The precise location of tumors is an important step in surgical planning that can be obtained from mechanical properties of soft tissues. In this paper we propose a roboticassisted palpation system that automatically moves an ultrasound probe to optimize the elastography process and improve the resulting elastogram. The main contribution of this work is the use of the elastography modality directly as input of the robot controller. Force measures are also considered in the probe control in order to automatically induce soft tissue deformation needed for real-time elastography imaging process. Moreover, an automatic exploration process is implemented to orient the probe to reach different views of a soft tissue target of interest. This allows to improve the elastogram quality of the element of interest by fusing the information observed from different positions.

Detecting stiff tissue using ultrasound elastography has been used as a non-invasive technique in the assessment of important diseases. The real-time estimation of tissue elastic parameters depends on the continuous application of an appropriate palpation motion with an ultrasound probe, which can be achieved through the use of a robotic system. To complement ultrasound elastography and further profit from the information it provides, we propose to give to the clinician the ability to physically feel in real-time during the examination the stiffness of a tissue observed in the elastography image by rendering it with a haptic force feedback, enhancing therefore the capacity of the examiner to detect anomalies. We also propose in our robotic palpation system a teleoperation control of the ultrasound probe for navigation purpose during the tissue examination. Experimental results obtained on an abdominal phantom demonstrated the feasibility of our approach.

In this paper we present a novel approach to track and explore stiff tissues within 3-D ultrasound volumes acquired by a medical 3-D ultrasound probe mounted on a six degrees of freedom robotic arm. Autonomous palpation and on-line elastography process are implemented to estimate the elastic property of the tissues (strain) in a volume of interest (VoI) indicated by the user. The compression motion, required for the elastography, is performed by controlling the force applied by the ultrasound probe to the tissues. A visual servoing control for centering a rigid tissue (target) inside the field of view (FoV) of the ultrasound probe is established to always maintain the target visible. Additionally, rotations around the contact point between the tissue and the ultrasound probe are teleoperated through a haptic device handled by the user in order to allow exploration of the target surrounding areas. Results show a stable system that can be used in the future for diagnosis of diseases or tumor location.

Abstract-This paper presents a robot-assisted system to obtain elastic information of a moving tissue using a 2-D ultrasound probe actuated by a 6 degrees of freedom robotic arm. The proposed method combines ultrasound image-based visual servoing, force control and non-rigid motion estimation. We present how the motion estimation, while the force control and visual sevoing are enabled, is useful to compute the strain map of the tissue. Ex-vivo experiments performed on a moving abdominal phantom demonstrate the efficiency and robustness of this methodology to compute the strain information of a tissue in motion.