Flexible Needle Steering in Moving Biological Tissue With Motion Compensation Using Ultrasound and Force Feedback

Needle insertion procedures under ultrasound guidance are commonly used for diagnosis and therapy. It is often critical to accurately reach a targeted region, and this can be difficult to achieve due to intraoperative tissue motion. In this letter, we present a method to steer a beveled-tip flexible needle toward a target embedded in moving tissue. Needle steering is performed using a needle insertion device attached to a robot arm. Closed-loop 3-D steering of the needle is achieved using tracking of an artificial target in 2-D ultrasound images and tracking of the needle tip position and orientation with an electromagnetic tracker. Tissue motion compensation is performed using force feedback to reduce targeting error and forces applied to the tissue. The method uses a mechanics-based interaction model that is updated online. A novel control law using task functions is proposed to fuse motion compensation, steering via base manipulation and tip-based steering. Validation of the tracking and steering algorithms are performed in gelatin phantom and bovine liver. Tissue motion up to 15 mm is applied and average targeting error is 1.2 +/- 0.8 mm and 2.5 +/- 0.7 mm in gelatin and liver, respectively, which is sufficiently accurate for commonly performed needle insertion procedures.