弥散张量成像在脑肿瘤手术中的应用

目前,手术仍是脑肿瘤的首选治疗方法。如何在最大范围切除肿瘤的同时最大程度地保留神经功能,以减少术后并发症,是神经外科医生面临的一个挑战。肿瘤浸润生长及占位效应可导致脑功能区变形及重建,单纯解剖学定位不能满足对神经功能保护的要求。随着MRI技术的发展,脑功能定位成为可能,特别是磁共振弥散张量成像（diffusion tensorimaging,DTI）可以对脑白质纤维束走形进行示踪。     

磁共振弥散张量成像在脑部疾病诊断中的应用

磁共振弥散张量成像(DTI)是近年来在常规MRI技术和弥散加权(DWI)技术的基础上发展的一种新的MRI技术,是一种能在活体显示脑白质纤维束走向的无创成像方法[1～3]。1DTI的基本原理弥散是指水分子的随机运动,即布朗运动。在这一运动模式中,水分子在各个方面所受的弥散阻力相等,称为各向同性弥散。在脑组织中,由于神经纤维束的限制,水分子更倾向于沿着脑白质走行的方向进行弥散,称为各向异性弥散。由于各向异性的存在,弥散需要用张量描述。在DWI中,仅在1个或3个方向上施加弥散梯度磁场,因此只有表观弥散系数(ADC)1个标量值用于描述弥散…     

精神发育迟滞脑白质磁共振弥散张量成像研究

目的:通过检查精神发育迟滞(MR)患者脑白质磁共振弥散张量成像(DTI)来了解该病患者脑白质发育情况,以寻找MR患者新的诊断手段,并探讨发病机制中脑白质纤维束发育障碍的根据.方法:用DTI扫描技术对45例MR患者作了皮质脊髓束、枕额束、扣带束、胼胝体束的检查.结果:45例患者中仅4例未发现异常,枕额束有异常为27例,皮...     

弥散张量成像定位初级运动功能区的研究

目的 探讨弥散张量成像在定位初级运动功能区的价值.方法 20例脑深部肿瘤患者,分别进行常规MRI、fMRI及DTI检查,获取fMRI脑激活图、DTI图、3D解剖图.DTI通过三维重建皮质脊髓束定位初级运动功能区.fMRI采用手握拳激发模式,获取激活信号定位初级运动功能区.比较两种技术的吻合度,以评价DTI三维重建皮质脊髓束定位的初级运动功能区的准确性.结果 20例患者fMRI获得的激活信号主要位于对侧中央沟处,围绕着"Ω"形柄状结构分布,中央前回位于激活信号前方.所有患者均成功地完成DTI皮质脊髓束的三维重建,重建的皮质脊髓束也定位于激活信号前的脑回,两者均较好显示初级运动功能区且具有较好的一致性.结论 DTI可较好地定位初级运动功能区,这对于有肢体瘫痪患者及不能合作的儿童的初级运动功能区的定位有重要意义.     

磁共振张量成像对脑梗死预后的评价

目的利用磁共振弥散张量成像(DTI)探讨脑梗死病人脑白质纤维束各向异性特征和白质纤维束受损与临床预后关系。方法对23例脑梗死患者行DTI检查,以三维立体弥散张量成像为基础的色彩图进行图像后处理,评价脑梗死区周边纤维束的情况,将纤维束分为受压移位、变细萎缩和破坏中断三类,并与临床预后、神经功能缺损程度比较。结果三维成像所见与病人预后关系密切。所有脑白质纤维束萎缩和中断的患者,在随访过程中存在不同程度脑功能损伤,而脑白质受压移位的病人神经功能完全或近乎完全恢复。结论在脑梗死中,DTI能直接观察到白质纤维束的变化,对于评估临床预后具有重要作用。     

弥散张量成像在精神分裂症的研究

弥散张量成像（diffusion tensor imaging,DTI）是目前在活体直视脑白质主要纤维柬三维结构的唯一方法。国内外已将其应用于神经精神疾病的研究。本文就DTI在精神分裂症的应用作一综述。     

磁共振弥散张量成像在脑梗死中的应用

目的应用磁共振弥散张量成像(DTI)技术分析缺血性脑梗死不同时期的表观弥散系数(ADC)、各向异性分数(FA)变化,并通过弥散张量纤维束成像(DTT)观察梗死灶与皮质脊髓束(CST)位置关系,以评估预后。方法 45例由于皮质脊髓束受损所致运动功能障碍的不同时期脑梗死患者作为研究组,分为超急性期(<6h)、急性期(6h～3d)、亚急性期(4d～8w)和慢性期(>8w),分析其DTI参数的变化特点,并与正常组进行比较。结果患侧FA值在超急性期无明显变化,在急性期、亚急性期及慢性期逐渐降低,与健侧和对照组比较有显著性差异(P值均<0.05);患侧ADC值在超急性期、急性期明显减低,亚急性期逐渐恢复接近于健侧,慢性期再度增高;DTT成像显示CST受损严重其预后较差。结论不同时期脑梗死病灶其FA、ADC值有一定规律变化,DTT图像可无创性的显示梗死灶与皮质脊髓束的空间位置关系,可作为评估预后的客观依据。     

核磁共振弥散张量纤维素成像对脑血管病患者预后的判定

目的观察急性脑血管病患者皮质脊髓束的损伤状况,分析运动功能变化并对临床预后进行判定。方法对18例脑卒中患者(其中脑梗死患者16例,脑出血患者2例)进行磁共振弥散张量纤维素成像(DTI)检查纤维束的连续性及破坏情况。于患者入院时、发病后2周、1月及2月分别进行肌力判定和神经功能评分。结果皮质脊髓束受累情况分为2级,1级:皮质脊髓束完整,共5例;2级:皮质脊髓束中断,共13例。16例脑梗死患者不同时期肌力及NIHSS评分与皮质脊髓束级别明显相关(P<0.05),发病后2月NIHSS评分转归情况与皮质脊髓束级别有显著性差异(P=0.0202)。2例脑出血患者入院时肌力均为0级但DTI显示皮质脊髓束完整的其预后也较好。18例受试者均进入结果分析,不同时期NIHSS评分与皮质脊髓束级别明显相关(P<0.05),发病后2月NIHSS评分转归情况与皮质脊髓束级别有显著性差异(P=0.0269)。结论三维纤维束示踪成像图可以更立体直观的显示皮质脊髓束状况,并在脑血管病初期即可对其损伤情况进行判定,同时可以提示脑血管病患者的预后。     

磁共振弥散张量成像在神经外科中的应用

弥散张量成像（diffusion tensorimaging，DTI）是在常规MRI和DWI基础上发展起来的一种新技术。这个概念由Basser等^[1]提出。DTI可在三维空间内定量分析组织内水分子的弥散运动，利用特定的算法可以提供其他成像方法所无法实现的脑的解剖结构和功能信息，重建脑白质纤维束。它对脑白质病、脑血管病等的诊断、神经外科术前病灶的定位、病灶与纤维束的毗邻关系的确定有重要意义。本文就DTI相关的基本概念及其在神经外科领域中的应用加以综述。     

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。     

神经导航辅助显微手术治疗脑功能区肿瘤

目的探讨神经导航系统辅助下脑重要功能区肿瘤显微手术的治疗效果和应用价值。方法1999年12月～2002年6月应用StealthStation神经导航系统辅助切除邻近脑重要功能区肿瘤10例,对神经导航系统术中应用的优越性、精确性等进行分析。结果本组平均注册误差为(2.8±0.9)mm,肿瘤和重要解剖功能结构定位准确,肿瘤全切除率77.8%。术后神经功能未受明显影响,无手术并发症及死亡。结论神经导航系统对于切除邻近脑重要功能区肿瘤具有定位准确,动态示踪和实时导航,侵袭性小,安全、可靠等特点,有助于提高肿瘤全切率及降低手术并发症。     

Model-based variational smoothing and segmentation for diffusion tensor imaging in the brain

This article applies a unified approach to variational smoothing and segmentation to brain diffusion tensor image data along user-selected attributes derived from the tensor, with the aim of extracting detailed brain structure information. The application of this framework simultaneously segments and denoises to produce edges and smoothed regions within the white matter of the brain that are relatively homogeneous with respect to the diffusion tensor attributes of choice. This approach enables the visualization of a smoothed, scale invariant representation of the tensor data field in a variety of diverse forms. In addition to known attributes such as fractional anisotropy, these representations include selected directional tensor components and additionally associated continuous valued edge fields that might be used for further segmentation. A comparison is presented of the results of three different data model selections with respect to their ability to resolve white matter structure. The resulting images are integrated to provide better perspective of the model properties (edges, smoothed image, and so forth) and their relationship to the underlying brain anatomy. The improvement in brain image quality is illustrated both qualitatively and quantitatively, and the robust performance of the algorithm in the presence of added noise is shown. Smoothing occurs without loss of edge features because of the simultaneous segmentation aspect of the variational approach, and the output enables better delineation of tensors representative of local and long-range association, projection, and commissural fiber systems.     

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.     

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.     

抑郁症患者弥散张量成像与认知功能的关系

目的:探讨抑郁症患者全脑白质纤维受损状况及其与认知功能的关系.方法:对 24 例抑郁症患者及 30 名健康对照者进行临床测评、常规磁共振成像(MRI)、弥散张量成像(DTI)及神经心理学检查.结果:抑郁症组在左额中回、左额上回、右额内侧回、左楔前叶、左颞上回、右扣带回等区域各向异性(FA)值较对照组显著下降(P＜0.001).抑郁症组威斯康星卡片分类测验(WCST)的分类数、总错误率明显高于对照组(P＜0.01 或 P＜0.05).两组持续注意操作测试(CPT)差异无显著性;抑郁症组 CPT 与 WCST 部分结果均呈负相关(P均＞0.05).结论:DTI 与 WCST 结果的相互印证反映重性抑郁症患者可能存在白质区域神经功能的异常,DTI 技术有助于发现影响认知改变的脑微细结构和功能的异常.     

Children's reading performance is correlated with white matter structure measured by diffusion tensor imaging

We investigated the white matter structure in children (n = 14) with a wide range of reading performance levels using diffusion tensor imaging (DTI), a form of magnetic resonance imaging. White matter structure in a left temporo-parietal region that had been previously described as covarying with reading skill in adult readers also differs between children who are normal and poor readers. Specifically, the white matter structure measured using fractional anisotropy (FA) and coherence index (CI) significantly correlated with behavioral measurements of reading, spelling, and rapid naming performance. In general, lower anisotropy and lower coherence were associated with lower performance scores. Although the magnitude of the differences in children are smaller than those in adults, the results support the hypothesis that the structure of left temporoparietal neural pathways is a significant component of the neural system needed to develop fluent reading.     

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.     

Microstructural basis of contusion expansion in traumatic brain injury: insights from diffusion tensor imaging

Traumatic brain injury (TBI) is often exacerbated by events that lead to secondary brain injury, and represent potentially modifiable causes of mortality and morbidity. Diffusion tensor imaging was used to characterize tissue at-risk in a group of 35 patients scanned at a median of 50 hours after injury. Injury progression was assessed in a subset of 16 patients with two scans. All contusions within the first few days of injury showed a core of restricted diffusion, surrounded by an area of raised apparent diffusion coefficient (ADC). In addition to these two well-defined regions, a thinner rim of reduced ADC was observed surrounding the region of increased ADC in 91% of patients scanned within the first 3 days after injury. In patients who underwent serial imaging, the rim of ADC hypointensity was subsumed into the high ADC region as the contusion enlarged. Overall contusion enlargement tended to be more frequent with early lesions, but its extent was unrelated to the time of initial imaging, initial contusion size, or the presence of hemostatic abnormalities. This rim of hypointensity may characterize a region of microvascular failure resulting in cytotoxic edema, and may represent a ‘traumatic penumbra'' which may be rescued by effective therapy.