An analysis of the magnetic resonance imaging and pathology of intracal lymphoplasmacyte-rich meningioma

Objective

To discuss the MRI features of the intracranial lymphoplasmacyte-rich meningioma and the correlation between the MRI features and pathology.

Methods

Review retrospectively the MRI and pathologic data of seven patients with lymphoplasmacyte-rich meningioma which were confirmed by surgery and pathology.

Results

The seven cases of lymphoplasmacyte-rich meningioma were solitary, six cases demonstrated flat growth along the meninges, five cases had not yet formed specific nodules, and two cases exhibited irregular lobulation. Seven cases had no clear boundary, peritumoral brain edema was obvious and adjacent brain tissues were invaded to varying degrees. After plain MRI scans, the focuses of seven cases exhibited lower-isointense signal in T1WI, five cases revealed higher-isointense signal and two cases showed lower-isointense signal in T2WI. Enhancement scans demonstrated marked enhancement in seven cases, and the meninges in six cases thicken irregularly and extensively. Pathology showed the richness and diversity of cells, an infiltration containing plasma cells and lymphocytes, as well as the unequal areas of neoplastic spindle cells and meninge epithelial cells.

Conclusion

Lymphoplasmacyte-rich meningioma is a subtype meningioma of WHO I-grade, which is seldom seen and whose imaging appearances are varied from ordinary meningioma. Its features include growing flat along the meninges, irregular forms, unclear boundary, obvious edema, notable strengthening effect, usual invasion of adjacent brain tissues, and similar inflammation.     

富于淋巴浆细胞型脑膜瘤的MRI与病理分析

目的 探讨脑膜瘤亚型富于淋巴浆细胞型的MRI表现特征.方法 回顾性分析7例经手术病理证实的富于淋巴浆细胞型脑膜瘤的影像资料及病理资料,结合相关文献进行对比分析.结果 7例富于淋巴浆细胞型脑膜瘤均为单发病灶,6例病灶沿脑膜匍匐性生长,5例未形成具体瘤结节,2例为不规则分叶状;7例病灶均界限不清,瘤周水肿明显,邻近脑组织不同程度受累.MR平扫T1WI 7例均呈等、略低信号,T2WI 5例呈等、略高信号,2例呈等、略低信号;增强扫描见7例病灶均有显著强化效应,6例脑膜广泛不均匀增厚.病理示细胞丰富,成分多样,见大量淋巴细胞、浆细胞浸润,可见多少不等的梭形瘤细胞及典型脑膜上皮细胞区域.结论 富于淋巴浆细胞型脑膜瘤影像表现不同于常见脑膜瘤,具有一定的影像表现特征,有助于该肿瘤的诊断和鉴别.     

Spinal clear cell meningioma without dural attachment: a case report and literature review

Clear cell meningiomas (CCM) are a very rare histologic subtype of meningioma usually affecting younger patients. The reported data on spinal CCM are extremely rare. Until today, only 89 cases have been reported. Furthermore, CCM without dural attachment is even rarer since only 19 cases have been reported in English literature. In this article, we present the twentieth case of a spinal CCM without dural attachment. Our patient was a 58-year-old female who was presented with pain in her lower back and bilateral sciatica for 6 months. Magnetic resonance imaging showed an intra-dural well-demarcated lesion at L3. Via a posterior approach, total resection was possible due to the lack of dural adhesion of the tumor. Histologic diagnosis was clear cell meningioma.     

MR characteristics of meningioma subtypes at 1.5 tesla.

Analysis of MR signal characteristics and histopathologic findings confirms the strong correlation between meningioma subtype and observed signal intensity (SI) changes in 24 patients imaged at 1.5 T. On T2-weighted images, 90% of fibroblastic and transitional tumors were hypointense relative to cerebral cortex (SI intermediate greater than SI T2-weighted images); conversely, 66% of meningothelial subtypes displayed persistent hyperintensity (SI intermediate less than or equal to SI T2-weighted images), and the remaining one-third demonstrated mixed high-signal changes. Subtype specific differences in collagen distribution and cellularity, i.e., tumor geometry, appeared to account for these signal trends. Based solely on SI characteristics, correct histologic subgrouping of tumors as either fibroblastic/transitional or meningothelial/angioblastic was possible in 80% (19 of 24) of patients. Utilization of adjunctive imaging features (i.e., mass effect, peritumoral edema, intratumoral cyst formation) in conjunction with signal changes permitted a correct histologic pattern in 96% (23 of 24) of patients.     

Skull base chordoid meningioma: imaging features and pathology

The clinical, imaging and pathological features of a skull base chordoid meningioma (CM) are described. The huge tumour resulted in obstructive hydrocephalus and partial erosion of the clivus such that a chordoma was suspected. The lesion's MRI findings were similar to those of a meningioma. Light microscopic, immunohistochemistry and ultrastructural features were diagnostic of CM. Chordoid meningioma is a rare subtype of meningioma and has a great tendency to recur should surgical resection be incomplete.     

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     

Rhabdoid meningioma: clinical features and MR imaging findings in 15 patients

BACKGROUND AND PURPOSE: Rhabdoid meningioma (RM) is a recently described variant of malignant meningioma, with radiologic features currently not well characterized in the medical literature. The purpose of this study was to describe and characterize clinical features and imaging findings associated with RM. MATERIALS AND METHODS: CT (n = 8) and MR (n = 15) images of 15 patients (4 men and 11 women; mean age, 52 years; range, 22-75 years) with 16 pathologically proved RMs along with associated clinical records were retrospectively reviewed. All of the patients underwent surgical resection and had additional radiation therapy except for 1 patient. After surgery, the patients had follow-up brain MR imaging to evaluate for tumor recurrence. RESULTS: Nine lesions (56%) were located in the cerebral convexity, and 4 lesions (25%) were located in the parasagittal areas. The tumors were isointense (n = 15) to gray matter on T1-weighted images, whereas they were hyperintense (n = 14) on T2-weighted images. On gadolinium-enhanced T1-weighted images, homogeneous enhancement was seen in 10 lesions, and heterogeneous enhancement was seen in 6 lesions that had cysts. Cystic components were noted in 6 lesions (38%). Severe peritumoral edema was seen in 12 lesions (75%). Nine lesions (56%) had hyperostosis, and 5 of them also had bone destruction. Among the 8 cases with initial CT scans, only 1 had amorphous calcifications (13%). There was only 1 recurrence of RM found during the follow-up period after surgical resection. CONCLUSION: RMs tend to have prominent peritumoral edema, cystic components, and bone involvement.     

Primary intraosseous meningioma: CT and MRI appearance

Benign primary intraosseous meningioma presenting with osteolytic skull lesion and soft-tissue component is rare. CT and MR imaging of a patient with frontoparietal scalp swelling showed an osteolytic intracalvarial lesion with an extradural soft-tissue component. Following wide surgical resection, the histological examination revealed an intraosseous chordoid meningioma. The clinical and radiological findings of primary intraosseous meningioma are discussed and the relevant literature is reviewed.     

Intraosseous microcystic meningioma

Extradural ectopic meningioma is a rare tumor. We report on an example of microcystic meningioma arising in the skull of an elderly woman. Radiological examination revealed a localized osteolytic lesion in the left parietal bone. At surgery, it was discovered that the tumor was located within the skull without any evidence of extraosseous extension. The light microscopic, immunohistochemical and ultrastructural features were consistent with a microcystic variant of meningioma. To our knowledge, this is the first case of an intraosseous microcystic meningioma, and we believe that this type of meningioma should be considered in the differential diagnoses of myxoid bone tumors of the calvarium. Received: 10 January 2000 Revision requested: 21 February 2000 Revision received: 8 March 2000 Accepted: 13 March 2000     

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.     

Magnetic resonance imaging findings of intracranial papillary meningioma: a study on eight cases

ObjectivesTo increase the awareness on intracranial papillary meningiomas (PMs) by presenting magnetic resonance imaging (MRI) findings on this disease.Materials and methodsThe MRI findings and clinical presentations of nine discrete lesions in eight patients with pathologically documented PMs were retrospectively analyzed.ResultsMost tumors occurred in young adults. The tumors originated from the convexity meninges in five cases and from the parasagittal regions in four cases. The tumor shape was irregular in six cases, lobulated in two cases, and round in one case. By MRI, nine masses were primarily isointense (n=5) or mildly hypointense (n=4) to gray matter on T1-weighted images and inhomogeneous hyperintense (n=3) or isointense (n=6) to the cortex on T2-weighted and fluid-attenuated inversion recovery images. On diffusion-weighted imaging, the signal intensity of the tumor was increased in all lesions compared with the adjacent parenchyma. Tumor and brain interfaces were unclear in seven cases, cyst formation was observed in eight tumors, scattered hemorrhage was observed in three tumors, signal voids due to vessels were visible in four cases, and eight tumors had moderate or marked irregular peritumoral edema. Enhancement was homogeneous (n=2) or heterogeneous (n=7), an area of focal nodular enhancement was observed in three lesions, and the dural tail sign was visible in seven cases.ConclusionAlthough PM is rare, it should be considered in the differential diagnosis when evaluating intracranial neoplasms. Younger patient age, as well as imaging features such as unclear tumor–brain interface, internal heterogeneity including cyst formation, irregular enhancement, signal voids of vessels, and marked peritumoral edema can help distinguish PM from typical benign meningiomas.     

Meningiomas with brain edema: radiological characteristics on MRI and review of the literature

OBJECT: Despite their benign characteristics, meningiomas are often accompanied by perifocal brain edema. The aims of this study are to determine what kind of characteristics on magnetic resonance (MR) image are indicative of a meningioma that produces brain edema and to investigate the mechanism responsible for brain edema accompanying meningiomas. METHODS: Fifty-one patients with meningioma were examined by magnetic resonance imaging (MRI), and tumor size, tumor location, shape of tumor margin, peritumoral rim, and signal intensity of tumor on T2-weighted image (T2WI) were compared and correlated with the presence versus absence of brain edema. Surgical histopathology was also examined and correlated with the MRI findings and brain edema. RESULTS: Shape of tumor margin, peritumoral rim, and signal intensity of tumor on T2WI correlated with brain edema on multivariate analyses. CONCLUSION: Invasive pattern of brain-tumor interface and hyperintensity on T2WI were indicative factors of meningiomas producing brain edema.     

Asynchrony in Peritumoral Resting-State Blood Oxygen Level–Dependent fMRI Predicts Meningioma Grade and Invasion

BACKGROUND AND PURPOSE:Meningioma grade is determined by histologic analysis, with detectable brain invasion resulting in a diagnosis of grade II or III tumor. However, tissue undersampling is a common problem, and invasive parts of the tumor can be missed, resulting in the incorrect assignment of a lower grade. Radiographic biomarkers may be able to improve the diagnosis of grade and identify targets for biopsy. Prior work in patients with gliomas has shown that the resting-state blood oxygen level–dependent fMRI signal within these tumors is not synchronous with normal brain. We hypothesized that blood oxygen level–dependent asynchrony, a functional marker of vascular dysregulation, could predict meningioma grade.MATERIALS AND METHODS:We identified 25 patients with grade I and 11 patients with grade II or III meningiomas. Blood oxygen level–dependent time-series were extracted from the tumor and the radiographically normal control hemisphere and were included as predictors in a multiple linear regression to generate a blood oxygen level–dependent asynchrony map, in which negative values signify synchronous and positive values signify asynchronous activity relative to healthy brain. Masks of blood oxygen level–dependent asynchrony were created for each patient, and the fraction of the mask that extended beyond the contrast-enhancing tumor was computed.RESULTS:The spatial extent of blood oxygen level–dependent asynchrony was greater in high (grades II and III) than in low (I) grade tumors (P < 0.001) and could discriminate grade with high accuracy (area under the curve = 0.88).CONCLUSIONS:Blood oxygen level–dependent asynchrony radiographically discriminates meningioma grade and may provide targets for biopsy collection to aid in histologic diagnosis.

The 2016 World Health Organization guidelines for meningiomas were notable for the inclusion of brain invasion as a criterion sufficient for assignment to “high-grade” status (ie, grade II or III) and may explain the greater incidence of high-grade meningiomas since 2016.¹ In addition to brain invasion, a meningioma is considered grade II or III if it demonstrates an elevated mitotic index and ≥3 aggressive histologic features or demonstrates a loss of meningothelial differentiation.² While roughly 80% of all meningiomas are grade I, with excellent prognosis following surgical resection, the remaining 20% are grade II or III and more likely to recur.³ Furthermore, grade I tumors have a 10-year survival of 83%, compared with 61% for grade II and III tumors,⁴ making the accurate determination of meningioma grade important for both prognostic and treatment purposes.Histologic assessment remains the criterion standard for grading meningiomas; however, an accurate noninvasive prediction of tumor grade could benefit both clinicians and patients by improving preoperative planning and patient counseling and potentially guiding difficult management decisions. Furthermore, routine surgical biopsy may undersample regions that have histologic features, such as invasion, that are diagnostic for grade II or III meningioma, resulting in possible misdiagnosis. Identifying radiographic features that correlate with tumor invasion would, therefore, be useful for guiding biopsy location. Prior studies using standard-of-care structural imaging have attempted to predict meningioma grade by evaluating a mix of objective radiographic features, such as mean voxel intensity, and subjective radiographic features, such as the presence of hyperostosis.⁵ Peritumoral edema detected by T2-FLAIR has also been associated with higher-grade meningiomas.^6,7 Additionally, histogram analysis of diffusion tensor imaging has also been shown to correlate with tumor grade and tumor subtype in meningiomas.⁸ However, it would be beneficial to develop a single, simple, visual criterion that could be easily applied by radiologists and surgeons to predict meningioma grade with high accuracy.Prior work using resting-state blood oxygen level—dependent (BOLD) fMRI in diffuse glioma has revealed that the BOLD signal in and around the tumor is temporally asynchronous with radiographically normal parts of the brain.⁹ BOLD asynchrony maps provide a quantitation of this phenomenon and are generated by comparing each voxel with the mean global signal intensity of both the contralesional hemisphere and the contrast-enhancing tumor. Stereotactically localized biopsies collected from peritumoral regions have demonstrated that the degree of BOLD asynchrony correlates with local tumor burden.¹⁰ Furthermore, the spatial extent of the asynchrony can discriminate IDH wild-type and IDH-mutated gliomas with high fidelity.¹¹Meningiomas have also been shown to cause disruptions in vascular function observable with resting-state BOLD fMRI.¹¹ We, therefore, hypothesized that brain invasion, a common feature of high-grade meningiomas, would be detectable using BOLD asynchrony maps derived from resting-state BOLD fMRI and that the spatial extent of BOLD asynchrony could be used to discriminate meningioma grade. Furthermore, we evaluated whether combining the spatial features of BOLD asynchrony and T2-FLAIR hyperintensity could improve tumor grading accuracy over either measure alone.     

非典型性脑膜瘤的MRI表现

目的：分析非典型性脑膜瘤MRI征象及其预后。方法：回顾性分析经手病理证实为非典型性脑膜瘤共20例;探究其预后情况。结果：20例非典型性脑膜瘤中17例部位均较典型,不典型部位在侧脑室三角区、视神经各1例,多发者1例。病灶呈类圆形或半圆形,略呈分叶状状,信号多表现不均匀,其中出血者2例,明显囊变者3例,瘤周不同程度水肿,有脑膜尾征15例,表现为均匀线状或粗细不一。4例骨质改变,术后残留或复发6例。20例术前MRI诊断为脑膜瘤者18例,误诊2例,误诊率为10%。结论：非典型性脑膜瘤的MRI表现有一定特征性,具有一定的侵袭性;充分认识非典型性脑膜瘤的MRI特点及肿瘤与邻近结构的关系,对肿瘤的定性以及制定手术方案有重要的指导作用。     

脑室脑膜瘤的MRI诊断

目的分析脑室脑膜瘤的MRI表现特点,旨在提高对其诊断的准确率。方法对经手术病理证实的14例脑室内脑膜瘤进行回顾性分析,均行颅脑MR平扫及增强扫描检查。结果肿瘤6例位于右侧侧脑室,7例位于左侧侧脑室,其中11例位于侧脑室三角区,1例位于三脑室。肿瘤9例呈类圆形,体积较大,边界较清,T1WI表现为等或稍低信号,T2WI表现为等、稍高或稍低信号,内可见斑片状短T1长T2或长T1长T2信号,增强扫描肿瘤实性部分呈明显均匀强化;可伴有不同程度的占位效应及瘤周水肿;多伴有脑室的明显扩张。结论脑室脑膜瘤的MRI表现有一定的特征性,结合临床和发病部位、年龄、性别,可提高诊断准确率。     

False-positive indium 111 pentetreotide scan for recurrent meningioma due to radiation fibrosis

A patient with recurrent meningioma in the right frontal lobe, treated with resection and radiation, had a routine magnetic resonance imaging scan that was suspicious for recurrent disease. Follow-up Octreoscan showed moderately increased focal uptake in same region, compatible with recurrence of meningioma; however, the histopathology was consistent with radiation fibrosis. There are reported cases of uptake on Octreoscans at other sites of the body due to chronic inflammation, but only one other case has been reported in the brain. Caution must be taken in interpretation of brain tumors on Octreotide scan, when treatment history includes prior radiation therapy.     

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．     

磁共振常规成像及DWI对脑膜瘤的诊断价值

目的:比较磁共振常规成像序列(T1WI、T2WI及FLAIR)与DWI对脑膜瘤的检出率,探讨其鉴别病理亚型及良恶性的价值。方法:回顾性分析70例经手术病理证实的脑膜瘤患者的MRI图像,计算不同序列对脑膜瘤的检出率;测量并比较不同病理亚型、不同病理分级的肿瘤实质的平均ADC值和相对ADC值(rADC值)。结果:在T2WI上出现低信号的多是纤维型、过渡型和砂粒体型,出现高信号的多是脑膜上皮型和血管瘤型。在各个序列中,以DWI对脑膜瘤病变的检出率最高(87.1%),T2WI次之(74.3%),T1WI最低(38.6%)。恶性脑膜瘤的囊变发生率(67%)明显高于良性脑膜瘤(22%)。良性组各亚型间、良恶性两组间平均ADC值及rADC值差异均无统计学意义(P>0.05)。结论:DWI可提高对脑膜瘤的检出率,但单独根据ADC值并不能鉴别脑膜瘤的亚型及良恶性。DWI结合常规MRI表现对脑膜瘤亚型及良恶性的鉴别有一定意义。     

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.     

常规MRI结合DWI在良恶性脑膜瘤鉴别诊断中的应用

目的：探讨常规MRI结合扩散加权成像（DWI）在良、恶性脑膜瘤鉴别诊断中的临床应用。方法：对56例良性（Ⅰ级）、11例非典型性（Ⅱ级）和4例间变性脑膜瘤（Ⅲ级）患者行常规MRI和DWI检查,所有病例均经手术和病理证实。结果：①良、恶性脑膜瘤的最常见部位均位于额部;两者在肿瘤大小、形态和信号特点等方面均无明显差异;但恶性脑膜瘤在肿瘤囊变坏死、边缘不规整、周围水肿、肿瘤强化方式和脑膜尾征等征象发生率上明显高于良性脑膜瘤,两者之间差异有明显统计学意义;肿瘤侵犯脑实质或（和）破坏周围颅骨是诊断恶性脑膜瘤较为特异性征象;②良、恶性脑膜瘤的扩散系数（ADC）值分别为（8.73±1.68）×10^-9mm^2/s、（7.26±3.22）×10^-9mm^2/s,两者之间差异存在显著性意义。结论：常规MRI对于良恶性脑膜瘤的鉴别诊断有一些特征性征象,结合ADC值的变化,能明显提高对于良恶性脑膜瘤的鉴别诊断。