Real-time implementation of vector velocity measurement along an M-mode line

Standard Doppler ultrasound investigations are limited to detect the axial blood velocity component, as they cannot directly estimate the flow direction. A typical approach for obtaining a 2D velocity vector consists in combining the echoes received from two PW lines investigating the region of interest (ROI) from different angles. The estimate is usually limited to the sample volume where the focused lines intersect. The transmission of plane waves has been recently proposed for overcoming this limitation. In particular, steered plane waves can be transmitted into different directions from 2 sub-apertures of a linear probe, so that they overlap over a large ROI. A line perpendicular to the probe surface is beamformed, and the Doppler shifts from 512 points of this line are combined to produce the velocity vectors. In this work, we report the real-time implementation of this vector Doppler method in the research system ULA-OP. An immediate and intuitive display has been developed where the velocity vectors are overlapped to the live B-mode image. Experiments on the carotid artery of a volunteer are reported which show the effectiveness of the real-time implementation in reducing the analysis time and in detecting the complex flow configurations.