Beamforming Approaches for Reconstruction of Overlapping Wavefields in Multi-Line Transmit Imaging

Achieving higher frame rates in ultrasound imaging is of great importance, especially in echocardiography where capturing rapid events associated with heart dynamics can provide valuable information in terms of disease diagnosis. Several approaches have been proposed to acquire higher frame rate cardiac images, however almost all of them suffer from degradation in image quality mainly in terms of spatial resolution, contrast and signal-to-noise ratio (SNR). Multi-line transmit (MLT) imaging, which sends focused beams in different spatial directions within a single transmit event, is one of the proposed approaches to improve the frame rates in cardiac imaging. While MLT has the potential to preserve spatial resolution and signal-to-noise ratio, the main drawback of the technique is the generation of crosstalk artifacts between simultaneous MLT beams. In this work we have explored synthetic aperture beamforming techniques that more accurately characterize the overlapping transmitted waves and hence are able to suppress the artifacts associated with MLT due to the improved focusing. It has been shown that synthetic focusing methods could improve cystic contrast and lower side lobe levels up to 80% for a simulated point target. Furthermore, the experimental phantom results demonstrated up to 12.8% improvement in the generalized contrast-to-noise ratio when applying synthetic aperture methods in comparison to dynamic receive focusing.