Faculty Collaboration Database

Effect of magnetic resonance imaging on internal magnet strength in Med-El Combi 40+ cochlear implants. Laryngoscope 2004 Aug;114(8):1355-61

Date

07/29/2004

Pubmed ID

15280707

DOI

10.1097/00005537-200408000-00007

Scopus ID

2-s2.0-3843071110 (requires institutional sign-in at Scopus site)   44 Citations

Abstract

OBJECTIVE: Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med-El Combi 40+ cochlear implant internal magnets after MRI studies.

STUDY DESIGN/METHODS: Two fresh cadavers were used to study demagnetization using a repeated measures design and a magnetometer. Pre- and postMRI measurement of magnetic field strength was completed. Five sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 0.2 Tesla in the device-up and device-down positions. In the other cadaver, 15 sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 1.5 Tesla were conducted, 5 each with the head oriented at 80, 90, and 100 degrees rotated around the yaw plane (rotated around the z-axis). Subsequently, three cochlear implant patients completed 0.2 Tesla MRIs. For these patients, subjective and objective assessment of cochlear implant performance was performed.

SETTING: Academic medical center.

RESULTS: In the cadaver studies, analysis of variance showed no significant difference in the magnetic field strength after the 0.2 or 1.5 Tesla scans. There was no significant difference in the magnetic field strength for the three patients undergoing 0.2 Tesla MRIs and no adverse consequences, including no changes in telemetry, auditory sensations, nonauditory sensations, and sound quality.

CONCLUSIONS: No significant demagnetization of the internal magnet occurred during repeated 1.5 Tesla MRI scans with the head orientations used in this study. In the cochlear implant patients, no significant demagnetization of the internal magnet occurred after a 0.2 Tesla MRI.

Author List

Wackym PA, Michel MA, Prost RW, Banks KL, Runge-Samuelson CL, Firszt JB

Author

Michelle A. Michel MD Adjunct Professor in the Radiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Artifacts
Cochlear Implants
Contraindications
Humans
In Vitro Techniques
Magnetic Resonance Imaging
Magnetics