WO2018082458A1 - 一种定量剪切波弹性成像方法及系统 - Google Patents

一种定量剪切波弹性成像方法及系统 Download PDF

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WO2018082458A1
WO2018082458A1 PCT/CN2017/107120 CN2017107120W WO2018082458A1 WO 2018082458 A1 WO2018082458 A1 WO 2018082458A1 CN 2017107120 W CN2017107120 W CN 2017107120W WO 2018082458 A1 WO2018082458 A1 WO 2018082458A1
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shear wave
arfi
pulse generator
point
wave velocity
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PCT/CN2017/107120
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English (en)
French (fr)
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尹皓
石丹
刘西耀
刘东权
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声泰特（成都）科技有限公司
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Priority claimed from CN201610973110.5A external-priority patent/CN106618639B/zh
Priority claimed from CN201610973108.8A external-priority patent/CN106618638B/zh
Application filed by 声泰特（成都）科技有限公司 filed Critical 声泰特（成都）科技有限公司
Priority to US16/346,079 priority Critical patent/US11357480B2/en
Publication of WO2018082458A1 publication Critical patent/WO2018082458A1/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
    • A61B8/54—Control of the diagnostic device
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
    • A61B8/0833—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving detecting or locating foreign bodies or organic structures
    • A61B8/085—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving detecting or locating foreign bodies or organic structures for locating body or organic structures, e.g. tumours, calculi, blood vessels, nodules
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/13—Tomography
    • A61B8/14—Echo-tomography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/48—Diagnostic techniques
    • A61B8/485—Diagnostic techniques involving measuring strain or elastic properties

Definitions

  • the present invention relates to the field of medical ultrasound imaging technology, and in particular to a quantitative shear wave elastic imaging method and system.
  • Medical ultrasound elastography is an ultrasonic imaging method that shows the elastic modulus or softness of tissue through tissue motion.
  • the traditional squeezed elastic imaging method requires the doctor to use the probe to squeeze the detection site to force the movement, thereby obtaining tissue elasticity.
  • Information, the shortcoming of this method is that the doctor needs to squeeze the detection site with appropriate operation, which is subjective; because of the need for doctors to squeeze, the results of different doctors' operations or the same doctor's operation at different times are difficult to directly compare, the test results It is difficult to reproduce, and it can only be used as a qualitative test result. It is impossible to obtain quantitative test information for disease tracking and postoperative observation.
  • Ultrasound elastography which is currently capable of quantitative analysis, is based on Acoustic Radiation Force Imaging (ARFI).
  • ARFI uses focused ultrasound excitation pulses in the medical ultrasound power range to generate acoustic radiation in the focal region of bio-viscoelastic tissue. The force is used to deform the tissue, and then the echo signal of the detection pulse is used to detect the deformation displacement of the tissue at different time points by the correlation time delay calculation method, and the image is qualitatively reflected to reflect the viscoelastic property of the tissue.
  • ARFI elastography Overcoming the shortcomings of traditional freehand elastography that can not effectively exert pressure on deep tissues from outside the body and poor reproducibility due to different operator habits.
  • the image shows the relative deformation displacement of the tissue, and the elastic modulus of the tissue cannot be estimated completely quantitatively.
  • the shear wave velocity of lateral propagation is estimated according to the displacement-time curve of multiple points in the horizontal direction by adjusting the pulse excitation mode, and then the shear wave propagation is performed.
  • the intrinsic link between the characteristics and the elastic characteristics of the biological tissue ultimately quantifies the elastic modulus of the tissue to form a two-dimensional image.
  • the existing quantitative elastography SWI requires the use of the original RF signal data before the ultrasound front-end beamforming, which needs to be based on plane wave transmission and reception.
  • the plane wave technology requires N ⁇ c/2z calculations per second, where N is the number of parallel received beams. , c is the speed of sound, and z is the depth of the scan.
  • the computational complexity of the traditional beamforming method is much smaller, only one of the M/P fractions, where M is the number of transmissions, P is the number of parallels, for example, M is equal to 100, and when P is equal to 2, the calculation amount of the plane wave method is At least 50 times (sometimes even hundreds of times) of the traditional ARFI method; in addition to the huge difference in the amount of calculation, the beam-synthesis of the receiver-side software based on the plane wave technology also needs to store a large number of original echo signals, which greatly improves the data storage and Transmission hardware costs are not convenient for integration and promotion with medical ultrasound systems.
  • the object of the present invention is to overcome the problems that the existing quantitative elastography technology requires large amount of calculation, difficult hardware design and high cost due to the use of the original radio frequency signal (without beamforming), and provides a low requirement for the device and calculation. A small amount of ultrasonic quantitative elastography methods and systems.
  • the present invention provides the following technical solutions:
  • a quantitative shear wave elastography method comprising the following steps:
  • the shear wave wave velocity is calculated according to the strain at each position to obtain the quantitative shear wave elastic image E at each position.
  • N is the gradient sliding calculation window size
  • z i represents the specified position depth coordinate
  • y i represents the current point displacement in the gradient sliding calculation window.
  • the single-point shear wave velocity is calculated by a two-dimensional linear fitting method according to the lateral distance, the axial distance of the specified measurement point, and the time required for each specified measurement point to reach the maximum lateral displacement.
  • the physical meaning of the parameter ⁇ 1 is the single-point shear wave velocity c ref of the specified measurement point, and m represents the number of sampling points.
  • ⁇ 0 and ⁇ 2 are regression parameters calculated simultaneously in the calculation of the single-point shear wave velocity c ref by the above formula, and these two parameters are not used in the method.
  • the shear wave velocity of each position is further wherein, in the focus area, ⁇ ⁇ takes a value of 1; in an axial region outside the focus area, Where z is the axial distance, n and ⁇ are system constants representing the excitation sound field, the value ranges from 0 to 10, and the values of the two parameters n and ⁇ may be the same or different.
  • the focus area DoF 8(f#) 2 ⁇ , wherein ⁇ represents a wavelength, f# is an aperture control parameter, and f# ranges from a real number between 0 and 5.
  • the invention also provides an ultrasonic quantitative elastic imaging system with low requirements on equipment and small calculation amount, including:
  • a shear wave pulse generator for transmitting a shear wave excitation pulse and detecting a pulse signal
  • ARFI pulse generator for transmitting ARFI excitation pulses and detecting pulse signals
  • a control device for controlling a shear wave pulse generator, a switch of the ARFI pulse generator, receiving a shear wave echo signal and an ARFI echo signal, and calculating a specified position strain ⁇ ref according to the ARFI echo signal;
  • the echo signal calculates the single-point shear wave velocity c ref at the specified position; the shear wave velocity c at each position is calculated according to the single-point shear wave velocity; the shear wave velocity c and the strain ⁇ ref are obtained according to the strain gauges at each position to obtain the quantitative shear of each position.
  • a display device for displaying the quantitative shear wave elastic image E is a display device for displaying the quantitative shear wave elastic image E.
  • the probe includes a beam combiner for using an ARFI echo signal or a shear wave back
  • the wave signal is beam-synthesized and synthesized into an echo RF signal.
  • control device includes a shear wave signal processing module and a single point shear wave velocity calculation module;
  • the shear wave signal processing module receives the shear wave echo RF signal from the probe, and obtains shear wave displacement-time data of the specified position of the measured tissue through demodulation and displacement estimation;
  • control device further includes an ARFI signal processing module and a strain calculation module;
  • the ARFI signal processing module is configured to receive an ARFI echo RF signal from the probe, and obtain ARFI displacement-time data of a specified position of the measured tissue through demodulation and displacement estimation;
  • the strain calculation module calculates a specified position strain according to the ARFI displacement-time data
  • N is the gradient sliding calculation window size
  • z i represents the specified position depth coordinate
  • y i represents the current point displacement in the gradient sliding calculation window.
  • control device further includes an elastic modulus calculation module
  • the control device further includes a wave speed calculation module and an elastic modulus calculation module;
  • the wave speed calculation module is configured to calculate shear wave velocity at each position according to a single point shear wave velocity at a specified position
  • ⁇ ⁇ takes a value of 1
  • z is the axial distance
  • n and ⁇ are system constants representing the excitation sound field, the value ranges from 0 to 10, and the values of the two parameters n and ⁇ may be the same or different;
  • control device controls the shear wave pulse generator and the ARFI pulse generator to alternately transmit.
  • shear wave pulse generator and the ARFI pulse generator are implemented by the same circuit, and the control device controls to transmit a shear wave pulse or an ARFI pulse;
  • the shear wave pulse generator and the ARFI pulse generator are implemented as separate circuits that control the start and stop times by the control device.
  • shear wave pulse generator and/or the ARFI pulse generator have a total of 24 or more channels.
  • the shear wave pulse generator or the ARFI pulse generator includes a drive amplifier, a pulse generator, an overcurrent and overvoltage protection circuit, a Tx/Rx switch, and a limiter from the Tx/Rx switch feedback.
  • Amplifier digital to analog conversion circuit.
  • the ultrasonic quantitative elastography method and system provided by the invention are based on the linear fitting of the sliding window and the shear wave velocity detecting algorithm using the two-dimensional linear fitting, and the result is better robustness, stronger anti-noise ability and more result. reliable.
  • ultrasonic whole-domain quantitative elastography is realized without additionally increasing the load of the ultrasonic front-end storage and transmission module, which greatly reduces the design of the ultrasonic quantitative elastography system.
  • Degree and equipment cost sets an effective circuit switching and protection module, so that the system satisfies the different transmission timing requirements of the ARFI and the shear wave, effectively protects the human body and the system circuit, and maximizes the acoustic excitation to achieve a better detection effect.
  • FIG. 1 is a flow chart of a method for ultrasonic quantitative elastography provided by the present invention.
  • FIG. 2 is a block diagram of an ultrasonic quantitative elastography system provided by the present invention.
  • Fig. 3 is a block diagram showing the construction of an example of a shear wave pulse generator and/or the ARFI pulse generator in the present invention.
  • Figure 4 is a schematic illustration of a sequence of firing pulses used in the acoustic excitation of the present invention in the present invention.
  • Fig. 5 is a schematic diagram showing the pulse emission mode used in the calculation of the shear wave velocity.
  • Embodiment 1 As described in FIG. 1, the present invention provides a quantitative shear wave elastic imaging method, comprising the following steps:
  • the echo signal can also detect one or more of an IQ echo signal, a channel echo radio frequency (RF) signal, and a beamformed radio frequency (RF) signal;
  • the specified position strain in the focus area Where N is the gradient sliding calculation window size, z i represents the specified position depth coordinate, Indicates the mean value of the coordinates of each position in the gradient sliding calculation window, and y i represents the current point displacement in the gradient sliding calculation window. Indicates the mean of the displacement of each position in the gradient slip calculation window.
  • the single-point shear wave velocity is calculated by a two-dimensional linear fitting method according to the lateral distance, the axial distance of the specified measurement point, and the time required for each specified measurement point to reach the maximum lateral displacement.
  • we usually preset 1 depth in the axial depth, and preset J specified positions (points) on each depth, a total of m specified positions (points), m I*J; we will each position (Point)
  • the time at which the maximum displacement is reached by the shear wave is regarded as the time at which the shear wave propagates to the position (point), and the shear wave is transmitted to the position (point) by the shear wave displacement-time data.
  • Shear wave velocity at each position Wherein, in the focus area, ⁇ ⁇ takes a value of 1; in an axial region outside the focus area, Where z is the axial distance, n and ⁇ are system constants representing the excitation sound field, the value ranges from 0 to 10, and the values of the two parameters n and ⁇ may be the same or different.
  • the quantitative shear wave elastic image E 3 ⁇ c 2 , where ⁇ is the medium density of the measured region.
  • the invention also provides an ultrasonic quantitative elastic imaging system with low requirements on equipment and small calculation amount, including:
  • a shear wave pulse generator for transmitting a shear wave excitation pulse and detecting a pulse signal
  • ARFI pulse generator for transmitting ARFI excitation pulses and detecting pulse signals
  • a control device 1 for controlling a shear wave pulse generator, a switch of an ARFI pulse generator, receiving a shear wave echo signal and an ARFI echo signal, and calculating a specified position strain ⁇ ref according to the ARFI echo signal;
  • the wave echo signal calculates the single-point shear wave velocity c ref at a specified position; the shear wave velocity c at each position is calculated according to the single-point shear wave velocity; and the respective positions are obtained according to the shear wave velocity c and the strain ⁇ ref of each position strain gauge.
  • a display device for displaying the quantitative shear wave elastic image E Specifically, before the display, a series of processing processes such as scan conversion, smoothing processing, and the like are performed on the elastic image E data calculated by the control device, and finally the image is presented to the user through the display.
  • the probe includes a beam combiner 2 for beamforming an ARFI echo signal or a shear wave echo signal into an echo RF signal.
  • the control device 1 includes a shear wave signal processing module 13, a single point shear wave speed calculation module 14;
  • the shear wave signal processing module 13 receives the shear wave echo RF signal from the probe, and demodulates it into IQ data, and further performs displacement estimation on the IQ data to obtain a shear wave displacement-time at a specified position of the measured tissue. data;
  • the control device 1 further includes an ARFI signal processing module 11 and a strain calculation module 12;
  • the ARFI signal processing module 11 is configured to receive an ARFI echo radio frequency signal from the probe, and demodulate to form IQ data, and further obtain ARFI displacement-time data of a specified position of the measured tissue by performing displacement estimation on the IQ data;
  • the strain calculation module 12 calculates a specified position strain according to the ARFI displacement-time data.
  • N is the gradient sliding calculation window size
  • z i represents the specified position depth coordinate
  • y i represents the current point displacement in the gradient sliding calculation window.
  • the control device 1 further includes a wave speed calculation module 15 and an elastic modulus calculation module 16;
  • the wave speed calculation module 15 is configured to calculate shear wave velocity at each position according to a single point shear wave velocity at a specified position Wherein, in the focus area, ⁇ ⁇ takes a value of 1; in an axial region outside the focus area, Where z is the axial distance, n and ⁇ are system constants representing the excitation sound field, the value ranges from 0 to 10, and the values of the two parameters n and ⁇ may be the same or different;
  • the control device 1 controls the shear wave pulse generator and the ARFI pulse generator to alternately emit.
  • the hardware part of the control device 1 may be composed of a PC, a control circuit board, and an FPGA chipset. In other embodiments, the control device may also be a fully integrated integrated circuit.
  • the shear wave signal processing module, the single point shear wave velocity calculation module, the ARFI signal processing module, the strain calculation module, and the elastic modulus calculation module are distributed in the above hardware device according to functions.
  • the shear wave pulse generator and the ARFI pulse generator are implemented by the same circuit, and the control device controls the transmission of the shear wave pulse or the ARFI pulse; or
  • the shear wave pulse generator and the ARFI pulse generator are implemented as separate circuits that control the start and stop times by the control device.
  • the generator includes a drive amplifier 100 and a pulse generator 101 which are sequentially connected in series.
  • Overcurrent and overvoltage protection circuit 102 allows the system to meet ARFI and shear waves At the same time of different emission timing requirements, the human body and system circuits are effectively protected, and the sound excitation is maximized to achieve better detection results.
  • the shear wave pulse generator and/or the ARFI pulse generator have a total of 24 or more channels, such as 48 channels, 64 channels, 128 channels, 256 channels, and the like.
  • the control device controls the pulse generator (shear wave pulse generator and/or the ARFI pulse generator) to generate excitation and detection pulse signals according to parameter information such as voltage, pulse length and phase set by the user, at T/
  • the ultrasonic wave generated by the transmitting circuit under the control of the R switch enters the biological tissue, and the receiving circuit receives the echo signal.
  • the system transmits or receives a signal, it sets the aperture control parameter f# and the depth of focus z, and uses the formula.
  • D is the probe aperture size, that is, the user controls the aperture size of the active probe by setting the aperture control parameter f# and the depth of focus z to achieve the number of active array elements.
  • the user can select the actual number of active array elements in the largest active array element (such as 64 channels) according to the situation.
  • the maximum probe aperture size that the system can achieve is The area where the 64 elements are distributed, the aperture control parameter f# is usually a real number greater than 0 and less than or equal to 5. Since the force that causes the deformation of the tissue to be generated is formed in the focus area by the short-length pulse wave emitted by the probe according to the option set by the user, regardless of the operator's operation method, it can be considered that the force is uniform in the effective imaging area. Consistent.
  • ARFI elastography uses a line-by-line scan. Each horizontal position emits an excitation pulse according to the same system parameters to cause a slight deformation of the tissue. Therefore, it can be considered that the acoustic radiation force within a range of 1 cm near the focus can be regarded as uniform. Consistently, this region is called the focal region, as described above, in the focal region, the shear wave velocity calculation formula The value of ⁇ ⁇ is 1.
  • the transmission pulse sequence is schematically shown in FIG. 4, and the transmission pulse sequence is controlled according to the ROI (Region of Interest) window depth position, signal center frequency magnitude, PRF (pulse repeat frequency), excitation voltage, and pulse length.
  • the head of the sequence is one or more detection pulses (detection beam), a higher voltage (eg 80V, generally the same as B mode), a short pulse (eg 2 cycles) as a reference signal for tissue displacement information.
  • detection pulses detection beam
  • a higher voltage eg 80V, generally the same as B mode
  • a short pulse eg 2 cycles
  • multiple sets of excitation/detection pulse pairs, excitation pulses push beam, lower voltage (eg 20-40V), long pulses (100-250 cycles)
  • the local area excitation produces a small displacement.
  • the detection pulse (short pulse of high voltage) is used to track the deformation of the tissue during the loading process of the acoustic radiation force load; followed by a series of detection pulses to track the deformation of the tissue after the acoustic radiation force load disappears.
  • the effect of the excitation pulse is to make the local tissue at the focus position vibrate under safe conditions.
  • the long echo signal cannot be used for displacement estimation due to the difference in spatial resolution, so the probe array element turns off the signal apodization when the excitation pulse is emitted.
  • the amplitude of the transmitted signals of all active elements is the same, enhancing the energy carried by the signals to produce greater acoustic radiation under safe conditions.
  • the long pulse wave frequency used for excitation and the short pulse wave center frequency used for detection may be the same or different, and the preferred scheme is that the center frequency is different, so that the excitation pulse can be prevented from interfering with the detection pulse echo signal, and at the same time, signal processing It is easy to distinguish between the excitation and detected echo signals.
  • the number of long pulse waves in the transmitted pulse sequence is variable, and the number of waves in the entire sequence is also variable.
  • the number of long pulse waves (excitation wave) + the number of short pulse waves (reference and detection wave) the number of sampling volumes, the size of the gradient sliding calculation window N is any value between 0 and the number of sampling volumes, specifically using an adaptive algorithm Automatic selection, no longer repeat here.
  • a set of shear wave transmitting pulses comprises a plurality of different spatial positions as shown in FIG. 4, wherein the excitation pulse spatial position is fixed, and the detection pulse spatial positions of different emission sequences are different; as shown in FIG. 5, D is detection.
  • Wave, P is the excitation wave.
  • five transmission pulse sequences with an interval of 1 mm are used.
  • the excitation waves P1, P2, P3, P4 and P5 of the five sequences are all in the same spatial position, and 5
  • the detection waves D1, D2, D3, D4, D5 in the transmission pulse sequence are at the same or different spatial positions, and at the same time, the spatial position of the at least one detection pulse and the excitation pulse position are the same, as D1 in the figure.
  • the ARFI pulse generator uses the same transmit pulse sequence as the shear wave pulse generator, but the excitation wave remains in the same spatial position as the detected wave during one frame of ARFI imaging scanning.

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Abstract

一种定量剪切波弹性成像方法及系统，涉及医学超声成像技术领域。提供的超声定量弹性成像方法及系统基于滑动窗口线性拟合的应变和使用二维线性拟合的剪切波波速检测算法，抗噪声能力更强，结果更可靠。同时在不额外增加超声前端存储与传输模块负荷的情况下，实现了超声全域定量弹性成像，大幅地减低了超声定量弹性成像系统的设计难度和设备成本。

Description

一种定量剪切波弹性成像方法及系统 技术领域
本发明涉及医学超声成像技术领域，特别涉及一种定量剪切波弹性成像方法及系统。
背景技术
临床上，人体组织的力学特征变化往往是肿瘤疾病最为重要的早期预警信号。随着肿瘤的生长，病变组织与正常组织相比，黏弹性发生较大变化，如乳腺癌与周围正常组织大约相差90倍，纤维化组织、非浸润性癌变和浸润性癌变组织的剪切弹性系数亦存在较大差异，因此，获得人体组织与黏弹性相关的参数信息(例如形变位移，剪切波速等)在医学诊断领域具有重要意义。
医学超声弹性成像是一种通过组织运动显示组织弹性模量或软硬程度的超声成像方式，传统的挤压式弹性成像方式需要医生利用探头挤压检测部位使其受力运动，从而得到组织弹性信息，这种方式的不足在于：医生需要以适当的操作挤压检测部位，主观性强；由于需要医生挤压，不同医生操作或同一医生不同时期的操作的结果很难直接进行对比，检测结果难以复现，往往只能作为定性的检测结果，无法获得定量的检测信息，用以疾病的跟踪和术后观察。
目前能进行定量分析的超声弹性成像技术，主要是基于声辐射力弹性成像(Acoustic Radiation Force Imaging，ARFI)，ARFI利用医学超声功率范围内的聚焦超声激励脉冲在生物黏弹性组织聚焦区域产生声辐射力，使组织发生形变，然后利用检测脉冲的回波信号通过相关性的时延计算方法在不同时间点检测组织的形变位移情况，将其成像后定性地反映组织的黏弹性特性。ARFI弹性成像 克服了传统徒手弹性成像无法从体外对深部组织有效施压以及因操作者的使用习惯不同造成可重复性较差的缺点。但不足之处在于图像显示的是组织相对的形变位移差异，而无法完全定量地估算组织的弹性模量。基于ARFI技术衍生的超声剪切波成像(SWI，shear wave imaging)，通过调整脉冲激励方式，根据水平方向多个点的位移-时间曲线估算横向传播的剪切波波速，然后利用剪切波传播特性与生物组织弹性特征之间的内在联系，最终定量重构组织的弹性模量以形成二维的图像。
但是，现有的定量弹性成像SWI需要使用超声前端波束合成前的原始射频信号数据，需要基于平面波发射和接收，平面波技术每秒需要N×c/2z次计算，其中N为并行接收声束数目，c为声速，z为扫描深度。而传统波束合成方法的计算量则要小得多，仅为M/P分之一，其中M为发射次数，P为并行数，例如M等于100，P等于2时，平面波方法的计算量是传统ARFI方法的至少五十倍(有时甚至高达数百倍)；除了计算量的巨大差异外，基于平面波技术的接收端软件波束合成还需要存储大量原始回波信号，大幅度提高了数据存储和传输硬件成本，不便于与医学超声系统集成和推广应用。
发明内容
本发明的目的在于克服现有定量弹性成像技术需要采用原始射频信号(不经过波束合成)带来的计算量大、所需硬件设计困难和成本高昂的问题，提供一种对设备要求低、计算量小的超声定量弹性成像方法及系统。
为了实现上述发明目的，本发明提供了以下技术方案：
一种定量剪切波弹性成像方法，包含如下步骤：
进行ARFI检测，获取聚焦区域中指定位置应变εref；
进行剪切波检测，获取聚焦区域中指定位置单点剪切波波速cref；
根据所述指定位置单点剪切波波速计算各个位置剪切波波速c；
根据各个位置应变计算剪切波波速获取各个位置定量剪切波弹性图像E。
进一步的，所述聚焦区域中指定位置应变
Figure PCTCN2017107120-appb-000001
其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
Figure PCTCN2017107120-appb-000002
表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
Figure PCTCN2017107120-appb-000003
表示梯度滑动计算窗口内各个位置位移的均值。
进一步的，所述单点剪切波波速根据指定测量点的横向距离、轴向距离，及各个指定测量点达到最大横向位移所需要的时间采用二维线性拟合法计算得出。
进一步的，所述单点剪切波波速cref通过公式X＝Aβ得出，其中，
Figure PCTCN2017107120-appb-000004
Figure PCTCN2017107120-appb-000005
式中，xi表示指定测量点的横向距离，ti表示指定测量点达到最大位移所需时间，zi表示指定测量点的轴向距离，β0,β1,β2是线性拟合模型参数，β1的物理意义即为所求的指定测量点单点剪切波速cref，m表示采样点的个数。β0和β2为利用上式计算单点剪切波速cref过程中同时计算得出的回归参数，本方法中不使用这两个参数。
进一步的，所述各个位置剪切波波速
Figure PCTCN2017107120-appb-000006
其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
Figure PCTCN2017107120-appb-000007
其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同。
进一步的，所述聚焦区域DoF＝8(f#)2λ，其中，λ表示波长，f#为孔径控制参数，f#的取值范围为0～5之间的实数。
进一步的，所述定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
本发明同时提供一种对设备要求低、计算量小的超声定量弹性成像系统，包括：
剪切波脉冲发生器，用于发射剪切波激励脉冲及检测脉冲信号；
ARFI脉冲发生器，用于发射ARFI激励脉冲及检测脉冲信号；
探头，用于接收剪切波回波信号和ARFI回波信号；
控制装置，用于控制剪切波脉冲发生器、ARFI脉冲发生器的开关，接收剪切波回波信号和ARFI回波信号，并根据ARFI回波信号计算指定位置应变εref；根据剪切波回波信号计算指定位置单点剪切波波速cref；根据单点剪切波波速计算各个位置剪切波波速c；根据各个位置应变计剪切波波速c及应变εref获取各个位置定量剪切波弹性图像E；
显示装置，用于将所述定量剪切波弹性图像E显示。
进一步的，所述探头包括波束合成器，其用于将ARFI回波信号或剪切波回 波信号经过波束合成，合成为回波射频信号。
进一步的，所述控制装置包括剪切波信号处理模块、单点剪切波速计算模块；
所述剪切波信号处理模块自探头接收剪切波回波射频信号，并经过解调、位移估算得出被测组织指定位置的剪切波位移-时间数据；
所述单点剪切波速计算模块根据剪切波位移-时间数据计算指定位置剪切波波速cref，其通过公式X＝Aβ得出，其中，
Figure PCTCN2017107120-appb-000008
式中，xi表示指定测量点的横向距离，ti表示指定测量点达到最大位移所需时间，zi表示指定测量点的轴向距离，β0,β1,β2是线性拟合模型参数，β1的物理意义即为所求的指定测量点单点剪切波速cref，m表示采样点的个数。
进一步的，所述控制装置还包括ARFI信号处理模块、应变计算模块；
所述ARFI信号处理模块用于自探头接收ARFI回波射频信号，并经过解调、位移估算得出被测组织指定位置的ARFI位移-时间数据；
所述应变计算模块根据所述ARFI位移-时间数据计算指定位置应变
Figure PCTCN2017107120-appb-000009
其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
Figure PCTCN2017107120-appb-000010
表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
Figure PCTCN2017107120-appb-000011
表示梯度滑动计算窗口内各个位置位移的均值。
进一步的，所述控制装置还包括弹性模量计算模块；
所述控制装置还包括波速计算模块及弹性模量计算模块；
所述波速计算模块用于根据指定位置单点剪切波波速计算各个位置剪切波波速
Figure PCTCN2017107120-appb-000012
其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
Figure PCTCN2017107120-appb-000013
其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同；
所述弹性图像计算模块用于根据c及应变εref获取各个位置定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
进一步的，所述控制装置控制所述剪切波脉冲发生器、ARFI脉冲发生器交替发射。
进一步的，所述剪切波脉冲发生器及所述ARFI脉冲发生器为同一电路实现，其由所述控制装置控制发送剪切波脉冲或ARFI脉冲；，
所述剪切波脉冲发生器及所述ARFI脉冲发生器为各自独立电路实现，其由所述控制装置控制启动、关闭时间。
进一步的，所述剪切波脉冲发生器和/或ARFI脉冲发生器共有24路以上。
进一步的，所述剪切波脉冲发生器或ARFI脉冲发生器包括依次串接的驱动放大器、脉冲发生器、过流过压保护电路、Tx/Rx开关，以及自Tx/Rx开关反馈的限幅放大器、数模转换电路。
与现有技术相比，本发明的有益效果：
本发明提供的超声定量弹性成像方法及系统基于滑动窗口线性拟合的应变和使用二维线性拟合的剪切波波速检测算法，其结果鲁棒性更好、抗噪声能力更强，结果更可靠。同时在不额外增加超声前端存储与传输模块负荷的情况下，实现了超声全域定量弹性成像，大幅地减低了超声定量弹性成像系统的设计难 度和设备成本。本发明设置有效电路切换和保护模块，让系统满足ARFI与剪切波不同发射时序要求的同时，有效保护人体和系统电路，并最大限度的进行声激励以达到更好检测效果。
附图说明：
图1为本发明提供的超声定量弹性成像方法流程图。
图2是本发明提供的超声定量弹性成像系统框图。
图3是本发明中剪切波脉冲发生器和/或所述ARFI脉冲发生器构成示例的结构框图。
图4是本发明中本发明中声激励使用的发射脉冲序列示意图。
图5是剪切波波速计算使用的脉冲发射方式示意图。
具体实施方式
下面结合附图及具体实施例对本发明作进一步的详细描述。但不应将此理解为本发明上述主题的范围仅限于以下的实施例，凡基于本发明内容所实现的技术均属于本发明的范围。
实施例1：如图1所述，本发明提供一种定量剪切波弹性成像方法，包含如下步骤：
S100：进行ARFI检测，获取聚焦区域中指定位置应变εref；
S200：进行剪切波检测，获取聚焦区域中指定位置单点剪切波波速cref；
步骤S100和S200的执行顺序并无特殊要求，如可以先执行S100，再执行S200，也可以先执行S200，再执行S100；图1中的示例采用的是正交解调(IQ) 回波信号，也可以检测包括IQ回波信号、通道回波射频(RF)信号、波束成形后的射频(RF)信号中的一种或几种；
S300：根据所述单点剪切波波速计算各个位置剪切波波速c；
S400：根据各个位置应变计剪切波波速获取各个位置定量剪切波弹性图像E。
具体的，所述聚焦区域中指定位置应变
Figure PCTCN2017107120-appb-000014
其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
Figure PCTCN2017107120-appb-000015
表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
Figure PCTCN2017107120-appb-000016
表示梯度滑动计算窗口内各个位置位移的均值。
所述单点剪切波波速根据指定测量点的横向距离、轴向距离，及各个指定测量点达到最大横向位移所需要的时间采用二维线性拟合法计算得出。
所述单点剪切波波速cref通过公式X＝Aβ得出，其中，
Figure PCTCN2017107120-appb-000017
Figure PCTCN2017107120-appb-000018
式中，通常我们在轴向深度上预设I个深度，每个深度上预设J个指定位置(点)，共m个指定位置(点)，m＝I*J；我们将每个位置(点)在剪切波作用下达到最大位移的时间看做是剪切波传播到该位置(点)的时间，通过剪切波位移-时间数据可以得到剪切波传递到该位置(点)的时间，即ti；同时，zi表示指定测量位置(点)在轴向深度的轴向距离(表征深度位置)，xi表示指定测量位置(点)的横向距离(表征横向位置)，即，当各个指定位置(点)选定时，X中各个元素值以及zi值便已确定，我们只需从剪切波位移-时间数据中找出各个指定位置(点)达到最大位移所需时间ti即可完成计算；公式中，β1即为所求 的指定测量点单点剪切波速cref；同时，应注意的是，β0和β2为利用上式计算单点剪切波速cref过程中同时计算得出的回归参数，本方法中并不使用这两个参数，其作用和含义对本发明没有实质意义。
所述各个位置剪切波波速
Figure PCTCN2017107120-appb-000019
其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
Figure PCTCN2017107120-appb-000020
其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同。
所述定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
本发明同时提供一种对设备要求低、计算量小的超声定量弹性成像系统，包括：
剪切波脉冲发生器，用于发射剪切波激励脉冲及检测脉冲信号；
ARFI脉冲发生器，用于发射ARFI激励脉冲及检测脉冲信号；
探头，用于接收剪切波回波信号和ARFI回波信号；
控制装置1，用于控制剪切波脉冲发生器、ARFI脉冲发生器的开关，接收剪切波回波信号和ARFI回波信号，并根据ARFI回波信号计算指定位置应变εref；根据剪切波回波信号计算指定位置单点剪切波波速cref；根据单点剪切波波速计算各个位置剪切波波速c；根据各个位置应变计剪切波波速c及应变εref获取各个位置定量剪切波弹性图像E。
显示装置，用于将所述定量剪切波弹性图像E显示。具体的，在显示之前，还包括对控制装置计算得出的弹性图像E数据进行扫描转换，平滑处理等一系列的处理过程，最后将该图像通过显示器展现给用户。
所述探头包括波束合成器2，其用于将ARFI回波信号或剪切波回波信号经过波束合成，合成为回波射频信号。
所述控制装置1包括剪切波信号处理模块13、单点剪切波速计算模块14；
所述剪切波信号处理模块13自探头接收剪切波回波射频信号，并经过解调成为IQ数据，进一步对该IQ数据进行位移估算得出被测组织指定位置的剪切波位移-时间数据；
所述单点剪切波速计算模块14根据剪切波位移-时间数据计算指定位置剪切波波速cref，其通过公式X＝Aβ得出，其中，
Figure PCTCN2017107120-appb-000021
式中，xi表示指定测量点的横向距离，ti表示指定测量点达到最大位移所需时间，zi表示指定测量点的轴向距离，β0,β1,β2是线性拟合模型参数，β1的物理意义即为所求的指定测量点单点剪切波速cref，m表示采样点的个数。
所述控制装置1还包括ARFI信号处理模块11、应变计算模块12；
所述ARFI信号处理模块11用于自探头接收ARFI回波射频信号，并经过解调形成IQ数据，并进一步通过对IQ数据进行位移估算得出被测组织指定位置的ARFI位移-时间数据；
所述应变计算模块12根据所述ARFI位移-时间数据计算指定位置应变
Figure PCTCN2017107120-appb-000022
其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
Figure PCTCN2017107120-appb-000023
表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
Figure PCTCN2017107120-appb-000024
表示梯度滑动计算窗口内各个位置位移的均值。
所述控制装置1还包括波速计算模块15及弹性模量计算模块16；
所述波速计算模块15用于根据指定位置单点剪切波波速计算各个位置剪切波波速
Figure PCTCN2017107120-appb-000025
其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
Figure PCTCN2017107120-appb-000026
其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同；
所述弹性图像计算模块16用于根据c及应变εref获取各个位置定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
所述控制装置1控制所述剪切波脉冲发生器、ARFI脉冲发生器交替发射。
具体的，如图3所述，一些实施例中，控制装置1硬件部分可由PC、控制电路板和FPGA芯片组组成，另外一些实施例中，控制装置也可以是完全集成在一起的集成电路构成，上述的剪切波信号处理模块、单点剪切波速计算模块、ARFI信号处理模块、应变计算模块、弹性模量计算模块按功能分布在上述硬件装置中。
所述剪切波脉冲发生器及所述ARFI脉冲发生器为同一电路实现，其由所述控制装置控制发送剪切波脉冲或ARFI脉冲；或，
所述剪切波脉冲发生器及所述ARFI脉冲发生器为各自独立电路实现，其由所述控制装置控制启动、关闭时间。
具体的，在所述剪切波脉冲发生器及所述ARFI脉冲发生器为同一电路实现的实施例中，如图3所示，发生器包括依次串接的驱动放大器100、脉冲发生器101、过流过压保护电路102、Tx/Rx开关103，以及自Tx/Rx开关反馈的限幅放大器104、数模转换电路105。过流过压保护电路102可以让系统满足ARFI与剪切波 不同发射时序要求的同时，有效保护人体和系统电路，并最大限度的进行声激励以达到更好检测效果。
所述剪切波脉冲发生器和/或ARFI脉冲发生器共有24路以上，如48路、64路、128路、256路等。
使用时，控制装置根据用户设定的电压、脉冲长度和相位等参数信息控制脉冲发生器(剪切波脉冲发生器和/或所述ARFI脉冲发生器)产生激励和检测脉冲信号，在T/R开关的控制下发射电路产生的超声波进入生物组织，接收电路接收回波信号。系统在发射或接收信号时，通过设置孔径控制参数f#及聚焦深度z，并利用公式
Figure PCTCN2017107120-appb-000027
来控制活动阵元(脉冲发生器)的个数，公式中，D是探头孔径大小，即用户通过设置孔径控制参数f#及聚焦深度z来控制活动探头孔径的大小来实现对活动阵元个数的控制，用户可根据情况在最大活动阵元数(如64路)内选择实际需要的活动阵元数量，例如，系统如果包括64路脉冲发生器，则系统可以实现的最大探头孔径大小即为64个阵元所分布的面积，孔径控制参数f#通常为大于0且小于或等于5的实数。因为激励组织产生形变的力是由探头根据用户设定的选项发射的短时长脉冲波在聚焦区域形成的，与操作者的操作手法无关，因此可以认为在有效成像区域内力的大小是均匀的，一致的。聚焦区域的深度(Depth of Focus)可以描述为：DoF＝8(f#)2λ，λ表示波长；例如，对于5MHz的激励脉冲，如果孔径控制参数f#＝2，生物组织中的声速近似等于1540m/s，那么聚焦区域的深度DoF的值接近1cm；当f#＝5时，对应的DoF为2.5cm。ARFI弹性成像采用的是逐线方式扫描，每一个水平位置都会根据相同的系统参数发射激励脉冲使得组织产生微小形变，因此可以认为在焦点附近1cm范围内的声辐射力可以看作是均匀的，一致的，这个区域我们称为聚焦区域，如上所述，在聚 焦区域中，剪切波波速计算公式
Figure PCTCN2017107120-appb-000028
中的γε取值为1。
发射脉冲序列示意如图4所示，根据ROI(Region of Interest)窗口深度位置，信号中心频率大小、PRF(pulse repeat frequency，脉冲重复频率)、激励电压以及脉冲长度等参数控制发射脉冲序列。序列的头部是1个或多个检测脉冲(检测波束(Detect beam),较高电压(例如80V，一般与B模式相同)，短脉冲(例如2个周期))作为组织位移信息的参考信号；接下来是多组激励脉冲/检测脉冲对，激励脉冲(激励波束(Push beam),较低电压(例如20～40V)，长脉冲(100～250个周期))用于在组织内焦点附近的局部区域激励产生微小位移。
检测脉冲(高电压的短脉冲)用于跟踪声辐射力载荷在加载的过程中组织的形变情况；之后是一系列的检测脉冲跟踪声辐射力载荷消失后组织的形变情况。激励脉冲的作用是使焦点位置处的局部组织在安全条件下能够振动起来，长回波信号由于其空间分辨率差不能用于位移估算，所以探头阵元在发射激励脉冲时关闭信号变迹，所有活动阵元的发射信号幅值相同，增强信号携带的能量以便在安全条件下产生更大的声辐射力。用于激励的长脉冲波频率和用于检测的短脉冲波中心频率可选择相同或不同，优选方案是中心频率不同，这样可以为了避免激励脉冲对检测脉冲回波信号的干扰，同时在信号处理时易于区分激励和检测的回波信号。
另外发射脉冲序列中的长脉冲波数目是可变的，整个序列的波数目也是可变的，这里我们将一次激励整个序列的波数目定义为取样容积数目(ensemble size)，例如16，24，32。长脉冲波数目(激励波)+短脉冲波数目(参考和检测波)＝取样容积数目，梯度滑动计算窗口N的大小为0～取样容积数之间的任意值，具体其为采用自适应算法自动选择，此处不再赘述。
一组剪切波发射脉冲包含若干个不同空间位置如图4所示的发射脉冲序列，其中激励脉冲空间位置固定，而不同发射序列的检测脉冲空间位置不同；如图5所示，D为检测波，P为激励波，假如有一组剪切波发射脉冲采用5个间隔为1mm的发射脉冲序列，这5个序列的激励波P1、P2、P3、P4、P5均在同一空间位置，而5个发射脉冲序列中的检测波D1、D2、D3、D4、D5在相同或不同空间位置，同时，至少一个检测脉冲的空间位置和激励脉冲位置相同，如图中的D1。
ARFI脉冲发生器使用的发射脉冲序列与剪切波脉冲发生器相同，但一帧ARFI成像扫描过程中激励波保持与检测波为同一空间位置。

Claims (16)

  1. 一种定量剪切波弹性成像方法，其特征在于，包含如下步骤：
    进行ARFI检测，获取聚焦区域中指定位置应变εref；
    进行剪切波检测，获取聚焦区域中指定位置单点剪切波波速cref；
    根据所述单点剪切波波速计算各个位置剪切波波速c；
    根据各个位置应变计剪切波波速获取各个位置定量剪切波弹性图像E。
  2. 如权利要求1所述的成像方法，其特征在于，
    所述聚焦区域中指定位置应变
    Figure PCTCN2017107120-appb-100001
    其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
    Figure PCTCN2017107120-appb-100002
    表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
    Figure PCTCN2017107120-appb-100003
    表示梯度滑动计算窗口内各个位置位移的均值。
  3. 如权利要求1所述的成像方法，其特征在于，所述单点剪切波波速根据指定测量点的横向距离、轴向距离，及各个指定测量点达到最大横向位移所需要的时间采用二维线性拟合法计算得出。
  4. 如权利要求3所述的成像方法，其特征在于，所述单点剪切波波速cref通过公式X＝Aβ得出，其中，
    Figure PCTCN2017107120-appb-100004
    式中，xi表示指定测量点的横向距离，ti表示指定测量点达到最大位移所需时间，zi表示指定测量点的轴向距离，β0,β1,β2是线性拟合模型参数，β1的物理意义即为所求的指定测量点单点剪切波速cref，m表示采样点的个数。
  5. 如权利要求1所述的成像方法，其特征在于，所述各个位置剪切波波速
    Figure PCTCN2017107120-appb-100005
    其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
    Figure PCTCN2017107120-appb-100006
    其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同。
  6. 如权利要求5所述的成像方法，其特征在于，所述聚焦区域DoF＝8(f#)2λ，其中，λ表示波长，f#为孔径控制参数，f#的取值范围为0～5之间的实数。
  7. 如权利要求1所述的成像方法，其特征在于，所述定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
  8. 一种定量剪切波弹性成像系统，其特征在于，包括，
    剪切波脉冲发生器，用于发射剪切波激励脉冲及检测脉冲信号；
    ARFI脉冲发生器，用于发射ARFI激励脉冲及检测脉冲信号；
    探头，用于接收剪切波回波信号和ARFI回波信号；
    控制装置，用于控制剪切波脉冲发生器、ARFI脉冲发生器的开关，接收剪切波回波信号和ARFI回波信号，并根据ARFI回波信号计算指定位置应变εref；根据剪切波回波信号计算指定位置单点剪切波波速cref；根据单点剪切波波速计算各个位置剪切波波速c；根据各个位置应变计剪切波波速c及应变εref获取各个位置定量剪切波弹性图像E；
    显示装置，用于将所述定量剪切波弹性图像E显示。
  9. 如权利要求8所述的系统，其特征在于，所述探头包括波束合成器，其用于将ARFI回波信号或剪切波回波信号经过波束合成，合成为回波射频信号。
  10. 如权利要求9所述的系统，其特征在于，所述控制装置包括剪切波信号处理模块、单点剪切波速计算模块；
    所述剪切波信号处理模块自探头接收剪切波回波射频信号，并经过解调、位移估算得出被测组织指定位置的剪切波位移-时间数据；
    所述单点剪切波速计算模块根据剪切波位移-时间数据计算指定位置剪切波波速cref，其通过公式X＝Aβ得出，其中，
    Figure PCTCN2017107120-appb-100007
    式中，xi表示指定测量点的横向距离，ti表示指定测量点达到最大位移所需时间，zi表示指定测量点的轴向距离，β0,β1,β2是线性拟合模型参数，β1的物理意义即为所求的指定测量点单点剪切波速cref，m表示采样点的个数。
  11. 如权利要求9所述的系统，其特征在于，所述控制装置还包括ARFI信号处理模块、应变计算模块；
    所述ARFI信号处理模块用于自探头接收ARFI回波射频信号，并经过解调、位移估算得出被测组织指定位置的ARFI位移-时间数据；
    所述应变计算模块根据所述ARFI位移-时间数据计算指定位置应变
    Figure PCTCN2017107120-appb-100008
    其中，N为梯度滑动计算窗口大小，zi表示指定位置深度坐标，
    Figure PCTCN2017107120-appb-100009
    表示梯度滑动计算窗口内各个位置坐标的均值，yi表示梯度滑动计算窗口内当前点位移，
    Figure PCTCN2017107120-appb-100010
    表示梯度滑动计算窗口内各个位置位移的均值。
  12. 如权利要求8所述的系统，其特征在于，所述控制装置还包括波速计算模块及弹性模量计算模块；
    所述波速计算模块用于根据指定位置单点剪切波波速计算各个位置剪切波波速
    Figure PCTCN2017107120-appb-100011
    其中，在聚焦区域，γε取值1；在聚焦区域之外的轴向区域，
    Figure PCTCN2017107120-appb-100012
    其中，z为轴向距离，n和σ为表示激励声场的系统常数，取值范围均为0～10，n和σ两个参数的取值可以相同或不同；
    所述弹性图像计算模块用于根据c及应变εref获取各个位置定量剪切波弹性图像E＝3ρc2，其中，ρ为被测区域介质密度。
  13. 如权利要求8至12之一所述的系统，其特征在于，所述控制装置控制所述剪切波脉冲发生器、ARFI脉冲发生器交替发射。
  14. 如权利要求8至12之一所述的系统，其特征在于，所述剪切波脉冲发生器及所述ARFI脉冲发生器为同一电路实现，其由所述控制装置控制发送剪切波脉冲或ARFI脉冲；
    所述剪切波脉冲发生器及所述ARFI脉冲发生器为各自独立电路实现，其由所述控制装置控制启动、关闭时间。
  15. 如权利要求8至12之一所述的系统，其特征在于，所述剪切波脉冲发生器和/或ARFI脉冲发生器共有24路以上。
  16. 如权利要求8至12之一所述的系统，其特征在于，所述剪切波脉冲发生器或ARFI脉冲发生器包括依次串接的驱动放大器、脉冲发生器、过流过压保护电路、Tx/Rx开关，以及自Tx/Rx开关反馈的限幅放大器、数模转换电路。
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