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MRI and cochlear implants

 

MRI is a well-established technique used in clinical settings around the world to provide professionals with valuable diagnostic and prognostic information about a patient’s health. It is used for body, as well as brain scans. MRI scans range in strength from 0.2 Tesla to 7 Tesla but recent estimates show that 79% of MRI scanners in use around the world are 1.5 Tesla, making this the most common type by far1.

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The Neuro Zti is fully compatible

The Neuro Zti implant is fully compatible with 1.5 Tesla scans with the magnet in place for both body and head scans.

The implant has been designed to ensure this type of scan is safe and painless and does not produce "magnet flip"3 as the magnet is held firmly in place by the rigid implant structure2. This means it can’t dislodge and remains locked in even after multiple MRI exams, while the implant itself remains stable throughout the MRI scan thanks to a unique screw fixation system that securely attaches it to the bone.

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Why radiologists often want the magnet removed regardless of Tesla strength

Brain scans account for 20-25% of MRI scans among people worldwide1,4. For CI patients, this figure increases to 49%5, making brain scans the most common MRI exams they are likely to undergo. Leaving the implant magnets in place during head scans of either 1.5 Tesla or 3 Tesla usually influences the image quality and creates artefacts that distort the result and prevents reliable diagnosis. This is even more common in scans of 3 Tesla because of the additional magnetic strength. See fig. 1. 

Therefore, for an MRI brain scan, the easy removal of the magnet is a very important factor when considering an implant.

 

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Neuro Zti – direct, easy and quick magnet removal

The Neuro Zti is 3 Tesla compatible without the magnet and designed for easy magnet removal under local anesthesia with only a small skin incision. The implant is attached using screws and not drilled into the skull, which makes the magnet easily accessible. With the dedicated Oticon Medical surgical tool, the magnet is removed in a few steps and can then be replaced again after the scan.

1.The Royal College of Radiologists, the College of Radiographers and the Institute of Physics and Engineering in Medicine (2017). Magnetic resonance imaging (MRI) equipment, operations and planning in the NHS - Report from the Clinical Imaging Board. London, UK.
Retrieved from www.rcr.ac.uk/sites/default/files/cib_mri_equipment_report.pdf
2. Oticon Medical CI Unique – January 2019 (the Oticon Medical Unique logo Indicates an Oticon Medical unique technology or accessory in the CI industry at the time of this publication) 
3. Todt, I., Rademacher, G., Grupe G., Stratmann A., Ernst, A., Mutze S., Mittmann P. (2018). Cochlear implants and 1.5 T MRI scans: the effect of diametrically bipolar magnets and screw fixation on pain. Journal of Otolaryngology - Head and Neck Surgery (2018) 47:11
4. Saadat S. et al, Overuse or underuse of MRI scanners in private radiology centers in Tehran, International Journal of Technology Assessment in Health Care 24(3):277-81 · February 2008
5. Grupe G, Wagner J, Hofmann S, Stratmann A, Mittmann P, Ernst A, Todt I. Prevalence and complications of MRI scans of cochlear implant patients: English version. HNO. 2017 Jan;65(Suppl 1):35-40. doi: 10.1007/s00106-016-0129-7. PMID: 26886493
6. Wagner, F., Wimmer, W., Leidolt, L., Vischer, M., Weder, S., Wiest, R., Mantokoudis, G. and Caversaccio, M.D., 2015. Significant artifact reduction at 1.5 T and 3T MRI by the use of a cochlear implant with removable magnet: an experimental human cadaver study. PloS one, 10(7), p. e0132483