Cochlear implant surgery allows surgeons to restore partial hearing to patients suffering from severe hearing loss due to damaged neuroepithelial (hair) cells. During this surgery surgeons insert long, thin, and flimsy electrodes into the scala tympani inside cochlea. Our goal is to develop a robotic system to help surgeons achieve atraumatic cochlear implant surgery using novel steerable cochlear implant electrode arrays. The research focuses on path planning for robotic-assisted insertion of steerable electrode arrays into 3D cavities (scala tympani) using partial force feedback information. An example of an early experimental system used for testing some of our insertion path planning algorithms is shown in the following figure.
Experimental setup used to evaluate steerable electrode arrays for cochlear
Robotic-Assisted Cochlear Implant Surgery System
The above figure shows an overview of the robotic-assisted cochlear implant surgery system using steerable electrode arrays. Surgeons insert the electrode array by controlling the parallel robot/insertion module through the master with force feedback. An online insertion force reading will be displayed on screen for reference.
The following figure shows the design of a scaled up (3:1) steerable electrode array with actuation strand inside. Upon pulling, it will bend into the desired shape that best approximates the shape of the scala tympani during the insertion process. In the figure, there are different bending shapes of the same steerable electrode array.
The bending shape of the steerable electrode array is calibrated after fabrication shown in the following figures. Once the characteristics of the electrode array are determined, the bending of the steerable electrode array is controlled by one of the actuation unit.
We also fabricated scaled up (3:1) planar and 3D scala tympani model based on literatures. Its high precision substitutes real cadavers for experiments.
Insertion experiments in preliminary research are achieved using two Degrees of Freedom (DoF) robotic system and four DoF robotic system. For the 2 DoF system, one actuation is used for insertion, the other one is for the steering of the electrode array. In the 4 DoF system, besides steering the electrode array, in-plane movement and rotation are achieved.
4 DoF insertion simulation video
The following video shows the insertion simulation process with optimal path planning for the 4 DoF robot. Notice the bending shape of implant changes according to the curve of the cochlea.
2 DoF steerable insertions in 3D scala tympani model
This video is a comparison of insertion process with steerable and non-steerable implant. The bottom one is using a steerable implant. The top one is using the same implant without steering. Notice the buckling of the electrode when it is inserted without steering it.
The results show that an obvious force decrease in observed in planar scala tympani model using 2 DoF system (steerable electrode array). This is due to the increased distance between steerable electrode array and scala tympani external wall by steering the electrode.
The following figure shows different experiment conditions and force reading results. It’s obvious from the figure that using steerable electrode array (2 DoF) can reduce 59.6% of the insertion force. Using 4 DoF system can further reduce 31.8% of the insertion force.
Degrees of Freedom ST
= Scala Tympani
Zhang, J., Bhattacharyya, S., Simaan, N., “Model and Parameter Identification of Friction During Robotic Insertion of Cochlear-Implant Electrode Arrays,” IEEE International Conference on Robotics and Automation (ICRA’2009), pp. 3859-3864, 2009.
Zhang, J., Wei, W., Roland, J., Manolidis, S., Simaan, N., “Optimal Path Planning for Robotic Insertion of Steerable Electrode Arrays in Cochlear Implant Surgery”, in ASME Journal on Medical Devices, Vol 3., No. 1, pp. 011001, 2009.