JPH0775604B2 - In-vivo temperature measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an ultrasonic device for measuring a body temperature suitable for use in so-called hyperthermia for forcibly raising body temperature and treating cancer and the like, and The present invention relates to an ultrasonic device capable of obtaining a propagation time difference of sound waves between different reflecting objects in a reflected signal (reflected image).

[Conventional technology]

In order to detect the temperature inside the body of the subject (deep body temperature), a method such as heating a temperature detector that is in close contact with a certain area on the body surface to near body temperature and detecting the temperature at which heat does not move with the subject is detected. known. However, it is not possible to accurately know the temperature of any part of the subject.

On the other hand, I E E Transactions
On Biomedical Engineering (IEEE Tra
nsactions on Biomedical Engineerling), BME-31,
No. 1 (January 1984), pp. 161-167, it was shown that measurement of the inside of a subject is possible using a nuclear magnetic resonance imaging apparatus.

In hyperthermia, which is regarded as an important effective treatment for cancer, the body temperature must be controlled to a temperature at which normal cells are not destroyed but only cancer cells are destroyed. Therefore, it is necessary to perform heating while monitoring the accurate temperature distribution in each part of the body. However, in the detection of the in-vivo temperature distribution using each of the magnetic resonance imaging devices described above, it is necessary to place the subject under a high magnetic field, and accurate detection of temperature can be performed if another device that disturbs the magnetic field is present nearby. I can't do it.
Further, a power supply for generating a high magnetic field, a coil, an electronic computer for processing data of measurement results, and the like are required, which makes the entire device large and expensive, and there is a problem in detecting a body temperature when performing hyperthermia. A pulse reflection method is well known as a conventional technique for measuring the propagation time of a sound wave between two points in an object (for example, "Ultrasonic flaw detection method", page 2, Nihon Kogyo Shimbun (Showa 39). )).

[Problems to be solved by the invention]

Therefore, an object of the present invention is to provide a method for detecting a change in body temperature of a specific part in the body with a small and simple device, and an ultrasonic device for obtaining a propagation time difference of a sound wave between different reflection objects among reflection signals. .

[Means for Solving Problems] The above-mentioned object is to measure the phase angle of ultrasonic reflection signals from a plurality of reflection points existing at different positions in the distance direction, and to calculate reflection signals from a plurality of reflection objects ( This is achieved by determining the propagation time difference of the sound waves between the reflecting objects based on the reflection image) and measuring the change in the sound velocity of the relevant part.

[Action]

With this method, the body temperature immediately before the start of hyperthermia can be measured, and the sound wave propagation speed in the living body is 1 ° C, which is the increase in body temperature.
It is used to increase about 1m / sec. Also,
The fact that the propagation time of a sound wave between two points can be determined by obtaining the phase angle of the ultrasonic reflection signal from two reflecting objects in the living body is utilized.

〔Example〕

The configuration of the present invention will be described in detail below with reference to examples.

FIG. 2 is a sound wave transmitter / receiver used in this method, in which high-frequency power from the heating wave transmission circuit 1 is applied to the heating element unit 3 selected by the first selection circuit 2 to enter the living body. Convergent irradiation. The heated area is shown at 13. Here, 4 is a one-dimensionally arranged piezoelectric vibrator, and 5 is an element selection circuit for receiving waves. Such irradiation is performed for a specific period, and then normal B-mode tomography is performed. The tomographic image obtained in this case is shown in FIG. Here, 6 is an image of the diaphragm, and a large number of images of intrahepatic reflection objects are drawn in the region 7. Here, for the sake of simplicity, the reflection images on the specific tomographic image sound beam 14 will be referred to as A, B, and C. Where A, B
Is a reflection image from different reflection objects in the liver, and C is a diaphragm reflection image. FIG. 4 shows the reflected signal S of the ultrasonic wave that gives such an acoustic image. Here, the corresponding reflected signal portions are S _A , S _B , and S _C , respectively. FIG. 5A is an enlarged view of the portion where S _A and S _B exist. This signal and the fifth
Signals gc (t) gs (t) 90 ° phase-shifted from each other as shown in FIG.
Is multiplied (M) by the configuration shown in FIG. 1 to obtain a low-pass filter.
Apply to LPF. The LPS outputs hs (t) and hc (t) are as shown in FIG. 5 (c). For example, corresponding to the reflection signal A
The combination of hs and hc R _A and I _A determines the phase θ _A of S _A as shown in FIG. Similarly, for S _B corresponding to _B , θ _B is also determined. The part that performs this calculation is the ATAN part.

The output _AT of the ATAN part is as shown in Fig. 5 (d).

The time T _A T _B (Fig. 8) designated by the instruction part shown in P of Fig. 1 TIM is a circuit that draws the origin positions T _MA and T _MB from the envelope waveform u _(t) obtained by the ABS circuit that calculates. V _(t) , which is one of the outputs of TIM, and signal A _T are applied to the HLD circuit.
The circuit HLD selectively outputs the phase angles θ _A and θ _B at two times designated by v _(t) . The TET circuit calculates this phase angle difference θ _D = θ _A −θ _B and outputs it as 11. on the other hand
TIM holds and outputs the time difference between T _MA and T _MB , T _D = T _MB −T _MA . Circuit TDF is a circuit for calculating the propagation time difference P _D between the reflected signal AB from the above theta _D and T _D by the following relation.

Where ω is the center frequency of the sound wave. As shown in the above equation, the propagation time P _D between the two points is corrected by the time difference T _D of the peak value of the envelope waveform of the received signal with the phase difference θ _D obtained from the received signal from the two points and the reference signal. Get in the form. The phase angle repeatedly takes a value up to 2π. Although it is not possible to measure the time difference of the reference signal period T ₀ or more only with the second term on the right side of the above equation (θ _D / ω), by using the first term on the right side of the above equation (T _D ) together It is possible to measure even when the propagation time P _{D of} is longer than the period T _{0 of the} reference signal. That is, the time difference T _D of the peak value of the envelope waveform of the reception signal is corrected by the phase difference θ _D , and more accurately 2
The propagation time P _D between the points can be measured. Such method is by the theta _D measurement accuracy nearly 2 [pi / 100 of (rad) in, because if the frequency is 3 MHz omega is ^{2π × 3 × 10 6 (rad} / sec), the theta _D / omega accuracy will be ^{1 / (3 × 10 8)} ≒ 3 × 10- 9 (sec). Therefore, T _D , which is the time difference between T _MA and T _MB , is 10 μsec.
(10- ⁵ sec) to the measurement accuracy of P _D becomes ^{10- 5 / (3 × 10- 9} ) ≒ 3 × 10 3 ≒ 3000. On the other hand, the speed of sound in the living body changes 1/1500 with respect to 1 ° C, so it is possible to measure a temperature change of about 0.5 ° C according to this method. It is possible to continuously measure the time change of θ _D , and it is also possible to continuously monitor the temperature change and the propagation time of the sound wave between the images A and B of the reflecting object. Moreover, as shown in FIG. 7, the output of the LPF is applied to the storage units Is and Ic,
A configuration is also possible in which hc and hs are accumulated for a plurality of times of transmission and reception to improve the signal ratio S / N ratio and then applied to the ATAN and ABS circuits to obtain the phase angle.

Further, the configuration of the HLD is changed as shown in FIG. 9 so that the output is a complex number X, Y. here Is. The output of such a complex holding circuit HLD is applied to the conjugate complex multiplier CMP to obtain the output Z, where Z is Therefore, the phase difference between the two signals is held, and the phase difference which is the phase component of Z can be obtained by applying Z to the complex phase detector CTET described later.

This signal is cumulatively added by I _Z for multiple transmissions and receptions.
With such a configuration, when the reflected signals S _A and S _B move in the same direction, the phase angle difference θ _B −θ _A does not change, and therefore effective accumulation is not affected by pulsation or the like. Is possible. In this way, the signal Z _I from which fluctuation components due to pulsation etc. have been removed is applied to the complex phase detector CTET, and the phase angle difference θ
A configuration for obtaining _D is also possible.

The above is a description of the reflected signal on the same beam 14 of FIG. Focusing on two or more reflection points distant in the distance direction, the present invention is not limited to the reflection points on the same beam in particular, and it is obvious that the same measurement is performed for two groups of reflection points distant in the distance direction. It is possible.

[Effects of the Invention] As described above, according to the present invention, the time difference between the peak values of the envelope waveform of the received signal is corrected by the phase difference, the propagation time between two points can be measured more accurately, and the size is small It was possible to detect the change in body temperature at a specific site in the body and to detect the propagation time of the sound wave between the reflection points.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention, FIG. 2 is a diagram showing a heating system, FIG. 3 is a diagram showing an example of a tomographic image, FIG. 4 is a diagram showing reflected waveforms, and FIG. FIG. 6 is a diagram showing a signal, FIG. 6 is a diagram showing a phase angle, FIGS. 7 and 9 are configuration diagrams for improving S / N, and FIG. 8 is an explanatory diagram of a TIM circuit. 1 ... Wave sending circuit for heating, 2 ... First selection circuit, 3 ... Heating element section, 4 ... Piezoelectric vibrator, 5 ... Element selection circuit.

Claims (7)

[Claims] 1. A piezoelectric vibrator in which a plurality of elements are arranged and driven at a predetermined center frequency, and a transmitting element selection for selecting a transmitting element for converging and transmitting ultrasonic waves to a subject. Means, a wave-receiving element selecting means for selecting a wave-receiving element for receiving an ultrasonic wave reflected signal from the subject, and a phase shift of 90 ° with each other having a frequency substantially the same as the center frequency. Multiplying means for obtaining each multiplication signal of each of the two types of reference signals and the ultrasonic reflection signal, and phase angle change detection for detecting a time change of the phase angle of the ultrasonic reflection signal from the multiplication signal. Means, having an envelope signal detection means for detecting an envelope signal from the multiplication signal, from the output of the phase angle change detection means and the output of the envelope signal detection means,
An ultrasonic device characterized by measuring the propagation time of an ultrasonic wave between two of a plurality of reflection points existing at different positions in the depth direction in the subject. 2. A piezoelectric vibrator in which a plurality of elements are arranged and driven at a predetermined center frequency, and a wave transmission element selection for selecting a wave transmission element for converging and transmitting ultrasonic waves to a subject. Means, a wave receiving element selecting means for selecting a wave receiving element for receiving an ultrasonic wave reflected signal from the subject, a first reference signal having a frequency substantially the same as the center frequency, and First multiplication means for obtaining a multiplication signal with the ultrasonic reflection signal, and the first reference signal and the first reference signal are phase-shifted from each other by 90 °,
Second multiplication means for obtaining a multiplication signal of the second reference signal having substantially the same frequency as the center frequency and the ultrasonic reflection signal, and outputs of the first and second multiplication means, respectively. Applied first and second low-pass filtering means, and phase angle change detecting means for detecting a time change of the phase angle of the ultrasonic reflected signal from the outputs of the first and second low-pass filtering means. When,
Envelope signal detecting means for detecting an envelope signal from the outputs of the first and second low-pass filtering means, and a signal maximum time detecting means for detecting a plurality of maximum times at which the envelope signal becomes maximum. And holding means for selectively holding and outputting the phase angle at each of the plurality of maximum times from the output of the phase angle change detecting means and the output of the signal maximum time detecting means. From the difference between the two phase angles at each of the maximum times and the difference between each of the maximum times that gives the two phase angles and the value of the center frequency. An ultrasonic device characterized by measuring the propagation time of an ultrasonic wave between two of a plurality of reflection points existing at different positions. 3. A first means for storing and accumulating an output of the first low-pass filtering means between an output end of the first low-pass filtering means and an input end of the phase angle change detecting means. For accumulating and accumulating the output of the second low pass filter means between the output end of the second low pass filter means and the input end of the envelope signal detecting means. The ultrasonic device according to claim 2, further comprising a second signal cumulative storage means for transmitting and receiving ultrasonic waves a plurality of times. 4. A wave transmitting means for transmitting an ultrasonic wave to a subject, and a wave receiving means for receiving an ultrasonic wave reflected signal from the subject.
A first frequency having substantially the same frequency as the center frequency of the transmitted wave
First multiplication means for obtaining a multiplication signal of the reference signal and the ultrasonic reflection signal, and the first reference signal
Second multiplication means for obtaining a multiplication signal of the ultrasonic reference signal and a second reference signal having a frequency substantially the same as the center frequency of the transmitted wave, shifted by 90 °; First and second low-pass filtering means to which respective outputs of the second multiplying means are applied, and an envelope for detecting an envelope signal from the outputs of the first and second low-pass filtering means. Signal detection means,
From the output of the first and second low-pass filtering means and the output of the signal maximum time detecting means, the plurality of signal maximum time detecting means for detecting a plurality of maximum times at which the envelope signal becomes maximum; Complex holding means for selectively holding and outputting a phase angle at each of the local maximum times of, and a complex complex multiplying means for obtaining a conjugate complex product of any two complex numbers of the outputs of the complex holding means. , A complex phase detector for detecting a phase component from the output of the conjugate complex multiplication means, and from the value of the center frequency and the difference between each of the local maximum times giving the phase component and the phase component, An ultrasonic device characterized by measuring the propagation time of an ultrasonic wave between two of a plurality of reflection points existing at different positions in the depth direction in the subject. 5. An accumulating means for accumulating the output of the conjugate complex multiplying means is further provided between the output end of the conjugate complex multiplying means and the input end of the complex phase detector, and the accumulating means is provided a plurality of times. The ultrasonic device according to claim 4, which transmits and receives a sound wave. 6. A transmitting means for transmitting an ultrasonic wave to a subject, a means for receiving an ultrasonic reflected signal from the subject, and a means for receiving the ultrasonic reflected signal from the subject at different positions in the depth direction. Means for measuring the temporal change of the phase of the ultrasonic reflection signal from a plurality of existing reflection points, and means for measuring the propagation time difference between the ultrasonic signals from the plurality of reflection points, the reflection An ultrasonic device characterized by measuring the propagation time of an ultrasonic wave between two of the points. 7. The ultrasonic device according to claim 6, wherein said transmitting means also serves as means for heating a predetermined part of said subject.