Doppler angle and flow velocity estimations using the classic and transverse Doppler effects

Current clinical Doppler ultrasound systems could only measure the flow vec tor parallel to the ultrasound beam axis, and the knowledge of the Doppler angle (beam-to-flow angle) is needed to calculate the real Row velocity. Cu rrently, the Doppler angle is determined visually by manually aligning a ve ssel axis marker along the blood vessel on the duplex scan image of the ult rasound. The application of this procedure is often limited by practical co nstraints; therefore, measurements are not reliable. In order to overcome t his problem, we developed a simple Doppler angle and flow velocity estimati on method using a combination of the classic and transverse Doppler effects . This method uses only a single focused annular array transducer to estima te the Doppler angle and the Row velocity. We have verified experimentally that this method is successful for measuring constant flow in a flow phanto m between 45 degrees and 80 degrees Doppler angle. The standard deviation o f the estimated Doppler angles is less than 4.5 degrees. This method could be implemented easily in medical Doppler ultrasound systems to automaticall y estimate the Doppler angle and the flow velocity.