一种改进的脑白质纤维束连续跟踪算法

目的:改进脑白质纤维束连续跟踪算法,提高纤维束跟踪的连续性和准确性。方法:使用山东第一医科大学第二附属医院影像科和国际人脑连接组共享数据库网站提供的弥散张量图像对算法进行验证。首先,对磁共振弥散张量图像进行中值滤波和高斯平滑滤波,去除噪声对纤维束连续跟踪算法的影响,利用脑模板消除颅骨对后续跟踪的影响。然后,利用最小二乘法获得每一个体素的弥散张量和各向异性指数。最后,从各向异性指数大于阈值的起始体素开始,利用跟踪编辑技术和基于弥散熵的线性跟踪方法完成纤维束连续跟踪。结果:同传统的纤维束连续跟踪算法相比,本研究提出的算法能得到更连续、更准确的跟踪结果,算法具有较好的抗噪声能力和较强的鲁棒性。结论:改进的纤维束跟踪方法可以应用于脑结构网构建以及脑疾病的研究。     

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。     

应用DTI技术对人脑白质纤维束的初步研究

目的建立扩散张量纤维束成像对人脑白质纤维的显示方法,并应用中国数字化可视人体数据进行对照观察,验证扩散张量成像(DTI)方法的可靠性。方法选择5名健康志愿者进行DTI成像,采用DtiStudio软件进行分析处理,重建出部分各向异性(FA)图、容积比(VR)图、相对各向异性(RA)图、表面扩散系数(ADC)图以及二维彩色张量图。应用中国数字化可视人体数据集断面图像、FA图及彩色FA图进行对照观察,利用fibertracking纤维跟踪软件及3DMRI软件进行三维重建显示脑内主要白质纤维束,辨认脑内白质纤维束的位置、形态。结果应用DTI纤维束成像可以清晰准确地描绘脑白质内主要神经纤维束的解剖图谱,包括联络纤维如弓形纤维、钩束、扣带束、上纵束和下纵束,连合纤维如胼胝体、前连合和穹隆,投射纤维如锥体束、视放射、内侧丘系等。DTI纤维束成像结果与已知解剖知识、中国可视化人体断面图像具有很好的一致性。结论应用DTI纤维束成像可以清晰准确地描绘脑白质内主要神经纤维束的解剖图谱,其结果与中国可视化人体断面图像、已知解剖知识是一致的,应用DTI纤维束成像研究脑内纤维连通性是可靠的。     

正常成人近段坐骨神经的弥散张量成像**

背景：弥散张量成像及神经纤维束示踪的出现为外周神经细微结构的显示及定量分析提供了新的方法。 目的：前瞻性分析健康成人大腿近段坐骨神经纤维束示踪、弥散张量成像的可行性及最佳成像参数。 方法：采用单次激发自旋回波-平面回波技术对28名健康志愿者双侧坐骨神经进行弥散张量成像及神经纤维束示踪,b值分别为1 200,1 400,1 600 s/mm2。 结果与结论：弥散张量成像及神经纤维束示踪成功者26名,成功率93%,神经纤维束示踪图上能清晰显示近段坐骨神经,与T1WI上解剖图像融合较好。两侧坐骨神经具有相同的弥散特征：随着b 值增加,信噪比逐渐减少,b值为1 200 s/mm2,信噪比值最大为142.72±32.25,神经纤维束长度最长,所占体素最大,但不同b值的弥散张量参数无差异(P > 0.05),且两侧坐骨神经弥散张量参数无差异。说明正常成人大腿近段坐骨神经的弥散张量成像及经纤维束示踪是可行的,可清晰显示坐骨神经走行及弥散特征;最佳b值为1 200 s/mm2。 关键词：弥散张量成像;坐骨神经;磁共振成像;神经纤维束示踪术;成年人 doi:10.3969/j.issn.1673-8225.2012.09.030     

应用白质束成像显示缺氧缺血性脑病患儿的视放射

目的：利用白质束成像显示HIE患儿的视放射，并与正常幼儿进行比较。方法：对8例HIE患JL和8例正常幼儿进行了弥散张量成像扫描，应用白质束成像技术对他们的双侧视放射进行追踪显示其形态，并对HIE患儿和正常幼儿的视放射进行比较。结果：自质束成像显示正常幼儿的双侧视放射能够到达皮层下，并可见分支，而HIE患儿的双侧视放射明显短，分支难以显示：结论：白质束成像在显示脑白质中纤维束的走行和形态，能反映儿童发育中纤维束的异常。     

弥散张量成像纤维束跟踪中噪声去除方法研究

对弥散张量成像(DTI)中影响纤维束跟踪效果的几种噪声去除方法进行研究。仿真结果表明:高斯平滑滤波、中值滤波和形态学最大最小值滤波对DTI中的噪声都有一定的抑制作用。高斯平滑滤波能够去除高频白噪声,引起图像边缘模糊,影响纤维束跟踪的连续性;中值滤波在去除随机噪声的同时,较好地保存了图像细节,能提高纤维束跟踪效果;最大最小值滤波能抑制较大噪声的影响,提高纤维束跟踪的连续性。此外,提出一种联合运用最大最小值滤波和中值滤波的混合滤波去噪法,该方法能更好地抑制噪声对DTI纤维束跟踪的影响,获得了令人满意的跟踪效果。     

成人岛叶纤维连接的显示和分析

目的:显示和分析岛叶与端脑额叶、顶叶、颞叶、枕叶及边缘系统和丘脑等的连接情况.方法:联合应用DSI-studio和Brian Suite软件对20例脑连接组项目的T1加权数据和磁共振弥散进行处理,通过纤维束重建、脑结构配准、纤维束连接分析等过程,分析岛叶与脑其他结构连接情况.结果:Brian Suite软件生成的脑连接分析图中可见左右两侧岛叶与额叶、顶叶、颞叶、边缘系统、丘脑、基底核均有联系.通过三维纤维束重建,可见连接岛叶与其他脑区的纤维束有钩束、下额枕束、外囊、上额枕束、弓状束等.结论:通过成人脑岛叶与其他脑区纤维联系的研究,可为后续岛叶相关功能和临床研究提供结构和方法学上的帮助.     

基于扩散形状的DTI纤维跟踪算法研究

到目前为止，研究者们已经提出了许多种神经纤维束的三维可视化技术，其中，基于扩散跟踪的白质束成像技术在白质纤维束的可视化和分析中使用得最多。本文针对现有纤维跟踪算法存在的问题，提出了基于扩散形状的纤维跟踪算法，该算法结合了流线跟踪（streamline tracking，STT）法与张量弯曲（tensor deflection，TEND）法的优点，对不同的扩散形状采用不同的跟踪方向，尤其在平面扩散的情况提出了更接近纤维走行的跟踪方法，减少了跟踪方向与实际纤维走行的误差，能更完整、更准确地显示大脑白质的纤维走行。     

弥散张量成像预测3D打印支架促进脊髓损伤后运动功能恢复

文题释义：分数各向异性：通常用于提供关于推断组织特征和组织生理状态的定量信息,反映扩散的各向异性。分数各向异性值来自弥散张量成像数据,并且与运动结果大致相符,可用于评估脊髓损伤严重程度。分数各向异性值是脊髓损伤后敏感的特异性生物标志物,可量化脊髓损伤严重程度。实际上分数各向异性值反映白质的完整性,包括轴突结构损伤和脱髓鞘。分数各向异性值减少反映的是神经变性和轴突损失。损伤恢复越好分数各向异性值则越高。相比之下弥散张量成像比常规MRI检测脊髓损伤的恢复程度更敏感。分数各向异性值与损伤处的神经再生程度相关。弥散张量纤维束成像：作为一个定性指标可直观地追踪脊髓损伤处的神经纤维束,清晰地观察轴突束的损伤。结合定量弥散张量成像扫描,弥散张量纤维束成像可有效显示脊髓损伤处神经纤维的变化,有效显示移植部位神经纤维束的变化。弥散张量纤维束成像结果能追踪到脊髓损伤大鼠损伤处的局部纤维,弥散张量纤维束成像图像可直观地表明脊髓损伤,展示脊髓损伤部位的脊髓连接。 背景：弥散张量成像作为一种基于MRI相对较新的方法,目前已成为神经影像学领域检查诊断的重要手段。目的：使用弥散张量成像数据预测3D打印胶原/丝素蛋白支架在脊髓损伤后运动功能恢复中的作用,并探讨运动功能与弥散张量成像之间的相关性。方法：制备普通胶原/丝素蛋白支架和3D打印胶原/丝素蛋白支架。取成年雌性SD大鼠40只(由中国人民解放军军事医学科学院实验动物中心提供),随机分为4组,每组10只：假手术组仅切除T₁₀椎板;模型组制作T₁₀脊髓全横断损伤模型;普通支架组、3D打印支架组建立T₁₀脊髓全横断损伤模型后分别植入普通胶原/丝素蛋白支架和3D打印胶原/丝素蛋白支架。术后1,2,3,4,6,8周进行后肢BBB评分与斜板实验,术后8周进行后肢电生理检测,评估运动功能;术后8周进行腰椎弥散张量成像检查,并分析弥散张量成像参数与大鼠运动功能的相关性。动物实验获得中国人民武装警察部队特色医学中心研究动物伦理委员会的批准(伦理号：27653/58)。结果与结论：①自术后3周起,3D打印支架组的BBB评分高于模型组、普通支架组(P < 0.05或P < 0.01);自术后2周起,3D打印支架组的斜板实验角度高于模型组、普通支架组(P < 0.05或P < 0.01);②3D打印支架组的运动诱发电位振幅大于模型组、普通支架组(P < 0.05或P < 0.01),运动诱发电位潜伏期短于模型组、普通支架组(P < 0.05或P < 0.01);③弥散张量成像显示,造模3组的神经纤维轨迹不规则,均缺乏神经纤维的连续性,但3D打印支架组的断端再生神经纤维束数量多于模型组、普通支架组(P < 0.01);3D打印支架组距离脊髓损伤正中心9,7.5,4.5,-3,-6,-7.5,-9 mm处的分数各向异性值均高于模型组、普通支架组 (P < 0.05或P < 0.01);④术后8周,BBB评分、斜坡角度、运动诱发电位振幅、运动诱发电位潜伏期与从大鼠头到尾的弥散张量成像分数各向异性值之间存在正相关;⑤结果表明,弥散张量成像可被用作有效预测指标来评估实验和临床病例中脊髓损伤的神经系统修复。 ORCID: 0000-0001-9409-4201(刘晓银) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

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。     

Evidence of a middle longitudinal fasciculus in the human brain from fiber dissection

A rostrocaudal pathway connecting the temporal and parietal lobes was described in monkeys using autoradiography and was named the middle longitudinal fasciculus (MdLF). Recently, the use of diffusion tensor tractography has allowed it to be depicted in human volunteers. In the present study, a technique of fiber dissection was used in 18 cadaveric human brains to investigate the presence of this fasciculus and to detail its anatomical relationships. On the basis of our findings, fiber dissection provides evidence for a long horizontal bundle medial to the arcuate fasciculus and extending to the superior temporal gyrus. Its fibers occupy the lateral-most layer of the upper portion of the stratum sagittale and partially cover the inferior fronto-occipital fasciculus, which is situated deeper and slightly inferiorly. Whereas MdLF fibers continue on a relatively superficial level to reach the superior temporal gyrus, the inferior fronto-occipital fasciculus penetrates the deep temporal white matter and crosses the insular lobe. Although diffusion tensor imaging suggests that the MdLF terminates in the angular gyrus, this was not confirmed by the present study. These long association fibers continue onward posteriorly into upper portions of the occipital lobe. Further studies are needed to understand the role of the MdLF in brain function.     

Subcortical anatomy of the lateral association fascicles of the brain: A review

Precise knowledge of the connectivities of the different white matter bundles is of great value for neuroscience research. Our knowledge of subcortical anatomy has improved exponentially during recent decades owing to the development of magnetic resonance diffusion tensor imaging tractography (DTI). Although DTI tractography has led to important progress in understanding white matter anatomy, the precise trajectory and cortical connections of the subcortical bundles remain poorly determined. The recent literature was extensively reviewed in order to analyze the trajectories and cortical terminations of the lateral association fibers of the brain.The anatomy of the following tracts is reviewed: superior longitudinal fasciculus, middle longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto‐occipital fasciculus, uncinate fasciculus, frontal aslant tract, and vertical occipital fasciculus. The functional role of a tract can be inferred from its topography within the brain. Knowing the functional roles of the cortical areas connected by a certain bundle, it is possible to develop new insights into the putative functional properties of such connections. Clin. Anat. 563–569, 2014. © 2014 Wiley Periodicals, Inc.     

Quantification of the spatiotemporal microstructural organization of the human brain association, projection and commissural pathways across the lifespan using diffusion tensor tractography

Using diffusion tensor tractography, we quantified the microstructural changes in the association, projection, and commissural compact white matter pathways of the human brain over the lifespan in a cohort of healthy right-handed children and adults aged 6–68 years. In both males and females, the diffusion tensor radial diffusivity of the bilateral arcuate fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, corticospinal, somatosensory tracts, and the corpus callosum followed a U-curve with advancing age; fractional anisotropy in the same pathways followed an inverted U-curve. Our study provides useful baseline data for the interpretation of data collected from patients.     

Ventral and dorsal visual streams in posterior cortical atrophy: A DT MRI study

Using diffusion tensor magnetic resonance imaging tractography, ventral (inferior longitudinal fasciculus) and fronto-occipital (inferior fronto-occipital fasciculus) and dorsal (fronto-parietal superior longitudinal fasciculus) visual pathways were assessed in 7 patients with posterior cortical atrophy (PCA), showing either predominantly ventral or additional dorsal cognitive deficits. Corpus callosum and corticospinal tracts were also studied. Gray and white matter atrophy was assessed using voxel-based morphometry. In all PCA patients, abnormal diffusivity indexes were found in bilateral inferior longitudinal fasciculus and inferior fronto-occipital fasciculus, with a left-side predominance. Patients also had mild microstructural damage to the corpus callosum. The 2 patients with more dorsal symptoms also showed right fronto-parietal superior longitudinal fasciculus abnormalities. Corticospinal tracts were normal, bilaterally. When studied separately, patients with ventral clinical impairment showed a pattern of atrophy mainly located in the ventral occipitotemporal regions, bilaterally; patients with both ventral and dorsal clinical deficits showed additional atrophy of the bilateral inferior parietal lobe. Magnetic resonance imaging patterns of abnormalities mirror closely the clinical phenotypes and could provide reliable ante mortem markers of tissue damage in PCA.     

Cortex‐sparing fiber dissection: an improved method for the study of white matter anatomy in the human brain

Classical fiber dissection of post mortem human brains enables us to isolate a fiber tract by removing the cortex and overlying white matter. In the current work, a modification of the dissection methodology is presented that preserves the cortex and the relationships within the brain during all stages of dissection, i.e. ‘cortex‐sparing fiber dissection’. Thirty post mortem human hemispheres (15 right side and 15 left side) were dissected using cortex‐sparing fiber dissection. Magnetic resonance imaging study of a healthy brain was analyzed using diffusion tensor imaging (DTI)‐based tractography software. DTI fiber tract reconstructions were compared with cortex‐sparing fiber dissection results. The fibers of the superior longitudinal fasciculus (SLF), inferior fronto‐occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF) and uncinate fasciculus (UF) were isolated so as to enable identification of their cortical terminations. Two segments of the SLF were identified: first, an indirect and superficial component composed of a horizontal and vertical segment; and second, a direct and deep component or arcuate fasciculus. The IFOF runs within the insula, temporal stem and sagittal stratum, and connects the frontal operculum with the occipital, parietal and temporo‐basal cortex. The UF crosses the limen insulae and connects the orbito‐frontal gyri with the anterior temporal lobe. Finally, a portion of the ILF was isolated connecting the fusiform gyrus with the occipital gyri. These results indicate that cortex‐sparing fiber dissection facilitates study of the 3D anatomy of human brain tracts, enabling the tracing of fibers to their terminations in the cortex. Consequently, it is an important tool for neurosurgical training and neuroanatomical research.     

Neural tracts injuries in patients with hypoxic ischemic brain injury: Diffusion tensor imaging study

Many studies have reported on vulnerable areas of the brain in hypoxic ischemic brain injury (HI-BI). However, little is known about the involvement of neural tracts following HI-BI. We investigated neural tract injuries in adult patients with HI-BI, using diffusion tensor tractography (DTT). Twelve consecutive patients with HI-BI and 12 control subjects were recruited for this study. We classified the patients into two subgroups according to the preservation of alertness: subgroup A-5 patients who had intact alertness and subgroup B-7 patients who had impaired alertness. DTI-Studio software was used for evaluation of seven neural tracts: corticospinal, cingulum, fornix, superior longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, and optic radiation. We measured the DTT parameters (fractional anisotropy, apparent diffusion coefficient and voxel number) of each neural tract. In the individual analysis, all 12 patients showed injuries in all 24 neural tracts in terms of both DTT parameters and integrity, except for the corticospinal tract (75.0% injury). In the group analysis, the patient group showed neural injuries in all 24 neural tracts. In comparison of subgroups A and B, subgroup B showed more severe injuries: subgroup B showed a higher rate of disruption (39.8%) than subgroup A (12.9%) on individual DTTs and subgroup B had more severe injuries in both the cingulum and superior longitudinal fasciculus. In conclusion, we found that extensive injuries in the neural tracts were accompanied by HI-BI. Patients with impaired alertness appeared to show more severe injuries of neural tracts.     

Tracing superior longitudinal fasciculus connectivity in the human brain using high resolution diffusion tensor tractography

The major language pathways such as superior longitudinal fasciculus (SLF) pathways have been outlined by experimental and diffusion tensor imaging (DTI) studies. The SLF I and some of the superior parietal lobule connections of the SLF pathways have not been depicted by prior DTI studies due to the lack of imaging sensitivity and adequate spatial resolution. In the current study, the trajectory of the SLF fibers has been delineated on five healthy human subjects using diffusion tensor tractography on a 3.0-T scanner at high spatial resolution. We also demonstrate for the first time the trajectory and connectivity of the SLF fibers in relation to other language pathways as well as the superior parietal lobule connections of the language circuit using high spatial resolution DTI in the healthy adult human brain.     

Analysis of the subcomponents and cortical terminations of the perisylvian superior longitudinal fasciculus: a fiber dissection and DTI tractography study

The anatomy of the perisylvian component of the superior longitudinal fasciculus (SLF) has recently been reviewed by numerous diffusion tensor imaging tractography (DTI) studies. However, little is known about the exact cortical terminations of this tract. The aim of the present work is to isolate the different subcomponents of this tract with fiber dissection and DTI tractography, and to identify the exact cortical connections. Twelve postmortem human hemispheres (6 right and 6 left) were dissected using the cortex-sparing fiber dissection. In addition, three healthy brains were analyzed using DTI-based tractography software. The different components of the perisylvian SLF were isolated and the fibers were followed until the cortical terminations. Three segments of the perisylvian SLF were identified: (1) anterior segment, connecting the supramarginal gyrus and superior temporal gyrus with the precentral gyrus, (2) posterior segment, connecting the posterior portion of the middle temporal gyrus with the angular gyrus, and (3) long segment of the arcuate fasciculus that connects the middle and inferior temporal gyri with the precentral gyrus and posterior portion of the inferior and middle frontal gyri. In the present study, three different components of the perisylvian SLF were identified. For the first time, our dissections revealed that each component was connected to a specific cortical area within the frontal, parietal and temporal lobes. By accurately depicting not only the trajectory but also cortical connections of this bundle, it is possible to develop new insights into the putative functional role of this tract.     

Clinical correlations of microstructural changes in progressive supranuclear palsy

In patients with progressive supranuclear palsy (PSP), previous reports have shown a severe white matter (WM) damage involving supra and infratentorial regions including cerebellum. In the present study, we investigated potential correlations between WM integrity loss and clinical-cognitive features of patients with PSP. By using magnetic resonance imaging and diffusion tensor imaging with tract based spatial statistic analysis, we analyzed WM volume in 18 patients with PSP and 18 healthy controls (HCs). All patients and HCs underwent a detailed clinical and neuropsychological evaluation. Relative to HCs, patients with PSP showed WM changes encompassing supra and infratentorial areas such as corpus callosum, fornix, midbrain, inferior fronto-occipital fasciculus, anterior thalamic radiation, superior cerebellar peduncle, superior longitudinal fasciculus, uncinate fasciculus, cingulate gyrus, and cortico-spinal tract bilaterally. Among different correlations between motor-cognitive features and WM structural abnormalities, we detected a significant association between fronto-cerebellar WM loss and executive cognitive impairment in patients with PSP. Our findings, therefore, corroborate the hypothesis that cognitive impairment in PSP may result from both “intrinsic” and “extrinsic” frontal lobe dysfunction, likely related to cerebellar disconnection.