Magnetic Resonance Imaging Safety of the Floating Mass Transducer

Adverse events associated with Vibrant Soundbridge: A MAUDE study

OBJECTIVE

To summarize adverse events and their root causes reported to the United States Food and Drug Administration (FDA) on Vibrant Soundbridge (VSB) hearing device (Med-El, Innsbruck, Austria), an active middle ear implant for patients with moderate to severe hearing loss.

MATERIALS AND METHODS

The FDA's Manufacturer and User Facility Device Experience (MAUDE) database was queried for reports of VSB adverse events from January 1, 2012, to July 27, 2022.

RESULTS

Six hundred sixty-three total medical device reports were identified, from which 913 adverse events were extracted. Of these, 498 (54.5 %) were adverse events to patients (AEPs), while 415 (45.5 %) were device malfunctions (DMs). The most common AEPs were hearing performance issues 428 (85.9 %). The most common DMs were compromised conductive link 125 (30.1 %). Root causes identified for DMs were iatrogenic 85 (58.6 %), patient-related 28 (19.3 %), and trauma and external causes 32 (22.1 %). The most common iatrogenic root cause 12 (14.1 %) involved damage to the conductive link during revision surgery. The most common patient-related causes of DMs were excessive middle ear tissue growth 16 (57 %), and abrupt body movements 5 (28.6 %). The most common external cause of DM was cleaning of the ear canal or mastoid cavity 20 (62.5 %).

CONCLUSIONS

Despite its well-known limitations, the MAUDE database provides valuable information on possible complications of VSB as it relates to device malfunction or adverse events for patients. Implementation of standardized reports with relevant and well-defined categories could certainly allow for a more meaningful analysis.

Stability of the standard incus coupling of the Carina middle ear actuator after 1.5T MRI

Limited data is available concerning the safety of active middle ear implants (AMEI) during Magnetic Resonance Imaging (MRI). Measurements in temporal bones are the gold standard for preclinical assessment of device safety. In this study the coupling stability of an actuator as used in a fully implantable AMEI was determined in temporal bones. Eleven temporal bones were implanted with the actuator according to the manufacturer’s surgical guidelines. The actuator was coupled on the incus short process as recommended for sensorineural hearing loss. Temporal bones were exposed 10 times to the MRI magnetic field by entering the MRI suite in a clinically relevant way. Computed Tomography (CT) images were acquired before and after the experiment to investigate the risk of actuator dislocation. Based on the electrical impedance of the actuator, the loading of the actuator to the incus was confirmed. Relative actuator displacement was determined on the CT images by comparing the initial with the final actuator position in 3D space. Impedance curves were analyzed after each exposure to check the loading of the actuator to the ossicles. Analysis of CT images with a 0.30.6 mm in-plane resolution indicate no actuator displacement. The maximum detected change in impedance for all actuators was 8.43 Ω at the actuator’s resonance frequency. Impedance curves measured when the actuator was retracted from the short process after the experiment still indicate the presence of a clear resonance peak. No actuator displacement or dislocation could be detected in the analysis of CT images and the measured impedance curves. Impedance curves obtained when the actuator was retracted from the incus short process still show a clear resonance peak, indicating the device is still functional after the MRI exposures.

In vivo experiences with magnetic resonance imaging scans in Vibrant Soundbridge type 503 implantees

OBJECTIVE

To observe the effects of magnetic resonance imaging scans in Vibrant Soundbridge 503 implantees at 1.5T in vivo.

METHODS

In a prospective case study of five Vibrant Soundbridge 503 implantees, 1.5T magnetic resonance imaging scans were performed with and without a headband. The degree of pain was evaluated using a visual analogue scale. Scan-related pure tone audiogram and audio processor fitting changes were assessed.

RESULTS

In all patients, magnetic resonance imaging scans were performed without any degree of pain or change in pure tone audiogram or audio processor fitting, even without a headband.

CONCLUSION

In this series, 1.5T magnetic resonance imaging scans were performed with the Vibrant Soundbridge 503 without complications. Limitations persist in terms of magnetic artefacts.

Magnetic Resonance Imaging Compatibility of a New Generation of Active Middle Ear Implant: A Clinically Relevant Temporal Bone Laboratory Study

OBJECTIVE

Magnetic resonance imaging (MRI) has become an essential tool of modern medical imaging and disease diagnosis. In November 2014, a new MRI-conditional (up to 1.5 T) generation of an active middle ear implant (AMEI) was released to the market.The aim of the study was to test the MRI compatibility of the new implant system in a clinical-anatomical study.

DESIGN

Experimental cadaver head model.

SETTING

Temporal bone laboratory.

PARTICIPANTS

AMEIs were implanted in 28 fixed temporal bones at three different floating mass transducer (FMT)-coupling positions (N = 8 short process of the incus, N = 16 long process of the incus, N = 4 round window).

MAIN OUTCOME MEASURES

The position of the FMT and the integrity of the ossicular chain was monitored through microscopy, microendoscopy, and computed tomography (CT) scans before and after the MRI (1.5 T) was conducted. Proper function of the implant was tested with reverse transfer function (RTF) measurements.

RESULTS

Neither positional nor functional changes after MRI were observed.

CONCLUSION

The new generation of the AMEI is a MRI-compatible system, which features an easier and quicker implant fixation method. The option of MRI in patients with AMEI should be taken into consideration during the preoperative discussion with potential candidates.

MRI scanning in patients implanted with a round window or stapes coupled floating mass transducer of the Vibrant Soundbridge

Conclusion MRI examinations in patients with an alternatively coupled VSB can lead to unpleasant side-effects. However, the residual hearing was not impaired, whereas the hearing performance with the VSB was decreased in one patient which could be fixed by a surgical revision. Different experiences for the VSB 503 can be expected. Objective To investigate the in vivo effects of MRI scanning on the Vibrant Soundbridge system (VSB) with an alternatively coupled Floating Mass Transducer (FMT). Method Sixty-five VSB (502) implantees were included in this study. Of them, 42 questionnaires could be evaluated with the patients' statements about their medical, otological, and general condition before, during, and after an MRI scan which was indicated for different medical reasons, despite the previous implantation of an alternatively coupled Vibrant Soundbridge System. Results In four patients (9.5%), five MRI examinations were performed. These were done for different indications (e.g. knee and shoulder joint diagnostics). During the scanning, noise and subjectively perceived distortion of the implant were described. A deterioration of the hearing gain with the VSB in place was found in one patient. A decrease of the hearing threshold was not observed.

MRI Information for Commonly Used Otologic Implants

Objective

To review information on magnetic resonance imaging (MRI) issues for commonly used otologic implants.

Data Sources

Manufacturing companies, National Library of Medicine’s online database, and an additional online database ( www.MRIsafety.com ).

Review Methods

A literature review of the National Library of Medicine’s online database with focus on MRI issues for otologic implants was performed. The MRI information on implants provided by manufacturers was reviewed.

Results

Baha and Ponto Pro osseointegrated implants’ abutment and fixture and the implanted magnet of the Sophono Alpha 1 and 2 abutment-free systems are approved for 3-Tesla magnetic resonance (MR) systems. The external processors of these devices are MR Unsafe. Of the implants tested, middle ear ossicular prostheses, including stapes prostheses, except for the 1987 McGee prosthesis, are MR Conditional for 1.5-Tesla (and many are approved for 3-Tesla) MR systems. Cochlear implants with removable magnets are approved for patients undergoing MRI at 1.5 Tesla after magnet removal. The MED-EL PULSAR, SONATA, CONCERT, and CONCERT PIN cochlear implants can be used in patients undergoing MRI at 1.5 Tesla with application of a protective bandage. The MED-EL COMBI 40+ can be used in 0.2-Tesla MR systems. Implants made from nonmagnetic and nonconducting materials are MR Safe.

Conclusion

Knowledge of MRI guidelines for commonly used otologic implants is important. Guidelines on MRI issues approved by the US Food and Drug Administration are not always the same compared with other parts of the world.

Implications for Practice

This monograph provides a current reference for physicians on MRI issues for commonly used otologic implants.

Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging

Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.