Magnetic resonance imaging (MRI) has the potential to offer several advantages over x-ray methods when obtaining high-quality soft-tissue visualization or precisely locating lesions in small vessels, for example. But because MRI-safe guidewires cannot feature electrically conductive metal cores like their x-ray counterparts, manufacturers have struggled with how to design very thin, MRI-safe guidewires that exhibit the necessary stiffness without the use of metal. Overcoming this obstacle, MaRVis Technologies GmbH (Aachen, Germany) has developed micro-guidewire prototypes from glass-fiber epoxy rods that possess mechanical properties similar to those of commercial x-ray guidewires.
"Currently, there are no MRI [safe] guidewires on the market. Commercial, non-MRI-safe guidewires contain stainless-steel or nitinol cores, which lead to heating and electric current in the MR scanner," explains Klaus Duering, CEO of MaRVis Technologies. "The metal core cannot simply be removed and replaced by another material because the mechanical properties [will be] lost."
Seeking to replace the metal cores with a material that offers the right combination of stiffness, flexibility, and torque, MaRVis settled on glass-fiber epoxy rods. A common composite material, glass-fiber epoxy rods are recognized for their desirable mechanical properties, according to Duering.
Although the company avoided metal use for the core of the micro-guidewire, it doped the glass-fiber epoxy rods in the micro-guidewire with metal particles to serve as visualization markers. Because these particles are separated from each other and do not form a conductor, the particle doping does not lead to any electric conductivity or heat generation during MRI use.
"Not only mechanically, but also in terms of the MR imaging, we have developed a much more powerful technology than with discrete markers," Duering says. "Due to the continuous doping with optimized metal particles, we produce a continuous stripe on the image of the guidewire, just as the physicians are used to seeing from x-ray imaging." In addition to optimizing the micro-guidewire, the company is collaborating with researchers at the Freiburg University Hospital in Germany, which is developing software settings--or MR sequences--to enable very focused and precise imaging of the guidewire.
"We are proud to be the first to have a 0.012-in.-diam [MRI-safe] micro-guidewire prototype devoid of a metal core, which possesses valuable mechanical properties," Duering says. "This tremendous progress will allow physicians to perform applications in cardiological or neurological interventions, which eventually will strongly support the breakthrough of MRI-guided interventions."