Waterjet Fracture-directed Steerable Needles

Mahdieh Babaiasl

Robotic needle steering is a proposed method in the literature for controlling flexible needles through curved paths in the soft tissue. Needle steering is proven to be effective in correction of insertion errors, steering around obstacles to reach the targets unreachable through conventional methods, and reaching to multiple targets from a single insertion. In spite of their many advantages and potential applications, they are limited by a number of factors. First off, they have constant curvatures and the attainable radius of curvature is a function of the needle and soft tissue parameters. Buckling is another issue that happens when the needle goes through structures and tissues that it cannot penetrate. This imposes a large force at the base of the needle and causes it to buckle. The use of the waterjet in medical applications has been developed more recently and it is used for different applications such as soft tissue resection, bone cutting, wound debridement, and surgery. Because of the many advantages that the waterjet provides like selective cutting of the tissue layers in which the tissue layers can cut deliberately by controlling the pressure of the waterjet, it is an appealing technique for surgery instead of knife. From the marriage between conventional steerable needles and the waterjet technology, waterjet steerable needles is born. In this technique, the direction of the fracture is controlled by high velocity waterjet and then the flexible needle follows the fractured path. This process continues until the needle can be steered in the soft tissue. Waterjet steerable needles resemble "drilling" in the sub-millimeter scale which has been proven to have superior advantages to conventional steerable needles. Our results showed that cutting the tissue with the waterjet can eliminate the cutting force and thus reduces the force at the base of the needle resulting in reduced buckling. Moreover, waterjet steerable needles showed the possibility of smaller radius of curvature with reduced tissue damage. Waterjet steerable needles promise tissue-agnostic steering in which the needle can be chosen to have a low bending stiffness (because the waterjet does the cutting) to obtain super small radii of curvature.

Waterjet Fracture-directed Steerable Needles

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