JPS6216743A - Apparatus for measuring temperature in living body - 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 Application Field] The present invention relates to an in-vivo temperature measurement device, and particularly to an apparatus for transmitting and receiving ultrasonic pulses within a subject to analyze and process reflected echoes from a predetermined test site. The present invention relates to an improved IC device that can non-invasively measure the temperature inside a living body.

[Prior Art] Applying wave energy to a living body using ultrasonic waves, microwaves, RF waves, etc. to generate humidity within the living body has been put to practical use in various therapeutic devices, especially hyperthermia (thermia therapy). d3 is attracting attention as an effective treatment method for cancerous tumors.

This thermotherapy treats cancer by applying a temperature of about 43°C to malignant tumors to cause their tissues to shrink, so it also has a great effect on the internal tissues of the body, and normal tissues. The necrosis l! There are cases where this happens.

Therefore, when administering thermotherapy to an in-vivo II machine, it is necessary to pay sufficient attention to the humidity of the tissue surrounding the malignant tumor, and for this reason, it is necessary to use ultrasound, etc. J4′? It is extremely important to accurately measure the temperature distribution of a given tissue.

“Problems to be Solved by the Invention” However, with conventional devices, it has been almost impossible to accurately measure the temperature deep inside the subject in a non-invasive manner. One way to do this is to insert a thermocouple into the subject, but this conventional invasive method not only causes great pain to the subject, but also causes the thermocouple to penetrate into the malignant tumor. There were major problems such as the risk of cancer cells metastasizing to other normal tissues during insertion and removal.

Invention No. 1 The present invention has been made in view of the above-mentioned conventional problems.
The purpose is to provide a device that can non-invasively measure thirst using ultrasonic waves.

Means and Action for Solving Problem 1] In order to achieve the above object, the present invention transmits ultrasonic waves into the subject to induce reaction from the internal silk. Received ultrasonic wave transde = t - Shin J - super? A complex signal converter that converts a received signal into a complex signal by IrA combining a set of complex reference signals having a carrier frequency of 1 wave (li wave) and a received signal (high frequency signal) having a complex relationship. , a one-angle calculator for calculating the declination angle of the complex signal, a memory for storing the declination before and after heating outputted from the declination calculator, and a pre-warming heating unit 19. a phase difference calculator that calculates the phase difference of a complex signal of c3TI-, a sound speed ratio calculator that calculates the sound speed ratio inside the heated liquid sample from the phase difference, and a sound speed ratio calculator that calculates the temperature from the sound speed ratio. It is characterized in that it includes a temperature calculator that measures the internal temperature of the subject after heating based on the sound velocity ratio obtained by converting the ultrasonic reception signal before heating into a complex signal.

With the above-mentioned configuration, firstly, the received signal 1Q obtained by ultrasonic waves 1 to 4 is orthogonally detected by the complex signal converter and converted into a complex signal. This is performed both before and after heating, and by calculating the phase difference of these complex signals, the sound speed ratio of the ultrasound propagated in the living body is calculated.

As is well known, the body temperature of adults is constant except for the body surface, and is usually maintained at around 37°C. Therefore, it can be assumed that the sound speed of ultrasound waves in each tissue kept at a constant temperature within a living body is constant. However, when ultrasonic waves or the like are irradiated into a living body, the heating effect of each tissue is different due to the difference in absorption coefficient of ultrasonic waves, etc. of each tissue, resulting in a temperature distribution within the subject. Since the sound speed of ultrasonic waves propagating through II tissue at a high temperature is faster than the sound speed when the temperature is low, it is possible to non-invasively inject tissue into the living body by determining the ratio of sound speeds before and after heating the tissue in the living body. temperature measurement or temperature distribution.

In this way, it is possible to easily measure the temperature inside a living body by capturing changes in the speed of sound, without going through the extremely difficult method of trying to measure temperature by determining the absolute speed of sound, which is the case with conventional devices. is possible.

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

FIG. 1 shows a first embodiment of the in-vivo temperature measuring device, in which the output of a crystal oscillator 10 that generates a stable high-frequency signal is supplied to a frequency division synchronization circuit 12. : Various output signals of desired frequencies can be obtained. These output signals are, for example, transmission signals 100 . Complex reference signals 102.104. for complex transforms. These are clock signals 106 and the like that synchronize each part of the device.

The transmission signal 100 which is the output of the frequency dividing synchronization circuit 12 is
The ultrasonic pulse beam is supplied to a transducer 16 via a wave transmitting/receiving controller 14 including a drive circuit, a transmitting/receiving switching circuit, etc., and the ultrasonic pulse beam is emitted from the transducer 16 to a subject 17 .

Then, the reflected echoes from the subject 17 are 1 to Lancege:
The signal is converted into an electric signal by the 1-Lee 16, and is supplied from the wave transmitting/receiving controller 17'I to the high frequency amplifier 18, where it is subjected to a desired amplification effect. Here, when displaying in-vivo tomographic images in 8 modes using ultra-rich wave diagnostic equipment, the output of the amplifier 18 is transmitted to the detector 20. It is supplied via an A/D converter 22 to a digital scan converter (DSO) 24 .

The characteristic 4T of the present invention is to convert the received ultrasonic signals before humidification and after heating into complex signals, detect the phase difference of these complex signals, and calculate the sound speed ratio before and after heating. The purpose is to calculate the temperature inside the living body from the sound speed ratio, and the other output of the high frequency amplifier 18 is supplied to the complex signal converter 26 and converted into a complex signal.

In the first embodiment, the complex signal converter 26
is a set of mini 1:s 28a containing a phase detector.

281), low-pass filters 3Qa, 30t), A/D converters 32a, 32b, etc.
, 281) are supplied with complex 7% signals 102 and 104, which are the outputs of the frequency dividing synchronization circuit 12, respectively. This complex reference signal 102, 104 has a carrier frequency for transmitting and receiving waves, and has a phase difference of 90°.
)ot, CO3ωot signal, and the complex reference signal 102.104 signal is Miki → No 28a, 28
1) is mixed with the received signal that has already been input, and a signal having a frequency of the sum and difference of the image frequencies is output. This signal is the low pass filter 30a.

301), and only the difference frequency component is extracted.

Next, the above-described complex transformation will be explained in detail using arithmetic expressions. Here, although the transmitted and received ultrasonic waves are actually pulse waves, they are expressed as continuous waves to simplify the explanation.

The transmitted wave Wt(t) before and after heating is W(t)−
△ ・51n(IJol... Expressed as (1). However, A is the amplitude of the transmitted wave, ω.

For example, let it be the fundamental angular frequency of the transmitted wave.

In addition, the received wave W from the subject before heating
,,(t) can be expressed as Wl) (t) =Ab-sin(ωo(t-τb)toφb) (2). However, Ai is the amplitude of the received wave before heating, τ1. is the time required for propagation of the transmitted wave, and φb is the initial phase of the received wave.

In addition, the influence on the reflected waves caused by the heating of the subject is more greatly influenced by the propagation time of the received waves than by the peak value of the received waves. Therefore, the received wave W([) before heating and the received wave Wa(t) after heating can be considered to have waveforms with different propagation times G-1. Therefore, the received wave Wa(11) after heating is w m = Wb(t+Δτ(t)) −Al)・5in(ωo(1+Δτ(1)−τb)+φ
b) ...(3) becomes. However, Δτ(1) is the difference in arrival time of the reflector from the same region before and after heating.

Here, the received wave Wb(t) before heating is transferred to the complex signal converter 2.
6, the output of the mixer 28a is the product of the complex reference signal 102 and the received high frequency signal.

As mentioned above, the complex reference signal 102 is 5inω01
and the other complex reference signal 104 is COS゛ω. t, so if the amplitude of these reference signals is 1, the output signals x and m of MIKI-'J28a are Xb(t) -wb
m ・sinωot−cos(2ω to −ω0τb
”φb)). And this output is filtered by a low-pass filter (
Since the 2ω0 angular frequency component is removed by the LPF) 30a, the output signal Xb(t) of the low-pass filter 30a is
...(4) becomes.

On the other hand, the output j signal Vb(t) of the mixer 28b is y
(t)-Wb(t) fist cosωot+φb)→-
5 inches (φb−ω0τb)). Similarly to Xb(t:), the output signal of the low-pass filter (1-PF) 30b becomes...(5).

Now, the complex reference signal 102. In other words, sinω. The output signal multiplied by 1 is the real part of the complex number, and is also the complex reference signal 104, ie, COSω. Correspond the output signal multiplied by t to the imaginary part of the complex number! By doing so, the received high frequency signal is complex transformed.

Therefore, when the received signals W, , (t) before humidification are subjected to complex conversion, the complex signal 7b(t) can be expressed as the following J:.

Zb m =xb(t) 10,1Yb(t)...
・(6)+jsin(φb−ω0τb)) −8boj(φ1.−ω0τb) ・・・(7) Similarly, the complex signal 7a(t) obtained by complex transforming the received signal Wa(t) after heating is , Z (t) =X (t:) +jY (t)
...(8)a a
a0φ,, )−+jsin(ω0(
Δτ (1) − τl, ) 1φ1 month b −□. j(ω0(△τ(1)−τ1ripφ1.)−Z,
, (t)・ej″)0△4(1) ...(9)
becomes.

J: The complex transformed signal gZ, , (t).

Za(t) is converted into a digital signal by the A/D converters 32a, 321]. The D/D converter 32 receives a signal 10 outputted from the frequency dividing cycle circuit 12.
6 is supplied, and this clock signal 106 is subjected to sampling.

In the first embodiment, in d5, this complex-transformed signal Zl
)(t), Za(t) are sent to the argument calculator 3/I; then = 11 - each argument θ of the complex signal output, (1).

θa(() is determined. That is, each argument is determined by how many times.

Then, this argument θ(1) is calculated from 71 to the logic memory 36.
to be memorized. A clock signal 106 is supplied to the matrix memory 36, and writing and reading are performed in accordance with the clock signal.

In this way, the scanning line (
The received signals Wb(t) of all the reflectors before heating corresponding to B mode) are complex-transformed, and the deflection angle θb(1) is stored in the matrix memory 36b. Similarly, the received signal W (t) from the same region after heating is subjected to complex transformation, and the deflection angle θ, (t) is converted to the 71 helix memory 36a.
to be memorized.

After that, apply the same part before humidification and after heating 1
2 - When the declination angle Obm and θa(t) are simultaneously read out and the difference between them is determined by the phase difference calculator 38, the arrival of the reflection echo before heating at the same depth and the reflection echo 1 after humidification is found. Time difference △τ(
[) is the next J: sea urchin.

θ (1) − θ1) (1) = aro(Z (t)) −arg(Z (t)
) ・(12)a +) Zb(t) -ω0△τ(1) ・・・(1
3) However, since ω0 is the fundamental angular frequency of the transmitted wave,
It is a known constant.

The phase difference represents an arrival time difference Δτ(1), and this arrival time difference Δτ(1) is supplied to the next sound speed ratio oil cylinder device 40,
From the arrival time difference Δτ(1), the ratio between the sound velocity before heating and the sound velocity after heating in the same region is determined.

The operation of this sound speed ratio calculator 40 will be explained below.

If the average sound velocity inside the object 17 before heating is 6, then depth x
The following relationship holds true for the arrival time τ(x) of the reflected echo from the distance.

τ(×); knee
t) MI (depth> x depth・1).

Here, the total speed i+r in the subject 17 before heating is C, .
(X) Let the sound velocity distribution after heating be Ca(x). Let's consider the case of humidifying the depth x position inside the cow's body.
Before heating, the high speed distribution becomes constant as shown in Figure 3 (a), and after HIA, the maximum point is the position of depth x, as shown in Figure 3 (1)). How is the sound speed distribution? Therefore, as shown in FIG. 4, the reflections before and after heating reflected from the depth
（×）reach）ヱIt will be a deviation between 14.

Reflector before heating from depth x inside the object] - If the time from transmission time to reception time is expressed as arrival time τ, , (X), then γ ×
...(14) C.Fudonaru.

In addition, the sound velocity distribution C(X) inside the subject after heating is calculated by C8(
×) −Cb(×)→−ΔC(x), the arrival time τa(×
) is ... (15) yelling.

Therefore, the arrival time difference Δτ(×) between the arrival time τb(×) before heating and the arrival time τa(×) after heating is Δτ(×)
=τh(x)-τa(x)...(16) Howl.

Furthermore, based on the arrival time τb(x) before heating, the sign of the arrival time difference Δτ(x) is determined to be positive if the reflected echo after heating advances, and negative if it is delayed. (12)
The sign of the argument in the equation advances, representing a lag.

Here, when the arrival time difference Δτ(×) is differentiated by the distance tlfx, we get dΔτ(X) dx.

Then, by differentiating the arrival time difference Δτ(1) in equation (13) with respect to time and substituting equation (17), dt 2 dx is obtained.

(Here, the relationship Δτ(1)−Δτ(×) was used.

) The sound velocity distribution Cb(x) inside the object before heating is the average sound velocity 6.
Equation (18) becomes as follows.

Next, the sound speed ratio C8 at distance -1 of depth X before and after heating
(×)/Cb(×) is calculated as Cb(×) C
b(x) yell.

When formula (19) is transformed and substituted into formula (20), the sound speed ratio becomes:

Therefore, the sound speed ratio calculator 40 converts the output signal from the phase difference calculator 38 into the fundamental angular frequency ω of the transmission signal. By time-differentiating the value divided by dΔτ(t) /dt and substituting this value into equation (21), the sound speed ratio C(
X) /Cb (X) can be obtained.

The output of the sound speed ratio calculator/IO is supplied to the temperature calculator 42 to determine the temperature inside the living body.

In-vivo sound velocity CI is In Vitro, In V
iv.

In the temperature range of 35℃ to 45℃,
It can be approximately approximated to the following function of temperature T. , sound speed C1
is expressed as nun LCt-brain function as follows.

(,=a −T, 10b ・(22
)1, where a and b are constants determined by the tissue in the living body.

-19= Now, the temperature of the biological tissue before the depth x depth in the subject 17 is i-1, (x) (=37℃), the temperature after heating T, ( X) Why before humidifying the same area? When I try to find the ratio between the R speed C,, (X) and the sound velocity Ca(x) after heating, I hear the following: Cb(x) a-TI, (x)+1).

Therefore, the temperature T, (X) of the heated living tissue at a distance 1l111 of depth x in the subject 17 is given by the following equation.

However, the temperature Tb(x) before heating is a substantially constant value within the subject, and can usually be approximated by 37°C. J-da, (
The value of b/a) is determined by the biological tissue to be measured. Therefore, each silk to be measured is actually measured in advance. For example, the value of (b/a) is approximately 865 r °C for water and 1 m Vitr for liver.
o, rm Vivo is slightly different, but 1220-12
It is set to a value of 30 [°C].

In this way, the temperature calculator 42 calculates the equation (23) based on the output signal of the sound speed ratio calculator 40. At this time, the maximum temperature value within the measurement target area is compared with a set temperature, for example 45°C, and if the set temperature is exceeded, a signal 110- (temperature calculator 12) is output to notify this condition.
be done.

This output signal 110 is then supplied to the heating wave transmission controller 44 connected to the frequency dividing synchronous circuit 12 via the switch 48, and controls the power amplifier in the heating wave transmission controller 44. The irradiation power is then lowered. Furthermore, the heating area can be moved without reducing the irradiation power.
J: The temperature distribution within the heating area is widely heated at the set temperature.
It is also done to make

Note that such heating control is performed based on the control signal 108 output from the frequency division synchronization circuit 12, and controls the irradiation time of the heating irradiator 46 and the period of irradiation 1:J IPt.

In the present invention, when used in conjunction with an ultrasonic diagnostic device, the temperature distribution is displayed in color superimposed on the in-vivo tomographic image projected on the display image of the diagnostic device. The output of the temperature calculator 42 is supplied to the DSC 2/l via a switch 50 and stored therein.

The humidity signal output from the DSC 24 is then supplied to the color converter 52. This color converter 52
In this case, the color tone is set to correspond to the magnitude of the signal including temperature information, so for example, red (R) is used.

Converts into green (G) and blue (B) signals and sends to D/A converter 54
The signal is supplied to the color TV monitor 56 via the. Therefore, the wet information is superimposed and displayed in color on each part of the ultrasonic tomographic image projected on the color TV'[- monitor 56, so that the temperature distribution inside the living body can be confirmed at a glance.

Next, a second embodiment of the present invention will be described based on FIG. 2. It should be noted that the same parts as in the first embodiment will be omitted and their descriptions will be omitted.

A characteristic feature of the second embodiment is that after the received signal before and after heating is converted into a complex signal, the real part and imaginary part of the complex signal are After that, the phase difference between the complex signals before and after heating is directly determined. That is, J shown in FIG. 2 is a complex signal converter 2.
The real part and imaginary part of the complex signal output from the Δ/D converters 32a and 3211 of 6 are supplied to matrix memories 58a and 58b. Then, based on the real part and heart number part of the complex signal before and after humidification stored in the matrix memory 5B, the phase difference calculator 60 calculates the phase difference between the complex reception signals of the same part before and after heating to 0. , 1 μ[
) is obtained according to the following formula.

10) oΔτ(1)...
(25) The output of the phase difference calculator 60 is supplied to the temperature calculator 42 via the sound speed ratio calculator 40. As explained in the first embodiment, the phase difference 08b(1) (51 arrival time difference Δτ(1)) indicates the delay in the sound speed of the ultrasound (arrival time difference Δτ(t)), that is, the position of the complex signal. The temperature change inside the subject can be determined from the phase difference by performing a predetermined oil cylinder treatment.

As mentioned above, since the argument calculation unit 371 of the first embodiment is omitted, the second embodiment has the advantage that the process of calculating the phase difference of the complex signal is simplified.

[Effect of the invention 1] According to the present invention, the ultrasonic reception signals before and after heating are converted into complex signals, and the sound speed ratio is determined from the phase difference between the complex signals and the temperature is calculated. This makes it possible to visually measure the humidity in the living body accurately, quickly, and non-invasively, making it extremely useful for measuring the temperature in the living body in cases such as hyper1nomia.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a preferred first embodiment in which the in-vivo temperature measuring device according to the present invention is applied to an ultrasonic diagnostic device, and Fig. 2 is an explanatory diagram showing a second embodiment of the present invention. , FIG. 3 is an explanatory diagram showing the sound velocity distribution within the subject, and FIG. 4 is an explanatory diagram showing the arrival time of reflected echoes from the subject. 10... Crystal oscillator 12... Frequency division synchronization circuit 14... Wave transmission/reception controller 16... J ~ Lance duzer 26... Complex signal converter 28... Mixer 30... Low pass filter 32 ... A/D converter 34 ... Declination angle calculator 36.58 ... Matrix memory 38.60
... Phase difference calculator 40 ... Sound speed ratio calculator 42 ... Temperature calculator. Applicant Aloka Co., Ltd. Ne1 [7-33]

Claims (2)

[Claims] (1) An ultrasonic transducer that transmits ultrasonic waves into the subject and receives reflected echoes from internal tissues, and a set of complex reference signals that have a carrier frequency of the ultrasonic transmission waves and have a complex relationship with each other. a complex signal converter that converts the received signal into a complex signal by mixing it with a received signal; a declination calculator that calculates the declination of the complex signal; A memory that stores the declination angle after heating, a phase difference calculator that calculates the phase difference between the complex signals before and after heating, and a sound speed ratio inside the subject before and after heating from the phase difference. Includes a sound speed ratio calculator and a temperature calculator that calculates temperature from the sound speed ratio, and measures the in-vivo temperature after heating based on the sound speed ratio obtained by converting the received ultrasonic signals before and after heating into a complex signal. An in-vivo temperature measuring device characterized by: (2) In the apparatus according to claim (1), the real part and imaginary part of the complex signal outputted from the complex signal converter before and after heating are stored in a memory, and the real part and imaginary part are An in-vivo temperature measuring device characterized by calculating a phase difference between complex signals before and after direct heating.