颈动脉粥样硬化斑块内血管化和出血的影像学研究进展

斑块内出血是动脉粥样硬化斑块不稳定的主要因素之一,斑块内出血的诊断对于颈动脉斑块患者的正确分期、治疗以及预防缺血性脑卒中至关重要。组织病理学检查是评价斑块内出血的“金标准”,但需要通过颈动脉内膜切除术来收集组织样本。然而,影像检查可作为一种非侵入性的方法来检测斑块内出血。笔者就颈动脉粥样硬化斑块内血管化和斑块内出血在超声、CT、MRI和核医学等方面的主要特点和发展前景进行综述。     

Molecular imaging of inflammation and intraplaque vasa vasorum: A step forward to identification of vulnerable plaques?

Current developments in cardiovascular biology and imaging enable the noninvasive molecular evaluation of atherosclerotic vascular disease. Intraplaque neovascularization sprouting from the adventitial vasa vasorum has been identified as an independent predictor of intraplaque hemorrhage and plaque rupture. These intraplaque vasa vasorum result from angiogenesis, most likely under influence of hypoxic and inflammatory stimuli. Several molecular imaging techniques are currently available. Most experience has been obtained with molecular imaging using positron emission tomography and single photon emission computed tomography. Recently, the development of targeted contrast agents has allowed molecular imaging with magnetic resonance imaging, ultrasound and computed tomography. The present review discusses the use of these molecular imaging techniques to identify inflammation and intraplaque vasa vasorum to identify vulnerable atherosclerotic plaques at risk of rupture and thrombosis. The available literature on molecular imaging techniques and molecular targets associated with inflammation and angiogenesis is discussed, and the clinical applications of molecular cardiovascular imaging and the use of molecular techniques for local drug delivery are addressed.     

Coronary plaque imaging by coronary computed tomography angiography

Coronary computed tomography angiography (CTA) has become the useful noninvasive imaging modality alternative to the invasive coronary angiography for detecting coronary artery stenoses in patients with suspected coronary artery disease (CAD). With the development of technical aspects of coronary CTA, clinical practice and research are increasingly shifting toward defining the clinical implication of plaque morphology and patients outcomes by coronary CTA. In this review we discuss the coronary plaque morphology estimated by CTA beyond coronary angiography including the comparison to the currently available other imaging modalities used to examine morphological characteristics of the atherosclerotic plaque. Furthermore, this review underlies the value of a combined assessment of coronary anatomy and myocardial perfusion in patients with CAD, and adds to an increasing body of evidence suggesting an added diagnostic value when combining both modalities. We hope that an integrated, multi-modality imaging approach will become the gold standard for noninvasive evaluation of coronary plaque morphology and outcome data in clinical practice.     

Carotid atherosclerotic plaque: noninvasive MR characterization and identification of vulnerable lesions.

Measurement of vessel stenosis by using ultrasonography or angiography remains the principal method for determining the severity of carotid atherosclerosis and the need for endarterectomy. The ipsilateral stroke rate, however--even in patients with severely stenotic vessels--is relatively low, which suggests that the amount of luminal narrowing may not represent the optimal means of assessing clinical risk. As a result, some patients may undergo unnecessary surgery. Improved imaging techniques are, therefore, needed to enable reliable identification of high-risk plaques that lead to cerebrovascular events. High-spatial-resolution magnetic resonance (MR) imaging has been described as one promising modality for this purpose, because the technique allows direct visualization of diseased vessel wall and can be used to characterize the morphology of individual atherosclerotic carotid plaques. The purpose of this report is to review the current state of carotid plaque MR imaging and the use of carotid MR to evaluate plaque morphology and composition.     

PET imaging of aortic atherosclerosis: Is combined imaging of plaque anatomy and function an amaranthine quest or conceivable reality?

Traditionally, blood vessels have been studied using contrast luminography to determine the site, extent and severity of luminal compromise by atherosclerotic deposits. Similar anatomical data can now be acquired non-invasively using ultrasound, computed tomography or magnetic resonance imaging. Plaque stability is an important determinant of subsequent vascular events and currently functional data on the stability of plaque is less well provided by these methods. The search for non-invasive techniques to image combined plaque anatomy and function has been pursued with visionary anticipation. This expectation may soon be realised as imaging with radionuclide-labelled atheroma-targeted contrast agents has demonstrated that plaque functional characteristics can now be shown. Increasingly positron emission tomography/computed tomography (PET/CT) imaging with ¹⁸F fluorodexoyglucose (FDG) and other radionuclides is being used to determine culprit plaques in complex clinically scenarios. Clinically, this information may prove extremely valuable in the assessment of stable and unstable patients and its use in prime time medical practice is eagerly awaited. We will discuss the current clinical applications of functional atheroma imaging in the aorta and highlight the promising preclinical data on novel image biomarkers of plaque instability. If clinical science is able to successfully translate these advances in vascular imaging from the bench to the bedside, a new paradigm will be achieved in cardiovascular diagnostics.     

Techniques for high-resolution MR imaging of atherosclerotic plaque

Atherosclerotic cardiovascular disease is the most common cause of death in the United States. Investigation of atherosclerotic plaque morphology and composition is important because the findings may be useful in predicting prognosis or response to therapy. This study presents high-resolution magnetic resonance (MR) imaging techniques developed on a 1.5-T whole-body imager with a custom-built surface coil, for characterizing the composition and morphology of plaque removed at carotid endarterectomy. The initial comparison of MR imaging and histologic results showed good correlation. In conjunction with MR angiography, these techniques could be used in in vivo imaging to define the size, location, and contents of atherosclerotic plaque at the carotid bifurcation.     

The Potential Role of Optical Coherence Tomography in the Evaluation of Vulnerable Carotid Atheromatous Plaques: A Pilot Study

Purpose The decision to intervene surgically in patients with carotid artery disease is based on the presence of symptoms, along with the severity of carotid artery stenosis as assessed by ultrasound or X-ray computed tomography (CT). Optical coherence tomography (OCT) is a relatively new imaging technique that offers potential in the identification of, as well as the distinction between, stable and unstable atherosclerotic plaques. The purpose of our study was to evaluate whether OCT can be used as a noninvasive diagnostic tool to reveal the morphology of carotid stenosis from the adventitial surface of the carotid artery. To achieve this aim, excised atheromatous plaques were scanned by OCT from the external surface. Methods Plaques removed at carotid endarterectomy were scanned by OCT from the external surface within 72 hr of surgery and then examined histologically. The images of the histologic slides and the scans were then compared. Results We examined 10 carotid endarterectomy specimens and were able to identify calcification, cholesterol crystal clefts, and lipid deposits in the OCT images with histologic correlation. The strong light scattering from the calcified tissue and cholesterol crystal clefts limited the depth of light penetration, making observation of the intimal surface and the detail of the fibrous cap difficult. However, we were able to confidently identify the absence of an atherosclerotic plaque by OCT scans even from the external surface. Conclusion The results of this pilot study demonstrate that OCT can reveal the main features of carotid stenosis but that plaque vulnerability cannot be reliably and precisely assessed if scanned from the external surface with OCT in its present form.     

Noninvasive imaging of coronary arteries: current and future role of multi-detector row CT

While invasive imaging techniques, especially selective conventional coronary angiography, will remain vital to planning and guiding catheter-based and surgical treatment of significantly stenotic coronary lesions, the comprehensive and serial assessment of asymptomatic or minimally symptomatic stages of coronary artery disease (CAD) for preventive purposes will eventually need to rely on noninvasive imaging techniques. Cardiovascular imaging with tomographic modalities, including computed tomography (CT) and magnetic resonance imaging, has great potential for providing valuable information. This review article will describe the current and future role of cardiac CT, and in particular that of multi-detector row CT, for imaging of atherosclerotic and other pathologic changes of the coronary arteries. It will describe how tomographic coronary imaging may eventually supplement traditional angiographic techniques in understanding the patterns of atherosclerotic CAD development.     

症状性缺血性脑卒中颈动脉斑块成分的 高分辨MRI分析

目的应用高分辨MRI(HRMRI)探讨颈动脉斑块不同成分在症状性缺血性脑卒中病人中的危险性。方法选取2016年1月—2017年6月于我院行超声检查发现存在颈动脉斑块的病人50例,其中女21例,男29例,年龄43~77岁,平均(61.62±7.96)岁。依据病人近3个月来是否发生过与患侧颈动脉相关的缺血性脑卒中临床症状分为有症状组(22例,存在斑块血管40支)及无症状组(28例,50支),所有病人行3.0 T HRMRI以评估颈动脉血管及斑块内成分。采用χ~2检验或t检验对2组病人的临床资料、斑块成分及血管管腔狭窄程度进行比较,采用logistic回归分析缺血性脑卒中病人症状的独立危险因素。结果检出存在斑块纤维帽破溃(FCR)的血管,症状组15支,检出率为37.5%,无症状组8支,检出率为16.0%,症状组FCR的检出率高于无症状组(P0.05)。检出斑块内出血(IPH)的血管,症状组21支,检出率为52.5%,无症状组15支,检出率为30.0%,症状组IPH的检出率高于无症状组(P0.05)。检出存在斑块钙化(CA)的血管,症状组15支,检出率为37.5%,无症状组13支,检出率为26.0%,2组间检出率差异无统计学意义(P0.05)。症状组管腔狭窄程度为57.64%±13.36%,无症状组为53.86%±11.19%,2组间管腔狭窄程度差异无统计学意义(t=1.460,P=0.148)。FCR在症状性缺血性脑卒中危险性最高(OR=3.012),IPH危险性次之(OR=2.478)。结论 HRMRI可以分析斑块内成分,而这些成分是缺血性脑卒中临床症状发生的危险因素,是斑块易损性的表现。     

Imaging of carotid arterial diseases with contrast-enhanced ultrasound (CEUS)

Carotid duplex ultrasound is the standard of care for the initial diagnosis of carotid artery bifurcation diseases. But in difficult examinations, carotid abnormalities are commonly encountered and may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow up after carotid endarterectomy or carotid artery stenting. Contrast enhanced ultrasound (CEUS) with low mechanical index (low MI) is a promising new method in the diagnosis and follow up of pathological carotid diseases.Unlike most contrast agents used for magnetic resonance imaging or computed tomography, the microbubbles used in CEUS with SonoVue^® remain within the vascular space and hence can be used to study vascular disease. In addition to improving current carotid structural scans, CEUS has potential to improve or add extra information on carotid arterial diseases.This review describes the current carotid duplex ultrasound examination and compares the pathological findings with CEUS.     

颈动脉斑块内出血的高分辨力MRI研究进展

颈动脉斑块内出血是颈动脉粥样硬化斑块不稳定的重要表现之一,其可以引起斑块扩大及破裂,是发生缺血性脑卒中的重要危险因素之一。诊断斑块内出血的影像方法主要包括MRI、CT及超声,高分辨力MRI技术具有无创、空间分辨力高、多对比成像等特点,是目前检测斑块内出血最有效的影像方法,其主要包括2D和3D序列,其中近年来发展的部分3D序列进一步提高了空间分辨力及诊断敏感性和特异性。就颈动脉斑块内出血的高分辨力MRI的研究进展予以综述。     

MR测定颈动脉易损斑块特征与急性缺血性脑卒中的关系

目的 分析急性缺血性脑卒中患者症状侧颈动脉粥样硬化病变特征与扩散加权成像(DWI)证实的急性脑梗死(ACI)发生及严重程度的关联性.方法 入组发生单侧肢体症状(颈内动脉供血区)的ACI患者103例,均在发病后1周内行颈动脉磁共振黑血成像(MR-BBI)及头颅常规MRI,测得症状侧颈动脉粥样硬化病变参数(管腔狭窄率、斑块负荷和成分)和相应供血区ACI病灶分布及大小,借此分析症状侧颈动脉斑块特征与ACI发生、大小的关联程度.结果 研究发现,症状侧颈动脉管壁体积标准化指数(PWV)及富脂质核(LRNC)含量是同侧供血区ACI病灶发生及大小的独立危险因素(校正管腔狭窄和临床因素前后,P<0.05).结论 ACI发生及大小与同侧供血颈动脉的斑块易损特征(高斑块负荷和大LRNC)相关联.MR-BBI能细致化评估斑块易损特征,有利于临床分层急性缺血性脑卒中的风险性及严重程度.     

Magnetic resonance chemical shift imaging and spectroscopy of atherosclerotic plaque

An in vivo magnetic resonance imaging (MRI) technique for identification and characterization of atherosclerotic plaque was assessed in animal and human models. Atherosclerosis was induced in the abdominal aorta of four rabbits by a combination of balloon denudation and a high cholesterol diet. In vivo conventional spin-echo and fat/water suppressed images of the rabbit aortae were obtained at 1.5 T. Chemical shift imaging (CSI) was achieved using a hybridization of selective excitation and modified Dixon techniques. These techniques were then used to obtain images of atherosclerotic lesions in the carotid arteries of four patients prior to endarterectomy. The MRI results were corroborated by histologic and high-resolution proton MR spectroscopic (8.5 T) analysis of rabbit aorta, human carotid endarterectomy, and six additional human superficial femoral and iliac atherectomy specimens. All animal and human lesions were classified as either fatty streaks or fibrotic plaque. When compared to conventional spin-echo images, fat suppression by CSI substantially improved the measured contrast-to-noise ratio between plaque and vessel lumen, and enhanced its discrimination from periadventitial fat. In contrast, water suppression eliminated visualization of plaque due to the negligible amount of isotropic (liquid-like) signal from the immobilized lesion lipids. Magnetic resonance spectroscopy corroborated the CSI results by demonstrating broad, ill-defined fat resonances characteristic of nonmobile lipids in both human and rabbit atherosclerotic lesions. These findings indicate that in vivo MRI of plaque is technically feasible and can be markedly improved using chemical shift imaging.     

High-resolution multicontrast-weighted MR imaging from human carotid endarterectomy specimens to assess carotid plaque components

The American Heart Association modified classification for atherosclerotic plaque lesions has defined vulnerable plaques as those prone to rupture. The aim of our study was to assess the sensitivity and specificity of 1.5-T magnetic resonance imaging (MRI) in the evaluation of the characteristics of plaque components. Twelve carotid endarterectomy specimens were imaged by ex-vivo high-resolution 1.5-T MRI. Thirty-four cross-section axial images were selected for pixel-by-pixel basis analysis to demonstrate the most significant tissue features. Data were then submitted for histopathological examination and each specimen analysed in the light of the histological components (lipid core, fibrous tissue, fibrous/loose connective tissue, calcifications). The overall sensitivity and specificity rates for each tissue type were, respectively, 92% and 74% for the lipid core, 82% and 94% for the fibrous tissue, 72% and 87% for the fibrous/loose connective tissue, and 98% and 99% for calcification. The use of 1.5-T MRI appears to be a reliable tool to characterise plaque components and could help in the screening of patients with high risk of plaque rupture. The possibility of applying MRI in clinical daily practice may change the non-invasive approach to carotid artery diagnostic imaging, thus allowing an early identification of patients with vulnerable plaques.     

Duplex sonography of the cerebral arteries: efficacy, limitations, and indications.

This review considers the capabilities and limitations of duplex sonography in the diagnosis of abnormalities of the cerebral vasculature. Duplex sonography is an elegant union of B-mode and Doppler sonography that provides valuable information about atherosclerotic obstruction of the carotid arteries. Duplex sonography also can be used to evaluate, in a general way, the composition of carotid atherosclerotic plaque, and in this respect, it is unique among imaging procedures. Duplex sonography is not very effective in providing a "global" perspective of the cerebral vasculature, because only the cervical portion of the carotid arteries can be examined in detail. The best documented and most clearly effective use of duplex sonography is for detecting severe obstructive lesions in the carotid artery that might warrant endarterectomy in patients with cerebral hemispheric symptoms. The role of duplex sonography in the choice between medical and surgical therapy in asymptomatic patients with carotid artery stenosis is controversial, because the indications for endarterectomy are unclear in these patients. The capacity of duplex sonography to assess plaque composition may ultimately prove to be quite valuable for selecting therapeutic options and for evaluating the effectiveness of medical therapy. Meanwhile, information concerning the clinical value of this use of duplex sonography remains limited.     

Progress in atherosclerotic plaque imaging

Cardiovascular diseases are the primary cause of mortality in the industrialized world,and arterial obstruction, triggered by rupture-prone atherosclerotic plaques,lead to myocardial infarction and cerebral stroke.Vulnerable plaques do not necessarily occur with flow-limiting stenosis,thus conventional luminographic assessment of the pathology fails to identify unstable lesions.In this review we discuss the currently available imaging modalities used to investigate morphological features and biological characteristics of the atherosclerotic plaque. The different imaging modalities such as ultrasound, magnetic resonance imaging,computed tomography, nuclear imaging and their intravascular applications are illustrated,highlighting their specific diagnostic potential.Clinically available and upcoming methodologies are also reviewed along with the related challenges in their clinical translation,concerning the specific invasiveness, accuracy and cost-effectiveness of these methods.     

Molecular imaging of atherosclerosis in translational medicine

Functional characterization of atherosclerosis is a promising application of molecular imaging. Radionuclide-based techniques for molecular imaging in the large arteries (e.g. aorta and carotids), along with ultrasound and magnetic resonance imaging (MRI), have been studied both experimentally and in clinical studies. Technical factors including cardiac and respiratory motion, low spatial resolution and partial volume effects mean that noninvasive molecular imaging of atherosclerosis in the coronary arteries is not ready for prime time. Positron emission tomography imaging with fluorodeoxyglucose can measure vascular inflammation in the large arteries with high reproducibility, and signal change in response to anti-inflammatory therapy has been described. MRI has proven of value for quantifying carotid artery inflammation when iron oxide nanoparticles are used as a contrast agent. Macrophage accumulation of the iron particles allows regression of inflammation to be measured with drug therapy. Similarly, contrast-enhanced ultrasound imaging is also being evaluated for functional characterization of atherosclerotic plaques. For all of these techniques, however, large-scale clinical trials are mandatory to define the prognostic importance of the imaging signals in terms of risk of future vascular events.     

MRI detects increased coronary wall thickness in asymptomatic individuals: the multi-ethnic study of atherosclerosis (MESA)

PURPOSE: To evaluate the use of coronary wall MRI as a measure of atherosclerotic disease burden in an asymptomatic population free of clinical cardiovascular disease. Coronary wall magnetic resonance imaging (MRI) is a noninvasive method for evaluation of arterial wall remodeling associated with atherosclerosis. MATERIALS AND METHODS: Asymptomatic participants of the Multi-Ethnic Study of Atherosclerosis (MESA) study were studied using black blood MRI. MRI-assessed coronary wall thickness was compared with computed tomography calcium score, carotid intimal-medial thickness, and risk factors for coronary artery disease. RESULTS: Eighty-eight arterial segments were evaluated in 38 MESA participants (mean age, 61.3+/-8.7 years). The maximum coronary wall thickness was greater for participants with two or more cardiovascular risk factors than for those with one or no risk factors (2.59+/-0.33 mm vs. 2.36+/-0.30 mm, respectively, P=0.05.) For participants with zero calcium score, the mean and maximum coronary wall thickness for subjects with two or more risk factors for coronary artery disease were greater than the wall thickness for subjects with one or no risk factors (mean thickness: 1.95+/-0.17 mm vs. 1.7+/-0.19 mm; maximum thickness: 2.67+/-0.24 mm vs. 2.32+/-0.27 mm, respectively, P<0.05). Subjects with increased carotid intimal-medial thickness also had increased coronary artery wall thickness (P<0.05). CONCLUSION: Coronary artery wall MRI detects increased coronary wall thickness in asymptomatic individuals with subclinical markers of atherosclerotic disease and in individuals with zero calcium score.     

Vulnerable plaque detection by 3.0 tesla magnetic resonance imaging

RATIONALE AND OBJECTIVES: A clinical case report is presented on a 76-year-old man who volunteered for a 3.0 T magnetic resonance (MR) carotid protocol. The subject was referred for carotid endarterectomy and histology was performed on the ex vivo specimen and compared with the in vivo images. METHODS: The 3.0 and 1.5 T (obtained for comparison) MR protocol consisted of 2-dimensional (2D) and 3-dimensional (3D) multicontrast bright and black blood imaging for detecting the lumen and vessel wall. RESULTS: The combination of multicontrast black blood transverse images and the 3D time of flight transverse images provided visualization of a narrowed internal carotid artery lumen 4 mm above of the bifurcation and the presence of a complex atherosclerotic plaque containing a large lipid pool, calcification, and intact fibrous cap. Quantitative comparisons including vessel lumen and plaque area, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were obtained for 1.5 and 3.0 T image data. Plaque composition was verified with histology. Macrophages were also detected in the shoulders of the plaque as demonstrated by CD68 staining and corresponded with a small hyperintense area in the T2W images at 3.0 T, but not observed in comparable 1.5 T images. CONCLUSIONS: High field 3.0 T multicontrast MRI of atherosclerotic plaque has been validated with histology comparison and provides improved detection of complex atherosclerotic plaque with increased SNR and CNR compared with 1.5 T. Further studies validating contrast mechanisms of plaque at 3.0 T are required, but atherosclerotic plaque imaging has clear benefit from application at the higher magnetic field strength.     

Carotid plaque formation and its evaluation with angiography,ultrasound, and MR angiography

The accurate assessment of carotid artery disease is an important challenge for magnetic resonance (MR) angiography. Studies indicate that the detection and grading of stenosis and the evaluation of plaque morphology are all important steps in the clinical assessment of atherosclerosis. The prevalence of significant carotid artery stenosis in the elderly population and even in patients with symptoms of carotid artery disease is low; clinical risk seems to correlate more closely with plaque morphology and surface characterization than with the degree of stenosis. This highlights the importance of MR angiography and ultrasound, which can help characterize plaque morphology in addition to showing the degree of stenosis. The authors review the present understanding of plaque formation, comparisons of plaque imaging with conventional angiography, ultrasound, and MR angiography, and recent progress in MR angiography techniques. Several studies, including the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial, are discussed regarding the current objectives of carotid artery imaging. The sensitivity and specificity of plaque detection and morphologic evaluation continue to improve.