Research underway at the University of California, San Francisco (UCSF) has produced a new, steerable MRI-guided catheter called the MARC (Magnetically Assisted Remote Controlled). The MARC can navigate through the blood vessels in the brain in search of blood clots. Previoulsy when searching for blood clots in the brain as a result of an ischemic stroke, a guided catheter is used during an arteriogram to navigate through blood vessels to find and dissolve the blood clot. This procedure can lead to a significant amount of radiation to the patient and does not offer a ‘real-time’ picture of tissue health. However, retrieving or dissolving clots with a MARC catheter instead of X-ray guidance could help clinicians determine much faster if the brain tissue around the clot is alive or dead. Typically a patient has to undergo a CT perfusion study or MRI before they are brought to the angio suite for removal of the clot. Knowing tissue viability sooner can help clinicians make a more informed decision and lead to better patient safety and outcomes. Often, if the tissue is already dead then opening the vessel has the potential to hemorrhage.. Researchers at UCSF have suggested that if clots could be retrieved or dissolved under MRI instead of X-ray, then it might be possible to decide in ‘real-time’ if clots should be opened or not. The MARC catheter which is undergoing animal testing has a solenoid coil at the distal tip and is controlled with a foot pedal actuator that delivers a current of 300 mA. In an interview with AuntMinnie.com primary researcher Dr. Steven Hetts, explained:
There are microcoils embedded on the tip of the catheter, and by running a small electrical current that creates a strong magnetic field on the tip of the catheter that interacts with the strong magnetic field of the scanner, we can steer by remote control.
As a result, this new catheter is faster and more agile than previous MRI-guided catheters, able to navigate all the twists and turns in between the femoral artery and the brain. In an article published in Radiology, the MARC catheter was easy to visualize under real-time MRI and 192 out of 240 (80%) turns were completed successfully with this catheter compared to 144 of 260 (60%) turns using a standard x-ray guidance. The MARC catheter also proved faster than the manually directed catheter with a mean procedure time of 37 seconds per turn compared to 55 seconds per turn. This technology is at least two years away from being used in the clinical setting setting and will have to be rigorously evaluated in humans in order to receive U.S. Food and Drug Administration clearance.