title: Measuring Cochlear Duct Length - a historical analysis of methods and results.
abstract: BACKGROUND
  Cochlear Duct Length (CDL) has been an important measure for the development and advancement of cochlear implants. Emerging literature has shown CDL can be used in preoperative settings to select the proper sized electrode and develop customized frequency maps. In order to improve post-operative outcomes, and develop new electrode technologies, methods of measuring CDL must be validated to allow usage in the clinic.
  
  
  OBJECTIVE
  The purpose of this review is to assess the various techniques used to calculate CDL and provide the reader with enough information to make an informed decision on how to conduct future studies measuring the CDL.
  
  
  RESULTS
  The methods to measure CDL, the modality used to capture images, and the location of the measurement have all changed as technology evolved. With recent popularity and advancement in computed tomography (CT) imaging in place of histologic sections, measurements of CDL have been focused at the lateral wall (LW) instead of the organ of Corti (OC), due to the inability of CT to view intracochlear structures. After analyzing results from methods such as directly measuring CDL from histology, indirectly reconstructing the shape of the cochlea, and determining CDL based on spiral coefficients, it was determined the three dimensional (3D) reconstruction method is the most reliable method to measure CDL. 3D reconstruction provides excellent visualization of the cochlea and avoids errors evident in other methods. Due to the number of varying methods with varying accuracies, certain guidelines must be followed in the future to allow direct comparison of CDL values between studies.
  
  
  CONCLUSIONS
  After summarizing and analyzing the interesting history of CDL measurements, the use of standardized guidelines and the importance of CDL for future cochlear implant developments is emphasized for future studies.
authors.affiliation: Biomedical Engineering, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada. rkoch2@uwo.ca.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Koch
authors.affiliation: Biomedical Engineering, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada.|Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada.|Department of Medical Biophysics, Western University, London, ON, Canada.|Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
authors.forename: Hanif M
authors.initials: HM
authors.lastname: Ladak
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada.
authors.forename: Mai
authors.initials: M
authors.lastname: Elfarnawany
authors.affiliation: Biomedical Engineering, Western University, 1151 Richmond Street, London, ON, N6A 3K7, Canada.|Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada.|Department of Electrical and Computer Engineering, Western University, London, ON, Canada.|London Health Science Centre, University Hospital, Room B1-333, 339 Windermere Rd, London, ON, Canada.
authors.forename: Sumit K
authors.initials: SK
authors.lastname: Agrawal
mesh_terms: D003053:Cochlear Duct / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000601:surgery; D019929:Cochlear Implantation / Q000009:adverse effects / Q000379:methods*; D003054:Cochlear Implants; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000517:prevention & control; D011300:Preoperative Care / Q000379:methods; D011474:Prosthesis Design; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
keywords: Cochlear duct length; Cochlear implants; Computed tomography; Histology; Inner Ear; organ of Corti