Efficient mechanism design and systematic operation planning for tube-wire flexible needles

Needles are widely used in medicine for minimally invasive procedures. A steerable flexible needle was first introduced about 15 years ago, which was a new type of needle and could follow three-dimensional curved trajectory during medical procedures. The flexible needle has the limit of a single and low curvature. In this paper, we overcome this limit by designing mechanisms for tube-wire type flexible needles. We also provide a systematic planning method for an automated operation of the needle insertion using the mechanisms. Using the new system, we can achieve high and multiple curvatures from needle trajectories. The proposed design consists of an inner prebent wire and an outer tube, which are connected to two special mechanisms, an extension switch and a friction cart. It allows the trajectory of the needle to have high and multiple curvatures, which will enable the needle to easily reach target positions while efficiently avoiding obstacles. Users can efficiently control the needle device with simple inputs (insertion and rotation) using the special operation mechanism, which achieves three system functions (insertion/retraction, rotation, curvature changes) using only two actuation motors. Compared to prebent needles or duty-cycled spinning, this needle design causes less tissue damage. We build an automatic system to operate the new design of the steerable needle and test it. The performance of the new needle is verified by experiments with ballistic gelatin and animal tissue samples.