Towards the Development of an Ultrasound-Guided Robotically Steerable Guidewire

Minimally-invasive treatments for chronic total occlusions (CTO) involve the manual routing of a guidewire under fluoroscopy. However, navigation remains clinically challenging with high rates of procedural failure and trauma to the vessel. In this paper, we present a proof-of-concept robotic guidewire capable of acquiring forward-viewing ultrasound (US) images, thereby enhancing maneuverability through complex vasculature. We present a statics model based on Castigliano's theorem and its validation by controlling a notched nitinol tube used as a guidewire. A feedback control system was employed for precise control of robotic actuation of the guidewire. Based on our analysis of a set of designs, we chose the guidewire sample with the highest depth of cut (80% of outer diameter) and greatest number of notches (20). Additionally, we document the design, fabrication, and characterization of a 17.2MHz US transducer with 41% fractional bandwidth, as well as image formation with this transducer via synthetic aperture beamforming. Insertion loss and SNR were found of -60 dB and 28 dB, respectively. These components were then combined and used to image a series of wires in water to establish feasibility. The developed kinematic model and experimental data were used to compute the guidewire pose, which informed the image formation. The data obtained were used to create a visualization of the objects, demonstrating the feasibility of the system. SNR for the resulting images was 52 dB, and axial and lateral -6 dB ranges were 97 ± 11 μm and 339 ± 80 μm respectively.