A method for real-time three-dimensional vector velocity Imaging

The paper presents an approach for making real-time three-dimensional vector flow imaging. Synthetic aperture data acquisition is used, and the data is beamformed along the flow direction to yield signals usable for flow estimation. The signals are cross-correlated to determine the shift in position and thereby velocity. The data can be beamformed after reception in any direction and any vectorial velocity can be found. More than 60 independent velocity volumes can be made per second with this approach. A 3 MHz 2D matrix transducer consisting of 64 x 64 elements with lambda/2 pitch is used. The emissions are done using 16 x 16 = 256 elements at a time, and the received signals from the same elements are sampled. Access to the individual elements is done through 16-to-1 multiplexing, so that only a 256 channel transmitting and receiving system is needed. The method has been investigated using Field II. Parabolic flow in a 10 mm radius vessel inclined at 60 degrees to the acoustical axis of the transducer was simulated. The mean standard deviation of the estimates was 0.0098 m/s over the whole vessel cross-section, which is 3.3 % relative to the peak velocity. The bias was 0.023 m/s (7.5 %). False peaks were found mainly at the edges of the vessel due to the echo-canceling, and the probability of false detection was 2.2 %.