Design of a Steerable Guidewire with Adjustable Tip Stiffness based on SMA ActuatorsMittwoch (22.05.2019) 15:54 - 15:58 Uhr Bestandteil von:
Shape memory alloys (SMAs) with superelastic characteristics are used in numerous medical devices like vascular stents and orthodontic wires. However, there is also a wide field of medical devices for SMA actuator wires. Typically, shape memory alloy wires are Nickel-Titanium alloys (NiTi), which can be plastically deformed at low temperatures and return back to their original shape when heated above their transition temperature. Their high energy density makes them ideal for light weight and compact devices such as catheter guidewires with a typical diameter of 360 µm. Guidewires are used to penetrate stenoses in coronary arteries as well as position catheters to dilate an occlusion. Guidewire tips with varying stiffness are needed during a percutaneous transluminal coronary angioplasty (PTCA) to fulfill these tasks without damaging the blood vessel. Exchanging the guidewire during an intervention increases the patient’s exposure to radiation and contrast agent. In this paper, the design of an actively steerable guidewire with adjustable tip stiffness is presented. On the one hand, bending the guidewire tip facilitates navigation through complex vessel geometries. On the other hand, the adjustable tip stiffness decreases the exposure of the patient by avoiding multiple guidewire changes. The first scaled-up prototype is a tube with an outer diameter of 4 mm and three shape memory alloy wires arranged in an 120° configuration. The special structure of the tube element combined with the arrangement of the SMA wires enables the guidewire to bend as well as changing the tip stiffness.