Imaging procedures in cochlear implant patients – evaluation of different radiological techniques

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Abstract
The purpose of this study was to evaluate the feasibility and usability of different radiologic methods (single-slice computed tomography (CT), multi-slice CT and rotational tomography (RT)) for assessment of the position of cochlear implant electrodes. Cochlear implants in an isolated human temporal bone and in a complete formalin-fixed cadaver head were examined and the electrode position was determined. Subsequently, the labyrinth bone was isolated out of the cadaver head and histologically examined to compare the results of histology with imaging. Single-slice CT reliably identifies the electrode inside the human cochlea; however, due to the technically based large electrode artifact its position inside the cochlear spaces (e.g. electrode position in scala tympani or scala vestibuli) cannot be detected. Multi-slice CT of the cadaver head also showed artifacts that complicate the assessment of electrode position. Using RT the electrode artifact is small and therefore the electrode position within the cochlear spaces, scala tympani versus scala vestibuli, can be assessed. This technique was also applicable in a complete cadaver head, which is in contrast with former studies. In conclusion, CT allows the identification of electrode arrays inside the human cochlea. Multi-slice CT permits a much more precise depiction of the electrode inside the cochlea. RT alone has minimized electrode artifacts to a high extent and permits the assessment of the electrode position within the scala tympani or scala vestibuli. As RT was performed successfully in a complete cadaver head, further studies for evaluation of the intracochlear electrode position can now be performed in patients.