS) (r=0.263, p=0.008), oscillatory shear index (OSI) (r=-0.374, p<0.001), and peakWSS (r=0.232, p=0.019) were significantly associated with carotid IPH. The logistic regression with GEE revealed that peakWSS (OR, 1.206; 95% CI, 1.026-1.418; p, 0.023) and TAWSS (OR, 0.364, 95% CI, 0.138-0.959; p, 0.041) were significantly associated with presence of IPH after adjusting for age and BMI. In discriminating carotid IPH, the AUC of TAWSS, OSI, combined TAWSS with maximum wall thickness (MWT) and combined OSI with MWT was 0.656, 0.722, 0.761, and 0.764, respectively. ConclusionsSlice-based and time-specific hemodynamic characteristics could effectively discriminate carotid IPH. Combination of hemodynamic measurements with carotid plaque burden might be a stronger indicator for carotid vulnerable plaque features than each measurement alone.

Comparison of carotid atherosclerotic plaque characteristics between symptomatic patients with transient ischemic attack and stroke using high-resolution magnetic resonance imaging

BackgroundThis study aimed to compare the characteristics of carotid plaques between patients with transient ischemic attack (TIA) and ischemic stroke using magnetic resonance (MR) imaging.MethodsPatients with a recent ischemic stroke or TIA who exhibited atherosclerotic plaques of carotid arteries in the symptomatic sides determined by MR vessel wall imaging were recruited. The plaque morphology and compositions including intraplaque hemorrhage (IPH), lipid-rich necrotic-core (LRNC) and calcification were compared between TIA and stroke patients. Logistic regression was performed to relate the plaque characteristics to the types of ischemic events.ResultsA total of 270 patients with TIA or ischemic stroke were recruited. Stroke patients had a significantly higher prevalence of diabetes (42.2% vs. 28.2%, p = 0.021), greater mean wall area (35.1 ± 10.1 mm2 vs. 32.0 ± 7.7 mm2, p = 0.004), mean wall thickness (1.3 ± 0.2 mm vs. 1.2 ± 0.2 mm, p = 0.001), maximum normalized wall index (NWI)(63.9% ± 6.0% vs. 62.2% ± 5.9%, p = 0.023) and %volume of LRNC (9.7% ± 8.2% vs. 7.4% ± 7.9%, p = 0.025) in the carotid arteries compared to those with TIA. After adjustment for clinical factors, above characteristics of carotid arteries were significantly associated with the type of ischemic events. After further adjustment for maximum NWI, this association remained statistically significant (OR, 1.41; CI, 1.01–1.96; p = 0.041).ConclusionsIschemic stroke patients had larger plaque burden and greater proportion of LRNC in carotid plaques compared to those with TIA. This study suggests that ischemic stroke patients had more vulnerable plaques compared to those with TIA.

MRA-free intracranial vessel localization on MR vessel wall images

Analysis of vessel morphology is important in assessing intracranial atherosclerosis disease (ICAD). Recently, magnetic resonance (MR) vessel wall imaging (VWI) has been introduced to image ICAD and characterize morphology for atherosclerotic lesions. In order to automatically perform quantitative analysis on VWI data, MR angiography (MRA) acquired in the same imaging session is typically used to localize the vessel segments of interest. However, MRA may be unavailable caused by the lack or failure of the sequence in a VWI protocol. This study aims to investigate the feasibility to infer the vessel location directly from VWI. We propose to synergize an atlas-based method to preserve general vessel structure topology with a deep learning network in the motion field domain to correct the residual geometric error. Performance is quantified by examining the agreement between the extracted vessel structures from the pair-acquired and alignment-corrected angiogram, and the estimated output using a cross-validation scheme. Our proposed pipeline yields clinically feasible performance in localizing intracranial vessels, demonstrating the promise of performing vessel morphology analysis using VWI alone.

Co-existing Hypertension and Hyperhomocysteinemia Increases the Risk of Carotid Vulnerable Plaque and Subsequent Vascular Event: An MR Vessel Wall Imaging Study

PurposeThis study sought to determine the associations of co-existing hypertension and hyperhomocysteinemia (H-Hcy) with carotid vulnerable plaque features and subsequent vascular events.MethodsSymptomatic patients with carotid atherosclerosis were enrolled and underwent carotid magnetic resonance (MR) vessel wall imaging. The patients were divided into the following groups: co-existing hypertension and H-Hcy group; isolated hypertension group; isolated H-Hcy group; and control group. The morphological and compositional characteristics of carotid plaques were assessed on MR images and compared among different groups. Univariate and multivariate cox regressions were used to calculate the hazard ratio (HR) and corresponding 95% confidence interval (CI) of co-existing hypertension and H-Hcy in predicting subsequent vascular events after at least 1-year followed-up.ResultsIn total, 217 patients (mean age, 59.4 ± 11.9 years; 154 males) were recruited. Patients in co-existing hypertension and H-Hcy group had a significantly higher prevalence of carotid lipid-rich necrotic core (LRNC) than isolated H-Hcy and control group (73.2 vs. 43.3 vs. 50%, p = 0.015). During the median follow-up time of 12.2 ± 4.3 months, 61 (39.8%) patients experienced vascular events. After adjusting for baseline confounding factors, co-existing hypertension and H-Hcy (HR, 1.82; 95% CI, 1.01–3.27; p = 0.044), presence of carotid LRNC (HR, 2.25; 95% CI, 1.09–4.65; p = 0.029), and combination of co-existing hypertension and H-Hcy and carotid LRNC (HR, 2.39; 95% CI, 1.26–4.43; p = 0.007) were significantly associated with subsequent vascular events.ConclusionsCo-existing hypertension and H-Hcy are associated with carotid vulnerable plaque features, such as LRNC. Combining co-existing hypertension and H-Hcy with carotid vulnerable plaque features has a stronger predictive value for subsequent vascular events than each measurement alone.

Risk Factors for Asymptomatic and Symptomatic Intracranial Atherosclerosis Determined by Magnetic Resonance Vessel Wall Imaging in Chinese Population: A Case-Control Study.

Background and PurposeThe association between risk factors and intracranial atherosclerosis disease (ICAD) determined by magnetic resonance (MR) vessel wall imaging in Chinese population has not been investigated. The aim of this study was to investigate the associations of conventional vascular risk factors with asymptomatic and symptomatic ICAD using MR vessel wall imaging in Chinese population.MethodsThe study population was recruited from two cohort studies of ICASMAP and CAMERA comprised 104 symptomatic ICAD subjects (57.1 ± 11.1 years; 35.6% females), 51 asymptomatic ICAD subjects (70.1 ± 8.4 years; 50.0% females) and 418 controls (58.0 ± 13.3 years; 61.0% females) defined as asymptomatic subjects without ICAD on MR vessel wall imaging. We compared the vascular risk factors between the three groups using a multivariate logistic regression analysis.ResultsCompared with controls, there was a significant positive association between age (OR: 1.07, 95% CI: 1.03–1.10, p < 0.001) and hypertension (OR: 3.03, 95% CI: 1.45–6.36, p = 0.003) and asymptomatic ICAD. There was a positive association of smoking (OR: 3.41, 95% CI: 1.57–7.42, p = 0.001), hypertension (OR: 7.43, 95% CI: 3.81–14.49, p < 0.001) and diabetes (OR: 3.54, 95% CI: 1.93–6.49, p < 0.001) and an inverse association of high-density lipoprotein (HDL) (p < 0.017) with symptomatic ICAD. Compared to asymptomatic ICAD, there was a significant inverse association of age (OR: 0.86, 95% CI: 0.81–0.92, p < 0.001) and HDL (p < 0.001) with symptomatic ICAD.ConclusionOld age and hypertension are associated with asymptomatic ICAD and smoking, hypertension, diabetes and lower HDL are associated with an increased risk of symptomatic ICAD in Chinese population.Clinical Trial RegistrationURL: http://www.clinicaltrials.gov. Unique identifier: NCT03417063.

Quantitative assessment of carotid artery atherosclerosis by three-dimensional magnetic resonance and two-dimensional ultrasound imaging: a comparison study.

It has been proven that magnetic resonance (MR) and ultrasound imaging are useful tools in the quantification of carotid atherosclerotic plaques. However, there are only a few pieces of evidence to illustrate the links of quantitative measurements of carotid plaques between MR and ultrasound imaging. This study looked to compare the quantitative measurements of carotid plaques and investigate their relationship between three-dimensional (3D) MR vessel wall imaging and two-dimensional (2D) ultrasound imaging. Seventy-five asymptomatic elderly subjects (mean age: 73.3±5.7 years; 45 males) with carotid atherosclerotic plaques diagnosed by both ultrasound and MR imaging were included in this study. The plaque size, including the maximum wall thickness (Max WT), plaque length, and plaque area, was measured by 3D MR and ultrasound imaging on longitudinal and cross-sectional views. The quantitative assessments of carotid plaque size were compared and correlated between 3D MR and 2D ultrasound imaging. In total, the quantitative measurements of 101 plaques on longitudinal views or 44 plaques on cross-sectional views of both MR and ultrasound imaging were compared. The Max WT of the plaques (longitudinal: 2.9±0.8 vs. 2.4±0.9 mm; cross-sectional: 3.2±1.1 vs. 2.6±0.7 mm) and plaque areas (longitudinal: 24.3±13.4 vs. 17.0±12.7 mm2; cross-sectional: 24.9±24.6 vs. 16.8±13.3 mm2) measured by MR imaging were found to be significantly higher than those measured by ultrasound imaging (all P<0.001). Moderate to strong correlations were found in Max WT, plaque area, plaque length between 3D MR and ultrasound imaging. The quantitative measurements of carotid plaques using 3D MR and 2D ultrasound are significantly correlated. The plaque area and Max WT measured by 3D MR imaging are more significant than these parameters measured by 2D ultrasound imaging, which might be explained by the resolution of MR imaging and the workflow of measurements.

Abstract WMP44: Differential Middle Cerebral Artery Plaque Characteristics in Patients With Transient Ischemic Attack and Ischemic Stroke: A High-Resolution MR Vessel Wall Imaging Study

Introduction: Intracranial atherosclerotic disease (ICAD) correlates highly with transient ischemic attack (TIA) and acute ischemic stroke (AIS). Magnetic Resonance (MR) vessel wall imaging (VWI) is an emerging non-invasive imaging modality for directly assessing ICAD lesions. Methods: We retrospectively analyzed MR-VWI from 42 TIA patients and 45 AIS patients with ICAD. All patients fulfilled the following criteria: (1) stenosis &gt;30% of a middle cerebral artery (MCA), (2) symptoms contralateral to stenotic MCA, (3) no coexisting stenosis at other major vessels; (4) lack of compelling evidence to other etiologies of stroke/TIA. Vascular lesions were analyzed with MR-VWI with respect to the stenosis degree, vessel wall irregularity, plaque burden (PB), remodeling index (RI), plaque-wall contrast ratio (CR) and plaque enhancement grade (EG). Results: EG (OR 3.88, 95%CI 1.42-10.57, P=0.006) was a risk factor for AIS while PB (OR 0.65, 95%CI 0.27-1.54, P=0.008) was a risk factor for TIA. In patients with 30-70% degree stenosis, CR (OR 5.38, 95%CI 1.39-20.75, P=0.008) was a risk factor for stroke, while PB (OR 0.4, 95%CI 0.1-1.65, P=0.006) remained a risk factor for TIA. Conclusions: In our study, PB appeared as a risk factor for TIA but not for AIS. This suggests that unstable plaque accounting for AIS may have a wide range of PB. We further found that CR and EG are more associated with AIS than TIA. Lesions with high CR and strong enhancement may be more prone to producing the permanent ischemic injury. Further study is needed to elucidate the role of MR-VWI in differential diagnosis and management of TIA and AIS.

Comparison of Carotid Atherosclerosis between Patients at High Altitude and Sea Level: A Chinese Atherosclerosis Risk Evaluation Study

Objectives: To investigate the differences in characteristics of carotid plaques between patients Xining at high altitude and Jinan at sea level using magnetic resonance (MR) imaging. Methods: Subjects were recruited from a cross-sectional, observational, multicenter imaging study of CARE-II study. Forty-nine (mean age 63.3 ± 12.0 years, 33 males) and 51 (mean age 64.5 ± 12.0 years, 34 males) patients were recruited from a site located in a high altitude region and a site located near sea level, respectively. All patients underwent multicontrast MR vessel wall imaging for carotid arteries on 3.0 T MR scanner. The carotid plaques features were compared between 2 patient groups. Results: Compared with patients at sea level, those at high altitude had significantly greater lumen area (58.5 ± 17.8 mm2 versus 50.0 ± 19.6 mm2, P = .008), smaller maximum normalized wall index (48.6% ± 14.2% versus 57.8% ± 16.3%, P = .002), and smaller percentage volume of calcium (0.9% versus 5.6%, P < .001) in the symptomatic carotid artery. After adjustment for clinical risk factors including age, sex, systolic blood pressure, LDL-C, and statin use, these differences in plaque morphology and composition remained statistically significant. After further adjustment for normalized wall index as a measure of plaque burden, percentage volume of calcification was still significantly smaller in patients at high altitude area than that in patients at sea level area (P = .047). Conclusion: Symptomatic subjects from a high altitude area have lower plaque burden and less calcification in the carotid artery compared to those from an area near sea level.

Wall Enhancement in Evolving Cerebral Aneurysms on Magnetic Resonance Vessel Wall Imaging

Abstract INTRODUCTION Recent magnetic resonance (MR) vessel wall imaging studies have indicated cerebral aneurysms in the active state could show wall enhancement along the aneurysm wall (CEAW). While ruptured aneurysms frequently show CEAW, CEAW in the unruptured aneurysms at evolving state, ie growing or symptomatic, has not been studied in detail. We assessed the degree of CEAW in evolving unruptured aneurysms by comparing separately with each of those in stable unruptured aneurysms and ruptured aneurysms. METHODS We performed quantitative analyses of CEAW in consecutive 26 evolving aneurysms using MR vessel wall imaging. Three-dimensional T1-weighted fast spin-echo sequence was obtained before and after contrast media injection, and the contrast ratio of aneurysm wall against the pituitary stalk (CRstalk) was calculated as the indicator of CEAW. We compared aneurysm characteristics of evolving aneurysms with those of 69 stable unruptured and 67 ruptured aneurysms. RESULTS The CRstalk in evolving aneurysms was significantly higher than those in stable aneurysms (0.54 vs 0.34; P &lt; .0001), and lower than those in ruptured aneurysms (0.54 vs 0.83; P &lt; .0002). In multivariable analysis, CRstalk remained significant in comparing evolving with stable aneurysms (odds ratio, 12.23; 95% confidence interval, 3.53-42.41), and with ruptured aneurysms (odds ratio, 0.083; 95% confidence interval, 0.022-0.310). CONCLUSION The CEAW in evolving aneurysms was higher than those in stable aneurysms, and lower than those in ruptured aneurysms.

Decreased Antiatherogenic Protein Levels are Associated with Aneurysm Structure Alterations in MR Vessel Wall Imaging

Objective: Thickened intracranial aneurysm wall with atherosclerotic remodeling is a part of its degenerative scenario. Current magnetic resonance (MR)-vessel wall imaging enables the detection of atherosclerotic wall thickening as aneurysm wall enhancement. The purpose of this study was to examine the correlation between identified atherosclerotic remodeling in vessel wall imaging, and systemic atherosclerosis-related risk factors. Methods: A total of 39 aneurysms in 38 consecutive patients scheduled to undergo microsurgical clipping or endovascular coiling of intracranial aneurysms were prospectively evaluated. All patients underwent aneurysm MR-vessel wall imaging and the presence of aneurysm wall enhancement on contrast-enhanced vessel wall imaging was evaluated. The relationship between aneurysm wall enhancement and patient demographic data, aneurysm morphology and atherosclerosis-related risk factors including blood laboratory data were assessed. Results: Aneurysm wall enhancement was detected in 19 of 39 intracranial aneurysms (48.7%). The maximum diameter of the intracranial aneurysm (P < .01), apolipoprotein A2 (P < .01) and apolipoprotein C2 (P = .01) was significantly associated with the presence of aneurysm wall enhancement. In multivariate logistic regression analyses, the maximum diameter of the intracranial aneurysm (odds ratio: 1.67, 95% confidence interval: 1.17-3.05) and decreased apolipoprotein A2 (odds ratio: 0.62, 95% confidence interval: 0.34-0.97) was significantly correlated with aneurysm wall enhancement. Conclusions: Rather than atherosclerotic factors, antiatherogenic proteins reduction was associated with aneurysm wall enhancement in vessel wall imaging. To elucidate antiatherogenic factors might to help find out promoting factor of unruptured intracranial aneurysms instability.

Intracranial Vessel Wall Segmentation Using Convolutional Neural Networks.

To develop an automated vessel wall segmentation method using convolutional neural networks to facilitate the quantification on magnetic resonance (MR) vessel wall images of patients with intracranial atherosclerotic disease (ICAD). Vessel wall images of 56 subjects were acquired with our recently developed whole-brain three-dimensional (3-D) MR vessel wall imaging (VWI) technique. An intracranial vessel analysis (IVA) framework was presented to extract, straighten, and resample the interested vessel segment into 2-D slices. A U-net-like fully convolutional networks (FCN) method was proposed for automated vessel wall segmentation by hierarchical extraction of low- and high-order convolutional features. The network was trained and validated on 1160 slices and tested on 545 slices. The proposed segmentation method demonstrated satisfactory agreement with manual segmentations with Dice coefficient of 0.89 for the lumen and 0.77 for the vessel wall. The method was further applied to a clinical study of additional 12 symptomatic and 12 asymptomatic patients with >50% ICAD stenosis at the middle cerebral artery (MCA). Normalized wall index at the focal MCA ICAD lesions was found significantly larger in symptomatic patients compared to asymptomatic patients. We have presented an automated vessel wall segmentation method based on FCN as well as the IVA framework for 3-D intracranial MR VWI. This approach would make large-scale quantitative plaque analysis more realistic and promote the adoption of MR VWI in ICAD management.

Reduction of cerebral blood flow in community-based adults with subclinical cerebrovascular atherosclerosis: A 3.0T magnetic resonance imaging study

Reduction in cerebral blood flow (CBF), one of the major metrics for cerebral perfusion, is associated with many brain disorders. Therefore, early characterization of CBF prior to occurrence of symptoms is essential for prevention of cerebral ischemic events. We hypothesized that large artery atherosclerosis might be a potential indicator for decline in cerebral perfusion. The aim of this study was to investigate the relationship between large artery atherosclerosis and CBF in asymptomatic adults. A total of 134 asymptomatic subjects (mean age, 56.2 ± 12.8 years; 54 males) were recruited and underwent magnetic resonance (MR) imaging for brain and intracranial and extracranial carotid arteries. Presence or absence of cerebrovascular atherosclerosis was determined on MR vessel wall images. The CBF was measured with pseudo-continuous arterial spin labeling (pCASL) imaging. The CBF values in internal carotid artery (ICA) (37.2 ± 5.8 vs. 39.0 ± 4.9 ml/100 g/min, P = 0.049) and vertebrobasilar artery (VA-BA) territories (42.0 ± 6.8 vs. 44.8 ± 7.0 ml/100 g/min, P = 0.023) were significantly reduced in subjects with cerebrovascular plaque compared to those without. Presence of cerebrovascular plaque was significantly associated with CBF of VA-BA territory before (odds ratio, 2.89; 95% confidence interval, 1.37–6.08; P = 0.005) and after adjusted for confounding factors including age, gender, body-mass-index, diabetes, systolic blood pressure, hyperlipidemia and history of cardiovascular disease (odds ratio, 2.76; 95% confidence interval, 1.18–6.46; P = 0.019). In conclusion, presence of cerebrovascular atherosclerosis is independently associated with reduction in CBF measured by pCASL in asymptomatic adults, suggesting that cerebrovascular large artery atherosclerosis might be an effective indicator for impairment of cerebral microcirculation hemodynamics.

Feasibility of vessel wall imaging in assessing unruptured paraclinoid aneurysms: Clinical observations and preliminary experience

IntroductionThe determination of the precise location of unruptured paraclinoid aneurysms with respect to the dura is essential in order to establish the risk of subarachnoid hemorrhage (SAH). In equivocal cases, current imaging modalities are often limited when trying to distinguish the precise relationship of these aneurysms with respect to the dura. We assessed the utility of vessel wall magnetic resonance (VW-MR) imaging in identifying the definitive location of unruptured paraclinoid aneurysms. MethodsWe performed an observational retrospective review using a prospective database of patients undergoing 3T VW-MR of the brain. We included patients that underwent VW-MR gadolinium-enhanced T1-weighted black-blood sequences with fat suppression and saturation band to evaluate unruptured paraclinoid region aneurysms. The dural locations of the aneurysms were first identified on DSA or TOF-MRA and subsequently with VW-MR. The location of aneurysms on VW-MR were then compared qualitatively with the reference standard DSA/TOF-MRA by 2 neurovascular imaging experts. ResultsFifteen patients with unruptured paraclinoid region aneurysms were imaged with VW-MR. The extradural or intradural locations of the aneurysms were determined in 80% of patients using VW-MR compared to 47% with DSA/MRA. ConclusionsVW-MRI may be a feasible imaging technique for identifying the extradural or intradural location of unruptured paraclinoid aneurysms and may help guide management. Further larger studies may be warranted.

Abstract 17357: Magnetic Resonance Imaging Detected Intraplaque Hemorrhage and Expansive Remodeling in Superficial Femoral Artery

Introduction: Compared to coronary and carotid arteries, there is much less knowledge on atherosclerotic plaque characteristics and their clinical relevance in lower-extremity arteries. Magnetic resonance (MR) vessel wall imaging allows for in vivo detection of intraplaque hemorrhage (IPH), which has been consistently associated with increased risks for clinical events in coronary and carotid artery disease. Objective: In a pilot study, we sought to estimate the prevalence of IPH in peripheral artery disease and examine plaque progression in the presence of IPH. Methods: Ten patients with ankle brachial index &lt;0.90 in one or both legs were recruited. A 3D MR imaging protocol with a large coverage (30 or 45 cm in the head-feet direction) and isotropic resolution (voxel size: 0.8x0.8x0.8 mm 3 ) was used to scan bilateral legs in the coronal plane from the common femoral artery bifurcation to the popliteal artery at baseline and 6 months later. Images were reformatted into axial slices for detailed visualization of vessel wall. Following previous publications on carotid MRI, IPH was detected as hyperintense signals on heavily T1-weighted images. Superficial femoral artery (SFA) segments (3 cm in length) with IPH were identified, of which lumen and outer wall were segmented on black-blood images (motion-sensitized flow suppression for improved vessel wall delineation) to measure plaque progression and remodeling. Image analysis was performed in a blinded fashion without knowing time relationship between serial images. Results: Twenty SFAs were analyzed. After excluding 4 arteries with total occlusion, 5 out of the 16 arteries (31%) or 50% of the subjects showed IPH in 1 or more SFA segments. After 6 months, there was significant progression in vessel wall area in SFA segments with IPH (mean ± standard deviation: 43.5 ± 13.9 mm 2 versus 47.3 ± 17.3 mm 2 , p=0.045), which resulted in outer wall expansion (mean [95% confidence intervals]: +3.9 mm 2 [+0.4, +7.4], p=0.035) rather than lumen reduction (-0.02 mm 2 [-2.6, +2.5], p=0.99). Conclusions: MR vessel wall imaging revealed that IPH is likely a common feature in femoral atherosclerosis. SFA segments with IPH showed expansive remodeling in 6 months, of which the clinical significance needs to be further studied.

Atherosclerosis in stroke-related vascular beds and stroke risk: A 3-D MR vessel wall imaging study.

ObjectivesTo investigate the characteristics of atherosclerotic plaques in stroke‐related vascular beds and their relationship with stroke using three‐dimensional magnetic resonance (MR) vessel wall imaging.MethodsFifty‐two symptomatic patients (mean age: 56.3 ± 13.4 years; 38 males) were enrolled and underwent MR vessel wall imaging for stroke‐related vascular beds including intracranial and extracranial carotid arteries and aortic arch and routine MR imaging for brain. The maximum wall thickness (Max WT) and luminal stenosis of each plaque were measured. The presence/absence of atherosclerotic plaque, intraplaque hemorrhage (IPH), and severe stenosis (stenosis >50%) at each vascular bed and acute ischemic lesion (AIL) were determined. The correlation between Max WT of each vascular bed and AIL was analyzed.ResultsOf 52 patients, 24 (46.2%) had AILs, and 30 (57.7%), 34 (65.4%), and 11 (21.2%) had plaques in intracranial artery, extracranial carotid artery, and aortic arch, respectively. The prevalence of IPH and severe stenosis was 25% and 26.9% for intracranial arteries, 13.5% and 9.6% for extracranial carotid artery, and 3.8% and 0% for aortic arch, respectively. In discriminating AIL, Max WT of intracranial artery had the highest area‐under‐the‐curve (AUC = 0.84), followed by extracranial carotid artery (AUC = 0.83) and aortic arch (AUC = 0.78) after adjusted for confounding factors. The AUC of Max WT combined three stroked‐related vascular beds reached 0.87.ConclusionExtracranial carotid arteries have the highest prevalence of plaques and intraplaque hemorrhage and severe stenosis are most frequently seen in intracranial arteries in Asian symptomatic patients. The Max WT combined three stroke‐related vascular beds show stronger predictive value for AIL than each vascular bed alone.

Circumferential Wall Enhancement on Magnetic Resonance Imaging is Useful to Identify Rupture Site in Patients with Multiple Cerebral Aneurysms.

Identification of rupture sites in patients with multiple intracranial aneurysms is largely based on aneurysm size, location, and shape. Finding circumferential enhancement along the aneurysm wall (CEAW) on magnetic resonance (MR) vessel wall imaging was recently shown to be indicative of ruptured aneurysm. To investigate the hypothesis that a higher degree of CEAW would identify the site of rupture in patients with multiple aneurysms. We prospectively performed quantitative analysis of CEAW in consecutive patients with both aneurysmal subarachnoid hemorrhage and multiple aneurysms (26 patients with a total of 62 aneurysms), using MR vessel wall imaging. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast media, and the wall enhancement index (WEI) was calculated. Aneurysm characteristics (size, location, irregular shape, aspect ratio [neck-to-dome length/neck width], and WEI) were compared between ruptured and unruptured aneurysms. Odds ratios with 95% confidence intervals for ruptures were calculated with conditional univariable logistic regression analysis. Analyses were repeated after adjustment for aneurysm size. Large aneurysm size, high aspect ratio, WEI (above the median values), and irregular shape were significantly associated with aneurysm rupture. After adjustment for aneurysm size, WEI (adjusted odds ratio: 8.8; 95% confidence interval, 1.1-72.6) as well as irregular shape and aspect ratio showed a strong association with rupture. CEAW is associated with rupture of intracranial aneurysm independent of aneurysm size and patient characteristics. Contrast-enhanced MR vessel wall imaging helps to identify the site of rupture in patients with multiple aneurysms.