A system for imaging flow of ultrasound scatterers, comprising: an ultrasound transducer array comprising a multiplicity of transducer elements; transmit means coupled to said transducer array for pulsing a set of selected transducer elements which form a transmit aperture with a first coded pulse sequence during first and third transmit firings and with a second coded pulse sequence during second and fourth transmit firings, said first through fourth transmit firings being focused at substantially the same transmit focal position, said first coded pulse sequence being a function of a first transmit code convolved with a base pulse sequence, said second coded pulse sequence being a function of a second transmit code convolved with said base pulse sequence, and said first and second transmit codes being complementary; acquisition means coupled to said transducer array for acquiring first through fourth beamsummed signals subsequent to said first through fourth transmit firings respectively; means for matched filtering said first and third beamsummed signals using a first set of filter coefficients which match said first transmit code to form first and third partly decoded signals and matched filtering said second and fourth beamsummed signals using a second set of filter coefficients which match said second transmit code to form second and fourth partly decoded signals; means for forming a first signal representing a difference between a sum of said first and second partly decoded signals and a sum of said third and fourth partly decoded signals; means for estimating a flow parameter as a function of at least said first signal to form a flow image signal; and means for displaying an image which is a function of said flow image signal. 1578 ב' באב התשס" ג - July 31, 2003
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