Wackym P Ashley, Michel Michelle A, Prost Robert W, Banks Kristin L, Runge-Samuelson Christina L, Firszt Jill B
Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Laryngoscope. 2004 Aug;114(8):1355-61. doi: 10.1097/00005537-200408000-00007.
Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med-El Combi 40+ cochlear implant internal magnets after MRI studies.
STUDY DESIGN/METHODS: Two fresh cadavers were used to study demagnetization using a repeated measures design and a magnetometer. Pre- and postMRI measurement of magnetic field strength was completed. Five sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 0.2 Tesla in the device-up and device-down positions. In the other cadaver, 15 sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 1.5 Tesla were conducted, 5 each with the head oriented at 80, 90, and 100 degrees rotated around the yaw plane (rotated around the z-axis). Subsequently, three cochlear implant patients completed 0.2 Tesla MRIs. For these patients, subjective and objective assessment of cochlear implant performance was performed.
Academic medical center.
In the cadaver studies, analysis of variance showed no significant difference in the magnetic field strength after the 0.2 or 1.5 Tesla scans. There was no significant difference in the magnetic field strength for the three patients undergoing 0.2 Tesla MRIs and no adverse consequences, including no changes in telemetry, auditory sensations, nonauditory sensations, and sound quality.
No significant demagnetization of the internal magnet occurred during repeated 1.5 Tesla MRI scans with the head orientations used in this study. In the cochlear implant patients, no significant demagnetization of the internal magnet occurred after a 0.2 Tesla MRI.
由于担心扭矩、力、退磁、伪影、感应电压和发热等问题，当体内植入含有内置磁体的人工耳蜗时，磁共振成像（MRI）一直被视为禁忌。本研究的目的是确定在进行MRI检查后，美敦力Combi 40+型人工耳蜗内置磁体的磁场强度。
研究设计/方法：使用两具新鲜尸体，采用重复测量设计和磁力计研究退磁情况。完成了MRI检查前后磁场强度的测量。在一台0.2特斯拉的磁共振成像仪上，对一具尸体在设备开启和关闭位置分别进行了五组矢状面T1加权、横断面T1加权和横断面T2加权序列扫描。在另一具尸体上进行了15组矢状面T1加权、横断面T1加权和横断面T2加权序列扫描，扫描在1.5特斯拉的磁共振成像仪上进行，每组扫描时头部分别绕偏航平面（绕z轴）旋转80度、90度和100度，各进行5次。随后，三名人工耳蜗植入患者完成了0.2特斯拉的MRI检查。对这些患者进行了人工耳蜗性能的主观和客观评估。
学术医疗中心。
在尸体研究中，方差分析显示，在0.2或1.5特斯拉扫描后，磁场强度没有显著差异。三名接受0.2特斯拉MRI检查的患者的磁场强度也没有显著差异，并且没有出现不良后果，包括遥测、听觉感受、非听觉感受和音质均无变化。
在本研究使用的头部方位下，进行重复的1.5特斯拉MRI扫描期间，内置磁体未发生明显退磁。在人工耳蜗植入患者中，0.2特斯拉MRI检查后，内置磁体也未发生明显退磁。
