Dynamic elastography using delay compensated and angularly compounded high frame rate 2D motion vectors

This paper describes a new ultrasound-based system for high frame rate measurement of periodic motion in 2D for tissue elasticity imaging. The system acquires the RF signals from the region of interest from multiple steering angles in order to reconstruct the 2D motion from ID estimation along each angle. To increase the temporal resolution, the acquisition area is divided into groups of scan lines called sectors. Each sector is acquired multiple times before moving onto the next sector. Following the data acquisition, ID motions are estimated along the beam direction from the sequences of echo signals. Using a recently introduced delay compensation algorithm, the intra- and inter-sector delays in the motion estimates are compensated to create high frame rate images. In-plane 2D motion vectors are then reconstructed from these delay compensated ID motions. Finally, modulus images are estimated from these 2D motion vectors using planar algebraic inversion of the Helmholtz equation. The performance of the system is validated quantitatively using a commercial elasticity phantom. At frame rate of 1250 Hz, phantom Young´s moduli of 29kPa, 6kPa, and 54kPa for the background, the soft inclusion, and the hard inclusion of a phantom, are estimated to be 30kPa, 11kPa, and 53kPa, respectively, for an excitation frequency of 150 Hz.