Doppler ultrasound velocity estimation

Abstract

A spatial-temporal doppler velocity estimation method expands the detectable frequency range by extending the frequency boundary at which aliasing artifacts may occur. In various embodiments the detectable frequency range is extended beyond the Nyquist limit. To do so, multiple velocity estimation functions are defined. One function is the conventional function typically bound by the Nyquist limit. For additional functions, the (n-1)-th echo is spatially shifted with respect to the n-th echo, (i.e., temporal/spatial pulse-pairs are averaged). For example, in one embodiment a shift of +Δ is inserted to define one additional estimation function, while a shift of -Δ is inserted to define another additional estimation function. A power function then is calculated for each velocity estimation function. The estimation function having the highest power is selected for use in deriving the doppler shift frequency of a given sample point. By selecting a one of the K+1 velocity estimation functions with the highest power, the detectable frequency range, f, becomes: -(2 K /2)f s <f<(2 K /2)f s , where f s is the Doppler sampling frequency.