Benefits of 3.0 Tesla MRI Safety for Cochlear Implant Recipients
AudiologyOnline: Why might a physician order an MRI rather than a CT or X-ray?
Dr. Martin Zimmerling: While both imaging modalities (CT and MRI) can show anatomical structures, there are fundamental differences between them. Computed Tomography (CT) is based on the X-ray principal. As gamma rays pass through the body, they are attenuated. The higher the density of the body structures, the more the rays are attenuated. CT is well-suited for bony structures and for scans of the lung.
In contrast, MRI uses magnetic fields to measure changes of water and fat concentration in different tissues. MRI is optimally suited for soft tissues of any kind, for neurological assessment and for musculoskeletal imaging. MRI works without ionizing radiation and can be a preferred choice when considering a person’s exposure to ionizing radiation over their lifetime, especially children.
There are situations where an MRI is clearly preferred over a CT from the diagnostic standpoint. If a CT is chosen instead of an MRI because the patient has a hearing implant with poor MRI safety, this could result in suboptimal diagnostic imaging. Fortunately, with MED-EL’s SYNCHRONY cochlear implant (CI) and its unique diametric magnet approved for MRI at 3.0 Tesla without magnet removal, the physician can choose the appropriate imaging for the situation. This means your patient will have the peace of mind that comes with knowing they’ve chosen the only implant that delivers unmatched comfort and security during an MRI scan.
AudiologyOnline: How common is 3.0 Tesla MRI as a diagnostic procedure?
Dr. Martin Zimmerling: Although the percentage of 3.0 Tesla scanners vary from country to country, the availability of 3.0 Tesla MRI has increased over the past decade. At university hospitals especially, 1.5 Tesla MRI scanners are frequently being replaced by 3.0 Tesla MRI scanners. There are now radiology departments which have (one or more) 3.0 Tesla scanners but not a single 1.5 Tesla scanner. The SYNCHRONY implant, allows patients the freedom to choose imaging centers, saving them time!
AudiologyOnline: What is the value of 3.0 Tesla MRI versus 1.5 Tesla?
Dr. Martin Zimmerling: 3.0 Tesla MRI offers a higher signal-to-noise ratio, higher spatial resolution and a better signal quality. In other words, a clearer picture. Patients with the SYNCHRONY cochlear implant will have confidence in knowing that their 3.0 Tesla scan is providing their physician the clearest image.
AudiologyOnline: How does the SYNCHRONY magnet, only available with MED-EL, compare to other cochlear implant company’s offerings?
Dr. Martin Zimmerling: The SYNCHRONY magnet is the only CI magnet on the market that can align parallel to the main magnetic field in the MRI scanner. Therefore, it cannot weaken, even in a 3.0 Tesla scanner, and it virtually exerts no torque on the implant and surrounding tissue. This means increased comfort and no hearing downtime for MED-EL SYNCHRONY patients!
AudiologyOnline: Is there excess artifact with SYNCHRONY magnets on an MRI?
Dr. Martin Zimmerling: The artifact of SYNCHRONY is about the same as that of other cochlear implants. Artifact is also impacted by scanning orientation and other parameters. In general, the MRI artifact in a 3.0 Tesla scanner is slightly larger than in a 1.5 Tesla scanner. Remember, though, that artifact from a CI can be an issue only with a subset of head scans where the area immediately surrounding the implant needs to be viewed, but not for MRI scans of other areas of the head. It’s not an issue with scanning other parts of the body, and these account for the majority (about 70%) of MRI scans.
AudiologyOnline: Is removing the magnet with Synchrony common? Is it more difficult than with other devices?
Dr. Martin Zimmerling: SYNCHRONY was designed so that the implant magnet can remain in the device, even for a 3.0 Tesla MRI. Therefore, the magnet only needs to be removed in very rare cases, and can be done without concern. You can read a first-hand report from a surgeon about his experiences removing a SYNCHRONY magnet and how it compares here: https://blog.medel.pro/brain-mri-synchrony-cochlear-implant/.
Further information, resources, and CE courses from MED-EL can also be found on the MED-EL Partner Page on AudiologyOnline, as well as on our website, www.medel.com/us
Martin Zimmerling, PhD
Head of Implant Development/Research & Development, MED-EL
Martin Zimmerling is the head of implant development within R&D at MED-EL worldwide headquarters in Innsbruck, Austria. He has lead the team developing cochlear implants since 2005. Additionally, he is an expert on MRI safety with hearing implants. Martin received his Doctorate in Physics from the University of Innsbruck in Austria in 1999 before joining MED-EL as an R&D engineer and project leader. Continuing to search for solutions that provide further benefit to implant users is a top priority for Martin.