  Coherent Plane Wave Compounding (CPWC) is widely used for ultrasound imaging.
This technique involves sending plane waves into a sample at different transmit
angles and recording the resultant backscattered echo at different receive
positions. The time-delayed signals from the different combinations of transmit
angles and receive positions are then coherently summed to produce a beamformed
image. Various techniques have been developed to characterize the quality of
CPWC beamforming based on the measured coherence across the transmit or receive
apertures. Here, we propose a more fine-grained approach where the signals from
every transmit/receive combination are separately evaluated using a quality
metric based on their joint spatio-angular coherence. The signals are then
individually weighted according to their measured Joint Coherence Factor (JCF)
prior to being coherently summed. To facilitate the comparison of JCF
beamforming compared to alternative techniques, we further propose a method of
image display standardization based on contrast matching. We show results from
tissue-mimicking phantoms and human soft-tissue imaging. Fine-grained JCF
weighting is found to improve CPWC image quality compared to alternative
approaches.
