Design and Modeling of a Compact Spooling Mechanism for the COAST Guidewire Robot

The treatment of many intravascular procedures begins with a clinician manually placing a guidewire to the target lesion to aid in placing other devices. Manually steering the guidewire is challenging due to the lack of direct tip control and the high tortuosity of vessel structures, potentially resulting in vessel perforation or guidewire fracture. These challenges can be alleviated through the use of robotically steerable guidewires that can improve guidewire tip control, provide force feedback, and, similar to commercial guidewires, are inherently safe due to their compliant structure. However, robotic guidewires are not yet clinically viable due to small robot lengths or large actuation systems. In this letter, we develop a highly compact spooling mechanism for the COaxially Aligned STeerable (COAST) guidewire robot, capable of dispensing a clinically viable length of 1.5 m of the robotic guidewire. The mechanism utilizes a spool with several interior armatures to actuate each component of the COAST guidewire. The kinematics of the robotic guidewire are then modeled considering additional friction forces caused by interactions within the mechanism. The actuating mechanisms of the compact spooling mechanism are calibrated and the kinematics of the guidewire are validated resulting in an average curvature RMSE of 0.24 m$^{-1}$.