3-D companding using linear arrays for improved strain imaging

Three-dimensional (3-D) companding is applied to volume sets of rf echo signals to reduce decorrelation noise in strain images. Companding conditions echo signals to be cross-correlated to improve coherence and minimize decorrelation noise caused by complex 3-D motion. Previously, we showed that 2-D companding was able to eliminate decorrelation noise in strain images up to 5% compression if the out-of-plane displacement was negligible. This paper extends those methods to three dimensions, thus reducing the need to control boundary conditions. 3-D companding is also limited at high compressions (>5%) because of high strain gradients and rotation and shearing motions. A series of phantom studies illustrate the advantages and limitation of 3-D companding with and without aberrating layers.