Force sensitive robotics for automated ultrasonic diagnostics and therapy

Ultrasound imaging, while being widely used due to its low risks and low costs, is highly user dependent and time-consuming to perform. Robotic automation has the potential to make the image acquisition process more reproducible and facilitate retrospective diagnosis. However, special safety precautions for robot-assisted ultrasound imaging are mandatory to prevent patient and staff injury. When using conventional industrial robots, entry into the robot’s working space is prohibited for reasons of safety. In this project, we use the KUKA LBR iiwa 7 featuring a high degree of freedom, a workspace diameter of 1.6 m and the necessary force sensitivity for human collaboration. Each of its seven revolute joints contains a torque sensor, which is constantly monitored by our application software. The goal for robotic ultrasound is to maintain a defined contact force (5 N) in all spatial directions, especially during movement. When the maximum contact force is exceeded, the robot stops its forward motion. Consequently, the robot arm is able to dynamically adapt to physiological motion like respiration. Additionally, an adapted hand guiding mode was implemented, allowing for manual position corrections and enabling the patient to push the robot arm away in case of hazard or discomfort. The high articulation of this robot allows free positioning of the probe on the patient's body and makes this system universally usable. For remote control, a 3D input device (3DConnexion SpaceNavigator) is used. Its control signals are transmitted to the robot in real-time with latencies <1 ms. In a next step, the use of haptic input devices will be investigated to also provide tactile feedback to the operator. This force-sensitive collaborative robot motion control prototype was implemented within a larger project. It is an important building block for the development of a universal automatic robotic 4D ultrasound platform for diagnostics and therapy.