KR101221309B1 - Ultrasound system and method for providing doppler mode image based on extrapolation - Google Patents

Abstract

An ultrasound system and method for providing Doppler mode images based on extrapolation is disclosed. An ultrasound system according to the present invention is operable to transmit ultrasound signals to an object including a flowing object of interest, and to receive ultrasound echo signals reflected from the object to obtain ultrasound data corresponding to an ensemble number. An ultrasonic data acquisition unit; And convert the ultrasound data into ultrasound data in a frequency domain, perform extrapolation on the converted ultrasound data, and increase the number of converted ultrasound data. And a processor configured to perform filtering on the ultrasound data and to form a Doppler mode image using the filtered ultrasound data.

Description

ULTRASOUND SYSTEM AND METHOD FOR PROVIDING DOPPLER MODE IMAGE BASED ON EXTRAPOLATION}

TECHNICAL FIELD The present invention relates to an ultrasound system, and more particularly, to an ultrasound system and method for providing a Doppler mode image based on extrapolation.

Ultrasound systems have non-invasive and non-destructive properties and are widely used in the medical field for obtaining information inside an object. Ultrasound systems are very important in the medical field because they can provide a doctor with a high-resolution image of the inside of a subject in real time, without the need for a surgical operation to directly incise and observe the subject.

The ultrasound system uses the B mode (Doppler effect), the B mode (Doppler effect), which shows a reflection coefficient of an ultrasound signal (i.e., an ultrasound echo signal) reflected from an object, to a Doppler spectrum. A visible D mode image (i.e., a spectral Doppler image), a color Doppler mode image (i.e., a color Doppler image) that displays the speed of a moving object in color using the Doppler effect, The present invention provides an elastic mode image that shows a difference in response before and after compression. In particular, the ultrasound system transmits an ultrasound signal to an object including the object of interest flowing through blood, receives an ultrasound echo signal reflected from the object, forms a Doppler signal, and based on the formed Doppler signal, a Doppler mode image, that is, a D mode image. And form a C mode image.

On the other hand, the Doppler signal includes not only the blood flow signal caused by the blood flow, but also the low frequency Doppler signal caused by the movement of the blood vessel wall, the heart wall, and the heart plate. The low frequency Doppler signal, also called the clutter signal, has an amplitude approximately 100 times greater than the blood flow signal due to the blood flow. Since the clutter signal interferes with the accurate detection of blood flow information, it is essential to remove the clutter signal from the Doppler signal in order to detect the accurate blood flow rate. Ultrasonic systems use a clutter filter, which is a type of high pass filter to remove clutter signals.

Since the clutter signal is mainly distributed in the low frequency band and the Doppler signal is distributed in the high frequency band, a high pass filter must be designed to extract the Doppler signal. However, since the clutter signal has a larger signal size than the Doppler signal, a high pass filter having a fairly good performance is required to extract only the Doppler signal.

The present invention provides an ultrasonic system and method capable of higher-order clutter filtering by performing extrapolation on ensemble data in the frequency domain.

An ultrasound system according to the present invention is configured to transmit an ultrasound signal to an object including an object of interest flowing through blood and to receive an ultrasound echo signal reflected from the object to obtain ultrasound data corresponding to an ensemble number. An ultrasonic data acquisition unit; And converting the ultrasound data into ultrasound data in a frequency domain and performing extrapolation on the converted ultrasound data to increase the number of the converted ultrasound data. And a processor configured to perform filtering on the increased ultrasound data and to form a Doppler mode image using the filtered ultrasound data.

In addition, according to the present invention, a method of providing a Doppler mode image includes: a) transmitting an ultrasound signal to an object including an object of interest flowing through blood, receiving an ultrasound echo signal reflected from the object, and obtaining ultrasound data corresponding to an ensemble number; Making; b) converting the ultrasound data into ultrasound data in a frequency domain; c) performing extrapolation on the converted ultrasound data to increase the number of the converted ultrasound data; d) performing filtering on the increased ultrasound data; And e) forming a Doppler mode image using the filtered ultrasound data.

The present invention can implement a higher-order clutter filter by increasing the number of ensemble data using extrapolation, thereby realizing an ideal clutter filter. Therefore, the present invention can effectively remove the clutter signal from the Doppler signal to detect even the slow blood flow component.

1 is a block diagram showing the configuration of an ultrasonic system according to an embodiment of the present invention.
2 is an exemplary view showing a sample volume set in a B mode (brightness mode) image.
3 is an exemplary view showing a color box set in a B mode image.
Figure 4 is a block diagram showing the configuration of the ultrasonic data acquisition unit according to an embodiment of the present invention.
5 is a flowchart showing a procedure of forming a Doppler mode image based on extrapolation according to an embodiment of the present invention.
6 is an exemplary view showing a procedure for performing extrapolation according to an embodiment of the present invention.
7 is an exemplary view showing a window function according to an embodiment of the present invention.
8A and 8B are exemplary views showing a spectrum of ensemble data according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention. The term "Doppler mode" as used in this embodiment includes color Doppler mode, spectral Doppler mode and the like.

1 is a block diagram showing the configuration of an ultrasound system 100 according to an embodiment of the present invention. Referring to FIG. 1, the ultrasound system 100 may include a user input unit 110, an ultrasound data obtainer 120, a processor 130, a storage 140, and a display 150.

The user input unit 110 receives user input information. In the present embodiment, the input information includes input information for setting a region of interest SV or CB for obtaining a Doppler mode image in the B mode (BI) as shown in FIG. 2 or 3. . The region of interest may be a sample volume (SV) for obtaining a spectral Doppler mode image as shown in FIG. 2 or a color box (CB) for obtaining a color Doppler mode image as shown in FIG. 3. ). However, the region of interest is not necessarily limited thereto. The user input unit 110 may include a control panel, a mouse, a trackball, a keyboard, and the like.

The ultrasound data acquisition unit 120 transmits an ultrasound signal to the object and receives ultrasound signals (that is, ultrasound echo signals) reflected from the object to obtain ultrasound data.

4 is a block diagram showing the configuration of the ultrasonic data acquisition unit 120 according to an embodiment of the present invention. Referring to FIG. 4, the ultrasonic data acquisition unit 120 includes an ultrasonic probe 410, a transmission signal forming unit 420, a beamformer 430, and an ultrasonic data forming unit 440.

The ultrasonic probe 410 includes a plurality of transducer elements (not shown) that operate to mutually convert an electrical signal and an ultrasonic signal. The ultrasound probe 410 transmits an ultrasound signal to the object along each of the plurality of scanlines and receives an ultrasound echo signal reflected from the object to form a received signal. The received signal is an analog signal. The ultrasonic probe 410 includes a convex probe, a linear probe, and the like.

The transmission signal forming unit 420 forms a transmission signal for obtaining an ultrasound image in consideration of the conversion element and the focal point. The ultrasound image includes a B mode image and a Doppler mode image corresponding to the ROI.

In the present embodiment, the transmission signal forming unit 420 forms a first transmission signal for obtaining a B mode image. Therefore, when the first transmission signal is provided from the transmission signal forming unit 420, the ultrasound probe 410 converts the first transmission signal into an ultrasound signal, transmits the ultrasound signal to the object, and receives the ultrasound echo signal reflected from the object. Form a receive signal. In addition, the transmission signal forming unit 420 forms a plurality of second transmission signals for obtaining a Doppler mode image based on a preset ensemble number. The ensemble number represents the number of times an ultrasound signal is transmitted and received to obtain a Doppler signal corresponding to one scan line. Therefore, when the second transmission signal is provided from the transmission signal forming unit 420, the ultrasound probe 410 converts the second transmission signal into an ultrasound signal, transmits the ultrasound signal to the object, and receives the ultrasound echo signal reflected from the object. Form a receive signal.

The beam former 430 converts the received signal provided from the ultrasonic probe 410 into analog and digital to form a digital signal. In addition, the beam former 430 receives and focuses the digital signal in consideration of the conversion element and the focal point to form the reception focus signal.

In the present embodiment, when the first received signal is provided from the ultrasonic probe 410, the beam former 430 converts the first received signal into analog and digital to form a digital signal. The beam former 430 receives and focuses the digital signal in consideration of the conversion element and the focusing point to form a first reception focusing signal. In addition, when the second receive signal is provided from the ultrasonic probe 410, the beam former 430 converts the second received signal into analog and digital to form a digital signal. The beam former 430 receives and focuses a digital signal in consideration of the conversion element and the focal point to form a second reception focused signal.

The ultrasonic data forming unit 440 forms ultrasonic data by using the reception focus signal provided from the beam former 430. In addition, the ultrasound data forming unit 440 may perform various signal processing (for example, gain adjustment, etc.) necessary for forming the ultrasound data on the reception focus signal.

In the present embodiment, when the first reception focusing signal is provided from the beam former 430, the ultrasound data forming unit 440 forms the first ultrasound data by using the first reception focusing signal. The first ultrasound data includes radio frequency (RF) data. However, the first ultrasound data is not necessarily limited thereto. In addition, when the second reception focus signal is provided from the beam former 430, the ultrasound data forming unit 440 forms second ultrasound data corresponding to the ensemble number (ie, ensemble data) by using the second reception focus signal. do. The second ultrasound data includes in-phase / quadrature (IQ) data. However, the second ultrasound data is not necessarily limited thereto.

Referring back to FIG. 1, the processor 130 is connected to the user input unit 110 and the ultrasound data acquisition unit 120. The processor 130 may include a central processor unit (CPU), a graphic processor unit (GPU), a microprocessor, and the like.

5 is a flowchart showing a procedure of forming a Doppler mode image based on extrapolation according to an embodiment of the present invention. 5, when the first ultrasound data is provided from the ultrasound data acquirer 120, the processor 130 performs a scan conversion on the first ultrasound data to form a B mode image (S502). The B mode image is displayed on the display unit 150. Accordingly, the user may set the region of interest SV or CB on the B mode image as illustrated in FIG. 2 or 3 using the user input unit 110.

When the second ultrasound data (ie, ensemble data) is provided from the ultrasound data acquisition unit 120, the processor 130 performs a discrete fourier transform (DFT) on the second ultrasound data to frequency the second ultrasound data in the time domain. The second ultrasound data of the domain is converted (S504).

In one example, the processor 130 converts the second ultrasound data in the time domain into the second ultrasound data in the frequency domain based on a discrete fourier transform (DFT) as shown in Equation 1 below.

In Equation 1, X (k) represents ensemble data in the frequency domain, and x (n) represents ensemble data in the time domain.

The processor 130 performs extrapolation on the second ultrasound data in the frequency domain to increase the number of second ultrasound data (ie, the number of ensemble data) (S506). In the present embodiment, the extrapolation includes minimal weighted norm extrapolation. However, the extrapolation law is not necessarily limited thereto.

이라 하면, 앙상블 데이터(X(n))와 개수가 증가한 앙상블 데이터(

)는 아래의 수학식 2로 표현될 수 있다.A step S506 will be described with reference to the accompanying drawings. Ensemble data (ie, second ultrasound data in the frequency domain) is called X (n), and ensemble data whose number is increased by the extrapolation method

In this case, the ensemble data X (n) and the ensemble data whose number is increased (

) May be expressed by Equation 2 below.

In Equation 2, T is a transformation matrix, and is a zero vector in which each row is "1" at the position of m _i .

= T^-1 X(n))를 구하기 위해서는 변환행렬(T)의 역행렬(T^-1)을 구해야 하며, 역행렬(T^-1)은 아래의 수학식 3과 같이 정의될 수 있다.Increased ensemble data (

= T ^-1 To obtain X (n)), the inverse matrix T ^-1 of the transformation matrix T must be obtained, and the inverse matrix T ^-1 can be defined as Equation 3 below.

In Equation 3, T ^* denotes a conjugate transpose matrix of the matrix T, and Q is defined by a matrix such as Equation 4 below.

)를 출력한다. 프로세서(130)는 개수가 증가한 앙상블 데이터(

)에 윈도우 함수(window function)(p(n))를 곱하여 h₁(n)을 산출한다. 여기서, 윈도우 함수는 도 7에 도시된 바와 같은 가우시안 윈도우(Gaussian window) 함수를 포함한다. 그러나, 윈도우 함수는 반드시 이에 한정되지 않는다. 프로세서(130)는 h₁(n)에 DFT를 수행하여 |H₁(K)|²을 산출하고, 산출된 |H₁(K)|²에 기초하여 T^-1을 산출한다. 프로세서(130)는 산출된 T^-1에 기초하여 주파수 도메인의 앙상블 데이터에 보외법을 수행하여 개수가 증가한 앙상블 데이터(

)를 출력한다. 프로세서(130)는 전술한 바와 같은 절차를 반복적으로 수행하여 |H_λ(K)|²를 갱신한다. In Equation 4, a _h (n) is represented by | H (K) | Represents the inverse DFT coefficient of ² , where | H (K) | ² is a frequency weighted function, which can be obtained by repeatedly performing a procedure as shown in FIG. 6. In other words, the processor 130 may execute the preset | H ₀ (K) | Ensemble data whose number is increased by performing an extrapolation method on the ensemble data X ₀ (n) in the frequency domain based on ² (

) The processor 130 stores the ensemble data having an increased number (

) Is multiplied by the window function p (n) to yield h ₁ (n). Here, the window function includes a Gaussian window function as shown in FIG. 7. However, the window function is not necessarily limited thereto. Processor 130 performs a DFT on h ₁ (n) to execute | H ₁ (K) | ² is calculated and the calculated | H ₁ (K) | Based on ² , T- ¹ is calculated. The processor 130 performs extrapolation on the ensemble data of the frequency domain based on the calculated T ⁻¹ to increase the number of ensemble data (

) The processor 130 repeatedly performs the procedure as described above, so that | H _λ (K) | Update ²

8A and 8B are exemplary views showing spectrums of ensemble data according to an embodiment of the present invention. In Figs. 8A and 8B, portions indicated by dotted lines represent frequency spectra of ensemble data in the frequency domain. In the case of FIG. 8A, | H (K) | ² is in the form of a rectangle, whereas for FIG. 8B, | H (K) | ² is a Gaussian window form similar to the ensemble data of the frequency domain. As shown in Figs. 8A and 8B, | H (K) | It can be seen that ² is a frequency spectrum almost similar to the frequency spectrum of the original ensemble data in the case of Gaussian window form.

Referring back to FIG. 5, the processor 130 performs data processing on the ensemble data (ie, the second ultrasound data) of which the number is increased to include Doppler signals including blood flow information (eg, blood velocity, power, etc.). To form (S508). The Doppler signal includes a blood flow signal due to blood flow, a clutter signal and a noise signal due to movement of the heart wall, the heart plate, and the like.

Since the signal required to form the Doppler mode image is a blood flow signal, the clutter signal and the noise signal should be removed from the Doppler signal. Each signal included in the Doppler signal has a high signal strength in the order of clutter signal> blood flow signal> noise signal. In order to effectively remove the clutter signal, the stop band attenuation and stop bandwidth, which are coefficients of the clutter filter, must be appropriately set. The stop band attenuation and stop bandwidth are determined by the characteristics of the clutter signal. The stop bandwidth is the bandwidth of the clutter signal, and the stop band attenuation is determined by the magnitude of the clutter signal. However, in the design of the clutter filter, the stop band attenuation and the stop bandwidth have a mutually conflicting relationship. That is, increasing the stop band attenuation decreases the stop bandwidth, and decreasing the stop band attenuation increases the stop bandwidth.

The processor 130 filters the Doppler signal to remove the clutter signal and the noise signal from the Doppler signal (S510). The processor 130 includes a high pass filter for separating only the blood flow signal from the Doppler signal. Since the Doppler signal according to the present embodiment is formed based on the ensemble data having an increased ensemble number, that is, an increased number, a high order high pass filter may be used. In addition, since the processor 130 removes the noise signal by setting a preset power threshold, if the noise signal is reduced to the magnitude level of the noise signal without completely removing the clutter signal during the clutter filtering process, the noise signal may be removed. The clutter signal can also be eliminated.

The processor 130 forms a Doppler mode image using the filtered Doppler signal (S512). The Doppler mode image using the Doppler signal may be formed using various known methods and thus will not be described in detail in this embodiment.

Referring back to FIG. 1, the storage 140 stores the first ultrasound data and the second ultrasound data acquired by the ultrasound data acquirer 120. In addition, the storage 140 stores the second ultrasound data processed by the extrapolation by the processor 130.

The display unit 150 displays the B mode image formed by the processor 130. In addition, the display unit 150 displays the Doppler mode image formed by the processor 130. The display unit 150 may include a cathode ray tube (CRT) display, a liquid crystal display (LCD), an organic light emit diode (OLED) display, or the like.

While the invention has been described and illustrated by way of preferred embodiments, those skilled in the art will recognize that various changes and modifications can be made therein without departing from the spirit and scope of the appended claims.

100: ultrasound system 110: user input unit
120: ultrasonic data acquisition unit 130: processor
140: storage unit 150: display unit
210: ultrasonic probe 220: transmission signal forming unit
230: beam former 240: ultrasonic data forming unit
BI: B-mode video SV: sample volume
CB: color box

Claims (8)

As an ultrasound system,
An ultrasound data acquisition unit configured to transmit ultrasound signals to an object including an object of interest flowing through blood and to receive ultrasound echo signals reflected from the object to obtain ultrasound data corresponding to an ensemble number; And
Connected to the ultrasound data acquisition unit, the ultrasound data is converted into ultrasound data in a frequency domain, and the number of the converted ultrasound data is increased by performing extrapolation on the converted ultrasound data. And a processor configured to filter the increased ultrasound data and form a Doppler mode image using the filtered ultrasound data.
. The ultrasound system of claim 1, wherein the Doppler mode image comprises a spectral Doppler image or a color Doppler image. The ultrasound system of claim 1, wherein the extrapolation comprises minimal weighted norm extrapolation. The method of claim 1, wherein the processor,
Performing the extrapolation on the ultrasound data of the frequency domain based on a frequency weighted function to output the increased ultrasound data,
Update the frequency weighting function based on the increased ultrasound data,
And perform the extrapolation on the ultrasound data in the frequency domain based on the updated frequency weighting function to output the increased ultrasound data. As a Doppler mode image providing method,
a) transmitting an ultrasound signal to an object including an object of interest flowing through blood and receiving an ultrasound echo signal reflected from the object to obtain ultrasound data corresponding to an ensemble number;
b) converting the ultrasound data into ultrasound data in a frequency domain;
c) performing extrapolation on the converted ultrasound data to increase the number of the converted ultrasound data;
d) performing filtering on the increased ultrasound data; And
e) forming a Doppler mode image using the filtered ultrasound data
Doppler mode image providing method comprising a. The method of claim 5, wherein the Doppler mode image comprises a spectral Doppler image or a color Doppler image. The method of claim 5, wherein the extrapolation includes a least weighted norm extrapolation. The method of claim 5, wherein step c)
Outputting the increased ultrasound data by performing the interpolation on ultrasound data of the frequency domain based on a frequency weighting function;
Updating the frequency weighting function based on the increased ultrasound data; And
Outputting the increased ultrasound data by performing the extrapolation method on the ultrasound data of the frequency domain based on the updated frequency weighting function.
Doppler mode image providing method comprising a.

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