Frequency-domain high frame-rate 2D vector flow imaging

Conventional ultrasound flow imaging systems are limited to estimate only the axial component of blood velocity. In this work, a method to produce 2D vector Doppler maps is proposed and experimentally tested. The local displacements between consecutive high frame-rate (HFR) radio-frequency (RF) images are estimated in the frequency domain. Each image is subdivided in partially overlapped matching blocks, and the average local displacements in a block are calculated from the difference of spectral phases in consecutive frames. The method has been tested by simulations and experiments by using the ULA-OP research scanner. Preliminary in-vivo tests have been conducted and an example of the femoral vessels of a healthy volunteer is presented. The performance of the method are evaluated through the relative error bias and standard deviation, presenting values lower than 10% in standard conditions.