Method and apparatus for pulsed doppler imaging using coded excitation on transmit and pulse compression on receive

A method for estimating and displaying Doppler frequency shifts produced by moving ultrasound scatterers, comprising the steps of:

• producing a first coded pulse sequence which is a function of a first transmit code convolved with a base pulse sequence;
• driving a first set of transducer elements forming a transmit aperture in a transducer array with said first coded pulse sequence during a first transmit firing;
• receiving a first set of echo signals from a second set of transducer elements forming a receive aperture in the transducer array subsequent to said first transmit firing;
• forming a first beamsummed signal derived from said first set of echo signals;
• compressing said first beamsummed signal to form a first compressed pulse sequence;
• driving said first set of transducer elements forming said transmit aperture with said first coded pulse sequence during a second transmit firing, said first and second transmit firings being focused at substantially the same transmit focal position;
• receiving a second set of echo signals from said second set of transducer elements forming said receive aperture subsequent to said second transmit firing;
• forming a second beamsummed signal derived from said second set of echo signals;
• compressing said second beamsummed signal to form a second compressed pulse sequence;
• acquiring a set of Doppler frequency shift data which is dependent in part on said first and second compressed pulse sequences;
• and
• displaying a spectral line which is a function of said set of Doppler frequency shift data.

A system for estimating and displaying Doppler frequency shifts produced by moving ultrasound scatterers, comprising:

• an ultrasound transducer array for transmitting ultrasound waves and detecting ultrasound echoes reflected by said ultrasound scatterers, said transducer array comprising a multiplicity of transducer elements;
• transmit means coupled to said transducer array for pulsing selected transducer elements which form a transmit aperture with a coded pulse sequence during first and second transmit firings which are focused at substantially the same transmit focal position, said coded pulse sequence being a function of a transmit code convolved with a base pulse sequence;
• receive means coupled to said transducer array for receiving first and second sets of signals from selected transducer elements which form a receive aperture subsequent to said first and second transmit firings respectively;
• means for forming a first and second beamsummed signals respectively derived from said first and second sets of signals;
• means for demodulating said first and second beamsummed signals to form first and second demodulated signals respectively;
• a decoding filter for compressing said first and second demodulated signals to form first and second compressed pulse sequences respectively;
• processing means for producing a set of Doppler frequency shift data which is dependent in part on said first and second compressed pulse sequences;
• and
• means for displaying a spectral line which is a function of said set of Doppler frequency shift data.