JPH0716226A - Ultrasonic doppler diagnostic device - Google Patents

Abstract

PURPOSE:To enhance the estimated accuracy of interpolated speeds, and concurrently prevent a deletion phenomenon in display by producing imaginary complex interpolated data between actual scanning lines based on complex data in a plurality of actual scanning lines. CONSTITUTION:A vector interpolating unit 14 which processes vector interpolation for the real number section and the imaginary number section of the output of a self correlation unit respectively, is connected to the self correlation unit 13 estimating the moving speed of a moving reflector. A speed operator 15 operating the speed in scalar quantity based on complex data outputted out of the vector interpolating unit 14, and a dispersion operator 16 operating dispersion data on the same basis are connected in parallel. In this place, the complex data R(i+1) of an imaginary scanning line #1+1 between real scanning lines out of the complex signal outputs of the self correlation unit 13, is operated based on the average output Rn (i+1) of the complex number data R(i) of a real scanning line #i and the complex data R(i+2) of a real scanning line #(i+2), so that it is switched over by a multiplexer in response to the output timing of an imaginary scanning line so as to be outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a blood flow velocity in a living body,
More particularly, the present invention relates to an ultrasonic Doppler diagnostic apparatus that generates virtual complex interpolated data between actual scan lines in order to improve the scan line density of color flow display.

[0002]

2. Description of the Related Art In an ultrasonic Doppler diagnostic apparatus, in order to improve the S / N ratio of color flow display, ultrasonic waves are transmitted and received about 10 times on the same scanning line and averaged to obtain speed data of scalar quantity. ing. Then, the same calculation is performed for the next scanning line, and the scanning lines that are sequentially scanned are moved to form a two-dimensional color flow image.

Therefore, the complete image time for one frame of the color flow image becomes longer than the complete image time for one frame of the normal echo tomographic image, and the decrease in the frame rate makes it difficult to perform detailed time phase analysis. There was a problem.

Therefore, in order to solve this problem, as shown in FIG. 8, the scanning line density of the black and white echo display and the scanning line density of the color flow display are set to about 2: 1 to display the color flow roughly. We are trying to prevent the frame rate from decreasing. That is, the color flow is displayed by scanning lines shown by broken lines, and the black and white (B / W) echo is displayed by scanning lines shown by solid lines and broken lines. However, since the display is rough as it is, the speed output of the scalar amount is subjected to interpolation processing (scalar interpolation processing) such as Rθ conversion (polar coordinate conversion) in a display system such as a digital scan converter (DSC) to smooth the color flow display. ing.

For example, the autocorrelation values R ₁ and R _{2 at} two points are
As shown in FIG. 9, when R ₁ = A ₁ e ^{j θ} 1 R ₂ = A ₂ e ^{j θ} 2, the respective deviation angles are θ ₁ = Arg {R ₁ } θ ₂ = Arg {R ₂ } And the value to be interpolated is θ = (θ ₁ + θ ₂ ) / 2.

Here, A ₁ is the amplitude of R ₁ and A ₂ is the amplitude of R ₂ .

[0007]

However, in the above-described scalar interpolation processing, when the velocities are spatially distributed near the turnaround velocity, the maximum value of the positive velocity and the maximum value of the negative velocity are averaged. However, there is a problem that it is erroneously estimated to be almost zero, and a blackout phenomenon occurs in the color flow display.

Therefore, in order to solve this problem, for speeds above a predetermined value, the speed interpolation processing is performed in consideration of the turning back condition, or the maximum value of the positive speed and the maximum value of the negative speed are increased. A method of displaying the same color in the vicinity of the value has been proposed.

However, in the above-mentioned scalar interpolation processing,
Since only the argument (velocity) of the autocorrelation value is simply interpolated, there is a problem that the estimation accuracy of the interpolated velocity is poor. Furthermore, in the above-described scalar interpolation processing, as shown in FIG. 10, interpolation is also performed on isolated color noise, which increases the frequency of occurrence of noise, and the SN ratio of the color flow before interpolation. There was a problem that it was worse than that.

The present invention has been made to solve the above problems, and an object thereof is to obtain real part and imaginary part data of a complex autocorrelator output obtained from real scanning lines of a plurality of color flows. Based on the original, complex data interpolated between actual scanning lines is generated by vector interpolation processing that interpolates each component of complex data, the speed is calculated from this data, and the scanning line density of color flow display is improved, An object of the present invention is to provide an ultrasonic Doppler diagnostic apparatus capable of increasing speed estimation accuracy and reducing noise.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. First, an ultrasonic pulse is transmitted to a living body at a predetermined repetition period, and An ultrasonic Doppler diagnostic device that detects the Doppler shift frequency of the reflected reflected wave and displays the motion velocity of the motion reflector, and performs an interpolation process that generates interpolation data from the data acquired from the actual scanning line. At
A real part data interpolating circuit for estimating data on the motion velocity of the motion reflector and outputting a complex signal, and performing data interpolation based on the real part of the complex signal output of the autocorrelation calculator and the autocorrelation A vector interpolator having an imaginary part data interpolation circuit that performs data interpolation based on the imaginary part of the complex signal output of the arithmetic unit is provided, and virtual complex interpolation data is generated between complex data in a plurality of real scanning lines and real scanning lines. The second feature is that the first feature is
In the above configuration, an average value calculator for calculating an average value of a plurality of autocorrelator outputs in the ultrasonic pulse transmission direction is provided between the autocorrelation calculator and the vector interpolator.

[0012]

In the ultrasonic Doppler diagnostic apparatus based on the above configuration, the complex output from the autocorrelation calculator is sent to the vector interpolator. The real part data interpolation circuit in the vector interpolator performs data interpolation based on the real part of the complex signal output, and the imaginary part data interpolation circuit in the vector interpolator performs data interpolation based on the imaginary part of the complex signal output.

Data interpolation is performed as described above, virtual complex interpolated data is generated between real scanning lines from complex data on a plurality of real scanning lines, and the motion speed is calculated from this data to calculate the scanning lines in the display. Improves density. Therefore,
Since the interpolation is performed in consideration of the amplitude of the autocorrelation value as well, the estimation accuracy of the interpolated speed can be increased and the loopback determination is not necessary. Further, when a plurality of complex data are averaged in the distance direction, the variance of noise becomes small, so that the frequency of appearance of noise becomes low and the SN ratio is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an ultrasonic Doppler diagnostic apparatus according to the present invention. The ultrasonic Doppler diagnostic apparatus includes a probe 1 that transmits and receives ultrasonic waves to and from the living body 100. The probe 1 transmits an electric signal to the probe 1 at a predetermined repetition period, and at the same time, a motion reflector inside the living body 100. A transmitter / receiver 2 for receiving the reception signal of the probe 1 that receives the reflected wave reflected by is connected. Then, the transmitter / receiver 2 scans the ultrasonic pulse beam emitted from the probe 1 by mechanical or electrical angle deflection or the like, and periodically scans the living body 100 with the ultrasonic pulse beam or makes a desired deflection. A scan controller 3 that stops scanning at an angle, an amplifier 4 that amplifies a reception signal received by the transceiver 2, and a quadrature detector 5 that converts the reception signal received by the transceiver 2 into a complex signal are arranged in parallel. Connected,
The scanning controller 3 is connected to a timing signal generator 6 that generates a reference signal input to the quadrature detector 5 and an interpolation control signal input to the vector interpolator 14.

A detector 7 is connected to the amplifier 4, and an A / D converter 8 for converting an analog output of the detector 7 into a digital signal is connected to the detector 7. Further, a digital scan converter (DSC) 9 is connected to the A / D converter 8, and the DSC 9 is connected to the DSC 9.
A D / A converter 10 for converting the output of 9 into an analog signal is connected, and a display 11 is connected to the D / A converter 10.

On the other hand, a clutter removing filter 12 is connected to the quadrature detector 5, and the clutter removing filter 12 is connected.
Includes an autocorrelator 13 for estimating the motion velocity of the motion reflector.
Are connected. Further, the autocorrelator 13 is connected to a vector interpolator 14 that performs vector interpolation processing on the real number part and the imaginary number part of the output of the autocorrelator 13, respectively. A speed calculator 15 that calculates a speed V of a scalar amount from complex data output from 14 and a dispersion calculator 16 that calculates distributed data are connected in parallel, and the speed calculator 15 and the dispersion calculator 16 are connected to each other. Are connected to the DSC 9.

FIG. 2 shows a vector interpolator 14 according to the present invention.
3 is a block diagram showing the configuration of FIG.

The vector interpolator 14 comprises a real part data interpolation circuit part 14a and an imaginary part data interpolation circuit part 14b. The real part data interpolation circuit part 14a is a multiplexer 1.
9 and a delay line 17 and an adder 18, and performs data interpolation based on the real part R _x of the complex output of the autocorrelator 13. Similarly, the imaginary part data interpolation circuit part 14b is also composed of a multiplexer 22, a delay line 20, and an adder 21, and performs data interpolation based on the imaginary part R _y of the complex output of the autocorrelator 13. The delay lines 17 and 20 perform delay processing equal to the transmission repetition period.

Here, the principle of the vector interpolation processing will be described.

For example, as shown in FIG. 3, the autocorrelation values R ₁ and R ₂ at two points of the complex data from the actual scanning line in the complex signal output of the autocorrelator 13 are R ₁ = A _{When 1} e ^{j θ} 1 R ₂ = A ₂ e ^{j θ} 2, the value to be interpolated is R = R ₁ + R ₂ .

Next, the operation of this embodiment will be described.
Of the complex signal output of the autocorrelator 13, # in FIG.
The complex data from the actual scanning line i, # i + 2 are directly input to the multiplexers 19 and 22 shown in FIG. 2 and output at the display timing of the actual scanning line.

On the other hand, virtual scan line # i + between real scan lines
The complex data R (i + 1) of 1 is the complex data R (i) of the actual scanning line #i and the complex data R of the actual scanning line # (i + 2).
It is calculated from the average output R _m (i + 1) of (i + 2), and the multiplexer 1 according to the output timing of the virtual scanning line.
The output is switched by switching 9 and 22. That is, it is calculated according to the following formula.

R _m (i + 1) = {R (i) + R (i + 2)} / 2 (1) This vector-interpolated complex data R _m (i + 1) is input to the velocity calculator 15 and the dispersion calculator 16. V (i + 1) = Arg {R _m (i + 1)} (2) σ ² (i + 1) = 1- {| R _m (i + 1) | / R _m0 (i + 1)} (3) Scalar amount Compute the velocity and variance data of. R _m0 (i + 1) is a vector-interpolated amount of the power of the autocorrelator input.

In the present invention, as described above, the autocorrelator 13
Since not only the declination angle but also the amplitude value is taken into consideration in the output from, the black void phenomenon does not occur even when the velocity is spatially distributed in the vicinity of the turnaround velocity. As shown, the point on the real scan line # i + 2 has a velocity of 0.
Even if the point of the actual scanning line #i has color noise, the interpolation value of the scanning line # i + 1 of the virtual color flow to be interpolated has a speed close to 0 and is not displayed.

The second embodiment shown below performs the vector interpolation processing in the same manner as the first embodiment, but the feature of this embodiment is that two points of the complex adjacent to each other in the transmission / reception direction of the ultrasonic beam are complex. The SN ratio is improved by adding the data. That is, as shown in FIG. 5, the ultrasonic Doppler diagnostic apparatus discriminates noise from blood flow by a predetermined threshold value in amplitude when displaying blood flow. However, as shown by the shaded area in FIG. 5, some noise may exceed the threshold value and be mixed into the output of the display. Generally, the variance (σ ² ) of a random signal such as noise is proportional to the reciprocal of the data length (N). Therefore, when the complex data of two points adjacent in the distance direction are added, the variance of noise becomes small and the frequency of occurrence of noise above the threshold becomes low. As a result, the SN ratio of the color flow display is improved.

The operation of this embodiment will be specifically described below.
The configuration of this embodiment is almost the same as that of the above embodiment,
As shown in FIG. 7, the autocorrelator 13 and the vector interpolator 1
4 and the average value calculator 25. Here, in the average value calculator 25, the scanning line is # i-th and the depth is #j.
Th output of autocorrelator 13 and R (i, j), the complex data obtained by averaging the distance direction When _{R m (i, j),} R m (i, j) = {R (i, j ) + R (i, j + 1)} / 2 (4) is calculated.

Similarly, the actual scan line # i + given by the following equation:
The second average value {R _m (i + 2, j)} is calculated.

R _m (i + 2, j) = {R (i + 2, j) + R (i + 2, j + 1)} / 2 (5) Then, the vector interpolator 14 calculates the distance direction calculated by the fourth and fifth equations. Of the virtual color flow scanning line # i + 1th interpolation data R _m (i +
1, j) is calculated from the following equation.

R _m (i + 1, j) = {R _m (i, j) + R _m (i + 2, j)} / 2 (6) Then, the complex interpolation data is sent to the speed calculator 15 and the dispersion calculator 16. Then, the velocity and dispersion data of the scalar amount are calculated from the second and third equations and input to the DSC 9. Then, the DSC 9 superimposes the color flow on the monochrome echo image and displays it on the display 11. Here, the variance of the variance data calculated by averaging the complex data is small, and the frequency of occurrence of noise above the threshold is low.

In the above embodiment shown in FIG. 6,
Data of four points R (i, j), R (i, j + 1), R (i
The complex data R (i + 1, j) of the virtual scanning line # i + 1 is obtained by + 2, j) and R (i + 2, j + 1), but the data is not limited to this and may be data of 6 points, 8 points, or the like. .

[0032]

As described above, according to the ultrasonic Doppler diagnostic apparatus of the present invention, the real part data interpolation circuit in the vector interpolator performs data interpolation based on the real part of the complex output from the autocorrelation calculator. At the same time, the imaginary part data interpolation circuit in the vector interpolator performs data interpolation based on the imaginary part of the complex output from the autocorrelation calculator, and the virtual complex interpolation data between the complex data in the multiple actual scanning lines and the actual scanning lines. Since it is configured so as to improve the scanning line density, the interpolation is performed in consideration of the amplitude of the autocorrelation value, so that the estimation accuracy of the interpolated speed can be increased, and the return determination is not necessary, and It is possible to prevent the blackout phenomenon. Furthermore, when averaging a plurality of complex data in the distance direction, noise can be reduced and the S / N ratio of the color flow can be improved, whereby a smooth and continuous color flow image can be obtained.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a vector interpolator according to the present invention.

FIG. 3 is a diagram for explaining the principle of vector interpolation processing according to the present invention.

FIG. 4 is an explanatory diagram for explaining reduction of color noise by vector interpolation processing according to the present invention, and FIG. 4 (a) is a diagram showing display positions of captured data and interpolation data,
(B) is a figure which shows the speed of each display position.

FIG. 5 is a diagram showing a relationship between noise amplitude and blood flow amplitude histogram.

FIG. 6 is a diagram for explaining vector interpolation processing after averaging processing in the distance direction according to the present invention.

FIG. 7 is a block diagram showing a part of a configuration of an ultrasonic Doppler diagnostic apparatus according to a second embodiment of the present invention.

FIG. 8 is a diagram showing scanning line densities of black and white echo and color flow.

FIG. 9 is a diagram for explaining a conventional scalar interpolation process.

FIG. 10 is a diagram for explaining that color noise appears in a conventional scalar interpolation process.

[Explanation of symbols]

 1 probe 2 transceiver 11 indicator 13 autocorrelator 14 vector interpolator 14a real part data interpolation circuit part 14b imaginary part data interpolation circuit part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Okada 6-22-1, Mure, Mitaka City, Tokyo Aloka Co., Ltd.

Claims (2)

[Claims] 1. An ultrasonic Doppler system for transmitting ultrasonic pulses to a living body at a predetermined repetition period, detecting a Doppler shift frequency of a reflected wave reflected by an in-vivo motion reflector, and displaying a motion velocity of the motion reflector. An ultrasonic Doppler diagnostic device that performs interpolation processing to generate interpolation data based on the data acquired from the actual scanning line in the diagnostic device has an autocorrelation calculator that estimates the motion velocity of the motion reflector and outputs a complex signal. A real part data interpolation circuit that performs data interpolation based on the real part of the complex signal output of the autocorrelation calculator and an imaginary part data interpolation circuit that performs data interpolation based on the imaginary part of the complex signal output of the autocorrelation calculator An ultrasonic Doppler characterized by including a vector interpolator having the above, and generating virtual complex interpolation data between real scanning lines from complex data at a plurality of real scanning lines. Cross-sectional devices. 2. An average value calculator for calculating an average value of a plurality of autocorrelator outputs in the ultrasonic pulse transmission direction is provided between the autocorrelation calculator and the vector interpolator. The ultrasonic Doppler diagnostic apparatus according to 1.