Technical Papers and Presentations

Magnetic insertion of a cochlear implant can reduce intracochlear physical trauma by 50% compared to traditional manual insertion. The magnet attached to the tip of the cochlear implant electrode array must be detached and removed after surgery. This detachment process requires Joule heating, such that thermal energy is released in the cochlea that may cause thermal trauma within the ear. To ensure thermal safety of the heating process, heat transfer within the cochlea should be studied. Initially, an analysis of simultaneous heat transfer and fluid flow in an uncoiled model of the cochlea is performed. Insertion of the electrode array drives cochlear fluid (perilymph) out of the cochlea. The remaining fluid does not flow easily due to the internal “no slip” boundary conditions around the electrode array and magnet boundaries. Therefore, natural convection is tempered and is not modeled. As a result, the thermal analysis within a cochlea can be modeled using the Heat Transfer in Solids and Fluids interface of COMSOL Multiphysics^® simulation software. The main goal of the study is to identify a safe range of input power to detach the magnet without causing thermal trauma. A 3D model of the cochlea was downloaded from the SICAS Medical Image repository (http://doi.org/10.22016/smir.o.207473), and meshed using COMSOL Multiphysics^® . The main challenge in this analysis is meshing the cochlea due to the small edges contained in the SICAS 3D model. Thus, the 3D model must be edited to facilitate the meshing process and to produce a higher mesh quality. Based on preliminary results, the maximum safe input power to detach the magnet is 1.17×10⁷ W/m³, which is comparable to the power predicted from a 1D thermal model of a cochlea cross-section (1.35×10⁷ W/m³). The temperature profile in a coiled model of the cochlea after heating the magnet with an input power of 1.17×10⁷
W/m³ for 114 s; is depicted in Figure 1.

Figure caption: 

Figure 1. Temperature profile in a coiled cochlea model after 114 s of power applied to the magnet at 1.17×10⁷ W/m³.