Image examination of postoperative evaluation for the cochlear implanted electrode

OBJECTIVE: To evaluate the image feature of the X-ray plain film, the spiral computed tomography (CT) scans and three dimension reconstruction of inner ear with implanted electrode. METHODS: Eighteen patients of cochlear implant (MEDEL Combi 40+) recipients were involved in this study. The implanted electrode of all patients were examined on the fifth to seventh postoperative day, by the use of X-ray plain film with either anteroposterior transorbital projection (nine cases) or lateral position with coronal 60 degrees away from the examine table (nine cases). Three of the cochlear implant recipients were examined by the way of spiral CT scans with axial 1 mm image slices. The data of the CT scans was transferred to workstation for three-dimensioned reconstruction (direct volume rendering) of the inner ear. RESULTS: The X-ray plain film from both of anteroposterior projection and lateral with coronal 60 degrees projection provide satisfactory image of implanted electrode including the shape and the position in the temporal bone. The insertion depth of the electrode can be evaluated indirectly. In contrast, the images from CT scans with 3D reconstruction of the inner ear demonstrate more accurately the shape, the position, and the insertion depth of the electrode. Moreover, each of the electrode pairs can be identified clearly. CONCLUSIONS: X-ray plain film can meet the routine needs of postoperative evaluation of the implanted electrode with several kinds of head position of projection. But CT scans with 3D reconstruction of inner ear provide more accurate image of the spacial relationship of the electrode in the cochlear canal with direct demonstration of electrode insertion depth in the cochlea.