弥漫性轴索损伤的胼胝体DTI研究

目的：利用磁共振扩散张量成像(DTI)技术对中重型脑损伤(TBI)患者胼胝体损伤进行量化,探讨其对早期弥漫性轴索损伤(DAI)的诊断及预后的应用价值。方法应用 T1 WI(MPRAGE 序列)和 DTI(EPI 序列)对30例中重型 TBI 患者和30例健康体检者(对照组)进行检查。进行图像后处理得到各向异性分数彩色图(FA color map),选取胼胝体整体和膝部、胼胝体干、压部分别作为兴趣区(ROI),测量不同 ROI 的 FA 值和表观扩散系数(ADC)值。进行组间比较,以及 TBI 组内比较。对 TBI 组胼胝体整体和分段 FA 值和 ADC 值与昏迷时间进行直线相关分析。结果与对照组相比,TBI 组胼胝体整体和膝部、胼胝体干、压部的 FA值下降,ADC 值上升,差异有统计学意义。TBI 组胼胝体整体和分段 FA 值和 ADC 值与昏迷时间密切相关。结论磁共振 DTI 技术能较敏感地检测出神经纤维的损伤,胼胝体 FA 值与 DAI 损伤程度有密切的相关性对早期诊断 DAI 和评估预后有较高的应用价值。     

DTI 和 SWI 序列在弥漫性轴索损伤中的应用价值

目的：探讨扩散张量成像(DTI)和磁敏感加权成像(SWI)在急性期脑弥漫性轴索损伤(DAI)中的诊断价值。方法回顾性分析45例经临床确诊的 DAI 患者的影像学资料,在 FLAIR、DTI 及 SWI 的扫描图像上对病灶信号特征及分布特点进行分析,并将各序列观察到的病灶数据用χ2检验进行统计学分析。结果共检出497个 DAI 病灶,其中 FLAIR 检出265个,检出率53.3%;DTI检出313个,检出率为62.9%;SWI 检出448个,检出率为90.1%。对于急性期 DAI 病灶的检出率,DTI 及 SWI 明显高于 FLAIR,差异有统计学意义(P <0.05)。结论 DTI 联合 SWI 可全面检出 DAI 病灶,DTI 三维扩散张量纤维束成像技术可直观了解 DAI病灶区的纤维束中断现象,客观证实 DAI 的存在。     

联合SWI及DTI对急性、亚急性弥漫性轴索损伤的诊断价值

目的探讨联合磁敏感成像(susceptibility weighted imaging,SWI)及扩散加权成像(diffusion tensor ima-ging,DTI)在急性、亚急性弥漫性轴索损伤(diffuse axonal injury,DAI)中的应用价值。方法 19例弥漫性轴索损伤(DAI)患者于急性或亚急性期(外伤后2周内)行头颅SWI、DTI及常规序列扫描,比较各序列对病灶显示的灵敏度。将检出的病灶数目与患者入院格拉斯哥昏迷评分(GCS)行相关性分析。结果 T2WI共检出DAI病灶128个,DTI-扩散图(TRACEW图)检出279个,SWI检出538个,联合SWI及DTI检出589个。SWI、DTI(TRACEW图)对DAI病灶的检出率均显著高于常规T2WI(Z=-3.764,Z=-3.245;P<0.01)。联合SWI及DTI两种技术对DAI病灶的检出显著高于单独应用DTI(Z=-3.551,P<0.01)或SWI(Z=-2.351,P<0.05)。联合SWI及DTI两种技术检出的病灶数目与患者入院GCS呈高度负相关(r=-0.775,P<0.01)。结论联合SWI及DTI两种检查技术,能够较单独应用一种技术观察到更多的DAI病灶,有助于较准确地对DAI患者的病情进行评估。三维扩散张量纤维束成像(diffusion tensor tracking,3D-DTT)还可以直观显示DAI患者脑白质纤维束的损伤情况。     

联合多种MRI序列评估弥漫性轴索损伤

目的:探讨弥漫性轴索损伤(DAD在MR扩散加权成像,T2加权液体衰减翻转恢复序列(T2- FLAIR)及增强梯度回波T2*加权血管成像序列(ESWAN)上的影像学特征及各序列的诊断价值,合理规划DAI患者的MRI检查方案.方法:10例DAI患者在伤后两周内行DWI、T2-FLAIR及ESWAN检查,DWI为3个垂直方向...     

多种序列联合应用在弥漫性轴索损伤中的诊断价值

目的探讨联合扩散加权成像(diffusion weighted imaging,DWI)与多回波采集重度T2*WI三维梯度回波序列(enhanced gradient echo T2 star weighted angiography,ESWAN)在急性期脑弥漫性轴索损伤(diffuse axonal injury,DAI)中的应用及联合ESWAN和扩散张量成像(diffusion tensor imaging,DTI)在慢性期DAI的应用价值。方法29例急性期DAI患者均行常规MRI、DWI及ESWAN序列全脑扫描;对29例中的14例慢性期DAI患者,另选14例轻度脑外伤复查患者及14名健康志愿者行T2*WI、ESWAN、DTI全脑扫描。由两名高年资MRI诊断医师共同分析MR图像,对病灶进行计数。在各向异性指数(fractional anisotropy,FA)图上分别测量脑内多个感兴趣区(regionof interest,ROI)的FA值,并将发现出血灶的数量及测得的FA值进行统计分析。结果急性期DAI共检出病灶322个,ESWAN显示284个微出血灶,其他常规序列共显示170个微出血灶。ESWAN、DWI病灶检出率高于液体衰减反转恢复序列(FLAIR)(χ2=67.904,χ2=45.475;P<0.001),ESWAN及DWI病灶检出率差异无统计学意义(χ2=2.859;P>0.05);对于慢性期DAI组,与T2*WI相比,ESWAN能发现更多的出血灶,差异有统计学意义(P<0.001);轻度脑外伤组及健康对照组均未发现微出血灶。轻度脑外伤组及健康对照组间所有ROI FA值差异均无统计学意义(P>0.05)。然而,与轻度脑外伤组相比,DAI组除丘脑、胼胝体压部,其他ROI的FA值差异均有统计学意义;与健康对照组相比,DAI组所有ROI的FA值差异均有统计学意义(P<0.01)。结论联合ESWAN与DWI有利于提高急性DAI的检出率;ESWAN和DTI有利于显示慢性期DAI病变,并可量化评价其损伤的程度。多种序列联合应用对各期DAI的诊断有重要临床价值。     

联合DTI和SWI对外伤性胼胝体损伤的诊断价值

目的 探讨扩散张量成像(DTI)和磁敏感加权成像(SWI)在外伤性胼胝体损伤中联合应用的价值.方法 对16例外伤性胼胝体损伤的患者进行DTI、SWI及MRI常规序列扫描,比较各序列对检出病灶数目的差异.结果 16例均存在不同程度的胼胝体损伤,DTI检出病灶43个[直径(d)≥10 mm者17个,d＜10 mm者26个],其中3个病灶于SWI上未显示；SWI检出105个(d≥10 mm者9个,d＜10 mm者96个),其中49个病灶于DTI上未显示；常规序列检出病灶30个(d≥10 mm者15个,d＜10 mm者15个).对于d＜10 mm病灶的敏感性,DTI、SWI明显优于常规序列(Z=2.716,Z=3.302;P ＜0.01)；对于d≥10 mm的病灶,DTI、SWI在数目统计上与常规序列差异不显著,但是病灶的范围要广于常规序列.结论 DTI和SWI可以相互补足,联合DTI和SWI两种技术,能够较全面地观察胼胝体的损伤,为临床提供更多有价值的信息.三维扩散张量纤维束成像还可以直观显示胼胝体的损伤情况.     

多序列MRI评估脑外伤微出血及弥漫性轴索损伤

目的探讨MR常规序列(T1WI、T2WI、T2FLAIR)、扩散加权成像(diffusion-weighted imaging, DWI)及磁敏感序列(susceptibility weighted imaging, SWI)在脑外伤微出血及弥漫性轴索损伤(DAI)中的应用价值。方法对48例脑外伤患者,应用3.0T MR行常规MRI、DWI及SWI序列成像,比较各序列微出血灶及DAI病灶的检出率差异,并分析病灶在这些序列上的位置分布特点、信号特征。结果联合多种序列共检出547个剪切灶及微出血灶。T1WI检出205个病灶,T2WI检出358个病灶,T2FLAIR检出432个病灶,DWI检出396个病灶,SWI检出471个病灶,SWI病灶检出率高于常规T1WI(χ^2=273.94)、T2WI(χ^2=63.59)、T2FLAIR(χ^2=9.648)、DWI序列(χ^2=31.27),其检出率差异具有统计学意义(P<0.01)。DWI检出的大部分(80%)非出血性剪切灶表现为扩散受限、ADC值减低。SWI图像上微出血灶表现为条状、点状及类圆形低信号,病灶主要分布在皮髓质交界区及深部脑白质区域,位于皮髓交界区病灶排列呈甩鞭样或串珠状,具有特征性。结论 SWI序列对脑外伤微出血的敏感性高,多种序列联合应用对脑外伤微出血和DAI各期的诊断有重要的临床价值。     

磁共振FLAIR序列和DTI在脑弥漫性轴索损伤诊断中的价值

目的 探讨磁共振FLAIR序列和DTI在急性期脑弥漫性轴索损伤(DAI)中的诊断价值及DAI病灶平均ADC值及FA值变化.方法 回顾性分析23例经临床确诊的DAI患者的影像学资料,所有患者及20例健康成人均在常规MRI扫描基础上行液体衰减翻转恢复(FLAIR)序列及弥散加权成像(DTI)扫描,比较两者DAI病灶的检出数目,分析信号特征,分区(大脑半球、胼胝体区、脑干区、小脑半球)测量DAI病灶的平均ADC值及FA值,并与正常对照组相应分区的平均ADC值及FA 值进行比较.结果 联合FLAIR序列和DTI共发现DAI病灶98个,其中DTI显示病灶而FLAIR为阴性的病灶数为11个,FLAIR显示出病灶而DTI为阴性的为5个,各区DAI病灶较之对照组,平均ADC值以降低为主,无变化及升高并存,而FA值降低.结论 对于急性期DAI病灶的显示,DTI比FLAIR序列敏感,FA值变化较平均ADC值敏感,差异有统计学意义(P<0.05).     

应用DWI和ADC预测弥漫性轴索损伤患者昏迷时间

目的:探讨磁共振扩散成像(DWI)和表观扩散系数(ADC)在预测弥漫性轴索损伤(DAI)患者昏迷时间的应用。方法:将57例伤后2h~20d、临床与影像诊断均符合弥漫性轴索损伤(DAI)的患者,进行磁共振常规 T1WI、T2WI和DWI检查,在其DWI表观扩散系数图上测定兴趣区ADC值。昏迷时间预测模型的建立采用逐步回归分析。结果:分析结果显示预测模型预测的昏迷时间与患者实际昏迷的时间非常接近。结论:昏迷时间预测模型可为临床提供昏迷时间预测。     

弥漫性轴索损伤救治

回顾分析近2年来收治的6例弥漫性轴索损伤（DAI）患者的临床表现、治疗方法及效果。提高综合治疗及有效地防治并发症,仍是临床倡导的治疗方案。     

正常成人胼胝体磁共振轴位及矢状位DTI定量研究

目的:研究正常成人胼胝体磁共振轴位扩散张量成像(DTI)与矢状位DTI各向异性(FA)可能的差异,探讨2种测量方法的可靠性。方法:对68例健康志愿者分别行轴位和矢状位DTI扫描,年龄18～78岁。分别测量胼胝体膝部及压部的FA值。对相同部位的轴位和矢状位测量结果进行比较,并行相关性分析。结果:矢状位上测量的胼胝体膝部FA值大于轴位,且两者之间差异有统计学意义(t=-5.833,P<0.001)。胼胝体压部FA值在矢状位与轴位上差异无统计学意义(t=0.435,P>0.05)。结论:矢状位与轴位DTI测量的胼胝体膝部及压部FA值不同,矢状位DTI能研究胼胝体各个区域各向异性的变化。     

Diffusion tensor fractional anisotropy of the normal-appearing seven segments of the corpus callosum in healthy adults and relapsing-remitting multiple sclerosis patients

PURPOSE: To investigate the utility of whole-brain diffusion tensor imaging (DTI) in elucidating the pathogenesis of multiple sclerosis (MS) using the normal-appearing white matter (NAWM) of the corpus callosum (CC) as a marker of occult disease activity. MATERIALS AND METHODS: A high signal-to-noise ratio (SNR) and optimized entire brain DTI data were acquired in 26 clinically-definite relapsing and remitting multiple sclerosis (RRMS) patients and 32 age-matched healthy adult controls. The fractional anisotropy (FA) values of seven functionally distinct regions in the normal-appearing CC were compared between patients and controls. RESULTS: This study indicates that 1) there was a gender-independent FA heterogeneity of the functionally specialized CC segments in normal volunteers; 2) FA in the MS group was significantly decreased in the anterior (P=0.0039) and posterior (P=0.0018) midbody subdivisions of the CC, possibly due to a reduction of small-caliber axons; and 3) the FA of the genu of the CC was relatively intact in the MS patients compared to the healthy age-matched controls (P=0.644), while the splenium showed an insignificant trend of reduced FA values (P=0.248). The decrease in FA in any of the CC subdivisions did not correlate with disease duration (DD) or the expanded disability status scale (EDSS) score. CONCLUSION: The preliminary results are consistent with published histopathology and clinical studies on MS, but not with some published DTI reports. This study provides insights into the pathogenesis of MS, and the role played by compromised axonal integrity in this disease.     

Diffusion properties of NAA in human corpus callosum as studied with diffusion tensor spectroscopy.

In diffusion tensor imaging (DTI) the anisotropic movement of water is exploited to characterize microstructure. One confounding issue of DTI is the presence of intra- and extracellular components contributing to the measured diffusivity. This causes an ambiguity in determining the underlying cause of diffusion properties, particularly the fractional anisotropy (FA). In this study an intracellular constituent, N-acetyl aspartate (NAA), was used to probe intracellular diffusion, while water molecules were used to probe the combined intra- and extracellular diffusion. NAA and water diffusion measurements were made in anterior and medial corpus callosum (CC) regions, which are referred to as R1 and R2, respectively. FA(NAA) was found to be greater than FA(Water) in both CC regions, thus indicating a higher degree of anisotropy within the intracellular space in comparison to the combined intra- and extracellular spaces. A decreasing trend in the FA of NAA and water was observed between R1 and R2, while the radial diffusivity (RD) for both molecules increased. The increase in RD(NAA) is particularly significant, thus explaining the more significant decrease in FA(NAA) between the two regions. It is suggested that diffusion tensor spectroscopy of NAA can potentially be used to further characterize microscopic anatomic organization in white matter.     

Preferential occult injury of corpus callosum in multiple sclerosis measured by diffusion tensor imaging

PURPOSE: To investigate the feasibility of diffusion tensor imaging (DTI) assessment of microscopic fiber tract injury in the corpus callosum (CC) and other normal-appearing white matter (NAWM) in patients with early multiple sclerosis (MS). MATERIALS AND METHODS: DTI was performed in 12 healthy volunteers and 15 patients who have relatively short disease duration (mean = 2.7 years). Both fractional anisotropy (FA) and mean diffusivity (MD) were obtained in different regions of normal-appearing CC (NACC) and NAWM in frontal and occipital regions. RESULTS: The data showed significantly lower FA (P < 0.001) and higher MD (P < 0.04) for NACC regions, but not for frontal and occipital NAWM regions, in patients than in those in healthy volunteers after Bonferroni adjustment. The increase of MD in the entire NACC regions was correlated with the total cerebral lesion volume (r = 0.75, P = 0.001) in patients. CONCLUSION: The water diffusion changes indicate that in the early phase of disease there is a preferential occult injury of CC, which is likely due to the Wallerian degeneration from distant lesions.     

Noninvasive detection of cuprizone induced axonal damage and demyelination in the mouse corpus callosum

Previously, we tested the prediction that axonal damage results in decreased axial diffusivity (λ_∥) while demyelination leads to increased radial diffusivity (λ_?). Cuprizone treatment of C57BL/6 mice was a highly reproducible model of CNS white matter demyelination and remyelination affecting the corpus callosum (CC). In the present study, six C57BL/6 male mice were fed 0.2% cuprizone for 12 weeks followed by 12 weeks of recovery on normal chow. The control mice were fed normal chow and imaged in parallel. Biweekly in vivo DTI examinations showed transient decrease of λ_∥ in CC at 2–6 weeks of cuprizone treatment. Immunostaining for nonphosphorylated neurofilaments demonstrated corresponding axonal damage at 4 weeks of treatment. Significant demyelination was evident from loss of Luxol fast blue staining at 6–12 weeks of cuprizone ingestion and was paralleled by increased λ_? values, followed by partial normalization during the remyelination phase. The sensitivity of λ_? to detect demyelination may be modulated in the presence of axonal damage during the early stage of demyelination at 4 weeks of cuprizone treatment. Our results suggest that λ_∥ and λ_? may be useful in vivo surrogate markers of axonal and myelin damage in mouse CNS white matter. Magn Reson Med, 2006. Published 2006 Wiley‐Liss, Inc.     

弥漫性轴索损伤影像学分析

目的探讨弥漫性轴索损伤(DAI)影像学表现及诊断价值。方法回顾性分析2010年9月~2015年9月26例DAI患者临床与CT、低场MRI资料,其中男性19例,女性7例;年龄16~65岁,平均34.6岁。患者均有创伤史,道路交通伤22例,高处坠落伤3例,重物打击伤1例。伤后均立即出现昏迷或持续昏迷,入院时格拉斯哥昏迷量化表(GCS)评分,重度(≤8分)4例,中度(9~12分)6例,轻度(13~15分)16例。结果 26例均使用CT及低场MRI诊断,主要表现为颅内不同部位单发或多发点状病变,DAI病灶分为出血灶和非出血灶,主要分布在灰白质交界区、基底节区、丘脑、深部白质、胼胝体等区域。低场MRI敏感性明显高于CT(χ2=14.567,P=0.012),各序列中GRE-T2*WI对出血灶检出数(97.59%)最高,DWI对非出血灶检出数(95.18%)最高。结论 CT及低场MRI对DAI的早期诊断很有价值,低场MRI能弥补CT检查阴性颅脑损伤而症状较重患者,能明显提高颅脑损伤的检出率、诊断率,能有效避免漏诊,提示预后。     

Diffusion-weighted MRI in diffuse axonal injury of the brain

The goal of this study was to identify and describe the different types and patterns of tissue injury which are encountered by diffusion-weighted imaging (DWI) in diffuse axonal injury (DAI) of the brain. The DWI data sets of 98 patients who suffered from a closed-head injury were retrospectively evaluated. Medical records were reviewed to rule out pre-existing neurological diseases. Lesions were studied for their DWI signal characteristics and lesion size or extension. Traumatic lesions were classified into three categories depending on their signal characteristica on DWI and apparent diffusion coefficient (ADC) maps: type 1, DWI- and ADC-hyperintense most likely representing lesions with vasogenic edema; type 2, DWI-hyperintense, ADC-hypointense indicating cytotoxic edema; type 3, central hemorrhagic lesion surrounded by an area of increased diffusion. According to the size and extent of lesions, injury was classified into three groups: group A, focal injury; group B, regional/confluent injury; and group C, extensive/diffuse injury. Our study showed that diffusion-weighted imaging differentiates between lesions with decreased and increased diffusion in patients with DAI. Different degrees of tissue injury extent were noticed. Future prospective studies should study if this additional information can be used as a predictor of injury reversibility, final outcome and prognosis.