脑膜瘤瘤周水肿的64层螺旋CT灌注成像定量研究

目的:应用64层螺旋CT灌注成像定量估计脑膜瘤瘤周水肿的灌注状况.方法:对15例脑肿膜瘤伴瘤周水肿患者进行MSCT灌注成像,经灌注软件处理分别计算近瘤周水肿区及远瘤周水肿区局部脑血流量(rCBF)、局部脑血容量(rCBV)、表面通透性(PS),并与对侧脑白质灌注参数进行比较;测量并计算水肿指数EI[(V水肿+V肿瘤)/V肿瘤],并与rrCBV(rCBV水肿平均/rCBV对侧脑白质)的进行相关性分析.结果:脑膜瘤近瘤周水肿区、远瘤周水肿区的rCBF和rCBV明显低于对侧脑白质(rCBF:t=5.78和4.34,P=0.001,0.005; rCBV:t=6.46和8.46,P=0.001,0.003),近瘤周水肿区的rCBF和rCBV低于远瘤周水肿区(rCBF:t=3.49,P=0.013;rCBV:t=4.10,P=0.006),三组间PS值的差异均没有统计学意义(P值均＞0.05);水肿指数跟瘤周水肿区的rrCBV值呈负相关(r=-0.72,P＜0.01);2例恶性脑膜瘤近瘤周水肿区的rCBV、rCBF、PS值的均数明显高于良性脑膜瘤近瘤周水肿区.结论:脑膜瘤瘤周水肿区的灌注具有一定特征,有助于鉴别肿瘤良恶性,优化手术方案及相关辅助治疗、评价手术疗效、鉴别肿瘤复发和坏死.     

Peritumoral brain edema in intracranial meningiomas evaluated by dynamic perfusion-weighted MR imaging: a preliminary study

Our objective was to semi-quantitatively evaluate the cerebral perfusion in the peritumoral brain edema of meningiomas using dynamic perfusion-weighted MR imaging. Six patients with intracranial meningiomas accompanied by peritumoral brain edema were prospectively examined by perfusion-weighted MR imaging. One patient was examined twice, once before and once 5 months after the surgical resection. The relative regional cerebral blood volume (rrCBV), the relative regional cerebral blood flow (rrCBF), and the relative regional mean transit time (rrMTT) were calculated for peritumoral brain edema and the contralateral white matter. These parameters were compared between peritumoral brain edema and the contralateral white matter. The time–concentration curve of the peritumoral brain edema was less prominent than that of the contralateral white matter, resulting in a significantly lower rrCBV (mean 46%) and rrCBF (mean 45%) in peritumoral brain edema than those of contralateral white matter. The serial perfusion-weighted MR imaging also demonstrated the recovery of these parameters after the removal of meningioma by means of surgical resection. Perfusion-weighted MR imaging can demonstrate significantly decreased rrCBV and rrCBF in peritumoral brain edema compared with those in normal white matter. Electronic Publication     

磁共振扩散加权成像对恶性胶质瘤及脑转移瘤瘤周水肿的鉴别诊断价值

目的 探讨磁共振扩散加权成像(DWI)对恶性胶质瘤及脑转移瘤瘤周水肿的鉴别诊断价值.资料与方法 42例恶性胶质瘤(Ⅲ级及Ⅲ级以上)和32例脑转移瘤,所有病例均行T_1WI、T_2WI、T_1WI Gd-DTPA增强扫描和DWI检查,均经病理或临床证实.分析肿瘤的边缘特征并测量瘤周近、远侧水肿带的表观扩散系数(ADC)和相对表观扩散系数(rADC).用统计分析软件SPSS 14.0分别对ADC值和rADC值进行统计学分析,统计结果均以哥x±s表示,P<0.05为差异有统计学意义,P>0.05为差异无统计学意义.结果 DWI上36例恶性胶质瘤边缘毛糙,其中27例呈"晕"状改变;28例脑转移瘤边缘清楚,4例稍毛糙但无"晕"状改变.恶性胶质瘤近瘤水肿带的ADC.值及rADC值分别为(1.44±0.15)×10~(-3)mm~2/s和2.01 ±0.24,远瘤水肿带分别为(1.81±0.21)×10-3mm2/s和2.49±0.33.脑转移瘤近瘤水肿带的ADC值及rADC值分别为(1.70±0.22)×10~(-3)mm~2/s和2.43±0.44,远瘤水肿带分别为(1.81±0.18)×10~(-3)mm~2/s和2.54±0.41.恶性胶质瘤和脑转移瘤近瘤水肿带的ADC值和rADC值之间的差异有统计学意义(P<0.01),而远瘤水肿带间的差异无统计学意义(P>0.1);恶性胶质瘤近、远瘤水肿带的ADC值和rADC值之间的差异有统计学意义(P<0.001);脑转移瘤近、远瘤水肿带的ADC值和rADC值之间的差异无统计学意义(P>0.1).结论 在DWI上,恶性胶质瘤和脑转移瘤瘤周近、远侧水肿带的ADC值及rADC值的统计学分析以及它们的边缘特征对两者的鉴别诊断具有重要价值.     

Tumor extension in high-grade gliomas assessed with diffusion magnetic resonance imaging: values and lesion-to-brain ratios of apparent diffusion coefficient and fractional anisotropy

Purpose: To determine whether the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) can distinguish tumor-infiltrated edema in gliomas from pure edema in meningiomas and metastases.

Material and Methods: Thirty patients were studied: 18 WHO grade III or IV gliomas, 7 meningiomas, and 5 metastatic lesions. ADC and FA were determined from ROIs placed in peritumoral areas with T2-signal changes, adjacent normal appearing white matter (NAWM), and corresponding areas in the contralateral healthy brain. Values and lesion-to-brain ratios from gliomas were compared to those from meningiomas and metastases.

Results: Values and lesion-to-brain ratios of ADC and FA in peritumoral areas with T2-signal changes did not differ between gliomas, meningiomas, and metastases (P = 0.40, P = 0.40, P = 0.61, P = 0.34). Values of ADC and FA and the lesion-to-brain ratio of FA in the adjacent NAWM did not differ between tumor types (P = 0.74, P = 0.25, and P = 0.31). The lesion-to-brain ratio of ADC in the adjacent NAWM was higher in gliomas than in meningiomas and metastases (P = 0.004), but overlapped between tumor types.

Conclusion: Values and lesion-to-brain ratios of ADC and FA in areas with T2-signal changes surrounding intracranial tumors and adjacent NAWM were not helpful for distinguishing pure edema from tumor-infiltrated edema when data from gliomas, meningiomas, and metastases were compared.     

The contribution of diffusion-weighted MR imaging to distinguishing typical from atypical meningiomas

Introduction Atypical/malignant meningiomas recur more frequently then typical meningiomas. In this study, the contribution of diffusion-weighted MR imaging to the differentiation of atypical/malignant and typical meningiomas and to the determination of histological subtypes of typical meningiomas was investigated.Methods The study was performed prospectively on 39 patients. The signal intensity of the lesions was evaluated on trace and apparent diffusion coefficient (ADC) images. ADC values were measured in the lesions and peritumoral edema. Student’s t-test was used for statistical analysis. P<0.05 was considered statistically significant.Results Mean ADC values in atypical/malignant and typical meningiomas were 0.75±0.21 and 1.17±0.21, respectively. Mean ADC values for subtypes of typical meningiomas were as follows: meningothelial, 1.09±0.20; transitional, 1.19±0.07; fibroblastic, 1.29±0.28; and angiomatous, 1.48±0.10. Normal white matter was 0.91±0.10. ADC values of typical meningiomas and atypical/malignant meningiomas significantly differed (P<0.001). However, the difference between peritumoral edema ADC values was not significant (P>0.05). Furthermore, the difference between the subtypes of typical meningiomas and atypical/malignant meningiomas was significant (P<0.001). Conclusion Diffusion-weighted MR imaging findings of atypical/malignant meningiomas and typical meningiomas differ. Atypical/malignant meningiomas have lower intratumoral ADC values than typical meningiomas. Mean ADC values for peritumoral edema do not differ between typical and atypical meningiomas.     

MR扩散加权成像瘤周水肿区ADC值在脑肿瘤鉴别诊断中的价值

目的探讨MR扩散加权成像(DWI)瘤周水肿区表观扩散系数(ADC)值在脑内肿瘤鉴别诊断中的价值。资料与方法82例脑肿瘤患者进行常规MRI扫描和DWI检查,对照分析病变的实质部分、周围水肿区的ADC值、相对表观扩散系数(rADC)值、指数表观扩散系数(EADC)值、相对指数表观扩散系数(rEADC)值。结果高级别胶质瘤与低级别胶质瘤、转移瘤、脑膜瘤、淋巴瘤的瘤周水肿ADC值、rADC值差异有统计学意义(P<0.05)。高级别胶质瘤与低级别胶质瘤瘤周水肿的EADC值、rEADC值差异有统计学意义。结论瘤周水肿区ADC值有助于高级别胶质瘤与其他脑内肿瘤鉴别,也可有助于胶质瘤分级。     

CT perfusion parameter values in regions of diffusion abnormalities

BACKGROUND AND PURPOSE: Dynamic CT perfusion imaging is a rapid and widely available method for assessing cerebral hemodynamics in the setting of ischemia. Nevertheless, little is known about perfusion parameters within regions of diffusion abnormality. Since MR diffusion-weighted (DW) imaging is widely considered the most sensitive and specific technique to examine the ischemic core, new knowledge about CT perfusion findings in areas of abnormal diffusion would likely provide valuable information. The purpose of our study was to measure the CT-derived perfusion values within acute ischemic lesions characterized by 1) increased signal intensity on DW images and 2) decreased apparent diffusion coefficient (ADC) and compare these values with those measured in contralateral, normal brain tissue. METHODS: Analysis was performed in 10 patients with acute middle cerebral artery territory stroke of symptom onset less than 8 hours before imaging who had undergone both CT perfusion and DW imaging within 2 hours. After registration of CT perfusion and DW images, measurements were made on a pixel-by-pixel basis in regions of abnormal hyperintensity on DW images and in areas of decreased ADC. RESULTS: Significant decreases in cerebral blood flow and cerebral blood volume with elevated mean transit times were observed in regions of infarct as defined by increased signal intensity on DW images and decreased ADC. Comparison of perfusion parameters in regions of core infarct differed significantly from those measured in contralateral normal brain. CONCLUSION: CT perfusion findings of decreased cerebral blood flow, mean transit time, and cerebrovascular volume correlate with areas of abnormal hyperintensity on DW images and regions of decreased ADC. These findings provide important information about perfusion changes in acute ischemia in areas of diffusion abnormality.     

CT灌注成像对脑肿瘤瘤周水肿的评价

目的　应用CT灌注成像半定量估计脑肿瘤瘤周水肿的灌注状况。方法　应用SomatomPlus4螺旋CT机,对21例脑肿瘤瘤周水肿患者[脑膜瘤4例,胶质瘤(Ⅲ~Ⅳ级)7例、转移瘤10例]进行CT灌注成像,经灌注软件处理分别计算瘤周水肿区局部脑血流量(rCBF)、局部脑血容量(rCBV)、对比剂平均通过时间(MTT),并与对侧脑白质和不同肿瘤瘤周水肿间的灌注参数进行比较。结果　脑膜瘤和转移瘤瘤周水肿的rCBF和rCBV明显低于对侧脑白质(rCBF:t=2 .92和3 .82,P值均<0. 05, 0. 005;rCBV:t=2 .42和3. 53, P<0 .05, 0 .01),胶质瘤瘤周水肿的rCBF和rCBV与正常脑白质无明显差别(t=1 .00和1 .33, P值均>0 .05)。瘤周水肿区与对侧正常脑白质rCBF、rCBV比值,脑膜瘤和转移瘤之间差异无统计学意义(t=0 .23和0. 73, P值均>0 .05),胶质瘤明显大于脑膜瘤和转移瘤(t=3 .05和3. 37, P<0 .01, 0 .005)。结论　脑膜瘤和转移瘤瘤周水肿区的rCBF、rCBV显著降低,而胶质瘤瘤周水肿区接近或高于对侧脑白质,CT灌注能定量脑肿瘤瘤周水肿血流灌注状况,有助于肿瘤的鉴别和随访。     

Can the apparent diffusion coefficient be used as a noninvasive parameter to distinguish tumor tissue from peritumoral tissue in cerebral gliomas?

PURPOSE: To determine whether the apparent diffusion coefficient (ADC) can be used to distinguish between tumor tissue and peritumoral brain tissue in cerebral gliomas. MATERIALS AND METHODS: Twenty-two patients with 44 biopsies were enrolled in this study. ADC maps calculated from a diffusion-weighted (DW) multislice EPI sequence were coregistered with conventional MR images. Neuronavigated biopsies and intraoperative markers were used for correlation with the histologic specimens. ADC values and lesion-to-brain ratios of the different sequences were calculated and compared for tumor tissue and peritumoral brain tissue. A logistic regression analysis was performed to determine the diagnostic value of the ADC maps. RESULTS: The ADC values and ratios demonstrated a large overlap between tumor tissue and peritumoral tissue. Group comparisons revealed a significantly (P=0.03) lower ADC ratio in tumor tissue (mean=1.28 +/- 0.39) compared to peritumoral tissue (mean=1.48 +/- 0.30), whereas the absolute ADC values did not differ significantly. In the logistic regression analysis, the lesion-to-brain ratio of the gadolinium (Gd)-enhanced T1-weighted sequence was the most valuable predictor of the presence of tumor tissue. The ADC value and ratio were not identified as significant predictors. CONCLUSION: The ADC is not helpful for distinguishing tumor tissue from peritumoral brain tissue in gliomas.     

Perfusion MR imaging for differentiation of benign and malignant meningiomas

INTRODUCTION: Our purpose was to determine whether perfusion MR imaging can be used to differentiate benign and malignant meningiomas on the basis of the differences in perfusion of tumor parenchyma and/or peritumoral edema. METHODS: A total of 33 patients with preoperative meningiomas (25 benign and 8 malignant) underwent conventional and dynamic susceptibility contrast perfusion MR imaging. Maximal relative cerebral blood volume (rCBV) and the corresponding relative mean time to enhance (rMTE) (relative to the contralateral normal white matter) in both tumor parenchyma and peritumoral edema were measured. The independent samples t-test was used to determine whether there was a statistically significant difference in the mean rCBV and rMTE ratios between benign and malignant meningiomas. RESULTS: The mean maximal rCBV values of benign and malignant meningiomas were 7.16+/-4.08 (mean+/-SD) and 5.89+/-3.86, respectively, in the parenchyma, and 1.05+/-0.96 and 3.82+/-1.39, respectively, in the peritumoral edema. The mean rMTE values were 1.16+/-0.24 and 1.30+/-0.32, respectively, in the parenchyma, and 0.91+/-0.25 and 1.24+/-0.35, respectively, in the peritumoral edema. The differences in rCBV and rMTE values between benign and malignant meningiomas were not statistically significant (P>0.05) in the parenchyma, but both were statistically significant (P<0.05) in the peritumoral edema. CONCLUSION: Perfusion MR imaging can provide useful information on meningioma vascularity which is not available from conventional MRI. Measurement of maximal rCBV and corresponding rMTE values in the peritumoral edema is useful in the preoperative differentiation between benign and malignant meningiomas.     

What’s the clinical significance of adding diffusion and perfusion MRI in the differentiation of glioblastoma multiforme and solitary brain metastasis?

Objective

To evaluate the additional diagnostic value of diffusion and perfusion MRI in the differentiation of glioblastoma multiforme (GBM) and solitary brain metastasis.

磁共振成像对颅内脑膜瘤水肿分析

目的：探讨脑膜瘤周围脑水肿的程度和肿瘤的生长部位．质地．组织学亚型的相关性．研究其瘤周水肿的形成原因．材料和方法：使用经手术和病理证实的65例脑膜瘤MRI和临床病理资料．观察分析脑膜瘤的瘤周水肿的程度．肿瘤的质地，组织学亚型等．结果：发生于大脑颅盖部或／和有矢状窦受累的脑膜瘤有明显的脑水肿．而发生于其它部位(颅底，丘脑、小脑、脑池等)无或只有轻度脑水肿．结论：轻度脑水肿主要是脑膜瘤对脑组织的直接压迫，而中，重度脑水肿主要是脑膜瘤对大脑表面引流静脉尤其是矢状窦的压迫或阻塞．脑水肿和肿瘤的发生部位有关，面和肿瘤的质地、组织学亚型无关．     

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.     

ASSET联合EPI-DWI技术在脑梗死中的应用探讨

目的 探讨并行采集技术(ASSET)联合平面回波扩散加权像(EPI-DWI)技术在脑梗死中的应用.资料与方法 搜集40例脑梗死患者资料,均行T1WI、T2WI、ASSET-EPI-DWI及EPI-DWI扫描.比较分析ASSET-EPI-DWI及EPI-DWI对脑梗死灶显示图像质量和表观扩散系数(ADC)值.结果 (1)ASSET-EPI-DWI的对比噪声比(CNR)均值高于对应EPI-DWI(t=6.327,P=0.0001).(2)ASSET-EPI-DWI丘脑的ADC值均高于对应EPI-DWI的ADC值(t=10.494,P=0.0001);其梗死灶/对侧的脑组织ADC值的比值均大于对应EPI-DWI的ADC值的比值(t=4.844,P=0.0001).(3)与EPI-DWI相比,ASSET-DWI序列的病灶清晰显示率高(EPI-DWI:80%,ASSET-DWI:100%,P＜0.05).结论 ASSET-EPI-DWI技术不但具有成像时间短的优势,而且图像质量较高,正常的ADC值及病灶与对侧脑组织的比值有助于对脑梗死临床分期诊断,在脑梗死诊断中的应用优于EPI-DWI技术.     

Reliability of cerebral blood volume maps as a substitute for diffusion‐weighted imaging in acute ischemic stroke

Purpose:

To assess the reliability of cerebral blood volume (CBV) maps as a substitute for diffusion‐weighted MRI (DWI) in acute ischemic stroke. In acute stroke, DWI is often used to identify irreversibly injured “core” tissue. Some propose using perfusion imaging, specifically CBV maps, in place of DWI. We examined whether CBV maps can reliably subsitute for DWI, and assessed the effect of scan duration on calculated CBV.

Materials and Methods:

We retrospectively identified 58 patients who underwent DWI and MR perfusion imaging within 12 h of stroke onset. CBV in each DWI lesion's center was divided by CBV in the normal‐appearing contralateral hemisphere to yield relative regional CBV (rrCBV). The proportion of lesions with decreased rrCBV was calculated. After using the full scan duration (110 s after contrast injection), rrCBV was recalculated using simulated shorter scans. The effect of scan duration on rrCBV was tested with linear regression.

Results:

Using the full scan duration (110 s), rrCBV was increased in most DWI lesions (62%; 95% confidence interval, 48–74%). rrCBV increased with increasing scan duration (P < 0.001). Even with the shortest duration (39.5 s) rrCBV was increased in 33% of lesions.

Conclusion:

Because DWI lesions may have elevated or decreased CBV, CBV maps cannot reliably substitute for DWI in identifying the infarct core. J. Magn. Reson. Imaging 2012;36:1083–1087. © 2012 Wiley Periodicals, Inc.     

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.     

Glucocorticoid treatment of brain tumor patients: changes of apparent diffusion coefficient values measured by MR diffusion imaging

Glucocorticoids (GCC) generally are administered to patients with brain tumors to relieve neurological symptoms by decreasing the water content in a peritumoral zone of edema. We hypothesized that diffusion imaging and apparent diffusion coefficient (ADC) values could detect subtle changes of water content in brain tumors and in peritumoral edema after GCC therapy. The study consisted of 13 patients with intra-axial brain tumor, and ADC was measured in the tumor, within peritumoral edema, and in normal white matter remote from the tumor before and after GCC therapy. ADC also was measured in normal white matter in four control patients with no intracranial disease who were treated with GCC for other indications. Conventional MR images showed no visually evident interval change in tumor size or the extent of peritumoral edema in any subject after GCC therapy, which nonetheless resulted in a decrease in mean ADC of 7.0% in tumors (P<0.05), 1.8% in peritumoral edema (P>0.05, not significant) and 5.8% in normal white matter (P<0.05). In patients with no intracranial disease, GCC therapy decreased mean ADC in white matter by 5.4% (P<0.05). ADC measurement can demonstrate subtle changes in the brain after GCC therapy that cannot be observed by conventional MR imaging. Measurement of ADC proved to be a sensitive means of assessing the effect of GCC therapy, even in the absence of visually discernible changes in conventional MR images.     

MR弥散加权成像在鉴别颅内环形强化病变的价值

目的 研究弥散加权成像(DWI)及表观弥散系数(ADC)像在鉴别胶质瘤、转移瘤及脑脓肿中的应用，观察病变中心的坏死、瘤周水肿的ADC值对三者的鉴别诊断价值。资料与方法搜集50例颅内单发环形强化病变．所有病例均行平扫、增强及DWI检查。其中胶质瘤20例，脑脓肿10例，单发转移瘤20例。分别计算病变的中心坏死区、周围水肿、对侧正常脑实质及脑脊液的ADC值，用方差分析法比较不同病变的坏死灶与脑脊液、周围水肿与正常脑实质的ADC值有无差别。结果脑脓肿、转移瘤及胶质瘤中心坏死区的ADC值间均有统计学差异，而且三者与脑脊液的ADC值亦有统计学差异。中心坏死区与脑脊液的ADC值从大到小为：脑脊液、胶质瘤、转移瘤和脑脓肿。脑脓肿和转移瘤周围水肿的ADC值间无统计学差异．二者与胶质瘤周围水肿均有统计学差异，后者的ADC值低于前二者。水肿区的ADC值明显高于正常脑实质。结论DWI及ADC像对鉴别颅内环形强化病变有较高的价值。     

Measurements of diagnostic examination performance using quantitative apparent diffusion coefficient and proton MR spectroscopic imaging in the preoperative evaluation of tumor grade in cerebral gliomas

Purpose

Tumor grading is very important both in treatment decision and evaluation of prognosis. While tissue samples are obtained as part of most therapeutic approaches, factors that may result in inaccurate grading due to sampling error (namely, heterogeneity in tissue sampling, as well as tumor-grade heterogeneity within the same tumor specimen), have led to a desire to use imaging better to ascertain tumor grade. The purpose in our study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy of diffusion-weighted MR imaging (DWI), proton MR spectroscopic imaging (MRSI) or both in grading primary cerebral gliomas.

Materials and methods

We performed conventional MR imaging (MR), DWI, and MRSI in 74 patients with newly diagnosed brain gliomas: 59 patients had histologically verified high-grade gliomas: 37 glioblastomas multiform (GBM) and 22 anaplastic astrocytomas (AA), and 15 patients had low-grade gliomas. Apparent diffusion coefficient (ADC) values of tumor and peritumoral edema, and ADC ratios (ADC in tumor or peritumoral edema to ADC of contralateral white matter, as well as ADC in tumor to ADC in peritumoral edema) were determined from three regions of interest. The average of the mean, maximum, and minimum for ADC variables was calculated for each patient. The metabolite ratios of Cho/Cr and Cho/NAA at intermediate TE were assessed from spectral maps in the solid portion of tumor, peritumoral edema and contralateral normal-appearing white matter. Tumor grade determined with the two methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to determine optimum thresholds for tumor grading. Measures of diagnostic examination performance, such as sensitivity, specificity, PPV, NPV, AUC, and accuracy for identifying high-grade gliomas were also calculated.

Results

Statistical analysis demonstrated a threshold minimum ADC tumor value of 1.07 to provide sensitivity, specificity, PPV, and NPV of 79.7%, 60.0%, 88.7%, and 42.9% respectively, in determining high-grade gliomas. Threshold values of 1.35 and 1.78 for peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 83.3%, 85.1%, 41.7%, 97.6%, and 100%, 57.4%, 23.1% and 100% respectively for determining high-grade gliomas. Significant differences were noted in the ADC tumor values and ratios, peritumoral Cho/Cr and Cho/NAA metabolite ratios, and tumoral Cho/NAA ratio between low- and high-grade gliomas. The combination of mean ADC tumor value, maximum ADC tumor ratio, peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 91.5%, 100%, 100% and 60% respectively.

Conclusion

Combining DWI and MRSI increases the accuracy of preoperative imaging in the determination of glioma grade. MRSI had superior diagnostic performance in predicting glioma grade compared with DWI alone. The predictive values are helpful in the clinical decision-making process to evaluate the histologic grade of tumors, and provide a means of guiding treatment.     

急性大脑中动脉阻塞模型的磁共振弥散成像及相关病理基础研究

目的观察兔大脑中动脉阻塞后常规MRI及DWI表现,阐明活体脑缺血后DWI的演变规律及其病理生理机制方法40只成年新西兰大白兔随机分成2组,对照组4只,实验组36只实验组采用Yamamoto法制作急性大脑中动脉阻塞(MCAO)模型,对照组仅曝露大脑中动脉,而不结扎观察MCAO后缺血区在各时段ADC值的变化规律,并进行病理学检查结果对照组:T2WI及DWI均无高信号出现,光镜检查均无异常改变实验组:DWI上,MCAO后0.5h基底节区出现高信号;T2WI最早于2h出现高信号,早期ADC值快速下降的病理基础是缺血后细胞内的水含量的增加;ADC值下降减慢及相对平台期的病理基础是血脑屏障破坏的逐渐加重及血管源性水肿的出现;而ADC值的上升的病理基础是细胞的死亡、溶解,血脑屏障的破坏结论早期的扩散异常区域并不意味着病灶已发生梗死,当持续缺血达6h以上,脑组织将产生不可逆的损伤