New MRI-Guided Catheter Shows Major Potential for Stroke Treatment
A new investigative tool can navigate through blood vessels from the groin to the brain in search for blood clots using MRI-guided navigation. This MRI-guided catheter, called the MARC catheter, and developed here at UCSF, shows vast potential for the treatment of stroke and other diseases under MRI guidance, as it is faster and more agile than previous devices.
Because MRI is much more useful than x-ray when brain tissue is involved, this steerable MRI-guided catheter could mean big things for stroke treatment. When treating someone who has ischemic stroke, we don't know whether their brain tissue is alive or dead at that time of intervention. We usually have a CT perfusion study or MRI that was done before the patient gets on our angiogram table, then we try to remove the blood clot from the vessels in the brain. We don't have any way of knowing in real-time if the tissue beyond the point of the occlusion is alive or dead. The gold standard way of knowing that is diffusion-weighted MRI.
However, with this technology, retrieving and dissolving clots can be performed under MRI rather than x-ray guidance, making it possible to decide in real-time whether the blood vessel should be opened up or left alone. This is of utmost importance, as opening up dead tissue is likely to result in hemorrhage and a potentially devastating outcome. Having access to information about tissue viability in real-time would lead to better decision-making, and ultimately result in the optimization of patient safety and outcomes.
The MARC - or magnetically assisted remove-controlled – catheter is based on a commercially available catheter, but made with nonmetallic fibers. There are microcoils embedded on the tip of catheter. By running a small electrical current a strong magnetic field on the tip of the catheter is created. That tip interacts with the strong magnetic field of the scanner, so we can steer through the body with remote control. The MRI guidance was done with a 1.5-tesla scanner.
This tool was easy to visualize under real-time MRI during the tests, as shown by research presented at last year’s Society of NeuroInterventional Surgery conference. Under magnetically assisted guidance, 192 of 240 turns (80 percent) were completed successfully, compared with 144 of 240 turns (60 percent) using standard x-ray guidance. Further, previous technologies for navigating under MRI are much slower rendering them more or less useless in clinical practice. The MARC catheter moved through blood vessels with a speed of 37 seconds per turn, compared to 55 seconds per turn of the conventional catheter- the manually directed catheter under MRI guidance.
The magnetic nature of the MARC system makes it more adept than conventional catheters for navigating twists and turns, though magnetism isn't used to advance the device to the target. We still use our hand to push the catheter to the target, but the magnetic field allows us to steer much easier.
The MARC catheter is still in the research stages, with animal experimentation done successfully. This is the first study showing that you can navigate under MRI guidance anywhere close to as fast as under x-ray guidance, which makes us very excited!