MRI Safety

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MRI Safety Information

Magnetic resonance imaging (MRI) may be safely performed under certain conditions on a patient with a Freedom Stimulator, however, the Wearable Antenna Assembly (WAA) unit (i.e., the external component of this neuromodulation system) MUST NOT be present in the MR system room at ANY TIME. Failure to adhere to the specific requirements described in this manual can result in tissue damage, severe injury, or death.

Preparation for an MRI

The following steps must be performed prior to an MRI on a patient with an implanted Freedom Stimulator:

1. Remove the WAA (the external component of the Freedom System) from the patient before allowing the patient to enter the room where the MRI procedure will take place.
2. Do not conduct an MRI procedure if the patient has any other implant or health condition that prohibits or contraindicates an MRI examination. If the patient has another implant, especially an electronically activated or “active” device, the safety of performing an MRI with the addition of Freedom Receiver Stimulator is unknown.
3. Instruct the patient to immediately inform the MRI system operator (i.e., the MRI technologist) if any discomfort, stimulation, shocking, or heating occurs during the examination.
4. The patient must be conscious during the MRI in order to be able to inform the MRI operator of any problems.
5. Verify with the MRI operator that all proposed MRI conditions comply with the requirements specified in this manual.  If any MRI parameter is not met and cannot be modified, do not perform the MRI procedure.

 

MRI Conditions

Freedom-8A (FR8A) Stimulator Receiver for SCS

Non-clinical testing has demonstrated the Freedom-8A SCS Stimulator Receiver is MR Conditional. The Freedom-8A  Stimulator Receiver can be scanned safely under the following conditions.

  • Static magnetic field of 1.5-Tesla or 3-Tesla.
  • Maximum spatial gradient field of 10 T/m (1,000 Gauss/cm).
  • Whole Body Scans at 1.5Tesla/64MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 2.0 W/kg (Normal Operating Mode).
  • Head and Extremity Scans at 3Tesla/128MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 2.0 W/kg (Normal Operating Mode).
  • Torso Scans at 3Tesla/128MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 1.0 W/kg. This SAR limitation is more restrictive than the Normal Operating Mode.
  • No other components of Freedom SCS System (e.g. WAA, wireless charging pad, needle, stylets, guidewire) may be taken into the MR system room.
  • No restrictions on position of the Stimulator with respect to MR system bore or body part undergoing MR imaging.
  • No restrictions on use of transmit RF coils.

NOTE: Enter the patient’s weight into the MR system console to ensure that the whole body averaged specific absorption rate (SAR) is estimated correctly.

Freedom-4 (FRE4) Stimulator for Spinal Cord Stimulation (SCS)

Non-clinical testing has demonstrated the Freedom-4 SCS Stimulator is MR Conditional. The Freedom-4 Stimulator can be scanned safely under the following conditions.

  • Static magnetic field of 1.5-Tesla or 3-Tesla.
  • Maximum spatial gradient field of 30 T/m (3,000 Gauss/cm).
  • Maximum whole body averaged specific absorption rate (SAR) of 2.9 W/kg for 15 minutes of continuous scanning.
  • No restrictions on position of the Freedom-4 Stimulator with respect to MR system bore or body part undergoing MR imaging.
  • No other components of Freedom SCS System (e.g. WAA, wireless charging pad, needle, stylets, guidewire) may be taken into the MR system room.
  • No restrictions on use of transmit RF coils.

NOTE: Enter the patient’s weight into the MR system console to ensure that the whole body averaged specific absorption rate (SAR) is estimated correctly.

Freedom-4A (FR4A) Stimulator for SCS

The Freedom-4A SCS System is MR Unsafe. Since the Freedom-4A SCS System is MR Unsafe, the strong magnetic field of the MR system could attract or otherwise damage the System, and in the process cause serious harm to the patient or other people or damage to the MR system.

Freedom-4A (FR4A) StimQ Stimulator for Peripheral Nerve Stimulation (PNS)

Non-clinical testing demonstrated that the Freedom-4A (StimQ) Stimulator/Spare Lead with Receiver/RF Stylet is MR Conditional. A patient with this device can be safety scanned in an MR system meeting the following conditions.

  • Static magnetic field of 1.5-Tesla.
  • Maximum spatial gradient magnetic field of 2000 Gauss/cm (20 T/m).
  • Stimulators/Leads Implanted in Upper Arm (e.g. located between elbow and shoulder):
    • Scanning the upper arm region (i.e. radial and ulnar nerves near the implant) at 1.5Tesla/64MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 1.0 W/kg. This SAR is more restrictive than Normal Operating Mode.
    • Scanning any other region (e.g. lower arm, shoulder, head, torso, leg) at 1.5 Tesla/64MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 2.0 W/kg (Normal Operating Mode).
  • Stimulators/Leads Implanted in Lower Arm, Low Back, Pelvis, Leg:
    • Whole Body Scans (i.e. near or far from implant) at 1.5Tesla/64MHz – Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 2.0W/kg (Normal Operating Mode).
  • No other components of StimQ PNS System (e.g. StimQ Wearable Assembly Gear, battery charger, needles, stylets, introducer assembly, trial lead) may be taken into the MR system room.

 

During an MRI examination

The patient should be conscious during the MRI procedure.  Monitor the patient both visually and audibly. Check the patient between each MR imaging sequence. Discontinue the MRI examination immediately if the patient is unable to respond to questions or reports any problem.