Estimation of sound velocity based on evaluation of edge conspicuity

In this paper, a new method is proposed to minimize defocusing effects due to wrong selection of sound velocity used in dynamic receive beamforming. To find an optimal sound velocity, the proposed method calculates the degree of edge conspicuity by using a nonlinear anisotropic diffusion (NAD) technique. For this, images are formed with different sound velocities ranging 1400 to 1600 m/s and subsequently the region of interest (ROI) is chosen. In ROI, the degrees of edge conspicuity are calculated. The sound velocity can be considered as an optimal one for the ROI if it is used for the image that provides the maximum degree of edge conspicuity. To evaluate the performances of proposed method, pre-beamformed RF data were acquired from a phantom with a sound velocity of 1460 m/s by using a commercial ultrasound scanner (SA-9900, Medison, Corp., Korea) and the edge gradient was calculated. The estimation error and variance were 0.99% and 9.89%, respectively. These results indicate that the proposed method for sound velocity estimation is capable of providing accurate and consistent sound velocity in the ROI.