Estimation of Doppler shift frequency using selected phase information for high frame rate color flow mapping

We describe a new approach to processing signals used to estimate shift in Doppler shift frequency in high frame-rate color flow mapping (CFM) with fewer pulse transmissions. When an ultrasound pulse is transmitted to a large number of scatterers, the echoes from the scatterers overlap and interfere with one another. This interference causes the phase of the received echo signal to fluctuate, thus disturbing the estimated shift in Doppler frequency. The technique proposed here eliminates this disturbed phase information, leaving the remaining information for use in estimating the shift in Doppler frequency. The instantaneous frequency of the echo signal can serve as an index of the influence of interference. To test this technique in vivo, we used radio-frequency (RF) echo signals from the carotid artery for simulation and evaluated the error of the estimated Doppler shift frequency in several cases. Performance was enhanced when number of pulses transmitted was limited and this technique was used.