A software for online monitoring of orientation-compensated forces during CI insertion

Abstract

The electrode array insertion is a critical point during CI surgery and should be performed as gently as possible to preserve residual hearing. In order to measure occurring forces, an insertion tool with an integrated force sensor and an inertial measurement unit (IM U) is being developed. The weight of the electrode holder and the sensor add an unknown offset to the measured forces, depending on the tool orientation. To address this problem, a software which calculates the orientation-induced error and computes a corrected force was developed. The software was written in C++ using the library Qt 5.12.9. For maximization of the computing frequency, the data acquisition of both sensors and the monitoring was parallelized. An algorithm was developed to calculate the error caused by the electrode holder and sensor. For this purpose both weights were determined in a calibration procedure and merged with the provided IM U data. The evaluation was done in two test series (each n=5) with different initial tool orientations. To this end a stepwise 360° rotation around the horizontal axis was performed, while recording the corrected forces. The developed software allows a computing frequency up to 100 Hz with a latency of 10 ms for the online monitoring of the processed data. The evaluation of the corrected force shows a residual error of 0.347 mN ± 0.325 mN for the first and 0.176 mN ± 1.971 mN for the second test series. With the created algorithm, the impact of the extra weight on the sensor can be almost fully equalized. The highly responsive software offers a new possibility to process insertion forces and provide feedback to surgeons. Determining the influence of the tool orientation on the corrected forces is the subject of future researches.