Differentiation of cerebellopontine angle neuromas and meningiomas with MR imaging

Postcontrast CT of the temporal bone is the neuroradiological study of choice for investigation of cerebellopontine angle (CPA) and internal auditory canal (IAC) lesions. Nonenhancing or small lesions may need CT combined with air or metrizamide cisternography for their detection. Magnetic resonance (MR) imaging has shown interesting capabilities as a noninvasive study for the visualization of the IAC, the neural bundle entering the canal, the brain stem, and cerebellum. In the present series of 24 cases, MR imaging detected the lesion in all 11 verified tumors. We feel that MR can replace invasive air and metrizamide cisternography in the diagnosis of CPA lesions and can help in the differentiation between acoustic neuromas and meningiomas.     

Diagnostic Accuracy of Screening MR Imaging Using Unenhanced Axial CISS and Coronal T2WI for Detection of Small Internal Auditory Canal Lesions

BACKGROUND AND PURPOSE:While enhanced T1WI is considered the “gold standard” for detection of internal auditory canal pathology, unenhanced fluid-sensitive sequences have shown high sensitivity for lesion identification. Our purpose was to evaluate the diagnostic accuracy of an unenhanced MR imaging protocol using axial CISS and coronal T2WI for detection of small (10 mm or less) internal auditory canal lesions.MATERIALS AND METHODS:Twenty-three patients with small internal auditory canal lesions and 13 patients without lesions who had undergone MR imaging using the screening protocol and confirmatory gadolinium-enhanced thin section T1WI were identified. Two blinded neuroradiologists retrospectively evaluated all examinations using 1) only axial CISS, 2) only coronal T2WI, and 3) axial and coronal sequences together. Accuracy, specificity, sensitivity, and interobserver agreement were assessed.RESULTS:Median maximum lesion dimension was 4 mm (range, 2–10 mm). Accuracy, specificity, and sensitivity for axial CISS alone were 0.94, 0.96, and 0.91 for observer 1 and 0.94, 0.92, and 1.00 for observer 2. The data for the coronal T2WI sequence only were 0.94, 0.96, and 0.91 for observer 1, and 0.99, 1.00, and 0.96 for observer 2. Using axial and coronal sequences, the data were 0.97, 0.96, and 1.00 for observer 1, and 0.99, 0.98, and 1.00 for observer 2. κ coefficients were 0.84 for the axial sequence only, 0.90 for coronal only, and 0.91 for axial and coronal both.CONCLUSIONS:Screening noncontrast MR imaging using a combination of axial CISS and coronal T2WI sequences can detect small internal auditory canal lesions with 100% sensitivity and excellent interobserver agreement.

Vestibular schwannoma is the most common lesion diagnosed during MR imaging evaluation of unilateral sensorineural hearing loss.^1,2 Nevertheless, only 2.7%–4.7% of contrast-enhanced MRIs performed for audiovestibular symptoms will diagnose vestibular schwannomas.^3,4 Although gadolinium-enhanced thin section MR imaging has historically been considered the “gold standard” for detection of internal auditory canal (IAC) tumors such as vestibular schwannomas, lower cost unenhanced, fluid-sensitive sequences have demonstrated pooled sensitivities ranging from 96% to 98% for detection of IAC lesions ranging from 2 mm to >20 mm in diameter.⁵ In the era of rising health care costs, especially for diagnostic imaging, the cost savings associated with a low-cost screening IAC MR imaging may become an important factor in decision-making.At our institution, we have performed screening MR imaging of the IACs since the 1990s using fluid-sensitive axial and coronal sequences. In 1996, Allen et al⁶ demonstrated 98% accuracy of an axial and coronal T2-weighted IAC screening MR imaging protocol in 25 patients whose lesions had a mean diameter of 12 mm. Two lesions measuring <5 mm were missed. In 2006, the axial T2 FSE sequence at our institution was replaced by an axial dual-excitation balanced steady-state interference sequence termed CISS (Siemens, Erlangen, Germany), as 3D CISS had been reported to have twice the contrast-to-noise ratio compared with 3D T2WI.⁷ As no study has evaluated the accuracy of a 2-plane screening IAC MR imaging protocol using CISS for detection of small (≤10 mm) lesions, we chose to evaluate the diagnostic accuracy of a 2-sequence screening MR imaging protocol using unenhanced axial CISS and coronal T2WI for detection of small IAC lesions.     

The cerebellopontine angle and internal auditory canal: neurovascular anatomy on gas CT cisternograms

We reviewed 103 normal gas CT cisternograms to delineate the appearance of normal neurovascular structures in the cerebellopontine angle (CPA) and internal auditory canal (IAC). Cranial nerves VII and VIII were identified in the CPA in 97% of cases, either separately (53%) or as a bundle (44%). Intracanalicular branches of the VIIIth cranial nerve were identified in 20% of cases, and cranial nerve V was visualized in the CPA in 14%. The characteristic vascular loop, usually the anterior inferior cerebellar artery, was visible in 35% of cases, and, in 22% of visualized cases, was in an intracanalicular location. The internal auditory artery was questionably visualized in one case. In 10% of cases, greater than 66% of the IAC was occupied by the neurovascular bundle. Familiarity with the normal anatomy and variants seen on gas CT cisternograms is necessary to prevent false-positive interpretations.     

3D-重T_2W水成像技术显示面听神经及内耳结构的研究

目的：探讨MR薄层3D-重T2W水成像技术对内听道面听神经分支和迷路解剖结构的显示情况。方法：选择40例(80侧)无耳部疾病患者，使用GE Signal．5T超导MR成像仪，头部环形线圈或3in(7．62cm)环形线圈，0．5mm层厚3IL重T2WIFSE序列与常规T2WIFSE序列对两例子部同时进行扫描，比较两者对内听道面听神经分支和迷路解剖结构的显示率，并作统计分析。结果：3D-重T2WIFSE序列与常规T2WIFSE序列对其细微结构的显示率分别为螺旋板(98％：0％，P＜0．01)、前庭阶(98％：0％，P＜0．01)、鼓阶(98％：0％，P＜0．01)、椭圆囊(95％：0％，P＜0．01)、球囊(95％：0％，P＜0．01)、前庭嵴(95％：0％，P＜0．01)、前庭上神经(100％：40％，P＜0．01)、前庭下神经(98％：20％，P＜0．01)，其差异均有显著性意义，而在3个半规管、前庭、耳蜗、内听道面神经、蜗神经等结构的显示率方面差异无显著性意义(P＞0．05)。结论：薄层3D-重T2WFSE水成像技术在显示内听道前庭上下神经分支和迷路的螺旋板、前庭阶、鼓阶、椭圆囊、球囊等细微结构方面明显优于常规T2WI。     

MRI增强联合3D FIESTA—C序列对管状微小听神经瘤的诊断价值

目的 探讨MRI增强扫描联合3D FIESTA-C序列对内听道内管状微小听神经瘤的诊断价值.方法 经手术和病理证实的管状微小听神经瘤7例,均行GE3.0T超导磁共振T1FLAIR、FSE-T2WI、3D FIESTA-C及T1FLAIR增强扫描.结果 7例病灶均呈管状且位于内听道内,与脑实质相比,病灶T1FLAIR为等信号,T2WI呈稍低信号,3D FI-ESTA-C呈低信号,患侧较健侧内听道增宽2～5mm不等.T1FLAIR增强扫描7例病变均呈明显强化,其中5例强化均匀,2例强化欠均匀,病灶内可见点状未强化区.结论 T1 FLAIR增强扫描联合3D FIESTA-C更易于检出病灶,可清晰显示病变范围,并提示病变性质,对管状微小听神经瘤的诊断有重要价值.     

MR三维稳态进动快速成像序列在内耳扫描中的初步应用研究

目的探讨三维稳态进动快速成像（3D—FIESTA）列在内耳及内听道扫描中的技术及临床应用。资料与方法使用GE Signa HD MR1．5T超导磁共振仪，3D-FIESTA序列，对43名健康志愿者及1例单侧先天性耳聋者行内耳扫描，并行最大强度投影（MIP）、多平面重组（MPR）及表面容积重组（VR）后处理。结果44例共88个部位均能良好地显示内耳及内听道的形态结构。结论3D-FIESTA序列对内耳及内听道的结构显示清晰，具有较高的临床应用价值。     

Spatial relationship between vestibular schwannoma and facial nerve on three-dimensional T2-weighted fast spin-echo MR images

BACKGROUND AND PURPOSE: During surgical removal of a vestibular schwannoma, correct identification of the facial nerve is necessary for its preservation and continuing function. We prospectively analyzed the spatial relationship between vestibular schwannomas and the facial nerve using 3D T2-weighted and postcontrast T1-weighted spin-echo (SE) MR imaging. METHODS: Twenty-two patients with a unilateral vestibular schwannoma were examined with MR imaging. The position and spatial relationship of the facial nerve to adjacent tumor within the internal auditory canal (IAC) and cerebellopontine angle cistern (CPA) were assessed on multiplanar reformatted 3D T2-weighted fast spin-echo (FSE) images and on postcontrast transverse and coronal T1-weighted SE images. The entrance of the nerve into the bony canal at the meatal foramen and the nerve root exit zone along the brain stem were used as landmarks to follow the nerve course proximally and distally on all images. RESULTS: The spatial relationship between vestibular schwannoma and facial nerve could not be detected on postcontrast T1-weighted SE images. In 86% of the patients, the position of the nerve in relation to the tumor was discernible on multiplanar reformatted 3D T2-weighted FSE images. In tumors with a maximal diameter up to 10 mm, the entire nerve course was visible; in tumors with a diameter of 11 to 24 mm, only segments of the facial nerve were visible; and in tumors larger than 25 mm, the facial nerve could not be seen, owing to focal nerve thinning and obliteration of landmarks within the IAC and CPA. CONCLUSION: Identification of the facial nerve and its position relative to an adjacent vestibular schwannoma is possible on multiplanar reformatted 3D T2-weighted FSE images but not on postcontrast T1-weighted SE images. Detection of this spatial relationship depends on the tumor's size and location.     

Dumbbell schwannomas of the internal auditory canal

BACKGROUND AND PURPOSE: Benign tumors of the internal auditory canal (IAC) may leave the confines of the IAC fundus and extend into inner ear structures, forming a dumbbell-shaped lesion. It is important to differentiate dumbbell lesions, which include facial and vestibulocochlear schwannomas, from simple intracanalicular schwannomas, as surgical techniques and prognostic implications are affected. In this article, the imaging and clinical features of these dumbbell schwannomas are described. METHODS: A dumbbell lesion of the IAC is defined as a mass with two bulbous segments, one in the IAC fundus and the other in the membranous labyrinth of the inner ear or the geniculate ganglion of the facial nerve canal, spanned by an isthmus. Twenty-four patients with dumbbell lesions of the IAC had their clinical and imaging data retrospectively reviewed. Images were evaluated for contour of the mass and extension into the membranous labyrinth or geniculate ganglion. RESULTS: Ten of 24 lesions were facial nerve dumbbell lesions. Characteristic features included an enhancing "tail" along the labyrinthine segment of the facial nerve and enlargement of the facial nerve canal. Dumbbell schwannomas of the vestibulocochlear nerve (14/24) included transmodiolar (8/14), which extended into the cochlea, transmacular (2/14), which extended into the vestibule, and combined transmodiolar/transmacular (4/14) types. CONCLUSION: Simple intracanalicular schwannomas can be differentiated from transmodiolar, transmacular, and facial nerve schwannomas with postcontrast and high-resolution fast spin-echo T2-weighted MR imaging. Temporal bone CT is reserved for presurgical planning in the dumbbell facial nerve schwannoma group.     

脊膜瘤的低场MR诊断

目的 总结脊膜瘤的低场MRI表现，资料与方法 搜集经手术病理证实的脊膜瘤27例，使用开放式0.23TMR扫描仪，行常规矢状位扫描，增强加轴位和冠状位扫描。对肿瘤的部位，形态，大小，边缘，信号，椎间孔改变及增强情况等进行总结分析。结果 颈椎7例，胸椎20例，肿瘤大多呈椭圆形或圆形，平均直径为1.92cm，呈均匀等T1等T2信号19例，5例呈略短T1信号，3例信号欠均匀。25例增强扫描患者，22例均匀强化，2例强化略不均匀，1例不强化，结论 脊髓瘤的低场MRI表现与高场MR一样，具有诸多特征性表现，认真观察分析，一般均可做出准确诊断。     

MR imaging of cerebellopontine angle and internal auditory canal lesions at 1.5 T

The high-field, thin-section (3-5 mm) MR imaging characteristics of 49 cerebellopontine angle and internal auditory canal lesions were reviewed. The diverse abnormalities include 20 acoustic neurinomas, eight neurinomas of other cranial nerves (six involving the fifth cranial nerve and two involving cranial nerves IX-XI), seven meningiomas, five subdural fluid collections, four brainstem tumors with exophytic components, three glomus jugulare tumors, one epidermoid tumor, and one basilar artery aneurysm. T1-, T2-, and proton-density-weighted images were obtained in all cases. T1-weighted images most accurately showed the margins of the seventh and eighth nerves in the internal auditory canal and were most sensitive in detecting small tumors in the cerebellopontine angle. Differentiation of meningioma from acoustic neurinoma by MR was provided most reliably by separation of the meningioma from the porus acusticus and seventh and eighth nerves and not by signal-intensity differences. A hypointense vascular rim was noted on MR in seven of 13 extracanalicular acoustic tumors and in three of seven meningiomas.     

The anatomical classification of AICA/PICA branching and configurations in the cerebellopontine angle area on 3D-drive thin slice T2WI MRI

BackgroundWith the technical advance of magnetic resonance imaging (MRI), we have been able to observe not only the small cranial nerves arising from the brain stem but also the branches of vertebrobasilar artery in the cerebellopontine angle (CPA) cistern.PurposeThe purpose was to demonstrate the courses and configurations of the anterior inferior cerebellar artery (AICA) or posterior inferior cerebellar artery (PICA) branch including the internal auditory artery in the CPA cistern and evaluate the relationship between the facial–vestibulocochlear (VIIth–VIIIth) nerves and AICA/PICA on high-resolution, thin-slice, three-dimensional T2-weighted MRI using driven equilibrium pulse.Material and methodsThirty-three men and 27 women aged 8–85 years old with sensory hearing loss or vertigo, and/or tinnitus were evaluated by thin-slice (0.75 mm) T2-weighted MRI. Five subjects (3 men, 2 women) without any auditory symptoms were also examined.ResultsThin-slice T2WI drive MRI revealed several variations of the AICA/PICA coursing, such as a loop formation (n=30, 48 sides) or the IAC extension (n=19, 30 sides). Contact with the vestibulocochlear nerve was seen in 31.7% subjects (n=19, 27 sides). The AICA/PICA branching and shape patterns relative to the CPA and IAC were classified into four major types: type 1A, nonloop AICA/PICA in the CPA cistern; type 1 B, nonloop AICA/PICA (internal auditory artery) entering the IAC; type 2A, loop-type AICA/PICA in the CPA cistern; and type 2B, loop-type AICA/PICA entering the IAC.ConclusionThere was statistically significant association between types 1A and 2A (P<.01) regarding the existence of any auditory 3 symptoms. The results of our study suggest that this classification is simple and very useful for the elucidation of the mechanism of auditory symptoms and deciding the therapeutic strategies.     

Screening protocol for MR imaging of the internal auditory canal

We have previously shown that 5 mm axial T1-weighted images following Gd-diethylenetriamine pentaacetic acid (DTPA) administration were sufficient as a screening examination of the internal auditory canal (IAC) and cerebellopontine angle cistern in 80% of cases with sensorineural hearing loss. In the remaining 20% of cases 3 mm slices were necessary for confirmation of the diagnosis. To reduce the number of cases requiring the additional examination, we have modified our protocol to include a coronal "scout" T1-weighted sequence followed by 5 mm axial sections angled through the IACs. Routine axial T2-weighted images of the posterior fossa were also obtained. One hundred eleven patients were studied with this protocol. In all but two of these the 5 mm sections unequivocally provided the diagnosis and in those two cases the coronal images confirmed the diagnosis suspected on the axial study. Three millimeter slices were not necessary in any patient. This three sequence, post-Gd-DTPA protocol, which requires only 12 min of scan time, is recommended as a screening protocol for IAC and cerebellopontine angle disease.     

椎管内微小占位性病变的MRI诊断

目的:研究椎管内微小占位性病变的MRI特征及其对病变定性、定位诊断的意义。材料与方法:24例椎管内微小占位性病变患者(男12例,女12例,年龄23～67岁,平均29.1岁)均经PHILIPS 1.0NT型MR仪行常规T_1WI、T_2WI磁共振成像,其中6例又经Gd-DTPA增强扫描。全部病例的椎管内占位病变均经病理证实,并对其MRI表现进行了回顾性分析。结果:24例的病变经病理证实,18例为胚胎源性肿瘤(10例表皮样囊肿,4例皮样囊肿,4例畸胎瘤),4例为神经源性肿瘤(3例神经鞘瘤,1例神经纤维瘤),以及脊膜瘤与脂肪瘤各1例。各种占位性病变的MRI表现随其不同的组织学来源而有很大差别。表皮样囊肿多为均质长T_1长T_2信号。皮样囊肿以短T_1,长T_2信号为主。畸胎瘤呈混杂信号。神经鞘瘤为T_1WI低信号、T_2WI高信号,Gd-DTPA增强扫描后,囊壁均匀强化,偶见强化附壁结节。神经纤维瘤呈均质长T_1、长T_2信号,Gd-DTPA增强扫描后,病灶呈异常对比增强。脊膜瘤呈长T_1、稍长T_2信号,Gd-DTPA增强扫描后,病灶呈异常对比强化,并见局部硬脊膜增厚强化而形成的硬膜尾征。结论:各种病变的MRI表现随其组织学来源不同而有明显差异,它们在椎管内微小占位性病变的定性、定位诊断中起着重要作用,其诊断准确性优于X线椎管造影与CT。     

Detection of acoustic schwannoma: use of constructive interference in the steady state three-dimensional MR.

PURPOSETo compare constructive interference in the steady state (CISS) three-dimensional Fourier transform (3DFT) MR imaging with contrast-enhanced T1-weighted spin-echo MR imaging for accuracy in detecting acoustic schwannoma.METHODSOne hundred twenty-five consecutive patients with possible acoustic schwannoma were examined. The accuracy of CISS-3DFT MR imaging in detecting abnormalities of the cerebellopontine angle, the internal auditory canal, and the inner ear was compared with T1-weighted contrast-enhanced spin-echo MR imaging by independent assessment of both image sets by two observers.RESULTSThe postcontrast T1-weighted MR images revealed 18 cases of unilateral disease of the cerebellopontine angle and/or the internal auditory canal and no case of an abnormal bilateral cerebellopontine angle and/or internal auditory canal. Twelve cases were pathologically proved acoustic schwannomas. One meningioma of the cerebellopontine angle and one metastatic ependymoma to the cerebellopontine angle and the internal auditory canal was encountered. The four remaining cases had a provisional diagnosis of acoustic schwannoma and were scheduled for follow-up imaging and clinical review. Analysis of whether contrast material would have been administered to the appropriate patients (ie, those with disease of the cerebellopontine angle and/or internal auditory canal) according to CISS MR imaging findings revealed a sensitivity of 100% and a specificity of 98% for observer 1 and a sensitivity of 94% and a specificity of 94% for observer 2.CONCLUSIONCISS-3DFT MR imaging, in this patient population, provided high sensitivity and specificity in detecting lesions of the cerebellopontine angle and internal auditory canal; however, further experience is required before a definitive statement regarding the suitability of this technique as a screening procedure can be made. When contrast material cannot be administered, CISS MR imaging may be considered an adequate examination for the evaluation of possible acoustic schwannoma.     

Does the location of a vascular loop in the cerebellopontine angle explain pulsatile and non-pulsatile tinnitus?

The purpose was to investigate patients with unexplained pulsatile and non-pulsatile tinnitus by means of MR imaging of the cerebellopontine angle (CPA) and to correlate the clinical subtype of tinnitus with the location of a blood vessel (in the internal auditory canal or at the cisternal part of the VIIIth cranial nerve). Clinical presentation of tinnitus and perceptive hearing loss were correlated. In 47 patients with unexplained tinnitus, an MR examination of the CPA was performed. Virtual endoscopy reconstructions were obtained using a 3D axial thin-section high-resolution heavily T2-weighted gradient echo constructive interference in steady state (CISS) data-set. High-resolution T2-weighted CISS images showed a significantly higher number of vascular loops in the internal auditory canal in patients with arterial pulsatile tinnitus compared to patients with non-pulsatile tinnitus (P<0.00001). Virtual endoscopy images were used to investigate vascular contacts at the cisternal part of the VIIIth cranial nerve in patients with low pitch and high pitch non-pulsatile tinnitus. A significantly different distribution of the vascular contacts (P=0.0320) was found. Furthermore, a correlation between the clinical presentation of non-pulsatile tinnitus (high pitch and low pitch) and the perceptive hearing loss was found (P=0.0235). High-resolution heavily T2-weighted CISS images and virtual endoscopy of the CPA can be used to evaluate whether a vascular contact is present in the internal auditory canal or at the cisternal part of the VIIIth cranial nerve and whether the location of the vascular contact correlates with the clinical subtype of tinnitus. Our findings suggest that there is a tonotopical structure of the cisternal part of the VIIIth cranial nerve. A correlation between the clinical presentation of tinnitus and hearing loss was found.     

Prediction of the origin of intracanalicular neoplasms with high-resolution MR imaging

Correct diagnosis of intracanalicular neoplasms is important to avoid unnecessary operations or an unsuitable surgical approach. We investigated the capability of high-resolution three-dimensional MR imaging in predicting the origin of intracanalicular neoplasms. Twenty cases underwent three-dimensional Fourier-transformation (3DFT) constructive interference in steady state and contrast-enhanced 3DFT-fast low angled shot MR imaging and surgery. Seventeen cases underwent caloric test. MR diagnosis on the origin of intracanalicular neoplasms was compared with surgical results. For MR diagnosis, the origin of intracanalicular neoplasms was predicted according to the location of the tumor in the internal auditory canal (IAC) in two ways, i.e., determining (1) a single specific nerve of origin and (2) whether the tumor originated from the superior or inferior aspect of the IAC. Surgery could determine the nerve of origin in 16 cases (14 inferior and 2 superior vestibular schwannomas), but it was indeterminate in 4. Comparison between MR prediction and surgical results on a single nerve origin revealed exact agreement in five, but inconsistent in three. Regarding whether the tumor was derived from superior or inferior aspect of the IAC, agreement was found in 10 of the 16 cases (62.5%). Caloric test was abnormal in all patients examined but one with superior vestibular schwannoma. 3DFT-MR imaging was not particularly useful in predicting a precise nerve of origin of intracanalicular neoplasms. The prediction on whether the tumor originated in the superior or inferior aspect of the IAC was superior to caloric test, which might have clinical significance in treatment planning especially for hearing preservation surgery.     

CT和MRI对颅内表皮样囊肿诊断价值的评价

目的：评估CT和MRI对颅内表皮样囊肿的诊断价值，分析误诊原因，提高诊断水平。方法：44例经手术和病理证实的颅内表皮样囊肿，术前全部行常规MRI检查，其中19例行Gd-DTPA增强MRI检查；17例作CT平扫，其中12例作静脉注射增强CT检查。结果：颅内表皮样囊肿多位于桥小脑角池，本组病例中占34．9％(15／4例)；肿瘤多呈不规则形态，占70．45％(31／44例)；CT平扫多呈均匀低密度，占70．59％(12/17例)，造影后多无强化，占91．71％(11／12例)；MRT1加权像上多呈均匀低信号，但略高于脑脊液，T2加权像上多呈均匀高信号，占61．36％(27／44例)，Gd-DTPA增强后多无强化，占84．21％(16／19例)。肿瘤周围的脑组织均无水肿，占100％，肿瘤较大时可以挤压、推移周围脑组织或脑室结构，引起比较明显的占位效应，占70．45％(31／44例)；肿瘤较大时，很少引起阻塞性脑积水。结论：颅内表皮样囊肿在CT和MRI像上有特征性表现，MRI无论在定位和定性诊断上优于CT，Gd-DTPA的应用有助于颅内囊性占位的诊断与鉴别诊断。     

MR detection of tumor in the internal auditory canal

The MR appearance of 15 tumors within or near the internal auditory canal was analyzed in detail and compared with the subsequent surgical observations. In most cases, nonenhanced MR showed the precise extent of the intracanalicular and extracanalicular tumor despite minor variations in appearance. In a case of facial nerve neurinoma, the extent to which the tumor invaded the canal was underestimated by MR. Gadolinium-DTPA enhancement is expected to eliminate uncertainties in MR imaging of the internal auditory canal.     

蜗神经发育异常影像学诊断

目的:探讨蜗神经发育异常的影像学表现。方法:回顾性分析17例影像诊断为蜗神经发育异常患者的CT及MRI表现,总结相关征象。17例患者均行MRI检查,常规行横轴面和冠状面SE T_1 WI,FSE T_2 WI,并采用三维快速平衡稳态(3D FIESTA)序列进行内耳成像;CT检查采用横轴面HRCT扫描。结果:MRI检查显示17例33耳蜗神经发育异常中,25耳蜗神经未显示,8耳显示细小。蜗神经未显示的25耳中,进行了HRCT检查的19耳均显示蜗神经孔异常改变.其中伴有内耳道狭窄18耳,骨迷路畸形15耳,前庭神经异常10耳,面神经细小2耳。蜗神经显示细小的8耳中,4耳伴有蜗神经孔异常改变,4耳内耳道呈壶腹状或喇叭状,5耳伴有内耳Mondini畸形。结论:HRCT显示蜗神经孔区异常改变可初步提示蜗神经发育异常。HRCT及MRI联合使用可较准确的显示蜗神经发育异常,对于临床人工耳蜗术前评价具有重要的指导意义。     

MRI在肝脏占位性病变诊断中的应用

目的:探讨MRI在肝脏占位病变诊断中的应用价值。材料与方法:对98例肝肿瘤患者的MRI影像分析了图像质量、病灶显示清晰度及病变信号特征。全部病例均用1.0T超导磁共振机检查,采用自旋回波(SE)及快速自旋回波(TSE)序列摄取横轴位T_1及T_2加权像。36例患者接受了Gd-DTPA增强,其中12例进行了动态增强检查。结果:图像优良者89％,较差者占11％。MRI能显示的最小病灶为0.5～1.4cm。转移瘤均呈不同程度的长T_1、长T_2信号,信号不均匀,无包膜。肝细胞癌呈不均匀长T_2信号,T_1加权像上7例呈等信号或轻度高信号,其余呈轻度低信号。5例可清晰显示包膜,3例可见门静脉内瘤栓形成。海绵状血管瘤呈均匀性长T_1低信号、长T_2显著高信号,轮廓清晰,边缘光整或呈分叶状。结论:MRI对肝占位病变的诊断敏感度高,特异性好,对发现病变及定性、定量诊断均具有重要价值,值得广泛应用。