Design Considerations for Robotic Needle Steering

Many medical procedures involve the use of needles, but targeting accuracy can be limited due to obstacles in the needle’s path, shifts in target position caused by tissue deformation, and undesired bending of the needle after insertion. In order to address these limitations, we have developed robotic systems that actively steer a needle in soft tissue. A bevel (asymmetric) tip causes the needle to bend during insertion, and steering is enhanced when the needle is very flexible. An experimental needle steering robot was designed that includes force/torque sensing, horizontal needle insertion, stereo image data acquisition, and controlled actuation of needle rotation and translation. Experiments were performed with a phantom tissue to determine the effects of insertion velocity and bevel tip angle on the needle path, as well as the forces acting on the needle during insertion. Results indicate that needle steering inside tissue does not depend on insertion velocity, but does depend on bevel tip angle. In addition, the forces acting on the needle are directly related to the insertion velocity.