Magnet resonance imaging safety of the Vibrant Soundbridge system: a review

Abstract

Objective: To review the current knowledge on magnetic resonance imaging (MRI) safety of the Vibrant Soundbridge (VSB) system, an implantable, active middle ear implant.

Data sources: National Library of Medicine's online database and clinical reports.

Study selection: All available articles from 1995 to 2010 on MRI compatibility of the VSB and other active middle ear implants.

Results: Minor demagnetization was found for alignments of the magnets antiparallel to the magnetic field of the scanner, which played no clinically important role. In some cases, the torque forces upon MRI scanning can lead to pain and/or dislocation of the implant or dislocation of the floating mass transducer (FMT) depending on its type of positioning and attachment in the middle ear. Consecutive need of revision surgery is possible. Voltage induction may cause loud audible sounds; however, there were no reports for cochlear hearing loss. No significant heating effects upon MRI scanning were reported. Image artifacts occur especially because of the large magnet. In none of the patient or temporal bone studies, the ossicles, round or oval window, or other middle ear structures were injured, and there was no functional loss of the implant performance (i.e., demagnetization of the FMT).

Conclusion: MRI examinations of up to 1.5T may be of crucial diagnostic importance to the patients implanted with a VSB, but there seems no serious risk of harm to the patient or damage to the VSB. A dislocation of the FMT can be possible during MRI, and this does depend on transducer position and the security of the transducer to the vibratory structure and the coupling mode used. The next generation of VSB systems should consider those possible changes in its design.