MRI labeling information for the Sophono Alpha Magnetic Implant (also referred to as the Alpha (M) Bone Conduction Hearing System) (Sophono, Inc., www.sophono.com; now owned by Medtronic, Inc.) is, as follows:
Do not perform Magnetic Resonance Imaging (MRI) on a patient wearing an Otomag Alpha Sound Processor, Magnetic Spacer, Headband or Softband. The external portions of the device must be removed prior to entering the MR environment. Severe injury may result if the external portions of the device are not removed prior to entering the MR environment.
- The Alpha (M) Magnetic Implant can be scanned safely using MRI only under certain conditions.
MR Unsafe: The Alpha Sound Processor, Magnetic Spacer, Headband or Softband must be removed before entering the MR environment
Non-clinical testing demonstrated the Alpha (M) Magnetic Implant is MR Conditional and can be scanned safely using MRI only under the following conditions:
- remove all external components including the Otomag Alpha Sound Processor, Magnetic Spacer, Headband or Softband before entering the MR environment
- static magnetic field of 3 Tesla or less
- spatial gradient field of 720 Gauss/cm or less
- maximum whole-body averaged specific absorption rate (SAR) of 4 W/kg in the First Level Controlled Mode for a maximum scan time of 15 minutes of continuous scanning.
In non-clinical testing the Alpha (M) Magnetic Implant produced a maximum temperature rise less than 3.2°C during 15 minutes of continuous MR scanning in the First Level Controlled Mode at a maximum whole-body averaged SAR of 4 W/kg. The computed implant temperature increase in response to the worst-case, time-averaged gradient field (94.7-Tesla/sec) for the 15 minute possible exposure for a series of clinical MRI scans is less than 2.6°C.
The maximum image artifact size extends approximately 5-cm relative to the size and shape of the implant when scanned in nonclinical testing using the Gradient echo (GRE) pulse sequence in a 3 Tesla/128-MH, Excite, Software 14X.M5, General Electric Healthcare, Milwaukee, WI; active-shielded, horizontal field MR system with a send receive RFcoil. Artifacts were less with the T1-weighted, spin echo pulse sequence.
Implant Function Following MR Scanning
In non-clinical testing, when positioned parallel to the patient table, the Alpha (M) Magnetic Implant maintained over 95% of its original magnetic strength after 10 insertions into a static MRI field and over 10 minutes of pulse sequence in a 3 Tesla Siemens Tri Clinical MRI Scanner (MRC20587). To minimize demagnetization of the internal magnets, Sophono recommends that the patient’s head is positioned along the long axis of the MRI scanner and that the patient is instructed to avoid head movement while lying on the patient table. If the head is tilted at an angle to the long axis of the patient table during a scan, the internal magnets may be demagnetized and a stronger external magnet may be needed to keep the device in place.
-After MRI exposure the Magnetic Spacer Strength should be adjusted as necessary following the instructions “Instructions for Placement / Sizing of the Magnetic Spacers and Alpha Sound Processor” included in the manual for this product (see www.sophono.com).
MR healthcare professionals are advised to contact the manufacturer to ensure that the latest safety information is obtained and carefully followed in order to ensure patient safety relative to the use of an MR procedure.