JPH0222659B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic diagnostic device, and particularly an improved ultrasonic diagnostic device that can measure and display the amount of velocity deviation regarding the motion velocity distribution of a moving part in a living body. Regarding.

[Prior Art] The ultrasonic pulse Doppler method has been put to practical use in order to measure the movement velocity 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. , movement speed can be electrically detected by the Doppler frequency shift of reflected echoes from moving parts in the body, but such conventional devices require complicated calculation methods such as Fourier transformation. Therefore, only the motion speed of the motion part at a limited specific point 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, it is necessary to transmit and receive ultrasonic pulses many times to different target points (in the depth direction) and then synthesize them. It will take a long time to measure the velocity distribution. Therefore, with conventional methods, it is not possible to measure the velocity distribution that follows the fluctuations of the moving parts in the living body.
It has been impossible to observe changes in blood flow conditions due to pulsation in real time.

Therefore, the present applicant has developed a device that measures and displays the motion velocity distribution of a moving part on the passing line of the transmitted and received ultrasonic pulse beam at once in real time (Japanese Unexamined Patent Publication No. 188433/1982).

Therefore, with this device, it is possible to display the movement of blood flow within the heart together with its velocity distribution, for example, superimposed on a tomographic image (B mode) of the heart. In other words, the blood flow is displayed in red (for example, positive velocity) and blue (for example, negative velocity) as if it were flowing through the heart, which is displayed in black and white, and the velocity is further displayed by modulating the brightness depending on its height. ing. As a result,
The real-time flow of blood within the heart can be determined extremely accurately, and it is possible to provide important information for diagnosing valvular disease, ischemic/congenital heart disease, aortic disease, etc.

[Problems to be Solved by the Invention] Problems of the Prior Art However, although the above-mentioned device can obtain the velocity distribution of blood flow, etc. over the entire desired range in real time, the degree of dispersion of the velocity of the moving part, that is, the It was not possible to accurately determine whether the flow was laminar or turbulent (vortex-like) or 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 the Doppler frequency signal generally represents the broadening of the spectrum.

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

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

[Means and actions for solving the problems] In order to achieve the above object, the present invention provides an ultrasonic wave that transmits an ultrasonic pulse beam into a living body at a constant repetition frequency, receives and amplifies reflected waves, and displays them. In the diagnostic device, a complex signal converter mixes the 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 lie canceler for removing signals of low-speed moving parts in a living body from a complex signal, a declination calculator for calculating a declination angle of the complex signal, and a declination calculator for calculating a declination angle of the complex signal delayed for a certain period of time. an argument difference calculator for calculating the argument difference between two complex signals having a delay time difference, and an averaging circuit for averaging fluctuation components of the output signal of the argument difference calculator; The apparatus is characterized in that it includes a deviation calculator that calculates the amount of deviation of the deviation angle difference from the output signal of each part, 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 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 difference in declination is used as the final Doppler frequency deviation corresponding to the speed of the target moving part. Since this corresponds to the displacement, the actual speed of the moving part can be determined from the difference in the deviation angle.

The present invention is to find the dispersion (deviation) of the declination difference, and this dispersion indicates how much the declination difference (frequency) is scattered around the average value. Therefore, this dispersion is obtained from the deviation of the complex signal, specifically, the difference between the average value of the argument differences obtained by the averaging circuit and the argument difference representing the velocity of each component of the moving part. By calculating this and the power of the Doppler frequency signal, the deviation of the Doppler frequency signal is determined.

[Embodiments] Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an ultrasonic diagnostic apparatus according to the present invention, in which the output of a crystal oscillator (OSC) 10 that generates a stable high-frequency signal is supplied to a frequency division synchronization circuit 12. 12, various output signals of desired frequencies can be obtained.

These output signals include a repetition frequency signal 100 for ultrasonic pulse beam transmission and reception, complex reference signals 102 and 104 for complex conversion, a sweep synchronization signal 106 for displaying the ultrasonic transmission and reception results, and synchronization of each part of the device. It includes a clock signal 108 that performs the operation. The complex reference signals 102 and 104 have signal waveforms having a complex relationship that is equal to the frequency f ₀ of a transmission burst wave having a frequency that is an integral multiple of the transmission repetition frequency signal, and whose phases differ from each other by π/2.
It consists of sin2πf ₀ t and cos2πf ₀ t.

The repetition frequency signal 100 for transmission and reception is supplied to the electronic scanning probe 16 via the transmission/reception controller 14, excites the probe, and transmits an ultrasonic pulse beam into the subject 90. The reflected echo from the object 90 is converted into an electrical signal by the probe, and is sent from the wave transmitting/receiving controller 14 to the high frequency amplifier 18 where it is amplified as desired and then displayed in B mode or M mode. DSC as an output signal for performing
24, and is brightness-modulated and displayed on a color TV monitor 30.

The wave transmission/reception controller 14 scans the ultrasonic pulse beam of the probe 16 by electrically angular deflection or the like, and uses this ultrasonic pulse beam to scan the object 90.
The deflection angle is provided for periodically scanning the deflection angle, or for stopping the scanning at a desired deflection angle.

The present invention is characterized in that it measures in real time the amount of deviation of the difference in declination with respect to the movement velocity distribution of the moving part in the living body and obtains the dispersion of the velocity of each component in the moving part. Before calculation, 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,
The present invention performs complex conversion on an ultrasonic reception signal,
The other output of the high frequency amplifier 18 is supplied to a complex signal converter 32 and converted into a complex signal.

This complex signal converter 32 has a pair of mixers 34a and 34b including phase detectors, and in each mixer, the received high frequency signal is operated on the complex reference signals 102 and 104, respectively, and these complex reference signals are As described above, since they are in a complex relationship with phases different from each other by π/2, each mixer can output a complex signal corresponding to a high frequency signal.

Each mixer uses the received high-frequency signal and the complex reference signal sin2πf ₀ t, cos2πf ₀ t input by mixed detection.
Outputs the signal of the sum and difference of both frequencies,
Both these signals are passed through low pass filters 36a and 36b.
, and only the difference frequency component is extracted. The received high-frequency signals, which are input signals to the mixers 34a and 34b, are pulse numbers containing Doppler information, and the complex reference signals 102 and 104 are continuous waves of a single frequency. Therefore, the frequency component of the difference also includes Doppler information, and 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 ₀ that is an integral multiple of the repetition frequency f _r of the transmission high-frequency signal, and when its amplitude is 1, it is represented by a sinusoidal voltage signal as follows: sin2πf ₀ t (1) It will be done. The received high-frequency signal received by the probe 16 is expressed as sin(2πf ₀ t+2πf _d t) (2), where f ₀ is the transmission frequency. However, f _d is the Doppler shift frequency.

On the other hand, in the mixer 34a, the product of the complex reference signal 102 and the received high frequency signal is taken, so equations (1) and (2)
The product with Eq. To simplify the equation, the output signal of the mixer 34a is expressed by the following equation, which is obtained by doubling this product.

cos2πf _d t−cos(4πf ₀ t+2πf _d t) …(3) This output is 2f ₀ +f _d at the low-pass filter 36a
Since the frequency of is removed, the output signal becomes cos2πf _d t (4).

Further, the other complex signal 104 has a phase different from the complex reference signal by π/2, so it is represented by a cosine wave voltage signal cos2πf ₀ t (5).

Similarly to the above, due to the mixed detection action of the mixer 34b and the action of the low-pass filter 36b, the output signal of the filter 36b becomes a signal sin2πf _d t (6). 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, it can be set as Z=cos2πf _d t+jsin2πf _d t (7).

The complex signal Z that has been complex-transformed as described above
are converted into digital signals by the AD converters 38a and 38b, and input to the complex delay line canceller 40 at the next stage. 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 received signals 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 are mixed with reflected signals (clutter) from almost stationary living tissues such as blood vessel walls and heart walls, and these signals are normal compared to reflected signals from blood flow. Because of its strength, it causes significant interference with blood flow measurements. For this reason, the complex delay line canceller 4
If only the signal from the moving part is detected at 0, the quality of the image signal can be improved.

This complex delay line canceler 40 includes delay lines 42a and 42b having a delay time corresponding to one period T 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 elements 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, since there is no change or a small change between the signal at the current time and the signal one cycle ago in the reflected signal from the stationary or low-velocity living tissue, the output of the difference calculator 44 is 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 aforementioned 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 explained.

The output of the input cos2πf _d t of the delay line 42a delayed by one period is expressed as cos2πf _d (t-T), and as a result, the output x ₁ of the difference calculator 44a
is, x ₁ = cos2πf _d t−cos2πf _d (tT) = −2sin2πf _d T/2・sin2πf _d (t−T/2)…(
8) becomes.

In addition, the input sin2πf _d t of the delay line 42b
The output delayed by one period is represented by sin2πf _d (t-T), and as a result, the output y ₁ of the difference calculator 44b is y ₁ =sin2πf _d t-sin2πf _d (t-T) = 2sin2πf _d T /2・cos2πf _d (t-T/2)...(9).

As described above, each difference calculator 44a, 44b
The signals x ₁ and y ₁ are outputted respectively. Therefore, the signals x ₁ and y ₁ from which the low-speed signals have been removed are processed by the argument calculation unit 46 according to the following equation to determine the argument θ ₁ .

θ ₁ = tan ^-1 (y ₁ / x ₁ ) = tan ^-1 (2sin2πf _d T/2・cos2πf _d (t-T/2)
/-2sin2πf _d T/2・sin2πf _d (t-T/2) = tan ^-1 (-cos2πf _d (t-T/2)/sin2πf _d (t
-T/2)) (10) Furthermore, the output signals x ₂ and y ₂ delayed by one period are obtained in the same manner, and these output signals are expressed by the following equation.

x ₂ = −2sin2πf _d T/2 ・sin2πf _d {(t−T)−T/2} =−2sin2πf _d T/2・sin2πf _d (t−3T/2)…(
11) y ₂ =2sin2πf _d T/2 ・cos2πf _d {(t-T)-T/2} =2sin2πf _d T/2・cos2πf _d (t-3T/2)...(12
) These output signals x ₂ and y ₂ are processed by the argument calculation unit 46 according to the following equation, and the argument angle θ ₂ of the signal delayed by one period is determined.

θ ₂ = tan ^-1 (y ₂ / x ₂ ) = tan ^-1 (−cos2πf _d (t-3T/2) / sin2πf _d (
t-3T/2))...(13) Next, from the declination angles θ ₁ and θ ₂ , the declination angle difference θ ₁ −θ ₂ (Δθ)
is calculated by the argument difference calculator 48 using the following calculation formula.

Δθ=θ ₁ −θ ₂ = tan ⁻¹ (y ₁ / x ₁ ) − Tan ⁻¹ (y ₂ / x ₂ ) = tan ⁻¹ ((y ₁ / x ₁ ) − (y ₂ / x ₂ )/ 1+(y ₁ /x ₁
)・(y ₂ /x ₂ ) Substituting equations (8), (9), (11), and (12) into the above equation and rearranging the equation results in the following equation.

Δθ=tan ^-1 (tan2πf _d T) = (2πT)・f _d (14) In other words, since the transmission repetition period T is a constant, the argument difference Δθ is proportional to the Doppler shift frequency f _d ,
Therefore, it is proportional to the blood flow velocity. Also, since the declination difference Δθ takes positive and negative values, respectively, ±π
The directionality of the velocity of movement can be obtained through this measurement.

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.

Furthermore, since the declination difference Δθ includes a signal fluctuation component and a noise component generated from the device, the average circuit 54 calculates the average declination difference in order to remove these noise components (this average declination difference ).

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 again supplying this output to the delay line 58. However, if this operation is simply repeated, the output value will gradually increase as the number of additions increases, and will eventually reach saturation. Therefore, in the embodiment, a weighting circuit 60 is provided to attenuate the output and add it to the input. In other words, if the attenuation amount is α, a signal that is, for example, 10 cycles before the current time signal will be attenuated by α ¹⁰ and added to the current time signal, so the influence on the output will be small, and it will not be necessary to use a low-speed filter or It becomes possible to perform the same averaging function as a moving average circuit. Further, by changing the weighting amount of the weighting circuit 60, it is possible to change the degree of averaging.

As described above, the average argument difference is obtained as follows: = (2πT)· _d (15) As a result, the average argument difference proportional to the average Doppler shift frequency _d can be obtained very easily.

Next, the dispersion of the speeds of the individual components in the moving part, which is determined from the average deviation angle difference, will be explained. This variance is calculated by a deviation calculator 62, and the outputs of the difference calculators 44a and 44b are squared by square multipliers 68 and 70.
The output signals of 8 and 70 are added by an adder 72.
This will be explained using an arithmetic expression.

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

x ₁ ² =4sin ² 2πf _d T/2 ・sin ² 2πf _d (t-T/2) y ₁ ² =4sin ² 2πf _d T/2 ・cos ² 2πf _d (t-T/2) x ₁ ² +y ₁ ² = 4sin ² 2πf _d T/2 (16) The output signal of this adder 72 is a value proportional to the power of the Doppler shift frequency signal, that is, the power (voltage squared), and the amplitude of this signal is The signal is input to a smoother 74 in order to smooth the signal and to remove noise signals generated from the device (the smoother 74 does not necessarily need to be used in the present invention).

Further, the argument difference Δθ and the average argument difference are input to the difference calculator 64, and the difference (Δθ−) is obtained. Next, the difference signal is input to the 2 multiplier 66, and the difference signal is 2
Find the power (Δθ−)2. This signal is multiplied by the output of the smoother 74 in a multiplier 76.

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 period (T) before (the above-mentioned averaging circuit 54 may be used), and this signal is expressed as follows.

ΣP·(Δθ−) ² (17) However, P=4sin ² 2πdT/2 Further, the output of the smoother 74 is supplied to a summator 80 to obtain the sum.

This signal is expressed as follows.

ΣP...(18) Next, the output of each summator 78, 80 is divided into divider 8
2 and divides the output of summer 78 by the output of 80. Further, the averaging circuit 54 may be used as the summators 78 and 80. Therefore, if the output of the divider 82 is represented by D, then D=ΣP·(Δθ−Δθ/−) ² /ΣP. Since D approximates the variance and its square root approximates the standard deviation, it is also easy to find the square root of D.

The Doppler signal information obtained in the manner described above 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 is 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 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 to provide extremely high-density diagnostic information.

[Effects of the Invention] As explained above, according to the present invention, the ultrasonic reception signal is complex-transformed to obtain the deviation angle representing the Doppler frequency shift, and the deviation amount is obtained from this deviation angle difference. Therefore, the motion velocity distribution of the moving parts 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 Accurate diagnostic information can be obtained. At this time, since the delay time for arithmetic processing is only several times the transmission repetition period, it is possible to display these distributions in substantially real time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. 10... Crystal oscillator (OSC), 12... Frequency division synchronization circuit, 14... Wave transmission/reception controller, 16... Electronic scanning probe, 30... Color TV monitor, 32...
...Complex signal converter, 34a, 34b...Mixer,
36a, 36b...Low frequency filter, 40...Complex delay line canceller, 42a, 42b, 5
0...Delay line, 44a, 44b, 52...
...Difference calculator, 46... Argument angle calculator, 48... Argument difference calculator, 54... Average circuit, 62... Deviation calculator, 74... Smoother, 100... Repetition frequency signal, 102, 104...complex reference signal, 106...
...Sweep synchronization signal, 108...Clock signal.

Claims (1)

[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 reflected waves, the ultrasonic pulse beam has a frequency that is an integral multiple of the transmission repetition frequency and is complex with respect to each other. a complex signal converter that mixes a set of related complex reference signals and a received high-frequency signal to convert the received high-frequency signal into a complex signal; and a complex delay that removes signals from low-speed moving parts in the living body from the complex signal. A line canceller, a declination calculator for calculating the declination of the complex signal, and a delay line for obtaining the declination of the complex signal delayed for a certain period of time, the declination of two complex signals having a delay time difference. an argument difference calculator that calculates the difference; an averaging circuit that averages the fluctuation components of the output signal of the argument difference calculator; and a deviation calculator that calculates the deviation amount of the argument difference from the output signals of each part. An ultrasonic diagnostic apparatus comprising: measuring and displaying a deviation distribution of movement speed of a moving part in a living body. 2. An ultrasonic diagnostic device according to claim 1, further comprising a smoother for removing noise components included in the complex signal or noise components generated from the device.