Ultrasound researcher working on fast microvascular imaging here. Depends on the datarates, you can generally get pretty good blood flow data pretty fast, with

Ultrasound researcher working on fast microvascular imaging here. Depends on the datarates, you can generally get pretty good blood flow data pretty fast, with <.5 seconds per slice if you do it with appropriate algorithms. A lot of this depends on motion though as you said, as the issue is generally getting a high-enough SNR (blood flow is generally 30-40 dB below tissue in energy, except for the biggest of vessels). Generally, higher frequencies have less of a separation between blood and tissue, but they have issue with attenuation. But I think with enough SNR (and with their element count that may indeed be possible), they could get pretty good blood flow data across the whole body.