基于弥散张量白质网络的阿尔茨海默病研究

【摘 要】 目的:利用弥散张量成像（DTI）技术构建大脑白质结构网络,通过网络拓扑参数研究阿尔茨海默病（AD）患者大脑微观结构的异常。 方法:重建19例正常人和20例AD患者的结构脑网络,采用双样本t检验,从全脑和特定脑区两个水平对AD患者与正常对照组的网络拓扑参数进行差异性分析。 结果:在全脑水平上,AD患者的加权特征路径长度（[Lp]）值上升,全局效率（[Eg]）、网络强度（[Sp]）、局部效率（[Elocal]）值下降,并且进一步研究发现:AD患者左半球[Lp]、加权簇系数（[Cp]）值上升,[Eg]值下降比右半球明显。在特定脑区水平上,选取楔前叶为感兴趣脑区,发现两侧楔前叶脑区的[Lp]值上升、[Eg]值下降,而[Cp]、[Elocal]值并没有明显差异。 结论:网络拓扑参数可以作为评估AD患者微观结构异常的指标,对早期诊断AD具有重要的指向作用。     

首发重症抑郁症的弥散张量成像研究:基于纤维束示踪的空间统计学分析结果

目的:应用基于纤维束示踪的空间统计分析(Tract-Based Spatial Statistics,TBSS)方法,探讨重症抑郁症病患者全脑白质纤维的完整性是否受到损害。方法:对20(8男,12女)例重症抑郁症病患者组和20(8男,12女)例与抑郁症组按性别、年龄、教育程度匹配的正常人进行全脑弥散张量成像扫描。应用TBSS方法来比较两组的各向异性分数。结果:抑郁症组的左侧内囊前肢、右侧海马旁回、左侧后扣带回的各向异性分数显著低于正常组(P<0.05,t>3,校正),患者组内囊前肢的各向异性分数和抑郁症严重程度呈现负相关。结论:白质病变在抑郁症发病早期即已存在,这些病变区域主要涉及前额叶和边缘系统等与认知和情感调节关系较密切的神经环路的纤维束,这些改变可能导致皮层和皮层下连接受损,从而有利于深入了解抑郁症疾病的发病机理。     

弥散张量成像在缺陷型精神分裂症患者认知功能评估中的应用

目的:探讨弥散张量成像(diffusion tensor imaging,DTI)在缺陷型精神分裂症患者认知功能评估中的应用价值.方法:选取2019年6月至2021年6月淮安市第三人民医院缺陷型精神分裂症患者68例为研究组,另选取同期健康体检者39例为对照组.所有受检者均接受影像学检查,测定左侧大脑脚、右侧额叶、左侧内...     

弥散张量成像对常规性临床应用的初步建立和实现

根据目前国际上被广泛认可的磁共振弥散张量成像(DT-MRI或DTI)处理和表达方法,自行开发出基于PC机的程序(DTI Toolbox based on MATLAB),有效结合第三方软件,为弥散张量成像在常规性临床诊断初步建立有效和完整的测量与分析处理体系,主要包括数据获取、图像预处理、张量可视化、以及脑神经纤维成像。为DTI进入常规性临床应用和检查提供了初步的方案和测量分析体系。     

磁共振弥散张量成像对正常成年人胼胝体性别差异的初步研究

目的:描述正常成年人胼胝体的微结构特征,探讨磁共振弥散张量成像(diffusion tensorimaqinq,DTI)对其微结构评价的价值。方法:对61例健康成年人(20-30岁:男30例,女31例)行脑部常规MRI和DTI扫描,DTI使用自旋回波一平面回波成像(SE-EPI)序列。在基底节层面,选定胼胝体膝部和压部为兴趣区,测量部分各向导性值(fractional anisotropy,FA)并做相应统计学处理。结果:在胼胝体膝部,男性的FA值为0.724±0.04,女性的FA值为0.698±0.05,男女胼胝体膝部的各向异性值存在显著性差异(P<0.05);胼胝体压部,男性的FA值为0.716±0.05,女性的FA值为0.695±0.05,男女胼胝体压部的各向异性值存在显著性差异(P<0.05)。结论:(1)正常成年男女胼胝体膝、压部神经纤维排列存在差异;(2)DTI可以无创地对活体白质纤维束排列进行定量研究。     

弥散张量成像在中枢神经系统中的应用

在磁共振成像(MRI)研究中，弥散张量成像(DTI)是最近几年提出并迅速发展的一个研究方向，本介绍了弥散张量成像的原理以及国际上主要的研究热点，并结合实际介绍了弥散张量成像在中枢神经系统(CNS)中的应用。     

弥散张量磁共振成像的新进展

弥散张量磁共振成像技术是近年来出现的一项新技术，由于其对脑白质纤维具有高度敏感性以致在临床上的应用日益广泛，并为人体中枢神经系统的深人研究提供了有效的工具。     

弥散张量成像在中枢神经系统中的应用

在磁共振成像(MRI)研究中,弥散张量成像(DTI)是最近几年提出并迅速发展的一个研究方向,本文介绍了弥散张量成像的原理以及国际上主要的研究热点,并结合实际介绍了弥散张量成像在中枢神经系统(CNS)中的应用。     

重复经颅磁刺激对精神分裂症患者弥散张量成像及阴性症状的影响

目的:探讨高频重复经颅磁刺激(r TMS)联合利培酮对精神分裂症患者脑白质磁共振弥散张量成像(DTI)及阴性症状的影响。方法:以符合ICD-10诊断标准的71例阴性症状为主的精神分裂症患者为研究对象,按照随机数字表法分为研究组(n=36)和对照组(n=35)。研究组给予4周10Hz r TMS真刺激治疗,对照组给予4周10Hz r TMS伪刺激,治疗期间均联合应用利培酮片。治疗前后完成阳性和阴性症状量表(PANSS)评估和FA值检测。结果:1治疗前研究组和对照组额叶、颞叶、胼胝体、海马FA值差异无统计学意义。治疗后,研究组左右额叶、胼胝体压部、胼胝体膝部、胼胝体体部、左右海马FA值明显高于对照组,差异有统计学意义(t=2.007,2.239,2.158,2.732,2.627,2.113,2.108;P0.05或0.01);2治疗前,研究组和对照组PANSS总分及各因子分差异无统计学意义。治疗后,研究组阳性症状分、阴性症状分、一般精神病理分及PANSS总分的改善优于对照组,差异有统计学意义(t=2.251,2.756,2.151,2.061;P0.05或0.01);3患者左额叶、胼胝体压部、胼胝体膝部FA值变化与PANSS总分及各因子分变化呈正相关(r=0.367,0.386;0.373,0.346,0.338;0.357,0.337,0.357,0.333;P0.05)。结论:10Hz r TMS联合利培酮治疗有助于改善精神分裂症患者的脑白质FA值及阴性症状,阴性症状与患者左额叶、胼胝体压部、胼胝体膝部的脑区连接异常有关。     

弥散张量磁共振成像的新进展

弥散张量磁共振成像技术是近年来出现的一项新技术,由于其对脑白质纤维具有高度敏感性以致在临床上的应用日益广泛,并为人体中枢神经系统的深入研究提供了有效的工具。     

The association between physical fitness parameters and white matter microstructure in older adults: A diffusion tensor imaging study

The present study was designed to examine whether different measures of physical fitness are differentially associated with white matter (WM) microstructure in older adults. Fifty-six healthy adults (mean age: 59.14 years) completed a standardized evaluation of physical fitness measurements (e.g., VO_2peak, push-ups, abdominal sit-ups, sit-and-reach, t test, and vertical jump). Fractional anisotropy (FA), an index of WM microstructure, was assessed using diffusion tensor imaging. The findings indicated that the cardiorespiratory fitness was positively associated with FA in the right cingulum hippocampus and the left cerebral peduncle. However, other physical fitness metrics were not significantly associated with FA in any region. These results suggest that cardiorespiratory fitness, but not other metrics of fitness, might be sensitive to WM microstructure.     

Diffusion tensor imaging in fixed brain tissue at 7.0 T

The purpose of this work is to assess the feasibility of performing quantitative in vitro brain tissue diffusion tensor imaging (DTI) measurements and to examine their comparability to in vivo measurements. DTI of fixed tissue at high field strength is potentially a very valuable investigative tool as very high spatial resolution can be achieved. DTI was applied to human and mouse brain fixed tissue samples as well as in vivo measurements of the mouse brain. T(1) and T(2) relaxography of the fixed tissue samples was also performed to provide further characterization of the tissue. All experiments were performed at 7 T. The fractional anisotropy (FA) of the human fixed brain tissue samples is found to be higher in the corpus callosum than in the occipital white matter region, consistent with in vivo measurements reported in the literature. Our FA measurements of the corpus callosum of a mouse brain are also found to be the same both in vitro and in vivo. This preliminary work supports the use of DTI in both fixed human and fixed animal brain tissue as a valid investigative tool. With the increased availability of brain banks in different brain disorders, DTI in fixed tissue may prove to be a very useful method for the study of white matter abnormalities.     

Gray matter density and white matter integrity in pianists' brain: a combined structural and diffusion tensor MRI study

The current study combined structural magnetic resonance imaging (sMRI) and diffusion tensor MRI (DT-MRI) to investigate both gray matter density (GMD) and white matter integrity (WMI) in 18 pianists and 21 age-matched non-musicians. The pianists began their piano training at a mean age of 12. Voxel-based morphometry of the sMRI data showed that the pianists had higher GMD in the left primary sensorimotor cortex and right cerebellum. Voxel-based analysis of the DT-MRI data showed that pianists had higher fractional anisotropy (FA) (indicating higher WMI) in the right posterior limb of the internal capsule. The sMRI and DT-MRI results indicate that both the GMD and WMI of pianists may exhibit movement-related increases during adolescence or even early adulthood compared with non-musicians.     

联合应用VBM方法和DTI技术对精神分裂症小脑结构的研究

目的分别应用磁共振扩散张量成像技术(DTI)和基于体素的形态分析法(VBM)对精神分裂症患者小脑中脚和上脚白质纤维情况与小脑的灰白质密度进行初步探究。方法应用GESigna3.0TMRI扫描仪,分别对按照精神分裂症诊断标准确诊的14例患者及14名健康对照者行DTI和三维快速扰相梯度翻转恢复(3D-SPGR)序列扫描,检测双侧小脑中脚和上脚感兴趣区的各向异性分数值(FA)及小脑灰白质密度,应用成组t检验对病例组和正常对照组的以上数据进行比较。结果精神分裂症病例组左侧小脑上脚的FA值较正常对照组显著降低(<0.05),小脑局部脑区的灰质密度与正常组相比发生了显著改变,差异区域主要位于小脑前叶(<0.05),小脑的白质密度与正常组相比未发现显著改变脑区。结论 DTI技术和VBM方法的联合应用对精神分裂症患者的研究有着重要的应用价值。     

Fiber type characterization in skeletal muscle by diffusion tensor imaging

Fiber type distribution within a skeletal muscle, i.e. the quantification of the relative amount of type 1 (slow‐twitching) and type 2 (fast‐twitching) muscle fibers, is of great interest for the monitoring of the effects of training or the treatment of muscle diseases. The purpose of this study was to determine the feasibility of diffusion tensor imaging (DTI) as a tool for noninvasive fiber type quantification in human skeletal muscle. The right calves of 12 healthy volunteers were examined using DTI at 1.5 T. Standard DTI parameters, including fractional anisotropy (FA), and mean, radial and parallel diffusivity (MD, RD and PD, respectively), were determined in the soleus muscle. Fiber type proportion and mean fiber diameter within the soleus muscle were quantified from tissue specimens obtained via a fine needle biopsy. Linear regression analysis tested for associations between DTI and biopsy results. FA values were correlated significantly with fiber type proportion, such that higher FA values indicated a higher proportion of type 1 fibers (R² = 0.5, p = 0.01). This was based on lower diffusivity perpendicular to the main axis of the fiber in subjects with a higher type 1 fiber proportion (RD: R² = 0.52, p = 0.008). MD was also correlated with the proportion of type 1 fibers (R² = 0.37, p = 0.037), whereas PD showed no significant correlation. DTI is a promising method for the noninvasive estimation of fiber type proportion in skeletal muscle. This technique may be used to monitor training effects or may be further developed as a biomarker in certain muscle diseases. Copyright © 2013 John Wiley & Sons, Ltd.     

Considerations for measuring the fractional anisotropy of metabolites with diffusion tensor spectroscopy

Diffusion tensor spectroscopy of metabolites in brain is challenging because of their lower diffusivity (i.e. less signal attenuation for a given b value) and much poorer signal‐to‐noise ratio relative to water. Although diffusion tensor acquisition protocols have been studied in detail for water, they have not been evaluated systematically for the measurement of the fractional anisotropy of metabolites such as N‐acetylaspartate, creatine and choline in the white and gray matter of human brain. Diffusion tensor spectroscopy was performed in vivo with variable maximal b values (1815 or 5018 s/mm²). Experiments were also performed on simulated spectra and isotropic alcohol phantoms of various diffusivities, ranging from approximately 0.54 × 10^?3 to 0.13 × 10^?3 mm²/s, to assess the sensitivity of diffusion tensor spectroscopic parameters to low diffusivity, noise and b value. The low maximum b value of 1815 s/mm² yielded elevated fractional anisotropy (0.53–0.60) of N‐acetylaspartate in cortical gray matter relative to the more isotropic value (0.25–0.30) obtained with a higher b value of 5018 s/mm²; in contrast, the fractional anisotropy of white matter was consistently anisotropic with the different maximal b values (i.e. 0.43–0.54 for b = 1815 s/mm² and 0.47–0.51 for b = 5018 s/mm²). Simulations, phantoms and in vivo data indicate that greater signal attenuation, to a degree, is desirable for the accurate quantification of diffusion‐weighted spectra for slowly diffusing metabolites. Copyright © 2010 John Wiley & Sons, Ltd.     

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。     

Diffusion tensor imaging in studying white matter complexity: A gap junction hypothesis

The role of the prefrontal cortex as an executive oversight of posterior brain regions raises the question of the extent to which the anterior regions of the brain interconnect with the posterior regions. The aim of this study is to test the complexity of rostral white matter tracts, which connect anterior and posterior brain regions, in comparison to caudal white matter tracts and the corpus callosum. Diffusion tensor imaging (DTI) is a modality that measures fractional anisotropy (FA). Higher white matter complexity could result in a decrease of FA, possibly through denser intersection of fiber tracts. DTI was used to determine regional FA in 9 healthy bonnet macaques (Macaca radiata). Four regions of interest were included: anterior and posterior limbs of the internal capsule, the occipital lobe white matter, and the corpus callosum. FA of the anterior limbs of the internal capsule was lowest compared to all other regions of interest (Newman–Keuls (N–K); p < 0.0001), whereas FA of the corpus callosum was highest (N–K; p < 0.0001). The posterior limbs of the internal capsule and the occipital white matter were not distinguishable but exhibited intermediate FA in comparison to the former (N–K; p < 0.0001) and the latter (N–K; p < 0.0001). The current study demonstrates that FA, a measure of white matter complexity, can vary markedly as a function of region of interest. Moreover, validation of these findings using neurohistological studies and replication in human samples appears warranted.     

首发精神分裂症患者的运动协调功能与前额叶白质及皮质脊髓束完整性

目的:应用弥散张量成像(DTI)探讨首发精神分裂症患者神经系统软体征中的运动协调功能与前额叶白质及皮质脊髓束各向异性比值(FA)的关系。方法:纳入42例符合美国精神障碍诊断与统计手册第4版(DSM-IV)诊断标准的首发精神分裂症患者和46例年龄、性别及受教育年限相匹配的健康对照。两组研究对象均用剑桥神经科检查(CNI)评定神经系统软体征,并接受头颅磁共振成像检查。用阳性与阴性症状量表(PANSS)评估患者组基线和半年后的临床症状。用感兴趣区测定的方法,分析患者组和对照组神经系统软体征中的运动协调领域分与前额叶白质及皮质脊髓束各层面(内囊、大脑脚、小脑中脚水平)FA值间的关系。结果:神经系统软体征中的运动协调领域分在患者组中与前额叶白质FA值呈正相关(r=0.35,P0.05),在健康对照中则与小脑中脚水平皮质脊髓束FA值呈正相关(r=0.34,P0.05)。将患者按半年后阴性症状分为高分组和低分组,高分组运动协调领域分与前额叶白质(r=0.68,P0.05)呈正相关,与小脑中脚水平皮质脊髓束(r=-0.67,P0.05)FA值呈负相关;低分组则与内囊FA值呈正相关(r=0.60,P0.05)。结论:本研究提示首发精神分裂症患者半年后阴性症状高分组、低分组及正常人群中,运动协调功能相关的脑区分别为前额叶、内囊和小脑中脚层面的皮质脊髓束,提示有必要进一步研究运动协调功能相关的脑区不同对患者预后的预测意义。