结合fMRI与DTI在脑胶质瘤诊治中的初步应用

目的：探讨DTI在脑胶质瘤定性、定级诊断中的作用,并尝试联合应用fMRI与DTI技术进行脑肿瘤术前定位及术中导航。方法：对18例脑胶质瘤患者进行常规T1WI、T2WI扫描及DTI、fMRI功能成像,测量肿瘤的实质部分、坏死或囊变区以及瘤周水肿区域的ADC值、FA值等参数。采用SPM软件对fMRI图像数据进行处理和统计分析,观察运动功能激活区、重要白质纤维束与颅内肿瘤病灶之间的相互关系。结果：高级别胶质瘤实体部分ADC值明显低于低级别胶质瘤,而FA值明显高于低级别胶质瘤,两者之间有显著性差异。高、低级别胶质瘤实质部分ADC值的分界点为1.21×10-3mm2/s,FA值分界点为0.17。联合应用fMRI与DTI可全面观察脑运动或视觉等重要功能激活区、重要白质纤维束与颅内肿瘤病灶之间的相互关系。结论：应用DTI可以在术前对胶质瘤进行分级,将fMRI与DTI功能影像应用于脑肿瘤导航手术可为术前计划提供必要信息,在术中避免损伤脑功能区及锥体束等重要结构,为手术提供双重保障。     

弥散张量成像在胎儿脑发育中的研究进展

胎脑从妊娠第3周末一个简单的神经管结构发育成出生后功能结构复杂的脑组织,期间经历了脑原始诱导发育、神经细胞增殖、神经元移行、两侧大脑半球皮质层状结构形成、脑室、沟、裂、脑回发育,以及白质纤维出现到成熟的髓鞘化过程。这些发育过程极其精确复杂,但是遵从严格的顺序。产前超声仅能筛查早期胎脑较明显的先天异常,无法评估这些细微的脑结构发育情况。近年来发展的磁共振成像技术为胎脑发育的研究提供了有用工具,尤其是弥散张量成像技术通过检测脑组织的水分子弥散运动,提供了从微观结构层面观察胎脑信息的视角,同胎脑组织学研究形成互补。本文将简要介绍弥散张量成像(diffusion tensor imaging,DTI)技术应用于胎脑方面的优势及其主要应用手段,DTI对皮质层状结构的显示,以及显示白质纤维束出现的时间、顺序、胎脑纤维束连接的变化、白质髓鞘化前成熟过程等,还总结了目前DTI技术用于胎儿脑成像的主要技术难题与解决办法,为进一步应用弥散张量成像研究正常胎儿脑发育奠定理论基础。     

DTI及Tractography对原发性进行性失语症的语言功能区分析

目的利用DTI及纤维追踪技术对语言功能区神经纤维分析,试图揭示原发性进行性失语主要白质结构的改变.方法男,56岁,语言能力进行性下降3年.SIEMENS Trio 2003T完成全脑MRI和DTI数据收集和后处理.结果常规MRI额叶、颞叶轻度萎缩.DTI左Broca区与其他脑区间纤维联系减少,三角区与Wernicke区无纤维联络.左侧Wernicke通过弓状纤维到达额叶岛盖部的纤维减少.Broca及Wernicke区平均FA及纤维束较正常人减少.结论原发性进行性失语患者的语言功能区的纤维减少,脑内语言功能区纤维结构及其与其他脑区间纤维联系是语言功能完成的结构基础,尤其是前后语言功能区之间的弓状纤维束.     

伴认知功能障碍的颞叶癫痫MRI研究进展

颞叶癫痫（TLE）是癫痫最常见的类型,其反复发作可致患者记忆力、语言及执行力等认知功能损害,使患者生存质量进一步下降。但颞叶癫痫导致认知功能障碍的机制尚不清楚,无法进行相关治疗。随着MR和图像后处理技术的发展,采用DTI、基于体素的形态学分析（VBM）和fMRI技术研究颞叶癫痫伴认知障碍患者脑结构和脑网络变化,发现认知障碍与部分脑区的结构和功能改变具有相关性。本文对伴认知障碍的TLE患者脑结构和功能改变的研究进展进行综述。     

磁共振弥散张量成像在偏瘫型脑瘫儿童的应用

磁共振弥散张量成像(diffusion tensor imaging,DTI)是近年发展起来的一种弥散成像技术,是在弥散加权成像(diffusion weighted imaging,DWI)基础上发展起来新的功能成像技术,可在三维空间内定量分析组织内水分子的弥散运动,利用组织内水分子弥散呈各向异性的特征进行成像。DTI是目前惟一无创性活体研究脑白质纤维束形态结构的方法,可以清晰勾画出脑内     

DTI纤维追踪法定量分析90名正常国人脑白质老化

目的 采用DTI纤维追踪法定量比较不同年龄组正常自愿者椎体束从大脑脚到中央前回部分(PRPT)FA值的差别及其意义.方法 将90名正常志愿者按年龄分为6组,进行基于纤维追踪的定量DTI研究,图像标准化后分析各组PRPT的FA值与年龄组老化的关系.结果 各年龄组双侧PRPT的FA值分布相似,最低点在放射冠处,最高峰为内囊后肢;各段FA值随年龄增长呈下降趋势,表明这些部位的纤维随年龄增长发生了老化,其中以额叶老化最为明显;并发现额叶及大脑脚白质老化过程中存在突然变化.结论 DTI可以作为评价脑组织细微结构变化和老化过程的敏感工具;额叶及大脑脚白质老化过程中存在突变是否为脑生理上老化的标志有待进一步研究.     

弥散张量成像在脑卒中康复中应用的研究进展

弥散张量成像(DTI)是一种非侵袭性MRI技术,能够识别脑微观结构改变,特别是神经纤维束的变化。DTI在脑卒中预后评估、动物实验和康复疗效评估等方面均有应用。     

弥散张量成像在缺血性脑卒中的应用研究进展

近几年随着各种脑成像技术的发展,核磁共振弥散张量成像（diffusion tensor imaging,DTI）对脑缺血的诊断和判断预后逐渐成为研究热点之一。DTI能够显示脑白质纤维束的走形及其完整性,因此主要用于脑部尤其对白质束的观察、追踪和脑发育和脑认知功能的研究。本文对DTI在缺血性脑卒中的应用研究进展进行综述。     

MR扩散张力成像原理及其在脑肿瘤中的研究进展

有关脑肿瘤研究的MRI新技术层出不穷,其中弥散加权成像(DWI)、灌注成像(PWI)、磁共振波谱(MRS)以及血氧水平依赖法(BOLD)脑功能成像研究在脑肿瘤的影像评价中均发挥着重要作用。但是,这些方法对于脑肿瘤与周围脑白质纤维关系的显示上都显得无能为力。随着扩散张力成像(diffusiontensorimaging,DTI)研究犤1-4犦的不断深入,目前已越来越多地应用于存在纤维定向组织的微观结构方面,在脑肿瘤的临床评价中也发挥重要的作用。1DTI的基本原理DTI是利用组织中水分子扩散运动存在的各向异性来探测组织微观结构的成像方法,是通过观察随扩散…     

磁共振弥散加权及张量技术在新生儿缺血缺氧性脑病中的应用

缺血缺氧性脑病（HIE）是新生儿危害最大的常见病之一,其病理生理机制及损伤特点复杂。根据脑成熟度、损伤严重程度及持续时间不同,MRI的影像表现各异。本文总结了磁共振弥散加权成像（DWI）及弥散张量成像（DTI）的原理和检查优势。回顾性分析了新生儿HIE的DWI和DTI的各参数变化及其规律。提示DWI能早期检出脑组织缺血缺氧改变的范围,并能一定程度反映细胞分子水平的改变;DTI能连续性反映脑组织轴索、髓鞘细微结构的改变,显示解剖构造与脑功能区域的关联。上述MRI技术的临床应用将为新生儿缺血缺氧性脑病的早期诊断、预后评估、疗效评价提供新的有益支持和保证,具有明显的临床应用优势。     

Age-related alterations in the modular organization of structural cortical network by using cortical thickness from MRI

Normal aging is accompanied by various cognitive functional declines. Recent studies have revealed disruptions in the coordination of large-scale functional brain networks such as the default mode network in advanced aging. However, organizational alterations of the structural brain network at the system level in aging are still poorly understood. Here, using cortical thickness, we investigated the modular organization of the cortical structural networks in 102 young and 97 normal aging adults. Brain networks for both cohorts displayed a modular organization overlapping with functional domains such as executive and auditory/language processing. However, compared with the modular organization of young adults, the aging group demonstrated a significantly reduced modularity that might be indicative of reduced functional segregation in the aging brain. More importantly, the aging brain network exhibited reduced intra-/inter-module connectivity in modules corresponding to the executive function and the default mode network of young adults, which might be associated with the decline of cognitive functions in aging. Finally, we observed age-associated alterations in the regional characterization in terms of their intra/inter-module connectivity. Our results indicate that aging is associated with an altered modular organization in the structural brain networks and provide new evidence for disrupted integrity in the large-scale brain networks that underlie cognition.     

膳食因素对脑老化小鼠皮层和海马乙酰胆碱酯酶活性的影响

目的探讨高脂和限食对脑老化及脑内乙酰胆碱酯酶(AChE)的影响,为合理膳食健脑防衰提供科学依据。方法雄性ICR小鼠60只分为6组,即脑老化模型组、脑老化+高脂膳食组、脑老化+限食组、高脂对照组、限食对照组、普通对照组,每组10只。以D-半乳糖100 mg/kg·d颈背部皮下注射制备脑老化模型。实验干预期共9周。以Morris水迷宫测试小鼠空间记忆和学习能力,羟胺比色法测定脑组织乙酰胆碱酯酶(AChE)活性。结果①水迷宫实验：脑老化组小鼠的逃避潜伏期高于普通对照组(P<0.05),脑老化+高脂膳食组逃避潜伏期与脑老化组无显著性差异(P>0.05),高脂膳食组与普通对照组之间逃避潜伏期亦显著无差异(P>0.05)。脑老化+限食组的逃避潜伏期低于脑老化组(P<0.05),而与普通对照组无显著性差异(P>0.05),限食对照组与普通对照组之间逃避潜伏期无显著性差异(P>0.05)。②AChE活性：脑老化组、脑老化+高脂膳食组和脑老化+限食组小鼠高于普通对照组和限食对照组(P<0.05),限食对照组与普通对照组无显著性差异(P>0.05)。脑老化+高脂膳食组高于脑老化组和其他非模型对照组(P<0.05)。结论高脂膳食可使脑内AChE活性升高,但对小鼠学习记忆能力无明显影响;限食可提高脑老化小鼠学习记忆能力,但对脑内AChE活性无明显影响。     

限食与运动对D-半乳糖诱导的脑老化小鼠的神经保护作用

目的:探讨限食和运动在抗脑老化中的神经保护作用。方法:雄性ICR小鼠60只,随机分为6组,即脑老化模型组(A组)、脑老化模型限食组(B组)、脑老化模型运动组(C组)、运动组(D组)、限食组(E组)和对照组(F组),每组10只,A、B、C组制备脑老化模型,B、E组限食,C、D组运动训练,分别干预10周后,以Morris水迷宫测试小鼠空间记忆和学习能力,以dUTP缺口末端标记(TUNEL)法测定海马神经元凋亡率。结果:A组逃避潜伏期(EL)大于F组(P<0.05),B、C组EL均小于A组(P<0.05)而与F组无差异,D、E组的EL与F组之间无差异;A组海马神经元凋亡率高于F组(P<0.05),B、C组神经元凋亡率低于A组(P<0.05)而与F组之间无差异,D、E组小鼠神经元凋亡率与F组比较亦无差异。结论:限食、运动具有防止脑老化性学习记忆能力下降的效应,并能有效减轻脑老化性神经元凋亡,但对正常小鼠学习记忆能力和神经元凋亡率无明显影响。     

Magnetic resonance approaches to brain aging and Alzheimer disease-associated neuropathology

The noninvasive, nonradioactive, quantitative nature of magnetic resonance techniques has propelled them to the forefront of neuroscience and neuropsychiatric research. In particular, recent advances have confirmed their enormous potential in patients with Alzheimer disease (AD). Structural and functional magnetic resonance (MR) imaging have demonstrated significant correlation with clinical outcomes and underlying pathology and are used increasingly in the AD clinic. This review will highlight the role of high-resolution structural MR imaging and functional magnetic resonance imaging in the identification of atrophic and hemodynamic changes in AD and their potential as diagnostic biomarkers and surrogates of therapeutic response. Advanced MR techniques based on diffusion, perfusion, and neurochemical abnormalities in the aging brain will be presented briefly. These newer techniques continue to expand our understanding of neuropathology in the aging brain and are likely to play an important clinical role in the future.     

Migraine and Cognitive Decline: A Topical Review

Migraine has been linked with an increased risk of stroke and an increased prevalence of clinically silent brain lesions and white‐matter hyperintensities. As it is known that stroke and structural brain lesions are associated with an increased risk of cognitive decline, it has been hypothesized that migraine may be a progressive brain disorder and associated with an increased risk of cognitive impairment. Given the prevalence of migraine in the population, especially among women, and the aging of the population, an association between migraine and cognitive impairment would have substantial public health implications. In this review, we will summarize the existing evidence evaluating the association between migraine and cognitive function. Additionally, we will discuss methodological issues in migraine and cognitive function assessment and elaborate on study design strategies to address this important question.     

利用新型扩散成像技术研究年老对大脑微观结构的影响

了解年老过程中大脑在细胞水平上发生的变化对于揭示老年人认知功能下降的原因有重要意义。扩散MRI(diffusion MRI,d MRI)技术是目前惟一可以无创探查活体组织微观结构的方法。扩散张量成像(DTI,diffusion tensor imaging)是临床上最常用的一种d MRI技术,但是由于某些固有缺陷,它不能充分刻画大脑组织的微观结构。作者介绍三种可以有效弥补DTI不足的新型扩散成像方法:扩散峰度成像(diffusion kurtosis imaging,DKI),扩散的受阻受限合成模型(composite hindered and restricted model of diffusion,CHARMED)和神经突方向离散度与密度成像(neurite orientation dispersion and density imaging,NODDI)。联合使用DTI和这些新技术,研究者可以更深入地了解年老如何影响大脑的微观结构。     

Neural stem cell therapy in the aging brain: pitfalls and possibilities

As aging progresses, there is a decline in the brain's capacity to produce new neurons in the two neurogenic regions, the subventricular zone surrounding the lateral ventricles and the subgranular layer of the hippocampal dentate gyrus. The underlying cause of the declining neurogenesis is unknown, but is presumably related to age-related changes that occur during normal aging of the brain. It is exacerbated by age-related neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Stem cell-based therapy to replace lost and/or damaged cells in the aging brain is currently the focus of intense research. The two most promising approaches involve transplantation of exogenous tissue and promoting proliferation of endogenous cells. However, age-related changes in the brain environment, including elevated oxidative stress and accumulation of protein and lipid by-products, present several unique challenges that must be addressed before cell-based therapy can be used as a viable option. Although progress has been made toward replacement of lost cells and recovery of lost function, there are fundamental issues that need to be addressed for stem cell therapy to be successful in the aging brain. In this review, we focus on recent progresses made toward understand the biology of neural stem cells in the aging brain, as well as progress toward using stem cells to replace cells lost during disease.     

Application of an automated voxel-based morphometry technique to assess regional gray and white matter brain atrophy in a canine model of aging

In recent years, voxel-based morphometry (VBM) has emerged as a technique to examine regional brain changes associated with normal and pathological aging. Despite its popularity in studies of human aging, application of VBM to animal models of brain aging is rare. In the present study, VBM techniques were developed to validate earlier region of interest (ROI) measures of brain aging in the dog and to provide a more comprehensive analysis of local changes in a canine model of brain aging. Consistent with previous findings, frontal lobe atrophy increased with age, most notably in aged male dogs. Age-related gray matter reductions were also observed in parietal and temporal lobes, thalamus, cerebellum, and brainstem. Temporal lobe atrophy was particularly prominent in old females. A number of age-related changes in white matter not previously explored in the dog were also identified with VBM. Specifically, aged males exhibited greater decreases in the internal capsula and cranial nerve bundles compared to decreased volumes in the alveus of the hippocampus in old female dogs. Together, the present results indicate that application of VBM techniques in a canine model of aging yields more comprehensive information regarding topographical patterns of brain aging in male and female dogs than previously reported using traditional manual ROI methods.     

正常人脑白质ADC值与年龄的相关性研究

目的探讨不同年龄组正常人脑白质的ADC值的特点及规律,建立正常人脑不同部位白质的标准ADC值,为弥散的临床应用及研究提供客观依据。方法收集60名正常健康体检者,对所有研究对象行头颅常规MR检查及平面回波弥散加权成像检查,获得各相同性弥散加权图。每个研究对象选16个感兴趣区,通过公式ADC=ln（S低／S高）／（b高-b低）计算每个感兴趣区的平均ADC值。结果正常人脑白质总的平均ADCave值为0．76±0．03（0．65～0．83）×10^-3mm^2／s,白质的平均ADC值随着年龄增长而增加,与年龄呈正相关,相关系数为0．46。结论不同年龄组正常人脑白质的ADC值有一定的变化规律,在临床对疾病的诊断时要考虑到该变化,以免误诊和漏诊;弥散定量测量在一定程度上可以用来评价正常人脑随着年龄增长伴随微观水平的改变,弥散技术有可能在脑老化研究中起到举足轻重的作用。     

Diagnosis of Cognitive Deficit in the Aged

The main effects of aging on the brain are similar to those of diffuse brain damage and are manifested as behavioral change or cognitive deficit. Changes due to aging must be differentiated from those due to focal cerebral lesions, including remediable pathologic disorders, and from involutional psychosis. The classic neurologic examination can be extended to aid in the diagnostic process.