WO2017121170A1

WO2017121170A1 - Tissue parameter detection method and system

Info

Publication number: WO2017121170A1
Application number: PCT/CN2016/103651
Authority: WO
Inventors: 邵金华; 孙锦; 段后利; 王强
Original assignee: 无锡海斯凯尔医学技术有限公司
Priority date: 2016-01-11
Filing date: 2016-10-27
Publication date: 2017-07-20
Also published as: CN105662473A

Abstract

A tissue parameter detection method and system. The method comprises: controlling an excitation apparatus (2) to excite, in a tissue, N shear waves with different excitation characteristics by taking a pre-set time interval as a period, and controlling a first ultrasonic transducer (3) to transmit, to a tissue, an ultrasonic signal corresponding to each shear wave during each period; receiving an ultrasonic echo signal corresponding to each shear wave via the first ultrasonic transducer (3); according to the ultrasonic echo signal corresponding to each shear wave, respectively acquiring a propagation characteristic parameter of each shear wave; according to the propagation characteristic parameters of N shear waves with different excitation characteristics, obtaining a tissue parameter through calculation. By exciting N shear waves with different excitation characteristics, since a tissue has different responses to each shear wave, a more accurate tissue parameter can be obtained by measurement; thereby improving the precision and sensitivity of tissue parameter measurement.

Description

Tissue parameter detection method and system

Technical field

The invention belongs to the technical field of medical instruments, and in particular relates to a method and system for detecting tissue parameters.

Background technique

Tissue parameters such as elasticity of biological tissues are closely related to the characteristics of the lesions, and have important reference value for the diagnosis of the diseases. Therefore, taking the elastic parameters of the tissue as an example, an elastic detecting technique for performing non-destructive elastic detection on a viscoelastic medium such as a human liver has been widely used in recent years.

At present, when detecting parameters such as elasticity for an organization, a single excitation characteristic is often used to excite a shear wave in the tissue, and the propagation characteristics of the shear wave inside the tissue are analyzed and processed to obtain a tissue parameter. The parameters can be characterized by the propagation characteristic parameters of the shear wave.

The above method of measuring tissue parameters by a single shear wave propagation characteristic makes it difficult to ensure the accuracy, measurement accuracy, and sensitivity of the tissue parameters obtained by the measurement.

Summary of the invention

In order to solve at least one of the problems mentioned in the background, the present invention provides a tissue parameter detecting method and system for improving the accuracy of tissue parameter detection results.

The invention provides a method for detecting tissue parameters, comprising:

Controlling the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and controlling the first ultrasonic transducer to emit to the tissue and each of the shears in each cycle The ultrasonic signal corresponding to the cut wave, N is an integer greater than one;

Receiving, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each of the shear waves;

Acquiring, according to the ultrasonic echo signals corresponding to each of the shear waves, propagation characteristic parameters of each of the shear waves;

Calculated according to the propagation characteristic parameters of the N shear waves with different excitation characteristics The tissue parameters are obtained.

Optionally, the calculating, according to the propagation characteristic parameters of the N shear waves having different excitation characteristics, obtaining the tissue parameters, including: according to the propagation characteristic parameters of the N shear waves having different excitation characteristics And the tissue density of the tissue, the elastic parameters of the tissue are calculated.

Optionally, the calculating, according to the propagation characteristic parameters of the N shear waves having different excitation characteristics and the tissue density of the tissue, calculating the elastic parameters of the tissue, including: calculating the N different excitations a statistical value of the M propagation characteristic parameters of the characteristic shear wave propagation characteristic parameter, the statistical value including: any one of a mean value, a median value, and a weighted mean value, M≤N; according to the M propagation characteristic parameters The statistical value and the tissue density are calculated to obtain the elastic parameters of the tissue.

Optionally, the excitation device comprises a vibrator that excites the N shear waves having different excitation characteristics by applying an instantaneous vibration on the outer surface of the tissue; correspondingly, the excitation characteristics include: At least one of a vibration frequency, a vibration amplitude, and a vibration duration; or the excitation device includes a second ultrasonic transducer that excites the ultrasonic wave by focusing on the tissue N shear waves having different excitation characteristics; correspondingly, the excitation characteristics include: at least one of an ultrasonic transmission frequency, an ultrasonic emission energy, an ultrasonic focus position, and an ultrasonic emission duration;

The second ultrasonic transducer is the same as or different from the first ultrasonic transducer.

Optionally, the obtaining, according to the ultrasonic echo signals corresponding to each of the shear waves, obtaining propagation characteristic parameters of each of the shear waves, respectively: comprising: respectively, ultrasonic waves corresponding to each of the shear waves The wave signal is subjected to signal processing, and the tissue motion parameters corresponding to each of the shear waves are obtained; and the propagation characteristic parameters of each of the shear waves are obtained according to the tissue motion parameters corresponding to each of the shear waves.

Optionally, the signal processing includes at least one of the following: time domain cross correlation, spectral cross correlation, absolute error sum, square error sum, speckle tracking, scale invariant feature point tracking, dynamic programming, zero cross tracking , peak search, optical flow method; the tissue motion parameter includes: displacement or strain; the propagation characteristic parameter includes a propagation speed or a propagation attenuation coefficient.

Optionally, the method further includes: mapping the elastic parameter of the tissue to a corresponding grayscale image or a color image by using grayscale mapping or color mapping.

The invention provides a tissue parameter detecting system, comprising:

Controlling the host, the excitation device, and the first ultrasonic transducer;

The control host includes:

a control module, configured to control the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and control the first ultrasonic transducer in each cycle Transmitting, to the tissue, an ultrasonic signal corresponding to each of the shear waves, N being an integer greater than one;

a receiving module, configured to receive, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each of the shear waves;

Obtaining a module, configured to acquire propagation characteristic parameters of each of the shear waves according to ultrasonic echo signals corresponding to each of the shear waves;

And a calculation module, configured to calculate the tissue parameter according to the propagation characteristic parameters of the N shear waves having different excitation characteristics.

Optionally, the calculating module is specifically configured to:

The elastic parameters of the tissue are calculated according to the propagation characteristic parameters of the N shear waves having different excitation characteristics and the tissue density of the tissue.

Optionally, the excitation device includes a vibrator; the control module is configured to control the vibrator to excite the N shear waves having different excitation characteristics by applying instantaneous vibration on an outer surface of the tissue; The excitation characteristic includes: at least one of a vibration frequency, a vibration amplitude, and a vibration duration; or the excitation device includes a second ultrasonic transducer; the control module is configured to control the second ultrasonic wave The transducer excites the N shear waves having different excitation characteristics by emitting ultrasonic waves focused within the tissue; correspondingly, the excitation characteristics include: ultrasonic emission frequency, ultrasonic emission energy, ultrasonic focus position, and ultrasonic waves At least one of emission durations; the second ultrasonic transducer being the same or different than the first ultrasonic transducer.

The method and system for detecting tissue parameters provided by the present invention, when it is required to perform tissue parameter detection on a tissue, controls the excitation device to respectively excite N shear waves having different excitation characteristics in the tissue at a preset time interval. Furthermore, by analyzing and processing a plurality of ultrasonic echo signals corresponding to each shear wave, the propagation characteristic parameters of each shear wave are obtained, and finally calculated according to the propagation characteristic parameters of the N shear waves having different excitation characteristics. Organizational parameters. By stimulating N with Shear waves with different excitation characteristics, because the tissue response to each shear wave is different, can be measured to obtain more accurate tissue parameters, improve the accuracy and sensitivity of tissue parameter measurement.

DRAWINGS

1 is a flowchart of Embodiment 1 of a method for detecting a tissue parameter according to the present invention;

2 is a flowchart of Embodiment 2 of a method for detecting a tissue parameter according to the present invention;

FIG. 3 is a schematic diagram of Embodiment 1 of a tissue parameter detecting system of the present invention.

detailed description

1 is a flowchart of Embodiment 1 of a method for detecting a tissue parameter according to the present invention. In this embodiment, the method for detecting a tissue parameter is performed by a tissue parameter detecting system, which is controlled by a control host, an excitation device, and a first ultrasonic wave. The energy component is configured, and the method for detecting the tissue parameter is specifically performed by a control host in the tissue parameter detecting system. As shown in FIG. 1 , the method for detecting the tissue parameter includes:

Step 101: Control the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and control the first ultrasonic transducer to emit to the tissue and each cut in each cycle. The ultrasonic signal corresponding to the wave.

Where N is an integer greater than one.

In this embodiment, when it is required to perform elastic detection on the tissue, the control host controls the excitation device to periodically excite N shear waves having different excitation characteristics propagating in the tissue at a preset time interval. And after each excitation of a shear wave having a certain excitation characteristic, controlling the first ultrasonic transducer to emit a plurality of ultrasonic signals corresponding to the shear wave, and receiving a corresponding ultrasonic echo signal for use in The propagation characteristics of the shear wave in the tissue are analyzed.

For example, the first ultrasonic transducer transmits an ultrasonic signal at a pulse repetition frequency between 1 Hz (Hz) and 100000 Hz.

In this embodiment, the shear wave excitation device includes any one of the following devices: a vibrator and a second ultrasonic transducer. Wherein, the second ultrasonic transducer can be the same as the first ultrasonic transducer, or be different from the other.

Correspondingly, the shear wave can be excited by: controlling the vibrator to be applied on the outer surface of the tissue. Short-term transient vibration to generate N shear waves with different excitation characteristics in the tissue;

At this time, the excitation characteristics include at least one of a vibration frequency, a vibration amplitude, and a vibration duration.

Specifically, the vibration frequency f of the low frequency vibration of the vibrator may be between 0.5 Hz and 3000 Hz. The duration of the low frequency vibration is between 1/2f and 40f. The amplitude of the vibration is between 5 microns and 30 mm. When the shear wave is excited by the vibrator vibration, for example, the excitation characteristic can be used to take the excitation frequency f at 50 Hz for a duration of 10/f seconds, that is, 0.2 seconds.

Alternatively, the shear wave may be excited by controlling the ultrasonic wave emitted by the second ultrasonic transducer to focus on the inside of the tissue to generate an acoustic radiation force to generate N shear waves having different excitation characteristics in the tissue.

At this time, the excitation characteristics include at least one of an ultrasonic transmission frequency, an ultrasonic emission energy, an ultrasonic focus position, and an ultrasonic emission duration.

Specifically, the ultrasonic transmission frequency can be between 1 MHz and 10 MHz. The ultrasonic emission energy is between 0.1 W/cm 2 and 300 W/cm 2 . The ultrasonic focusing position is between 1 cm and 9 cm. The ultrasonic emission duration is between 10 ^-9 seconds and 0.01 seconds.

Step 102: Receive, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each shear wave.

The first ultrasonic transducer sends the received ultrasonic echo signal corresponding to each shear wave to the main control host, so that the control host performs subsequent processing on each ultrasonic echo signal.

Step 103: Acquire propagation characteristic parameters of each shear wave according to ultrasonic echo signals corresponding to each shear wave.

Step 104: Calculate and obtain a tissue parameter according to propagation characteristic parameters of N shear waves having different excitation characteristics.

In this embodiment, after receiving the ultrasonic echo signals corresponding to the respective shear waves, the control host may separately analyze and process each ultrasonic echo signal to obtain corresponding propagation characteristic parameters of each shear wave, and then according to The propagation characteristic parameters of each shear wave are used to obtain tissue parameters.

Specifically, the control host may perform signal processing on the ultrasonic echo signals corresponding to each shear wave to obtain tissue motion parameters corresponding to each shear wave, and further, respectively, according to the tissue motion corresponding to each shear wave. Parameters to obtain the propagation characteristic parameters of each shear wave.

Wherein, the signal processing of each ultrasonic echo signal includes at least one of the following processes: time domain cross correlation, spectral cross correlation, absolute error sum, square error sum, speckle tracking, scale invariant feature point tracking, dynamic programming, Zero cross tracking, peak search, optical flow method. By performing signal processing on each ultrasonic echo signal, tissue motion parameters, such as displacement or strain, of each corresponding shear wave can be obtained. Thereby, the propagation characteristic parameters of the respective shear waves, such as the propagation speed or the propagation attenuation coefficient, are obtained based on the tissue motion parameters.

In this embodiment, the tissue parameters can be characterized by the propagation characteristic parameters of the shear wave. Therefore, according to the propagation characteristic parameters of the shear waves with N different excitation characteristics, the obtained tissue parameters can be obtained, which can be obtained by performing certain data processing on the propagation characteristic parameters of the shear waves with different excitation characteristics. For example, the N propagation characteristic parameters are averaged to obtain an average value, and the mean value is used to characterize the tissue parameters. Of course, the tissue parameter can also be an elastic parameter of the tissue, which will be introduced in the subsequent embodiments.

In this embodiment, when it is required to perform tissue parameter detection on the tissue, the control excitation device respectively excites N shear waves having different excitation characteristics in the tissue at a preset time interval. Furthermore, by analyzing and processing a plurality of ultrasonic echo signals corresponding to each shear wave, the propagation characteristic parameters of each shear wave are obtained, and finally calculated according to the propagation characteristic parameters of the N shear waves having different excitation characteristics. Organizational parameters. By exciting N shear waves with different excitation characteristics, since the response of the tissue to each shear wave is different, it is possible to measure more accurate tissue parameters and improve the accuracy and sensitivity of tissue parameter measurement.

2 is a flowchart of Embodiment 2 of a method for detecting a tissue parameter according to the present invention. As shown in FIG. 2, the method includes the following steps:

Step 201: Control the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and control the first ultrasonic transducer to emit to the tissue and each cut in each cycle. The ultrasonic signal corresponding to the wave.

Step 202: Receive, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each shear wave.

Step 203: Acquire propagation characteristic parameters of each shear wave according to ultrasonic echo signals corresponding to each shear wave.

Step 204: Propagation characteristic parameters and groups according to N shear waves having different excitation characteristics Weaving density, calculated to obtain the elastic parameters of the tissue.

Steps 201 to 203 are the same as the corresponding steps in the foregoing embodiment, and are not described again.

In this embodiment, after obtaining the propagation characteristic parameters of the respective shear waves, the elastic parameters of the tissue can be calculated according to the propagation characteristic parameters of the shear waves having different excitation characteristics and the tissue density of the tissue, and the elastic parameters include the following At least one of the parameters: shear modulus, Young's modulus, shear elasticity, shear viscosity, mechanical impedance, mechanical relaxation time, anisotropy. Among them, in general, it is mainly to obtain a shear modulus or a Young's modulus.

It is worth noting that the propagation characteristic parameters of the shear wave used in calculating the elastic parameters of the tissue may be the propagation characteristic parameters obtained by performing certain data processing on the propagation characteristic parameters of the shear waves of N different excitation characteristics. For example, the N propagation characteristic parameters are averaged to obtain an average value, and the elastic parameters of the tissue are calculated by the mean value and the tissue density.

For example, taking the propagation characteristic parameter as the propagation velocity as an example, the shear modulus μ and the Young's modulus of the tissue are calculated from the average shear wave propagation velocity V _s E: E = 3 μ = 3ρV _s ² , where ρ is the tissue Density.

In addition, in the embodiment, in order to ensure the accuracy of the elastic detection and the calculation load, the M propagation characteristic parameters may be selected from the N propagation characteristic parameters, and the statistical values of the M propagation characteristic parameters are calculated. Values include: mean, median, weighted mean, M ≤ N. Further, based on the statistical values of the M propagation characteristic parameters and the tissue density, the elastic parameters of the obtained tissue are calculated.

Wherein, the selection of the M propagation characteristic parameters may be randomly selected, or may be separately selected for each excitation characteristic, that is, for example, a shear wave is excited by a vibrator, and the excitation characteristics include The above vibration frequency, vibration amplitude and vibration duration. Then, when there are more than one parameter of each excitation characteristic, for example, the vibration frequency includes f1, f2, and f3. For f1, the values of the other two parameters are different. When M species are selected from the N kinds of excitation characteristics, at least one of the plurality of different combinations of the same f1 is selected. Similarly, at least one of the plurality of combinations of the same f2 is selected, and the same combination of f3 is used. Choose at least one. It is also true for other excitation characteristics.

In this embodiment, in order to more intuitively understand the elasticity of the tissue, the calculated elasticity parameters may be color mapped to obtain a corresponding elastic image. Therefore, after step 204, optionally, the following step 205 may also be included.

Step 205: Map the elastic parameters of the tissue to a corresponding grayscale image or color image by using grayscale mapping or color mapping.

In this embodiment, when it is required to perform elastic detection on the tissue, the excitation device is controlled to respectively excite N shear waves having different excitation characteristics in the tissue at a preset time interval. Furthermore, by analyzing and processing a plurality of ultrasonic echo signals corresponding to each shear wave, the propagation characteristic parameters of each shear wave are obtained, and finally the propagation characteristic parameters and organization of the shear waves of the N different excitation characteristics are obtained. Density, calculated to obtain the elastic parameters of the tissue. By exciting N shear waves with different excitation characteristics, since the response of the tissue for each shear wave is different, it is possible to measure more accurate elastic parameters and improve the accuracy and sensitivity of tissue elasticity measurement.

FIG. 3 is a schematic diagram of Embodiment 1 of a tissue parameter detecting system according to the present invention. As shown in FIG. 3, the system includes:

The host 1, the excitation device 2 and the first ultrasonic transducer 3 are controlled.

The control host 1 includes a control module 11, a receiving module 12, an obtaining module 13, and a computing module 14.

The control module 11 is configured to control the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and control the first ultrasonic transducer in each cycle An ultrasonic signal corresponding to each of the shear waves is transmitted to the tissue, N being an integer greater than one.

The receiving module 12 is configured to receive, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each of the shear waves.

The obtaining module 13 is configured to acquire propagation characteristic parameters of each of the shear waves according to the ultrasonic echo signals corresponding to each of the shear waves.

The calculating module 14 is configured to calculate and obtain the tissue parameter according to the propagation characteristic parameters of the N shear waves having different excitation characteristics.

Optionally, the calculating module 14 is configured to calculate an elastic parameter of the tissue according to a propagation characteristic parameter of the N shear waves having different excitation characteristics and a tissue density of the tissue.

Optionally, the excitation device 2 includes a vibrator 21 .

The control module 11 is configured to control the vibrator 21 to excite the N shear waves having different excitation characteristics by applying instantaneous vibration on the outer surface of the tissue.

Correspondingly, the excitation characteristics include at least one of a vibration frequency, a vibration amplitude, and a vibration duration.

Optionally, the excitation device comprises a second ultrasonic transducer 22 .

The control module 11 is configured to control the second ultrasonic transducer 22 to excite the N shear waves having different excitation characteristics by emitting ultrasonic waves focused in the tissue.

Correspondingly, the excitation characteristics include at least one of an ultrasonic transmission frequency, an ultrasonic emission energy, an ultrasonic focus position, and an ultrasonic emission duration.

The second ultrasonic transducer 22 is the same as or different from the first ultrasonic transducer 3.

Optionally, the elastic detecting device further includes: an imaging device 4.

The imaging device 4 is configured to map the elastic parameters of the tissue into corresponding grayscale images or color images by using grayscale mapping or color mapping.

The elastic detecting device of this embodiment can be used in the technical solution of the foregoing method embodiment, and the implementation principle and the technical effect are similar, and details are not described herein again.

A person skilled in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by using hardware related to the program instructions. The foregoing program may be stored in a computer readable storage medium, and the program is executed when executed. The foregoing steps include the steps of the foregoing method embodiments; and the foregoing storage medium includes: a medium that can store program codes, such as a ROM, a RAM, a magnetic disk, or an optical disk.

Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that The technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and the modifications or substitutions do not deviate from the technical solutions of the embodiments of the present invention. range.

Claims

A method for detecting tissue parameters, comprising:

Controlling the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and controlling the first ultrasonic transducer to emit to the tissue and each of the shears in each cycle The ultrasonic signal corresponding to the cut wave, N is an integer greater than one;

Receiving, by the first ultrasonic transducer, an ultrasonic echo signal corresponding to each of the shear waves;

Acquiring, according to the ultrasonic echo signals corresponding to each of the shear waves, propagation characteristic parameters of each of the shear waves;

The tissue parameters are calculated based on the propagation characteristic parameters of the N shear waves having different excitation characteristics.
The method according to claim 1, wherein the obtaining the tissue parameters according to the propagation characteristic parameters of the N shear waves having different excitation characteristics comprises:

The elastic parameters of the tissue are calculated according to the propagation characteristic parameters of the N shear waves having different excitation characteristics and the tissue density of the tissue.
The method according to claim 2, wherein said calculating an elastic parameter of said tissue based on a propagation characteristic parameter of said N shear waves having different excitation characteristics and a tissue density of said tissue, including :

Calculating a statistical value of M propagation characteristic parameters in the propagation characteristic parameters of the N shear waves having different excitation characteristics, the statistical value including: any one of mean, median, and weighted mean, M≤N;

Obtaining an elastic parameter of the tissue according to a statistical value of the M propagation characteristic parameters and the tissue density.
The method according to any one of claims 1 to 3, wherein the excitation means comprises a vibrator that excites the N different excitations by applying an instantaneous vibration on an outer surface of the tissue Characteristic shear wave;

Correspondingly, the excitation characteristic comprises: at least one of a vibration frequency, a vibration amplitude, and a vibration duration;

Or,

The excitation device includes a second ultrasonic transducer that excites the N shear waves having different excitation characteristics by emitting ultrasonic waves focused within the tissue;

Correspondingly, the excitation characteristic comprises: at least one of an ultrasonic transmission frequency, an ultrasonic emission energy, an ultrasonic focus position, and an ultrasonic emission duration;

The second ultrasonic transducer is the same as or different from the first ultrasonic transducer.
The method according to any one of claims 1 to 3, wherein the propagation characteristic parameters of each of the shear waves are acquired according to ultrasonic echo signals corresponding to each of the shear waves, respectively. include:

Performing signal processing on each ultrasonic echo signal corresponding to each of the shear waves, and acquiring tissue motion parameters corresponding to each of the shear waves;

A propagation characteristic parameter of each of the shear waves is obtained according to a tissue motion parameter corresponding to each of the shear waves.
The method according to claim 5, wherein said signal processing comprises at least one of: time domain cross correlation, spectral cross correlation, absolute error sum, square error sum, speckle tracking, scale invariant characteristics Point tracking, dynamic programming, zero cross tracking, peak search, optical flow method;

The tissue motion parameter includes: displacement or strain; the propagation characteristic parameter includes a propagation velocity or a propagation attenuation coefficient.
The method of claim 2, wherein the method further comprises:

The grayness mapping or color mapping is used to map the elastic parameters of the tissue into corresponding grayscale images or color images.
A tissue parameter detecting system, comprising:

Controlling the host, the excitation device, and the first ultrasonic transducer;

The control host includes:

a control module, configured to control the excitation device to excite N shear waves having different excitation characteristics in the tissue at a preset time interval, and control the first ultrasonic transducer in each cycle Transmitting, to the tissue, an ultrasonic signal corresponding to each of the shear waves, N being an integer greater than one;

a receiving module, configured to receive each of the shear wave pairs by the first ultrasonic transducer The ultrasonic echo signal should be

Obtaining a module, configured to acquire propagation characteristic parameters of each of the shear waves according to ultrasonic echo signals corresponding to each of the shear waves;

And a calculation module, configured to calculate the tissue parameter according to the propagation characteristic parameters of the N shear waves having different excitation characteristics.
The system according to claim 8, wherein the calculation module is specifically configured to:

The elastic parameters of the tissue are calculated according to the propagation characteristic parameters of the N shear waves having different excitation characteristics and the tissue density of the tissue.
The system of claim 8 wherein:

The excitation device includes a vibrator;

The control module is configured to control the vibrator to excite the N shear waves having different excitation characteristics by applying instantaneous vibration on an outer surface of the tissue;

Correspondingly, the excitation characteristic comprises: at least one of a vibration frequency, a vibration amplitude, and a vibration duration;

or,

The excitation device includes a second ultrasonic transducer;

The control module is configured to control the second ultrasonic transducer to excite the N shear waves having different excitation characteristics by emitting ultrasonic waves focused in the tissue;

Correspondingly, the excitation characteristic comprises: at least one of an ultrasonic transmission frequency, an ultrasonic emission energy, an ultrasonic focus position, and an ultrasonic emission duration;

The second ultrasonic transducer is the same as or different from the first ultrasonic transducer.