Ultrasound Shear Wave Elastography and Microvessel Imaging

Tissue stiffness measured by ultrasound shear wave elastography is useful for liver fibrosis staging and cancer imaging. Comb-push Shearwave Ultrasound Elastography (CUSE) uses multiple push beams spaced out like a comb to generate shear waves covering the entire field of view for high signal-to-noise ratio and fast 2D shear wave imaging. External mechanical vibrations can also be used to generate shear waves for deep penetration measurements. Quantitative 2D shear wave images can be obtained at the depth of at least 10 cm in liver in vivo using mechanical vibrations. Microvessel imaging is useful for cancer imaging, functional imaging, and evaluation of inflammatory diseases. We have used high frame rate ultrasound imaging and Singular Value Decomposition to resolve small vessels in the kidney cortex in human without using ultrasound contrast agents. The technology can separate severe from mild inflammation in patients with Crohn's disease. A second technology, which achieves super-resolution by tracking the centers of individual microbubbles, can resolve microvessels with size below 50 µm using 2 seconds of data accumulation in a freely breathing rabbit with several millimeters of breathing motion. The principles of these imaging technologies will be presented with preliminary in vivo results.