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Compatibility of a Magnetic Position Tracker with a Cochlear Implant System

Kerber, Stefan; Seeber, Bernhard U.

doi: 10.1097/AUD.0b013e31819e69f1
Brief Reports

Objectives: The aim of this study was to reveal possible interspersion of a magnetic position tracking device into a cochlear implant system, which could lead to harmful signals on the implanted electrode.

Design: Signals at the output of the speech processor’s compression stage and at the implant’s electrode were recorded and analyzed for unwanted distortion or corrupted pulses related to the presence of the magnetic tracking device.

Results: No systematic impact of a Polhemus Liberty Latus magnetic tracking system on the output signals of an Advanced Bionics HiRes90k cochlear implant and Platinum Series speech processor was found.

Conclusions: The results suggest no objections for using the Polhemus Liberty Latus magnetic position tracker with the Advanced Bionics Platinum series speech processor and HiRes90k cochlear implant in research, for example, on spatial hearing. This result is likely transferable to other cochlear implants because (i) all manufacturers adhere to equally high electromagnetic interference standards and (ii) electromagnetic signals used by the transmission links of current cochlear implants and trackers differ in frequency by roughly 2 decades, making interference unlikely.

Tracking of positions in space allows innovative and intuitive experiments and magnetic trackers have become increasingly popular for research on spatial hearing. Because cochlear implant (CI) systems are susceptible to magnetic interspersion, this article aims to quantify the impact of the Polhemus Liberty Latus tracking system on an Advanced Bionics HiRes 90k CI with Platinum Series speech processor. The intention was to reveal alterations in the output signals of the CI system due to interspersion of the magnetic tracker to prevent corrupted or even harmful signals reaching the CI user. No such systematic alterations were found in the measurements.

MRC Institute of Hearing Research, Science Road, University Park, Nottingham, United Kingdom.

This work was funded through the intramural program of the Medical Research Council (UK).

Address for correspondence: Dr. Bernhard Seeber, MRC Institute of Hearing Research, Science Road, University Park, Nottingham NG7 2RD, United Kingdom. E-mail:

Received August 5, 2008; accepted January 19, 2009.

© 2009 Lippincott Williams & Wilkins, Inc.