Zone-based color flow imaging

A zone-based technique for real-time color flow imaging is described. The technique utilizes a broad transmit beam which is equivalent to 20-50 focused transmit beams, such that the full field of view can be scanned using only 3-5 firings, times the flow sample count (FSC) required for color flow estimation. On receive, the channel domain RF data is pre-processed and accumulated in memory, and then transferred to a software-based image formation system, which performs dynamic receive focusing, clutter filtering, mean velocity estimation and scan conversion. Various methods of compensating for the lack of transmit focusing gain are discussed, including a larger FSC, over-sampling pulsed repetition frequencies, and coded excitation using FM chirp, Barker and Golay codes. Both 7.5 MHz linear array and 3 MHz curved array images obtained using a research platform show very good agreement with the predicted signal-to-noise-ratio (SNR) gain for a 5-chip Barker coded signal.