3-D Ultrasound Elastography Reconstruction Using Acoustically Transparent Pressure Sensor on Robotic Arm

Biopsy of breast lesions only visible on MRI may benefit from patient-specific finite-element modeling of the breast. This requires acquisition of the heterogeneous elasticity distribution. An acoustically transparent pad has been developed which enables strain elastography imaging using ultrasound without need for additional force or pressure sensors. The elasticity of the pad is known a priori while the change in thickness is detectable on ultrasound by edge detection. Based on the calculated pressure distribution across the pad, the pressure in inner tissue can be approximated. The strain is measured using a cross-correlation block matching algorithm and from these measurements the heterogeneous elasticity distribution can be estimated. The ultrasound probe with pad is moved over the breast surface by a robot arm. At sixteen sites on the surface of one phantom the probe with pad performed an inward push movement perpendicular to the breast surface. The ultrasound scans were post-processed to reconstruct a heterogeneous elasticity map in the local imaging plane. While it is challenging to accurately estimate the stress and strain in deeper tissue, certain features such as the skin can be effectively distinguished from the underlying soft tissue which demonstrates the potential of the system.