Measurement of Instantaneous Velocity Vector of Scatterers by Transmitting a Dual-Chirp Plane Wave

Plane-wave and divergent-wave ultrasound imaging can speed up Doppler measurements compared to methods that use a sharp transmit beam. However, conventional pulsed Doppler and color Doppler methods can only measure the average velocity over multiple frames. We propose a method for measuring the instantaneous velocity vector based on chirp-modulated plane-wave pulse transmission. The Doppler shift of the chirp pulse produces a measurable time shift in its compressed waveform. By transmitting a dual-chirp pulse, which is the sum of the up-chirp and down-chirp pulses, and compressing the echoes with up-chirp and down-chirp, respectively, the time interval between the two compressed signals can be measured. Based on this principle, we construct a velocity vector estimation method using multidirectional Doppler shift measurements from B-mode images using steered beamforming.