title: In vivo measures of cochlear length and insertion depth of nucleus cochlear implant electrode arrays.
abstract: Three-dimensional cochlear canal lengths, electrode array intracochlear insertion depths, and characteristic frequency ranges were estimated for 20 Nucleus implant recipients on the basis of in vivo computed tomography (CT) scans. Ultra-high resolution images were reconstructed from spiral CT data with 0.1-mm slicing and expanded attenuation scales. Canal length estimates (mean 33.01 mm; SD 2.31) were consistent with previous findings for normal human temporal bones. Intracochlear array insertion depths estimated by 3-dimensional (3-D) spiral calculations (mean 20.19 mm; SD 2.86) and by a computerized array tracking algorithm (mean 20.36 mm; SD 2.66) were not significantly different. Estimates from surgical observations were significantly longer (mean 21.03 mm; SD 2.31) because array compressions were not detectable. Characteristic frequencies at apical electrodes estimated from Greenwood's equations ranged from 387 Hz to 2,596 Hz. The results show that significant variations in cochlear anatomy and array distribution among implant patients that may impact implant performance can be reliably detected and quantified by using in vivo high-resolution CT and 3-D reconstructions.
authors.affiliation: Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Ketten
authors.forename: M W
authors.initials: MW
authors.lastname: Skinner
authors.forename: G
authors.initials: G
authors.lastname: Wang
authors.forename: M W
authors.initials: MW
authors.lastname: Vannier
authors.forename: G A
authors.initials: GA
authors.lastname: Gates
authors.forename: J G
authors.initials: JG
authors.lastname: Neely
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003051:Cochlea / Q000033:anatomy & histology*; D019929:Cochlear Implantation / Q000379:methods; D017626:Cochlear Nucleus / Q000502:physiology*; D003638:Deafness / Q000534:rehabilitation; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged