Influence of Factors on Motion Artifacts in Strain Estimation with Spatial Angular Compounding

Spatial angular compounding (SAC) has been developed to improve the performance of lateral estimation. It is a promising method for cross-sectional carotid elastography to image the strain distribution within carotid atherosclerotic plaque and identify the vulnerable plaque. However, in strain estimation with SAC, arterial motion and deformation during multi-angle acquisitions may cause motion artifacts. In this study, the influence of the key factors on motion artifacts, including the pulse repetition frequency (PRF) and number of steering angles (NSA), is investigated. Simulations and in vivo experiments are conducted using a linear array with plane wave transmission. The elastographic signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) are used to evaluate the quality of the strain image. The simulation results show that the SNR and CNR of lateral strain increase with the PRF when it is lower than 4 kHz, the CNR and SNR of lateral strain with an NSA of 7 are lower than those with an NSA of 3 when PRF <; 500 Hz, and the SNRs and CNRs of lateral strain with NSAs of 3 and 7 are similar when PRF > 4 kHz. The in vivo experimental results show that the radial and circumferential strain images at a PRF of 3 kHz are smoother and more homogeneous than those at a PRF of 429 Hz. In conclusion, both the PRF and NSA have influence on motion artifacts in strain estimation with SAC. For carotid elastography, a PRF of more than 4 kHz and an NSA of 3 are suggested to obtain strain images with smaller motion artifacts.