急性一氧化碳中毒后迟发性脑病的MR扩散张量表现一例

急性一氧化碳中毒后迟发性脑病是指急性一氧化碳中毒后 ,患者经过 1～ 2周左右的“假愈期”又出现一系列神经精神症状。其发病率约为一氧化碳中毒的 9% [1] 。由于其预后较差 ,常导致患者出现痴呆、智力及记忆力下降、生活不能自理和其他神经系统功能障碍 ,故早期诊断对本病的治疗具有重要意义。本科近来通过ＭＲＩ和扩散张量成像 (ｄｉｆｆｕ ｓｉｏｎｔｅｎｓｏｒｉｍａｇｉｎｇ ,ＤＴＩ)诊断 1例急性一氧化碳中毒后迟发性脑病患者 ,报道如下。患者　男 ,75岁。于 2 0 0 1年 10月 2 6日晨起出现头晕、神志不清、呕吐等症状入院 ,5小时后神…     

急性期放射性脑损伤磁共振扩散张量成像的定量研究

目的 利用磁共振扩散张量成像(DTI)定量分析,探讨正常脑组织不同部位急性期放射损伤的敏感性。方法 44例欲行全颅放疗的颅内肿瘤患者,在放疗前及放疗后3周行磁共振常规扫描、增强扫描及扩散张量成像,测量非肿瘤侧大脑半球接受总放射剂量为27 Gy时的等剂量区域内脑回灰质、脑回白质、深部灰质、深部白质的表观扩散系数(ADC)、部分各向异性(FA)、相对各向异性(RA)、容积比率(VR)等指标,并进行对比分析。 结果 所有患者常规及增强磁共振扫描非肿瘤侧大脑半球均未发现异常信号,而放疗后脑回灰质ADC值升高(t=-3.819,P<0.05),脑深部灰质核团ADC、容积比率值升高(t=-3.31、-2.810,P<0.05),脑深部灰质核团FA、RA值降低(t=2.906、2.349,P<0.05),其余部位放疗前后DTI各指标差异无统计学意义。结论 在急性期脑灰质较白质对放疗损伤敏感,DTI能从组织细胞功能水平对放射性脑损伤急性反应进行评价。     

磁共振扩散张量成像在阿尔茨海默病中的应用

阿尔茨海默病是导致痴呆的主要发病因素。对于阿尔茨海默病的早期诊断和监控，MRI检查是有效的。扩散张量成像较常规MRI对显示阿尔茨海默病早期纤维束的受损情况更敏感，不仅可在一定程度上反映该病的病理变化，而且可反映其微观结构的变化，有助于在脑皮质发生明显萎缩之前对阿尔茨海默病进行早期诊断。     

扩散张量MR成像

扩散张量成像(DTI)是在分子水平上研究组织中水分子随机运动的一种无创性的功能性磁共振成像技术。在人体生理条件下，水分子在各个方向上的扩散率不同，即扩散异向性，DTI能够测量到水分子在三维空间扩散的方向和扩散程度，描述组织的各向异性特点，精确地研究纤维走行方向。     

磁共振弥散加权成像对急性一氧化碳中毒的诊断价值

目的 :评价磁共振弥散加权成像对急性一氧化碳中毒的诊断价值。方法 :回顾性分析 6例急性一氧化碳中毒的MRI表现 ,分别采用SE序列T1WI、T2 WI、FLAIR和DWI。结果 :急性一氧化碳中毒MRI表现为两侧大脑皮层、皮层下区及苍白球T1WI等信号、T2 WI高信号 ,所有异常信号均呈两侧对称性改变。结论 :磁共振弥散加权成像对急性一氧化碳中毒具有重要诊断价值。     

正常前列腺的磁共振扩散张量成像研究

目的探讨前列腺磁共振扩散张量成像(DTI)的可行性及正常外周带和中央腺区DTI特征。方法研究对象为20例健康男性志愿者,DTI都采用Siemens Sonata1.5T超导成像仪和腹部相控阵线圈,应用西门子Leonardo工作站相应的软件进行数据处理。DTI记录感兴趣区各向异性(FA)比值和平均ADC值,并绘制相应参数图和纤维示踪影像。对比不同感兴趣区的相应成像指标的差异。结果正常外周带(PZ)和中央区(CZ)的FA值分别为0.16±0.03和0.23±0.04,两者差异具有统计学意义(P0.05)。PZ和CZ的平均ADC值分别为(1.85±0.34)×10-3mm2/s和(1.37±0.27)×10-3mm2/s,两者差异具有统计学意义(P0.05)。结论正常前列腺DTI具有可行性,中央腺区与外周带DTI指标存在明显差异。     

脑磁共振扩散张量成像术及其进展

分子扩散是一个三维空间的运动,在某些组织如脑白质中的运动是各向异性的.磁共振脑扩散张量可分辨出分子扩散运动方向上的差异,因而可显示组织扩散各向异性的细微异常.就磁共振扩散张量成像的基本原理、技术特点及成像可视化技术的基本概念予以综述.     

脑磁共振扩散张量成像术及其进展

分子扩散是一个三维空间的运动,在某些组织如脑白质中的运动是各向异性的。磁共振脑扩散张量可分辨出分子扩散运动方向上的差异,因而可显示组织扩散各向异性的细微异常。就磁共振扩散张量成像的基本原理、技术特点及成像可视化技术的基本概念予以综述。     

脑的磁共振扩散张量成像及其临床应用

与传统扩散加权MR不同,扩散张量成像(DTI)可以采集6个或更多方向上的水分子的扩散情况,因此能更准确地显示脑白质水分子的各向异性扩散.它是目前惟一能够无创地显示活体白质纤维束的方法,为评价白质纤维束间的联系及其病变开拓了新的前景.从DTI的技术原理以及临床应用方面介绍其应用现状.     

磁共振扩散张量成像在前列腺疾病诊断中的应用

目的 探讨磁共振扩散张量成像(DTI)在诊断良性前列腺增生(benign prostate hyperplasia,BPH)和前列腺癌(PCa)中的价值.资料与方法 研究对象为经病理证实的20例PCa和25例BPH患者,DTI都采用Siemens Sonata 1.5 T超导成像仪和腹部相控阵线圈,应用Siemens Leonardo工作站相应的软件进行数据处理.DTI记录感兴趣区各向异性(FA)值和平均表观扩散系数(ADC)值并绘制相应参数图和纤维示踪图像.对比不同感兴趣区的相应成像指标的差异.结果 正常外周带、BPH和PCa的FA值分别为0.16±0.03、0.23±0.04和0.46±0.02(P＜0.05).正常外周带、BPH和PCa的平均ADC值分别为(1.85±0.34)×10-3 mm2/s、(1.37±0.27)×10-3mm2/s和(0.61±0.09)×10-3 mm2/s,三者差异具有统计学意义(P＜0.05).结论 正常前列腺组织、BPH和PCa组织DTI指标存在差异,结合常规MRI检查有助于PCa的鉴别诊断.     

脊髓肿瘤的扩散张量成像研究

目的：探讨磁共振扩散张量成像(DTI)在评估脊髓肿瘤患者神经功能方面的应用价值。方法对22例脊髓肿瘤患者和22例健康志愿者进行脊髓常规磁共振成像(MRI)和 DTI 扫描,分析各向异性分数(FA 值)、表观扩散系数(ADC)值和纤维束比值(FTR)的组间差异,及其与 McCormik 评分的相关性。结果2组病灶层的 FA 值(t =-5.587,P =0.000)、ADC 值(t =7.232, P =0.000)有显著差异;病灶上层的 FA 值(t=-0.438,P =0.666)、ADC 值(t =0.303,P =0.765)无显著差异;病灶下层的 FA 值(t=-1.777,P =0.090)无显著差异,ADC 值(t=2.113,P =0.047)有显著差异;2组的 FTR 值(t =-7.902,P =0.000)有显著差异。髓外肿瘤与髓内肿瘤的 FA 值、ADC 值和 FTR 值均有显著差异(P <0.05)。脊髓肿瘤组病灶层 FA 值、ADC 值、FTR 值与McCormik 分级均存在直线相关关系。结论DTI 能够直观地反映脊髓肿瘤患者的脊髓神经功能和损伤情况。     

急性征兆性脑外伤扩散张量成像研究

目的 探讨急性征兆性脑外伤患者脑内微结构的变化.方法 对12例急性征兆性脑外伤患者以及13例性别、年龄、受教育程度、利手均匹配的健康对照者进行全脑扩散张量成像(DTI)及临床行为认知评估,采用的评估量表包括:汉密顿抑郁量表(HAMD),临床痴呆量表(CDR),疲劳严重程度量表(FSS),脑震荡后遗症评分(PSS),简易精神状态检查量表(MMSE),任务A、任务B(Trial-making A、Trial-making B).应用基于纤维束示踪的空间统计得出2组间有差异的脑区,应用方差分析得出行为认知差异.结果 与健康组对照,急性征兆性脑外伤患者存在广泛的各向异性分数(FA)值降低区域(P＜0.05,TFCE校正),尤其在边缘-皮层下结构.2组间在CDR,PSS,Trial-making A、Trial-making B有显著差异(P＜0.01),在MMSE、FSS有差异(P＜0.05),在HAMD无差异.结论 DTI能全面、准确地评估征兆性脑外伤患者脑组织微结构的改变,为临床治疗提供依据.     

Diffusion tensor imaging using single-shot SENSE-EPI.

SENSitivity Encoding (SENSE) greatly enhances the quality of diffusion-weighted echo-planar imaging (EPI) by reducing blurring and off-resonance artifacts. Such improvement would also be desirable for diffusion tensor imaging (DTI), but measures derived from the diffusion tensor can be extremely sensitive to any kind of image distortion. Whether DTI is feasible in combination with SENSE has not yet been explored, and is the focus of this study. Using a SENSE-reduction factor of 2, DTI scans in eight healthy volunteers were carried out with regular- and high-resolution acquisition matrices. To further improve the stability of the SENSE reconstruction, a new coil-sensitivity estimation technique based on variational calculus and the principles of matrix regularization was applied. With SENSE, maps of the trace of the diffusion tensor and of fractional anisotropy (FA) had improved spatial resolution and less geometric distortion. Overall, the geometric distortions were substantially removed and a significant resolution enhancement was achieved with almost the same scan time as regular EPI. DTI was even possible without the use of quadrature body coil (QBC) reference scans. Geometry-factor-related noise enhancement was only discernible in maps generated with higher-resolution matrices. Error boundaries for residual fluctuations in SENSE reconstructions are discussed. Our results suggest that SENSE can be combined with DTI and may present an important adjunct for future neuroimaging applications of this technique.     

Diffusion tensor imaging of the anal canal at 3 tesla: feasibility and reproducibility of anisotropy measures

Purpose:

To assess the feasibility and reproducibility of 3‐tesla diffusion tensor imaging (DTI) of the anal canal.

Materials and Methods:

DTI was performed in 25 men with no clinical history of anal canal disease undergoing MRI for prostate cancer. Analysis of fractional anisotropy (FA), relative anisotropy (RA), and apparent diffusion coefficient (ADC) were determined for the epithelial/subepithelial layer, internal sphincter, external sphincter, and puborectalis. The directionality of diffusion was recorded from color‐coded tractography maps. Obturator internus and gluteus maximus served as reference muscles. Mean (SD) of values for FA, RA, and ADC were compared using analysis of variance. Intra and inter‐rater agreement and test reproducibility (n = 5) was assessed by Bland‐Altman statistics.

Results:

Mean (SD) for the epithelial/subepithelial layer, internal, external sphincter, and puborectalis were as follows: FA: 0.283 (0.099); 0.337 (0.049); 0.415 (0.072); and 0.407 (0.062), respectively. RA: 0.241 (0.094); 0.292 (0.050); 0.371 (0.083); 0.361 (0.067), respectively; and ADC: 1.49 (0.23); 1.59 (0.19); 1.51 (0.28); and 1.54 (0.29) × 10^?3mm²/s, respectively. Good overall intra and inter‐rater agreement and test–retest reproducibility was noted (coefficient of variation of 4.8–19.4% and 5.9–12.9%, respectively).

Conclusion:

Anisotropy is evident in the anal canal with good inter‐rater agreement and test reproducibility. J. Magn. Reson. Imaging 2012;35:820–826. © 2011 Wiley Periodicals, Inc.

     

Susceptibility tensor imaging

Heterogeneity of magnetic susceptibility within brain tissues creates unique contrast between gray and white matter in magnetic resonance phase images acquired by gradient echo sequences. Detailed understanding of this contrast may provide meaningful diagnostic information. In this communication, we report an observation of extensive anisotropic magnetic susceptibility in the white matter of the central nervous system. Furthermore, we describe a susceptibility tensor imaging technique to measure and quantify this phenomenon. This technique relies on the measurement of resonance frequency offset at different orientations with respect to the main magnetic field. We propose to characterize this orientation variation using an apparent susceptibility tensor. The susceptibility tensor can be decomposed into three eigenvalues (principal susceptibilities) and associated eigenvectors that are coordinate‐system independent. We show that the principal susceptibilities offer strong contrast between gray and white matter, whereas the eigenvectors provide orientation information of an underlying magnetic network. We believe that this network may further offer information of white matter fiber orientation. Magn Reson Med 63:1471–1477, 2010. © 2010 Wiley‐Liss, Inc.     

Diffusion tensor imaging and magnetic resonance spectroscopy of the brain in a patient with Sturge-Weber syndrome

Quantitative brain MR spectroscopy (MRS) and diffusion tensor imaging (DTI) were used to characterize one patient with Sturge-Weber syndrome. Choline increases and N-acetylaspartate decreases were observed in pathologic frontal gray matter tissue compared to contralateral unaffected brain tissue without any change in the diffusion tensor imaging parameters (fractional anisotropy, apparent diffusion coefficient). The N-acetylaspartate decreases and/or choline increases observed here and in eight previously described Sturge-Weber patients probably reflect neuronal loss or dysfunction and demyelination as a result of recurrent seizures.     

Diffusion tensor imaging of the brain: review of clinical applications

Abstract We review the theoretical background to diffusion tensor imaging (DTI) and some of its commoner clinical applications, such as cerebral ischemia, brain maturation and traumatic brain injury. We also review its potential use in diseases such as epilepsy, multiple sclerosis, and Alzheimers disease. The value of DTI in the investigation of brain tumors and metabolic disorders is assessed.     

急性酒精中毒大鼠脑干部DTI与AQP4表达的相关性研究

目的:探讨急性酒精中毒大鼠脑干部水通道蛋白4(Aquaporin 4,AQP4)表达与DTI参数ADC值及部分各向异性(fractional anisotropy,FA)值的相关性。方法:30只SD大鼠随机分为对照组(n=5)和急性酒精中毒组(n=25),急性酒精中毒组于造模后1、3、6、12、24h行MRI扫描。MRI检查序列包括T2WI、T1WI及DTI序列,病理学检查包括HE染色、AQP4免疫组化染色,对DTI及病理结果进行分析。结果:急性酒精中毒组ADC值、FA值、AQP4表达光密度值变化表现为先持续降低后逐步回升趋势,在3h达最低点。1、3、6h的ADC值与对照组之间差异有统计学意义(P<0.01),各实验组FA值与对照组之间差异均无统计学意义(P>0.05),3、6h的AQP4表达光密度值与对照组比较差异有统计学意义(P<0.05)。结论:DTI检查能够反映急性酒精中毒早期的细胞毒性水肿,同时间段AQP4表达下调与ADC值下降的演变趋势表明AQP4在细胞毒性水肿演变过程中具有保护性机制。