Research on the Stability of Needle Insertion Force

The unstable needle insertion, contributing to imprecise insertion, can be reflected from insertion force stability. To improve the accuracy of needle-based intervention procedures and guide the investigation on needle steering technologies, a series of needle insertion experiments were performed on different soft tissues including single-layer PVA (Polyvinyl Alcohol) phantoms, multi-layer PVA phantoms and porcine livers. The effects of insertion velocities, tissue properties and tissue structures on insertion force stability were investigated. For mechanical noises in force data vary with interventional equipment, they were filtered before quantitative analysis of insertion force stability. The unit amplitude of insertion force was directly used to reflect the insertion stability. The results from both the single-layer PVA phantoms and porcine livers show that there is a critical velocity, under which the unit amplitude sharply decreases with the increase of velocity and above which it almost does not vary with velocity. In the actual application, insertion velocity above this critical value can be adopted to improve the insertion stability. The multi-layer PVA phantom tests show that the unit amplitude increases firstly and then decreases with the increase of PVA composition. By changing the direction of insertion into the same multi-layer PVA phantom, results indicate that both friction and cutting force can lead to unstable insertion.