Magnetic Resonance Plaque Imaging Research Articles

Carotid Plaque MRI and Stroke Risk: A Systematic Review and Meta-analysis

Dedicated magnetic resonance imaging (MRI) of plaque composition offers stroke risk information beyond measurement of luminal stenosis in carotid atherosclerotic disease.

The Influence of Inaccuracies in Carotid MRI Segmentation on Atherosclerotic Plaque Stress Computations

Biomechanical finite element analysis (FEA) based on in vivo carotid magnetic resonance imaging (MRI) can be used to assess carotid plaque vulnerability noninvasively by computing peak cap stress. However, the accuracy of MRI plaque segmentation and the influence this has on FEA has remained unreported due to the lack of a reliable submillimeter ground truth. In this study, we quantify this influence using novel numerical simulations of carotid MRI. Histological sections from carotid plaques from 12 patients were used to create 33 ground truth plaque models. These models were subjected to numerical computer simulations of a currently used clinically applied 3.0 T T1-weighted black-blood carotid MRI protocol (in-plane acquisition voxel size of 0.62 × 0.62 mm2) to generate simulated in vivo MR images from a known underlying ground truth. The simulated images were manually segmented by three MRI readers. FEA models based on the MRI segmentations were compared with the FEA models based on the ground truth. MRI-based FEA model peak cap stress was consistently underestimated, but still correlated (R) moderately with the ground truth stress: R = 0.71, R = 0.47, and R = 0.76 for the three MRI readers respectively (p < 0.01). Peak plaque stretch was underestimated as well. The peak cap stress in thick-cap, low stress plaques was substantially more accurately and precisely predicted (error of -12 ± 44 kPa) than the peak cap stress in plaques with caps thinner than the acquisition voxel size (error of -177 ± 168 kPa). For reliable MRI-based FEA to compute the peak cap stress of carotid plaques with thin caps, the current clinically used in-plane acquisition voxel size (∼0.6 mm) is inadequate. FEA plaque stress computations would be considerably more reliable if they would be used to identify thick-cap carotid plaques with low stresses instead.

Higher critical plaque wall stress in patients who died of coronary artery disease compared with those who died of other causes: A 3D FSI study based on ex vivo MRI of coronary plaques

Mechanical forces play an important role in the rupture of vulnerable plaques. This process is often associated with cardiovascular syndromes, such as heart attack and stroke. In this study, magnetic resonance imaging (MRI)-based models were used to investigate the association between plaque wall stress (PWS) and coronary artery disease (CAD).Ex vivo MRI data of coronary plaques from 12 patients were used to construct 12 three-dimensional (3D) fluid-structure interaction (FSI) computational models. Six of the patients had died from CAD and six had died from non-CAD causes. PWS was assessed using all nodal points on the lumen surface of each plaque. The maximum PWS from all possible vulnerable sites of each plaque was defined as the 3D critical plaque wall stress (CPWS).Mean 3D CPWS in the CAD group was 94.3% higher than that in the non-CAD group (265.6 vs. 136.7kPa, P=0.0029). There was no statistically significant difference in global maximum plaque wall stress (GMPWS) between the two groups (P=0.347). There was also no statistically significant difference in plaque burden between the CAD group (84.4±5%) and the non-CAD group (82.0±8%, P=0.552). The results indicate that plaques from patients who died from CAD were associated with higher CPWS compared with those from patients who died from non-CAD causes. With further validation, analysis of CPWS may prove to be an important component in assessment of plaque vulnerability.

Predicting Carotid Plaque Characteristics Using Quantitative Color-Coded T1-Weighted MR Plaque Imaging: Correlation with Carotid Endarterectomy Specimens

MR plaque imaging is used to evaluate the risk of embolic complications during carotid endarterectomy and carotid artery stent placement. However, its performance for characterizing intraplaque components has varied across studies and is generally suboptimal. Hence, we correlated MR imaging results with histologic findings to determine whether a combination of high-contrast T1-weighted imaging and quantitative image analysis could readily determine plaque characteristics. We prospectively examined 40 consecutive patients before carotid endarterectomy by using a 1.5T scanner and axial T1-weighted spin-echo images under optimized scanning conditions. The percentage areas of intraplaque fibrous tissue, lipid/necrosis, and hemorrhage were calculated automatically by using the software with previously reported cutoff values and were compared with those of the specimens. The thickness of the fibrous cap was also measured manually. The percentage areas of fibrous, lipid/necrotic, and hemorrhagic components were 5.7%-98.7%, 1.3%-65.7%, and 0%-82.0%, respectively, as determined by the MR images, whereas the corresponding values were 4.8%-92.3%, 7.0%-93.8%, and 0%-70.4%, respectively, as determined by histologic examination. Significant positive correlation and agreement were observed between MR images and histologic specimens (r = 0.92, 0.79, and 0.92; intraclass correlation coefficients = 0.91, 0.67, and 0.89; respectively). Thickness of the fibrous caps on MR images (0.21-0.87 mm) and in the specimens (0.14-0.83 mm) also showed positive correlation and agreement (r = 0.61, intraclass correlation coefficient = 0.59). Quantitative analysis of high-contrast T1-weighted images can accurately evaluate the composition of carotid plaques in carotid endarterectomy candidates.

CD44 Targeting Magnetic Glyconanoparticles for Atherosclerotic Plaque Imaging

The cell surface adhesion molecule CD44 plays important roles in the initiation and development of atherosclerotic plaques. We aim to develop nanoparticles that can selectively target CD44 for the non-invasive detection of atherosclerotic plaques by magnetic resonance imaging. Magnetic glyconanoparticles with hyaluronan immobilized on the surface have been prepared. The binding of these nanoparticles with CD44 was evaluated in vitro by enzyme linked immunosorbent assay, flow cytometry and confocal microscopy. In vivo magnetic resonance imaging of plaques was performed on an atherosclerotic rabbit model. The magnetic glyconanoparticles can selectively bind CD44. In T2* weighted magnetic resonance images acquired in vivo, significant contrast changes in aorta walls were observed with a very low dose of the magnetic nanoparticles, allowing the detection of atherosclerotic plaques. Furthermore, imaging could be performed without significant delay after probe administration. The selectivity of hyaluronan nanoparticles in plaque imaging was established by several control experiments. Magnetic nanoparticles bearing surface hyaluronan enabled the imaging of atherosclerotic plaques in vivo by magnetic resonance imaging. The low dose of nanoparticles required, the possibility to image without much delay and the high biocompatibility are the advantages of these nanoparticles as contrast agents for plaque imaging.

Abstract MP79: Association of Long-term Risk Factor Levels with Carotid Atherosclerosis: The Chicago Healthy Aging Magnetic Resonance Imaging Plaque Study (CHAMPS)

Background: The absence of risk factors (RFs) in early middle-age is associated with a markedly lower risk for cardiovascular disease across the lifespan. However, the mechanism for this association is not fully understood. Methods: We performed carotid MRI on 440 randomly-selected participants of the Chicago Healthy Aging Study in 2009-11, whose RFs were measured in 1967-73. We examined association of the burden of RFs at baseline with measures of carotid atherosclerosis (i.e., wall thickness and lipid-rich necrotic core (LRNC)) at follow-up. High resolution carotid MR images were acquired (Siemens, 1.5T) using Time of Flight and standard, Turbo Spin Echo T1 and T2 sequences; 16 consecutive images were acquired, and centered on the bifurcation. Risk groups were defined according to RFs present ~40 years earlier (baseline examination): blood pressure, cholesterol, diabetes, and smoking. Participants were divided into 4 groups (See Table footnote for definitions). The association of wall thickness measures and LRNC with baseline low-risk status was assessed in models adjusted for age, current RF, and mean wall thickness. Results: Among 423 ppts with evaluable images, the mean age was 32±5 y at baseline and 71±5 y at follow-up; 65% were male, 84% white, and 37% were “Low Risk” at baseline. Higher risk status at baseline was associated with greater burden of carotid atherosclerosis as measured by mean and maximum wall thickness and LRNC, with the lowest burden among individuals with low-risk status (see Table). In age-adjusted models, low-risk status was associated with a lower risk for LRNC in older age [OR 0.58 (95% CI, 0.35-0.97)]. This association persisted after adjustment for current RF burden [0.59 (0.35-0.99)] and mean wall thickness [0.57 (0.33-0.99)]. Conclusions: The presence of low-risk status in early life is associated with a lower prevalence of carotid LRNC in older age. These findings suggest that the decades-long protective effect of low risk status might be mediated through a lower burden of high-risk plaque.

Abstract WP158: Validation of a Preliminary Prediction Model with MR Plaque Imaging to Estimate Risk for New Ischemic Brain Lesions after Carotid Endarterectomy or Stenting

[Objective] Recently, we reported a preliminary prediction model with carotid plaque MRI to estimate risk for new ischaemic brain lesions after CEA or CAS. The objective of this study was to validate this model in new set of patients with carotid stenosis. [Methods] One hundred four patients with carotid stenosis undergoing treatment (63 CEA, 41 CAS) were used as a training set for construction of a preliminary prediction model to estimate risk for new ischemic brain lesions after CEA or CAS. T1 and T2 signal intensity of carotid plaque were measured on black-blood MRI. Associations among MRI findings, treatment, clinical factors, and occurrence of new ischemic lesions on DWI 1 day after treatment were studied by logistic regression. The validity of the prediction model was examined using a new set of patients with carotid stenosis (n = 43) as a validation set. [Results] In the training set, new DWI lesions after treatment were observed in 25 patients (24%). The model demonstrated that T1-signal intensity and CAS were positively associated with new lesions on post-treatment DWI scans, and T2 signal intensity was negatively associated (Fig. 1). The C-index was 0.79, which indicated some predictive value. In the validation set, new DWI lesions after treatment were observed in 10 patients (23%). However, C-index was 0.6 and positive predictive value was 33% (Fig. 2), which suggested overfitting of our model and/or differences in case-mix between the training set and validation set. [Conclusions] Our preliminary prediction model may provide some useful information for decision-making regarding treatment strategy, but needs further collection of patients to improve its predictive value.

Quantitative evaluation using the plaque/muscle ratio index panels predicts plaque type and risk of embolism in patients undergoing carotid artery stenting

ObjectiveWe sought to use a magnetic resonance (MR) plaque imaging technique to establish the plaque/muscle ratio (PMR) index panel to identify vulnerable plaques in subjects undergoing carotid artery stenting (CAS). MethodsBetween 2008 and 2010 we treated 69 patients (71 lesions) by elective carotid endarterectomy (CEA) and 35 patients (36 lesions) by CAS. All patients underwent preoperative MR plaque imaging and the ratio of plaque signal intensity to the sternocleidomastoid muscle was calculated. In the CEA group, we categorized the histopathological findings made on the surgical specimens. In the CAS group, we assessed the post-procedure diffusion-weighted images. ResultsPMR index panels for each plaque type were created using the cut-off value obtained from the receiver operating characteristic (ROC) curves of each plaque type. The probability of each of the four plaque types on each panel was assessed by Fisher's exact test. Multinomial logistic regression analysis of the DWI-positive findings determined significant probability (p=0.042). ConclusionThe results of this study suggest quantitative evaluation using the PMR index panel has a probability to predict both the plaque type and risk of embolism in patients being considered for treatment with CAS.

Contrast enhancement by lipid-based MRI contrast agents in mouse atherosclerotic plaques; a longitudinal study

The use of contrast-enhanced MRI to enable in vivo specific characterization of atherosclerotic plaques is increasing. In this study the intrinsic ability of two differently sized gadolinium-based contrast agents to enhance atherosclerotic plaques in ApoE(-/-) mice was evaluated with MRI. We obtained a kinetic profile for contrast enhancement, as the literature data on optimal imaging time points is scarce, and assessed the longer-term kinetics. Signal enhancement in the wall of the aortic arch, following intravenous injection of paramagnetic micelles and liposomes, was followed for 1 week. In vivo T(1)-weighted MRI plaque enhancement characteristics were complemented by fluorescence microscopy of NIR(664) incorporated in the contrast agents and quantification of tissue and blood Gd-DTPA. Both micelles and liposomes enhanced contrast in T(1)-weighted MR images of plaques in the aortic arch. The average contrast-to-noise ratio increased after liposome or micelle injection to 260 or 280% respectively, at 24 h after injection, compared with a pre-scan. A second wave of maximum contrast enhancement was observed around 60-72 h after injection, which only slowly decreased towards the 1 week end-point. Confocal fluorescence microscopy and whole body fluorescence imaging confirmed MRI-findings of accumulation of micelles and liposomes. Plaque permeation of contrast agents was not strongly dependent on the contrast agent size in this mouse model. Our results show that intraplaque accumulation over time of both contrast agents leads to good plaque visualization for a long period. This inherent intraplaque accumulation might make it difficult to discriminate passive from targeted accumulation. This implies that, in the development of targeted contrast agents on a lipid-based backbone, extensive timing studies are required.

Clinical use of magnetic resonance plaque imaging for intracranial arteries.

To summarize the value and limitations of magnetic resonance (MR) plaque imaging for intracranial arteries. The data of MR plaque imaging of intracranial arteries in 422 patients performed in Peking Union Medical College Hospital from December 2006 to September 2010 were analyzed retrospectively. The success rate for MR plaque imaging of intracranial arteries was 97%. MR plaque imaging clearly displayed the wall structure of the arteries trunk (M1 segment of middle cerebral arteries, M2-3 segment of anterior cerebral arteries, and basilar arteries). Good inter-observer (k=0.91, 95% CI=0.80-1.03) and intra-observer reproducibility (k=0.96,95% CI=0.88-1.03) was observed in the evaluation of middle cerebral arteries' atherosclerosis. The wall features had significant difference between symptomatic and asymptomatic intracranial arteries'stenosis; compared with asymptomatic middle cerebral artery stenosis(35 cases), symptomatic middle cerebral artery stenosis(26 cases) had a significantly larger wall area (P=0.000), greater remodeling ratio (P=0.000), higher prevalence of expansive remodeling (outward expansion of the vessel wall) (P=0.003), and lower prevalence of constrictive remodeling (P=0.008). Arteritis of middle cerebral artery (3 cases) showed circular wall-thickening with apparent gadolinium-diethylene triamine pentaacetic acid-biotin enhancement. The MR plaque imaging is helpful in the evaluation of intracranial arteries stenosis, although it still has the limitations such as short scan range and low resolution.

Selection of Carotid Artery Stenting or Endarterectomy Based on Magnetic Resonance Plaque Imaging Reduced Periprocedural Adverse Events

The aim of this study was to elucidate the impact of treatment selection, either carotid stenting or endarterectomy, based on preoperative magnetic resonance (MR) plaque imaging on periprocedural events. A total of 205 consecutive patients with high-grade carotid artery stenosis scheduled for elective revascularization with stenting or endarterectomy were retrospectively analyzed. In period 1, 95 patients were treated regardless of preoperative plaque imaging. In period 2, 110 patients received time of flight MR angiography, and endarterectomy was selected when a high-intensity signal in the plaque was observed on MR angiography because it indicated an unstable plaque. Periprocedural clinical results and outcome at 30 days were analyzed. In period 1, 5 patients (5.3%) were treated with endarterectomy and the other 90 patients (94.7%) were treated with stenting. In period 2, 35 patients (31.8%) were treated with endarterectomy and the other 75 patients (68.2%) were treated with stenting. Periprocedural adverse events, including any stroke, myocardial infarction, or death, were significantly more frequent in period 1 than in period 2 (9.5% v 1.8%; P = .034). Ischemic stroke was significantly reduced from period 1 to period 2 (7.4% v 0.9%; P = .043). Multivariate logistic regression analysis revealed "treatment selection by plaque imaging" was the only factor identified as an independent predictor of periprocedural events (P = .043). Treatment selection based on preoperative plaque imaging appears useful for reducing periprocedural events of carotid artery revascularizations.

Prediction of Carotid Plaque Characteristics Using Non-Gated MR Imaging: Correlation with Endarterectomy Specimens

Electrocardiographic gating, commonly used in MR carotid plaque imaging, can negatively affect intraplaque contrast if the TR is inappropriate. The present study aimed to determine whether a non-gated technique with appropriate TRs can accurately evaluate intraplaque characteristics in specimens excised by CEA. We prospectively examined 40 consecutive patients who underwent CEA (59-82 years of age) by using a 1.5T scanner. Axial T1WI with a TR of 500 ms and PDWI and T2WI with a TR of 3000 ms with a self-navigated rotating-blade scan instead of cardiac gating were obtained. Signal intensities of the plaque and adjacent muscle were measured, and the CR on T1WI, PDWI, and T2WI as well as the gray-scale median on US were correlated with the pathologic findings of the CEA specimens. On T1WI, the CRs of the carotid plaques differed significantly among groups in which the main components were histologically confirmed as fibrous tissue, lipid/necrosis, and hemorrhage (0.54-1.17, 1.16-1.53, and 1.40-2.29, respectively). The sensitivity and specificity for discriminating lipid/necrosis/hemorrhage from fibrous tissue were 96% and 100%, respectively. On T2WI, the CRs of plaques with lipid/necrosis were significantly higher than those of other groups, but the CRs on PDWI and the gray-scale median on US were not significantly different among the groups. Non-gated MR plaque imaging, particularly T1WI, can readily predict the intraplaque main components of the carotid artery with high sensitivity and specificity.

High-Field Atherosclerotic Plaque Magnetic Resonance Imaging

Manifestations of atherosclerotic plaque in different arterial beds range from perfusion deficits to overt ischemia such as stroke and myocardial infarction. Atherosclerotic plaque composition is associated with its propensity to rupture and cause vascular events. Magnetic resonance (MR) imaging of atherosclerotic plaque using clinical 1.5 T scanners can detect plaque composition. Plaque MR imaging at higher field strengths offers both opportunities and challenges to improving the high spatial resolution and contrast required for this type of imaging. This article summarizes the technological requirements required for high-field plaque MR imaging and its application in detecting plaque components.

Improved Radiological Localization of Spinal Cord Lesions in Multiple Sclerosis (P03.060)

Objective: To classify spinal cord lesions in multiple sclerosis (MS) based on white matter (WM) columns, and grey matter (GM) and WM involvement using magnetic resonance imaging (MRI). Background The localization of spinal cord lesions has not been well documented on MRI, although morphology and distribution of plaques have been characterized in post-mortem studies. Design/Methods: MRI was performed on the cervical cord in 16 MS patients (10 female, mean age 44.8) (8 relapsing remitting (RR) MS, 7 secondary progressive (SP) MS, 1 clinically isolated syndrome (CIS)). Axial phase sensitive inversion recovery (PSIR) and gradient-echo sequences were acquired. Two readers reviewed both images simultaneously and reached a consensus about classification of lesions by location: anterior (AC), lateral (LC) or posterior columns (PC). A sub-classification of lesions in mixed WM/GM and those involving WM only was also performed. Lesions were outlined manually on PSIR images and compared with mean cord area. Results: 51 lesions were identified, 24 in RRMS, 22 in SPMS, 5 in CIS. Three lesions were seen in AC (5.8%), 18 in PC (35.3%) and 30 in LC (58.9%). 33% of lesions involved WM alone and 67% involved both GM and WM; no pure GM lesions were identified. Mean lesion area in AC was 4.3mm2, LC 8.5mm2, PC 11.3mm2, with lesions in each column covering 6.1%, 12% and 16.1% of mean cord area respectively, mean lesion length in AC 18.3mm, LC 17.6mm and PC 24.8mm. Conclusions: Most lesions seen involved GM and WM, and were in the PC and LC, in agreement with post-mortem studies. However, no pure GM lesions were seen, suggesting technical limitations or a difference in patient characteristics from post-mortem studies. MRI may permit classification of spinal cord lesion location, area and length, which maybe correlated in future with disability to provide new insights into their functional effects. Supported by: MS Society. Disclosure: Dr. Kearney has nothing to disclose. Dr. Miszkiel has received research support from Biogen Idec and GlaxoSmithKline, Inc. Dr. Yiannakas has nothing to disclose. Dr. Ciccarelli has nothing to disclose. Dr. Miller has received personal compensation for activities with UCL Institute of Neurology, Biogen Idec, GlaxoSmithKline, and Bayer Schering Pharma. Dr. Miller has received personal compensation in an editorial capacity for Journal of Neurology. Dr. Miller has received research support from GlaxoSmithKline, Biogen Idec, and Novartis.

Plaque Features Associated With Increased Cerebral Infarction After Minor Stroke and TIA: A Prospective, Case-Control, 3-T Carotid Artery MR Imaging Study

The goal of this study was to determine whether a 3-T magnetic resonance imaging (MRI) protocol combining carotid atherosclerotic plaque and brain imaging can identify features of high-risk acutely symptomatic plaque that correlate with brain injury. It has previously been demonstrated that, in asymptomatic patients, MRI can identify features of carotid plaque that are associated with stroke, such as the presence of a large lipid core. We hypothesized that the early phase (<7 days) after a cerebrovascular event, when risk of recurrence is highest, may be associated with particular plaque characteristics that associate with cerebral injury. Eighty-one patients (41 presenting acutely with transient ischemic attack [TIA] or minor stroke and 40 asymptomatic controls) underwent multicontrast carotid artery MRI on 2 separate occasions, each accompanied by diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) imaging of the brain. Complex (American Heart Association [AHA] type VI) plaques were seen in 22 of 41 patients (54%) in the symptomatic group versus 8 of 40 (20%) in the asymptomatic group (p < 0.05). They were caused by intraplaque hemorrhage (34% vs. 18%; p = 0.08), surface rupture (24% vs. 5%; p = 0.03), or luminal thrombus (7% vs. 0%; p = 0.24). Noticeably, 17 of 30 (57%) cases of AHA type VI plaque were in vessels with <70% stenosis. At follow-up scanning (>6 weeks later), only 2 cases of symptomatic AHA type VI plaque showed evidence of full healing. The presence of fibrous cap rupture was associated with higher DWI brain injury at presentation and higher total cerebral FLAIR signal at follow-up (p < 0.05). Early carotid wall MRI in patients experiencing minor stroke or TIA showed a higher proportion of "complex" plaques compared with asymptomatic controls; a majority were in arteries of <70% stenosis. Fibrous cap rupture was associated with increases in DWI and FLAIR lesions in the brain. Combined carotid plaque and brain MRI may aid risk stratification and treatment selection in acute stroke and TIA.

A Preliminary Prediction Model with MR Plaque Imaging to Estimate Risk for New Ischemic Brain Lesions on Diffusion-Weighted Imaging after Endarterectomy or Stenting in Patients with Carotid Stenosis

Findings on MR imaging of carotid plaques correlate with histologic findings and may be useful in identifying vulnerable plaques. The objective of this study was to show how MR imaging findings and clinical factors could be used to construct a preliminary model and a nomogram for predicting the risk of new ischemic lesions on DWI following CEA or CAS. One hundred four patients with carotid stenosis undergoing treatment (63 CEA, 41 CAS) were prospectively enrolled (mean age, 71.7 ± 7.0 years; 11 women). T1-SIR and T2-SIR of carotid plaque were measured on MR imaging. Associations among carotid MR imaging findings, treatment procedures, degree of stenosis, cardiovascular risk factors, and occurrence of new ischemic lesions on DWI 1 day after treatment were studied by multivariate logistic regression. One stroke occurred after CAS (2.4%), and none after CEA. New DWI lesions after treatment were observed in 25 patients (24%). Our preliminary prediction model demonstrated that T1-SIR (OR [per 0.5 increase], 3.99; 95% CI, 2.18-7.31; P < .0001) and CAS (OR, 2.06; 95% CI, 1.01-4.24; P = .048 compared with CEA) were positively associated with new DWI lesions on posttreatment DWI scans. T2-SIR (OR [per 0.5 increase], 0.74; 95% CI, 0.55-0.98; P = .037) was negatively associated. The C-index of this model was 0.79 (95% CI, 0.69-0.89), which indicated some utility in predicting the response. Our preliminary prediction model and nomogram may provide an individualized risk estimate of new ischemic lesions after CEA or CAS and useful information for decision-making regarding treatment strategy.

Abstract 2663: The Impact of Preoperative Magnetic Resonance Plaque Imaging on Treatment Results of Carotid Artery Stenosis

Background and Purpose: Selection of carotid artery stenting (CAS) or carotid endarterectomy (CEA) remains controversial. The aim of this study was to elucidate whether treatment selection based on preoperative magnetic resonance (MR) plaque imaging can improve treatment results of carotid artery stenosis. Methods: A total of 205 consecutive patients with high-grade carotid artery stenosis scheduled for elective revascularization with CAS or CEA were analyzed. From 1 2004 to June 2007 (period I: 3.5 years), 95 patients were treated regardless of preoperative plaque imaging. From July 2007 to March 2011 (period II: 3.5 years), 110 patients received time-of-flight MR angiography (TOF-MRA), and CEA was basically selected when a high intensity signal (HIS) was observed on TOF-MRA ( Fig.1 a), because this finding indicates intraplaque hemorrahge ( Fig.1 b,c). Periprocedural clinical events and clinical outcome at 30 days later were analyzed. Results: In period I, 5 patients (5.3%) were treated using CEA and the other 90 patients (94.7%) were treated with CAS (Table). In period II, 35 patients (31.8%) were treated with CEA and the other 75 patients (68.2%) were treated using CAS. Major adverse events including any stroke, myocardial infarction and death, were significantly more frequent in period I than in period II (9.5% vs 1.8%; p=0.034). Ischemic stroke was significantly reduced from period I to period II (7.4% vs 0.9%; p=0.043). In particular, a striking difference in incidence of stroke existed between the periods in HIS-positive plaques (21.7%, 2.0%, respectively; p=0.018, Fig.2). Conclusions: Preoperative MR plaque imaging appears useful for improving treatment results of carotid artery stenosis when it was used for treatment selection.

Quantitative assessment of changes in carotid plaques during cilostazol administration using three-dimensional ultrasonography and non-gated magnetic resonance plaque imaging

Cilostazol, an antiplatelet agent, is reported to induce the regression of atherosclerotic changes. However, its effects on carotid plaques are unknown. Hence, we quantitatively investigated the changes that occur within carotid plaques during cilostazol administration using three-dimensional (3D) ultrasonography (US) and non-gated magnetic resonance (MR) plaque imaging. We prospectively examined 16 consecutive patients with carotid stenosis. 3D-US and T1-weighted MR plaque imaging were performed at baseline and 6 months after initiating cilostazol therapy (200 mg/day). We measured the volume and grayscale median (GSM) of the plaques from 3D-US data. We also calculated the contrast ratio (CR) of the carotid plaque against the adjacent muscle and areas of the intraplaque components: fibrous tissue, lipid, and hemorrhage components. The plaque volume on US decreased significantly (median at baseline and 6 months, 0.23 and 0.21 cm(3), respectively; p = 0.03). In the group exhibiting a plaque volume reduction of more than 10%, GSM on US increased significantly (24.8 and 71.5, respectively; p = 0.04) and CR on MRI decreased significantly (1.13 and 1.04, respectively; p = 0.02). In this group, in addition, the percent area of the fibrous component on MRI increased significantly (68.6% and 79.4%, respectively; p = 0.02), while those of the lipid and hemorrhagic components decreased (24.9% and 20.5%, respectively; p = 0.12) (1.0% and 0.0%, respectively; p = 0.04). There were no substantial changes in intraplaque characteristics in either US or MRI in the other group. 3D-US and MR plaque imaging can quantitatively detect changes in the size and composition of carotid plaques during cilostazol therapy.

MRIプラークイメージングに基づく頚動脈ステント留置術の治療成績

【目的】我々は頚部頚動脈狭窄症に対しMRIプラークイメージングによる検討を行ってきた．Black-blood法T1強調画像（BB-MRI）にて高信号を示しプラークボリュームの多いプラークを有する症例は頚動脈ステント留置術（carotid artery stenting；CAS）ハイリスク症例と考え，頚動脈内膜剥離術（carotid endarterectomy；CEA）を可能な限り施行することとしてきた．その方針に基づいたCASの治療成績につき後方視的に解析した．【方法】対象は，2002年9月より2010年3月の間，緊急をのぞく頚部頚動脈狭窄症に対して，術前にMRIプラークイメージングを施行しえたCAS 78症例．【結果】BB-MRIにて，プラーク全体の近傍筋組織に対する信号相対比（relative overall signal intensity；roSI）は平均1.20±0.31であった．roSI 1.5以上の著しい高信号を呈する病変は7病変（9.0％）であった．新規同側DWI陽性病変は23症例（37.1％）に認めた．術後30日以内の脳卒中，心筋梗塞および死亡は2例（2.7％）であった．【結論】術前に非侵襲的なMRIプラーク診断による精査を行うことで，CASハイリスク症例を選別し，より安全にCASを施行することができると考えられる．

Relationships Between Recent Intraplaque Hemorrhage and Stroke Risk Factors in Patients With Carotid Stenosis

Intraplaque hemorrhage (IPH) is an emerging marker of plaque instability. However, little is known about the relationships between IPH and traditional risk factors and whether these relationships differ between symptomatic and asymptomatic disease. Two hundred thirty-four patients with symptomatic (n=114) or asymptomatic (n=120) carotid stenosis underwent high-resolution plaque magnetic resonance imaging. Seventy-five patients had recent IPH (symptomatic, 33%; asymptomatic, 31%). In symptomatic stenosis, recent IPH was independently associated with degree of stenosis (odds ratio [OR]=4.21, 1.61-10.98 for North American Symptomatic Carotid Endarterectomy Trial >35%; OR=2.92, 1.18-7.24 for European Carotid Surgery Trial >60%), qualifying event (OR=4.13; 1.11-15.32 for stroke or hemispheric transient ischemic attack ≥1 hour versus transient ischemic attack <1 hour or ocular symptoms), time from ischemic event (OR=6.65, 1.56-28.35 for ≤2 weeks; OR=2.24, 0.87-5.81 for 2-12 weeks versus >12 weeks; P for trend=0.03). In asymptomatic stenosis, IPH was only associated with stenosis severity >70% by ECST (OR=6.65; 1.95-22.73) but not by the NASCET method. Our findings support the potential link between recent IPH and risk of ipsilateral stroke in symptomatic disease but also imply that prognostic studies should adjust for known stroke risk factors in multivariate analyses. In asymptomatic stenosis, the potential predictive value of recent IPH is less likely to be confounded by stroke risk factors.