弥散张量成像在脑肿瘤手术中的应用

目前,手术仍是脑肿瘤的首选治疗方法。如何在最大范围切除肿瘤的同时最大程度地保留神经功能,以减少术后并发症,是神经外科医生面临的一个挑战。肿瘤浸润生长及占位效应可导致脑功能区变形及重建,单纯解剖学定位不能满足对神经功能保护的要求。随着MRI技术的发展,脑功能定位成为可能,特别是磁共振弥散张量成像（diffusion tensorimaging,DTI）可以对脑白质纤维束走形进行示踪。     

颞叶癫痫患者磁共振弥散张量成像及记忆损害的研究

目的利用磁共振弥散张量成像技术(DTI)研究颞叶癫痫(TLE)患者脑内微观改变及记忆损害的相关脑区。方法对颞叶癫痫患者15例和健康对照者15例,进行DTI检查,利用韦氏记忆量表检测记忆功能。结果 TLE患者部分各向异性弥散(FA)值降低激活区域有颞叶、边缘叶、扣带回和岛叶,升高区有:额叶、顶叶、枕叶,表观系数(ADC)值升高激活区域在颞叶、额叶、枕叶、顶叶;无ADC值降低区域。与健康者相比,颞叶癫痫患者的记忆商数(MQ)(90.73±19.72)显著下降,P<0.01。对照组FA值在左岛叶、颞叶与MQ值正相关;患者组FA值在右额、顶、枕叶、左顶叶与MQ值正相关,在左颞叶与MQ值负相关。对照组ADC与MQ正相关区域在左边缘叶,与MQ成负相关区域在左顶叶、患者组正相关区域在左、右颞叶。结论初步证实TLE患者的脑内结构变化不局限于颞叶,还包括颞叶外网络结构;TLE患者全脑DTI与MQ存在着相关激活脑区,表明记忆功能损害与脑内相关结构改变有关。     

弥散张量成像在认知功能中的研究现状

近年来磁共振弥散张量在认知功能的临床研究中正逐步地开展。它能检测出联系大脑功能分区间的纤维变化,从而反映正常人脑白质随年龄改变的情况。此外对于多发性硬化、缺血性脑白质病、阿尔茨海默病、精神分裂症患者的认知功能的研究也有一定意义。     

脑梗死的MRI弥散张量成像

目的 用MRI弥散张昼成像(DTI)分析腩梗死的弥散张量改变,探讨脑梗死的DTI表现及其临床意义.方法 采用肓法分析临床及常规MRI和(或)CT确诊的69例脑梗死患者的DTI图像.分析脑梗死的DTI信号改变,测量病变区域的各向同性(ADCiso)值和各向异性(FA)值,并与健侧相应正常解剖区域进行比较.结果 根据ADCiso图和FA图上病变区的信号改变和定量测量,总结归纳出69例脑梗死病例分以下4种类型:I型(8例):病变区ADCiso值降低,FA值升高:ADCiso图表现为低信号,FA图表现为高信号.Ⅱ型(23例):病变区ADCiso值和FA值均降低,但病变周围区域ADCiso值降低.FA值升高;ADCiso图为低信号,FA图呈中央低信号,周围高信号改变.Ⅲ型(7例):病变区ADCiso值和FA值均降低;ADCiso图和FA图上均为低、等信号.Ⅳ型(31例):病变区ADCiso值升高,FA值降低;ADCiso图表现为高信号,FA图表现为低信号.以上病变区弥散张量参数与健侧镜像区比较差异有统计学意义(P<0.05).结论 DTl定性、定量分析有可能更好地揭示脑梗死病变的病理生理过程,有望为临床提供更精确的影像学分期,成为指导临床诊疗、监测病情进展和评定预后等的客观指标.     

磁共振弥散张量成像在脑膜瘤诊断中的应用研究

目的探讨磁共振弥散张量成像在诊断脑膜瘤中的应用价值。方法选取30例脑膜瘤的患者为研究对象,采用Siemens Sonata 1.5T型磁共振扫描仪对其进行磁共振弥散张量成像检查,比较良性脑膜瘤、恶性脑膜瘤内不同部位及组间相应部位ADC值、FA值。结果Ⅰ级脑膜瘤患者中脑膜上皮细胞型10例,纤维型7例,沙粒体型2例,过渡型3例,微囊型1例,化生型1例,血管瘤型1例;良性脑膜瘤瘤周水肿ADC值高于肿瘤实质及瘤周白质,三者比较差异有统计学意义（P〈0.05）;良性脑膜瘤瘤周白质FA值高于肿瘤实质及瘤周水肿,其中瘤周白质FA值与肿瘤实质FA值比较和瘤周白质FA值与瘤周水肿FA值比较差异均有统计学意义（P〈0.05）;良性脑膜瘤与恶性脑膜瘤肿瘤实质ADC值及瘤周白质ADC值比较差异均有统计学意义（P〈0.05）。结论磁共振弥散张量成像能用于诊断脑膜瘤的恶性程度,在区别脑膜瘤的具体部位方面具有很高的应用价值,值得临床推广应用。     

弥散张量成像在高血压脑出血中的应用研究

高血压脑出血(hypertensive intracerebral hemorrhage,HICH)是脑血管病中病死率和致残率都很高的一种疾病,在我国,发病率占全部脑卒中的21%～48%[1],在HICH患者存活者中,约有50%～75%的患者有不同程度的残疾,其中以肢体偏瘫最为常见。皮质脊髓束损伤是其致残的重要机制。所以,如何在HICH急性期准确判断皮质脊髓束受损情况,从而     

磁共振弥散张量成像在中枢神经系统中的临床应用

磁共振弥散张量成像是在磁共振成像基础上发展起来的,利用水分子的弥散来成像的影像学方法,可以定量观察活体组织的弥散特征,了解组织纤维的走行方向和完整性,为临床提供组织早期病变的微观结构和微观动力学信息;是无创性检查深部组织的有效方法,尤其是在脑白质病变的应用。     

磁共振弥散张量成像在脑部疾病诊断中的应用

磁共振弥散张量成像(DTI)是近年来在常规MRI技术和弥散加权(DWI)技术的基础上发展的一种新的MRI技术,是一种能在活体显示脑白质纤维束走向的无创成像方法[1～3]。1DTI的基本原理弥散是指水分子的随机运动,即布朗运动。在这一运动模式中,水分子在各个方面所受的弥散阻力相等,称为各向同性弥散。在脑组织中,由于神经纤维束的限制,水分子更倾向于沿着脑白质走行的方向进行弥散,称为各向异性弥散。由于各向异性的存在,弥散需要用张量描述。在DWI中,仅在1个或3个方向上施加弥散梯度磁场,因此只有表观弥散系数(ADC)1个标量值用于描述弥散…     

弥散张量成像在脑胶质瘤中的应用

胶质瘤呈侵袭性浸润生长,与周围组织分界不清,致残率和致死率高,预后差.目前胶质瘤手术切除主要依靠术者经验行肉眼下全切除,往往不超过影像学边界,留有残余肿瘤,术后易复发.因此,进行影像学引导的胶质瘤手术研究具有十分重要的意义[1].弥散张量成像(diffusion tensor image,DTI)是近年发展的磁共振成像新技术,是目前惟一能在活体无创地显示脑白质纤维束的成像方法[2].     

磁共振弥散张量成像在腰骶丛神经急性损伤诊断中应用价值

目的 探讨磁共振弥散张量成像（DTI）在腰骶丛神经急性损伤诊断中的临床价值。方法 选取经影像学和临床诊断为腰骶丛神经急性损伤60例为研究对象，均采用磁共振进行扫描检查，分析图像并记录相关数据。测量受损和正常L4~S1神经根各向异性分数（FA）与表观扩散系数（ADC）值。利用ROC曲线分析诊断敏感性和特异性。结果 与正常神经相比，受损神经FA值明显降低（P<0.05），而ADC值明显增高（P<0.05）。ROC曲线结果显示FA值曲线下面积为0.887，阈值为0.198时，诊断腰骶丛神经损伤的敏感度为71.7%、特异度为91.7%；当FA值≤0.188时，诊断特异度为100.0%。FA值与腰骶丛神经急性损伤呈明显负相关（r=-0.647，P<0.001）。结论 DTI技术应用于腰骶丛神经急性损伤诊断，具有显著效果，可较为直观地显示神经束走向和损伤具体位置，从而指导临床诊断     

Diffusion tensor imaging in late posttraumatic epilepsy

PURPOSE: The main objective of this study was to use diffusion tensor imaging (DTI) to search and quantify the extent of abnormality beyond the obvious lesions seen on the T2 and fluid-attenuation inversion recovery (FLAIR) magnetic resonance images in patients with chronic traumatic brain injury (TBI) with and without epilepsy. METHODS: DTI was performed on 23 chronic TBI patients (with late posttraumatic epilepsy, n=14; without epilepsy, n=9) and 11 age-matched controls. The ratios of fractional anisotropy (FA) and mean diffusivity (MD) between the regions of interest beyond the T2/FLAIR-visualized abnormality and the corresponding contralateral normal-appearing region were calculated. FA and MD ratios were compared for relative changes in these parameters among the TBI subjects with and without epilepsy and controls. Tissue volumes exhibiting abnormalities on DTI also were measured in these patients. RESULTS: The mean regional FA ratio was significantly lower, whereas the mean regional MD value was higher in patients with TBI compared with controls. The mean regional FA ratio was significantly lower in TBI patients with epilepsy (0.57+/-0.059) than in those without epilepsy (0.68+/-0.039). Although the regional MD ratio was higher in TBI patients with epilepsy (1.15+/-0.140) relative to those without epilepsy (1.09+/-0.141), the difference did not reach statistical significance. The tissue volume with low FA value also was found to be higher in TBI patients with epilepsy than without. CONCLUSIONS: Severity of injury as predicted by the DTI-derived increased volume of microstructure damage is associated with delayed posttraumatic epilepsy in TBI patients. These findings could be valuable in predicting epileptogenesis in patients with chronic TBI.     

Diffusion tensor imaging reliably differentiates patients with schizophrenia from healthy volunteers

The objective of this research was to determine whether fractional anisotropy (FA) and mean diffusivity (MD) maps derived from diffusion tensor imaging (DTI) of the brain are able to reliably differentiate patients with schizophrenia from healthy volunteers. DTI and high resolution structural magnetic resonance scans were acquired in 50 patients with schizophrenia and 50 age‐ and sex‐matched healthy volunteers. FA and MD maps were estimated from the DTI data and spatially normalized to the Montreal Neurologic Institute standard stereotactic space. Individuals were divided randomly into two groups of 50, a training set, and a test set, each comprising 25 patients and 25 healthy volunteers. A pattern classifier was designed using Fisher's linear discriminant analysis (LDA) based on the training set of images to categorize individuals in the test set as either patients or healthy volunteers. Using the FA maps, the classifier correctly identified 94% of the cases in the test set (96% sensitivity and 92% specificity). The classifier achieved 98% accuracy (96% sensitivity and 100% specificity) when using the MD maps as inputs to distinguish schizophrenia patients from healthy volunteers in the test dataset. Utilizing FA and MD data in combination did not significantly alter the accuracy (96% sensitivity and specificity). Patterns of water self‐diffusion in the brain as estimated by DTI can be used in conjunction with automated pattern recognition algorithms to reliably distinguish between patients with schizophrenia and normal control subjects. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

Diffusion tensor imaging in patients with primary cervical dystonia and in patients with blepharospasm

Diffusion tensor imaging (DTI) analyses the movement of water molecules within the cerebral white matter thus providing information on ultrastructural brain changes. We studied 18 patients with cervical dystonia (CD), 16 with blepharospasm (BSP) and 35 years age-matched healthy controls. DTI data were obtained with a Philips 1.5 Tesla scanner and then processed to obtain maps of fractional anisotropy (FA) and mean diffusivity (MD). Twenty-three square regions of interest of uniform size were positioned on the FA maps and then automatically transferred to the MD maps. FA and MD values in the corpus callosum, left and right putamen, right caudate, left and right pre-frontal cortical area and left supplementary motor area in CD patients differed significantly from those in healthy controls. No significant regional differences were found between patients with BSP and healthy controls. In the CD group, age, duration and severity of dystonia did not correlate with regional FA/MD values, whereas the duration of botulinum toxin treatment correlated significantly with the MD value in the right-pre-frontal cortex. The abnormal DTI findings in patients with CD suggest the presence of brain ultrastructural changes in adult-onset primary CD.     

Diffusion tensor magnetic resonance imaging at 3.0 tesla shows subtle cerebral grey matter abnormalities in patients with migraine

BACKGROUND AND OBJECTIVE: Diffusion tensor (DT) magnetic resonance imaging (MRI) has the potential to disclose subtle abnormalities in the brain of migraine patients. This ability may be increased by the use of high field magnets. A DT MRI on a 3.0 tesla scanner was used to measure the extent of tissue damage of the brain normal appearing white (NAWM) and grey matter in migraine patients with T2 visible abnormalities. METHODS: Dual echo, T1 weighted and DT MRI with diffusion gradients applied in 32 non-collinear directions were acquired from 16 patients with migraine and 15 sex and age matched controls. Lesion load on T2 weighted images was measured using a local thresholding segmentation technique, and brain atrophy assessed on T1 weighted images using SIENAx. Mean diffusivity and fractional anisotropy histograms of the NAWM and mean diffusivity histograms of the grey matter were also derived. RESULTS: Brain atrophy did not differ between controls and patients. Compared with healthy subjects, migraine patients had significantly reduced mean diffusivity histogram peak height of the grey matter (p=0.04). No diffusion changes were detected in patients' NAWM. In migraine patients, no correlation was found between T2 weighted lesion load and brain DT histogram derived metrics, whereas age was significantly correlated with grey matter mean diffusivity histogram peak height (p=0.05, r=-0.52). CONCLUSIONS: DT MRI at high field strength discloses subtle grey matter damage in migraine patients, which might be associated with cognitive changes in these patients.     

Diffusion tensor imaging in schizophrenia.

BACKGROUND: Alignment of white matter axons as inferred from diffusion tensor imaging has indicated changes in schizophrenia in frontal and frontotemporal white matter. METHODS: Diffusion tensor anisotropy and anatomical magnetic resonance images were acquired in 64 patients with schizophrenia and 55 normal volunteers. Anatomical images were acquired with a magnetization prepared rapid gradient echo sequence, and diffusion tensor images used a pulsed gradient spin-echo acquisition. Images were aligned and warped to a standard brain, and anisotropy in normal volunteers and patients was compared using significance probability mapping. RESULTS: Patients showed widespread areas of reduced anisotropy, including the frontal white matter, the corpus callosum, and the frontal longitudinal fasciculus. CONCLUSIONS: These findings, which are consistent with earlier reports of frontal decreases in anisotropy, demonstrate that the effects are most prominent in frontal and callosal areas and are particularly widespread in frontal white matter regions.     

Diffusion tensor imaging and voxel based morphometry study in early progressive supranuclear palsy

BACKGROUND: A comprehensive characterisation of grey and white matter changes in progressive supranuclear palsy (PSP), the second most common extrapyramidal syndrome after Parkinson disease, is still not available. OBJECTIVE: To evaluate grey and white matter changes in mild PSP patients by voxel based morphometry (VBM) and diffusion tensor imaging (DTI), respectively. METHODS: 14 mild PSP patients and 14 healthy controls entered the study and underwent a clinical and neuropsychological evaluation according with a standardised assessment. Each subject had a structural magnetic resonance imaging (MRI) study. Processing analysis of MRI data was carried out according to optimised VBM and fractional anisotropy was determined. RESULTS: Compared with the controls, in PSP patients VBM analysis showed a significant clusters of reduced grey matter in premotor cortex, frontal operculum, anterior insula, hippocampus, and parahippocampal gyrus, bilaterally. With regard to subcortical brain regions, the pulvinar, dorsomedial and anterior nuclei of the thalamus, and superior and inferior culliculum were affected bilaterally. A bilateral decrease in fractional anisotropy in superior longitudinal fasciculus, anterior part of corpus callosum, arcuate fascicolus, posterior thalamic radiations, and internal capsule, probably involving the cortico-bulbar tracts, was present in PSP patients. CONCLUSIONS: These data provide evidence for both grey and white matter degeneration in PSP from the early disease stage. These structural changes suggest that atrophy of cortical and subcortical structures and neurodegeneration of specific fibre tracts contribute to neurological deficits in PSP.