MR imaging of the temporal stem: anatomic dissection tractography of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer's loop of the optic radiation

BACKGROUND AND PURPOSE: The MR anatomy of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer's loop of the optic radiation, which traverse the temporal stem, is not well known. The purpose of this investigation was to study these structures in the anterior temporal lobe and the external and extreme capsules and to correlate the dissected anatomy with the cross-sectional MR anatomy. METHODS: Progressive dissection was guided by three-dimensional MR renderings and cross-sectional images. Dissected segments of the tracts and the temporal stem were traced and projected onto reformatted images. The method of dissection tractography is detailed in a companion article. RESULTS: The temporal stem extends posteriorly from the level of the amygdala to the level of the lateral geniculate body. The uncinate and inferior occipitofrontal fasciculi pass from the temporal lobe into the extreme and external capsules via the temporal stem. Meyer's loop extends to the level of the amygdala, adjacent to the uncinate fasciculus and anterior commissure. These anatomic features were demonstrated on correlative cross-sectional MR images and compared with clinical examples. CONCLUSION: This study clarified the MR anatomy of the uncinate and inferior occipitofrontal fasciculi and Meyer's loop in the temporal stem and in the external and extreme capsules, helping to explain patterns of tumor spread. The inferior occipitofrontal fasciculus is an important yet previously neglected tract. These results provide a solid anatomic foundation for diffusion tractography of the normal temporal stem and its tracts, as well as their abnormalities in brain disorders such as epilepsy, postoperative complications, trauma, schizophrenia, and Alzheimer disease.     

颞干解剖及白质纤维示踪成像对比研究

目的 应用扩散张量纤维素成像(DTT)技术确定钩状束、前连合、额枕下束和视辐射的三维关系,及其解剖定位标志.方法 研究10个成人尸体头颅标本,观察和测量:岛叶、岛阈、下限沟、Heschl回、颢角和外侧膝状体.并对10名健康志愿者进行脑DTT研究,应用解剖学知识基础上的感兴趣区法进行白质纤维重建.对两者的结果 进行对比.结果 下限沟长(46.3±3.1)mm,从下限沟到颞角上壁的最短距离为(6.5±1.8)mm.岛叶后下点位于Heschi回和下限沟交叉的最前端.在下限沟,此点是视辐射的后界.颞干开始于岛阈,结束于岛叶后下点,长(33.0±2.9)mm.从岛阈到颢角尖端的距离为(10.9±1.7)mm,这正好是颞十长度的1/3.钩状束构成颞干前部的核心,其后为前连合,它们占据颞十前1/3.额枕下束走行于整个颞干.Meyer袢最前界位于颞角前尖端和岛阈之间.视辐射大部存在于颞干中后2/3.结论 在下限沟,岛叶后下点是视辐射后界可靠的标志.岛阈、颢角尖端及岛叶后下点可作为颢干白质纤维束在MRI及术中的解剖标志.     

A method for clustering white matter fiber tracts

BACKGROUND/PURPOSE: Despite its potential for visualizing white matter fiber tracts in vivo, diffusion tensor tractography has found only limited applications in clinical research in which specific anatomic connections between distant regions need to be evaluated. We introduce a robust method for fiber clustering that guides the separation of anatomically distinct fiber tracts and enables further estimation of anatomic connectivity between distant brain regions. METHODS: Line scanning diffusion tensor images (LSDTI) were acquired on a 1.5T magnet. Regions of interest for several anatomically distinct fiber tracts were manually drawn; then, white matter tractography was performed by using the Runge-Kutta method to interpolate paths (fiber traces) following the major directions of diffusion, in which traces were seeded only within the defined regions of interest. Next, a fully automatic procedure was applied to fiber traces, grouping them according to a pairwise similarity function that takes into account the shapes of the fibers and their spatial locations. RESULTS: We demonstrated the ability of the clustering algorithm to separate several fiber tracts which are otherwise difficult to define (left and right fornix, uncinate fasciculus and inferior occipitofrontal fasciculus, and corpus callosum fibers). CONCLUSION: This method successfully delineates fiber tracts that can be further analyzed for clinical research purposes. Hypotheses regarding specific fiber connections and their abnormalities in various neuropsychiatric disorders can now be tested.     

Diffusion abnormalities of the uncinate fasciculus in Alzheimer’s disease: diffusion tensor tract-specific analysis using a new method to measure the core of the tract

Introduction Our aim was to determine diffusion abnormalities in the uncinate fasciculus (UF) in Alzheimer’s disease (AD) by diffusion tensor tractography (DTT) using a new method for measuring the core of the tract. Methods We studied 19 patients with AD and 19 age-matched control subjects who underwent MRI using diffusion tensor imaging (DTI). DTT of the UF was generated. The mean diffusivity (MD) and fractional anisotropy (FA) of the core of the tract were measured after voxelized tract shape processing. Student’s t-test was used to compare results between patients with AD and controls. Intraobserver correlation tests were also performed. Results FA was significantly lower (P < 0.0001) in the UF of patients with AD than of controls. There was no significant difference in MD along the UF between the two groups. Intraobserver reliability (intraclass correlation coefficient) for the first and second measurement was r > 0.93 for measured FA and r > 0.92 for measured MD. Conclusion Our results suggest that FA reflects progression of AD-related histopathological changes in the UF of the white matter and may represent a useful biological index in monitoring AD. Diffusion tensor tract-specific analysis with voxelized tract shape processing to measure the core of the tract may be a sensitive tool for evaluation of diffusion abnormalities of white matter tracts in AD.     

磁共振扩散张量纤维束成像技术在内侧颞叶癫痫中的应用研究

目的采用扩散张量纤维束成像(DTT)技术对内侧颞叶癫痫(mesial temporal lobe epilepsy,mTLE)中特定的脑白质纤维完整性的改变进行研究,探讨其在mTLE中的应用价值。资料与方法 25例单侧mTLE患者(左侧13例,右侧12例)及21名健康自愿者(对照组)纳入本研究。在1.5 T MR扫描仪下行扩散张量成像(DTI)数据采集。采用Trackvis软件对受检者颞叶相关的5对白质纤维束进行追踪显示,测量其整体部分各向异性分数(FA)值。将两组mTLE患者的左、右侧纤维束FA值分别与对照组相应侧纤维束FA值进行两样本t检验。最后将病例组纤维束FA值与临床因素进行相关分析。结果相对于对照组,左侧mTLE组5个患侧纤维束FA值均减低(P<0.05),而对侧仅扣带束(t=2.458,P<0.05)、上纵束(t=2.112,P<0.05)、下纵束(t=2.093,P<0.05)的FA值减低;右侧mTLE组5个患侧纤维束FA值均减低(P<0.05),而对侧仅下纵束FA值减低(t=2.384,P<0.05)。左侧mTLE组左侧钩束FA值与始发年龄呈线性正相关关系(r=0.764,P<0.01),与发病时长呈线性负相关关系(r=-0.678,P<0.05)。结论 DTT可用于颞叶癫痫相关白质纤维束完整性的检测,并有助于mTLE定侧研究,加深对mTLE病理生理机制的进一步理解。     

Human subinsular asymmetry studied by diffusion tensor imaging and fiber tracking

BACKGROUND AND PURPOSE: Our aim was to improve our understanding of the subinsular white matter microstructural asymmetries in healthy right-handed subjects. Structural brain asymmetries could be related to functional asymmetries such as hemisphere language dominance or handedness. Besides the known gray matter asymmetries, white matter asymmetries could also play a key role in the understanding of hemispheric specialization, notably that of language. MATERIALS AND METHODS: White matter asymmetries were studied by diffusion tensor imaging at 1.5T (41 diffusion-gradient directions; b-value set to 700 s/mm(2); matrix, 128(2); in-plane resolution, 1.875 x 1.875 mm; section thickness, 2.0 mm) and fiber tracking (BrainVISA software). The main white matter bundles passing through the subinsular area were segmented, and fractional anisotropy (FA) was measured along each of the segmented bundles. RESULTS: In line with published results, we found an asymmetry of the arcuate fasciculus and the subinsular white matter, namely left-greater-than-right FA in right-handed controls. Furthermore, by segmenting major tracts coursing through this region, we showed that the subinsular portions of the uncinate fasciculus (UF) and the inferior occipitofrontal fasciculus (IOF) contribute to this FA asymmetry. Those tracts have been reported to be likely implicated in the language network. CONCLUSION: Because the left hemisphere hosts language functions in most right-handers, the significant leftward asymmetry observed within the arcuate fasciculus, the subinsular part of the UF and IOF may be related to the hemispheric specialization for language.     

High-resolution line scan diffusion tensor MR imaging of white matter fiber tract anatomy

BACKGROUND AND PURPOSE: MR diffusion tensor imaging permits detailed visualization of white matter fiber tracts. This technique, unlike T2-weighted imaging, also provides information about fiber direction. We present findings of normal white matter fiber tract anatomy at high resolution obtained by using line scan diffusion tensor imaging. METHODS: Diffusion tensor images in axial, coronal, and sagittal sections covering the entire brain volume were obtained with line scan diffusion imaging in six healthy volunteers. Images were acquired for b factors 5 and 1000 s/mm(2) at an imaging resolution of 1.7 x 1.7 x 4 mm. For selected regions, images were obtained at a reduced field of view with a spatial resolution of 0.9 x 0.9 x 3 mm. For each pixel, the direction of maximum diffusivity was computed and used to display the course of white matter fibers. RESULTS: Fiber directions derived from diffusion tensor imaging were consistent with known white matter fiber anatomy. The principal fiber tracts were well observed in all cases. The tracts that were visualized included the following: the arcuate fasciculus; superior and inferior longitudinal fasciculus; uncinate fasciculus; cingulum; external and extreme capsule; internal capsule; corona radiata; auditory and optic radiation; anterior commissure; corpus callosum; pyramidal tract; gracile and cuneatus fasciculus; medial longitudinal fasciculus; rubrospinal, tectospinal, central tegmental, and dorsal trigeminothalamic tract; superior, inferior, and middle cerebellar peduncle; pallidonigral and strionigral fibers; and root fibers of the oculomotor and trigeminal nerve. CONCLUSION: We obtained a complete set of detailed white matter fiber anatomy maps of the normal brain by means of line scan diffusion tensor imaging at high resolution. Near large bone structures, line scan produces images with minimal susceptibility artifacts.     

Diffusion abnormality in posterior cingulate fiber tracts in Alzheimer’s disease: tract-specific analysis

Purpose

The aim of this study was to determine diffusion abnormalities in the posterior cingulate fiber tracts (PCFTs) in patients with Alzheimer’s disease (AD) by diffusion tensor tractography (DTT).

Materials and methods

We studied 23 AD patients and 18 age-matched normal controls who underwent magnetic resonance imaging using diffusion tensor imaging (DTI). DTT of PCFTs was generated from DTI. Mean diffusivity (MD) and fractional anisotropy (FA) were measured in co-registered voxels along with DTT of PCFTs. Student’s t-test was used to compare results between the AD patients and normal controls.

Results

The MD in PCFTs was significantly higher in AD patients than in normal controls (P = 0.019). The FA in PCFTs was significantly lower in AD patients than in normal controls (P = 0.007).

Conclusion

The abnormal MD increase and FA decrease, which is considered to indicate a net loss of barriers that restrict water molecular motion and tissue anisotropy of white matter, is consistent with neuropathological data that demonstrate partial loss of myelin, axons, and oligodendrial cells in white matter of AD brains. Our results suggest that MD and FA reflect progression of AD-related histopathological changes in the PCFTs and may represent a useful biological index for monitoring AD.     

Impact of white matter hyperintensities on surrounding white matter tracts

Purpose

It is unclear how white matter hyperintensities disrupt surrounding white matter tracts. The aim of this tractography study was to determine the spatial relationship between diffusion characteristics along white matter tracts and the distance from white matter hyperintensities.

Methods

Diffusion tensor 3-T MRI scans were acquired in 29 participants with white matter hyperintensities. In each subject, tractography by the fiber assignment by continuous tracking method was used to segment corticospinal tracts. Mean diffusivity, radial diffusivity, axial diffusivity, and fractional anisotropy were measured along corticospinal tracts in relation to white matter hyperintensities. Diffusion characteristics along tracts were correlated with distance from white matter hyperintensities and were also compared between tracts traversing and not traversing white matter hyperintensities.

Results

In tracts not traversing through white matter hyperintensities, increasing distance from white matter hyperintensities was associated with decreased mean diffusivity (p?=?0.002) and increased fractional anisotropy (p?=?0.006). In tracts traversing white matter hyperintensities, compared to tracts not traversing white matter hyperintensites, the mean diffusivity was higher at 6–8 voxels, axial diffusivity higher at 4–8 voxels, and radial diffusivity higher at 7 voxels away from white matter hyperintensities (all p?<?0.006).

Conclusion

White matter hyperintensities are associated with two patterns of altered diffusion characteristics in the surrounding white matter tract network. Diffusion characteristics along white matter tracts improve further away from white matter hyperintensities suggestive of a local penumbra pattern. Also, altered diffusion extends further along tracts traversing white matter hyperintensities suggestive of a Wallerian-type degenerative pattern.

     

人脑联合纤维的扩散张量纤维束成像初步研究

目的 :利用扩散张量纤维束成像显示人脑内联合纤维的三维结构 ,探讨其与解剖学描述的一致性。方法 :对5例正常志愿者进行单次激发回波平面扩散张量成像 ,利用纤维束成像软件包显示人脑联合纤维的三维结构 ,观察重建的联合纤维与解剖学描述的一致性。结果 :通过选择恰当的兴趣区 ,设置不同的分数各向异性阈值、角度阈值、步长和体素长度内采样数目等参数 ,扩散张量纤维束成像可以清楚地显示弓状纤维、扣带、钩束、上纵束、下纵束、上枕额束和下枕额束等联合纤维的三维结构 ,除上枕额束以外 ,其显示结果与解剖学描述具有良好的一致性。结论 :联合纤维束成像的结果与解剖学描述具有高度一致性 ,该方法是一种可靠的研究人脑纤维连接的方法。     

阿尔茨海默病患者脑白质束铁沉积的磁共振相位成像

目的：利用磁共振相位成像和扩散张量成像(DTI)技术,探讨阿尔茨海默病(AD)患者的脑白质束损伤与相应白质束铁沉积的相关性。方法：对25例AD患者及20例年龄相匹配的健康老年志愿者进行MR扩散张量成像及相位成像。DTI数据经后处理生成平均扩散系数(MD)和部分各向异性(FA)图,分别测量穹窿、胼胝体膝部、胼胝体压部、双...     

Diffusion tensor MR imaging tractography of the pyramidal tracts correlates with clinical motor function in children with congenital hemiparesis

BACKGROUND AND PURPOSE: Children with congenital hemiparesis have greater asymmetry in diffusion parameters of the pyramidal tracts compared with control subjects. We hypothesized that the asymmetry correlates with the severity of hemiparesis and that diffusion metrics would be abnormal in the affected tracts and normal in the unaffected tracts. MATERIALS AND METHODS: Fifteen patients with congenital hemiparesis and 17 age-matched control subjects were studied with diffusion tensor MR imaging tractography. Hemipareses were scored as mild, moderate, or severe. We measured tract-specific diffusion parameters (fractional anisotropy, mean, and directional diffusion coefficients) of the pyramidal tracts. We compared tract-specific parameters and asymmetry between the right and left tracts of the differing severity groups and control subjects. RESULTS: We observed many different causes of congenital hemiparesis including venous infarction, arterial infarction, and polymicrogyria. Clinical severity of hemiparesis correlated with asymmetry in fractional anisotropy (P < .0001), transverse diffusivity (P < .0001), and mean diffusivity (P < .03). With increasing severity of hemiparesis, fractional anisotropy decreased (P < .0001) and transverse diffusivity (P < .0001) and mean diffusivity (P < .02) increased in the affected pyramidal tract compared with controls. Diffusion metrics in the unaffected tract were similar to those in the control subjects. CONCLUSION: Asymmetry in fractional anisotropy, transverse diffusivity, and mean diffusivity, as well as the degree of abnormality in the actual values of the affected pyramidal tracts themselves, correlates with the severity of motor dysfunction in infants and children with congenital hemiparesis from different causes. This suggests that abnormalities detected by diffusion tensor MR imaging tractography in the affected pyramidal tract are related to the functional ability of the affected pyramidal tract, regardless of the etiology of motor dysfunction.     

Six is enough? Comparison of diffusion parameters measured using six or more diffusion‐encoding gradient directions with deterministic tractography

Diffusion tensor imaging tractography is commonly used to quantify white matter tracts in the human brain via parameters such as fractional anisotropy and mean diffusivity. Simulation studies recommend the use of more than six directions for robust parameter estimates; however, no study has examined the impact of the number of gradient directions on deterministic tractography-derived diffusion parameters in human brain. Here, for 10 major white matter tracts in 11 healthy volunteers at 1.5 T, six-direction diffusion tensor imaging data were compared to 30- or 60-direction data, keeping scan time and number of b = 0 images constant within each test. Mean diffusivity was systematically lower for six-direction protocols (20/40 comparisons); six-direction data had higher fractional anisotropy in the superior longitudinal fasciculus and smaller tract volume for the genu of the corpus callosum. In general, parameter differences due to the number of directions were smaller than those from intersubject variation or signal-to-noise ratio. Despite some absolute differences, standard deviations were significantly different for only one of 160 comparisons. Thus, six-direction data provide diffusion measures with comparable robustness to 30- or 60-direction data and yield appropriate parameter values for most white matter tracts, although there are clear advantages in acquiring higher angular resolution data.     

DTI-based three-dimensional tractography detects differences in the pyramidal tracts of infants and children with congenital hemiparesis

PURPOSE: To test the hypothesis that there is greater asymmetry in diffusion properties between right and left pyramidal tracts in patients with congenital hemiparesis than in patients with normal motor function. MATERIALS AND METHODS: Four congenitally hemiparetic patients and four age-matched controls underwent magnetic resonance diffusion tensor imaging (DTI)-based three-dimensional tractography of the pyramidal tracts. Relative anisotropy, individual eigenvalues, and directionally averaged apparent diffusion coefficient were measured and degree of asymmetry was calculated. RESULTS: Compared with age-matched controls, congenitally hemiparetic patients had greater asymmetry in all measured diffusion properties. The asymmetry was characterized primarily by lower anisotropy, lower parallel diffusion, higher transverse diffusion, and slightly higher mean diffusivity in the pyramidal tract contralateral to the hemiparesis (i.e., affected pyramidal tract) compared with the unaffected pyramidal tract. CONCLUSIONS: There appears to be greater diffusion asymmetry between the pyramidal tracts in congenitally hemiparetic patients compared to controls. These differences suggest that there are alterations in the microstructure of the pyramidal tract that controls the motor function of the hemiparetic side. Our results suggest that DTI-based three-dimensional tractography is potentially useful in the assessment of motor dysfunction in infants and children with congenital hemiparesis.     

Nonketotic hyperglycinemia: spectrum of imaging findings with emphasis on diffusion-weighted imaging

Purpose

The purpose of this study was to explore brain abnormalities in nonketotic hyperglycinemia (NKH) using diffusion-weighted imaging (DWI) and when feasible, diffusion tensor imaging (DTI) and tractography.

Methods

Seven patients with confirmed diagnosis of NKH (8 days–2 years) underwent brain MRI. Conventional T1 and T2WI were acquired in all patients, DWI in six and DTI and tractography in two (4 months and 2 years). Measurements of fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD) and Trace from eight white matter regions were compared between the two patients and age-matched controls. Tractography of corpus callosum, superior longitudinal fasciculus and corticospinal tracts was performed with extraction of their FA and diffusivity indices.

Results

MRI showed nonspecific brain atrophy in three children. Corpus callosum atrophy was found as a part of these atrophic changes. Cerebellar vermian hypoplasia and supratentorial hydrocephalus were seen in one patient. The topographic distribution of diffusion restriction was different among patients. The affected white matter regions were not predominantly following the expected areas of myelination according to patients’ age. Deep grey matter nuclei were affected in one patient. DTI revealed lower FA with higher RD in most of the measured white matter regions and tracts. These changes were more appreciated in the 2-year-old patient. However, Trace was higher in the 2-year-old patient and lower in the 4-month-old one. The extracted tracts were decreased in volume.

Conclusion

DWI, DTI and tractography with FA and diffusivity measurements can give insights into white matter microstructural alterations that can occur in NKH.

     

White matter microstructural abnormalities in children with spina bifida myelomeningocele and hydrocephalus: a diffusion tensor tractography study of the association pathways

PURPOSE: To quantify microstructural abnormalities in the major association pathways of children affected by spina bifida myelomeningocele (SBM) and shunted hydrocephalus using whole-brain diffusion tensor imaging (DTI). MATERIALS AND METHODS: The institutional review board approved this Health Insurance Portability and Accountability Act (HIPAA)-compliant study and written informed consent/assent were obtained prior to the study. The 69 participants included 38 children with SBM and shunted hydrocephalus (age mean +/- SD = 12.30 +/- 2.10 years; 22 boys; 10 left-handed) and 31 age- and sex-matched normally-developing children (11.56 +/- 2.72 years; 15 boys, four left-handed). Diffusion tensor tractography (DTT) was performed to delineate and quantify bilaterally four major association pathways (arcuate, inferior longitudinal, inferior fronto-occipital, and uncinate fasciculi). RESULTS: The group with SBM did not exhibit the pattern of age-related decreases in the diffusivities observed in the controls. The transverse and axial diffusivities were significantly elevated in most of the white matter pathways of the participants with SBM. The fractional anisotropy (FA) was significantly lower in most of the association pathways. Many of the association pathways were not traceable in some participants with SBM compared to the controls at the selected FA thresholds. CONCLUSION: DTT revealed diffusion tensor characteristics of abnormal development (nonvisualization/poor visualization of tracts, downward arrow FA, upward arrow diffusivities), impairment in myelination (upward arrow transverse diffusivity) as well as abnormalities in intrinsic axonal characteristics and extraaxonal/extracellular space (upward arrow axial diffusivity) in the association pathways of the SBM children. The differences in the diffusion metrics observed in the children with SBM are suggestive of abnormal white matter development and persistent degeneration with increased age.     

In vivo visualization of white matter fiber tracts of preterm- and term-infant brains with diffusion tensor magnetic resonance imaging

OBJECTIVE: The goal of this study was to test the feasibility of visualizing a 3-dimensional structure of cerebral white matter fiber tracts in preterm infants, postconceptional age (PCA) 28 weeks to term, by using volumetric diffusion tensor magnetic resonance imaging (DTI) data. MATERIALS AND METHOD: We combined tractography algorithms and visualization methods, currently available for adult DTI data, to trace the pixelated principal direction of a diffusion tensor originating from regions-of-interest with high fractional anisotropy. Consequently, white matter fiber bundles from the genu and the splenium of corpus callosum, the corticospinal tracts, the inferior fronto-occipital fasciculi, and optic radiations were visualized. RESULTS: Our results suggest that major white matter tracts of preterm infant brains, with PCAs ranging from 28 weeks to term (40 weeks old), can be successfully visualized despite the small brain volume and low anisotropy. CONCLUSION: The feasibility of fiber tractography in preterm neonates with DTI may add a new dimension in detection and characterization of white matter injuries of preterm infants.     

Three-tesla diffusion tensor imaging of Meyer's loop by tractography, color-coded fractional anisotropy maps, and eigenvectors

The aim of this study was to evaluate Meyer's loop by 3-T MRI with fiber tractography, color-coded fractional anisotropy maps, and eigenvector maps. The anteroposterior distance from the anterior bundle of the Meyer's loop to temporal pole ranged from 26.3 to 34 mm, overlapping with the previously published anatomical dissection studies. Diffusion tensor imaging with fiber tractography, color-coded FA maps, and color maps of the principal eigenvector at 3 T appear to be promising techniques for the virtual dissection of Meyer's loop.     

Diffusion tensor tractography and neuropsychological assessment in patients with vitamin B12 deficiency

Introduction

Structural imaging of the brain does not demonstrate any changes in a vast majority of patients with vitamin B12 deficiency, even in advanced stages. In this study, we aimed to assess and correlate the functional integrity of the brain fiber tracts using diffusion tensor tractography with neuropsychological examination in patients with vitamin B12 deficiency.

Methods

The study was conducted at two tertiary care centers. Thirty-two patients with vitamin B12 deficiency were enrolled and subjected to diffusion tensor tractography, as an extension of diffusion tensor imaging, and neuropsychological assessment. Tests of significance were done to detect changes, pre- and post-vitamin B12 supplementation in the diffusivity parameters (fractional anisotropy and mean diffusivity) and the neuropsychological test scores.

Results

Statistically significant changes were observed in the diffusivity parameters and the neuropsychological test scores between the controls and the patients with vitamin B12deficiency in the pre- and post-treatment phases.

Conclusions

This is the first study to evaluate the diffusion tensor tractography (DTT) parameters in the light of clinical neuropsychological assessment in patients with vitamin B12 deficiency. Utilization of DTT parameters may antedate structural changes and may quantify the neurocognitive deficits.     

A tracking-based diffusion tensor imaging segmentation method for the detection of diffusion-related changes of the cervical spinal cord with aging

PURPOSE: To compare region of interest (ROI)-based and diffusion tensor tractography (DTT)-based methods for evaluating diffusion properties of the spinal cord as a function of age. MATERIALS AND METHODS: Commonly, an ROI segmentation is used to delineate the spinal cord. In this work, new segmentation methods are developed based on DTT. In a first, DTT-based, segmentation approach, the diffusion properties are calculated on the tracts. In a second method, the diffusion properties are analyzed in the spinal cord voxels that contain a certain number of tracts. We studied the changes in diffusion properties of the human spinal cord in subjects of different ages. Diffusion tensor imaging (DTI) measurements of the cervical spinal cord were acquired on 42 healthy volunteers (age range = 19-87 years). The fractional anisotropy (FA), the mean diffusivity (MD), and eigenvalues (lambda(1), lambda(2), and lambda(3)) were compared for the ROI- and DTT-based segmentation methods. RESULTS: Our automatic techniques are shown to be highly reproducible and sensitive for detecting DTI changes. FA decreased (r = -0.38; P < 0.05), whereas MD and eigenvalues increased (r = +/- 0.45; P < 0.05) with age. These trends were not statistically significant for the ROI-based segmentation (P > 0.05). CONCLUSION: DTT is a robust and reproducible technique to segment the voxels of interest in the spinal cord.