JPH0693889B2 - Ultrasonic body temperature measuring device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrasonic living body temperature measuring apparatus for measuring the temperature of living body tissue using ultrasonic waves, and particularly to a non-linearity due to interaction between the ultrasonic wave and the living body tissue. Regarding those that utilize the effect.

[Technical background of the invention and its problems]

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

Although various methods can be considered as the selective heating method for the tissue to be destroyed, it is extremely important to accurately grasp the temperature of the tissue to be destroyed in the thermotherapy in order to examine the effect of the thermotherapy or to perform an appropriate thermotherapy. is important.

By the way, in the conventional hyperthermia, for example, a thermocouple or the like is pierced in a living body, and the temperature of the crushed tissue is directly measured by the punctured thermocouple or the like to monitor the temperature of the crushed tissue.

However, such temperature measurement by puncture is not only invasive to the living body, but also has the drawback that cancer cells, which are tissues to be destroyed, are scattered in normal tissues.

In addition, there is a demand for two-dimensional understanding of the temperature distribution of the tissue to be destroyed and its surrounding tissue during hyperthermia treatment.
The direct measurement method using the above-mentioned thermocouple or the like cannot meet the above demands at all because the temperature measurement at several points in the tissue to be destroyed is limited.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to rapidly obtain temperature distribution information of a living tissue without being invasive to the living body and without adversely affecting normal tissues of the living body. Another object of the present invention is to provide an ultrasonic living body temperature measuring device that can be obtained.

[Outline of Invention]

An outline of the present invention for achieving the above object is to provide a plurality of ultrasonic transducers constituting an ultrasonic transducer array for transmitting a first ultrasonic wave.
Used by switching to the second transducer group for receiving and the second transducer group for receiving waves, and obtains the temperature distribution information of the desired portion of the living body based on the reflected wave from the living body of the ultrasonic wave transmitted toward the living body. In the ultrasonic living body temperature measuring apparatus, a drive voltage control unit for gradually changing a drive voltage used for exciting the first transducer group, and reflection of ultrasonic waves transmitted every time the drive voltage is changed. By calculating the driving voltage dependent parameter of the received signal based on the received signal by the wave and obtaining the local voltage dependent parameter in the living body region from the calculated driving voltage dependent parameter, the temperature of the desired part of the living body is different from each other. The voltage-dependent parameter calculation circuit that creates the local voltage-dependent parameter image, the change-rate calculation circuit that calculates the change rate between images from the created multiple local voltage-dependent parameter images, and the calculated change rate It is characterized in that it has structure and a display for displaying the dimensions image.

Example of Invention

 Hereinafter, the present invention will be specifically described.

First, the principle of the present invention will be described. The present invention relates to the relationship between the magnitude of a drive voltage supplied to a vibrator and the magnitude of a received signal that receives a reflected wave that is transmitted from the vibrator driven by the drive voltage and that is reflected in the living body. The temperature in the living body is measured from the temperature dependence of the driving voltage dependence parameter shown. The following relationship exists between the voltage-dependent parameter K, the non-linear parameter B / A, and the ultrasonic wave propagation velocity (hereinafter referred to as sound velocity) C.

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

On the other hand, since the temperature dependence of the sound velocity is generally larger than the temperature dependence of the nonlinear parameter by one digit or more, the temperature dependence of the voltage dependence parameter K is approximately represented by the following equation.

That is, since the temperature change rate of the voltage-dependent parameter K is almost twice the temperature change rate of the sound velocity, the temperature change rate of the voltage dependent parameter can be obtained with twice the sensitivity as compared with the measurement of the sound velocity change. . The voltage-dependent parameter change rate ξ (x, y) is expressed by the following equation.

By displaying ξ (x, y) obtained by executing the calculation of the equation (3) as an image, it is possible to clearly distinguish the portion where the temperature changes and the portion where the temperature does not change on the display screen. When obtaining the absolute value of the temperature, the absolute value of the ξ change rate and the temperature for each part is measured by an experiment using a human-like phantom or an animal, and m = dK / dT is calculated from the measured value. Substituting the obtained m into the following equation, the temperature change ΔT
Should be calculated.

3 (a) to 3 (c) schematically show images generated based on the above principle, and FIG. 3 (a) shows an image of the voltage-dependent parameter K _T0 (x, y) before heating. , (B) is a voltage-dependent parameter K _T (x, y) image during heating, (c) is a voltage-dependent parameter change rate ξ (x, y) image, that is, a temperature change rate image. The part is clearly expressed.

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

<Scanning of ultrasonic wave propagation path> As shown in FIG. 4, a linear electronic scanning probe 1 is used, and one end A _{1 of} an ultrasonic wave transmitting / receiving surface 2 in contact with a living body surface is used.
An ultrasonic pulse is emitted from a first transducer group centered on the direction of (0) in a direction perpendicular to the surface of the living body (ultrasonic deflection angle θ = 0 °). Then, the ultrasonic pulse is transmitted in the living body by the transmission path A ₁
Go straight through −P ₁₁ , the reflected wave at the point P ₁₁ passes through the receiving path P ₁₁ −B _11, and is received by the second transducer group centered on B ₁₁ . When the average drive voltage dependent parameter ( ₁₁ ) in this ultrasonic wave propagation path A ₁ -P ₁₁ -B ₁₁ is calculated (described later), the first transducer centered around A ₁ again produces an ultrasonic wave in the same manner as above. The sound wave is transmitted, and the reflected wave of the transmitted ultrasonic wave at the point P ₁₂ is received by the second transducer, which is centered on B ₁₂ this time. Then, the ultrasonic propagation path A ₁ -P _{12 in} this case
Average drive voltage dependent parameters in -B _{12 (12)} is calculated. Similarly, by dividing the ultrasonic transducer array that transmits waves as shown in Fig. 4 into two parts and folding back the left side scan line on the right side, m × n pieces on one side, 2 m × total on both sides.
The n average drive voltage dependent parameters are calculated.

<Calculation of Average Driving Voltage Dependent Parameter ()> Next, taking the case of the ultrasonic propagation path A ₁ -P ₁₁ -B ₁₁ as an example,
The calculation of the average drive voltage dependent parameter ₁₁ will be described. The drive voltage used for exciting the ultrasonic transducers constituting the first transducer group centering on A ₁ or the pulser output voltage u is changed to, for example, 10, 20, ..., 100 [volt]. , For each voltage, the amplitude v [volt] of the echo received by the second transducer group centered on B ₁₁ is obtained and stored. Next, the slope γ and the intercept δ are obtained by the plot (FIG. 4) of the following equation (5).

At this time, the average drive voltage dependent parameter And the nonlinear parameter (B / A) and sound velocity (C), the following equation (3) is established.

Here, ₀ is a constant that depends on frequency and distance.
Similarly, 2m × n _{i, j} are obtained.

<Calculation of Local Voltage Dependent Parameter> Using the 2m × n average driving voltage dependent parameters _{i, j} thus obtained, the local voltage dependent parameter K (i, j) can be calculated by the following equation. .

That is, the average drive voltage parameter _{i, j} represents the average drive voltage parameter of the ultrasonic wave propagation path Ai-Pij-Bij. The average drive voltage parameter _{i, j + 1} represents the average drive voltage parameter of the ultrasonic wave propagation path Ai-Pij ₊₁ -Bij ₊₁ . Therefore, the local drive voltage parameter K _{(i, j)} near Pij can be expressed by the following equation.

K (i, j) = _{i, j + 1} - _{i, j} (7) Next, an embodiment of the present invention based on the above principle will be described.

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

The transducer array 11 is the ultrasonic wave transmitting / receiving surface 2 of the probe shown in FIG.
When the voltage pulse is applied, an ultrasonic pulse is emitted, and when the ultrasonic wave is incident, a voltage is generated to detect the ultrasonic wave.

Transducer array 11 {T _{1 to} T ₁₂₈ } has transducer element width a of 0.45 mm
These are arranged on a straight line of 128 elements with the element center distance d = 0.5 mm. Transmission and reception of electric signals to and from each of these transducer elements are performed through the lead wire 12 in the cable 3.

The CPU (central processing unit) 21 has a pulse generator that generates, for example, a 10 MHz reference clock, divides the reference clock to generate a rate pulse of, for example, 4 KHz, and outputs 16 pulses via 16 transmission delay circuits 15. Drive the pulsar 14 of Ke. The output of the pulsar 14 is sent to the A ₁ of the oscillator array 11 by the multiplexer 13.
They are connected to vibrator groups T _{1 to} T ₁₆ centered on (FIG. 4), respectively. The vibration array 11 is in contact with the body surface through the coating material of the probe, and the ultrasonic wave generated from the vibration element is radiated into the living body. The sound velocity of standard living tissue is C ₀ = 1530m /
If s is used, the delay time τ ₀ between adjacent elements to radiate the ultrasonic beam in the θ ₀ direction is τ ₀ = (d / C ₀ ) · sin θ (8) The transmission delay circuit 15 is set so that each element is driven with a time difference. That is, PD ₁ = 0, PD ₂
= Τ ₀ , PD ₃ = 2τ ₀ , ......, PD ₁₆ = 15τ ₀

If the ultrasonic beam if the acoustic velocity is a C ₀ of the biological tissue is generally proceeds to theta ₀ direction is C ₀ a different value C is not limited to C _0. At this time, the propagation direction θ of the ultrasonic wave has a value represented by sin θ / C = sin θ ₀ / C ₀ (9) according to Snell's law.

After emitting the ultrasonic pulse, the multiplexer 13
Switching is performed so that 16 units of transducer groups Tm to Tm ₊₁₅ centered on ₁₁ (Fig. 4) and the reception delay circuit 16 are connected.
The ultrasonic reflected wave signals received by Tm ₊₁₅ are delayed by the same delay as in the case of transmission, combined, and input to the reception circuit 19. That is, the delay time of the reception delay circuit 16 is RD ₁ = 15τ ₀ , RD ₂
= 14τ ₀ , ..., RD ₁₅ = τ ₀ , RD ₁₆ = 0. In this way, the transducer groups Tm to Tm ₊₁₅ have directivity in the θ ₀ (θ) direction if the speed of sound of the living body is C ₀ (C), and θ
_The reflected wave is received from the ₀ (θ) direction. The reception signal is amplified and detected by the reception circuit 19, A / D converted by the A / D converter 20, and stored in the buffer memory 22. The address of the buffer memory 22 is determined by a clock of 10 MH ₂ with reference to the timing of the rate pulse, and the address of the sample value of the received waveform stored in the buffer memory 22 is 100 ns at the time from the ultrasonic pulse emission time point. The accuracy is exactly the same.

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 pulser 1
The output voltage u of 4 changes in the order of 10, 20, ..., 100 [V]. Application of each voltage (u) excites a predetermined group of actuators, and ultrasonic waves are transmitted. The reflected wave of the ultrasonic wave transmitted for each voltage (u) is received by a predetermined transducer group, and the amplitude (v) of the received signal is written in the buffer memory 22 for each voltage (u). . When the ultrasonic transmission / reception under the same condition is performed a plurality of times, the adder circuit 23 operates to perform the averaging process of the received signals.

Next, the u, v information (received signal for each drive voltage (u)) written in the buffer memory 22 is read out by the control of the CPU 21 and transmitted to the voltage-dependent parameter calculation circuit 24. Then, the voltage-dependent parameter circuit 24 finds the slope γ and the intercept δ of the equation (5), and finally the average voltage-dependent parameters _{i and j} are written in the frame memory 25. After 2m × n average dependent parameters are written in the frame memory 25, _{i, j} and _{i, j + 1} are read out immediately, and the read _{i, j} are returned to the voltage dependent parameter calculation circuit 24. , And is used for calculation of the local voltage dependent parameter K (i, j) by the equation (7). The calculated locally dependent parameter (i, j) is replaced with the value of the memory location of _{i, j in} the frame memory 25.

The above is the creation routine of the K (i, j) image. Locally dependent parameter K (i, j) written in the frame memory 25
Is K _TO (i, j) the image formed by the parameter if it is before heating the tissue to be destroyed in the living body, and K _T (i, j) if it is during heating. Differentiate each. The image creation routine itself is the same before and during heating. K _TO (i,
j) The image, K _T (i, j) is read out by the control of the CPU 21 and transmitted to the change rate calculation circuit 26. Then, in the change rate calculation circuit 26, the calculation of the equation (3) is executed to obtain the temperature change rate image ξ (i, j). The obtained temperature change rate image ξ (i, j) is transferred to the D / A converter via the display memory 27.
It is input to 28, converted into a digital signal by this D / A converter 28, and then displayed two-dimensionally on a CRT display 29.

FIG. 2 shows an example of the display on the CRT display 29. An ultrasonic B-mode image 31 of the living body is displayed on the left side of the screen 30, and a tissue to be destroyed (a heating target site) 32 can be confirmed in the displayed ultrasonic B-mode image 31. 33
Is an ultrasonic wave propagation path, and is superimposed and displayed on the ultrasonic wave B mode image 31 as needed. A temperature change image 35 is displayed on the right side of the screen 30. The temperature change image 35 can be subjected to brightness modulation of the output of the D / A converter 28 to be displayed in black and white, but color conversion to color display is better for grasping the temperature change. In the case of color display, it is preferable to display the color bar 37 together. Further, the voltage-dependent parameter change rate ξ at the cursor point 36 set in the temperature change image 35 and the calibrated temperature change ΔT are numerically displayed on the lower right of the screen 30.

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

As described above, in the device of the present embodiment, the temperature of a desired part of the living body is measured by positively utilizing the non-linear effect due to the interaction between the ultrasonic wave and the living tissue, and the conventional thermocouple etc. Since it is not used, there is no inconvenience that it is non-invasive to the living body and adversely affects the normal tissue of the living body. Further, according to the apparatus of this embodiment,
Since it can be used simultaneously with the real-time tomography equipment that has been clinically used for routine examinations, and it can be inspected with the same probe, the sound velocity and non-linear parameter measurement mode can be used at an appropriate cross section while observing a tomographic image. The ideal inspection method can be implemented with one-touch switching.

Although one embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above embodiment and can be appropriately modified within the scope of the gist of the present invention. For example, in the above-described embodiment, the case where the ultrasonic wave transmission directivity (deflection angle) is set to 0 ° as shown in FIG. 4 has been described, but the temperature measurement can be performed even if the deflection angle is set to other than 0 °. It can be carried out.

〔The invention's effect〕

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

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic living body temperature measuring apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view showing an example of a display in the apparatus according to the present embodiment, and FIGS. 3 (a), (b), ( c) to FIG. 5 are for explaining the principle of the present invention.
(A), (b) and (c) are explanatory views of an image generated based on the principle of the present invention, FIG. 4 is an explanatory view of a scanning method of an ultrasonic propagation path, and FIG. 5 is 1 / u It is a relationship diagram between ² and 1 / v ² . 11 …… Ultrasonic transducer array, 17 …… Driving voltage controller, 24 …… Voltage-dependent parameter calculation circuit, 26 …… Change rate calculation circuit, 29 …… Display.

Claims (1)

[Claims] 1. A living body in which a plurality of ultrasonic transducers forming an ultrasonic transducer array are used by switching to a first transducer group for wave transmission and a second transducer group for wave reception. In the ultrasonic living body temperature measuring apparatus for obtaining the temperature distribution information of the desired portion of the living body based on the reflected wave of the ultrasonic wave transmitted toward the body, the driving voltage used for exciting the first transducer group is The drive voltage control unit is variable stepwise, and the drive voltage dependent parameter of the received signal is calculated based on the received signal by the reflected wave of the ultrasonic wave transmitted for each variable of the drive voltage, and is calculated. A voltage-dependent parameter calculation circuit that creates a plurality of local voltage-dependent parameter images in which the temperature of the desired part of the living body is different by obtaining the local voltage-dependent parameter in the living body from the driving voltage-dependent parameter, and the created plurality of local voltage-dependent parameters parameter A change rate calculating circuit for calculating the rate of change between the images from the data images, ultrasonic biometric temperature measuring apparatus characterized by being configured and a display for displaying the calculated rate of change as a two-dimensional image.