Beam steering in pulsed ´Doppler´ ultrasound velocity estimation

We have investigated the significance of beam steering as a potential source of error in ultrasound pulse-wave flow velocity estimation using computer simulation and experimental methods. A typical clinical transducer was simulated using a wide aperture setting for spectral flow estimation. It is shown that the effective beam-flow angle increases with the beam steering angle. For steering angles of ±20°, and beam-flow angles in the range of 60 to 70°, the resulting velocity error was found to be in the range from -5 to +7%. Much higher errors can occur at higher beam-flow angles, larger apertures and greater steering. With a tissue mimicking phantom and a pulsatile flow waveform, peak velocity estimations were made using a linear array pulsed system. From these, the overall velocity estimation error was determined for various beam-to-flow and steering, angles, and showed good qualitative agreement with the simulation.