JPS60253863A - Ultrasonic non-linear type parameter distribution measuring apparatus - Google Patents

Abstract

PURPOSE:To enable a highly accurate measurement of distribution by providing an ultrasonic vibrator and a means of detecting a spatial distribution of phase transition level of a measuring wave as a pumping wave to determine a coded geometrical means of the phase transition level by a special formula. CONSTITUTION:A distribution measuring apparatus is made up of a timing control section 1 for generating a transmission timing of a pumping wave, an oscillator 2, drivers 3 and 4 which produces an output in response to the output of the oscillator 2 to drive vibrators as controlled by the control section 1, vibrators 5 and 6, phase detectors 10 and 11, drivers 12 and 13 for pumping waves and the like. Vibrators 14 and 15 for generation of pumping waves are provided. The results of measurement are fed to an arithmetic circuit 17 to determine the distribution of non-linear parameters by calculating the geometrical mean according to a specified formula. This can reduce the pumping pulse to measure a highly accurate distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field of the Invention The present invention relates to an ultrasonic nonlinear parameter distribution measuring device, and particularly to a method for measuring the spatial distribution of physical properties of an ultrasonic medium such as a biological tissue. The spatial distribution of this nonlinear parameter is measured as a characteristic value of the medium by taking advantage of the fact that the sound pressure exhibits nonlinearity, which is a constant value in the − order approximation, but is proportional to the sound pressure in the quadratic approximation. Furthermore, the present invention relates to a measuring device capable of quickly and easily visualizing the spatial distribution of the pumping pulse, if necessary, which is capable of eliminating the influence of sound pressure attenuation of the pumping pulse.

(B) Technical Background and Problems The principle of the nonlinear parameter imaging method used in the present invention is detailed in Japanese Patent Application No. 119100/1982. Where,
As shown in Figure 1 (bl), a relatively low-frequency pumping pulse wave is applied coaxially with the relatively high-frequency continuous ultrasonic beam for measurement and whose traveling direction is opposite to that of the measurement beam. The nonlinear parameters on the measurement wave beam scanning line were determined at high speed by phase demodulating the measurement wave phase-modulated by the pumping pulse.However, this method still has the following problems.

That is, since the pumping pulse has a relatively low frequency, there is less attenuation in the ultrasonic medium.

For example, in living tissue, 1dB/(MHz-
cn+), and if a pulse with a center frequency of 500 Ktlz is used as the pumping wave, for example, 1c
This means that the attenuation will be approximately 0.5 dB for every m distance. Therefore, as the distance from the pumping transducer increases, the effect of the pumping pulse on the measurement wave beam decreases.
The degree of phase modulation also becomes smaller, and the final B/A
In reality, the distribution of
/A, and the output shown in Figure 1(d) is expected, but the spatial distribution of B/A obtained is as shown in Figure 1(el
As shown in the figure, the evaluation becomes smaller as the distance from the pumping vibrator increases.

In order to eliminate this kind of influence, Japanese Patent Application No. 119100/1983 discloses the following:
The process involved passing the phase demodulated output through an amplifier that can provide a gain that changes over time. This method is effective when the sound pressure of the pumping pulse at each distance from the pumping transducer is known in advance, but when actually used as an ultrasound diagnostic device, the ultrasound medium to be observed It is not possible to know exactly how the sound pressure changes inside the human body, and it has been difficult to determine the distribution of the distribution of A that is empirically valid.

(C) Object and structure of the invention As shown in FIG. 1 fbl, the present invention provides a B/A distribution ( Figure 1(e)) and Figure 1fc)
As shown in Figure 1, the geometric mean of the B/^ distribution (Figure 1 (f)) obtained when the direction of the continuous ultrasonic beam for measurement and the bombing pulse were opposite to Figure 1 (bl). By adjusting It is a feature.It will be explained in detail below.

(D) Examples of the invention Nonlinear parameters used in the present invention.

and - and the pressure of the pumping wave.

Regarding the phase modulation of the measurement wave, please refer to Japanese Patent Application No. 11910/1986.
It is detailed in No. 0.

Also for the ratio IQβ, the sound speed when the sound pressure in the ultrasound medium is zero is C6, and the density is ρ. , the nonlinear parameter of the medium is −, then the sound velocity of the measurement wave is 2ρ due to the pumping wave sound pressure 1]. Due to the change Co A, the phase demodulation ratio j of the device configured as shown in Fig. 3 is changed to φ(Zi), and the waveform of the pumping wave is changed to P(
Z), and the nonlinear parameter at position Z is −(Z), then φ(Zi)−−(f(i*g(y))−−−−
−−−−−−−−−(21 holds, therefore −(Z)
is the 1-phase demodulated output φ(Z), and G(ω) is P (-27
It is stated that what can be obtained by passing it through the Fourier transform of

According to this method, if the pumping wave is not attenuated and maintains a constant waveform regardless of Z, then Equation 2 (2)
-(Zl) can be correctly obtained from the output of a filter having an output characteristic proportional to -(Zi).

However, in general, pump waves undergo attenuation with distance. Assume now that the band of the pumping wave is not so wide, and therefore its attenuation constant is approximately constant within the frequency band of the pumping wave, and is expressed in the form α(Z) at distance Z. In this case, the waveform of the pumping wave when it comes out from the pumping vibrator is P. (Z), then P (Z) in Z-Zi of Figure 2 (at, (bl) becomes in the case of Figure 2 (81) corresponding to Figure 1 (b), and ) in the case of Fig. 2(b) corresponding to -f α(Z)dZ P b (Zi) = P o (Z) e ' --
--(41) Therefore, the phase demodulation outputs ψa(Zi) and φb(Zi) in the case of FIG. 2 (al, fb) are respectively.

(However, go(Zi-y)=P(y-Zi)) Therefore, the exponential function term is a definite integral and is a constant that does not depend on Z, so φ, (Zi)・φb(Zi)= constant Therefore, 5gn-1$a (Zi ``$b (Zi shoulder 1 ゛-(f(y)*go(y))-1--------(s
It becomes 1. po(z) is the pumping waveform immediately after leaving the pumping vibrator, and therefore.

This is because go(Zi-y) = Po(y-Zi) has a constant waveform regardless of Z.

Equation (8) is not affected by the attenuation of the pumping wave.

It represents a quantity that depends (proportional) only on f (y) = f (2Z) = - (Z).

Therefore, the Fourier transform of go(y) is G. By passing equation (8), which is the signed geometric mean of the two-phase demodulated output when (ω), through a filter with a constant frequency characteristic,
−(Zi) can be obtained.

, AZ is the total attenuation received from Z=0 to Z=L, and it goes without saying that it can be actually measured prior to measuring -(Zi).

Although the theoretical explanation has been given above, one embodiment of the present invention will now be explained with reference to FIG. 4.

In FIG. 4, 1 is a timing control unit that generates the timing for transmitting a pumping wave and the timing for switching between transmission and reception of a measurement wave; 2 is an oscillator for continuous waves for measurement; and 3
and 4 is a driver for driving the vibrator upon receiving the oscillator output, and its output is made 0N10FF possible by the control signal given from the timing control section 1; 5 and 6 are vibrations used for both transmission and reception of measurement waves. children xA and xi, 7
is the ultrasonic medium T to be measured, and 8 and 9 are receiving amplifiers.

10 and 11 are phase detectors, and 12 and 13 are pumping wave drivers. Further, 14 and 15 are pumping wave generation oscillators Xn and Xc.

FIG. 4 shows a case in which a transmitting/receiving transducer X6 or XA is surrounded in a ring shape, as shown in FIGS. 4(B) and 4(C). 1
G is a delay circuit that has a delay time corresponding to the time from the timing at which the pumping wave is transmitted by the oscillator 14 to the timing at which the pumping wave is transmitted by the oscillator 15, and outputs the input with the temporal order reversed; A circuit for calculating the geometric mean as shown in (8), 18 is a peak detection circuit, 19
The effective range of the ultrasonic pulse beam emitted from the sump wave generation transducer I4 is shown by a broken line, and the shaded area is the area that causes phase modulation in the measurement wave. In FIG. 4(A), the vibrator 5°6.14. For convenience, the arrangement of '15 is assumed to be symmetrical as shown in Figure 2.

Z2 is the distance of the section to be measured, that is, the section where phase modulation occurs in the measurement wave, and Z+ is the distance between the section to be measured and the vibrator 5 or 6. Measurement section and bombing wave generation vibrator 14
15 is slightly different from z+, but in the following explanation, it is assumed to be equal to Z1 for convenience. FIG. 5 shows time waveforms of the main parts of FIG. 4, and FIG. 5 shows the same signal names as FIG. 4. First, the timing control section 1
According to the transmission instruction signal DvB (Fig. 5(a)) from
The vibrator 14 is driven by the driver I2, and a pumping wave is sent out. At this time, the measurement wave driver 3 has already been enabled to operate by the data 1 signal G, and the transducer 5
The time from when the continuous wave for measurement passes through the medium to be measured and begins to arrive at the transducer 6 is 1tc+, the time from the transmission of the pumping wave by the transducer 14 is Later it starts to undergo phase modulation and the Bonn oscillator 2
Compare the phase of the output of VIIB with the phase of It will be man-powered by 16.

After a time T from the transmission of the pumping wave by the vibrator 14, as shown in FIG. 5(b), the pumping wave is transmitted in the opposite direction to that in the previous case with the control signal DV set to 1-RIG. In exactly the same manner, the phase demodulation output φAft+ is outputted from the two-phase detector 11 as shown in FIG. (t), the one corresponding to Z=Z, +Z2 was obtained first, and the one corresponding to Z=Z, was obtained last, but in the case of φ7(t), the one corresponding to As shown,
The one corresponding to Z=ZI is obtained first, Z=ZI÷z2
The one corresponding to is finally obtained. So, φ
8(t) and the Z axis (therefore, the time axis) are reversed.

As shown in FIG. 5, tel (g), the delay circuit 16 has a φ
The waveform φD (tl) obtained by reversing the front and rear of 8(t) is outputted in accordance with the timing of φ of FIG.

Needless to say, it can be configured by an A/D converter, a memory, a D/A converter, and a memory address control circuit. Furthermore, it goes without saying that data can be transferred in the opposite direction and can be configured using a BD, CCD, or the like. φ obtained in this way. (tl is the geometric mean sent to the arithmetic circuit 17 together with φ7(t) and shown in equation 2 (8), D-(t) a n
(tl- is output. The arithmetic circuit 17 has two signals, for example, as shown in FIG.
It goes without saying that this can be realized with a circuit consisting of M), D, and l/A converters. or.

Needless to say, this can be realized by a multiplication/square root circuit using an analog multiplier.

It is clear that the function set forth in claim 1 can be realized by using the configuration as described above.

The present invention further provides means for compensating for changes in total attenuation due to changes in one diagnostic location. Equation (7) or −f α(
Z) dZ As is clear from the above, when the thickness of the total attenuation amount e 0 changes, φ, (Zi)·φb (Zi) also changes. -f
α(Z) dZ So, when e '3 becomes smaller due to large attenuation,
φ, (Zi)·φb (Zi) also becomes smaller. Therefore, it is necessary to correctly calculate -(f(y) *go(y)) and correctly divide sgn-rra-=gonko.Constitutions 18 to 21 shown in Fig. 4 are for this reason. The peak detection circuit 18 outputs the peak value of the signal received by the transducer 5. The sample hold circuit 19 outputs the peak value of the signal received by the transducer 5. It is clear that the pumping wave sent out maintains the output voltage of the peak detection circuit at the timing received by the vibrator 5. ■ is sent to the square root circuit 20.

It is sent to the division circuit 21 and is divided by 5Bn-ζ17 and T7.

By doing the above, the influence of the amount of attenuation caused by the change in the diagnosis position is removed and the true −·f (y) tree g is obtained. (y), and furthermore, as shown in Figure 4 (A), as shown in Fig. 4 (A), due to <, -, an output -(1) proportional to -(Z) can be obtained without being affected by attenuation. is clear.

In the above explanation, the detected phase φA(tl, φ, (t)
The geometric mean of .

log it= (tL to (t)−< logφ
It goes without saying that by setting A<tl+, an output can be obtained in which the influence of the attenuation amount dependent on Z is removed.

(E) Effects of the Invention As described above, according to the present invention, compared to the previously proposed measurement of the nonlinear parameter (Z) of an ultrasonic medium, the influence of attenuation is reduced and its distribution can be measured with higher precision. I can do something.

[Brief explanation of drawings]

FIGS. 1 to 3 are explanatory diagrams for explaining detailed explanations of the present invention, FIG. 4 is an embodiment of the present invention, FIG. 5 is an explanatory diagram of the operation of the configuration shown in FIG. 4, and FIG. 4 shows the structure of an embodiment of the delay circuit (DL) shown in FIG. 4, and FIG. 7 shows the structure of an embodiment of the arithmetic circuit (CALC) shown in FIG. In the figure, 1 is a timing control section, 2 is an oscillator, 3 and 4 are drivers, and 5 and 6 are transducers for transmission and reception, respectively. 7 is an ultrasonic medium to be measured, and 8 and 9 are receiving amplifiers, respectively. 12.13 is the driver of the pumping wave phase, 14゜1
5 represents a pumping wave generating vibrator. Patent applicant: Fujitsu Ltd. Representative Patent Attorney Mori 1) Hiroshi (1 other person) ('f) [''
]”]”]”] - d ＾ Nノ - NONA Figure 4 (3) (C) d Yama Shin Dan 3 Ra Village -

Claims (1)

[Claims] (t) (4) Time-divisionally transmitting a continuous ultrasonic beam for measurement of relatively high frequency and low sound pressure that passes through an ultrasonic medium from transducer XA to XB or from transducer XB to XA. receiving XA,
A pair of ultrasonic transducers or an ultrasonic transducer array called XB. (b) Parallel or almost parallel to the continuous ultrasonic beam, and having common parts with the continuous ultrasonic beam almost everywhere between the pair of transmitting and receiving ultrasonic transducers, and in the direction of propagation of the ultrasonic wave. A pumping pulse ultrasonic wave of relatively low frequency and high sound pressure is transmitted to the transducer
XC transmitted from D or from the vibrator xc in a time-sharing manner;
A pair of ultrasonic transducers or an ultrasonic transducer array named XD. (c) When the continuous ultrasonic beam for measurement is heading from the measurement transducer XA to XB, the amount of phase transition of the measurement wave due to the pumping wave traveling in the opposite direction to the ultrasonic beam is on the axis of the continuous ultrasonic beam. means for detecting the spatial distribution φhB(Z). (d) When the continuous ultrasonic beam for measurement is heading from the measurement transducer XB to XA, the continuous ultrasonic beam axis of the amount of phase transition of the measurement wave due to the pumping wave traveling in the opposite direction to the ultrasonic beam and means for detecting the spatial distribution φIIA(Z) above. (B) Same spatial coordinate Z on the above continuous ultrasound beam axis
Signed geometric mean sgn (φAB (Z)・φBA (Z)) of the phase transition amounts determined in (c) and (d) above in
・Iψ^B(Z)・φBA(Z) l Perform the operation 1 over the entire observation area on the continuous ultrasound beam axis, and calculate the amount of phase transition determined in (c) and (d). A means of determining the spatial distribution of the signed geometric mean. An ultrasonic nonlinear parameter distribution measuring device characterized by: (2) The continuous ultrasound beam sent out from the transducer or transducer array XA or xp
means for measuring the amount of attenuation received until reaching B or XA; and means for dividing the signed geometric mean of the amount of phase transition by the amount of attenuation. An ultrasonic nonlinear parameter distribution measuring device according to claim (1), characterized in that: (3) The ultrasonic nonlinear parameter distribution measuring device according to claim (1) or (2), further comprising a filter having characteristics substantially equal to the inverse characteristics of the frequency characteristics of the pumping wave.