Systematic evaluation of different approaches for cochlear duct length estimation – a radiological and temporal bone study

Introduction The prediction of the cochlear duct length (CDL) is of high relevance for patients who do not profit from treatment with conventional hearing aids and who aim to undergo cochlear implant surgery. As it is known that the size and shape of the human cochlea vary, a preoperative determination of the CDL may enable a patient-specific choice of CI-electrodes. A study is presented which applies and compares different software-based approaches to determine the CDL in human temporal bones.

Material and Methods A total of 20 human temporal bones were examined using HRCT and CBCT. Based on this imaging, the cochlea is measured using three different software-based procedures: (1.) length estimation based on the established A-value method, (2.) length estimation based on a recently introduced clinical measuring tool based on a combination of A- and B-value methods (Otoplan), and (3.) length determination based on a highly detailed 3D reconstruction of the cochlea using special 3D software. To determine the most appropriate method to predict the postoperative Cochlear coverage (CC) and insertion angle, the insertion depth was verified by postoperative radiological imaging (Stenvers projection) after implantation of a CI-electrode. The insertion angle was measured using the method of Xu et al. (4).

Results and Conclusion Different CDL values depending on the measurement method were found. All preoperatively performed methods tended to underestimate the CDL. CBCT-based measurements showed a higher correlation with the postoperative reference values than HRCT-based methods. The preoperative prediction is likely to underestimate the CDL and may consequently lead to a shorter electrode choice. As a side note, CBCT may be recommended as standard imagine tecnique prior CI-surgery.

Poster-PDF A-1111.pdf

Publication History

Article published online:
13 May 2021