JPH0139057B2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Technical Field of the Invention The present invention relates to a device for measuring the temperature or spatial distribution of temperature change in an ultrasonic medium such as a biological tissue, and particularly relates to an apparatus for measuring the spatial distribution of the temperature or the amount of temperature change in an ultrasonic medium such as a biological tissue, and in particular, the present invention relates to an apparatus for measuring the temperature or spatial distribution of temperature change in an ultrasonic medium such as a living tissue. The present invention relates to an ultrasonic temperature measurement device that utilizes the temperature dependence of the parameter (B/A) _e , temperature velocity C, and density ρ.

(B) Prior art and its problems Conventionally, as a method for obtaining the temperature distribution in an ultrasonic medium such as a living tissue, the temperature dependence of the sound velocity C is used to measure the spatial distribution of the sound velocity. There are known methods to obtain spatial distribution, but
This method has the following problems.

First, the sound velocity is measured using the so-called transmission method, and the spatial distribution of the sound velocity is obtained using an image reconstruction method similar to that used in X-ray CT, which requires a huge amount of calculations and takes a long time. It takes.

Second, in order to reconstruct an image, it is necessary to be able to measure the sound velocity over the entire circumference (360 degrees) of the object to be measured using the transmission method. In most cases, there are parts where ultrasonic waves cannot pass through due to the influence of gas, making it impossible to measure the entire circumference. Therefore, the image will be reconstructed using missing data, and the obtained sound velocity distribution, and hence the temperature distribution obtained from the sound velocity distribution, will have many errors.

(C) Object and Structure of the Invention The object of the present invention is to quickly and easily measure temperature distribution or temperature change distribution in an ultrasonic medium without using image reconstruction techniques such as those used in X-ray CT. We are here to provide you with the equipment you need.

In the present invention, f((B/A) _{e ,} C, ρ) = 1/ρC(B /A) _e
can be easily obtained in real time without using image reconstruction methods such as X-ray CT, and since (B/A) _e , C, and ρ have temperature dependence, 1/ρC (B/A ) Taking advantage of the fact that _e is also observed as a different value depending on the temperature,
The temperature distribution or temperature change distribution within the ultrasonic medium is estimated by observing 1/ρC(B/A) _e .

In the following, the principle will be explained first, and then embodiments will be explained.

(D) Embodiment of the invention The sound speed when the sound pressure in the ultrasonic medium is zero is C ₀ ,
If the density is ρ ₀ , the sound speed C when a sound pressure of P is applied from the direction perpendicular to the measurement wave is C=C ₀ +1/2ρ ₀ C ₀ (B/A) _e P ……(1) Here (B/A) _e is defined by the following equation and is called an "equivalent nonlinear parameter" and takes different values depending on the location in a non-uniform medium.

(B/A) _e = 2ρ ₀ C ₀ (∂Ci/∂Pj) _s ...(2) i and j are orthogonal directions, and S indicates isentropy.

On the other hand, the nonlinear parameter B/A, which is generally used in the field of acoustics, is defined as follows.

B/A=2ρ ₀ C ₀ (∂Ci/∂Pj) _s ...(3) If it is an isotropic body, Poisson's ratio is ν and (B/A) between _e and B/A is (B/ A) _e = (1+2ν-1/1-ν)B/A...(4
), and in liquids and biological tissues, ν≒0.5
Therefore, it can be regarded as (B/A) _e B/A.

Therefore, due to the sound pressure P of the pumping wave, the sound speed C
will change by △C=1/2ρ ₀ C ₀ (B/A) _e・P ...(5).

Now, as shown in Figure 1, the transmitting ultrasonic transducer
A continuous wave ultrasonic beam Wm for measurement is sent from X _A into the medium to be measured in the Z-axis direction in the figure, and this beam is received by the transmitting ultrasonic transducer X _B. At this time,
A plane pulse wave Wp is sent as a pumping wave in the X-axis direction by another ultrasonic transducer Xp from a direction intersecting the measurement beam Wm as shown in the figure. In the following, for simplicity, it is assumed that the intersection angle is a right angle. Also, Wm
The sound pressure of Wp is sufficiently small compared to the sound pressure of Wp, and formula (1)
As for P in ~(5), it is only necessary to consider what is due to Wp.

While the pumping wave Wp intersects the measurement beam Wm, the waveform at each Z of the measurement beam Wm changes depending on the location according to equation (5). △C(z)=1/2ρ ₀ C ₀ ( B/A) _e (z)・P……(
6) Therefore, it will receive a phase change proportional to △C(z) that differs depending on the location (z). Therefore, (B/A) _e (z) can be estimated conversely using the phase information of the received signal from the receiving transducer X _B and P measured in advance.

The method for estimating (B/A) _e (z) will be explained in detail below.

FIG. 2 schematically shows what kind of sound pressure the measurement beam Wm receives from the pumping wave Wp as it advances.

Let P(f) be the sound pressure of the pumping wave. Time t=0
At time t=△t, the measurement wave receiving sound pressure P(o) at z=z ₀ becomes z=z ₀ at time t=△t.
+△z=z ₀ +C ₀ △t, and at this time P
It receives a sound pressure of (t+Δt) (see Figure 2B). Thereafter, in the same manner, the sound pressure is received as shown in FIG. 2C at time t=2Δt and as shown in FIG. 2D at time t=3Δt. As you can see, in general, the measurement wave at z=z ₀ at t=0 is
The change in sound speed at z=z is △C(z)=1/2ρ ₀ C ₀ (B/A) _e (z)P(△t
) = 1/2ρ ₀ C ₀ (B/A) _e (z)P(z-z ₀ /C)
...(7) However, here the value of △C(z) is smaller than C ₀ , and △t is the time required for the measurement wave to move from z = z ₀ to z = z. △t = z- It was approximated to be given by z ₀ /C ₀ ...(8).

Therefore, the measurement wave that was at z=z ₀ at t=0 becomes z=
The change in phase experienced by z is expressed as △φ(z)=K・(B/A) _e (z)・P(z−z ₀ /C
₀ ) ...(9), and the total phase change that this measurement wave undergoes from the time it leaves the transmitting oscillator X _A until it is received by the receiving oscillator X _B is φ(z ₀ ) = ∫ ^∞ _{- ∞} △φ(z)dz =K∫ ^∞ _-∞ (B/A) _e (z) ・P(z-z ₀ /C ₀ ) dz ...(10). Here, if we set g(z ₀ −z)=P(z−z ₀ /C)...(11), equation (10) becomes φ(z ₀ )=K∫ ^∞ _-∞ (B/A) _e ( z) g(z ₀ −z) dz = K [(B/A) _e (z) * g(z)] ...(12).

Here, "*" in equation (12) is a so-called convolution integral. This equation shows that for (B/A) _e (z), the function g (z) serves as a weighting function and gives φ(z ₀ ).

Formula (b) If we perform Fourier transformation, Φ(w)=K・(B/A) _e (w)・G(w)……(13
) (However, Φ(w), (B/A) _e (w), and G(w) are the Fourier transforms of φ(z), (B/A) _e (z), and g(z), respectively, and w is the coordinate axis spatial frequency for Z), and from this (B/A) _e (w)=1/K1/G(w)Φ(w)...
...(14) (B/A) _e (z) = 1/K 〓 ^-1 [1/G(w)・Φ(w)] ...(15) Find (B/A) _e (z) I can do things.

Equation (14) shows that (B/A) _e (w) can be obtained by passing Φ(w) through a filter with a frequency characteristic of 1/K1/G(w). Therefore, when calculating (B/A) _e (z), it is not necessarily necessary to perform inverse Fourier transform as shown in equation (15); instead, a filter with a frequency characteristic of 1/K1/G(w) is prepared in advance. By inputting φ(z) into it, (B/A) _e (z) is obtained as the output. Further, G(w) can be obtained from P(t) using Equation 11. If B/A(z) obtained in this way is displayed as an image, a spatial distribution image of B/A(z) can also be obtained.

In the above explanation, C ₀ and ρ ₀ were treated as constants, but
In fact, these are also functions of location, and strictly speaking, they are not (B/A) _e (z) but [1/ρ ₀ C ₀ (B/A) _e (
z) is obtained.

Now, when the temperature of the ultrasonic medium changes, ρ ₀ ,
C ₀ and (B/A) _e also change. Therefore, [1/ρ ₀ C ₀ (B/A)] (before and after the temperature of the ultrasonic medium to be measured changes)
By knowing the change in z), it is possible to know the temperature change in each part.

As a special case, assuming that the density ρ ₀ does not change much with temperature, and that the sound velocity C ₀ and the equivalent nonlinear parameter (B/A) _e change approximately linearly with temperature, the temperature of the medium is an unknown value. T ₀ to unknown value T ₁
ρ ₀ (z) _T1 = ρ ₀ (z) _T0 = ρ ₀ (z) c ₀ (z) _T1 = C ₀ (z) _T0 +α△T However, △T=T ₁ −T ₀ (B /A) _e (z) _T1 = (B/A) _e (z
) _T0 + β△T α, β are constants...(16), and [1/ρ ₀ C ₀ (B/A) _e ] (
z) The difference △ is △=[1/ρ ₀ C ₀ (B/A) _e ] (z) _T0 − [1/ρ ₀ C ₀ (B/A) _e ] (z) _T1 = 1/ρ ₀ (z)1/C ₀ (z) _T0 (B/A) _e (z)
_T0・−1/ρ ₀ (z) 1/C ₀ (z) _T0 + α△T [(B/A) _e (z) _T0 + β△T] = 1/ρ ₀ (z) 1/C ₀ (z ) _T0 (B/A) _e (z)
_T0 [1-(1/1+α△T/Co( ₂ )T0) (1+β△T/(B/A) _e (z) _T0 )] ≒1/ρ ₀ (z)1/C ₀ (z) _T0 (B/A) _e (z)
_T0 [β/(B/A) _e (z) _T0 −α/C ₀ (z) _T0 ]△
T = [1/ρ ₀ C ₀ (B/A) _e ] (z) _T0 [β/(B/A) _e (z) _T0 −α/C ₀ (z) _T0 ]△
T...(17) becomes. However, during the calculation of equation (17), assuming that β/(B/A) _e (z) _T0 , α/C ₀ (z) _T0 ≪1, β△T/(B/A) _e (z) _T0・α△T/C ₀ (z) _T0
The section was ignored.

[1/ρ ₀ C ₀ (B/A) _e ] (z) _T0 and [1/ρ ₀ C ₀ (B/A) _e ] (z) _T1 can be measured as described above, so α, β, C ₀ (z) _T0 ,
(B/A) _e (z) If _T0 is known, △T can be found from equation (17). In fact, α, β, C ₀ (z) _T
0 and ρ ₀ (z) can be measured in advance for various ultrasound media such as liver and fat. Also, for (B/A) _e (z) _T0 , [1/ρ ₀ C ₀ (B
/A) _e (z) _T0 can be measured and ρ ₀ (z) and C ₀ (z) _T0 can be known in advance, so find the value of (B/A) _e (z) _T0 alone. I can do things. Therefore, from equation (17), △T
It becomes possible to find.

It goes without saying that if there is a correspondence between the amount given by equation (17) and the amount of temperature change, the amount given by equation (17) may be directly output.

The principle of the present invention has been explained above, and an embodiment will be explained below with reference to FIG. 3.

In Fig. 3, 1 is a timing control unit that generates the timing for transmitting a pumping wave, 2 is an oscillator for continuous waves for measurement, 3 is a driver for driving the vibrator in response to the oscillator output, and 4 is for measurement. A transducer X _A for wave transmission, 5 is an ultrasonic medium M to be measured,
6 is a vibrator X _B for receiving measurement waves, 7 is a receiving amplifier,
8 is a phase detector, 9 is a filter defined by 1/K1/G(w) of equation (14), 10 is a driver for pumping waves, and 11 is a vibrator Xp for generating pumping waves. 12 is a storage unit that stores [1/ρC (B/A) _e ](z) before the temperature of the ultrasonic medium to be measured is changed by a temperature manipulation means (not shown); 13 is an output of the storage unit 12; This is a subtraction unit that obtains the difference between the output of the filter 9 and the output of the filter 9. Also, x ₁ is the distance from Xp to the measurement beam, z _x is the distance of the measured section, and z ₁ is the distance of the measured section.
It is the distance from X _B. In Figure 3, oscillator 2
Although shown as operating independently of the timing control section 1, it goes without saying that they may operate synchronously. The filter 9 can be realized, for example, by a transversal filter using a CCD. For example, as shown in FIG. 4, the storage unit 12 can be realized by an A/D converter 15, an IC memory 16, a D/A converter 17, and a control unit 18, and is configured to operate in synchronization with the transmission of pump waves. It is controlled by a timing control section 1. FIG. 5 shows time waveforms of the main parts of FIG. 3, and FIG. 5 shows the same signal names as in FIG. 3. The time from when the pumping wave is transmitted until the pumping wave reaches the position of the measurement wave (x ₁ /C ₀ ) and the time it takes for the measurement wave that has undergone phase modulation by the pumping wave to reach the transducer X _B for the first time. Assuming that the sum of the required time (z ₁ /C ₀ ) is t ₁ , the output _VR of the receiving amplifier 7 begins to undergo phase modulation after time t ₁ from the transmission of the pumping wave, as shown in FIG. The phase modulated output continues to be output for the time t ₂ =z ₂ /C ₀ until the measurement wave that has been phase modulated by the pumping wave passes through the measured section. The phase detector 8 compares the phase of the output of the oscillator 2 and V _R and outputs the phase of V _R as a function of time φ(t) and therefore as a function of the coordinate z. This output is input to the filter 9, and 1/ρ ₀ C ₀ (B/A) _e is expressed as a function of time.
Therefore, it is obtained as a function of the coordinate z. The filter output before the temperature of the ultrasonic medium 5 is changed by a temperature operating means (not shown) is stored in the storage section 12 under the control of the timing control section 1. After the temperature of the medium is changed by the temperature manipulation means, the difference between the output of the storage section 12 and the output of the filter 9, that is, the amount expressed by equation (17), is obtained by subtraction 13 as the final output.

As described above, according to the present invention, the spatial distribution of the quantity (expressed by equation (17)) equivalent to the temperature change of the ultrasonic medium can be reproduced in complex and time-consuming images such as in the case of X-ray CT. It can be obtained quickly with a simple configuration without using any configuration method.

The second claim states that the filter 9 in FIG. 3 may be inserted after the subtraction section 13. Since the filter 9 in FIG. 3 is a linear filter with characteristics almost equal to the inverse of the frequency characteristics of the pumping wave, the difference between the two inputs x ₀ (t) and x ₁ (t) is x ₀ (t) - The output F [x ₀ (t) - x ₁ (t ₎ ] obtained by passing x 1 (t) through a filter is
Difference between filter output F [x ₀ (t)] of x ₀ (t) and filter output F [x ₁ (f)] of x ₁ (t) F [x ₀ (f)] - F [x ₁
(t)]. Therefore, the device having the structure set forth in claim 2 can also achieve the same effect as the device having the structure described in claim 1. FIG. 6 shows an example of the configuration of the device described in Section 2. Each component in FIG. 6 is given the same number as the corresponding component in FIG. 3, and a description thereof will be omitted.

Claim 3 describes a measure against the case where a correct plane wave cannot be obtained as a pumping wave. Generally, to obtain a perfect plane wave, it is necessary to use an infinitely wide flat plate resonator.
This is practically impossible. One way to obtain a plane wave approximately is to use a part of a spherical wave whose radius of curvature has become sufficiently large at a sufficient distance from the vibrator surface, but to use it as a pumping wave,
This is not necessarily suitable because the energy density per unit area becomes too small. Therefore, a pumping wave with sufficient sound pressure will not actually become a plane wave, and the sound pressure will vary not only with time t but also with coordinate z, and it will not be possible to change the sound pressure from a plane wave. If the deviation becomes so large that it cannot be ignored, it will be necessary to correct it. This correction can be performed as follows.

First, the sound pressure distribution of the pumping wave is measured in advance on the line of the measurement wave beam as a function P(z, t) of time t and coordinates. From this P(z, t),
The sound pressure change that the measurement wave, which was at z = z ₀ at t = 0, receives on the measurement wave beam line is expressed as z, where z is a parameter.
It can be found as a function g _z0 (z). This g _z0 (z) corresponds to (z−z ₀ /C ₀ ) in equation (9). Using this, calculate the weighting function (corresponding to g(z ₀ - z) in equation (11)) for the measurement wave with z = z ₀ at t = 0 in the same way as for plane waves. I can do it. Therefore, a filter having the inverse characteristic of this weighting function can be prepared in advance as in the case of plane waves, and therefore 1/PC(B/A) _e (z) can be obtained. However, unlike the case of a plane wave, depending on where the part of the measurement wave of interest is on the z-axis at t = 0, that is, depending on the value of z ₀ ,
The sound pressure distribution that the part of interest receives on the z-axis will be different. This situation is schematically shown in FIG. Note that Fig. 7A shows the sound pressure distribution when a spherical wave arrives at time t = 0, and Fig. 7B shows the sound pressure distribution originally for the measurement wave when z = z ₁ at t = 0. The sound pressure distribution on the z-axis when receiving a plane wave pumping wave, Figure 7C shows z=z ₁ at t=0.
Figure 7D shows the zero sound pressure distribution on the z-axis when the measurement wave at t = 0 receives a spherical pumping wave. The sound pressure distribution on the z-axis is shown for each case. Therefore, the weighting function corresponding to g(z) in equation (11) and the filter corresponding to 1/G(w) in equation (14) also differ with z ₀ as a parameter. In other words, this filter 9 changes depending on which z coordinate 1/ρ ₀ C ₀ B/A(z) is to be obtained, but as shown in FIG.
Since it is possible to find the sound pressure that the measurement wave of interest receives on the z-axis for each value of z ₀ , we can calculate each value from now on.
The filter characteristics for the value of z ₀ can be calculated in advance. Looking at the output of the phase detector 8 in FIG. 3 in terms of time, this means that phase changes corresponding to successively different z ₀ are output, so the above-mentioned filters for each z ₀ are sequentially applied to this output. When applied, 1/ρ ₀ C ₀ B/ as in the case of a plane pumping wave.
The distribution of A (z) can be obtained. At this time, the method of sequentially applying filters with different characteristics is as follows:
For example, the phase detector output may be A/D converted and then digital filtered.

As a special case, consider the case where the measurement wave beam is in the far sound field of the pumping wave. Since the pumping wave is a spherical wave, the sound pressure distribution on the measurement wave beam is P(wt−k√ ² + ² + ² ) can be written. Here, if y>x, z and the pump wave is in a sufficiently far-field sound field, then on the beam (y=y ₀ ) P(wt−k√ ² + ² + ² ) ≒P(wt−k (y ₀ +x ² +z ² /2y ₀ )) ≒P((wt−ky ₀ )−kx ² +z ² /2y ₀ ) ...(16) The first term is (x, y, z) = (0, y ₀ , 0), which is the phase at the center of the image plane, and the second term represents the phase shift due to position. Therefore, if we perform the variable transformation Z=z+kx ² +y ² /2y ₀ ...(17), equation (9) becomes △φ(Z)=K(B/A) _e (Z)P(Z- Z ₀ /C ₀ ) ...(18), and the image of 1/ρ ₀ C ₀ (B/A) _e (Z) is obtained by the following equations (9) to (15). Therefore, if we change the image back from Z to Z based on the relationship in equation (17), we get
An image of 1/ρ ₀ C ₀ (B/A) _e (z) is obtained. By providing a certain distance between the pumping wave and the measurement wave beam in this way, signal processing becomes very easy.

The present invention further provides the measured 1/ρ ₀ C ₀ (B/A) _e (z)
This provides a means for improving the S/N ratio of distribution such as the amount of change in . When the amount of phase change of the measurement wave due to the product of the equivalent nonlinear parameter and the sound pressure is small, noise generated within the circuit and elsewhere cannot be ignored with respect to the original amount of phase change φ(z). For this reason, φ
1/ρ ₀ C ₀ (B/A) _e (z) obtained from (z) also contains large noise. This situation is shown in FIG. By adding the noise N shown in FIG. 8B to the noise-free phase detector output φ(z) shown in FIG. 8A, a signal as shown in FIG. 8C is actually output. As a countermeasure for this, the same measurement site is measured K times and S ₁ to S _k shown in FIG.
If we obtain a noise-added signal like , and add these points at the same z coordinate, the signal component will be multiplied by K in amplitude at each point, but the noise component will only be multiplied by K in power. If the noise is random noise, the noise amplitude at each point will be multiplied by √. Therefore, the S/N ratio is improved by √ times as shown in Figure 8D.
The output shown in the figure will be obtained.

An example of a system configuration using this method is shown in FIG. In FIG. 9, the same components as in FIG. 3 are given the same numbers, and their explanations will be omitted. 9th
In the figure, 21 is a delay circuit that delays the signal by the transmission repetition period T of the pumping wave, for example.
Needless to say, it may be realized by analog means such as CCD or BBD, or by digital means using an A/D converter and a shift register or memory. 20 is an adder, which may be of either analog or digital type depending on the type of delay circuit. In the case of the configuration shown in Figure 9,
It is clear that the output Si of the phase detector 8 is added for each point on the same z-axis coordinate, and the S/N ratio can be improved by so-called synchronous addition.

In the present invention, 1/ρ ₀ C ₀ (B/A) _e (z)
It becomes possible to obtain a two-dimensional or three-dimensional distribution of the amount of change, etc. As is clear from the previous explanation, it is possible to obtain the distribution of the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z) on a specific scanning line, so the pairing of transmitting and receiving oscillators can be determined. is moved in the x, 1, and y directions while keeping the relative position constant, and the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z) is written to the memory address corresponding to each x, 1, and y coordinate. By storing the value of , it is possible to obtain two-dimensional, one- and three-dimensional distributions such as the amount of change of 1/ρ ₀ C ₀ (B/A) _e (z).

FIG. 10 shows an example of its configuration, in which the same components as in FIG. 9 are given the same numbers, and their explanation will be omitted.
In FIG. 10, a drive unit 22 is a part that moves the pair of vibrators 4 and 6 using, for example, a stepping motor, and moves the pair of vibrators in response to control pulses from the timing control unit 1. The position detection section 23 is a section that detects the position of the pair of vibrators 4 and 6 using, for example, a rotary encoder attached to the shaft of a stepping motor. The memory control section 24 receives the pumping wave transmission synchronization signal, clock, etc. from the timing control section 1 and generates a memory address corresponding to the output from the position detection section 23. The memory 25 outputs 1/ρ ₀ C ₀ (B/A) _e (z
) is A/D converted and then stored. The display unit 26 reads out the stored distribution of the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z) from the memory and displays it.

It is clear that by doing the above, it is possible to obtain a two-dimensional or three-dimensional distribution of the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z).

In Fig. 10, the pair of transducers 4 and 6 are moved mechanically, but by using a pair of so-called electronic scan probes as the pair of transducers, mechanical scanning can be avoided. Needless to say, a two-dimensional distribution of the amount of change of 1/ρ ₀ C ₀ (B/A) _e (z) can be obtained even if Furthermore, in FIG. 10, it is also possible to obtain a two-dimensional distribution image of the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z) by using the afterglow characteristics of the display tube without using the memory 25. Needless to say.

Claim 6 is the amount of change in [1/ρ ₀ C ₀ (B/A) _e ](z) obtained as described above before and after the temperature change (see equation (17)). △=[1/ρ ₀ C ₀ (B/A) _e ] (z) _T0 − [1/ρ ₀ C ₀ (B/A) _e ] (z) The coefficient appropriate for _T1 , for example, the final value of equation (17) △T of row
Reciprocal of the coefficient of K = {[1/ρ ₀ C ₀ (B/A) _e ] (z ₀ ) _T0 [β/(B/A) _e (z) _T0 −α/C ₀ (z) _T0 ])
} It states that by multiplying by ^-1 , the temperature change, etc. △T(z) itself can be obtained, and as mentioned above,
Since K ₁ can be determined in advance, in order to realize claim 6, it is sufficient to provide, for example, an amplifier of K ₇ times after the subtraction unit 13 in FIG. 10.
If K ₇ is a function of z, and therefore a function of time, it goes without saying that this amplifier may be a so-called TGC (Time Gain Control) amplifier whose gain changes with time.

Claim 7 _, as _{shown in} FIG. The relationship between △T and the amount of change in 1/ρ ₀ C ₀ (B/A) _e (z) is measured, and the 1/ρ ₀ C ₀ (B/A) _e (z) obtained by actual measurement is Or 1/ρ ₀ C ₀ (B/A
) From the amount of change in _e (z), calculate the temperature T or the amount of temperature change △T
This is an attempt to estimate the In order to realize this, the signal conversion circuit 27 corresponding to the curve in FIG. 11 must be constructed as shown in FIG. It is obvious that it can be inserted as shown in Figure 13. As the signal conversion circuit, for example, a well-known diode broken line approximation circuit may be constructed, or an A/D converter, as shown in FIG.
It goes without saying that a line consisting of a ROM for code conversion and a D/A converter may be used.

(E) Effects of the Invention As described above, according to the present invention, the spatial distribution of temperature or temperature change in an ultrasonic medium or a quantity closely related thereto can be easily realized using relatively simple means. I can do things.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams explaining the concept of the present invention, FIG. 3 is an embodiment of the configuration of the present invention, FIG. 4 is an embodiment of the configuration of the storage unit 12 in FIG. 3, and FIG. is an explanatory diagram illustrating the operation of the configuration shown in FIG. 3,
FIG. 6 is an explanatory diagram illustrating the configuration of another embodiment of the present invention, FIG. 7 is an explanatory diagram illustrating a case where a spherical pumping wave arrives, and FIG. 8 is an explanatory diagram illustrating a mode of improving the S/N ratio. FIG. 9 shows an example configuration corresponding to FIG. 8, FIG. 10 shows an example configuration for obtaining two-dimensional or three-dimensional images, and FIG. 11 shows temperature or temperature change amount and 1/ρ ₀ C ₀ (B/A) A diagram showing an example of the correspondence relationship with _e or the amount of change thereof. Figure 12 is an example configuration for determining temperature distribution. Figure 13 is an example configuration for determining temperature change distribution. , FIG. 14 shows an example configuration of the signal conversion circuit 27 in FIGS. 12 and 13. In FIG. In the figure, 1 is a timing control section, 2 is an oscillator, and 3
is a driver, 4 is a transmitting transducer, 5 is an ultrasonic medium to be measured, 6 is a receiving transducer, 7 is a receiving amplifier, 8
9 is a phase detector, 9 is a filter, 10 is a pumping wave driver, 11 is a pumping wave generation oscillator, 12 is a storage section, 13 is a subtraction circuit, 15 is an A/
D converter, 16 I/C memory, 17 D/A converter, 18 control section, 20 addition section, 21 delay circuit, 22 drive section for changing the position of the vibrator, 23 vibration 24 is a memory control unit, 25 is a memory, and 26 is a display unit.

Claims (1)

[Scope of Claims] 1. (a) A pair of ultrasonic transducers that transmit and receive a continuous ultrasonic beam for measurement that passes through an ultrasonic medium; (c) means for detecting the spatial distribution of the amount of phase transition of the received wave due to the pumping wave on the measurement beam scanning line; (iv) By passing the spatially distributed output of the phase shift amount on the measurement beam scanning line through a filter with characteristics almost equal to the inverse of the frequency characteristics of the pumping wave, the equivalent nonlinearity of the ultrasonic medium is determined. Obtain and store the spatial distribution of the quantity f ((B/A) _e , C, ρ) determined by the parameter (B/A) _e , sound speed C, and density ρ on the measurement beam scanning line. (e) obtaining the spatial distribution of f ((B/A) _e , C, ρ) on the measurement beam scanning line after the ultrasonic medium undergoes a temperature change; ) memorized f
((B/A) _e , C, ρ) A temperature measuring device using ultrasonic waves, comprising: means for obtaining a difference from a spatial distribution of (B/A) e, C, ρ). 2. (a) A pair of ultrasonic transducers that transmit and receive a continuous ultrasonic beam for measurement that passes through the ultrasonic medium, and (b) A beam width that is sufficient to intersect the ultrasonic beam and cover the area to be observed. (c) detecting and storing the spatial distribution of the amount of phase transition of the received wave due to the pumping wave on the measurement beam scanning line; (d) After the ultrasonic medium undergoes a temperature change, obtain a spatial distribution of the amount of phase transition of the received wave on the measurement beam scanning line, and the amount of phase transition stored in (c). (e) passing the spatial distribution output of the difference in the amount of phase transition through a filter having characteristics almost equal to the inverse characteristics of the frequency characteristics of the pumping wave; Means for obtaining the spatial distribution of the amount of change due to temperature change in the amount f ((B/A) _e , C, ρ) determined by the equivalent nonlinear parameter (B/A) _e of the medium, the sound speed C, and the density ρ An ultrasonic temperature measuring device characterized by having and. 3. The sound pressure distribution of the pumping wave is measured in advance as a function of location and time, and when performing the processing in claim 1 (d) or 2 (e),
3. The ultrasonic temperature measuring device according to claim 1, further comprising means for performing correction based on the pre-measured sound pressure distribution. 4. Add the amount of phase shift corresponding to the same position on the same measurement beam scanning line every time the pumping wave is transmitted multiple times. Claims 1 to 3 are characterized by having a so-called synchronous countable function.
The ultrasonic temperature measuring device according to any one of the above items. 5. By scanning the transmitting/receiving transducer pair one-dimensionally or two-dimensionally, the
Two-dimensional or three-dimensional f for temperature change
((B/A) _e , C, ρ), comprising a scanning unit/display unit for obtaining a variation distribution image of ((B/A) e, C, ρ), according to any one of claims 1 to 4. of,
Ultrasonic temperature measuring device. 6. Multiply the difference in the obtained f((B/A) _e , C, ρ) by an appropriate coefficient (it may be different depending on the location if necessary) to calculate the distribution of temperature change. An ultrasonic temperature measuring device according to any one of claims 1 to 5, characterized in that the ultrasonic temperature measuring device is configured to obtain a temperature measurement device using ultrasonic waves. 7 Temperature or temperature change of each part in the ultrasonic medium to be measured and f((B/A) _e , C, ρ) or f((B
/A) By measuring the correspondence with the amount of change in _e , C, ρ) in advance and measuring f((B/A) _e , C, ρ) or its amount of change, the ultrasonic wave to be measured can be Claims 1 to 5 are characterized in that the absolute temperature or temperature change amount of each part within the medium is obtained.
The ultrasonic temperature measuring device according to any one of paragraphs.