title: Determination of the curling behavior of a preformed cochlear implant electrode array.
abstract: OBJECTIVE
  Accurate insertion of a cochlear implant electrode array into the cochlea's helical shape is a crucial step for residual hearing preservation. In image-guided surgery, especially using an automated insertion tool, the overall accuracy of the operative procedure can be improved by adapting the electrode array's intracochlear movement to the individual cochlear shape.
  
  
  METHODS
  The curling characteristic of a commercially available state-of-the-art preformed electrode array (Cochlear Ltd. Contour Advance(TM) Electrode Array) was determined using an image-processing algorithm to detect its shape in series of images. An automatic image-processing procedure was developed using Matlab and the Image Processing Toolbox (MathWorks, Natick, Massachusetts, USA) to determine the complete curvature of the electrode array by identifying the 22 platinum contacts of the electrode. A logarithmic spiral was used for a comprehensive mathematical description of the shape of the electrode array. A fitting algorithm for nonlinear least-squares problems was used to provide a complete mathematical description of the electrode array. The system was tested for curling behavior as a function of stylet extraction using nine Contour Advance Research Electrodes (RE) and additionally for nine Contour Advance Practice Electrodes (PE).
  
  
  RESULTS
  All arrays show a typical pattern of curling with adequate predictability after the first 2 or 3 millimeters of stylet extraction. Although non-negligible variations in the overall curling behavior were detected, the electrode arrays show a characteristic movement due to the stylet extraction and only vary minimally after this initial phase.
  
  
  CONCLUSIONS
  These results indicate that the risk of intracochlear trauma can be reduced if the specific curling behavior of the electrode carrier is incorporated into the insertion algorithm. Furthermore, the determination of the curling behavior is an essential step in computer-aided cochlear implant electrode development. Experimental data are required for accurate evaluation of the simulation model.
authors.affiliation: Department of Otolaryngology, Medical University Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. rau.thomas@mh-hannover.de
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Rau
authors.forename: Omid
authors.initials: O
authors.lastname: Majdani
authors.forename: Andreas
authors.initials: A
authors.lastname: Hussong
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenarz
authors.forename: Martin
authors.initials: M
authors.lastname: Leinung
mesh_terms: D000465:Algorithms; D019929:Cochlear Implantation / Q000295:instrumentation / Q000379:methods*; D003054:Cochlear Implants; D004567:Electrodes, Implanted; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation; D019060:Minimally Invasive Surgical Procedures; D010984:Platinum; D017755:Prosthesis Fitting / Q000295:instrumentation / Q000379:methods*
chemical_list: D010984:Platinum