Optimizing the Magnetic Dipole-Field Source for Magnetically Guided Cochlear-Implant Electrode-Array Insertions.

Area of Science:

• Biomedical Engineering
• Medical Devices
• Neurosurgery

Background:

• Magnetic guidance of cochlear implant electrode arrays can reduce insertion forces and trauma.
• Previous studies constrained the magnetic dipole-field source (MDS) to the modiolar axis, limiting optimization.

Purpose of the Study:

• To determine the optimal size and location of a spherical-permanent-magnet MDS for guided cochlear implant insertions.
• To develop a general methodology for optimizing MDS configurations.

Main Methods:

• Computed-tomography scans from 30 human subjects were analyzed.
• The optimal MDS configuration (size and location) was calculated for a 100 mT field strength at the cochlea.

Main Results:

• The optimal MDS location is lateral and slightly anterior to the cochlea, with a mean radius of 64 mm (SD 4.5 mm).
• This optimal configuration reduces MDS volume by five-fold and radius by 43% compared to the modiolar configuration.
• Magnetic forces are estimated to be two orders of magnitude below the threshold for basilar membrane puncture.

Conclusions:

• An optimal, subject-specific MDS configuration can improve magnetic guidance for cochlear implants.
• A practical, one-size-fits-all MDS with a 75 mm radius offers robustness to registration errors.
• The methodology can be extended to electromagnetic MDS designs.