Dong Chang, Liu Yang, Hua Qing-quan, Lin Wei, Sun Jian-jun, Huang Wei-ning, Liu Fang, Liu Xu-hui
Department of Otorhinolaryngology Head and Neck Surgery, People's Hospital of Wuhan University, Wuhan, China.
Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2011 Aug;46(8):669-74.
To observe the distribution of Gd-DTPA in the inner ear of guinea pig by MRI at different time points after intratympanic administration, explore the optical time for observing the whole inner ear. To study the pharmacokinetic feature of Gd-DTPA in the inner ear, and find out whether discrimination of endolymph and perilymph can be obtained under current conditions.
Sixty-five guinea pigs were randomly divided into 13 groups, after diluted Gd-DTPA intratympanic injection, each group of guinea pigs were scanned through MRI (3D-T1 FSE sequence) at different time points (0 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 24 h, 48 h, 72 h, 96 h). Pixel intensity values of some locations in the inner ear were analyzed using e-Film software, then pixel intensity was converted into concentration using the results of previous in-vitro study. ABR thresholds of bilateral ears before, 1 d and 7 d after intratympanic injection were compared.
Six hours after transtympanic Gd-DTPA injection was the time point when contrast agent was distributed all over the inner ear, and reached a high concentration: 589.29, 552.54, 570.17, 255.08, 107.09 and 139.18 µmol/L in the vestibule, scala vestibuli and scala tympani of basal turn, the 2(nd), the 3(rd) and the apical turn individually, that was also the optimal time for observing the whole inner ear by MRI. Perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a distinction between the scales of the inner ear. There was no significant difference between the experimental ear (diluted GD-DTPA injected ear) and contrast ear (physiological saline injected ear) on 1 d and 7 d.
The best time getting MRI imaging after intratympanic diluted GD-DTPA injection is 6 h. After diluted agent injection perilymph can be enhanced so as to be differentiated with endolymph by MRI, diluted agent have no obvious effect on the ABR threshold. The pharmacokinetic feature of Gd-DTPA in the inner can be studied using MRI.
通过鼓膜内给药后不同时间点的MRI观察钆喷酸葡胺（Gd-DTPA）在豚鼠内耳的分布情况，探寻观察整个内耳的最佳时间。研究Gd-DTPA在内耳的药代动力学特征，明确在当前条件下能否区分内淋巴和外淋巴。
将65只豚鼠随机分为13组，鼓膜内注射稀释后的Gd-DTPA后，每组豚鼠在不同时间点（0 h、0.5 h、1 h、2 h、4 h、6 h、8 h、10 h、12 h、24 h、48 h、72 h、96 h）通过MRI（3D-T1 FSE序列）进行扫描。使用e-Film软件分析内耳某些部位的像素强度值，然后根据先前体外研究结果将像素强度转换为浓度。比较鼓膜内注射前、注射后1 d和7 d双侧耳朵的听性脑干反应（ABR）阈值。
鼓膜内注射Gd-DTPA后6 h是造影剂在内耳分布均匀且达到高浓度的时间点，在前庭、蜗底转前庭阶、蜗底转鼓阶、第二转、第三转和顶转中的浓度分别为589.29、552.54、570.17、255.08、107.09和139.18 μmol/L，这也是通过MRI观察整个内耳的最佳时间。外淋巴相对于内淋巴似乎优先增强，从而使内耳各阶得以区分。实验耳（注射稀释GD-DTPA的耳朵）和对照耳（注射生理盐水的耳朵）在1 d和7 d时无显著差异。
鼓膜内注射稀释后的GD-DTPA后进行MRI成像的最佳时间为6 h。注射稀释剂后外淋巴可增强，从而通过MRI与内淋巴区分，稀释剂对ABR阈值无明显影响。可利用MRI研究Gd-DTPA在内耳的药代动力学特征。
