MRI artefacts after Bonebridge implantation

Magnetic Resonance Imaging with Active Implantable Hearing Devices: Reports from the Daily Radiological Routine in an Outpatient MR Center

PURPOSE

For people with hearing implants (HI), magnetic resonance imaging (MRI) still presents some difficulties due to the built-in magnet. Radiologists often have concerns regarding complications associated with HIs. The aim of this study was to record the experiences of HI users during and after MRI examinations.

METHOD

A survey including 15 questions regarding MRI specifics, namely changes in hearing ability, hearing/sound impressions, pain, uncomfortable feelings, etc., were mailed to our patients.

RESULTS

Overall, 79 patients with HI had a total of 159 MR examinations in our institute. A total of 45 HI recipients reported back: 35% stated that they had been rejected by an MRI Institute because of their HI. Their feelings/impression ratings during the measurements were not present and therefore were not rated for the majority (49%), 42% of the HI users rated the pain with 0 (no pain), 2% with 1 (very light pain), 4% with 5 (acceptable pain), and 2% rated the pain with 7, which is between acceptable and strong pain. One examination resulted in a dislocation of the magnet of a cochlear implant (CI 512 Cochlear Limited). No adverse events were reported for MED-EL HI users in the survey (none of the contacted AB users answered the questionnaire). The reported mean daily wearing time was 11.6 ± 4.6 h per day for 6.3 ± 1.7 days per week.

CONCLUSIONS

Based on these results and our experience we conclude that MRI examinations with HI are safe given that the measurements are performed according to the safety policies and procedures released by the manufacturers.

Comparison of artefact reduction possibilities with the new active transcutaneous bone conduction implant (Bonebridge)

OBJECTIVE

This study aimed to evaluate the possibilities of artefact reduction using different anatomical implant positions with the Bonebridge bone-conduction hearing implant 602 for a patient with an acoustic neuroma requiring regular diagnostic magnetic resonance imaging of the tumour position.

METHOD

Three implant positions and magnetic resonance imaging examinations with and without customised sequences for metal artefact suppression were investigated. The diagnostic usefulness was rated by a radiologist (qualitative evaluation), and the relation between the area of artefact and the total head area was calculated (quantitative evaluation).

RESULTS

Following the qualitative analysis, the radiologist rated the superior to middle fossa implant placement significantly better for diagnostic purposes, which is in agreement with the calculated artefact ratio (p < 0.0001). The customised slice-encoding metal artifact correction view-angle tilting metal artifact reduction technique sequences significantly decreased the relative artefact area between 5.13 per cent and 25.02 per cent. The smallest mean artefact diameter was found for the superior to middle fossa position with 6.80 ± 1.30 cm (range: 5.42-9.74 cm; reduction of 18.65 per cent).

CONCLUSION

The application of artefact reduction sequencing and special anatomical implant positioning allows regular magnetic resonance imaging in patients with the bone-conduction hearing implant 602 without sacrificing diagnostic imaging quality for tumour diagnosis.

Safety of active auditory implants in magnetic resonance imaging

Magnetic resonance imaging (MRI) has become the gold standard for the diagnosis of many pathologies. Using MRI in patients with auditory implants can however raise concerns due to mutual interactions between the implant and imaging device, resulting in potential patient risks. Several implant manufacturers have been working towards more MRI safe devices. Older devices are however often labelled for more stringent conditions, possibly creating confusion with patients and professionals. With this myriad of different devices that are implanted in patients for lifetimes of at least 20 years, it is crucial that both patients and professionals have a clear understanding of the safety of their devices. This work aims at providing an exhaustive overview on the MRI safety of active auditory implants. The available industry standards that are followed by manufacturers are outlined and an overview of the latest scientific developments focusing on the last five years is provided. In addition, based on the analysis of the adverse events reported to the Food and Drug Administration (FDA) and in literature within the past ten years, a systematic review of the most commonly occurring issues for patients with auditory implants in the MRI environment is provided. Results indicate that despite the release of more MRI conditional active hearing implants on the market, adverse events still occur. An extensive overview is provided on the MRI safety of active auditory implants, aiming to increase the understanding of the topic for healthcare professionals and contribute to safer scanning conditions for patients.

Long-Term, Multicenter Results With the First Transcutaneous Bone Conduction Implant

OBJECTIVE

Investigation of long-term safety and performance of an active, transcutaneous bone conduction implant in adults and children up to 36 months post-implantation.

STUDY DESIGN

Prospective, single-subject repeated-measures design.

SETTING

Otolaryngology departments of eight German and Austrian hospitals.∗†‡§||¶#∗∗†† Affiliations listed above that did not participate in the study.‡‡§§||||¶¶.

PATIENTS

Fifty seven German-speaking patients (49 adults and eight children) suffering from conductive or mixed hearing loss, with an upper bone conduction threshold limit of 45 dB HL at frequencies between 500 and 3000 Hz.

INTERVENTION

Implantation of the Bonebridge transcutaneous bone conduction hearing implant (tBCI).

MAIN OUTCOME MEASURES

Patients' audiometric pure tone averages (PTA4) (0.5, 1, 2, 4 kHz) thresholds (air conduction, bone conduction, and sound field) and speech perception (word recognition scores [WRS] and speech reception thresholds [SRT50%]) were tested preoperatively and up to 36 months postoperatively. Patients were also monitored for adverse events and administered quality-of-life questionnaires.

RESULTS

Speech perception (WRS: pre-op: 17.60%, initial activation [IA]: 74.23%, 3M: 83.65%, 12M: 83.46%, 24M: 84.23%, 36M: 84.42%; SRT50%: pre-op: 65.56 dB SPL, IA: 47.67 dB SPL, 3M: 42.61 dB SPL, 12M: 41.11 dB SPL, 24M: 41.74 dB SPL, 36M: 42.43 dB SPL) and sound field thresholds (pre-op: 57.66 dB HL, IA: 33.82 dB HL, 3M: 29.86 dB HL, 12M: 28.40 dB HL, 24M: 28.22 dB HL, 36M: 28.52 dB HL) improved significantly at all aided postoperative visits. Air and bone conduction thresholds showed no significant changes, confirming preservation of patients' residual unaided hearing. All adverse events were resolved by the end of the study.

CONCLUSIONS

Safety and performance of the tBCI was demonstrated in children and adults 36 months postoperatively.

Efficacy of cartilage conduction hearing aids in children

OBJECTIVES

Cartilage conduction hearing aids (CC-HAs) are novel hearing aids that use the third hearing pathway of cartilage conduction. We assessed the efficacy of CC-HAs and the hearing effects and safety of additional tape compression over the transducer in children with hearing loss.

METHODS

The patients (n = 42) underwent a one-month free trial of CC-HAs. Forty of them were patients with auditory canal atresia or stenosis. CC-HA-aided and unaided hearing thresholds (48 fitted ears) were determined using standard audiograms, after which participants could choose to purchase the device or not. We calculated the purchase rates and compared the patient characteristics between the purchase and non-purchase groups along with the purchase reason (or not). We applied additional tape compression over the CC-HA transducer and assessed the hearing effects and side effects.

RESULTS

CC-HA led to hearing improvements at all frequencies. Overall, 72.92% of participants purchased a CC-HA after the trial. By applying additional tape compression over the CC-HA transducer, the stability and hearing gains were improved mainly at low frequencies, and no side effects such as dermatitis were observed.

CONCLUSIONS

CC-HAs are efficacious in producing hearing improvements in children, especially in patients with atresia or canal stenosis who cannot use air conduction hearing aids. Furthermore, we found that the additional tape compression over the transducer was an easy and a safe method for improving the hearing effects and stability of the CC-HA.

Device profile of the Bonebridge bone conduction implant system in hearing loss: an overview of its safety and efficacy

INTRODUCTION

The Bonebridge is an active transcutaneous semi-implantable bone conduction hearing device suitable for several types of hearing loss. It has unique benefits over some more established technologies. It consists of an internal active implant and an external sound processor. It was first launched in 2012, with a newer model released in late 2019.

AREAS COVERED

The structure and features of the device are described. Indications, audiological criteria, and contraindications to implantation are discussed. The planning and procedure of implantation surgery are also described. Research outlining the outcomes of implant use and risk of adverse events is highlighted.

EXPERT OPINION

The evidence included in this article demonstrates the successful audiological outcomes and patient satisfaction with Bonebridge implantation. The rate of adverse events following surgery is low and compares well with other devices which may be considered for Bonebridge candidates. The device should be considered as an option for suitable candidates and in many cases may be the better option available, given the low incidence of skin complications and the absence of a skin penetrating abutment. Future advances are likely to affect sound processor technology, connectivity, and possibly further reduction in implant size and gain.

MRI after Bonebridge implantation: a comparison of two implant generations

PURPOSE

Analysis of head magnetic resonance images (MRI) of patients with active bone conduction implants (BCIs) is challenging. Currently, there are two generations of the transcutaneous Bonebridge system (BCI601 and BCI602), the main difference between them being the transducer design and thickness. The aim was to compare the effect of transducer placement and artifact reduction sequences on legibility of MRI scans.

METHODS

Four Thiel-fixed human head specimens were used: BCI601 was implanted in sinodural and middle fossa placement, and BCI602 in middle fossa and retrosigmoid approach. Images were obtained with a Signa^® 1.5T MR. A metal artifact reduction sequence known as MAVRIC (multiacquisition variable-resonance image combination) was used. Each specimen was scanned using standard axial T2 SE and compared with axial MAVRIC artifact reduction sequences.

RESULTS

Qualitatively, limits of the artifact produced by the implant were better defined with MAVRIC than with standard T2 sequences. Assessment of contralateral internal auditory canal (IAC) was possible in all cases. Placement of the BCI602 in the middle fossa allowed the view of the ipsilateral IAC using MAVRIC sequence. Quantitatively, the artifact was reduced with MAVRIC sequence from 6.3 to 59.7%, depending on the position of implant and model; the middle fossa placement and the BCI602 being those generating shorter artifact radio.

CONCLUSION

Artifact optimized sequences as MAVRIC reduce the artifact caused by the Bonebridge system. The middle fossa approach allows a better visualization of IAC canal in the ipsilateral ear with both implant versions, but the effect is more prominent with the BCI602.

Retrospective Analysis of Hearing-Impaired Adult Patients Treated With an Active Transcutaneous Bone Conduction Implant

OBJECTIVE

To determine the therapeutic success and safety of an active transcutaneous bone conduction implant (tBCI) in adult patients with conductive or mixed hearing loss.

STUDY DESIGN

Retrospective case review.

SETTING

Five university hospitals in Frankfurt, Hannover, Dresden, Würzburg, and Vienna.

PATIENTS

Data were analyzed from 61 patients (31 women, 30 men) with a mean age of 50 years (min. 26, max. 80). Forty patients had mixed, and 21 conductive hearing loss. Typical etiologies were history of otitis media (n = 20) and cholesteatoma (n = 17).

INTERVENTIONS

Implantation of the active tBCI.

MAIN OUTCOME MEASURES

Data were analyzed for the following time points: up to 6 months postoperatively ("short-term"), 6 to 37 months postoperatively ("long-term"), and the last available measurement per patient ("most recent"). Pure-tone audiometry (air and bone conduction, AC and BC) and sound field thresholds with warble tones (WT), word recognition scores with Freiburger monosyllables (WRS), as well as speech reception thresholds (SRT) using the Oldenburg sentence test (OLSA) in quiet (SRT) and in noise (signal-to-noise ratio, SNR) were collected.

RESULTS

No significant changes in air- and bone-conduction thresholds were observed after implantation. A mean WRS improvement of 54% using the active tBCI was shown at the short-term assessment, i.e., a mean score of 79% compared with 25% in the unaided condition. Results remained stable, with a mean score of 75% at the long-term assessment. SRT in noise improved by 3.6 dB SNR in the implanted ear at the short-term assessment. Overall six adverse events and four serious adverse events were reported, resulting in a rate of 9.84 and 6.56%, respectively.

CONCLUSION

The tBCI clearly improves speech intelligibility in patients with conductive or mixed hearing loss, showing stable results up to 1 year post-implantation.

[Postoperative imaging of the internal auditory canal : Visualization of active auditory implants. German version]

BACKGROUND

Assessment of the internal auditory canal (IAC) and the cochlea is of central importance in neurotology. The artefacts and visibility of the different types of active auditory implants in MRI vary, due to their specific ferromagnetic components. Knowledge of the size of MRI artefacts and the options for handling these is important for the auditory rehabilitation of specific diseases (e. g., vestibular schwannoma).

METHODS

The current paper is a literature review RESULTS: MRI assessment of the IAC and cochlea after surgical placement of an active auditory implant is feasible only with a percutaneous bone-anchored hearing aid (BAHA, Ponto). When specific factors (implant position and MRI sequence) are taken into consideration, these structures can be visualized even after cochlear implantation. Complications such as magnet dislocation and pain may occur.

CONCLUSION

The possibility of assessing the IAC and cochlea by MRI is an important aspect that needs to be taken into consideration when planning the auditory rehabilitation of patients after acoustic neuroma surgery.

MRI Metal Artifact Reduction Sequence for Auditory Implants: First Results with a Transcutaneous Bone Conduction Implant

Objective: Magnetic resonance imaging (MRI) is often limited in patients with auditory implants because of the presence of metallic components and magnets. The aim of this study was to evaluate the clinical usefulness of a customized MRI sequence for metal artifact suppression for patients with implants in the temporal bone region, specifically patients with a transcutaneous bone conduction implant. Methods: Two whole head specimens were unilaterally implanted with a transcutaneous bone conduction implant. MRI examinations with and without a primarily self-build sequence (SEMAC-VAT WARP) for metal artifact suppression were performed. The diagnostic usefulness of the acquired MRI scans was rated independently by two neuroradiologists. The sequence was also used to acquire postimplantation follow-up MRI in a patient with a transcutaneous bone conduction implant. Results: The customized SEMAC-VAT WARP sequence significantly improved the diagnostic usefulness of the postimplantation MRIs. The image acquisition time was 12 min and 20 s for the T1-weighted and 12 min and 12 s for the T2-weighted MRI. There was good agreement between the two blinded raters (Cohen’s κ = 0.61, p < 0.001). Conclusion: The sequence for metal artifact reduction optimized in Bern enables MRI at 1.5 T in patients with active transcutaneous bone conduction implants without sacrificing diagnostic imaging quality. Particularly on the implanted side, imaging of intracranial and supra- and infratentorial brain pathologies is clinically more valuable than standard diagnostic MRI without any artifact reduction sequences.

Postoperative imaging of the internal auditory canal : Visualization of active auditory implants

BACKGROUND

Assessment of the internal auditory canal (IAC) and cochlea is of central importance in neurotology. The artefacts and visibility of active auditory implants on magnetic resonance imaging (MRI) vary because of their specific magnetic components. Knowledge of the size of MRI artefacts and the options for handling them is important for the auditory rehabilitation of specific diseases (e. g., vestibular schwannoma).

METHODS

The current article is a literature review.

RESULTS

MRI assessment of the IAC and cochlea after surgical placement of an active auditory implant is feasible only with a percutaneous bone-anchored hearing aid (BAHA, Ponto). When specific factors (implant position and MRI sequence) are taken into consideration, these structures can be visualized even after cochlear implantation. Complications such as magnet dislocation and pain may occur.

CONCLUSION

The possibility of assessing the IAC and cochlea by MRI is an important aspect that needs to be taken into consideration when planning the auditory rehabilitation of patients after acoustic neuroma surgery.

Osseointegrated Auditory Devices: Bonebridge

Bonebridge is an active bone conduction device that consists of a bone conduction-floating mass transducer (BC-FMT) and magnet internally and an audio processor externally. Surgery for implantation can be performed under local anesthesia but requires surgical planning for adequate bone depth for the BC-FMT well. Bonebridge does not require osseointegration to function, so the device can be activated early. One disadvantage of Bonebridge is the sizable artifact on MRI created by the internal magnet. Studies of Bonebridge implantation demonstrate few complications, and hearing outcomes are audiologically equivalent to other bone conduction devices.

Temporary Explant of a Transcutaneous Bone Conduction Hearing Implant for Imaging of the Pituitary Gland

OBJECTIVE

Clinical report on feasibility and outcome of a surgical procedure.

PATIENT

Nine-year-old child, supplied with a transcutaneous bone conduction hearing implant, requiring magnetic resonance imaging of the head to exclude a tumor of the pituitary gland.

INTERVENTION

Temporal removal and subsequent reimplantation of the implant in a single surgical procedure.

MAIN OUTCOME MEASURE

Postoperative audiometric results.

CONCLUSION

Under specific clinical circumstances, temporary removal of the transcutaneous bone conduction implant described, is technically accomplishable.

Hearing outcomes of the active bone conduction system Bonebridge® in conductive or mixed hearing loss

OBJECTIVE

The active transcutaneous bone conduction implant Bonebridge^®, is indicated for patients affected by bilateral conductive/mixed hearing loss or unilateral sensorineural hearing loss, showing hearing outcomes similar to other percutaneous bone conduction implants, but with a lower rate of complications. The aim of this study was to analyze the hearing outcomes in a series of 26 patients affected by conductive or mixed hearing loss and treated with Bonebridge^®.

METHODS

26 of 30 patients implanted with Bonebridge^® between October 2012 and May 2017, were included in the study. We compared the air conduction thresholds at the frequencies 500, 1000, 2000, 3000, 4000Hz, the SRT50% and the percentage of correct answers at an intensity of 50dB with and without the implant.

RESULTS

"Pure tone average" with the implant was 34.91dB showing an average gain of 33.46dB. Average SRT 50% with the implant was 34.33dB, whereas before the surgery no patient achieved 50% of correct answers at a sound intensity of 50dB. The percentage of correct answers at 50dB changed from 11% without the implant to 85% with it. We only observed one complication consisting of an extrusion of the implant in a patient with a history of 2 previous rhytidectomies.

CONCLUSIONS

The hearing outcomes obtained in our study are similar to those published in the literature. Bonebridge^® represents an excellent alternative in the treatment of conductive or mixed hearing loss, and with a lower rate of complications.

A New Transcutaneous Bone Conduction Hearing Implant: Short-term Safety and Efficacy in Children

OBJECTIVE

To investigate the safety and efficacy of a new bone conduction hearing implant in children, during a 3-month follow-up period.

STUDY DESIGN

Prospective, single-subject repeated-measures design in which each subject serves as his/her own control.

SETTING

Otolaryngology departments of four Austrian hospitals.

PATIENTS

Twelve German-speaking children aged 5 to 17 suffering from conductive or mixed hearing loss, with an upper bone conduction threshold limit of 45 dB HL at frequencies between 500 and 4000 Hz.

INTERVENTION

Implantation of the Bonebridge transcutaneous bone conduction hearing implant (tBCI).

MAIN OUTCOME MEASURES

The subjects' audiometric thresholds (air conduction, bone conduction, and sound field at frequencies 500 Hz to 8 kHz) and speech perception (word recognition scores [WRS] and 50% word intelligibility in sentences [SRT50%]) were tested preoperatively and at 1 and 3 months postoperatively. The patients were also monitored for adverse events and they or their parents filled out questionnaires to analyze satisfaction levels.

RESULTS

Speech perception as measured by WRS and SRT50% improved on average approximately 67.6% and 27.5 dB, respectively, 3 months after implantation. Aided thresholds also improved postoperatively, showing statistical significance at all tested frequencies. Air conduction and bone conduction thresholds showed no significant changes, confirming that subjects' residual unaided hearing was not damaged by the treatment. Only minor adverse events were reported and resolved by the end of the study.

CONCLUSION

Safety and efficacy of the new bone conduction implant was demonstrated in children followed up to 3 months postoperatively.

Contemporary imaging of auditory implants

There have been significant advances in the diversity and effectiveness of hearing technologies in recent years. Implanted auditory devices may be divided into those that stimulate the cochlear hair cells (bone conduction devices and middle ear implants), and those that stimulate the neural structures (cochlear implants and central auditory implants). Contemporary preoperative and postoperative imaging may be used to help individualise implant selection, optimise surgical technique and predict auditory outcome. This review will introduce the concepts behind auditory implants, and explains how imaging is increasingly used to aid insertion and evaluation of these devices.

Hearing Restoration in Neurofibromatosis Type II Patients

Patients with neurofibromatosis type II will eventually succumb to bilateral deafness. For patients with hearing loss, modern medical science technology can provide efficient hearing restoration through a number of various methods. In this article, several hearing restoration methods for patients with neurofibromatosis type II are introduced.

Magnetic resonance imaging investigation of the bone conduction implant - a pilot study at 1.5 Tesla

PURPOSE

The objective of this pilot study was to investigate if an active bone conduction implant (BCI) used in an ongoing clinical study withstands magnetic resonance imaging (MRI) of 1.5 Tesla. In particular, the MRI effects on maximum power output (MPO), total harmonic distortion (THD), and demagnetization were investigated. Implant activation and image artifacts were also evaluated.

METHODS AND MATERIALS

One implant was placed on the head of a test person at the position corresponding to the normal position of an implanted BCI and applied with a static pressure using a bandage and scanned in a 1.5 Tesla MRI camera. Scanning was performed both with and without the implant, in three orthogonal planes, and for one spin-echo and one gradient-echo pulse sequence. Implant functionality was verified in-between the scans using an audio processor programmed to generate a sequence of tones when attached to the implant. Objective verification was also carried out by measuring MPO and THD on a skull simulator as well as retention force, before and after MRI.

RESULTS

It was found that the exposure of 1.5 Tesla MRI only had a minor effect on the MPO, ie, it decreased over all frequencies with an average of 1.1±2.1 dB. The THD remained unchanged above 300 Hz and was increased only at lower frequencies. The retention magnet was demagnetized by 5%. The maximum image artifacts reached a distance of 9 and 10 cm from the implant in the coronal plane for the spin-echo and the gradient-echo sequence, respectively. The test person reported no MRI induced sound from the implant.

CONCLUSION

This pilot study indicates that the present BCI may withstand 1.5 Tesla MRI with only minor effects on its performance. No MRI induced sound was reported, but the head image was highly distorted near the implant.