Quantitative flow measurements with Doppler ultrasound: techniques, accuracy, and limitations.

Using Doppler ultrasound, blood-filled structures appearing on a real-time ultrasound image may be interrogated for flow information. Quantitation of the Doppler signal may yield estimates of instantaneous and time-averaged velocity, volume flow rate, and pressure difference. In this article, the techniques of signal analysis used are discussed, together with the sources of error that confront their clinical application.