Diffusion tensor imaging at term-equivalent age in extremely-low-birth-weight infants with periventricular leukomalacia

It is important to predict the neurological prognoses of preterm infants as part of their normal follow-up. Previous reports have shown that conventional magnetic resonance imaging (MRI) and electroencephalography are useful in predicting neurological prognoses. Diffusion tensor imaging (DTI) is a relatively new method of evaluating the central nervous system (CNS) that can detect abnormalities quantitatively. We compared DTI at term-equivalent age in two extremely-low-birth-weight infants diagnosed with periventricular leukomalacia (PVL) with conventional MRI and DTI in three control extremely-low-birth-weight infants. DTI was analyzed using the free software, "Volume-one" and "dTVII SR." We compared the fractional anisotropy (FA) values at the corpus callosum, posterior limbs of the internal capsule, cerebral peduncle, and corticospinal tract using manual region of interest (ROI) analysis, and at the commissural fibers and corticospinal tract using tract-specific analysis. The FA values were lower in patients with PVL than in control infants at all measurement points, except the commissural fibers on tract-specific analysis. These measurement points showed no abnormality using conventional MRI. This suggests that DTI can detect CNS abnormalities that cannot be detected with conventional MRI. However, our sample size was very small and we examined only cases in which PVL was detected with conventional MRI. Further study is necessary to examine the correlation of DTI findings and neurological prognoses in infants who have no abnormality on conventional MRI.     

基于弥散张量成像技术的双相障碍患者脑白质纤维束异常分析

目的探讨抑郁期双相障碍患者脑白质纤维束的变化。方法选取42例未用药双相障碍抑郁期患者(患者组)和年龄、性别及右利手与之相匹配的59名对照者(对照组)进行DTI检查,根据约翰霍普金斯大学人类白质纤维束图谱,将大脑白质组织分割为20条公认存在的粗大纤维束,应用PANDA软件计算每个被试者每条白质纤维束的4项平均弥散属性,采用非参数置换检验比较2组在20条白质纤维束上弥散指标的差异,将差异有统计学意义的脑白质纤维束弥散指标与临床指标进行Pearson相关分析。结果患者组左侧钩束各向异性分数(fractional anisotropy,FA)值低于对照组(0.40±0.01与0.41±0.01,P=0.001);胼胝体辐射线额部FA值低于对照组(0.36±0.02与0.38±0.02,P<0.001);左侧钩束径向弥散率(radial diffusivity,RD)值高于对照组(6.57×10^-4±2.41×10^-5与6.40×10^-4±2.42×10^-5,P=0.0017)。Pearson相关分析显示,2组弥散指标差异有统计学意义的白质纤维束与临床指标之间均无相关性。结论抑郁期双相障碍患者钩束及胼胝体辐射线额部存在脑白质完整性破坏。     

Diffusion tensor imaging assesses white matter injury in neonates with hypoxic-ischemic encephalopathy

With improvements in care of at-risk neonates, more and more children survive. This makes it increasingly important to assess, soon after birth, the prognosis of children with hypoxic-ischemic encephalopathy. Computed tomography, ultrasound, and conventional magnetic resonance imaging are helpful to diagnose brain injury, but cannot quantify white matter damage. In this study, ten full-term infants without brain injury and twenty-two full-term neonates with hypoxic-ischemic encephalopathy (14 moderate cases and 8 severe cases) underwent diffusion tensor imaging to assess its feasibility in evaluating white matter damage in this condition. Results demonstrated that fractional anisotropy, voxel volume, and number of fiber bundles were different in some brain areas between infants with brain injury and those without brain injury. The correlation between fractional anisotropy values and neonatal behavioral neurological assessment scores was closest in the posterior limbs of the internal capsule. We conclude that diffusion tensor imaging can quantify white matter injury in neonates with hypoxic-ischemic encephalopathy.     

Diffusion tensor imaging reveals white matter abnormalities in Attention-Deficit/Hyperactivity Disorder

The specific brain structures or neural mechanisms underlying dysfunction in individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) are not well established, particularly in regard to white matter (WM). Diffusion tensor imaging (DTI) was used to investigate WM in 12 adolescent males diagnosed with ADHD only and 12 typically developing controls (group matched; mean age=15.64 years, SD=1.15). In addition to fractional anisotropy (FA), we also examined axial and radial diffusivity (AD and RD) in an effort to help elucidate conflicting findings suggesting that both lower and higher FA values are characteristic of ADHD. Tract-based spatial statistics and voxel-wide analyses were conducted on the data utilizing a pre-frontal mask to enable focus on fronto-striatal and prefrontal pathways. Adolescents with ADHD had significantly higher FA and AD values in fronto-striatal pathways compared with controls. No differences were observed for RD. These results contribute to the growing literature implicating prefrontal WM variations in neuropsychiatric disorders, and are consistent with findings suggesting a role for fronto-striatal pathways in ADHD pathophysiology.     

Diffusion tensor magnetic resonance imaging of disruption of regional white matter in schizophrenia

Diffusion tensor imaging provides a new approach for quantifying anisotropic diffusion of white matter in vivo. We used this technique to investigate subtle disruption of regional white matter in schizophrenia. Twelve patients with schizophrenia were compared with 11 healthy controls. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale. A significant fractional anisotropy (FA) reduction was found in all white matter regions bilaterally in schizophrenic patients. Higher FA of left frontal white matter correlated significantly with higher dosage of antipsychotic medication. These findings support the view that the pathological process is a distortion of the central nervous system myelination affecting the whole white matter. Our findings also show the effects of antipsychotics on the white matter in the left frontal region in schizophrenia.     

Diffusion tensor imaging of lesions and normal-appearing white matter in multiple sclerosis.

OBJECTIVE: To determine whether diffusion tensor imaging (DTI) can detect structural changes in normal-appearing white matter, and to distinguish between plaques of different pathologic severity, in patients with MS. BACKGROUND: Conventional MRI detects lesions sensitively in MS but has limited pathologic specificity. The diffusion of water molecules in brain tissue, most fully expressed mathematically by a tensor quantity, reflects its intrinsic microstructure. It is now possible to estimate the diffusion tensor noninvasively in the human brain using MR DTI. This method is unique in providing precise and rotationally invariant measurements of the amount and directional bias (anisotropy) of diffusion in white matter tracts relating to tissue integrity and orientation. METHODS: DTI was performed in six patients with MS and in six age-matched control subjects. Diffusion was characterized in normal-appearing white matter in both groups, and in lesions of different pathologic subtypes (inflammatory, noninflammatory, T1 hypointense, and T1 isointense). RESULTS: DTI identified significantly altered water diffusion properties in the normal-appearing white matter of patients compared with control subjects (p < 0.001), and distinguished between lesion types. The highest diffusion was seen in destructive (T1 hypointense) lesions, whereas the greatest change in anisotropy was found in inflammatory (gadolinium-enhancing) lesions. CONCLUSIONS: DTI detects diffuse abnormalities in the normal-appearing white matter of MS patients, and the findings in lesions appear to relate to pathologic severity. Its use in serial studies and in larger clinical cohorts may increase our understanding of pathogenetic mechanisms of reversible and persistent disability.     

Diffusion tensor imaging of white matter injury in a rat model of infantile hydrocephalus

Objective  

Diffusion tensor imaging (DTI) is a non-invasive MRI technique that has been used to quantify white matter (WM) abnormality in both clinical and experimental hydrocephalus (HCP). However, no DTI study has been conducted to characterize anisotropic diffusion properties in an animal model of infantile HCP. This DTI study was designed to investigate a rat model of HCP induced at postnatal day 21, a time developmentally equivalent to the human infancy.     

精神分裂症患者及其健康同胞的弥散张量成像研究

目的 探索精神分裂症患者及其健康同胞是否存在类似的脑白质完整性异常.方法 采用弥散张量成像技术扫描精神分裂症患者(患者组)、患者的健康同胞(同胞组)和健康对照(对照组)的全脑,用基于体素的分析方法比较3组的白质纤维分数各向异性(fractional anisotropy,FA)值.结果 在左侧前额叶和海马区,患者组(左侧前额叶:0.303±0.006,海马:0.310±0.O05)和同胞组(左侧前额叶:0.320±0.006,海马:0.318±0.006)的白质FA值显著小于对照组(左侧前额叶:0.338±0.007,海马:0.338±0.005),差异均有统计学意义(P＜0.05),患者组与同胞组的差异无统计学意义(P＞0.05);在左侧前扣带区,患者组白质FA值(0.391±0.006)显著小于同胞组(0.423±0.006)和对照组(0.412±0.007),差异有统计学意义(P＜0.05),同胞组的FA值大于对照组,但差异无统计学意义(P＞0.05).结论 精神分裂症患者及其健康同胞存在相似的脑白质完整性异常,左侧前额叶和海马白质FA值降低可能意味着精神分裂症的患病风险,左侧前扣带的白质FA值降低则可能是向该病转换的决定因素.     

Diffusion tensor imaging for evaluation of the childhood brain and pediatric white matter disorders

Magnetic resonance (MR) imaging has been used by investigators and clinicians to assess the development of the brain in childhood to understand both patterns of normal growth and patterns by which a maturing brain may deviate from normal. Advanced MR techniques such as diffusion tensor imaging (DTI) have gained prominence as a means of assessing brain development. This review explains the sequence of brain maturation and the means by which DTI can be used to assess it in normal children.     

Diffusion tensor imaging tractography and reliability analysis for limbic and paralimbic white matter tracts

Diffusion tensor imaging (DTI) provides the opportunity to study white matter tracts in vivo. The goal was to estimate the reliability of DTI tractography for the analysis of limbic and paralimbic white matter. Normative data from 24 healthy subjects and reliability data from four healthy and four depressed subjects were acquired at 1.5 Tesla, using twice-refocused spin-echo, echoplanar DTI and Fluid-Attenuated Inversion Recovery (FLAIR) DTI sequences. Fiber tracking was performed using the Fiber Assignment by Continuous Tracking algorithm. Fractional Anisotropy (FA), trace Apparent Diffusion Coefficient and tract volumes were calculated. The inter-rater (and intra-rater) intraclass correlation coefficients for FA values were as follows: rostral cingulum 0.89 (0.87), dorsal cingulum 0.85 (0.90), parahippocampal cingulum 0.85 (0.95), uncinate fasciculus 0.85 (0.87), medial prefrontal white matter 0.97 (0.99), ventromedial prefrontal white matter 0.92 (0.93), crus of fornix 0.80 (0.81). The reported DTI protocol provides a reliable method to analyze limbic and paralimbic white matter tracts relevant to psychiatric disorders.     

Diffusion tensor imaging study of white matter fiber tracts in adolescent attention-deficit/hyperactivity disorder

A diffusion tensor imaging (DTI) study was conducted in 12 adolescents with attention deficit/hyperactivity disorder and 14 age- and IQ-matched healthy controls. Inter-subject comparison of fractional anisotropy (FA) of the whole brain between the groups was obtained using the tract-based spatial statistics method. Results revealed significantly lower FA in widespread white matter tracts in cases relative to controls. Also, the FA measure of identified regions was associated with cognitive performance.     

Visualizing white matter pathways in the living human brain: diffusion tensor imaging and beyond

Biologic connectionism holds as its central tenet that the cognitive, behavioral, and motor functions of the brain are derived from the complex interconnections of simple neural processing units. Much can be learned about the human mind through the study of the brain's connections in normal and diseased states. This article summarizes the essential features of the tensor model of diffusion, outlines newer approaches to overcoming the limitations of the tensor, and provides normal and clinical examples of white matter anatomy derived using diffusion tensor imaging and more sophisticated high angular resolution diffusion imaging methods. Diffusion MR imaging is a powerful adjunct to techniques for studying brain function.     

Clinicopathologic correlations of cranial magnetic resonance imaging of periventricular white matter

We studied clinical, imaging, and autopsy data on 7 patients who underwent magnetic resonance imaging (MRI) during life. Small periventricular zones of increased T2 signal corresponded to a periventricular cap consisting of subependymal glial accumulations, with some loss of the ependymal lining, and a surrounding pale-staining area of finely textured myelin and axons with an altered glial pattern. The fine-fiber zone is identifiable anatomically as the subcallosal fasciculus. This histologic pattern of subependymal glial accumulations and fine fibers is normal and is often associated with fibrotic small blood vessels. More extensive subcortical MRI changes corresponded, in 1 case, to multiple sclerosis, and in another to subcortical arteriosclerotic encephalopathy (Binswanger's disease) with widespread fiber loss and lacunar changes. Wallerian degeneration secondary to infarction occurred in some areas of MRI abnormality.