Tissue elasticity reconstruction using linear perturbation method.

A new method to reconstruct the elastic modulus of soft tissue subjected to an external static compression is presented. In this approach the Newton-Raphson method is used to vary a finite element (FE) model of the elasticity equations to fit, in a least squared sense, a set of axial tissue displacement fields estimated using a correlation technique applied to ultrasound signals. The ill-conditioning of the Hessian matrix is eliminated using the Tikhonov regularization technique. This regularization provides a compromise between fidelity to the observed data and a priori information of the solution. Using an echographic image formation model, it is shown that the method converges within a few iterations (8-10) and that strain images artifacts which are common in elastography are significantly reduced after the resolution of the inverse problem.