A Unified Framework Combining Doppler-Based Motion Compensation, Harmonic Imaging, and Angular Coherence for High-Quality B-Mode in Ultrafast Echocardiography

Various methods have been proposed to enhance image quality in ultrafast ultrasound. Coherent compounding can improve image quality using multiple steered diverging transmits when motion occurring between transmits is corrected. Harmonic imaging has been adapted for ultrafast imaging to reduce clutter. Coherence-based approaches have also been shown to increase contrast in clinical settings by enhancing signals from coherent echoes. Herein, we introduce a simple, unified framework that combines motion correction, harmonic imaging, and angular coherence, showing for the first time that their benefits can be combined in real time. To do so, harmonic imaging was achieved through pulse inversion (PI), phase delay between successive transmits was assessed to perform motion compensation (MoCo), and ensemble autocorrelation between transmits was used to generate a weight applied to the coherently compounded frames. Validation was conducted through in vitro testing on a spinning disk model and in vivo on four volunteers. In vitro results confirmed the unified framework capability to achieve high contrast in large-motion contexts up to 17 cm/s. In vivo testing highlighted proficiency in generating images of high quality during low and high tissue velocity phases of the cardiac cycle. Specifically, during ventricular filling, the unified framework increased the generalized contrast-to-noise ratio (gCNR) from 0.47 to 0.87 when compared against coherent compounding.