Experimental Studies of NiTi Self-expanding Stent Designs

Preliminary investigations to apply thermoelastic stress analysis (TSA) to Nitinol self-expanding stents are described. Tests conducted at high resolution indicated that a viable thermoelastic signal can be obtained from the fine stent structure. It is shown that it is possible to digitally compensate for errors arising from motion at this high resolution. High variability in Nitinol's material properties with stress and temperature result in a complex thermoelastic response. Correction strategies are proposed to account for variation in material properties and to minimize errors due to thermal variations in order to derive calibration factors for the austenite and martensite material phases. The greatest challenge is identified as calibrating the thermoelastic response from the radially loaded stent structure where it is likely the material is highly inhomogeneous.