Force Controlled Ultrasound Probe

Technology

This invention, a group of related cases, presents an ergonomic, handheld, force-controlled ultrasound probe for medical imaging applications. The device, which consists of an ultrasound probe mounted to a backlash-free ball screw actuator and driven by a compact servo motor, maintains a prescribed contact force between the ultrasound probe and the patient’s body. A control system, which combines both a position controller and a force controller, enables ergonomic operation by keeping the actuator centered within its range of motion and permits the repeated making and breaking of probe-patient contact. By controlling ultrasound probe contact force and consequently the amount of tissue deformation, the system enhances the repeatability, usability, and diagnostic capabilities of ultrasound imaging.

Problem Addressed

In current medical practice, the ultrasound probe acquisition state (position, orientation, and contact force of the probe) is manually controlled by an ultrasonographer, and therefore, the acquisition state at any given time is not repeatable at a later time, making ultrasound imaging difficult to reproduce. This can lead to imaging variations; hence, clinicians may not be able to determine, for instance, whether a tumor has grown larger over time or the change is due to the variations in the acquisition state. In addition, clinicians performing a biopsy must pay attention to the ultrasound probe force, the image display, and the needle in hand, so additional challenges caused by fluctuating contact force can lead to incorrect placement of the biopsy needle. Controlling the acquisition state through real-time feedback leads to more consistent ultrasound images and safer medical procedures.

Advantages 

• Maintains a constant contact force between the ultrasound probe and patient’s body
• Improved repeatability and diagnostic capabilities; eliminates image variations with controlled acquisition state
• Easier to control & more user-friendly
• Provides the user with visual and audio feedback, informing them of the position, orientation, and contact force of the device
• Provides pushbuttons on the device itself, enabling the user to initiate events (e.g., data recording, zeroing the angle) without needing to interact with a computer; hence users can focus on the device rather than the computer screen
• Fits comfortably in an ultrasound technician’s hand

Publications 

• Force and Position Control System for Freehand Ultrasound. IEEE Transactions on Robotics. August 2015. http://ieeexplore.ieee.org/document/7123185/.
• Evaluating the Clinical Relevance of Force-correlated Ultrasound. Biomedical Imaging (ISBI), IEEE 11th International Symposium. 2014. http://ieeexplore.ieee.org/document/6868084/.
• Accessing Duchenne Muscular Dystrophy with Force-controlled Ultrasound. Biomedical Imaging (ISBI), IEEE 11th International Symposium. 2014. http://ieeexplore.ieee.org/document/6867965/.
• An Ergonomic, Instrumented Ultrasound Probe for 6-axis Force/torque Measurement. Engineering in Medicine and Biology Society (EMBC), 35th Annual International Conference of the IEEE. July 2013. http://ieeexplore.ieee.org/document/6609457/.