Alteration of fractional anisotropy and apparent diffusion coefficient in obsessive-compulsive disorder: a diffusion tensor imaging study

BACKGROUND: Abnormalities of fractional anisotropy (FA) have been reported in previous diffusion tensor imaging (DTI) studies in patients with obsessive-compulsive disorder (OCD). However, there are some inconsistencies in the results and the apparent diffusion coefficient (ADC) has not been investigated. The goal of this study was to investigate white matter abnormalities and water diffusivity, as reflected by FA and ADC, using DTI in patients with OCD. METHODS: Fifteen patients with OCD and 15 healthy volunteers underwent DTI. Voxelwise analysis was used to compare FA in white matter and ADC in gray matter/white matter of the two groups. RESULTS: Compared with healthy volunteers, the patients had higher FA in the bilateral semioval center extending to the subinsular white matter; and a higher ADC in the left medial frontal cortex. There were no areas with a significantly lower FA or ADC in patients compared with healthy volunteers. CONCLUSIONS: A significantly higher FA was found in regions associated with the emotion of disgust and a trend for a higher ADC was found in a region associated with the regulation of emotions. These findings suggest that neurocircuits involved in disgust processing may play an important role in the pathophysiology of OCD.     

A voxel-based diffusion tensor imaging study of temporal white matter in patients with schizophrenia

Diffusion tensor imaging (DTI) is a relatively new technique used to detect changes in the anisotropic diffusion of white matter. The study of the disruption of brain connectivity may increase our understanding of cognitive deficits associated with schizophrenia. Here we analysed DTI data in 25 patients with DSM-IV schizophrenia and 24 healthy controls. Two complementary measures, fractional anisotropy (FA) and the apparent diffusion coefficient (ADC), were considered and analysed using voxel-based morphometry. Declarative memory functions were also investigated and their associations with DTI data were analysed. FA was significantly reduced, and the ADC increased in the left sub-gyral white matter of the temporal lobe, which involves the posterior part of the fornix. In the schizophrenic group, females had lower FA than males in the genu of the corpus callosum. Memory functions correlate with FA values. These data provide further evidence for the disruption of white matter connectivity in the left medial temporal lobe, and for its contribution to the declarative memory deficit in schizophrenia.     

Involvement of motor pathways in corticobasal syndrome detected by diffusion tensor tractography

Corticobasal syndrome (CBS) is a progressive parkinsonian disease characterized by cortical and subcortical neuronal loss. Although motor disabilities are a core feature of CBS, the involvement of motor pathways in this condition has not been completely clarified. We used magnetic resonance diffusion tensor imaging (DTI) to study corticospinal and transcallosal motor projections in CBS, and applied fiber tractography to analyze the axonal integrity of white matter projections. Ten patients with CBS were compared with 10 age‐matched healthy controls. Fiber tracts were computed using a Monte‐Carlo simulation approach. Tract‐specific mean values of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were determined. CBS patients showed a reduction of corticospinal tract (CST) fibers on the first affected side with significantly increased ADC and reduced FA values. In the corpus callosum (CC), particularly in the posterior trunk, patients also had significantly reduced fiber projections, with a higher ADC and lower FA than controls. This pattern indicates changes of the white matter integrity in both CST and CC. Thus, magnetic resonance DTI can be used to assess motor pathway involvement in CBS patients. © 2008 Movement Disorder Society     

轻微型肝性脑病磁共振扩散加权成像和扩散张量成像的定量研究

目的通过磁共振扩散加权成像(DWI)和扩散张量成像(DTI)定量分析轻微型肝性脑病(MHE)患者脑功能的异常改变,探讨DWI和DTI在MHE中的应用价值。方法30例肝硬化患者经神经心理测试评分量表测试后,分为MHE组16例和无MHE单纯肝硬化组14例,同时选取15例健康志愿者为正常对照组。所有受试者均行DWI与DTI扫描,选取脑内8个部位为感兴趣区,计算各部位的表观扩散系数(ADC)值和各向异性分数(FA)值。结果18例肝硬化患者于T1WI图像上可见到双侧内囊、苍白球对称性高信号。额叶、枕叶白质、胼胝体膝部、胼胝体压部、内囊前肢、内囊后肢、尾状核头部由正常组、单纯肝硬化组至MHE组ADC值逐渐增加,且MHE组的ADC值较肝硬化组和正常组增加,差异有统计学意义(P<0.05);胼胝体膝部和压部的FA值由正常组、单纯肝硬化组至MHE组逐渐降低,差异有统计学意义(P<0.05)。结论DWI与DTI联合应用能够预测肝硬化患者MHE的进展程度,具有潜在的临床价值。     

磁共振弥散张量成像在脑膜瘤诊断中的应用

目的探讨磁共振弥散张量成像在脑膜瘤诊断中的应用价值。方法选择60例脑膜瘤患者为研究对象,均接受颅脑MRI平扫及DTI检查,测量并比较肿瘤实质区、瘤周水肿区及瘤周白质区ADC值及FA值。结果1I级脑膜瘤中,上皮细胞型比例最高,为40%,其次为纤维型,比例为28%。各病理亚型ADC值比较,血管瘤型最低,为(7.55±1.17)×10-9 mm2/s,微囊型最高,为(14.24±2.43)×10-9 mm2/s。2良性脑膜瘤中,瘤周水肿ADC值最高,与肿瘤实质及瘤周白质比较,差异具有统计学意义(P0.05)。瘤周白质FA值最高,显著高于肿瘤实质及瘤周水肿,差异具有统计学意义(P0.05)。恶性脑膜瘤中,瘤周水肿ADC值最高,与肿瘤实质及瘤周白质比较,差异具有统计学意义(P0.05)。瘤周白质FA值最高,显著高于肿瘤实质及瘤周水肿,差异具有统计学意义(P0.05)。良恶性脑膜瘤比较,恶性脑膜瘤肿瘤实质ADC值及瘤周白质FA值均显著低于良性脑膜瘤,差异具有统计学意义(P0.05)。结论 DTI能够显示脑膜瘤实质及瘤周组织特征,可以为其诊断和治疗提高有价值的信息。     

精神分裂症首次发病患者的磁共振弥散张量显像研究

目的探讨从未用过药的精神分裂症首次发病(以下简称首发)患者的重要白质及部分灰质区的磁共振弥散张量显像(DTI)的特点。方法选取9例首发精神分裂症患者(患者组)及9名年龄、性别、受教育程度与患者组相配对的健康者,应用DTI成像技术检测脑额颞交界处、内囊等白质区和颞中回灰质、中央前回、中央后回等灰质区的各向异性(FA)、表观扩散系数(ADC)及双侧海马体积。结果患者组及对照组组内左右两侧兴趣区FA值及ADC值的差异无统计学意义(P>0.05);患者组与对照组各感兴趣区FA值差异无统计学意义(P>0.05),但患者组颞中回灰质(8.655×10-9)、中央前回(7.816×10-9)、中央后回(7.855×10-9)ADC值高于对照组(分别为7.428×10-9,6.921×10-9,7.013×10-9;P=0.049,0.009,0.005);两组内及组间双侧海马体积比较,差异均无统计学意义(P>0.05)。结论首发精神分裂症患者与健康者DTI参数之间没有明显区别。     

弥散张量成像在脑深部肿瘤术前评估中的应用

目的 探讨弥散张量成像(DTI)在脑深部肿瘤术前评估和手术设计中的作用.方法 回顾性分析20例脑深部肿瘤病人的临床资料,利用各向异性分数(FA)图和纤维示踪图(DTT),观察白质纤维束结构、走行及其与肿瘤的毗邻关系,测量病侧白质纤维束及其对应健侧白质纤维束的FA值、弥散系数(ADC)值.结果 白质纤维束单纯推移5例,单纯破坏7例,推移并破坏8例.单纯破坏、推移并破坏者.其病侧与健侧FA值、ADC值比较均有显著差异(P <0.05);而单纯推移者,其病侧与健侧队值、ADC值比较无显著差异(P >0.05).肿瘤全切除15例,次全切除3例,部分切除2例.12例随访6个月-2年,平均1年.正常工作、学习8例,生活自理但未参加工作3例,死亡1例.结论 DTI有助于准确判断肿瘤与周围白质纤维束的毗邻关系,对脑深部肿瘤术前评估和手术设计有重要指导意义.     

Abnormalities of magnetic resonance spectroscopy and diffusion tensor imaging are correlated with executive dysfunction in patients with ischemic leukoaraiosis

Abnormal diffusion tensor imaging (DTI) results have been observed in the periventricular white matter in patients with ischemic leukoaraiosis (ILA). However, the underlying pathological changes and their relationship to cognitive impairments are obscure. In addition, damage in the thalamus, an important structure in the executive function network, has been suggested in ILA, but is poorly understood. Twenty patients with ILA and 20 healthy volunteers with similar ages and educational histories underwent DTI, magnetic resonance spectroscopy (MRS) and a neuropsychological assessment. In patients with ILA, we observed an increased mean diffusivity (MD) and decreased levels of N-acetylaspartate (NAA)/creatine (Cr) in the anterior and posterior periventricular region and the thalamus, as well as decreased fractional anisotropy (FA) in the anterior and posterior periventricular regions. MD and NAA/Cr levels in the anterior and posterior periventricular white matter and NAA/Cr levels in the thalamus were correlated with executive function. DTI and MRS abnormalities were consistent with axonal and/or neuronal loss and dysfunction in the anterior and posterior periventricular white matter and the thalamus. This study demonstrates that DTI and MRS techniques can be used to investigate pathological changes in the anterior and posterior periventricular white matter and the thalamus; these changes may be correlated with executive functional changes in patients with ILA.     

Abnormal anterior cingulum in patients with schizophrenia: a diffusion tensor imaging study

Diffusion tensor imaging (DTI) can non-invasively examine the molecular diffusion of water in vivo and directly reflects the anatomical integrity of neural fibers in white matter. Fractional anisotropy (FA) can be calculated from DTI data, and utilized to evaluate white matter integrity. DTI was performed on 30 patients with schizophrenia and 19 healthy controls, and their FA values were subsequently measured in multiple brain regions. Statistical analyses revealed that FA values were decreased in the anterior cingulum of schizophrenia subjects. There were no significant differences between patients and controls in any other regions. This study supports the hypothesis that schizophrenia is associated with abnormal white matter integrity of the anterior cingulum.     

Corticospinal tract degeneration and possible pathogenesis in ALS evaluated by MR diffusion tensor imaging.

BACKGROUND: MR diffusion tensor imaging (DTI) appears to be a powerful method to investigate the neuronal and axonal fibre distribution in the human brain. Changes in diffusion characteristics of water molecules in the white matter can be estimated as the apparent diffusion coefficient (ADC) and the fractional anisotropy index (FA). OBJECTIVES: To characterize DTI changes at three different levels in the corticospinal tract (CST) (corona radiata, internal capsule and pons) in order to elucidate if pathogenesis of ALS is due to an anterograde or retrograde axonal degeneration. METHODS: We studied eight ALS patients with clinical signs of upper motor neuron involvement. The patients were compared with 11 healthy age-matched controls. RESULTS: ADC was significantly increased in the CST in ALS patients at the level of the internal capsule and also increased in the pons, but without statistical significance. ADC was unchanged at the level of the corona radiata. FA was significantly reduced at the lowest level (pons), only tended to be reduced in the internal capsule, but was also unchanged in the corona radiata. CONCLUSIONS: Segmentation of the CST into three regions supports the hypothesis of a 'dying back' mechanism in ALS and suggests that ADC is a more sensitive measure than FA to detect pathological changes in ALS.     

Quantitative analysis of glioma cell invasion by diffusion tensor imaging

We aimed to quantitatively analyze the invasion of glioma cells by diffusion tensor imaging (DTI). Twenty patients with glioma, who required surgical decompression, were included in this study. Peritumoral edematous regional tissues were harvested for tumor cell counting and cell density analysis to establish standards for degrees of tumor infiltration. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of water molecules in brain in five regions of interest (ROI) were measured by DTI: (i) the glioma region; (ii) peritumoral edematous tissue; (iii) surrounding edematous tissue; (iv) white matter; and (v) contralateral white matter. The correlation between FA and ADC values from different ROI, and degree of tumor infiltration was analysed. FA values tended to increase from the glioma region outwards, and the maximum amplification appeared between peritumoral edematous and surrounding edematous regions. FA values from peritumoral edematous regions were negatively correlated with the degree of glioma infiltration. ADC values increased significantly in the peritumoral edematous region, but changes in other regions were variable. FA values from peritumoral edematous regions should be used as an evaluation index for the invasion of glioma cells.     

Reduced white matter fractional anisotropy and clinical symptoms in schizophrenia: a voxel-based diffusion tensor imaging study

Although not consistently replicated, diffusion tensor imaging (DTI) studies in schizophrenia have revealed lower fractional anisotropy (FA) in various white matter regions, a finding consistent with the disruption of white matter integrity. In this study, we used voxel-based DTI to investigate possible whole-brain differences in the white matter FA values between 58 schizophrenia patients and 58 healthy controls. We also explored the association between FA values and clinical symptoms in schizophrenia. Compared with the controls, the schizophrenia patients showed significant FA reductions in bilateral superior longitudinal fasciculus, bilateral inferior fronto-occipital fasciculus, and genu of right internal capsule. Furthermore, in the patient group, the FA value of the anterior part of the corpus callosum was negatively correlated with the avolition score on the Scale for the Assessment of Negative Symptoms. These findings suggest widespread disruption of white matter integrity in schizophrenia, which could partly explain the severity of negative symptomatology.     

Diffusion tensor imaging abnormalities in focal cortical dysplasia

PURPOSE: Focal cortical dysplasia (FCD) is one of the most common underlying pathologic substrates in patients with medically intractable epilepsy. While magnetic resonance imaging (MRI) evidence of FCD is an important predictor of good surgical outcome, conventional MRI is not sensitive enough to detect all lesions. Previous reports of diffusion tensor imaging (DTI) abnormalities in FCD suggest the potential of DTI in the detection of FCD. The purpose of this study was to study subcortical white matter underlying small lesions of FCD using DTI. METHODS: Five patients with medically intractable epilepsy and FCD were investigated. Diffusion tensor imaging images were acquired (20 contiguous 3 mm thick axial slices) with maps of fractional anisotropy (FA), trace apparent diffusion coefficient (trace/3 ADC), and principal eigenvalues (ADC parallel and ADC perpendicular to white matter tracts) being calculated for each slice. Region of interest analysis was used to compare subcortical white matter ipsilateral and contralateral to the lesion. RESULTS: Three subjects with FCD associated with underlying white matter hyperintensities on T2 weighted MRI were observed to have increased trace/3 ADC, reduced fractional anisotropy and increased perpendicular water diffusivity which was greater than the relative increase in the parallel diffusivity. No DTI abnormalities were identified in two patients with FCD without white matter hyperintensities on conventional T2-weighted MRI. CONCLUSIONS: While DTI abnormalities in FCD with obvious white matter involvement are consistent with micro-structural degradation of the underlying subcortical white matter, DTI changes were not identified in FCD lesions with normal appearing white matter.     

磁共振弥散张量成像在运动功能区星形胶质细胞瘤手术中的运用

目的 探讨磁共振弥散张量成像(DTI)在运动区脑星形胶质细胞瘤恶性程度预测及手术方案制定的临床应用价值.方法 33例运动功能区星形细胞瘤患者,术前进行DTI检查,测量表观弥散系数(ADC值)及各向异性分数(FA值)并重建i维白质纤维束示踪图(DTT图).结果 不同级别星形细胞瘤的肿瘤实质区ADC值及瘤周水肿区FA值存在差异;DTT图可以清楚显示运动区锥体束形态变化及与肿瘤之间的关系,在此基础上指导手术,效果满意.结论 DTI中ADC、FA值可以区别肿瘤组织与正常神经组织,有助于星形细胞瘤分级;DTT图可以优化运动功能区星形细胞瘤切除的手术方案,可最大范围切除肿瘤并有效保护重要白质纤维束.     

Neuroradiological study of a possible progressive multifocal leukoencephalopathy using diffusion tensor imaging and proton magnetic resonance spectroscopy]

We report a possible case of progressive multifocal leukoencephalopathy (PML) that was attempted to evaluate the pathogenesis by a novel brain MRI techniques. A 72-year-old woman had developed subacute visual disturbance, right hemiparesis and sensory disturbance. Laboratory examinations revealed liver dysfunction and pancytopenia due to liver cirrhosis (type C) and preclinical status of multiple myeloma. Thus, this patient had these two underlying diseases, while anti-HIV antibody was negative. She was suspected with PML by detection of JCV-DNA in cerebrospinal fluid using with PCR. MRI showed multifocal T2-high signals in the bilateral parieto-occipital deep white matter, basal ganglia and right cerebellar hemisphere. No gadolinium enhancement was found. On FLAIR and diffusion weighted images (DWI), the lesion showed hyperintensity. The hyperintense areas on DWI showed various pattern on apparent diffusion coefficient (ADC) and fractional anisotropy (FA). In particular white matter changes, the course of FA reflected the clinical course more than ADC. Proton magnetic resonance spectroscopy (1H-MRS) in deep brain white matter showed ratios of reduced N-acetyl aspartate (NAA) and increased choline (Cho) to creatine. 1H-MRS by chemical shift imaging were undergone three times between 4 and 6 months after the onset. The change of these chemical markers correlated with her clinical course. We conclude that the approach of diffusion tensor imaging (DTI) and 1H-MRS are useful for evaluating neuropathologic observations and clinical course.     

Abnormal frontal white matter tracts in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES: Prefrontal white matter has been hypothesized to be integral to the pathophysiology of bipolar disorder. Recent morphometric studies however, have not observed changes in white matter in bipolar patients. We hypothesized that changes in prefrontal function in bipolar disorder, widely reported in the literature, may be related to a loss of white matter tract integrity with a resultant dysconnectivity syndrome. In this study we utilized diffusion tensor imaging (DTI) to examine prefrontal white matter in patients with bipolar disorder. METHODS: Nine patients with bipolar disorder and nine healthy controls were recruited. DTI and localizing anatomic data were acquired, and regions of interest (ROIs) identified in the prefrontal white matter at 15, 20, 25, and 30 mm superior to the anterior commissure (AC). Fractional anisotropy (FA) and trace apparent diffusion coefficient (TADC) were compared by ROI between study groups. RESULTS: The FA of ROIs 25 and 30 mm above the AC was significantly reduced in patients with bipolar disorder; FA of all ROIs showed high-medium to large effect sizes. No significant group differences were identified in TADC. CONCLUSIONS: Our findings suggest that a loss of bundle coherence is present in prefrontal white matter. This loss of coherence may contribute to prefrontal cortical pathology in patients with bipolar disorder.     

Leukoencephalopathy with vanishing white matter: serial MRI of the brain and spinal cord including diffusion tensor imaging

Vanishing white matter disease (VWM) is one of the most frequent inherited childhood white matter disorders. We present the brain and spinal cord disease progression on serial conventional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in a 4-year-old boy. Consecutive MRI examinations demonstrated a progression of the signal abnormalities in the cerebral white matter. Globally, apparent diffusion coefficient (ADC) values as well as axial and radial diffusivity increased over time, while fractional anisotropy (FA) values decreased. Involvement of the cervical posterior spinal tracts and mild global spinal cord atrophy was found. In conclusion, serial MRI and DTI studies may help to better understand the selective injury of the myelin and axons in VWM disease. These data may help in monitoring disease progression. Our data also show that complete neuroimaging work-up in VWM should also include the spinal cord.     

A preliminary report of cerebral white matter microstructural changes associated with adolescent sports concussion acutely and subacutely using diffusion tensor imaging

Diffusion tensor imaging (DTI) has demonstrated its utility in detecting microscopic post-concussion cerebral white matter structural changes, which are not routinely evident on conventional neuroimaging modalities. In this study, we compared 10 adolescents with sports concussion (SC) to 12 orthopedically-injured (OI) individuals within 96 h and three months post injury to 12 typically-developing (TD) participants using DTI and volumetric analyses. In terms of volume, no group differences were noted between SC, OI and TD groups at both 96 h and three months post concussion. Results did not show significant differences between SC, OI, and TD groups for both fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in all regions of interest within 96 h post concussion. However, at three months post-injury, the SC group exhibited significantly lower FA than the TD group in various regions of interest. In terms of ADC, significant group differences between SC and TD groups were found in some regions, with SC group having higher ADC than TD. No group differences for FA and ADC were noted between SC and OI groups at three months post-injury. However, several moderate effect sizes on between-group analyses were noted such that FA was lower and ADC was higher in SC relative to OI. Longitudinally, the SC group demonstrated decreased FA and increased ADC in some areas. The findings highlight the fact that the brain continues to change during the post-injury recovery period, and raises the possibility that adverse changes may result from the neurometabolic cascade that purportedly ensues following SC. DTI may potentially be used to characterize the nature of brain changes that occur following sports-related concussions.     

皮质下缺血性血管性痴呆患者脑白质损害的磁共振弥散张量成像研究

目的:应用磁共振弥散张量成像技术(DTI)观察皮质下缺血性血管性痴呆(SIVD)患者脑白质损害程度,探讨DTI对SIVD白质损害的评估及与阿尔茨海默病(AD)鉴别诊断价值。方法:研究对象分为3组,分别是健康老年人(NC)、皮质下缺血性血管性痴呆(SIVD)患者、AD患者,每组各20例。行常规MR I和DTI扫描后,测定相同感兴趣区(RO I)的各向异性分数(FA)值和表观扩散系数(ADC)值进行比较。结果:SIVD组下额枕束、胼胝体膝部、胼胝体压部、上纵束等部位FA值下降,ADC值升高,与NC、AD组比较差异有统计学意义(P<0.05)。与NC组比较,AD组前额叶、颞叶、海马、下额枕束、胼胝体膝部和扣带束等部位FA值降低,颞叶、海马等部位ADC值升高,两组差异具有显著性(P<0.05);结论:DTI可以用来评估痴呆患者白质损害的程度,SIVD患者以下额枕束、胼胝体膝部、胼胝体压部、上纵束等部位受累为主,可作为与AD鉴别的客观指标。     

Alterations of white matter tracts following neurotoxic hippocampal lesions in macaque monkeys: A diffusion tensor imaging study

Diffusion tensor imaging (DTI) is a valuable tool for assessing presumptive white matter alterations in human disease and animal models. The current study used DTI to examine the effects of selective neurotoxic lesions of the hippocampus on major white matter tracts and anatomically related brain regions in macaque monkeys. Two years postlesion, structural MRI, and DTI sequences were acquired for each subject. Volumetric assessment revealed a substantial reduction in the size of the hippocampus in experimental subjects, averaging 72% relative to controls, without apparent damage to adjacent regions. DTI images were processed to yield measures of fractional anisotropy (FA), apparent diffusion coefficient (ADC), parallel diffusivity (lADC), and perpendicular diffusivity (tADC), as well as directional color maps. To evaluate potential changes in major projection systems, a region of interest (ROI) analysis was conducted including the corpus callosum, fornix, temporal stem, cingulum bundle, ventromedial prefrontal white matter, and optic radiations. Lesion‐related abnormalities in the integrity of the fiber tracts examined were limited to known hippocampal circuitry, including the fornix and ventromedial prefrontal white matter. These findings are consistent with the notion that hippocampal damage results in altered interactions with multiple memory‐related brain regions, including portions of the prefrontal cortex. © 2010 Wiley‐Liss, Inc.