JPH08215194A - Ultrasonic wave diagnosis device - Google Patents

Abstract

PURPOSE: To prevent a flow value from being underestimated lower than its true value when a part of flow components is removed by a MTI filter. CONSTITUTION: Ultrasonic waves are transmitted to a testee' body by an ultrasonic wave probe 1, ultrasonic wave echo signals from the testee' body are received, the low frequency components of the ultrasonic wave echo signals are removed by MTI filters 9 and 10 based on filter characteristics selected in advance, and a flow dispersion value σ is thereby obtained by a CFM operation section 12 based on the ultrasonic wave echo signals from which the low frequency components are removed. Besides, the ratio α of a reference band width to the band width of selected filter characteristics is obtained, a connection factor γ is computed by a correction factor computing section 18 by letting the band width ratio α be multiplied by an adjusting factor β, and a correction dispersion value σ" is thereby computed by a correction multiplying section 20 by letting the aforesaid flow dispersion value σ' be multiplied by the correction factor γ. By this constitution, the flow dispersion value can be prevented from being underestimated to a value parted from its true value because of the characteristics of the MTI filter, so that the reliability of diagnosis can thereby be enhanced.

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. More specifically, the present invention relates to an ultrasonic diagnostic apparatus capable of preventing a dispersion value of a flow from being evaluated to a value apart from a true value due to the characteristics of an MTI filter.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of an example of a conventional ultrasonic diagnostic apparatus. In this ultrasonic diagnostic apparatus 500, the ultrasonic probe 1 and the transmitter / receiver 2 are used to set M for each sound ray.
Emitting (for example, 15) ultrasonic pulses are transmitted at time intervals T (for example, 1 ms). And N in the depth direction of each sound ray
Ultrasonic echo signals corresponding to sampling points (for example, 1000 points) are collected. CFM (Color Flow Mappi)
ng) When displaying an image, the ultrasonic echo signal is input to the quadrature detection unit 4. Mixer 4 of quadrature detector 4
a and 4b multiply the reference signal from the reference signal generators 4c and 4d by the ultrasonic echo signal to obtain an LPF (Low Pa).
The quadrature component Q and the in-phase component I are output through the ss Filter) 4g and 4h. The A / D converters 5 and 6 A / D-convert the quadrature component Q and the in-phase component I, respectively, and write them in the memories 7 and 8.

The MTI filters 9 and 10 have a quadrature component Q.
Several filter characteristics for removing clutter components (components from tissues such as a relatively slow moving heart wall) from the in-phase component I are stored. The operator operates the input device 1
1 can be used to select one of the filter characteristics stored in the MTI filters 9 and 10. The MTI filters 9 and 10 call the quadrature component Q and the in-phase component I from the memories 7 and 8, and remove the clutter component from the quadrature component Q and the in-phase component I based on the selected filter characteristic.

The CMF calculator 12 has sampling points n (n = 1, 2, ...,) on one sound ray for the quadrature component Q and the in-phase component I from which the unnecessary clutter components have been removed.
The average velocity value v and the variance value σ ′ of the flow in N)
Calculated by the autocorrelation calculation between the emitted ultrasonic pulses, D
Pass to SC (Digital Scan Convertor) 13. DSC1
3 converts the average velocity value v and the variance value σ ′ of the flow into display values (color and brightness) and two-dimensionally maps them according to the positions of sampling points to generate CFM image data. In general, the average velocity value v of the flow is a red or blue color depending on its sign, and the brightness is determined by the magnitude of the absolute value. The variance value σ ′ is a green color, and the brightness is determined by its size. CRT14
Displays a velocity color image or a dispersed color image on the screen based on the CFM image data.

On the other hand, when obtaining a B-mode image, an ultrasonic echo signal is input to the B-mode processing unit 3. The B-mode processing unit 3 generates B-mode data from the strength of the ultrasonic echo signal and transfers it to the DSC 13. DSC13 is the B
The mode data is converted into display values (color and brightness) and two-dimensionally mapped according to the position of the sampling point,
B-mode image data is generated. Generally, the B-mode data is a gray color, and the brightness is determined by its size. The CRT 14 displays a B-mode image on the screen based on the B-mode image data.

FIG. 6 shows clutter components, blood flow components, and MTI.
It is explanatory drawing which shows the relationship of the filter characteristics of the filters 9 and 10. The sizes of the clutter component C and the blood flow component B are calculated by the square root of the sum of squares of the orthogonal component Q and the in-phase component I. Pulse repetition frequency PRF
(Pulse Repetation Frequency) is the reciprocal of the time interval T for transmitting ultrasonic pulses. The filter characteristic M is selected so that its cutoff frequency fc1 is higher than the clutter component C and lower than the blood flow component B.

FIG. 7 is an explanatory diagram showing the signal component after the clutter component C has been removed based on the filter characteristic M of FIG. Since only the signal component b corresponding to the blood flow component B is extracted, the correct variance value σ ′ can be obtained.

[0008]

Generally, in the heart region, as shown in FIG. 8, the frequency band of the clutter component C is wide and the frequency bands of the clutter component C and the blood flow component B are not so far apart from each other. Therefore, the cut-off frequency fc1 is relatively low as the filter characteristic of the MTI filters 9 and 10.
When the filter characteristic M of is selected, the clutter component C is not removed well, and as shown in FIG.
The signal component c'corresponding to is left. However, if the signal component c ′ corresponding to the clutter component C remains, motion artifact will occur. In addition, the variance value σ1 ′ is excessively calculated from the true value due to the influence of the signal component c ′ corresponding to the clutter component C. On the other hand, as shown in FIG. 10, when the filter characteristic M of the relatively high cutoff frequency fc2 is selected as the filter characteristic of the MTI filters 9 and 10, the clutter component C is completely removed, so that a motion artifact occurs. Absent. However,
Since the blood flow component B is also partially cut, FIG.
As shown in, the signal component b2 corresponding to the blood flow component B becomes smaller, and due to this, the variance value σ2 ′ is smaller than the true value.
Is calculated. Therefore, an object of the present invention is MT
An object of the present invention is to provide an ultrasonic diagnostic apparatus in which a flow dispersion value is evaluated close to a true value even when a filter characteristic having a relatively high cutoff frequency is selected as the filter characteristic of the I filter.

[0009]

According to a first aspect of the present invention, an ultrasonic probe transmits an ultrasonic wave into a subject, receives an ultrasonic echo signal from the inside of the subject, and preselects the ultrasonic echo signal. In the ultrasonic diagnostic apparatus, the low frequency component of the ultrasonic echo signal is removed through the MTI filter, and at least the dispersion value of the flow is acquired and displayed based on the ultrasonic echo signal from which the low frequency component is removed. Selected MTI
There is provided an ultrasonic diagnostic apparatus comprising a dispersion value correcting means for acquiring a filter characteristic of a filter and correcting the dispersion value of the flow based on the filter characteristic.

According to a second aspect of the present invention, in the ultrasonic diagnostic apparatus having the above structure, the dispersion value correcting means calculates a bandwidth ratio for obtaining a bandwidth ratio between the bandwidth of the selected MTI filter and the reference bandwidth. Means, correction coefficient calculation means for calculating a correction coefficient by multiplying the bandwidth ratio by an adjustment coefficient, and correction multiplication means for calculating a correction dispersion value by multiplying the dispersion value of the flow by the correction coefficient. An ultrasonic diagnostic apparatus is provided.

In the above structure, it is preferable to further include a switching unit for the operator to select whether the dispersion value correcting unit is enabled (corrected) or disabled (not corrected).

[0012]

In the ultrasonic diagnostic apparatus according to the first aspect, M
The variance value calculated after removing the low frequency components of the ultrasonic echo signal through the TI filter is corrected based on the filter characteristic of the MTI filter. For example, if a filter characteristic with a relatively low cutoff frequency is selected as the filter characteristic of the MTI filter, the clutter component may not be completely removed, and the variance value may be excessively calculated, as described above. Therefore, in the case of a filter characteristic having a relatively low cutoff frequency, a dispersion value close to a true value can be obtained by multiplying by a correction coefficient smaller than "1". on the other hand,
If a filter characteristic having a relatively high cutoff frequency is selected as the filter characteristic of the MTI filter, the clutter component can be completely removed as described above, but the blood flow component B is also partially cut, so that the dispersion value is too small. May be calculated. Therefore, in the case of a filter characteristic having a relatively high cutoff frequency, a dispersion value close to a true value can be obtained by multiplying by a correction coefficient larger than "1".

In the ultrasonic diagnostic apparatus according to the second aspect, the bandwidth ratio between the bandwidth of the selected MTI filter and the reference bandwidth is obtained, the bandwidth ratio is multiplied by the adjustment coefficient, and the correction coefficient is calculated. The correction variance value is calculated by multiplying the flow variance value by the correction coefficient. For example, when the MTI filter has a relatively low cutoff frequency fc1 and a relatively high cutoff frequency fc2 as filter characteristics, the bandwidth corresponding to the relatively low cutoff frequency fc1 is used as the reference bandwidth. Then, when the filter characteristic of the comparatively low cutoff frequency fc1 is selected, the bandwidth ratio becomes "1". Here, if the adjustment coefficient is set to a value smaller than "1", a correction coefficient smaller than "1" is obtained. Therefore, when this is multiplied, a variance value close to a true value can be obtained. On the other hand, when the filter characteristic of the relatively high cutoff frequency fc2 is selected, the bandwidth ratio becomes a value larger than "1". Here, if the product multiplied by this bandwidth ratio becomes a value larger than "1" and an adjustment coefficient having a value smaller than "1" is selected, the correction coefficient becomes larger than "1". Then, a variance value close to the true value can be obtained.

If the switching means for the operator to select whether the dispersion value correcting means is to be enabled (corrected) or disabled (not corrected) is provided, the heart having a relatively wide clutter component bandwidth. It is possible to perform switching such that the dispersion value correction means is enabled in the partial diagnosis, and the dispersion value correction means is disabled in the abdominal diagnosis in which the clutter component bandwidth is relatively narrow.

[0015]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a block diagram of an embodiment of the ultrasonic diagnostic apparatus of the present invention. This ultrasonic diagnostic device 1
At 00, the ultrasonic probe 1 and the transceiver 2 transmit M (for example, 15) ultrasonic pulses at time intervals T (for example, 1 ms) for each sound ray. Then, ultrasonic echo signals corresponding to N (for example, 1000) sampling points in the depth direction of each sound ray are collected.

When displaying a CFM image, the ultrasonic echo signal is input to the quadrature detection section 4. Quadrature detector 4
Mixers 4a, 4b of the reference signal generators 4c, 4d multiply the ultrasonic echo signal by the reference signal,
The quadrature component Q and the in-phase component I are output through F4g and 4h. The A / D converters 5 and 6 have a quadrature component Q and an in-phase component I.
Are A / D converted and written in the memories 7 and 8.

The MTI filters 9 and 10 have a quadrature component Q.
And four-stage filter characteristics for removing the clutter component from the in-phase component I are stored. FIG. 2 shows the filter characteristics. The filter characteristic M0 has the lowest cutoff frequency fc0. That is, the widest bandwidth B
Has zero. The filter characteristic M1 has the second lowest cutoff frequency fc1. That is, it has the second largest bandwidth B1. The filter characteristic M2 has the second highest cutoff frequency fc2. That is, it has the second narrowest bandwidth B2. The filter characteristic M3 has the highest cutoff frequency fc3. That is, it has the narrowest bandwidth B3. Returning to FIG. 1, the operator can use the input device 11 to select one filter characteristic Mi from the filter characteristics M0 to M3 stored in the MTI filters 9 and 10.

The MTI filters 9 and 10 include memories 7 and 8, respectively.
To call the quadrature component Q and the in-phase component I, and remove the clutter component from the quadrature component Q and the in-phase component I based on the selected filter characteristic Mi. The CMF calculator 12
For each of the quadrature component Q and the in-phase component I from which the unnecessary clutter component has been removed, each sampling point n on one sound ray
The average velocity value v and the dispersion value σ ′ of the flow at (n = 1, 2, ... hand over.

The dispersion value correction unit 15 includes a bandwidth ratio calculation unit 16
An adjustment coefficient setting unit 17, a correction coefficient calculation unit 18, a valid / invalid switching unit 19, and the correction multiplication unit 20. The bandwidth ratio calculator 16 includes the MTI filter 9,
Bandwidth B0 corresponding to 10 filter characteristics M0 to M1
M3 is stored. When the operator uses the input device 11 to select the filter characteristics Mi of the MTI filters 9 and 10, the bandwidth ratio calculation unit 16 sets the widest bandwidth B0 as the reference bandwidth and sets the bandwidth Bi of the selected MTI filter. The bandwidth ratio α = B0 / Bi of the reference bandwidth is calculated. The adjustment coefficient setting unit 17 holds the adjustment coefficient β set by the operator using the input device 11. This adjustment coefficient β is for preventing excessive correction, and is set empirically by the operator. The correction coefficient calculation unit 18 calculates the correction coefficient γ = α · β by multiplying the bandwidth ratio α by the adjustment coefficient β.
When 1 is used to select “valid”, the correction coefficient γ is input to the correction multiplication unit 20, and when “invalid” is selected, “1” is input.
Is input to the correction multiplication unit 20. The correction multiplication unit 20
Multiplies the variance value σ ′ by the correction coefficient γ or “1” and passes the corrected variance value σ ”to the DSC 13.
3 converts the average velocity value v and the variance value σ ″ of the flow into display values (color and luminance) and performs two-dimensional mapping according to the position of the sampling point to generate CFM image data. A velocity color image or a dispersed color image is displayed on the screen based on the CFM image data.

As shown in FIG. 3, when the filter characteristic M of the relatively high cutoff frequency fc2 is selected as the filter characteristic of the MTI filters 9 and 10, the clutter component C is completely removed, so that the motion artifact is generated. Does not occur. However, since the blood flow component B is also partially cut, the signal component b2 corresponding to the blood flow component B becomes small as shown in FIG. 4, and due to this, the variance value σ2 is too small from the true value. 'Is calculated. However, for example, the bandwidth ratio α = 2.0 and the adjustment coefficient β = 0.7
And the correction coefficient γ = α · β = 1.4 is the variance value σ
Since it is multiplied by 2 ′, the result is that the variance value σ2 ″ close to the true value is calculated. The operation for obtaining the B-mode image is the same as the conventional one, and the description thereof is omitted.

According to the above ultrasonic diagnostic apparatus 100, the variance value correction unit 15 is enabled in the heart part diagnosis, and the variance value correction unit 15 is disabled in the abdominal part diagnosis, so that the variance value of the flow is true. It comes to be evaluated close to the value of. That is, it is possible to prevent the variance value of the flow from being evaluated to a value apart from the true value due to the characteristics of the MTI filter.

[0022]

According to the ultrasonic diagnostic apparatus of the present invention, M
It is possible to prevent the variance value of the flow from being evaluated to a value apart from the true value due to the characteristics of the TI filter.
Therefore, the reliability of diagnosis can be improved.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of filter characteristics.

FIG. 3 is an explanatory diagram showing a relationship among clutter components, blood flow components, and filter characteristics of an MTI filter.

FIG. 4 is an explanatory diagram of correction of a variance value.

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

FIG. 6 is an explanatory diagram of clutter component removal by an MTI filter.

FIG. 7 is an explanatory diagram showing a signal component after the clutter component is removed.

FIG. 8 is an explanatory diagram of clutter component removal by a filter characteristic of a relatively low cutoff frequency.

FIG. 9 is an explanatory diagram illustrating a signal component after the clutter component is incompletely removed.

FIG. 10 is an explanatory diagram of clutter component removal by a filter characteristic of a relatively high cutoff frequency.

FIG. 11 is an explanatory diagram showing a signal component in which a blood flow component is also partially removed.

[Explanation of symbols]

 100 ultrasonic diagnostic apparatus 1 ultrasonic probe 9,10 MTI filter 11 input device 15 dispersion value correction unit 16 bandwidth ratio calculation unit 17 adjustment coefficient setting unit 18 correction coefficient calculation unit 19 valid / invalid switching unit 20 correction multiplication unit σ, σ ', σ ”variance value α bandwidth ratio β adjustment coefficient γ correction coefficient

Claims (2)

[Claims] 1. An ultrasonic echo signal is transmitted from an ultrasonic probe into a subject, an ultrasonic echo signal is received from the subject, and the ultrasonic echo signal is passed through a preselected MTI (Moving Target Indication) filter. In the ultrasonic diagnostic apparatus that removes the low frequency component of, and acquires and displays at least the dispersion value of the flow based on the ultrasonic echo signal from which the low frequency component has been removed, the filter characteristic of the selected MTI filter is acquired. An ultrasonic diagnostic apparatus is provided with a dispersion value correcting means for correcting the dispersion value of the flow based on the filter characteristic. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the dispersion value correcting means determines a bandwidth ratio between the bandwidth of the selected MTI filter and the reference bandwidth, and the bandwidth ratio calculating means. It is characterized by comprising a correction coefficient calculation means for calculating a correction coefficient by multiplying the width ratio by an adjustment coefficient, and a correction multiplication means for calculating a correction dispersion value by multiplying the dispersion value of the flow by the correction coefficient. Ultrasonic diagnostic equipment.