Anisotropic Constructive Shearwave Interference Measurement of Transversely Anisotropic Materials
Fibrous tissues, such as skeletal muscle, tendons, and myocardium, have been shown to support orientation-dependent shear wave propagation. It has been shown that shear waves can be induced and measured with ultrasound to assess such anisotropy. Existing methods have required either a successively-rotated linear array, precluding real-time imaging, or a matrix array, requiring complex system architectures. Constructive Shearwave Interference (CSI) is a new shear wave technique that uses an annular array to generate shear waves with ring-shaped cross-sections, and a single concentric tracking element to monitor the resulting constructive interference at the center. A method is proposed and demonstrated here, called Anisotropic CSI (ACSI), which uses angular apodization of CSI sectors to impose directionality on the constructively-interfering shear waves, enabling visualization and quantification of anisotropic elasticity. ACSI is demonstrated in tissue mimicking anisotropic phantoms with various spatial apodization functions, and shown to be sensitive to the degree of anisotropy in the target material.
