3D Vector Velocity Estimation using a 2D Phased Array

A method to estimate the three dimensional (3D) velocity vector is presented is this paper. 3D velocity vector techniques are needed to measure the full velocity and characterize the complicated flow patterns in the human body. The Transverse Oscillation (TO) method introduces oscillations transverse to the ultrasound beam, which enables the estimation of the transverse velocity. To expand the method from 2D to 3D, it is proposed to decouple the velocity estimation into separate estimates of v(x), v(y), and v(z) in combination with a 2D phased matrix array. Through simulations the feasibility of using the TO method for estimation 3D velocity vectors, and the proposed decoupling is demonstrated. A 64x64 and a 32x32 elements transducer are emulated using Field II. Plug flow with a speed of 1 m/s in a small region is rotated in the XY-plane. A binary flow example with [v(x), v(y)]=[1,0] and [0,1] m/s shows, that the velocity estimation can be decoupled into the transverse and elevation velocity components. This is substantiated by the results for seven different angles, where the mean and the standard deviation of the estimated speed are 0.97 +/- 0.05 m/s and of the angle bias are -0.73 +/- 3.3 degrees for the 64x64 matrix transducer. For the 32x32 transducer, the mean and standard deviation for the speed are 0.94 +/- 0.11 m/s and for the angle bias -0.48 +/- 7.7 degrees. The simulation study clearly demonstrates, that the new method can be used to estimate the 3D velocity vector using a 2D phased matrix array, and that the velocity vector estimation can be decoupled into separate estimates of v(x), v(y), and v(z).