Ferromagnetic movements of middle ear implants and stapes prostheses in a 3-T magnetic resonance field.
OBJECTIVE
A 3-T magnetic resonance field may cause motion or displacement of middle ear implants not seen in studies with 1.5-T magnets.


BACKGROUND
Previous publications have described the safety limitations of some otologic implants in 1.5-T magnetic resonance fields. Several company-wide recalls of implants were issued. No studies to date have been reported for otologic implants within a 3-T magnetic resonance field, nor have there been comparisons with a 1.5-T field strength.


METHODS
Eighteen commonly used middle ear implants and prostheses were selected. In Part 1, the prostheses were placed in Petri dishes and exposed to a 3-T magnetic resonance field. In Part 2, the particular prostheses that showed movement in Part 1 were placed into their intended use positions within temporal bone laboratory specimens and exposed to a 3-T field. Both parts were repeated in a 1.5-T field.


RESULTS
In Part 1, three prostheses moved dramatically from their start positions when exposed to the 3-T magnetic resonance field. In Part 2, the three particular prostheses that showed movement in Part 1 showed no gross displacement or movement from their start positions within the temporal bone laboratory specimens. No implants moved in the 1.5-T field in either Part 1 or Part 2.


CONCLUSIONS
Certain stapes prostheses move dramatically in Petri dishes in 3-T fields. When placed into temporal bone laboratory specimens, the same prostheses show no signs of movement from the surgical site in a 3-T field, and it appears that the surgical position holds the implants firmly in place. Results of published 1.5-T field studies should not be used directly for safety recommendations in a 3-T magnetic resonance. Heat, voltage induction, and vibration during exposure to the magnetic resonance fields should be considered as additional possible safety issues. Preference should be given to platinum and titanium implants in manufacturing processes and surgical selection.
Fritsch
Michael H
MH
Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA. mfritsch@iupui.edu
Gutt
Jason J
JJ
D000075202:Contraindications; D004432:Ear, Middle / Q000601:surgery*; D019544:Equipment Failure Analysis / Q000379:methods; D005290:Ferric Compounds / Q000009:adverse effects*; D006310:Hearing Aids; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D008953:Models, Anatomic; D009998:Ossicular Prosthesis; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods*; D013201:Stapes Surgery; D014732:Vibration / Q000009:adverse effects
D005290:Ferric Compounds; C001215:ferrite