A mechanics-based model for a tendon-driven active needle navigating inside a multiple-layer tissue.

Percutaneous minimally invasive procedures such brachytherapy and biopsy require a flexible active needle for precise movement inside tissue and accurate placement at target positions for higher success rates for diagnosis and treatment, respectively. In a previous work, we presented a tendon-driven active needle to navigate inside tissue. This work presents a new model to predict the deflection of the tendon-driven needle while steering in a multiple-layer soft tissue. A multi-layer phantom tissue with different localized stiffness was developed for needle insertion tests followed by indentation tests to identify its mechanical properties. Using a robot that inserts and actively bends the tendon-driven needle inside the soft tissue while simultaneously tracking the needle through ultrasound imaging, various experiments were conducted for model validation. The proposed model was verified by comparing the simulation results to the empirical data. The results demonstrated the accuracy of the model in predicting the tendon-driven needle deflection in multiple-layer (different stiffness) soft tissue.