Scala-Tympani Phantom With Cochleostomy and Round-Window Openings for Cochlear-Implant Insertion Experiments

Leon, Lisandro; Cavilla, Matt S.; Doran, Michael B.; Warren, Frank M.; Abbott, Jake J.

doi:10.1115/1.4027617

Cited by 31 publications

(45 citation statements)

References 33 publications

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“…This physical trauma not only decreases the residual hearing ability but also reduces the functionality of the cochlear implant [1], [2]. To prevent physical trauma during surgery, researchers have suggested magnetic guidance of the electrode array [1], [2], [3]. In this technique, a magnet attached to the tip of the electrode array is guided in the cochlear turns via an external magnetic field (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

Esmailie

Francoeur

Ameel

2020

International Journal of Heat and Mass Transfer

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Magnetic cochlear implant surgery requires removal of a magnet via a heating process after implant insertion, which may cause thermal trauma within the ear. Intra-cochlear heat transfer analysis is required to ensure that the magnet removal phase is thermally safe. The objective of this work is to determine the safe input power density to detach the magnet without causing thermal trauma in the ear, and to analyze the effectiveness of natural convection with respect to conduction for removing the excess heat. A finite element model of an uncoiled cochlea, which is verified and validated, is applied to determine the maximum safe input power density to detach a 1-mm-long, 0.5-mm-diameter cylindrical magnet from the cochlear implant electrode array tip. It is shown that heat dissipation in the cochlea is primarily mediated by conduction through the electrode array. The electrode array simultaneously reduces natural convection due to the no-slip boundary condition on its surface and increases axial conduction in the cochlea. It is concluded that natural convection heat transfer in a cochlea during robotic cochlear implant surgery can be neglected. It is found that thermal trauma is avoided by applying a power density up to 2.265 × 10 7 W/m 3 for 114 s, resulting in a maximum temperature increase of 6 • C on the magnet boundary.

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Section: Introductionmentioning

confidence: 99%

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

Esmailie

Francoeur

Ameel

2020

International Journal of Heat and Mass Transfer

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“…Our previous work (31) suggests that magnetic guidance can reduce insertion forces; however, experiments were conducted with 3-to-1 scale dummy EAs. Progress toward clinical translation requires that similar yields be achievable with at-scale clinical EAs in higher fidelity phantoms (33). This article presents the first attempt at steering actual clinical EAs, modified to have a magnetic tip, using magnetic guidance.…”

Section: E64mentioning

confidence: 99%

An In-Vitro Insertion-Force Study of Magnetically Guided Lateral-Wall Cochlear-Implant Electrode Arrays: Erratum

2019

Otology &Amp; Neurotology

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Hypothesis: Insertion forces can be reduced by magnetically guiding the tip of lateral-wall cochlear-implant electrode arrays during insertion via both cochleostomy and the round window. Background: Steerable electrode arrays have the potential to minimize intracochlear trauma by reducing the severity of contact between the electrode-array tip and the cochlear wall. However, steerable electrode arrays typically have increased stiffness associated with the steering mechanism. In addition, steerable electrode arrays are typically designed to curve in the direction of the basal turn, which is not ideal for roundwindow insertions, as the cochlear hook's curvature is in the opposite direction. Lateral-wall electrode arrays can be modified to include magnets at their tips, augmenting their superior flexibility with a steering mechanism. By applying magnetic torque to the tip, an electrode array can be navigated through the cochlear hook and the basal turn. Methods: Automated insertions of candidate electrode arrays are conducted into a scala-tympani phantom with either a cochleostomy or round-window opening. The phantom is mounted on a multi-degree-of-freedom force sensor. An external magnet applies the necessary magnetic bending torque to the magnetic tip of a modified clinical electrode array, coordinated with the insertion, with the goal of directing the tip down the lumen. Steering of the electrode array is verified through a camera. Results: Statistical t-test results indicate that magnetic guidance does reduce insertion forces by as much as 50% with certain electrode-array models. Direct tip contact with the medial wall through the cochlear hook and the lateral wall of the basal turn is completely eliminated. The magnetic field required to accomplish these insertions varied from 77 to 225 mT based on the volume of the magnet at the tip of the electrode array. Alteration of the tip to accommodate a tiny magnet is minimal and does not change the insertion characteristic of the electrode array unless the tip shape is altered. Conclusion: Magnetic guidance can eliminate direct tip contact with the medial walls through the cochlear hook and the lateral walls of the basal turn. Insertion-force reduction will vary based on the electrode-array model, but is statistically significant for all models tested. Successful steering of lateral-wall electrode arrays is accomplished while maintaining its superior flexibility.

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“…In that study, Flex-24 electrode arrays provided by MED-EL (Innsbruck, Austria) with a 4.73×10 −5 A·m 2 permanent magnet embedded in the EAT were guided successfully through a plastic scala-tympani phantom [7]. The maximum magnetic field used in those experiments was determined to be 80 mT and 100 mT if inserted through a simulated cochleostomy and round window, respectively.…”

Section: Magnetic Modelingmentioning

confidence: 99%

“…We will define the location of the cochlea as the intersection of the modiolar axis and the basal plane [7]. …”

Section: Magnetic Modelingmentioning

confidence: 99%

“…1) [6]. Repeatable automated insertions have recently been conducted in at-scale scala-tympani phantoms, designed with simulated cochleostomy and round-window openings [7], using clinical lateral-wall type EAs with magnets embedded at their tips [8]. Insertion forces were reduced by as much as 50% compared to nonguided insertions, and at the first turn in the basal plane, where a high percentage of basilar-membrane perforations occur, the EAT was never in contact with the lateral wall.…”

Section: Introductionmentioning

confidence: 99%

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

Leon

Warren

Abbott

2018

J. Med. Robot. Res.

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Magnetic guidance of cochlear-implant electrode arrays during insertion has been demonstrated in vitro 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.

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Scala-Tympani Phantom With Cochleostomy and Round-Window Openings for Cochlear-Implant Insertion Experiments

Cited by 31 publications

References 33 publications

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

An In-Vitro Insertion-Force Study of Magnetically Guided Lateral-Wall Cochlear-Implant Electrode Arrays: Erratum

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

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