Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Ear Hear. 2021 Sep/Oct;42(5):1276-1283. doi: 10.1097/AUD.0000000000001013.
Dislocation of the magnet inside the implanted component of a cochlear implant (CI) can be a serious risk for patients undergoing a magnetic resonance imaging (MRI) exam. CI manufacturers aim to reduce this risk either via the design of the implant magnet or magnet housing, or by advising a compression bandage and cover over the magnet. The aim of this study is to measure forces and torque on the magnet for different CI models and assess the effectiveness of the design and preventative measures on the probability of magnet dislocation.
Six CI models from four manufacturers covering all the current CI brands were included. Each model was positioned on a polystyrene head with compression bandage and magnet cover according to the recommendations of the manufacturer and tested for dislocation in a 1.5T whole-body MRI system. In addition, measurements of the displacement force in front of the MRI scanner and torque at the MRI scanner isocenter were obtained.
Chance of CI magnet dislocation was observed for two CI models. The design of the magnet or magnet housing of the other models proved sufficient to prevent displacement of the magnet. The main cause for magnet dislocation was found to be the rotational force resulting from the torque experienced inside the magnet bore, which ranges from 2.4 to 16.2 N between the models, with the displacement force being lower, ranging from 1.0 to 1.8 N.
In vitro testing shows that two CI models are prone to the risk of magnet dislocation. In these CI models, preparation before MRI with special compression bandage and a stiff cover are of importance. But these do not eliminate the risk of pain and dislocation requiring patient consulting before an MRI exam. Newer models show a better design resulting in a significantly reduced risk of magnet dislocation.
植入式人工耳蜗（CI）内部磁铁的脱位可能对接受磁共振成像（MRI）检查的患者构成严重风险。CI 制造商旨在通过设计植入磁铁或磁铁外壳，或通过建议使用压缩绷带和磁铁覆盖物来降低这种风险。本研究的目的是测量不同 CI 模型的磁铁上的力和扭矩，并评估设计和预防措施对磁铁脱位概率的有效性。
纳入了来自四个制造商的六个 CI 模型，涵盖了所有当前的 CI 品牌。根据制造商的建议，将每个模型放置在聚苯乙烯头上，并使用压缩绷带和磁铁盖，然后在 1.5T 全身 MRI 系统中对其进行脱位测试。此外，还测量了 MRI 扫描仪前的位移力和 MRI 扫描仪等中心的扭矩。
观察到两个 CI 模型存在 CI 磁铁脱位的可能性。其他模型的磁铁或磁铁外壳设计被证明足以防止磁铁移位。磁铁脱位的主要原因是由于磁铁孔内产生的扭矩而产生的旋转力，在模型之间，该扭矩范围为 2.4 至 16.2 N，而位移力较低，范围为 1.0 至 1.8 N。
体外测试表明，有两个 CI 模型容易发生磁铁脱位的风险。在这些 CI 模型中，在 MRI 检查前使用特殊压缩绷带和硬盖进行准备非常重要。但这并不能消除在 MRI 检查前需要患者咨询的疼痛和脱位风险。新型号显示出更好的设计，从而大大降低了磁铁脱位的风险。
