Force Modeling for Needle Insertion Into Soft Tissue

TLDR

Modeling forces during needle insertion into soft tissue is crucial for accurate surgical simulation, preoperative planning, and robotic assistance in percutaneous therapies. The study presents a force model for needle insertion and outlines experimental procedures to acquire data from ex vivo tissue to populate that model. Data were collected from bovine livers using a one‑degree‑of‑freedom robot with a load cell, segmented via CT imaging into phases of relative velocity, and modeled in three components—nonlinear capsule stiffness, modified Karnopp friction, and constant cutting—while also assessing needle diameter and tip effects on a silicone phantom. Bevel tips cause greater needle bending and are more sensitive to tissue density variations, and larger diameter needles produce higher forces due to increased cutting and friction.

Abstract

The modeling of forces during needle insertion into soft tissue is important for accurate surgical simulation, preoperative planning, and intelligent robotic assistance for percutaneous therapies. We present a force model for needle insertion and experimental procedures for acquiring data from ex vivo tissue to populate that model. Data were collected from bovine livers using a one-degree-of-freedom robot equipped with a load cell and needle attachment. computed tomography imaging was used to segment the needle insertion process into phases identifying different relative velocities between the needle and tissue. The data were measured and modeled in three parts: 1) capsule stiffness, a nonlinear spring model; 2) friction, a modified Karnopp model; and 3) cutting, a constant for a given tissue. In addition, we characterized the effects of needle diameter and tip type on insertion force using a silicone rubber phantom. In comparison to triangular and diamond tips, a bevel tip causes more needle bending and is more easily affected by tissue density variations. Forces for larger diameter needles are higher due to increased cutting and friction forces.