Preclinical evaluation of a novel fiber compound MR guidewire in vivo.

PURPOSE: Interventional magnetic resonance imaging requires dedicated and MR-compatible devices. The guidewire is a key item for intravascular interventions. Mechanical stability, good visibility during real-time imaging, and RF safety are essential. A novel fiber-compound MR guidewire (GW) was evaluated in different MR-guided interventional scenarios. MATERIALS AND METHODS: The GW (diameter 0.032") consists of a fiber-compound produced using a micropultrusion technique doped with iron particles and a 10-cm Nitinol tip. Several iron splints are additionally attached at regular distances to visualize GW-movement. A protective polymer jacket with hydrophilic coating covers the core material. As approved by the government committee on animal investigations, the GW was evaluated in 5 pigs. Under complete MR-guidance, catheterization of the carotid and renal arteries, segmental arteries of the kidneys, the contralateral inguinal artery, and the left ventricle was performed using real-time gradient echo sequences in a 1.5 Tesla scanner. Different interventional applications including balloon dilatation, stent deployment, and embolization of small vessels were investigated. The time to probe the vessels under magnetic resonance imaging guidance and visibility of the GW are assessed. Handling and visibility under fluoroscopy were compared with a standard Nitinol guidewire as a benchmark. RESULTS: On real-time magnetic resonance imaging, the iron-induced artifacts enabled a distinct visualization of the GW shaft and of its markings with a mean size of 2.6 mm and 5.4 mm, respectively. This facilitated fast navigation to the target vessels (averages: renal arteries 16 seconds, carotid artery 5 seconds, and contralateral inguinal artery 42 seconds.) with an exact depiction of the respective vessel. All interventional procedures were performed successfully. No GW-related side effects as kinking or breakage of the wire or GW induced blood-clotting were observed. All interventionalists assessed handling of the GW to be nearly equal in terms of stiffness, flexibility, and guidance compared with a standard Nitinol guidewire. X-ray visibility was less distinct but still diagnostically good. CONCLUSION: With the aid of the GW, different fully real-time MR-guided endovascular interventions become feasible.

An MR guidewire based on micropultruded fiber-reinforced material.

A novel fiber-reinforced material for the realization of MR guidewires, made using a newly-developed production process, is presented. The MR-safe artificial material provides a high stiffness and torque and allows the production, in a large range of sizes, of nonmetallic MR guidewires with similar mechanical properties as conventional metallic guidewires. Based on this material, a passively visualized MR guidewire has been developed, and was found to conform to existing standards on mechanical stability. Handling and steerability were evaluated in animal studies and were found to be comparable with conventional metallic guidewires. X-ray visibility is provided by a BaSO(4)- and tungsten-doped jacket. A hydrophilic coating improves sliding properties and hemocompatibility.