颅脑磁共振弥散张量成像应用进展

磁共振弥散张量成像技术是利用水分子的弥散运动各向异性进行成像,是目前唯一反映人体活体组织空间组成信息及病理状态下各组织成分之间水分子交换功能状况的检查方法,可以从细胞及分子水平来研究疾病状况。本文回顾DTI的原理和潜在的临床应用,如脑缺血性疾病、脑发育、脑肿瘤、外伤性脑损伤和癫痫、多发性硬化、代谢性疾病等。     

磁共振弥散张量成像在脑肿瘤放射治疗中的应用

弥散张量成像（diffusion tensor imaging，DTI）利用水分子弥散运动描述大脑空间结构，获得脑肿瘤的浸润破坏情况，使得疾病的诊断方式实现从宏观至微观、从形态学上升至形态与代谢并重，为脑肿瘤的诊疗研究带来新的机遇。在这篇综述中，概述了DTI技术的理论基础及目前的局限性，并对其在脑肿瘤放射治疗及其疗效预判中的应用价值进行全面讨论。DTI为脑肿瘤的放疗方案制定提供重要的影像学信息。     

多发性硬化脑内病灶的扩散张量成像

目的研究多发性硬化(MS)的脑内病灶在磁共振扩散张量成像(DTI)上的主要特征,量化分析不同时期病灶的ADC值的差异,探讨DTI在反映MS病理变化中的价值。方法应用3.0 T磁共振设备对34例MS病人行常规头颅MRI和DTI检查,根据病灶有无强化和在T1WI上的信号强度,进行急慢性期病灶的分组。分析不同时期MS病灶在DTI后处理所获得的DWI、ADC、FA图上的特征,并测量各组病灶的ADC值。结果35个急性期病灶中的33个病灶(94.3%)于DWI上呈高信号,5个环形强化病灶在DWI上亦呈环形高信号。急、慢性期病灶的ADC值均升高。慢性期病灶的ADC值明显高于急性期病灶[(12.43±3.78)×10-4 mm2/s∶(10.10±2.28)×10-4 mm2/s,P=0.001]。急性期环形强化病灶的ADC值较非环形强化病灶的高,慢性期T1WI低信号病灶的ADC值较T1WI等信号病灶的高,T1WI明显低信号病灶的ADC值最高。急、慢性期病灶的FA值均降低。FA图能够清晰显示纤维通路上的病灶和纤维束的中断,定位上明显优于常规MRI。病灶于FA图上显示的范围较常规MRI T2WI上显示的大。结论DTI可以反映MS不同时期病灶的病理变化,为观测疾病演变和评价临床疗效提供有效的指标。     

扩散张量成像在颅内肿瘤周围白质区的应用

目的：评价MR扩散张量成像技术在不同级别胶质瘤、脑膜瘤及转移瘤周围正常脑白质区的应用价值。方法：对43例颅内肿瘤患者行常规MRI及扩散张量成像检查,其中高级别胶质瘤12例,低级别胶质瘤10例,脑膜瘤12例、转移瘤9例。测量瘤周正常脑白质的FA值及对侧相应解剖部位正常脑白质的FA值,行组间统计学分析。结果：高级别胶质瘤瘤周正常脑白质FA值低于对侧正常脑白质FA值,差异有统计学意义（P〈0.05）;低级别胶质瘤、脑膜瘤及转移瘤FA值的差异无统计学意义。高级别胶质瘤瘤周正常脑白质FA值与低级别胶质瘤、脑膜瘤、转移瘤瘤周正常脑白质之间差异有统计学意义,后三者之间的差异比较无统计学意义。结论：MR扩散张量成像技术有助于颅内肿瘤的定性诊断及推测肿瘤细胞的浸润范围。     

MR扩散张量成像对脑肿瘤的初步应用研究

目的 :评价MR扩散张量成像在脑肿瘤中的应用价值。方法 :搜集经手术及病理证实的脑膜瘤和星形细胞瘤病例共 3 3例 ,行常规MRI、扩散张量成像 (DTI)检查。构建各向异性分数 (FA)图 ,并测量肿瘤及周围白质的FA值。结果 :正常白质纤维在FA图上表现为高信号。在肿瘤存在时 ,周围白质纤维可表现为受推压移位或浸润破坏 ,破坏后FA值降低 ,表现为低信号。这些表现在常规MRI上均未清楚显示。结论 :DTI可清楚显示肿瘤与周围白质纤维的解剖关系 ,指导临床制订手术方案。     

扩散张量成像技术及各指标的初步应用与评价

目的　探讨正常脑组织及脑肿瘤的扩散张量 (DTI)成像技术及各种评价指标的变化规律及临床应用价值。方法　 10例正常志愿者和 19例脑肿瘤患者进行常规MRI和DTI扫描并重建参数图 ,测量正常志愿者脑组织各主要白质束和神经核团的部分各向异性值 (FA)、各向同性值 (Iso)、衰减指数值 (ExAt)和容积比异向性值 (VrA) ,肿瘤患者测量受累白质束及对侧正常白质束的上述各参数 ,取值并进行统计学分析 ,包括配对t检验 ,相关性分析及方差分析。结果　DTI图上 ,正常脑组织FA、Iso、ExAt、VrA值按组织结构呈规律分布 ;脑肿瘤病例则清楚显示肿瘤对周围结构的破坏、占位效应及水肿所致的改变。各指标中 ,患、健侧间差异有显著性意义 (FA组 :t=9 12 5 ,P <0 0 0 1;Iso组 :t= 5 5 37,P <0 0 0 1;ExAt组 :t=7 16 8,P <0 0 0 1;Vra组 :t=7 12 8,P <0 0 0 1) ,FA与VrA的患侧测量值之间相关性较高 (r=0 92 2 ,P <0 0 0 1) ,其他各指标间无显著相关性 ,单因素方差分析 4种指标变化幅度 [|(患侧 -健侧 ) |/健侧 ) ]的差异具有显著性意义 (F =2 0 4 30 ,P <0 0 0 1) ,FisherLSD检验显示Vra的变化幅度与另 3种指标间差异有显著性意义 (P <0 0 0 1)。另外 ,FA与Iso比较 ,P =0 0 0 6 ,其他无显著性意义。结论　DTI能清楚     

超急性和急性脑梗死的扩散张量成像研究

目的：探讨扩散张量成像（DTI）技术在超急性和急性脑梗死患者中的临床应用价值。方法：对19例超急性脑梗死、22例急性脑梗死患者行常规颅脑MRI及DTI检查。测量梗死灶中心区、边缘区及对侧镜像区的FA、DCavg值,并得到DWI图、DCavg图、FA图、彩色编码FA图及皮质脊髓束图。结果：DWI图、DCavg图、FA图及彩色编码FA图可清楚显示超急性和急性脑梗死病灶。超急性和急性脑梗死组梗死灶中心区FA值分别为（0.481,0.284）×10-4mm2/s,边缘区FA值分别为（0.473,0.306）×10-4mm2/s,急性脑梗死组梗死灶中心区、边缘区FA值与超急性脑梗死组之间差异有统计学意义。超急性和急性脑梗死组梗死灶中心区DCavg值分别为（4.207,4.924）×10-4mm2/s,边缘区DCavg值分别为（5.805,5.420）×10-4mm2/s,急性脑梗死组梗死灶中心区、边缘区与超急性脑梗死组DCavg值之间差异亦有统计学意义。白质纤维束三维重建显示皮质脊髓束为无受累、部分受累、完全受累,其临床肌力分别表现为无减退、治疗后肌力恢复或大部分恢复、无恢复。结论：DTI技术对超急性和急性脑梗死的诊断、治疗及判断预后具有重要的价值。     

Diffusion tensor imaging of partial intractable epilepsy

Our aim was to assess the value of diffusion tensor imaging (DTI) in patients with partial intractable epilepsy. We used DTI (25 non-collinear directions) in 15 patients with a cortical lesion on conventional MRI. Fractional anisotropy (FA) was measured in the internal capsule, and in the normal-appearing white matter (WM), adjacent to the lesion, and away from the lesion, at a set distance of 2–3 cm. In each patient, increased or decreased FA measurements were those that varied from mirror values using an arbitrary 10% threshold. Over the whole population, ipsi- and contralateral FA measurements were also compared using a Wilcoxon test (p<0.05). Over the whole population, FA was significantly reduced in the WM adjacent to and away from the lesion, whilst being normal in the internal capsule. FA was reduced by more than 10% in the WM adjacent to and distant from the lesion in 13 and 12 patients respectively. For nine of the ten patients for whom the surgical resection encompassed the limits of the lesion on conventional MRI, histological data showed WM alterations (gliosis, axonal loss, abnormal cells). DTI often reveals WM abnormalities that are undetected on conventional MRI in patients with partial intractable epilepsy.     

复发性视神经脊髓炎脑扩散张量成像研究

目的利用扩散张量成像（DTI）探讨复发性视神经脊髓炎（RNMO）患者是否存在隐匿性脑组织损伤及其发生机制。方法对16例RNMO患者和16例性别和年龄匹配的正常志愿者脑组织的平均扩散系数（ND）和部分各向异性（FA）进行直方图和感兴趣区（ROI）分析，以P≤0．005为差异有统计学意义。结果与志愿者比较，RNMO患者脑的平均MD升高[脑组织：RNMO患者（0．95±0．02）×10^-3mm^2／s，志愿者（0．91±0．03）×10^-3mm^2，t=3．940，P〈0．001；脑白质：RNMO患者（0．82±0．02）×10^-3mm^2／s，志愿者（0．80±0．02）×10^-3mm^2／s，t=3．117，P=0．004；脑灰质：RNMO患者（1．06±0．04）×10^-3mm^2／s，志愿者（0．88±0．05）×10^-3mm^2／s，t=4．031，P〈0．001]、脑白质的FA直方图峰高抬高[RNMO患者（2．61±0．18）‰，志愿者（2．38±0．18）‰，t=3．627，P=0．001]及脑灰质的MD直方图峰高降低[RNMO患者（7．37±0．89）‰，志愿者（8．91±1．71）‰，t=3．210，P=0．003]和峰位置抬高[RNMO患者（0．83±0．02）×10^-3mm^2／s，志愿者（0．81±0．02）×10^-3mm^2／s，t=4．373，P〈0．001]；与脊髓和视神经有直接联系ROI的平均MD升高[延髓：RNMO患者（1．27±0．11）×10^-3mm^2／s，志愿者（1．11±0．10）×10^-3mm^2／s，t=4．260，P〈0．001；大脑脚：RNMO患者（1．01±0．11）×10^-3mm^2／s，志愿者（0．87±0．05）×10^-3mm^2／s，t=4．391，P〈0．001；内囊：RNMO患者（0．74±0．01）×10^-3mm^2／s，志愿者（0．72±0．01）×10^-3mm^2／s，t=4．683，P〈0．001；视放射：RNMO患者（0．88±0．03）×10^-3mm^2／s，志愿者（0．82±0．03）×10^-3mm^2／s，t=4．619，P〈0．001）、平均FA降低（延髓：RNMO患者0．27±0．01，志愿者0．29±0．03，t=2．996，P=0．005；大脑脚：RNMO患者0．49±0．04，志愿者0．54±0．03，t=4．280，P〈0．001；内囊：RNMO患者0．66±0．02，志愿者0．69±0．02，t=3．953，P〈0．001；视放射：RNMO患者0．53±0．04，志愿者0．59±0．03，t=4．705，P〈0．001）；而与脊髓和视神经无直接联系的胼胝体的平均MD[膝部：RNMO患者（0．76±0．04）×10^-3mm^2／s，志愿者（0．73±0．03）×10^-3mm^2／s；压部：RNMO患者（0．77±0．05）×10^-3mm^2／s，志愿者（0．73±0．04）×10^-3mm^2／s]和FA值（膝部：RNMO患者0．82±0．03，志愿者0．82±0．03；压部：RNMO患者0．83±0．03，志愿者0．83±0．02）差异无统计学意义（P值均〉0．005）。结论RNMO患者存在隐匿性脑组织损伤，这可能与继发于脊髓和视神经病灶的顺行和逆行性变性有关。     

3.0T磁共振扩散张量成像对特发性癫痫的初步研究

目的:利用磁共振扩散张量成像(DTI)探讨特发性癫痫患者脑微观结构的改变,分析其与临床变量的相关性。方法:21例特发性癫痫患者及21例年龄、性别及教育程度相匹配的健康人作为对照组参与本研究。所有受试者均为右利手。原始扫描图像首先经DTI Studio软件处理获得表观扩散系数(ADC)图、部分各向异性(FA)图。数据处理用SPM2软件进行基于体素的全脑分析,主要步骤有图像配准、标准化、平滑。统计分析采用两独立样本t检验。结果:病例组与对照组的年龄、性别及教育程度差异均无统计学意义(P>0.05)。特发性癫痫患者FA值减低区域位于右侧颞叶、岛叶、前扣带及小脑齿状核,ADC值升高区域位于右侧内囊前肢及外囊(P<0.05,成簇水平cluster>100)。相关分析发现右侧颞叶、额叶、枕叶及左侧内囊前肢的ADC值与病程呈正相关(P<0.05,成簇水平cluster>100)。结论:DTI检查能发现特发性癫痫患者脑微观病理改变,为特发性癫痫的病理生理机制研究提供了理论依据。     

DTI对两种肝纤维化动物模型的定量研究

目的:探讨扩散张量成像(DTI)对肝纤维化的定量研究价值。方法:10只CCl4诱导肝纤维化SD大鼠模型及5只同期对照鼠在造模后20周行DTI检查(EPI序列,TR 1600ms,TE 68.1ms,6个方向,b=500s/mm2),完成检查后立即断头处死,4h内行离体肝组织DTI检查,18只血吸虫腹贴法诱导肝纤维化兔模型及10只同期对照兔在造模后8、10和12周分别行DTI扫描,完成扫描后将实验动物处死并取组织切片行HE、Masson染色,按肝纤维化分级分期标准将两种模型组的肝组织炎症活动及纤维化程度分为轻、中、重度三级。扫描图像经AW 4.2工作站处理,计算并分析肝纤维化鼠和对照鼠的在体、离体ADC值和FA值,肝纤维化兔各个时期的ADC值和FA值,并与纤维化程度行相关性分析,采用SSPS 13.0进行统计分析,显著水平取0.05。结果:①病理学证实两种模型纤维化程度分布相似,肝纤维化鼠炎症活动度高于肝纤维化兔(P<0.05);②模型组和对照组间在体、离体ADC值差异具有统计学意义,模型组ADC值、FA值在离体与在体间差异具有统计学意义,在体ADC值与纤维化程度呈负相关(r=-0.607,P=0.016);③肝纤维化兔ADC值在10和12周时,FA值在10周时模型组和对照组间差异具有统计学意义,不同时间点ADC值差异具有统计学意义(F=30.169,P<0.01),而FA值差异无统计学意义(F=1.147,P=0.326);ADC值与纤维化程度呈负相关(r=-0.765,P<0.01),而FA值与纤维化程度无相关性(r=0.189,P=0.356)。结论:两种肝纤维化模型纤维化程度与ADC值均有相关性,ADC值可成为定量评价肝纤维化指标。     

白血病脑实质浸润的弥散张量成像应用研究

目的探讨1．5T磁共振弥散张量成像（diffusiontensorimaging,DTI）,部分各向异性（fractionalanisotropy,FA）和表观扩散系数（apparentdiffusioncoefficient,ADC）及弥散张量纤维束成像（diffusiontensortractography,DTT）在成人白血病脑实质浸润的应用价值。方法回顾性分析经临床证实的8例白血病脑实质浸润病例DTI之ADC、FA参数图,分别测量病变、水肿及健侧相应部位FA值和ADC值;观察各例在DTT图的变化。结果白血病脑实质浸润的肿瘤实质部分FA值8例全部较健侧降低,ADC值5例减低,3例增高;周围水肿区FA值全部降低,ADC值全部增高;脑白质纤维束DTT显示有中断、移位、浸润。结论DTI对脑侵犯神经纤维束损伤具有独特诊断价值;DTI的参数变化能够量化神经纤维受压后微细结构的变化,DTT图像重建能直观显示脑白质纤维束的完整性及损伤程度,DTI联合DTT可更加准确地评估白血病脑侵犯的损害程度。     

肝硬化患者基于体素的全脑扩散张量成像研究

目的：探讨基于体素的扩散张量成像（DTI）对无肝性脑病肝硬化（non-HE）到轻微肝性脑病（MHE）进展的潜在应用价值。方法：对45例无明显肝性脑病症状的肝硬化患者和27例年龄、性别相匹配的健康志愿者（对照组）进行常规MRI和DTI检查。采用神经心理学测试中的数字连接实验-A（NcT-A）和数字符号实验（DST）对受试者认知功能进行评估,根据测试结果将肝硬化患者分为MHE组和non-HE组;采用基于体素的sPM8软件对三组受试者的平均扩散率（MD）图及各向异性分数（FA）图进行ANOVA分析,观察MHE和non-HE组MD值和FA值发生改变的脑区。结果：三组间MD值差异脑区主要位于额叶、颞叶、顶叶区;与non-HE组相比,MHE组右侧颞上／中回、右侧角回、右侧顶叶MD值升高。三组间FA值差异脑区主要位于胼胝体、前扣带回、顶叶及额叶区;与non-HE组相比,MHE组在胼胝体及前扣带皮层的FA值减低。结论：基于体素的DTI技术可观察无明显肝性脑病症状的肝硬化患者脑结构的异常;肝硬化患者存在间质性脑水肿,且与疾病进展有关。     

Magnetic resonance diffusion tensor imaging of the testis: Preliminary observations

IntroductionTo evaluate the feasibility of testis diffusion tensor imaging (DTI), to determine normative apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values and to assess the efficacy of DTI in characterizing testicular pathology.Materials and methodsFifty-six men underwent MRI of the scrotum, including DTI. Parametric and non-parametric statistical tests were used to compare the ADC and FA between the cranial, middle and lower thirds of normal testis and between the bilateral testicular thirds. Comparison between the ADC and FA of normal testis, malignant and benign testicular lesions was performed.ResultsNo significant differences of the ADC and FA in normal testis between the cranial, middle and lower thirds and between the bilateral testicular thirds were found. ADC was significantly lower in malignancies compared to normal testis (P = 0.006) and benign testicular lesions (P = 0.006). FA was significantly higher both in malignancies (P = 0.001) and benign lesions (P < 0.001) compared to normal testis. FA in malignancies did not differ from FA in benign lesions (P = 0.221)ConclusionsThis study shows the feasibility of testis DTI. Both ADC and FA significantly differ between testicular lesions and normal testis, although FA did not show an incremental diagnostic value compared to ADC in lesion differentiation.     

弥散张量成像定量分析脑肿瘤对皮质脊髓束的损伤

目的应用弥散张量成像技术,比较毗邻脑肿瘤皮质脊髓束(CST)与健侧相应位置CST的FA值,计算FA值的变化范围,以期达到术前准确量化分析CST受损情况。方法对26例毗邻CST的脑肿瘤患者术前行弥散张量成像检查,在FA彩色编码图上将邻近脑肿瘤的CST受累情况分成水肿、移位、浸润和破坏四种类型。测量毗邻脑肿瘤CST的FA值和健侧CST的FA值。计算FA值的变化范围,并划分为3个范围,将CST受损类型与ΔFA%值相关性用多个独立样本非参数检验的Fisher确切概率法进行统计分析。结果 26例脑肿瘤患者中,邻近的CST表现为水肿3例、移位8例、浸润8例、破坏7例。当ΔFA%大于0时,与CST水肿相关,ΔFA%介于0%和负30%之间与CST的位移或浸润相关。ΔFA%小于负30%的与CST破坏相关。结论术前分析邻近脑肿瘤的CST的FA值的变化程度,能准确判断CST受损程度,有助于指导脑肿瘤的手术切除。     

Clinical applications of diffusion tensor tractography of the spinal cord

Diffusion tensor imaging (DTI) can visualize the white matter tracts in vivo. The aim of this study was to assess the clinical utility of DTI in patients with diseases of the spinal cord. Fourteen subjects underwent magnetic resonance imaging of the spine at 1.5 T. Preliminary diagnosis of the patients suggested traumatic, tumorous, ischemic or inflammatory lesions of the spinal cord. In addition to T2-weighted images, DTI was performed with the gradients in 30 orthogonal directions. Maps of the apparent diffusion coefficient and of fractional anisotropy were reconstructed. Diffusion tensor imaging showed a clear displacement and deformation of the white matter tracts at the level of the pathological lesions in the spinal cord. This capability of diffusion tensor imaging to reliably display secondary alterations to the white matter tracts caused by the primary lesion has the potential to be of great utility for treatment planning and follow-up.     

磁共振扩散张量成像在诊断脑膜瘤及星形细胞瘤中的应用

磁共振扩散张量成像（diffusion tensor imaging,DTI）是在扩散加权成像（diffusion-weighted imaging, DWI）基础上发展起来的一种水成像新技术,是通过测定表观扩散系数（apparent diffusion coefficient, ADC）和各向异性分数（fractional anisotropy, FA）来量化组织内水分子的扩散速度和方向,反映脑白质纤维束病理状态及其与邻近肿瘤关系,进而鉴别肿瘤良恶性,为临床制定手术方案和预后评估提供有价值的信息。     

梗阻性脑积水的弥散加权成像及弥散张量成像研究

目的探讨磁共振弥散加权成像(DWI)与弥散张量成像(DTI)对梗阻性脑积水的诊断价值。方法 25例梗阻性脑积水患者和30例志愿者均行3.0T磁共振常规序列以及DWI和DTI扫描,重建出ADC图、MD图、FA图、RA图、VR图及AI图,并对各参数图进行测量和记录,所得数据进行统计学分析。结果 30例志愿者及25例梗阻性脑积水患者分别测量双侧侧脑室周围脑白质、胼胝体膝部及压部区域的ADC、MD、FA、RA、VR及AI进行测量,ADC图中胼胝体膝部两组ADC值差异具有统计学意义(P<0.05),双侧侧脑室外侧脑白质两组所测得MD、FA、VR、AI值均有统计学意义(P<0.05),两组胼胝体压部RA值有统计学差异(P<0.05),两组间胼胝体膝部所有测得DTI各参数值均无统计学差异(P>0.05)。结论 DWI和DTI在脑积水的诊断中具有重要的诊断价值。     

Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis

Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8×8×2 cm³ containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm³ were compared. The water content was increased in patients compared with controls (GM: 244±21 vs. 194±10 a.u.; WM: 245±32 vs. 190±11 a.u.), FA decreased (GM: 0.226±0.038 vs. 0.270±0.020; WM: 0.337±0.044 vs. 0.402±0.011) and ADC increased [GM: 1134±203 vs. 899±28 (×10⁻⁶ mm²/s); WM: 901±138 vs. 751±17 (×10⁻⁶ mm²/s)]. Correlations of water content with FA and ADC in WM were strong (r=−0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=−0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=−0.88; P<0.00001) than in GM (r=−0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue.     

Three-dimensional white matter tractography by diffusion tensor imaging in ischaemic stroke involving the corticospinal tract

Diffusion tensor MR imaging (DTI) provides information on diffusion anisotropy, which can be expressed with three-dimensional (3D) white matter tractography. We used 3D white matter tractography to show the corticospinal tract in eight patients with acute or early subacute ischaemic stroke involving the posterior limb of the internal capsule or corona radiata and to assess involvement of the tract. Infarcts and the tract were shown simultaneously, providing information on their spatial relationships. In five of the eight patients, 3D fibre tract maps showed the corticospinal tract in close proximity to the infarct but not to pass through it. All these patients recovered well, with maximum improvement from the lowest score on manual muscle testing (MMT) up to the full score through rehabilitation. In the other three patients the corticospinal tract was shown running through the infarct; reduction in MMT did not necessarily improve favourably or last longer, other than in one patient. As 3D white matter tractography can show spatial relationships between the corticospinal tract and an infarct, it might be helpful in prognosis of gross motor function.