Methods and apparatus to determine shear wave propagation property

1. A method comprising:

applying a first plurality of focused ultrasound pulses to biological tissue to create shear waves in the biological tissue, each of the first plurality of focused ultrasound pulses being focused at a different focal point;

simultaneously transmitting a second plurality of focused ultrasound pulses into the biological tissue;

after applying the first plurality of ultrasound pulses and simultaneously transmitting the second plurality of focused ultrasound pulses, receiving a plurality of ultrasound signals from the biological tissue generated in response to the second plurality of focused ultrasound pulses;

determining displacement of the biological tissue based on the received plurality of ultrasound signals;

detecting the shear waves in the biological tissue based on the received plurality of ultrasound signals;

determining a shear wave propagation velocity based on the detected shear waves and on a square root of a ratio between a temporal second-order derivative of the displacement of the biological tissue and a spatial second-order derivative of the displacement of the biological tissue; and

displaying the shear wave propagation velocity.

2. A method according to claim 1 , wherein determining the shear wave propagation velocity comprises calculating a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the detected shear waves at one or multiple instances.

3. A method according to claim 1 wherein the second plurality of focused ultrasound pulses comprise coded waveform signals.

4. A method according to claim 3 wherein the coded waveform signals comprise one or more of Chirp codes, Barker codes, Golay codes or Hadamard codes.

5. A method according to claim 1 , wherein detecting the shear waves comprises determining a velocity of the biological tissue using a color Doppler technique.

6. A method according to claim 1 , wherein determining a displacement of the biological tissue comprises calculating a time integral of tissue color Doppler velocity.

7. A method according to claim 1 , wherein transmitting the second plurality of focused ultrasound pulses comprises transmitting a third focused ultrasound pulse from a transducer after transmitting a fourth focused ultrasound pulse and before the fourth focused ultrasound pulse returns to the transducer from a deepest position in an ultrasound field.

8. A method according to claim 1 , wherein transmitting the second plurality of focused ultrasound pulses comprises transmitting the second plurality of focused ultrasound pulses into the biological tissue more than one time; and

wherein receiving the plurality of ultrasound signals from the biological tissue comprises receiving the plurality of ultrasound signals from the biological tissue generated in response to the second plurality of focused ultrasound pulses at one or more instances.

9. A method according to claim 1 , wherein detecting the shear waves comprises calculating a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the received ultrasound signals at one or multiple positions in time.

10. A non-transitory medium storing processor-executable program code, the program code executable by a device to:

apply a first plurality of focused ultrasound pulses to biological tissue to create shear waves in the biological tissue, each of the first plurality of focused ultrasound pulses being focused at a different focal point;

simultaneously transmit a second plurality of focused ultrasound pulses into the biological tissue;

receive, after application of the first plurality of ultrasound pulses and simultaneous transmission of the second plurality of focused ultrasound pulses, a plurality of ultrasound signals from the biological tissue generated in response to the second plurality of focused ultrasound pulses;

determine displacement of the biological tissue based on the received plurality of ultrasound signals;

detect the shear waves in the biological tissue based on the received plurality of ultrasound signals;

determine a shear wave propagation velocity based on the detected shear waves and on the square root of a ratio between a temporal second-order derivative of the displacement of the biological tissue and a spatial second-order derivative of the displacement of the biological tissue; and

display the shear wave propagation velocity.

11. A medium according to claim 10 , wherein determination of the shear wave propagation velocity comprises calculating a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the detected shear waves at one or multiple instances.

12. A medium according to claim 10 , wherein the second plurality of focused ultrasound pulses comprise coded waveform signals.

13. A medium according to claim 12 , wherein the coded waveform signals comprise one or more of Chirp codes, Barker codes, Golay codes or Hadamard codes.

14. A medium according to claim 10 , wherein detection of the shear waves comprises determination of a velocity of the biological tissue using a color Doppler technique.

15. A medium according to claim 10 , wherein determination of a displacement of the biological tissue comprises calculation of a time integral of tissue color Doppler velocity.

16. A medium according to claim 10 , wherein transmission of the second plurality of focused ultrasound pulses comprises transmission of a third focused ultrasound pulse from a transducer after transmission of a fourth focused ultrasound pulse and before the fourth focused ultrasound pulse returns to the transducer from a deepest position in an ultrasound field.

17. A medium according to claim 10 , wherein transmission of the second plurality of focused ultrasound pulses comprises transmission of the second plurality of focused ultrasound pulses into the biological tissue more than one time; and

wherein reception of the plurality of ultrasound signals from the biological tissue comprises reception of the plurality of ultrasound signals from the biological tissue generated in response to the second plurality of focused ultrasound pulses at one or more instances.

18. A medium according to claim 10 , wherein detection of the shear waves comprises calculation of a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the received ultrasound signals at one or multiple positions in time.

19. A system comprising:

a memory storing processor-executable program code; and

a processor to execute the processor-executable program code in order to cause the system to:

apply a first plurality of focused ultrasound pulses to biological tissue to create shear waves in the biological tissue, each of the first plurality of focused ultrasound pulses being focused at a different focal point;

simultaneously transmit a second plurality of focused ultrasound pulses into the biological tissue;

receive, after application of the first plurality of ultrasound pulses and simultaneous transmission of the second plurality of focused ultrasound pulses, a plurality of ultrasound signals from the biological tissue generated in response to the plurality of focused ultrasound pulses;

determine displacement of the biological tissue based on the received plurality of ultrasound signals;

detect the shear waves in the biological tissue based on the received plurality of ultrasound signals;

determine a shear wave propagation velocity based on the detected shear waves and on the square root of a ratio between a temporal second-order derivative of the displacement of the biological tissue and a spatial second-order derivative of the displacement of the biological tissue; and

display the shear wave propagation velocity.

20. A system according to claim 19 , wherein determination of the shear wave propagation velocity comprises calculating a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the detected shear waves at one or multiple instances.

21. A system according to claim 19 , wherein the plurality of focused ultrasound pulses comprise coded waveform signals.

22. A system according to claim 21 , wherein the coded waveform signals comprise one or more of Chirp codes, Barker codes, Golay codes or Hadamard codes.

23. A system according to claim 19 , wherein detection of the shear waves comprises determination of a velocity of the biological tissue using a color Doppler technique.

24. A system according to claim 19 , wherein transmission of the second plurality of focused ultrasound pulses comprises:

transmission of a third focused ultrasound pulse from a transducer after transmission of a fourth focused ultrasound pulse and before the fourth focused ultrasound pulse returns to the transducer from a deepest position in an ultrasound field.

25. A system according to claim 19 , wherein transmission of the second plurality of focused ultrasound pulses comprises transmission of the second plurality of focused ultrasound pulses into the biological tissue more than one time; and

wherein reception of the plurality of ultrasound signals from the biological tissue comprises reception of the plurality of ultrasound signals from the biological tissue generated in response to the second plurality of focused ultrasound pulses at one or more instances.

26. A system according to claim 19 , wherein detection of the shear waves comprises calculation of a correlation, a sum of absolute differences (SAD), a sum of square differences (SSD), a sum of absolute cubic differences (SCD) or a sum of absolute power differences (SPD) between the received ultrasound signals at one or multiple positions in time.