基于体素的健康中国成人概率性弥散张量成像脑图谱的建立

目的 使用计算机医学图像处理技术在标准人脑空间建立基于体素的健康中国成人概率性弥散张量成像（DTI）脑图谱,以期为脑白质的功能研究和相关疾病的诊治提供基础信息。 方法 选择50例健康成年志愿者进行常规MRI扫描,确认未发现异常后,再行DTI扫描,获取相应图像数据。首先使用MRIcron软件包中的相关程序,将原始的DICOM数据格式转换为图像处理所需要的格式,然后运用DtiStudio和DiffeoMap软件,结合自动图像配准算法对DTI数据进行数据预处理、张量计算和图像归一化,最后在MATLAB中对图像进行平均计算,构建图谱。结果 成功构建出基于50例健康中国成人的概率性DTI脑图谱,图谱清晰。各向异性（FA）图和彩色编码图上均可见脑白质结构和纤维束走向,在彩色编码图上以特定颜色代表了不同纤维束的走行方向。结论 运用图像处理技术可以构建国人概率性DTI脑图谱。该图谱以通用数据格式保存,可被大部分医学图像处理软件及分析软件识别读取,能为研究脑白质正常结构功能及相关疾病服务。     

基于DT-MRI的纤维跟踪及可视化研究

磁共振扩散张量成像(DT-MRI)是一种新的成像技术,比传统的扩散加权成像(DWI)能够更加准确地反映分子扩散的方向.在脑白质这样具有大量纤维束的组织中,水分子的扩散表现出显著的各向异性,从而有可能从张量信息的各向异性入手,跟踪得到白质纤维束的走行方向.本文介绍了DTI的原理、数据采集与处理方法,提出了一种可变步长的纤维跟踪方法,并以VC /ITK/VTK为开发工具实现了DTI分析和纤维跟踪与可视化.     

基于扩散张量的脑白质内神经纤维束的可视化技术

介绍了在功能磁共振成像的研究中发展非常快的扩散张量成像技术的基本原理，以及如何利用扩散张量数据来重建脑白质内的神经纤维柬图像。其中主要介绍了白质束成像技术及其优缺点，并且分析了神经纤维束可视化技术的应用前景及其局限性。     

磁共振DTI技术和锰离子示踪方法活体定位鼠脑神经纤维

本文应用磁共振(MR)DTI的方法清晰准确描绘出鼠脑白质内主要神经纤维的位置、方向和形态,包括胼胝体、前联合、内囊、外囊、视束、大脑脚、锥体束等。皮质内注射MnCl2后MR成像,可见皮质脊髓束、皮质丘脑束、皮质纹状体束和纹状体黑质通路被示踪,可重复性地表现为特定部位的MR3D-FSPGR图像和T1W像高信号改变,相应区域T2WI为低信号。LFB染色各纤维束位置、形态与DTI-DEC张量图和MnCl2示踪MR图像结果相一致。因此,磁共振DTI技术和锰离子示踪的方法都能够对鼠脑主要神经纤维和投射通路进行定位,能够作为活体示踪脑内神经纤维束的手段。     

磁共振扩散张量成像评价小儿脑病的初步应用

目的应用扩散张量成像（DTI）来进一步评价小儿脑疾病，探讨DTI的诊断价值。方法对15例患各种脑病的小儿进行MRI检查，其中男性10例，女性5例，年龄为生后3天至11岁（平均年龄4．8岁）。采用Philips Intera Achieva 3．0 Tesla的超导MRI仪，用回波平面成像（EPI）的DTI技术，b为800s／mm^2，15个方向。观察彩色分数各向异性（FA）图和三维彩色编码图。结果15例患儿中，发育畸形2例，分别是胼胝体发育不良、巨脑回；脑室旁白质软化（PVL）7例；缺氧缺血性脑病3例；脑软化2例；脑积水1例。在巨脑回病例，常规MRI见右侧脑回发育不良，呈巨脑回畸形，右侧脑室扩大，在DTI上见右侧病变区白质束明显较对侧少。胼胝体发育不良病例在DTI张量图见胼胝体菲薄。在PVL和缺氧缺血性脑病病例均可见白质纤维束在放射冠颜色混杂，方向性混乱。脑软化病例可见白质纤维束部分中断。在脑积水病例可见白质束受压推移。结论DTI能够显示白质束的走向、绕行、交叉及推挤、中断等异常，可能对今后评估小儿脑病的预后转归有帮助。     

3.OT MR三维重建脑干小脑上脚纤维交叉的研究

目的 应用3.0T MR扩散张量成像(DTI)和白质纤维成像技术(DTT),研究脑干小脑上脚纤维(SCP)交叉的微观结构和特性.方法 Siemens 3.0T MR对20例健康志愿者行头颅轴位DTI (b=0和b=1000)检查,应用工作站纤维束跟踪软件三维重建脑干SCP纤维交叉,选择参数:FA为0.08、角度阈值为80°、体素为1.2 mm×1.2 mm×3 mm.测量SCP和SCP交叉的各向异性分数(FA)值,比较两者之间的差异.结果 脑干SCP纤维交叉出现三种不同形态:(1)交叉,占65％(13例);(2)对吻,占25％(5例);(3)分叉,占10％(2例).SCP交叉和SCP的FA值分别为:0.40±0.13和0.65±0.08,两者之间差异有统计学意义( t=7.22,P＜0.05)结论 DTT三维重建技术能显示脑干SCP交叉纤维束的解剖类型,3.0T MR对于活体脑干交叉纤维束的研究有较好的临床应用价值.     

长期舞蹈训练对白质纤维微结构影响的TBSS比较研究

舞蹈涉及复杂的感觉运动信息处理,长期舞蹈训练可能让脑产生功能与结构的可塑性改变。目前关于舞蹈训练导致的白质结构研究相当有限,缺乏统一的结果,因此对舞蹈家与正常对照组的白质纤维微结构指标进行比较研究,以探索舞蹈家白质纤维微结构的特异性改变。采集18名舞蹈家及与之匹配的25名对照被试的磁共振扩散张量成像(DTI)数据,使用基于纤维束示踪的空间统计分析(TBSS)技术,对被试白质纤维的部分各向异性分数(FA)和平均弥散率(MD)图谱进行体素级别统计分析。采用t检验,对比两组被试数据的差异。结果表明,舞蹈家在涉及感觉运动信息处理的白质纤维微结构的一致性降低:在胼胝体压部、左侧内囊前肢(左侧丘脑辐射前部)、左侧内囊后肢(左侧皮质脊髓束)存在显著降低的FA值,在左侧内囊后肢(含部分左侧下纵束、左侧上纵束与左侧皮质脊髓束)、左侧外囊(含部分下额枕束与钩束)、左侧冠状束前部与胼胝体膝部存在显著升高的MD值。以上结果提示,舞蹈训练可能导致脑内特定白质纤维束的交错更多,连接不同脑区的轴突纤维更为发散,进而影响感觉运动信息的上下行传递与左右脑信息整合效率。同时,长期舞蹈训练可能对主导运动控制的左半脑的白质通路影响明显。     

三维脑白质纤维束示踪成像

目的使用磁共振弥散张量成像数据三维示踪大脑白质纤维束。方法对18名健康自愿者使用弥散加权-回波平面成像(DW-EPI)序列进行头部DTI检查。输出DICOM格式的DTI图像数据并根据已知的脑白质纤维束的解剖学知识,选取起始区、目标区、回避区,使用Diffusion Tensor VisualizerⅡ软件进行脑白质纤维束示踪三维重建。结果大脑的连合系、联络系和投射系的各种脑白质纤维束的结构和其在三维空间的走行可在每例实验对象的三维示踪结果显示,与解剖学所描述相对比基本一致。结论使用三维脑白质纤维束示踪成像可以在活体立体直观地显示大脑的各种脑白质纤维束。不仅可以用于解剖学教学,还对临床神经系统疾病的辅助诊断和科学研究有潜在的应用价值。     

磁共振弥散张量成像联合纤维束成像在脑梗死中的应用研究

目的 分析脑梗死患者磁共振弥散张量成像(DTI)和纤维束成像(DTT)的特点,探讨DTI、DTT在对不同时期脑梗死患者诊断的价值。方法分别对58例不同时期脑梗死患者和25名健康志愿者行MRI检查,包括T1WI、T2WI成像、FLAIR及DTI成像,重建部分各向异性(FA)图,对梗死区、健侧相应部位及正常对照组相应部位进...     

腰椎间盘MR扩散张量成像及其定量分析

目的　研究正常成人腰椎间盘MR扩散张量成像及其量化特征。 方法 采用Philips 1.5T超导MR成像系统,对20例健康志愿者的L1/2～L5/S1椎间盘进行扫描,得到常规T1W、T2W,DTI扫描采用单次激发SE-EPI序列,扫描后处理获得纤维环示踪图（DTT）、FA彩图、FA图、e ADC图、Trance D图,观察DTT图上纤维环形态,通过ADC值、Trace D值、FA值的测量,定量分析纤维环、髓核的扩散特征。 结果　应用MR扩散张量成像可获取椎间盘纤维示踪图（DTT）、FA彩图、FA图、e ADC图、Trance D图,正常纤维环呈连续、规则均匀的环形,不同板层纤维束呈交错排列。纤维环的FA值显著高于髓核FA值(P<0.05),髓核Trace值显著高于纤维环(P<0.05),在髓核和纤维环内,轴向扩散高于放射状扩散　(P<0.05),腰椎不同节段椎间盘内髓核、纤维环的扩散特征无显著性差别(P>0.05)。 结论　磁共振DTI能够显示纤维环内纤维束板层形态、排列;纤维环和髓核具有不同的扩散特征,纤维环的各向异性更显著,髓核更易于发生扩散;椎间盘内的主要扩散方向呈轴向。     

纤维跟踪技术在模拟显示人脑联络纤维中的应用

目的：应用弥散张量（DTI）纤维跟踪技术来模拟显示脑的联络纤维，探讨结果与经典解剖学知识的一致性。方法：对1个志愿者行单次激发回波平面弥散张量成像，利用纤维跟踪技术来模拟显示其联络纤维，并观察与经典解剖学知识的一致性。结果：通过选择恰当的感兴趣区，各向异性阈值、角度阈值、步长和体素内采样数目等参数，利用弥散张量纤维跟踪技术可模拟显示扣带、上枕额束、下枕额束、钩束、下纵束等联络纤维。结论：利用弥散张量纤维跟踪技术可模拟显示人脑联络纤维，且与经典解剖学有高度一致性，是在活体中研究人脑联络纤维的一种新方法。     

融合白质fMRI的dMRI纤维追踪重建研究

基于弥散磁共振成像(dMRI)的纤维束重建,是分析大脑白质结构的主要工具。现有的纤维追踪成像算法受dMRI分辨率及成像机理约束,在构建大脑白质灰质边界区域的纤维时成像性能和准确性大大下降。为克服该缺陷,提出一种结合功能磁共振成像(fMRI)的新型dMRI纤维追踪成像算法。该算法引入表征白质中fMRI信号各向异性的空间相关张量间接描述纤维束的几何结构信息,结合粒子滤波理论估算追踪下一体素的方向概率分布,重建可靠连接白质灰质边界区域的三维结构。将所提出算法在8位成年人视觉刺激的功能图像上进行追踪成像实验,每例重建800根纤维,重建纤维的平均长度可达(18.47±1.82)mm,沿白质灰质界面流线端点的覆盖率为25.15%±1.86%。通过在视放射区域与DWI重建结果对比可看出,所提出的方法可有效重建大脑白质纤维路径,特别对由于部分容积效应导致对灰白质交界面纤维束重建存在较大误差的区域,较现有方法可获得更准确效果。     

Amyotrophic lateral sclerosis: diffusion tensor tractography and voxel-based analysis

The purpose of this study is to investigate whether the diffusional anisotropy of water molecules is disrupted in the pyramidal and extra-pyramidal regions in patients with amyotrophic lateral sclerosis (ALS). We studied seven patients with probable ALS (four women, mean age +/- SD, 57.3 +/- 6.2 years old) according to the criteria of the World Federation of Neurology. A control group consisted of 11 age- and sex-matched volunteers (six women, 57.1 +/- 4.5) without disorders affecting the central nervous system. Voxel-based diffusion tensor analysis was made with statistical parametric mapping (SPM99). We also created the normalized corticospinal tractography from the diffusion tensor data. The significant fractional anisotropy (FA) decrease in the ALS group was found in the right frontal subgyral white matter and left frontal precentral white matter. These clusters with significant FA decrease corresponded well to the average group map of the corticospinal tract in a standard reference frame. These results suggested that the combination of voxel-based diffusion tensor analysis and diffusion tensor tractography might help determine the location of the affected neuronal tissues among ALS patients in a non-invasive manner.     

应用弥散张量成像技术检测慢性原发性闭角型青光眼患者脑白质结构

目的 采用磁共振弥散张量成像(DTI)检测慢性闭角型青光眼(PACG)患者脑白质病变,用各向异性指数(FA)改变分析病变部位。方法 回顾性分析2008-2009年在天津医科大学总医院眼科就诊并行颅脑MRI检查患者的临床资料,其中确诊为慢性PACG并同时行DTI扫描的患者25例为慢性PACG组,根据视野损害程度分为轻度组和重度组;选取同一时间段行颅脑DTI扫描的健康人25例为正常对照组。采用FSL和DTIstudio软件处理原始数据得到FA图,输入SPM5软件做标准化处理,然后进行灰白质分割,对分割后的白质FA图进行平滑处理,最后对慢性PACG组和正常对照组FA图进行两样本t检验比较,采用FWE方法校正统计结果,取P＜0.05有统计学意义,将结果叠加于标准模板,显示阈值设定为10个体素。采用同样方法分析慢性PACG轻度组和重度组FA图差异。结果剔除头动明显受试者图像后,慢性PACG组和正常对照组各有22例入组,慢性PACG组分为轻度组13例、重度组9例。与正常对照组比较,慢性PACG患者双侧视束脚周段FA值明显降低(P＜0.05,FWE校正),左侧包含98个体素,右侧包含56个体素。慢性PACG轻度组与重度组FA值差异无统计学意义(P＞0.05)。结论 DTI可检测慢性PACG患者脑白质结构病变。FA值可反应双侧视束脚周段病变。     

Semi-automated 3D segmentation of major tracts in the rat brain: comparing DTI with standard histological methods

Researchers working with rodent models of neurological disease often require an accurate map of the anatomical organization of the white matter of the rodent brain. With the increasing popularity of small animal MRI techniques, including diffusion tensor imaging (DTI), there is considerable interest in rapid segmentation methods of neurological structures for quantitative comparisons. DTI-derived tractography allows simple and rapid segmentation of major white matter tracts, but the anatomic accuracy of these computer-generated fibers is open to question and has not been rigorously evaluated in the rat brain. In this study, we examine the anatomic accuracy of tractography-based segmentation in the adult rat brain. We analysed 12 major white matter pathways using semi-automated tractography-based segmentation alongside manual segmentation of Gallyas silver-stained histology sections. We applied four fiber-tracking algorithms to the DTI data—two integration methods and two deflection methods. In many cases, tractography-based segmentation closely matched histology-based segmentation; however different tractography algorithms produced dramatically different results. Results suggest that certain white matter pathways are more amenable to tractography-based segmentation than others. We believe that these data will help researchers decide whether it is appropriate to use tractography-based segmentation of white matter structures for quantitative DTI-based analysis of neurologic disease models.     

Group‐averaged anatomical connectivity mapping for improved human white matter pathway visualisation

Anatomical connectivity mapping (ACM) is a measure of anatomical connectivity obtained by initiating streamline diffusion tractography from all parenchymal voxels and then counting the number of streamlines passing through each voxel of the brain. ACM highlights WM structures that present multiple connections to the rest of the brain but not necessarily strong microstructural orientation coherence. In this study, ACM was used to develop an atlas of the human brain. The ACM template was constructed from 3 T diffusion‐weighted data from 19 healthy adults. To account for multiple diffusion directions in a voxel, a high angular resolution diffusion imaging (HARDI) technique, namely Q‐ball, was used to model diffusion. To bring data from different subjects into a common space, an algorithm for rotating and averaging the principal directions was implemented, which can be generalized to any application requiring algebraic operations on principal directions derived from any HARDI method. ACM from the average dataset was computed and several white matter connections of interest were identified and highlighted. Fractional anisotropy (FA) from standard diffusion tensor modelling was also derived and FA‐modulated colour coded images obtained from the mean tensor were also shown for comparison, highlighting differences and similarities. The ACM template can serve for educational purposes and as future reference for studies based on the evaluation of ACM in subjects affected by neurological and psychiatric disorders. Copyright © 2012 John Wiley & Sons, Ltd.     

White Matter Integrity Following Traumatic Brain Injury: The Association with Severity of Injury and Cognitive Functioning

Traumatic brain injury (TBI) frequently results in impairments of memory, speed of information processing, and executive functions that may persist over many years. Diffuse axonal injury is one of the key pathologies following TBI, causing cognitive impairments due to the disruption of cortical white matter pathways. The current study examined the association between injury severity, cognition, and fractional anisotropy (FA) following TBI. Two diffusion tensor imaging techniques—region-of-interest tractography and tract-based spatial statistics—were used to assess the FA of white matter tracts. This study examined the comparability of these two approaches as they relate to injury severity and cognitive performance. Sixty-eight participants with mild-to-severe TBI, and 25 healthy controls, underwent diffusion tensor imaging analysis. A subsample of 36 individuals with TBI also completed cognitive assessment. Results showed reduction in FA values for those with moderate and severe TBI, compared to controls and individuals with mild TBI. Although FA tended to be lower for individuals with mild TBI no significant differences were found compared to controls. Information processing speed and executive abilities were most strongly associated with the FA of white matter tracts. The results highlight similarities and differences between region-of-interest tractography and tract-based spatial statistics approaches, and suggest that they may be used together to explore pathology following TBI.     

Mapping brain anatomical connectivity using white matter tractography

Integration of the neural processes in the human brain is realized through interconnections that exist between different neural centers. These interconnections take place through white matter pathways. White matter tractography is currently the only available technique for the reconstruction of the anatomical connectivity in the human brain noninvasively and in vivo. The trajectory and terminations of white matter pathways are estimated from local orientations of nerve bundles. These orientations are obtained using measurements of water diffusion in the brain. In this article, the techniques for estimating fiber directions from diffusion measurements in the human brain are reviewed. Methods of white matter tractography are described, together with the current limitations of the technique, including sensitivity to image noise and partial voluming. The applications of white matter tractography to the topographical characterization of the white matter connections and the segmentation of specific white matter pathways, and corresponding functional units of gray matter, are discussed. In this context, the potential impact of white matter tractography in mapping the functional systems and subsystems in the human brain, and their interrelations, is described. Finally, the applications of white matter tractography to the study of brain disorders, including fiber tract localization in brains affected by tumors and the identification of impaired connectivity routes in neurologic and neuropsychiatric diseases, are discussed.     

Influence of citalopram and environmental temperature on exercise-induced changes in BDNF

Differences and similarities in microstructural white matter alterations between bipolar I and bipolar II disorder were investigated. Twelve patients with bipolar I disorder, 12 patients with bipolar II disorder and 22 healthy controls underwent diffusion tensor imaging. Fractional anisotropy (FA) and mean apparent diffusion coefficient (ADC) maps were compared between groups using voxel-based whole brain analyses. Both bipolar I and II groups had a FA decrease in the corpus callosum, cingulate and right prefrontal regions, and a ADC increase in the medial frontal, anterior cingulate, insular and temporal regions, compared to controls. The bipolar I group had a FA decrease in the right temporal white matter and a ADC increase in the frontal, temporal, parietal and thalamic regions, compared to the bipolar II group. The results suggest disrupted integrity of commissural fibers and white matter in the anterior paralimbic structures in bipolar disorder. Relative sparing of the dorsal system and long association fibers may differentiate bipolar II from I disorder.