Article
Magnetic Resonance Imaging (MRI) Safety of Nucleus 24 Implants
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Authors
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H. Mauch
- Cochlear AG, Basel, Switzerland
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E. von Wallenberg
- Cochlear AG, Basel, Switzerland
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F. Risi
- Cochlear Ltd, Lane Cove, Australia
| Published: | May 31, 2005 |
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Outline
Text
Introduction
With infants as young as 12 months receiving cochlear implants that are designed to last more than 70 years, magnetic resonance imaging (MRI) safety is an important consideration since there is a high likelihood that most people will require an MRI procedure throughout their lifetime.
Materials and Methods
The interactions between the MRI magnetic and Radio Frequency (RF) fields and the Nucleus 24 implants were measured at field strengths of 0.2T, 1.5T and 3.0T with both the magnet removed and the magnet in place. Results show that at each of these field strengths, with the magnet removed, all interactions are within the acceptance criteria of internationally recognized standards for active implantable devices.
Results
With the magnet left in place at each of these field strengths the results show that at 0.2T there is no risk of the magnet becoming dislodged or demagnetized. At 1.5T, the increased torque results in greater displacement of the implant magnet, however the use of a simple compression bandage wrapped around the implant site was shown to safely retain the magnet, and demagnetization was measured at <10%. At 3.0T the torque produced is too severe to safely retain the magnet, and demagnetization was measured at >90%. In each case the image artifact is approximately 60% greater with the magnet in place compared to the magnet removed.
Conclusions
Nucleus 24 Implants therefore have the option of either leaving the magnet in place for MRI scans at field strengths of 0.2T (without conditions) and 1.5T (with the use of a simple compression bandage) or alternatively removing the magnet to reduce the artifact size. At 3.0T however removal of the magnet will be required to ensure safety.
