JPH0323054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasound Doppler diagnostic device, and particularly to a moving reflector within a subject, such as a heart, for detecting blood flow velocity,
The present invention relates to an ultrasonic Doppler diagnostic device that measures blood flow and displays images.

[Prior art] An ultrasonic pulse wave with a constant repetition frequency is emitted into a subject, a reflected wave from a moving reflector inside the subject is received, and a frequency shift of the received Doppler signal is detected. A pulsed Doppler device that measures and displays the velocity of a moving reflector from this Doppler frequency shift is well known.

This pulsed Doppler device frequency-analyzes the received Doppler signal from a certain region (sample volume) within the subject and modulates its power spectrum in brightness, and displays temporal changes in brightness on the time axis, that is, in M mode. By displaying this, the distribution state of the velocity of the motion reflector can be represented on the CRT screen.

Therefore, in M mode display, the upper end, lower end, and average values of the power spectrum can be calculated, and the maximum frequency, minimum frequency, and average frequency of the Doppler frequency deviation can be displayed as the maximum velocity, minimum velocity, and average velocity. .

[Problems to be Solved by the Invention] However, the conventional M-mode display apparatus has a problem in that it is only possible to obtain blood flow information in a very limited area within the subject.

That is, the frequency analysis requires a lot of time, and it is impossible to perform the frequency analysis in real time over the entire area to be diagnosed. Therefore, the current situation is to selectively perform frequency analysis on a part of the diagnostic region displayed as an image, and display detailed data only on that part.

On the other hand, in recent years, the so-called Doppler tomography method, which two-dimensionally displays blood flow velocity distribution within a subject, has been put into practical use (Japanese Patent Laid-Open No. 119929/1983). According to this method, the average value of the velocity and the variance of the velocity of the motion reflector within the subject are immediately determined by an autocorrelation method, and the velocity distribution in a wide diagnostic region is displayed as an image in real time. However, the display speed of such a device is an average speed, and it is not possible to display the maximum speed or minimum speed of a moving reflector in a region of one tomographic image in real time.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to quantitatively detect the maximum or minimum velocity of a moving reflector within a subject over the entire tomographic plane, and to detect it in real time. An object of the present invention is to provide an ultrasonic Doppler diagnostic device that displays images.

[Means for Solving the Problems] In order to achieve the above object, the present invention mixes a received Doppler signal obtained by transmitting and receiving an ultrasonic pulse wave into a subject and a complex reference signal. A complex signal converter that converts the received Doppler signal into a complex signal, and outputs an average frequency signal of a Doppler shift frequency corresponding to the average velocity of a moving reflector within the subject based on the output of the complex signal converter. In an ultrasonic Doppler diagnostic apparatus that has an average frequency calculator and a variance calculator that calculates the dispersion of the average frequency signal of the Doppler shift frequency, and displays an image of the velocity distribution of a moving reflector, complex signal conversion is performed. The maximum and minimum values of the Doppler shift frequency or their The present invention is characterized in that it includes a maximum/minimum shift frequency calculator that calculates either one of them.

[Operation] According to the above configuration, first, the complex signal converter mixes the received Doppler signal obtained by transmitting and receiving the ultrasonic pulse wave into the subject and the complex reference signal, and converts the Doppler frequency shift. The received Doppler signal is converted into a complex signal, and this complex signal is output by an average frequency calculator as an average frequency signal having a Doppler shift frequency corresponding to the average velocity signal. Further, the dispersion of the average frequency signal of the Doppler shift frequency is computed by the dispersion computing unit. Then, based on these complex signals, average frequency signals, and dispersion signals, a maximum value and/or minimum value of the Doppler shift frequency is calculated by a maximum/minimum shift frequency calculator.

This Doppler shift frequency represents the speed of the moving reflector, and the maximum and minimum values allow quantitative image display of the maximum and minimum values of the speed.

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

FIG. 1 shows the circuit configuration of an ultrasonic Doppler diagnostic apparatus according to the present invention, in which the output of an oscillator 10 that generates a stable high-frequency signal is transmitted to a frequency dividing synchronization circuit 12.
The frequency dividing synchronization circuit 12 obtains various output signals of predetermined frequencies. In the embodiment, a transmission repetition frequency signal 100 for transmission, complex reference signals 101 and 102 for complex signal conversion are output, and in addition, a clock signal of the apparatus and the like are output.

The transmission repetition frequency signal 100 is transmitted to the drive circuit 1
4 and the transmission/reception switching circuit 16 to the probe 18, and by exciting the probe 18,
An ultrasonic pulse beam is transmitted into the subject.

The reflected echo returning from the subject is the probe 18
is converted into an electrical signal, sent from the transmitting/receiving switching circuit 16 to the amplifier 20, where the desired amplification effect is applied, and one of the outputs is sent to the display section as a display signal for the normal B mode or M mode. and the other output is supplied to the arithmetic processing section as a signal for calculating in-vivo blood flow information.

That is, the received signal for displaying the former B mode or M mode is sent to the detector 22, the video amplifier 24, and further to a DSC (Digital Scan Converter).
26 to the CRT display 28;
The brightness of the screen of the display 28 is modulated.

Further, by swinging the ultrasonic pulse beam of the probe 18 by mechanically or electrically deflecting the ultrasonic pulse beam, the ultrasonic pulse beam is periodically scanned within the subject. A scan controller 30 is provided to stop scanning at a desired deflection angle, and a control signal from this scan controller 30 is output to the probe 18 and is also used to control the display position.
It is output to DSC26.

On the other hand, the latter received Doppler signal for in-vivo blood flow information calculation is supplied to the complex signal converter 32, and this received Doppler signal is combined with the complex reference signals 101 and 102 input from the frequency division synchronization circuit 12. The signals are mixed to form a complex signal consisting of a real part I(t) and an imaginary part Q(t).

Then, the speed of the moving reflector is determined based on this complex signal, and in this embodiment, the speed is determined by an autocorrelation method. That is, the autocorrelation calculation is described in detail in Japanese Patent Application Laid-open No. 188433/1982, but by performing predetermined multiplication and addition/subtraction on the real part signal and the imaginary part signal of a complex signal, for example, the calculation of the complex signal is performed. Autocorrelation is calculated by calculating the conjugate product or complex product, and a complex autocorrelation signal expressed by the following equation is obtained.

=+j...(1) Then, this complex autocorrelation signal is supplied to the average frequency calculator 3 and the variance calculator 38, and the average frequency calculator 36 calculates the average frequency of the Doppler shift frequency corresponding to the average velocity signal. distributed computing unit 3
8, the state of variation in the speed signal is calculated.

That is, the former average frequency calculation is calculated by =tan ^-1 (/)/2πT...(2), and the latter variance value calculation is calculated by σ ² 2 (1-√ ² + ² )/T ² ... ...(3) is calculated. Here, T is the repetition period of the ultrasonic pulse wave.

The average frequency of the Doppler shift frequency obtained in this way corresponds to the average velocity of the moving reflector, and the dispersion value corresponds to the variation in the average velocity,
In other words, it represents the state of turbulence in blood flow, and by supplying these signals to the CRT display 28, blood flow information in the living body is displayed as an image.

A characteristic feature of the present invention is to calculate the maximum and minimum values of the Doppler shift frequency corresponding to the maximum and minimum values of the velocity of the moving projectile within the subject. A shift frequency calculator 40 is provided.

In the embodiment, the maximum and minimum deviation frequency calculation unit 40 includes a power calculation circuit 42 and a standard deviation calculation circuit 4.
4. It is composed of an equivalent band calculation circuit 46 and a maximum/minimum frequency calculation circuit 48, and the power calculation circuit 42 converts the complex signal output from the complex signal converter 32 by the sum of squares of the real part and the imaginary part. The power is calculated, and the standard deviation calculation circuit 44 calculates the standard deviation σ from the square root of the variance value output from the previous variance calculation unit 38.

Further, the equivalent band calculation circuit 46 calculates the equivalent band parameter k of the complex signal power spectrum from the outputs of the power calculation circuit 42 and the standard deviation calculation circuit 44 and the constant ε of the device, and the maximum and minimum frequency calculation circuit 48 calculates the equivalent band parameter k of the complex signal power spectrum. The maximum and minimum values of the Doppler shift frequency are calculated from the output of the circuit 46 and the output of the average frequency calculation unit 36. Note that if these arithmetic circuits are digital, they can be easily constructed using a ROM or a high-speed signal processing IC.

Next, the principle for determining the maximum and minimum values of the Doppler shift frequency will be explained.

The power spectrum of the Doppler signal received by the probe 18 is determined by the velocity distribution of the moving reflector, the spread of the ultrasound beam, the angle between the ultrasound beam and the moving reflector, for example, the direction of blood flow, or the ultrasound transmission. It depends on the frequency characteristics of the device, etc., and has a spectral distribution as shown in Figure 2a. However, the maximum and minimum values of the Doppler shift frequency cannot be specified from this spectrum.

Therefore, in the present invention, the maximum and minimum values of the Doppler shift frequency are determined by converting the spectrum shown in FIG. 2a to the box-shaped spectral distribution shown in FIG. 2b.

That is, if the upper end of the box-shaped spectrum in FIG. 2b is f max and the lower end is f min, the power spectral density Prect is expressed by the following equation.

Prect=Mo/(f max - f min)...(4) Here, Mo represents the total power obtained by integrating the power spectral density P(f) in Figure 2 a, and is expressed by the following formula. Then, the power calculation circuit 42 calculates the power.

Mo= _∞ ∫ P(f)df (5) Then, assuming that the spectral distribution is symmetric, the f max and f min are the average frequencies of the Doppler shift frequencies, and are calculated by the standard deviation calculation circuit 44. Using the standard deviation σ, it is expressed as follows.

f max=+k·σ (6) f min=−k·σ (7) Then, the above equation (4) can be expressed as follows using the above equations (6) and (7).

Prect=Mo/(2k・σ)...(8) Here, k is an equivalent band parameter that satisfies the condition shown by the following formula, and the equivalent band calculation circuit 46
It is calculated by.

−Prect/k=Mo/(2k ² σ)≦ε ...(9) This ε is determined from the S/N ratio of the device, the dynamic range of the CRT display, or the correlation with clinical data, etc. of the device itself. is a constant.

Therefore, the equivalent band parameter k is calculated from k ² =Mo/(2σε)...(10), and by substituting the data of Mo, σ, and ε into this equation (10), the equivalent band parameter k
is required.

This equivalent band parameter k is multiplied by the standard deviation σ in the equivalent band calculation circuit 46, and k.σ is output. Then, this k·σ and the output of the average frequency calculator are outputted to the maximum and minimum frequency calculation circuit 48,
Here, the maximum value f max and minimum value f min of the Doppler shift frequency are calculated from equations (6) and (7) above.

The maximum and minimum values of the Doppler shift frequency determined in this manner are supplied to the DSC 26 via the blood flow information display controller 50, where they are converted into image display signals and displayed on the CRT display 28. Ru.
The blood flow information display controller 50 simultaneously displays the average value of the Doppler shift frequency, the variance of the average value, and the blood flow velocity information corresponding to the Doppler shift frequency, the maximum value, and the minimum value, or displays a part thereof. control etc. In this case, the maximum and minimum values of the Doppler shift frequency corresponding to the maximum and minimum velocities of the motion reflector may be displayed individually using different colors and superimposed on the B-mode tomographic image, and the M-mode Alternatively, it may be displayed numerically on the B mode screen.

Furthermore, the pressure loss ΔP of blood flow, which is clinically useful diagnostic data, is calculated from the maximum velocity V of blood flow by ΔP4.
(Vmax) ² , and this pressure loss ΔP may be displayed as an image.For example, it can be obtained for the region of interest in B-mode display and used as a basis for determining the degree of valve stenosis or valve insufficiency of the aortic valve of the heart. can.

[Effects of the Invention] As explained above, according to the present invention, a maximum and minimum shift frequency calculator that calculates the maximum and minimum values of Doppler shift frequencies corresponding to the maximum and minimum velocities of a motion reflector is provided. Because of this provision, the quantitative values of the maximum velocity and minimum velocity of the motion reflector can be expressed on the image using different color displays or numerical displays.

Furthermore, diagnostic data such as pressure loss of blood flow from the maximum velocity of blood flow can be calculated in real time and displayed in two dimensions. Therefore, it is possible to contribute to image diagnosis by providing an ultrasonic Doppler diagnostic apparatus that can obtain maximum and minimum velocity information in addition to the average velocity and variance of the average velocity obtained by conventional Doppler tomography.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of the ultrasonic Doppler diagnostic device according to the present invention, FIG. 2 shows the signal spectrum, and FIG. a shows the power spectrum distribution of the Doppler signal,
FIG. b is a diagram showing a box-shaped spectral distribution transformed by the equivalent band arithmetic circuit. 12... Frequency division synchronous circuit, 18... Probe, 28
...CRT display, 32 ...Complex signal converter, 3
4... Autocorrelator, 36... Average frequency calculator,
38... Dispersion computing unit, 40... Maximum and minimum deviation frequency computing unit, 42... Power computing circuit, 44... Standard deviation computing circuit, 46... Equivalent band computing circuit, 4
8... Maximum and minimum frequency calculation circuit, 50... Blood flow information display controller.

Claims (1)

[Claims] 1. A complex signal converter that converts the received Doppler signal into a complex signal by mixing the received Doppler signal obtained by transmitting and receiving an ultrasonic pulse wave into a subject and a complex reference signal. , an average frequency calculator that outputs an average frequency signal of the Doppler shift frequency corresponding to the average velocity of the moving reflector within the subject based on the output of the complex signal converter, and an average frequency signal of the Doppler shift frequency. and a dispersion computing unit that computes the dispersion of
In an ultrasonic Doppler diagnostic device that displays an image of the velocity distribution of a moving reflector, a complex signal output from a complex signal converter, an average frequency signal of a Doppler shift frequency output from the average frequency calculator, and a variance calculation are performed. 1. An ultrasonic Doppler diagnostic device comprising a maximum and minimum shift frequency calculator that calculates a maximum value and/or a minimum value of a Doppler shift frequency based on a dispersion signal output from the device. 2. In the device according to claim 1, the maximum/minimum deviation frequency calculation unit includes a power calculation circuit that calculates the power of the received signal from the output of the complex signal converter, and a power calculation circuit that calculates the standard deviation from the output of the dispersion calculation unit. An ultrasonic Doppler diagnostic apparatus comprising: a standard deviation calculation circuit that calculates an equivalent band parameter; and an equivalent band calculation circuit that calculates an equivalent band parameter from the outputs of the power calculation circuit and the standard deviation calculation circuit.