Ultrasound diagnostic flow imaging with coded excitation

1. A method for ultrasound diagnostic motion imaging, the method comprising the acts of:

transmitting a plurality of coded excitation pulses;

estimating a motion parameter as a function of the coded excitation pulses, the motion parameter comprising velocity, energy, variance or combinations thereof, the motion parameter estimated for each of a plurality of locations;

generating a tissue image;

accounting for a misalignment caused by decoding the coded excitation pulses; and

offsetting a spatial position, by the misalignment due to the use of the coded excitation pulses, of the motion parameters of the plurality of the locations relative to the tissue image.

2. The method of claim 1 wherein transmitting comprises transmitting chirp coded excitation pulses, estimating comprises estimating the velocity, energy, variance or combinations thereof from decoded signals received in response to the chirp coded excitation pulses, and generating the tissue image comprises generating a B-mode image; and further comprising:

displaying a flow image with the B-mode image, the flow image being of the plurality of locations and being a function of the velocity, energy, variance or combination thereof;

wherein offsetting comprises registering the flow image relative to the B-mode image.

3. The method of claim 1 wherein offsetting comprises offsetting along a range dimension.

4. The method of claim 1 wherein offsetting comprises compensating, at least in part, for a range shift from a depth varying decoding filter responsive to depth dependent demodulation.

5. The method of claim 1 wherein offsetting comprises applying an offset delay in addition to focusing delays.

6. The method of claim 1 wherein offsetting comprises:

demodulating with a depth dependent demodulation center frequency;

modulating signals as a function of a difference between the depth dependent demodulation center frequency and a transmit modulation center frequency;

decoding the modulated signals; and

demodulating the decoded signals back to base-band.

7. The method of claim 1 wherein offsetting comprises remapping spatially a motion parameter location relative to the tissue image.

8. The method of claim 1 further comprising:

correcting the motion parameters or the estimation for a depth-dependent frequency shift.

9. The method of claim 1 wherein estimating comprises estimating the motion parameter at a first frequency band as a function of the coded excitation pulses;

further comprising:

estimating an additional flow parameter at a second frequency band as a function of the coded excitation pulses, the second frequency band different than the first frequency band; and

anti-aliasing as a function of the flow parameters.

10. The method of claim 1 wherein accounting for a misalignment caused by decoding the coded excitation pulses comprises accounting for the misalignment caused by decoding the coded excitation pulses having a frequency sweep, the frequency sweep resulting in the misalignment.

11. A method for ultrasound diagnostic motion imaging, the method comprising the acts of:

transmitting a plurality of coded excitation pulses into an object;

estimating values of a motion parameter as a function of the coded excitation pulses for different locations, the motion parameter comprising velocity, energy, variance, or combinations thereof;

correcting the values or the estimation of the values for a depth-dependent frequency shift due to frequency dependent tissue attenuation caused by use of the coded excitation pulses; and

generating, using the values, an image as a function of the corrected motion parameter or estimation, the image comprising a velocity, energy, or variance image representing the different locations.

12. The method of claim 11 wherein correcting comprises compensating variation of an imaging center frequency with depth.

13. The method of claim 11 wherein estimating comprises estimating the velocity or Doppler frequency shift as a function of a speed of sound and an estimated receive imaging center frequency.

14. The method of claim 13 wherein correcting comprises correcting the estimation by varying the estimated receive imaging center frequency as a function of depth.

15. The method of claim 13 wherein estimating comprises estimating with the imaging center frequency substantially fixed as function of depth, and correcting comprises altering the velocity.

16. The method of claim 15 wherein altering the velocity comprises color mapping.

17. The method of claim 11 further comprising:

offsetting a spatial position of the motion parameter relative to a tissue image.

18. The method of claim 11 wherein estimating comprises estimating the flow parameter at a first frequency band as a function of the coded excitation pulses;

further comprising:

estimating an additional flow parameter at a second frequency band as a function of the coded excitation pulses, the second frequency band different than the first frequency band; and

anti-aliasing as a function of the flow parameters.

19. A method for ultrasound diagnostic flow imaging, the method comprising the acts of:

transmitting a plurality of coded excitation pulses into an object;

estimating a first flow parameter at a first frequency band as a function of the coded excitation pulses;

estimating a second flow parameter at a second frequency band as a function of the coded excitation pulses, the second frequency band different than the first frequency band;

anti-aliasing a velocity estimate as a function of the first and second flow parameters; and

generating an image as a function of the anti-aliased velocity estimate.

20. The method of claim 19 wherein:

estimating the first flow parameter comprises demodulating to a first center frequency of the first frequency band, filtering to the first frequency band and estimating flow; and

estimating the second flow parameter comprises demodulating to a second center frequency of the second frequency band, filtering to the second frequency band and estimating flow.

21. The method of claim 19 wherein estimating the first flow parameter comprises estimating the first flow parameter with data from the first frequency band, the first frequency band more narrow than the second frequency band.

22. The method of claim 21 wherein the second frequency band generally corresponds to 60% or more of a transducer response or a spectrum of signals received in response to the coded excitation pulses, the first frequency band generally corresponds to 40% or less of the transducer response or the spectrum, and the first frequency band has a first center frequency lower than a second center frequency of the second frequency band.

23. The method of claim 19 wherein anti-aliasing comprises:

predicting a third flow parameter as a function of the first flow parameter and a ratio of a second center frequency of the second frequency band to a first center frequency of the first frequency band, and

comparing a difference from the third flow parameter and the second flow parameter to a threshold.

24. The method of claim 23 wherein comparing comprises comparing to the threshold, the threshold being a pulse repetition frequency of the coded excitation pulses divided by about two.

25. The method of claim 23 wherein anti-aliasing further comprises estimating the velocity estimate as a function of the first flow parameter where the difference is greater than the threshold or less than a negative of the threshold or, otherwise, as a function of the second flow parameter and an inverse of the ratio.

26. The method of claim 23 wherein anti-aliasing further comprises truncating velocities greater than a scale setting.

27. The method of claim 19 further comprising:

offsetting a spatial position of the anti-aliased velocity estimate relative to a tissue image; and

correcting the anti-aliased velocity estimate or velocity estimation for a depth-dependent frequency shift.