JPS6234538A - 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 Field of Application] The present invention relates to an ultrasonic diagnostic apparatus, and particularly to an improved ultrasonic diagnostic apparatus that can accurately display the motion velocity distribution of a moving part in a living body. [Prior Art] The ultra-high frequency pulsed Doppler method has been put to practical use in order to measure the speed of movement of moving parts in a living body, such as blood flow or body fluid flow in organs such as the heart, circulatory organs, and blood vessels. Therefore, the speed of movement can be measured by detecting the Doppler frequency shift of the reflected echo from the moving part in the living body. In this case, it is necessary to receive the reflected echo from the constantly changing reflector and perform quick signal processing, and conventionally only the motion speed of a limited specific In motion part that falls at a predetermined depth is determined. I couldn't. Therefore, the speed 1 position that follows the fluctuations of the biological body's both speeds and 4's section. Various devices have been developed to measure li. For example, an ultrasonic pulsed Doppler device with a large number of channels

[pu,
There is a device that can measure the blood flow velocity distribution in a desired area at once. However, since this device 6 consists of a narrow band (usually several kHz), it is not possible to collect Doppler information at high speed, and it is not possible to observe changes in blood flow status with B-mode scanning. It was a national crisis, and because it required a large number of tunnels, it had the disadvantage of increasing the size of the shield and increasing its height. Therefore, as a device that distributes the motion velocity within the desired range of the diagnostic region at a higher speed than before and in real time,
A device was proposed to convert the received high-frequency signal into a complex signal,
Various improved devices related to this have been disclosed. This device is highly sensitive to received high-frequency signals obtained from within a living body. [The received high-frequency signal is generated by mixing a single-wave pulse beam transmission A with a frequency that is an integer multiple of the repetition frequency A, j, and a set of complex λ, jJ Il'-signals that are in a complex relationship. Convert it into a complex signal and find the 1Q angle of the complex, +: (, "; of this received high-frequency signal. This declination angle corresponds to the Doppler frequency deviation of the velocity of the moving part in the body. The motion velocity distribution of the moving parts in the living body can be measured from this declination value. Although it is possible to depict the motion state of the moving parts in the living body, there is a problem in that there is a limit to the speed that can be measured.In other words, the measurable speed range is limited to the By shortening the transmission repetition period and increasing the frequency, high-speed measurement becomes possible. The attenuation that occurs when the waves are transmitted and received is large, and because of this, it is difficult to obtain a signal with a good S/N ratio from deep within the body. Therefore, there is a limit to increasing the ultrasound transmission repetition frequency, and there is a drawback that the motion velocity distribution of the moving part cannot be accurately measured. OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to provide an ultrasonic diagnostic apparatus that can measure and display the motion velocity distribution of moving parts within a living body over a wide range. Our goal is to provide the following. [Means for Solving the Problems] In order to achieve the above object, the present invention (1) transmits an ultrasonic pulse beam into a living body at a constant repetition frequency and receives and amplifies the reflected waves. The received 8-frequency signal is converted into a complex signal.
] Weird JIJ! The complex signal transformer and the complex (c
A fighting angle calculation book that calculates the declination angle of the Doppler signal from the 'i,
The above-mentioned ? ! Two ?obtained from the 2-Mokubutsu-go converter? It consists of a sum calculator and a difference calculator that calculate the sum and difference of the components of 12-tooth number 3, and a divider that performs the division Q of the error output of this sum wave () and the output of the difference oil mouth unit. A Doppler signal Σ extractor is installed, and from the declination of the Doppler signal obtained by this Doppler signal extractor, 1fIs luck 1PI
It is characterized by determining the J speed distribution. In the above J, Una configuration, if J:, B! contains Doppler frequency shift information! One rri-wave received signal is converted into a complex signal having a real part and an imaginary part, and the sum and difference of the real part and imaginary part of these two complex signals are determined, for example, +Jj By dividing the number part by the real part, a Doppler signal containing Doppler frequency shift information in a wide range of frequencies is extracted. Then, by controlling the declination angle of this Doppler signal, a wide range of transport fJJ velocities can be obtained. That is, since the declination angle of the Doppler signal corresponds to the Doppler frequency shift, the magnitude of the velocity of the moving part can be determined from the magnitude of the value of this declination angle. [Example 1 Based on the following drawings, preferred 4 for Mizumoto? An example will be explained. FIG. 1 shows an ultrasonic diagnosis Igi device according to the present invention, in which a crystal oscillation 3 (O
20) The output of 10 is supplied to a frequency division synchronization circuit 12, and each output signal of a desired frequency is obtained by this frequency division synchronization circuit 12. These output signals are a repetition frequency signal 100 for ultrasonic pulse beam transmission, a complex 1! for complex transform! It includes quasi-signals 102 and 104, a station reference signal 106 for displaying the results of ultrasonic transmission and reception, and a clock signal 108 for synchronizing each part of the apparatus. The 11α complex reference signals @102 and 104 are synchronized with the transmission repetition frequency im (or transmission repetition period) and are transmitted to the transmission burst 1 at the carrier frequency f. , and the signal waveforms 5in2πft and cos2πrot have a complex relationship of π/2 in phase with each other. This complex radical I (ξ signal 102.104 has a frequency that is an integral multiple of the transmission repetition frequency signal, is equal to the carrier frequency (fo-ω0/2π) of the transmission burst wave, and has a phase difference of π/2 from each other. The repetition frequency signal 100 for transmission is supplied to the electronic scanning probe 16 via the wave transmitting/receiving controller 14, excites the probe 16, and generates an ultrasonic pulse beam. is transmitted into the subject 70.Then, the reflected echo from the subject 70 is converted into an electrical signal by the probe 16, and sent from the wave transmitting/receiving controller 14 to the high frequency amplifier 18, where it is amplified by a certain amount of T. After that, the output of the high frequency amplifier 2A18 becomes B
mode or M mode display, DSC (digital scan 1
The signal is supplied to a thin converter) 24, and is brightness-modulated and displayed on a color TV monitor 30. The wave transmission/reception controller 14 periodically scans the object 70 with the ultrasonic pulse beam output from the probe 16 based on techniques such as electrical angle deflection, or adjusts the angle of deflection to a desired angle. Controls such as stopping scanning are performed at . A characteristic feature of the present invention is that a Doppler signal having a wide range of velocity information is extracted from the complex (++n) obtained by complex-transforming the received high-frequency signal, thereby determining the accurate velocity of the motion reflector. Therefore, in this embodiment, the other output of the high frequency amplifier 18 is first supplied to the complex signal converter 32 and converted into a complex signal. mixers 34a and 34b, and in each section F, the received high frequency signal is mixed with the multiple reference signals 102 and 104, respectively.
These complex reference signals 102.10/
Since l has a complex relationship with phases different from each other by π/2 as described above, each measer 34 outputs a complex signal corresponding to a high frequency signal. In other words, the mixer 34 performs a mixed detection function by combining the received high frequency signal inputted with J: and the towing reference (, i 5 in 2 π
Fot, cos2π fot, and other sum and difference frequency signals are output, and both of these signals are supplied to low-pass filters 36a and 36b, and only the difference frequency component is extracted. Also, this Miki 34a, 34b
The received high-frequency signal, which is an input signal, is a pulse wave containing Doppler information, and the complex reference signals 102 and 104 are continuous waves of a single frequency. Therefore, Doppler information is also included in the frequency component of the difference, and by detecting the frequency component of this difference, the speed of the moving part can be determined. The above signal processing will be explained using mathematical expressions below. The complex reference signal 102 has a frequency r that is an integral multiple of the repetition frequency r of the transmission high frequency signal. (or a frequency that is synchronized with the transmission repetition period and equal to the frequency f of the transmission high-frequency signal), and is a continuous wave signal. If the amplitude is 1, the complex 10M signal 102 is represented by a sinusoidal voltage signal sinω0[...(1). In addition, the reception high frequency signal received by the probe 16 has a transmission frequency of ro(
= ωo/2π), then sin (ωot+ω, 11
)...9 shown in (2), however,
ωd is the Doppler shift angular frequency Z! ; is. Next d, 'nee AlJ-34a F is compound, g jJ i
Product of the frequency signal to No. 102 and Buddhism, that is,
The product of equation (1) and equation (2) is taken, but the equation is
The output of Mi%4J-34a is expressed by the following formula, which is twice the product of 6 and φ. Co5(/Jdt −cos(20Jot +−ωd
t) - (3) This output signal is passed through the low-pass filter 3
In Ga, 2a)! Since the frequency of −ωd is removed,
The output g of the filler 36a is cosωdt...(
4) Yell. Also, the other one? l! The two-base unit M104 is π/2 with respect to the reference signal 102, and the IJ phase is 'll, so the CO
Sωot...(5)
Naru cosine, 72! Indicated by a voltage signal. Similarly to the above, due to the mixed detection action of the mirror 34b and the action of the low-pass filter 36b, the output signal of the filter 36b is sinωd
6) It becomes a signal. 11, the signal of equation (4) is the real part, and the signal of equation (6) is the imaginary part. What do you say? These confidences; 3 is expressed in double book format/1゛-, and 7r-
cosωL 4 jsinω, t −(7
) and r3Gnoru. Low] υY堡KunVself-obligation moxibustion Å The compound tree Buddhist name Zr, which has been complex-transformed in the above manner, is A/
The signal is converted into a digital signal by D-transformer 1% p38a, 38b), and in this embodiment, it is manually inputted to the next stage complex air line ink I/Nhira 40. , na(b, said Δ2/
[] When the lock signal 108 is supplied to the converter 38, leanbring is performed on the cock signal. However, it is possible to extract the velocity signal of only the moving part by removing the reception interference from the 1'+9 part or low-speed moving part in the living body.In general, for example, blood flow signals from the living body can be extracted. Reverse signals (clutter) from almost stationary living tissues such as blood vessel walls and heart walls are mixed in, and this signal is usually stronger than the reverse signal from the blood flow, so it is difficult to measure blood flow. cause significant interference. Therefore, if only the signal from the moving part is detected by the complex delay line ↑Yanrera 40,
The quality of Doppler signals can be improved. This complex f erase line number 1! The controller 40 includes delay lines 42a, 42b having a delay time corresponding to one period T of the repetitive signal, each delay line 42 consisting of storage elements equal to the number of clock pulses that are combined in one period 'F. It can be replaced with memory or shift register. And, following these delay lines 42a and 42b,
Differential portions t5 units 44a and 44b are connected to each other,
Difference wave σ2! Input of delay line 42 by i44,
In other words, the signal at the current time and the signal from one cycle before are compared successively at the same - Fukamaro, and the difference in one cycle section of the signal is calculated f1-J.
-ru. Therefore, since there is no change or a small change between the signal at the current time and the signal at the current time and the signal from the 4i signal one cycle ago, the difference signal from the static 1 signal or from a low-velocity moving part (living tissue) is small. The output of device 714 will be close to zero. Further, the output of the blood flow No. 15 having a high velocity, for example, is detected as a large value, and thereby the above-mentioned clutter can be reliably suppressed. In addition, in the embodiment, the delay wine canceller 4
The input t31 to 0 is a digital signal, but the A/D converters 38a and 38b are eliminated and a low-pass filter 36a is used.
, 36b output signal directly to -f erase line-! F p
The signal can be input to the analyzer 40 and processed using an analog signal. In this case, it is necessary to insert an A/D converter between the averaging circuit 60 and the argument calculator 62, which will be described later. The operation of the delay wine canceller 40 is illustrated below.
I will explain it in Type 7. In addition, in the examples, a continuous wave will be used to explain the explanation in detail. The current ■, 1 hour human power signal to delay line 42a is CO
When expressed as Sωdt, (ij ′;j s, that is, the output signal of the delay line 42a one period before
(t-T), and the output signal X of the difference wave p unit 44a is expressed as x=cosω(t-T)-CO3ωd[...(
8) It becomes. In addition, the current time input signal to the delay line 42b is
When expressed as inωd[, the signal one cycle before, that is, the output signal of the delay line 42b, is expressed as Sinωd(tr), and as a result, the output signal y of the difference part tAiZ44b
is, V=S! nωd(j T) S! nωdj...
(9) becomes. As described above, the signals x and {circle around (2)} are outputted to the outputs of the difference sections n/14a and 44b, respectively. This signal is obtained after the reflected echo signals from stationary parts and slow moving parts are removed. Doppler Signal Extraction Next, Doppler signal extraction, which is a feature of the present invention, will be explained. Extraction of the Doppler signal is performed by a Doppler signal extractor 46,
This Doppler signal extractor 46 includes a delay line 48a,
48b, summation unit 50a, difference wave isolater 50b, and divider 5
It is composed of 2. Then, the signal X (representing the real part) outputted from the complex delay line canceller/IO is supplied to the delay line 48a, and the signal y (representing the imaginary part) is supplied to the delay line 48b, and the signal X (representing the imaginary part) is supplied to the delay line 48b. It is manually inputted to the difference wave Q device 50b. This summation unit 50a converts the signal Rx delayed by one round to 0.
1, the sum of these two signals is stopped, and the other difference calculator 50b similarly receives the signal y after one period d and calculates the difference between the two signals as FAo. The outputs of these sum operators', + ('4, 'j and the difference operator 50b are supplied to the divider 52, and the sum output representing the real part is divided into the output of the difference part representing the imaginary part. The output of this W divider 52 is a Doppler signal having a wide range of speed information, and from this it is possible to obtain the accurate speed of the moving part.This Doppler signal is obtained using the following formula. The process for this will be explained. If the input signal at the current time to the delay line 48a is the equation (8) above, then the signal one cycle before, that is, the output signal of the delay line 48a, is expressed as follows. As a result, the sum The output signal X of the arithmetic unit 50a is as follows. Further, if the input signal of the current row time to the delay line 48b is expressed by the above equation (9), then the signal of one cycle before, that is, the output signal of the delay line 48b is expressed as follows. As a result, the output signal Y of the difference wave converter 50b is: ■=4sinωd() ” Slnω6 (j-T)
■ -3! n'')d(T)-(il).Then, the division of the output signals X and Y is calculated by the divider 52.
However, when the output j of this split C7 vine 52 is expressed by the Doppler signal S, it is expressed by the following equation. One -- X 43! nωd(-)・S! nωd(t-T) ■ 4sinωd(=)・sinω, (t-T)■ ■ cosωd(--) ■ The Dovry No. 3 S, which has been given 1g in this way, has a wider range of speed information than before. This is a Doppler signal, and as will be described later, since the output signal of the υ07 unit 52 includes signal fluctuation components and noise components generated from the device, an averaging circuit 6o is provided to remove these components. In other words, this averaging circuit 60 outputs an output signal extended by one period H on the delay line 56, adds it to the input signal at - time in the adder 54, and sends this output again to the delay line 5.
Repeat the operation of supplying to 6-1 but simply this P2
As the operation is repeated, the output candy of the adder increases successively as the number of additions increases, and finally saturates. Therefore, a circuit 58 is provided to reduce or subtract the output and add the input signal C'f 1J. In this case, if the attenuation amount is α and V, then the signal 10 cycles earlier than the current signal is α10.
Since the signal is attenuated and added to the signal at the current time, the degree of influence on the output is reduced, and the 4T average can perform the same function as a low-frequency noirter or a moving average circuit. Also,
By changing the opening of the assembly circuit 58, it is possible to change the degree of averaging. Therefore, the average 1(i E; of the Doppler signal output from the averaging circuit 60 is: ■ H= tanωd(-) =-(
13). Then, the output of the averaging circuit 60 is supplied to a one-angle Q-factor 62, and the argument angle θ of the Doppler signal S is determined by the following equation. (14) Since the transmission repetition period T is a constant, the argument θ, which is the output of the argument calculation unit 62 obtained in this way, is determined by the Doppler shift frequency ``d (=ωd/2π)''. It is understood that it is proportional, and therefore the declination angle O is proportional to the blood flow velocity. Also, since the declination angle θ takes positive and negative values, respectively, ±π
/2 is measurable. Furthermore, if we distinguish the sign S2 of the signal ViX r Y in the Doppler name extraction unit 46, ±π
It becomes possible to measure the deflection angle θ up to the point where the direction of the velocity of motion can be determined. Here, the Doppler shift frequency range of the Doppler signal obtained by the present invention and the Doppler signal obtained by the conventional apparatus will be compared. The conventional device a-3 uses a device similar to the complex signal converter 32 used in this embodiment to calculate the Doppler shift frequency rd.
When (-ωd/2π) is detected, the final Doppler signal So' including the Doppler shift frequency is obtained by the following equation. 3D= = −= janωd−T = tan2π
rdT× Therefore, the Doppler shift frequency [d is given by: However, frp (= 1./T) is the transmission repetition frequency. In this case, the measurement range of the above formula tan-'(y/x) (corresponding to the shoulder angle of the present invention) is up to -π/2-·π/2. However, a folding phenomenon occurs in this range! This is a range that does not cause any damage. Therefore, the range of Doppler shift frequencies that can be measured is conventionally expressed by the following equation. In addition, in order to widen the frequency range that can be determined by ζ, Jil+ in the conventional device, the signal X which is the output of the complex signal converter 32 is
It is done to determine the sign of y and y, which is V/X
J: To determine which quadrant the value of belongs to,
The target of tan-1(y/ , in the present invention, the above-mentioned Doppler signal S is expressed as the final Doppler signal from the above-mentioned equation (12) as follows: ■ 3 − tanωd=jan7r 1dT Therefore, a measurable Doppler deviation in which no aliasing phenomenon occurs The transfer frequency range is as follows.Comparing the above equation (15) and this equation (16), equation (15) distinguishes the sign and shifts the frequency range to 2.
Since this is the Doppler shift frequency range when expanded to A8, it is understood that in the present invention, the measurable Doppler shift frequency range in J3 is expanded to A28. As a result, it is possible to iq a wide range of velocity distribution of the moving part in the living body, and it is possible to provide velocity information useful for diagnosis. Further, in the present invention, the movement direction can be identified by different colors on the color TV monitor 30 shown in the figure. For example, by displaying positive velocities in red, negative velocities in blue, and echoes reflected from stationary tissues in white, phase information within the body and directional velocity information of blood flow can be displayed simultaneously, resulting in extremely high Density diagnostic information can be provided. [Effect of the invention 1 As explained above, according to the present invention, a Doppler signal extractor is provided to obtain a Doppler signal that provides a wide range of velocity information, so that the motion velocity distribution of the moving parts in the living body can be improved. The measurement ability can be improved by about 2 times, making accurate speed measurement 1TIQj more accurate. In addition, the present invention t.1 is an apparatus that can continuously determine the motion velocity distribution of a moving part in a 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. Therefore, extremely accurate diagnostic information can be obtained for moving parts, and the delay time for declination calculation processing at this time is a delay of an integral multiple of the transmission repetition period.
．． Since the distribution is only for one period, it is possible to display these distributions substantially in real time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention. 10... Crystal oscillator (O20) 12... Frequency division synchronization circuit 16... Probe 30... Color TV monitor 32... Complex signal change 19! mixers 36a, 36b... low-pass filter 40...
・ Complex delay line chitonsera 42a, 42b
... Delay lines 44a, 44b ---
Difference wave n346... Doppler + sign extractor 48a, 48t)... Delay line 50a
... Sum calculator 50b ... Difference calculator 52 ... Divider 60 ... Average circuit 100 ... Repetition frequency signal 102.10/l ... Complex reference signal 106
... h1 weight-specific signal 108 ... clock signal.

Claims (3)

[Claims] (1) A complex signal converter that converts the received high-frequency signal obtained by transmitting an ultrasonic pulse beam into a living body at a constant repetition frequency and receiving and amplifying the reflected wave into a complex signal, and converting the complex signal into a Doppler signal. An ultrasonic diagnostic apparatus that measures and displays a motion velocity distribution of a moving part in a living body, including a declination angle calculator that calculates a declination angle, and which measures and displays a motion velocity distribution of a moving part in a living body. A Doppler signal extractor is provided, which includes a sum operator and a difference operator that calculate sums and differences, and a divider that divides the output of the sum operator and the output of the difference operator. An ultrasonic diagnostic device characterized by determining an accurate motion velocity distribution from the declination angle of a Doppler signal obtained by the device. (2) An ultrasonic diagnostic apparatus according to claim (1), further comprising a complex delay line canceller that removes a signal of a low-speed moving part in a living body from a complex signal. (3) In the apparatus described in claims (1) and (2), an averaging circuit is provided for removing a fluctuation component of the output signal of the Doppler signal extractor or a noise component generated from the apparatus. Features of ultrasonic diagnostic equipment.