Leon Lisandro, Warren Frank M, Abbott Jake J
Department of Mechanical Engineering and the Robotics Center, University of Utah, Salt Lake City, UT, USA.
Sarcos Robotics, Salt Lake City, UT, USA.
J Med Robot Res. 2018 Mar;3(1). doi: 10.1142/S2424905X18500046. Epub 2018 Jan 22.
Magnetic guidance of cochlear-implant electrode arrays during insertion has been demonstrated to reduce insertion forces, which is believed to be correlated to a reduction in trauma. In those prior studies, the magnetic dipole-field source (MDS) was configured to travel on a path that would be coincident with the cochlea's modiolar axis, which was an unnecessary constraint that was useful to demonstrate feasibility. In this paper, we determine the optimal configuration (size and location) of a spherical-permanent-magnet MDS needed to accomplish guided insertions with a 100 mT field strength required at the cochlea, and we provide a methodology to perform such an optimization more generally. Based on computed-tomography scans of 30 human subjects, the MDS should be lateral-to and slightly anterior-to the cochlea with an approximate radius (mean and standard deviation across subjects) of 64 mm and 4.5 mm, respectively. We compare these results to the modiolar configuration and find that the volume of the MDS can be reduced by a factor of five with a 43% reduction in its radius by moving it to the optimal location. We conservatively estimate that the magnetic forces generated by the optimal configuration are two orders of magnitude below the threshold needed to puncture the basilar membrane. Although subject-specific optimal configurations are computed in this paper, a one-size-fits-all version with a radius of approximately 75 mm is more robust to registration error and likely more practical. Finally, we explain how to translate the results obtained to an electromagnetic MDS.
在人工耳蜗电极阵列插入过程中，磁场引导已被证明可降低插入力，而插入力的降低被认为与创伤的减少相关。在那些先前的研究中，磁偶极场源（MDS）被配置为沿与耳蜗蜗轴重合的路径移动，这是一个不必要的限制，对证明可行性很有用。在本文中，我们确定了在耳蜗处需要100 mT场强来完成引导插入的球形永磁MDS的最佳配置（尺寸和位置），并且我们提供了一种更通用地执行这种优化的方法。基于对30名人类受试者的计算机断层扫描，MDS应位于耳蜗的外侧且略靠前，其近似半径（各受试者的平均值和标准差）分别为64 mm和4.5 mm。我们将这些结果与蜗轴配置进行比较，发现通过将MDS移至最佳位置，其体积可减少五倍，半径减少43%。我们保守估计，最佳配置产生的磁力比刺穿基底膜所需的阈值低两个数量级。尽管本文计算了针对特定受试者的最佳配置，但半径约为75 mm的通用版本对配准误差更具鲁棒性，可能也更实用。最后，我们解释了如何将获得的结果转化为电磁MDS。
