Towards Steering a High-Dose Rate Brachytherapy Needle With a Robotic Steerable Stylet

Steerable needles are desired for many applications within the medical field. One such application is high-dose rate (HDR) brachytherapy. In this paper, an adaptive control system is proposed to provide control of the planar bending angle or deflection distance of a tendon-driven continuum joint, which can be inserted as the stylet in a commercial hollow needle for HDR brachytherapy. Proportional–integral–derivative (PID) controllers are a common method of control. However, significant tuning may be required to achieve the desired dynamic response, and the tuned gains may not achieve the desired response in a different environment or if the system model varies. Steerable needles must navigate through tissues of differing viscoelastic properties and the use of nitinol for the joint and tendons of a steerable needle leads to change in the system parameters due to change in the phase of the nitinol material. In this article, we propose the real-time adaptation of PID gains using model reference adaptive control techniques to control the planar bending angle or deflection distance of a steerable stylet and needle system.