Dynamic Path Planning for Inserting a Steerable Needle Into a Soft Tissue

Steerable bevel-tip needles are widely used in modern, minimally invasive percutaneous procedures to reach specific areas inside the body. In this paper, we propose an optimized path planner for manipulating such steerable needles, which can generate the shortest path from the starting position to the target position with the least number of rotation times. The shortest traveling path produces less damage to the body, thus shortening the recovery period. We first investigate the insertion problem in a nondeformable environment, which is termed as the static environment in this paper. As the needle is flexible, the moving path is a curve. We propose to regulate the curved path within two parallel lines and then determine the optimal distance between the two parallel lines such that the generated moving path of the needle has the shortest length with the least number of needle rotations. We then investigate the insertion problem in a deformable environment, which is termed as the dynamic environment. Taking deformation and nonhomogenous properties of soft tissue into account, the target position and the radius of the curve path vary as the needle is inserted. By using a mass-spring model to formulate the deformable environment and a vision system to measure the time-varying radius of the curve, we propose a dynamic path planner that replans the path to adapt to the change of the target position and the curve radius. Simulations and experiments are performed to demonstrate the effectiveness of the proposed approach.