Abstract

A velocity estimation technique is provided for a pulse-echo ultrasonic diagnostic system in which a two dimensional array of samples is acquired from a sample volume. The two dimensions of the array are depth, in which echo signal samples are acquired in response to transmission of a pulse to the sample volume, and pulse time, in which samples are acquired in response to transmission of the pulses in the pulse ensemble to the sample volume. Two autocorrelation calculations are performed on the array, one in the depth dimension and another in the pulse time dimension to yield two correlation functions, the first related to echo frequency and the second related to the Doppler frequency. The two correlation functions are then employed in a Doppler velocity estimation to determine the velocity of motion at the sample volume. The technique utilizes the full information content present in the bandwidth of the received echo signals, thereby overcoming inaccuracies due to depth dependent frequency decline or coherent signal cancellation. Since accuracy is premised upon the number of samples in the array and not its size in a particular dimension, performance can be tailored to favor frame rate or axial resolution while maintaining the accuracy of velocity estimation.