Scala tympani phantom 3D model with heat source

Citation Author(s):
Fateme
Esmailie
University of Utah
Mathieu
Francoeur
University of Utah
Tim
Ameel
University of Utah
Submitted by:
Tim Ameel
Last updated:
Tue, 05/17/2022 - 22:18
DOI:
10.21227/5kdq-r569
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Abstract 

Magnetic guidance of cochlear implants is a promising technique to reduce the risk of physical trauma during surgery. In this approach, a magnet attached to the tip of the implant electrode array is guided within the scala tympani using a magnetic field. After surgery, the magnet must be detached from the implant electrode array via localized heating, which may cause thermal trauma, and removed from the scala tympani .

Objectives: The objective of this work is to experimentally validate a three-dimensional (3D) heat transfer model of the scala tympani which will enable accurate predictions of the maximum safe input power to avoid localized hyperthermia when detaching the magnet from the implant electrode array. 

Methods: Experiments are designed using a rigorous scale analysis and performed by measuring transient temperatures in a 3D-printed scala tympani phantom subjected to a sudden change in its isothermal environment and localized heating via a small heat source.

Results: The measured and predicted temperatures are in good agreement with an error less than 6% (p=0.84). For the most conservative case where all boundaries of the model except the insertion opening are adiabatic, the power required to release the magnet attached to the implant electrode array by 1 mm³ of paraffin is approximately half of the predicted maximum safe input power.

Conclusions: A 3D heat transfer model of the scala tympani is successfully validated and enables predicting the maximum safe input power required to detach the magnet from the implant electrode array.  

Significance: This work will enable the design of a thermally safe magnetic cochlear implant surgery procedure. 

Instructions: 

The excel file contains the initial conditions. Please make sure the excel file is in the correct directory.

For more info please email: fateme.esmailie@utah.edu or ameel@mech.utah.edu.

This file MUST be cited properly if it is used directly or with changes. You are not allowed to use this file for commercial purposes.

This model of the scale tympani (phantom) was developed by Leon et al [1]. The 3D model of the scala tympani is imported to COMSOL Multiphysics and modified for validation purposes.

[1] L. Leon et al., “Scala-Tympani phantom with cochleostomy and round- window openings for cochlear-implant insertion experiments,” in Journal of Medical Devices,, vol. 8, no. 2, 2014, pp. 041010 – 041020. Available: https://doi.org/10.1115/1.4027617