title: Safety study of the Cochlear Nucleus 24 device with internal magnet in the 1.5 Tesla magnetic resonance imaging scanner.
abstract: OBJECTIVE
  To evaluate the effect of the 1.5 Tesla magnetic resonance imager (MRI) on the Cochlear Nucleus 24 Device without removing the internal magnet. To determine whether device fixation using a compression dressing could prevent internal magnet displacement in the MRI scanner and potentially obviate the need for surgical removal of the internal magnet.
  
  
  METHODS
  Prospective cadaveric study.
  
  
  METHODS
  Four cadaver heads were implanted bilaterally with the Nucleus device with the internal magnet in place and placed into the 1.5 Tesla MRI scanner. The devices were then explanted after interaction with the MRI and evaluated for displacement of the internal magnet. Conditions tested include device fixation with a commercially available compression dressing and no fixation (worst-case scenario). Magnet strength was measured before and after each of the test conditions.
  
  
  RESULTS
  Moderate to severe displacement of the magnet from the internal device occurred in 14 of 16 (87%) implants when no compression dressing was placed. Displacement occurred in 0 of 16 (0%) implants when the compression dressing was applied. No decrease in the strength of the implant magnet was found with the initial or subsequent MRI/implant interactions.
  
  
  CONCLUSIONS
  Use of the 1.5 Tesla MRI on subjects with Cochlear Nucleus 24 implants did not result in any significant demagnetization of the internal magnet and did not cause displacement of the magnet when an external compression dressing was applied. Surgical removal of the internal magnet before scanning with the 1.5 Tesla MRI may not be necessary if a compression dressing is applied.
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, OR Health and Science University, Portland, Oregon 97239, USA. gubbelss@ohsu.edu
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Gubbels
authors.forename: Sean O
authors.initials: SO
authors.lastname: McMenomey
mesh_terms: D002102:Cadaver; D003054:Cochlear Implants; D006801:Humans; D008279:Magnetic Resonance Imaging; D011446:Prospective Studies; D012449:Safety