CN109199448B - Pulse wave Doppler imaging method and device based on HPRF - Google Patents
Pulse wave Doppler imaging method and device based on HPRF Download PDFInfo
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- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/06—Measuring blood flow
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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
- A61B8/488—Diagnostic techniques involving Doppler signals
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/58—Testing, adjusting or calibrating the diagnostic device
Abstract
The invention relates to a pulse wave Doppler imaging method and a device based on HPRF, wherein the pulse wave Doppler imaging method based on HPRF comprises the following steps: calculating a plurality of emission parameters according to the position of the target sampling frame, wherein each emission parameter comprises different emission time and emission frequency; traversing a plurality of the transmitting parameters, transmitting ultrasonic waves to a target sampling frame and at least one virtual sampling frame according to the transmitting time and the transmitting frequency traversed to the transmitting parameters, and acquiring echo signals; processing the acquired echo signals to obtain signals to be imaged; and after the plurality of transmitting parameters are traversed, carrying out spectrum processing imaging on a plurality of paths of signals to be imaged, wherein each path of signal to be imaged corresponds to one transmitting parameter. The pulse wave Doppler imaging method and device based on the HPRF solve the problem that Doppler frequency shift information measured by the pulse wave Doppler imaging method based on the HPRF in the prior art is not accurate enough.
Description
Technical Field
The invention relates to the technical field of Doppler imaging, in particular to a pulse wave Doppler imaging method and device based on HPRF.
Background
In an ultrasonic diagnostic system, a doppler imaging technique is widely used for measuring blood flow of a human body. Specifically, the pulse Wave Doppler Imaging (Pulsed Wave Spectral Doppler Imaging) method repeatedly transmits ultrasonic waves to a target tissue of a human body at fixed time intervals, collects an echo signal reflected by the target tissue of the human body, and measures Doppler shift information of the target tissue of the human body due to blood flow according to the echo signal to reflect blood flow changes of the target tissue of the human body. Here, the fixed time Interval at which the ultrasonic waves are repeatedly transmitted is defined as a Pulse Repetition Interval (PRI), which determines a maximum blood flow velocity range that can be recognized by the doppler shift information.
It will be appreciated that in some cases, for example, where the target tissue of the human body is some large arterial blood vessels, where the blood flow velocity is high, a higher Pulse Repetition Frequency (PRF), i.e. the inverse of the Pulse repetition time interval, is required, but due to the deeper location of such arterial blood vessels within the human body, the round trip time of the ultrasound waves is longer, resulting in a larger Pulse repetition time interval, and a higher Pulse repetition Frequency cannot be achieved.
For this reason, a pulse wave doppler imaging method based on hprf (high prf) is proposed, which can reflect the change of blood flow in the human body when the target tissue of the human body is deep. Specifically, a plurality of echo signals can be simultaneously acquired by transmitting ultrasonic waves at a higher pulse repetition frequency, which is equivalent to reflection from different depth positions in a human body, wherein the different depth positions comprise positions of human target tissues in the human body, and accordingly, Doppler imaging can be completed aiming at the echo signals obtained by reflection from the positions.
However, in the process of acquiring the echo signals, the acquired echo signals are substantially the superposition result of the echo signals reflected by a plurality of positions with different depths, because of a higher pulse repetition frequency, the center frequencies of the echo signals reflected by the positions with different depths are very close, the echo signals reflected by the position (the position of the target sampling frame) of the human target tissue in the human body will be interfered by the echo signals reflected by the other positions (the positions of the virtual sampling frames), so that the measured doppler shift information is not accurate enough, and further the HPRF imaging performance is affected.
Disclosure of Invention
In order to solve the above technical problems, an object of the present invention is to provide a method and an apparatus for HPRF-based pulsed wave doppler imaging.
The technical scheme adopted by the invention is as follows:
in a first aspect, a method of HPRF-based pulsed wave doppler imaging, comprises: calculating a plurality of emission parameters according to the position of the target sampling frame, wherein each emission parameter comprises different emission time and emission frequency; traversing a plurality of the transmitting parameters, transmitting ultrasonic waves to a target sampling frame and at least one virtual sampling frame according to the transmitting time and the transmitting frequency traversed to the transmitting parameters, and acquiring echo signals; processing the acquired echo signals to obtain signals to be imaged; and after the plurality of transmitting parameters are traversed, carrying out spectrum processing imaging on a plurality of paths of signals to be imaged, wherein each path of signal to be imaged corresponds to one transmitting parameter.
In a second aspect, an HPRF-based pulsed wave doppler imaging apparatus includes: the parameter calculation module is used for calculating a plurality of emission parameters according to the position of the target sampling frame, and each emission parameter comprises different emission time and emission frequency; the ultrasonic wave transmitting module is used for traversing the plurality of transmitting parameters, transmitting ultrasonic waves to the target sampling frame and the at least one virtual sampling frame according to the transmitting time and the transmitting frequency which are traversed to the transmitting parameters, and acquiring echo signals; the signal processing module is used for carrying out signal processing on the acquired echo signals to obtain signals to be imaged; and the frequency spectrum imaging module is used for performing frequency spectrum processing imaging on a plurality of paths of signals to be imaged after the plurality of transmitting parameters are traversed, wherein each path of signal to be imaged corresponds to one transmitting parameter.
In an exemplary embodiment, the apparatus further comprises: the parameter adjusting module is used for adjusting the transmitting frequency in the plurality of transmitting parameters if the frequency spectrum corresponding to the first demodulation signal and the frequency spectrum corresponding to the at least one second demodulation signal are aliased on the frequency domain; wherein the first demodulation signal is generated by demodulating an echo signal reflected by the target sampling frame, and at least one second demodulation signal is generated by demodulating an echo signal reflected by at least one virtual sampling frame.
In an exemplary embodiment, the parameter calculation module includes: the first time calculation unit is used for calculating the pulse repetition time interval corresponding to the target sampling frame according to the position of the target sampling frame; the second time calculation unit is used for acquiring a set pulse time interval and calculating to obtain the pulse repetition time interval and the number corresponding to the virtual sampling frame according to the set pulse time interval and the pulse repetition time interval corresponding to the target sampling frame; the position calculation unit is used for calculating the position of the virtual sampling frame according to the pulse repetition time interval corresponding to the virtual sampling frame; and the parameter calculation unit is used for calculating and obtaining a plurality of emission parameters according to the number and the positions of the virtual sampling frames.
In an exemplary embodiment, the signal processing module includes: the demodulation unit is used for demodulating the acquired echo signals to generate demodulation signals; and the frequency offset calibration unit is used for carrying out frequency offset calibration on the demodulation signal according to the estimated blood flow velocity of the human target tissue to obtain the signal to be imaged.
In an exemplary embodiment, the demodulation unit includes: the demodulation subunit is used for demodulating the acquired echo signals according to the effective demodulation frequency and calling a low-pass filter to filter the echo signals so as to generate demodulation signals; wherein the effective demodulation frequency is related to a transmit frequency traversed into transmit parameters.
In an exemplary embodiment, the frequency offset calibration unit includes: the Fourier transform subunit is used for carrying out Fourier transform processing on the demodulation signal if the estimated blood flow velocity of the human target tissue is in a low-speed blood flow range; and the first calibration subunit is used for calibrating the demodulated signal subjected to the Fourier transform processing according to the calibration factor to obtain the signal to be imaged.
In an exemplary embodiment, the frequency offset calibration unit includes: the frequency setting subunit is configured to set a reference frequency for the frequency offset calibration according to the transmission frequency in the plurality of transmission parameters if the estimated blood flow velocity of the human target tissue is within a high-speed blood flow range; a Coordinate Rotation calculating subunit, configured to calculate an amplitude and a phase angle of the demodulated signal by using a CORDIC (Coordinate Rotation Digital Computer) algorithm, and convert the phase angle according to the reference frequency; and the third calibration subunit is used for calibrating the converted phase angle according to the calibration factor, and taking the amplitude and the calibrated phase angle as the signal to be imaged.
In a third aspect, an HPRF-based pulsed wave doppler imaging apparatus includes a processor and a memory, the memory having stored thereon computer readable instructions, which when executed by the processor, implement the HPRF-based pulsed wave doppler imaging method as described above.
In a fourth aspect, a computer-readable storage medium has stored thereon a computer program which, when executed by a processor, implements the HPRF-based pulsed wave doppler imaging method as described above.
In the technical scheme, the ultrasonic waves are transmitted by adopting different transmitting time and transmitting frequency, so that the mutual influence among multiple transmissions is reduced, the interference of the echo signals reflected by the virtual sampling frame on the echo signals reflected by the target sampling frame is effectively eliminated, and the problem that the HPRF imaging performance is influenced due to the fact that the Doppler frequency shift information is not accurately measured in the prior art is solved.
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 invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic illustration of an implementation environment in accordance with the present invention.
Fig. 2 is a block diagram illustrating a hardware configuration of a medical ultrasound imaging apparatus according to an exemplary embodiment.
Fig. 3 is a flow chart illustrating a method of HPRF-based pulsed wave doppler imaging according to an exemplary embodiment.
FIG. 4 is a flow chart of one embodiment of step 310 in the corresponding embodiment of FIG. 3.
Fig. 5 is a schematic diagram of a target sample box and a virtual sample box according to the corresponding embodiment in fig. 4.
FIG. 6 is a flow chart of one embodiment of step 350 of the corresponding embodiment of FIG. 4.
FIG. 7 is a flowchart of one embodiment of step 353 of the corresponding embodiment of FIG. 6.
FIG. 8 is a flow chart of step 353 in the corresponding embodiment of FIG. 6 in another embodiment.
Figure 9 is a flow chart illustrating another HPRF-based pulsed wave doppler imaging method in accordance with an exemplary embodiment.
Fig. 10 is a schematic diagram of sample box locations according to a corresponding embodiment of fig. 9.
Fig. 11 is a schematic diagram of ultrasound transmission timing according to the corresponding embodiment of fig. 9.
Fig. 12 is a schematic diagram of the first and second demodulated signals according to the corresponding embodiment of fig. 9 without aliasing in the frequency domain.
Fig. 13 is a block diagram illustrating an HPRF-based pulsed wave doppler imaging apparatus according to an exemplary embodiment.
Fig. 14 is a block diagram illustrating a hardware configuration of an HPRF-based pulse wave doppler imaging apparatus according to an exemplary embodiment.
While specific embodiments of the invention have been shown by way of example in the drawings and will be described in detail hereinafter, such drawings and description are not intended to limit the scope of the inventive concepts in any way, but rather to explain the inventive concepts to those skilled in the art by reference to the particular embodiments.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
Fig. 1 is a schematic diagram of an implementation environment involved in a HPRF-based pulsed wave doppler imaging method. The implementation environment includes a user 110, a medical ultrasound imaging device 130 and a doppler ultrasound probe 150 carried thereby.
The medical ultrasonic imaging apparatus 130 is an electronic apparatus that performs pulse wave doppler imaging by emitting ultrasonic waves, and is not limited herein, and examples thereof include a B-ultrasonic machine, a fetal monitor, and a doppler ultrasonic apparatus.
The medical ultrasonic imaging device 130 and the doppler probe 150 carried by the medical ultrasonic imaging device are connected in advance through wireless or wired communication, so that signal transmission is realized based on the communication connection. For example, the transmitted signal may be an ultrasonic wave, an echo signal, or the like.
With the interaction between the medical ultrasonic imaging apparatus 130 and the doppler ultrasonic probe 130, when the doppler probe 130 transmits ultrasonic waves to the user 110 to measure the blood flow change of the human target tissue of the user 110, for the medical ultrasonic imaging apparatus 130, the echo signal reflected by the human target tissue of the user 110 can be received, and then the doppler shift information is measured according to the echo signal, thereby completing the pulse wave doppler imaging process.
Fig. 2 is a block diagram illustrating a hardware configuration of a medical ultrasound imaging apparatus according to an exemplary embodiment. The medical ultrasonic imaging device is suitable for the implementation environment shown in fig. 1 and is used for realizing the pulse wave Doppler imaging method based on HPRF.
It should be noted that the medical ultrasonic imaging apparatus is only an example adapted to the present invention, and should not be construed as providing any limitation to the scope of the present invention. This medical ultrasound imaging device is also not to be construed as requiring reliance on, or necessity of, one or more components of the exemplary medical ultrasound imaging device 200 shown in fig. 2.
The hardware structure of the medical ultrasonic imaging apparatus 200 may have a large difference due to the difference of configuration or performance, as shown in fig. 2, the medical ultrasonic imaging apparatus 200 includes: a power supply 210, an interface 230, at least one memory 250, and at least one Central Processing Unit (CPU) 270.
The power supply 210 is used to provide operating voltage for each hardware device on the medical ultrasonic imaging apparatus 200.
The interface 230 includes at least one wired or wireless network interface 231, at least one serial-to-parallel conversion interface 233, at least one input/output interface 235, and at least one USB interface 237, etc. for communicating with external devices.
The memory 250 is used as a carrier of resource storage, and can be understood as a computer-readable storage medium, including but not limited to read-only memory, random access memory, magnetic or optical disk, etc., on which the stored resources include an operating system 251, computer programs 253, data 255, etc., and the storage manner may be transient storage or permanent storage. The operating system 251 is used to manage and control various hardware devices and computer programs 253 on the medical ultrasound imaging apparatus 200, so as to implement the computation and processing of the mass data 255 by the central processing unit 270, which may be Windows server, Mac OS XTM, unix, linux, FreeBSDTM, or the like. The computer program 253 is a computer program for performing at least one specific task on the operating system 251, and may include at least one instruction module (not shown in fig. 2), each of which may respectively include a series of computer readable instructions for the medical ultrasound imaging apparatus 200. The data 255 may be photographs, pictures, etc. stored in a disk.
The central processor 270 may include one or more processors and is arranged to communicate with the memory 250 via a bus for computing and processing the mass data 255 in the memory 250.
As described in detail above, the medical ultrasound imaging apparatus 200 to which the present invention is applied will complete the HPRF-based pulsed wave doppler imaging method by the central processor 270 reading a series of computer readable instructions in a computer program 253 stored in a computer readable storage medium (i.e., the memory 250).
Furthermore, the present invention can be implemented by hardware circuits or by a combination of hardware circuits and software, and thus, the implementation of the present invention is not limited to any specific hardware circuits, software, or a combination of both.
Referring to fig. 3, in an exemplary embodiment, a HPRF-based pulse wave doppler imaging method is applied to the medical ultrasound imaging apparatus in the implementation environment shown in fig. 1, and the structure of the medical ultrasound imaging apparatus may be as shown in fig. 2.
The HPRF-based pulse wave Doppler imaging method can be executed by a medical ultrasonic imaging device and comprises the following steps:
in step 310, a plurality of emission parameters are calculated according to the position of the target sampling frame.
First, the target sampling frame refers to the position of the target tissue of the human body in the human body. Correspondingly, the virtual sampling frame refers to other depth positions in the human body, and is not the position of the human target tissue in the human body.
Second, each transmit parameter contains a different transmit time and transmit frequency.
In a specific implementation of an embodiment, as shown in fig. 4, step 310 may include the following steps:
and 311, calculating the pulse repetition time interval corresponding to the target sampling frame according to the position of the target sampling frame.
And 313, acquiring a set pulse time interval, and calculating to obtain the pulse repetition time interval and the number corresponding to the virtual sampling frame according to the set pulse time interval and the pulse repetition time interval corresponding to the target sampling frame.
It is understood that the pulse repetition time interval, corresponding to a target sample frame or a virtual sample frame, refers to a fixed time interval of repeatedly transmitting ultrasound waves for the same sample frame location.
The Pulse repetition Time interval (PRT) is a Time interval in which the ultrasonic wave makes one round trip between the positions of two adjacent sampling frames, which is different from the Pulse repetition Time interval.
In this embodiment, the pulse time interval is preset, that is, the pulse time interval is set.
In order to set the acquisition of the pulse time interval, the medical ultrasonic imaging device provides a setting entrance for a user, if the user desires to preset the pulse time interval, the setting entrance triggers related operation, and the medical ultrasonic imaging device is made to know the pulse time interval preset by the user through the related operation.
And step 315, calculating the position of the virtual sampling frame according to the pulse repetition time interval corresponding to the virtual sampling frame.
And 317, calculating according to the number and the positions of the virtual sampling frames to obtain a plurality of transmitting parameters.
Specifically, the calculation process of the transmission parameters is as follows:
BPRT＝2*Depth/C (1)。
wherein Depth represents the Depth of the human target tissue in the human body, namely the position of the target sampling frame, C represents the propagation speed of the ultrasonic wave in the human target tissue, and BPRT represents the pulse repetition time interval corresponding to the target sampling frame.
Where DPRT denotes a set pulse interval, and Nv denotes the number of virtual sample frames.
VPRT＝(Nv-1)*DPRT+BPRT-Nv*DPRT (3.1)，
As shown in fig. 5, VPRT represents the pulse repetition time interval corresponding to the virtual sampling frame V0, and DPRT represents the set pulse time interval, then VPRTNv-n+1Then the virtual sample boxes V1, V2, V3, … …, V are representedNCorresponding pulse repetition time interval.
Further, after the pulse repetition time interval corresponding to the virtual sampling frame is obtained, the position of the virtual sampling frame can be reversely deduced according to the calculation formula (4):
VPRTn＝2*Depthn/C (4)。
wherein VPRTnIndicating the pulse repetition time interval, Depth, corresponding to the nth virtual sample framenRepresenting other depth positions in the human body, namely the position of the virtual sampling frame, and C representing the propagation speed of the ultrasonic wave in the target tissue of the human body.
After the number and the positions of the virtual sampling frames are obtained, the emission time sequence of the ultrasonic waves can be set according to the number and the positions of the virtual sampling frames.
Specifically, the number N of different transmission frequencies is setf＞＝Nv+1. For simple calculation, in this embodiment, the number of different transmission frequencies is set to be Nf＝Nv+1, where Nv denotes the number of virtual sample boxes.
The setting of different transmission frequencies is premised on reducing the mutual influence between the multiple transmissions as much as possible.
For example, the center frequency of the transmitted ultrasonic wave is set to fiThen f needs to be satisfiedi-fi-1>2PRF, where PRF denotes the i-1 th pulse repetition frequency, in relation to the position of the virtual sampling frame.
Furthermore, along with the measurement of Doppler frequency shift information, the center frequency of ultrasonic waves transmitted each time can be correspondingly adjusted, so that the Doppler imaging cannot generate spectrum aliasing in a frequency domain, the accuracy of Doppler frequency shift information measurement is ensured, and the HPRF imaging performance is further improved.
And step 330, traversing a plurality of transmitting parameters, transmitting ultrasonic waves to the target sampling frame and the at least one virtual sampling frame according to the transmitting time and the transmitting frequency traversed to the transmitting parameters, and acquiring echo signals.
That is, for the traversed transmission parameters, assuming that n-1 virtual sample frames exist, each acquired echo signal substantially includes the superposition result of n reflected echo signals, i.e., the echo signal reflected by 1 target sample frame and the echo signal reflected by n-1 virtual sample frames.
It can also be understood that each acquired echo signal is substantially a superposition of echo signals reflected by the respective sampling frames by the ultrasonic waves transmitted at the n different transmission frequencies.
And 350, processing the acquired echo signals to obtain signals to be imaged.
Signal processing includes, but is not limited to: demodulation, filtering, frequency offset calibration and the like.
In a specific implementation of an embodiment, as shown in fig. 6, step 350 may include the following steps:
Specifically, the acquired echo signal is demodulated according to the effective demodulation frequency, and a low-pass filter is called for filtering to generate a demodulation signal.
Wherein the effective demodulation frequency is related to the transmit frequency traversed into the transmit parameters.
It can be understood that, due to the different positions of the sampling frames, the echo signals reflected by the sampling frames reach the medical ultrasonic imaging device at different times for the ultrasonic waves transmitted at the same transmission frequency.
For example, as shown in fig. 5, for an ultrasound wave transmitted at a current transmission frequency, the medical ultrasound imaging apparatus first acquires an echo signal reflected by the virtual sampling frame V3, then acquires an echo signal reflected by the virtual sampling frame V2, and so on, and finally acquires an echo signal reflected by the target sampling frame.
And traversing the transmission parameters to circularly transmit the ultrasonic waves, and aiming at the ultrasonic waves transmitted at the latter transmission frequency, the medical ultrasonic imaging equipment firstly acquires echo signals reflected by the virtual sampling frame V3, … … and finally acquires echo signals reflected by the target sampling frame.
In other words, the acquired echo signals are for different transmit frequencies for the same acquisition time. Therefore, each time the signal is effectively acquired, the echo signal reflected by the target sampling frame is acquired as a measure.
Accordingly, in the signal demodulation, the central frequency of the echo signal reflected by the target sampling frame is used as the effective demodulation frequency, and it can also be understood that when the ultrasonic wave is transmitted through the transmission frequency in the transmission parameter, and the ultrasonic wave is collected through the echo signal reflected by the target sampling frame, the transmission frequency traversed in the transmission parameter is the effective demodulation frequency.
In other words, the demodulation process essentially also experiences the traversal of the transmission parameters, i.e. the effective demodulation frequency is set according to the transmission frequency traversed into the transmission parameters.
It should be understood that the measurement of blood flow velocity by using ultrasonic waves is essentially to measure the doppler shift information of the target tissue of the human body due to blood flow, and then to estimate the blood flow velocity.
Specifically, after the ultrasonic wave is reflected by the target tissue of the human body, a Doppler frequency shift phenomenon, frequency offset f, occursdThe calculation formula (5) is as follows:
fd＝2v/C*f0*cos a (5)。
wherein f is0Which represents the center frequency of the transmitted ultrasonic wave, i.e., the transmission frequency, a represents the angle between the propagation direction of the ultrasonic wave in the human target tissue and the blood flow direction in the human target tissue, v represents the blood flow velocity, and C represents the propagation velocity of the ultrasonic wave in the human target tissue.
From the calculation formula (5), if the transmission frequency f0Differently, even if the direction and speed of blood flow in the target tissue of the human body are the same, different frequency deviations f will be generatedd。
Therefore, it is necessary to eliminate the influence of different frequency offsets caused by different transmission frequencies, that is, to perform frequency offset calibration on the demodulated signal.
Further, as mentioned above, when the blood flow velocity in the target tissue of the human body is high, a higher pulse repetition frequency is often required, so that the requirements of different blood flow velocities on the pulse repetition frequency are different on the premise of satisfying the nyquist sampling law, and the frequency offset calibration methods for different pulse repetition frequencies are different.
Based on this, before performing frequency offset calibration on the demodulated signal, the blood flow velocity in the human target tissue needs to be estimated, so as to select a corresponding frequency offset calibration mode.
In one embodiment, the blood flow velocity estimation may be performed based on human target tissue set by a user. For example, when the target tissue of the human body is the heart aorta, the blood flow velocity is estimated to be 18-22cm/s, when the target tissue of the human body is the vena cava, the blood flow velocity is estimated to be 7-8cm/s, and when the target tissue of the human body is the capillary, the blood flow velocity is estimated to be 0.3-0.7 mm/s. In another embodiment, the blood flow velocity estimate may also be estimated from the Doppler shift profile of the echo signals.
And step 370, after the plurality of emission parameters are traversed, performing spectrum processing imaging on the plurality of paths of signals to be imaged.
Wherein, each path of signal to be imaged corresponds to one emission parameter.
The spectral processing imaging is to measure the doppler shift information of the human target tissue generated by the blood flow according to the doppler shift distribution of the echo signal, and then to display the corresponding pulse wave spectrum in the medical ultrasonic imaging device, so as to reflect the blood flow change in the human target tissue.
Through the process, the influence of the blood flow distribution at the position of the virtual sampling frame on the blood flow distribution at the position of the target sampling frame is effectively filtered, so that the HPRF imaging performance is improved.
Referring to FIG. 7, in an exemplary embodiment, step 353 may include the following steps:
Specifically, if the estimated blood flow velocity of the human target tissue is within the low-velocity blood flow range, i.e., the blood flow velocity in the human target tissue is considered to be low, accordingly, the pulse repetition frequency may be slightly low. The low-speed blood flow range can be flexibly adjusted according to the actual requirements of the application scene, and is not limited herein.
In order to satisfy the Nyquist sampling law, the pulse repetition frequency is at least 2fd. Wherein f isdRepresenting a frequency offset.
Thus, the sampling frequency of the echo signal is regarded as the pulse repetition frequency, and for a relatively low-speed blood flow, when the pulse repetition frequency is N of the Nyquist sampling ratefWhen the power is doubled or more, the power is passed through NfThe cyclic traversal of each transmission parameter can obtain NfAnd (3) demodulating the signals by paths, independently finishing Fourier transform processing aiming at each path of demodulated signal, and multiplying the signals by a calibration factor to obtain the signals to be imaged.
Wherein the calibration factor is f0/fi_demo，fi_demoThe effective demodulation frequency in the i _ demo +1 th demodulation signal processing is shown, and f0 is the effective demodulation frequency in the 1 st demodulation signal processing.
Referring to fig. 8, in another exemplary embodiment, step 353 may include the steps of:
Specifically, if the estimated blood flow velocity of the human target tissue is within the high-speed blood flow range, it is considered that the blood flow velocity in the human target tissue is high, and accordingly, the pulse repetition frequency is high. The high-speed blood flow range can be flexibly adjusted according to the actual requirements of the application scene, and is not limited herein.
In order to satisfy the Nyquist sampling law, the pulse repetition frequency is at least 2fd. Wherein f isdRepresenting frequency offset。
Thus, the sampling frequency of the echo signal is regarded as the pulse repetition frequency, and the pulse repetition frequency does not satisfy N, which is the Nyquist sampling rate, for a high-speed blood flowfTimes and more.
For this reason, in the present embodiment, the demodulation signals at different effective demodulation frequencies are calibrated to a single effective demodulation frequency, that is, an effective demodulation frequency is selected from a plurality of effective demodulation frequencies as the reference frequency.
Since the effective demodulation frequency is substantially the transmission frequency in the transmission parameters, the reference frequency is the transmission frequency in a certain transmission parameter.
For the periodic cyclic transmission of ultrasonic waves at different transmission frequencies, the center frequency of the ultrasonic waves transmitted for the first time in the first period, i.e. the first transmission frequency f0The reference frequency will be described as an example.
Assuming that the demodulated signal includes IQ two paths, the demodulated signal is as shown in calculation formulas (6.1) and (6.2).
Coordinate rotation is carried out on the demodulation signal by using a CORDIC algorithm, and the corresponding amplitude value E (t) and phase angle of the demodulation signal are obtained through calculation
According to the calculated phase angle E (t) and the calibration factor
Multiplying to obtain the calibrated phase angle 2 pi fd00t, and then according to the amplitude E (t) and the phase angle 2 pi fd after calibration00t is obtained to convert to the reference frequency f0Signal to be imaged:
and
through the process, different frequency offset calibration modes corresponding to different blood flow speeds are realized, the accuracy of frequency offset calibration is effectively improved on the premise of meeting the Nyquist sampling law, the accuracy of Doppler frequency shift information is improved, and the imaging performance of the HPRF is fully ensured.
Referring to fig. 9, in another exemplary embodiment, an HPRF-based pulse wave doppler imaging method may be performed by a medical ultrasound imaging apparatus, which performs steps 610 to 650 to implement the HPRF-based pulse wave doppler imaging method.
For simplicity, in this embodiment, the number of the target sample box and the number of the virtual sample boxes are each 1, and the positions of the sample boxes are shown in fig. 10.
Accordingly, the transmission parameters are 2, which respectively include transmission frequencies f0 and f1, and the transmission timing at which the ultrasonic waves are transmitted according to the above 2 transmission parameters is shown in fig. 11. It is understood that the time interval between two ultrasound transmissions is the PRT (pulse time interval).
Wherein f is1And f0The requirement is satisfied that the two-part signal spectrum is not aliased, as shown in fig. 12.
It should be noted that, since the ultrasonic wave transmitted for the first time reaches the position of the target sampling frame after the second transmission, that is, the echo signal reflected from the target sampling frame starts to be effectively received after the second transmission, the transmission frequency is f1The received echo signal is then at the transmission frequency f0Demodulated as an effective demodulation frequency. For the same reason, the transmission frequency is f0The received echo signal is then at the transmission frequency f1Demodulation is performed as an effective demodulation frequency.
In other words, after the second transmission, the echo signal includes the echo signal reflected from the target sampling frame, so that the first effective reception is started.
Specifically, for the first effective reception, the echo signals are as follows:
x0(t)＝A(t)cos(2π(f0+fd00)t)+B(t)cos(2π(f1+fd11)t) (7)。
wherein A (t) cos (2 π (f)0+fd00) t) represents the echo signal reflected from the target sample box,
B(t)cos(2π(f1+fd11) t) represents the echo signal reflected from the virtual sample box,
For the second effective reception, the echo signals are as follows:
x1(t)＝A(t)cos(2π(f1+fd10)t)+B(t)cos(2π(f0+fd01)t)(8)。
wherein the content of the first and second substances,
representing the frequency deviation resulting from the reflection of the ultrasonic wave at the transmit frequency f1 by the target sample box,
representing the frequency offset resulting from the reflection of the ultrasonic wave at the transmit frequency f0 by the target sample box.
For the first effective reception, using an effective demodulation frequency f0And demodulating to obtain:
after low-pass filter filtering, the IQ two-way of the demodulated signal is represented as follows:
second effective reception with effective demodulation frequency f1And demodulating to obtain:
after low-pass filter filtering, the IQ two-way of the demodulated signal is represented as follows:
since the ultrasonic waves are periodically and cyclically transmitted, in the present embodiment, the effective demodulation frequency used for the first effective reception is used for the subsequent third, fifth, seventh and … … effective receptions; the effective demodulation frequency used for the second effective reception is used for the subsequent fourth, sixth, eighth and … … effective receptions, and the description is not repeated here.
When the two terms on the right side of the equations in the above calculation formulas (9.1), (9.2), (10.1) and (10.2) do not alias in the frequency domain, the interference of the blood flow signal at the virtual sampling frame position on the blood flow signal at the target sampling frame position can be effectively filtered out, as shown in fig. 12.
Otherwise, the transmission frequencies f0 and f1 are adjusted.
Further, if the blood flow is estimated to be relatively low-speed blood flow, FFT may be performed on the demodulated signal formed by each effective reception, and then frequency offset calibration may be performed according to the calibration factor.
If the blood flow is estimated to be higher speed, the demodulation signals under different effective demodulation frequencies need to be calibrated to a single effective demodulation frequency, so as to perform frequency offset calibration according to the calibration factor based on the reference frequency.
Further, the frequency offset calibrated signal to be imaged is subjected to spectrum processing imaging, so that HPRF-based pulse wave Doppler imaging is realized.
In the implementation process of the embodiment, the influence of the blood flow distribution at the position of the virtual sampling frame on the blood flow distribution at the position of the target sampling frame is effectively filtered, so that the HPRF imaging performance is improved.
The following is an embodiment of the apparatus of the present invention, which can be used to perform the HPRF-based pulsed wave doppler imaging method according to the present invention. For details which are not disclosed in the embodiments of the apparatus of the present invention, please refer to the method embodiments of the HPRF-based pulsed wave doppler imaging method according to the present invention.
Referring to fig. 13, in an exemplary embodiment, an HPRF-based pulsed wave doppler imaging device 900 includes, but is not limited to: a parameter calculation module 910, an ultrasound transmission module 930, a signal processing module 950, and a spectral imaging module 970.
The parameter calculating module 910 is configured to calculate a plurality of transmission parameters according to the position of the target sampling frame, where each transmission parameter includes different transmission time and transmission frequency.
The ultrasonic wave transmitting module 930 is configured to traverse the plurality of transmitting parameters, and transmit ultrasonic waves to the target sampling frame and the at least one virtual sampling frame according to the transmitting time and the transmitting frequency traversed to the transmitting parameters, so as to perform echo signal acquisition.
The signal processing module 950 is configured to perform signal processing on the acquired echo signal to obtain a signal to be imaged.
The spectrum imaging module 970 is configured to perform spectrum processing imaging on multiple paths of signals to be imaged after the multiple transmission parameters complete traversal, where each path of signal to be imaged corresponds to one transmission parameter.
It should be noted that, when the HPRF-based pulse wave doppler imaging apparatus provided in the foregoing embodiment performs the HPRF-based pulse wave doppler imaging process, only the division of the above functional blocks is taken as an example, and in practical applications, the functions may be allocated to different functional blocks according to needs, that is, the internal structure of the HPRF-based pulse wave doppler imaging apparatus is divided into different functional blocks to complete all or part of the functions described above.
In addition, the HPRF-based pulse wave doppler imaging apparatus provided in the above embodiments and the embodiments of the HPRF-based pulse wave doppler imaging method belong to the same concept, and specific ways for the respective modules to perform operations have been described in detail in the method embodiments, and are not described herein again.
Referring to fig. 14, in an exemplary embodiment, an HPRF-based pulsed wave doppler imaging device 1000 includes at least one processor 1001, at least one memory 1002, and at least one communication bus 1003.
The at least one memory 1002 stores computer readable instructions, and the at least one processor 1001 reads the computer readable instructions stored in the memory 1002 through the at least one communication bus 1003.
The computer readable instructions, when executed by the processor 1001, implement the HPRF based pulsed wave doppler imaging method in the embodiments described above.
In an exemplary embodiment, a computer readable storage medium 250 has stored thereon a computer program 253, as shown in fig. 2, which when executed by a processor 270, implements the HPRF based pulsed wave doppler imaging method in the above embodiments.
The above-mentioned embodiments are merely preferred examples of the present invention, and are not intended to limit the embodiments of the present invention, and those skilled in the art can easily make various changes and modifications according to the main concept and spirit of the present invention, so that the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. An HPRF-based pulsed wave doppler imaging method, comprising:
calculating a plurality of emission parameters according to the position of the target sampling frame, wherein each emission parameter comprises different emission time and emission frequency;
traversing a plurality of the transmitting parameters, transmitting ultrasonic waves to a target sampling frame and at least one virtual sampling frame according to the transmitting time and the transmitting frequency traversed to the transmitting parameters, and acquiring echo signals;
processing the acquired echo signals to obtain signals to be imaged;
after the plurality of transmitting parameters are traversed, carrying out spectrum processing imaging on a plurality of paths of signals to be imaged, wherein each path of signal to be imaged corresponds to one transmitting parameter;
wherein the calculating a plurality of emission parameters according to the position of the target sampling frame comprises:
calculating a pulse repetition time interval corresponding to the target sampling frame according to the position of the target sampling frame;
acquiring a set pulse time interval, and calculating to obtain the pulse repetition time interval and the number corresponding to the virtual sampling frame according to the set pulse time interval and the pulse repetition time interval corresponding to the target sampling frame;
calculating the position of the virtual sampling frame according to the pulse repetition time interval corresponding to the virtual sampling frame;
and calculating according to the number and the positions of the virtual sampling frames to obtain a plurality of emission parameters.
2. The method of claim 1, wherein the method further comprises:
if the frequency spectrum corresponding to the first demodulation signal and the frequency spectrum corresponding to the at least one second demodulation signal are aliased on the frequency domain, adjusting the transmission frequency in the plurality of transmission parameters; wherein the first demodulation signal is generated by demodulating an echo signal reflected by the target sampling frame, and at least one second demodulation signal is generated by demodulating an echo signal reflected by at least one virtual sampling frame.
3. The method according to claim 1 or 2, wherein the signal processing of the acquired echo signals to obtain the signals to be imaged comprises:
demodulating the collected echo signals to generate demodulated signals;
and carrying out frequency offset calibration on the demodulation signal according to the estimated blood flow velocity of the human target tissue to obtain the signal to be imaged.
4. The method of claim 3, wherein demodulating the acquired echo signals to generate demodulated signals comprises:
demodulating the collected echo signals according to the effective demodulation frequency, and calling a low-pass filter to generate demodulation signals;
wherein the effective demodulation frequency is related to a transmit frequency traversed into transmit parameters.
5. The method of claim 3, wherein the frequency offset calibration of the demodulated signal according to the estimated blood flow velocity of the target tissue of the human body to obtain the signal to be imaged comprises:
if the estimated blood flow velocity of the human target tissue is in a low-speed blood flow range, performing Fourier transform processing on the demodulation signal;
and calibrating the demodulated signal subjected to the Fourier transform processing according to the calibration factor to obtain the signal to be imaged.
6. The method of claim 3, wherein the frequency offset calibration of the demodulated signal according to the estimated blood flow velocity of the target tissue of the human body to obtain the signal to be imaged comprises:
if the estimated blood flow velocity of the human target tissue is within a high-speed blood flow range, setting a reference frequency for the frequency offset calibration according to the emission frequency in the plurality of emission parameters;
calculating the amplitude and the phase angle of the demodulation signal by using a CORDIC algorithm, and converting the phase angle according to the reference frequency;
and calibrating the converted phase angle according to the calibration factor, and taking the amplitude and the calibrated phase angle as the signal to be imaged.
7. An HPRF-based pulsed wave doppler imaging apparatus, comprising:
a parameter calculating module, configured to calculate a plurality of transmission parameters according to the position of the target sampling frame, where each transmission parameter includes different transmission time and transmission frequency, and the calculating the plurality of transmission parameters according to the position of the target sampling frame includes: calculating a pulse repetition time interval corresponding to the target sampling frame according to the position of the target sampling frame; acquiring a set pulse time interval, and calculating to obtain the pulse repetition time interval and the number corresponding to the virtual sampling frame according to the set pulse time interval and the pulse repetition time interval corresponding to the target sampling frame; calculating the position of the virtual sampling frame according to the pulse repetition time interval corresponding to the virtual sampling frame; calculating according to the number and the position of the virtual sampling frames to obtain a plurality of emission parameters;
the ultrasonic wave transmitting module is used for traversing the plurality of transmitting parameters, transmitting ultrasonic waves to the target sampling frame and the at least one virtual sampling frame according to the transmitting time and the transmitting frequency which are traversed to the transmitting parameters, and acquiring echo signals;
the signal processing module is used for carrying out signal processing on the acquired echo signals to obtain signals to be imaged;
and the frequency spectrum imaging module is used for performing frequency spectrum processing imaging on a plurality of paths of signals to be imaged after the plurality of transmitting parameters are traversed, wherein each path of signal to be imaged corresponds to one transmitting parameter.
8. An HPRF-based pulsed wave doppler imaging apparatus, comprising:
a processor; and
a memory having stored thereon computer readable instructions which, when executed by the processor, implement the HPRF based pulsed wave doppler imaging method of any one of claims 1 to 6.
9. A computer readable storage medium having stored thereon a computer program, which when executed by a processor implements the HPRF based pulsed wave doppler imaging method of any one of claims 1 to 6.
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