Effects of Beam Steering Angle in Vector Doppler Method with Plane Wave Imaging

The ultrasonic Doppler method is widely used for quantitative blood flow measurements. One of the shortcomings of the method is that only the axial velocity is estimated. To address such an issue, angle-independent velocity estimators have been investigated. The vector Doppler method is one of such methods and estimates velocity vectors by measuring axial velocities from different directions. Recently the vector Doppler method were implemented in high-frame-rate plane wave imaging with steered beams. The autocorrelation method is one of the methods widely used for estimation of axial velocities. The method estimates axial velocities from the phase of the complex correlation function of the complex beamformed ultrasonic signal and requires the center frequency of the received signal. We developed a method for estimation of center frequency and beam steering angle by evaluating two-dimensional autocorrelation and showed that the accuracy was improved significantly using the estimated steering angle in reception. In the present study, the effect of the beam steering angle was further investigated. The simulations with Field II showed that the standard deviations in estimated velocities were reduced further using the estimated steering angle in both transmission and reception.