1. A method comprising: acquiring a first shear wave image of at least one shear wave propagation property; acquiring a strain image; and converting the strain image to a second shear wave image of at least one shear wave propagation property based on the first shear wave image, wherein converting the strain image to the second shear wave image of at least one shear wave propagation property comprises: dividing the strain image and the first shear wave image into plural areas; calculating a regression line and a correlation coefficient between the strain image values and the first shear wave image values in each area of the plural areas; if the correlation coefficient in the area is greater than a preset value, the strain image values are converted to shear wave values based on the regression line in each area; and if the correlation coefficient in the area is not greater than the preset value, the strain image values are converted to shear wave values based on a regression line in a nearest neighbor area.