Needle Deflection during Insertion into Soft Tissue Based on Virtual Spring Model

Needle insertion is the most common procedure of minimally invasive interventions. During insertion into a soft tissue, the needle with bevel tip can deflect due to the asymmetric forces acting on the tip of the needle. In this paper, a mechanics-based model is developed to predict the needle deflection. In the model, the needle is considered as a cantilever beam supported by a series of nonlinear springs each of which has stiffness different from each other. The value of stiffness can be calculated by cutting force acting on the needle tip. Based on the model and the analysis of cutting force and friction force, Rayleigh-Ritz method is used to estimate the amount of needle deflection. Experiment shows that the simulation model can accurately predict the deflection of the bevel-tipped needle.