Diffusion tensor imaging in fixed brain tissue at 7.0 T

The purpose of this work is to assess the feasibility of performing quantitative in vitro brain tissue diffusion tensor imaging (DTI) measurements and to examine their comparability to in vivo measurements. DTI of fixed tissue at high field strength is potentially a very valuable investigative tool as very high spatial resolution can be achieved. DTI was applied to human and mouse brain fixed tissue samples as well as in vivo measurements of the mouse brain. T(1) and T(2) relaxography of the fixed tissue samples was also performed to provide further characterization of the tissue. All experiments were performed at 7 T. The fractional anisotropy (FA) of the human fixed brain tissue samples is found to be higher in the corpus callosum than in the occipital white matter region, consistent with in vivo measurements reported in the literature. Our FA measurements of the corpus callosum of a mouse brain are also found to be the same both in vitro and in vivo. This preliminary work supports the use of DTI in both fixed human and fixed animal brain tissue as a valid investigative tool. With the increased availability of brain banks in different brain disorders, DTI in fixed tissue may prove to be a very useful method for the study of white matter abnormalities.     

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。     

Quantification of cerebral edema on diffusion tensor imaging in acute-on-chronic liver failure

Cerebral edema is a major complication of acute liver failure but may also be seen in other forms of liver failure such as acute-on-chronic liver failure (ACLF) and chronic liver failure (CLF). ACLF develops in patients with previously well-compensated chronic liver disease following acute hepatitis A or E superimposed on underlying liver cirrhosis. The aim of this study was to detect the occurrence, and determine the nature, of cerebral edema in patients with the defined subset of ACLF using diffusion tensor imaging (DTI) metrics. Twenty-three patients with ACLF were studied and compared with 15 healthy controls and 15 patients with CLF. DTI metrics including fractional anisotropy (FA), mean diffusivity (MD), linear anisotropy (CL), planar anisotropy (CP), and spherical isotropy (CS) were calculated by selecting regions of interest in the white matter and deep grey matter of the brain. Significantly decreased FA and increased CS were observed in the anterior limb (ALIC) and posterior limb (PLIC) of the internal capsule and frontal white matter (P<0.05) in patients with different grades (1-4) of ACLF when compared with healthy controls. No significant changes in MD and CP were seen in any brain region. However, significantly decreased CL was observed in the PLIC, caudate nuclei and putamen. In patients with CLF, significantly decreased FA with increased CS in the ALIC and PLIC along with significantly increased MD in the ALIC and caudate nuclei were observed. The presence of significantly decreased FA and CL and increased CS along with no significant change in MD and CP suggests the presence of both intracellular and extracellular components of cerebral edema in patients with ACLF.     

Accelerated white matter aging in schizophrenia: role of white matter blood perfusion

Elevated rate of age-related decline in white matter integrity, indexed by fractional anisotropy (FA) from diffusion tensor imaging, was reported in patients with schizophrenia. Its etiology is unknown. We hypothesized that a decline of blood perfusion to the white matter may underlie the accelerated age-related reduction in FA in schizophrenia. Resting white matter perfusion and FA were collected using pseudo-continuous arterial spin labeling and high-angular-resolution diffusion tensor imaging, respectively, in 50 schizophrenia patients and 70 controls (age = 18–63 years). Main outcome measures were the diagnosis-by-age interaction on whole-brain white matter perfusion, and FA. Significant age-related decline in brain white matter perfusion and FA were present in both groups. Age-by-diagnosis interaction was significant for FA (p < 0.001) but not white matter perfusion. Age-by-diagnosis interaction for FA values remained significant even after accounting for age-related decline in perfusion. Therefore, we replicated the finding of an increased rate of age-related white matter FA decline in schizophrenia and observed a significant age-related decline in white matter blood perfusion, although the latter did not contribute to the accelerated age-related decline in FA. The results suggest that factors other than reduced perfusion account for the accelerated age-related decline in white matter integrity in schizophrenia.     

Diffusion tensor imaging of two unrelated Chinese men with hereditary spastic paraplegia associated with thin corpus callosum

Hereditary spastic paraplegia (HSP) associated with thin corpus callosum is a rare autosomal recessive neurodegenerative disorder characterized by an abnormally thin corpus callosum, normal motor development, slowly progressive spastic paraparesis and cognitive deterioration. To investigate and localize abnormalities in the brains of two Chinese patients with HSP-TCC, with mutations in the spatacsin gene. Diffusion tensor imaging (DTI) was used to determine the mean diffusion (MD) and fractional anisotropy (FA) in the brains of the patients in comparison to 20 healthy subjects. Voxel-based analysis (VBA) of both the diffusion and anisotropy values were performed using statistical parametric mapping (SPM). Significant changes with MD increase and FA reduction were found in the already known lesions including the corpus callosum, cerebellum and thalamus. In addition, changes were also found in regions that appear to be normal in conventional MRI, such as the brain stem, internal capsule, cingulum and subcortical white matter including superior longitudinal fascicle and inferior longitudinal fascicle. Neither increase in FA nor reduction in MD was detected in the brain. Our study provides clear in vivo MR imaging evidence of a more widespread brain involvement of HSP-TCC. MD is more sensitive than FA in detecting lesions in thalamus and subcortical white matter, suggesting that MD may be a better marker of the disease progression.     

Diffusion tensor and magnetization transfer MRI measurements of periventricular white matter hyperintensities in old age

Regions of diffuse periventricular white matter hyperintensities (PVWMH) are a common finding on T(2)-weighted MRI scans of older subjects, but their aetiology remains unclear. The aim of this study was to characterize differences in water diffusion and magnetization transfer MRI parameters between macroscopically normal-appearing white matter (NAWM) and PVWMH in a cohort of normal older subjects. Forty-two non-demented 83-year olds underwent structural, diffusion tensor and magnetization transfer MRI. Mean diffusivity (), fractional anisotropy (FA), axial (lambda(ax)) and radial (lambda(rad)) diffusivity, and magnetization transfer ratio (MTR) were measured in both NAWM and PVWMH in frontal and parieto-occipital white matter, and centrum semiovale. For all three regions, PVWMH had greater , lambda(ax) and lambda(rad) than NAWM, while FA and MTR were significantly reduced compared with normal tissue (p<0.01). For PVWMH, MTR was significantly correlated (Spearman's rho in the range -0.93 to 0.70; p<0.01) with , FA, lambda(ax) and lambda(rad) in all three regions. Conversely, for NAWM, the only significant correlation between MTR and a water diffusion parameter was for lambda(rad) in parieto-occipital white matter (rho=-0.40; p<0.05), with all other correlations close to the rho=0 level. These data indicate that in normal white matter, characterized by structurally coherent cell membranes, the degree of water molecule diffusion and myelination are held within relatively tight limits. However, within PVWMH, MTR correlates strongly with water diffusion parameters probably because of the pathologically associated neuronal loss, demyelination and gliosis.     

The role of diffusion tensor imaging in the evaluation of ischemic brain injury - a review

Water diffusion in brain tissue is affected by the presence of barriers to translational motion such as cell membranes and myelin fibers. The measured water apparent diffusion coefficient (ADC) value is therefore frequently anisotropic and varies depending upon the orientation of restricting barriers (such as white matter tracts) relative to the diffusion-sensitive-gradient direction. Anisotropic water diffusion can be specified using indices of diffusion anisotropy [e.g. standard deviation of the individual ADC values, fractional anisotropy (FA), lattice index (LI)], which are derived from measurements of the full diffusion tensor. The rotationally invariant nature of particular diffusion anisotropy indices (e.g. FA, LI) allows orientation-independent comparisons of these parameters between different subjects. Pathophysiological processes (such as cerebral ischemia) that modify the integrity of the tissue microstructure result in significant alterations in tissue anisotropy and make this metric a useful endpoint for characterizing the temporal evolution of the disease. Diffusion-tensor imaging (DTI) studies of both experimental and human stroke suggest that DTI may provide additional information about the evolution of the disease that is not available from diffusion-weighted MRI (DWI) alone. Acute reductions in the average diffusivity [ = (lambda(1) + lambda(2) + lambda(3))/3 where lambda(1), lambda(2), and lambda(3) are the eigenvalues of the diffusion tensor] following the onset of cerebral ischemia are often accompanied by increases in diffusion anisotropy. In the transition from acute to sub-acute and chronic stroke, renormalizes and subsequently increases whereas diffusion anisotropy measures (e.g. FA) decline and remained reduced in chronic infarcts. Overall isotropic ADC changes during infarct evolution have been observed to be greater in white matter (WM) than in gray matter (GM) lesions (although there have been conflicting reports on this issue) and GM lesions tend to renormalize prior to WM lesions as the infarct evolves. Ischemic WM exhibits a significant decrease in diffusion anisotropy (relative to normal WM) during ischemic evolution whereas that of ischemic GM remains statistically unchanged. Furthermore, the percentage decrease in ischemic WM is largely determined by reductions in lambda(1), the eigenvalue that coincides with the long axis of the WM fiber tract. Variations in unidirectional ADC or over the ischemic time course limit the usefulness of this parameter alone as a predictor of ischemic injury. Consequently, ADC information has been combined with that of other MR parameters (including DTI) to unambiguously stage and predict ischemic brain injury over its entire temporal evolution. Combined and diffusion anisotropy measurements have identified three phases of diffusion abnormality: (1) reduced and elevated anisotropy; (2) reduced and reduced anisotropy; and (3) elevated and reduced anisotropy. However, variations in the differential patterns of and diffusion anisotropy evolution have been observed by a number of investigators and more work is needed to clarify the role of these measurements in characterizing the severity of the ischemic insult as well as the potential outcome in response to the initial ischemic injury. The use of DTI, in combination with more sophisticated analysis methods for performing multiparametric segmentation, such as multispectral analysis, may enhance the use of MRI for accurate diagnosis and prognosis of stroke. Furthermore, these techniques may also play an important role in the clinical evaluation of new stroke treatments.     

Neurodevelopment of C57B/L6 mouse brain assessed by in vivo diffusion tensor imaging

Heterogeneous spatiotemporal patterns of C57B/L6 murine brain maturation during the first 7 weeks after birth (i.e. P15 to P45) were assessed in vivo by diffusion tensor imaging (DTI) at 9.4 T. Maps of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were used to assess developmental changes. Because directionally encoded color (DEC) maps provide an efficient and straightforward way to visualize anisotropy direction, they were used to highlight the orientation-dominant anisotropic tissues. In the corpus callosum, the increases in FA (approximately 0.4 to approximately 0.6 from P15 to P45) were primarily dominant in the medial-lateral direction, whereas the ADC decreased slightly (approximately 0.8 x 10(-3) to approximately 0.5 x 10(-3) mm(2)/s from P15 to P45). Similar increases in FA (approximately 0.3 to approximately 0.4 from P15 to P45) and decreases in ADC (approximately 0.8 x 10(-3) to approximately 0.5 x 10(-3) mm(2)/s from P15 to P45) were found in the cingulate, but these anisotropic changes were dominant in the anterior-posterior direction. In the caudate putamen, there were significant FA increases (approximately 0.1 to approximately 0.2 from P15 to P45) dominant in the dorsal-ventral and anterior-posterior directions, whereas the ADC increased rapidly early in development (approximately 0.3 x 10(-3) to approximately 0.7 x 10(-3) mm(2)/s from P15 to P17). There were no significant changes in tissue anisotropy in the somatosensory regions (whisker, forelimb), but the ADC decreased slightly (approximately 0.7 x 10(-3) to approximately 0.5 x 10(-3) mm(2)/s from P15 to P45). Although the major differences in DEC values were mainly observed in white matter pathways, other cortical and subcortical regions showed some potential morphological changes that were consistent with classical histological findings. In summary, these results show that high-resolution DTI at high magnetic fields allows detection and quantification of brain structures throughout normal development in C57B/L6 mice in vivo.     

Postmortem delay does not change regional diffusion anisotropy characteristics in mouse spinal cord white matter

It has been demonstrated previously that water diffusion anisotropy in vivo is equivalent to that observed ex vivo after perfusion fixation in the mouse brain. This finding supports the practice of ex vivo diffusion tensor imaging (DTI) measurement on perfusion-fixed tissues. However, the validity of extrapolating ex vivo DTI measurements from immersion-fixed autopsy specimens to the in vivo state is questionable because of variable postmortem delays often encountered before fixation. In this study, we investigated the effect of postmortem delay on the water diffusion anisotropy of ventrolateral spinal cord white matter from mice. Mouse spinal cords, each from the same animal, were examined using DTI in vivo, in situ after death before fixation, and ex vivo immersion fixed 10 h after death. Our results suggest that diffusion anisotropy in mouse spinal cord is preserved up to 10 h after death. Regional characteristics of diffusion anisotropy in mouse spinal cord white matter are equivalent in vivo, in situ after death (up to 10 h before fixation), and ex vivo 15 weeks after immersion fixation.     

White matter changes in mild cognitive impairment and AD: A diffusion tensor imaging study

Diffusion tensor imaging (DTI) can detect, in vivo, the directionality of molecular diffusion and estimate the microstructural integrity of white matter (WM) tracts. In this study, we examined WM changes in patients with Alzheimer's disease (AD) and in subjects with amnestic mild cognitive impairment (MCI) who are at greater risk for developing AD. A DTI index of WM integrity, fractional anisotropy (FA), was calculated in 14 patients with probable mild AD, 14 participants with MCI and 21 elderly healthy controls (NC). Voxel-by-voxel comparisons showed significant regional reductions of FA in participants with MCI and AD compared to controls in multiple posterior white matter regions. Moreover, there was substantial overlap of locations of regional decrease in FA in the MCI and AD groups. These data demonstrate that white matter changes occur in MCI, prior to the development of dementia.     

Diffusion Tensor Imaging (DTI) Findings Following Pediatric Non-Penetrating TBI: A Meta-Analysis

This study meta-analyzed research examining Diffusion Tensor Imaging following pediatric non-penetrating traumatic brain injury to identify the location and extent of white matter changes. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) data from 20 studies were analyzed. FA increased and ADC decreased in most white matter tracts in the short-term (moderate-to-large effects), and FA decreased and ADC increased in the medium- to long-term (moderate-to-very-large effects). Whole brain (short-term), cerebellum and corpus callosum (medium- to long-term) FA values have diagnostic potential, but the impact of age/developmental stage and injury severity on FA/ADC, and the predictive value, is unclear.     

Aging in the CNS: comparison of gray/white matter volume and diffusion tensor data

This study investigated the global and regional effects of aging on brain volume, mean diffusivity (MD), and fractional anisotropy (FA) in 73 normal female subjects using voxel-based analysis. On a global scale, gray matter volume and FA were negatively correlated, whereas MD was positively correlated with age. Voxel-wise analyses showed brain volume and FA were negatively correlated predominantly in anterior structures, whereas MD was positively correlated in the cortical gray matter and periventricular white matter. Volume preservation was observed in the cingulate gyrus and subjacent white matter. FA increase was observed in the putamen. Voxel-based direct comparisons of volume and diffusion properties showed FA was more strongly negatively correlated in the fronto-temporal white matter, compared with volume and MD. Stronger positive correlation of MD was observed in the thalamus, caudate nucleus, and midbrain and stronger negative correlation of brain volume was observed in the frontal lobe and basal ganglia, compared with the other. These results indicate that diffusion properties and brain volume are complementary markers to the effects of aging.     

Grey and white matter GABA level differences in the human brain using two-dimensional, J-resolved spectroscopic imaging

A novel, two-dimensional, J-resolved chemical-shift imaging sequence was used to collect gamma-aminobutyric acid (GABA) spectroscopic imaging data on six healthy subjects at 4 T. Using image segmentation and a linear-regression analysis relating brain GABA level to tissue-type, a consistent and significant (n = 6, p < 0.01) elevation of mean GABA levels was measured in the cortical grey matter (0.96 +/- 0.24 mm) compared with white matter (0.44 +/- 0.16 mm) across all six subjects. The results suggest an approximately two-fold elevation of GABA levels in cortical grey matter compared with white matter in vivo. Our findings are consistent with ex vivo studies in the literature of both animal and human brain and demonstrate the significant potential of this technique for detecting and quantifying tissue-specific neurochemical pathology in vivo.     

The role of early life stress in development of the anterior limb of the internal capsule in nonhuman primates

Deep brain stimulation (DBS) of the anterior limb of the internal capsule (ALIC) may be effective in treating depression. Parental verbal abuse has been linked to decreased fractional anisotropy (FA) of white matter and reduced FA correlated with depression and anxiety scores. Utilizing a nonhuman primate model of mood and anxiety disorders following disrupted mother–infant attachment, we examined whether adverse rearing conditions lead to white matter impairment of the ALIC. We examined white matter integrity using Diffusion Tensor Imaging (DTI) on a 3T-MRI. Twenty-one adult male Bonnet macaques participated in this study: 12 were reared under adverse [variable foraging demand (VFD)] conditions whereas 9 were reared under normative conditions. We examined ALIC, posterior limb of the internal capsule (PLIC) and occipital white matter. VFD rearing was associated with significant reductions in FA in the ALIC with no changes evident in the PLIC or occipital cortex white matter. Adverse rearing in monkeys persistently impaired frontal white matter tract integrity, a novel substrate for understanding affective susceptibility.     

Rest-activity rhythms and white matter microstructure across the lifespan

Study ObjectivesThe purpose of this study was to examine how rest-activity (RA) rhythm stability may be associated with white matter microstructure across the lifespan in healthy adults free of significant cardiovascular risk.MethodsWe analyzed multi-shell diffusion tensor images from 103 healthy young and older adults using tract-based spatial statistics (TBSS) to examine relationships between white matter microstructure and RA rhythm stability. RA measures were computed using both cosinor and non-parametric methods derived from 7 days of actigraphy data. Fractional anisotropy (FA) and mean diffusivity (MD) were examined in this analysis. Because prior studies have suggested that the corpus callosum (CC) is sensitive to sleep physiology and RA rhythms, we also conducted a focused region of interest analysis on the CC.ResultsGreater rest-activity rhythm stability was associated with greater FA across both young and older adults, primarily in the CC and anterior corona radiata. This effect was not moderated by age group. While RA measures were associated with sleep metrics, RA rhythm measures uniquely accounted for the variance in white matter integrity.ConclusionsThis study strengthens existing evidence for a relationship between brain white matter structure and RA rhythm stability in the absence of health risk factors. While there are differences in RA stability between age groups, the relationship with brain white matter was present across both young and older adults. RA rhythms may be a useful biomarker of brain health across both periods of adult development.     

In vivo brain viscoelastic properties measured by magnetic resonance elastography

Magnetic resonance elastography (MRE) is a non-invasive imaging technique used to visualise and quantify mechanical properties of tissue, providing information beyond what can be currently achieved with standard MR sequences and could, for instance, provide new insight into pathological processes in the brain. This study uses the MRE technique at 3 T to extract the complex shear modulus for in vivo brain tissue utilizing a full three-dimensional approach to reconstruction, removing contributions of the dilatational wave by application of the curl operator. A calibrated phantom is used to benchmark the MRE measurements, and in vivo results are presented for healthy volunteers. The results provide data for in vivo brain storage modulus (G'), finding grey matter (3.1 kPa) to be significantly stiffer than white matter (2.7 kPa). The first in vivo loss modulus (G') measurements show no significant difference between grey matter (2.5 kPa) and white matter (2.5 kPa).     

Proton MRS of early post-natal mouse brain modifications in vivo

NMR provides a non-invasive tool for the phenotypic characterisation of mouse models. The aim of the present study was to apply reliable in vivo MRS techniques for non-invasive investigations of brain development in normal and transgenic mice, by monitoring metabolite concentrations in different brain regions. The conditions of anaesthesia, immobilisation and respiratory monitoring were optimized to carry out in vivo MRS studies in young mice. All the experiments were performed in normal mice, at 9.4 T, applying a point-resolved spectroscopy (PRESS) sequence (TR = 2,000 ms; TE = 130 ms). We obtained reproducible in vivo (1)H NMR spectra of wild-type mouse brains as early as post-natal day 5, which allowed us to follow brain maturation variations from post-natal days 5 to 21. The survival rate of animals was between 66 and 90% at post-natal days 5 and 21, respectively. Developmental changes of metabolite concentrations were measured in three brain regions: the thalamus, a region rich in cell bodies, the olfactory bulb, rich in fibre tracts actively myelinated during brain maturation, and the cerebellum. The voxel size varied from 2 to 8 microL according to the size of the brain structure analysed. The absolute concentrations of the total creatine, taurine, total choline, N-acetylaspartate and of the glutamate/glutamine pool were determined from (1)H NMR spectra obtained in the different brain regions at post-natal day 5, 10, 15 and 21. Variations observed during brain development were in accordance with those previously reported in mice using ex vivo MRS studies, and also in rats and humans in vivo. Possibilities of longitudinal MRS analysis in maturing mice brains provide new perspectives to characterise better the tremendous number of transgenic mutant mice generated with the aim of decrypting the complexity of brain development and neurodegenerative diseases but also to follow the impact of environmental and therapeutic factors.     

Arterial and microvascular supply of cerebral hemispheres in the nude mouse revealed using corrosion casting and scanning electron microscopy

Morphological analyses of cerebral vascularization are not only important for the characterization of the anatomical and physiological relationships between vascular and nervous tissue, but also required to understand structural modifications that occur in many pathological conditions affecting the brain. The aim of this study was to generate a three‐dimensional vascular map of the cerebral hemispheres in the nude mouse brain, a widely used animal model for studying tumour biology. We used the corrosion casting (CC) technique to isolate blood vessels from 30 nude mouse brains. All casts were analysed using scanning electron microscopy (SEM), which generated quantitative data regarding vessel length and diameter as well as inter‐vascular and inter‐branching distances. We identified three different topographical regions: (i) the cortical region, characterized by a superficial wide sheet of vessels giving rise to terminal perforant vessels that penetrate the grey matter; (ii) the inner part of the grey matter, in which dense capillary nets form many flake‐like structures extending towards the grey–white matter boundary, where perforant vessels finally change direction and form a well‐defined vascular sheet; and (iii) the white matter layer, characterized by a more disorganized vascular architecture. In this study, we demonstrate the accuracy of the CC‐SEM method in revealing the 3D‐topographical organization of the vascular network of the normal nude mouse brain. These baseline data will serve as a reference for future anatomical investigations of pathological alterations, such as tumour infiltrations, using the nude mouse model.     

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。     

White Matter Integrity Following Traumatic Brain Injury: The Association with Severity of Injury and Cognitive Functioning

Traumatic brain injury (TBI) frequently results in impairments of memory, speed of information processing, and executive functions that may persist over many years. Diffuse axonal injury is one of the key pathologies following TBI, causing cognitive impairments due to the disruption of cortical white matter pathways. The current study examined the association between injury severity, cognition, and fractional anisotropy (FA) following TBI. Two diffusion tensor imaging techniques—region-of-interest tractography and tract-based spatial statistics—were used to assess the FA of white matter tracts. This study examined the comparability of these two approaches as they relate to injury severity and cognitive performance. Sixty-eight participants with mild-to-severe TBI, and 25 healthy controls, underwent diffusion tensor imaging analysis. A subsample of 36 individuals with TBI also completed cognitive assessment. Results showed reduction in FA values for those with moderate and severe TBI, compared to controls and individuals with mild TBI. Although FA tended to be lower for individuals with mild TBI no significant differences were found compared to controls. Information processing speed and executive abilities were most strongly associated with the FA of white matter tracts. The results highlight similarities and differences between region-of-interest tractography and tract-based spatial statistics approaches, and suggest that they may be used together to explore pathology following TBI.