Enabling Distal Rotation in a Robotically Steerable Guidewire: An Initial Approach

Endovascular interventions encompassing highly tortuous vessels would benefit from robotically steerable guidewires, which exhibit high dexterity. Existing studies on tendon-driven robotically steerable guidewires mainly employ rotation motion of the guidewire from the proximal end in an attempt to vary the bending plane of the steerable tip. While this strategy has contributed towards enhanced steerability of the guidewire, rotation from the proximal end of the guidewire often causes issues such as snapping due to non-uniform propagation of the rotation motion. This paper introduces the design of a guidewire capable of achieving rotation motion at the distal end by utilizing a mechanism, which converts linear motion into rotation motion. The proposed robot consists of two tubes: the inner tube with a notched section capable of bending, and an outer tube with a helical guide. The two tubes are coupled together such that the linear motion of the outer tube facilitates the rotation motion of the inner tube. We present the design of the robot and experimentally investigate the effects of the design parameters on the robot behavior. Modeling of the kinematic behavior of the system to estimate the rotation and bending of the robot is presented and validated. The derived models performed satisfactorily: The bending model exhibited an RMSE-value of $2.77 ~\mathrm{m}^{-1}$ curvature, which corresponds to 8.66 % of the maximum output curvature, for the inner tube rotation angle of 150°. For the outer tube consisting of a helical guide with a pitch angle of 80°, the rotation model exhibited an RMSE-value of 9.19° inner tube rotation angle, which corresponds to 4.38 % of the maximum inner tube rotation angle.