CN113633313B - Acoustic radiation force elastic imaging method and system based on multi-frequency ultrasonic probe - Google Patents
Acoustic radiation force elastic imaging method and system based on multi-frequency ultrasonic probe Download PDFInfo
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Abstract
The invention provides an acoustic radiation force elastography method and system based on a multi-frequency ultrasonic probe, wherein the acoustic radiation force elastography method comprises the following steps: acquiring a region to be observed of biological tissues; b-mode signal acquisition is carried out on the initial state of the region to be observed and the initial state is stored as first channel data, and the first channel data are used for acquiring the information of the region to be observed; determining an excitation source and an excitation mode of the acoustic radiation force according to the information of the region to be observed; generating local displacement and vibration of tissues in a region to be observed by using the excitation source and the excitation mode; transmitting and receiving ultrasonic signals in the region to be observed to obtain second channel data for tracking local displacement and vibration of tissues; and carrying out post-processing on the acquired second channel data to obtain the elasticity information of the biological tissue of the region to be observed. The method performs simultaneous, multi-frequency, multi-region acoustic radiation force excitation, and can rapidly and elastically measure and image the region from the superficial to the deeper region of the tissue without moving or switching the probe.
Description
Technical Field
The invention relates to the technical field of ultrasonic imaging, in particular to an acoustic radiation force elastic imaging method and system based on a multi-frequency ultrasonic probe.
Background
Ultrasound elastography based on acoustic radiation force, including shear wave elastography (SHEAR WAVE Elastography, SWE), acoustic radiation force pulse imaging (Acoustic radiation force impulse (ARFI) imaging), and the like, has been widely used to quantify elasticity (or stiffness) of various biological soft tissues and to evaluate tissue and body health accordingly. The basic principle of acoustic radiation force elastography is to focus an external acoustic beam at the tissue site to be examined, the acoustic radiation force generated by the focused acoustic beam exciting local tissue displacements and subsequently generating mechanical vibrations that propagate in the tissue in the form of shear waves; by analyzing the changes of the ultrasonic echo signals before and after excitation or in the propagation process of the shear waves, the local displacement of the tissue or the propagation characteristics of the shear waves can be calculated, and the elastic parameters of the tissue can be obtained.
The technology for simultaneously exciting and imaging by the same array probe is the mainstream of the current ultrasonic elastography by acoustic radiation force due to the characteristics of convenience, easiness in operation and the like. However, there is a trade-off between spatial resolution and depth of penetration due to ultrasound imaging: high-frequency ultrasound can obtain higher spatial resolution, but the attenuation is too fast to penetrate deeper tissues; the low-frequency ultrasound has stronger penetrability and can image deeper tissues, but the spatial resolution of the image is not high, and the imaging quality is poor. This is particularly significant for single array probe acoustic radiation force ultrasound elastography quality, making the method more limited in detection range. The existing method for exciting acoustic radiation force by using the single array transducer near-bandwidth lower edge frequency has the problem that the bandwidth upper edge frequency imaging method has a large limit on the application range because the frequency band cannot be too wide, usually only about 80%; in addition, the method needs to rapidly switch the two emission modes of the array transducer, has high requirements on an imaging system, and cannot ensure the imaging quality, especially when measuring deeper tissues.
On the other hand, when ultrasound elastography based on acoustic radiation force is used for a block tissue, it is desirable to obtain a shear wave wavefront as close to a plane (in two-dimensional imaging) or a cylinder (in three-dimensional imaging) as possible. The current common method is supersonic shear wave imaging (Supersonic SHEAR IMAGING) proposed by 2004J re myBercoff et al (J re myBercoff,and Mathias Fink,Supersonic Shear Imaging:A New Technique for Soft Tissue Elasticity Mapping.IEEE Transactions on Ultrasonics,Ferroelectrics,and Frequency Control,2004,51:396-409). The method is characterized in that single-point focused beams are continuously emitted along the depth direction, and the shear wave speed is far smaller than the moving speed of the wave sources, so that tissue vibration generated by different wave sources is overlapped to form quasi-plane shear waves (quasiplane SHEAR WAVES) close to a plane. However, since these wave sources (i.e. focused beams) do not reach different depths of tissue at the same time, but rather there is a time interval such that the superimposed wave fronts are not cylindrical but conical (Mach cone), this phenomenon is particularly pronounced when measuring thicker tissue or when the response speed of the ultrasound hardware system is slow. For shear wave elastography, an excessive included angle between the polarization direction of the shear wave wavefront and the direction of the detected sound wave can cause elasticity estimation errors, and the correction method is too complicated.
Disclosure of Invention
In view of the above, in order to overcome the above-mentioned drawbacks of the prior art, the present invention provides an acoustic radiation force elastography method and system based on a multi-frequency ultrasound probe.
Specifically, the acoustic radiation force elastic imaging method based on the multi-frequency ultrasonic probe comprises the following steps:
Acquiring a region to be observed of biological tissues;
B-mode signal acquisition is carried out on the initial state of the region to be observed and the initial state is stored as first channel data, and the first channel data are used for acquiring information of the region to be observed;
determining an excitation source and an excitation mode of the acoustic radiation force according to the information of the region to be observed;
generating local displacement and vibration of tissues in the region to be observed by using the excitation source and the excitation mode;
Transmitting and receiving ultrasonic signals in the region to be observed to obtain second channel data for tracking the local displacement and vibration of the tissue;
post-processing the acquired second channel data to obtain elastic information of the biological tissue of the region to be observed;
The excitation source is a multi-frequency ultrasonic probe, the multi-frequency ultrasonic probe is used for transmitting first frequency ultrasonic waves and second frequency ultrasonic waves, the frequency of the second frequency ultrasonic waves is smaller than that of the first frequency ultrasonic waves, the first frequency ultrasonic waves are used for acquiring the second channel data, and the second frequency ultrasonic waves are used for generating an excitation source and an excitation mode of sound radiation force.
After the ultrasonic signals are transmitted and received by the region to be observed to obtain second channel data, and before the acquired second channel data is subjected to post-processing, the acoustic radiation force elastography method based on the multi-frequency ultrasonic probe can further comprise the following steps:
adjusting the focus position of the excitation pulse, repeating the operations of exciting the local displacement and vibration of the tissue and transmitting and receiving ultrasonic signals, and scanning the region to be observed;
And/or, carrying out post-processing on the acquired first channel data.
In some embodiments, the multi-frequency ultrasound probe has one probe with a plurality of ultrasound frequencies, the probe having ultrasound frequencies including the first frequency ultrasound and the second frequency ultrasound.
In some embodiments, the multi-frequency ultrasound probe includes a first transducer assembly and a second transducer assembly, the second transducer assembly including two or more transducers, the two or more transducers being disposed on either side or around the first transducer assembly, the second transducer assembly having a frequency that is lower than the frequency of the first transducer assembly.
The excitation source and the excitation mode of the acoustic radiation force comprise:
Individually exciting using a first transducer assembly array of the multi-frequency ultrasound probe; or, a plurality of second transducer assembly arrays using the multi-frequency ultrasound probe are individually or collectively excited; or, co-exciting with the first transducer assembly array and the second transducer assembly array of the multi-frequency ultrasound probe; or, transmitting a primary focusing beam by using the multi-frequency ultrasonic probe for excitation; or, transmitting a plurality of focusing beams to the biological tissue for excitation by using the multi-frequency ultrasonic probe.
When the excitation mode of the acoustic radiation force is common excitation, the same frequency or different frequencies can be used for simultaneously exciting the same focus or different focuses; or, the same frequency or different frequencies are used for time-sharing excitation on the same focus or different focuses.
The "determining the excitation source and the excitation mode of the acoustic radiation force according to the information of the region to be observed" includes:
separately energizing a shallowest layer of the biological tissue or a thicker shallowest layer of the biological tissue with a first transducer assembly array of the multi-frequency ultrasound probe;
Separately or jointly exciting a thicker deeper of the biological tissue with a second transducer assembly array of the multi-frequency ultrasound probe;
The biological tissue with greater acoustic attenuation along the way is co-excited with the second array of transducer assemblies using the first array of transducer assemblies.
The "transmitting and receiving ultrasonic signals in the region to be observed to obtain second channel data" includes:
Transmitting a longitudinal wave ultrasonic sequence to the region to be observed by using the multi-frequency ultrasonic probe, and receiving the echo generated in the biological tissue by using the first transducer assembly to obtain the second channel data, or receiving the echo generated in the biological tissue by using the first transducer assembly and the second transducer assembly in a cooperative manner to obtain the second channel data.
The "post-processing the acquired first channel data and second channel data to obtain the elasticity information of the biological tissue of the region to be observed" includes:
performing filtering reconstruction on the acquired second channel data to obtain IQ data;
performing corresponding algorithm processing on the IQ data to obtain local displacement or vibration of the biological tissue generated by the acoustic radiation force in the region to be observed or the propagation speed of shear waves generated by the local displacement or vibration;
The elasticity of the biological tissue is estimated based on the local tissue displacement or the propagation velocity of the shear wave.
The "performing corresponding algorithm processing on the IQ data" includes:
performing correlation processing on the IQ data; or, carrying out cross-correlation processing on the IQ data; or, carrying out absolute difference summation processing on the IQ data.
The "estimating elasticity of the biological tissue from the local tissue displacement or the propagation velocity of the shear wave" includes:
obtaining the relative elasticity or the relative hardness of the tissue according to the amplitude of the local tissue displacement obtained by scanning;
Or estimating elasticity of the biological tissue according to a relation between the propagation speed of shear waves and the elastic modulus of the biological tissue.
The "relation between the shear wave propagation velocity and the elastic modulus of the biological tissue" includes: Wherein E represents the elastic modulus of the isotropic pure elastic bulk tissue, c s represents the shear wave propagation velocity of the isotropic pure elastic bulk tissue, ρ represents the tissue density of the isotropic pure elastic bulk tissue;
Or alternatively, the first and second heat exchangers may be, Wherein μ 1 represents the shear elastic modulus of the isotropic Kelvin-Voigt viscoelastic material, μ 2 represents the shear viscosity of the isotropic Kelvin-Voigt viscoelastic material, ω s represents the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material, and c s(ωs) represents the shear wave propagation velocity at the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material of ω s.
The invention also provides an acoustic radiation force elastography system based on the multi-frequency ultrasonic probe, which is used for executing the shear wave imaging method based on the multi-frequency ultrasonic probe, and comprises the following steps:
And the reference data acquisition module: the method comprises the steps of performing B-mode signal acquisition on an initial state of a region to be observed of biological tissues and storing the initial state as first channel data, wherein the first channel data are used for acquiring information of the region to be observed;
and a judging module: the excitation source and the excitation mode are used for determining the sound radiation force according to the information of the region to be observed;
the original data acquisition module: the ultrasonic sensor is used for exciting tissue vibration in a region to be observed of biological tissue, transmitting and receiving ultrasonic signals to track the tissue vibration, and obtaining second channel data;
The channel data processing module: the first channel data and/or the second channel data are/is used for carrying out filtering reconstruction on the second channel data and/or the first channel data to obtain IQ data;
an IQ data processing module: the IQ data is used for carrying out related algorithm processing to obtain local tissue displacement generated by acoustic radiation force in the region to be observed or the propagation speed of shear wave generated by the local tissue displacement;
Elasticity estimation and imaging module: for estimating the elasticity of the biological tissue from the local tissue displacement or shear wave propagation velocity and generating a tissue elasticity image.
In summary, the acoustic radiation force elastic imaging method and system based on the multi-frequency ultrasonic probe have the following beneficial effects: simultaneous, multi-frequency and multi-region acoustic radiation force excitation can be realized by using a single probe; the defect of the conical wave front of the existing supersonic shear wave source is overcome, and a real cylindrical wave front can be formed; the probe does not need to be moved or switched, and the rapid elastic measurement and imaging from the tissue superficial to the deeper region can be realized by only using one probe; the bandwidth limitation of the conventional single-frequency transducer array is broken through, and the first transducer assembly can be used for image acquisition while the high-efficiency acoustic radiation force excitation is carried out on a deeper region, so that the elastography quality is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of an acoustic radiation force elastography method based on a multi-frequency ultrasound probe of the present invention;
FIG. 2 is a schematic diagram of a structure of a multi-frequency ultrasonic probe used in the acoustic radiation force elastography method based on the multi-frequency ultrasonic probe according to the present invention;
FIG. 3 is a schematic illustration of an arrangement of the array of multi-frequency ultrasound probes shown in FIG. 2;
FIG. 4a is a diagram of one acoustic radiation force excitation scheme employing the multi-frequency ultrasound probe arrangement shown in FIGS. 2 and 3;
FIG. 4b is another acoustic radiation force excitation pattern employing the multi-frequency ultrasound probe arrangement shown in FIGS. 2 and 3;
FIG. 4c is a further acoustic radiation force excitation pattern employing the multi-frequency ultrasound probe arrangement shown in FIGS. 2 and 3;
FIG. 4d is a further acoustic radiation force excitation pattern employing the multi-frequency ultrasound probe arrangement shown in FIGS. 2 and 3;
Fig. 5 is a schematic structural diagram of an acoustic radiation force elastography system based on a multi-frequency ultrasound probe of the present invention.
Reference numerals:
1-a first transducer assembly; 11-a first array of transducer assemblies; 2-a second transducer assembly; a second array of transducer assemblies; 3-backing layer; 4-a piezoelectric layer; 5-matching layer; 6-a flexible circuit board; 7-acoustic lens.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The acoustic radiation force elastic imaging method based on the multi-frequency ultrasonic probe provided by the embodiment is applied to a variable-focus multi-row phased array ultrasonic probe. Specifically, the multi-frequency ultrasonic probe used in the present embodiment is a variable-focus multi-row phased array ultrasonic probe, including a first transducer assembly and a second transducer assembly, where the second transducer assembly includes two or more transducers, the first transducer assembly is centered, the second transducer assembly is arranged around the first transducer assembly, specifically, the second transducer assembly is arranged at two sides of the first transducer assembly or around the first transducer assembly, and the transmission and the reception of each transducer can be controlled independently. Wherein the frequency of the second transducer assembly is lower than the frequency of the first transducer assembly, such that the multi-frequency ultrasound probe includes a portion having a higher frequency and a portion having a lower frequency.
The multi-frequency ultrasonic probe can simultaneously perform super-harmonic imaging and elastic imaging modes of low-frequency excitation high-frequency imaging and non-interference synchronous high-quality ultrasonic imaging modes of multi-frequency energy converters because the energy converters are not mutually affected. For example, a multi-band transducer performs multi-frequency synchronous imaging on a single target; or synchronously imaging targets at different positions and depths on the same cross section or different cross sections, so that the imaging range and the imaging efficiency of the transducer are enhanced; or, performing ultra-harmonic imaging and elastography of low-frequency signal excitation and high-frequency signal reception on the same focus target position; or simultaneous low frequency excitation and high frequency imaging of target locations of different depths, or simultaneous super-harmonic/elastography of the same target location using a pair of a first transducer assembly with a higher frequency and a second transducer assembly with a lower frequency while fundamental imaging or steering with another transducer, etc.
Referring to fig. 1 of the specification, the acoustic radiation force elastic imaging method based on the multi-frequency ultrasonic probe of the invention comprises the following steps:
s1: a region of biological tissue to be observed is acquired.
S2: b mode signal acquisition is carried out on the initial state of the region to be observed once by using a first transducer assembly in the multi-frequency ultrasonic probe, the B mode signal acquisition is stored as first channel data, and the first channel data are used for acquiring information such as the position, thickness and acoustic attenuation of the region to be observed and are used as initial state references of ARFI imaging.
S3: and determining an appropriate excitation source and an excitation mode of the acoustic radiation force according to the information such as the position, the thickness, the acoustic attenuation and the like of the region to be observed.
The excitation source of the acoustic radiation force varies depending on the position, thickness, acoustic attenuation, etc. of the region to be observed. The present embodiment provides a multi-frequency ultrasonic probe as shown in fig. 2 of the specification, which comprises a first transducer assembly 1 and second transducer assemblies 2 disposed on both sides of the first transducer assembly 1, the first transducer assembly 1 comprising one transducer, the second transducer assembly 2 comprising two transducers each of the first transducer assembly 1 and each of the second transducer assemblies 2 comprising a backing layer 3, a piezoelectric layer 4 and a matching layer 5 disposed in a stacked manner, the electrical interconnection of the piezoelectric layer 4 and an external circuit being achieved through a flexible circuit board 6, the multi-frequency ultrasonic probe further comprising an acoustic lens 7. An arrangement of the array of the multi-frequency ultrasonic probe of this embodiment is shown in fig. 3 of the specification: the array element spacing of the second transducer assembly 2 is twice that of the first transducer assembly 1, and the array of the multi-frequency ultrasonic probe is arranged according to two groups of first transducer assembly arrays 11 corresponding to one group of second transducer assembly arrays 21.
The excitation source and the excitation mode of the acoustic radiation force by using the multi-frequency ultrasonic probe comprise:
The first transducer assembly array 11 using the multi-frequency ultrasound probe is individually excited; alternatively, multiple second transducer assembly arrays 21 using a multi-frequency ultrasound probe are excited individually or together; alternatively, the first transducer assembly array 11 and the second transducer assembly array 21 are co-excited using a multi-frequency ultrasound probe; or, transmitting a primary focusing beam by using a multi-frequency ultrasonic probe for excitation; or, the multi-frequency ultrasonic probe is used for transmitting a plurality of focusing beams to biological tissues for excitation.
Wherein when excited together, multiple excitation sources can excite simultaneously with the same frequency or different frequencies for the same focus or different focuses. That is, when the common excitation is performed, the plurality of second transducer assembly arrays 21 are excited simultaneously with the same frequency or different frequencies for the same focal point; or, multiple second transducer assembly arrays 21 are excited simultaneously with the same frequency or different frequencies for different focal points; alternatively, the first transducer assembly array 11 and the second transducer assembly array 21 are excited simultaneously with different frequencies for the same focal point; alternatively, the first transducer assembly array 11 and the second transducer assembly array 21 are excited using different frequencies for different focal points.
Alternatively, the co-excitation may be performed simultaneously or time-division. For example: the plurality of second transducer assembly arrays 21 are time-shared excited for the same focus or different focuses; alternatively, the first transducer assembly array 11 and the second transducer assembly array 21 are time-shared for excitation for the same focus or different focuses.
S4: an effective local displacement and vibration of the tissue are generated in the region to be observed, and then ultrasonic signals are transmitted and received to obtain second channel data for tracking the local displacement and vibration of the tissue caused by the acoustic radiation force.
S41: the excitation source and the excitation mode are used for generating effective tissue local displacement and vibration in the region to be observed.
Taking the excitation of the multi-frequency ultrasonic probe as shown in fig. 2 as an example, different acoustic radiation force excitation sources and excitation modes are set for biological tissues to be observed at different positions and thicknesses: as shown in fig. 4a, elasticity measurements of superficial tissue of thinner biological tissue are stimulated with acoustic radiation force alone using the first transducer assembly array 11. As shown in fig. 4b, elasticity measurement of thicker biological tissue: the first transducer assembly array 11 is used for shallowest excitation thereof, the second transducer assembly array 21 is used for deeper excitation, and the plurality of second transducer assembly arrays 21 may be excited individually or collectively. The second transducer assembly arrays 21 are focused on different focuses respectively, and focus beams emitted by the different transducer arrays reach focuses at different depths simultaneously by adjusting emission delay, so that local shear vibration at different depths is excited, and plane (two-dimensional observation) or cylindrical (three-dimensional observation) shear waves are formed by superposition. As shown in fig. 4c, if the biological tissue is thin but the sound attenuation along the way is large, the first transducer assembly array 11 and the second transducer assembly array 21 may be co-excited: so that sound waves emitted by different transducer arrays are focused at the same location of the tissue at the same time. As shown in fig. 4d, if the biological tissue is thicker and the along-the-way sound attenuation is larger, the focal position excitation is rapidly changed along the thickness direction by using the mode of jointly exciting the first transducer assembly array 11 and the second transducer assembly array 21, so that local vibration generated at different depths is overlapped to form quasi-plane (two-dimensional) or conical (three-dimensional) shear waves. If the area to be observed is shallow or the span in the depth direction is small, the focused beam needs to be transmitted only once. Otherwise, if the region to be observed is deeper or the span in the depth direction is larger, plane shear waves can be formed by overlapping focused beams sequentially emitted at supersonic speeds to different depths of the tissue.
The method can be used for simultaneously measuring the elasticity of the ultra-shallow and deeper tissues without switching the probe; because a plurality of different frequency transducers can be focused on the same target spot for excitation, the tissue with higher sound attenuation or deeper can be excited to vibrate or displace with higher amplitude, thereby improving the elastography quality; in addition, as the focusing depth of each transducer can be controlled respectively, the excitation time can be regulated and controlled freely, which is equivalent to the flexible control of the space and time distribution of the shear wave source by the method, and the shear wave characteristics in the tissue can be regulated and controlled by the interference superposition equivalent of the wave, such as the plane and quasi-plane shear wave mentioned above. Other characteristics of shear waves may be similarly modulated for reasons of spread and are not intended to be exhaustive.
S42: ultrasonic signals are transmitted and received in the region to be observed to track the local displacement and vibration in the step S41, and second channel data are acquired. Specifically, a multi-frequency ultrasonic probe is used for transmitting a longitudinal wave ultrasonic sequence to an area to be observed at a high repetition frequency and receiving echoes generated in tissues to obtain second channel data. The second channel data may be obtained by transmitting and collecting ultrasonic signals by using the first transducer assembly 1 in the multi-frequency ultrasonic probe alone or by transmitting and collecting ultrasonic signals by using the first transducer assembly 1 and the second transducer assembly 2 in cooperation.
S5: and adjusting the focus position of the excitation pulse, repeating the operations of exciting the local displacement and vibration of the tissue and transmitting and receiving ultrasonic signals, and scanning the region to be observed.
S6: and carrying out filtering reconstruction on the acquired channel data to obtain IQ data, and storing the IQ data in a system buffer area. The method comprises the step of carrying out filtering reconstruction on acquired second channel data to obtain IQ data. In some embodiments, filtering the first channel data to reconstruct IQ data may be included as a reference for Acoustic Radiation Force Impulse (ARFI) imaging.
S7: the IQ data is subjected to corresponding algorithmic processing including, but not limited to, correlation, cross-correlation, sum of absolute differences processing or other similar methods to obtain the local displacement or vibration of the biological tissue in the region to be observed, or the propagation velocity of the shear wave generated thereby, caused by the acoustic radiation forces.
S8: the elasticity of biological tissue is estimated from the local tissue displacement or the propagation velocity of shear waves: the relative stiffness of the tissue to be observed is estimated from the local tissue displacement, or the elasticity of the biological tissue is estimated from the relationship between the shear wave propagation velocity and the elastic modulus of the biological tissue.
For example, for isotropic pure elastic bulk tissue, young's modulus (E) is related to shear wave velocity and tissue densityWherein E represents the elastic modulus of the isotropic pure elastic bulk tissue, c s represents the shear wave propagation velocity of the isotropic pure elastic bulk tissue, ρ represents the tissue density of the isotropic pure elastic bulk tissue.
The relationship between shear wave velocity and shear elastic modulus, shear viscosity, shear wave angular frequency for uniformly isotropic Kelvin-Voigt viscoelastic materials can be expressed asWherein μ 1 represents the shear elastic modulus of the isotropic Kelvin-Voigt viscoelastic material, μ 2 represents the shear viscosity of the isotropic Kelvin-Voigt viscoelastic material, ω s represents the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material, and c s(ωs) represents the shear wave propagation velocity at the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material of ω s.
In this embodiment, the excitation source of the acoustic radiation force is a multi-frequency ultrasonic probe, and the multi-frequency ultrasonic probe is configured to emit a first frequency ultrasonic wave and a second frequency ultrasonic wave, where the frequency of the second frequency ultrasonic wave is smaller than that of the first frequency ultrasonic wave, the first frequency ultrasonic wave is configured to acquire the second channel data, and the second frequency ultrasonic wave is configured to generate the excitation source and the excitation mode of the acoustic radiation force. Further, the frequency of the ultrasonic wave for acquiring the first channel data may be the same as or different from the frequency of the first frequency ultrasonic wave. In the present embodiment, the frequency of the ultrasonic wave for acquiring the first channel data may be any frequency. The method can realize rapid elastic measurement and imaging from the tissue superficial to the deeper region by only using one probe.
Example 2
The embodiment provides an acoustic radiation force elastic imaging method based on a multi-frequency ultrasonic probe, which is applied to a variable-focus multi-row phased array ultrasonic probe. Specifically, the multi-frequency ultrasonic probe used in the present embodiment has one probe having a plurality of ultrasonic frequencies. The multi-frequency ultrasonic probe of the embodiment can work at a plurality of ultrasonic frequencies, and can emit ultrasonic waves with different frequencies to perform acoustic radiation force excitation.
The acoustic radiation force elastic imaging method based on the multi-frequency ultrasonic probe of the embodiment comprises the following steps:
s1: a region of biological tissue to be observed is acquired.
S2: b mode signal acquisition is carried out on the initial state of the region to be observed once by using a first transducer assembly in the multi-frequency ultrasonic probe, the B mode signal acquisition is stored as first channel data, and the first channel data are used for acquiring information such as the position, thickness and acoustic attenuation of the region to be observed and are used as initial state references of ARFI imaging.
S3: and determining an appropriate excitation source and an excitation mode of the acoustic radiation force according to the information such as the position, the thickness, the acoustic attenuation and the like of the region to be observed.
S4: an effective local displacement and vibration of the tissue are generated in the region to be observed, and then ultrasonic signals are transmitted and received to obtain second channel data for tracking the local displacement and vibration of the tissue caused by the acoustic radiation force.
S41: the excitation source and the excitation mode are used for generating effective tissue local displacement and vibration in the region to be observed.
S42: ultrasonic signals are transmitted and received in the region to be observed to track the local displacement and vibration in the step S41, and second channel data are acquired.
S5: and adjusting the focus position of the excitation pulse, repeating the operations of exciting the local displacement and vibration of the tissue and transmitting and receiving ultrasonic signals, and scanning the region to be observed.
S6: and carrying out filtering reconstruction on the acquired channel data to obtain IQ data, and storing the IQ data in a system buffer area. The method comprises the step of carrying out filtering reconstruction on acquired second channel data to obtain IQ data. In some embodiments, filtering the first channel data to reconstruct IQ data may be included as a reference for Acoustic Radiation Force Impulse (ARFI) imaging.
S7: the IQ data is subjected to corresponding algorithmic processing including, but not limited to, correlation, cross-correlation, sum of absolute differences processing or other similar methods to obtain the local displacement or vibration of the biological tissue in the region to be observed, or the propagation velocity of the shear wave generated thereby, caused by the acoustic radiation forces.
S8: the elasticity of biological tissue is estimated from the local tissue displacement or the propagation velocity of shear waves: the relative stiffness of the tissue to be observed is estimated from the local tissue displacement, or the elasticity of the biological tissue is estimated from the relationship between the shear wave propagation velocity and the elastic modulus of the biological tissue.
The probe of the multi-frequency ultrasonic probe of the present embodiment has ultrasonic frequencies including a first frequency ultrasonic wave and a second frequency ultrasonic wave. The frequency of the second frequency ultrasonic wave is smaller than that of the first frequency ultrasonic wave, the first frequency ultrasonic wave is used for acquiring second channel data, and the second frequency ultrasonic wave is used for generating an excitation source and an excitation mode of acoustic radiation force. Further, the frequency of the ultrasonic wave for acquiring the first channel data may be the same as or different from the frequency of the first frequency ultrasonic wave. In the present embodiment, the frequency of the ultrasonic wave for acquiring the first channel data may be any frequency.
The multi-frequency ultrasonic probe of the embodiment can work at a plurality of ultrasonic frequencies, and multi-frequency elastic ultrasonic imaging is realized by emitting ultrasonic waves with different frequencies as excitation sources of acoustic radiation force and acquiring second channel data. The method can realize rapid elastic measurement and imaging from the tissue superficial to the deeper region by only using one probe.
Example 3
The present embodiment is an acoustic radiation force elastography system based on a multi-frequency ultrasound probe using the acoustic radiation force elastography method based on a multi-frequency ultrasound probe provided in embodiment 1 or 2.
Referring to fig. 5 of the drawings, an acoustic radiation force elastography system based on a multi-frequency ultrasound probe includes:
and the reference data acquisition module: b-mode signal acquisition is carried out on the initial state of the region to be observed and the initial state is stored as first channel data, and the first channel data is used for acquiring information of the region to be observed and is used as an initial state reference of ARFI imaging.
And a judging module: and determining an appropriate excitation source and an excitation mode of the acoustic radiation force according to the information such as the position, the thickness, the acoustic attenuation and the like of the region to be observed.
The excitation source of the acoustic radiation force varies depending on the position, thickness, acoustic attenuation, etc. of the region to be observed, for example: elastic measurements of thinner superficial tissue are stimulated with acoustic radiation forces using the first transducer assembly 1. Elasticity measurement of thicker tissue: the first transducer assembly 1 is used for shallowest excitation and the second transducer assembly 2 is used for deeper excitation. If the tissue to be observed is thin but the sound attenuation along the way is large, the mode of co-excitation of the first transducer assembly 1 and the second transducer assembly 2 can be used: so that the sound waves emitted by different transducers are focused at the same location of the tissue at the same time. If the tissue to be observed is thicker and the sound attenuation along the way is larger, the first transducer assembly and the second transducer assembly are jointly excited, and the focal position excitation is rapidly changed along the thickness direction.
The original data acquisition module: for exciting tissue vibrations in a region of biological tissue to be observed and transmitting and receiving ultrasonic signals to track the tissue vibrations, resulting in second channel data, comprising: an acoustic radiation force excitation unit and an ultrasonic signal transmitting and receiving unit.
An acoustic radiation force excitation unit: the multi-frequency ultrasonic probe is used for exciting local tissue displacement or shear wave in the region to be observed by utilizing acoustic radiation force by using an excitation source and an excitation mode determined by the judging module.
Ultrasonic signal transmitting and receiving unit: the multi-frequency ultrasonic probe is used for transmitting longitudinal wave ultrasonic signals, the first transducer assembly 1 of the multi-frequency ultrasonic probe is used for receiving echo signals, or the first transducer assembly 1 and the second transducer assembly 2 are used for cooperatively receiving echoes, so that second channel data are obtained.
The channel data processing module: and the IQ data is obtained by filtering and reconstructing the second channel data and/or the first channel data acquired by the data acquisition module.
An IQ data processing module: the IQ data is used for carrying out related algorithm processing to obtain local tissue displacement generated by acoustic radiation force in the region to be observed or propagation speed of shear wave generated by the local tissue displacement. The method for carrying out correlation algorithm processing on the IQ data comprises the following steps: correlation processing is performed on the IQ data, cross-correlation processing is performed on the IQ data, absolute difference summation processing is performed on the IQ data, or other similar method processing is performed on the IQ data. And performing correlation algorithm processing on the IQ data to obtain a tissue displacement or a change result of the tissue displacement along with time, wherein the tissue displacement is directly generated by acoustic radiation force or generated by shear wave propagation in the region to be observed.
Elasticity estimation and imaging module: for estimating the elasticity of the biological tissue from the local tissue displacement or shear wave propagation velocity and generating a tissue elasticity image: the relative stiffness of the biological tissue is estimated from the local tissue displacement, or the elasticity of the biological tissue is estimated from the relationship between the shear wave propagation velocity and the elastic modulus of the biological tissue and a tissue elasticity image is generated.
In summary, the invention provides an acoustic radiation force elastic imaging method based on a multi-frequency ultrasonic probe, which uses a single probe to measure the elasticity of tissues with different depths and thicknesses, and can realize simultaneous, multi-frequency and multi-region acoustic radiation force excitation by using the single probe; the method overcomes the defects of the conical wave fronts of the prior supersonic shear wave sources and can generate true cylindrical wave fronts. Further, a quick elastic measurement and imaging of the region from the superficial to the deeper tissue can be achieved by just a single probe without moving or switching the probe. The bandwidth limitation of the conventional single-frequency transducer array is broken through, and the first transducer assembly can be used for image acquisition while the high-efficiency acoustic radiation force excitation is carried out on a deeper region, so that the elastography quality is improved.
The foregoing description is only of the preferred embodiments of the present invention, and there are no limitations to the present invention, but rather, the embodiments may be modified in various ways, and the technical features of the above embodiments may be combined with each other, so that any modification, equivalent replacement, improvement, etc. that are within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (11)
1. An acoustic radiation force elastic imaging method based on a multi-frequency ultrasonic probe, the multi-frequency ultrasonic probe comprises a first transducer assembly and a second transducer assembly, the second transducer assembly comprises two or more transducers, the two or more transducers are arranged at two sides or around the first transducer assembly, the frequency of the second transducer assembly is lower than that of the first transducer assembly, the method is characterized in that,
Acquiring a region to be observed of biological tissues;
B-mode signal acquisition is carried out on the initial state of the region to be observed and the initial state is stored as first channel data, wherein the first channel data are used for acquiring information of the region to be observed, and the information comprises the position, thickness and sound attenuation of the region to be observed;
determining an excitation source and an excitation mode of the acoustic radiation force according to the information, wherein the excitation source and the excitation mode of the acoustic radiation force comprise:
individually exciting using a first transducer assembly array of the multi-frequency ultrasound probe;
Or, a plurality of second transducer assembly arrays using the multi-frequency ultrasound probe are individually or collectively excited;
or, co-exciting with the first transducer assembly array and the second transducer assembly array of the multi-frequency ultrasound probe;
or, transmitting a primary focusing beam by using the multi-frequency ultrasonic probe for excitation;
or, transmitting a plurality of focusing beams to the biological tissue for excitation by using the multi-frequency ultrasonic probe;
generating local displacement and vibration of tissues in the region to be observed by using the excitation source and the excitation mode;
Transmitting and receiving ultrasonic signals in the region to be observed to obtain second channel data for tracking the local displacement and vibration of the tissue;
post-processing the acquired second channel data to obtain elastic information of the biological tissue of the region to be observed;
The excitation source is a multi-frequency ultrasonic probe, the multi-frequency ultrasonic probe is used for transmitting first frequency ultrasonic waves and second frequency ultrasonic waves, the frequency of the second frequency ultrasonic waves is smaller than that of the first frequency ultrasonic waves, the first frequency ultrasonic waves are used for acquiring the second channel data, and the second frequency ultrasonic waves are used for generating an excitation source and an excitation mode of sound radiation force.
2. The method of claim 1, wherein after the second channel data is obtained by transmitting and receiving ultrasonic signals in the region to be observed, and before post-processing the acquired second channel data, the method further comprises:
adjusting the focus position of the excitation pulse, repeating the operations of exciting the local displacement and vibration of the tissue and transmitting and receiving ultrasonic signals, and scanning the region to be observed;
And/or, carrying out post-processing on the acquired first channel data.
3. The acoustic radiation force elastography method based on multi-frequency ultrasound probe of claim 1, wherein the multi-frequency ultrasound probe has one probe having a plurality of ultrasound frequencies, the ultrasound frequencies of the probe comprising the first frequency ultrasound and the second frequency ultrasound.
4. The method of acoustic radiation force elastography based on multi-frequency ultrasound probe according to claim 1, wherein when the excitation pattern of the acoustic radiation force is a common excitation,
The same frequency or different frequencies can be used for simultaneous excitation of the same focus or different focuses;
or, the same frequency or different frequencies are used for time-sharing excitation on the same focus or different focuses.
5. The method for elastic imaging of acoustic radiation force based on a multi-frequency ultrasonic probe according to claim 1, wherein the determining the excitation source and the excitation mode of the acoustic radiation force according to the information of the region to be observed comprises:
separately energizing a shallowest layer of the biological tissue or a thicker shallowest layer of the biological tissue with a first transducer assembly array of the multi-frequency ultrasound probe;
Separately or jointly exciting a thicker deeper of the biological tissue with a second transducer assembly array of the multi-frequency ultrasound probe;
The biological tissue with greater acoustic attenuation along the way is co-excited with the second array of transducer assemblies using the first array of transducer assemblies.
6. The method of claim 1, wherein transmitting and receiving ultrasonic signals at the region to be observed to obtain second channel data comprises:
Transmitting a longitudinal wave ultrasonic sequence to the region to be observed by using the multi-frequency ultrasonic probe, and receiving the echo generated in the biological tissue by using the first transducer assembly to obtain the second channel data, or receiving the echo generated in the biological tissue by using the first transducer assembly and the second transducer assembly in a cooperative manner to obtain the second channel data.
7. The acoustic radiation force elastography method based on multi-frequency ultrasound probe of claim 1, wherein the post-processing the acquired second channel data to obtain elasticity information of the biological tissue of the region to be observed comprises:
performing filtering reconstruction on the acquired second channel data to obtain IQ data;
performing corresponding algorithm processing on the IQ data to obtain local displacement or vibration of the biological tissue generated by the acoustic radiation force in the region to be observed or the propagation speed of shear waves generated by the local displacement or vibration;
The elasticity of the biological tissue is estimated based on local tissue displacement or propagation velocity of the shear wave.
8. The acoustic radiation force elastography method based on multi-frequency ultrasound probe of claim 7, wherein said performing corresponding algorithmic processing of said IQ data comprises:
performing correlation processing on the IQ data;
or, carrying out cross-correlation processing on the IQ data;
Or, carrying out absolute difference summation processing on the IQ data.
9. The acoustic radiation force elastography method based on multi-frequency ultrasound probe of claim 7, wherein said estimating elasticity of said biological tissue from said local tissue displacement or propagation velocity of said shear wave comprises:
obtaining the relative elasticity or the relative hardness of the tissue according to the amplitude of the local tissue displacement obtained by scanning; or estimating elasticity of the biological tissue according to a relation between the propagation speed of shear waves and the elastic modulus of the biological tissue.
10. The acoustic radiation force elastography method based on multi-frequency ultrasound probe of claim 9, wherein the relation between the shear wave propagation velocity and the elastic modulus of the biological tissue comprises: Wherein E represents the elastic modulus of the isotropic pure elastic bulk tissue, cs represents the shear wave propagation velocity of the isotropic pure elastic bulk tissue, ρ represents the tissue density of the isotropic pure elastic bulk tissue;
Or alternatively, the first and second heat exchangers may be, Wherein μ1 represents the shear elastic modulus of the isotropic Kelvin-Voigt viscoelastic material, μ2 represents the shear viscosity of the isotropic Kelvin-Voigt viscoelastic material, ω s represents the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material, and c s(ωs) represents the shear wave propagation velocity at which the shear wave angular frequency of the isotropic Kelvin-Voigt viscoelastic material is ω s.
11. An acoustic radiation force elastography system based on a multi-frequency ultrasound probe for performing the method of any of claims 1-10, comprising:
And the reference data acquisition module: the method comprises the steps of performing B-mode signal acquisition on an initial state of a region to be observed of biological tissues and storing the initial state as first channel data, wherein the first channel data are used for acquiring information of the region to be observed;
and a judging module: the excitation source and the excitation mode are used for determining the sound radiation force according to the information of the region to be observed;
the original data acquisition module: the ultrasonic sensor is used for exciting tissue vibration in a region to be observed of biological tissue, transmitting and receiving ultrasonic signals to track the tissue vibration, and obtaining second channel data;
The channel data processing module: the first channel data and/or the second channel data are/is used for carrying out filtering reconstruction on the second channel data and/or the first channel data to obtain IQ data;
an IQ data processing module: the IQ data is used for carrying out related algorithm processing to obtain local tissue displacement generated by acoustic radiation force in the region to be observed or the propagation speed of shear wave generated by the local tissue displacement;
elasticity estimation and imaging module: for estimating the elasticity of the biological tissue from the local tissue displacement or shear wave propagation velocity and generating a tissue elasticity image.
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| CN101912278A (en) * | 2010-08-12 | 2010-12-15 | 陈庆武 | Ultrasound dynamic elastic imaging probe and method |
| CN106175831A (en) * | 2016-09-28 | 2016-12-07 | 重庆理工大学 | A kind of tissue viscoelasticity based on shearing wave amplitude and phase-detection measuring method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101912278A (en) * | 2010-08-12 | 2010-12-15 | 陈庆武 | Ultrasound dynamic elastic imaging probe and method |
| CN106175831A (en) * | 2016-09-28 | 2016-12-07 | 重庆理工大学 | A kind of tissue viscoelasticity based on shearing wave amplitude and phase-detection measuring method |
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