The MRI labeling for the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc., www.2-sight.com) is, as follows:
The Argus II Implant has been classified as an MR Conditional device. Individuals with an Argus II Implant may undergo a magnetic resonance imaging (MRI) procedure ONLY if it is performed using a 1.5 or 3.0 Tesla MRI System and ONLY following the MRI Instructions provided later in this insert. Individuals with an Argus II Implant should not enter a room housing an MRI System that has a rating other than 1.5 or 3.0 Tesla, even if the Argus II System is not being used. The external equipment (i.e. VPU and glasses) should remain outside the MR system room, as severe harm to people in the MR system room could occur. If any pain is experienced during the MRI procedure the patient should be instructed to notify the technician immediately.
Information about Specific Procedures
Magnetic Resonance Imaging (MRI) – Refer to the Warnings section above and the MRI Information section below for more information about MRI.
The Argus II Implant is MR Conditional according to the terminology specified in the American Society for Testing and Materials (ASTM) International, Designation: F2503, Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment. Non-clinical testing demonstrated that the Argus II Implant meets the MR Conditional classification.
Do NOT take the Argus II VPU or glasses into the MR system room. The VPU and glasses are MR Unsafe. The VPU and glasses were not tested in the MRI environment and are not permitted to be worn by the patient in the MR system room. Severe harm to the patient and/or damage to the external equipment may occur.
An individual with an Argus II Implant may safely undergo an MRI procedure under the conditions specified below:
- Static magnetic field of 1.5-Tesla or 3-Tesla
- Maximum spatial gradient magnetic field of 720‑Gauss/cm or less
- Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 2-W/kg for 15 minutes of scanning (i.e. per pulse sequence)
- Normal Operating Mode of operation for the MR system
In non-clinical testing, the Argus II Implant produced the following temperature rise during MRI performed for 15-min of scanning (i.e., per pulse sequence) in the 1.5-Tesla (1.5-Tesla/64-MHz, Symphony, Siemens Medical Solutions, Erlangen, Germany) MR system: Highest temperature change was +0.6˚C.
Therefore, the MRI-related heating for the Argus II Implant at 1.5-Tesla using a transmit/receive RF body coil at an MR system reported whole body averaged SAR of 3.5-W/kg indicated that the greatest amount of heating that occurred in association with these specific conditions was equal to or less than +0.6˚C.
MRI-Related Heating, 3-Tesla
In non-clinical testing, the Argus II Implant produced the following temperature rise during MRI performed for 15-min of scanning (i.e., per pulse sequence) in a 3-Tesla (3-Tesla/128-MHz, Excite, HDx, Software 14X.M5, General Electric Healthcare, Milwaukee, WI) MR system: Highest temperature change was +2.1˚C.
Therefore, the MRI-related heating for the Argus II Implant at 3-Tesla using a transmit/receive RF body coil at an MR system reported whole body averaged SAR of 2.9-W/kg indicated that the greatest amount of heating that occurred in association with these specific conditions was equal to or less than +2.1˚C.
MR image quality may be compromised if the area of interest is in the exact same area or relatively close to the position of the Argus II Implant. Therefore, optimization of MR imaging parameters to compensate for the presence of the implant may be necessary.
During the MRI Procedure
The MRI technologist should tell the patient to notify the MRI system operator if pain or unusual sensation occurs during the MRI examination. If the patient experiences any pain or unusual sensation, the MRI procedure should be stopped immediately and the source of the problem should be investigated.
In non-clinical MRI tests, the Argus II implant was exposed to eight different pulse sequences using 1.5-T/64MHz (Symphony, Siemens Medical Solution, Erlangen, Germany) and 3.0-T/128MHz Excite, HDx, Software 14X.M5, General Electric Healthcare, Milwaukee, WI) MR systems. The results indicated that exposing the Argus II implant to these MRI conditions did not damage or alter the function of the device nor did it have adverse effects on the device’s functionality. However, it is strongly recommended that the Argus II Implant be tested by a qualified clinician or Second Sight personnel as soon as possible following an MRI procedure to confirm that it is still functioning properly.
*Additional MRI labeling information exists. Contact Second Sight Medical Products, Inc., www.2-sight.com for more information.
[MR healthcare professionals are advised to contact the respective manufacturer in order to obtain the latest safety information to ensure patient safety relative to the use of an MR procedure.]
Second Sight Medical Products, Inc., www.2-sight.com
Weiland JD, Faraji B, Greenberg RJ, Humayun MS, Shellock FG. Assessment of
MRI issues for the Argus II retinal prosthesis. Magnetic Resonance Imaging 2012;30:382-389.