CN113827278B - Method and device for determining propagation speed of shear wave - Google Patents
Method and device for determining propagation speed of shear wave Download PDFInfo
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- CN113827278B CN113827278B CN202111255031.8A CN202111255031A CN113827278B CN 113827278 B CN113827278 B CN 113827278B CN 202111255031 A CN202111255031 A CN 202111255031A CN 113827278 B CN113827278 B CN 113827278B
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- 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
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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
- A61B8/48—Diagnostic techniques
- A61B8/485—Diagnostic techniques involving measuring strain or elastic properties
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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
- A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/5215—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data
Abstract
The application relates to the technical field of ultrasonic imaging, and provides a method and a device for determining the propagation speed of shear waves, which are used for solving the problem that the propagation speed of shear waves is not accurate enough in the related technology. In order to simultaneously consider the imaging width and the imaging depth, the application provides a special excitation mode to fill the whole imaging area with shear waves, and then carries out detection to obtain ultrasonic echo signals. In order to overcome the mutual influence among the shear waves propagating in different directions, the shear wave signal components in different directions are extracted and separated through direction filtering, then the shear wave propagation speed of each shear wave signal component is obtained, and finally the shear wave propagation speeds in all directions are fused, so that the accurate overall shear wave propagation speed of an imaging area is obtained.
Description
Technical Field
The present application relates to the field of ultrasound imaging technologies, and in particular, to a method and an apparatus for determining a propagation speed of a shear wave.
Background
In the current ultrasonic shear wave elastography application, there are two methods of ultrasonic shear wave elastography based on Mach-Zehnder excitation and shear wave elastography based on comb pulse excitation. According to the propagation speed of the shear wave, after knowing the density of the imaged tissue, the Young's modulus of the tissue, that is, the elasticity value of the tissue, can be calculated by a relational expression.
In ultrasound elastography, estimation of shear wave propagation velocity is particularly important. However, when the imaging area is large, the method cannot be applied to a scene with a large imaging area due to a small ultrasonic shear wave elastography range based on mach cone excitation. Whereas shear wave elastography based on comb pulse excitation can only focus at the same imaging depth. As such, the shear wave propagation velocity estimated by both methods is not sufficiently accurate and reliable.
Disclosure of Invention
The embodiment of the application provides a method and a device for determining the propagation speed of shear waves, which are used for solving the problem that the propagation speed of the shear waves is not accurate and reliable in the related technology.
In a first aspect, the present application provides a method of determining the propagation velocity of shear waves, an imaging region comprising a plurality of imaging tiles, the method comprising:
transmitting ultrasonic focusing long pulse excitation to each imaging block in sequence, wherein the transmission time interval of two adjacent ultrasonic focusing long pulse excitation is smaller than a preset value;
transmitting detection pulses to obtain ultrasonic echo signals of the imaging region;
determining a shear wave signal by adopting a motion detection method for the ultrasonic echo signal;
separating shear wave signal components of the shear wave signal in all directions from the shear wave signal based on a direction filtering method;
determining the shear wave propagation velocity of the shear wave signal components in each direction;
the shear wave propagation velocity of the imaging region is determined based on the shear wave propagation velocities of the respective shear wave signal components.
In one possible implementation, the first excitation mode includes a plurality of emission angles, each emission angle corresponding to one imaging zone, and the sequentially emitting ultrasonic focusing long pulse excitation to each imaging zone includes:
an ultrasonic focal length pulse excitation is sequentially transmitted to the imaging region at each of the transmit angles, wherein the depth of focus of each transmit angle is the same or different.
In one possible implementation, the ultrasound focus long pulse excitation is emitted multiple times within each imaging zone in the second excitation mode, and at least one depth of focus is employed within the same imaging zone; the sequentially transmitting ultrasonic focus long pulse excitation to each imaging zone comprises:
and transmitting ultrasonic focusing long pulse excitation in each imaging block in sequence in the second excitation mode.
In one possible implementation manner, the direction-based filtering method separates shear wave signal components of the shear wave signal in each direction from the shear wave signal, including:
aiming at ultrasonic focusing long pulse excitation transmitted each time, acquiring a first direction filter corresponding to the transmission angle of the ultrasonic focusing long pulse excitation, and performing up-down overturning treatment on the filter to obtain a second direction filter;
multiplying the two-dimensional data of each focusing depth in the shear wave signal by the first direction filter to obtain a first shear wave signal component corresponding to the ultrasonic focusing long pulse excitation; and multiplying the two-dimensional data of each focusing depth in the shear wave signal by the second direction filter to obtain a second shear wave signal component corresponding to the ultrasonic focusing long pulse excitation.
In one possible embodiment, acquiring a direction filter corresponding to an emission angle of the ultrasonic focusing long pulse excitation includes:
if the emission angle is a specified deflection angle, a first direction filter of the specified deflection angle is obtained and used as a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation;
if the transmitting angle deflects relative to the designated deflection angle, a first direction filter of the designated deflection angle is used as a reference filter; and rotating the reference filter from the appointed deflection angle to the emission angle of the ultrasonic focusing long pulse excitation to obtain a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation.
In one possible embodiment, the determining the shear wave propagation velocity of the imaging region based on the shear wave propagation velocity of each shear wave signal component includes:
determining the reliability corresponding to the propagation speed of the shear wave of each shear wave signal component and the sum of the reliability;
and taking the credibility as a weight, carrying out weighted summation on the shear wave propagation speeds of the shear wave signal components, and dividing the weighted summation result by the summation to obtain the shear wave propagation speed of the imaging region.
In one possible implementation manner, the determining the reliability of the shear wave propagation speeds of the respective shear wave signal components includes:
for each shear wave signal component, acquiring two scanning lines in the shear wave signal component, which are used for determining the propagation speed of the shear wave signal component;
and determining the similarity between the two scanning lines as the credibility of the shear wave propagation speed of the shear wave signal classification.
In a possible implementation manner, the determining the shear wave signal by using an autocorrelation method on the ultrasonic echo signal includes:
and carrying out autocorrelation analysis on the ultrasonic echo signal data with any continuous appointed frame number in the ultrasonic echo signal, and obtaining shear wave signal data corresponding to the ultrasonic echo data with the continuous appointed frame number.
Optionally, determining the shear wave propagation velocity of the shear wave signal component in each direction includes:
acquiring signals of two scanning lines corresponding to the same point of the shear wave signal component;
analyzing the time delay between the signals of the two scanning lines by adopting a cross-correlation method;
and dividing the distance between the two scanning lines by the time delay to obtain the shear wave propagation speed of the shear wave signal component.
In a second aspect, the present application also provides an ultrasound apparatus comprising: the device comprises a processor, a memory, a display unit and a probe;
a probe for transmitting an ultrasonic signal;
a display unit for displaying the ultrasound image;
a processor, coupled to the probe and the display unit, respectively, configured to perform any of the methods provided in the first aspect.
In a third aspect, an embodiment of the application also provides a computer readable storage medium, which when executed by a processor of an electronic device, causes the electronic device to perform any of the methods as provided in the first aspect of the application.
In a fourth aspect, an embodiment of the application provides a computer program product comprising a computer program which, when executed by a processor, implements any of the methods as provided in the first aspect of the application.
The technical scheme provided by the embodiment of the application at least has the following beneficial effects: the embodiment of the application adopts a mode of dynamic excitation in tissues to realize ultrasonic imaging so as to improve the estimation precision of the propagation speed of shear waves. In order to simultaneously consider the imaging width and the imaging depth, the application provides a special excitation mode to fill the whole imaging area with shear waves, and then detects the shear waves to obtain ultrasonic echo signals. In order to overcome the mutual influence among the shear waves propagating in different directions, the shear wave signal components in different directions are extracted and separated through direction filtering, then the shear wave propagation speed of each shear wave signal component is obtained, and finally the shear wave propagation speeds in all directions are fused to obtain the whole shear wave propagation speed of an imaging area.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a frame of an ultrasound apparatus according to an embodiment of the present application;
fig. 2 is a schematic diagram of an ultrasonic device implementing an ultrasonic image according to an embodiment of the present application;
FIG. 3 is a flow chart illustrating a method for determining propagation velocity of shear waves according to an embodiment of the present application;
FIG. 4a is a schematic diagram of a first excitation method according to an embodiment of the present application;
FIG. 4b is a schematic diagram of a second excitation method according to an embodiment of the present application;
fig. 5 is a schematic diagram of a directional filter according to an embodiment of the application.
Detailed Description
In order to enable a person skilled in the art to better understand the technical solutions of the present application, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the application described herein may be implemented in other sequences than those illustrated or otherwise described herein. The implementations described in the following exemplary examples do not represent all implementations consistent with the application. Rather, they are merely examples of apparatus and methods consistent with aspects of the application as detailed in the accompanying claims.
In the following, some terms in the embodiments of the present application are explained for easy understanding by those skilled in the art.
(1) The term "plurality" in embodiments of the present application means two or more, and other adjectives are similar.
(2) "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.
Ultrasonic elastography is a technology based on the related fields of tissue elastography, wave propagation theory and the like, and the basic principle is as follows: by applying internal or external, static or dynamic acting force to the biological tissue, the tissue generates corresponding effect under the interaction of physical rules such as elastomechanics and the like. Since the normal biological tissue and the pathological tissue have different mechanical properties, the response of the normal biological tissue and the pathological tissue to the applied excitation is inconsistent, and the difference of parameters such as displacement, strain, speed and the like is mainly expressed.
The ultrasonic elastography at the present stage can be classified into quasi-static excitation and dynamic excitation according to excitation modes. Quasi-static ultrasound elastography is the application of slight compression to the tissue to be examined, typically by slowly squeezing the soft tissue with an ultrasound probe. Dynamic excitation is a time-varying excitation pattern applied to tissue. The generation sources of the excitation can be classified into internal motion of the tissue itself, external excitation, and internal excitation. Autonomous movement of tissue includes spontaneous systolic and diastolic movement of the heart, pulsatile movement of blood vessels, and respiratory movement. The internal excitation of the tissue transmits ultrasonic energy to the tissue through energy transfer, so that the internal part of the tissue is locally vibrated to generate deformation. The external excitation of the tissue is to apply a quasi-static pressure or low frequency vibration to the tissue surface, thereby causing a corresponding deformation of the tissue.
The tissue internal excitation modes based on ultrasonic focusing mainly comprise: supersonic shear wave elastography based on mach-cone excitation and shear wave elastography based on comb pulse excitation.
In the current ultrasonic shear wave elastography application, there are two methods of ultrasonic shear wave elastography based on Mach-Zehnder excitation and shear wave elastography based on comb pulse excitation. According to the propagation speed of the shear wave, after knowing the density of the imaged tissue, the Young's modulus of the tissue, that is, the elasticity value of the tissue, can be calculated by a relational expression.
However, when the imaging area is large, the method cannot be applied to a scene with a large imaging area due to a small ultrasonic shear wave elastography range based on mach cone excitation. Whereas shear wave elastography based on comb pulse excitation can only focus at the same imaging depth. The shear wave propagation speed estimated by both methods is to be improved.
In view of the above, the present application provides a method and apparatus for determining a propagation velocity of a shear wave. The embodiment of the application adopts a mode of dynamic excitation in tissues to realize ultrasonic imaging so as to improve the estimation precision of the propagation speed of shear waves. In order to simultaneously consider the imaging width and the imaging depth, the application provides a special excitation mode to fill the whole imaging area with shear waves, and then detects the shear waves to obtain ultrasonic echo signals. In order to overcome the mutual influence among the shear waves propagating in different directions, the shear wave signal components in different directions are extracted and separated through direction filtering, then the shear wave propagation speed of each shear wave signal component is obtained, and finally the shear wave propagation speeds in all directions are fused to obtain the whole shear wave propagation speed of an imaging area.
The ultrasound apparatus and the interference suppression method for ultrasound images provided by the embodiments of the present application are described below with reference to the accompanying drawings.
Referring to fig. 1, a block diagram of an ultrasonic apparatus according to an embodiment of the present application is shown.
It should be understood that the ultrasound device 100 shown in fig. 1 is only one example, and that the ultrasound device 100 may have more or fewer components than shown in fig. 1, may combine two or more components, or may have a different configuration of components. The various components shown in the figures may be implemented in hardware, software, or a combination of hardware and software, including one or more signal processing and/or application specific integrated circuits.
A hardware configuration block diagram of an ultrasound apparatus 100 according to an exemplary embodiment is illustrated in fig. 1.
As shown in fig. 1, the ultrasound apparatus 100 may include, for example: a processor 110, a memory 120, a display unit 130, and a probe 140; wherein, the liquid crystal display device comprises a liquid crystal display device,
a probe 140 for transmitting ultrasonic focused long pulse excitation;
a display unit 130 for displaying an ultrasonic elastic image;
the memory 120 is configured to store data required for ultrasound imaging, which may include software programs, application interface data, and the like;
a processor 110, coupled to the probe 140, the display unit 130, and the memory 120, respectively, is configured to perform:
the imaging area comprises a plurality of imaging blocks, ultrasonic focusing long pulse excitation is sequentially transmitted to each imaging block, wherein the transmission time interval of two adjacent ultrasonic focusing long pulse excitation is smaller than a preset value;
transmitting detection pulses to obtain ultrasonic echo signals of the imaging region;
determining a shear wave signal by adopting a motion detection method for the ultrasonic echo signal;
separating shear wave signal components of the shear wave signal in all directions from the shear wave signal based on a direction filtering method;
determining the shear wave propagation velocity of the shear wave signal components in each direction;
the shear wave propagation velocity of the imaging region is determined based on the shear wave propagation velocities of the respective shear wave signal components.
In one possible implementation, the first excitation mode includes a plurality of emission angles, each emission angle corresponding to one imaging zone, and the sequentially emitting ultrasonic focusing long pulse excitation to each imaging zone includes:
an ultrasonic focal length pulse excitation is sequentially transmitted to the imaging region at each of the transmit angles, wherein the depth of focus of each transmit angle is the same or different.
In one possible implementation, the ultrasound focus long pulse excitation is emitted multiple times within each imaging zone in the second excitation mode, and at least one depth of focus is employed within the same imaging zone; the sequentially transmitting ultrasonic focus long pulse excitation to each imaging zone comprises:
and transmitting ultrasonic focusing long pulse excitation in each imaging block in sequence in the second excitation mode.
In one possible implementation manner, the direction-based filtering method separates shear wave signal components of the shear wave signal in each direction from the shear wave signal, including:
aiming at ultrasonic focusing long pulse excitation transmitted each time, acquiring a first direction filter corresponding to the transmission angle of the ultrasonic focusing long pulse excitation, and performing up-down overturning treatment on the filter to obtain a second direction filter;
multiplying the two-dimensional data of each focusing depth in the shear wave signal by the first direction filter to obtain a first shear wave signal component corresponding to the ultrasonic focusing long pulse excitation; and multiplying the two-dimensional data of each focusing depth in the shear wave signal by the second direction filter to obtain a second shear wave signal component corresponding to the ultrasonic focusing long pulse excitation.
In one possible embodiment, acquiring a direction filter corresponding to an emission angle of the ultrasonic focusing long pulse excitation includes:
if the emission angle is a specified deflection angle, a first direction filter of the specified deflection angle is obtained and used as a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation;
if the transmitting angle deflects relative to the designated deflection angle, a first direction filter of the designated deflection angle is used as a reference filter; and rotating the reference filter from the appointed deflection angle to the emission angle of the ultrasonic focusing long pulse excitation to obtain a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation.
In one possible embodiment, the determining the shear wave propagation velocity of the imaging region based on the shear wave propagation velocity of each shear wave signal component includes:
determining the reliability corresponding to the propagation speed of the shear wave of each shear wave signal component and the sum of the reliability;
and taking the credibility as a weight, carrying out weighted summation on the shear wave propagation speeds of the shear wave signal components, and dividing the weighted summation result by the summation to obtain the shear wave propagation speed of the imaging region.
In one possible implementation manner, the determining the reliability of the shear wave propagation speeds of the respective shear wave signal components includes:
for each shear wave signal component, acquiring two scanning lines in the shear wave signal component, which are used for determining the propagation speed of the shear wave signal component;
and determining the similarity between the two scanning lines as the credibility of the shear wave propagation speed of the shear wave signal classification.
In a possible implementation manner, the determining the shear wave signal by using an autocorrelation method on the ultrasonic echo signal includes:
and carrying out autocorrelation analysis on the ultrasonic echo signal data with any continuous appointed frame number in the ultrasonic echo signal, and obtaining shear wave signal data corresponding to the ultrasonic echo data with the continuous appointed frame number.
In one possible embodiment, the determining the shear wave propagation velocity of the shear wave signal component in each direction includes:
acquiring signals of two scanning lines corresponding to the same point of the shear wave signal component;
analyzing the time delay between the signals of the two scanning lines by adopting a cross-correlation method;
and obtaining the shear wave propagation speed of the shear wave signal component based on the time delay of the distance between the two scanning lines.
Fig. 2 is a schematic diagram of an application principle according to an embodiment of the present application. The portion may be implemented by a portion of a module or a functional component of the ultrasound apparatus shown in fig. 1, and only major components will be described below, while other components, such as a memory, a controller, a control circuit, etc., will not be described herein.
As shown in fig. 2, a user interface 210, a display unit 220 for displaying the user interface, and a processor 230 may be included in the application environment.
The display unit 220 may include a display panel 221, a backlight assembly 222. Wherein the display panel 321 is configured to display an ultrasonic image, the backlight assembly 222 is disposed at the back of the display panel 221, and the backlight assembly 222 may include a plurality of backlight partitions (not shown in the drawings), each of which may emit light to illuminate the display panel 221.
The processor 230 may be configured to control the backlight brightness of each backlight partition in the backlight assembly 222 and to control the probe to transmit ultrasonic focused long pulse excitation and detection pulses and to receive ultrasonic echo signals.
Wherein the processor 230 may process the ultrasound echo signals to determine a shear wave propagation velocity of the imaging region.
Fig. 3 is a schematic flow chart of a shear wave propagation velocity method according to an embodiment of the application, which includes the following steps:
in order to make the whole imaging area full of shear waves as much as possible, in the embodiment of the present application, the imaging area may be divided into a plurality of imaging areas, and then, in step 301, ultrasonic focusing long pulse excitation is sequentially transmitted to each of the imaging areas, where the transmission time interval between two adjacent ultrasonic focusing long pulse excitation is smaller than a preset value.
For example, as shown in fig. 4a, the imaging zone may be divided based on the deflection angle of the ultrasonic focusing long pulse excitation, for example, the emitted sound field when the deflection angle is 0 corresponds to the first imaging zone, the second imaging zone when the deflection angle is 20 ° to the left, and the third imaging zone when the deflection angle is 20 ° to the right. Similarly, the number of deflection angles can be set according to the requirement, and each deflection angle corresponds to one imaging block. This excitation pattern is hereinafter also referred to as the first excitation pattern for convenience of description.
In the first excitation mode, the depth of focus may be the same or different when long pulse excitation is emitted at different deflection angles. Continuing with the example of FIG. 4a, the first depth of focus is used when undeflected, the second depth of focus is used when deflected 20℃left, and the third depth of focus is used when deflected 20℃right. Thus, the same imaging region is not only excited by long pulses of multiple deflection angles to fill the shear wave as much as possible, but also different depths of focus result in shear wave conditions. Therefore, the first excitation mode has no limit on the focusing depth and no display on an imaging area, and is an ultrasonic imaging mode capable of combining the focusing depth and the imaging width, so that the obtained shear wave propagation speed is more accurate and reliable.
When the first excitation mode is adopted for ultrasonic imaging, each deflection angle sequentially emits long pulse excitation, for example, the long pulse excitation is sequentially emitted in an undeflected mode, a 20-degree left deviation mode and a 20-degree right deviation mode, or is sequentially emitted in an undeflected mode, a 20-degree right deviation mode and a 20-degree left deviation mode, or is sequentially emitted in a 20-degree right deviation mode, a 20-degree left deviation mode and an undeflected mode. It should be noted that the emission sequence may be set according to the requirement, so long as each emission angle set by coverage is applicable to the embodiment of the present application.
According to the first excitation mode, the emitted sound fields of all angles can be overlapped, so that the whole imaging area is filled with the generated shear wave signals, meanwhile, the shear wave signals generated by the emission of all angles are coherently overlapped, so that strong shear wave signals exist in a wider area and a deeper area, and the stronger the shear wave signals are, the higher the accuracy of the obtained shear wave speed is.
In another possible embodiment, the present application also provides a second excitation pattern. In the second excitation mode the same imaging volume may emit long pulse excitation multiple times and the depth of focus may be different for each transmission. As shown in fig. 4b, the imaging region may be divided into left and right imaging tiles. The left imaging block transmits long pulse excitation according to focus 1 and focus 2, and the right imaging block transmits long pulse excitation according to focus 1 and focus 2. After the left imaging block and the right imaging block are overlapped, the overlapped generation can be shown in fig. 4 b. Thereby, the shear wave can fill the entire imaging region, and then an ultrasonic echo signal of the imaging region is obtained with the detection pulse.
Because the imaging focal points are different, the imaging depths are different, and the whole imaging area can be filled with the shear wave, the second excitation mode of the embodiment of the application can be suitable for any imaging depth and imaging width.
As shown in fig. 4b, a long pulse excitation may be sent to the left imaging block in accordance with focal point 1, after which the long pulse excitation is sent on the same side as shown in fig. 4b, acting on focal point 2. And then the long pulse excitation is emitted to the other side of the probe, namely the imaging block on the right side, and acts on the focal point 1, and finally the long pulse excitation is emitted to the same side (namely the imaging block on the right side) and acts on the focal point 2, and the emitted sound fields emitted by the ultrasonic waves for 4 times are overlapped, so that an effect diagram after the sound fields are overlapped in the step 4b is obtained. The four focuses may be located at different depths and at different horizontal positions, and the firing order may be unrestricted. Because of the combination of the multiple emission modes, each emission sound field can be overlapped, so that the whole imaging area is filled with the generated shear wave signals, meanwhile, the shear wave signals generated by the emission of each ultrasonic wave are coherent, so that strong shear wave signals exist in a wider area and a deeper area, and compared with the mode that long pulse excitation is sent to a plurality of apertures at the same time, the long pulse excitation acts on the same position in the embodiment of the application, the shear wave signals are stronger, and the accuracy of the obtained shear wave speed is higher.
In step 302, transmitting a detection pulse to obtain an ultrasonic echo signal of the imaging region;
the application can transmit the detection pulse for multiple times to obtain the ultrasonic echo signal corresponding to the detection pulse transmitted each time.
In step 303, a shear wave signal is determined for the ultrasonic echo signal using a motion detection method.
The motion detection method includes, for example, an autocorrelation method, and both one-dimensional and two-dimensional autocorrelation methods are suitable for use in the embodiments of the present application. The method is suitable for carrying out autocorrelation processing by adopting time dimension information, namely frame data dimension information, to obtain a shear wave signal, and carrying out autocorrelation processing by adopting time dimension information and point dimension information in a two-dimensional autocorrelation method to obtain the shear wave signal.
In the embodiment of the application, the ultrasonic echo signal comprises multi-frame data, and the shear wave signal can be determined by adopting continuous multi-frame data. The method can be implemented as follows: and carrying out autocorrelation analysis on the ultrasonic echo signal data with any continuous appointed frame number in the ultrasonic echo signal, and obtaining shear wave signal data corresponding to the ultrasonic echo data with the continuous appointed frame number.
For example, using the first excitation mode or the second excitation mode described above, the tissue is displaced by the order of microns, thereby producing a shear wave signal. A detection pulse is then transmitted to track the propagation of the shear wave. After the ultrasound echo data is obtained, the shear wave signal is calculated using the usual Kasai algorithm. The calculation formula is shown as the following formula (1):
in the formula (1), IQ signals represent acquired ultrasonic echo data, IQ signals are three-dimensional data, and i, j represent two dimensions thereof. i and j represent two-dimensional spatial positions of IQ signals, len represents the number of frames used for autocorrelation, frame represents the number of frames of the total acquired ultrasound echo signals, * the symbol representation conjugates the IQ signal,representing complex multiplication of two IQ signals. m represents a frame number index in the ultrasound echo data. The resulting shear wave signal is represented by shearvavesignal.
With IQ signals, the shear wave signals are also three-dimensional. One dimension is a dot, one dimension is a scan line, and the other dimension is a frame. The same frame comprises a plurality of points and a plurality of scanning lines, and the same points of different frames form a one-dimensional signal which represents a shear wave motion track changing along with time.
The shearing wave signals which are transmitted in all directions are obtained after the processing of the autocorrelation algorithm, and the shearing wave signals which are transmitted in all directions can interfere with each other, so that great discontinuity exists between waveforms of the shearing waves. To eliminate the effect of shear wave interference, step 304 may be performed.
In step 304, shear wave signal components of the shear wave signal in each direction are separated from the shear wave signal based on a direction filtering method.
Wherein for any emission angle, two directions of shear wave signal components can be obtained. The method can be implemented as follows:
aiming at ultrasonic focusing long pulse excitation transmitted each time, acquiring a first direction filter corresponding to the transmission angle of the ultrasonic focusing long pulse excitation, and performing up-down overturning treatment on the filter to obtain a second direction filter;
multiplying the two-dimensional data of each focusing depth in the shear wave signal by the first direction filter to obtain a first shear wave signal component corresponding to the ultrasonic focusing long pulse excitation; and multiplying the two-dimensional data of each focusing depth in the shear wave signal by the second direction filter to obtain a second shear wave signal component corresponding to the ultrasonic focusing long pulse excitation.
For the first excitation pattern, each transmission angle corresponds to a first direction filter. For example, one first direction filter for undeflected conditions, 20 for left-hand conditions, and another first direction filter for 20 for right-hand conditions. When the shear wave signal is not deflected, the shear wave signal component which propagates from left to right is obtained by adopting the corresponding first direction filter, the second direction filter is obtained after the first direction filter is overturned upwards, and the shear wave signal component which propagates from right to left can be obtained by adopting the second direction filter. And the same processing is carried out on other transmission angles, so that the shear wave signal components propagated in different directions can be obtained.
For the second excitation mode, if the emission angle is only one (i.e. not deflected), only the corresponding first direction filter and the corresponding second direction filter when not deflected are needed to obtain the shear wave signal components in two directions.
In one possible embodiment, the first direction filter of the other deflection angle may be obtained based on the first direction filter of the specified deflection angle. If the emission angle is a specified deflection angle, a first direction filter of the specified deflection angle is obtained and used as a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation;
if the transmitting angle deflects relative to the designated deflection angle, a first direction filter of the designated deflection angle is used as a reference filter; and rotating the reference filter from the appointed deflection angle to the emission angle of the ultrasonic focusing long pulse excitation to obtain a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation.
For example, a direction filter in the undeflected state is used as the reference filter. The left diagram as shown in fig. 5 is a schematic diagram of the reference filter in which the black partial region is 0 and the white partial region is 1. For the shear wave signal obtained for undeflected emission, for the two-dimensional data at each depth (i.e., one frame of data in the shear wave signal), multiplying the two-dimensional data with a first direction filter shown in the left graph of fig. 5, thereby obtaining a shear wave signal component propagating from left to right; meanwhile, the first direction filter shown in the left diagram in fig. 5 is turned upside down, two-dimensional data at each depth is multiplied by the direction filter, and then a shear wave signal component propagating from right to left can be obtained. The left diagram of fig. 5 shows the direction filter for undeflected emission, and for deflected emission excitation, the direction filter shown in the left diagram of fig. 5 needs to be rotated by an angle equal to the angle of deflected emission. For example, 20 ° left-shifted, the resulting first direction filter is shown in the right-hand diagram of fig. 5, so that the shear wave signal components propagating in all directions can be extracted and separated.
In step 305, the shear wave propagation velocities of the shear wave signal components of the respective directions are determined.
In a possible implementation manner, for each direction of the shear wave signal component, signals of two scan lines corresponding to the same point of the shear wave signal component can be acquired; then, a cross-correlation method is used to analyze the time delay between the signals of the two scan lines, and then the shear wave propagation velocity of the shear wave signal component is obtained based on the distance between the two scan lines divided by the time delay.
For example, the number of the cells to be processed, let the shear wave signal component be data of (100 x 100). Wherein the first 100 represents the data amount of the dot, the second 100 represents the number of scan lines, and the third 100 represents the frame number. For point a, the data of line 1 may be scanned, i.e. point a may be obtained from the data of (100 x 100), all the data corresponding to scan line 1 may be taken as data 1, all data corresponding to the scan line 2 of the point a are acquired as data 2, and then the distance between the scan lines in the two data is calculated. For example, when the scanning line 1 and the scanning line 9 are selected, the distance is (9-1) the distance between adjacent points. When the detection pulse is emitted, the distance between adjacent points is a known value, so that the distance between the two scanning lines can be calculated.
The shear wave signal component is a three-dimensional array, which is the number of points, the number of lines and the number of frames, respectively, and the time delay between the two pairs of signals can be obtained by performing a cross-correlation algorithm on the two pairs of one-dimensional signals (namely, the two scanning line signals adopted in the process of calculating the distance) at different scanning line positions at the same depth (namely, the same point). And then, the shear wave propagation speed of the shear wave signal component is obtained by adopting the time delay of the distance between the pair of one-dimensional signals.
In step 306, the shear wave propagation velocity of the imaging region is determined based on the shear wave propagation velocities of the respective shear wave signal components.
In order to measure the shear wave propagation velocity of the whole imaging region, in the embodiment of the application, fusion processing is performed on the shear wave propagation velocity of each shear wave signal component. The manner of fusion may be implemented as:
determining the reliability corresponding to the propagation speed of the shear wave of each shear wave signal component and the sum of the reliability; and taking the credibility as a weight, carrying out weighted summation on the shear wave propagation speeds of the shear wave signal components, and dividing the weighted summation result by the summation to obtain the shear wave propagation speed of the imaging region.
Summarizing, the shear wave propagation velocity of the whole of the imaging region is determined using the following equation 2:
in the formula (2), M represents a shear wave signal component propagating in several different directions in total, i and j represent two-dimensional spatial positions of the shear wave signal component, shearWaveSpeed (M) represents a shear wave propagation speed of the mth shear wave signal component, coeff represents a reliability corresponding to the shear wave propagation speed of the shear wave signal component, and SWS represents an image constituted by the shear wave speeds of the entire imaging region after the adaptive fusion.
Regarding the reliability of the shear wave propagation velocity, in one embodiment it may be determined based on scan line data that determines the shear wave propagation velocity of the shear wave signal component. Such as:
for each shear wave signal component, acquiring two scanning lines in the shear wave signal component, which are used for determining the propagation speed of the shear wave signal component;
and determining the similarity between the two scanning lines as the credibility of the shear wave propagation speed of the shear wave signal classification.
In another embodiment, instead of performing the fusion in the above manner, a direct linear addition manner may be adopted, that is, the above formula (2) does not use a correlation coefficient, which is also applicable to the embodiment of the present application.
In summary, in the embodiment of the application, during ultrasonic elastography, the imaging depth is not limited, the imaging width is not limited, imaging requirements of various depths and widths can be well adapted, and the whole imaging area can be covered to obtain shear waves and accurately obtain the propagation speed of the shear waves.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (8)
1. A method of determining shear wave propagation velocity, wherein an imaging region comprises a plurality of imaging tiles, the method comprising:
transmitting ultrasonic focusing long pulse excitation to each imaging block in sequence, wherein the transmission time interval of two adjacent ultrasonic focusing long pulse excitation is smaller than a preset value;
transmitting detection pulses to obtain ultrasonic echo signals of the imaging region;
determining a shear wave signal by adopting a motion detection method for the ultrasonic echo signal;
separating shear wave signal components of the shear wave signal in all directions from the shear wave signal based on a direction filtering method;
determining the shear wave propagation velocity of the shear wave signal components in each direction;
for each shear wave signal component, acquiring two scanning lines in the shear wave signal component, which are used for determining the propagation speed of the shear wave signal component;
determining the similarity between the two scan lines as the confidence level of the shear wave propagation velocity of the shear wave signal classification, and determining the sum of the respective confidence levels;
and taking the credibility as a weight, carrying out weighted summation on the shear wave propagation speeds of the shear wave signal components, and dividing the weighted summation result by the summation to obtain the shear wave propagation speed of the imaging region.
2. The method of claim 1, wherein the first excitation pattern comprises a plurality of emission angles, each emission angle corresponding to an imaging zone, and wherein said sequentially emitting ultrasound focused long pulse excitation to each of said imaging zones comprises:
an ultrasonic focal length pulse excitation is sequentially transmitted to the imaging region at each of the transmit angles, wherein the depth of focus of each transmit angle is the same or different.
3. The method of claim 2, wherein the ultrasound focused long pulse excitation is emitted multiple times within each imaging zone in the second excitation pattern, and at least one depth of focus is employed within the same imaging zone; the sequentially transmitting ultrasonic focus long pulse excitation to each imaging zone comprises:
and transmitting ultrasonic focusing long pulse excitation in each imaging block in sequence in the second excitation mode.
4. A method according to any one of claims 1-3, wherein the direction-based filtering method separates shear wave signal components of the shear wave signal in each direction from the shear wave signal, comprising:
aiming at ultrasonic focusing long pulse excitation transmitted each time, acquiring a first direction filter corresponding to the transmission angle of the ultrasonic focusing long pulse excitation, and performing up-down overturning treatment on the filter to obtain a second direction filter;
multiplying the two-dimensional data of each focusing depth in the shear wave signal by the first direction filter to obtain a first shear wave signal component corresponding to the ultrasonic focusing long pulse excitation; and multiplying the two-dimensional data of each focusing depth in the shear wave signal by the second direction filter to obtain a second shear wave signal component corresponding to the ultrasonic focusing long pulse excitation.
5. The method of claim 4, wherein obtaining a direction filter corresponding to an emission angle of the ultrasonic focused long pulse excitation comprises:
if the emission angle is a specified deflection angle, a first direction filter of the specified deflection angle is obtained and used as a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation;
if the emission angle deflects relative to the designated deflection angle, a first direction filter of the designated deflection angle is used as a reference filter; and rotating the reference filter from the appointed deflection angle to the emission angle of the ultrasonic focusing long pulse excitation to obtain a first direction filter corresponding to the emission angle of the ultrasonic focusing long pulse excitation.
6. The method of claim 1, wherein said determining a shear wave signal using an autocorrelation method on said ultrasound echo signal comprises:
and carrying out autocorrelation analysis on the ultrasonic echo signal data with any continuous appointed frame number in the ultrasonic echo signal, and obtaining shear wave signal data corresponding to the ultrasonic echo data with the continuous appointed frame number.
7. The method of claim 1, wherein determining the shear wave propagation velocity of the shear wave signal component in each direction comprises:
acquiring signals of two scanning lines corresponding to the same point of the shear wave signal component;
analyzing the time delay between the signals of the two scanning lines by adopting a cross-correlation method;
and dividing the distance between the two scanning lines by the time delay to obtain the shear wave propagation speed of the shear wave signal component.
8. An ultrasound device, comprising: the device comprises a processor, a memory, a display unit and a probe;
a probe for transmitting an ultrasonic signal;
a display unit for displaying the ultrasound image;
a processor, connected to the probe and the display unit, respectively, configured to perform the method of any of claims 1-7.
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