JPH0543381B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic Doppler diagnostic device, in particular, which emits an ultrasonic pulse wave into a subject and performs operation inside the subject based on a signal subjected to the Doppler effect. The present invention relates to an ultrasonic Doppler diagnostic device that displays on a screen information useful for knowing the movement state of a reflector.

[Prior Art] Ultrasonic Doppler diagnostic equipment is well known, which displays an image of the state of cardiac blood flow using a moving reflector that emits an ultrasonic pulse beam into a subject such as a living body. By receiving reflected echoes from within and detecting the Doppler effect on the reflected echoes as a shift in the ultrasonic carrier frequency, the velocity state of blood flow, etc. is determined.

Conventionally, as such a device, the
There is one shown in No. 44494. According to this,
By complex-transforming the reflected echo signal into a complex signal and performing autocorrelation calculations based on this complex signal, an accurate velocity distribution can be obtained in real time. This velocity distribution can then be displayed superimposed on the B-mode tomographic image.

[Problems to be Solved by the Invention] However, in conventional devices, the velocity information displayed as an image is distributed as a set of velocity information at each point within the subject, and it is difficult to determine how the velocity distribution is within a predetermined space. It was not possible to obtain detailed information such as whether the situation had changed.

In ultrasound diagnosis, which observes the state of movement, the velocity may change rapidly in a certain area (space), such as blood flow near heart valves in the heart, and it is difficult to accurately display images of such situations. if you can,
It becomes possible to provide new information that can improve the efficiency of diagnosis.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an ultrasonic Doppler diagnostic device that is capable of displaying new information indicating the state of velocity change in a spatial domain as an image. .

[Means for Solving the Problem] In order to achieve the above object, the invention according to the first claim emits an ultrasound pulse into a subject, demodulates the reflected echo signal, and then converts the Doppler shift frequency to In an ultrasonic Doppler diagnostic device having a velocity distribution calculator that detects and calculates a motion velocity distribution, a velocity distribution signal on the ultrasound radiation beam axis (radial direction) obtained by the velocity distribution calculator is inputted. Velocity gradient calculation has a delay circuit that delays by a time sufficiently smaller than the repetition period, and calculates the spatial velocity gradient on the ultrasound radiation beam axis by calculating the difference between the input signal and output signal of this delay circuit. It is characterized by having a container.

In addition to the speed gradient calculator, the invention according to claim 2 also brightens the speed gradient obtained by the speed gradient calculator according to its magnitude, and changes the polarity of the gradient using different hues. It is characterized by being equipped with a display device that identifies and displays the information in color.

[Operation] According to the above configuration, the ultrasound reflected echo reflected from within the subject is supplied to the velocity distribution calculator,
First, velocity information at consecutive points on the ultrasonic radiation axis is obtained as a velocity distribution signal. This speed distribution signal is supplied to the speed gradient calculator, delayed by a time sufficiently smaller than the repetition period and outputted by the delay circuit, and this output signal is subtracted from the input signal of the delay circuit. This difference signal corresponds to the differentiation of the waveform of the velocity distribution signal, and unlike mere acceleration information, it indicates the gradient (rate of change) of velocity in space, thereby providing new diagnostic information for the subject space. can be provided.

Further, the speed gradient information is converted into an image signal by the display device, and the positive and negative speed gradients are converted into image signals of different colors, and the magnitude of the gradient is brightness-modulated. As a result, the velocity gradient information is displayed in color, superimposed on the conventional tomographic image displayed in white.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit block diagram of a schematic configuration of an ultrasonic Doppler diagnostic apparatus according to the present invention.
The oscillator 10 is composed of a crystal oscillator, etc., and a stable high frequency signal is supplied to a frequency division synchronization circuit 12, which converts the transmission repetition frequency signal 10 into a frequency division synchronization circuit 12.
0, complex reference signals 101, 102, sweep signal 10
3 etc. can be obtained.

The transmission repetition frequency signal 100 is supplied to the probe 18 via the drive circuit 14 and the transmission/reception switching circuit 16, and by exciting the transducer within the probe 18, the ultrasonic pulse beam is transmitted into the subject 20. is output to.

The reflected echo from the subject 20 is converted into an electrical signal by the probe 18, and is sent from the transmission/reception switching circuit 16 to the high frequency amplifier 22 where it is subjected to a desired amplification action, and then the output of one of the signals is It is supplied to the display device 28 side using a CRT as a normal B mode or M mode display signal, and the other output 10
4 is a complex signal converter 3 for calculating the motion velocity.
4.

The output signal for the B-mode display etc. is outputted to the display device 28 via the detector 24 and the video amplifier 26 (105), which modulates the brightness of the reflected echo signal to display an image such as a tomographic image. becomes.

Further, a scan controller 30 for scanning the ultrasonic pulse beam of the probe 18 by mechanical or electronic angular deflection (sector scanning);
Sweep signal 10 obtained from the frequency division synchronization circuit 12
A sweep circuit 32 is provided which performs sweep control of the display device 28 by inputting the signal 3.

On the other hand, the output of the high frequency amplifier 22 (received high frequency signal 104) is sent to two mixers 36a and 36b.
and two low pass filters (LPF) 38a,
38b, and the mixer 36 converts the received high frequency signal into two complex reference signals 10 having a phase difference of 90 degrees.
1,102. Then, a signal with a frequency of the sum and difference of both frequencies of the received high-frequency signal and the complex reference signal is output, and by passing this signal to the next-stage low-pass filter 38, the frequency component of the difference is extracted. If one is the real part and the other is the imaginary part, it is converted into a complex signal.

The complex signal obtained in this way is supplied to the speed distribution calculator 40, for example,
As shown in Japanese Patent No. 44494, the velocity can be determined from the argument of the autocorrelation signal of the complex signal.
That is, the deviation of the ultrasonic carrier frequency that appears as the Doppler effect can be obtained from the calculation of the declination of the complex signal, and the declination θ is expressed as follows, where R is the real part of the complex signal and I is the imaginary part. The relational expression holds true.

θ=tan ^-1 (I/R) = 2π _d T...(1) (where _d is the Doppler shift frequency, T is the transmission repetition period) Therefore, the Doppler shift frequency _d is _d = θ/2πT... Calculated from (2).

Note that this velocity calculation can also be obtained by other methods instead of using autocorrelation, and the velocity can be calculated by pushing out the Doppler shift frequency component received by the reflected echo.

The characteristic feature of the present invention is that it not only shows velocity information at each point as described above, but also extracts new information such as velocity gradient in the spatial domain. Arithmetic unit 42
It is equipped with

The velocity gradient calculator 42 is composed of a delay circuit 44 and a difference calculator 46, and the delay circuit 44 transmits the velocity distribution signal 106 on the ultrasonic radiation axis outputted from the velocity distribution calculator 40.
It is delayed by a delay time Δt that is sufficiently smaller than
The difference between this delayed signal and the input signal of the delay circuit 44 is calculated. That is, the output of the velocity distribution calculator 40 is a signal indicating the velocity distribution at each point in the depth direction on the ultrasonic beam axis, and as shown in A in FIG. (distance from the tentacle 18) is a signal of waveform a in which the vertical axis represents the magnitude of velocity.

The output of the delay circuit 44 is a signal b obtained by shifting the speed distribution signal by a minute delay time Δt, as shown in FIG. As shown in
It is obtained by subtracting signal waveform b from signal waveform a. The output of this difference calculator 46 is a signal that has been processed equivalent to differentiation, and indicates the velocity gradient on the ultrasound beam axis, and from this it is possible to know the velocity gradient in a certain spatial region in the depth direction. I can do it. In this case, in order to improve the accuracy of the velocity gradient value, it is preferable to make Δt as small as possible.

Further, in the embodiment, an averaging circuit 52 consisting of an adder 48, a delay line 50, and a weighting circuit 51 is provided in order to improve the accuracy of the speed gradient signal. And 1 at day line 50
After applying a predetermined weight to the output delayed by a period (T), it is added to the input signal at the current time in an adder 48, and by accumulating this multiple times, the output of the velocity gradient calculator 42 becomes smaller. It is possible to extract a large output even if the In this case, by changing the weighting of the weighting circuit 51, the degree of averaging can be changed, and in this way, noise components can be removed and a good signal can be extracted.

The average speed gradient information output from the averaging circuit 52 is sent to the display device 2 via the changeover switch 53.
8, and by performing predetermined display processing here, it is possible to display in various display methods such as color image display and numerical display.

That is, as shown in FIG. 3, the display device 28 includes memories 54a, 54b, 54c,
A switch 56 that switches the output of this memory 54
a, 56b, 56c, a color calculation unit 58 that converts various signals into color image signals, and D/A converters 60a, 60b, 60c that converts digital signals output from the color calculation unit 58 into analog signals.
and a CRT display 62.

The video amplifier 2 is stored in the memory 54a.
The tomographic image information 105 output from the memory 5
4b stores speed information 106 output from the speed distribution calculator 40, and memory 54c stores speed gradient information 107, which is characteristic of the present invention.
These information are processed by color calculator 58 as red (R signal),
It is converted into three color image signals: green (G signal) and blue (B signal). Thereafter, the RGB signals are supplied to the CRT display 62 via the D/A converter 60, and a color image is displayed in a mixed hue of the respective RGB signals.

For example, tomographic image information is displayed as white because each of the RGB signals is output as an equal signal. In addition, the velocity signal displays its velocity direction in different colors, and in the example, the positive direction with respect to the ultrasonic beam emission direction is yellow, which is a mixture of red (R signal) and green (G signal), and the negative The direction is shown in blue-green, which is a mixture of blue (B signal) and green (G signal), and the magnitude of the speed is displayed in brightness.

A characteristic feature of the invention according to the second claim is that in order to display the speed gradient information obtained by the speed gradient calculator 42 in easy-to-read color, the brightness is modulated according to the magnitude of the speed gradient, and the gradient is This is to identify positive and negative signals using different hues and display them in color.

In the example, a positive velocity gradient in the ultrasonic beam radiation direction (depth direction) is shown in red (R signal).
A negative velocity gradient is represented in blue (B signal), and the magnitude of the gradient is displayed in brightness. This velocity gradient information is displayed in place of the velocity information and is displayed superimposed on the tomographic image, but it is also possible to display the velocity gradient information and velocity information in a superimposed manner.

Furthermore, in the embodiment, the speed gradient value can be displayed numerically, and by specifying a predetermined location with a cursor provided on the screen, the gradient value can be displayed at a predetermined location on the screen. is displayed numerically.

The embodiment has the above configuration, and its operation will be explained below.

First, as described above, pulsed ultrasound is output from the deep probe 18 to the subject 20 by the scan controller 30, while a reflected echo signal reflected from the subject 20 is received by the probe 18. One side is sent to a detector 24 as a tomographic image signal via a high frequency amplifier 22.
The other signal is supplied to a complex signal converter 34 as a velocity signal.

The received signal supplied to this complex signal converter 34 is converted into a complex signal, and then the velocity distribution calculator 4
By performing an autocorrelation calculation using 0, a velocity distribution signal in the ultrasonic beam radiation direction is obtained as shown in FIG. 2A.

This speed distribution signal is then processed by a speed gradient calculator 4.
By calculating the difference between the output signal and the input signal of the delay circuit 44, a velocity gradient signal shown in FIG. 2C is output.

This velocity gradient signal indicates a spatial velocity gradient on the ultrasound beam axis, and is different information from acceleration information at a specific point. That is, while acceleration information indicates a temporal change in velocity at a specific point, the present invention indicates a gradient in velocity in a space (area) in the ultrasound beam direction, that is, in the depth direction. This makes it possible to know the velocity gradient distribution state in a desired range of region, such as within the heart.

This velocity gradient information is provided to a display device 28,
Although it will be displayed in color, this information is displayed superimposed on the tomographic image signal displayed using white luminance modulation.

As shown in FIG. 3, input/output control of the tomographic image signal 105, velocity signal 106, and velocity gradient signal 107 is performed by the sweep signal 103, and first, by closing the switch 56a, an image with equal RGB values is generated. A signal is formed, thereby displaying a tomographic image inside the subject using white luminance modulation. Then, the velocity gradient information is transmitted by closing the switch 56c, and in the case of the positive direction, the red image signal (R
signal), and in the negative direction, a blue image signal (B
signal). In this case, the magnitude of the velocity gradient is expressed by the amplitude of the signal, which is converted into brightness information on the CRT display 62. This velocity gradient information can be displayed by specifying a predetermined region, or can be displayed in the entire tomographic image, so that velocity gradient information can be observed in the tomographic image showing the actual organ. .

Although the speed information can be displayed as an image by closing the switch 56b, the speed gradient information can also be displayed superimposed on this speed information.

In the embodiment described above, the speed gradient information is displayed in color, but it is also possible to display the output of the speed gradient calculator 42 as it is as an image. That is,
As shown in FIG. 2C, the output of the velocity gradient calculator 42 displays the change in gradient value in the depth direction as a curve, so this waveform can be directly processed for monochrome display and output. For example, the state of the velocity gradient can be displayed in a format that is easy to check at a glance.

Further, the velocity gradient information computed by the velocity gradient computing unit 42 can be taken out from the terminal 64, so that it can be subjected to other arithmetic processing and used for analyzing the motion state.

[Effects of the Invention] As explained above, according to the first claim of the present invention, it is possible to provide unprecedented new information such as spatial velocity gradient, and according to the second claim, Velocity gradient information can be displayed in an easily observable form by superimposing it on the image.

As a result, it is possible to easily determine the spatial gradient (rate of change) of velocity in a certain area, such as the heart, and it is possible to provide information useful for image diagnosis of regions where velocity changes rapidly.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing a schematic configuration of an ultrasonic Doppler diagnostic apparatus according to the present invention, FIG. 2 is a waveform diagram showing signal processing of the velocity gradient calculator of FIG. 1, and FIG. 1 is a block diagram showing a circuit configuration of a display device. FIG. 12... Frequency division synchronization circuit, 16... Transmission/reception switching circuit, 1
8... Probe, 28... Display device, 30... Scan controller, 32... Sweep circuit, 34... Complex signal converter, 4
0... Speed distribution calculator, 42... Speed gradient calculator, 4
4... Delay circuit, 46... Difference calculator, 52... Average circuit, 54... Memory, 58... Color calculator, 62...
CRT display.

Claims (1)

[Claims] 1. Ultrasonic Doppler diagnosis having a velocity distribution calculator that emits ultrasound pulses into a subject and demodulates the reflected echo signal, then detects the Doppler shift frequency and calculates the motion velocity distribution. The apparatus has a delay circuit that inputs the velocity distribution signal on the axis of the ultrasonic radiation beam obtained by the velocity distribution calculator and delays it by a time sufficiently smaller than the repetition period, and the input signal and output of this delay circuit An ultrasound Doppler diagnostic device comprising a velocity gradient calculator that computes a spatial velocity gradient on an axis of an ultrasound radiation beam by computing a difference between the signals and the ultrasound beam. 2. In an ultrasonic Doppler diagnostic apparatus having a velocity distribution calculation unit that emits an ultrasound pulse into a subject and demodulates its reflected echo signal, and then detects a Doppler shift frequency and calculates a motion velocity distribution. It has a delay circuit that inputs the velocity distribution signal on the ultrasonic radiation beam axis obtained by the calculator and delays it by a time sufficiently smaller than the repetition period, and calculates the difference between the input signal and output signal of this delay circuit. A velocity gradient calculator that calculates the spatial velocity gradient on the axis of the ultrasound radiation beam, and a velocity gradient calculator that modulates the brightness of the velocity gradient obtained by this velocity gradient calculator according to its magnitude, and also changes the sign of the gradient. An ultrasonic Doppler diagnostic device comprising: a display device that identifies and displays colors using different hues. 3. In the apparatus according to claim 1, the velocity gradient value on the ultrasound beam axis obtained by the velocity gradient calculator is
An ultrasonic Doppler diagnostic device characterized by displaying a distribution curve with depth as the horizontal axis or numerically.