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。     

Directional colour encoding of the human thalamus by diffusion tensor imaging

The potential of diffusion tensor imaging (DTI) in brain imaging in terms of the in vivo mapping of neuroanatomy is generally accepted. Mostly, analyses of deep brain structures were based on complex methodical backgrounds. In the present study, the delineation of groups of thalamic nuclei with similar projection characteristics was investigated in healthy human subjects using a novel differentiated colour encoding approach of DTI data without the use of statistical calculations. With the application of this directional colour encoding of the longest eigenvector of every voxel-specific tensor, at least three functional groups in the thalamus with different projection directions could be differentiated. The method displayed, furthermore, a high symmetry and stability in the analysis of the individual subjects. In summary, substantial neuroanatomical information can be gained for deep subcortical gray matter structures such as the thalamus with an improved detection and directional differentiation of voxel-specific tensors.     

Lack of the cerebral peduncle involvement in a series of adult supratentorial AVM: A diffusion tensor imaging study

Congenital as arteriovenous malformation(AVM) is, most patients with AVM would be asymptomatic until adults. During the past 2 years, 23 cases of adult supratentorial AVM patients had DTI after admission. The region of interest was placed in the cerebral peduncle. Their FA value and fiber number was compared with those of cavernous malformation (CM) and tumor (glioma and meningioma). In the AVM group, there was no significant difference in FA of the cerebral peduncle (ipsilateral 0.758 ± 0.055 versus contralateral 0.755 ± 0.049; P > 0.05) and fiber number (319.6 ± 82.9 versus 304.7 ± 89.1; P > 0.05). In the CM group, FA of the cerebral peduncle on ipsilateral side (0.711 ± 0.092) was significantly lower than that of contralateral side (0.768 ± 0.043) (P < 0.01). Similar result was in fiber number of the CM group (251 ± 82.1 versus 307.3 ± 77.0; P < 0.05). In tumor group, FA of ipsilateral side (0.713 ± 0.084) was lower than that of contralateral (0.751 ± 0.052) without significant difference. There was no significant difference in fiber number between ipsilateral and contralateral sides in the tumor group (308.9 ± 112.4 versus 287.9 ± 62.4). Unlike non-AVM lesions (CM and tumor), FA value and fiber number of the ipsilateral cerebral peduncle is less influenced in the AVM group. The lack of the cerebral peduncle involvement indicates that there is plasticity of white matter in AVM.     

Effects of aging on the ventral and dorsal substantia nigra using diffusion tensor imaging

Dopaminergic neurons in the substantia nigra produce dopamine for the nigrostriatal pathway that facilitates motor function. Postmortem examinations demonstrate an age-related loss of cells in the substantia nigra, with most of the cell loss focused on the dorsal substantia nigra compared with the ventral substantia nigra. The current study used diffusion tensor imaging (DTI) to provide the first in vivo assessment of age-related degeneration in specific segments of the substantia nigra of humans. Measures extracted from DTI of 16 young adults (19-27 years) and 15 older adults (55-71 years) showed that in the dorsal substantia nigra, fractional anisotropy was reduced and radial diffusivity was increased with age. In the ventral substantia nigra and red nucleus, there were no differences across age for the DTI measures. DTI provides a noninvasive technique that accurately reflects the established pattern of age-related cell loss in the dorsal and ventral substantia nigra, further suggesting the robust potential for using DTI to characterize degeneration in the nigrostriatal pathway in both health and disease.     

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.     

磁共振弥散张量成像对瘤样炎性脱髓鞘病与低级别胶质瘤鉴别诊断的研究

目的 探讨MR弥散张量成像(DTI)在瘤样炎性脱髓鞘病(TIDD)与低级别胶质瘤(LGG)鉴别诊断中的应用价值。方法 纳入2012年1月—2016年2月在重庆医科大学附属第一医院确诊的10例TIDD患者及15例经病理证实的LGG患者资料进行回顾性分析。所有患者行3.0 T MR DTI检查,在表观弥散系数(ADC) 图及部分各向异性(FA) 图上定量测定患者病变区及其对侧镜像部位正常脑白质区(镜像区)的 ADC 值及 FA值,并进行统计分析;同时重建白质纤维素的3D图像,观察白质纤维素与病变区的空间位置关系。结果 TIDD组病变区和镜像区的ADC值、FA值分别为(1.484±0.14)×10³ mm²/s、0.109±0.02和(0.725±0.05)×10³ mm²/s、0.443±0.08,LGG组病变区和镜像区的ADC值、FA值分别为(1.368±0.09)×10³ mm²/s、0.163±0.01和(0.684±0.03)×10³ mm²/s、0.471±0.04。TIDD组与LGG组两组内病变区与镜像区ADC值和FA值差异均有统计学意义 (P值均<0.01),组间病变区ADC值和FA值差异均有统计学意义(P值均<0.05)。LGG的纤维重建图主要表现为肿瘤部位明显受压外移,较对侧稀疏、中断及形态改变;TIDD的纤维重建图主要表现为纤维稍稀疏,未见明显中断及移位改变。结论 TIDD与LGG在DTI上的弥散指标存在明显差异,可为两者的鉴别诊断提供量化依据。     

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.     

精神分裂症白质损害与发病年龄的弥散张量成像研究

目的:应用弥散张量成像(DTI)比较精神分裂症患者脑白质与正常人群间的差异,并探究各向异性比值(FA)的改变与发病年龄之间的相关性。方法:纳入27例精神分裂症患者和29名性别、年龄及受教育程度相匹配的健康对照。两组研究对象均接受头颅磁共振检测。患者组按照发病年龄分为早发组(发病年龄18岁)和成年发病组(发病年龄≥18岁)。采用基于体素的分析方法,分别比较患者组和对照组、早发组和成年发病组之间FA值的差异,并在控制性别、病程和药物剂量影响的前提下,分析FA值与患者发病年龄的相关性。结果:与健康对照比较,患者组在右侧上纵束、右侧放射冠上部的FA值降低;患者组中早发组和成年发病组间FA值的差异无显著性。患者组FA值与发病年龄呈正相关的脑区包括右侧放射冠前部(r=0.70,P0.01)、右侧胼胝体膝部(r=0.65,P0.01);未发现呈负相关的脑区。结论:本研究提示精神分裂症患者右侧脑区上纵束及放射冠部位存在白质损害,发病年龄愈早,右侧放射冠及胼胝体膝部白质纤维的受损愈重。这对精神分裂症病理生理改变及脑结构异常的进一步研究具有提示作用。     

Assessment of the diagnostic value of diffusion tensor imaging in patients with spinal cord compression: a meta-analysis

We investigated the diagnostic value of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of magnetic resonance diffusion tensor imaging (DTI) in patients with spinal cord compression (SCC) using a meta-analysis framework. Multiple scientific literature databases were exhaustively searched to identify articles relevant to this study. Mean values and standardized mean differences (SMDs) were calculated for the ADC and FA in normal and diseased tissues. The STATA version 12.0 software was used for statistical analysis. Of the 41 articles initially retrieved through database searches, 11 case-control studies were eligible for the meta-analysis and contained a combined total of 645 human subjects (394 patients with SCC and 251 healthy controls). All 11 studies reported data on FA, and 9 contained data related to the ADC. The combined SMDs of the ADC and FA showed that the ADC was significantly higher and the FA was lower in patients with SCC than in healthy controls. Subgroup analysis based on the b value showed higher ADCs in patients with SCC than in healthy controls at b values of both ≤500 and >500 s/mm². In summary, the main findings of this meta-analysis revealed an increased ADC and decreased FA in patients with SCC, indicating that DTI is an important diagnostic imaging tool to assess patients suspected to have SCC.     

MR弥散张量成像在脊柱脊髓疾病诊断中应用的研究进展

目的 探讨MR弥散张量成像(DTI)在脊髓疾病诊断中的应用进展。方法 在PubMed、Springer Link、中国知网数据库中,以“弥散张量成像、脊髓疾病、椎间盘”关键词,查阅2003年1月—2014年12月有关MR-DTI在脊髓疾病应用进展的相关文献,进行分析和总结。结果 MR-DTI体现脊髓病变早期组织空间组成和各组织成分之间水交换功能的改变,并能显示神经纤维束的走行方向,反映脊髓束功能的完整性。MR-DTI已逐渐应用于脊髓型颈椎病的早期诊断、脊髓损伤时期的判断和腰骶椎神经根病变的诊断以及腰椎间盘退变的早期诊断。DTI应用于脊髓疾病的诊断时,由于存在脊髓体积过小、扫描时间过长、运动伪影等不足,阻碍其在脊髓疾病诊断领域的发展。目前,随着并行成像技术、单次激发快速自旋回波序列等新技术的应用,这些问题正在逐步得到解决。结论DTI已在脊柱脊髓领域发挥出常规MR检查不可替代的作用。随着影像学的进步、新技术的应用及经验的丰富,DTI应用存在的阻碍必将得到解决,DTI在脊髓疾病领域的应用具有广阔的前景。     

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。     

磁共振扩散张量成像在评价儿童脑内部分皮质脊髓束发育中的应用

目的 应用磁共振扩散成像技术探讨儿童皮质脊髓束年龄和性别差异及其变化规律。 方法 90例无中枢神经系统症状及体征且颅脑磁共振检查正常的儿童（年龄5d～18岁）。按年龄分为5组: 婴儿组（组1,≤1岁）,幼儿组（组2,＞1～3岁）,学龄前组（组3,＞3～6岁）,学龄组（组4,＞6～12岁）,青春发育期组（组5,＞12～18岁）。每个年龄组内再按性别分为男、女2组。各组儿童分别行头部扩散张量成像, 根据感兴趣法选取皮质脊髓束感兴趣区并重建,测量重建的皮质脊髓束的扩散张量参数并进行统计学分析。 结果 各年龄组的表观扩散系数(ADC)值、分数各向异性(FA)值、纤维示踪平均长度、体积以及示踪的纤维束数量不完全相同（P<0.01）;组间的两两比较间发现,1组与2组间ADC值、FA值及示踪纤维平均长度差异具有统计学意义;2组与3组间FA值差异具有统计学意义;3组与4组间ADC值、FA值、示踪纤维平均长度、纤维束数目及体积差异均具有统计学意义。ADC值与年龄间呈负相关,余参数与年龄间呈正相关。结论 儿童皮质脊髓束发育具有阶段性,且具有阶段性特征;磁共振扩散张量技术可用于观测儿童皮质脊髓束,评价其发育状况。     

Effects of sustained cognitive activity on white matter microstructure and cognitive outcomes in healthy middle-aged adults: A systematic review

Adults who remain cognitively active may be protected from age-associated changes in white matter (WM) and cognitive decline. To determine if cognitive activity is a precursor for WM plasticity, the available literature was systematically searched for Region of Interest (ROI) and whole-brain studies assessing the efficacy of cognitive training (CT) on WM microstructure using Diffusion Tensor Imaging (DTI) in healthy adults (> 40 years). Seven studies were identified and included in this review. Results suggest there are beneficial effects to WM microstructure after CT in frontal and medial brain regions, with some studies showing improved performance in cognitive outcomes. Benefits of CT were shown to be protective against age-related WM microstructure decline by either maintaining or improving WM after training. These results have implications for determining the capacity for training-dependent WM plasticity in older adults and whether CT can be utilised to prevent age-associated cognitive decline. Additional studies with standardised training and imaging protocols are needed to confirm these outcomes.     

A meta-analysis of diffusion tensor imaging in mild cognitive impairment and Alzheimer's disease

We reviewed case-control studies of diffusion tensor imaging (DTI) in patients with Alzheimer's dementia (AD) and mild cognitive impairment (MCI), in order to establish the relative severity and location of white matter microstructural changes. EMBASE and MEDLINE were searched using the keywords, ([“diffusion tensor”] and [“Alzheimer*” or “mild cognitive impairment”]), as were reference lists of relevant papers. Forty-one diffusion tensor imaging studies contained data that were suitable for inclusion. Group means and standard deviations for fractional anisotropy and mean diffusivity, or p values from 2-sample tests, were extracted and pooled, using standard methods of meta-analysis and metaregression. Fractional anisotropy was decreased in AD in all regions except parietal white matter and internal capsule, while patients with MCI had lower values in all white matter regions except parietally and occipitally. Mean diffusivity was increased in AD in all regions, and in MCI in all but occipital and frontal regions.     

前交叉韧带弥散张量纤维示踪成像观测及临床应用

目的　为前交叉韧带损伤程度的分级诊断提供影像学数据。 方法　选取新乡医学院附属医院膝关节弥散张量成像扫描检查的正常者100例和单侧前交叉韧带撕裂伤患者100例,按照损伤程度分为Ⅰ~Ⅳ级,在工作站划分前交叉韧带不同部位及损伤处的感兴趣区,生成纤维示踪图像,测量感兴趣区的各向异性分数（fractional anisotropy,FA）和表观弥散系数（apparent diffusion coefficient,ADC）。比较前交叉韧带不同部位及不同程度损伤处的FA和ADC数值。 结果　前交叉韧带上端、上中部、中部、下中部、下端的FA值和ADC值差异有统计学意义（P<0.05）,FA随前交叉韧带部位自上而下逐渐降低呈负相关,ADC则逐渐增高呈正相关;组间比较,上端与上中部FA值和ADC值差异无统计学意义（P>0.05）,其他部位之间FA值和ADC值差异均有统计学意义（P<0.05）。前交叉韧带Ⅰ级、Ⅱ级、Ⅲ级、Ⅳ级损伤处FA值和ADC值差异有统计学意义（P<0.05）,FA随损伤程度增高而逐渐降低,ADC则逐渐增高;组间比较,Ⅰ级与Ⅱ级FA值和ADC值差异无统计学意义（P>0.05）,其他损伤分级之间FA值和ADC值差异均有统计学意义（P<0.05）。 结论　前交叉韧带的FA和ADC与部位、损伤程度等密切相关,弥散张量纤维示踪成像为前交叉韧带损伤的微细结构变化提供了客观影像诊断依据。     

MR扩散张量成像和纤维束示踪技术评价经阴道分娩初产妇肛提肌损伤

目的 探讨MR扩散张量成像(DTI)和纤维束示踪技术在经阴道分娩初产妇肛提肌损伤评价中的应用价值,为产后盆底康复治疗及盆腔器官脱垂的预防提供客观依据。方法 纳入2014年6月—2015年1月在天津市第一中心医院经阴道自然分娩后6个月初产妇50名(观察组),无症状未孕未产志愿者33名(对照组)进行前瞻性研究。受试者行盆底横断面、冠状面FSE T₂WI MR及DTI检查。对DTI图像进行后处理获得肛提肌各分支(耻骨内脏肌、髂尾肌)的3D肌肉纤维束图像,并评价其纤维示踪的精确性,对能够得到较为精确纤维束示踪图像者测量其各向异性分数(FA)、表观扩散系数(ADC)值。应用FSE T₂WI MRI影像评价产妇肛提肌损伤情况,并将其分为耻骨内脏肌无损伤组、耻骨内脏肌损伤组,采用方差分析比较对照组、无损伤组及损伤组间FA、ADC值的差异。结果 2组受试者均获得较为精确的耻骨内脏肌3D肌肉纤维束图像及对应的FA及ADC值,而髂尾肌3D肌肉纤维束图像均不精确。12例(24.0%,12/50)产妇存在耻骨内脏肌损伤,其中9例表现为单侧部分缺损,3例表现为双侧萎缩;4例(8.0%,4/50)产妇存在髂尾肌损伤,均表现为单侧部分缺损。对照组未发现肛提肌损伤。对照组、耻骨内脏肌无损伤组和损伤组耻骨内脏肌的FA值分别为0.49±0.08、0.52±0.11、0.53±0.13,ADC值分别为(1.79±0.29)×10^-3 mm²/s、(1.75±0.34)×10^-3 mm²/s、(1.93±0.35)×10^-3 mm²/s,差异均无统计学意义(F=1.217、1.747, P值均>0.05)。结论 DTI纤维束成像能够3D显示耻骨内脏肌纤维束结构,但髂尾肌的显示较为困难。目前DTI尚不能准确定量诊断肛提肌损伤情况。     

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。     

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.     

The neural connectivity of the inferior olivary nucleus in the human brain: A diffusion tensor tractography study

Objectives

Many animal studies have reported on the neural connectivity of the inferior olivary nucleus (ION). However, the neural connectivity of the ION has not been clearly elucidated in the human brain. In this study, the neural connectivity of the ION in the human brain was investigated by diffusion tensor imaging (DTI).

Methods

Forty healthy subjects were recruited. DTIs were acquired using a sensitivity-encoding head coil at 1.5 T. Connectivity was defined as the incidence of connection between the ION and regions of interest (ROIs) in the brain.

Results

In these subjects, the ION showed higher connectivity to the reticular formation (100%), the posterior limb of internal capsule (100%), the red nucleus (93.75%), the cerebral peduncle of midbrain (91.25%), the primary motor cortex (86.25%), the primary somatosensory cortex (85%), the periaqueductal gray mater (81.25%), the globus pallidus (81.25%), the anterior limb of internal capsule (62.5%), the pontine basis (62.5%), and the posterior parietal cortex (60%).

Conclusions

The ION shows high connectivity with motor function-related areas, such as, the posterior limb of internal capsule, the red nucleus, the cerebral peduncle of midbrain, the primary motor cortex, and the pontine basis. These results indicate that the ION is closely related to motor function in the human brain.