The feasibility of a novel sensing system for robotic cochlear electrode array feed for hearing preservation

Abstract

A cochlear implant (CI) was a small electronic device that could provide direct electrical stimulation to the auditory nerve. Unlike a hearing aid, a cochlear implant turned sounds into electrical pulses which were sent directly to the auditory nerve. During a cochlear implant surgery, intracochlear electrode array insertion was considered to be a crucial process. However, the behaviour of the intracochlear electrode array during the insertion remained unclear to surgeons and the behaviour was hardly diagnosed by normal methods. In order to minimize or eliminate the trauma induced by electrode array insertion, we proposed an electrode capacitive sensing method to discriminate among certain signal patterns and notify the surgeons whether the array was placed correctly during the insertion process. In this thesis, we firstly investigated the mechanical behaviour of a CI electrode array during the insertion process. A force model simulating the first contact between the array tip and cochlear inner wall was proposed. Experimental results demonstrated that insertion force was not an effective method for detecting the array behaviours inside of the cochlea. Secondly, we investigated the theory and influencing factors of the capacitive sensing measurements. The relationship between capacitance measured and environmental effect, structural effect and applied force were examined and assessed. Our exploration demonstrated that the measured bipolar capacitive signals were recognised to be sensitive, consistent and reliable. Experiment results revealed that electrode capacitance values were systematically affected by intracochlear forces between the scala tympani wall and the contact electrode. Thirdly, by analysing the bipolar capacitance experimental results, three CI electrode array insertion patterns between the array and the cochlear lateral wall were classified. The possibility of the three patterns which an unknown insertion would fall into could be discriminated by the Principal Component Analysis (PCA) and The Pearson Correlation Coefficient (PCC) analysis. Experiment results showed the overall identification success rate was over 80%. Finally, a multi-channel switch board was proposed to measure multiple electrode pairs at the same time during the array insertion. Measurements and verification based on the board were carried out and shown to be efficient for capacitive signals measuring and recording.