Flat-Panel CT for Cochlear Implant Electrode Imaging: Comparison to Multi-Detector CT.

Abstract

Flat-panel computed tomography (FPCT) will allow more accurate localization of cochlear implants with decreased metallic artifact and decreased radiation dose when compared with multi-detector CT (MDCT). The measurement of scalar location and intra-scalar position of cochlear implantation (CI) electrodes using computed tomography (CT) is complicated by metallic image artifact and insufficient scalar resolution. FPCT has been shown to improve upon the resolution of MDCT while reducing artifact. Previous studies of FPCT imaging employed isolated temporal bones and did not compare FPCT with MDCT. A total of 11 CI electrodes (Flex-24, MED-EL Corp, Innsbruck, Austria) were intentionally placed into either the scala tympani (ST) or scala vestibule (SV) in whole cadaver heads and imaged with MDCT and FPCT. The relative radiation dose was measured at the ocular lens for each modality. The implanted cochleae were then isolated and imaged with micro-CT which was used to assess electrode position. Images were reviewed and scored according to electrode array scalar compartment (ST, SV, scala media [SM]), intra-scalar position within each compartment (perimodiolar, mid modiolor, lateral wall) and for the presence of artifact by five readers blinded to the imaging method and approach for electrode insertion. FPCT showed less metallic CI artifact (p = 0.002) and decreased radiation dosage when compared with MDCT. Reviewers were able to identify the scalar compartment and intra-scalar position of all electrodes more accurately with FPCT than with MDCT (p < 0.001). FPCT more accurately resolves the scalar compartment and intra-scalar position of CI electrodes with reduced radiation exposure and metallic artifact than MDCT.