A Flexible Catheter System for Ultrasound-Guided Magnetic Projectile Delivery

Magnetic actuation is a versatile technology, widely applied in medical robotics for noncontact steering of flexible instruments and untethered agents. In this article, we exploit the benefits of this technology by developing a magnetically actuated flexible catheter capable of the controlled ejection and retrieval of an untethered magnetic capsule. The catheter is actuated by the advanced robotics for magnetic manipulation system. The scanning ultrasound is used for 3-D shape reconstruction of the catheter, with a mean error of 0.37 mm. We use a closed-loop position controller to steer the catheter, reporting a mean error of 0.82 mm. We develop a dynamic model of the capsule and use it to predict the trajectory of the projectile. We demonstrate the targeting of the capsule utilizing the null-space of the catheter actuation (mean residual tip displacement of 0.8 mm). Finally, we perform a delivery of a capsule to and retrieval from a target inaccessible for the catheter tip, demonstrating the capability of our instrument to reach challenging locations.