利用扩散张量成像及纤维跟踪技术分析 胼胝体发育不良脑内主要纤维束

目的 利用扩散张量成像(DTI)和纤维跟踪技术显示胼胝体发育不良状态下脑内纤维结构的变化。方法患者，男，9岁，头痛1周。采用SIEMENS Trio2003T完成全脑MRI和DTI数据收集和后处理。结果常规MRI显示胼胝体体中部以后缺如，半球间蛛网膜囊肿，右侧向上延伸。纤维跟踪技术显示左侧弓状纤维柬、下纵行纤维柬、扣带柬、海马及外囊等主要的连合、联合纤维走行方向与正常发育不同，有左右侧相互支援的趋势。结论DTI纤维跟踪技术能精确、直观显示先天性发育畸形的脑内白质纤维柬，有助于预后的评估。     

磁共振弥散张量成像技术在颈椎外科应用的研究进展

正磁共振弥散张量成像技术(diffusion tensor imaging,DTI)通过反映水分子在不同组织中弥散运动各向异性的差异实现观察人体解剖结构的完整性,也可以通过弥散张量纤维束示踪成像技术(diffusion tensor tractography,DTT)显示白质纤维的走行~([1])。目前DTI在颅脑疾病中应用较多,在早期诊断脑梗塞、判断多发性硬化症分期、判断肿     

核磁共振扩散张量成像辅助评估腰肌扭伤

目的应用核磁共振扩散张量成像（MR-DTI）辅助常规MRI诊断腰肌扭伤。方法应用3.0 TMR对13例腰肌扭伤成像：常规序列tse-T1WI,tse-T2WI-FS,tse-T1WI-CE和辅助诊断序列DTI。基于DTI完成组织结构解剖和分数各向异性的融合图（Anat-FA）,肌纤维束追踪图（MFT）。对照评价T1WI、T2WI、T1WI-CE、Anat-FA图在显示损伤程度、范围方面的差异,应用MFT图显示肌纤维结构破坏情况。结果腰肌损伤的严重性与组织弥散张量的分数各向异性（FA）下降、表观弥散系数（ADC）和张量轨迹加权值（TraceW）上升以及T2WI、T1WI-CE信号增加相关。T2WI图与T1WI-CE图显示的损伤区面积差异无统计学意义（P=0.42）,Anat-FA图显示的损伤面积大于T2WI图（P〈0.001）和T1WI-CE图（P=0.01）所显示的损伤面积。MFT图显示的肌纤维断裂程度与T2WI和T1WI-CE显示的损伤程度一致。结论与常规MRI相比,MR-DTI可以定量化诊断腰肌损伤的严重程度。     

使用磁共振弥散张量成像技术对心肌带结构的初步研究

目的初步研究用磁共振弥散张量成像(MRDTI)技术显示离体猪心心肌带结构的可能性。方法以MRDTI技术为基础,检测5个成年离体猪心,在猪心离体后2h内使用25个方向的弥散张量成像(DTI)序列扫描心室部分,之后使用脑白质纤维束成像重建方式显示心肌纤维的走行、分布和排列方式。结果MRDTI可以清晰显示离体1h心室肌纤维整体具有一定的连续性,在空间上螺旋、缠绕而形成左、右心室;左室壁的心肌纤维大体呈现心内膜下纵向排列、心肌中层斜行排列和心外膜下环行排列,这与心肌带理论相符合。结论MRDTI技术可以显示离体心肌纤维的完整性和排列方式,并能部分地证实心肌带理论的真实性。     

磁共振弥散张量成像在中枢神经系统中的应用

DTI是基于DWI的MRI新技术,不仅能反映脑组织的细微结构,还可通过纤维示踪技术显示白质纤维束。DTI对研究脑的发育、成熟及老化过程及诊断许多中枢神经系统（CNS）疾病具有重要意义。本文就DTI在CNS中的应用予以综述。     

扩散张量纤维束示踪成像诊断无小脑病灶的多发性硬化患者共济失调

目的探讨扩散张量纤维束示踪成像诊断无小脑病灶的多发性硬化患者共济失调的价值。方法对18例有共济失调症状的MS患者(MS组)和18名健康志愿者(对照组)进行头部MR扫描,利用纤维束示踪技术追踪穿过小脑双侧齿状核和双侧丘脑白质的纤维束,计算FA值、ADC值和纤维束条数,并进行统计学分析。结果与对照组比较,MS组右侧丘脑白质纤维束FA值减低、ADC值增加(P均0.05);左侧丘脑、双侧齿状核FA值、ADC值差异均无统计学意义(P均0.05);双侧丘脑、双侧齿状核的白质纤维束条数差异均无统计学意义(P均0.05)。MS组双侧丘脑、双侧齿状核的FA值、ADC值、纤维束条数与临床扩展残疾状态量表评分、病程均无相关性(P均0.05)。结论扩散张量纤维束示踪成像诊断无小脑病灶的多发性硬化患者共济失调有一定临床应用价值。     

DTI在脊髓型颈椎病诊断及预后判定中应用的研究进展

正脊髓型颈椎病是一种常见退行性疾病,临床表现为四肢麻木无力、躯体感觉障碍或大小便障碍等。弥散张量成像(DTI)是一种在弥散加权成像(DWI)技术基础上发展起来的MRI功能成像技术,其利用体内水分子弥散的各向异性无创地追踪和观察神经纤维的走行及完整性,同时通过相关参数的定量分析反映神经组织微观结构的改变~([1-2])。笔者就脊髓DTI在脊髓型颈椎病诊断及预后判定中的研究和应用进展综述如下。     

磁共振扩散张量成像与纤维束成像在脊髓型颈椎病中的应用研究

目的 :评价磁共振扩散张量成像技术(diffusion tensor imaging,DTI)对脊髓型颈椎病的诊断价值。方法 :对收集的2014年1月至2015年4月20例健康志愿者和50例脊髓型颈椎病(CSM)患者行颈髓DTI。以健康志愿者作为对照组。依据颈髓MRI平扫结果将CSM患者分A、B、C组,A组17例(单纯硬膜囊受压),B组23例(颈髓受压,信号正常),C组10例(颈髓受压,T2高信号)。分析4组颈髓的平均表观扩散系数(ADC)、平均分数各向异性值(FA)之间的差异,对所有受检者行颈髓纤维束成像。结果:对照组C_2/C_3、C_3/C_4、C_4/C_5、C_5/C_6、C_6/C_7之间ADC值及FA值差异无统计学意义(P0.05),平均ADC值为(0.875±0.096)×10~(-3)mm~2/s,平均FA值为0.720±0.051;对照组与A组比较,平均ADC值、FA值差异无统计学意义,对照组与B、C组及A、B、C组间比较,平均ADC值、FA值差异均有统计学意义。结论:颈髓DTI较常规MRI能够早期、准确地量化脊髓型颈椎病的颈髓微结构改变,颈髓纤维束成像可以反映脊髓纤维束受压损伤的范围。     

基于弥散张量成像分析非病灶性颞叶癫痫患者脑白质网络结构变化与其执行功能障碍的关系

目的 基于弥散张量成像(DTI)评估非病灶性颞叶癫痫(nl-TLE)患者脑白质网络结构变化,分析其与患者执行功能障碍的关系。方法 比较40例nl-TLE患者(nl-TLE组)与43名健康志愿者(对照组)的神经心理学测试评分和执行功能特征;基于DTI分析组间脑白质体积存在显著差异脑区的分布,对比脑白质纤维束各向异性分数(FA)和平均扩散率(MD);以Pearson相关分析观察nl-TLE患者脑白质体积及脑白质纤维束FA、MD值与其执行功能特征的相关性。结果 nl-TLE组蒙特利尔认知评估(MOCA)、波士顿命名测试(BNT)、雷伊听觉语言学习测试(RAVLT)即刻记忆及延迟回忆评分均低于对照组;其数字广度顺向、词语流畅性低于对照组,Stroop C、朝向一致目标RT、双朝向目标RT、执行网络效率值均高于对照组(P均<0.01)。nl-TLE组左(L)-海马、右(R)-颞上回、R-楔前叶、R-后扣带回脑白质体积均小于对照组(P均<0.001);R-下纵束、L-扣带回、L-穹隆脑白质纤维束FA值较对照组降低,L-额枕下束、R-穹隆的脑白质纤维束MD值较对照组增加(P均<0....     

功能和纤维成像在脑功能区胶质瘤中的应用

目的研究功能磁共振成像（fMRI）定位脑运动功能区和弥散张量纤维束示踪成像（diffusion tensor tractography,DTT）显示锥体束与肿瘤位置关系在脑胶质瘤行直接皮质电刺激手术的指导作用。方法对28例邻近或累及脑运动功能区的患者,术前在常规成像基础上,分别行双手握拳刺激策略的血氧水平依赖性功能磁共振成像（BOLD-fMRI）和弥散张量成像（DTI）,经工作站提供的BOLD．fMRI和DTI图像分析软件包获得脑运动功能区的激活图像、二维的部分各向异性伪彩图（fractional anisotropy,FA Color）和三维的白质纤维束示踪图。提供脑肿瘤与脑运动皮质区和运动传导束即锥体束的位置关系信息,制定手术方案。所有患者均行术中皮质直接电刺激定位运动区。术前、术后均行Karnofsky生活状态（KPS）评分,判断患者的状态。结果28例患者的fMRI和DTI获得良好的脑双手握拳运动功能区激活图像和锥体束纤维束走形图像,显示初级运动皮质区、运动前皮质区、辅助运动皮质区等手运动相关的脑功能区和运动传导束——锥体束与肿瘤的位置关系。在术前脑功能磁共振图像指导下,直接皮质电刺激快捷、准确定位初级运动皮质区,发现两者具有良好的一致性。术后患者KPS评分结果较术前提高。结论术前BOLD-fMRI和DTT可于活体、无创地描绘脑运动功能区和锥体束与肿瘤的功能解剖位置关系,优化手术方案,在唤醒麻醉下指导直接皮质电刺激定位运动区的手术,实现最大程度保护患者重要的功能,并最大程度地切除肿瘤。     

Selective age-related degradation of anterior callosal fiber bundles quantified in vivo with fiber tracking

The corpus callosum, the principal white matter structure enabling interhemispheric information transfer, is heterogeneous in its microstructural composition, heterotopic in its anteroposterior cortical connectivity, and differentially susceptible to aging. In vivo characterization of callosal features is possible with diffusion tensor imaging (DTI), a magnetic resonance imaging method sensitive to the detection of white matter's linear structure. We implemented a quantitative fiber tracking approach to examine age-related variation in regional microstructural characteristics [fractional anisotropy (FA) and apparent diffusion coefficient (ADC)] of callosal fibers in 10 younger (29 +/- 5 years) and 10 older (72 +/- 5 years) healthy adults. Fiber tracking was performed on 2.5 mm isotropic voxels collected at 3 T. Fiber targets comprised the midsagittal corpus callosum, divided into six regions based on known callosal anatomical projections. FA and ADC for each voxel of each fiber identified were determined; lower FA and higher ADC reflect degraded microstructural tissue integrity. Older subjects had lower FA (P < 0.002), higher ADC (P < 0.006), and fewer (P < 0.005) fibers than younger subjects. Group x region interactions indicated disproportionately lower FA (P = 0.0001) and higher ADC (P < 0.006) in the older than younger group in frontal fiber bundles relative to posterior bundles. As a test of the functional significance of the fiber bundle metrics, the older subjects were administered the Stroop Task, which showed significant correlations between regional fiber bundle integrity and performance. These results validate this quantitative fiber tracking approach and confirm the selective vulnerability of frontal white matter systems to normal aging, likely substrates of age-related declines in cognitive processes dependent on prefrontal circuitry integrity.     

Analysis of the diffusion tensor imaging parameters of a normal cervical spinal cord in a healthy population

Background: Diffusion tensor imaging (DTI) shows great advantage in the diagnosis of brain diseases, including cervical spinal cord (CSC) disease. This study aims to obtain the normal values of the DTI parameters for a healthy population and to establish a baseline for CSC disease diagnosis using DTI.

Methods: A total of 36 healthy adults were subjected to magnetic resonance imaging (MRI) for the entire CSC using the Siemens 3.0?T MR System. Sagittal DTI acquisition was carried out with a single-shot spin-echo echo-planar imaging (EPI) sequence along 12 non-collinear directions. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were determined at different cervical levels using a region of interest (ROI) method, following which they were correlated with parameters, like age and sex. Further, diffusion tensor tracking (DTT) was carried out to reconstruct the white matter fiber bundles of the CSC.

Results: The full and complete fiber bundle structure of a normal CSC was confirmed in both the T2-weighted and DTI images. The FA and ADC values were significantly negatively correlated with each other and showed strongly negative and positive correlations with age, respectively, but not with sex. Additionally, there was no significant difference between the FA and the ADC values at different cervical levels.

Conclusion: The DTI technique can act as an important supplement to the conventional MRI technique for CSC observation. Moreover, the FA and ADC values can be used as sensitive parameters in the DTI study on the CSC by taking the effects of age into consideration.     

Diffusion tensor imaging fiber tractography for evaluating diffuse axonal injury

Patients with Diffuse axonal injury (DAI) frequently exhibit cognitive disorders chronically. Radiologic recognition of DAI can help understand the clinical syndrome and to make treatment decisions. However, CT and conventional MRI are often normal or demonstrate lesions that are poorly related to the cognitive disorders. Recently, diffusion tensor imaging (DTI) fiber tractography has been shown to be useful in detecting various types of white matter damage. The aim of this study was to evaluate the feasibility of using DTI fiber tractography to detect lesions in DAI patients, and to correlate the DAI lesions with the cognitive disorders. We investigated two patients with chronic DAI. Both had impaired intelligence, as well as attention and memory disorders that restricted their activities of daily living. In both patients, DTI fiber tractography revealed interruption of the white matter fibers in the corpus collosum and the fornix, while no lesions were found on conventional MRI. The interruption of the fornix which involves the circuit of Papez potentially correlates with the memory disorder. Therefore, DTI fiber tractography may be a useful technique for the evaluation of DAI patients with cognitive disorders.     

Detection of tumour infiltration in axonal fibre bundles using diffusion tensor imaging

We present a method for the detection and quantification of white matter infiltration from human brain tumours based on Diffusion Tensor Imaging (DTI). Since white matter destruction alters the local diffusion properties, DTI has the potential to sensitively detect tumour infiltration and to quantify the degree thereof. Here, we consider three tumour patients with gliomas, two with and one without contralateral tumour progress. We use DTI to identify specific fibre systems, where infiltration has to be assessed. On this basis, the problem of arbitrary region of interest definition is solved such that tumour infiltration can be reliably quantified in particular fibre bundles. It is demonstrated at the Corpus Callosum (CC) and the Pyramidal Tract (PT) that fibre bundle infiltration can be well detected by specific visualisation techniques of diffusion tensor data. Infiltration of the CC is quantified by using a reliable method for the determination of diffusion properties inside particular fibre bundles. For an age normalised quantification of white matter infiltration we introduce the Integrity Index, which measures the diffusion anisotropy inside an infiltrated fibre bundle normalised by the diffusion anisotropy in a specific region of healthy fibre tissue. It turns out that the quantification of CC infiltration correlates with contralateral tumour progression and has the potential to serve as a surrogate marker for this process, which is crucial for surgical therapy decisions and intervention planning.     

Eye Movement Network Originating from Frontal Eye Field: Electric Cortical Stimulation and Diffusion Tensor Imaging

This study investigated the networks originating from frontal eye fields (FEFs) using electric cortical stimulation and diffusion tensor imaging (DTI). Seven patients with intractable focal epilepsy, in which FEFs were identified by electrical cortical stimulation, were enrolled in this study. Electric stimulation at 50 Hz was applied to the electrodes for functional mapping. DTI was used to identify the subcortical fibers originating from the FEFs with two regions of interests (ROIs) in the FEF and contralateral paramedian pontine reticular formation (PPRF). FEFs were found in the superior precentral sulcus (pre-CS) in six patients and superior frontal gyrus (SFG) in three patients. DTI detected fibers connecting FEFs and contralateral PPRFs, passing within the internal capsule. The fibers were located close to the lateral antero-superior border of the subthalamic nucleus (STN) and medial posterior border of the globus pallidus internus (GPi). This study found the characteristic subcortical networks of the FEF. These tracts should be noted to prevent complications of deep brain stimulation (DBS) of the STN or GPi.     

Monitoring In-Vivo the Mammary Gland Microstructure during Morphogenesis from Lactation to Post-Weaning Using Diffusion Tensor MRI

Lactation and the return to the pre-conception state during post-weaning are regulated by hormonal induced processes that modify the microstructure of the mammary gland, leading to changes in the features of the ductal / glandular tissue, the stroma and the fat tissue. These changes create a challenge in the radiological workup of breast disorder during lactation and early post-weaning. Here we present non-invasive MRI protocols designed to record in vivo high spatial resolution, T₂-weighted images and diffusion tensor images of the entire mammary gland. Advanced imaging processing tools enabled tracking the changes in the anatomical and microstructural features of the mammary gland from the time of lactation to post-weaning. Specifically, by using diffusion tensor imaging (DTI) it was possible to quantitatively distinguish between the ductal / glandular tissue distention during lactation and the post-weaning involution. The application of the T₂-weighted imaging and DTI is completely safe, non-invasive and uses intrinsic contrast based on differences in transverse relaxation rates and water diffusion rates in various directions, respectively. This study provides a basis for further in-vivo monitoring of changes during the mammary developmental stages, as well as identifying changes due to malignant transformation in patients with pregnancy associated breast cancer (PABC).     

Preoperative and intraoperative brain mapping for the resection of eloquent-area tumors. A prospective analysis of methodology, correlation, and usefulness based on clinical outcomes

Background

Localization of brain function is a fundamental requisite for the resection of eloquent-area brain tumors. Preoperative functional neuroimaging and diffusion tensor imaging can display cortical functional organization and subcortical anatomy of major white matter bundles. Direct cortical and subcortical stimulation is widely used in routine practice, however, because of its ability to reveal tissue function in eloquent regions. The role and integration of these techniques is still a matter of debate. The objective of this study was to assess surgical and functional neurological outputs of awake surgery and intraoperative cortical and subcortical electrical stimulation (CSES) and to use CSES to examine the reliability of preoperative functional magnetic resonance (fMRI) and diffusion tensor imaging fiber tracking (DTI-FT) for surgical planning.

Patients and methods

We prospectively studied 27 patients with eloquent-area tumors who were selected to undergo awake surgery and direct brain mapping. All subjects underwent preoperative sensorimotor and language fMRI and DTI tractography of major white matter bundles. Intra- and postoperative complications, stimulation effects, extent of resection, and neurological outcome were determined. We topographically correlated intraoperatively identified sites (cortical and subcortical) with areas of fMRI activation and DTI tractography.

Results

Total plus subtotal resection reached 88.8%. Twenty-one patients (77.7%) suffered transient postoperative worsening, but at 6 months follow-up only three (11.1%) patients had persistent neurological impairment. Sensorimotor cortex direct mapping correlated 92.3% with fMRI activation, while direct mapping of language cortex correlated 42.8%. DTI fiber tracking underestimated the presence of functional fibers surrounding or inside the tumor.

Conclusion

Preoperative brain mapping is useful when planning awake surgery to estimate the relationship between the tumor and functional brain regions. However, these techniques cannot directly lead the surgeon during resection. Intraoperative brain mapping is necessary for safe and maximal resection and to guarantee a satisfying neurological outcome. This multimodal approach is more aggressive, leads to better outcomes, and should be used routinely for resection of lesions in eloquent brain regions.