JPS6216747A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an ultrasonic diagnostic apparatus, particularly an improved ultrasonic diagnostic apparatus capable of measuring and displaying the amount of velocity deviation regarding the motion velocity distribution of a moving part in a living body. Regarding.

[Prior Art] The ultrasonic pulse alignment method has been put to practical use in order to measure the speed of movement of blood flow or body fluid flow in moving parts of a living body, such as organs such as the heart, or the circulatory system and blood vessels. Although the velocity of movement can be electrically detected by the Doppler frequency shift of the reflected echo from the moving part of the living body, such conventional devices require complicated calculation methods such as Fourier transformation. Therefore, only the movement speed of the movement part at a limited specific point located at a predetermined depth can be determined. In other words, in order to obtain the required velocity distribution of blood flow, etc. over a wide range, ultra-8 wave pulses are transmitted and received many times in the depth direction of different target points.
Therefore, it takes a long time to measure the velocity distribution. Therefore, in the conventional method, it is difficult to measure the velocity distribution that follows the fluctuations of the moving parts in the living body. Therefore, it was impossible to observe changes in blood flow conditions due to pulsation in real time.

Therefore, the present applicant has developed a device that can measure and display the motion velocity distribution of a moving part on the path line of the transmitted and received ultrasonic pulse beam in real time (Japanese Patent Application Laid-Open No. 11n 58-).
188/I33).

Therefore, according to this device, for example, a tomographic image of the heart (B
The movement of blood flow within the heart can be displayed together with the velocity distribution of the heart. Lee <r That is, blood flow shown in red (for example, positive velocity) and blue (for example, negative velocity) flows inside the heart, which is displayed in black and white.
In addition, the velocity is displayed by modulating the brightness depending on its height1.As a result, it is possible to judge the real-time flow of blood within the heart extremely accurately, and it is possible to prevent valvular disease, ischemia (1, predecessor 1). ) It is possible to capture and provide important information for the diagnosis of heart disease or aortic disease, etc.

[Problems to be Solved by the Invention I VL艮扼Δ坪机力However, although the above-mentioned device can measure the velocity distribution of blood flow, etc. over the entire desired range by 4:1 in real time, it is difficult to It was not possible to accurately determine whether the blood flow was laminar or turbulent (vortex-like), or to determine the degree of turbulence in the blood flow.

This dispersion corresponds to the amount of deviation of the Doppler frequency signal corresponding to the average velocity of the moving reflector, and the amount of deviation of this Doppler frequency signal generally represents the spread of the spectrum.

Therefore, by determining the deviation h) of the Doppler frequency signal, it is possible to display the dispersion (J) in the motion velocity distribution of the moving part.

Purpose of the Invention-3 The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to reduce the deviation m of the Doppler frequency signal corresponding to the average velocity of the moving part on the transmission and reception ultrasound beam passing line. The aim is to provide an improved ultrasonic diagnostic device that measures in real time and displays the dispersion of velocities of individual components entering the moving part.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides an ultrasonic pulse beam that transmits an ultrasonic pulse beam into a living body at a constant repetition frequency, receives and amplifies the reaction waves, and displays them. In a sound wave diagnostic device, a complex signal converter mixes a received high-frequency signal with a set of complex reference signals having a frequency that is an integral multiple of the transmission repetition frequency and has a complex relationship with each other to convert the received high-frequency signal into a complex signal. , a complex delay reikisen that removes signals of low-speed moving parts in the living body from the complex signal; and a declination calculator for calculating the declination of the complex signal; Equipped with a delay line of n\fi! an argument difference calculator for calculating the difference in argument between two complex signals that make up the difference; an averaging circuit for averaging fluctuation components of the output signal of the argument difference calculator; and output signals of each part. The device is characterized in that it includes a deviation oil C function which calculates the deviation ff1) of the deviation angle difference from ff1), and measures and displays the deviation distribution of the movement speed of the moving part in the living body.

According to the above configuration, the received high-frequency signal obtained from the moving part is converted into a complex signal, and then the argument representing the motion velocity component of this received complex signal is determined. Next, the difference in declination between the declination of the received signal and the declination of the received signal delayed by a predetermined period is calculated, and this declination difference is converted into a final Doppler frequency signal corresponding to the speed of the target moving part. Since they are equivalent, the actual speed of the moving part can be determined from the deviation angle difference.

The present invention is to obtain the dispersion (deviation) of the declination difference, and this dispersion indicates whether the declination difference (frequency) is scattered around the average value. Therefore, this variance is obtained from the deviation of the complex signal, and specifically, the difference between the average value of the argument differences calculated by the averaging circuit and the argument differences representing the speeds of the individual components of the moving part is calculated. Then, the deviation of the Doppler frequency signal is determined from this and the power of the Doppler frequency signal.

[Actual IAI! EXAMPLES Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the ultra-blind wave diagnosis according to the present invention! I′i device N is shown in which the output of a crystal oscillator (O20) 10 which generates a stable high frequency signal is supplied to a frequency dividing synchronization circuit 12,
Each scale output signal of a desired frequency is obtained by the frequency division synchronization circuit 12.

These output signals include a repetition frequency for ultrasonic pulse beam transmission and reception (No. 51 1001, a complex reference signal 102.ioa for complex conversion, a sweep same signal 106 for displaying the ultrasonic transmission and reception results, and each part of the device). a clock signal 108 for synchronizing the complex reference signal 102;
．． 10/1 is equal to the frequency fo of the transmission pulse 1 to wave that has a frequency that is an integral multiple of the transmission repetition frequency 1Δ,
The signals have a complex relationship in which the phases differ by π/2 and consist of signal waveforms 5in2π fot and cos2π fot.

The repetition frequency signal 100 for transmission and reception is supplied to the electronic scanning probe 1G via the transmission/reception controller 14, excites the probe, and transmits an ultrasonic pulse beam into the subject 90. The reflector =1- from the object 90 is converted into an electrical signal by the probe, sent from the wave transmitting/receiving controller 11 to the high frequency amplifier 18, where it is subjected to the desired amplification action, and then displayed in B mode or M mode. The signal is supplied as an output signal to the DSC 24 via the detector 20 and the Δ/D converter 22, and is pyroxene-modulated and displayed on the color TV monitor 30.

The wave transmitting/receiving controller 14 scans and lowers the ultrasonic pulse beam of the probe 16 by electrical angle deflection or the like, and periodically scans the object 90 with the ultrasonic pulse beam, or adjusts the ultrasonic pulse beam to a desired deflection angle. It is provided for purposes such as stopping scanning.

The present invention is characterized by measuring in real time the amount of deviation of the declination difference with respect to the motion method 1 good distribution of the moving part in the living body and finding the dispersion of the velocity of each component that falls into the moving part. First, before calculating the amount of deviation, the argument difference (Doppler frequency shift) between the received signal at the current time and the received signal one cycle before is determined at high speed. For this purpose, in the present invention, the ultrasonic reception signal is subjected to complex conversion, and the other output of the high frequency amplifier 18 is supplied to the complex signal converter 32 and converted into a complex signal.

This complex signal converter 32 includes a set of micro-4s including a phase detector.
- mixers 34a and 34b, and in each mixer, the received high frequency signal is mixed with the complex reference signal 102.1 (
As mentioned above, these complex reference signals have a complex relationship with different phases of π/2, so each mixer can output a complex signal corresponding to a high frequency signal. .

Each mixer receives a received high frequency signal and a complex reference signal 5tn2πfot inputted by a mixed detection function.

It outputs signals of the sum and difference frequencies of image frequencies with CO32π fot, and these two signals are passed through a low-pass filter 36a,
36b, and only the difference frequency component is extracted. The received high-frequency signals, which are the input signals of the mixers 34a and 34b, are pulse waves containing Doppler information, and the complex reference signals 102 and 104 are single-frequency signals. It is a continuous wave.Therefore, the frequency component of the above difference also contains Doppler information.By detecting the frequency component of this difference, the speed of the moving part can be determined.

The complex reference signal 102 has a frequency f that is an integral multiple of the repetition frequency f of the transmission high-frequency signal. to the right and its amplitude to 1
What to do, 5in2πfot −(i)
i [indicated by a sinusoidal voltage signal. And probe 1
The received high frequency signal received at 6 has a transmission frequency of f. Then, 5in(2πf t +2πf6 t) −(
2). However, fd is the Doppler shift frequency.

On the other hand, since the mixer 34a multiplies the complex reference signal 102 and the received high frequency signal, the product of equations (1) and (2) is obtained. Now, to simplify the equation [J], mixer 34. represents the output signal of a.

cos2πf6 j C03(4πfot +2πf
d t)...(3) This output is filtered by the low-pass filter 36a to remove the frequency of 2fo+fa, so the output signal is CO327T
f6 t...(4).

Moreover, the complex signal 104 used is the complex reference signal π/
2. Since the phase is different, it is expressed as a cosine wave voltage signal cos2πfot (5).

As above, mixer 34. By the mixed detection action of b and the action of the low-pass filter 36b, the filter 36b
The output j signal is 5102π fdt ・
...(6) becomes the signal. If the signal of equation (4) is made to correspond to the real part and the signal of equation (6) is made to correspond to the imaginary part, the received high frequency signal is converted into a complex signal.

When these two signals are expressed in complex form Z, Z=cos2y
r fdt +jsin2yr fdt −
(7) can be placed.

The complex signals Z1, △D, which have been complex-transformed as described above
The signal is converted into a digital signal by converters 38a and 38b, and input to the next stage 40 which completes the complex delay line scan. A clock signal 108 is supplied to the AD converter, and sampling is performed using the clock signal.

The above-described complex delay line canceller 40 is used to remove signals received from stationary parts or low-speed moving parts in the living body and extract velocity signals from only the moving parts. In general, for example, blood flow signals from a living body include blood vessel walls,
Reflected signals (clutter) from stationary biological tissues such as the heart wall are mixed in, and this signal is usually stronger than the countersignal from the blood flow, so it significantly interferes with the blood flow measurement.

Therefore, the quality of the image signal can be improved by detecting only the signal from the moving part using the complex delay line canceller/IO.

This complex delay line canceller 40 includes delay lines/I2a and 42b having an I delay time corresponding to one period of a repetitive signal, and each delay line has a memory equal to the number of clock pulses included in one period. It can be formed from a memory consisting of an element or a shift register. Difference calculators 44a and 44b are connected to these delay lines 42a and 42b, respectively.
That is, the signal at the current time and the signal one cycle before are successively compared at the same depth to calculate the difference between one cycle of the signals.

Therefore, there is no change in the reflected signal from stationary or low-velocity living tissue between the current time signal and the signal one cycle ago.
Alternatively, since the change is small, the output of the difference calculator 44 becomes close to zero. In addition, a high-velocity output, for example, a blood flow signal, is detected as a large value, thereby making it possible to reliably suppress the above-mentioned clutter.

The operation of the delay line canceller 40 will be explained below using an arithmetic expression. In the embodiment, the input to the delay line canceller 40 is a digital signal, but to simplify the explanation, an analog signal will be used.

Delay line 4.2a input cos2π fdt 1
The period-delayed output is expressed as cos2π fd(t-■), and as a result, the output ×1 of the difference calculator 44a is: X = cos2πf t −CO327E fd
(t-T)d...(8) Shout.

In addition, the input of the delay line 42b is 5in2π fdt
The output delayed by one period is denoted by 5in2π fd (t-T), and as a result, the output y1 of the difference calculator 441) is
1=sin2yr fdt-stn2πfd(t-r
)...(9) becomes.

As described above, each difference calculator 4-4a, 44.1
), the outputs are x and ■ (i), respectively. Therefore, 11 is the signal from which the speed signal has been removed x 1゜y
l is computed by the argument calculator 46 according to the following equation, and the argument θ1 is obtained.

°i"1fd(t--;) In addition, the output signals x and y delayed by one period are obtained in the same way, and these output signals are expressed by the following formula% formula% These output signals ×, ■2 are biased By the angle calculator 46,
Arithmetic processing is performed according to the following equation, and the argument angle θ2 of the signal delayed by one period is determined.

(13) Next, the argument difference θ1-02 (80) is calculated from the argument angles θ and θ by the argument difference calculator 48 using the following calculation formula.

80=01-02 In the above formula, (8), (9), (11), (12)
Substituting the formula and rearranging the formula yields the following formula.

△θ−tan (tan2πfdT )−(2π■)
・ fd (14) That is, since the transmission repetition period T is a constant, the argument difference Δθ is proportional to the Doppler shift frequency fd, and therefore proportional to the blood flow velocity. Since the declination angle difference 〇 takes positive and negative values, respectively, it can be measured only between ±π, and thereby the directionality of the motion speed can be obtained.

In this way, if two complex signals with a fixed time interval are continuously obtained at each point on the ultrasound beam's passage line and the argument difference calculation processing is performed, ultrasound can be transmitted extremely quickly in real time. It is possible to obtain a wide range of motion speeds for the moving parts.

In addition, since the declination difference 〇 includes signal fluctuation components and noise components generated from the device, the average circuit 54 calculates the average declination difference in order to remove these noise components. The angle difference is expressed as tSO).

The averaging circuit 54 repeats the operation of adding the output delayed by one cycle on the delay line 58 to the input signal at the current time using the adder 56 and supplying this output to the delay line 58 again. However, if you simply repeat this operation,
As the number of additions increases, the output value increases successively and finally reaches saturation. Therefore, in the embodiment, the weight circuit 60
is installed, the output is attenuated and added to the input.

In other words, if the attenuation amount is α, then a signal that is, for example, 10 cycles before the current time signal will be attenuated by α10 and added to the current time signal, so the influence of 9i degrees on the output will be small, and a slow filter or It becomes possible to perform the same averaging function as a moving average circuit. Furthermore, by changing the weighting amount of the weighting circuit 60, it is possible to change the degree of averaging.

As described above, the average declination difference △0 is ΔO−ku2π■
〉・fd (15) As a result, the average Doppler shift frequency can be easily obtained.

Next, add a3 to the moving part obtained from ○ to the average declination angle difference
This explains the dispersion of the velocities of the individual constituents. This variance is calculated by the deviation calculator 62, and the outputs of the difference calculators 44a, 441) are squared by the square multipliers 68, 70, and the output signals of the square multipliers 68, 70 are squared by the adder 72.
is added. This will be explained using an arithmetic expression.

The following equation can be obtained from equations (8) and (9) above.

The output signal of this adder 72 is the power of the Doppler shift frequency signal, ? J is a value proportional to the power (voltage squared), and is input to the smoother 74 in order to smooth the amplitude of this signal and to remove the one-tone signal generated from the device. In the invention, the smoother 74 does not necessarily have to be used.

Further, the argument difference Δθ and the average argument difference 0 are input to the difference calculator 64, and the difference (Δθ−80) is calculated.

Next, the t signal is input to the square multiplier 66, and the square of the difference (
Find 2 to Δθ−8θ. This signal and the smoother 74
A multiplier 76 multiplies the output of

This signal is input to a summator 78 to obtain the sum of the argument signal system. Here, the sum is added to the value of the repeated signal one cycle (T) before (the above-mentioned averaging circuit 54 may be used), and this signal is expressed as the following J:.

ΣP·(Δθ−])2 (17) Also, the output of the smoother 74 is supplied to a summator 80 to obtain the sum.

This signal is expressed as follows.

ΣP...(18)
The output of each summer 78 and 80 is then provided to a divider 82 to divide the output of summer 78 by the output of 80. Further, the averaging circuit 54 may be used as the summator 78.80. Therefore, if the output j of the divider 82 is represented by D, it becomes as follows. Since D approximates the dispersion and its square root approximates the standard deviation, it is easy to find the square root of D.

As described above, the Doppler signal information obtained is supplied to the DSC 24 via the switch 84, and a B-mode or M-mode deviation and motion velocity distribution image is displayed on the color TV monitor 30. . Therefore, for example, the flow of blood in the heart can be displayed extremely accurately, and laminar flow or turbulent/eddy flow can be confirmed.

Further, in the present invention, a color cathode ray tube is used as the cathode ray tube of the monitor 30, and the direction of movement is identified by different colors. For example, if positive velocity is displayed in red, negative velocity is displayed in blue, the magnitude of velocity deviation is displayed in green, and the reflected echo from the restraining tissue is displayed in white, the magnitude of the deviation is displayed as a change in color tone. In-vivo tissue structure, blood flow direction, velocity, and velocity deviation information can be displayed simultaneously, and extremely high-density diagnostic information can be captured and provided.

[Effects of the Invention] As described in Section 1-Explanation 1, according to the present invention, the received ultrasonic signal is complex-transformed to represent the Doppler frequency shift, the Lie declination difference is obtained, and the Lie declination difference is calculated from this declination difference. Since the amount of deviation is determined, the motion velocity distribution of the moving part in the living body on the passage line of the transmitted and received ultrasound pulse beam along the ultrasound beam axis, for example, the blood flow velocity distribution, is continuously determined, and the motion Very accurate 2-7 diagnostic information can be obtained for certain parts of the system. Nowadays, since the delay time for abstract processing is only several times the transmission repetition period, it is possible to display these distributions in substantially real time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. 10... Crystal oscillator (O20) 12... Frequency division synchronization circuit 14... Wave transmission/reception controller 16... Electronic scanning probe 30... Color-FV monitor 32... Complex signal Converter 34a, 3.11)...Mikiri 36a, 36b...Low pass filter/10
... Complex delay line Chiton Sera 42a,
42b, 50-tilay in 44a,
44b, 52-M computing unit 46... polarization wave 9γ unit 48... polarization difference computing unit 54... averaging circuit 62... deviation computing unit 7/l... smoother 100... Repetition frequency signal 102.10/I... Complex reference signal 106...
- Sweep synchronization signal 108... Clock signal.

Claims (2)

[Claims] (1) In an ultrasonic diagnostic device that transmits an ultrasonic pulse beam into a living body at a constant repetition frequency and receives, amplifies, and displays the reflected waves, two beams having a frequency that is an integral multiple of the transmission repetition frequency and have a complex relationship with each other are used. a complex signal converter that mixes a set of complex reference signals and a received high-frequency signal to convert the received high-frequency signal into a complex signal; a complex delay line canceller that removes a signal of a low-speed moving part in the living body from the complex signal; An argument calculating unit that calculates the argument angle of a complex signal, and a argument calculator that calculates the argument difference between two complex signals having a delay time difference, which is equipped with a delay line to obtain the argument angle of the complex signal delayed by a certain time. A difference calculator, an averaging circuit for averaging the fluctuation components of the output signal of the argument difference calculator, and a deviation calculator for calculating the amount of deviation of the argument difference from the output signals of each part, and An ultrasonic diagnostic device characterized by measuring and displaying a deviation distribution of motion speeds of moving parts in the body. (2) The deviation calculator according to claim (1), characterized in that a smoother is provided to remove noise components contained in the complex signal or noise components generated from the device. Diagnostic equipment.