The internal magnet is surgically removed and possibly replaced with the temporary non-magnetic plug before the patient undergoes an MRI procedure.
Do not allow patients with a HiRes Ultra cochlear implant to be in the area of an MRI scanner unless the following conditions have been met:
The bandaging protocol [Refer to the MRI Antenna Coil Cover (CI-7521) IFU for details] recommended by Advanced Bionics is followed when the patient undergoes an MRI procedure with the magnet left in place, or
For cases that would clinically benefit from reduced device artifact (for example some head or neck scans), the internal magnet is surgically removed and possibly replaced with the temporary nonmagnetic plug before the patient undergoes an MRI procedure.
The external sound processor and headpiece are MR Unsafe and must be removed before entering a room containing an MR scanner.
The recommended minimum duration of time post implant surgery prior to undergoing an MRI scan is 2 to 4 weeks in order to allow any inflammation to subside.
An MRI scan is not recommended if the patient has a fever.
For additional information regarding the use of an MRI scanner with a HiRes Ultra device, please contact Advanced Bionics Technical Support.
3.0T MRI Scans with the Magnet Removed
- Horizontal closed bore scanners with a static magnetic field of 3.0T (magnet removed)
- Maximum MR system reported, whole body averaged specific absorption rate (SAR) of ≤ 2 W/kg at 3.0T for quadrature transmit RF body coils.
- Maximum MR system reported, head averaged SAR of ≤ 2.6 W/kg at 3.0T for quadrature transmit RF head coils.
- RMS gradient field of 30 T/s and peak gradient field of 150 T/s.
- Maximum spatial field gradient of 6.90T/m at 3.0T with magnet removed
When tested under the scan conditions defined above the HiRes Ultra implant produced a maximum temperature of < 3° after 15 minutes of continuous 3.0T Scanning.
In MRI testing of unilateral recipient conditions, the image artifact caused by the device extends from the HiRes Ultra implant approximately 4.7 cm in a 3.0T MRI with the temporary non-magnetic plug.
In MRI testing of bilateral recipient conditions 4.7 cm in a 3.0T MRI with the temporary non-magnetic plug using a spin echo or gradient echo pulse sequence.
These artifacts may result in a loss of diagnostic information in the implant vicinity.
Please note that the MRI Antenna Coil Cover CI-7521 and bandaging supplies must be on hand at the time of the MRI procedure.
Magnet Removal / Replacement Using the Hires Ultra Magnet Tool Kit, Ci-1418
These tools must be sterilized prior to use. See the ”Guide for Reprocessing HiRes Ultra Reusable Tools” provided in the kit.