Research Papers

Optimal Path Planning for Robotic Insertion of Steerable Electrode Arrays in Cochlear Implant Surgery

[+] Author and Article Information
Jian Zhang

Department of Mechanical Engineering, Columbia University, New York, NY 10027

J. Thomas Roland

Department of Otolaryngology and Neurosurgery, New York University Medical Center, New York, NY 10016

Spiros Manolidis

Department of Head & Neck Surgery, Beth Israel Hospital, New York, NY 10003

Nabil Simaan1

Department of Mechanical Engineering, Columbia University, New York, NY 10027


Corresponding author.

J. Med. Devices 3(1), 011001 (Dec 18, 2008) (10 pages) doi:10.1115/1.3039513 History: Received April 04, 2008; Revised October 21, 2008; Published December 18, 2008

This paper presents an optimal path planning method of steerable electrode arrays for robot-assisted cochlear implant surgery. In this paper, the authors present a novel design of steerable electrode arrays that can actively bend at the tip. An embedded strand in the electrode array provides an active steering degrees-of-freedom (DoF). This paper addresses the calibration of the steerable electrode array and the optimal path planning for inserting it into planar and three-dimensional scala tympani models. The goal of the path planning is to minimize the intracochlear forces that the electrode array applies on the walls of the scala tympani during insertion. This problem is solved by designing insertion path planning algorithms that provide best fit between the shape of the electrode array and the curved scala tympani during insertion. Optimality measures that account for shape discrepancies between the steerable electrode array and the scala tympani are used to solve for the optimal path planning of the robot. Different arrangements of DoF and insertion speed force feedback (ISFF) are simulated and experimentally validated in this paper. A quality of insertion metric describing the gap between the steerable electrode array and the scala tympani model is presented and its correspondence to the insertion force is shown. The results of using 1DoF, 2DoF, and 4DoF electrode array insertion setups are compared. The 1DoF insertion setup uses nonsteerable electrode arrays. The 2DoF insertion setup uses single axis insertion with steerable electrode arrays. The 4DoF insertion setup allows full control of the insertion depth and the approach angle of the electrode with respect to the cochlea while using steerable electrode arrays. It is shown that using steerable electrode arrays significantly reduces the maximal insertion force (59.6% or more) and effectively prevents buckling of the electrode array. The 4DoF insertion setup further reduces the maximal electrode insertion forces. The results of using ISFF for steerable electrodes show a slight decrease in the insertion forces in contrast to a slight increase for nonsteerable electrodes. These results show that further research is required in order to determine the optimal ISFF control law and its effectiveness in reducing electrode insertion forces.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Problems with different DoF arrangements considered: (a) underactuated robot, (b) known 3D helical cavity, (c) 1DoF insertions, (d) 2DoF insertions, and (e) 4DoF insertions

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Figure 2

Cochlear implant system components and cochlear anatomy

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Figure 3

Steerable electrode array: (a) side view, (b) top view, and (c) physical model

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Figure 4

(a) Electrode calibration setup, (b) shallow insertion depth with supporting ring position, and (c) deep insertion depth with supporting ring position

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Figure 5

Angle and offset optimization of the underactuated robot

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Figure 6

Inverse kinematics of the underactuated robot

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Figure 7

Simulation results of bent electrodes

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Figure 8

Results for path planning: (a) bending of the electrode array q1 and electrode array base rotation q3 and (b) prismatic joint q2 and prismatic joint q4

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Figure 9

Spline results of end effector path for the underactuated robot

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Figure 10

Comparison of a simulated insertion with images taken during the electrode calibration: (a) simulation results for insertion based on (b) the calibrated model of the electrode

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Figure 11

Simulations for 2DoF insertion and 4DoF insertion

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Figure 12

Simulated average angle and distance variations

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Figure 13

System setup with 3D scala tympani model

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Figure 14

Insertion results for average and maximal sensed forces for each experimental condition

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Figure 15

Insertions using 2DoF system into planar scala tympani model: (a) nonsteerable electrode without ISFF, (b) steerable electrode without ISFF, (c) nonsteerable electrode with ISFF, and (d) steerable electrode with ISFF

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Figure 16

Insertions using 2DoF system into 3D scala tympani model with ISFF for nonsteerable electrode array and steerable electrode array

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Figure 17

Insertions using 2DoF system into 3D scala tympani model with ISFF: (a) nonsteerable electrode array, buckling happened and (b) steerable electrode array, no buckling happened

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Figure 18

Steerable electrode array insertions using 4DoF system without ISFF: (a) planar scala tympani model and (b) 3D scala tympani model

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Figure 19

(a) Digitization of the average distance and (b) quality of insertion metric




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