Recent technological advancements in cardiovascular surgery such as transapical transcatheter aortic valve implantation (TA-TAVI) enabled treatment to elderly that were initially declined surgery. However, valve malpositioning during TA-TAVI have been reported in several cases. In this preliminary study, we present a novel approach in which a Robotically-Actuated Delivery Sheath (RADS) is used to potentially facilitate valve positioning. A model is developed that describes the shape and articulating tip position of the RADS. We developed a two-dimensional ultrasound tracking method that evaluates the tip position of the RADS in ultrasound images. Both modeling and ultrasound tracking are combined into an integrated system that facilitates closed-loop control of the articulating tip of the RADS. Experiments are performed in order to evaluate the tracking accuracy of the RADS. Experiments show mean positioning errors of approximately 2 mm along the x- and y-axes. Our study demonstrates that the RADS can potentially provide compensation for beating heart and respiratory motions during valve positioning and deployment in TA-TAVI.

Needle insertion is one of the most commonly performed minimally invasive procedures. Visualization of the needle during insertion is key for either successful diagnosis or therapy. This work presents the real-time three-dimensional tracking of flexible needles during insertion into a soft-tissue simulant using a two-dimensional (2D) ultrasound transducer. The transducer is placed perpendicular to the needle tip to measure its position. During insertion the transducer is robotically repositioned to track the needle tip. Positioning of the transducer is accomplished by a compensator, that uses the needle insertion velocity corrected by needle tip velocities to determine out-of-plane motion. Experiments are performed to validate the needle tip pose during tracking. The maximum mean errors in needle tip position along the x-, y- and z-axes are 0.64 mm, 0.25 mm and 0.27 mm, respectively. The error in tip orientations (θ-about the y-axis and φ-about the z-axis) are 2.68° and 2.83°, respectively. This study demonstrates the ability to compute the needle tip pose using a 2D ultrasound transducer. The tip pose can be used to robotically steer needles, and thereby improve accuracy of medical procedures.