Elastography using ultrasound imaging of a thin volume

Patent metadata

Field	Value
Publication number	US-10667791-B2
Application number	US-201214239775-A
Country	US
Kind code	B2
Filing date	Aug 17, 2012
Priority date	Aug 19, 2011
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

The embodiments described herein relate generally to an elastography method and system for obtaining ultrasound images of an excited tissue over a certain time period, then computationally determining one or more mechanical properties of the tissue within a real time refresh rate. This method can perform elastography in real time as only a thin volume of the excited tissue is imaged and processed. The thin volume includes a desired cross-sectional plane of the tissue and at least two adjacent planes that are adjacent to the desired cross-sectional plane. A maximum number of adjacent planes is selected so that a computer system is capable of computationally determining mechanical properties within a real time refresh rate.

First claim

The invention claimed is:

1. An elastography method for imaging at least one mechanical property of a tissue in a desired cross-sectional plane of said tissue, the method comprising:
applying a steady-state vibration to said tissue to generate time varying tissue displacements in said tissue;
ultrasound imaging a thin volume of said tissue over a time period by acquiring a set of image data representing the thin volume over said time period, the thin volume including said desired cross-sectional plane and at least two planes adjacent to said desired cross-sectional plane;
for each of a plurality of spatial points in the thin volume, computationally estimating a time varying estimated displacement of the tissue at the point over the time period using the set of image data, wherein at least one of the spatial points is located on each of the cross-sectional plane and the adjacent planes; and
adjusting the time varying estimated displacements to compensate for phase differences among the estimated displacements for different ones of the spatial points, the phase differences resulting from differences in times at which the ultrasound imaging images the different ones of the spatial points, the adjusting causing phases of the plurality of time varying estimated displacements to be synchronized relative to a common reference time; and
computationally determining said at least one mechanical property of said tissue on said desired cross-sectional plane by using said plurality of phase-synchronized estimated displacements;
wherein the number of adjacent planes is selected such that said at least one mechanical property of said tissue can be computationally determined within a real time refresh rate.

2. A method as claimed in claim 1 wherein real time refresh rate is at least one new frame per five seconds.

3. A method according to claim 1 , wherein said thin volume is imaged by a single three dimensional (3D) ultrasound probe.

4. A method according to claim 1 , wherein the estimated displacement is in a direction of propagation of ultrasound of the ultrasound imaging.

5. A method according to claim 1 , wherein said at least one mechanical property includes any one or more properties selected from absolute elasticity, absolute shear modulus, absolute shear wave speed, and absolute viscosity.

6. A method according to claim 4 , wherein said at least one mechanical property is calculated from said plurality of estimated displacements by using any one or a combination of finite element method, local frequency estimators, travelling wave expansion and direct inversion.

7. A method according to claim 1 , wherein said image data comprises a plurality of RF-lines, a time of acquisition for each of the plurality of RF-lines is recorded, and the method comprises:
computing a delay of each of the RF: lines with respect to a period of the steady-state vibration based on the time of acquisition.

8. A method according to claim 1 , wherein said image data comprises a plurality of RF-lines which are acquired line-by-line with equal time intervals, and the method comprises:
computing a delay of each RF-line with respect to a period of the steady-state vibration based on the time intervals.

9. A method according to claim 8 , wherein the steady-state vibration is synchronized with the acquisition of the RF-lines, so that each RF-line is acquired at a constant delay with respect to the period of vibration.

10. A method according to claim 1 , wherein the acquisition of image data of each of the planes in the thin volume is synchronized with a period of the steady-state vibration.

11. A method according to claim 1 , wherein the steady-state vibration is a harmonic sinusoidal excitation.

12. A method according to claim 1 , wherein the steady-state vibration is a sum of multiple sinusoidal excitations with different frequencies, and different amplitudes and phases.

13. A method according to claim 12 , wherein the ultrasound imaging comprises acquiring a plurality of RF-lines, the frequencies of excitation share a common period and the acquisition of each of the plurality of RF-lines is synchronized with the common period, a rational fraction or an integer multiple of the common period.

14. A method according to claim 1 , wherein said thin volume has extents of the volume in the desired plane that are larger than the extent of the volume in a third dimension perpendicular to the desired plane by a factor of at least 3.

15. An elastography system for imaging at least one mechanical property of a tissue in a desired cross-sectional plane of said tissue, comprising:
at least one vibration source configured to generate a steady-state vibration in the tissue;
a three dimensional (3D) ultrasound probe configured to acquire a set of image data over a time period, the image data representing a thin volume of a tissue including a desired cross-sectional plane and at least two adjacent planes adjacent to said desired plane;
circuitry communicative with the ultrasound probe to receive the image data therefrom and comprising a processor with a memory having programmed thereon steps and instructions for execution by the processor to:
computationally estimate a time varying estimated displacement of tissue for each of a plurality of spatial points in said thin volume wherein at least one of the spatial points is located on each of the cross-sectional plane and the adjacent planes; and
adjust the time varying estimated displacements to compensate for phase differences among the estimated displacements for different ones of the spatial points, the phase differences resulting from differences in times at which the image data corresponding to the different ones of the spatial points were acquired, the adjusting causing phases of the plurality of time varying estimated displacements to be synchronized relative to a common reference time; and
computationally determine said at least one mechanical property of the tissue on the desired cross-sectional plane by using said plurality of phase-synchronized estimated displacements, wherein the number of adjacent planes is selected such that said at least one mechanical property of the tissue can be computationally determined within a real time refresh rate; and

a display device communicative with the circuitry to receive and display one or more images of the desired cross-sectional plane and said determined at least one mechanical property of the tissue within the real-time refresh rate.

16. An elastography system according to claim 15 , wherein said image data comprises a plurality of RF-lines, and the circuitry is configured to record the time of acquisition for each of the plurality of RF-lines.

17. An elastography system according to claim 15 , wherein said image data comprises a plurality of RF-lines, and said ultrasound probe is configured to acquire the RF-lines one-by-one with equal time intervals.

18. An elastography system according to claim 15 , wherein said image data comprises a plurality of RF-lines and said at least one vibration source and said ultrasound probe are configured in a manner that the steady-state vibration is synchronized with the acquisition of the RF-lines, so that each RF-line is acquired at a constant delay with respect to the period of vibration.

19. An elastography system according to claim 15 , wherein said at least one vibration source is configured to generate a harmonic sinusoidal excitation.

20. An elastography system according to claim 15 , wherein said at least one vibration so

Assignees

• Baghani Ali
• Eskandari Hani
• Rohling Robert N
• Salcudean Septimu E
• Univ British Columbia

Inventors

• Baghani Ali
• Eskandari Hani
• Rohling Robert N
• Salcudean Septimu E

Classifications

• A61B8/12

  in body cavities or body tracts, e.g. by using catheters · CPC title

• A61B8/5223

  for extracting a diagnostic or physiological parameter from medical diagnostic data (for algorithms to analyse biomedical images G06T7/0012) · CPC title

• A61B8/483

  involving the acquisition of a 3D volume of data · CPC title

• A61B8/463

  characterised by displaying multiple images or images and diagnostic data on one display · CPC title

• A61B8/485 Primary

  involving measuring strain or elastic properties · CPC title