Pyykkö Ilmari, Zou Jing, Poe Dennis, Nakashima Tsutomu, Naganawa Shinji
Department of Otolaryngology, University of Tampere, Teiskontie 35, 33520, Tampere, Finland.
Otolaryngol Clin North Am. 2010 Oct;43(5):1059-80. doi: 10.1016/j.otc.2010.06.001.
Recent magnetic resonance imaging (MRI) techniques have made it possible to examine the compartments of the cochlea using gadolidium-chelate (GdC) as a contrast agent. As GdC loads into the perilymph space without entering the endolymph in healthy inner ears, the technique provides possibilities to visualize the different cochlear compartments and evaluate the integrity of the inner ear barriers. This critical review presents the recent advancements in the inner ear MRI technology, contrast agent application and the correlated ototoxicity study, and the uptake dynamics of GdC in the inner ear. GdC causes inflammation of the mucosa of the middle ear, but there are no reports or evidence of toxicity-related changes in vivo either in animals or in humans. Intravenously administered GdC reached the guinea pig cochlea about 10 minutes after administration and loaded the scala tympani and scala vestibuli with the peak at 60 minutes. However, the perilymphatic loading peak was 80 to 100 minutes in mice after intravenous administration of GdC. In healthy animals the scala media did not load GdC. In mice in which GdC was administered topically onto the round window, loading of the cochlea peaked at 4 hours, at which time it reached the apex. The initial portions of the organ to be filled were the basal turn of the cochlea and vestibule. In animal models with endolymphatic hydrops (EH), bulging of the Reissner's membrane was observed as deficit of GdC in the scala vestibuli. Histologically the degree of bulging correlated with the MR images. In animals with immune reaction-induced EH, MRI showed that EH could be limited to restricted regions of the inner ear, and in the same inner ear both EH and leakage of GdC into the scala media were visualized. More than 100 inner ear MRI scans have been performed to date in humans. Loading of GdC followed the pattern seen in animals, but the time frame was different. In intravenous delivery of double-dose GdC, the inner ear compartments were visualized after 4 hours. The uptake pattern of GdC in the perilymph of humans between 2 hours and 7 hours after local delivery needs to be clarified. In almost all patients with probable or suspected Ménière's disease, EH was verified. Specific algorithms with a 12-pole coil using fluid attenuation inversion recovery sequences are recommended for initial imaging in humans.
最近的磁共振成像（MRI）技术使得使用钆螯合物（GdC）作为造影剂来检查耳蜗的各个腔室成为可能。由于在健康的内耳中，GdC会进入外淋巴间隙而不进入内淋巴，该技术为可视化不同的耳蜗腔室和评估内耳屏障的完整性提供了可能。这篇综述介绍了内耳MRI技术、造影剂应用以及相关耳毒性研究的最新进展，以及GdC在内耳中的摄取动态。GdC会引起中耳黏膜炎症，但在动物或人类体内均无毒性相关变化的报道或证据。静脉注射GdC后约10分钟到达豚鼠耳蜗，并在60分钟时在外淋巴阶和前庭阶达到峰值。然而，静脉注射GdC后，小鼠外淋巴的加载峰值在80至100分钟。在健康动物中，中阶不加载GdC。在将GdC局部应用于圆窗的小鼠中，耳蜗的加载在4小时达到峰值，此时到达蜗顶。首先被填充的器官部分是耳蜗和前庭的基底转。在内淋巴积水（EH）的动物模型中，观察到Reissner膜膨出，表现为前庭阶中GdC缺失。组织学上，膨出程度与MR图像相关。在免疫反应诱导的EH动物中，MRI显示EH可能局限于内耳的特定区域，并且在同一内耳中可以同时观察到EH和GdC渗漏到中阶。迄今为止，已对人类进行了100多次内耳MRI扫描。GdC的加载模式与动物相似，但时间框架不同。在静脉注射双倍剂量GdC时，4小时后可观察到内耳腔室。局部给药后2至7小时内GdC在人体外淋巴中的摄取模式有待阐明。在几乎所有可能或疑似梅尼埃病的患者中，均证实存在EH。建议使用具有12极线圈的特定算法和液体衰减反转恢复序列进行人体的初始成像。
