Method and device for shear wave elasticity imaging

• US 5,606,971 A
• Filed: 11/13/1995
• Issued: 03/04/1997
• Est. Priority Date: 11/13/1995
• Status: Expired due to Term

• Current Assignee: Armen P. Sarvazyan
• Original Assignee: Artann Corporation
• Inventors: Sarvazyan, Armen P.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US08/555,851
• Time in Patent Office: 477 Days
• Field of Search: 128/660.01, 128/660.02, 128/774, 73/597, 73/602
• US Class Current: 600/438
• 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 8/0858 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 ultrasound transducer which remotely induces a shear wave in a tissue by sending modulated ultrasonic pulses. The shear wave of the frequency of the modulating signal is detected. The values of the shear modulus and dynamic shear viscosity of tissue are evaluated from the measured values of velocity and attenuation of shear waves. 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.

Claims

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

(a) remotely generating shear waves in the tissue using a focused ultrasonic wave transmitted to a focal region of a focused ultrasonic 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 these 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 tissue.

2. The method of claim 1, wherein said focused ultrasonic wave is amplitude modulated for generating said shear waves.

3. The method of claim 1, wherein step (b) comprises measuring an amplitude and a phase of shear waves on the surface of the tissue.

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

(a) remotely generating shear waves in the tissue using an amplitude modulated focused ultrasonic wave;

(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 tissue, wherein step (a) comprises the further step of focusing the amplitude modulated focused ultrasound 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 amplitude modulated focused ultrasound 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.

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

(a) remotely generating shear waves in the tissue using an amplitude modulated focused ultrasonic wave,

(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 tissue, wherein step (b) comprises the further steps of sending and receiving the interrogating ultrasonic waves; and

step (c) includes determining shear wave propagation related parameters in at least one point of the tissue by analyzing sent and received interrogating ultrasonic waves.

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

(a) remotely generating shear waves in the tissue using an amplitude modulated focused ultrasonic wave;

(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 tissue, wherein said amplitude modulated focused ultrasound wave comprises an ultrasound signal which is amplitude modulated with a signal having a frequency in the range 0.3 to 30 kHz.

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

transmitting means for transmitting an amplitude modulated focused ultrasound wave to a focal region of an ultrasonic source so as to induce a shear wave in the tissue;

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 the tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the tissue.

8. The device of claim 7, wherein said transmitting means comprises a single element focused transmitting transducer.

9. The device of claim 7, wherein said transmitting means comprises a phased array transmitting transducer.

10. The device of claim 9, wherein said phased array transducer comprises a piezoelectric flexible composite material and is in a direct contact with the tissue.

11. The device of claim 10, wherein said means to detect shear waves is said transmitting phased array disconnected from the driving circuit generating said amplitude-modulated ultrasonic signals and connected to the receiving circuit operating at the frequency of said modulating signal.

12. The device of claim 7, wherein said detecting means is a magnetic resonance imaging device.

13. The device of claim 7, wherein said detecting means are interrogating electromagnetic waves.

14. The device of claim 7, wherein said detecting means is an interrogating ultrasonic transducer.

15. The device of claim 14, wherein said interrogating ultrasonic transducer is a part of said transmitting transducer.

16. The device of claim 14, wherein said detecting means is an interrogating ultrasonic transducer is said transmitting transducer disconnected from the driving circuit generating said amplitude-modulated ultrasonic signals and connected to the interrogating circuit.

17. The device of claim 14, wherein said interrogating ultrasonic transducer is a separate ultrasonic transducer.

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

transmitting means for transmitting an amplitude modulated focused ultrasound wave to a focal region of a focused ultrasonic source so as to induce a shear wave in the tissue;

detecting means for detecting the shear wave induced in the tissue;

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 the tissue selected from the group of parameters consisting of shear elasticity modulus, Young'"'"'s modulus, dynamic shear viscosity, and mechanical impedance of the tissue, wherein said detecting means is a piezosensitive film placed on the surface of the tissue for detecting said shear waves in the tissue.

19. The device of claim 18, wherein said transmitting means and wherein said the piezosensitive film are mounted in a probe, said piezosensitive film being separated from said transducer by a coupling liquid.

20. The device of claim 18, wherein said transmitting means and wherein said the piezosensitive film are mounted in a probe, said piezosensitive film being mounted on the surface of said transducer.