Correlation analysis for angular compounding in strain imaging.

Spatial angular compounding for elastography is a new technique that enables the reduction of noise artifacts in elastograms. This technique is most effective when the angular strain estimates to be averaged or compounded are uncorrelated. In this paper, we present a theoretical analysis of the correlation between pre- and postcompression radio-frequency echo signals acquired from the same location but at different beam insonification angles. The accuracy of the theoretical results is verified using radiofrequency pre- and postcompression echo signals acquired using a real-time clinical scanner on tissue-mimicking uniformly elastic and homogenous phantoms. The theory predicts an increased signal decorrelation with an increase in the beam-steered insonification angle as the applied strain increases and for increasing depths in the medium. Theoretical results provide useful information regarding the correlation of the angular strain estimates obtained from different beam angles that helps in finding optimum compounding schemes for elastography.