JPH06327673A - Ultrasonic diagnosis equipment - Google Patents

Abstract

PURPOSE:To provide an ultrasonic diagnosis equipment which can extremely reduce the influence of the clutter component. CONSTITUTION:A transmission and reception means 2 to obtain reception signals by repeating designated times of ultrasonic transmission and reception in a constant period in an identical direction to the testee, a low pass filter 8 to extract Doppler information in the reception signals, and MTI filter to take out the blood flow information by removing the clutter component from the Doppler information are set up. A speed variation calculation part 11 to calculate the average speed and its variation of the blood flow using the blood flow information, a means to correct the average speed using the variation corresponding to the comparison result of the average speed and a designated threshold value, and a means to serve for displaying the output of the correction means are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus for acquiring blood flow information using the Doppler effect.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic diagnostic apparatus of this type is shown in FIG.
The configuration shown in is general. That is, in FIG. 5, reference numeral 1 is an ultrasonic probe in which a plurality of transducers are arranged one-dimensionally. A transmitting / receiving means 2 is connected to the ultrasonic probe 1. The transmitting / receiving means 2 supplies the driving pulse to each transducer of the ultrasonic probe 1 while delay-controlling it to focus the ultrasonic wave in an arbitrary direction and an arbitrary depth, and at the same time, each transducer of the ultrasonic probe 1 receives it. The reception directivity is determined by performing delay control on the reception signal of the reflected wave, which is the reverse of that at the time of transmission.

An adder 3 is connected to the output of the transmitting / receiving means 2. The adder 3 adds the received signals of the transducers input from the ultrasonic probe 1 through the transmission / reception means 2 for each scanning raster, and supplies the signals to the B-mode detection means 4 and the 2-channel mixer 7. The B-mode detection means 4 samples the envelope obtained by detecting the addition result from the adder 3, encodes each sampling result, and outputs it to the digital scan converter (DSC) 15.

The mixer 7 requires two channels in order to separate the forward and reverse directions of the blood flow. The reference frequency f0 from the oscillator 5 is supplied to the one mixer 7 as it is, and the reference frequency f0 is supplied to the other mixer 7 via the phase shifter 6 in a 90 ° phase-shifted state. The mixer 7 is the adder 3
And the reference signal of the reference frequency f0 is multiplied and this is supplied to the low pass filter 8. The low pass filter 8 removes the high frequency component of the output signal of the mixer 7 to form a phase detection signal having a frequency component of the Doppler shift frequency fd.

An MTI filter 9 is connected to the output of the low pass filter 8. The MTI filter 9 is a technique commonly used in the radar field, and plays a role of a high-pass filter for removing the clutter component due to the multiplex of the internal organ wall and the side lobe in real time for each of the two-dimensional multipoints. There is. The cutoff frequency fc required for the high-pass filter processing in the MTI filter 9 is supplied from the controller 16.

A velocity dispersion power calculator 11 is connected to the MTI filter 9 via a frequency analyzer 10. MTI
The output signal from the filter 9 is subjected to frequency analysis and then subjected to predetermined arithmetic processing to calculate the average velocity V at each point, its variance S, and power P.

A blank processing unit 14 is connected to the output of the velocity dispersion power calculator 11. The blank processing unit 14 performs the following blank processing. That is, MTI
In the filter 9, the clutter component is removed by performing high-pass processing based on the cutoff frequency fc, but the filter characteristic here is not so sharp. Therefore, the clutter component remains in the output signal of the MTI filter 9. The blank processing unit 14 selects the average speed V from the speed dispersion power calculator 11 with the speed level Vc corresponding to the cutoff frequency fc as a boundary to identify the average speed V containing a large amount of clutter components, and the speed level Vc. By discarding a smaller average velocity V (average velocity V having a larger velocity level Vc if the signs are opposite), MT
The non-sharp filter characteristic of the I filter 9 is compensated.

Average velocity V passing through the blank processing unit 14
Is sent to the digital scan converter 15. A display unit 19 is connected to the digital scan converter 15, and a B-mode image, a blood flow image, or a combination thereof is displayed according to an operator's instruction.

However, such a conventional ultrasonic diagnostic apparatus has the following problems. For example, the blood flow in the vicinity of the blood vessel wall in the abdominal region is relatively slow, and therefore is very close to the clutter component. At this time, as described above, the MTI
Since the filter characteristic of the filter 9 is not so sharp, the clutter component may not be completely removed from the phase detection signal. In this case, since the blood flow component is generally faster than the clutter component, the average velocity V is reduced by the low frequency component of the clutter component and becomes smaller than the true average velocity of the blood flow component alone, in other words, the average velocity V is There is a problem that it does not correspond to the true average velocity of only the blood flow component.

Further, the problem is that the average velocity V is discarded by the blank processing unit 14 and, as a result, the blood flow information in this portion is lost even though there is a blood flow component, resulting in a so-called black spot. It also spreads to the problem that it is not displayed.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned circumstances, and an object thereof is to provide an ultrasonic diagnostic apparatus capable of reducing the influence of clutter components as much as possible.

[0012]

An ultrasonic diagnostic apparatus according to the present invention comprises transmitting / receiving means for obtaining a reception signal by repeating transmission / reception of an ultrasonic wave in a same direction to a subject at a constant cycle a predetermined number of times, Extraction means for extracting Doppler information contained in the received signal, removal means for extracting blood flow information by removing clutter components from the Doppler information, and average speed of blood flow and its dispersion using the blood flow information. Calculation means for calculating, a means for comparing the average speed with a predetermined threshold value, means for correcting the average speed according to the comparison result using the variance, and means for providing the output of the correcting means for display. It is equipped with.

[0013]

According to the present invention, since the average speed obtained by the calculation means is corrected by using the variance, it is possible to reduce the influence of the clutter component which cannot be completely removed by the removing means on the average speed. The average velocity of true blood flow can be approximated when all clutter components are removed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ultrasonic diagnostic apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. In FIG. 1, reference numeral 1
Is an ultrasonic probe in which a plurality of transducers are arranged one-dimensionally. A transmitting / receiving means 2 is connected to the ultrasonic probe 1. The transmitting / receiving means 2 supplies the driving pulse to each transducer of the ultrasonic probe 1 while delay-controlling it to focus the ultrasonic wave in an arbitrary direction and an arbitrary depth, and at the same time, each transducer of the ultrasonic probe 1 receives it. The reception directivity is determined by performing delay control on the reception signal of the reflected wave, which is the reverse of that at the time of transmission.

An adder 3 is connected to the output of the transmitting / receiving means 2. The adder 3 adds the received signals of the transducers input from the ultrasonic probe 1 through the transmission / reception means 2 for each scanning raster, and supplies the signals to the B-mode detection means 4 and the 2-channel mixer 7. The B-mode detection means 4 samples the envelope obtained by detecting the addition result from the adder 3, encodes each sampling result, and outputs it to the digital scan converter (DSC) 15.

The reason why the mixer 7 requires two channels is to separate the forward and reverse directions of the blood flow. The reference frequency f0 from the oscillator 5 is supplied to the one mixer 7 as it is, and the reference frequency f0 is supplied to the other mixer 7 via the phase shifter 6 in a 90 ° phase-shifted state. The mixer 7 is the adder 3
And the reference signal of the reference frequency f0 is multiplied and this is supplied to the low pass filter 8. The low pass filter 8 removes the high frequency component of the output signal of the mixer 7 to form a phase detection signal having a frequency component of the Doppler shift frequency fd.

An MTI filter 9 is connected to the output of the low pass filter 8. The MTI filter 9 is a technique commonly used in the field of radar, and removes clutter components due to multiplex of internal organ walls and side lobes from a phase detection signal in real time for each of two-dimensional multipoints. The MTI filter 9 plays the same role as a high-pass filter from the viewpoint of removing clutter components having a slow moving speed.
The cutoff frequency fc required for the high-pass filter processing in the MTI filter 9 is supplied from the controller 16.

A velocity dispersion power calculator 11 is connected to the MTI filter 9 via a frequency analyzer 10. MTI
The output signal from the filter 9 is subjected to frequency analysis and then subjected to predetermined arithmetic processing to calculate the average speed V, its variance S, and power P.

Threshold value judging means 12 is connected to the output of the velocity dispersion power calculator 11. The threshold value setting means 17 is connected to the input of the threshold value judging means 12.
The threshold setting means 17 is connected to the controller 16 at its input. The threshold determination means 12 is
A threshold value Vc supplied from the threshold value setting means 17,
The magnitude of the average velocity V from the velocity dispersion power calculator 11 is determined, and the result of the determination together with the average velocity V and the like are corrected by the correction unit 1.
Output to 3. The threshold value setting means 17 converts the cutoff frequency fc supplied from the controller 16 into a speed level and sets the threshold value Vc.

The correction means 13 corrects or does not correct the average speed V according to the judgment result from the threshold value judgment means 12. Specifically, the correction is executed when the average speed V is larger than the threshold value Vc, and is not corrected when the average speed V is smaller than the threshold value Vc. The average velocity V in the correction means 13 is calculated by the velocity dispersion power calculator 1
Using the variance S from 1 and the correction coefficient K from the correction coefficient setting means 18, the correction value V ′ is calculated by the following equation (1).
Is corrected to.

V ′ = V + K × S (1) The correction coefficient setting means 18 sets a correction coefficient K (0 ≦ K ≦ 1). The positive / negative of the correction coefficient K is set so that the positive / negative of the average velocity V, that is, the blood flow matches the forward flow (the blood flow approaching the probe 1) or the reverse flow (the blood flow moving away from the probe 1). There are two methods for setting the correction coefficient K. The first method is a method of changing the correction coefficient K according to the cutoff frequency fc supplied from the controller 16 and the diagnosis region, and the second method is according to the sampling data number N or the rate frequency fr. It is a method of changing.

In the first method, when the diagnosis site is, for example, around the circulatory organ, since the blood flow velocity is very high, its frequency component is clearly separated from the clutter component.
A relatively high cutoff frequency f by the MTI filter
The clutter component can be sufficiently removed with c. Therefore, it is not necessary to perform correction by the correction means 13, and the correction coefficient K
Is set to 0. On the other hand, when the diagnosis site is, for example, around the abdomen, the blood flow velocity is slow and its frequency component is close to the clutter component. Therefore, the MTI filter requires a relatively low cutoff frequency fc, and the clutter component is sufficiently removed. Can not do it. In this case, the correction coefficient setting means 18 sets the correction coefficient K within the range of 0 <K ≦ 1 and executes the correction process. Here, when the cutoff frequency fc is set to be relatively low, the correction coefficient K is brought close to 1 to increase the correction amount. This is because when the cutoff frequency fc is low, a large amount of clutter components that cannot be removed remain, and the frequency components of blood flow are greatly affected by the clutter components. On the other hand, when the cutoff frequency fc is set relatively high, the correction coefficient K is brought close to 0 to reduce the correction amount. This is because if the cut-off frequency fc is high, the clutter components that cannot be completely removed do not remain so much that the frequency components of the blood flow are not significantly affected by the clutter components.

In the second method, when the number N of sampling data indicating the number of data in the depth direction per raster is relatively large, the correction coefficient K is brought close to 1 to increase the correction amount, while sampling is performed. When the number of data N is relatively small, the correction coefficient K is brought close to 0 to reduce the correction amount.
This is for the following reasons. Number of sampling data N
Is increased, the time resolution is improved, and as a result, the analysis result of the frequency analyzer 10 is not significantly blurred,
The variance S is small. On the other hand, when the number N of sampling data decreases, the variance S increases according to the opposite principle. In this way, the variance S changes depending on the number N of sampling data, so it is necessary to normalize the variance S. Therefore, as described above, when the number N of sampling data is relatively large, the correction coefficient K is brought close to 1 to increase the correction amount, and when the number N of sampling data is relatively small, the correction coefficient K is The correction amount is reduced by approaching 0.
Also, when the correction coefficient K is changed according to the rate frequency fr (ultrasonic wave repetition frequency), the same operation as in the case of the sampling data number N is performed. That is, when the rate frequency fr is increased, the time resolution is improved and the variance S is reduced, while when the rate frequency fr is decreased, the time resolution is degraded and the variance S is increased, so that the variance S is normalized. When the rate frequency fr is high, the correction coefficient K is brought close to 1, and when the rate frequency fr is low, the correction coefficient K is brought close to 0.

Which of the above-mentioned first and second methods is to be adopted may be appropriately selected, or both methods may be provided so that they can be selectively used at the time of use. The blank processing unit 14 is provided to the output of the correction unit 13.
Are connected. Here, the following blank processing is performed.

That is, the MTI filter 9 removes the clutter component by performing high-pass processing based on the cutoff frequency fc, but the filter characteristic here is not so sharp. Therefore, the clutter component remains in the average velocity V from the velocity dispersion power calculator 11, and there is an error from the average velocity of only the blood flow component. The blank processing unit 14 uses the velocity dispersion power calculator 11
From the velocity level Vc, the average velocity V supplied from the correction means 13 is selected at the velocity level Vc corresponding to the cut-off frequency fc to identify the average velocity V mainly composed of the clutter component. Small (or average speed V
If the sign of N is negative (distance blood flow), the average velocity V which is larger than the velocity level Vc is discarded so as not to be displayed.

The average speed V passing through the blank processing unit 14 without being discarded is the digital scan converter 15
Sent to. A display unit 19 is connected to the digital scan converter 15, and a B-mode image, a blood flow image, or a combination thereof is displayed according to an operator's instruction.

Next, the operation of the apparatus of this embodiment thus constructed will be described. Here, it is assumed that the examination site is an abdominal region containing a large amount of low-velocity blood flow. Transmission / reception means 2
Under the delay control of 1, the abdominal region of the subject is scanned with the ultrasonic beam from the ultrasonic probe 1. The reflected wave from the abdominal region is received by the ultrasonic probe 1, converted into an electric signal, and output as a received signal. This received signal is
The scanning raster is added by the adder 3 and the sum is sent to the B-mode detection means 4 and the 2-channel mixer 7.

The addition result of the adder 3 is detected by the B-mode detection means 4. The detected signal is output to the digital scan converter (DSC) 15, where it is two-dimensionally developed according to the scanning position at the time of scanning and is generated as a B-mode image.

On the other hand, the addition result of the adder 3 is multiplied by the reference frequency f0 having a 90 ° phase difference in the 2-channel mixer 7, and the high frequency component is removed by the low pass filter 8 to obtain the Doppler shift. It is formed into a phase detection signal having a frequency component of only the frequency fd.

This phase detection signal is sent to the MTI filter 9
Then, based on the cutoff frequency fc supplied from the controller 16, clutter components due to multiplex of the internal organ wall and side lobes are removed in real time for each of the two-dimensional multipoints. The cut-off frequency fc is set to a relatively low level because it collects a low-velocity blood flow that is included in the abdominal region in a relatively large amount.

FIG. 2 is a diagram showing the output signal from the low-pass filter 8 in the frequency space in order to explain the processing for removing the clutter component. As shown in FIG. 2, the phase detection signal from the low-pass filter 8 includes a blood flow component (diagonal line).
And clutter components are included. The MTI filter 9 removes the clutter component based on the cutoff frequency fc, but the filter characteristic at this time is not sharp as shown by the broken line in FIG. Therefore, the output signal from the MTI filter 9 is, as shown in FIG.
Not only that, the clutter component that remains without being removed by the MTI filter 9 is included. In addition, in FIG. 3, the broken line indicates the total frequency distribution of the blood flow component and the remaining clutter component.

The average frequency fa of this total frequency distribution is
As shown in FIG. 3, the true average frequency fr is pulled by the clutter component that cannot be completely removed by the MTI filter 9.
This corresponds to the average frequency fa deviated. The true average frequency fr here means the average frequency of only blood flow components.

Therefore, the average velocity V from the velocity dispersion power calculator 11 also contains a clutter component. The average speed V and the like are sent to the threshold value judging means 12.

This average speed V is determined by the threshold setting means 17
The threshold value Vc (speed level corresponding to the cutoff frequency fc) is compared with the threshold value determination means 12 to make a determination. FIG. 4 shows the average velocity V from the velocity dispersion power calculator 11.
It is the figure which showed on the velocity space. In the figure, Vr is the true average speed corresponding to the true average frequency fr.

When the average velocity V is larger than the threshold value Vc in the threshold value judging means 12, the average velocity V, the variance S and the power P calculated by the velocity dispersion power calculator 11 are corrected by the correcting means 1.
After passing through No. 3, it is directly supplied to the blank processing unit 14 without any correction. On the other hand, when the average speed V is smaller than the threshold value Vc, the average speed V is subjected to the following correction processing by the correction means 13 and converted into V '.

That is, the average speed V is obtained by multiplying the dispersion S from the speed dispersion power calculator 11 by the correction means 13 by the correction coefficient K from the correction coefficient setting unit 18 as shown in the above equation (1). Are added and corrected to the corrected average speed V '.

Therefore, the corrected average velocity V'approaches the true average velocity Vr of only the blood flow component, and MT
The influence of the clutter component that cannot be completely removed by the I filter 9 is reduced.

As shown in FIG. 4, the corrected average speed V'corrected based on the variance S in this way is, in many cases, larger than the speed level Vc corresponding to the cutoff frequency fc in the blank processing section 15. Become. Therefore, the corrected average speed V ′ is not discarded by the blank processing unit 15.

As a result, relatively low-speed blood flow information in the vicinity of the blood vessel wall in the abdominal region, for which clutter components cannot be removed by the MTI filter 9, is provided for display without being discarded by the blank processing unit 14, and is conventionally used. This solves the problem that the blank processing unit 14 discards the blood flow even though the blood flow is present and the data is no longer displayed.

The present invention is not limited to the above-described embodiments, but can be modified in various ways without departing from the scope of the invention. For example, in the above description, the determination process by the threshold value determination means 12 is always performed, but when the cutoff frequency fc is less than a certain value, in other words, there is a certain low flow velocity to be detected. The determination process may be performed only when the value is less than or equal to the value, and the correction process may be performed appropriately according to the determination result. In this case, when the cutoff frequency fc exceeds a certain value, the blood flow component is sufficiently separated from the clutter component, so that even if the filter characteristic of the MTI filter 9 is non-sharp, the clutter component is almost completely removed. It can be removed and is not discarded by the blank processing unit 14. As a result, no problem occurs even if the threshold determination unit 12 does not perform the determination process.

Further, in the above description, the threshold value setting means 17 converts the cutoff frequency fc supplied from the controller 16 into the speed level to thereby obtain the threshold value Vc.
However, the threshold value Vc may be adjusted to an arbitrary value by manual operation by the operator.

Further, in the above description, the correction coefficient setting means 17 sets the correction coefficient K on the basis of the cutoff frequency fc and the diagnostic region supplied from the controller 16, but the correction coefficient K is set by the operator. It may be possible to adjust to any value by manual operation of.

[0043]

The ultrasonic diagnostic apparatus according to the present invention comprises a transmitting / receiving means for obtaining a received signal by repeating transmission / reception of ultrasonic waves in the same direction at a constant cycle with respect to a subject a predetermined number of times,
Extraction means for extracting Doppler information included in the received signal, removal means for extracting blood flow information by removing clutter components from the Doppler information, and average velocity of blood flow and its dispersion using the blood flow information. Calculating means, means for comparing the average speed with a predetermined threshold value, means for correcting the average speed using the variance according to the result of the comparison, and means for displaying the output of the correcting means. And.

Therefore, according to the present invention, since the average velocity of the blood flow is corrected by using its variance, it is possible to reduce the influence of the clutter component which cannot be removed by the removing means on the average velocity. A diagnostic device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a diagram showing an output signal from a low-pass filter on a frequency space for explaining the clutter component removal processing in the MTI filter of FIG.

3 is a diagram showing clutter components that cannot be completely removed by the MTI filter of FIG.

FIG. 4 is a diagram showing a result of correction of an average speed by the correction means in FIG.

FIG. 5 is a block diagram of a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

1 ... Ultrasonic probe, 2 ... Transmission / reception means, 3 ... Adder, 4
... B-mode detection means, 5 ... Oscillator, 6 ... Phase shifter, 7 ... Mixer, 8 ... Low-pass filter, 9 ... MTI filter, 1
0 ... Frequency analyzer, 11 ... Velocity dispersion power calculation unit, 12
... threshold value judging means, 13 ... correcting means, 14 ... blank processing section, 15 ... digital scan converter, 16
... controller, 17 ... threshold value setting means, 18 ... correction coefficient setting means, 19 ... display means.

Claims (4)

[Claims] 1. A transmission / reception unit that obtains a reception signal by repeating transmission / reception of ultrasonic waves in the same direction in a fixed cycle with respect to a subject a predetermined number of times, and an extraction unit that extracts Doppler information included in the reception signal. Removing means for extracting blood flow information by removing clutter components from the Doppler information, calculating means for calculating an average velocity of blood flow and its variance using the blood flow information, the average velocity and a predetermined threshold value. An ultrasonic diagnostic apparatus comprising: means for comparing the average speed with the value and correcting the average speed according to the comparison result; and means for providing the output of the correcting means for display. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the correction means corrects the average speed by adding the variance multiplied by a correction coefficient to the average speed. 3. The ultrasonic diagnostic apparatus according to claim 2, wherein the correction means changes the correction coefficient according to the cycle. 4. The ultrasonic diagnostic apparatus according to claim 2, wherein the correction unit changes the correction coefficient according to the number of the Doppler information extracted by the extraction unit.