Haze Artifact reduction in cardiovascular synthetic aperture imaging in use of intertransmission coherence factor

Abstract

In cardiovascular medical ultrasound applications, the use of spatially decimated focused-transmission synthetic aperture (SA) imaging is promising to achieve both high SNR and high-frame-rate. But unlike prevailing planar/divergence SA, the use of focused transmission where the virtual source of SA is placed in the imaging area for the better penetration with up to 160-mm field-of-view result in severe haze artifacts in the heart chambers. We hypothesize the haze is caused by the grating lobe due to the decimated focused transmission of SA and propose a method for reducing artifacts by using the intertransmission coherence factor (ITCF) [1] focusing on the fact that SA grating lobe signal is less coherent than the main lobe signals. Simulation and in vivo experiment revealed that there is a strong relation between the grating lobe and haze artifact. When imaging a human heart (under approval of institutional review board) using 4-times transmission decimation (equivalent to 160 frames/s) with a phased array probe, the ITCF method was able to reduce the grating artifacts within heart chambers greatly by more than 15 dB, while maintaining the intensity of myocardium, LV/LA wall, mitral valve, and other tissue/organ structures. [1] Ikeda et al. IEEE Trans. UFFC, doi: 10.1109/TUFFC.2021.3088678 (2021).