In order to evaluate elasticity distribution based on a 3-D tissue structure, we propose a method of measuring 3-D displacement vector distribution based on the multi-beam technique. This method, which utilizes the phase shift at each element on the 2-D array aperture, is referred to as the 'weighted phase gradient method (WPGM)'. To make the proposed method applicable to the measurement of strain for large displacement (i.e., beyond wavelength), the 'combined autocorrelation method', previously proposed by us, is incorporated into the WPGM as the phase shift detector. Moreover, we attempt to reconstruct the elastic modulus distribution using the measured 3-D displacement vectors. Numerical simulation validated the feasibility of our methods in evaluating the 3-D tissue structure.
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