WO2024109776A1 - 一种超声平面波成像方法、装置及设备 - Google Patents

一种超声平面波成像方法、装置及设备 Download PDF

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WO2024109776A1
WO2024109776A1 PCT/CN2023/133079 CN2023133079W WO2024109776A1 WO 2024109776 A1 WO2024109776 A1 WO 2024109776A1 CN 2023133079 W CN2023133079 W CN 2023133079W WO 2024109776 A1 WO2024109776 A1 WO 2024109776A1
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imaging
radio frequency
target tissue
frequency signal
deflection angle
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PCT/CN2023/133079
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English (en)
French (fr)
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潘钥
杨戈
刘荣
王宁远
邱维宝
郑海荣
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中国科学院深圳先进技术研究院
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Publication of WO2024109776A1 publication Critical patent/WO2024109776A1/zh

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves

Definitions

  • the present invention relates to the field of image processing, and in particular to an ultrasonic plane wave imaging method, device and equipment.
  • Ultrasonic imaging has the advantages of being non-invasive, safe, convenient, and highly real-time. It is widely used in fetal, cardiac, and abdominal imaging and is one of the most important imaging modes in clinical diagnosis. Ultrasonic plane wave imaging uses plane wave pulses to image the entire study area at once, replacing the traditional focused beam transmission. Its image frame rate is greatly improved, reaching 4000 to 15000 frames per second, and plays an important role in ultrafast Doppler imaging, shear wave elastic imaging, brain function imaging, and other studies. In order to improve the imaging quality of ultrasonic plane waves, a plane wave coherent composite imaging method (CPWC) was developed. Multiple plane wave pulses are continuously emitted at different deflection angles, and then the imaging results at different angles are combined to form the final reconstructed image.
  • CPWC plane wave coherent composite imaging method
  • plane wave imaging obtains ultrasonic images through point-by-point delay superposition (DAS) wave number synthesis.
  • DAS point-by-point delay superposition
  • the speed of the entire medium is assumed to be uniform and the sound wave propagates in a straight line.
  • the sound speed in the actual tissue is variable, causing reflection, refraction, and deflection of the sound wave, and the imaging result shows noise reverberation.
  • real-time processing of ultrasound images at multiple angles results in a huge amount of calculation, which poses a huge challenge to data processing performance.
  • the embodiments of this invention provide an ultrasonic plane wave imaging method, device and apparatus.
  • the method performs imaging based on the reverse time migration of the wave equation, can estimate the sound velocity in a layered medium in a variable velocity medium, and uses less deflection angle data than the plane wave coherent composite imaging method. Achieve higher resolution and contrast images, and more reliable imaging results.
  • the embodiments of this invention provide an ultrasonic plane wave imaging method, comprising:
  • Each array element of the array ultrasound linear array probe transmits ultrasound to the target tissue in sequence according to the first predetermined transmission parameter to obtain an original radio frequency signal, rearranges the common reflection point data of the original radio frequency signal, performs energy superposition in the direction of the reflection event axis to obtain a velocity spectrum, and obtains a local velocity model at different depths;
  • Each array element of the array ultrasound linear array probe transmits a multi-angle ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and multiple deflection angles, images the tissue based on the received radio frequency signal combined with the local velocity model, and coherently superimposes the imaging results of the multiple deflection angles to obtain the imaging result of the target tissue.
  • step of obtaining the local velocity model further includes:
  • the first predetermined transmission parameter includes the delay time and imaging depth of each array element of the array ultrasound linear array probe for successive transmission, receives multiple reflected ultrasound waves from multiple layers of tissue in the target tissue, forms an original radio frequency signal, rearranges the common reflection point data of the original radio frequency signal, performs energy superposition in the direction of the reflection phase axis, obtains a velocity spectrum, calculates the velocity of the original radio frequency signal at different depths based on the velocity spectrum, and obtains the local velocity model.
  • the local velocity model describes the velocity relationship between the multiple array elements and the corresponding original radio frequency signals for different layers of tissue.
  • the array element includes a transmitting array element and a receiving array element, and the first predetermined transmitting parameter includes an interval time and an imaging depth;
  • the local velocity model is the velocity corresponding to the maximum amplitude of the velocity spectrum line A1 , and the formula is:
  • N is the time window length determined according to the initial time value and the interval time.
  • the step of obtaining the imaging result of the target tissue also includes:
  • Each array element of the array ultrasound linear array probe transmits an ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and a plurality of deflection angles, and obtains a radio frequency signal corresponding to each deflection angle, wherein the radio frequency signal includes the transmitted ultrasonic plane wave and the ultrasonic plane wave reflected by multiple layers of tissue in the target tissue;
  • the transmitted forward field and the received inversion field corresponding to a deflection angle are calculated according to the cross-correlation imaging condition to obtain the imaging result of the deflection angle;
  • the imaging results of multiple deflection angles are coherently superimposed to obtain the imaging result of the target tissue.
  • calculating the transmission forward field corresponding to a deflection angle according to the local velocity model and a second predetermined transmission parameter of the ultrasonic plane wave corresponding to the deflection angle further includes:
  • the first second-order partial differential acoustic wave equation is solved by using a staggered grid finite difference time domain method to obtain the extended wave fields at different times as the transmitting forward modeling field.
  • the second second-order partial differential acoustic wave equation is solved using a finite difference method to obtain extended wave fields at different times as the receiving inversion field.
  • the transmit forward field and receive inversion field corresponding to a deflection angle are calculated according to the cross-correlation imaging condition, and the formula for obtaining the imaging result of the deflection angle is:
  • T represents the total acquisition time in the second predetermined transmission sequence
  • t represents time
  • S ⁇ represents the transmission forward field corresponding to the deflection angle ⁇ k
  • R ⁇ represents the reception inversion field corresponding to the deflection angle ⁇ k
  • x (x, y, z) represents the spatial vector corresponding to each point in the imaging area.
  • Image(x) represents the imaging result of the target tissue
  • ⁇ represents the total number of the deflection angles
  • an ultrasonic plane wave imaging device comprising:
  • a local velocity model calculation unit is used for each array element of the array ultrasound linear array probe to transmit ultrasound to the target tissue in accordance with the first predetermined transmission parameter one by one to obtain an original radio frequency signal, rearrange the common reflection point data of the original radio frequency signal, perform energy superposition in the direction of the reflection event axis, obtain a velocity spectrum, and obtain local velocity models at different depths;
  • the target imaging result calculation unit is used for each array element of the array ultrasound linear array probe to transmit a multi-angle ultrasonic plane wave to the target tissue according to the second predetermined transmission parameter and multiple deflection angles, and to image the tissue according to the received radio frequency signal combined with the local velocity model, and to coherently superimpose the imaging results of the multiple deflection angles to obtain the imaging result of the target tissue.
  • an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored in the memory, and the processor implements the above method when executing the computer program.
  • an embodiment of the present invention further provides a computer storage medium on which a computer program is stored.
  • the computer program is executed by a processor of a computer device, the above method is executed.
  • each array element of the array ultrasound linear array probe successively transmits ultrasound to the target tissue according to the first predetermined transmission parameter, and the transmitted ultrasound and the ultrasound reflected by the multiple layers of tissue in the target tissue are combined.
  • the sound wave forms an original radio frequency signal, and then a local velocity model is constructed based on the original radio frequency signal.
  • the local velocity model can estimate the propagation speed of ultrasound in each layer of tissue.
  • the array elements of the array ultrasound linear array probe transmit ultrasonic plane waves to the target tissue according to the second predetermined transmission parameters and multiple deflection angles.
  • the transmitted ultrasonic plane waves and the ultrasonic plane waves reflected by multiple layers of tissue in the target tissue form radio frequency signals corresponding to each deflection angle, and the imaging results of the target tissue are obtained based on the radio frequency signal and the local velocity model.
  • FIG1 is a schematic diagram of an implementation system of an ultrasonic plane wave imaging method according to an embodiment of the present invention
  • FIG2 is a schematic diagram showing a flow chart of an ultrasonic plane wave imaging method according to an embodiment of the present invention
  • FIG3 is a schematic diagram showing a detailed flow chart of an ultrasonic plane wave imaging method according to an embodiment of the present invention.
  • FIG4 is a schematic diagram of a hyperbolic radio frequency signal in an embodiment of this invention.
  • FIG5 shows the steps of calculating the transmission forward field corresponding to a deflection angle according to the local velocity model and the second predetermined transmission parameter of the ultrasonic plane wave corresponding to the deflection angle in the embodiment of this invention
  • FIG6 shows the steps of calculating the receiving inversion field of the deflection angle according to the radio frequency signal corresponding to the deflection angle in the embodiment of this article
  • FIG7 is a schematic diagram showing the structure of an ultrasonic plane wave imaging device according to an embodiment of the present invention.
  • FIG8 is a schematic diagram showing the detailed structure of an ultrasonic plane wave imaging device according to an embodiment of the present invention.
  • FIG. 9 is a schematic diagram showing the structure of a computer device according to an embodiment of the present invention.
  • a schematic diagram of an implementation system of an ultrasonic plane wave imaging method may include a terminal 101 and a server 102.
  • a communication connection is established between the terminal 101 and the server 102 to enable data interaction.
  • a staff member may input a radio frequency signal obtained by scanning a target tissue with an array ultrasonic linear array probe into the server 102 through the terminal 101, and the server 102 generates an image of the target tissue according to the radio frequency signal input by the terminal 101.
  • the server 102 can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, content delivery networks (CDN, Content Delivery Network), and big data and artificial intelligence platforms.
  • cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, content delivery networks (CDN, Content Delivery Network), and big data and artificial intelligence platforms.
  • the terminal 101 may include but is not limited to electronic devices such as desktop computers, tablet computers, laptop computers, etc.
  • the operating system running on the electronic device may include but is not limited to Android system, IOS system, Linux, Windows, etc.
  • FIG. 1 is only one application environment provided by the present disclosure. In actual applications, other application environments may also be included, and this specification does not limit this.
  • an embodiment of the present invention provides an ultrasonic plane wave imaging method, which performs imaging based on the reverse time migration of the wave equation, can estimate the speed of sound in a layered medium in a variable speed medium, and uses less deflection angle data than the plane wave coherent composite imaging method to achieve higher resolution and contrast images, and the imaging results are more reliable.
  • FIG2 is a flow chart of an ultrasonic plane wave imaging method of an embodiment of the present invention. This figure describes the process of imaging the target tissue, but may include more or fewer operating steps based on conventional or non-creative labor. The steps listed in the embodiment are as follows: The step sequence is only one way of executing the steps in many order, and does not represent the only execution order. When the system or device product is executed in practice, it can be executed in sequence or in parallel according to the method shown in the embodiment or the accompanying drawings. Specifically, as shown in FIG2, it can be executed by a processor, and the method may include:
  • Step 201 each array element of the array ultrasound linear array probe transmits ultrasound to the target tissue in sequence according to the first predetermined transmission parameter to obtain an original radio frequency signal, rearranges the common reflection point data of the original radio frequency signal, performs energy superposition in the direction of the reflection event axis to obtain a velocity spectrum, and obtains a local velocity model at different depths;
  • Step 202 Each array element of the array ultrasound linear array probe transmits a multi-angle ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and a plurality of deflection angles, images the tissue based on the received radio frequency signal in combination with the local velocity model, and coherently superimposes the imaging results of the plurality of deflection angles to obtain an imaging result of the target tissue.
  • each array element of the array ultrasound linear array probe successively transmits ultrasound to the target tissue according to the first predetermined transmission parameter, and the transmitted ultrasound and the ultrasound reflected by the multiple layers of tissue in the target tissue form an original radio frequency signal, and then a local velocity model is constructed based on the original radio frequency signal.
  • the local velocity model can estimate the propagation speed of the ultrasound in each layer of tissue, and then each array element of the array ultrasound linear array probe transmits an ultrasound plane wave to the target tissue according to the second predetermined transmission parameter and multiple deflection angles, and the transmitted ultrasound plane wave and the ultrasound plane wave reflected by the multiple layers of tissue in the target tissue form a radio frequency signal corresponding to each deflection angle, and the imaging result of the target tissue is obtained according to the radio frequency signal and the local velocity model.
  • FIG3 a detailed flow chart of the ultrasonic plane wave imaging method described in the embodiment of this invention is shown in FIG3 , which specifically includes the following steps:
  • Step 301 each array element of the array ultrasound linear array probe successively transmits an ultrasonic wave to the target tissue according to a first predetermined transmission parameter, obtains a plurality of reflected ultrasonic waves from multiple layers of tissue in the target tissue, forms an original radio frequency signal according to the transmitted ultrasonic wave and the ultrasonic waves reflected from multiple layers of tissue in the target tissue, rearranges the common reflection point data of the original radio frequency signal, performs energy superposition in the direction of the reflection event axis, obtains a velocity spectrum, calculates the velocity of the original radio frequency signal at different depths according to the velocity spectrum, and obtains a local velocity model;
  • Step 302 each array element of the array ultrasound linear array probe transmits an ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and a plurality of deflection angles, and obtains a radio frequency signal corresponding to each deflection angle, wherein the radio frequency signal includes the transmitted ultrasonic plane wave and the ultrasonic plane wave reflected by multiple layers of tissue in the target tissue;
  • Step 303 calculating a transmit forward field corresponding to a deflection angle according to the local velocity model and a second predetermined transmit parameter of an ultrasonic plane wave corresponding to the deflection angle, and calculating a receive inversion field of the deflection angle according to a radio frequency signal corresponding to the deflection angle;
  • Step 304 Calculate the transmit forward field and receive inversion field corresponding to a deflection angle according to the cross-correlation imaging condition to obtain the imaging result of the deflection angle;
  • Step 305 coherently superimpose the imaging results of multiple deflection angles to obtain the imaging result of the target tissue.
  • each array element of the array ultrasound linear array probe is first controlled to transmit ultrasound to the target tissue in the manner of transmitting ultrasound one by one by a single array element.
  • the first predetermined parameter may include the transmission interval time and the imaging depth.
  • the interval time may be the interval time for each array element to transmit ultrasound one by one.
  • the imaging depth indicates the depth of the ultrasound reflection point in the target tissue.
  • the imaging depth can be controlled by controlling the energy of the ultrasound transducer. Multiple imaging depths correspond to multiple layers of tissue in the target tissue. After the ultrasound emitted by the transmitting array element reaches the corresponding layer of tissue in the target tissue according to the imaging depth, the ultrasound is reflected back and received by the receiving array element. The transmitted ultrasound and the reflected ultrasound are used as the original radio frequency signal.
  • the channel data symmetrical with the transmitting array element about the linear array center is extracted from the original radio frequency signal emitted by each array element, and the original signal is rearranged according to the receiving channel position, and the original data of all array elements are synthesized into a data matrix. Because the ultrasound waves emitted by each transmitting array element at the same imaging depth are reflected back at the same point on the corresponding layer of tissue at the imaging depth, this rearrangement of the original RF signal can be called common reflection point (or common center point) data rearrangement. Then, energy superposition is performed in the direction of the reflection phase axis to obtain a velocity spectrum. The velocity of the original RF signal at different depths is calculated based on the velocity spectrum to obtain a local velocity model.
  • each array element of the array ultrasound linear array probe is controlled to transmit an ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and a plurality of deflection angles, that is, the ultrasonic plane wave is controlled to be transmitted at different deflection angles, and the ultrasonic plane wave transmitted at a deflection angle and the received ultrasonic plane wave are used as the radio frequency signal corresponding to the deflection angle.
  • the reverse time migration method based on the wave equation is used to calculate the transmission forward field corresponding to a deflection angle according to the local velocity model and the transmission parameters of the ultrasonic plane wave corresponding to the deflection angle, and the reception inversion field of the deflection angle is calculated according to the radio frequency signal corresponding to the deflection angle.
  • the transmission forward field and the reception inversion field corresponding to the deflection angle are calculated according to the cross-correlation imaging conditions to obtain the imaging result of the deflection angle.
  • the above calculation process is repeated for the radio frequency signals corresponding to different deflection angles to obtain the imaging results of multiple deflection angles.
  • the imaging results of multiple deflection angles are coherently superimposed to obtain accurate and reliable high-resolution, high-contrast images of the target tissue.
  • the purpose of controlling the single array element of the array ultrasound linear array probe to transmit ultrasound waves one by one is to achieve velocity estimation of the target tissue, and the obtained local velocity model describes the velocity relationship between multiple array elements and the corresponding original radio frequency signal for different layers of tissue.
  • the second predetermined transmission parameters include aperture size, imaging depth, number of plane wave tilt angles, transmission frequency and pulse period.
  • the delay time of each array element of the ultrasonic transducer under different plane wave tilt angles is determined in sequence, and ultrasonic plane waves are emitted in sequence according to the delay time; and each array element of the ultrasonic transducer is used to sequentially receive the reflected ultrasonic plane waves under different deflection angles.
  • the common reflection point data of the original radio frequency signal is rearranged, energy is superimposed in the direction of the reflection event axis to obtain a velocity spectrum, and the velocities at different depths are calculated according to the velocity spectrum to obtain a local velocity model, which includes the following steps:
  • Each original RF signal is rearranged in the order of symmetry between the transmitting array element and the receiving array element about the center of the linear array to obtain a hyperbolic RF signal.
  • the deployment relationship between the transmitting array element and the receiving array element can be shown in Figure 3.
  • O center point of the linear array
  • S transmitting array element
  • G symmetric point about point O
  • the ultrasonic wave emitted by S is emitted at point R of the target tissue layer and received by G.
  • the horizontal projection point of R is O.
  • This common center point signal arrangement method makes the ultrasonic waves emitted by each array element at point R. Reflection occurs and is received by its symmetrical array element.
  • the horizontal distance between the transmitter S and the receiver G is x
  • the depth of the target interface is h 0 .
  • T SG of the ultrasonic wave emitted by the array element S is expressed as formula (1):
  • the transit time T SG and the horizontal distance x form a hyperbolic equation. represents the distance between the emission S and the reflection R, Represents the distance between the reflection R and the reception G.
  • the layer velocity is v, then a hyperbolic trajectory is uniquely determined on each data channel of the receiving array element.
  • fi (t) represents the hyperbolic radio frequency signal corresponding to the i-th array element
  • t represents time
  • M represents the number of array elements on the array ultrasound linear array probe.
  • point S represents the point of the transmitting array element
  • point R represents the reflection point on the tissue
  • point G is the point of the receiving array element symmetrical to the center of point S of the transmitting array element
  • point O is the calculated center point
  • h0 represents the depth.
  • X1, X2, ..., Xi, ..., XM represent multiple array elements
  • t0 corresponds to the vertex position of a hyperbolic radio frequency signal in the above original signal.
  • the initial time values corresponding to the L hyperbolic radio frequency signals are t01 , t02 , ..., t0L respectively; for each t0 , the initial value range of the velocity is defined as [ v1 , vL ], where v1 represents the starting value of the initial range of the velocity, and vL represents the ending value of the initial range of the velocity. It is necessary to ensure that the velocity in the area where the target tissue is located is within this initial range.
  • the ordinate represents speed and the abscissa represents time.
  • the time corresponding to the vertex of the hyperbolic RF signal of a layer of tissue corresponding to an array element is taken as the initial time value (that is, the fixed point of the hyperbola shown in (c) in FIG4 ), and the imaging depth corresponds to the tissue one by one.
  • the initial time value corresponds to the reflection time of the two-way vertical distance of a layer of tissue in the target tissue (that is, the round-trip time from point O to point R), and the vertical distance represents the vertical distance between the straight line formed by a transmitting array element and the corresponding receiving array element and the reflection point in the layer of tissue (that is, the distance from point O to point R).
  • the hyperbolic RF signal is scanned according to the experimental speed value, and the time delay of the i-th array element is calculated, and the formula is (4):
  • t ij represents the time delay corresponding to the jth experimental velocity value of the ith array element
  • t 0l represents the initial time value
  • M represents the number of array elements
  • xi represents the horizontal distance between the receiving array element of the ith array element and its corresponding transmitting array element
  • v j represents the jth experimental velocity value
  • the velocity spectra corresponding to the multiple initial time values are taken as the velocity spectrum set of the i-th array element
  • the velocity spectrum calculated by formula (5) is actually the superposition amplitude corrected and superimposed with different velocities.
  • calculating the transmission forward field corresponding to a deflection angle according to the local velocity model and a second predetermined transmission parameter of an ultrasonic plane wave corresponding to the deflection angle further includes:
  • Step 501 constructing first and second order partial differential acoustic wave equations at different imaging depths according to the local velocity model and the second predetermined transmission parameters;
  • the first and second order partial differential acoustic wave equations at different imaging depths are constructed according to the local velocity model and the second predetermined transmission parameters as formula (6):
  • c(x) is the local velocity model at different positions x
  • Laplace operator is the initial condition of the equation
  • f(t) is the sound source function located at xS at time t
  • ⁇ is the Kronecker function
  • ⁇ is the deflection angle of the plane wave.
  • Step 502 using a staggered grid finite difference time domain method to solve the first second-order partial differential acoustic wave equation, and obtaining extended wave fields at different times as the transmit forward modeling field.
  • calculating the receiving inversion field of the deflection angle according to the radio frequency signal corresponding to the deflection angle further includes:
  • Step 601 Arrange the radio frequency signals in descending order of data time to obtain a time reverse propagation signal P(x R ,t);
  • the second second-order partial differential acoustic wave equation is constructed according to the time reverse propagation signal as formula (7):
  • Step 603 using a finite difference method to solve the second second-order partial differential acoustic wave equation, and obtaining extended wave fields at different times as the receiving inversion field.
  • the transmit forward field and the receive inversion field corresponding to a deflection angle are calculated according to the cross-correlation imaging condition, and the imaging result of the deflection angle is obtained by formula (8),
  • T represents the total acquisition time in the second predetermined transmission sequence
  • t time
  • S ⁇ represents the transmission forward field corresponding to the deflection angle ⁇
  • R ⁇ represents the reception inversion field corresponding to the deflection angle ⁇
  • x (x, y, z) represents the spatial vector corresponding to each point in the imaging area.
  • the imaging results of multiple deflection angles are coherently superimposed to obtain the imaging result of the target tissue using the formula (9),
  • Image(x) represents the imaging result of the target tissue
  • ⁇ represents the total number of the deflection angles
  • the embodiment of this invention further provides an ultrasonic plane wave imaging device, as shown in FIG7 , comprising:
  • the local velocity model calculation unit 701 is used for each array element of the array ultrasound linear array probe to transmit ultrasound to the target tissue according to the first predetermined transmission parameter one by one to obtain an original radio frequency signal, rearrange the common reflection point data of the original radio frequency signal, perform energy superposition in the direction of the reflection event axis, obtain a velocity spectrum, and obtain a local velocity model at different depths;
  • the target imaging result calculation unit 702 is used for each array element of the array ultrasound linear array probe to transmit a multi-angle ultrasonic plane wave to the target tissue according to the second predetermined transmission parameter and multiple deflection angles, and to image the tissue according to the received radio frequency signal combined with the local velocity model, and to coherently superimpose the imaging results of the multiple deflection angles to obtain the imaging result of the target tissue.
  • FIG8 a detailed structural diagram of the ultrasonic plane wave imaging device described in the embodiment of this invention is shown, including:
  • the local velocity model calculation unit 701 is further used for each array element of the array ultrasound linear array probe to transmit ultrasonic waves to the target tissue in accordance with the first predetermined transmission parameter one by one, obtain multiple reflected ultrasonic waves of multiple layers of tissue in the target tissue, form an original radio frequency signal according to the transmitted ultrasonic waves and the ultrasonic waves reflected by the multiple layers of tissue in the target tissue, rearrange the common reflection point data of the original radio frequency signal, perform energy superposition in the direction of the reflection event axis to obtain a velocity spectrum, calculate the velocity of the original radio frequency signal at different depths according to the velocity spectrum, and obtain a local velocity model;
  • the target imaging result calculation unit 702 further includes:
  • the radio frequency signal acquisition module 7021 is used for each array element of the array ultrasound linear array probe to transmit an ultrasonic plane wave to the target tissue according to a second predetermined transmission parameter and a plurality of deflection angles, and obtain a radio frequency signal corresponding to each deflection angle, wherein the radio frequency signal includes the transmitted ultrasonic plane wave and the ultrasonic plane wave reflected by multiple layers of tissue in the target tissue;
  • the transmit forward field and receive inversion field calculation module 7022 is used to calculate the transmit forward field corresponding to a deflection angle according to the local velocity model and the transmit parameters of the ultrasonic plane wave corresponding to the deflection angle, and calculate the receive inversion field of the deflection angle according to the radio frequency signal corresponding to the deflection angle;
  • the sub-imaging result calculation module 7023 is used to calculate the transmission forward field and the reception inversion field corresponding to a deflection angle according to the cross-correlation imaging condition to obtain the imaging result of the deflection angle;
  • the target imaging result calculation module 7024 is used to perform coherent superposition on the imaging results of multiple deflection angles to obtain the imaging result of the target tissue.
  • the implementation of the above device can refer to the implementation of the above method, and the repeated parts will not be repeated.
  • the apparatus in the present invention may be a computer device in this embodiment, and executes the method of the present invention described above.
  • the computer device 902 may include one or more processing devices 904, such as one or more central processing units (CPUs), and each processing unit may implement one or more hardware threads.
  • the computer device 902 may also include any storage resource 906, which is used to store any kind of information such as code, settings, data, etc.
  • the storage resource 906 may include any one or more combinations of the following: any type of RAM, any type of ROM, flash memory device, hard disk, optical disk, etc. More generally, any storage resource may use any technology to store information.
  • any storage resource may provide volatile or non-volatile retention of information.
  • any storage resource may represent a fixed or removable component of the computer device 902.
  • the processing device 904 executes an associated instruction stored in any storage resource or a combination of storage resources, the computer device 902 may perform any operation of the associated instruction.
  • the computer device 902 also includes one or more drive mechanisms 908 for interacting with any storage resource, such as a hard disk drive mechanism, an optical disk drive mechanism, etc.
  • the computer device 902 may also include an input/output module 910 (I/O) for receiving various inputs (via input devices 912) and for providing various outputs (via output devices 914).
  • a specific output mechanism may include a presentation device 916 and an associated graphical user interface (GUI) 918.
  • GUI graphical user interface
  • the input/output module 910 (I/O), input device 912, and output device 914 may not be included, and only the computer device 910 (I/O) may be used as a display device.
  • the computer device 702 may also include one or more network interfaces 920 for exchanging data with other devices via one or more communication links 922.
  • One or more communication buses 924 couple the components described above together.
  • the communication link 922 may be implemented in any manner, for example, through a local area network, a wide area network (e.g., the Internet), a point-to-point connection, etc., or any combination thereof.
  • the communication link 922 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc. governed by any protocol or combination of protocols.
  • the embodiments of this document also provide a computer-readable storage medium, the computer-readable storage medium storing a computer program, and the computer program implements the above method when executed by a processor.
  • the embodiments of the present invention also provide a computer-readable instruction, wherein when a processor executes the instruction, the program therein causes the processor to execute the above method.
  • the disclosed systems, devices and methods can be implemented in other ways.
  • the device embodiments described above are only schematic.
  • the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.
  • the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.
  • the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this article.
  • each functional unit in each embodiment of this document may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.
  • the above integrated unit can be implemented in the form of hardware or in the form of software functional unit.
  • the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.
  • the technical solution of this article is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product.
  • the computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of this article.
  • the aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.

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Abstract

一种超声平面波成像方法、装置及设备，其中方法包括：阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超声波并接收目标组织的反射超声波，生成初始速度模型，对超声波在目标组织内的传播速度进行估计，能够在变速介质中估计分层介质中的声速，各阵元按照第二预定发射参数以及多个偏转角度对目标组织发射超声平面波并接收反射超声平面波，形成射频信号，根据初始速度模型和射频信号计算目标组织的成像。能够获得高分辨率、高对比度的图像，成像结果更可靠，解决了现有技术中成像的质量低、计算量大的问题。

Description

一种超声平面波成像方法、装置及设备 技术领域
本文涉及图像处理领域，尤其涉及一种超声平面波成像方法、装置及设备。
背景技术
超声成像具有非侵入、安全、便捷、实时性高等优点，广泛应用于胎儿、心脏和腹部成像，是临床诊断中最重要的影像模式之一。超声平面波成像通过发射平面波脉冲一次性对整个研究区域进行成像，代替了传统的聚焦束传输，其图像帧频大大提高，可以达到4000～15000帧/秒，在超快多普勒成像、剪切波弹性成像、脑功能成像等研究中发挥重要的作用。为了提高超声平面波的成像质量，发展了平面波相干复合成像方法(CPWC)，在不同的偏转角度下连续发射多个平面波脉冲，然后将不同角度的成像结果组合形成最终的重建图像。该方法虽然提高了图像质量，但是却大大降低了成像帧频。同时，平面波成像通过逐点延时叠加(DAS)波数合成得到超声图像，计算中将整个介质的速度假定为均匀速度、声波按直线传播，而实际组织中的声速是变化的、造成声波的反射、折射、偏转等，成像结果出现噪声混响。另外，通过实时处理多个角度(一般11～75个角度)的超声图像，导致计算量巨大，对数据处理性能提出了巨大的挑战。
现在亟需一种超声平面波成像方法，从而解决现有技术中成像的质量低、计算量大的问题。
发明内容
为解决现有技术中的问题，本文实施例提供了一种超声平面波成像方法、装置及设备，该方法基于波动方程的逆时偏移进行成像，能够在变速介质中估计分层介质中的声速，利用比平面波相干复合成像方法更少的偏转角度数据， 实现更高分辨率、对比度的图像，成像结果更可靠。
为了解决上述技术问题，本文的具体技术方案如下：
一方面，本文实施例提供了一种超声平面波成像方法，包括，
阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
进一步地，得到所述局部速度模型的步骤还包括：
所述第一预定发射参数包括阵列超声线阵探头的各阵元逐次发射的延迟时间和成像深度，接收目标组织中多层组织的多个反射的超声波，形成原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，根据该速度谱计算所述原始射频信号不同深度的速度，得到所述局部速度模型。
进一步地，所述局部速度模型描述了多个阵元针对不同层组织与相应的原始射频信号的速度关系。
进一步地，所述阵元包括发射阵元和接收阵元，所述第一预定发射参数包括间隔时间和成像深度；
所述局部速度模型为使速度谱线A1振幅最大时对应的速度，公式为：
其中，为第i个阵元在时间延迟tij的射频信号的幅值，A1表示所述速度谱线，vj表示扫描速度，M表示阵列超声线阵探头上的阵元个数，N表示根据时间初值以及所述间隔时间确定的时窗长度。
进一步地，得到所述目标组织的成像结果的步骤还包括：
所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射超声平面波，得到各偏转角度对应的射频信号，所述射频信号包括发射的超声平面波和所述目标组织中多层组织反射的超声平面波；
根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场，并根据该偏转角度对应的射频信号计算该偏转角度的接收反演场；
根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果；
对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
进一步地，根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场进一步包括，
根据所述局部速度模型以及所述发射参数构建不同成像深度上的第一二阶偏微分声波方程；
使用交错网格的时域有限差分方法求解所述第一二阶偏微分声波方程，得到不同时刻的延拓波场作为所述发射正演场。
根据该偏转角度对应的射频信号计算该偏转角度的接收反演场进一步包括，
按照数据时间的降序顺序对所述射频信号进行排列，得到时间反向传播信号；
根据所述时间反向传播信号构建第二二阶偏微分声波方程；
使用有限差分方法求解所述第二二阶偏微分声波方程，得到不同时刻的延拓波场作为所述接收反演场。
进一步地，根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果的公式为，
其中，表示第k个偏转角度θk对应的成像结果，T表示所述第二预定发射时序中的采集总时间，t表示时间，Sθ表示偏转角度θk对应发射正演场，Rθ表示偏转角度θk对应接收反演场，x＝(x,y,z)表示成像区内各点对应的空间向量。
进一步地，对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果的公式为，
其中，Image(x)表示所述目标组织的成像结果，Θ表示所述偏转角度的总数。
另一方面，本文实施例还提供了一种超声平面波成像装置，包括，
局部速度模型计算单元，用于阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
目标成像结果计算单元，用于所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
另一方面，本发明实施例还提供了一种计算机设备，包括存储器、处理器、以及存储在存储器上的计算机程序，处理器执行所述计算机程序时实现上述的方法。
另一方面，本发明实施例还提供了一种计算机存储介质，其上存储有计算机程序，计算机程序被计算机设备的处理器运行时，执行上述的方法。
利用本文实施例，首先阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超声波，将发射的超声波和目标组织中多层组织反射的超 声波形成原始射频信号，然后根据原始射频信号构建局部速度模型，该局部速度模型能够估计出超声波在每层组织的传播的速度，然后阵列超声线阵探头各阵元一同按照第二预定发射参数以及多个偏转角度对目标组织发射超声平面波，将发射的超声平面波和目标组织中多层组织反射的超声平面波形成各偏转角度对应的射频信号，根据射频信号和局部速度模型得到目标组织的成像结果。通过本文实施例的方法，能够获得高分辨率、高对比度的图像，成像结果更可靠。解决了现有技术中成像的质量低、计算量大的问题。
附图说明
为了更清楚地说明本文实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本文的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本发明实施例中一种超声平面波成像方法的实施系统示意图；
图2所示为本文实施例一种超声平面波成像方法的流程示意图；
图3所示为本文实施例一种超声平面波成像方法的详细流程示意图；
图4所示为本文实施例中双曲线射频信号的示意图；
图5所示为本文实施例中根据局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场的步骤；
图6所示为本文实施例中根据偏转角度对应的射频信号计算该偏转角度的接收反演场的步骤；
图7所示为本文实施例一种超声平面波成像装置的结构示意图；
图8所示为本文实施例一种超声平面波成像装置的详细结构示意图；
图9所示为本文实施例计算机设备的结构示意图。
【附图标记说明】：
101、终端；102、服务器；701、局部速度模型计算单元；702、目标成像
结果计算单元；7021、射频信号获取模块；7022、发射正演场和接收反演场计算模块；7023、子成像结果计算模块；7024、目标成像结果计算模块；902、计算机设备；904、处理设备；906、存储资源；908、驱动机构；910、输入/输出 模块；912、输入设备；914、输出设备；916、呈现设备；918、图形用户接口；920、网络接口；922、通信链路；924、通信总线。
具体实施方式
下面将结合本文实施例中的附图，对本文实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本文一部分实施例，而不是全部的实施例。基于本文中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本文保护的范围。
需要说明的是，本文的说明书和权利要求书及上述附图中的术语“第一”、“第二”等是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的本文的实施例能够以除了在这里图示或描述的那些以外的顺序实施。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、装置、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
需要说明的是，本申请技术方案中对数据的获取、存储、使用、处理等均符合国家法律法规的相关规定。
如图1所示为本发明实施例一种超声平面波成像方法的实施系统示意图，可以包括终端101和服务器102，所述终端101与所述服务器102之间建立通信连接，能够实现数据的交互。工作人员可以通过终端101将阵列超声线阵探头对目标组织进行扫描得到的射频信号输入到服务器102，服务器102根据终端101输入的射频信号生成目标组织的图像。
在本说明书实施例中，所述服务器102可以是独立的物理服务器，也可以是多个物理服务器构成的服务器集群或者分布式系统，还可以是提供云服务、云数据库、云计算、云函数、云存储、网络服务、云通信、中间件服务、域名服务、安全服务、内容分发网络(CDN,Content Delivery Network)、以及大数据和人工智能平台等基础云计算服务的云服务器。
在一个可选的实施例中，终端101可以包括但不限于台式计算机、平板电脑、笔记本电脑等类型的电子设备。可选的，电子设备上运行的操作系统可以包括但不限于安卓系统、IOS系统、Linux、Windows等。
此外，需要说明的是，图1所示的仅仅是本公开提供的一种应用环境，在实际应用中，还可以包括其他应用环境，本说明书不做限制。
为了解决现有技术中存在的问题，本文实施例提供了一种超声平面波成像方法，该方法基于波动方程的逆时偏移进行成像，能够在变速介质中估计分层介质中的声速，利用比平面波相干复合成像方法更少的偏转角度数据，实现更高分辨率、对比度的图像，成像结果更可靠。图2所示为本文实施例一种超声平面波成像方法的流程示意图。在本图中描述了对目标组织进行成像的过程，但基于常规或者无创造性的劳动可以包括更多或者更少的操作步骤。实施例中列举的步 骤顺序仅仅为众多步骤执行顺序中的一种方式，不代表唯一的执行顺序。在实际中的系统或装置产品执行时，可以按照实施例或者附图所示的方法顺序执行或者并行执行。具体的如图2所示，可以由处理器执行，所述方法可以包括：
步骤201：阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
步骤202：所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
利用本文实施例，首先阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超声波，将发射的超声波和目标组织中多层组织反射的超声波形成原始射频信号，然后根据原始射频信号构建局部速度模型，该局部速度模型能够估计出超声波在每层组织的传播的速度，然后阵列超声线阵探头各阵元一同按照第二预定发射参数以及多个偏转角度对目标组织发射超声平面波，将发射的超声平面波和目标组织中多层组织反射的超声平面波形成各偏转角度对应的射频信号，根据射频信号和局部速度模型得到目标组织的成像结果。通过本文实施例的方法，能够获得高分辨率、高对比度的图像，成像结果更可靠。解决了现有技术中成像的质量低、计算量大的问题。
进一步地，本文实施例所述的超声平面波成像方法的详细流程示意图如图3所示，具体包括如下步骤：
步骤301：阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超声波，获取目标组织中多层组织的多个反射的超声波，根据发射的超声波和所述目标组织中多层组织反射的超声波形成原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，根据该速度谱计算所述原始射频信号不同深度的速度，得到局部速度模型；
步骤302：所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射超声平面波，得到各偏转角度对应的射频信号，所述射频信号包括发射的超声平面波和所述目标组织中多层组织反射的超声平面波；
步骤303：根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场，并根据该偏转角度对应的射频信号计算该偏转角度的接收反演场；
步骤304：根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果；
步骤305：对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
在本文实施例中，首先控制阵列超声线阵探头的各阵元按照单阵元逐个发射超声波的方式对目标组织发射超声波，第一预定参数可以包括发射间隔时间和成像深度，间隔时间可以是各阵元逐个发射超声波的间隔时间，成像深度表示超声波反射点在目标组织内的深度，可以通过控制超声换能器的能量控制成像深度，多个成像深度对应目标组织中的多层组织，发射阵元发射出去的超声波按照成像深度达到目标组织中的对应层组织之后，超声波反射回来被接收阵元接收，将发射的超声波和反射的超声波作为原始射频信号。将每个阵元发射的原始射频信号中，与发射阵元关于线阵中心对称的通道数据提取出来，按照接收通道位置重新排列原始信号，所有阵元的原始数据合成为一个数据矩阵。因为各发射阵元按照同一个成像深度发射的超声波均在该成像深度的对应层组织上的同一点被反射回来，因此这种原始射频信号的重新排列可称为共反射点(或共中心点)数据重排，然后在反射同相轴方向上进行能量叠加，得到速度谱，根据速度谱计算原始射频信号不同深度的速度，得到局部速度模型。
然后控制阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对目标组织发射超声平面波，即控制超声平面波以不同偏转角度发射，将按照一个偏转角度发射的超声平面波和接收的超声平面波作为该偏转角度对应的射频信号。
然后使用基于波动方程的逆时偏移方法，根据局部速度模型以及一个偏转角度对应的超声平面波的发射参数计算该偏转角度对应的发射正演场，并根据该偏转角度对应的射频信号计算该偏转角度的接收反演场，然后根据互相关成像条件对该偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果。不同偏转角度对应的射频信号重复上述计算过程，得到多个偏转角度的成像结果。最后对多个偏转角度的成像结果进行相干叠加，获得目标组织的准确可靠的高分辨率、高对比度的图像。
在本文实施例中，控制阵列超声线阵探头的单个阵元逐次发射超声波的目的是实现对目标组织的速度估计，得到的局部速度模型描述了多个阵元针对不同层组织与相应的原始射频信号的速度关系。第二预定发射参数包括孔径大小、成像深度、平面波倾斜角度个数、发射频率与脉冲周期，根据偏转角度序列的倾斜角顺序，依次确定不同的平面波倾斜角下的超声换能器的各阵元的延迟时间，按照延迟时间依次发射超声平面波；利用超声换能器的各阵元依次接收不同偏转角度下的反射超声平面波。
进一步地，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，根据该速度谱计算不同深度的速度，得到局部速度模型包括如下步骤：
对每个原始射频信号按照发射阵元与接收阵元关于线阵中心对称的顺序重新排列，得到双曲线射频信号，在本文实施例中，发射阵元和接收阵元的部署关系可以如图3所示。定义线阵的中心点为O，某一发射阵元为S，其关于O点的对称点为G。由S发射的超声波在目标组织层的R点发生发射，并由G接收。R的水平投影点为O，这种共中心点的信号排列方式使得各阵元发射的超声波都在R点 发生反射，并由其对称的阵元接收。发射S与接收G的水平距离为x，目标界面的深度为h0，则该阵元S发射的超声波的渡越时间TSG表示为公式(1)：
渡越时间TSG与水平间距x构成了一个双曲线方程。表示发射S与反射R的距离，表示反射R与接收G的距离，对于某个h0深度上，该层速度为v，则在接收阵元的各个数据通道上唯一的确定了一条双曲线轨迹。
所述各个数据通道上的双曲线射频信号是关于时间的函数，如公式(2)所示：
fi(t)，(i＝1，2，3，...，M)         (2)
其中，fi(t)表示第i个阵元对应的双曲线射频信号，t表示时间，M表示阵列超声线阵探头上的阵元个数。如图4中的(a)所示，S点表示发射阵元的点，R点表示组织上的反射点，G点为该发射阵元的点S中心对称的接收阵元的点，O点为计算出来的中心点，h0表示深度，如图4中的(b)所示，X1、X2、…、Xi、…、XM表示多个阵元，t0对应某一层的双程垂直距离(OR)的反射时间，即t0＝2h0/v，t0对应上述原始信号中某一双曲线射频信号的顶点位置。L个双曲线射频信号对应的时间初值分别为t01、t02、...、t0L；对于每一个t0，定义速度的初值范围[v1,vL]，其中v1表示速度的初始范围的起始值，vL表示速度的初始范围的终止值。需要保证目标组织所在区域的速度在该初始范围内。
如图4中的(c)所示，纵坐标表示速度，横坐标表示时间。将一个阵元对应的一层组织的双曲线射频信号的顶点对应的时间作为时间初值(也就是图4中的(c)中示出的双曲线的定点)，成像深度与组织一一对应。所述时间初值对应所述目标组织中一层组织的双程垂直距离的反射时间(即从O点到R点往返的时间)，所述垂直距离表示一个发射阵元与对应的接收阵元二者构成的直线与该层组织中的反射点之间的垂直距离(即O点到R点的距离)。
对于每一个时间初值，在该范围[v1,vL]内扫描j次，按照公式(3)：
vj＝vB+(j-1)Δv(j＝1，2，...，J)       (3)
确定多个实验速度值，其中，vj表示第j个实验速度值，vB＝v1，Δv表示所述时间初值对应的速度增量，J表示所述实验速度值的个数；
按照所述实验速度值对所述双曲线射频信号进行扫描，计算第i个阵元的时间延迟，其公式为(4)：
其中，tij表示第i个阵元第j个实验速度值对应的时间延迟，t0l表示所述时间初值，M表示所述阵元个数，xi表示第i个阵元的所述接收阵元与其对应的发射阵元的水平距离，vj表示第j个所述实验速度值；
根据多个阵元的多个实验速度值的时间延迟，按照公式(5)，
计算第i个阵元的时间初值对应的速度谱线，其中，A1表示所述速度谱线，N表示根据所述时间初值以及所述间隔时间确定的时窗长度，fi表示第i个阵元的时间初值t0l对应的所述双曲线射频信号，Δt0表示所述时间间隔；
改变t0l＝t0？B+(l-1)Δt0,l＝1,2,L,(t0E-t0？B)/Δt0，其中，t0B表示所述时间初值对应的时间范围的起始时间，t0E表示所述时间初值对应的时间范围的终止时间，并计算改变后的时间初值对应的速度谱线；
将多个时间初值对应的速度谱线作为第i个阵元的速度谱线集合；
将多个阵元的多个速度谱线集合按照时间进行排列，得到时间-速度谱曲线，并通过时深转换得到深度-速度谱曲线。公式(5)计算的速度谱实际上是用不同的速度进行校正和叠加的叠加振幅。当扫描到正确的速度时，同相轴能够充分校平，实现同相位叠加，因此叠加后的振幅值最强，即存在vj使得A1(vj)＝A1max。所以，将各深度上A1对应最大的速度作为局部速度模型c＝vj。
根据本文的一个实施例，如图5所示，根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场进一步包括，
步骤501：根据所述局部速度模型以及所述第二预定发射参数构建不同成像深度上的第一二阶偏微分声波方程；
在本步骤中，根据所述局部速度模型以及所述第二预定发射参数构建不同成像深度上的第一二阶偏微分声波方程为公式(6)：
式中，为时刻t处位于xs处的声源在x处的声波场，c(x)为不同位置x处的局部速度模型，为拉普拉斯算子。项是该方程的初始条件，f(t)为时刻t处位于xS处的声源函数，δ为Kronecker函数，θ为平面波的偏转角度。
步骤502：使用交错网格的时域有限差分方法求解所述第一二阶偏微分声波方程，得到不同时刻的延拓波场作为所述发射正演场。
如图6所示，根据该偏转角度对应的射频信号计算该偏转角度的接收反演场进一步包括，
步骤601：按照数据时间的降序顺序对所述射频信号进行排列，得到时间反向传播信号P(xR,t)；
步骤602：根据所述时间反向传播信号构建第二二阶偏微分声波方程；
在本步骤中，根据所述时间反向传播信号构建第二二阶偏微分声波方程为公式(7)：
式中，为时刻t处位于xR处的接阵元在x处的声波场，P(xR,t)δ(x-xR)项是该方程的初始条件，反转的射频信号P(xR,t)作为方程(7)的源项。
步骤603：使用有限差分方法求解所述第二二阶偏微分声波方程，得到不同时刻的延拓波场作为所述接收反演场。
根据本文的一个实施例，根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果的公式为(8)，
其中，表示第k个偏转角度θk对应的成像结果，T表示所述第二预定发射时序中的采集总时间，t表示时间，Sθ表示偏转角度θ对应发射正演场，Rθ表示偏转角度θ对应接收反演场，x＝(x,y,z)表示成像区内各点对应的空间向量。
根据本文的一个实施例，对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果的公式为(9)，
其中，Image(x)表示所述目标组织的成像结果，Θ表示所述偏转角度的总数。
基于同一发明构思，本文实施例还提供了一种超声平面波成像装置，如图7所示，包括：
局部速度模型计算单元701，用于阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
目标成像结果计算单元702，用于所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
进一步地，如图8所示为本文实施例所述的超声平面波成像装置的详细结构示意图，包括：
局部速度模型计算单元701进一步用于阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超声波，获取目标组织中多层组织的多个反射的超声波，根据发射的超声波和所述目标组织中多层组织反射的超声波形成原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，根据该速度谱计算所述原始射频信号不同深度的速度，得到局部速度模型；
所述目标成像结果计算单元702进一步包括：
射频信号获取模块7021，用于所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射超声平面波，得到各偏转角度对应的射频信号，所述射频信号包括发射的超声平面波和所述目标组织中多层组织反射的超声平面波；
发射正演场和接收反演场计算模块7022，用于根据所述局部速度模型以及一个偏转角度对应的超声平面波的发射参数计算该偏转角度对应的发射正演场，并根据该偏转角度对应的射频信号计算该偏转角度的接收反演场；
子成像结果计算模块7023，用于根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果；
目标成像结果计算模块7024，用于对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
由于上述装置解决问题的原理与上述方法相似，因此上述装置的实施可以参见上述方法的实施，重复之处不再赘述。
如图9所示为本发明实施例计算机设备的结构示意图，本发明中的装置可以为本实施例中的计算机设备，执行上述本发明的方法。计算机设备902可以包括一个或多个处理设备904，诸如一个或多个中央处理单元(CPU)，每个处理单元可以实现一个或多个硬件线程。计算机设备902还可以包括任何存储资源906，其用于存储诸如代码、设置、数据等之类的任何种类的信息。非限制性的，比如，存储资源906可以包括以下任一项或多种组合：任何类型的RAM，任何类型的ROM，闪存设备，硬盘，光盘等。更一般地，任何存储资源都可以使用任何技术来存储信息。进一步地，任何存储资源可以提供信息的易失性或非易失性保留。进一步地，任何存储资源可以表示计算机设备902的固定或可移除部件。在一种情况下，当处理设备904执行被存储在任何存储资源或存储资源的组合中的相关联的指令时，计算机设备902可以执行相关联指令的任一操作。计算机设备902还包括用于与任何存储资源交互的一个或多个驱动机构908，诸如硬盘驱动机构、光盘驱动机构等。
计算机设备902还可以包括输入/输出模块910(I/O)，其用于接收各种输入(经由输入设备912)和用于提供各种输出(经由输出设备914)。一个具体输出机构可以包括呈现设备916和相关联的图形用户接口(GUI)918。在其他实施例中，还可以不包括输入/输出模块910(I/O)、输入设备912以及输出设备914，仅作为 网络中的一台计算机设备。计算机设备702还可以包括一个或多个网络接口920，其用于经由一个或多个通信链路922与其他设备交换数据。一个或多个通信总线924将上文所描述的部件耦合在一起。
通信链路922可以以任何方式实现，例如，通过局域网、广域网(例如，因特网)、点对点连接等、或其任何组合。通信链路922可以包括由任何协议或协议组合支配的硬连线链路、无线链路、路由器、网关功能、名称服务器等的任何组合。本文实施例还提供一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序被处理器执行时实现上述方法。
本文实施例还提供一种计算机可读指令，其中当处理器执行所述指令时，其中的程序使得处理器执行上述方法。
应理解，在本文的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本文实施例的实施过程构成任何限定。
还应理解，在本文实施例中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系。例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、计算机软件或者二者的结合来实现，为了清楚地说明硬件和软件的可互换性，在上述说明中已经按照功能一般性地描述了各示例的组成及步骤。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本文的范围。
所属领域的技术人员可以清楚地了解到，为了描述的方便和简洁，上述描述的系统、装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本文所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另外，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口、装置或单元的间接耦合或通信连接，也可以是电的，机械的或其它的形式连接。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本文实施例方案的目的。
另外，在本文各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以是两个或两个以上单元集成在一个单元中。 上述集成的单元既可以采用硬件的形式实现，也可以采用软件功能单元的形式实现。
所述集成的单元如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本文的技术方案本质上或者说对现有技术做出贡献的部分，或者该技术方案的全部或部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本文各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、磁碟或者光盘等各种可以存储程序代码的介质。
本文中应用了具体实施例对本文的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本文的方法及其核心思想；同时，对于本领域的一般技术人员，依据本文的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本文的限制。

Claims (10)

  1. 一种超声平面波成像方法，其特征在于，包括：
    阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
    所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
  2. 根据权利要求1所述的方法，其特征在于，得到所述局部速度模型的步骤还包括：
    所述第一预定发射参数包括阵列超声线阵探头的各阵元逐次发射的延迟时间和成像深度，接收目标组织中多层组织的多个反射的超声波，形成原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，根据该速度谱计算所述原始射频信号不同深度的速度，得到所述局部速度模型。
  3. 根据权利要求1所述的方法，其特征在于，所述局部速度模型描述了多个阵元针对不同层组织与相应的原始射频信号的速度关系。
  4. 根据权利要求1所述的方法，其特征在于，所述阵元包括发射阵元和接收阵元，所述第一预定发射参数包括间隔时间和成像深度；
    所述局部速度模型为使速度谱线A1振幅最大时对应的速度，公式为：
    其中，为第i个阵元在时间延迟tij的射频信号的幅值，A1表示所述速度谱线，vj表示扫描速度，M表示阵列超声线阵探头上的阵元个数，N表示根据时间初值以及所述间隔时间确定的时窗长度。
  5. 根据权利要求1所述的方法，其特征在于，得到所述目标组织的成像结果的步骤还包括：
    所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射超声平面波，得到各偏转角度对应的射频信号，所述射频信号包括发射的超声平面波和所述目标组织中多层组织反射的超声平面波；
    根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发 射参数计算该偏转角度对应的发射正演场，并根据该偏转角度对应的射频信号计算该偏转角度的接收反演场；
    根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果；
    对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
  6. 根据权利要求1所述的方法，其特征在于，根据所述局部速度模型以及一个偏转角度对应的超声平面波的第二预定发射参数计算该偏转角度对应的发射正演场进一步包括：
    根据所述局部速度模型以及所述第二预定发射参数构建不同成像深度上的第一二阶偏微分声波方程；
    使用交错网格的时域有限差分方法求解所述第一二阶偏微分声波方程，得到不同时刻的延拓波场作为所述发射正演场；
    根据该偏转角度对应的射频信号计算该偏转角度的接收反演场进一步包括，
    按照数据时间的降序顺序对所述射频信号进行排列，得到时间反向传播信号；
    根据所述时间反向传播信号构建第二二阶偏微分声波方程；
    使用有限差分方法求解所述第二二阶偏微分声波方程，得到不同时刻的延拓波场作为所述接收反演场。
  7. 根据权利要求1所述的方法，其特征在于，根据互相关成像条件对一个偏转角度对应的发射正演场和接收反演场进行计算，得到该偏转角度的成像结果的公式为：
    其中，表示第k个偏转角度θk对应的成像结果，T表示所述第二预定发射时序中的采集总时间，t表示时间，Sθ表示偏转角度θk对应发射正演场，Rθ表示偏转角度θk对应接收反演场，x＝(x,y,z)表示成像区内各点对应的空间向 量。
  8. 根据权利要求6所述的方法，其特征在于，对多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果的公式为：
    其中，Image(x)表示所述目标组织的成像结果，Θ表示所述偏转角度的总数。
  9. 一种超声平面波成像装置，其特征在于，包括：
    局部速度模型计算单元，用于阵列超声线阵探头的各阵元逐次按照第一预定发射参数对目标组织发射超，获得原始射频信号，对所述原始射频信号进行共反射点数据重新排列，在反射同相轴方向上进行能量叠加，得到速度谱，获得不同深度的局部速度模型；
    目标成像结果计算单元，用于所述阵列超声线阵探头各阵元按照第二预定发射参数以及多个偏转角度对所述目标组织发射多角度超声平面波，根据接收射频信号结合所述局部速度模型，对组织进行成像，多个偏转角度的成像结果进行相干叠加，得到所述目标组织的成像结果。
  10. 一种计算机设备，包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序，其特征在于，所述处理器执行所述计算机程序时实现权利要求1至8任一所述方法。
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