JPS6268439A - Ultrasonic apparatus for measuring temperature of 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] [Technical Field of the Invention] The present invention relates to an ultrasonic body temperature measurement device that measures the temperature of living tissue using ultrasonic waves, and particularly relates to an ultrasonic body temperature measuring device that measures the temperature of living tissue using ultrasound waves, and particularly to Concerning the use of nonlinear effects.

[Technical background of the invention and its problems]

As a method for destroying in vivo microorganisms such as cancer, there is a method of selectively heating only the tissue to be destroyed for a long time (referred to as "Hyperthermia 1").

Various methods can be used to selectively heat the tissue to be destroyed, but accurately grasping the temperature of the tissue to be destroyed during thermotherapy is extremely important for investigating the effects of thermotherapy and for performing appropriate thermotherapy. is important.

By the way, in conventional thermotherapy, the temperature of the tissue to be destroyed is monitored by, for example, puncturing a thermocouple or the like into a living body and directly measuring the temperature of the tissue to be destroyed with the punctured thermocouple or the like.

However, such temperature measurement by puncturing is not only invasive to the living body, but also has the disadvantage of scattering the destroyed Mi woven cancer cells into normal tissue.

In addition, there is a demand for two-dimensional understanding of the temperature distribution of the destroyed Mi tissue and its surrounding tissues during thermal treatment, but the direct measurement method using thermocouples, etc. mentioned above requires temperature measurement at several points in the destroyed tissue. Because of the limitations, it is impossible to meet the above request.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to obtain temperature distribution information of biological tissues without being invasive to living organisms and without adversely affecting normal tissues of living organisms. An object of the present invention is to provide an ultrasonic body temperature measuring device that can be quickly obtained.

[Summary of the Invention] The outline of the present invention for achieving the above object is to connect a plurality of ultrasound transducers constituting an ultrasound transducer array to a
A transducer group and a second transducer group for wave reception are used to obtain temperature distribution information of a desired part of the living body based on the reflected waves from the living body of the ultrasonic waves transmitted toward the living body. The ultrasonic biological temperature measurement device includes a drive voltage control unit that can stepwise vary the drive voltage used to excite the first transducer group, and a reflection of the transmitted ultrasound each time the drive voltage is varied. By calculating the driving voltage dependent parameter of the received wave signal based on the received wave signal, and obtaining the local voltage dependent parameter at the local body part from the calculated driving voltage dependent parameter, the temperature of the desired part of the living body is different. A voltage-dependent parameter calculation circuit that creates a local voltage-dependent parameter image, a rate-of-change calculation circuit that calculates a rate of change between images from the plurality of created local voltage-dependent parameter images, and a rate-of-change calculation circuit that calculates a rate of change between images from the plurality of created local voltage-dependent parameter images, and converts the calculated rate of change into a two-dimensional image. The present invention is characterized in that it is configured to have a display that displays images as follows.

[Embodiments of the invention]

The present invention will be explained in detail below.

First, the principle of the present invention will be explained.

The following relationship exists between the voltage dependent parameter, the nonlinear parameter B/A, and the ultrasonic propagation velocity (hereinafter referred to as sound velocity) C.

k is a constant that includes attenuation, one reflection, one frequency of ultrasonic waves, and the effect of the sound field. However, the temperature dependence of k is small.

On the other hand, since the temperature dependence of the sound speed is generally one or more orders of magnitude larger than the temperature dependence of the nonlinear parameter, the temperature dependence of the voltage dependent parameter can be approximately expressed as follows.

dK dependence In other words, the temperature change rate of the voltage-dependent parameter is almost twice the temperature change rate of the sound speed, so the temperature change rate of the voltage-dependent parameter can be obtained with twice the sensitivity than measuring the sound speed change. be able to. Further, the voltage-dependent parameter change rate ξ (x, y) is expressed by the following equation.

If ξ(x, y) obtained by executing the calculation of equation (3) is displayed as an image, it is possible to clearly distinguish between areas where the temperature has changed and areas where the temperature has not changed on the display screen. When obtaining the absolute value of temperature, measure the absolute value of the ξ change rate and temperature for each region through experiments using human body-like phantoms, animals, etc., and from the measured value m = d K
/ d T can be calculated by calculating T and substituting the calculated m into the following equation.

m m FIGS. 3(a) to 3(c) schematically show images generated based on the above principle, and FIG. 3(a) shows voltage-dependent parameters before heating. (x, y) image, same figure (
b) is the voltage-dependent parameter Kr (X, y) image during heating, and (c) is the voltage-dependent parameter change rate ξ(x,'
y) It is an image, that is, a temperature change rate image, and the temperature increase portion is clearly expressed.

Next, the principle of measuring the local voltage dependent parameter K (x, y) will be explained.

<Scanning the ultrasonic propagation path> As shown in Fig. 4, using the linear electronic scanning probe l, one end A of the ultrasonic wave transmitting/receiving surface 2 that is in contact with the biological surface is
From the first group of oscillators centered on
Ultrasonic pulses are emitted in the direction where the ultrasonic deflection angle θ=0°). Then, the ultrasonic pulse travels straight along the transmission path A+Pz in the living body, and the reflected wave at point pH follows the reception path p.
The wave passes through HB11 and is received by a second group of vibrators centered around B11. This ultrasonic propagation path A + P
+ + - When the average drive voltage dependent variation (R1) at Bll is calculated (described later), the ultrasonic wave is again transmitted from the first oscillator centered at A in the same manner as above. The reflected wave of the ultrasonic wave at point PI2 is now B
The wave is received by the second vibrator centered at 1□. And ultrasonic propagation path A in this case.

Average driving voltage dependent parameter at P+□-B1□ (
Kl□) is calculated. Thereafter, by similarly scanning the ultrasonic wave transmitting position and the ultrasonic wave receiving position, 2m×n average drive voltage dependent parameters are finally calculated.

<Calculation of average drive voltage dependent parameter (K)> Next, calculation of the average drive voltage dependent parameter K + l will be explained using the case of ultrasonic propagation path A+ P++ Bz as an example. For example, the driving voltage, that is, the pulsar output voltage U used for excitation of each ultrasonic transducer constituting the first transducer group centered on A, is 10.20. ..., 100 (
Porto], and for each voltage, the amplitude of the received echo by the second transducer group centered on B11 V[
bolt] and memorize it. Next, the slope γ and the intercept δ are determined by plotting the following equation (5) (FIG. 4).

At this time, the following equation (3) holds true between the average drive voltage dependent parameter (Kp), the nonlinear parameter (B/A), and the speed of sound (C).

Here, Ro is a constant that depends on frequency and distance.

Similarly, 2mXn K i + j are obtained.

<Calculation of local voltage dependent parameters> Using the 2m×n average driving voltage dependent parameters Ki+j obtained in this way, the local voltage dependent parameters K(i, j) can be calculated by the following equation.

K (i, j) = K□+j+1 K, j
(7) Next, an embodiment of the present invention based on the following principle will be described.

FIG. 1 is a block diagram of an ultrasonic body temperature measuring device according to an embodiment of the present invention.

The transducer array 11 is arranged on the ultrasonic wave transmitting/receiving surface 2 of the probe shown in FIG. 4, and when a voltage pulse is applied to it, it emits an ultrasonic pulse, and when an ultrasonic wave is incident, it generates a voltage and detects the ultrasonic wave. .

The transducer array 11 (T1 to T1□8) has a transducer element width a
is 0.451, the element center spacing d = 0.511
128 elements are arranged in a straight line. Electric signals are sent and received to and from each of these transducer elements using the lead wire 1 in the cable 3.
Do it through 2.

The CPII (central processing unit) 21 is, for example, l0M112.
It has a pulse generator that generates a reference clock, and divides the frequency of the reference clock to generate, for example, a 4K12 rate pulse, which drives 16 pulsers 14 via 16 transmission delay circuits 15. The output of the pulser 14 is connected by a multiplexer 13 to transducer groups T1 to TI6 centered on A1 in the transducer array 11, respectively. The vibration array 11 contacts the body surface through the probe coating (O), and the ultrasonic waves generated from the vibration elements are radiated into the living body.If the sound speed of standard biological Mi tissue is C8-1530 m/s, To radiate the beam in the direction θ, the delay time τ between adjacent elements is τo−(d/Co)
・sin θ −f8), and the transmission delay circuit 15 is set so that each element is driven with such a delay time difference.

That is, PD,=O, PD2=τ. , PD3=2τ. .

. . . , PD, 6=15τ0 is given as a delay time.

If the sound speed of the living tissue is 00, the ultrasound beam is θ.

A value C that is different from C8, but is generally not limited to C8.
It is. At this time, the propagation direction θ of the ultrasonic wave has the value shown by sin θ/C=sin θO/CO”' (91) from Snell's law.

After emitting the g-M wave pulse, the multiplexer 13
1 of the transducer group T1 to T m + + centered on 11
6 and the reception delay circuit 16,
The ultrasonic reflected wave signals received by T6 to T14□ are delayed in the same way as in the case of transmission, and then synthesized by the receiving circuit 1.
9 is input. That is, the delay time of the reception delay circuit 16 is RD,=15τ. .

RD2=14τo, --,RD +s-τ,,RD
, 6=0. In this way, the transducer group T, ~T,. , is θ if the sound speed in the living body is C3 (C)
. It has directivity in the (θ) direction, and θ. Receive reflected waves from the (θ) direction. The received signal is amplified and detected by the receiving circuit 19, A/D converted by the A/D converter 20, and sent to the memory 2.
2. The address of the memory 22 is determined by a clock of 10M) I based on the timing of the rate pulse, and the address of the sample value of the received waveform stored in the memory 22 is determined at a time of 100 ns from the time of ultrasonic pulse emission. Accurately matched.

The peak value of the stored waveform indicates the reflected wave from point P, and the amplitude value at point P indicates the amplitude (V) of the received echo.

The drive voltage control unit 17 operates under the control of the CPU 21, and the output voltage U of the balsa 14 is set to 10.20. ...1
100[:V). By applying each voltage (u), a predetermined group of transducers is excited, and ultrasonic waves are transmitted. The reflected waves of the ultrasonic waves transmitted for each voltage (u) are received by a predetermined group of transducers, and the amplitude of the received signal (V
) is written into the buffer memory 22 for each voltage (u). When ultrasonic wave transmission/reception is performed multiple times under the same conditions, the addition circuit 23 operates to perform averaging processing of the received signals.

Next, 1'' written into the buffer memory 22,
The information (received signal for each drive voltage (u)) is CPll 2
J is sold under the control of 1, and is transmitted to the voltage dependent parameter calculation circuit 24. Then, in this voltage dependent parameter circuit 24, the slope γ and the intercept δ of the equation (5) are determined, and finally the average voltage dependent parameter K i + j
is written into the frame memory 25. After 2mXn average dependent parameters are written into the frame memory 25, K i + J is immediately read out, and the read K i + J is returned to the voltage dependent parameter calculation circuit 24 and calculated according to the above equation (7). Local voltage dependent parameter K(I
IJ). The calculated locally dependent parameter K(i, j) is written to the frame memory 25 again.

The above is the K(i,j) image creation routine. The locally dependent parameter K(i
, j) is the one before heating the U-texture to be destroyed in the living body, then the image formed by the parameters is a. (
i, j), and KT (i
, j). The image creation routine itself is the same before and during heating. The KTO (i, j) image created in this way, Kt (IIJ)
is read out under the control of the CPU 21 and transmitted to the rate of change calculation circuit 26. Then, in this change rate calculation circuit 26, the calculation of the above equation (3) is executed, and the temperature change rate image ξ
(i, j) is found.

The obtained temperature change rate image ξ(i, j) is inputted to the D/A converter 28 via the display memory 27, converted into a digital signal by the D/A converter 28, and then displayed on the CRT display 29. Dimensions are displayed.

FIG. 2 shows an example of a display on the CRT display 29. As shown in FIG. An ultrasonic B-mode image 31 of a living body is displayed on the left side of the screen 30, and a tissue to be destroyed (part to be heated) 32 can be confirmed in the displayed ultrasonic B-mode image 31. Reference numeral 33 denotes an ultrasonic propagation path, which is displayed superimposed on the ultrasonic B-mode image 31 as necessary. Also, screen 3
A temperature change image 35 is displayed on the right side above 0. Although the temperature change image 35 can be displayed in black and white by brightness modulating the output of the D/A converter 28, it is better to display the image in color by converting the color to understand the temperature change.

When displaying in color, it is preferable to display a color bar 37 at the same time. Furthermore, the voltage dependent parameter change rate ξ and the calibrated temperature change T at the cursor point 36 set in the temperature change image 35 are
A numerical value is displayed at the bottom right of the screen 30.

According to the display as described above, the temperature distribution of the tissue to be destroyed 32 and its surrounding tissues can be recognized macroscopically and intuitively, which is extremely effective in performing appropriate thermal treatment.

In this way, the device of this embodiment actively utilizes the nonlinear effect caused by the interaction between ultrasonic waves and living tissue to measure the temperature of a desired part of the living body. Since the method does not use any of the following, it is non-invasive to the living body and does not cause any inconvenience such as adverse effects on the normal tissues of the living body. Furthermore, according to the device of this embodiment,
Since it can be used simultaneously with a real-time tomography device conventionally used for routine clinical examinations and can be examined with the same probe, it is possible to use sound velocity and nonlinear parameter measurement mode at an appropriate cross section while observing normal tomographic images. The ideal inspection method of one-touch switching can be implemented.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention. For example, in the above embodiment, the ultrasonic wave transmission directivity (
Although the case where the deflection angle (deflection angle) is set to Oo has been described, temperature measurement can be performed even if the deflection angle is set to a value other than O''.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide an ultrasonic body temperature measurement device that is non-invasive to a living body and can quickly obtain temperature distribution information of living tissue.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an ultrasonic body temperature measuring device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a display in the device of this embodiment, and FIG. 3(a). (b), (C) to FIG. 5 are for explaining the present invention in detail, and FIG. 3 (a), (b). (c) is an explanatory diagram of an image generated based on the principle of the present invention, FIG. 4 is an explanatory diagram of a scanning method of an ultrasound propagation path,
FIG. 5 is a diagram showing the relationship between 1/u2 and 1/v2. DESCRIPTION OF SYMBOLS 11... Ultrasonic transducer array, 17... Drive voltage control part, 24... Voltage dependent parameter calculation circuit, 26... Change rate calculation circuit, 29... Display. Agent Patent attorney Nori Ken Chika Yudo Norio Ogo Figure 3 (b) (C) 5PJ4 Figure PInl' 〆 / ------? mn

Claims (1)

[Claims] A plurality of ultrasonic transducers constituting an ultrasonic transducer array are used by switching between a first transducer group for transmitting waves and a second transducer group for receiving waves, and transmit waves toward a living body. In the ultrasonic body temperature measurement device that obtains temperature distribution information of a desired part of a living body based on reflected waves of ultrasound waves from the living body, the driving voltage used to excite the first group of transducers is varied in steps. The drive voltage control unit calculates the drive voltage dependent parameter of the received signal based on the received signal due to the reflected wave of the transmitted ultrasonic wave every time the drive voltage is changed, and also calculates the drive voltage dependent parameter of the received signal based on the calculated drive voltage dependent parameter. A voltage-dependent parameter calculation circuit that creates a plurality of local voltage-dependent parameter images each having a different temperature at a desired part of the body by obtaining a local voltage-dependent parameter in a biological region; What is claimed is: 1. An ultrasonic body temperature measuring device comprising: a rate-of-change calculation circuit that calculates a rate of change; and a display that displays the calculated rate of change as a two-dimensional image.