Modeling of needle steering via duty-cycled spinning.

As flexible bevel tip needles are inserted into tissue, a deflection force causes the needle to bend with a curvature dependent on relative stiffness and bevel angle. By constantly spinning the needle during insertion, the bevel angle is essentially negated and a straight trajectory can be achieved. Incorporating duty-cycled spinning during needle insertion provides proportional control of the curvature of the needle trajectory through tissue. This paper proposes a kinematic model for needle steering via duty-cycled spinning. Validation using experimental results is also presented.