Surgeon-in-the-loop 3 D Needle Steering Through Ultrasound-guided Feedback Control
Needle deflection during certain minimally invasive percutaneous procedures, such as prostate biopsy or brachytherapy, is undesired and can be reduced through the use of feedback control. This paper uses a depth-dependent reduced-order 3D nonholonomic model of needle tip motion to propose a needle deflection controller that works in a surgeon-in-the-loop fashion, where the surgeon is in charge of needle insertion, and the feedback controller is responsible for keeping the needle on its desired trajectory. The controller is based on a continuous-time control law that asymptotically brings needle deflection to zero, and is shown to remain effective even when the magnitude of the needle rotation velocity is limited. Limiting of the needle rotational velocity is due to practical considerations such as to reduce tissue damage during insertion and to show a measure of velocity-independence of the controller when high insertion speeds would require unfeasibly fast rotations. The velocitylimited controller is evaluated in three different ex-vivo tissue samples in a total of 30 needle insertion trials using real-time needle deflection measurements from ultrasound images. The exvivo results show an average absolute needle tip deflection of 0.54 mm away from the target location at a depth of 120 mm, and an average needle tip deflection of 0.36 mm away from the desired target axis throughout the entire insertion length.