A Real-Time Estimator for Needle Deflection During Insertion Into Soft Tissue Based on Adaptive Modeling of Needle-Tissue Interactions

This work proposes a real-time estimator for needle tip deflection and needle shape during needle insertion into soft tissue. The estimator is based on an adaptive quasi-static mechanics-based model for needle-tissue interactions. The model uses Euler-Bernoulli beam theory to model the needle as a cantilever beam that experiences loads imposed by the tissue. The modeled needle-tissue interactions consist of a distributed load along the inserted needle portion and tissue cutting-related point load at the needle tip. We propose a closed-form solution to quantify the magnitude of these needle-tissue interaction loads based on force and torque measured at the needle base. The model adaptively adjusts the shape of the distributed load as the needle is inserted. Experiments are carried out into gelatin phantom and porcine tissue to validate the deflection estimate's performance. The newly proposed model's performance is compared against a previously proposed quasi-static model for needle-deflection estimation. It is shown that the novel model outperforms the previously proposed model.