From the Wasp Ovipositor to a 3D Steerable Needle for Solid-Tissue Interventions

Abstract

In many percutaneous interventions, such as biopsies and brachytherapy, accuracy in reaching a specific target inside the human body is necessary for the success of the procedure. Maneuvering to the target site is challenging, particularly if sensitive structures such as blood vessels have to be avoided. For maneuvering along a curved trajectory, flexible steerable needles have been introduced. However, since needles generally require a push force to be advanced into the tissue, the flexible nature of steerable needles makes them prone to buckling. Moreover, many steerable needles require rotation for maneuvering in a 3D space, causing needle twisting which makes accurate control of the needle challenging. In this study, a novel approach for the design of a flexible needle inspired by the egg-laying channel (‘ovipositor’) of parasitic wasps is proposed which addresses the aforementioned steering and buckling challenges while being small enough to be used in biopsy and brachytherapy procedures. This approach has led to the development of a six-segmented needle prototype designed to be both steerable in 3D without the need for rotation and devoid of the need for an axial push force for insertion into tissue thereby eliminating the risk of needle buckling. Experimental validation of our Ø 1.2 mm needle prototype in porcine gelatin specimen showed promising results, with steering curvatures of 0.018 1/cm achievable; yet further refinement of the design and experimental setup is necessary for a conclusive experimental assessment of the needle prototype.