Multi-stage digital ultrasound beamformer

1. An ultrasound imaging method comprising:

activating at least one element of an electroacoustic array of elements to generate a series of transmit beams that insonify a region of interest;

performing a receive beamforming process with a receive beamformer, wherein the receive beamforming process comprises:

for each of at least two of the transmit beams of the series of transmit beams, determining a plurality of primary receive beams, and

computing at least one secondary receive beam as a temporally aligned combination of at least two of the primary receive beams corresponding to different transmit beams of the at least two of the transmit beams,

wherein the computing of the at least one secondary receive beam comprises applying dynamic, depth-dependent time delays to temporally align the at least two of the primary receive beams by computing the time delay of at least one of the primary receive beams relative to another one of the primary receive beams,

wherein computing the time delay includes:

simulating conditions corresponding to anticipated transmission conditions of a first prime transmit beam;

determining a first instant transmit pulse pressure field for a transmit pulse on the first prime transmit beam for the conditions at a specified time, which corresponds to a specified depth;

determining centers of the transmit pulse along at least one radius direction from a first beam origin of the first prime transmit beam, wherein the centers of the transmit pulse are determined based on locations of pulses from a plurality of transducer elements;

determining a first transit time between the first transmit origin and an intersection of the instant transmit pulse pressure field at the specified depth and the first prime transmit beam;

determining a second transit time between a second beam origin and an intersection of a second pulse pressure field for a second primary receive beam of the at least two of the primary receive beams; and

determining a time differential as a predetermined function of the first and second transit times; and

in computing at least one of the secondary receive beams, applying to the second primary receive beam a dynamic, depth-dependent delay profile computed as a predetermined function of the time differential, and

wherein the at least two of the primary receive beams comprise primary receive beams with a same focal point and a same receive beam origin; and generating an image as a function of the at least one secondary receive beam.

2. The method of claim 1 , wherein at least one of the plurality of primary receive beams is computed as a function of signals received at a plurality of electroacoustic elements.

3. The method of claim 1 , further comprising computing each secondary receive beam as a function of a time-delayed sum of the at least two of the primary receive beams.

4. The method of claim 3 , further comprising weighting a contribution of each primary receive beam in the sum.

5. The method of claim 4 , wherein weights are time-dependent.

6. An ultrasound imagining system comprising:

a main processing system including at least one processor and at least one memory;

an ultrasound probe that includes an array of electroacoustic elements;

a beamforming system including a transmit beamformer and a receive beamformer;

in which:

the transmit beamformer is provided for activating at least one element of the array to generate a series of transmit beams that insonify a region of interest;

the receive beamformer includes a first stage that is provided for determining a plurality of primary receive beams for each transmit beam of the series of transmit beams;

the receive beamformer includes a second stage provided for computing at least one secondary receive beam as a temporally aligned combination of at least two of the primary receive beams,

wherein the second stage of the receive beamformer computes the at least one secondary receive beam as a temporally aligned combination of at least two of the primary receive beams by computing a time delay of at least one of the primary receive beams relative to another one of the primary receive beams,

wherein computing the time delay is performed by:

simulating conditions corresponding to anticipated transmission conditions of a first prime transmit beam:

determining a first instant transmit pulse pressure field for a transmit pulse on the first prime transmit beam for the conditions at a specified time, which corresponds to a specified depth;

determining centers of the transmit pulse along at least one radius direction from a first beam origin of the first prime transmit beam, wherein the centers of the transmit pulse are determined based on locations of pulses from a plurality of transducer elements;

determining a first transit time between the first transmit origin and an intersection of the instant transmit pulse pressure field at the specified depth and the first prime transmit beam;

determining a second transit time between a second beam origin and an intersection of a second pulse pressure field for a second primary receive beam of the at least two of the primary receive beams; and

determining a time differential as a predetermined function of the first and second transit times; and

in computing at least one of the secondary receive beams, applying to the second primary receive beam a dynamic, depth-dependent delay profile computed as a predetermined function of the time differential,

wherein the at least two of the primary receive beams comprise primary receive beams with a same focal point and a same receive beam origin, and wherein the at least two of the primary receive beams correspond to different transmit beams of the series of transmit beams; and

the main processing system is provided for generating an image as a function of the at least one secondary receive beam and for creating corresponding signals for displaying the image on a display device.

7. The system of claim 6 , in which the first stage is provided for computing at least one of the plurality of primary receive beams as a function of signals received at a plurality of electroacoustic elements in the array.

8. The system of claim 6 , in which the second stage is further provided for computing each secondary receive beam as a function of a time-delayed sum of the at least two of the primary receive beams.

9. The system of claim 6 , in which the array is a one-dimensional array.

10. The system of claim 6 , in which the array is a two-dimensional array.

11. A beamforming system for ultrasound imaging comprising a transmit beamformer and a receive beamformer, in which:

the transmit beamformer is provided for activating at least one element in an array of electroacoustic elements to generate a series of transmit beams that insonify structures in a region of interest;

the receive beamformer includes

a first stage that is provided, for each transmit beam of the series of transmit beams, for determining a plurality of primary receive beams;

a second stage provided

for temporally aligning the plurality of primary receive beams that correspond to ultrasonic return signals from different transmit beams but that are received on a common beam line by applying dynamic, depth-dependent time delays to temporally align the plurality of primary receive beams, in which the common beam line is a line of ultrasound propagation that passes through a same focal point and a corresponding beam origin on the array, wherein temporally aligning the plurality of primary receive beams comprises determining centers of a transmit pulse along at least one radius direction from a first beam origin of a first transmit beam of the series of transmit beams, wherein the centers of the transmit pulse are determined based on locations of pulses from a plurality of electroacoustic elements, and

for computing at least one secondary receive beam as a function of at least two temporally aligned primary receive beams, the at least one secondary receive beam being included in an output of the beamforming system, and wherein the at least two temporally aligned primary receive beams correspond to different transmit beams of the series of transmit beams.

12. The system of claim 11 , in which the second stage is further provided for computing the at least one secondary receive beam as a function of a time-delayed sum of the at least two temporally aligned primary receive beams.