[Postoperative imaging and evaluation of the electrode position and depth of insertion of multichannel cochlear implants by means of high-resolution computed tomography and conventional X-rays].

Following cochlear implantation, postoperative imaging of the electrode is very important in order to measure the depth of insertion and the position of the electrode, so that kinking and incorrect electrode placement can be clearly identified. The aim of this study was to outline the diagnostic value of CT and conventional X-ray for these parameters. For this purpose we obtained radiographs of patients who had received a cochlear implant. Computed tomography was performed by obtaining axial sections. For conventional X-ray we used digital imaging, utilising a modified Chausse III projection. The images were then rated according to electrode position, insertion depth and possible complications. We also measured the radiation dose using a dummy and evaluated the cost of each examination. Both examinations permit excellent identification of electrode position and insertion depth. However, the depth of insertion can be measured much more accurately by means of digital X-ray. The radiation dose of CT was 230 times higher than that of conventional X-ray and the cost of CT 5 times that of digital X-ray.