应用弥散张量成像实现神经纤维追踪的方法*☆

背景：目前的神经纤维追踪方法众说纷纭,不同的追踪方法往往对数据的要求比较严格,格式比较单一,并且在特定的条件下,才能进行纤维追踪,但都没有统一可执行标准。因此需要研究一种简便通用的神经纤维追踪处理方法。 目的：提出一种简便通用,并且可以在不同的数据采集方法情况下,转变为固定的数据采集格式的弥散张量神经纤维追踪方法。 方法：首先采用MRIcro软件在原始DTI图像上,找出梯度因子b值,组成梯度方向文件并把DICOM原始文件软件转换成Analyze格式文件,然后利用SPM软件对格式文件标准化,最后采用DTI-track软件进行神经纤维追踪处理。 结果与结论：通过对DTI图像进行处理,证明该方法能有效的得出扩散梯度因子b值文件,并且能把不同的DTI数据转变为统一的格式进行DTI处理,得到预期的DTI纤维追踪图像,为DTI研究提供了一个简便有效的具体实现方法。 关键词：弥散张量成像;纤维追踪;扩散梯度因子;神经纤维;功能磁共振     

弥散张量纤维束成像在脑深部肿瘤手术中的应用

目的探讨弥散张量纤维束成像（DTT）在指导脑深部肿瘤手术中的价值。方法对25例脑深部肿瘤病人（实验组）利用DTT对肿瘤与毗邻纤维束的位置关系及纤维束状态进行评估,结合常规MRI设计手术入路及切除范围;另24例病人（对照组）仅根据常规MRI设计手术人路及切除范围。对两组肿瘤的全切除率及术后致残率进行对比分析。结果实验组中,肿瘤全切除18例,部分切除7例;术后出现神经功能缺损或障碍加重3例。对照组中,肿瘤全切除13例,部分切除11例;术后出现神经功能缺损或障碍加重11例。两组肿瘤全切除率差异无统计学意义（P〉0．05）,而对照组术后致残率明显高于实验组（P〈0．01）。结论DTT能清楚显示脑深部肿瘤与毗邻纤维束的位置关系及纤维束被侵犯的程度,有助于设计合理手术入路及切除范围．对最大程度切除肿瘤同时减少术后功能缺损具有重要作用。     

Cingulate fasciculus integrity disruption in schizophrenia: a magnetic resonance diffusion tensor imaging study.

Evidence suggests that a disruption in limbic system network integrity and, in particular, the cingulate gyrus (CG), may play a role in the pathophysiology of schizophrenia; however, the cingulum bundle (CB), the white matter tract furnishing both input and output to CG, and the most prominent white matter fiber tract in the limbic system, has not been evaluated in schizophrenia using the new technology of diffusion tensor imaging (DTI).We used line scan DTI to evaluate diffusion in the CB in 16 male schizophrenia patients and 18 male control subjects, group-matched for age, parental socioeconomic status, and handedness. We acquired 4-mm-thick coronal slices through the entire brain. Maps of fractional anisotropy (FA) were generated to quantify diffusion within the left and right CB on eight slices that included the central portion of the CB.Results showed group differences, bilaterally, in area and mean FA for CB, where patients showed smaller area and less anisotropy than controls. For patients, decreased left CB correlated significantly with attention and working memory measures as assessed by the Wisconsin Card Sorting Test.These data provide strong evidence for CB disruptions in schizophrenia, which may be related to disease-related attention and working memory abnormalities.     

Diffusion tensor imaging: background, potential, and utility in psychiatric research.

Diffusion tensor imaging is a variation of magnetic resonance imaging that measures the diffusion of water in tissues. This can help measure and quantify a tissue's orientation and structure, making it an ideal tool for examining cerebral white matter and neural fiber tracts. It is only beginning to be utilized in psychiatric research. This article reviews the theory behind diffusion tensor imaging, its potential to map fiber tracts in the brain, and its recent use in psychiatric research.     

磁共振弥散张量成像技术在神经外科疾病的应用进展

磁共振弥散张量成像(MR-DTI)可以无创地测量体内水的平移运动,提供关于其在不同组织中的各向异性的信息;在组织内水分子进行自由热运动时的各向异性特点进行成像,可以观察到神经纤维束损伤后的定性及定量的变化,对神经纤维束损伤后肢体功能恢复做出比较客观的预后评估。近些年来DTI已广泛应用于神经外科疾病,对疾病的诊断与鉴别诊断、肿瘤定性与分级、降低手术风险、评估术中切除和预后等方面具有重要意义。本文就DTI在神经外科疾病的临床应用做一综述。     

Diffusion tensor imaging fiber tracking with reliable tracking orientation and flexible step size

We propose a method of reliable tracking orientation and flexible step size fiber tracking. A new directional strategy was defined to select one optimal tracking orientation from each directional set, which was based on the single-tensor model and the two-tensor model. The directional set of planar voxels contained three tracking directions: two from the two-tensor model and one from the single- tensor model. The directional set of linear voxels contained only one principal vector. In addition, a flexible step size, rather than fixable step sizes, was implemented to improve the accuracy of fiber tracking. We used two sets of human data to assess the performance of our method; one was from a healthy volunteer and the other from a patient with low-grade glioma. Results verified that our method was superior to the single-tensor Fiber Assignment by Continuous Tracking and the two-tensor eXtended Streamline Tractography for showing detailed images of fiber bundles.     

应用弥散张量成像及纤维束示踪重建锥体束可重复性的定量研究

目的对应用弥散张量成像及纤维束示踪技术进行锥体束重建的可重复性进行研究。方法随机选取20例接受术中MRI及导航辅助切除颅内肿瘤的患者作为研究对象,分别应用两种不同的感兴趣区(ROI)选择对正常一侧锥体束进行重建,每种方法重复3次。针对同一方法不同次重建结果之间的一致性以及两种方法之间重建结果的一致性进行评估,计算重复性系数к。两种重建方法的主要不同是起始ROI的不同。第一种方法的起始ROI包含一侧半卵圆区白质。第二种方法起始ROI放置在脑干。结果同一方法的不同次重建结果一致性:方法一的к值为0.65715～0.81239,平均0.73616±0.04209。方法二的к值为0.58368～0.86336,平均0.76622±0.0712;二者к值无显著差别(P0.05)。方法一与方法二重建结果的к值为0.31508～0.67464,平均0.46962±0.07817,与前二组к值差异显著(P0.05)。方法一重建锥体束体积为(11.88505±2.06821)cm3,方法二重建锥体束体积为(7.02245±1.75883)cm3。二者差异显著(P0.05)。结论两种方法的不同次重建结果之间均能达到基本一致(к:0.61-0.8),而两种方法之间只能达到中等的一致(к:0.41-0.6)。方法一重建锥体束范围明显大于方法二,更接近锥体束的实际形态。     

运用磁共振弥散张量成像观察显微血管减压术后三叉神经的结构变化

目的：利用磁共振弥散张量成像（DTI）序列,观察显微血管减压术（MVD）后,三叉神经痛（TN）患者三叉神经的微观结构改变。方法9例原发性 TN 患者术前及术后行 DTI 扫描,测算两侧三叉神经向异性分数（FA）、平均弥散率（MD）、轴向弥散率（AD）、垂直弥散率（RD）和两侧各弥散参数差值比。按手术疗效分为治愈和未治愈两组,分析两组患者在手术前后,两侧三叉神经各 DTI 参数及两侧间各弥散参数差值比的变化。结果男性6例,女性3例;平均年龄52．1岁,平均病程5．1年。于术后第一次复查（平均12．3个月）时行 DTI ,术后疗效随访平均66个月。治愈组6例,均有明显的血管压迫,三叉神经有受压变形;未治愈组3例,2例有血管压迫,1例患者仅有严重的蛛网膜粘连而无血管压迫。治愈组术前患侧明显下降的 FA 值及明显上升的 MD 、RD 值,术后复查时均恢复。而未治愈组的各弥散参数及差值比则在手术前后无明显变化。结论 MVD 术后疼痛消失的患者,患侧三叉神经的脱髓鞘变恢复正常。然而术后疼痛仍然存在的患者,神经的脱髓鞘变依然存在。三叉神经的脱髓鞘变与 TN 关系密切。     

White matter abnormalities in bipolar disorder and schizophrenia detected using diffusion tensor magnetic resonance imaging

Objectives:  Strong qualitative and quantitative evidence exists of white matter abnormalities in both schizophrenia and bipolar disorder (BD). Diffusion tensor imaging (DTI) studies suggest altered connectivity in both disorders. We aim to address the diagnostic specificity of white matter abnormalities in these disorders.
Methods:  DTI was used to assess white matter integrity in clinically stable patients with familial BD (n = 42) and familial schizophrenia (n = 28), and in controls (n = 38). Differences in fractional anisotropy (FA) were measured using voxel-based morphometry and automated region of interest analysis.
Results:  Reduced FA was found in the anterior limb of the internal capsule (ALIC), anterior thalamic radiation (ATR), and in the region of the uncinate fasciculus in patients with BD and those with schizophrenia compared with controls. A direct comparison between patient groups found no significant differences in these regions. None of the findings were associated with psychotropic medication.
Conclusions:  Reduced integrity of the ALIC, uncinate fasciculus, and ATR regions is common to both schizophrenia and BD. These results imply an overlap in white matter pathology, possibly relating to risk factors common to both disorders.     

三叉神经痛的磁共振扩散张量成像研究

目的 研究血管压迫三叉神经桥池段的扩散张量成像(DTI)表现及临床应用价值.方法 对60例经手术证实的因责任血管压迫引起三叉神经痛(TN)患者(TN组)和50例健康志愿者(对照组)行常规MRI和横轴面DTI成像,测量其表观扩散系数(ADC)值、部分各向异性分数(FA)值. 结果 对照组的三叉神经的ADC值为(1.76±0.98)×10-3 mm2/s,FA值为0.40±0.18,左侧与右侧三叉神经桥池段的ADC值和FA值差异均无统计学意义(P>0.05);对照组与TN组中B组(轻度压迫组)、C(重度压迫组)、D组(受压变形并萎缩)3组比较,ADC、FA值差异均存在统计学意义(P均<0.05);压迫部位ADC值增高28例,不变4例,平均ADC值明显高于对照组(P<0.05);压迫部位FA值下降15例.不变11例,增高5例,平均FA值明显低于对照组(P<0.05). 结论 DTI对判断血管压迫三叉神经有一定价值,三叉神经压迫程度越大,ADC值越高,FA值越低.     

Frontal white matter anisotropy and symptom severity of late-life depression: a magnetic resonance diffusion tensor imaging study

OBJECTIVES: To investigate the disruption of neural circuits in the frontal lobes and limbic structures in late-life depressed patients compared with healthy controls, and to examine the correlation between the degree of microstructural abnormalities of white matter and clinical symptom severity in late-life depression. METHODS: Thirteen patients with late-life depression and matched control subjects underwent diffusion tensor imaging. Fractional anisotropy (FA), an index of the integrity of white matter tracts, was determined in the white matter of frontal, temporal, and occipital brain regions and the corpus callosum. RESULTS: A significant reduction was found in white matter FA values of widespread regions of the frontal and temporal lobes of depressed patients. Also, there was some evidence suggesting that white matter FA values of the inferior frontal brain region are inversely related to severity of depression. CONCLUSIONS: These results suggest the possible loss of integrity within frontal and temporal white matter fibre tracts and implicate the orbitofrontal circuit in symptom severity in late-life depression.     

健康者三叉神经磁共振扩散张量成像研究

目的 测量三叉神经桥池段的表观扩散系数(ADC)值和部分各向异性分数(FA)值,了解三叉神经桥池段各参数的特点。 方法 选择50例健康志愿者三叉神经桥池段距离脑干发出点0mm、3mm、6mm、9mm共四处,利用DTI图像与B-TFE或THRIVE图像融合成像,提高三叉神经桥池段显示的空间分辨率,并利用该图像测量并分别记录ADC值与FA值,对所有受检者行三叉神经桥池段追踪成像。 结果 受检者左侧与右侧三叉神经桥池段的ADC值和FA值差异均无统计学意义(P＞0.05)。越靠近脑干发出点,左右两侧三叉神经桥池段的各导出量越呈现左右不对称的趋势。双侧三叉神经桥池段距脑干不同距离各位置的DTI导出量分析发现：相邻两距离间ADC值差异均有统计学意义(P＜0.05),出脑干后随距离增加ADC值逐渐升高,但行至6～9 mm间突然回转下降;FA值在0～6 mm间随距离增加而逐渐降低,且相邻两距离间差异均有统计学意义(P＜0.05),但行至6～9 mm间FA值不再有明显变化。 结论 DTI图像能够清晰分辨双侧三叉神经桥池段,可实现DTI各项导出量的测量。随着距脑干发出点距离的不同,各导出量发生有规律的变化,预示着DTI在明确区分三叉神经的中枢神经系统段、过渡段和周围神经系统段以及检出颅神经血管压迫方面的应用前景。     

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。     

功能磁共振和弥散张量纤维束成像中的人脑皮质桥小脑束

The anatomical organization of the corticopontocerebellar tract(CPCT) in the human brain remains poorly understood.The present study investigated probabilistic tractography of the CPCT in the human brain using diffusion tensor tractography with functional magnetic resonance imaging.CPCT data was obtained from 14 healthy subjects.CPCT images were obtained from functional magnetic resonance imaging and diffusion tensor tractography,revealing that the CPCT originated from the primary sensorimotor cortex and descended to the pontine nucleus through the corona radiata,the posterior limb of the internal capsule,and the cerebral peduncle.After crossing the pons through the transverse pontine fibers,the CPCT entered the cerebellum via the middle cerebral peduncle.However,some variation was detected in the midbrain(middle cerebral peduncle and/or medial lemniscus) and pons(ventral and/or dorsal transverse pontine fibers).The CPCT was analyzed in 3 dimensions from the cerebral cortex to the cerebellum.These results could be informative for future studies of motor control in the human brain.     

弥散张量成像在胶质瘤术前评估中的应用

目的探讨磁共振弥散张量成像在胶质瘤术前评估中的价值。方法对19例经病理证实胶质瘤的患者术前进行弥散张量成像,观察白质纤维束与肿瘤的关系,测量肿瘤实质区和周边水肿区的FA值。结果颅内胶质瘤所致白质纤维异常有三种基本改变：移位、浸润和破坏。19例中10例移位伴破坏,5例单纯浸润,4例浸润伴破坏;肿瘤的实质区和周边水肿区的FA值与对侧大脑白质FA值相比较存在显著差异（P〈0．05）。肿瘤的实质区和周边水肿区FA值之间无统计学显著差异（P〉0．05）。结论弥散张量成像技术可以显示胶质瘤与周围白质纤维束的关系,FA值不能区分肿瘤实质与周边水肿区。     

Idiopathic spinal myoclonus: A clinical and neurophysiological assessment of a movement disorder of uncertain origin

Spinal Myoclonus (SM) is characterized by brief and sudden movements caused by the activation of muscles belonging to adjacent spinal myotomes. Recent reports have indicated that “typical” clinical and electrophysiological features of SM can be mimicked voluntarily. A useful tool that can distinguish between organic and psychogenic jerks is the detection of a Bereitschaftspotential (BP). In this study, we looked for evidence of a BP in a cohort of patients with idiopathic SM. A clinical and neurophysiological assessment of 20 patients affected by idiopathic SM was performed. A video EEG‐EMG multichannel recording was performed in each patient to detect BP. An expert neurophysiologist (PB) reviewed the BP recordings and divided them into those showing a definite, possible, and no BP. A clinical assessment of the videoed movements was performed by two neurologists expert in movement disorders (KB and MJE) who indicated if the movements were compatible with organic or psychogenic myoclonus. A definite or possible BP was recorded in 15 out of 20 patients. Clinical raters agreed in their clinical opinion on 15 patients (75%). All patients where both raters agreed the movements appeared to be organic had definite or possible BP. BP are commonly seen in patients with idiopathic SM. There is discordance between clinicians in their clinical rating of SM as organic or psychogenic, but even in those patients where movements appear clinically to be organic, a BP is commonly detected, indicating that the aetiology is psychogenic. This suggests that BP recordings are a useful adjunct to clinical assessment in the accurate diagnosis of patients with idiopathic SM. © 2009 Movement Disorder Society     

Relationship between suicidality and impulsivity in bipolar I disorder: a diffusion tensor imaging study

Mahon K, Burdick KE, Wu J, Ardekani BA, Szeszko PR. Relationship between suicidality and impulsivity in bipolar I disorder: a diffusion tensor imaging study.
Bipolar Disord 2012: 14: 80–89. © 2012 The Authors.
Journal compilation © 2012 John Wiley & Sons A/S. Background: Impulsivity is characteristic of individuals with bipolar disorder and may be a contributing factor to the high rate of suicide in patients with this disorder. Although white matter abnormalities have been implicated in the pathophysiology of bipolar disorder, their relationship to impulsivity and suicidality in this disorder has not been well‐investigated. Methods: Diffusion tensor imaging scans were acquired in 14 bipolar disorder patients with a prior suicide attempt, 15 bipolar disorder patients with no prior suicide attempt, and 15 healthy volunteers. Bipolar disorder patients received clinical assessments including measures of impulsivity, depression, mania, and anxiety. Images were processed using the Tract‐Based Spatial Statistics method in the FSL software package. Results: Bipolar disorder patients with a prior suicide attempt had lower fractional anisotropy (FA) within the left orbital frontal white matter (p < 0.05, corrected) and higher overall impulsivity compared to patients without a previous suicide attempt. Among patients with a prior suicide attempt, FA in the orbital frontal white matter region correlated inversely with motor impulsivity. Conclusions: Abnormal orbital frontal white matter may play a role in impulsive and suicidal behavior among patients with bipolar disorder.     

Early postnatal development of rat brain: in vivo diffusion tensor imaging

Perinatal hypoxia is a major cause of neurodevelopmental deficits. Neuronal migration patterns are particularly sensitive to perinatal hypoxia/ischemia and are associated with the clinical deficits. The rat model of hypoxia/ischemia at P7 mimics that of perinatal injury in humans. Before assessing the effects of postnatal injury on brain development, it is essential to determine the normal developmental trajectories of various brain structures in individual animals. In vivo longitudinal diffusion tensor imaging (DTI) was performed from postnatal day 0 (P0) to P56 on Wistar rats. The DTI metrics, mean diffusivity (MD), fractional anisotropy (FA), axial (lambdal) and radial (lambdat) diffusivities, were determined for four gray matter and eight white matter structures. The FA of the cortical plate and the body of corpus callosum decreased significantly during the first 3 weeks after birth. The decrease in the cortical plate's FA value was associated mainly with an increase in lambdat. The initial decrease in FA of corpus callosum was associated with a significant decrease in lambdal. The FA of corpus callosum increased during the rest of the observational period, which was mainly associated with a decrease in lambdat. The FA of gray matter structures, hippocampus, caudate putamen, and cortical mantle did not show significant changes between P0 and P56. In contrast, the majority of white matter structures showed significant changes between P0 and P56. These temporal changes in the DTI metrics were related to the neuronal and axonal pruning and myelination that are known to occur in the developing brain.