JPH0324862B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic Doppler diagnostic device, in particular, a method for displaying velocity information and velocity distribution deviation information of a designated part (designated region) of an in-vivo moving part in a waveform over time. The present invention relates to an ultrasonic Doppler diagnostic device.

[Prior Art] The ultrasonic pulsed Doppler method has been put to practical use in order to measure the velocity of blood flow or body fluid flow in moving parts of a living body, such as organs such as the heart, circulatory organs, and blood vessels. It is possible to receive Doppler-shifted reflected waves at the in-vivo moving part, extract Doppler information from the received signal, and display speed information and the like of the moving part. In addition, in recent years, B
Mode display and M mode display have become possible (Japanese Patent Laid-Open No. 58-188433), and are being put into practical use and becoming widespread.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional ultrasound Doppler diagnostic devices, blood flow velocity, etc. are displayed in black and white in correspondence with luminance values, or blood flow velocity, etc. are displayed in hue. However, with such brightness display or hue display, there is a problem that the velocity of the blood flow cannot be quantitatively recognized, that is, the magnitude of the physical quantity cannot be clearly recognized visually. It was hot.

In addition, the velocity of a specific part such as blood flow was also displayed numerically, but in this case,
Unable to recognize changes in speed over time,
There has been a need for a device that can clearly recognize speed information of a moving part, deviation information of speed distribution, etc. over time.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to display Doppler information in a specified region of an in-vivo moving part over time with the magnitude of the information corresponding to the amplitude, and to display the Doppler information An object of the present invention is to provide an ultrasonic Doppler diagnostic device that can clearly display changes over time.

[Means for Solving the Problems] In order to achieve the above object, the present invention transmits an ultrasonic beam into a living body, receives a reflected wave that has undergone a Doppler shift at a moving part in the living body, and In an ultrasonic Doppler diagnostic apparatus that extracts Doppler information including velocity information of the moving part and deviation information of velocity distribution from a received signal obtained by a gate circuit for extracting Doppler information,
an averaging circuit that averages the extracted Doppler information within the specified region outputted from the gate circuit; and an averaging circuit that averages the extracted Doppler information outputted from the averaging circuit over time by making the magnitude of the information correspond to the amplitude. A waveform display circuit for displaying a waveform on the screen.

[Operation] According to the above configuration, the Doppler information within the specified area along the ultrasound beam is extracted by the gate circuit, and further averaged within the specified area by the averaging circuit.

Then, the average extracted Doppler information is
The waveform display, that is, the magnitude of the information is displayed over time in correspondence with the amplitude.

Therefore, by specifying, for example, a specific position of blood flow in the living body, the operator can average the Doppler information at that position and recognize it as an amplitude display over time.

Furthermore, by displaying velocity information and deviation information as Doppler information on the same screen, it is possible to check their correlation on the same coordinate system.

Conventionally, Doppler information was expressed by hue changes or brightness changes, but in the present invention, the magnitude of Doppler information can be expressed by the height of a peak called amplitude, and this allows the Doppler information to be expressed over time. This makes it possible to easily understand the fluctuations.

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

FIG. 1 shows a two-dimensional ultrasonic Doppler diagnostic device according to an embodiment. In the embodiment, the information to be displayed is velocity and deviation, and the velocity signal and deviation signal of the moving part are first processed. The following circuit will be explained.

Calculation of Speed and Deviation In the figure, the output of a crystal oscillator 10 that generates a stable high frequency signal is supplied to a frequency division synchronization circuit 12, and various output signals of desired frequencies are obtained by the frequency division synchronization circuit 12. These output signals are the transmission repetition frequency signal 1 for ultrasonic pulse beam transmission.
00, complex reference signal 102,1 for complex transformation
04, a sweep synchronization signal 106 for displaying the ultrasonic diagnostic results, and a clock signal 108 for synchronizing each part of the apparatus. The complex reference signal 10
2 and 104 have a frequency that is an integral multiple of the transmission repetition frequency signal 100, and have a phase difference of 90° in the embodiment so that they have a complex relationship with each other.

The transmission repetition frequency signal 100 is transmitted to the drive circuit 1
4 and the transmission/reception switching circuit 16 to excite the probe 18, and an ultrasonic pulse beam is transmitted into the subject 20.

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 section for normal M mode display.

Normal M mode display (B mode display may also be used)
The output signal for performing is supplied to a CRT display 30 via a detector 24 and a video amplifier 26,
The brightness of the display surface of the CRT display 30 is modulated.

The ultrasonic pulse beam of the probe 18 is applied to the object 2 by mechanical or electrical angular deflection.
A scan controller 32 is provided for stopping toward a desired position of 0, and the scan position signal of the scan controller 32 and the sweep synchronization signal 106 obtained from the frequency division synchronization circuit 12 are sent to a sweep trigger generator 34. and sweep control of the CRT display 30 is performed.

The other output of the high-frequency amplifier 22 is then subjected to complex operations to obtain information such as desired motion information. For this purpose, the received high frequency signal obtained from the high frequency amplifier 22 is supplied to a complex signal converter 36 and converted into a complex signal.

That is, in the embodiment, the complex signal converter 36 includes a pair of mixers 38a, 38a and 38a, including a phase detector.
8b, and in each mixer 38, the received high frequency signal is connected to the complex reference signal 102, 1, respectively.
04, but complex reference signals 102, 10
4 are in a complex relationship with a phase difference of 90 degrees from each other as described above, so that the mixer 38 can output a complex signal corresponding to a high frequency signal. That is, each mixer 38 outputs a signal having a frequency that is the sum and difference of the frequencies of the received high-frequency signal and the complex reference signal input through mixed detection, and these two signals are supplied to the low-pass filters 40a and 40b. , only the difference frequency components are extracted.

In the mixed detection function of the mixer 38, the complex reference signals 102 and 104 are single-frequency continuous waves, but the other input signal, the received high-frequency signal, is a pulse wave containing Doppler information. A large number of spectral components will appear in the output. This complex transformation will be explained below using an arithmetic expression.

One complex reference signal 102 has a frequency fo that is an integral multiple of the repetition frequency fr for transmission, and its amplitude is 1
Then, sin2πfo t (1) is expressed as a sinusoidal voltage signal. On the other hand, the reception high frequency signal received by the probe 18 has a transmission frequency
If fo is sin(2πfo t+2πfd t)...(2), where fd is the Doppler shift frequency.

Note that this received high-frequency signal generally has the following equation: sin{2π(fo±n fr)t+2πfd・(1±
n fr/fo)t} (fr is the transmission repetition frequency, n is a natural number such as 0, 1, 2...), but to simplify the explanation below, we will use the spectrum when n = 0. (2)
Only the spectrum shown in the formula will be explained.

In the mixer 38a, the product of one complex reference signal 102 and the received high frequency signal is taken, so equations (1) and (2)
We obtain the following equation, which is twice the product of Eqs.

cos2πfd t-cos (4πfo t+2πfd t) And this output is 2fo by the low-pass filter 40a.
Since the +fd frequency has been removed, the output signal is cos2πfd t (3).

On the other hand, since the other complex reference signal 104 has a phase difference of 90° from the complex reference signal 102, it is represented by a cosine wave voltage signal cos2πfo t (4), and is expressed by the mixed detection of the mixer 38b and the filter of the low-pass filter 40b. By the action, it is converted into a signal sin2πfd t ...(5), and the above equation (3) is converted into the real part and
This means that the equation (5) has been converted into a complex signal with the imaginary part, and both of these signals can be expressed by the following complex equation.

Z ₁ = cos2πfd t + i sin2πfd t ...(6) The signal Z ₁ complex-transformed as above is AD
It is converted into a digital signal by converters 42a and 42b, and then sent to the next stage complex delay line canceller 4.
4 is input. A clock signal 108 is supplied to the AD converter 42, and sampling is performed using the clock signal.

In this embodiment, since the above-described complex delay line canceller 44 is provided, it is possible to remove received signals from stationary parts or low-speed moving parts in the living body, thereby significantly improving the quality of image signals. . That is, in general, for example, blood flow signals from a living body are mixed with reflected signals (clutter) from living tissues that are almost stationary, such as blood vessel walls and heart walls.
Significant interference with blood flow measurements. Therefore, in this embodiment, such low speed signals can be removed by the complex delay line canceler 44, so that only the signals from the moving parts can be detected.

As shown in FIG. 3, this complex delay line canceller 44 has delay lines 46a and 46b having a delay time corresponding to one period (T) of the repetitive signal, and these delay lines are, for example, It can be formed from a memory or a shift register consisting of storage elements equal to the number of clock pulses contained in one period. Difference calculators 48a and 48b are connected to these delay lines 46a and 46b, respectively. The difference between one period of the signal is calculated by successively comparing the signal with the signal at the same depth.

Therefore, since there is no change or a small change between the signal at the current time and the signal from one cycle ago in the reflected signal from a stationary or low-velocity biological tissue, the difference output of the difference calculator 48 is close to zero. On the other hand, a differential output of a fast-speed blood flow signal, for example, is detected as a large value, and thereby the above-mentioned clutter can be reliably suppressed.

The operation of the complex delay line canceller 44 will be explained below using an arithmetic expression. In FIG. 1, the input to the complex delay line canceller 44 is a digital signal, but in order to simplify the explanation of the calculation equation, the analog signal of equation (6) will be explained.

When the input Z ₁ of the delay line 46 is expressed by equation (6),
The output Z ₂ delayed by one period is expressed as Z ₂ = cos2πfd (t-T) + i sin2πfd (t-T) (7), and as a result, the difference output of the difference calculator 48 is Z ₃ = Z ₁ −Z ₂ =−2sin2πfd・(T/2)sin2πfd
{(t-(T/2)} +i2sin2πfd(T/2)・cos2πfd{t-(
T/2)}, and if the difference output Z ₃ is expressed as Z ₃ =x ₃ +iy ₃ , then each x ₃ and y ₃ become the following equation.

x ₃ = −2sin2πfd (T/2)・sin2πfd{t−(T/2)} ……(8) y ₃ =2sin2πfd(T/2)・cos2πfd{t−(T/2)} ……(9 ) As described above, each difference calculator 48a, 48b
The signals x ₃ and y ₃ will be outputted respectively.

The complex signal from which the low-speed signal has been removed as described above is then subjected to arithmetic processing by the autocorrelator 50, and the autocorrelation of Z ₃ where T is the amount of delay is determined.

First, the input signal Z ₃ is input to the delay lines 52a, 5
Z ₄ is obtained by delaying one period by 2b. This output Z ₄ is expressed by the following formula.

Z ₄ =x ₄ +iy ₄ x ₄ =-2sin2πfd(T/2)・sin2πfd{t-(3/2T)} ...(10) y ₄ =2sin2πfd(T/2)・cos2πfd{t-(3/ 2T)} ...(11) When Z ₄ ^* = x ₄ −iy ₄ , the correlation can be found by the following formula.

Z ₃ Z ₄ ^* = (x ₃ + iy ₃ ) (x ₄ − iy ₄ ) = x ₃ x ₄ + y ₃ + y
₄ +i(x ₄ y ₃ −x ₃ y ₄ ) Then, in order to find this correlation, autocorrelator 5
0 has four multipliers 54a, 54b, 56a, 5
6b, and adders and subtracters 58a and 58b are provided to perform the correlation calculation.

If the output of the adder/subtractor 58a is R, the above (8),
From each relational expression (9), (10), and (11), R=x ₃ x ₄ +y ₃ y ₄ =4sin ² 2πfd・(T/2)cos2πfdT...(12) is obtained, and the adder/subtractor 58b If the output of is I, then similarly I=x ₄ y ₃ −x ₃ y ₄ =4sin ² 2πfd・(T/2)
sin2πfdT...(13) is obtained, and the outputs of both adders and subtracters 58 are combined and expressed by the following equation.

S=R+iI...(14) Since this output S includes signal fluctuation components and noise components generated from the equipment, an average is calculated by an averaging circuit to remove these noise components, and this average is =+i, and complex correlation is calculated.

The average circuit includes delay lines 60a and 60b.
The adder 62a, 62b adds the output delayed by one period to the input signal at the current time, and repeats the operation of supplying this output to the delay line 60 again.
For example, if this addition is configured using a digital circuit, outputting the upper bits of the addition output will result in
You can get the average value. However, if this operation is simply repeated, the output value will increase successively as the number of additions increases, and will eventually reach saturation. Therefore, in the embodiment, weighting circuits 64a, 6
4b is provided to attenuate the output and add it to the input. In other words, if the amount of attenuation is α, the signal α10, which is ¹⁰ cycles earlier than the signal at the current time, will be attenuated and added to the signal at the current time, so the effect on the output will be small, and the low-pass filter and moving It becomes possible to perform the same averaging function as an averaging circuit. Further, by changing the weighting amount of the weighting circuit 64, the degree of averaging can be changed.

As described above, in this embodiment, the correlation of complex signals is obtained from the autocorrelator 50, and the argument angle θ of the correlation output is determined by the argument calculator 66, which is a speed calculator. It will be done. That is,
The declination angle θ is obtained from equations (12) and (13) as θ=tan ^-1 (/) = 2πT ... (15), and as a result, the Doppler shift frequency is calculated as = θ/2πT ... (16) This can be very easily determined from the declination angle θ.

On the other hand, the inputs x ₃ , y ₃ and the output I of the autocorrelator 50 are applied to the deviation calculator 68 of the present invention,
The deviation of the speed signal is calculated. In the embodiment, in addition to the speed information, the amount of deviation of the signal from the average speed (or average frequency), which is useful information for diagnosis, is measured and displayed. The amount of Doppler frequency deviation generally represents the spread of the spectrum, and is an amount that represents whether the flow of blood flow is laminar or turbulent, and the degree of turbulence. This deviation approximates the variance of the Doppler signal, and its square root approximates the standard deviation.

The declination signal and the deviation signal, which are the speed signals obtained as described above, are supplied to the display 30,
An image of the motion velocity distribution and deviation information in M mode (B mode may also be used) is displayed on the CRT display 30 as a brightness modulation signal. That is, a continuous distribution of velocity and dispersion on the ultrasound beam axis is calculated in a short time. However, this display method cannot quantitatively display changes over time.

Calculation of changes over time A characteristic feature of the present invention is that Doppler information such as velocity information and deviation information of an arbitrary part (area) hit by an ultrasound beam is converted into a waveform over time by making the magnitude of the information correspond to the amplitude. A time change calculator 70 is provided to perform the waveform display processing, and a detailed internal circuit of the time change calculator 70 is shown in FIG.

In FIG. 2, in the embodiment, two types of temporal change information to be displayed as images are used: a speed signal and a deviation signal indicating the dispersion with respect to the average value of speed.
Calculation of changes over time is performed on these two types of information. In other words, the range gate 72 is a gate circuit for detecting information of an arbitrarily selected part.
a, 72b, and averaging circuits 74a, 74b for averaging the output of the range gate 72, and the output of the averaging circuit 74 is used to display an image of the change in quantitative information over time.

Then, an operating signal for the range gate 72 is generated by a range gate generator 76 based on the depth position information. For example, as illustrated in FIG.
250μs). The predetermined time D and time width W can be freely adjusted by the operator to define the signal sample range at a depth corresponding to a desired region.

FIG. 5a shows an example of M-mode display in a conventional ultrasound diagnostic apparatus, and the figure shows the state of motion of the anterior and posterior walls of the heart. Here, the horizontal axis is the time axis, and the vertical axis shows the depth direction D, which is the direction of the ultrasonic beam. In the present invention, the range gate generator 76 determines a specified region (time width) W in the depth direction D, the range gate 72 extracts Doppler information within the W, and the averaging circuit 74 extracts Doppler information. hand,
This is to average the Doppler information within that W.
Note that the initial position (depth time) D of the designated area W is outputted from the range gate generator 76 to the display 30 as a gate position signal 109.

The time-varying calculator 70 also includes a memory latch 78a that stores the output of the averaging circuit 74 bit by bit and holds it for a period of time until the next output arrives.
78b, D/A converters 80a and 80b for analog-converting the output of this memory latch 78, and low-pass filters 82a and 82b for removing the 1/T frequency and other high frequencies of the signal. The operations from latching the average circuit output to filtering are repeated at a period of time T, and the output of the low-pass filter 82 appears as a continuous voltage value with respect to time.

In such a processing circuit, by supplying a velocity signal from terminal A to the range gate 72a and a deviation signal from terminal B to the range gate 72b, the low-pass filter 82a receives information about the average velocity of a moving part, for example, blood flow. A time-varying signal is output, and a time-varying signal of the deviation signal is output from the low-pass filter 82b.

In this case, the speed of blood flow fluctuates at a cycle of about 1 second per heartbeat, but since the ultrasound transmission cycle is about 250 μs, the heartbeat cycle is sufficiently long compared to this cycle, so the processing circuit This makes it possible to sufficiently capture changes in cardiac blood flow, and to display information on any part of the heart as a curved image in accordance with changes over time.

Since it is insufficient as information for quantitative diagnosis even if the change in the deviation signal is displayed as it is, it is preferable to display the change as an image together with the speed information. Therefore, in the embodiment, the speed information and the deviation information are added and subtracted and displayed on the screen, and for this purpose an adder 84 and a subtracter 86 are provided to add and subtract the output of the low-pass filter 82. In addition, in order to display this processing information on the screen,
Comparator 8 as image forming means for waveform display
8. A pulse generator 90 and an OR circuit 92 are provided.

That is, the screen of the CRT display 30 shows the fifth
As shown in Figure b, each output information is displayed simultaneously, and the electron beam is deflected by sweep voltages X and Y applied to the x- and y-axis deflection circuits. For each, the voltage Y is 4K
Repeated every Hz.

The comparator 88 compares two input voltages, one of which uses the sweep voltage Y, and the other voltage of 88a,
The outputs of terminals a, c, and b are used in this order for 88c and 88d, and Ov is used for 88e.

FIG. 6 shows the processed waveforms until the luminance signal is formed, and Y in FIG.
If we explain the comparator 88e, it will be compared with zero voltage, so Y
The square wave shown in Figure b is generated for each sweep for the time that . This voltage is output to the pulse generator 90e and is the rising edge of the square wave c in Figure b.
A pulse of the luminance signal shown in is generated.

This pulse is then passed through the OR circuit 92 to C
Output from the terminal to the CRT display 30, this CRT
The brightness of the screen of the display 30 is modulated to display a bright spot as shown in FIG. 5e. Since the time te at which this bright spot e occurs does not change with each sweep, it is displayed as a horizontal bright line 200 on the CRT screen. This is used as a base line indicating zero voltage.

Further, a voltage a is applied to the comparator 88a, and a bright spot a is generated on the CRT screen at time ta in the same manner as described above, and the varying voltage is displayed as a curve as shown in the diagram 201. .
In this case, the value represents the average flow velocity.

Similarly, comparators 88c and 88d and pulse generators 90c and 90d generate curve 202.
and 203 will be displayed as images. In this case, the value of will indicate the deviation.

Therefore, by displaying the temporal changes in the deviation information indicating the dispersion and standard deviation of the velocity simultaneously with the changes in the velocity information, it is possible to easily quantitatively judge the state of movement of a desired region in the living body.

In addition, other ultrasound diagnostic equipment may display images using a digital scan converter (DSC) that performs digital processing, but in this case, the digital signals output from terminals E and F in Figure 2 can be supplied to a digital scanning converter, and each signal can be processed using a digital adder or a digital subtracter without using the D/A converter 80, low-pass filter 82, adder 84, or subtracter 86. In addition, a digital comparator is used as the comparator 88,
By using the address data of the frame memory instead of the sweep voltage, it is possible to obtain the address signal corresponding to the bright spot.

Therefore, by storing the luminance signal in this address memory, various information can be displayed as images in the same way as in the case of analog processing. According to this digital processing, various information can be obtained as numerical values, so there is an advantage that highly accurate measurements can be performed.

Furthermore, a large amount of information can be displayed simultaneously by using a color cathode ray tube in the display CRT to display different types of information in different colors.

Note that the display of changes over time is not limited to the speed and deviation information, and various information such as acceleration can be used.

As explained above, according to the ultrasonic Doppler diagnostic apparatus according to the present invention, velocity information and velocity distribution deviation information within a specified region of an in-vivo moving part are extracted,
Furthermore, it is possible to average the extracted information and display it as a waveform over time, with the magnitude of the information corresponding to the amplitude, so it is possible to clearly display changes over time in the velocity of a specific part of the body's moving parts. is possible.

Therefore, the movement information of a specific part of the in-vivo movement part can be grasped over time, and useful information can be provided for diagnosing, for example, heart valve insufficiency.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing a preferred embodiment of the ultrasonic Doppler diagnostic apparatus according to the present invention, FIG. 2 is a block diagram showing an internal circuit of a time-dependent change calculator,
The figure is a block diagram showing the internal circuit of the complex delay line canceler and autocorrelator, Figure 4 is an explanatory diagram of the gate pulse of the gate circuit, and Figure 5 is the conventional M
FIG. 6 is an explanatory diagram showing the mode and the display of changes over time according to the present invention. FIG. 6 is an explanatory diagram showing the sweep action for displaying changes over time. 10... Crystal oscillator, 12... Frequency division synchronous circuit,
18... Probe, 20... Subject, 30...
CRT display, 36... Complex signal converter, 44...
...Complex delay line canceller, 50...Autocorrelator, 52a, 52b...Delay line, 5
4a, 54b, 56a, 56b...multiplier, 58
a, 58b... adder/subtractor, 66... argument calculator,
68... Deviation calculator, 70... Temporal change calculator,
72... Range gate, 74... Average circuit.

Claims (1)

[Claims] 1. An ultrasonic beam is transmitted into a living body, a Doppler-shifted reflected wave is received at a moving part in the living body, and velocity information and information about the moving part are obtained from the received signal obtained thereby. In an ultrasonic Doppler diagnostic device that extracts Doppler information including velocity distribution deviation information, a gate circuit that extracts Doppler information within a specified region specified along the ultrasound beam from among the extracted Doppler information; an averaging circuit that averages the extracted Doppler information within the specified region output from the gate circuit; and an averaging circuit that averages the extracted Doppler information output from the averaging circuit over time by making the magnitude of the information correspond to the amplitude. An ultrasonic Doppler diagnostic device comprising: a waveform display circuit that displays a waveform; 2. The ultrasonic Doppler diagnostic apparatus according to claim 1, characterized in that changes over time of the velocity information and the deviation information of the velocity distribution are displayed in waveforms on the same screen.