Ultrasound super resolution imaging

1. An apparatus, comprising:

a processor, including:

a combiner configured to combine sets of contrast data acquired with a same sub-aperture, for each of a plurality of sub-apertures, to create a contrast frame for each of the sub-apertures;

a microbubble detector configured to determine positions of microbubbles in the contrast frames;

a motion estimator configured to estimate a motion field based on frames of B-mode data for each of the plurality of sub-apertures; and

a motion corrector configured to motion correct the positions of the microbubbles in the contrast frames based on the motion field and time delays between emissions for the sets of contrast data and the corresponding emission for B-mode data, for each of the plurality of sub-apertures, to produce motion corrected contrast frames; and

a display configured to visually display the motion corrected contrast frames, wherein the motion corrected contrast frames include super resolution images.

2. The apparatus of claim 1 , wherein the motion corrector iteratively assigns motion estimates by:

1) calculating a time delay between each an image line of a contrast frame and an image line of the B-mode frame for a same sub-aperture;

2) updating a position of an estimated bubble in the contrast frame based on the motion field and the time delay;

3) updating the image line in the contrast frame; and

repeating 1), 2) and 3) until stopping criteria is satisfied.

3. The apparatus of claim 1 , wherein the processor further comprises:

a microbubble tracker configured to link the microbubbles from frame to frame across the motion corrected contrast frames to produce the super resolution images.

4. The apparatus of claim 3 , wherein the processor links the microbubbles across the motion corrected contrast frames based on hierarchical tracking.

5. The apparatus of claim 1 , wherein the microbubble detector extracts a centroid of a microbubble to determine a position of the microbubble in a contrast frame.

6. The apparatus of claim 5 , wherein the microbubble detector extracts the centroid of the microbubble by enhancing a signal-to-noise ratio of the frame and then localizing the centroid in the signal-to-noise ratio enhanced frame.

7. The apparatus of claim 1 , wherein the motion estimator determines the motion field using speckle tracking on envelope data.

8. The apparatus of claim 1 , wherein the motion estimator cross-correlates each of a plurality of sub-regions of a reference B-mode frame with corresponding sub-regions in the other B-mode frames, and motion in axial and lateral directions is determined.

9. The apparatus of claim 8 , wherein the sub-regions are partially overlapping sub-regions.

10. The apparatus of claim 8 , wherein the motion estimator assigns a motion estimate for a sub-region to a center region of the sub-region, and a collection of all of the motion estimates for all of the sub-regions of a frame is a discrete motion field through the frame.

11. The apparatus of claim 1 , wherein the super resolution images includes an intensity super resolution image.

12. The apparatus of claim 1 , wherein the super resolution images includes a velocity super resolution image.

13. The apparatus of claim 1 , further comprising:

a transducer array configured to transmit an ultrasound pressure field and receive an echo pressure field for a contrast-enhanced scan to acquire the contrast data and the B-mode data.

14. The apparatus of claim 13 , wherein the processor is configured employ a pulse amplitude modulation sequence to acquire the contrast data and the B-mode data.

15. A method, comprising:

combining sets of contrast data acquired with a same sub-aperture, for each of a plurality of sub-apertures, to create a contrast frame for each of the sub-apertures;

determining positions of microbubbles in the contrast frames;

estimating a motion field based on frames of B-mode data for each of the plurality of sub-apertures;

motion correcting the positions of the microbubbles in the contrast frames based on the motion field and time delays between emissions for the sets of contrast data and the corresponding emission for B-mode data, for each of the plurality of sub-apertures, to produce motion corrected contrast frames; and

displaying the motion corrected contrast frames, wherein the motion corrected contrast frames include super resolution images.

16. The method of claim 15 , further comprising:

1) calculating a time delay between an image line of a contrast frame and an image line of the B-mode frame for a same sub-aperture;

2) updating a position of an estimated bubble in the contrast frame based on the motion field and the time delay;

3) updating the image line in the contrast frame; and

repeating 1), 2) and 3) until stopping criteria is satisfied.

17. The method of claim 15 , further comprising:

linking the microbubbles across the motion corrected contrast frames to produce

the super resolution images via a hierarchical tracking.

18. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to:

combine sets of contrast data acquired with a same sub-aperture, for each of a plurality of sub-apertures, to create a contrast frame for each of the sub-apertures;

determine positions of microbubbles in the contrast frames;

estimate a motion field based on frames of B-mode data for each of the plurality of sub-apertures; and

motion correcting the positions of the microbubbles in the contrast frames based on the motion field and time delays between emissions for the sets of contrast data and the corresponding emission for B-mode data, for each of the plurality of sub-apertures, to produce motion corrected contrast frames.

19. The computer-readable storage medium of claim 18 , wherein, for microbubble position determination and motion correcting the positions, the instructions cause the computer to:

1) calculate a time delay between an image line of a contrast frame and an image line of the B-mode frame for a same sub-aperture;

2) update a position of an estimated bubble in the contrast frame based on the motion field and the time delay;

3) update the image line in the contrast frame; and

repeating 1), 2) and 3) until stopping criteria is satisfied.

20. The computer-readable storage medium of claim 18 , wherein the instructions further cause the computer to:

link the microbubbles across the motion corrected contrast frames to produce a super resolution images via a hierarchical tracking; and

display the super resolution image.