Safety evaluation of titanium middle ear prostheses at 3.0 tesla.
OBJECTIVE
To assess the magnetic resonance imaging (MRI) safety of titanium middle ear prostheses at 3.0 tesla (T).


METHODS
Titanium middle ear prostheses from 3 commercial vendors were examined for magnetic field interactions at 3 T. Initially, ex vivo studies were performed to test for rotational motion and forward displacement (translational motion) of the prostheses in a static magnetic field. If movement was observed during this screening study, then the prosthesis was tested to determine the translational or rotational force acting upon the prosthesis. In addition to testing for prosthesis displacement, temperature changes of the prostheses were measured to assess for radiofrequency heating during imaging.


RESULTS
Twenty-one of the 24 titanium prostheses tested revealed no movement when tested in the 3 T static magnetic field. Three prostheses revealed minimal movement during the screening study. A translational force test (string test) was performed upon these 3 prostheses, and the measured angle of displacement was used to determine the force. This calculated force acting upon each prosthesis was essentially zero. Therefore, we conclude that the magnetic field interaction is negligible. A positive control with a ferromagnetic stainless steel prosthesis demonstrated obvious displacement during the screening study, as well as deflection of the prosthesis by 90 degrees in the translational force test. Last, heating of the titanium prostheses did not occur in the 7 models tested.


CONCLUSIONS
Middle ear prostheses made from titanium are safe, neither deflecting nor heating during magnetic resonance examinations conducted at 3 T.


METHODS
C-1.
Martin
Angela D
AD
Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN 55901, USA.
Driscoll
Colin L W
CL
Wood
Christopher P
CP
Felmlee
Joel P
JP
D019544:Equipment Failure Analysis; D004869:Equipment Safety; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D009998:Ossicular Prosthesis; D011474:Prosthesis Design; D012306:Risk; D013193:Stainless Steel; D013696:Temperature; D014025:Titanium
D013193:Stainless Steel; D014025:Titanium