MR扩散加权成像在急性心肌梗死中的研究进展

心脏MR扩散加权成像(CMR DWI)是一种新研发的可用于急性心肌梗死诊断的MRI技术,与常规成像技术相比,DWI可以在心肌梗死早期进行成像,急性心肌梗死早期在心肌发生形态学及动力学改变之前,其心肌细胞在分子水平会发生一系列改变。因此,DWI对于疾病的早期诊断、治疗及病人预后具有重要意义。就DWI在急性心肌梗死成像中的原理、技术进展、发展现状及临床应用前景予以综述。     

颌下腺刺激前后扩散加权平面回波MRI功能成像

目的:研究扩散加权(DWI)平面回波成像(EPI)进行颌下腺成像的可行性,并描述其不同的功能状态。方法:27例健康志愿者在刺激前行扩散加权序列成像,给予口述柠檬汁刺激30s后重复扩散加权成像。所有检查均使用Siemens1.5T超导MR扫描仪(最大梯度场强为30mT/m,最大切换率为125mT/m/s),     

低b值扩散加权平面回波成像对急性心肌炎病人心肌水肿的检出

正目的评价低b值扩散加权(DW)平面回波(EP)成像序列检出急性心肌炎病人局限性及弥漫性心肌水肿的作用。方法该研究经伦理委员会同意,并均签署知情同意     

MR扩散加权成像在肝纤维化评估中的应用

目的评价MR扩散加权成像(DWI)对肝脏纤维化和炎症的检出及分期的应用价值。方法行DWI检查,b值选取0、500和1000s/mm2。在4个肝段放置圆形兴趣区获得ADC值。比较研究组(n=34)和对照组(n=25)间ADC值的差     

多发性硬化的MR扩散加权成像研究

目的：总结多发性硬化（multiple sclerosis,MS)的扩散加权成像（diffusion-weighted imaging,DWI)表现，定量研究MS病灶区水分子表观扩散系数(apparent diffusion coefficient,ADC）值、扩散各向异性指数（anisotropy index,AI)的变化规律。方法：18例218个病灶分为5组：A组为MS急性期活动性病灶9例72个病灶，B组为A组中4例治疗后随访的病例，共31个病灶，C组为缓解－复发型的缓解期静止病灶9例（115个病灶），D组取病灶对侧或邻近的正常表现白质区域(normal appearance white matter,NAWM)，共218个，E组为正常对照组18例。总结病灶在DWI与常规MRI上的表现。测量病灶及临近正常表现白质区以及正常对照组相应区的ADC、AI。结果：在DWI上，进展型MS表现为高信号（T2WI表现为水肿样高信号）。缓解－复发型的急性发作期MS表现为环形或圆形高信号病灶。缓解－复发型的缓解期病灶与白质相比表现为稍高信号。各种分型与分期的MS病灶的ADC升高，AI下降，与NAWM及正常对照组间存在明显差异（F＝26．89，P＜0．01）。AI在病程后期表现为明显下降。MS病灶在T2WI上表现为高信号。强化MS病灶的ADC值 比非强化病灶的ADC值低（t＝4．19，P＜0．01），而2组的AI值之间无显著性差异（t＝0．99，P＞0．05）。结论：DWI与常规MR相比可以提供定量的诊断信息。能够反映MS不同临床分期的病理变化。扩散定量研究在MS的诊断、鉴别诊断以及疾病预后疗效中有重要的价值。     

扩散加权成像在急性阑尾炎诊断中的应用

目的评价MR扩散加权成像(DWI)对急性阑尾炎的诊断价值。方法在本项前瞻性研究中共收集119例急性阑尾炎病人和50名对照者。由不同的b值:0、500、1000     

高b值扩散加权磁共振成像胆囊癌检出的初步研究与研究结果

本研究旨在回顾性评价高b值扩散加权成像（DWI）对于胆囊癌的检出价值。15例胆囊癌病人和14例其他病人纳入研究。所有病人均进行了DWI检查,由2位放射科医师评价影像。计算受试者工作特征曲线的曲线下面积（AUC）、测量得到的表观扩散系数（ADC）、敏感度和特异度。     

儿童头、颈部肿块的扩散加权成像检查

本研究的目的是评价由扩散加权平面回波MR成像计算出的表观扩散系数对儿童头、颈部肿瘤肿块的临床价 值。研究包括78例头、颈部肿块儿童（男46例、女32例,年龄范围3个月～15岁,平均为6岁）。在1．5T MR设备上行常规MRI和扩散加权成像,采用单次激发平面回波成像（EPI）,b值为0．500和1000s／mm^2,测量ADC值。     

结肠癌病人肝脏局灶性病变的检出及定性:MR扩散加权成像与Gd-EOB-DTPA增强成像的对比研究

目的比较MR扩散加权成像(DWI)与Gd-EOB-DTPA增强成像对结肠癌病人肝脏局灶性病变(FLLs)的检出及定性。方法 73例病人行MR成像,包括平面回波DWI     

MR扩散加权平面回波成像对良恶性椎体骨折鉴别诊断的价值

目的　探讨单次激发平面回波SE序列扩散加权成像对良、恶性椎体压缩性骨折鉴别诊断的价值。资料与方法　对 46例 5 9个骨折椎体MR常规平扫后行扩散加权成像 ,良性组 2 7例 40个骨折椎体 ,恶性组 19例 19个骨折椎体 ,取b =0 ,2 0 0 ,40 0s/mm2 。测量病变椎体的信号强度比和信噪比。结果　在DWI上 ,良性骨折椎体与邻近正常椎体相比均呈低或等信号 ,恶性骨折椎体则呈高信号 ,2组骨折椎体的信号强度比和信噪比间存在显著差异(P <0 .0 1) ,诊断准确率 98%。而常规T1WI、T2 WI及STIR的误诊率达 6 .8%。结论　单次激发平面回波扩散加权成像对良、恶性椎体压缩性骨折的鉴别诊断是一种简便、有效的补充手段。     

Diffusion-weighted echo planar imaging in patients with recent myocardial infarction

Objective  

To evaluate a diffusion-weighted (DW) black blood MR sequence for the detection of myocardium signal abnormalities in patients with recent myocardial infarction (MI).     

Diffusion-weighted multiple shot echo planar imaging of humans without navigation

A new method is proposed for reducing the artifacts produced in diffusion-weighted imaging. When data are acquired using multiple shot echo planar acquisitions, conventional reconstruction methods produce artifactual images as a consequence of diffusion weighting and small amounts of bulk motion of the subject. If the amount of motion can be determined, it is possible to correct the data before reconstruction, which removes the artifact. A method for estimating the motion from the acquired data has been developed and evaluated. This method assumes that ghost image effects will be minimized when motion has been correctly compensated. By considering the amount of signal in the background of the image, appropriate corrections to the data can be made, and the accuracy of the motion compensation may be estimated. This technique has been evaluated by computer simulation, and its performance has been demonstrated in a phantom and humans with both two- and four-shot echo planar acquisitions and using both “mosaic” and “interleaved” sampling schemes.     

Diffusion-weighted echo planar imaging of the normal human cervical spinal cord

We obtained diffusion-weighted echo planar images of the human cervical cord in vivo and correlated them with histopathologic findings. Images were obtained in 17 healthy volunteers using a 1.5 T clinical MR unit. When motion-probing gradients were added perpendicular to the long axis of the cord, the white matter was hyperintense because of anisotropic diffusion. However, the gracile fasciculus was hypointense probably due to the small diameter of neural fibers and the large extracellular space.     

Value of magnetic resonance imaging in patients with a recent myocardial infarction: Comparison with planar thallium-201 scintigraphy

The diagnostic accuracy of spin-echo Magnetic Resonance (MR) imaging in the detection and localization of a recent myocardial infarction (mean 4 days old) was compared to planar thallium-201 scintigraphy in 20 patients with a documented myocardial infarction. A control group of 10 subjects underwent a similar MR imaging procedure without thallium-201 scintigraphy. T1-weighted MR images (TE 30 msec) showed abnormal thinning of the infarcted left ventricular wall during systole (<50% of the opposite wall) in 11 patients (55%). On T2-weighted multi-echo MR images, (TE 30–60–90–120 msec) abnormally increased signal intensity was found in 17 patients and coincided with the location of the infarction. Thallium-201 scintigraphy detected the infarction in 18 patients. Comparison of T2-MR imaging and thallium-201 scintigraphy showed concordant findings in 82% of the left ventricular segments. In 9% of segements, thallium uptake was reduced with normal T2-MR and in 9% we found a normal thallium uptake with abnormal T2-MR findings. In all subjects of the control group, T1-MR images were normal, and only one subject showed increased signal intensity on T2-MR images. We conclude that the diagnostic accuracy of MR imaging in detecting a myocardial infarction is similar to that of T1-201 scintigraphy.     

Detection and quantification of recent myocardial infarction: diagnostic value of multiecho multislice spin echo imaging

Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038.     

MRI常规扫描序列与EPI序列对弥漫性轴索损伤诊断的对比研究

目的评价MRI常规FSET2WI、SET1WI序列与EPI序列对弥漫性轴索损伤的诊断价值.材料与方法42例弥漫性轴索损伤患者均进行MRI常规FSET2WI、SET1WI和EPI扫描.29例检查前静脉注射5～10毫克安定.结果FSET2WI、SET1WI序列运动伪影的发生率分别为83.3%、71.4%;EPI序列无一例出现运动伪影.EPI病灶与正常脑白质的对比度显著低于FSET2WI序列(p＜0.001),空间分辨率较FSET2WI、SET1WI序列差,信噪比最高.EPI共显示143个病灶,为FSET2WI显示病灶(174个)的82.2%,SET1WI序列显示133个病灶.对于直径大于1cm的病灶,EPI病灶显示数为FSET2WI序列的91.7%.FSET2WI、SET1WI序列所见的DAI主要并发症,EPI序列大都能显示.结论EPI的对比度与分辨率不如FSET2WI,对脑内小病灶、出血灶及脑底部病灶的显示还存在一定的限度,但EPI扫描时间极短,图像信噪比高、无运动伪影,能保证对脑内大多数病灶的显示,对弥漫性轴索损伤的诊断有重要的诊断价值,尤其对伴有烦噪的急性脑外伤患者或病情不允许进行长时间检查的患者,EPI可代替FSET2WI进行检查.     

Diffusion-weighted imaging of the sellar region: A comparison study of BLADE and single-shot echo planar imaging sequences

Purpose

The purpose of this study is to compare BLADE diffusion-weighted imaging (DWI) with single-shot echo planar imaging (EPI) DWI on the aspects of feasibility of imaging the sellar region and image quality.

Methods

A total of 3 healthy volunteers and 52 patients with suspected lesions in the sellar region were included in this prospective intra-individual study. All exams were performed at 3.0 T with a BLADE DWI sequence and a standard single-shot EP-DWI sequence. Phantom measurements were performed to measure the objective signal-to-noise ratio (SNR). Two radiologists rated the image quality according to the visualisation of the internal carotid arteries, optic chiasm, pituitary stalk, pituitary gland and lesion, and the overall image quality. One radiologist measured lesion sizes for detecting their relationship with the image score.

Results

The SNR in BLADE DWI sequence showed no significant difference from the single-shot EPI sequence (P > 0.05). All of the assessed regions received higher scores in BLADE DWI images than single-shot EP-DWI.     

Shared k-space echo planar imaging with keyhole.

Time-dependent phenomena are of great interest, and researchers have sought to shed light on these processes with MRI, particularly in vivo. In this work, a new hybrid technique based on EPI and using the concept of keyhole imaging is presented. By sharing peripheral k-space data between images and acquiring the keyhole more frequently, it is shown that the spatial resolution of the reconstructed images can be maintained. The method affords a higher temporal resolution and is more robust against susceptibility and chemical-shift artifacts than single-shot EPI. The method, termed shared k-space echo planar imaging with keyhole (shared EPIK), has been implemented on a standard clinical scanner. Technical details, simulation results, phantom images, in vivo images, and fMRI results are presented. These results indicate that the new method is robust and may be used for dynamic MRI applications. Magn Reson Med 45:109-117, 2001.     

Phase errors in multi-shot echo planar imaging

Field inhomogeneity related phase errors in multi-shot echo planar imaging (EPI) are directly visualized and analyzed in the spatial frequency domain data or ‘k-space’. The echo time shift (ETS) technique incrementally moves the position of the echo train and improves the phase error function by redistributing phase discontinuities away from the center of k-space.