title: The Intra-Cochlear Impedance-Matrix (IIM) test for the Nucleus® cochlear implant.
abstract: OBJECTIVE
  To describe the principles and operation of a new telemetry-based function test for the Nucleus® cochlear implant, known as the CS19 Intra-Cochlear Impedance Matrix (IIM) and to present results from a multicentre clinical study to establish reproducibility (test-retest reliability) and normative ranges.
  
  
  METHODS
  The IIM test measures bipolar impedances between all electrode pairs and employs a normalization procedure based on common ground impedances in order to identify abnormal current paths among electrodes. Six European clinics collected IIM data from a total of 192 devices.
  
  
  RESULTS
  Reproducibility was high between initial and repeat measurements. The normative analysis demonstrated narrow ranges among devices after normalization of impedance data. The IIM is able to identify abnormal current paths that are not evident from standard impedance telemetry and may otherwise only be found utilising average electrode voltage measurements (AEV).
  
  
  CONCLUSIONS
  The IIM test was found to be straightforward to perform clinically and demonstrated reproducible data with narrow ranges in normally-functioning devices. Because this test uses a very low stimulation level the IIM test is well suited for children or multiply handicapped CI users who cannot reliably report on their auditory percepts. The new algorithms show potential to improve implant integrity testing capabilities if implemented in future clinical software.
authors.forename: Matthias
authors.identifier: http://orcid.org/0000-0002-5957-205X
authors.initials: M
authors.lastname: Hey
authors.forename: Britta
authors.initials: B
authors.lastname: Böhnke
authors.forename: Norbert
authors.initials: N
authors.lastname: Dillier
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hoppe
authors.forename: Gunnar
authors.initials: G
authors.lastname: Eskilsson
authors.forename: Karolina
authors.initials: K
authors.lastname: Löwgren
authors.forename: Helen
authors.initials: H
authors.lastname: Cullington
authors.forename: Herbert
authors.initials: H
authors.lastname: Mauch
authors.forename: Joachim
authors.initials: J
authors.lastname: Müller-Deile
mesh_terms: D002648:Child; D003054:Cochlear Implants / Q000592:standards*; D017097:Electric Impedance; D004558:Electric Stimulation / Q000295:instrumentation*; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D013686:Telemetry / Q000295:instrumentation*