Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study

Wagner, Franca; Wimmer, Wilhelm; Leidolt, Lars; Vischer, Mattheus; Weder, Stefan; Wiest, Roland; Mantokoudis, Georgios; Caversaccio, Marco

doi:10.1371/journal.pone.0132483

Cited by 38 publications

(48 citation statements)

References 30 publications

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“…The artifact caused by the magnet is similar to our results in the 1.5T. Nevertheless they conclude that if the magnet is removed, MRIs at 1.5T and 3T can be done without sacrificing diagnostic imaging quality [ 9 ].…”

Section: Discussionsupporting

confidence: 79%

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Magnetic Resonance Imaging Artifacts and Cochlear Implant Positioning at 1.5 T In Vivo

Schröder

Grupe

Rademacher

et al. 2018

BioMed Research International

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Objective Cerebral magnetic resonance imaging with the magnet of the cochlear implant receiver/stimulator in place causes artifacts and hinders evaluation of intracerebral structures. The aim of this study was to evaluate the internal auditory canal and the labyrinth in a 1.5T MRI with the magnet in place. Study Design Observational study. Setting Tertiary referral center. Subjects and Methods The receiver/stimulator unit was placed and fixed onto the head of three volunteers at three different angles to the nasion–outer ear canal (90°–160°) and at three different distances from the outer ear canal (5–9 cm). T1 and T2 weighted sequences were conducted for each position. Results Excellent visibility of the internal auditory canal and the labyrinth was seen in the T2 weighted sequences with 9 cm between the magnet and the outer ear canal at every nasion–outer ear canal angle. T1 sequences showed poorer visibility of the internal auditory canal and the labyrinth. Conclusion Aftercare and visibility of intracerebral structures after cochlear implantation is becoming more important as cochlear implant indications are widened worldwide. With a distance of at least 9 cm from the outer ear canal the artifact induced by the magnet allows evaluation of the labyrinth and the internal auditory canal.

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Section: Discussionsupporting

confidence: 79%

“…Furthermore patients are required to undergo general anaesthesia for the removal and repositioning of the magnet. In the study by Wagner et al, cadaveric heads with implanted CIs underwent MRI scans at 1.5T and 3T with and without the magnet in place [ 9 ]. The artifact caused by the magnet is similar to our results in the 1.5T.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Resonance Imaging Artifacts and Cochlear Implant Positioning at 1.5 T In Vivo

Schröder

Grupe

Rademacher

et al. 2018

BioMed Research International

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show abstract

“…The Synchrony model (MED‐EL) is unique, and in our opinion represents a vital step forward in MRI safety. The Synchrony model (MED‐EL) features a freely rotating and self‐aligning diametric magnet that ultimately minimizes torque pressure and demagnetization . Similar industry‐driven technical innovations will be paramount as we address patient MRI safety in the future.…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance imaging with cochlear implants and auditory brainstem implants: Are we truly practicing MRI safety?

et al. 2018

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Objective Our objective is to evaluate the safety in patients with cochlear implants (CIs) and auditory brainstem implants (ABI) undergoing 1.5 Tesla (T) magnetic resonance imaging (MRI). Secondly, we want to raise awareness on CI and MRI safety, and advocate for continued improvement and advancement to minimize morbidity for our CI patients. Methods Retrospective case series from 2006 to 2018 at a single tertiary academic center. Data was collected on patients with CI or auditory brainstem implants undergoing MRI. Outcomes collected include demographic data, age at time of MRI, MRI characteristics, complications, CI manufacturer, and image quality. Results Eighteen patients with CI or ABI collectively underwent a total of 62 MRI scans. Five of 15 (33%) CI patients with magnet had complications: five total of 24 MRI scans (21%). Two patients had magnet removal prior to 29 MRI scans without complications. Four of five MRI‐related complications were equipped with a U.S. Food and Drug Administration‐approved head wrap. Three of five required a trip to the operating room to explore and reposition the CI magnet; two could not complete MRI secondary to pain. Of the complications, two were Cochlear (Sydney, Australia), two Advanced Bionics (Valencia, CA), and one MED‐EL (Innsbruck, Austria). Synchrony model (MED‐EL) had 0 of seven complications, with a total of 19 MRI scans, which features a freely rotating and self‐aligning magnet. Conclusion Our series offers a diverse number of CI manufacturers and is in accordance with other literature that CI MRI‐related adverse events are occurring at an unacceptable frequency. We can promote CI MRI safety through our institutions' MRI CI patient protocols, raise awareness that diagnostic MRI benefits must outweigh CI‐related complications, and advocate for continued industry technological innovation. Level of Evidence 4 Laryngoscope, 129:482–489, 2019

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“…The detachment process requires heating of the magnet, thus releasing thermal energy in the cochlea that may cause thermal trauma within the ear. Heat transfer in the ear has been studied for applications such as caloric test [6], [7], [8], stapedectomy [9], [10], [11], radio-frequency radiation [12], [13], [14], magnetic resonance imaging [5], [15], [16], [17], and infrared neural stimulation of cochlear implants [18], [19], [20], [21]. Yet, neither the heat source nor the targeted tissue in these applications are similar to the magnet detachment process.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

Esmailie

Francoeur

Ameel

2020

International Journal of Heat and Mass Transfer

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Magnetic cochlear implant surgery requires removal of a magnet via a heating process after implant insertion, which may cause thermal trauma within the ear. Intra-cochlear heat transfer analysis is required to ensure that the magnet removal phase is thermally safe. The objective of this work is to determine the safe input power density to detach the magnet without causing thermal trauma in the ear, and to analyze the effectiveness of natural convection with respect to conduction for removing the excess heat. A finite element model of an uncoiled cochlea, which is verified and validated, is applied to determine the maximum safe input power density to detach a 1-mm-long, 0.5-mm-diameter cylindrical magnet from the cochlear implant electrode array tip. It is shown that heat dissipation in the cochlea is primarily mediated by conduction through the electrode array. The electrode array simultaneously reduces natural convection due to the no-slip boundary condition on its surface and increases axial conduction in the cochlea. It is concluded that natural convection heat transfer in a cochlea during robotic cochlear implant surgery can be neglected. It is found that thermal trauma is avoided by applying a power density up to 2.265 × 10 7 W/m 3 for 114 s, resulting in a maximum temperature increase of 6 • C on the magnet boundary.

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Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study

Cited by 38 publications

References 30 publications

Magnetic Resonance Imaging Artifacts and Cochlear Implant Positioning at 1.5 T In Vivo

Magnetic Resonance Imaging Artifacts and Cochlear Implant Positioning at 1.5 T In Vivo

Magnetic resonance imaging with cochlear implants and auditory brainstem implants: Are we truly practicing MRI safety?

Heat transfer analysis in an uncoiled model of the cochlea during magnetic cochlear implant surgery

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