Fundamental performance assessment of 2-D myocardial elastography in a phased array configuration

Two-dimensional (2-D) myocardial elastography is a radio-frequency (RF)-based speckle tracking technique that uses one-dimensional (1-D) cross-correlation and recorrelation methods in a 2-D search, and can estimate and image the 2-D transmural motion and deformation of the myocardium so as to characterize the cardiac function. Based on a three-dimensional (3-D) finite-element (FE) canine left-ventricular model, a theoretical framework was previously developed by our group to evaluate the estimation quality of 2-D myocardial elastography using a linear array. In this paper, an ultrasound simulation program, Field II, was used to generate the RF signals of a model of the heart in a phased array configuration and under 3-D motion condition; simulating thus the standard echocardiography exams. The estimation method of 2-D myocardial elastography was adapted for use with such a configuration. All elastographic displacements and strains were found to be in good agreement with the FE solutions, as indicated by the mean absolute errors (MAE´s) between both. The results at different sonographic signal-to-noise ratios (SNR_s) showed that the MAE´s of the axial, lateral, radial and circumferential strains remained relatively unaffected, when the SNR_s was higher than 16 dB. The MAE´s of the strain estimation were not significantly affected when the acoustic attenuation was included in the simulations. The proposed framework can further be used to assess the quality, explore the theoretical limitation and investigate the effects of various parameters in 2-D myocardial elastography under more realistic conditions.