Standardization of CT depiction of cochlear implants

Purpose: Imaging an implant in the cochlea is challenging because of implant-induced image artifacts, anatomic variations, and lack of standard terminology when describing cochlear anatomy. Implant surgeons may have difficulty deciphering the radiologist's report as to how far the electrode array extends into the cochlea due to the lack of standard terminology. Methods: In this retrospective study, a neuroradiologist and an implant surgeon independently viewed temporal bone CT images of 35 ears (33 children) with cochlear implants over a 6-yr period. Images were compared and contrasted with the formal report of clinical neuroradiologist. Results: Inter-observer agreement was similar when comparing axialcoronal images and reformatted images among each individual and in comparison. Clinical radiology reports ambiguously described how far the electrode array extends into the cochlea. Conclusion: Easier determination of insertion depth of the cochlear implant array is enabled by: (1) cochlea specific reformation planes set in the plane of the basal turn of the cochleae (2) using the round window niche as the zero reference and the first 4 quadrants to designate the basal turn (3) using the term apicad to indicate toward the apex of the cochlea The combination of image manipulation and standard terms regarding cochlear anatomy results in an easier, more descriptive report of implant depth.