P1A-4 Elasticity Reconstruction from Displacement and Confidence Measures of an Multi-compressed Ultrasound RF Sequence

Ultrasound elasticity imaging (UEI) shows promise as a new way for early detection of cancers by assessing the elastic characteristics of soft tissue. So far the commonly used approach involves solving the so-called inverse elasticity problem of recovering elastic parameters from displacement measurements. We propose a finite-element based nonlinear scheme to estimate the elasticity distribution of soft tissue from multi-compressed ultrasound radio-frequency (RF) data. An assisted-freehand ultrasound workstation has been developed for elasticity imaging. A composite probe was employed as the compression plate. The contact forces and torques were acquired at the same time of imaging. Displacements under different static loads are estimated from the RF data before and after deformation using cross-correlation technique. The confidence of displacement estimates is employed as a weighting factor in solving the objective function describing the inverse elasticity reconstruction problem. A split-and-merge strategy is employed over the image sequence in which strain images are used to provide a priori knowledge of the relative stiffness distribution of the tissue to constrain the inverse problem solution. The experimental study has allowed us to investigate the performance of our approach in the controlled environment of simulated and phantom data. For a simulated single inclusion model with 5% noise level the L₂-error between the target and reconstructed Young´s modulus is found to be about 1%. In vivo validation of the proposed method has been carried out and some preliminary results illustrate the practicability and the effectiveness of the method