A Novel Method for Clinical Cochlear Duct Length Estimation toward Patient-Specific Cochlear Implant Selection

OBJECTIVE: In the field of cochlear implantation, the current trend toward patient-specific electrode selection and the achievement of optimal audiologic outcomes has resulted in implant manufacturers developing a large portfolio of electrodes. The aim of this study was to bridge the gap between the known variability of cochlea length and this electrode portfolio. DESIGN: Retrospective analysis on cochlear length and shape in micro–computed tomography and cone beam computed tomography data. SETTING: Tertiary care medical center. SUBJECTS AND METHODS: A simple 2-step approach was developed to accurately estimate the individual cochlear length as well as the projected length of an electrode array inside the cochlea. The method is capable of predicting the length of the cochlea and the inserted electrode length at any specific angle. Validation of the approach was performed with 20 scans of human temporal bones (micro–computed tomography) and 47 pre- and postoperative clinical scans (cone beam computed tomography). RESULTS: Mean ± SD absolute errors in cochlear length estimations were 0.12 ± 0.10 mm, 0.38 ± 0.26 mm, and 0.71 ± 0.43 mm for 1, 1.5, and 2 cochlea turns, respectively. Predicted insertion angles based on clinical cone beam computed tomography data showed absolute deviations of 27° ± 18° to the corresponding postoperative measurements. CONCLUSION: With accuracy improvements of 80% to 90% in comparison with previously proposed approaches, the method is well suited for the use in individualized cochlear implantation.