Computational Investigation of Nitinol Guidewire Handling in a Tortuous Path

Nitinol guidewires are used to facilitate the placement and exchange of interventional devices during diagnostic or therapeutic procedures. These guidewires are often constructed from a nitinol core enclosed within a polymer jacket, where the core behaviour dominates mechanical performance. The rotation of the guidewire tip in response to rotation applied by the surgeon is one of the primary measures of performance of guidewires. Phenomena such as lag, whereby the tip rotation is less than the user input rotation, and whip, whereby the lag suddenly recovers, are undesirable as they can considerably impede guidewire handling.

The properties of the core material influence steerability and torque control of the guidewire, which introduces the need for a thorough understanding of the mechanical properties that affect guidewire performance characteristics so that optimised devices can be developed. In this work, the role of nitinol material properties on guidewire handling is investigated through computational analysis. The properties of several nitinol filaments exhibiting a wide range of responses are determined from tensile testing. The various nitinol cores are evaluated using finite element modelling in a tortuous path model and effects on important aspects of guidewire handling such as lag and whip are evaluated. Further analysis is performed on more localised effects such as changes in plateau stresses, material stiffnesses and transformation strains through a parameter exploration study. Results of the work performed here provide a better understanding of how nitinol properties affect guidewire usability and particularly highlight the influence of the transitional region and austenitic properties.