Three-Dimensional Reconstructions of the Implanted Cochlea for the in Vivo Visualization of Scalar Dislocations in Contour Advance Recipients

Background

Recently, cone-beam computed tomography (CBCT) has emerged as a reliable technique for the detection of scalar dislocations. However, thorough examination of electrode placement remains difficult, even for experienced radiologists. Three-dimensional software reconstructions may now be clinically feasible, and could be used to study malpositioned electrodes in detail.

Objective

To evaluate the feasibility of using three-dimensional reconstructions based on CBCT for the detection and visualization of scalar dislocations.

Method

In a retrospective study, patient-specific intracochlear anatomy and electrode positions were automatically segmented from the pre- and postoperative CBCT scans of 23 Contour Advance recipients. Since the separation between scalae is indiscernible, a micro-computed tomography atlas was non-rigidly co-registered with custom software to segment the scala tympani, scala vestibuli, basilar membrane and osseous spiral lamina. Three-dimensional renderings based on the Marching Cubes algorithm allowed for a straightforward scalar localization. The scalar position derived from the renderings was more accurate than the description in a standard radiological protocol.

Results

A dislocation from the scala tympani to the scala vestibuli was evident from the reconstructions in 6 out of 23 patients. In 1 case a scala vestibuli placement was observed. In the remaining 16 cases the array was found to be placed fully in the scala tympani. In all cases the findings were in agreement with the blinded opinion of an experienced neuroradiologist.

Conclusion

Three-dimensional renderings of the implanted cochlea based on CBCT allow for the reliable assessment of scalar position and a clear visualization of the electrode array relative to intracochlear anatomy.