Handheld Force-Controlled Ultrasound Probe

An hand-held force controlled ultrasound probe has been developed. The controller maintains a prescribed contact force between the probe and a patient's body. The device will enhance the diagnostic capability of free-hand elastography, swept-force compound imaging, and make it easier for a technician to acquire repeatable (i.e. directly comparable) images over time. The mechanical system consists of an ultrasound probe, ballscrew-driven linear actuator, and a force/torque sensor. The feedback controller commands the motor to rotate the ballscrew to translate the ultrasound probe in order to maintain a desired contact force. In preliminary user studies it was found that the control system maintained a constant contact force with 1.7 times less variation than human subjects who watched a force gauge. Users without a visual force display maintained a constant force with 20 times worse variation. The system was also used to determine the viscoelastic properties of soft tissue. In three mock ultrasound examinations one hour apart in which the goal was two obtain two consistent images at the same force, an unassisted operator obtained the second image at a 20% lower force, while the operator assisted by the controller obtained the same force to within <2%. The device enables users to gather more force-consistent images over time. Thesis Supervisor: Brian W. Anthony Title: Research Scientist, Department of Mechanical Engineering