Patent ID: 7611467

Claim:
A method for extracting an envelope curve of a spectrogram, for use in measurement of blood flow velocity by using spectral Doppler techniques, comprising steps of: A. processing RF ultrasound echo signals to obtain Doppler signals; B. performing spectral analysis on the Doppler signals, to obtain a power spectrum P(f) of the Doppler signals which varies over time; C. estimating a forward maximum frequency f max+ and a backward maximum frequency f max− for the Doppler signals at a predetermined moment, according to the power spectrum P(f) of the Doppler signals at the predetermined moment; D. determining a noise frequency range based on the estimated forward maximum frequency and the estimated backward maximum frequency, and estimating an average noise power E within the determined noise frequency range; and E. correcting the forward maximum frequency and the backward maximum frequency by using the average noise power E to obtain the corrected forward maximum frequency F max+ and the corrected backward maximum frequency F max− .