Comparison of conventional and transesophageal echocardiography with magnetic resonance imaging for anatomical mapping of thoracic aortic dissection

Thirty-five consecutive patients with clinically suspected aortic dissection were subjected to a dual noninvasive imaging protocol using comprehensive echocardiography and ECG-triggered MRI with multi-slice spin echo and cine sequences in random order. The purpose of this dual imaging study was to compare the diagnostic accuracy of two-dimensional and color-coded Doppler echocardiography using the conventional transthoracic (TTE) and the transesophageal approach (TEE) with magnetic resonance imaging (MRI) for the exact morphologic evaluation and anatomical mapping of the thoracic aorta. The results of each diagnostic method were validated independently against the gold standard of intraoperative findings (n=17), necropsy (n=4) or contrast angiography (n=22).Compared to conventional transthoracic echocardiography both TEE and MRI were more reliable in detecting aortic dissections (TTE vs TEE: p<0.02; TTE vs MRI: p<0.01) and associated epiphenomena. Moreover, the reliability of TTE decreased significantly from proximal to distal segments of the aorta, e.g. from the ascending segment to the arch (p<0.05) and to the descending aorta (p<0.005), whereas the sensitivities of both TEE and MRI were excellent irrespective of the site of dissection. With regard to epiphenomena such as thrombus formation and entry location, MRI emerged as the optimal method for detailed morphologic information in all segments of the aorta. No serious side effects were encountered with either method.Thus, in patients with suspected acute or subacute aortic dissections the echocardiographic assessment should include the transesophageal approach for significant improvement of the moderate sensitivity and specificity of TTE. Both TEE and MRI are non-traumatic, safe and diagnostically accurate to identify and classify acute and subacute dissections of the thoracic aorta irrespective of their location. MRI provides superb anatomical mapping of all type A and B dissections and more detailed information on the site of entry and thrombus formation than TEE. These features of TEE and MRI may render retrograde contrast angiography obsolete in the setting of thoracic aortic dissection and may encourage surgical interventions exclusively on the basis of noninvasive imaging.     

卒中后失语患者的功能磁共振成像

失语是脑损害所致语言受损或丧失.卒中是失语的常见原因之一.无论是否经过语言康复治疗,大部分失语患者的语言功能都会有不同程度的恢复.近年来,功能磁共振成像(functional magnetic resonance imaging,fMRI)技术已被广泛应用于神经语言学研究中.文章埘探讨卒中后失语恢复机制的fMRI研究进展进行了综述.     

Perfusion magnetic resonance imaging of the liver

Perfusion magnetic resonance imaging (MRI) studies quantify the microcirculatory status of liver parenchyma and liver lesions, and can be used for the detection of liver metastases, assessing the effectiveness of antiangiogenic therapy, evaluating tumor viability after anticancer therapy or ablation, and diagnosis of liver cirrhosis and its severity. In this review, we discuss the basic concepts of perfusion MRI using tracer kinetic modeling, the common kinetic models applied for analyses, the MR scanning t...     

高分辨率磁共振成像评估椎动脉夹层的显示效果分析

目的探讨高分辨率磁共振成像(HR-MRI)在评估椎动脉夹层(VAD)方面对血管腔、血管壁结构及成分的显示效果。方法回顾性纳入2012年1月至2016年4月连续就诊且完成数字减影血管造影、磁共振血管造影、磁共振成像(MRI)和HR-MRI的5例VAD患者作为研究对象,比较和分析HR-MRI对VAD的诊断价值。结果HR-MRI能确定以下内容:(1)椎动脉粥样硬化斑块由大量脂质核心组成;(2)VAD内存在大面积的"假腔"和完全塌陷的"真腔";(3)HR-MRI能有效区分先天性椎动脉发育不全和动脉粥样硬化斑块。此外,基于经典MRI的病因诊断,在HR-MRI扫描后,2例患者加入了降脂药物治疗,2例患者在短时间内使用双重抗血小板药物。结论将HR-MRI应用于VAD患者的诊断中,能更详细地阐明受影响血管壁的状况,有助于临床医师更好识别个体患者的发病机制并选择最佳治疗药物。     

1个遗传性血色病家系的临床MRI诊断

目的探讨一个遗传性血色病（HH）家系（A）及其旁系（B）的临床MRI特点。方法对A、B家系成员进行临床、生化、肝穿活检组织铁染色及多器官MRI检查。结果 （1）部分成员有血色病相关临床表现及异常生化指标;（2）3例患者接受肝活检,发现2例肝细胞内较多铁质沉积,另1例未见明显铁沉积;（3）MRI：部分成员心肝脾胰有不同程度的铁质沉积,表现为低信号影,肾脏、大脑均未见铁沉积。结论 （1）该血色病家系HH患者铁质主要沉积在肝脏,其他脏器如心脏、脾脏、胰腺亦有累及;而其旁系可见部分成员生化异常及脏器铁沉着,但尚未发现相关血色病临床表现,是否处于发病早期尚待随访观察;（2）与肝活检相比,MRI对组织铁沉积诊断较为准确。     

Three-Tesla magnetic resonance elastography for hepatic fibrosis: Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging

AIM: To evaluate the feasibility of 3-Tesla magnetic resonance elastography (MRE) for hepatic fibrosis and to compare that with diffusion-weighted imaging (DWI) and gadoxetic acid-enhanced magnetic resonance (MR) imaging.METHODS: Forty-two patients were included in the study. On MRE, mean stiffness values were measured on the elastograms in kilopascals. The apparent diffusion coefficient (ADC) of the liver was measured using DWI. On gadoxetic acid enhanced MR, the contrast enhancement index (CEI) was calculated as signal intensity (SI)_post/SI_pre, where SI_post is liver-to-muscle SI ratio on hepatobiliary phase images and SI_pre is that on nonenhanced images. Correlation between aspartate aminotransferase to the platelet ratio index (APRI) and three MR parameters was assessed. Each MR parameter was compared between a hepatic fibrosis (HF) group and non-hepatic fibrosis (nHF) group.RESULTS: Liver stiffness showed strong positive correlation with APRI [Spearman correlation coeffiecient (r) = 0.773, P < 0.0001], while ADC and CEI showed weak or prominent negative correlation (r = -0.28 and -0.321, respectively). In the HF group, only liver stiffness showed strong correlation with APRI (r = 0.731, P < 0.0001). Liver stiffness, ADC, and APRI were significantly different between the HF group and nHF group.CONCLUSION: MRE at 3-Tesla could be a feasible method for the assessment of hepatic fibrosis.     

Role of diffusion-weighted magnetic resonance imaging in the diagnosis of extrahepatic cholangiocarcinoma

AIM: To determine the clinical value of diffusion-weight- ed imaging (DWI) for the diagnosis of extrahepatic cholangiocarcinoma (EHCC) by comparing the diagnostic sensitivity of DWI and magnetic resonance cholan-giopancreatography (MRCP). METHODS: Magnetic resonance imaging examination was performed in 56 patients with suspected EHCC. T1- weighted imaging, T2-weighted imaging, MRCP and DWI sequence, DWI using single-shot spin-echo echoplanar imaging sequence with different b values (100, 300, 500, 800 and 1...     

Magnetic resonance imaging of hepatocellular carcinoma: a pictorial review of novel insights into pathophysiological features revealed by magnetic resonance imaging

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Magnetic resonance (MR) imaging is one of the most powerful modalities for the assessment of HCC with sufficient sensitivity and specificity. In addition to its capacity for lesion detection, MR imaging delineates some unique in vivo pathophysiological features of tumors, which cannot be assessed by other modalities. Chemical shift imaging may depict steatosis of the tumor. Dynamic contrast-enhanced MR imaging is the most powerful tool to assess the vascularity of the tumor, which is closely related to malignant transformation in hepatocarcinogenesis. Diffusion-weighted imaging illustrates the cellularity of the tumor. Super-paramagnetic iron oxide, a liver-specific MR contrast agent accumulating in Kupffer cells, enables detection of the hepatocellular architecture in the lesion. Recently, a new liver-specific MR contrast agent, gadoxetic acid [gadolinium-ethoxybenzyl (Gd-EOB)-diethylenetriaminopentoacetic acid (DTPA)], has been introduced for clinical imaging. Gd-EOB-DTPA has a significant impact on the imaging of HCC, with potential capacity for the concurrent assessment of vascularity of the tumor and hepatocellular-specific properties within the tumor. Understanding the characteristics of MR imaging methods and contrast agents is essential for the optimal diagnosis and characterization of HCCs.     

Mesiotemporal changes on magnetic resonance imaging in neurosyphilis

We report a case of neurosyphilis with magnetic resonance imaging (MRI) brain scan findings compatible with a diagnosis of herpes simplex encephalitis with negative testing for herpes simplex virus in the cerebral spinal fluid. An extensive review of the literature has been undertaken revealing 24 cases worldwide where there are mesiotemporal changes on MRI concurrent with a diagnosis of neurosyphilis. Therefore, it is now well established that neurosyphilis, ‘the great imitator’, should be considered in the differential diagnosis in all patients demonstrating mesiotemporal changes on MRI, changes usually seen in herpes simplex encephalitis.     

Role of cardiac magnetic resonance imaging in ischaemic heart disease

Cardiac magnetic resonance imaging is a new imaging method that has much to offer clinicians caring for patients with ischaemic heart disease. This article describes briefly the basic principles and practical aspects of cardiac magnetic resonance imaging, and summarizes the pathophysiology of ischaemic heart disease. Then it discusses in detail the use of cardiac magnetic resonance imaging for detection of coronary artery disease, and for assessment of acute and stable coronary syndromes.     

Assessment of aortic regurgitation severity by magnetic resonance imaging of the thoracic aorta

A new method of assessing the severity of aortic regurgitationseverity by magnetic resonance imaging has been developed. Twogroups were studied: 20 controls (age=58 ± 19 years)without valvular aortic disease, and 24 patients (age=62 ±13 years) with chronic aortic insufficiency evaluated by magneticresonance and aortic root cineangiography within 1 week of eachother. A magnetic resonance sequence (TR=35 mslTE=12 mslflipangle=20°/magnet=1.5 T) was acquired in a plane containingthe thoracic aorta. A transverse saturation band 30 mm widewas positioned 30–40 mm above the aortic valve. Aorticinsufficiency was graded, the importance of end-diastolic retrogrademovement in the saturation band in the descending aorta wasnoted. Magnetic resonance was also compared to Doppler echocardiographyin 20 patients. In the controls, we found that retrograde blood flow was absent(18/20) or mild (2/20). In contrast, the presence of markedretrograde movement in a saturation band across the thoracicaorta was always associated with severe aortic regurgitation(angiographic grade III or IV). This rapid method (imaging time less than 20 min) can be appliedin most patients with aortic regurgitation and is likely tobe helpful when echocardiography is not possible or gives inconclusiveresults.     

Utility of in-office extremity magnetic resonance imaging in rheumatology

Introductionof magnetic resonance imaging (MRI) in diagnosis and management of inflammatory arthritides has ushered robust changes in patient outcomes. The efficacy of MRI in detecting inflammation and damage together has raised the expectation of imaging in rheumatology. In-office extremity MRI (eMRI) systems, designed to image the peripheral joints of upper and lower extremities, are small enough to be used in clinics, have smaller fringe magnetic field, are less expensive, and reduce patient discomfort, with comparable diagnostic power. Though less sensitive in detecting osteitis, these systems have been shown to be effective in early diagnosis and monitoring of treatment outcome in patients with rheumatoid arthritis. This review focuses on eMRI systems, outlining their principle, utility in different inflammatory arthritides, and shortcomings.     

弥散加权磁共振在脑梗死诊断中的作用

目的　探讨弥散加权磁共振 (DWI)在脑梗死急性期诊断中的作用。方法　以急性期脑梗死 3 6例为研究对象 ,在平均发病 71h进行摄影。分别进行T1WI、T2 WI、FLAIR影像以及应用EPI法进行DWI摄影。结果　在发病 2 4h内摄影的病例中 ( 10例 ) ,T1WI检出病灶 2例 ,T2 WI检出病灶 4例 ,FLAIR法检出病灶 6例 ,而DWI法则检出全部病灶。另外 ,在 14例多发性脑梗死中 12例以及PVH高度的 10例中 ,用通常的方法确定原发病灶困难 ,而在DWI则清楚地显示。结论　MRDWI对急性期脑梗死病灶的检出率有较高的准确性 ,不仅有利于超急性期的诊断 ,在确定原发病灶上亦具十分重要意义     

From the Cover: Nanoscale magnetic resonance imaging

We have combined ultrasensitive magnetic resonance force microscopy (MRFM) with 3D image reconstruction to achieve magnetic resonance imaging (MRI) with resolution <10 nm. The image reconstruction converts measured magnetic force data into a 3D map of nuclear spin density, taking advantage of the unique characteristics of the “resonant slice” that is projected outward from a nanoscale magnetic tip. The basic principles are demonstrated by imaging the ¹H spin density within individual tobacco mosaic virus particles sitting on a nanometer-thick layer of adsorbed hydrocarbons. This result, which represents a 100 million-fold improvement in volume resolution over conventional MRI, demonstrates the potential of MRFM as a tool for 3D, elementally selective imaging on the nanometer scale.     

Cardiac function by magnetic resonance imaging

Summary Gated magnetic resonance imaging of the heart displays cardiac structures with excellent resolution. This ability should be useful for assessment of cardiac physiology where acquisition of systolic and diastolic images is required. In this study, left ventricular ejection fraction was determined in 50 patients from oblique long axis views of the left ventricle using the area length formula. Angulated views were obtained by electronic gradient angulation. For comparison, all patients had monoplane angiocardiography in the RAO position. Forty-five patients were also studied by radionuclide ventriculography. Ejection fractions determined by MRI and angiocardiography were closely correlated (r=0.90). Correlation between MRI and radionuclide ventriculography was also acceptable (r=0.79).In addition to global left ventricular function, MR images provide information about regional wall motion. In order to acquire a three-dimensional set of images at various phases of the cardiac cycle, shorter imaging times are mandatory. A new imaging technique with potential for functional studies uses low flip angles, short repetition times and gradient refocused echoes. Up to 40 images can be obtained within one cardiac cycle. When displayed in a looped fashion, visual assessment of cardiac motion, intracardiac blood flow, and systolic wall thickening is possible. Potential advantages of functional studies by MRI are the concomitant acquisition of anatomical information and the three dimensional frame of reference.This work was supported by a research grant from Deutsche Forschungsgemeinschaft, Bonn.     

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 1: Common phenotypes

Cardiac magnetic resonance imaging(CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies,CMRI sequences are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition.This has led to CMRI becoming an effective non-invasive imaging gold standard for many cardiomyopathies.In this 2-part review,we outline the typical sequences used to image cardiomyopathy,and present the imaging spectrum of cardiomyopathy.Part 1 focuses on the current classification of cardiomyopathy,basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes.     

磁共振延迟增强显像诊断心肌梗死的临床研究

目的 了解磁共振延迟增强(MR-DE)显像在心肌梗死诊断中的临床意义。方法 42例拟诊冠心病的患者,按临床分为心肌梗死、心肌缺血、正常3组,行MR-DE显像,其中25例行冠状动脉造影(CAG),并按冠脉狭窄程度分为狭窄<50％,50％～99％和100％3组。计算MR-DE检出心肌梗死的敏感性与特异性,并分别分析临床分组和CAG分组的MR-DE结果。结果 利用延迟增强判断心肌梗死,敏感性、特异性和诊断准确性分别为87.5％,94.1％和92.8％。出现延迟增强的比例,在临床分组中,分别为87.5％,8.7％和0％;在CAG分组中,分別为0％,50％和100％。结论 MR-DE显像对心肌梗死诊断有较高临床意义。