Magnetic Resonance Imaging Safety for Patients with Active Hearing Implants

The use of medical technologies in both the diagnosis and treatment of several health issues has become common practice. In medical diagnostics, magnetic resonance imaging or MRI has become a widely accepted and preferred imaging technique for many pathologies. This is mainly thanks to the fact that MRI is superior in visualizing soft tissue structures, whilst it does not rely on the use of potentially harmful ionizing radiation. With respect to treating medical conditions, numerous medical devices are being used to alleviate symptoms and improve the quality of life for the patient. The presented work focuses active implantable hearing solutions, which are designed to compensate moderate to severe forms of hearing loss. According to the World Health Organization (WHO), hearing loss is a highly prevalent condition that severely impacts a person's quality of life. Estimates are that by 2050, over 2.5 billion people worldwide will suffer from a certain degree of hearing loss with 700 million of those requiring rehabilitation of some form. Active hearing implants like cochlear or bone conduction implants have been on the market for the past decades, and several hundreds of thousands of people have regained their hearing thanks to these technologies. Mutual interactions between a medical implant and the electromagnetic fields that are present during magnetic resonance (MR) imaging and spectroscopy can cause discomfort or harm to the patient. Several prior reports describing sometimes severe adverse events have led to international efforts towards standardization in order to make MR imaging and spectroscopy in implanted patients safer. Standardization efforts have been focused mainly on passive or active, electrically stimulating implants. The presented work untangles the potential risks for acoustically stimulating hearing implants in the MR environment. The problem is approached holistically, by developing several measurement techniques that allow de-risking MRI-induced risks early in the development process of new devices. First, a literature review is performed together with an analysis of adverse events reported to the American Food and Drug Administration (FDA). This allows to establish both the technical state-of-the-art together with the most common adverse events. As this study illustrates, dislocation of an implanted actuator is a phenomenon that could occur during MRI requiring post-MRI revision surgery. In the second part of this work, a measurement