Diffusion tensor imaging of spinocerebellar ataxias types 1 and 2

BACKGROUND AND PURPOSE: Structural MR imaging does not enable reliable differentiation of spinocerebellar ataxia (SCA) types 1 and 2 (SCA1 and SCA2), and imaging may be normal during the first years after the onset of symptoms. We aimed at determining whether measurements of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) may enable their differentiation. MATERIALS AND METHODS: We enrolled 14 patients with SCA1, 11 with SCA2, and 9 age-matched controls. Diffusion tensor imaging (DTI) was performed on a 1.5T scanner, with b = 1000s/mm2 and 12 directions. ADC and FA were measured by means of regions of interest, positioned in the corticospinal tract at the level of the cerebral peduncle and at the level of the pons, in the transverse pontine fibers, in the superior and middle cerebellar peduncle, and in the hemispheric cerebellar white matter. RESULTS: With respect to controls, the ADC was significantly elevated in the middle cerebellar peduncle and in hemispheric white matter in SCA1, and in all regions under consideration in SCA2. It was significantly higher in SCA2 than in SCA1 in all regions under consideration. With respect to controls, the FA was significantly reduced in all regions under consideration in SCA1 and in SCA2. It was significantly lower in SCA2 than in SCA1 in the transverse pontine fibers and in the corticospinal tract at the level of the cerebral peduncle. Correlations with clinical scores were found. CONCLUSIONS: DTI did not enable differentiation between SCA1 and SCA2. However, strongly significant differences between the 2 subtypes and with respect to controls and correlations with clinical scores were found.     

Diffusion tensor eigenvector directional color imaging patterns in the evaluation of cerebral white matter tracts altered by tumor

PURPOSE: To categorize the varied appearances of tumor-altered white matter (WM) tracts on diffusion tensor eigenvector directional color maps. MATERIALS AND METHODS: Diffusion tensor imaging (DTI) was obtained preoperatively in 13 patients with brain tumors ranging from benign to high-grade malignant, including primary and metastatic lesions, and maps of apparent diffusion coefficient (ADC), fractional anisotropy (FA), and major eigenvector direction were generated. Regions of interest (ROIs) were drawn within identifiable WM tracts affected by tumor, avoiding grossly cystic and necrotic regions, known fiber crossings, and gray matter. Patterns of WM tract alteration were categorized on the basis of qualitative analysis of directional color maps and correlation analysis of ADC and FA. RESULTS: Four basic patterns of WM alteration were identified: 1) normal or nearly normal FA and ADC, with abnormal tract location or tensor directions attributable to bulk mass displacement, 2) moderately decreased FA and increased ADC with normal tract locations and tensor directions, 3) moderately decreased FA and increased ADC with abnormal tensor directions, and 4) near isotropy. FA and ADC were inversely correlated for Patterns 1-3 but did not discriminate edema from infiltrating tumor. However, in the absence of mass displacement, infiltrating tumor was found to produce tensor directional changes that were not observed with vasogenic edema, suggesting the possibility of discrimination on the basis of directional statistics. CONCLUSION: Tumor alteration of WM tracts tends to produce one of four patterns on FA and directional color maps. Clinical application of these patterns must await further study.     

MR扩散张量成像对脑肿瘤的初步应用研究

目的 :评价MR扩散张量成像在脑肿瘤中的应用价值。方法 :搜集经手术及病理证实的脑膜瘤和星形细胞瘤病例共 3 3例 ,行常规MRI、扩散张量成像 (DTI)检查。构建各向异性分数 (FA)图 ,并测量肿瘤及周围白质的FA值。结果 :正常白质纤维在FA图上表现为高信号。在肿瘤存在时 ,周围白质纤维可表现为受推压移位或浸润破坏 ,破坏后FA值降低 ,表现为低信号。这些表现在常规MRI上均未清楚显示。结论 :DTI可清楚显示肿瘤与周围白质纤维的解剖关系 ,指导临床制订手术方案。     

3T MR with diffusion tensor imaging and single-voxel spectroscopy in giant axonal neuropathy

Magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and MR spectroscopy (MRS) data were obtained in a patient with giant axonal neuropathy (GAN) and compared to a control group. Fractional anisotropy (FA) and apparent coefficient diffusion (ADC) data were obtained from specific white matter tracts including the corticospinal tracts (CST), corpus callosum (CC), optic radiations (OR), and middle cerebellar peduncle (MCP). Analysis of the MRS was performed. DTI parameters and MRS results were correlated with the neuropathological findings described for GAN. No significant difference between the FA of the CC of the patient and the control group was found. However, there was a significant difference between the FA of the CST, OR, and MCP of the patient and the control group. The ADC values for all tracts of the patient were significantly increased. N-acetylaspartate to creatine (NAA/Cr) and N-acetylaspartate to choline (NAA-Cho) (choline) metabolite ratios were slightly decreased and choline to creatine (Cho/Cr) and myo-inositol to creatine (Ins/Cr) metabolite ratios were increased in the parietal gray and white matter of the patient as compared to the control group. Cerebellar involvement was less evident. The DTI and MRS findings suggest myelin and axonal damage.     

Early postnatal development of corpus callosum and corticospinal white matter assessed with quantitative tractography

BACKGROUND AND PURPOSE: The early postnatal period is perhaps the most dynamic phase of white matter development. We hypothesized that the early postnatal development of the corpus callosum and corticospinal tracts could be studied in unsedated healthy neonates by using novel approaches to diffusion tensor imaging (DTI) and quantitative tractography. MATERIALS AND METHODS: Isotropic 2 x 2 x 2 mm(3) DTI and structural images were acquired from 47 healthy neonates. DTI and structural images were coregistered and fractional anisotropy (FA), mean diffusivity (MD), and normalized T1-weighted (T1W) and T2-weighted (T2W) signal intensities were determined in central midline and peripheral cortical regions of the white matter tracts of the genu and splenium of the corpus callosum and the central midbrain and peripheral cortical regions of the corticospinal tracts by using quantitative tractography. RESULTS: We observed that central regions exhibited lower MD, higher FA values, higher T1W intensity, and lower T2W intensity than peripheral cortical regions. As expected, MD decreased, FA increased, and T2W signal intensity decreased with increasing age in the genu and corticospinal tract, whereas there was no significant change in T1W signal intensity. The central midline region of the splenium fiber tract has a unique pattern, with no change in MD, FA, or T2W signal intensity with age, suggesting different growth trajectory compared with the other tracts. FA seems to be more dependent on tract organization, whereas MD seems to be more sensitive to myelination. CONCLUSIONS: Our novel approach may detect small regional differences and age-related changes in the corpus callosum and corticospinal white matter tracts in unsedated healthy neonates and may be used for future studies of pediatric brain disorders that affect developing white matter.     

Tracking the neurodegeneration of parkinsonian disorders – a pilot study

The purpose of the study was to explore the possibilities of using diffusion tensor imaging (DTI) and tractography (DTT) for the differential diagnosis and monitoring of disease progression in idiopathic Parkinson’s disease (IPD), compared with the atypical parkinsonian disorders multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A 3.0-T MR scanner was used. DTI was acquired using a single-shot EPI sequence with diffusion encoding in 32 directions and a voxel size of 2 × 2 × 2 mm³. DTI data were analysed and DTT was performed using the PRIDE fibre tracking tool supplied by the manufacturer. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) within each tract were determined. DTI and DTT images in patients with moderate to advanced MSA demonstrated degeneration of the middle cerebellar peduncles and pontine crossing tracts, with decreased FA and increased ADC. This accounted for most of the pontine and cerebellar atrophy characteristic of this disease. In contrast, patients with PSP showed a selective degeneration of the superior cerebellar peduncle. Three-dimensional images of whole-brain white matter tracts demonstrated a reduction of cortical projection fibres in all patients with PSP. Visualization of the selective degeneration of individual fibre tracts, using DTI and DTT, adds qualitative data facilitating the differential diagnosis of parkinsonian disorders. Repeated measurements of FA and ADC values in a whole fibre tract might be used for monitoring disease progression and studying the effect of treatment in neuroprotective trials. The results are preliminary considering the small number of subjects in the study.     

婴幼儿脑白质发育的弥散张量磁共振成像

目的：应用弥散张量成像分析不同年龄段婴幼儿的不同部位脑白质的各向异性。材料和方法：将26例正常婴幼儿（年龄4d至24个月）分为4组：第一组7例，小于6个月；第二组8例，6—12个月；第三组6例，12—18个月；第四组5例，18—24个月。均进行常规头颅MR和弥散张量成像，并测量不同部位脑白质的FA值和ADC值。结果：随着年龄的增加，ADC值逐渐减低，FA值逐渐升高。不同组别大脑白质各部位的ADC值和FA值不同（P〈0．05）。结论：弥散张量成像可以反映活体脑白质的细微结构，可用于评价脑白质发育情况。     

白血病脑实质浸润的弥散张量成像应用研究

目的探讨1．5T磁共振弥散张量成像（diffusiontensorimaging,DTI）,部分各向异性（fractionalanisotropy,FA）和表观扩散系数（apparentdiffusioncoefficient,ADC）及弥散张量纤维束成像（diffusiontensortractography,DTT）在成人白血病脑实质浸润的应用价值。方法回顾性分析经临床证实的8例白血病脑实质浸润病例DTI之ADC、FA参数图,分别测量病变、水肿及健侧相应部位FA值和ADC值;观察各例在DTT图的变化。结果白血病脑实质浸润的肿瘤实质部分FA值8例全部较健侧降低,ADC值5例减低,3例增高;周围水肿区FA值全部降低,ADC值全部增高;脑白质纤维束DTT显示有中断、移位、浸润。结论DTI对脑侵犯神经纤维束损伤具有独特诊断价值;DTI的参数变化能够量化神经纤维受压后微细结构的变化,DTT图像重建能直观显示脑白质纤维束的完整性及损伤程度,DTI联合DTT可更加准确地评估白血病脑侵犯的损害程度。     

Role of diffusion tensor imaging in characterization and preoperative planning of brain neoplasms

Background and purpose

DTI is an MR imaging measure of brain tissue integrity. It gives precise information about the involvement and integrity of the white matter tracts in the immediate region surrounding tumors. The purpose of our study is to evaluate the role of DTI in characterization and preoperative assessment of brain neoplasm.

Materials and methods

32 patients with intracranial neoplasm were included in this study which was conducted during a 2 year period. Conventional MRI before and after IV Gadolinium administration was done followed by DTI and diffusion tensor tractography, with FA and ADC value measurements of different white matter tracts in direct relation to the tumor. The values obtained were compared to the normal unaffected tract in the contralateral side.

Results

White matter involvement by a tumor was classified according to the criteria of displacement, infiltration, disruption or edema. Patients were classified into two main groups according to the tumor type: benign and malignant groups. Prevalence of tract displacement was higher among benign group in comparison to the malignant group with significant difference in between by using chi-square test (P value <0.05). While prevalence of disruption was higher among the malignant group, in comparison to the benign group significant difference was noted in between by using chi-square test. (P value <0.05).

Conclusion

The information provided by DT imaging further defined precise relationships between the sub cortical white matter structures and the cerebral neoplasm. This potentially has a role in tumor characterization, and more importantly in surgical planning.     

脑星形胶质细胞瘤周围区域的磁共振DTI研究

目的：采用扩散张量成像（DTI）技术研究脑星形胶质细胞瘤周围区域的细微结构改变,探讨其确定肿瘤边界的价值。方法：将28例经手术病理证实的星形胶质细胞瘤患者分为低度恶性星形细胞瘤和恶性胶质瘤两组。利用DTI检测肿瘤区、肿瘤周围区和健侧脑组织区,计算各向异性（FA）和平均扩散系数（ADC）及脑白质纤维束的情况。结果：28例星形胶质细胞瘤的3个不同区域DTI数值有显著性差异。周围区域DTI各值的均数在低度恶性和恶性胶质瘤之间进行比较,ADC、FA值的差异均有统计学意义。FA图显示低度恶性星形胶质细胞瘤多以推移周围邻近白质为主,与邻近白质边界清楚,而恶性胶质瘤组则以破坏与浸润白质束为主,边界相对模糊。结论：应用DTI成像可能对确定星形胶质细胞瘤的边界具有一定的临床意义。     

弥散张量成像技术在星形细胞肿瘤中的应用价值初探

目的：评价MRI弥散张量成像技术在星形细胞肿瘤中的应用价值。材料和方法：采用GE1.5T超导MR成像系统，对16例1-2级星形细胞肿瘤及15例3-4级星形细胞肿瘤进行了MRI检查，检查序列包括T1WI、T2WI、FLAIR、弥散张量序列（diffusion tensor imaging，DTI）及增强后T1WI。结果：正常脑白质纤维在不同解剖平面，如半卵圆中心、内囊、胼胝体、视放射、锥体束、锥体交叉及内外侧丘系等，各向异性分数图（FA）均为高信号，白质纤维受到破坏后表现为低信号，而这些表现在常规T1WI、T2WI及FLAIR图上未能清楚显示。结论：DT1可以无创性检查脑白质纤维，用于脑肿瘤诊断及术前手术方案的制定。     

Line-scan diffusion tensor MR imaging at 0.2 T: feasibility study

PURPOSE: To investigate and measure apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values using data obtained with line-scan diffusion-weighted imaging (DWI) of human brains on a 0.2 Tesla MR imager. MATERIALS AND METHODS: Diffusion-tensor imaging (DTI) was performed on eight healthy volunteers. The signal-to-noise ratios (SNRs) of white matter and cerebrospinal fluid were measured. ADC and FA were also measured from the data obtained from all subjects. Three-dimensional corticospinal fiber tracts were reconstructed from the DT images and a qualitative evaluation was done. RESULTS: The total scan time was 52 minutes 30 seconds for 18 slices with full-tensor images covering the whole brain. The ADCs and FAs show the appropriate values, in comparison with values obtained at high field strength in previous studies. Corticospinal fibers were demonstrated more clearly on images obtained at 0.2 T than at 1.5T. CONCLUSION: DTI at low field strength may be feasible for clinical use to estimate the white matter of brain with limited coverage, which often may be sufficient.     

磁共振弥散张量成像对正常大脑白质纤维束构象的初步研究

目的利用磁共振弥散张量成像(DTI)研究正常成人脑内各部位各向异性程度及正常白质纤维束构象特征.方法对25名正常志愿者进行常规MR及DTI序列检查,重建FA图及三维彩色编码张量图.分别在半卵圆中心、基底节区和大脑脚层面测量主要白质束的FA值.结果DTI显示灰质与白质区各向异性存在显著差异,不同部位的白质纤维束各向异性程度亦不相同,且左右两侧基本对称,重建FA图和三维彩色编码张量图可显示白质内大部分主要的白质纤维束.结论DTI可清晰显示脑内白质纤维束的走行及分布,为了解脑功能与白质通路间关系提供了有力研究手段.     

大脑胶质瘤弥散张量磁共振成像定量研究

目的:应用弥散张量磁共振成像定量分析大脑胶质瘤的特点。方法:11例经病理证实的大脑胶质瘤患者,行弥散张量磁共振成像检查,在ADC图和FA图上分别测量肿瘤周围水肿区域、肿瘤强化区域、囊变区域、脑脊液及对侧正常大脑白质ADC值和FA值。结果:肿瘤周围水肿区域的ADC值和FA值与肿瘤囊变区域、脑脊液及对侧大脑白质相比较均有显著性差异(P<0.05),而与肿瘤强化区域相比较无显著性差异。肿瘤囊变区域的ADC值及FA值与脑脊液、对侧正常大脑白质相比较有显著性差异(P<0.05);肿瘤囊变区域与肿瘤强化区域相比较,ADC值无显著性差异,FA值却有显著性差异(P<0.05)。肿瘤强化区域的ADC值及FA值与对侧大脑白质相比较具有显著性差异(P<0.05)。高、低级别胶质瘤肿瘤周围水肿区域、肿瘤强化区域、肿瘤囊变区域的ADC值及FA值均无统计学显著差异。结论:磁共振弥散张量成像对定量分析大脑胶质瘤本身及其周围脑组织具有重要价值。     

正常成人大脑白质纤维磁共振弥散张量成像的定量研究

目的:运用弥散张量成像(DTI)定量研究正常成人脑白质不同解剖部位的各向异性特点.方法:对60名正常成人按年龄分成四组,均行DTI检查,分析其表面弥散系数(ADC)图及各向异性分数(FA)图的特点,并对不同解剖部位的脑白质进行ADC值及FA值的定量分析,通过统计学分析得出其弥散系数和各向异性特点.结果:不同年龄组间相同解剖部位脑白质ADC值及FA值的差异无统计学意义;不同解剖部位间FA值及ADC值的差异具有显著性.结论:DTI可清晰显示脑内白质的走行及方向,FA能准确定量分析正常成人不同部位脑白质纤维的各向异性程度.     

MR diffusion tensor imaging of white matter tract disruption in stroke at 3 T

Recent advances in MR diffusion weighted imaging (DWI) enable the identification of anisotropic white matter tracts with diffusion tensor imaging (DTI). We aimed to use a novel DTI technique to safely study patients with recent stroke in a high field (3 T) MR machine with its intrinsically higher spatial resolution and signal-to-noise ratio. Of ten patients studied, six had disruption of white matter tracts as determined by DTI. A further patient had distortion of white matter tracts around an infarct rather than actual disruption of the tracts themselves. The lack of tract destruction may imply a beneficial prognosis, information that is not available with conventional DWI.     

White matter reorganization after surgical resection of brain tumors and vascular malformations

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) and white matter tractography (WMT) are promising techniques for estimating the course, extent, and connectivity patterns of the white matter (WM) structures in the human brain. In this study, DTI and WMT were used to evaluate WM tract reorganization after the surgical resection of brain tumors and vascular malformations. METHODS: Pre- and postoperative DTI data were obtained in 6 patients undergoing surgical resection of brain lesions. WMT using a tensor deflection algorithm was used to reconstruct WM tracts adjacent to the lesions. Reconstructed tracts included corticospinal tracts, the corona radiata, superior longitudinal and inferior fronto-occipital fasciculi, cingulum bundles, and the corpus callosum. RESULTS: WMT revealed a series of tract alteration patterns including deviation, deformation, infiltration, and apparent tract interruption. In general, the organization of WM tracts appeared more similar to normal anatomy after resection, with either disappearance or reduction of the deviation, deformation, or infiltration present preoperatively. In patients whose lesions were associated with corticospinal tract involvement, the WMT reconstructions showed that the tract was preserved during surgery and improved in position and appearance, and this finding correlated with improvement or preservation of motor function as determined by clinical assessment. CONCLUSION: WMT is useful for appreciating the complex relationships between specific WM structures and the anatomic distortions created by brain lesions. Further studies with intraoperative correlation are necessary to confirm these initial findings and to determine WMT utility for presurgical planning and evaluation of surgical treatments.     

White matter anatomy using tensor diffusion tractography

Tractography of cerebral white matter fibers based on diffusion tensor imaging (DTI) is a recent magnetic resonance technique that enables the visualization of the anatomy and integrity of white matter tracts. This article aims to provide two- and three-dimensional representations of the main white matter tracts in the brain from high spatial resolution DTI data and to explain the physical basis of the technique, its main clinical applications, and how we use it. We provide examples of the use of DTI in the study of the corpus callosum, the anterior white commissure, the corticospinal tract, the limbic system, the long association fibers, the cerebellar peduncles, and the optic tract.     

弥散张量成像在鉴别卒中和短暂性脑缺血发作中的应用

目的:弥散张量成像(DTI)的各向异性分数(FA)值可用来定量评价脑白质的病理变化,并且FA对于检出Wallerian变性和判断预后非常重要。本研究用FA值和皮质脊髓束(CST)受损的类型及其损伤程度来鉴别短暂性脑缺血发作(TIA)和卒中。方法:45例TIA患者和33例小卒中患者纳入研究,都行常规MRI扫描、DWI及全脑DTI检查。DTI数据用Functool 2软件采用三个感兴趣区(ROI)并利用线性扩展法进行皮质脊髓束3D重建。通过比较缺血病灶和CST的空间关系判断TIA和卒中患者CST受损的类型及其损伤程度,同时也比较TIA和卒中患者的rAIFA值和病灶大小。结果:DWI阳性者中TIA患者的rAIFA明显比卒中患者的高(P<0.05)。以rAIFA>0.90诊断TIA的敏感度为75%,特异度为73%,阳性预测值为72%。TIA患者病灶不累及CST或仅累及小部分CST,病灶多位于半卵圆区、放射冠、丘脑或皮质;卒中患者病灶多累及大部分CST,病灶多位于内囊。TIA患者和卒中患者的病灶大小没有显著性差异。结论:本研究表明,在症状发作后24h内,TIA和小卒中可以通过rAIFA值来鉴别,TIA患者和卒中患者所累...     

病毒性脑炎扩散张量成像的初步研究

目的:比较病毒性脑炎脑内病灶和对照侧镜像区的扩散特性的差异,探讨扩散张量成像(DTI)在诊断病毒性脑炎中的应用价值。方法:分别对13例病毒性脑炎患者行常规MRI和DTI检查,经处理后分别获得每个层面的表观扩散系数(ADC)图、各向异性(FA)图、1-VR(VR)图和纤维束成像(DTT)图,并对DTI各输出参数ADC、FA、1-VR进行统计分析。结果:13例患者共计20个病灶,病灶区的FA值及1-VR值减低,病灶区与对照侧的FA值及1-VR值间的差异有统计学意义(P<0.01),病灶区与对照侧的ADC值间的差异无统计学意义(P=0.2026,P>0.05)。FA图显示病灶的范围比常规T2WI大。DTT图显示受累白质纤维束是浸润性改变,部分纤维中断。结论:DTI指标可以反映病毒性脑炎病变组织的微观结构变化信息,为常规MRI检查提供补充信息,对其临床诊疗和评估也有一定的价值。