JPS62159642A - Method and system for measuring temperature in living body by ultrasonic wave - 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 a method and system for measuring temperature in a living body using ultrasonic waves. The amplitude modulation strain of the piezoelectric vibrator is detected using the oscillator as a medium, and based on this, the output frequency irradiated to the sensor always matches the resonant frequency of the sensor, so that the temperature inside the body can be automatically and continuously measured. The present invention relates to a method and system for measuring temperature in a living body.

[Conventional technology]

For example, one method of treating cancer is to irradiate the affected area with high-frequency energy and heat the affected area to a temperature of 42.5° C. or higher to kill cancer cells. During this heating, if the normal cell portion exceeds 43° C., not only the cancer cells but also the surrounding normal cells will be killed. For this reason, multiple in-vivo measurement temperature sensors are implanted in the area to be heated to constantly measure the in-vivo temperature, and based on the measurement results, the amount and time of high-frequency energy irradiation are controlled automatically or manually. While heating the normal cell part above 42.5°C, it must be controlled so that the temperature of the normal cell part does not exceed 43°C.

Previously, a sensor containing only a piezoelectric vibrator whose resonant frequency changes according to temperature changes was implanted into a living body and its electromagnetic wave absorption phenomenon was used to measure the temperature inside the living body.
The level of electromagnetic waves absorbed by the sensor is extremely weak, and if the object to be measured is a living body, the electromagnetic waves are greatly attenuated even outside the living body.As a result, the signal with temperature information obtained from the in-vivo sensor The level was so small that it was very difficult to measure.

Therefore, a method has been proposed that utilizes ultrasonic waves that have relatively little attenuation in the living body and have a low noise component level, as shown in FIG. 2 (Japanese Patent Application No. 60-21542).

The sensor 1 shown in FIG. 2(a) includes an antenna coil 2,
The crystal oscillator 3 and the ultrasonic transducer 4 are connected in series, and these kings form a closed loop.

The ultrasonic transducer 4 uses a piezoelectric vibrator, such as a barium titanate vibrator or a crystal vibrator, in a thickness longitudinal vibration mode, and has a resonance frequency that is approximately the same as that of the crystal vibrator 3, for example, 13.56 MHz. do.

As the structure of the ultrasonic transducer 4, for example, the second
There is one as shown in Figure (Il+). That is, electrodes 12a and 12b are added to both ends in the vibration direction of a vibrator 1) using barium titanate in thickness longitudinal vibration mode, which has a resonance frequency almost equal to that of the crystal vibrator 3. By adding the epoxy resin 9 mixed with fine nickel powder 13 to a length approximately twice the thickness of the transducer 1) with the electrode 12b in between, the sensitivity of the ultrasonic transducer 4 can be increased within the operating frequency. The ultrasonic transducer 4, crystal oscillator 3, antenna coil 2, and electrode 12 are kept constant and prevent the appearance of unnecessary spurious signals.
a and 12b are connected in series.

FIG. 2(c) shows an embodiment of an external measuring device that measures the temperature inside a living body using the sensor l shown in FIG. 2(a). A variable frequency oscillator 20 equipped with a transmitting antenna coil 6 that irradiates electromagnetic waves of a predetermined frequency to the sensor 1, a frequency counter 5 connected to the variable frequency oscillator 20 and counting the output frequency, and a sensor 1 that oscillates. A microphone 7 that receives ultrasonic waves and converts them into electric signals, a high frequency amplifier 8 that amplifies the electric signals from the microphone 7 to a predetermined level, a filter 9 that extracts an electric signal of the same frequency as the ultrasonic waves, and a filter 9. It consists of a level meter 10 for observing the extracted electrical signal level.

In the above configuration, its operation will be explained. When the variable frequency oscillator 20 irradiates electromagnetic waves to the sensor 1 via the transmitting antenna coil 6 connected thereto, the sensor 1 emits an electromagnetic wave to the antenna coil 2. When the electromagnetic wave matches the resonant frequency of the crystal resonator 3, the largest high-frequency current flows into the closed loop, thereby causing the ultrasonic transducer to The user 4 is activated and generates an ultrasonic wave having the same resonance frequency. This ultrasonic wave is received by a microphone 7, the electric signal is amplified to a required level by a high frequency amplifier 8, an electric signal having the same frequency as the ultrasonic wave is extracted by a filter 9, and its level is observed by a level meter 10, The frequency (resonant frequency) at the point where the reading of the level meter 10 becomes maximum when the oscillation frequency of the variable frequency oscillator 20 is changed (Fig. 2 (N))
is read by the frequency counter 5, and the relationship between the resonant frequency of the temperature sensor 1, which is known in advance, and the temperature (Fig. 2 (=
)), the internal body temperature can be accurately determined.

This is because the resonant frequency f has a characteristic that changes depending on the temperature, so by understanding the relationship between the resonant frequency f1 and temperature in advance, it is possible to detect the resonant frequency f1. It is possible to remove the effects of electromagnetic wave noise and efficiently determine the internal body temperature.

[Problem that the invention seeks to solve]

However, in the above-mentioned method and system for measuring temperature in a living body, the oscillation frequency of the variable frequency oscillator is changed, and the resonance point is constantly read while reading the frequency at the point where the reading of the level meter is maximum with a frequency counter. Since the variable frequency oscillator must be operated to track the resonant frequency, it is difficult to automatically and continuously detect the resonant frequency, and the value thereof is inaccurate.

[Means and effects for solving the problems] The present invention has the following features:
This was done in view of the above, and in order to automatically and continuously detect the resonant frequency using ultrasound as a medium, frequency modulation is applied to the high frequency electromagnetic energy irradiated to the sensor, and the output is output from the ultrasound transducer. a microphone for receiving the ultrasonic waves received by the microphone, a detection means for detecting amplitude modulation distortion from the ultrasonic waves received by the microphone, and a reference for the amplitude modulation distortion at the resonance point of the crystal resonator detected by the detection means. Based on a phase detection means for comparing the phase of the signal and a signal outputted by the phase detection means,
Provided is an in-vivo temperature measurement system using ultrasonic waves, which is equipped with voltage-controlled oscillation means that controls the output of high electromagnetic energy irradiated to a sensor, and in which the output frequency of the voltage-controlled oscillation means always matches the resonance frequency of a piezoelectric element. It is something to do.

〔Example〕

Hereinafter, the in-vivo temperature measuring device according to the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an explanatory diagram showing an embodiment of the in-vivo temperature measurement system using ultrasound according to the present invention.

Similar to the system shown in the prior art, the sensor 50 has an antenna coil 51, a crystal oscillator 52, and an ultrasonic transducer 53 connected in a loop, and is an ultrasonic transducer implanted in a measurement target area in a living body. The user 53 uses, for example, a piezoelectric vibrator such as a barium titanate vibrator in a thickness longitudinal vibration mode, and has a resonance frequency that is approximately the same as that of the crystal vibrator 52.

Also, a microphone 54 receives ultrasonic waves generated from the ultrasonic transducer 53 of the sensor 50 and converts them into electrical signals, an AM detector 56 detects amplitude modulation distortion from the electrical signals, and a microphone 54 a high-frequency amplifier 55 that amplifies the electrical signal from the amplifier 55 to a predetermined level, a phase detector 57 that compares the output signal from the amplifier 55 with a reference low-frequency signal, and a low-frequency oscillator 58 that outputs the reference low-frequency signal. From the waveform obtained from the phase detector 57,
A filter 59 that forms a DC voltage according to the duty ratio, a voltage controlled oscillator 60 that adjusts the output frequency according to the DC voltage value, and a system for repeatedly scanning and controlling the output frequency of the voltage controlled oscillator 60 within a certain range. A lamp voltage orderer 61, a sensor coil 65 when an electromagnetic wave is irradiated to the antenna coil 51 of the sensor 50, a frequency counter 62 that counts the detected resonance frequency,
It is composed of a frequency temperature function generation circuit 63 that calculates the corresponding in-vivo temperature from the resonance frequency obtained by the frequency counter 62, and a display section 64 that displays the in-vivo temperature information obtained from the frequency temperature function generation circuit 63. ing.

The operation in the above configuration will be explained.

Let f be the resonant frequency of the temperature sensor 50. Here f,
The resonance frequency becomes a slightly low value due to the influence of the inductance of the crystal oscillator 52 and the antenna coil 51, etc.

On the other hand, when the output frequency from the sensor coil 65 is changed near the resonance frequency f1 of the temperature sensor 50, the voltage information using the ultrasonic wave as a medium from the ultrasonic transducer 53 becomes as shown in FIG. , the resonance frequency f of sensor 1 is maximum. This occurs because the high frequency energy applied to the sensor coil 65 is absorbed by the in-vivo temperature sensor 50 due to electromagnetic induction between the antenna coil 51 of the temperature sensor 50 and the sensor coil 65. Therefore, by reading the frequency at the point where the voltage is maximum and comparing it with the previously known relationship between the resonant frequency of the temperature sensor 50 and the temperature (FIG. 2 (d)), it is possible to accurately know the temperature in the living body. .

Furthermore, a voltage controlled oscillator 6 is used to detect the resonance frequency.
0, the resonance frequency is detected by repeatedly changing the oscillation frequency applied to the sensor coil 65 in a specific width in response to an input voltage of a specific width from the lamp oscillator 61.

Next, for example, 20Ml1z is applied to the sensor coil 65.
When frequency modulation (FM) is applied to the high frequency electromagnetic wave of , for example, by a low frequency of 801)z, amplitude modulation (AM) distortion occurs at both ends of the sensor coil 65. This amplitude modulation distortion differs at the resonance frequency fr of the sensor 50 and before and after it, and at the resonance point, an amplitude modulation distortion twice as large as that of the vomit modulation signal is generated. Therefore, this information using ultrasonic waves as a medium is transmitted to the microphone 54. Upon reception, the AM detector 56 extracts the amplitude modulation distortion therein, and the phase detector 57 compares the modulated signal from the low frequency oscillator 58 with a reference low frequency signal, which is twice the modulated signal, and generates a predetermined pulse waveform. get.

The duty ratio of this waveform changes according to the output from the AM detector 56, and when it passes through the filter 59, a DC voltage according to this duty ratio is obtained. The voltage controlled oscillator 60 is controlled by this DC voltage, and a feedback loop is configured so that the output frequency of the voltage controlled oscillator 60 always matches the resonant frequency of the temperature sensor 50,
After locking the phase and stopping the lamp voltage for a certain period of time, the output frequency of the voltage controlled oscillator 60 is read by the frequency counter 62, the frequency is temperature-converted by the frequency temperature function generating circuit 63, and the result is displayed on the display section 6.
4, the in-vivo temperature can be automatically and continuously observed.

After capturing the resonant frequency of one sensor, the voltage of the lamp is changed again to detect the resonant frequency of the other sensor.

In the present invention, amplitude modulation distortion of a crystal oscillator is detected using ultrasonic waves with excellent propagation characteristics as a medium, and a phase-locked loop is formed based on the detected information. By removing the influence, it becomes possible to detect the temperature inside the body with high efficiency.

〔Effect of the invention〕

As explained above, in the in-vivo temperature measurement system using ultrasound according to the present invention, frequency modulation is applied to the high-frequency electromagnetic energy irradiated to the sensor, and a microphone is used to receive the ultrasound output from the ultrasound transducer. , a detection means for detecting amplitude modulation distortion from the ultrasonic waves received by the microphone, and a phase detection means for comparing the amplitude modulation distortion at the resonance point of the crystal resonator detected by the detection means with the phase of a reference signal. and voltage-controlled oscillation means for controlling the output of high-frequency electromagnetic energy irradiated to the sensor based on the signal output by the phase detection means, the output frequency of the voltage-controlled oscillation means always being equal to the resonant frequency of the piezoelectric element. Since they match, the resonance frequency can be detected automatically and continuously using ultrasound as a medium.

[Brief Description of the Drawings] Figure 1 is a block diagram showing the structure of the in-vivo temperature measurement system using ultrasound according to the present invention, and Figure 2 (a)
(o) and (c) are explanatory diagrams showing a conventional method of measuring in-vivo temperature using ultrasound, and Fig. 2 (d) is a graph showing the relationship between frequency and temperature. ) is a graph showing the relationship between voltage and frequency. Explanation of symbols 50...Sensor 52...Crystal resonator,
53... Ultrasonic transducer, 54... Microphone, 56... AM detector, 57... Phase comparator, 58... Low frequency oscillator, 60... Voltage controlled oscillator. Patent Applicant: Toyo Tsushinki Co., Ltd. Agent Patent Attorney Shin Matsubara 2 Kiyoshi Muraki Dosage
Same as above Jun Shima - Same as above
Hiroshi Sakai Figure 1 Figure tr t 2

Claims (2)

[Claims] (1) A sensor in which a piezoelectric vibrator with temperature dependence and an ultrasonic transducer are electrically or acoustically coupled to each other is implanted at a measurement point in a living body, and high-frequency electromagnetic energy is applied to the sensor from outside the living body. is irradiated, and based on the current flowing through the piezoelectric vibrator due to its resonance effect,
In a method for measuring temperature in a living body using ultrasonic waves, which operates the ultrasonic transducer, detects ultrasonic waves emitted by the ultrasonic transducer outside the living body, and observes the temperature at the point to be measured, the method comprises: high-frequency electromagnetic energy irradiated to the sensor; At the same time, the ultrasonic waves output from the ultrasonic transducer are received by a microphone outside the living body, and the amplitude modulation distortion caused by the resonance characteristics of the piezoelectric vibrator is extracted from the electric signal converted by the microphone. A method for measuring temperature in a living body, comprising: extracting a component, detecting a resonant frequency of the piezoelectric vibrator based on the amplitude modulation distortion component, and measuring a temperature inside the living body based on the resonant frequency. (2) A sensor in which a temperature-dependent piezoelectric vibrator and an ultrasonic transducer are electrically or acoustically coupled to each other is implanted at a measurement point within a living body, and high-frequency electromagnetic energy is applied to the sensor from outside the living body. is irradiated, and based on the current flowing through the piezoelectric vibrator due to its resonance effect,
In the in-vivo temperature measurement system using ultrasound, which operates the ultrasound transducer, detects the ultrasound emitted by the ultrasound transducer outside the living body, and observes the temperature at the point to be measured, comprising: a microphone that converts the ultrasound into an electrical signal outside the living body; and a detection means that extracts an amplitude modulation distortion component caused by the resonance characteristics of the piezoelectric vibrator from the electrical signal output from the microphone. and a phase detection means for comparing the amplitude modulation distortion component extracted by the detection means with a phase of a reference signal, and controlling high frequency electromagnetic energy irradiated to the sensor based on the signal output by the phase detection means. 1. A system for measuring in-vivo temperature using ultrasonic waves, comprising voltage-controlled oscillation means, wherein the output frequency of the voltage-controlled oscillation means always matches the resonance frequency of the piezoelectric vibrator.