MRI DTI联合血氧水平依赖功能成像在星形细胞瘤术前的研究

目的探讨3.0T磁共振弥散张量成像(DTI)技术联合功能磁共振成像(fMRI)在星形细胞瘤与邻近脑白质纤维束解剖关系术前计划中的作用。方法对22例星形细胞瘤患者术前行常规MRI平扫,增强扫描及DTI技术fMRI检查,原始数据采集后进行图像分析处理,分别获得各项异性图(FA图),彩色编码张量图及脑白质纤维束图,并测定肿瘤的病灶区表观弥散系数(ADC值)及灶周水肿区各项异性分数(FA值)。分析肿瘤与相邻脑白质解剖关系,并对患者手术前后的临床症状进行评价。结果不同级别星形细胞瘤的肿瘤病灶区和灶周水肿区与正常白质区的ADC值和FA值存在差异,有统计学意义(P0.05﹚。白质纤维束可见受压、移位、浸润及破坏三种改变。4例Ⅰ~Ⅱ级星形细胞瘤推移相邻脑白质纤维束;8例Ⅱ~Ⅲ级星形细胞瘤侵润脑白质;10例Ⅲ~Ⅳ级星形细胞瘤破坏相邻脑白质纤维束。DTI图可以清晰显示运动区锥体束形态变化及与肿瘤之间的关系,在此基础上指导手术,效果满意。结论磁共振DTI技术联合fMRI是目前唯一在活体无创、三维清晰星形细胞瘤与周围白质纤维束的关系,由于二者的联合应用不仅能够显示大脑重要功能激活区在病理情况下的移位和改变,同时还能显示肿瘤与重要功能区和白质纤维束结构的关系,具有重要意义。     

磁共振弥散张量纤维束成像在评估脑肿瘤白质纤维束变化中的价值

目的 探讨磁共振弥散张量纤维束成像(DTT)在评估脑肿瘤中脑白质纤维束变化的价值.方法 运用DTT技术分别评价胶母细胞瘤、脑膜瘤、间变性星形细胞瘤脑白质纤维束的变化.结果 脑肿瘤旁脑白质纤维束在DTT可有以下3种表现:(1)中断,(2)移位,(3)浸润.其中,在胶母细胞瘤中,可见脑白质纤维束中断, 其终止纤维可通过胼胝体;在脑膜瘤中,可见肿瘤压迫引起的脑白质纤维移位以及残存、被分离的纤维束;在间变性星形细胞瘤中,DTT表现为肿瘤原发部位脑白质纤维束中断以及肿瘤对轴突的浸润.结论 DTT的异常表现与肿瘤临床病理特征相关.     

DTI多参数值及DTT技术在颅内肿瘤中的应用研究

目的 探讨MR扩散张量成像(DTI)多参数值在脑肿瘤中的诊断和鉴别诊断价值;评价扩散张量纤维柬成像(DTT)在显示脑肿瘤与周围脑白质纤维束关系中的应用.资料与方法 搜集经手术病理证实的星形细胞瘤(低级别、高级别)、脑膜瘤、转移瘤患者资料(低级别星形细胞瘤15例,高级别星形细胞瘤18例,脑膜瘤16例,转移瘤10例)共59例.行常规T_1WI、T_2WI、增强T_1WI及DTI.测量病灶肿瘤实质区、瘤周水肿区、囊变坏死区、水肿邻近正常白质区及对侧正常白质区的平均扩散系数(DCavg)值、部分各向异性分数(FA)值、1-容积比(1-VR)值及相对各向异性(RA)值,分析各测量值在肿瘤的诊断及良恶性鉴别诊断中的作用.利用DTI数据进行DTT重组病变周围脑白质纤维束,观察肿瘤与脑白质纤维束的关系.结果 低级别星形细胞瘤、高级别星形细胞瘤、脑膜瘤及转移瘤的肿瘤实体、瘤周水肿区的FA值、1-VR值及RA值差异均具有统计学意义(P<0.05);对侧正常白质区DCavg值、FA值、1-VR值及RA值差异均具有统计学意义(P<0.5).FA图、FA彩色编码图、DTT图均能显示脑白质纤维受累情况,而常规MRI难以显示;脑白质纤维束与脑肿瘤的位置关系可分为四型,即推挤型、水肿型、浸润型和破坏型.低级别星形细胞瘤及脑膜瘤良性肿瘤周围的白质纤维束多呈推挤水肿改变,而高级别星形细胞瘤及转移瘤恶性肿瘤周围的白质纤维束多表现为以浸润破坏为主.结论 DTI较常规MRI能更确切、直观地显示脑内肿瘤与周围脑白质的关系,结合FA值、1-VR值及RA值能为肿瘤的诊断及鉴别诊断提供更多的依据;DTT可以为临床提供更多的肿瘤及其周围白质纤维束的信息,指导术前计划的制定和术后的评估.     

弥散张量成像技术在星形细胞肿瘤中的应用价值初探

目的：评价MRI弥散张量成像技术在星形细胞肿瘤中的应用价值。材料和方法：采用GE1.5T超导MR成像系统，对16例1-2级星形细胞肿瘤及15例3-4级星形细胞肿瘤进行了MRI检查，检查序列包括T1WI、T2WI、FLAIR、弥散张量序列（diffusion tensor imaging，DTI）及增强后T1WI。结果：正常脑白质纤维在不同解剖平面，如半卵圆中心、内囊、胼胝体、视放射、锥体束、锥体交叉及内外侧丘系等，各向异性分数图（FA）均为高信号，白质纤维受到破坏后表现为低信号，而这些表现在常规T1WI、T2WI及FLAIR图上未能清楚显示。结论：DT1可以无创性检查脑白质纤维，用于脑肿瘤诊断及术前手术方案的制定。     

脑高级别星形细胞瘤瘤周DTI参数的测定及分析

目的：应用弥散张量成像（DTI）技术探讨脑高级别星形细胞瘤瘤周弥散各向异性特点。方法：25例脑高级别星形细胞瘤术前行DTI扫描,测定瘤周脑实质区及对侧正常脑实质的平均弥散系数（MD）值及各向异性分数（FA）值。并通过弥散张量纤维束成像（DTT）观察病灶与白质纤维束的关系。结果：高级别星形细胞瘤瘤周MD值为1．610±0．23,高于对侧正常脑实质（P〈0．01）。FA值为0．236±0．06,低于对侧正常脑实质（P〈0．01）。结论：DTI能够准确反应脑星形细胞瘤瘤周各向异性特点,DTT能够较为准确显示病灶与白质纤维束的关系。     

~1H-MRS及DTI在颅内肿瘤诊断及手术中应用的初步研究

目的:探讨质子磁共振波谱分析(~1H-MRS)对颅内肿瘤对脑肿瘤诊断价值,同时利用弥散张量成像(DTI)观察皮质脊髓束的累及情况,评价颅内肿瘤预后中的价值.方法:选取40例颅内肿瘤患者,于手术前进行~1H-MRS及DTI,并与术后病理结果进行对照,根据肿瘤内多种代谢产物水平对颅内肿瘤进行分型及胶质瘤恶性程度分级的能力,并行三维白质纤维重建,分析病灶侧白质纤维束的改变情况并观察手术前后肌力恢复情况.结果:星形细胞瘤25例,NAA减少到对侧正常组织的40%～70%,Cr明显下降与正常各半,比较Ⅰ～Ⅱ级与Ⅲ～Ⅳ级星形细胞瘤其肿瘤内代谢化合物NAA/Cr、NAA/Cho和Cho/Cr比值差异有统计学意义(P<0.05);转移瘤5例、脑膜瘤10例有NAA峰但明显低于星形细胞瘤,转移瘤及脑膜瘤NAA/Cho和NAA/Cr比值明显低于星形细胞瘤(P<0.05),转移瘤与脑膜瘤Cr低或缺乏,5例转移瘤都出现Lipid峰,3例出现Lac峰.星形细胞瘤、脑膜瘤、转移瘤Cho峰均显著增高,但脑膜瘤Cho显著升高更明显,其Cbo/Cr显著升高.皮质脊髓束表现为无受压中断、受压无中断及中断、破坏,其受累侧肢体肌力术后表现无明显减退、治疗后肌力恢复、治疗后肌力无恢复.结论:颅内肿瘤采用~1H-MRS的Cho/Cr、NAA/Cr、Lac/Cr、Lipid/Cr代谢物比值结合常规MRI对颅内肿瘤诊断及对胶质瘤进行无创性分级是可行的,DTI能够较直观地反映肿瘤对皮质脊髓束的影响情况,为判断手术后疗效提供重要预测依据.     

大脑胶质瘤DTT初步研究

目的:评价磁共振弥散张量纤维束成像技术在大脑胶质瘤所导致的大脑白质纤维异常改变中的价值。方法:分别对15例大脑胶质瘤患者进行弥散张量成像,对所获得的数据进行弥散张量纤维束成像,获得FA图、DEC图和DTT图,观察不同病变所引起的白质纤维束的改变情况。结果:15个病变累及的白质纤维束有弓状纤维、上纵束、内囊、上额枕束和胼胝体。白质纤维束的异常改变有2个类型:破坏 浸润5例、破坏 移位10例。结论:弥散张量纤维束成像可以显示颅内肿瘤所造成的白质纤维的异常改变,立体显示肿瘤与白质纤维束之间的关系,有利于肿瘤手术方案的制定和病人预后的预测。     

磁共振弥散张量成像在脑高级别星形细胞瘤和转移瘤瘤周实质区的诊断价值

目的 探讨磁共振弥散张量成像(diffusion tensor imaging,DTI)在高级别星形细胞瘤和单发脑转移瘤诊断中的价值.方法 25例脑高级别星形细胞瘤和16例单发脑转移瘤,术前行DTI扫描,测定瘤周脑实质区及对侧正常脑实质的平均弥散系数(MD)值及各向异性分数(FA)值,并重建白质纤维示踪图,观察病灶与白质纤维束的关系.结果 高级别星形细胞瘤与脑转移瘤瘤周实质区的FA值分别为0.227±0.05、0.169±0.07,两者存在统计学差异(P＜0.05).DTI白质纤维示踪图可以较为准确地反映病灶与白质纤维束的关系.结论瘤周实质区FA值有助于高级别脑星形细胞瘤与转移瘤的鉴别.     

磁共振扩散张量成像在星形细胞瘤分级中的价值

目的 探讨磁共振扩散张量成像（DTI）技术在星形细胞瘤分级中的应用价值。资料与方法对15例1-2级星形细胞瘤及22例3～4级星形细胞瘤进行了MR检查，扫描序列包括T1WI、T2WI、液体衰减反转恢复序列（FLAIR）、DTI及增强后T1WI。结果脑部分各向异性指数（FA）图、FA彩色编码图、纤维束追踪图均能显示脑白质纤维受累情况，而常规MRI难以显示。1—2级星形细胞瘤组肿瘤区表观扩散系数（ADC）值（1．33±0．17）与3—4级星形细胞瘤组肿瘤区ADC值（1.17±0．21）比较差异有统计学意义（P〈0．05）。两组瘤周白质FA值与ADC值比较差异均有统计学意义。结论DTI可无创性显示脑自质纤维，且肿瘤区ADC值对星形细胞瘤良恶性分级有重要价值。     

DWI及1HMRS在常见脑肿瘤中的联合应用价值

目的 探讨MR弥散加权成像(DWI)与MR氢质子波谱(1HMRS)技术联合应用对脑肿瘤的诊断价值.方法 对经手术和病理证实的17例星形细胞瘤、10例脑膜瘤和3例转移瘤以及5例结合病史与病程演变证实的转移瘤患者行常规MRI、DWI和1HMRS扫描.采用分析软件包FuncTool进行分析,获得病灶的表观弥散系数(ADC)和波谱图,并分别计算出肿瘤增强区和对侧正常区的NAA/Cho、NAA/Cr和Cho/Cr比值.用SPSS 12.0软件对资料进行处理.结果 星形细胞瘤与脑膜瘤、转移瘤的ADC值两两比较无明显差异(P＞0.05).星形细胞瘤Ⅰ～Ⅱ级及Ⅲ～Ⅳ级的ADC均值有显著性差异(P＜0.01).转移瘤、脑膜瘤有NAA峰但明显低于星形细胞瘤,转移瘤及脑膜瘤NAA/Cho和NAA/Cr比值明显低于星形细胞瘤(P＜0.05).转移瘤与脑膜瘤Cr低或缺乏.脑膜瘤Cho/Cr显著升高.星形细胞瘤Ⅰ～Ⅱ级与Ⅲ～Ⅳ级的NAA/Cho、NAA/Cr和Cho/Cr比值差异存在显著性(P＜0.05).结论 DWI及1HMRS在脑肿瘤联合应用可提高对脑肿瘤定性和分级的准确性.     

增强磁敏感成像在颅内常见肿瘤中的应用研究

目的 探讨增强磁敏感成像(contrast-enhanced susceptibility-weighted imaging,CE-SWI)在颅内常见肿瘤中的应用价值.资料与方法 14例颅内常见肿瘤中,脑膜瘤6例,高级别胶质瘤4例,脑转移瘤3例,髓母细胞瘤1例),分析其CE-SWI特点.结果 CE-SWI示所有肿瘤边界清楚,瘤内分布静脉血管.4例高级别胶质瘤、3例脑膜瘤(矢状窦旁2例,直窦旁1例)及3例转移瘤显示瘤周水肿,与液体衰减反转恢复序列(FLAIR)一致.3例高级别胶质瘤瘤内见出血灶.4例高级别胶质瘤、2例脑膜瘤、3例转移瘤及1例髓母细胞瘤明显强化,与常规增强T_1WI一致.4例脑膜瘤明显环形强化,常规增强T_1WI均匀明显强化.6例脑膜瘤与1例脑膜转移瘤均显示"脑膜尾征".结论 CE-SWI具有磁敏感效应、对比增强以及FLAIR等多重效应,有助于颅内常见肿瘤的术前诊断,减少扫描序列.     

3.0 T MR扩散张量成像在脑肿瘤中的应用价值

目的探讨脑肿瘤在MR扩散张量成像（DTI）的特点以及DTI在脑肿瘤中的诊断和鉴别诊断价值。资料与方法对60例病理证实的脑肿瘤患者（脑膜瘤17例，胶质瘤24例，神经鞘瘤7例，转移瘤12例）术前行3.0T MRDTI，重建成各向异性（FA）、表观扩散系数（ADC）图和三维纤维束成像，选择肿瘤实质为兴趣区（ROI），测量FA和ADC，进行单因素方差分析。结果脑膜瘤FA最高，其次是神经鞘瘤，再次为胶质瘤，转移瘤最低。FA在脑膜瘤与胶质瘤和转移瘤、神经鞘瘤与胶质瘤和转移瘤、胶质瘤与转移瘤均有统计学意义（P〈0．05），脑膜瘤与神经鞘瘤间的FA无统计学意义。神经鞘瘤的ADC值明显高于脑膜瘤、胶质瘤和转移瘤，具有统计学意义（P〈0．05）。结论DTI对脑肿瘤具有很高的临床应用价值。     

CT diagnosis of hyperdense intracranial neoplasms: review of the literature]

In contrast to typical astrocytic tumors that show hypodense areas on computed tomographic images, some intracranial tumors show hyperdense areas on CT images. The major reasons for hyperdensity on CT images are hypercellular lesions, intratumoral calcification, and intratumoral hemorrhage. Malignant lymphomas, germinomas, and medulloblastomas show homogeneous hyperdensity on CT images because of their hypercellularity. Tumorous lesions such as subependymal giant cell astrocytomas, oligodendrogliomas, ependymomas, central neurocytomas, craniopharyngiomas, and meningiomas often present with hyperdense calcified lesions on CT images. Intratumoral hemorrhage also causes hyperdensity on CT images, and is often associated with metastatic brain tumors, glioblastomas, pituitary adenomas, and rarely with any of the other intracranial tumors. Although magnetic resonance imaging is now the major diagnostic tool for diseases of the central nervous system, the first imaging studies for patients with neurologic symptoms are still CT scans. Hyperdense areas on CT images are a clue to making an accurate diagnosis of intracranial neoplasms.     

The role of diffusion-weighted imaging in patients with brain tumors.

BACKGROUND AND PURPOSE: Diffusion-weighted images (DWIs) have been used to study various diseases, particularly since echo-planar techniques shorten examination time. Our hypothesis was that DWIs and tumor apparent diffusion coefficients (ADCs) could provide additional useful information in the diagnosis of patients with brain tumors. METHODS: Using a 1.5-T MR unit, we examined 56 patients with histologically verified or clinically diagnosed brain tumors (17 gliomas, 21 metastatic tumors, and 18 meningiomas). We determined ADC values and signal intensities on DWIs both in the solid portion of the tumor and in the peritumoral, hyperintense areas on T2-weighted images. We also evaluated the correlation between ADC values and tumor cellularity in both gliomas and meningiomas. RESULTS: The ADCs of low-grade (grade II) astrocytomas were significantly higher (P =.0004) than those of other tumors. Among astrocytic tumors, ADCs were higher in grade II astrocytomas (1.14 +/- 0.18) than in glioblastomas (0.82 +/- 0.13). ADCs and DWIs were not useful in determining the presence of peritumoral neoplastic cell infiltration. The ADC values correlated with tumor cellularity for both astrocytic tumors (r = -.77) and meningiomas (r = -.67). CONCLUSION: The ADC may predict the degree of malignancy of astrocytic tumors, although there is some overlap between ADCs of grade II astrocytomas and glioblastomas.     

MR弥散张量成像在颅内肿瘤病变中的应用

目的:探讨磁共振弥散张量成像(DTI)FA值和ADC值在颅内肿瘤病变中的应用价值.方法:收集经手术及组织病理学证实胶质瘤患者12例,脑膜瘤10例,神经鞘瘤9例,淋巴瘤8例.术前行常规MRI平扫、增强扫描检查,DTI检查、工作站自动生成各向异性指数图(FA图)及表观弥散系数图(ADC图),分别测量肿瘤实质区的FA值、ADC值,分析比较不同肿瘤之间有无统计学差异.通过扩散张量纤维束示踪(DTT)在肿瘤区和健侧对应部位重建,主要为白质纤维束,并与肿瘤融合,观察纤维束的形态变化.结果:胶质瘤、脑膜瘤、淋巴瘤、神经鞘瘤肿瘤实质区平均FA值为FA1:0.318±0.0036,FA2:0.45±0.052,FA3:0.304±0.012,FA4:0.0362±0.071.ADC值为:ADC1:1.233±0.204,ADC2:1.061±0.039,ADC3:1.014±0.108,ADC4:1.469±0.062.脑膜瘤FA值最高,神经鞘瘤ADC值最高.DTT显示肿瘤与周围脑白质的关系.结论:不同肿瘤的FA值和ADC值存在明显差异,DTT较常规MRI可更好地观察肿瘤造成的白质纤维柬受压移位、浸润与破坏改变.为病变的诊断与鉴别诊断提供更多信息,为手术方案的制定,术后随访提供依据.     

Glioma grade assessment by using histogram analysis of diffusion tensor imaging-derived maps

Introduction  

Current endeavors in neuro-oncology include morphological validation of imaging methods by histology, including molecular and immunohistochemical techniques. Diffusion tensor imaging (DTI) is an up-to-date methodology of intracranial diagnostics that has gained importance in studies of neoplasia. Our aim was to assess the feasibility of discriminant analysis applied to histograms of preoperative diffusion tensor imaging-derived images for the prediction of glioma grade validated by histomorphology.     

MR digital subtraction angiography in the diagnosis of meningiomas

OBJECTIVE: MR digital subtraction angiography (DSA) is a technique for demonstrating the vasculature combining a rapid two-dimensional T1-weighted sequence with a bolus injection of gadolinium. We attempted to determine its contribution to the diagnosis of intracranial meningiomas. METHODS AND PATIENTS: MR DSA was performed in 18 patients with meningioma as well as in 28 patients with other tumors. The findings were analyzed regarding demonstration of tumor stain and tumor-related vessels. RESULTS: All meningiomas except one were visualized as a homogeneous and intense stain. Feeding arteries were visualized in 2 patients, and draining or abnormal veins in three. In 21 of the 28 patients with other tumors, tumor stains of varying degrees were demonstrated. CONCLUSION: MR DSA can serve as an adjunct to routine MR imaging, because it enables assessment of the hemodynamics of meningiomas and facilitates its differential diagnosis from other tumors.     

Differentiation between classic and atypical meningiomas with use of diffusion tensor imaging

BACKGROUND AND PURPOSE:The differentiation between classic and atypical meningiomas may have implications in preoperative planning but may not be possible on the basis of conventional MR imaging. Our hypothesis was that classic and atypical meningiomas have different patterns of intratumoral water diffusion that will allow for differentiation between them.MATERIALS AND METHODS:Preoperative diffusion tensor imaging (DTI) was performed in 12 classic and 12 atypical meningiomas. Signal intensity of solid-enhancing tumor regions on diffusion-weighted trace images and apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps was assessed. Regions of interest (ROIs) were placed in solid-enhancing regions, peritumoral edema, and contralateral normal-appearing white matter (NAWM) to measure tensor metrics including major (λ₁), intermediate (λ₂) and minor eigenvalues (λ₃) and FA and ADC values. Distribution of tensor shapes within enhancing tumors was calculated for all tumors. Differences between classic and atypical meningiomas in tumor signal intensity, intratumoral and peritumoral tensor metrics, as well as tensor shapes distribution were statistically analyzed.RESULTS:A significantly greater proportion of atypical meningiomas were isointense and hypointense on ADC maps (P = .007). Classic meningiomas had significantly lower FA (P = .012), higher ADC (P = .011), greater λ₂ (P = .020) and λ₃ (P = .003). There was significantly more spherical diffusion in classic than in atypical meningiomas (P = .020). All diffusion tensor metrics for peritumoral edema of the 2 tumor groups did not differ.CONCLUSION:DTI showed that intratumoral microscopic water motion is less organized in classic than in atypical meningiomas. This feature may allow for noninvasive differentiation between classic and atypical meningiomas.

Meningiomas account for between 16% and 20% of primary intracranial tumors.¹ According to the World Health Organization (WHO) classification system, 78% of meningiomas are grade I, 20.4% are grade II, and 1.6% are grade III.² Grades II and III meningiomas are more aggressive than grade I meningiomas. Five-year recurrence rates are 12% for benign meningiomas and 41% for atypical meningiomas.² Initial extent of tumor resection and histologic grade are key determinants for recurrence.³ Therefore, prospectively identifying their histologic grades can be clinically beneficial in treatment planning. Although conventional MR imaging can provide detailed morphologic information of meningiomas, its value in the prediction of WHO grades is limited.⁴According to the WHO classification,⁵ classic meningiomas differ from atypical ones in their number of mitoses, cellularity, and nucleus-to-cytoplasm ratio (N/C ratio) as well as their histologic patterns. Complex microstructural barriers in brain tissue, such as white matter tracts, cell membranes, and capillary vessels result in a tendency for water molecules to diffuse with direction (anisotropic diffusion) rather than equally in all directions (isotropic diffusion). Isotropic diffusion-weighted imaging (DWI), which measures average magnitude of water motion in apparent diffusion coefficient (ADC), has shown controversial results for differentiating classic from atypical meningiomas.^6-8 In contrast to isotropic DWI, diffusion tensor imaging (DTI) provides information about magnitude and directionality of water diffusion⁹ and thus may be able to measure the differences in intratumoral diffusion anisotropy as a result of histologic differences between classic and atypical meningiomas. On the other hand, peritumoral edema associated with meningiomas, regardless of classic or atypical subtypes, has always been considered a purely vasogenic edema (ie, absence of tumor cell infiltration).^10,11Our first hypothesis was that intratumoral diffusion anisotropy is different between these 2 tumor types and that differences in diffusion anisotropy as detected by DTI allow differentiation between them. Our second hypothesis was that anisotropic diffusion measured in peritumoral edema with DTI will not be different between classic and atypical meningiomas.