MRI-Ready Actuation System for a Self-Propelling Needle

Abstract

Standard treatment methods for prostate cancer often result in side-effects because of damage to the surrounding tissue. Magnetic resonance imaging (MRI) guided focal laser ablation to treat prostate cancer reduces the risk of adverse effects by preserving noncancerous tissue. Prostate cancer diagnosis and focal laser ablation treatment both require the insertion of a needle for biopsy and optical fibre positioning. The insertion of needles in soft tissues causes tissue motion and deformation, resulting in tissue damage. In this study, we propose an MRI-ready actuation system for a needle that can be inserted into tissue with a zero external push force and without buckling. The zero external push force is achieved by moving parallel needle segments in a reciprocating manner. The actuation unit’s design inspired by the click-pen mechanism actuates the reciprocating motion of six parallel needle segments by solely a discrete manual translating actuation as its input. A prototype, called the Ovipositor MRI-Needle, was built using 3D printed parts and six 0.25-mm diameter Nitinol rods. Experimental validation of the Ovipositor MRI-Needle in ex vivo human prostate tissue inside a preclinical MRI scanner showed that the needle could advance in three out of five measurements through the tissue. The Ovipositor MRI-Needle is a step forward in the direction of developing a self-propelling needle for MRI-guided transperineal laser ablation to treat prostate cancer.