Investigating the needle dynamic response during insertion into soft tissue

Abstract

This paper investigates the effect of the needle velocity on soft-tissue motion ex vivo and in vivo. In many needle-based intervention procedures, which are common minimally invasive surgical techniques, the needle can be assumed to be rigid and the tissue deforms and displaces considerably as the needle moves forwards to its target. This paper presents an energy-based fracture mechanics approach to show that the increasing needle velocity can reduce tissue motion during the insertion process. The main feature of this paper is that it extends the proposed approach to model the insertion dynamics, whereas most of the literature treats needle insertion as a quasi-static process. Ex-vivo test results on lamb heart samples show that the force required to initiate penetration decreases with increasing needle velocity up to a critical velocity, above which the rate-independent penetration force of the underlying tissue becomes the limiting factor. In-vivo tests show that increased needle velocity results in reduced force and displacement for needle insertion into the heart. Results indicate that automated insertion could substantially improve performance in some applications.