Magnetic Resonance Imaging Safety of the Floating Mass Transducer *Ingo Todt, †Grit Rademacher, *Friederike Wagner, *Eva Schedlbauer, *Jan Wagner, *Dietmar Basta, and *Arne Ernst Departments of *Otolaryngology, and ÞRadiology, Unfallkrankenhaus Berlin, Berlin, Germany Hypothesis: The goals of this study are to observe 1.5-T magnetic resonance imaging (MRI)Yrelated changes to the Vi- brant Soundbridge floating mass transducer (FMT) magnetiza- tion, function, and position in different coupling modes within the middle ear; changes to middle ear structures; and effects on the transfer function to the inner ear. Background: The MRI safety of implantable hearing devices is important in daily routine clinical care as well as in urgent care. Methods: Nine FMTs were repeatedly investigated before and after MRI scanning. Changes in the position of the FMT (round window, incus, and stapes) and in the ossicular chain in tem- poral bones were estimated by microscopy, microendoscopy, and flat panel angiography. Functional investigations of the FMT in different coupling modes were done using laser Doppler vibrometry. Results: Qualitative demagnetization could be ruled out in all specimens after up to 11 MRI scans. In FMT couplings to the long process of the incus (n = 18), positional changes were found in 5 temporal bones. A disarticulation or exarticulation of the ossicles was not observed. Mean laser Doppler vibrometry measurements showed MRI-related changes in the stapes ve- locity. In FMT couplings to the round window (n = 23), we observed a fixation-dependent influence of MRI scanning on the FMT position and mean transfer function. Conclusion: The functional integrity of the FMT was not sig- nificantly influenced after multiple MRI scans. Positional changes of the FMT within the middle ear are possible, but we observed no structural damage to middle ear structures. Effects on the transfer function are possible. Key Words: Floating mass transducerV Magnetic resonance imagingVVibrant Soundbridge. Otol Neurotol 31:1435Y1440, 2010. Magnetic resonance imaging (MRI) scanning in daily clinical routine is important and may be required for patients both with and without medical implants. This is true for hearing implants, and it is important to know the effects of MRI on the implant and nearby physical struc- tures. Stapes prostheses have been widely investigated in vitro (1,2) and in vivo (3) and have been shown to be MRI safe in the commonly applied T-range of conventional MRI scanners with 1 exception (1987, McGee piston). The recommendations of cochlear implant manufac- turers for MRI scanning at 1.5 T vary from removal of the internal magnet (Advanced Bionics, Sylmar, CA, USA; Cochlear Ltd, Melbourne, Australia) to using a tight headband on the patient during scanning. This is to decrease the risk of magnet dislocation and to minimize possible discomfort in the magnetic field (Cochlear Ltd, Melbourne, Australia; MED-EL, Innsbruck, Austria; MXM, Vallauris, France). The risk of MRI-induced currents has been shown to be insignificant in currently used cochlear implants (4Y7). However, demagnetization of the internal magnet has been described (7,8). Results with present systems vary between limited demagnetization (6) and no significant demagnetization (4). MRI safety studies of hearing implants other than co- chlear implants are limited. MRI scanning does not have any influence on the BAHA system because a nonmag- netic titanium screw is used (9). Most other published reports are of historical interest only because the devices are no longer available. Reports on a previous active middle ear implant showed a displacement of the incus- attached magnet in the temporal bone (TB) (10), and studies of the Soundtec implantable hearing aid showed that the device is MRI safe at 0.3 T (11). Our group published a case study of 2 patients who underwent 1.5 T MRI scanning without impairment to hearing or the functional integrity of the Vibrant Sound- bridge (VSB) (12). An experimental study of the influence Address correspondence and reprint requests to Ingo Todt, M.D., Department of Otolaryngology at ukb, Warener Str. 7, D-12683 Berlin, Germany; E-mail Ingo.Todt@ukb.de This study was supported by the Vibrant MED-EL Company. Otology & Neurotology 31:1435Y1440 Ó 2010, Otology & Neurotology, Inc. 1435 Copyright © 2010 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.