Heller J W, Brackmann D E, Tucci D L, Nyenhuis J A, Chou C K
Cochlear Corporation, Englewood, Colorado 80112, USA.
Am J Otol. 1996 Sep;17(5):724-9.
Magnetic resonance imaging (MRI) has been contraindicated for users of cochlear implants because of the internal magnet and other possible interactions. Users of the Nucleus Mini-22 Cochlear Implant (CI) or the experimental Multichannel Auditory Brainstem Implant (ABI) may have other disorders that are best diagnosed by MRI. The CI and ABI were modified by replacing the internal magnet and integrated circuit lid with nonmagnetic material. Tests were conducted in a 1.5-T MRI machine. Safety tests for force, heating, induced current, unintentional implant output, and implant damage were conducted by using various phantom models. Image distortion was evaluated in two subjects with implants. The maximum force measured was 2,818 dynes. There was < 0.1 degree C temperature increase in the vicinity of the implant. The maximum induced charge was > or = 667 times less than the minimum charge for auditory stimulation. There was no unintentional output during MRI scans and no change in implant function after 10 repeated scans. Image distortion consisted primarily of darkening and was worst in the axial plane, where it extended 1-2 cm medially and inferiorly from the receiver/stimulator. Compatibility-test results were acceptable, with a large margin of safety. Image distortion is limited to darkening in the immediate vicinity of the implant.
由于内置磁铁及其他可能的相互作用，磁共振成像（MRI）一直被视为人工耳蜗使用者的禁忌。使用Nucleus Mini-22人工耳蜗（CI）或实验性多通道听觉脑干植入物（ABI）的患者可能患有其他疾病，而MRI是诊断这些疾病的最佳方法。通过用非磁性材料替换内置磁铁和集成电路盖对CI和ABI进行了改进。测试在1.5-T的MRI机器中进行。使用各种仿真模型进行了力、加热、感应电流、意外植入物输出和植入物损坏的安全性测试。对两名植入者进行了图像失真评估。测得的最大力为2818达因。植入物附近的温度升高<0.1摄氏度。最大感应电荷比听觉刺激的最小电荷小≥667倍。MRI扫描期间没有意外输出，10次重复扫描后植入物功能没有变化。图像失真主要表现为变暗，在轴向平面最为严重，从接收器/刺激器向内和向下延伸1-2厘米。兼容性测试结果是可以接受的，有很大的安全余量。图像失真仅限于植入物紧邻区域的变暗。
