Acoustic neuromas: evaluation by magnetic resonance imaging

Proton magnetic resonance imaging (MRI) examinations were performed in six patients with seven acoustic neuromas, and the results were compared with conventional tomography of the internal auditory canals, contrast-enhanced computed tomography (CT), and air CT cisternography. All tumors were identified with MRI. The three largest tumors (greater than 1 cm diameter) looked similar to the tumors seen on CT scans, although the extent of the tumor was better seen with MRI in two cases. The four small (less than or equal to 1 cm diameter) cerebellopontine angle and intracanalicular tumors were well seen with MRI, with appearances corresponding to those seen with air CT cisternography. No side effects were encountered with the MRI examinations. MRI is an accurate, noninvasive alternative to contrast-enhanced CT and air CT cisternography in the diagnosis of acoustic neuromas.     

脑池气造影高分辨率CT诊断小听神经瘤

目的：评价脑池气造影高分辨率ＣＴ检查（Ｇａｓ－ＨＲＣＴＣ）对微小听神经瘤的诊断价值。方法：对临床及ＣＴ疑诊听神经瘤患者１０例１２个内耳道行Ｇａｓ－ＨＲＣＴＣ。结果：检出听神经瘤５例，其中３例为内耳道内微小听神经瘤；另７个内耳道检查阴性，诊断准确率为１００％。结论：Ｇａｓ－ＨＲＣＴＣ是诊断和排除小听神经瘤非常敏感、安全和可靠的方法     

MR增强检查在桥小脑角肿瘤的诊断价值

目的探讨MRI增强检查诊断桥小脑角肿瘤的价值.方法研究68例手术和病理证实的桥小脑角肿瘤的资料,其中听神经瘤34例,三叉神经瘤5例,脑膜瘤20例,胆脂瘤9例.所有病人均作了增强前后的MR扫描,包括轴位、矢状位和冠状位.结果34例听神经瘤中,23例增强呈结节-环状、多环状、花环状肿块,囊变率68%;11例呈均匀肿块;34例显示面听神经束增粗强化与肿瘤相连,其中呈"荸荠”征15例,为听神经瘤的典型征像.5例三叉神经瘤强化呈结节-环状、或多环状3例,哑铃状2例,5例患侧三叉神经均显示不清,同侧面听神经受压.20例脑膜瘤中度强化均匀肿块;"脑膜尾”征11例,同侧面听神经束鞘膜强化、不增粗5例.9例胆脂瘤长T2、长T1与脑脊液一致,T1低信号中有比脑脊液信号稍高的组织,无强化表现,病变沿蛛网膜下腔扩展,基底动脉包埋5例.结论MRI增强检查能显示听神经瘤、三叉神经瘤、脑膜瘤、胆脂瘤的特征表现,诊断桥小脑角肿瘤有独特的价值.     

Comparison between air CT and MRI in the detection of small acoustic neurinomas

Air CT proved useful in yielding images of acoustic tumors as an air filling defect in 11 (24%) of 46 patients. Six of the 11 tumors were small ones of less than 1 cm in diameter. Air CT was also able to exclude an intracanalicular tumor in 29 patients (63%). MRI was performed for comparison in eight patients (nine tumors) already diagnosed by air CT as having an acoustic tumor. MRI detected eight (89%) of nine tumors. A false negative result on MRI was obtained only in one intracanalicular tumor (4.3 mm in size). This was considered to be attributable to limitations of spatial resolution including the wide slice thickness. A protocol for radiological investigation and management of patients whose clinical symptoms and/or audiovestibular examination are highly indicative of acoustic tumor is proposed and discussed.     

颅内非颅神经主干的神经鞘瘤的影像学表现

目的 报告4例经手术病理证实的颅内非颅神经主干的神经鞘瘤，并结合文献讨论其组织发生及CT、MRI表现。方法 回顾性分析4例颅内非颅神经的神经鞘瘤，复习其病理特点，分析其起源与CT、MRI表现。结果 CT平扫肿瘤多为低等混杂密度，瘤内多有坏死、囊变区，甚至以大的囊性变为主要特征；MR平扫肿瘤T1WI以低和稍低信号，T2WI为不均匀高信号；CT及MR增强扫描实质部分及囊壁呈中等程度强化。病理的苏木精和伊红染色有2种组织学形态，即Antoni A型和Antoni B型，免疫组织化学染色S—100蛋白强阳性。结论 颅内非颅神经主干的神经鞘瘤影像学表现与颅神经鞘瘤相似，但有更高的囊变率，若在非颅神经位置出现类似颅神经鞘瘤的影像学征象时，应想到此瘤的可能。     

Air-CT cisternography and canalography for small acoustic neuromas

Disenchantment with the limitations, and in some cases the morbidity, of currently used radiologic techniques for the demonstration or exclusion of small acoustic neuromas prompted development of an examination using small amounts of intrathecal air and computed tomography (CT). A prospective study was designed to evaluate air CT cisternography/canalography, wherein patients with the clinical symptoms of acoustic neuroma but with negative enhanced CT, were evaluated by metrizamide CT cisternography followed by air CT cisternography/canalography. Pantopaque cisternography was then performed as a control procedure. Four patients had surgically proven tumors. In 13 others, accumulated evidence indicated no tumors were present. Results suggest that air-CT cisternography is superior to all other diagnostic methods in defining small acoustic neuromas, and may exclude an intracanalicular lesion without the potential hazards of Pantopaque cisternography or high concentration metrizamide tomocisternography. With air-CT cisternography, there were no errors in this series.     

CT in diagnosis of acoustic neuromas

A detailed analysis of the CT findings in 75 cases of acoustic neuroma is presented. The method of examination included plain and enhanced CT, metrizamide CT cisternography (M-CTC), and gas CT cisternography (gas-CTC). The common CT appearances of acoustic neuromas were as follows: 93.6% appeared as isodense or hypodense on precontrast scan; homogeneous enhancement was observed in 53.8% on postcontrast scan; the tumor center, mostly located at the level of the internal acoustic canal, was spherical in shape with an acute angle between the lateral tumor border and petrous bone; and there was widening of the internal acoustic canal or destruction of petrous bone. However, the presence of an acoustic neuroma could not be excluded if widening of the internal acoustic canal was absent. It was not certain whether contrast filling of the internal acoustic canal occurred at M-CTC in the four cases so examined. One case of intracanalicular neuroma was diagnosed by gas-CTC, which is the most sensitive and reliable technique for detecting and excluding small tumors. The significance of various CT appearances, early diagnosis, and differential diagnosis of acoustic neuroma from other cerebellopontine-angle tumors, particularly meningioma, are discussed.     

脑实质神经鞘瘤影像学表现及相关病理分析

目的：通过对脑实质神经鞘瘤的影像学表现及相关病理分析，提高该病的诊断准确率，有利于手术方案的制定及患者的预后。方法：回顾性分析4例经手术病理及免疫组织化学证实的脑实质神经鞘瘤。其中1例行CT平扫及增强检查，1例行MR平扫，2例行CT及MR平扫＋增强扫描，并结合文献进行分析。结果：4例中，3例年龄小于30岁，均位于幕上；均出现囊变征象，3例出现壁结节，3例增强者中壁结节呈明显强化2例，中度强化1例；1例壁结节内见钙化征象，1例周边水肿明显；病理上均见AntoniA区、B区；免疫组织化学检查，酸性钙结合蛋白（S100）、波形蛋白（Vim）阳性，胶质纤维酸性蛋白（GFAP）、上皮膜抗原（EMA）阴性。结论：脑实质神经鞘瘤好发于青少年，囊变及周围水肿为其特征性表现，结合病理及免疫组织化学检查有利于最终确诊。     

肝癌碘油栓塞后沉积良好患者的MRI随访临床研究

目的分析MRI评价碘油栓塞后沉积良好肝癌（HCC）患者肿瘤残存的价值。 方法经TACE治疗后3~6月,CT扫描碘油沉积良好的25例HCC患者,1个月内同时行MRI常规扫描及DSA检查,以DSA和临床随访6个月以上结果为标准,分析MRI对肿瘤残存灶的评价效果。 结果本组25例CT扫描无肿瘤残存的患者,MRI增强扫描发现14例存在肿瘤残存,其中1例可疑,DWI发现高信号而经DSA证实有肿瘤残存,而经DSA及6个月以上临床随访证实,16例患者有肿瘤残存。MRI随访诊断灵敏性为87.5%（14/16）,漏诊率为（2/16）,特异性为100%（9/9）,符合率为92%（（14+9）/25）。 结论TACE后碘油沉积良好的病灶中仍可能有肿瘤残存,MRI增强扫描结合DWI能更全面的评价TACE疗效。     

Computed tomography of acoustic neuromas with emphasis on small tumor detectability

Summary The results of CT analysis of 41 acoustic neuromas are presented. Large and medium-sized tumors are easily detected: our results are comparable to the reported findings of other authors. The detectability of small acoustic neuromas is considerably improved by the application of newer-generation CT apparatus and the use of specific scanning parameters, including extremely thin overlapping slices, low scan speed, high gantry tilt, short time between contrast agent application and tumor scanning, and computer-assisted magnification of the posterior fossa.     

桥小脑角区肿瘤的MRI诊断和鉴别诊断

目的 :探讨桥小脑角区肿瘤MRI的表现及特征。材料和方法 :分析 193例资料完整 ,均经手术和病理证实的桥小脑角区肿瘤 ,其中听神经瘤 135例 ,三叉神经瘤为 30例 ,脑膜瘤 12例 ,胆脂瘤 4例 ,蛛网膜囊肿 2例 ,动脉瘤 1例 ,血管母细胞瘤 4例 ,脉络丛乳头状瘤 3例 ,海绵状血管瘤 1例 ,转移瘤 1例。结果 :桥小脑角区肿瘤中 ,脑外肿瘤 95 .3% ,脑内肿瘤 4.7% ;良性肿瘤占 98.4% ,恶性肿瘤占 1.6%。发生于桥小脑角区的前三位肿瘤分别为听神经瘤 69.9% ,三叉神经瘤 15 .5 % ,脑膜瘤 6.2 % ,该区肿瘤大部分有特征性MRI表现 ,术前定位、定性诊断准确率分别为 10 0 %、96.4%。结论 :MRI是检查桥小角区肿瘤的首选方法 ,对桥小脑角区肿瘤诊断和鉴别有重要价值     

Radio-frequency ablation of hepatic metastases: postprocedural assessment with a US microbubble contrast agent--early experience.

PURPOSE: To evaluate contrast agent-enhanced ultrasonography (US) in the detection of untreated tumor after radio-frequency (RF) ablation of hepatic metastases. MATERIALS AND METHODS: Twenty patients with solitary colorectal liver metastases underwent percutaneous RF tumor ablation. Pre- and postablation imaging was performed with nonenhanced and enhanced color and power Doppler US and contrast-enhanced helical computed tomography (CT). Initial follow-up CT and US were performed 24 hours after ablation. The findings at US and CT were compared. RESULTS: Nonenhanced US demonstrated intratumoral signal in 15 of 20 metastases before ablation. This signal increased after contrast agent administration. Contrast-enhanced US performed 24 hours after ablation demonstrated residual foci of enhancement in three tumors, whereas no US signals were seen in any tumor on nonenhanced scans. CT demonstrated small (< 3-mm) persistent foci of residual enhancement in these three tumors and in three additional lesions that were not seen at US (US sensitivity, 50%; specificity, 100%; diagnostic agreement with CT, 85%). All six patients with evidence of residual tumor underwent repeat RF ablation. CONCLUSION: Contrast-enhanced US may depict residual tumor after RF application and thereby enable additional directed therapy. The potential reduction in treatment sessions and/or ancillary imaging procedures might increase the ease and practicality of percutaneous ablation of focal hepatic metastases.     

The value of T2(*)-weighted MR images for the diagnosis of acoustic neuromas

The aim of this study was to evaluate high resolution T2(*)-weighted MRI—in our case a 3D CISS sequence—for the diagnosis of acoustic neuromas. Especially to be clarified was if high-resolution T2-weighted sequences can substitute T1-weighted contrast-enhanced sequences, and in which circumstances they can give important additional information when compared with contrast-enhanced T1-weighted sequences. Methods and patients: The MR examinations were performed using a 1.5-Tesla unit with a circularly polarized head coil. All 20 patients (11 females, nine males, aged from 12 to 80 years) with acoustic neuromas underwent preoperative MRI with T2*-weighted 3D CISS (slice thickness, 0.7 mm; acquisition time, 8 min) and pre- and postcontrast T1-weighted 3D MP-RAGE (slice thickness, 0.9 mm; acquisition time, 8 min) sequences. The detectability of acoustic neuromas was evaluated following the consensus of three radiologists using a 3D work station (parameters: tumor presence, extent, nerve attribution). Results: All tumors were detected by both contrast-enhanced 3D MP-RAGE and 3D CISS and the diameters of the lesions were equally well measured. 3D CISS was the best sequence for the attribution of a lesion to a certain nerve. Labyrinthine involvement could be better detected using 3D CISS than contrast-enhanced 3D MP-RAGE. Conclusion: High-resolution T2(*)-weighted MRI is a very sensitive method for tumor screening which can also detect even small meatal and labyrinthine neuromas. In the case of abnormal findings (other pathology or variations, e.g. vascular loops); however, contrast-enhanced T1-weighted MRI is necessary in order to confirm the presence of a tumor with typical enhancement.     

The size of acoustic neuromas: CT and MRI

The growth rate of acoustic neuromas is very variable: some tumours grow rapidly, some do not grow and some even get smaller. When making treatment decisions, it may be important to have an idea of the growth rate of the individual tumour, and this is only possible when there are comparable examinations. We performed both CT and MRI on 15 patients. Two radiologists estimated the size of their acoustic neuromas. There was a significant difference between the two examiners' calculations of tumour volumes on CT and between the first examiner's CT and MRI volume calculations. No difference was found between the two MRI volume estimations or the second examiner's estimation of volumes on CT and MRI. Measurements of the maximal tumour diameter along the pyramid showed good concordance. We conclude that measurement the size of acoustic neuromas is reproducible with MRI and the measurement of the maximal tumour diameter is in practice a better parameter for comparison than calculation of real volume. Received: 16 May 1996 Accepted: 7 October 1996     

MR diagnosis of acoustic neuromas

Two hundred forty-three patients with clinically suspected acoustic neuroma were evaluated radiologically by CT, and in selected cases CT cisternography and/or magnetic resonance imaging. Fifty-one acoustic neuromas were diagnosed and surgically removed; 36 were large tumors with extracanalicular extension and 15 were strictly intracanalicular small tumors. With routine CT (without and with contrast medium) large and enhancing lesions (36 of 51) were visualized, but small intracanalicular tumors (15 lesions) were missed. The latter were visualized by CT cisternography (seven cases) or MR (eight cases). Magnetic resonance, when used with spin-echo technique using both short as well as long sequences for axial and coronal thin slices (5 mm or smaller), demonstrated all the surgically verified lesions.     

CT与MR对女性盆腔肿块诊断能力的对比研究

目的 分析女性盆腔肿块（FPM）的CT与MRI表现，并比较CT与MRI对FPM的诊断能力。方法 50例经手术病理证实的FPM（25例恶性和25例良性）患者均经常规CT与MRI检查。29例又经CT增强扫描，35例又经MRI增强扫描。结果 CT正确诊断恶性FPM15例和良性FPM18例，诊断敏感性60%，特异性72%，准确率66%。MRI正确诊断恶性FPM21例和良性FPM22例，诊断敏感性80%，特异性88%，准确率84%。CT增强扫描能显示常规扫描看不到的征象，如卵巢癌壁结节强化和卵巢囊腺瘤的壁与间隔轻度强化等。MRI增强扫描有类似发现。CT对囊性肿块的诊断与MRI相似，对钙化斑的显示优于MRI，但对囊实性肿块结构细节的显示不如MRI。结论 CT与MRI的诊断具有各自的优势，总的说来，MRI优于CT，然而，二者结合可明显提高诊断准确率。     

Acoustic neuromas: Gd-DTPA enhancement in MR imaging

Magnetic resonance (MR) imaging examinations were performed in ten patients with 12 acoustic neuromas before and after intravenous administration of 0.1 mmol/kg body weight gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). The degree of enhancement was greatest with the inversion recovery sequence 1,500/500/44 (repetition time [TR]/inversion time/echo delay time [TE]), followed by spin-echo (SE) 544/44 (TR/TE) sequences, then by SE 1,500/44 and SE 1,500/80 sequences. After enhancement there was a 50% reduction for measured T1 values, 33% for T2, and no significant change for proton density. There were no toxic effects on patients. Enhanced CT scans failed to demonstrate lesions in six of 12 cases. Air-CT technique improved sensitivity in four of five cases. Enhanced MR imaging added significant clinical information in two small intracanalicular tumors and in one recurrent tumor.     

Temporal bone region: high-resolution MR imaging using surface coils

Specially designed surface coils for the region of the temporal bone enable high-resolution magnetic resonance (MR) imaging of the structures of the inner ear. Eight healthy volunteers and 21 patients (six with cholesteatomas, five with acoustic neuromas, five with glomus tumors, and five with mastoiditis) were examined using a 0.5-T MR imager. The demarcation of tumor extent with MR imaging was better than with computed tomography because of improved soft-tissue contrast and because the surrounding bony tissue did not generate any signal. High-resolution MR imaging is particularly useful for small acoustic neuromas because of its higher specificity compared with gas cisternography.     

Leptomeningeal metastasis: a CT and MRI study

We evaluated 35 patients with leptomeningeal metastasis (LM) that was proved by repatd positive cytology (33 patients) and/or autopsy (10 patients) with T1-weighted Gadolinium-DTPA-enhanced MRI and contrast-enhanced CT. The patients (20 women and 15 men) ranged in age from 5–77 years (mean 56 years). Tumour histology included 26 carcinomas, 1 sqrcoma, 6 leucaemias, 1 medullo-blastoma and 1 primary CNS lymphoma. Intracranial abnormalities were noted in 58% of cases by CT and 88% by MRI, and included hydrocepahlus, meningeal or ependymal enhancement, subarachnoidal or intraparenchymal nodules. Leptomeningeal metastasis was detected by MRI is equal or superior to CT in demonstrating meningeal or ependymal enhancement and quantifying enhanced subrachnoidal or parenchymal nodules. However, in the evaluation of leptomeningeal metastasis both modalities had a high incidence of false-negative studies, 89% (31 of 35) by CT and 24% (4 of 17) by MRI. In contrast, two patients with initially negative cytology had pathological MRI findings. Our data indicate that Gadolinium-enhanced MRI is the preferrd imaging modality in letomeningeal metastasis, and suggest that CT does not add significant additional information. However, LM is primarily a histological diagnosis by detecting tumour cells in the cerebrospinal fluid.     

Comparison of 16-slice MSCT and MRI in the assessment of squamous cell carcinoma of the oral cavity

The goal of this retrospective study was to assess the accuracy of 16-slice multislice CT (MSCT) and MRI in staging of patients with primary squamous cell carcinoma (SCC) of the oral cavity. Fifty-two patients with histologically proven primary SCC were examined with contrast enhanced MSCT and MRI at 1.5 T with a combined head and surface neck coil. Image modalities were evaluated in a blinded fashion by two radiologists and an oral-maxillofacial surgeon in consensus concerning tumour depiction, local tumour infiltration and cervical lymph node metastases. Results of the radiological assessment were correlated with the intraoperative and histopathological findings in all patients. 36 of 52 primary tumours (69.2%) were depicted by MSCT while 44 were localized by MRI (84.6%). Regarding muscle infiltration MRI versus MSCT had a sensitivity of 81.8% versus 72.7%, but a low specificity and an accuracy of 63.4% versus 61% and 67.3% versus 63.5%, respectively, were found. There was a trend towards a better detection of bony infiltration by MRI than MSCT with a sensitivity of 100% versus 71.4%, a specificity of 93.3% versus 95.5% and an accuracy 94.2% versus 92.3%, respectively. Detection of cervical lymph node involvement was similar for MRI and MSCT with a sensitivity of 84.2% and 78.9%, a specificity of 63.6% and 75.7% and an accuracy of 71.1% and 76.9%, respectively. For N-staging both methods failed to detect small metastasis. For T-staging MRI was superior to MSCT, because there was a tendency to underestimate the tumour size by MSCT more often (19.4% versus 6.8% by MRI). Therefore, pre-operative MRI is recommended as the basic imaging modality of choice for treatment planning of oral SCC. MSCT is a valid alternative imaging method especially in cases with low patient compliance.