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MRIs and Cochlear Implants

Posted Dec 03 2008 6:57pm
Let's talk MRIs.


When I went to Chicago for the ALDA convention, I met several people that didn't want to get a cochlear implant because they need an MRI every six months. I will admit when I first started researching cochlear implants, MRIs was not a major concern of mine. I just read the I can have a MRI done if the magnet was removed. Fine. Great! That is all I needed to know but now I realize how much it means to others that suffer from other illnesses where they require MRIs.

Why would a person need to get one? MRIs provide better contrast in soft tissue, which helps to distinguish between normal and diseased tissue. MRIs do not show bones like a CAT scan or X-Ray. Brain tumors, strokes, multiple sclerosis and Neurofibromatosis, type 2 (NF2), are diagnosed by an MRI. Which means anything metal - paper clips, pens, keys, jewelry, scissors, underwire in your bra, belts, glasses and any other small objects can be pulled out of pockets and off the body or out of the body can become dangerous projectiles hurdling at the opening of the tube at incredibly high speeds.

Joy. Its a good thing that they make you remove anything metal.

Could you imagine if someone left a tongue piercing in and they turned the MRI machine on? Ouch.

Anyway, I did me a little research on MRIs. The magnet in an MRI system is rated using a unit of measure known as a Tesla and they are grouped into three fields.

Low-Field = Under .2 Tesla

Mid-Field = .2 to 0.6 Tesla

High-Field = 1.0 to 1.5 Tesla

What is the difference between low-field and high-field? The high-field setup has superior image quality AND has a higher rate of detecting tumor remnants. This abstract that I found supports that statement. The next generation of MRIs are circulating around at the strength of 3.0 Tesla.

Sounds like the higher the Tesla - the better the detection rate. I would imagine it would be like going from a two mega pixel camera to a ten mega pixel camera.

Now both Advanced Bionics, HiResolution Bionic Ear System's HiRes 90K implant and Cochlear Americas, Nucleus Freedom is MRI Safe up to 1.5 Tesla with the internal magnet removed.

I took a look at Med-El's website and discovered in bold letters, MRI Safe - Without Magnet Removal. Leaping lizards, no faking! They don't require the internal magnet to be removed. In fact, it is designed where the magnet can't be removed at all.

That cool!

But then I read the fine print:

In the US, PULSARCI100 and SONATATI100 are currently approved for use at a scanner strength of 0.2 Tesla.


Oh. That means recipients of a Med-El device can only use MRI's rated at low-field strength of 0.2 Tesla where they could be sacrificing image quality that could lead to a potential misdiagnoses.

What if one with a Med-EL device wants a high-field MRI that has a better image quality and higher rate of detection? Does that mean the entire implant has to be removed because they don't have a removable magnet?

Yikes.

This is a link to an article that talks about the latest MRI machines that are rated 3.0 Tesla which can demagnetize an implant. It also discusses how there is permanent damage to devices with non-removable magnets such as Med-El's PULSARCI100 and SONATATI100.

However, I'm privileged to know someone in my harem of cochlear implant users that had an MRI done and had the internal magnet removed and what he had to say really calmed my nerves if I ever had to get one.

First of all, it seems to be kind of a rare event. My surgeon has performed over 550 implant surgeries and has never had to do this procedure (taking the internal magnets out, then reinserting new magnets). In fact, of the 700+ Midwest Ear Institute patients, I believe I am the first to have an MRI. To get an MRI, the internal magnets need to be removed from the implant, then you get in the tube, then back to the OR to have new, sterile magnets and stitched up. The thought of having the internal magnets taken out probably bothers some people but it shouldn't - it was not a big deal at all. In fact, they asked if I wanted to be sedated and I said no - so they just did a local and it was fine. There is a little pain...but very little, and easily handled with OTC pain relievers. In fact, I haven't needed any today at all. I was going to write a great, detailed account of this but it is such a non-event that there is little to write. Kind of like getting some stitches in your head - that's it. The most irritating thing is being inside the MRI tube - at least you can't hear it though, because you are completely deaf while inside.

I wouldn't go get an MRI for fun, but if it is suggested that you need one, please do not hesitate to do it. An MRI is an incredible piece of technology and can be a difference maker in terms of diagnosing certain things.


And that is all he said folks!
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