1. A method for obtaining a distribution of a stiffness property in tissue, comprising: applying a plurality of loadings to the tissue; obtaining a plurality of two-dimensional (2-D) imaging projections of the tissue from different directions; measuring a force resulting from one of the plurality of loadings; measuring from at least one of the plurality of 2-D imaging projections a displacement of the tissue in response to the force; obtaining an initial set of input parameters for an estimation of the stiffness property of the tissue; and solving iteratively for the stiffness property using a computer.