The role of advanced MRI techniques in differentiating typical,from atypical and malignant meningiomas

Background

Meningiomas are the commonest primary, non-glial intracranial tumors. The diagnosis is often correctly predicted from characteristic imaging appearances. Some meningiomas have atypical imaging appearance that may cause diagnostic confusion.

Aim

Is to evaluate the role of advanced MR imaging techniques in differentiating typical from atypical and malignant meningiomas before surgery.

Patient

Thirty patients were retrospectively included in this study. They were referred from Neurosurgery Department and all of them suspected to have intracranial meningioma according to the contrast enhanced CT.

Methods

All patients were subjected to conventional magnetic resonance imaging followed by advanced magnetic resonance imaging in the form of diffusion weighted imaging, perfusion weighted imaging and MR spectroscopy by single-voxel techniques.

Results

The overall results based on differentiation of typical from atypical and malignant meningiomas by advanced MRI techniques. Twenty four patients had typical meningioma and 6 patients had atypical and malignant Meningiomas by advanced MRI techniques.

Conclusion

Appearance of meningiomas on DWIs and the calculation of ADC values could be correlated with their histopathological grading. On MRS, alanine was not found to be increased in all meningiomas, so MRS cannot reliably differentiate typical intracranial meningomas from atypical meningiomas.     

颅内脑膜瘤的MRI动态增强评价

目的评价MRI动态增强对颅内脑膜瘤的诊断价值。材料与方法采用1．0T超导MRI系统对32例颅内脑膜瘤进行动态增强扫描,分析各组织亚型脑膜瘤的对比增强率-时间(CER-T)曲线、增强峰值(EP)和最大增强百分率(MCER)的差别。结果4例血管瘤型脑膜瘤CER-T曲线均表现为快速陡峭上升,在60s内到达峰值,然后缓慢下降;8例上皮细胞型脑膜瘤CER-T曲线中有7例表现为快速上升,一般在60～210s内到达峰值,然后亦缓慢下降;9例纤维细胞型脑膜瘤CER-T曲线均表现为持续相对缓慢上升,峰值出现在210s以后或未见峰值;11例混合型脑膜瘤的CERT曲线则表现不一。血供丰富的脑膜瘤其EP值和MCER值较血供不丰富的脑膜瘤高。结论MRI动态增强对颅内脑膜瘤的组织亚型和血管丰富程度的判别有一定实用价值。     

Sequential MRI and MR spectroscopy in embolized meningiomas: correlation with surgical and histopathological findings

The preoperative embolization of meningiomas is commonly used to facilitate surgery. The purpose of this study was to evaluate the morphological and metabolic changes in embolized meningiomas and to correlate the results with surgical and histopathological findings. In a prospective study, 36 patients with intracranial meningiomas were included. The extent of devascularization was assessed by angiography and MR volumetry. MRI and MR spectroscopy (MRS) were performed before and sequentially after embolization. At surgery, blood loss was measured and intraoperative duplex-mode ultrasound was applied to identify avascular tumor portions. Histopathological specimens were evaluated for the histological subtype, localization and extent of necrotic tumor portions. Postembolization MRI revealed a variable pattern of secondary revascularization and devascularization with an early onset following embolization. In all patients, peripheral secondary enhancement was present which histopathologically represented a thin layer of vital tumor tissue. MRS revealed lactate in devascularized areas immediately after embolization. Lipids were not observed before the 3rd day after embolization and were always associated with avascular and soft tissue at the time of surgery. Embolized meningiomas feature a variable dynamic with the potential for revascularization and secondary devascularization. Lipid signals indicate avascular and soft tissue at surgery. In case of delayed surgery, MRI and MRS should be performed in order to exclude revascularization and to establish the fatty degeneration of the meningioma.     

Magnetic resonance imaging and diffusion-weighted images of cystic meningioma: correlating with histopathology

BACKGROUND AND PURPOSE: Cystic meningiomas are quite rare, accounting for between 2% and 4% of all intracranial meningiomas. To better understand all the types of cystic meningiomas with magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) and histopathology, we attempted to correlate the MRI and DWI features of cystic meningiomas with the histopathological findings. METHODS: We collected 15 cases of cystic meningiomas diagnosed between 1993 and 2000 (5 men and 10 women, 41-80 years old). Fifteen patients had conventional MRI and 14 patients had CT scan. DWI was also performed in three patients. Apparent diffusion coefficient (ADC) images were also done. In the classification of cystic meningiomas, we adopted Worthington's classification, which divides cystic meningiomas into five groups. RESULTS: Tumor resection was performed in all patients. Tumor locations were as follows: convexity (10), falx (2), pterion (2) and lateral ventricle (1). Regarding the types of cystic lesion, type I (3), type II (3), type III (3), type IV (1) and type V (5) were found. Histopathologically, there were six atypical, four meningothelial, two malignant, one fibroblastic, one angiomatous and one transitional. Intratumoral cystic meningiomas were more common in atypical types. Peritumoral cystic meningiomas were more common in meningothelial and atypical types. The cystic portion of the three cystic meningiomas was hypointense or mildly hyperintense on DWI. ADC ratio (ADCR) of DWI for cyst part of two type I cystic meningiomas was 1.25 and 0.82; for cyst part of one type III was 4.04. CONCLUSIONS: It is important to recognize the neuroimaging features of the cystic meningiomas. Conventional MRI and DWI may play an important role in the preoperative radiological evaluation and the recognition of these types of cysts for proper surgical treatment.     

颅脑血管外皮细胞瘤的CT、MRI与病理对照研究

目的：探讨颅脑血管外皮细胞瘤的临床、病理和ＣＴ、ＭＲＩ特征。材料与方法：收集经ＣＴ和ＭＲＩ诊断为脑膜瘤,经手术病理证实为血管外皮细胞瘤１２例,年龄３４￣５８岁。ＣＴ检查７例,均采用增强前、后常规扫描。ＭＲＩ检查１２例,采用ＳＥ序列增强前、后扫描。结果：１２例肿瘤全部发生在颅内脑外,７例ＣＴ平扫呈低等混合密度２例,呈等高混合密度５例;增强后扫描呈不均匀强化６例,均匀强化１例。骨窗显示病灶局部侵蚀性骨质破坏４例。ＭＲＩ平扫,Ｔ１ＷＩ呈等高不均匀信号１０例,呈等信号２例;Ｔ２ＷＩ呈不均匀等高信号１０例,呈等信号２例。１２例中７例显示脑膜尾征;增强后扫描１ 均呈不均匀强化。结论：血管外皮细胞瘤具有一定的ＣＴ、ＭＲＩ特征性表现：分叶状、丰富的血管流空、肿瘤内密度或信号不均匀、无肿瘤内钙化和骨质增生、局部颅骨呈溶骨性破坏。     

Low-field interventional MRI in neurosurgery: finding the right dose of contrast medium

MRI is increasingly being used as an interventional tool in neurosurgery. The field strength of “intraoperative” MR systems is usually lower than that of imagers commonly used for diagnostic purposes. However, lesion enhancement and apparent lesion extent depend on field strength. The aim of this study was to compare the contrast between intracranial, contrast-enhancing space-occupying lesions and the surrounding white matter obtained with low-field (0.2 T) and high-field (1.5 T) MR imaging and to find the contrast medium dosage for low-field MRI that produces the same lesion-to-white-matter contrast as the one obtained with high-field MRI after the administration of a standard dose of the contrast medium. A total of 38 patients with intracranial metastases or high-grade glioma were enrolled in this study. T1-weighted spin-echo sequences were acquired. High-field (1.5 T) studies were performed after the i. v. administration of 0.1 mmol gadolinium-DTPA /kg body weight. For low-field MRI (0.2 T) a dose escalation technique was used. T1-weighted sequences were repeated after each of three i. v. injections of 0.1 mmol gadolinium-DTPA/kg body weight. Thus, at the low-field examinations three T1-weighted sequences with a contrast medium dosage of 0.1, 0.2 and 0.3 mmol gadolinium-DTPA /kg body weight were obtained. Lesion-to-white-matter contrasts were calculated and compared. The average lesion-to-white-matter contrast obtained with high-field MR examinations was 1.63 (standard deviation 0.32). In the low-field MR examinations the average lesion-to-white-matter contrast was 1.34 (0.2) after a single dose, 1.57 (0.2) after a double dose, and 1.71 (.19) after a triple dose of contrast medium. The lesion-to-white-matter contrast of the high-field MR examination after a single dose of contrast medium was significantly higher than that of the low-field study after a single dose (P < 0.0001), but did not differ significantly from the low-field studies after a double (P = 0.28) or a triple dose (P = 0.17) of contrast medium. In a series of patients with contrast-enhancing space occupying brain lesions low-field MRI (0.2 T) after a double dose of contrast medium yielded the same lesion-to-white-matter contrasts as high-field MRI (1.5 T) after a standard dose. This is an important finding to avoid errors in intraoperative MRI due to the immanently lower degree of lesion enhancement in low-field MR imaging. Received: 14 September 1999 Accepted: 15 February 2000     

颅内血管外皮细胞瘤的MRI与病理结果(附13例报告)

目的 探讨颅内血管外皮细胞瘤的MRI表现，并与病理对照，分析误诊原因。资料与方法搜集术前MRI诊断脑膜瘤，而手术证实为血管外皮细胞瘤13例，所有病例均行MR平扫及增强扫描。结果 13例MRI示肿瘤位于颅内脑外，MR平扫TlWI呈高低不均信号9例，等信号4例；T2WI呈不均匀高信号9例，等信号4例；增强扫描11例呈不均匀强化。术后病理证实肿瘤来源于脑膜间质的血管外皮细胞。结论 颅内血管外皮细胞瘤MRI表现与脑膜瘤相似，但前者往往出现分叶征，有丰富的血管，肿瘤易出血、坏死致信号不均匀，无钙化及局部骨质反应性增生和有溶骨性破坏等特点，据此可资鉴别。病理免疫组织化学可确定肿瘤的起源。     

MRI changes in embolized meningiomas

Summary Study of the MRI changes that occur after superselective embolization of hypervascular meningiomas with Gelfoam powder (5 cases) and polyvinyl alcohol (PVA) particles 150–250 m in size (4 cases) has indicated that, after embolization, meningiomas showed loss of the signal void, decrease in gadolinium-DTPA contrast enhancement, and prolonged T1 and T2. Shortening of T1 and T2 was seen in two patients with Gelfoam-embolized meningiomas in whom CT showed pooling of iodinated contrast medium in the tissue. In vitro experimental data demonstrated that the shortening of T1 and T2 was due to the iodinated contrast medium.     

Pneumosinus dilatans in anterior skull base meningiomas

Introduction

Skull base meningiomas are often missed on non-contrast CT or MR examinations due to their close proximity to bone and low lesion to brain contrast. The purpose of this study is to illustrate that pneumosinus dilatans can be an indicator of anterior skull base meningiomas.

Methods

A retrospective search of the radiology information system and picture archiving and computing system database was performed. Search terms were “meningioma” in association with “pneumosinus dilatans.” Medical records and imaging studies were reviewed independently by two experienced neuroradiologists and were read in consensus. We recorded the patient age at the time of discovery of the meningioma, main presenting symptom(s), location of the tumor, and imaging characteristics. We also performed a comparative literature search for pneumosinus dilatans and its association with meningiomas.

Results

Ten patients (six women; four men) were identified in whom a meningioma of the anterior skull base was associated with a pneumosinus dilatans. Three patients had multiple meningiomas, so a total of 14 intracranial tumors were identified. Mean age at discovery was 59 years with an age range of ±20 years. All meningiomas were diagnosed by MRI and/or CT.

Conclusion

Pneumosinus dilatans can be a helpful sign to indicate the presence of a meningioma of the anterior skull base.     

颅内多发性脑膜瘤的影像学诊断

目的 探讨颅内多发性脑膜瘤的CT和MRI特征.资料与方法 对23例经手术病理证实的多发性脑膜瘤的CT和MRI资料进行回顾性分析.结果 多发性脑膜瘤双发16例,多发7例(平均4.7个),共61个肿瘤.CT平扫为颅内多发的等或略高密度病灶,MRI T1WI病灶呈等或略低信号,T2WI呈等或稍高信号,增强扫描明显均匀强化.结论 CT和MRI对颅内多发性脑膜瘤有重要诊断价值.     

Application of contrast agents in CT and MRI (NMR): their potential in imaging of brain tumors

Summary 21 patients with clinical and CT diagnoses of intracranial tumor were studied by MRI (NMR) prior to and after administration of intravenous Gadolinium-DTPA. Resultant MRI images were compared with corresponding CT sections with respect to lesion detection, contrast enhancement, tumor delineation and visualization of perifocal edema. All intracranial lesions shown on CT were identified on MRI. Contrast enhancement in MRI images was achieved in 19 out of 21 patients, as it was also with CT. In these cases improved differentiation between tumor, perifocal edema and adjacent brain structures were obtained. In most cases sufficient visualization of perifocal edema in MRI required T₂ weighted images (SE 1600/70) in addition to spin echo scans routinely performed prior to and after contrast medium (SE 400/30 or 800/30). No side effects were encountered following administration of Gadolinium-DTPA. The good tolerance and the efficacy justifies the use of Gadolinium-DTPA for contrast enhanced MRI imaging.Dedicated to Professor S. Wende on the occasion of his 60th birthday     

Intracranial meningiomas: How frequent are indicative findings in CT and MRI?

Summary Frequencies of CT and MRI findings characteristic of meningiomas were compared in 50 cases. Plain and contrast enhanced examinations with CT and MRI were evaluated retrospectively regarding 12 criteria known to be indicative of the diagnosis of meningiomas. CT proved to be superior in demonstrating calcifications and a typical tumor density. On the other hand, MRI was better suited for identifying the extraaxial location of tumors, the broad contact of tumors to the meninges, tumor capsules and meningeal contrast enhancement adjacent to the tumor. Both methods provided nearly equal results in demonstrating mass effects, hyperostoses, intensive and homogeneous contrast enhancement, and smooth tumor contours after contrast administration. On the whole, neither of the two methods demonstrated a universal superiority for the diagnosis of intracranial meningiomas. Rather, each method displayed distinct advantages.     

脑膜尾征”：与脑膜瘤相关的MR强化表现

目的分析脑膜瘤脑膜尾征的MR表现及组织学特点。方法对32例脑膜瘤患者均行MR平扫及增强扫描。结果32例34个脑膜瘤病灶中有23个病灶（67.6%）显示脑膜尾征,且与肿瘤的大小与位置无关。结论脑膜尾征是脑膜瘤在MR增强扫描时较常见和特有的表现,而且脑膜尾征与肿瘤侵犯脑膜部分相关。     

颅内脑膜瘤的MRI诊断(附63例分析)

目的　探讨脑膜瘤MRI的特征及其与病理分型之间的关系。方法　回顾性分析 63例经手术和病理证实的脑膜瘤的MRI表现。结果　 63例中 ,62例为单发 ,1例为多发。位于额、顶、枕区脑凸面 3 0例 ,鞍区 10例 ,蝶骨嵴 8例 ,嗅沟 5例 ,其他部位 10例。T1 加权像上脑膜瘤信号主要为等信号和略低信号 ,占 87.2 7%。T2 加权像脑膜瘤信号主要为等和略高信号 ,占 69.84% ,明显高信号占 19.0 5 % ,混杂信号占 7.94% ,略低信号占 3 .17%。病理分型 :上皮型 2 9例 ,纤维母细胞型 11例 ,沙粒体型 8例 ,血管母细胞型 5例 ,血管型 10例。MRI诊断 63例均与手术相符。结论　MRI对脑膜瘤的定性、定位诊断有很大的价值 ,血管型脑膜瘤在MRI中具有较强的流空效应。     

Clinical value of 24-hour delayed imaging in somatostatin receptor scintigraphy for meningioma.

Somatostatin receptor scintigraphy (SRS) using 111In-octreotide has proven useful in patients suspected of having meningiomas. Delayed imaging is regularly performed up to 24 h postinjection. However, this procedure is time consuming and expensive. Therefore, we investigated whether 24-h imaging may be omitted in these patients. METHODS: After clinical examination and standard MRI, 71 patients were suspected of having 92 meningioma lesions. Before surgery, all patients underwent SRS after intravenous injection of 200 MBq (5.4 mCi) 111In-octreotide. Planar whole-body images were obtained at 10 min and 1, 4 and 24 h, and SPECT was performed at 4 and 24 h. Results of SRS in all lesions were evaluated with respect to histology and time of image acquisition. RESULTS: SRS yielded 58 true-positive, 20 true-negative and 14 false-negative results, with the false-negatives all less than 5 mL (2.3+/-2.1 mL) in volume. In 52 of 58 true-positive lesions (89.7%), diagnosis could be established by 4-h imaging without further information by 24-h imaging. In 10 of the 52 lesions, SPECT was necessary to confirm planar findings. Imaging at 24 h was necessary in only 6 of 58 true-positive lesions (10.3%): 3 patients who had intracranial relapse of meningioma (volume < 5 mL) and 3 who had spinal meningioma. Thus, a diagnosis of intracranial meningioma could be established in 52 of 55 lesions (95%) using a 4-h imaging protocol. CONCLUSION: With a 4-h acquisition protocol that includes SPECT imaging, SRS yields sufficient information in patients suspected of having intracranial meningiomas. Delayed imaging at 24 h is recommended only for patients who have small meningiomas (volume < 5 mL), spinal localizations or negative SRS at 4 h.     

Time-resolved contrast-enhanced MR angiography of intracranial lesions

PURPOSE: To determine if contrast-enhanced (CE) MRI of intracranial lesions benefits from time-resolved MR angiography (MRA) during contrast agent injection. MATERIALS AND METHODS: For 126 patients with suspected intracranial lesions undergoing routine CE MRI at 3.0T (N = 88) or 1.5T (N = 38), time-resolved CE MRA (three-dimensional [3D] time-resolved imaging of contrast kinetics [TRICKS]) was performed during injection of the routine gadolinium (Gd) dose of 0.1 mmol/kg. Time to peak (TTP) enhancement of lesions as well as time to internal carotid artery (ICA), middle cerebral artery (MCA), superior sagittal sinus (SSS), and jugular vein enhancement were measured. Source and maximum intensity projection (MIP) images were reviewed to delineate the spatial relationship of lesions and the vasculature. RESULTS: In 61 patients (48%), additional important findings were detected on time-resolved MRA that were not seen on the routine CE protocol, including aneurysms (N = 6), arteriovenous malformations (N = 7), ICA stenoses (N = 2), vascular anomalies (N = 18), and relationships between lesions and vessels (N = 28). In addition, tumor TTP correlated with glioma grade (r = 0.87) and discriminated epithelial from nonepithelial meningiomas (P = 2.6 x 10(-5)). MRA added eight minutes to the total exam time. CONCLUSION: Time-resolved MRA performed during contrast agent injection adds information to the routine brain CE MRI examination of intracranial lesions with only a small time penalty and no additional risk to the patient.     

累及大脑皮层运动区的颅内病变手术前后磁共振功能成像

目的：作者利用功能性磁共振成像原理,对颅内病变累及运动皮层的病人进行了术前、术后的成像检查。即对患者进行手指运动功能区的皮层定位检查,分辨这些重要的功能皮层区与病变的相邻关系。方法：３１例需进行手术治疗的病人,采用血氧依赖水平（ＢＯＬＤ）原理进行扫描,并经过计算机后处理获得脑功能区的影像表现。结果：所有的病例均能在脑功能成像检查中表现出局部脑功能活动区（相应的手指运动支配功能区）规律的信号－时间变化曲线。以及由于病变造成的皮层功能区的移位和缩小等形态学改变。结论：在常规的ＭＲ成像后进行功能性ＭＲ成像研究,对需实施颅内占位病变、特别是对有累及运动皮层焦行切除术者有十分重要的临床指导意义。     

Diagnostic utility of an echo-contrast agent in patients with synovitis using power Doppler ultrasound: a preliminary study with comparison to contrast-enhanced MRI

The purpose of this study was to first evaluate Levovist (Schering, Berlin, Germany), an echo-contrast agent, during power Doppler sonography (PDS) in patients with synovitis using asymptomatic joints as controls. Then we evaluated the accuracy of this technique against contrast-enhanced MRI. Forty patients (19 men and 21 women; mean age 40 years) were enrolled on the basis of clinical signs, laboratory tests, and radiographic findings positive for articular inflammatory disease. They were examined with conventional ultrasonography (US) and PDS techniques before and after intravenous contrast medium injection. Fourteen patients then underwent MRI with and without contrast medium 8–14 days after PDS studies. Three expert readers independently evaluated each examination. After contrast medium, synovium in inflammatory arthritis enhanced on PDS compared with normal joints in the same patient. Power Doppler sonography after contrast medium and MRI were concordant in all cases. Power Doppler sonography with contrast medium showed a qualitative increase in signal from synovial vessels, the first sign of synovial changes in inflammatory diseases. Received: 10 February 2000 Revised: 27 July 2000 Accepted: 1 August 2000     

MRI在颅内血管母细胞瘤诊断中的应用价值

目的探讨MRI在颅内血管母细胞瘤诊断中的应用价值。方法18例经手术病理证实的颅内血管母细胞瘤患者，男11例，女7例，均行MRI平扫＋增强检查，分析其MRI征象。结果17例血管母细胞瘤位于后颅窝。14例表现为大囊小结节型，结节强化明显；4例表现为实质型。13例瘤内或瘤周可见血管流空信号。MRI术前诊断准确率为88．9％（16/18）。结论MRI是术前诊断血管母细胞瘤的有效检查方法。     

Utility of proton MR spectroscopy in the diagnosis of radiologically atypical intracranial meningiomas

Our aim was to evaluate the usefulness of proton MR spectroscopy ((1)H MRS) in the diagnosis of radiologically atypical brain meningiomas. We studied 37 patients with intracranial meningiomas with MRI and (1)H MRS (TE 136 ms). Their spectra were quantitatively assessed and compared with those of 93 other intracranial brain neoplasms: 15 low-grade and 14 anaplastic astrocytomas, 30 glioblastomas and 34 metastases. The most characteristic features of meningiomas were the presence of alanine, high relative concentrations of choline and glutamine/glutamate and low concentrations of creatine-containing compounds, N-acetyl-containing compounds and lipids. These resonances were assembled in algorithms for two-way differentiation between meningioma and the other tumours. The performance of the algorithms was tested in the 130 patients using the leave-one-out method, with 94% success in differentiating between meningioma and other tumour. Of the 37 meningiomas, five (14%) were thought atypical on MRI, and in only one of these, found to be malignant on histology, was a diagnosis other than meningioma suggested by the algorithm. The other four were correctly classified. We suggest that (1)H MRS provides information on intracranial meningiomas which may be useful in diagnosis of radiologically atypical cases.