Ultrasound coherence imaging using hardware receive beamforming and broad transmit beams
Conventional B-mode ultrasound images suffer from clutter composed of reverberation and aberration that exhibit only partial spatial coherence, making it possible to suppress these confounding signals using coherence- based imaging techniques. Coherence is typically measured by transmitting a focused wave into the tissue and computing the covariance of the returned echo signals across all combinations of receive channel pairs. We mathematically and experimentally prove the equivalence of the coherence measured as a function of transmit channel and as a function of receive channel. This forms the basis for an alternative method of coherence measurement using a synthetic aperture technique to store focused and summed receive channel data as a function of transmit channel. This technique avoids the need for access to individual receive channel data and is compatible with the existing signal pipeline on common commercial clinical scanners. We demonstrate in vivo short-lag spatial coherence imaging of the human liver to produce images with reduced clutter, using an ACUSON SC2000 ultrasound system to acquire data and perform full synthetic aperture focusing. The possibility to trade-off image quality for acquisition time is also presented in an effort to make the proposed sequences more accessible for real-time imaging.
