颅内动脉粥样硬化的磁共振成像研究进展

颅内动脉粥样硬化(ICAD)与缺血性卒中关系密切,在我国已经成为脑卒中最重要病因之一。MRA作为诊断ICAD的影像手段目前已广泛应用于临床。高分辨力MRI可以提供血管壁结构和斑块成分等信息,目前ICAD的高分辨力MRI研究主要集中于评估斑块特征和明确病理机制等方面。就ICAD的MRI研究现状及发展趋势予以综述。     

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented.     

颅内动脉粥样硬化的高分辨力血管壁成像特征及临床应用

颅内动脉粥样硬化是缺血性脑卒中最主要的原因。高分辨力磁共振血管壁成像（VM-MRI）可以直接对血管壁进行成像,评价血管狭窄程度、血管重构、斑块负荷、斑块成分与分布,被认为是唯一能对颅内血管壁进行成像的无创检查技术。近年来颅内VW-MRI发展迅速,现就VW-MRI技术、VW-MRI对颅内动脉粥样硬化斑块的评价及其临床应用做一综述。     

大动脉炎血管壁的磁共振表现特点

目的：分析大动脉炎血管壁的MR表现特征及其临床应用价值。方法：32例临床确诊为大动脉炎的患者接受了MR检查,其中处于病情活动期20例,非活动期12例。分析并比较了两组患者受累动脉管壁的MR表现特征。结果：所有受累动脉的血管壁均不同程度的环形增厚。活动期组患者的管壁厚度较非活动期组患者明显增厚[（4．6±0．4）mm vs（3．4±0．6）mm,P〈0．01];比较两组增厚的血管壁形态,管壁呈“多环征”（分别为89／100和25／60）、内层明显强化（分别为66／100和24／60）、血管外界模糊不清（分别为72／100和20／60）等征象,经Х^2检验差异均有统计学意义（P〈0．01）。结论：大动脉炎血管壁的MR主要征象是管壁增厚及其信号改变。MRI能观察血管壁精细的形态学变化,对大动脉炎管腔狭窄前的早期诊断以及活动性判断具有重要价值。     

消化道磁共振检查技术与诊断

随着MR技术的快速发展,胃肠道MR检查成为现实。本文将讨论最佳MR胃肠成像所需诊断技术要求及与已有的X线检查方法相比MR所处的位置。当前这一新的检查方法在食道、小肠、结肠中都有报道。这些发展显示胃肠道MR检查可能将由科学研究向常规的临床应用转变。     

Magnetic resonance imaging of the liver: New imaging strategies for evaluating focal liver lesions

The early detection of focal liver lesions, particularly those which are malignant, is of utmost importance. The resection of liver metastases of some malignancies (including colorectal cancer) has been shown to improve the survival of patients. Exact knowledge of the number, size, and regional distribution of liver metastases is essential to determine their resectability. Almost all focal liver lesions larger than 10 mm are demonstrated with current imaging techniques but the detection of smaller focal liver lesions is still relatively poor. One of the advantages of magnetic resonance imaging (MRI) of the liver is better soft tissue contrast (compared to other radiologic modalities), which allows better detection and characterization of the focal liver lesions in question. Developments in MRI hardware and software and the availability of novel MRI contrast agents have further improved the diagnostic yield of MRI in lesion detection and characterization. Although the primary modalities for liver imaging are ultrasound and computed tomography, recent studies have suggested that MRI is the most sensitive method for detecting small liver metastatic lesions, and MRI is now considered the pre-operative standard method for diagnosis. Two recent developments in MRI sequences for the upper abdomen comprise unenhanced diffusion-weighted imaging (DWI), and keyhole-based dynamic contrast-enhanced (DCE) MRI (4D THRIVE). DWI allows improved detection (b = 10 s/mm(2)) of small (< 10 mm) focal liver lesions in particular, and is useful as a road map sequence. Also, using higher b-values, the calculation of the apparent diffusion coefficient value, true diffusion coefficient, D, and the perfusion fraction, f, has been used for the characterization of focal liver lesions. DCE 4D THRIVE enables MRI of the liver with high temporal and spatial resolution and full liver coverage. 4D THRIVE improves evaluation of focal liver lesions, providing multiple arterial and venous phases, and allows the calculation of perfusion parameters using pharmacokinetic models. 4D THRIVE has potential benefits in terms of detection, characterization and staging of focal liver lesions and in monitoring therapy.     

Evaluation of inflammatory status of atherosclerotic carotid plaque before thromboendarterectomy using delayed contrast-enhanced subtracted images after magnetic resonance angiography

Objective

To investigate the correlation among carotid plaque contrast enhancement (CPCE) at MRI, inflammatory cell infiltration (ICI) at histopathology, and carotid stenosis degree.

Materials and methods

Twenty-eight patients (19 males; mean age 67 ± 9 years) scheduled for thromboendarterectomy prospectively underwent 1.5-T MR imaging using: (a) axial T1-weighted gradient-echo (T1wGRE) sequence centered on carotid bifurcations; (b) contrast-enhanced MR angiography (CE-MRA) with 0.1 mmol/kg of gadobenate dimeglumine; (c) enhanced axial T1wGRE sequence as in (a), 3 min after contrast injection. A three-point score system (absent, focal, wide) was used to assess CPCE on native and subtracted MRI images (c minus a) and ICI at histopathology. Carotid stenosis degree was determined on CE-MRA.

Results

Six CPCE studies were discarded due to patient movement. In the remaining 22 studies, CPCE was absent, focal and wide in 13, 6 and 3 cases, respectively; ICI was absent, focal and wide in 13, 7 and 2 cases, respectively (k = 0.57). On CE-MRA 21/28 stenoses were severe and 7/28 moderate. There was no correlation either with ICI (p = 1.000, n = 28) or CPCE (p = 0.747, n = 22).

Conclusion

The correlation between CPCE and ICI suggests a role for CPCE as an independent marker of plaque inflammation.     

Magnetic resonance imaging of pyomyositis

Pyomyositis is a relatively rare entity in temperate climates. Because of its rarity and its nonspecific clinical and radiographic findings, pyomyositis may be misdiagnosed and may cause severe morbidity and mortality. We present magnetic resonance imaging findings in two cases of pyomyositis. Magnetic resonance imaging was helpful in differentiating other pathological processes from pyomyositis, outlining the extent of involvement, and localizing the fluid collection.     

单倍剂量三维动态增强MR肾动脉造影

目的:评价单倍剂量三维动态增强MR肾动脉造影(3D DCE-MRA)的图像质量及临床应用价值。方法:60例疑肾动脉狭窄的患者,随机分为A、B两组(各30例)。预先推注1ml钆喷替酸葡甲胺(Gd-DTPA)测定对比剂循环时间,用三维快速小角度激发序列(3D FLASH)检查A、B两组患者,A组用单倍剂量Gd-DTPA(平均0.11mmol/kg体重),B组用双倍剂量Gd-DTPA(平均0.2mmol/kg体重)。比较A、B两组原始图像的信噪比和对比噪声比以及最大信号投影图像的质量。结果:A、B组的肾动脉信噪比为45.3±17.2和49.6±20.1,对比噪声比为37.6±15.6和39.7±18.5,两者差异无显著性意义(P>0.05)。两组MIP图像质量差异无显著性意义。单倍剂量3D DCE-MRA显示了12例(14条)肾动脉狭窄。结论:单倍剂量三维动态增强MR肾动脉造影图像清晰,能满足临床诊断需要。     

MR imaging of the vessel wall

Since the risks for thrombosis are more dependent on plaque composition than on the degree of luminal narrowing, the radiological assessment of atherosclerosis should extend beyond mere depiction of the arterial lumen. High-resolution MRI of the vessel wall can provide important information about the individual makeup of atherosclerotic plaques, potentially enabling early detection and characterization of lesions before narrowing of the vessel lumen occurs. The MR-based assessment of the vessel wall with sufficient spatial resolution and image contrast, however, remains challenging. Requirements include high signal-to-noise ratio, high contrast-to-noise ratio, good signal penetration depth and homogeneous signal throughout the vessel under investigation, as well as imaging protocols encompassing various contrast weightings. Numerous dedicated radiofrequency (RF) coils have been developed to achieve these goals employing either external surface phased-array coils, or alternatively, utilizing intravascular coils to image the vessel wall from inside the vessel and thus being invasive. For the non-invasive approach of imaging with surface coils, the carotid and the right coronary arteries have been favoured since they are of critical importance and since they are relatively superficial structures, accessible from the outside. To detect the early development of plaque and visualize it globally rather than locally, intravascular contrast agents on the basis of ultrasmall particles of iron oxide can be used as a marker of macrophage activity within the plaque. In the long run, it appears likely that the combination of luminal MR angiography with the administration of susceptibility-based contrast agents and subsequent high-resolution MR of detected atherosclerotic lesions with dedicated RF coils could evolve as the diagnostic concept of choice for the assessment of atherosclerotic disease.     

关节软骨MR成像进展

随着软骨序列的开发和应用，MRI对关节软骨的评价越来越重要。本文就关节软骨的MRI表现、关节软骨的MRI序列和扫描技术、关节软骨损伤以及修复术后MRI评价等方面进行了综述。     

烟雾病的MRI、MRA诊断价值

 目的探讨MRI、MRA对烟雾病(Moyamoya病)的诊断价值.方法对11例Moyamoya病患者行MRI和MRA检查,MRI包括横轴位和矢状位T1WI、T2WI、FLAIR;MRA采用3D TOF法,3例行增强MRA.结果MRI表现为:(1)Moyamoya血管:双侧3例,单侧8例;(2)脑梗死和脑软化灶11例;(3)局部脑萎缩3例.MRA表现为3例双侧颈内动脉狭窄,双侧大脑中、前动脉闭塞,大脑后动脉形成异常血管网;6例右侧颈内动脉、大脑中动脉狭窄;2例左侧颈内动脉、大脑中动脉狭窄.结论MRI能良好的显示脑内病变,MRA能较完整的显示异常血管,MRI与MRA相结合可作为烟雾病诊断的首选检查方法.     

Magnetic resonance imaging in glenohumeral instability

The glenohumeral joint is the most commonly dislocated joint of the body and anterior instability is the most common type of shoulder instability.Magnetic resonance (MR) imaging,and more recently,MR arthrography,have become the essential investigation modalities of glenohumeral instability,especially for pre-procedure evaluation before arthroscopic surgery.Injuries associated with glenohumeral instability are variable,and can involve the bones,the labor-ligamentous components,or the rotator cuff.Anterior instability is associated with injuries of the anterior labrum and the anterior band of the inferior glenohumeral ligament,in the form of Bankart lesion and its variants;whereas posterior instability is associated with reverse Bankart and reverse Hill-Sachs lesion.Multidirectional instability often has no labral pathology on imaging but shows specific osseous changes such as increased chondrolabral retroversion.This article reviews the relevant anatomy in brief,the MR imaging technique and the arthrographic technique,and describes the MR findings in each type of instability as well as common imaging pitfalls.     

粥样硬化易损斑块传统影像与分子影像检测与评价现状

易损斑块引发的心脑血管急性事件是威胁人类生命健康的主要原因之一,检测与评价斑块的易损性尤为重要.传统影像学技术多从形态结构方面评价粥样斑块,目前的扫描技术有一定进步,但在早期发现和评估斑块方面有其局限性.分子影像学方法在核素显像、MRI、超声和光学成像中均有应用,对易损斑块的显像靶点涉及斑块组成、炎症、血栓形成、新生血管、凋亡等方面,能反映斑块形态结构和功能代谢的改变.多模式分子影像综合了各单一显像模式的优势,将会为易损斑块的早期检测与评估提供帮助.该文就传统影像与分子影像在粥样硬化易损斑块检测与评价中的现状进行综述.     

黑血3D DANTE-CUBE磁共振管壁成像技术对动脉粥样硬化血管重复扫描的实验研究

目的:利用3.0T磁共振3D DANTE-CUBE序列对动脉进行重复扫描及可重复性分析,评价该序列在动物动脉管壁成像中的稳定性和可靠性。方法:研究对象为8只新西兰大白兔,其中实验组(5只)行高脂饲料喂养加腹主动脉内膜拉伤术造模。运用3D DANTE CUBE的TIWI和T2WI序列对腹主动脉扫描,2周后重复扫描一次。“观察者1”测量两次扫描图像,以计算重复扫描的一致性;针对第二次扫描,“观察者1”前后测量2次、“观察者2”测量1次,以计算组内和组间的一致性。定量参数为管腔面积(AL).血管总面积(Ay)和管壁面积(Aw)。最后对目标血管行病理检查。结果:最终6只兔(实验组3只)纳人统计,DANTE-CUBE的T1WI和T2WI序列均可清晰显示管壁病变和斑块成分,实验组的管壁面积显著大于对照组(P<0.001),重复扫描的一致性T1WI的AL,T2WI的A,和AW的一致性都非常好(ICC>0.75,CV<15%)。观察者内的一致性:TIWI的所有参数的一致性都非常好(ICC>0.75,CV<15%);T2WI的AL和Aw的一致性非常好(ICC>0.75,CV<15%)。观察者间的一致性分析:T1WI和T2WI的所有参数的一致性都非常好(ICC>0.75,CV<15%)。结论:本研究3D DANTE-CUBE管壁成像序列可以精准且稳定地评价动物的动脉粥样硬化管壁,为进一步的临床应用奠定了技术基础。     

细胞磁共振成像技术在体示踪免疫细胞的研究进展

肿瘤免疫治疗是继手术、放疗和化疗后出现的一种新的治疗方法。在体示踪免疫细胞有助于指导肿瘤的免疫治疗并预测和评估其治疗效果。细胞磁共振成像技术运用特殊的对比剂,能够无创、实时、可重复地监测体内细胞的活动。近年来,研究者对应用细胞磁共振成像技术在体示踪免疫细胞进行了大量的研究并取得了一定的进展,该文将就这一研究进展作一综述。     

Association of carotid atherosclerotic plaque features with acute ischemic stroke: A magnetic resonance imaging study

Background and purpose

It remains unclear whether direct vessel wall imaging can identify carotid high-risk lesions in symptomatic subjects and whether carotid plaque characteristics are more effective indicators for cerebral infarct severity than stenosis. This study sought to determine the associations of carotid plaque characteristics by MR imaging with stenosis and acute cerebral infarct (ACI) sizes on diffusion weighted imaging (DWI).

Materials and methods

One hundred and fourteen symptomatic patients underwent carotid and brain MRI. ACI volume was determined from symptomatic internal carotid artery territory on DWI images. Ipsilateral carotid plaque morphological and compositional characteristics, and stenosis were also determined. The relationships between carotid plaque characteristics, stenosis and ACIs size were then evaluated.

Results

In carotid arteries with 30–49% stenosis, 86.7% and 26.7% were found to have lipid-rich necrotic core (LRNC) and intraplaque hemorrhage, respectively. Furthermore, 45.8% of carotid arteries with 0–29% stenosis developed LRNCs. Carotid morphological measurements, such as % wall volume, and the LRNC size were significantly associated with ipsilateral ACIs volume before and after adjustment for significant demographic factors (age and LDL) or stenosis in patients with carotid plaque (all p < 0.05).

Conclusions

A substantial number of high-risk plaques characterized by vessel wall imaging exist in carotid arteries with lower grade stenosis. In addition, carotid plaque characteristics, particularly the % wall volume and LRNC size, are independently associated with cerebral infarction as measured by DWI lesions. Our findings indicate that characterizing atherosclerotic plaque by MR vessel wall imaging might be useful for stratification of plaque risk and infarction severity.     

Evaluation of carotid stenosis with axial high-resolution black-blood MR imaging

High-resolution axial black-blood MR imaging (BB MRI) has been shown to be able to characterise carotid plaque morphology. The aim of this study was to explore the accuracy of this technique in quantifying the severity of carotid stenosis. A prospective study of 54 patients with symptomatic carotid disease was conducted, comparing BB MRI to the gold standard, conventional digital subtraction X-ray angiography (DSA). The BB MRI sequence was a fast-spin echo acquisition (TE=42 ms, ETL=24, field of view = 100×100 mm, slice thickness = 3.0 mm) at 1.5 T using a custom-built phased-array coil. Linear measurements of luminal and outer carotid wall diameter were made directly from the axial BB MRI slices by three independent blinded readers and stenosis was calculated according to European Carotid Surgery Trial (ECST) criteria. There was good agreement between BB MRI and DSA (intraclass correlation = 0.83). Inter-observer agreement was good (average kappa = 0.77). BB MRI was accurate for detection of severe stenosis (80%) with sensitivity and specificity of 87 and 81%, respectively. Eight cases of DSA-defined moderate stenosis were overestimated as severe by BB MRI and this may be related to non-circular lumens. Axial imaging with BB MRI could potentially be used to provide useful information about severity of carotid stenosis.     

Magnetic resonance imaging of the brain in Wilson's disease

Summary Fifteen patients with Wilson's disease were examined, using spin-echo (SE) and gradient-echo (GE) sequences with 0.5 T and 1.5 T magnetic resonance (MR) imagers. They fell into three groups: groups 1 and 2 were examined retrospectively after 3–18 years of treatment, while group 3 was examined prospectively from the start of treatment, after recommencement of treatment, or inadequate treatment. MRI was sensitive to changes in the basal ganglia at sites typical of Wilson's disease and was useful for documenting the effects of treatment. It was found necessary to estimate the relaxation times T1 and T2, to better assess improvement or transient worsening of the disease in the prospective group. Residual cavitation and gliosis could be distinguished in the retrospective group using a subtraction technique.