A robot system for medical ultrasound S.E. Salcudean, W.H. Zhu, P. Abolmaesumi, S. Bachmann and P.D. Lawrence Department of Electrical and Computer Engineering University of British Columbia Vancouver, BC, V6T 1Z4, Canada {tims@ee.ubc.ca} Abstract A teleoperation approach to diagnostic ultrasound, in which the ultrasound transducer is positioned by a ro- bot, is described in this paper. An inherently safe counterbalanced robot has been designed and tested in carotid artery examinations. The feasibility of using visual servoing for motion in the plane of the ultra- sound probe has also been demonstrated using a mod- ified image correlation algorithm and feature tracking algorithms. Research issues that have arisen in de- veloping this and other systems designed for human augmentation are also presented. 1 Introduction Robotics has an increasingly important role to play in the development of human augmentation systems. Such systems can address tasks that can only be ac- complished with marginal success by people, or at the cost of work related injuries. Medical assistive devices and robots have been proposed for endoscopic surgery, microsurgery, rehabilitation, etc., and promise to sig- nificantly change healthcare delivery in a number of important areas. Motivated initially by the need to avoid the repeated musculoskeletal injuires that ultrasound technicians are suffering [16, 4], the authors have embarked upon the development of a teleoperation system for medical ultrasound. The system consists of a joystick/haptic interface, a slave manipulator carrying the ultrasound probe, and a computer control system that allows the operator to remotely position the ultrasound trans- ducer on the patient’s body. The problem considered first as a test-bed for robot-assisted ultrasound is that of carotid artery examination, carried out to detect occlusive disease in the left and right common carotid arteries - a major cause of strokes. A robot-assisted ultrasound examination system would provide other benefits, such as the ability to collect and optimize 3-D ultrasound images [1], the ability to provide guidance to interventions (e.g., per- cutaneous pericardial puncture) and register images. Teleradiology is another possibility - although a num- ber of methods for transmitting ultrasound images have been proposed in the literature [13], none allow the radiologist to view and manipulate the ultrasound transducer at the remote site. Research issues that need to be addressed in order to make such as system work are discussed in this paper. Robot system requirements are summarized in Section 2.1, with a suitable robot design and hap- tic interface being presented in Section 2.2. Unilat- eral and bilateral control are discussed in Section 3, including the feasibility of controlling the transducer using ultrasound image servoing. Research challenges are discussed in Section 4, where the particular issues that arise in designing human augmentation systems are discussed. Conclusions and plans for future work follow. The proposed robot-assisted ultrasound examination system has been discussed before in [11]. In this pa- per, the control, design and image tracking aspects have been expanded, while other aspects have been omitted. A similar system has been proposed recently in [7]. 2 Electromechanical desing 2.1 Ultrasound robot performance An ultrasound transducer was fitted with an electro- magnetic position and orientation sensor (ATC The Bird TM ) and a JR 3 force/torque sensor. Errors in the measurement setup were quantified and found to be minimal for orientation measurements and acceptable in translation because of design safety margins. During a carotid artery examination, the patient lies