Doppler Angle and Flow Velocity Estimations Using the Classic and Transverse

Current clinical Doppler ultrasound systems could only measure the flow vector parallel to the ultra- sound beam axis, and the knowledge of the Doppler angle (beam-to-flow angle) is needed to calculate the real flow ve- locity. Currently, the Doppler angle is determined visually by manually aligning a vessel axis marker along the blood vessel on the duplex scan image of the ultrasound. The ap- plication of this procedure is often limited by practical con- straints; therefore, measurements are not reliable. In order to overcome this problem, we developed a simple Doppler angle and flow velocity estimation method using a combi- nation of the classic and transverse Doppler effects. This method uses only a single focused annular array transducer to estimate the Doppler angle and the flow velocity. We have verified experimentally that this method is successful for measuring constant flow in a flow phantom between 45O and 80' Doppler angle. The standard deviation of the esti- mated Doppler angles is less than 4.5O. This method could be implemented easily in medical Doppler ultrasound sys- tems to automatically estimate the Doppler angle and the flow velocity.