Getting an MRI With Your CI
Getting an MRI With Your CI
What is an MRI?
The acronym MRI stands for Magnetic Resonance Imaging. This is a medical exam that takes special pictures of soft tissue such as muscles and organs. The MRI machine uses a magnetic field and radio frequencies to generate these images. The advantage of MRI is that it allows very precise images to be taken without using radiation or radioactive material like x-rays. There are different strengths of MRI and they are quantified in Tesla (T), a unit of measurement. The strength of the magnet used in the machine indicates the clarity of the image taken, with an image from a 3T MRI machine being brighter than that from a 1.5 T machine.
Cochlear implant and MRI
The cochlear implant system contains an internal magnet. This magnet is used to hold the external antenna against the head to communicate with the internal receiver. See the article Cochlear Implant 101 for more details. It is the presence of this magnet in the implant that explains the need to take certain precautions when you have a cochlear implant. This is because the magnetic field produced by the MRI machine will pull the magnet into the implant which can cause discomfort or other problems for the patient. Across the different cochlear implant manufacturers and models, some are MRI-compatible, while others are not. Even with MRI-compatible devices there may be certain restrictions and precautions that need to be taken. This is why it is important to check with your audiologist or cochlear implant manufacturer before any MRI exam. Read our article Safety first! for more details.
Some models of cochlear implants contain a rotary magnet. This means that the magnet can rotate on itself (horizontal axis) in order to position itself in the direction of a magnetic field. This system has the advantage of being able to undergo 1.5 and 3T MRIs without having to remove the magnet. One of the disadvantages of leaving the magnet in place is that it generates what is called an artefact (a shadow). This shadow can negatively impact the doctor’s ability to see structures in the head/brain. Therefore, in some cases it is necessary to completely remove the internal magnet which will require a minor surgery. Some models of cochlear implants, like the Neuro Zti from Oticon Medical, allow the magnet to be removed easily, and most importantly, as many times as needed.
Should I be afraid of having an MRI if I have a cochlear implant?
Absolutely not! You should not be afraid to have an MRI but you do need to be aware of and take the necessary precautions beforehand. The first thing to do is to tell your cochlear implant team at the hospital or your audiologist before having the exam. They can tell you what precautions to take and can also contact your radiologist to make sure they know the recommendations. On the day of the MRI exam, make sure to bring your CI patient card with you. This card will be provided to you at the hospital after your surgery. It will remind the radiologist that you have a cochlear implant and that preventive measures are likely to be taken. Finally, ask all your questions to the radiology team before getting into the machine and then, remove your sound processor.