[The interactions between metal stapes prostheses and high-intensity magnetic fields during magnetic resonance tomography].

The ever-increasing use of magnetic resonance tomography (MR) as an investigation mean has created a new interest in the biological effects of magnetic fields (MF) and in finding protective measures to be taken in their event. At the moment, use of MR is contraindicated in the presence of pacemakers, vascular clips, liquoral shunts and orthopedic prostheses, all of which may be dislocated by the MF created by MR or may interact with the MF itself creating distorted or falsified images. The aim of our study was to verify if metallic stapedectomy prostheses are dislocated by the MF and if they produce enough interference to falsify MR images. Five types of metallic stapedial prostheses exposed to a MF of 0.5T were studied. We may conclude from our results that MR does not create any otological risks for patients with these prostheses in that none of them were dislocated during exposure. However, all the prostheses studied did instead bring about alterations in the MF and the MR image to varying degrees. In some cases (Robinson) there was notable image distortion, while in others (Schuknecht wire teflon and platinum piston) the distortion was practically negligible. It is our opinion, however, that even if the image distortion does not interfere with routine MR, use of prostheses made of materials not affected by MF are advisable in view of an eventual development of visualization of the labyrinth and intratemporal facial nerve portion with MR.