颅颈动脉三维磁共振管壁成像技术及其应用进展

颅颈动脉粥样硬化是引起缺血性脑卒中的主要原因。MR管壁成像技术可直接显示动脉管壁的形态学特征,是目前评价颈动脉斑块的最佳无创性影像学手段之一。近年来,随着三维MR管壁成像技术的发展,其在颅内和颅外颈动脉粥样硬化病变的临床诊断中发挥着越来越重要的作用。本文主要对颅颈动脉三维磁共振管壁成像技术及其应用进展做一综述。     

High resolution 3D diffusion cardiovascular magnetic resonance of carotid vessel wall to detect lipid core without contrast media

Background

Without the need of contrast media, diffusion-weighted imaging (DWI) has shown great promise for accurate detection of lipid-rich necrotic core (LRNC), a well-known feature of vulnerable plaques. However, limited resolution and poor image quality in vivo with conventional single-shot diffusion-weighted echo planar imaging (SS-DWEPI) has hindered its clinical application. The aim of this work is to develop a diffusion-prepared turbo-spin-echo (DP-TSE) technique for carotid plaque characterization with 3D high resolution and improved image quality.

Methods

Unlike SS-DWEPI where the diffusion encoding is integrated in the EPI framework, DP-TSE uses a diffusion encoding module separated from the TSE framework, allowing for segmented acquisition without the sensitivity to phase errors. The interleaved, motion-compensated sequence was designed to enable 3D black-blood DWI of carotid arteries with sub-millimeter resolution. The sequence was tested on 12 healthy subjects and compared with SS-DWEPI for image quality, vessel wall visibility, and vessel wall thickness measurements. A pilot study was performed on 6 patients with carotid plaques using this sequence and compared with conventional contrast-enhanced multi-contrast 2D TSE as the reference.

Results

DP-TSE demonstrated advantages over SS-DWEPI for resolution and image quality. In the healthy subjects, vessel wall visibility was significantly higher with diffusion-prepared TSE (p < 0.001). Vessel wall thicknesses measured from diffusion-prepared TSE were on average 35% thinner than those from the EPI images due to less distortion and partial volume effect (p < 0.001). ADC measurements of healthy carotid vessel wall are 1.53 ± 0.23 × 10⁻³ mm²/s. In patients the mean ADC measurements in the LRNC area were significantly lower (0.60 ± 0.16 × 10⁻³ mm²/s) than those of the fibrous plaque tissue (1.27 ± 0.29 × 10⁻³ mm²/s, p < 0.01).

Conclusions

Diffusion-prepared CMR allows, for the first time, 3D DWI of the carotid arterial wall in vivo with high spatial resolution and improved image quality over SS-DWEPI. It can potentially detect LRNC without the use of contrast agents, allowing plaque characterization in patients with renal insufficiency.

Electronic supplementary material

The online version of this article (doi:10.1186/s12968-014-0067-z) contains supplementary material, which is available to authorized users.     

基底动脉夹层动脉瘤的磁共振血管壁成像表现

目的总结分析基底动脉夹层动脉瘤的MR血管壁成像表现特点。材料与方法 27例经临床证实的基底动脉夹层动脉瘤病例,对基底动脉夹层动脉瘤的磁共振血管壁成像表现特点进行总结分析。结果基底动脉夹层动脉瘤影像征象包括血管迂曲扩张、内膜征、双腔征、壁内血肿、长段不规则或丝线样狭窄、鼠尾状闭塞。结论对于基底动脉夹层动脉瘤患者,行基底动脉磁共振血管壁成像能够清晰显示血管迂曲扩张、内膜征、双腔征、壁内血肿、长段不规则或丝线样狭窄、鼠尾状闭塞异常,是基底动脉夹层动脉瘤的一种有效准确的检查方法。     

Imaging of carotid artery vessel wall edema using T2-weighted cardiovascular magnetic resonance

Background

Atherothrombosis remains a major health problem in the western world, and carotid atherosclerosis is an important contributor to embolic ischemic strokes. It remains a clinical challenge to identify rupture-prone atherosclerotic plaques before clinical events occur. Inflammation, endothelial injury and angiogenesis are features of vulnerable plaques and may all be associated with plaque edema. Therefore, vessel wall edema, which can be detected by 2D T2-weighted cardiovascular magnetic resonance (CMR), may be used as a dynamic marker of disease activity in the atherosclerotic plaque. However, 2D imaging is limited by low spatial resolution in the slice-select direction compared to 3D imaging techniques. We sought to investigate the ability of novel 3D techniques to detect edema induced in porcine carotid arteries by acute balloon injury compared to conventional 2D T2-weighted black-blood CMR.

Methods

Edema was induced unilaterally by balloon overstretch injury in the carotid artery of nine pigs. Between one to seven hours (average four hours) post injury, CMR was performed using 2D T2-weighted short-tau inversion recovery (T2-STIR), 3D volumetric isotropic turbo spin echo acquisition (VISTA) and 3D T2 prepared gradient-echo (T2prep-GE). The CMR images were compared in terms of signal-to-noise ratio (SNR) and contrast-to-noise (CNR) ratio. Furthermore, the presence of vessel wall injury was validated macroscopically by means of Evans Blue dye that only enters the injured vessel wall.

Results

All three imaging sequences classified the carotid arteries correctly compared to Evans Blue and all sequences demonstrated a significant increase in SNR of the injured compared to the non-injured carotid vessel wall (T2-STIR, p = 0.002; VISTA, p = 0.004; and T2prep-GE, p = 0.003). There was no significant difference between sequences regarding SNR and CNR.

Conclusion

The novel 3D imaging sequences VISTA and T2prep-GE perform comparably to conventional 2D T2-STIR in terms of detecting vessel wall edema. The improved spatial coverage of these 3D sequences may facilitate visualization of vessel wall edema to enable detection and monitoring of vulnerable carotid atherosclerotic plaques.     

Validation of 3D ultrasound vessel wall volume: an imaging phenotype of carotid atherosclerosis

Carotid atherosclerotic lesions are a major cause of stroke and the identification and quantification of such lesions in patients is important for the development of a better understanding of atherogenesis in high risk populations and for the design of studies to assess treatment efficacy. Our objective was to develop and validate a new three-dimensional ultrasound (3DUS) measurement or phenotype of carotid atherosclerosis, vessel wall volume (VWV), which is a three-dimensional measurement of vessel wall thickness and plaque within the carotid arteries measured in 3DUS images. To assess both intraobserver and interscan variability, 3DUS images were acquired from the right and left carotid arteries of ten subjects with carotid atherosclerosis scanned twice within a period of 2 wk. For both VWV and total plaque volume (TPV), an expert observer performed five measurement trials of all images acquired at baseline scan and 2-wk rescan with a 5-d period between measurement trials for images. Images were re-randomized for each measurement trial and both TPV and VWV were measured by observers who were blinded to subject identification for each time-point measurement. Coefficients of variation (COV) and intraclass correlation coefficients (ICC), for VWV measurements indicated higher intraobserver (scan COV = 4.6% ICC = 0.95, rescan COV = 3.4%, ICC = 0.96) and interscan reproducibility (COV = 5.7%, ICC = 0.85) than TPV measurements (intraobserver variability scan COV = 22.7% ICC = 0.85, rescan COV = 21.1% ICC = 0.88 and interscan variability, COV = 31.1%, ICC = 0.83), although absolute variances for both phenotypes were very similar (VWV = 90 mm3, TPV = 80 mm3).     

Non-invasive imaging of carotid arterial restenosis using 3T cardiovascular magnetic resonance

Background

Restenosis of the carotid artery is common following carotid endarterectomy, but analysis of lesion composition has mostly been based on histological study of explanted restenotic lesions. This study investigated the ability of 3T cardiovascular magnetic resonance (CMR) to determine the components of recurrent carotid artery disease and examined whether these differed from primary atherosclerotic plaque.

Methods

50 patients underwent 3T CMR of both carotid arteries using a standard multicontrast protocol: time-of-flight (TOF), T1-weighted (T1W), T2-weighted (T2W), and PD-weighted (PDW) Turbo-Spin-Echo (TSE) sequences. 25 patients had previously undergone carotid endarterectomy (mean time since surgery 1580 days, range 45–6560 days), and 25 with primary asymptomatic atherosclerotic plaques served as controls. Two experienced reviewers analysed the multicontrast CMR images according to the presence or absence of major plaque features and assigned an overall classification type.

Results

In patients with recurrent carotid disease following endarterectomy, the mean degree of restenosis was 51% (range 30–90%). Three distinct types of restenosis were identified: 5 patients (20%) showed CMR characteristics of fibro-atheromatous tissue, 11 patients (44%) had plaque features consistent with possible myointimal (fibromuscular) hyperplasia, and 6 patients (24%) had recurrent plaque suggestive of further lipid accumulation. Three patients (12%) showed evidence of post-surgical dissection of the carotid intima. Compared to primary atherosclerotic plaques, restenotic plaques were more likely to contain fibro-atheromatous tissue (p = 0.05) and smooth muscle (p < 0.01), and less likely to contain lipid (p < 0.01). Composition did not differ significantly between patients with early and late restenosis.

Conclusions

As defined by CMR, restenotic lesions of the carotid artery fall into three distinct types and differ in composition from primary atherosclerotic plaques. If validated by subsequent histological studies, these findings could suggest a role for CMR in detecting high-risk (i.e. lipid-rich) restenotic lesions.     

Contrast-enhanced cardiovascular magnetic resonance imaging of coronary vessel wall: state of art

Coronary wall imaging by cardiovascular magnetic resonance (CMR) emerges as a promising method to detect vascular injury and remodeling directly within the coronary vascular wall. In this review, the current evidence on coronary wall enhancement using CMR is presented and summarized, with particular focus on its ability to detect inflammation in atherosclerosis, Takayasu's arteritis, acute coronary syndromes and immune-mediated inflammatory vasculitides. The authors review the possible mechanisms of coronary wall contrast enhancement on CMR and discuss the technical considerations and limitations. Lastly, the potential clinical applications and possibilities for future research are proposed.     

磁共振血管壁成像技术现状及进展

磁共振血管壁成像是利用磁共振原理抑制血管内流动血液信号,获取血管壁等静态组织图像的一种成像方法。由于可以对血管壁进行直接成像,这种方法可以用于评估动脉粥样硬化斑块的形态、成分,进而确定斑块的风险程度。血管壁成像技术的核心问题在于如何有效抑制流动血液的信号,本文就目前磁共振血管壁成像技术的现状及进展做简要的总结回顾。     

颈动脉蹼的高分辨率磁共振血管壁成像的影像分析

目的探索颈动脉蹼(carotid web,CaW)的高分辨率磁共振血管壁成像(vessel wall magnetic resonance imaging,VW MRI)的信号及形态特点。材料与方法选取经计算机断层扫描血管造影术(computed tomography angiography,CTA)诊断的10例颈动脉蹼的患者,从多序列多方位分析颈动脉蹼磁共振的信号及形态特点。结果颈动脉蹼的磁共振信号特点为T1WI表现为均匀等信号,T2WI表现为稍高信号,抑脂序列信号不减低,增强后明显强化。10例颈动脉蹼患者中出现等信号管壁增厚10例(100%),突向管腔10例(100%),管腔内分隔9例(90%),双腔征8例(80%),瓣膜征6例(60%),对比剂瘀滞3例(30%)。结论颈动脉蹼与既往无明显心血管危险因素患者的缺血性卒中事件具有很高的相关性。VW MRI在颈动脉蹼的影像诊断中具有较高的临床应用价值和特征的影像表现,有利于为颈动脉蹼的未来研究提供参考。     

Association of high-density lipoprotein levels and carotid atherosclerotic plaque characteristics by magnetic resonance imaging

A low level of high-density lipoprotein cholesterol (HDL-C) is a risk factor for atherosclerotic disease. Magnetic resonance imaging (MRI) can provide detailed information on carotid atherosclerotic plaque size and composition. The purpose of this study was to correlate HDL levels with carotid plaque burden and composition by MRI. Thirty-four patients with coronary artery disease (CAD) receiving simvastatin plus niacin or placebo for both drugs for three years were randomly selected to undergo MRI of carotid arteries. Atherosclerotic plaque wall volumes (WVs) and plaque components including lipid rich/necrotic core (LR/NC), calcium, fibrous tissue, and loose matrix were measured. Mean WV or atherosclerotic burden was significantly associated with total HDL-C levels (r = −0.39, P = 0.02), HDL₂ (r = −0.36, P = 0.03), HDL₃ (r = −0.34, P = 0.04), and LDL/HDL ratio (r = 0.42, P = 0.02). Plaque lipid composition or LR/NC was significantly associated with HDL₃ (r = −0.68, P = 0.02). Patients with low HDL levels (≤35 mg/dL) had increased WV (97 ± 23 vs. 81 ± 19 mm³, P = 0.05) compared with patients with HDL levels > 35 mg/dL. Among CAD patients, low HDL-C levels were significantly associated with increased carotid atherosclerotic plaque burden and lipid content by MRI.     

高分辨MR血管壁成像用于颅内动脉粥样硬化疾病研究进展

颅内动脉粥样硬化疾病(ICAD)发病率、死亡率及致残率均较高,为全世界范围内缺血性脑卒中的最常见病因。高分辨率MR血管壁成像(HR VW-MRI)可覆盖全脑,对运动伪影较不敏感,能高度显示细节颅内血管壁成像,可作为血管造影管腔成像的补充,用于可视化成像观察神经血管、动静脉疾病。本文就HR VW-MRI技术及其评估ICAD研究进展进行综述。     

冠状动脉粥样硬化的高分辨磁共振管壁成像

目的探讨高分辨MR管壁成像显示冠心病冠状动脉管壁异常的可行性。方法收集18例经冠状动脉血管造影或CT血管成像证实有冠状动脉狭窄的冠心病患者,在1.5 T MR设备中进行冠状动脉管壁黑血成像。采集狭窄段及其邻近非狭窄段的横断面管壁图像,由两位MR医师协商评估,将显示不满意的图像剔除。在显示满意的狭窄段和非狭窄段管壁图像上分别其测量管壁厚度、管腔直径及横截面积并进行对比。结果 18例患者中有15例患者顺利完成检查,经冠状动脉造影或CT血管成像证实共有26个冠状动脉狭窄段,MR管壁成像共获得显示满意的图像34幅(狭窄段和非狭窄段各17幅),与非狭窄段相比,狭窄段管壁明显增厚(P0.01),管腔直径及横截面积明显减小(P0.05),差异均具有统计学意义。在MR管壁图像上,冠状动脉狭窄段的管壁呈局限性增厚者11例(64.7%),呈弥漫性增厚者6例(35.3%)。增厚的管壁呈高信号者4例(23.5%),等信号者5例(29.4%),低信号者1例(5.9%),高低混杂信号者7例(41.2%)。结论高分辨MR冠状动脉管壁成像可显示粥样硬化的冠状动脉狭窄段管壁及管腔异常,为冠心病的诊断提供了有力的影像证据,是一种很有潜力的检查方法。     

3D全心冠状动脉MRI技术

近十年来,三维冠状动脉成像技术的图像信躁比和空间分辨率明显提高,为冠状动脉的无创检查提供了一种安全可靠的手段.西门子公司在1.5和3.0 T系统上都提供了靶容积与全心扫描的冠状动脉成像序列,作者主要针对全心冠状动脉成像的技术进行介绍.     

高分辨率磁共振评价单侧大脑中动脉闭塞管腔形态特征及脑梗死类型

目的利用高分辨率磁共振(high-resolution magnetic resonance imaging,HR-MRI)评价单侧大脑中动脉M1段闭塞两种不同的管腔形态特征及对应脑梗死类型的差异。材料与方法回顾性分析因缺血性脑卒中住院诊断为单侧大脑中动脉M1段闭塞患者资料,所有患者均在发病1周内行HR-MRI及头颅扩散加权成像(diffusion weighted imaging,DWI)检查,观察大脑中动脉M1段闭塞管腔形态特征及头颅DWI上脑梗死类型。依照HR-MRI上闭塞管腔的形态学特征将患者分为斑块形成组与非斑块形成组;DWI上脑梗死类型分为单发脑梗死、多发脑梗死、无脑梗死灶。结果 44例患者纳入分析,斑块形成组30例,非斑块形成组14例。斑块形成组闭塞位置位于近端16例,远端14例,非斑块形成组闭塞部位为近端13例,远端1例,两组闭塞部位差别有统计学意义(P=0.025,χ~2=4.99),非斑块形成组闭塞部位多为M1段近端。斑块形成组与非斑块形成组单发性脑梗死分别为11例和5例,多发性梗死分别为15例和2例,无梗死灶分别为4例和7例,两组脑梗死类型差别有统计学意义(P=0.016,χ~2=8.29),斑块形成组脑梗死类型多为多发性脑梗死,而非斑块组多为单个脑梗死或无梗死灶。结论高分辨MRI对大脑中动脉闭塞管腔管壁形态特征评价具有重要价值,闭塞管腔内是否有斑块与主干周围有无侧支形成可能是大脑中动脉闭塞后不同脑梗死类型差异的一个重要原因。     

心血管MRI第二部分--心血管MRI的基本序列和常用技术

此文为第二部分,着重介绍心血管MRI(CMRI)的基本对比、序列及要求。首先,归纳CMRI的三种基本快速成像序列和图像的对比分类。然后,应对CMRI的技术挑战和难点,讲述CMRI质量控制的常用技术。     

高分辨率磁共振血管壁成像在颅内动脉粥样硬化性疾病中的应用

高分辨率磁共振血管壁成像（HR-VWI）是一种具有超高分辨率的磁共振成像技术。其抑制血流信号后能清晰显示动脉粥样硬化斑块的纤维帽、脂质核心、壁内血肿及管腔狭窄情况。HR-VWI能为临床诊疗提供关键影像学信息,在动脉粥样硬化性心脑血管疾病中具有重要诊断价值。本文就HR-VWI成像原理及其在颅内动脉粥样硬化性疾病的评估、在颅内动脉夹层及动脉瘤中的应用价值、在症状性非狭窄性颅内动脉粥样硬化性疾病中的应用、在脑小动脉病变及腔隙性脑梗死中的应用与动脉粥样硬化性疾病的科学研究等方面进行综述。      

急性颅内出血的MRI诊断价值与序列优化

目的分析急性颅内出血敏感MR序列的征象,明确急性颅内出血MRI诊断的最佳序列组合,探讨脑外伤、中风等急性颅脑损伤MRI一站式诊断的可行性.方法对40例颅内出血病例进行FLAIR、GRE-T2*WI、EPI-T2*WI序列扫描,对不同类型颅内出血敏感序列的征象进行总结,比较FLAIR和GRE-T2*WI序列组合和CT对颅内出血诊断的差异.结果脑实质内出血在GRE-T2*WI上表现为片状均质低信号或是低信号区内混杂点状高信号,FLAIR上表现为片状高信号;蛛网膜下腔出血在GRE-T2*WI上表现为沿脑沟分布的低信号,在FLAIR上表现为沿脑沟分布的高信号带;本病例组中2例硬膜下出血在GRE-T2*WI上无明显阳性发现,在FLAIR上表现为清晰可见的颅骨下方条形高信号;硬膜外出血在GRE-T2*WI上表现为颅骨下方梭形的等信号,与脑实质之间有不规则的低信号区相隔,FLAIR可见梭形高信号.GRE-T2*WI和FLAIR序列组合和CT对颅内出血的诊断价值的差异有显著性意义(P<0.05),GRE-T2*WI和FLAIR序列组合诊断敏感性高于CT.结论 GRE-T2*WI和FLAIR序列组合可以准确诊断不同类型的急性颅内出血,实现脑外伤和中风的一站式诊断.     

Multimodal cardiovascular magnetic resonance quantifies regional variation in vascular structure and function in patients with coronary artery disease: Relationships with coronary disease severity

Background

Cardiovascular magnetic resonance (CMR) of the vessel wall is highly reproducible and can evaluate both changes in plaque burden and composition. It can also measure aortic compliance and endothelial function in a single integrated examination. Previous studies have focused on patients with pre-identified carotid atheroma. We define these vascular parameters in patients presenting with coronary artery disease and test their relations to its extent and severity.

Methods and Results

100 patients with CAD [single-vessel (16%); two-vessel (39%); and three-vessel (42%) non-obstructed coronary arteries (3%)] were studied. CAD severity and extent was expressed as modified Gensini score (mean modified score 12.38 ± 5.3). A majority of carotid plaque was located in the carotid bulb (CB). Atherosclerosis in this most diseased segment correlated modestly with the severity and extent of CAD, as expressed by the modified Gensini score (R = 0.251, P < 0.05). Using the AHA plaque classification, atheroma class also associated with CAD severity (rho = 0.26, P < 0.05). The distal descending aorta contained the greatest plaque, which correlated with the degree of CAD (R = 0.222; P < 0.05), but with no correlation with the proximal descending aorta, which was relatively spared (R = 0.106; P = n. s.). Aortic distensibility varied along its length with the ascending aorta the least distensible segment. Brachial artery FMD was inversely correlated with modified Gensini score (R = -0.278; P < 0.05). In multivariate analysis, distal descending aorta atheroma burden, distensibility of the ascending aorta, carotid atheroma class and FMD were independent predictors of modified Gensini score.

Conclusions

Multimodal vascular CMR shows regional abnormalities of vascular structure and function that correlate modestly with the degree and extent of CAD.     

三英寸表面线圈在磁共振颈动脉斑块成像中的应用

目的研究三英寸表面线圈应用于颈动脉斑块高分辨率MR成像的可行性及临床应用价值。方法对33例动脉粥样硬化的患者行MR成像(GE1.5T)。使用两个3英寸线圈分别至于两侧颈动脉分叉处。成像序列包括横断面双翻转T1WI、快速自旋回波T2WI、PDWI,及3DTOF序列。由两位医师共同评价每个序列的图像质量并综合四个序列进行斑块成分分析,斑块成分的分析进行评价者之间的一致性检验。结果按图像质量分级评价系统(1~5分,5分为最好)对两侧颈动脉分别进行评价,共评价了264个序列图像,图像质量评分≤2分的序列27个(占10.2%)。评分≥4分的序列147个(55.7%)。将含一个序列≤2分的检查排除,共50支血管可用于斑块成分分析,显示了斑块32个(20例患者)。其中明确有脂核16个,出血10个,破裂纤维帽5个,钙化15个,一致性检验Kappa值分别是0.81(95%CI:0.61to1.01);0.86(0.66to1.04);0.45(0.05to0.85);0.87(0.70to1.00)。结论使用3英寸线圈进行颈动脉高分辨率磁共振成像可获得满意的图像质量,不同评价者进行斑块成分的分析具有较高的一致性,能够对斑块的组织成分作出较准确的判断。