1. A method comprising: acquiring a first shear wave image of at least one shear wave propagation property; acquiring a strain image; dividing the strain image and the first shear wave image into plural areas; calculating a regression line between values of the strain image and values of the first shear wave image in each area of the plural areas; and converting the strain image to a second shear wave image of at least one shear wave propagation property based on the regression line.