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Abstract
We present a Baha patient with demagnetization after repeated magnetic resonance imagings (MRIs) and demonstrate a novel way of monitoring magnet adherence. A 53-year-old man with a Baha Attract System reported reduced holding force of the external audio processor after nine MRIs (eight at 1.5 T and one at 3 T). Subsequently, the original external magnet was replaced by a stronger magnet without benefit. After three additional MRIs at 1.5 T, a total loss of magnetic adherence was reported. During revision surgery replacing the internal magnet, we used three different methods to document the magnetic field of the old and new internal magnet; a gaussmeter, a flux detector film and in-situ determination of the minimum adhesive magnetic force. Measurements performed with the gaussmeter served as the gold standard and were confirmed by the other two methods. The application of MR imaging at 3 T in patients with a Baha system is off-label use and initiates magnetic-implant damage, while repeated MRI at 1.5 T scans seems to be harmless. To document potential demagnetization, a flux detector film can be used in daily practice due to its simplicity of application and broad availability.
Acknowledgements
The authors thank Dr. Flurin Honegger for his input in the physical review.
Informed consent
The project conforms to the Code of Ethics of the World Medical Association in its current version (Declaration of Helsinki). We consulted the Ethikkomission Nordwest- und Zentralschweiz (EKNZ). According to HFG Art. 3, our case report does not require ethical approval as the patient’s personal details were kept anonymous. The authors certify that they have obtained all appropriate patient consent.
Disclosure statement
The authors report no conflict of interest.