A Spinal Cord Stimulator (SCS) is a small, implanted device that manages chronic pain by delivering mild electrical impulses to the spinal cord. This neurostimulation interrupts pain signals traveling to the brain, offering relief for conditions like failed back surgery syndrome. The presence of implanted metal components introduces safety concerns regarding Magnetic Resonance Imaging (MRI). Whether an MRI can be performed depends entirely on the specific SCS model and strict adherence to safety protocols.
Understanding MRI Compatibility for Spinal Cord Stimulators
Modern SCS systems are categorized as either “MRI Conditional” or “MRI Unsafe,” which determines if a scan can be safely performed. An “MRI Unsafe” label means the device contains ferromagnetic materials or cannot withstand the MRI environment. Exposure in this case is an absolute contraindication and could result in severe patient injury or permanent device damage.
The majority of contemporary SCS devices are labeled “MRI Conditional,” meaning a scan is permissible only if specific manufacturer-defined conditions are met. These conditions relate to the magnetic field strength of the scanner, typically 1.5 Tesla (T) or 3.0T, and the region of the body being imaged. Newer systems often allow for full-body scans at both 1.5T and 3.0T, while older devices may permit only a head scan.
Compatibility depends on the specific components, including the implanted pulse generator (IPG) and the leads that run along the spine. To determine eligibility, the patient must provide the exact model number and manufacturer of their SCS system, usually found on their patient identification card. The manufacturer’s guidelines specify parameters like the maximum specific absorption rate (SAR) that the MRI machine must adhere to, ensuring the radiofrequency energy remains within safe limits.
Why Magnetic Resonance Imaging Poses a Risk to Implanted Devices
The safety concerns surrounding an MRI with an implanted device stem from the powerful physical forces generated by the scanner. An MRI machine utilizes a static magnetic field, a gradient magnetic field, and radiofrequency (RF) energy. All three interact with the metallic components of the SCS, explaining the necessity of the strict protocols.
One primary danger is tissue heating, often referred to as the antenna effect. The RF fields used to create images can induce electrical currents in the long, thin metal leads of the SCS. This current causes the electrode tips and surrounding tissue, particularly near the spinal cord, to heat up rapidly. This heating can potentially result in thermal burns or permanent neurological damage.
A second risk comes from the powerful static magnetic field, which exerts a translational force on the device’s metallic parts. If the SCS system contains ferromagnetic materials, the magnetic field can cause the device or its leads to move or migrate. This dislodgement poses a risk of physical injury to the patient and can render the pain therapy ineffective.
The rapidly changing gradient magnetic fields can also induce electrical currents within the device’s circuitry. These induced currents can potentially damage the internal electronics of the pulse generator, leading to malfunction or failure. This electrical interference can also cause unintended stimulation, resulting in an uncomfortable sensation for the patient during the scan.
Mandatory Steps Before Undergoing an MRI Scan
Safely undergoing an MRI with an SCS begins with meticulous pre-scan verification. The patient’s entire medical team must confirm that the specific SCS model, including the leads, is “MRI Conditional” using the manufacturer’s official documentation. If the patient has abandoned or broken leads from a previous implant, the scan may be considered “off-label.” Such cases require an extensive risk-benefit assessment due to the unpredictable risks introduced by these components.
Effective coordination between the pain management specialist and the radiologist or MRI technologist is mandatory before the scan proceeds. The pain specialist must ensure the SCS is prepared according to the manufacturer’s specific protocol. This preparation includes verifying the device’s battery charge, as some rechargeable systems require a full charge to safely enter the MRI environment.
The device must be temporarily reprogrammed or placed into a specific “MRI Mode” prior to entering the scanner room. This specialized mode typically turns off the stimulation to prevent induced currents from causing patient discomfort or device damage. The patient should also bring their remote control or programmer and their patient identification card, which contains necessary device details for the radiology staff.
Immediately following the MRI scan, a post-scan check is required to ensure the system is functioning correctly. The SCS must be taken out of “MRI Mode” and reprogrammed back to its original therapeutic settings. This step is performed by the pain specialist or a trained representative to confirm the device’s integrity and restore the patient’s pain relief therapy.