JPH08280689A - Ultrasonic doppler diagnostic apparatus - Google Patents

Abstract

PURPOSE: To provide an ultrasonic Doppler diagnostic apparatus capable of enhancing the separation capacity of blood flow component and a noise component. CONSTITUTION: An ultrasonic Doppler diagnostic apparatus is equipped with an ultrasonic probe 11, the transmitting-receiving system 12 driving the ultrasonic probe 11, orthogonal phase detection means 15, 24a, 24b, 25 detecting the phase of an echo signal to obtain a Doppler signal, an autocorrelation device 30 calculating an autocorrelation value of one sample shift from the correlation of the Doppler signal and a Doppler signal shifted by one sample from the Doppler signal, a smoothing part 40 calculating the absorbute value of the autocorrelation value of one sample shift and a display means 39 displaying the absolute value of the autocorrelation value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler diagnostic apparatus for imaging blood flow by the pulse Doppler method.

[0002]

2. Description of the Related Art A basic configuration diagram of a conventional ultrasonic Doppler diagnostic apparatus is shown in FIG. When the ultrasonic probe is driven by the transmission / reception system 12, ultrasonic pulses are transmitted into the living body at a constant repetition frequency (referred to as “rate frequency”). The pulse Doppler method is to repeat transmission / reception of ultrasonic pulses a predetermined number of times in a certain azimuth direction, and after this repetition is completed, move to the next azimuth direction and repeat the same operation.

The reflected wave reflected in the living body is received by the ultrasonic probe 11. This received signal is transmitted / received by the transmission / reception system 1
After being given a reception directivity via 2, it is sent to the detector 18 and the mixers 24a and 24b. The reception signal sent to the detector 18 is subjected to envelope detection, and then displayed on the display unit 39 as B mode through the scan conversion unit 34, the multiplexer (MPX) 37, and the D / A conversion unit 38 in this order. On the other hand, the reception signals sent to the mixers 24a and 24b are respectively phase-detected by being multiplied by reference signals having different phases by 90 degrees, and high frequency components are removed by the low pass filters 26a and 26b. Thereby, the Doppler signal in which the blood flow component and the clutter component are mixed can be obtained. This Doppler signal is sent to a color flow mapping (CFM) processing system 27, converted into digital signals by A / D conversions 28a and 28b, and then clutter signals are removed at various positions by MTI filters 29a and 29b. It As a result, the Doppler signal of only the moving target object (here, blood cells) is obtained.

The Doppler signals output from the MTI filters 29a and 29b are sent to the autocorrelator 30. The autocorrelator 30 uses the following (1) based on the Doppler signal.
The autocorrelation value C with a shift width of zero according to equation (2)
_An autocorrelation value C ₁ of ₀ and 1 sample shift is calculated.

[0005]

[Equation 1]

Note that ^* indicates a complex conjugate, n indicates the number of times of transmission / reception in the same direction, i indicates how many times the transmission / reception is performed, and Si indicates a pixel obtained by the i-th transmission / reception. Means Doppler signal at. The zero-shift autocorrelation value is the cumulative value of the complex conjugate multiplication values of the same signals. The one-sample shifted autocorrelation value and the zero-shift autocorrelation value cause the transmission / reception timing to shift by one time. It is the cumulative value of the complex conjugate multiplication value of the existing signals.

These autocorrelation values C ₀ and C ₁ are respectively calculated by the arithmetic units 31 to 33 in accordance with the following equations (3), (4) and (5). It is processed into various blood flow information of dispersion σ and is displayed on the display means 39 through the scan conversion means 35, the color information conversion means 36, the multiplexer 37, and the D / A conversion means 38 in this order.
Is displayed in.

[0008]

[Equation 2]

As described above, the pulse Doppler method is a technique for two-dimensionally displaying the state of blood flow, based on the basic principle that the shift frequency due to the Doppler effect depends on the blood flow velocity. In addition to the blood flow component, the Doppler signal contains a clutter component from the in-vivo organ and a noise component. The MTI filter removes the clutter component from the Doppler signal. The removal of the noise component is equivalently performed by the rejection process. Rejection processing means when displaying various blood flow information such as average velocity, variance, and power, when the power value of a pixel is smaller than a threshold value, the display brightness of that pixel is displayed as zero, that is, black. This is the process of effectively removing the noise component.

Since the phase value and the velocity of noise change randomly, the variance of noise is generally large. However, since the power value of noise is generally smaller than that of blood flow, the rejection process based on this power value is expected to have some effect.

Thus, the rejection process based on the power value enables noise / blood flow separation to some extent, but the power of the blood flow reflected from a thin blood vessel or a blood vessel distant from the body surface is , Generally small. Therefore, there is a problem that such a blood flow portion having a low power value is not imaged together with noise, and a method capable of obtaining a noise separation ability higher than that of the rejection process is desired.

As a method for reducing this problem, there is a method called a power Doppler method. In this method, the power value is smoothed between frames so as to cancel out the noise whose power value greatly fluctuates temporally. However, in the conventional method of displaying average velocity, variance, and power, the blood flow direction can be obtained from the sign of the average velocity, and the turbulence can be obtained by the variance value. Since the value is smoothed between frames and the value is displayed, the direction of blood flow and the degree of turbulence could not be displayed.

[0013]

SUMMARY OF THE INVENTION A first object of the present invention is to provide an ultrasonic Doppler diagnostic apparatus capable of improving the separability of blood flow components and noise components. A second object is to provide an ultrasonic Doppler diagnostic apparatus capable of displaying the blood flow direction and the blood flow turbulence degree.

[0014]

The invention according to claim 1 is
While transmitting ultrasonic waves to the subject, a wave transmitting / receiving unit that receives an echo signal from the subject, a driving unit that drives the wave transmitting / receiving unit, and a phase detection of the echo signal to obtain a Doppler signal The phase detection means, the correlation means for obtaining the autocorrelation value shifted by one sample based on the correlation between the Doppler signal and the Doppler signal deviated by one sample from the Doppler signal, and the autocorrelation value shifted by one sample The ultrasonic Doppler diagnostic apparatus is provided with a calculation unit for obtaining an absolute value and a display unit for displaying the absolute value of the autocorrelation value.

According to a sixth aspect of the present invention, an ultrasonic wave is transmitted to the subject, and a wave transmitting / receiving means for receiving an echo signal from the subject, a driving means for driving the wave transmitting / receiving means, and Phase detection means for phase-detecting an echo signal to obtain a Doppler signal, the Doppler signal and 1 from the Doppler signal
Correlation means for obtaining an autocorrelation value of a Doppler signal with a shift width of zero and an autocorrelation value with a shift of one sample using a Doppler signal with a sample shift, and calculation for obtaining an absolute value of the autocorrelation value with a shift of one sample Means, a calculating means for obtaining a variance value based on the autocorrelation value of the shift width of zero and the absolute value, one of the autocorrelation value of the shift width of zero and the absolute value, and the variance value are displayed. The ultrasonic Doppler diagnostic apparatus is provided with:

The invention according to claim 9 is characterized in that the smoothing means smoothes the absolute value and the autocorrelation value of the shift width of zero with the sign of the average speed.

According to an eleventh aspect of the present invention, an ultrasonic wave is transmitted to the subject and a wave transmitting / receiving means for receiving an echo signal from the subject, a driving means for driving the wave transmitting / receiving means, and Phase detection means for phase-detecting an echo signal to obtain a Doppler signal, the Doppler signal and 1 from the Doppler signal
Correlation means for obtaining an autocorrelation value with a shift width of zero and an autocorrelation value with a shift of one sample using the Doppler signal with a sample shift, and the autocorrelation value with a shift width of zero and the 1
Smoothing means for smoothing each sample-shifted autocorrelation value between frames; calculation means for obtaining an absolute value of the one-sample-shifted autocorrelation value smoothed by the smoothing means; and an autocorrelation value of zero shift width A calculating means for obtaining a dispersion value from the absolute value, and a display means for displaying either the dispersion value alone, or the dispersion value together with the autocorrelation value of the shift width of zero and the absolute value. This is an ultrasonic Doppler diagnostic device.

[0018]

According to the first aspect of the present invention, the autocorrelation value shifted by one sample is obtained from the correlation between the Doppler signal and the Doppler signal shifted by one sample from the Doppler signal.
The absolute value of the autocorrelation value shifted by one sample is displayed. Since the direction of blood flow is stable, it is 1
The absolute value of the sample-shifted autocorrelation value is relatively large.
On the other hand, noise has random directions, so
The absolute value of the sample-shifted autocorrelation value is relatively small. Therefore, if the auto-correlation value shifted by one sample is applied by, for example, the power Doppler method, the noise separation ability can be expected to be improved.

According to the sixth aspect of the present invention, since either the autocorrelation value or the absolute value of which the shift width is zero or the dispersion value is displayed, both the intensity of the Doppler signal and the turbulence degree can be observed.

According to the invention of claim 9, the dominant direction component of the blood flow in the forward and reverse directions is given by the sign of the result of smoothing the signed power value. Therefore, the power value is distinguished by distinguishing the blood flow direction. Can be displayed.

According to the eleventh aspect of the present invention, the variance is calculated from the autocorrelation value having a zero shift amount smoothed between frames and the absolute value obtained from the autocorrelation value shifted by one sample smoothed between frames. Since it is obtained, it is possible to determine whether the blood flow is a pulsatile flow or a steady flow.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ultrasonic Doppler diagnostic apparatus according to the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram of an ultrasonic Doppler diagnostic apparatus according to the first embodiment of the present invention. FIG. 2 shows a detailed configuration of the smoothing unit shown in FIG. This ultrasonic Doppler diagnostic apparatus employs the pulse Doppler method. When the ultrasonic probe is driven by the transmission / reception system 12, an ultrasonic pulse having the reference frequency f0 is transmitted into the living body at a constant repetition frequency (called "rate frequency") fr. The pulse Doppler method is to sequentially change the azimuth direction while repeating transmission and reception of ultrasonic pulses in a certain azimuth direction a predetermined number of times. The reflected wave reflected in the living body is received by the ultrasonic probe 11. This reception signal is amplified by the preamplifier 13 via the transmission / reception system 12, is given a delay time by the delay line 16, and is further added by the adder 17. The received signal output from the adder 17 is sent to the detector 18, and after the envelope detection, the scan conversion means 3
4, multiplexer (MPX) 37, D / A conversion means 3
It is visually displayed as a B mode image on the display means 39 through 8 in order.

The output of the adder 17 is also sent to mixers (phase detectors) 24a and 24b. The reference signal of the reference frequency f0 from the oscillator 15 is directly supplied to the mixer 24a and is also supplied to the mixer 24b through the 90 ° phase shifter 25, and is multiplied by the received signal from the adder 17, respectively. As a result, the Doppler shift frequency component fd and the high frequency component 2 · f0 + fd are obtained.

The high frequency components are low pass filters 26a,
The Doppler signal having only the Doppler shift frequency component fd filtered by 26b is sent to the color flow mapping (CFM) processing system 27. The Doppler signal sent to the CFM processing system 27 is converted into a digital signal by the A / D converters 28a and 28b, and then clutter signals are removed at various positions by the MTI filters 29a and 29b. Then, a Doppler signal having only the Doppler shift frequency component fd due to blood cells) is obtained.

The Doppler signals from the MTI filters 29a and 29b are sent to the autocorrelator 30. Autocorrelator 30
Calculates the autocorrelation value C ₁ with a shift of 1 sample from the correlation between the signal with a shift width of 0 and the signal with a shift of 1 sample based on the Doppler signals from the MTI filters 29a and 29b according to the above-described equation (2). To do.

The average velocity calculator 31, the variance calculator 32, and the power calculator 33 calculate the average velocity, variance, and power based on the output of the autocorrelator 30, respectively. These are appropriately combined through the scan conversion means 35 and finally displayed on the display means 39.

The output of the autocorrelator 30, that is, the autocorrelation value C ₁ shifted by one sample, is used as the smoothing unit 40.
Sent to This one-sample shifted autocorrelation value C ₁
Is subjected to spatial smoothing processing (smoothing with C _{1 of} an adjacent point in the same frame) for each imaginary part and real part. Specifically, the imaginary part and the real part of the autocorrelation value C ₁ shifted by one sample are respectively the distance direction smoothing unit 4
1, 42 are subjected to smoothing processing in the distance direction (depth direction), and further, the azimuth direction smoothing units 43, 4
In step 4, smoothing processing is performed in the azimuth direction (movement direction of the ultrasonic beam). The amplitude calculator 46 calculates the absolute value | C ₁ | of the autocorrelation value C ₁ from the real number part and the imaginary number part subjected to the spatial smoothing process. The absolute value | C ₁ | of the autocorrelation value C ₁ is calculated by the interframe smoothing unit 4
In step 7, smoothing processing between frames (temporal smoothing processing), that is, smoothing processing with | C ₁ | at the same point in adjacent frames is performed.

The absolute value | C ₁ | of the autocorrelation value C ₁ thus spatially and temporally subjected to the smoothing process is assigned a luminance value in the Log (logarithm) conversion unit 49 according to its magnitude. It is output to the scan conversion means 35 as an angio output signal (blood flow signal). Then, this angio output signal is converted from the scan conversion means 35 to the color information conversion means 3
6, the multiplexer 37, and the D / A conversion means 38 are sequentially displayed on the display means 39 as a two-dimensional blood flow image with reduced noise.

Next, the operation of this embodiment will be described. 3 and 4 are explanatory diagrams related to a method of calculating the autocorrelation value C ₁ shifted by one sample. FIG. 3A shows a received signal before quadrature phase detection obtained by transmitting and receiving in a certain azimuth direction. It should be noted that the number of repetitions of transmission and reception in the same azimuth direction is n. 1 ≦ i ≦ n, s in the figure
_i (t) represents the received signal obtained by the i-th transmission / reception. This received signal s _i (t) is output to the mixers 24a and 24a.
FIG. 3B shows sample values at time t ₀ after being subjected to quadrature detection in b and further subjected to A / D. This complex number S _i depends only on i, not on the time function. Here, if the blood flow velocity does not change so much within the observation time,
The complex number S _i rotates at substantially constant intervals, as shown in FIG.

FIG. 4A shows 1 in the autocorrelator 30.
It is an explanatory diagram relating to the calculation procedure of the auto-correlation values C ₁ to shift the sample. Autocorrelator 30, and complex S _i at reception of i-th one sample offset, the complex number S _i-1 of the phase conjugate S of one sample previous i-1-th transmission and reception here
_i-1 ^* and complex multiplication. This complex multiplication is repeated until i = n, and the obtained complex multiplication results AC1 to ACn are shown in FIG.
By accumulating as shown in (b), the autocorrelation value C ₁ shifted by one sample is obtained. As described above, if the blood flow velocity does not change so much within the observation time, the phase difference (φ _i −φ _i-1 ) between the samples is almost constant within the accumulation range, and the vector does not depend on i. About the same direction. Therefore, the accumulated autocorrelation value C ₁ shifted by one sample reaches a position sufficiently distant from the origin, and its absolute value | C ₁ | also increases. However, in the case of noise, the direction of the vector is random as shown in FIG.
₁ of the absolute value | C ₁ | is not Ika become too large. In short, the autocorrelation value C _{1 of} the blood flow component shifted by one sample
The absolute value │C ₁ │ of the noise increases as the value of i increases, but the absolute value │C ₁ │ of the autocorrelation value C ₁ of one noise shift does not increase so much regardless of i. Therefore, this one-sample shifted autocorrelation value C
_When the absolute value | C ₁ | of ₁ is subjected to luminance conversion and displayed, the blood flow component is emphasized relatively to the noise component, and as a result, the noise component is suppressed. However, when the blood flow is also turbulent and the direction of the vector AC is random, the absolute value | C ₁ | of the autocorrelation value C ₁ shifted by one sample does not become so large as with noise, so C ₀ Instead of C ₁
There are few advantages to using.

On the other hand, the autocorrelation value C of zero shift width
As can be understood from the above-mentioned formula (1), ₀ is a scalar quantity, and corresponds to a scalar accumulation of the amplitude of each vector AC in FIG. Therefore,
Both the C ₀ of C ₀ and the noise component of the flow component, increases in response to receiving the repeat count, the difference between them is small,
The noise component cannot be separated from the blood flow component.

As described above, the autocorrelation value C ₁ of one sample shift uses the fact that the phase of each sample depends on the flow velocity in the blood flow signal and is random in noise, but the shift width is zero. The auto-correlation value C _{0 of} is used only for the amplitude of each sample and not for the phase. Therefore, for blood flow with little turbulence, the method based on the autocorrelation value C ₁ shifted by one sample has a better noise separation ability than the method based on the autocorrelation value C ₀ with a shift width of zero.

Next, the autocorrelation value C ₁ shifted by one sample
The effect of smoothing s between spatial samples and between frames will be described. If the velocity and direction of blood flow are similar spatially close to each other, the values of C ₁ vector before and after the smoothing process are the same since they have the same direction and have the same direction at those points. Fluctuation is small. However, since the C ₁ vector due to noise is independent between adjacent samples and between frames, its value is reduced by smoothing processing. Therefore, by smoothing the autocorrelation value C ₁ shifted by one sample between spatial samples and between frames, the noise separation capability is further improved. (Second Embodiment) FIG. 6 shows the structure of the smoothing portion of this embodiment. 6, the same parts as those in FIG. 2 are designated by the same reference numerals. The configuration other than the smoothing portion is the same as that of FIG. 1 of the first embodiment. The smoothing unit has an autocorrelation value C obtained by the autocorrelator 30 and shifted by one sample.
₁ and an autocorrelation value C ₀ with a shift width of zero are supplied. C
The real part of ₁ is sent to the amplitude calculation section 46 via the distance direction smoothing section 41 and the azimuth direction smoothing section 43. Also, the imaginary part of C ₁ is the distance direction smoothing part 42.
And the amplitude calculation unit 4 via the azimuth direction smoothing unit 44.
Sent to 6. The spatial smoothing process is defined as a superordinate concept of the distance direction smoothing process and the azimuth direction smoothing process. Amplitude calculation unit 46, the real part of the C _1, the absolute value of C _1, based on the imaginary part | C ₁ | a seek.

In addition, 1 which has undergone spatial smoothing processing
The sample-shifted autocorrelation value C ₁ is sent to the phase calculator 52. The phase calculator 52 determines the blood flow direction (direction approaching the probe and direction away from the probe) as a sign (positive and negative) based on the phase difference between the two. The obtained code is sent to the inter-frame smoothing unit 53 and the multiplexers 58 and 59.

The autocorrelation value C ₀ having a shift width of zero is spatially smoothed by the distance direction smoothing section 50 and the azimuth direction smoothing section 51, and the multiplexer 5
It is output to 7,59.

Further, the multiplexers 57 and 60 are supplied with a selection command C ₁ / C ₀ indicating which of C ₁ and C ₀ the display parameter should be. Select command C ₁ /
In accordance with C ₀ , the absolute value | C ₁ | of the autocorrelation value C ₁ from the amplitude calculation unit 46 or the autocorrelation value C ₀ with a shift width of zero is selectively supplied to the interframe smoothing unit 53.

The inter-frame smoothing section 53 has a | C ₁
| Or C ₀ is attached to a code and subjected to interframe smoothing processing. The processing result is output as a signed power value via the Log converter 54.

The absolute value | C ₁ | of the autocorrelation value C ₁ from the amplitude calculator 46 is sent to the multiplexer 58. The multiplexer 58 has a first operation mode for displaying blood flow in both a direction toward the ultrasonic probe 11 (forward direction) and a direction away from the ultrasonic probe 11 (reverse direction), and either direction. And a second operation mode for selectively displaying the blood flow in the first operation mode. In the first operation mode, the absolute value | C ₁ | is passed through the inter-frame smoothing unit 47 as it is, and in the second operation mode, the phase calculation is performed. The positive (or negative) absolute value | C ₁ | from the unit 52 is passed through the inter-frame smoothing unit 47 as it is, and the negative (or positive) absolute value | C ₁ | It is converted into a zero value and sent to the inter-frame smoothing section 47. The inter-frame smoothing unit 47 sends the sent absolute value | C
₁ | is subjected to interframe smoothing processing (temporal smoothing processing).

Similarly, the autocorrelation value C ₀ of the displacement width of zero from the azimuth direction smoothing section 51 is calculated by the multiplexer 5
Sent to 9. The multiplexer 59 is the ultrasonic probe 1
The first operation mode for displaying the blood flow in both the direction toward 1 (forward direction) and the direction away from the ultrasonic probe 11 (reverse direction) and the blood flow in either direction selectively. A second operation mode to be displayed. In the first operation mode, C ₀ is allowed to pass through the inter-frame smoothing section 47 as it is, and in the second operation mode, the sign from the phase calculation section 52 is positive (or negative). C ₀ of ₀ is passed through the inter-frame smoothing section 55 as it is, and the negative (or positive) C ₀ from the phase calculation section 52 is converted into a zero value and sent to the inter-frame smoothing section 55. The inter-frame smoothing unit 55 subjects the sent C ₀ to inter-frame smoothing processing (temporal smoothing processing).

The variance calculator 56 obtains the variance from the smoothed | C ₁ | and C ₀ according to the equation (5),
The calculated variance value is output. Similarly to the multiplexer 57, the multiplexer 60 selectively selects | C ₁ | from the interframe smoothing unit 47 or C ₀ from the interframe smoothing unit 55 selected as the display parameter as Lo.
It is supplied to the g conversion unit 49. The Log converter 49 uses | C ₁ |
Alternatively, C ₀ is subjected to luminance conversion and output as a power value without a code.

In this embodiment, by selecting the display parameter, it is possible to display any value of | C ₁ | and C ₀ . Further, only the dispersion value obtained from | C ₁ | and C ₀ may be displayed, or the unsigned power value and the dispersion value may be displayed. For example, |
If C ₁ | or C ₀ is used as the brightness parameter and the color tone is changed according to the dispersion value, both the intensity of the Doppler signal expressed by the brightness and the turbulence can be observed at the same time.

Since the dispersion is obtained from | C ₁ | or C ₀ subjected to the interframe smoothing processing with a certain time constant, the average turbulence within a certain period of time can be evaluated. Therefore, in general, a dispersion value that is not stable can be detected fairly stably, which is effective for detection of minute turbulence and quantitative evaluation of the degree of turbulence.

In this embodiment, the power value can be displayed by distinguishing the blood flow direction. That is, the unsigned power value (| C ₁ | or C ₀ ) from the Log converter 49 is used as the brightness parameter, and the signed power value (| C ₁ | or C ₀ ) from the Log converter 54 is used according to the sign. Change the tone. For example, if the sign of the signed power value (| C ₁ | or C ₀ ) is positive, it is displayed in a reddish color, and if it is negative, it is displayed in a bluish color.

When considering the action of this processing, it is necessary to consider the case where the blood flow direction is disordered by forward / reverse (positive / negative). When the multiplexers 58 and 59 are in the first operation mode, the inter-frame smoothing unit 47 simply smooths the power value (| C ₁ | or C ₀ ) between frames. The power values of the blood flow in the opposite direction are mixed without distinction between them. Therefore, when signing this result, it is necessary to depend on which directional component is dominant. This dominant directional component is given by the code resulting from interframe smoothing of the power value (| C ₁ | or C ₀ ) with a code in the interframe smoothing unit 53. Therefore, it becomes possible to distinguish the blood flow direction and display the power value.

When the multiplexers 58 and 59 operate in the second operation mode, only the blood flow in any one of the selected directions can be selectively displayed based on the power value output from the Log converter 49. . This method also has the following advantages. In general, blood flow has a constant direction of flow, so that the sign is relatively fixed, but the sign of noise is random. Therefore, the power value of noise tends to be smaller than the power value of blood flow, and noise separation is achieved. (Third Embodiment) FIG. 7 is a block diagram of a smoothing unit according to the third embodiment. The same parts as those in FIG. In the first embodiment, the amplitude calculator 46 uses C ₁
After performing the amplitude calculation of, the inter-frame smoothing unit 4
In step 7, smoothing processing between frames was performed. On the other hand, in the present embodiment, the inter-frame smoothing unit 47
After performing the inter-frame smoothing processing in a and 47b, the amplitude calculation unit 46 calculates the amplitude of C ₁ . That the absolute value of the autocorrelation value C ₁ of the inter-frame smoothing processing one sample shift | C ₁ | rather than to be performed on the autocorrelation value C ₁ of shifting one sample. Accordingly, the smoothing unit is configured such that inter-frame smoothing units 47a and 47b are arranged before the amplitude calculating unit 46.
The amplitude obtained by the amplitude calculator 46, that is, the absolute value | C ₁ | after subjecting C ₁ to the interframe smoothing process is
It is sent to the distributed calculation unit 56.

Further, in this embodiment, the distance direction smoothing unit 50, the azimuth direction smoothing unit 51, and the interframe smoothing unit 5 for the autocorrelation value C ₀ having the shift width of zero.
5 are provided. These smoothing parts 50, 51, 5
The C ₀ smoothed in 5 is sent to the variance calculator 56.

The variance calculator 56 calculates the variance from | C ₁ | and C ₀ according to the equation (5). With this configuration, it is possible to identify whether the blood flow is a pulsatile flow or a steady flow. In the case of a pulsatile flow, the flow velocity greatly changes between frames, so when C ₁ is subjected to interframe smoothing processing, its amplitude becomes smaller and the absolute value | C ₁ | becomes smaller than in the case of a steady flow. On the other hand, since C ₀ is not affected by the change in velocity, it does not change regardless of pulsatile flow or steady flow. Therefore, the pulsatile flow of an artery or the like has a high dispersion value, and the steady flow of a vein or the like has a low dispersion value. Therefore, it is possible to distinguish between a pulsatile flow and a steady flow. The present invention is not limited to the above-mentioned embodiments, but can be implemented with various modifications.

[0048]

According to the first aspect of the present invention, the autocorrelation value shifted by one sample is obtained from the correlation between the Doppler signal and the Doppler signal shifted by one sample from the Doppler signal. The absolute value of the autocorrelation value is displayed. Since the direction of the blood flow is stable,
The absolute value of the autocorrelation value shifted by one sample is relatively large. On the other hand, the direction of noise is random, so
The absolute value of the autocorrelation value shifted by one sample is relatively small. Therefore, if the auto-correlation value shifted by one sample is applied by, for example, the power Doppler method, the noise separation ability can be expected to be improved.

According to the sixth aspect of the present invention, since either the autocorrelation value or the absolute value of which the shift width is zero or the dispersion value is displayed, both the intensity of the Doppler signal and the turbulence degree can be observed.

According to the invention of claim 9, the dominant direction component of the blood flow in the forward and reverse directions is given by the sign of the result of smoothing the signed power value. Therefore, the power value is distinguished by distinguishing the blood flow direction. Can be displayed.

According to the eleventh aspect of the invention, the variance is calculated from the autocorrelation value having a zero shift amount smoothed between frames and the absolute value obtained from the autocorrelation value shifted by one sample smoothed between frames. Since it is obtained, it is possible to determine whether the blood flow is a pulsatile flow or a steady flow.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic Doppler diagnostic apparatus according to a first embodiment.

FIG. 2 is a block diagram of a smoothing unit shown in FIG.

FIG. 3 is an explanatory diagram of the first half of a procedure for calculating an autocorrelation value C ₁ .

FIG. 4 is an explanatory diagram of the latter half of the procedure for calculating the autocorrelation value C ₁ .

FIG. 5 is an explanatory diagram of noise discrimination ability based on an autocorrelation value C ₁ .

FIG. 6 is a block diagram of a smoothing unit according to a second embodiment.

FIG. 7 is a block diagram of a smoothing unit according to a third embodiment.

FIG. 8 is a configuration diagram of a conventional ultrasonic Doppler diagnostic apparatus.

[Explanation of Codes] 11 ... Ultrasonic probe, 12 ... Transceiver system, 13 ... Preamplifier, 14 ... Pulser, 15 ... Oscillator, 16 ...
Delay line, 17 ... Adder,
18 ... Detector, 24a, 24b ... Mixer,
25 ... Phase shifter, 26a, 26b ... Low pass filter, 27 ... CFM processing system, 28a, 28b ... A / D
Conversion means, 29a, 29b ... MTI filter, 3
0 ... Auto-correlator, 31 ... Average velocity calculation unit, 32 ... Variance calculation unit, 33
... Power calculator, 34, 35 ... Scan conversion means,
36 ... Color information conversion means, 37 ... Multiplexer, 38 ... D / A conversion means, 39 ... Display means, 40 ... Smoothing section.

Claims (12)

[Claims] 1. A wave transmitting / receiving unit for transmitting an ultrasonic wave to a subject and receiving an echo signal from the subject, a driving unit for driving the wave transmitting / receiving unit, and a phase detector for the echo signal. Phase detecting means for obtaining a Doppler signal by means of the above; correlating means for obtaining an autocorrelation value shifted by one sample based on the correlation between the Doppler signal and the Doppler signal deviated by one sample from the Doppler signal; An ultrasonic Doppler diagnostic apparatus, comprising: an arithmetic unit that obtains the absolute value of the autocorrelation value of 1. and a display unit that displays the absolute value of the autocorrelation value. 2. The ultrasonic Doppler diagnostic apparatus according to claim 1, wherein the display means assigns and displays a brightness or a display color based on the magnitude of the absolute value. 3. The smoothing means for smoothing at least one of the autocorrelation value and the absolute value with respect to at least one of spatial samples and frames.
The ultrasonic Doppler diagnostic apparatus described. 4. The ultrasonic Doppler according to any one of claims 1 to 3, wherein the correlating unit obtains the autocorrelation value of the Doppler signal having a shift width of zero together with the autocorrelation value. Diagnostic device. 5. The smoothing means smoothes any one of the autocorrelation value, the absolute value, and the autocorrelation value with a shift width of zero for at least one of spatial samples and frames. Item 3. The ultrasonic Doppler diagnostic apparatus according to Item 3. 6. A wave transmitting / receiving unit for transmitting an ultrasonic wave to a subject and receiving an echo signal from the subject, a driving unit for driving the wave transmitting / receiving unit, and a phase detector for the echo signal. Phase detection means for obtaining a Doppler signal by using the Doppler signal and the Doppler signal deviated by one sample from the Doppler signal, the autocorrelation value of the Doppler signal having a zero shift width and the autocorrelation value shifted by one sample are obtained. Correlation means for obtaining, an arithmetic means for obtaining an absolute value of the autocorrelation value shifted by one sample, a calculation means for obtaining a variance value based on the autocorrelation value of the shift width of zero and the absolute value, and the shift width of zero An ultrasonic Doppler diagnostic apparatus comprising: a display unit that displays any one of the autocorrelation value and the absolute value and the variance value. 7. The ultrasonic wave according to claim 5, further comprising calculation means for calculating a variance value based on the absolute value smoothed by the smoothing means and the autocorrelation value of the shift width of zero. Doppler diagnostic device. 8. The display means is smoothed by assigning a brightness and a display color to any of the absolute value smoothed by the smoothing means and the autocorrelation value of the shift width of zero, and the variance value. The ultrasonic Doppler diagnostic apparatus according to claim 7, wherein any one of the absolute value and the autocorrelation value of the shift width of zero and the variance value are simultaneously displayed. 9. The smoothing means smoothes the absolute value and the autocorrelation value of the shift width of zero by adding a sign of an average speed to smoothing. Item 9. The ultrasonic Doppler diagnostic apparatus according to any one of items 8. 10. The display means adds the sign of the average speed and smoothes the absolute value and the sign of the autocorrelation value of the shift width of zero, and the absolute value smoothed without a sign or the shift width. The ultrasonic Doppler diagnostic apparatus according to claim 9, wherein the display color is changed based on an autocorrelation value of zero. 11. A wave transmitting / receiving unit for transmitting an ultrasonic wave to a subject and receiving an echo signal from the subject, a driving unit for driving the wave transmitting / receiving unit, and a phase detector for the echo signal. When a Doppler signal is obtained by using the Doppler signal and the Doppler signal shifted by one sample from the Doppler signal, an autocorrelation value with a shift width of zero,
Correlating means for obtaining an autocorrelation value with a shift of one sample; smoothing means for smoothing the autocorrelation value with the shift width of zero and the autocorrelation value with a shift of one sample between frames; and the smoothing means smoothed by the smoothing means. 1
Calculation means for obtaining the absolute value of the autocorrelation value of the sample shift, calculation means for obtaining the variance value from the autocorrelation value of the shift width of zero and the absolute value, only the variance value, or the shift width together with the variance value An ultrasonic Doppler diagnostic apparatus comprising: a display unit that displays one of an autocorrelation value of zero and the absolute value. 12. The method according to claim 1, wherein the phase detection means phase-detects the echo signal to obtain a Doppler signal and removes a clutter component of the obtained Doppler signal. 11. The ultrasonic Doppler diagnostic apparatus according to any one of 11 above.