Question
Are there any concerns regarding a cochlear implant patient that needs an MRI of the knee due to a sport injury?
Answer
A MRI scanner utilizes a powerful magnetic field to image parts of the body. Regardless of what part of the body is being viewed (e.g. the knee), the whole body is exposed to the magnetic fields generated by the MRI scanner when a patient is in the imaging room. The magnetic properties of an MRI machine can potentially cause harm to a cochlear implant device and the user.
Newer cochlear implant devices have become available in recent years which allow removal of the magnet prior to an MRI. This requires a procedure with a small incision to remove the magnet from the subcutaneous portion of the implant resting behind the ear before MRI completion; a similar procedure is performed to replace the magnet to allow resumption of implant use after MRI. Magnet removal makes it safe for an implant recipient to have an MRI up to 1.5 Tesla in strength (a measure of magnetic field). Although some studies have suggested it may be safe for cochlear implant patients to undergo MRI with fixed (non-removable) magnets, especially in weaker strength MRI scanners (e.g. 0.2 Tesla), this has not been accepted for general use in the United States. A cochlear implant recipient should always consult with their implant surgeon before any imaging is performed, regardless of the imaging technique.
Lance E. Jackson, MD is an Otologist/Neurotologist and president of the Ear Institute of Texas in San Antonio, TX. Refer to his web site www.earsoftexas.com for a list of publications.
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