Method and apparatus for elasticity imaging using remotely induced shear wave

• US 5,810,731 A
• Filed: 03/04/1997
• Issued: 09/22/1998
• Est. Priority Date: 11/13/1995
• Status: Expired due to Term

• Current Assignee: Armen P. Sarvazyan
• Original Assignee: Artann Laboratories Inc.
• Inventors: Sarvazyan, Armen P., Rudenko, Oleg V.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US08/812,937
• Time in Patent Office: 567 Days
• Field of Search: 600/438, 600/587, 600/444, 73/597, 73/602
• US Class Current: 600/438
• CPC Class Codes: A61B 5/0051 by applying vibrations
• CPC Class Codes: A61B 5/0093 Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces
• CPC Class Codes: A61B 8/485 involving measuring strain or elastic properties
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/012 Phase angle
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/02475 Tissue characterisation
• CPC Class Codes: G01N 2291/02491 Materials with nonlinear acoustic properties
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/2456 Focusing probes focusing arrangements G01N29/221
• CPC Class Codes: G01N 29/346 with amplitude characteristics, e.g. modulated signal
• CPC Class Codes: G01S 15/8909 using a static transducer configuration
• CPC Class Codes: G01S 7/52042 determining elastic properties of the propagation medium or of the reflective target diagnostic techniques involving the measurement of strain A61B8/485

Abstract

A method and devices for Shear Wave Elasticity Imaging (SWEI). The method employs a focused acoustic pulse which remotely induces a shear wave in tissue. The values of the shear modulus and dynamic shear viscosity of tissue are evaluated from the values of propagation parameters of shear acoustic waves detected by various means including Doppler ultrasound and Magnetic Resonance Imaging. Several devices for carrying out the method are described. Devices based on the method can be used as a diagnostic tool in the detection of abnormalities in tissue, such as those caused by cancer or other lesions and characterizing processes in tissues accompanied by changes in their mechanical properties. The devices can also be used for assessment of brain tissue and evaluation of the biomechanical state of muscle.

Claims

1. A method for determining the elasticity of tissue, comprising the steps of:

(a) remotely generating shear waves in the tissue using radiation force of a focused acoustic wave transmitted to a focal region of a focused acoustic source;

(b) detecting shear waves generated in the tissue;

(c) determining at least one propagation parameter of the shear waves in the tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of tissue particles; and

(d) calculating, based on the results of step (c), at least one mechanical parameter of tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the of tissue.

2. The method of claim 1, wherein said focused acoustic wave is a single acoustic pulse with duration in the range 10^-2 to 10^-9 seconds.

3. A method for determining the elasticity of muscle tissue, comprising the steps of:

(a) remotely generating shear waves in the muscle tissue using a focused acoustic wave;

(b) detecting shear waves generated in the muscle tissue;

(c) determining at least one propagation parameter of the shear waves in the muscle tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of muscle tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of muscle tissue particles; and

(d) calculating, based on the results of step (c), at least one mechanical parameter of the muscle tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the muscle of the tissue.

4. The method of claim 3 wherein said focused acoustic wave is an amplitude modulated focused ultrasound wave.

5. The method of claim 3 wherein said focused acoustic wave is a single acoustic pulse.

6. The method of claim 5 wherein said single acoustic pulse has duration in the range of 10^-2 to 10^-9.

7. A method for determining the elasticity of brain tissue, comprising the steps of:

(a) remotely generating shear waves in the brain tissue using a focused acoustic pulse;

(b) detecting shear waves generated in the tissue;

(c) determining at least one propagation parameter of the shear waves in the brain tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of brain tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of brain tissue particles; and

(d) calculating, based on the results of step (c), at least one mechanical parameter of the brain tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the of tissue.

8. The method of claim 7 wherein step (a) comprises the further step of focusing the acoustic wave at different locations in the tissue so as to generate the shear waves in the different locations in the tissue;

and

wherein the method comprises the further steps of;

repeating steps (b), (c) and (d) for each focused acoustic wave focused at said different locations in the tissue, and

displaying the calculated values of dynamic shear viscosity and shear elasticity modulus as a function of the coordinates of said different locations in the tissue.

9. The method of claim 8 wherein said focused acoustic wave is a single acoustic pulse.

10. A device for determining elasticity of tissue, comprising:

transmitting means for transmitting a focused acoustic wave to a focal region so as to induce a shear wave in the tissue at said focal region;

detecting means for detecting the shear wave induced in the tissue at said focal region;

means for determining at least one propagation parameter of the shear waves in the tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of tissue particles; and

calculating means for evaluating at least one mechanical parameter of tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the of tissue.

11. The device of claim 10, wherein said transmitting means comprises an electrohydraulic acoustic transducer.

12. The device of claim 10, wherein said transmitting means comprises an optoacoustic source.

13. The device of claim 10, wherein said detecting means is a magnetic resonance imaging device.

14. The device of claim 10, wherein said detecting means is an interrogating ultrasonic transducer.

15. The device of claim 10, wherein said detecting means are electromagnetic waves induced by the shear motion of the tissue at said focal region.

16. The device of claim 10 where said detecting means is low frequency shear wave detector.

17. A device for determining elasticity of muscle tissue, comprising:

transmitting means for transmitting a focused acoustic wave to a focal region so as to induce a shear wave in the muscle tissue at said focal region;

detecting means for detecting the shear wave induced in the muscle tissue at said focal region;

means for determining at least one propagation parameter of the shear waves in the muscle tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of muscle tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of muscle tissue particles; and

calculating means for evaluating at least one mechanical parameter of muscle tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the of muscle tissue.

18. The device of claim 17, wherein said detecting means is an interrogating ultrasonic transducer.

19. The device of claim 17, wherein said transmitting means transmits a focused acoustic wave through intact skull bone.

20. A device for determining elasticity of brain tissue, comprising:

transmitting means for transmitting a focused acoustic wave to a focal region so as to induce a shear wave in the brain tissue at said focal region;

detecting means for detecting the shear wave induced in the brain tissue at said focal region;

means for determining at least one propagation parameter of the shear waves in the brain tissue selected from the group of parameters consisting of shear wave velocity, shear wave attenuation coefficient, amplitude and velocity of shear displacement of brain tissue particles in the propagating shear wave;

spatial and temporal dependencies of said amplitude and velocity of shear displacement of brain tissue particles; and

calculating means for evaluating at least one mechanical parameter of brain tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the of brain tissue.

21. The device of claim 20, wherein said detecting means is a magnetic resonance imaging device.

22. The device of claim 21, wherein said skull bone comprises temporal bone.

23. The device of claim 20 wherein said focused acoustic wave is a single acoustic pulse.