Hough Transform of the Transimpedance Matrix as a Tool for the Detection of Electrode Tip Fold Over

Background: The introduction of more flexible and thinner electrodes, such as Cochlear’s Slim Modiolar Electrode, increased the risk of electrode insertion problems, in particular tip foldovers. Detection of the problem during surgery would allow for direct intraoperative correction. Because few surgical centers can perform radiology intraoperatively, a nonradiological method for tip foldover detection would be the ideal solution for most surgical centers.

Objective: To explore tip foldover detection using the Hough transform of the transimpedance matrix measured by means of Electrode Voltage Telemetry.

Methods: The resistive component of the 22x22 impedance matrix from four CI recipients with radiographically proven tip foldover, is compared to that of 64 cases with proper electrode placement and without other electrode issues. Data from 44 Contour Advance, 23 Slim Modiolar, and 1 Slim Straight electrodes were analyzed. The Hough transform, a line detection technique from image processing, was applied to the 2D heatmap representation of the transimpedance matrix.

Results: Proper electrode placement shows up in the 2D heatmap representation of the transimpedance matrix as a diagonal line, reflecting the high voltage near the stimulation electrode. The voltage decreases monotonically with distance to the main diagonal. In the 4 cases of tip foldover, an addition line of higher voltage perpendicular to the main diagonal is observed. The bend positions between E14 and E20 are correctly detected by the Hough transform.

Conclusion: Potentially, the Hough transform of the impedance matrix is a technique for automatic detection of electrode tip foldover in the absence of other electrode issues.