Robot controller improves safety and accuracy in ultrasound imaging
Contact-Aware Impedance Controller for Robot-Assisted Ultrasound Imaging
Robotics
Summary
Getting clear ultrasound images with a robot requires careful control so the probe touches the body safely and accurately. The authors developed a way for the robot to detect contact with the body by looking directly at the ultrasound images, without relying on force sensors. This method helps the robot to adjust its movements and reduce the pressure it applies, making the procedure safer and more precise. Tests showed the system could find the contact point with about 1.5 mm accuracy and lower the pressing force by over 36%, while keeping good tracking of the probe position.
What this means in practice
- •For medical device engineers: Build safer robotic ultrasound systems that adjust probe pressure using image-based contact sensing without force sensors.
- •For robotic system integrators: Implement adaptive impedance control that updates contact points during ultrasound scanning for improved accuracy and safety.
Authors
MD Miraj Arefin, M Efe Tiryaki
Abstract
Safe robot-assisted ultrasound imaging requires a reliable controller able to detect and localize probe--tissue interaction. In this paper, we present a B-mode ultrasound image-based contact perception method and a contact-aware impedance controller for robotic ultrasound imaging. The proposed method detects acoustic contact independently of force measurements, enabling contact-conditioned force/torque taring to reduce residual wrench bias. During contact, the method continuously estimates the effective contact location along the curved probe surface and uses it to update the controller interaction frame, enabling visual servoing of the physical probe--tissue contact point during imaging. Experiments on an agar phantom demonstrated a contact-localization RMSE of $\mathbf{1.46 \pm 0.14}$~mm over probe roll angles from $\mathbf{-15^\circ}$ to $\mathbf{15^\circ}$. During static rolling, the proposed controller maintained task-space tracking accuracy comparable to a conventional fixed-frame impedance controller while reducing the maximum compressive interaction force from $\mathbf{31.56}$~N to $\mathbf{20.09}$~N, corresponding to a $\mathbf{36.3\%}$ reduction. These results demonstrate the potential of ultrasound images as direct contact feedback for safe and accurate robot-assisted ultrasound imaging.