P1C-6 Improved Ultrasonic Elasticity Imaging with Center Frequency Estimation and Global Shift Compensation

Ultrasonic elastography images the degree of hardness of a medium by estimating the displacement of ultrasonic signals before and after applying compression to the medium. The phase difference is first computed from the complex baseband signals using autocorrelation, and then the displacement is obtained from it. To obtain the displacement from the phase difference, one needs to know the center frequency of a wideband ultrasonic signal exactly, but it tends to change at every depth depending on the speckle and attenuation characteristics. Thus, accurate estimation of the displacement from the phase difference requires the knowledge of an exact center frequency. We show by simulation and experiment that the center frequency estimation combined with the global shift compensation greatly improves the strain image quality