Safety of MRI with metallic middle ear implants

Investigation of the effects of magnetic resonance fields on commonly used metallic middle ear implants.

Nine middle ear prostheses (seven containing stainless steel and two made of pure gold used as control) were tested in vitro and one stainless steel stapedectomy prosthesis was tested on a cadaveric temporal bone.

Each metallic prosthesis was placed in an empty Petri dish and introduced into a 1.5-tesla (T) magnetic resonance imaging (MRI) unit. Most of the prostheses were then placed in a water-filled Petri dish and reintroduced into the MRI unit. Eventual in vitro displacement was assessed visually by two means. In situ testing was done by implanting a piston in a cadaveric temporal bone and performing MR sequences ; any possible displacement was then assessed by CT scan and under microscopic vision.

None of the prostheses was displaced in the empty Petri dish. However, while in the water-filled Petri dish, three of these moved with the flux. The implanted piston in the temporal bone did not move.

The displacement of three of the prostheses in water is not relevant in real clinical situations. MRI can thus be considered safe in usual clinical settings, as far as our studied implants are concerned.