JPH0245719A - Method for measuring body temperature - Google Patents

Abstract

PURPOSE:To accurately measure a body temperature in a deep part by measuring the intensity of radiant energy of an electromagnetic wave radiated from a living body at two or more kinds of frequencies which are different from each other and analyzing the data on the radiant energy and the data on skin surface temperature. CONSTITUTION:The temperature of an electromagnetic wave sensor 2 integrated with a thermometer is controlled to be kept at nearly same temperature as the average skin surface temperature of a measured part 8 by using a sensor temperature controller 7. While the sensor 2 is made to approach, the skin surface temperature of the part 8 is measured without contact by the thermometer 5. Next, when the temperature of the living body 1 and that of the sensor 2 become nearly same, the sensor 2 is brought into contact with the surface of the living body 1 and the intensity of the radiant energy is measured at two or more kinds of measuring frequencies. Then, the measured intensity of the energy is transmitted to a temperature operation device 6 through a receiver 3. In the device 6 the temperature in the deep part can be operated from the radiant energy measured by the sensor 2, the skin surface temperature measured by the thermometer 5, the electric characteristic value of the tissue of the living body and the hypodermic structure of the measured part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for measuring body temperature that can non-invasively, highly accurately, and instantaneously measure the core body temperature of animals including humans.

[Prior Art] The fastest and non-invasive method for measuring the core body temperature of animals including humans is to use a so-called rod-shaped thermometer that includes a semiconductor sensor, etc., or a catheter-type thermometer such as an optical fiber, to measure the core body temperature of animals including humans. Insert it into a body cavity such as the rectum, wait for temperature equilibrium between the rod-shaped thermometer or catheter-type thermometer containing the sensor and the living tissue, and then measure the equilibrium temperature as the deep temperature, or measure the temperature rise from the initial temperature. Examples include a method of predicting the final equilibrium temperature from the time change in the rate.

According to this method, it is reported that in practice, it takes about one minute at the shortest to measure the temperature due to the limit of the thermal time constant of the sensor, and that the faster the temperature measurement, the lower the precision and accuracy.

Further, there has been research by the present inventor and others that attempts to estimate one-dimensional internal body temperature distribution by measuring the intensity of noise electromagnetic waves emitted from a living body using a plurality of frequencies. However, its purpose is to roughly estimate the entire temperature distribution artificially created by thermotherapy of cancer tissue, etc., and the temperature is estimated from as many parts of the body as possible, including the measurable skin surface temperature. The objective is to perform measurements at as many frequencies as possible and to find a temperature distribution function that minimizes the overall error.

[Problems to be Solved by the Invention] Therefore, even if an attempt is made to measure core body temperature using a device manufactured based on the above idea, it will take at least several minutes just to measure. Furthermore, with the above-mentioned device, there was originally no idea of estimating only the part that indicates core body temperature with high accuracy, and only algorithms that calculate the temperature distribution that minimizes the overall error, including skin surface temperature, have been reported. .

As a result, it has the disadvantage that a temperature distribution function with an error of several degrees Celsius is often given as the optimal solution for core body temperature.

In other words, conventional technology attempts to estimate temperature by measuring electromagnetic wave energy emitted from within a living body, but the purpose of this is not to measure core body temperature at high speed; (Instantaneous means within a few seconds) It was not possible to measure with high precision.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a body temperature measurement method that solves the above-mentioned problems, has a measurement accuracy equal to or higher than that of a normal temperature-balanced thermometer, and can measure core body temperature instantaneously and non-invasively. It is about providing.

[Means for Solving the Problem] In order to achieve such an object, the present invention measures the radiant energy intensity of electromagnetic waves emitted from a living body at frequencies of Z fl or higher, which are different from each other, and It is characterized by calculating the deep temperature inside the body by measuring the temperature of the skin surface of the body and analyzing the radiant energy data and the temperature data of the skin surface.

[Function] First, in order to non-invasively measure the body temperature deep inside the body from above the body surface, the bio-transmissive property of electromagnetic waves, which has the property of penetrating the living tissue up to a thickness comparable to the wavelength, is utilized.

In other words, as shown in Figure 1, the electromagnetic waves emitted from various points inside the living body 1 according to Blank's radiation law are captured by the electromagnetic wave sensor 2 placed on the body surface, and the intensity is measured by the receiver 3. Measure. At this time, different points Pa in the living body
, Pb, ..., Pn, the electromagnetic wave sensor 2 will capture the electromagnetic wave energy, but the intensity measurement can be done at the speed of light in principle, and in reality, even without averaging processing. . At this time, the radiant energy intensity measured by the receiver 3 is limited to the energy radiated from within the measurement region 4 determined by the frequency to be measured and the electrical characteristics of the measurement site of the living body 1 to be measured. Become. Here, the surface temperature of the living body 1 is measured by a thermometer 5, and the obtained data is sent to a temperature calculation device 6. Data on the radiant energy measured by the receiver 3 is also sent to the temperature calculation device 6.

If the above-mentioned measurements are performed at two or more different frequencies, and if the measurements are made at a location where there is little individual difference in internal structure, such as on the temporal bone, the biological penetration characteristics of electromagnetic waves and Since the electrical characteristics with the living tissue are known, the temperature distribution at the measurement site can be calculated by the temperature calculation device 6.

In order to obtain the temperature in the region that indicates core body temperature with particular precision, the temperature distribution from the body surface to the center of the body changes exponentially with distance (depth), as shown in Figure 2, and at a certain distance, We exploit the knowledge that the saturation value is reached and that the coefficient of the power of the exponential term sensitively reflects the ambient temperature.

As the distance from the skin surface increases, the temperature inside the body increases, and the difference between the deep temperature and the skin surface temperature Ts when it reaches a saturation value is expressed as ΔT. At this time, the core body temperature is Ts+
It is given by ΔT.

It is assumed that the temperature distribution inside the body is expressed by the following formula: % formula % (1). Here, T is the temperature inside the body, and Ts is the body surface temperature, which sensitively reflects the ambient temperature. This body surface temperature Ts is not based on estimation, but can be actually measured with high precision using, for example, a thermometer 5 such as an infrared thermospot sensor.

b is the coefficient of the power of the exponential function, and X is the value of the distance coordinate from the body surface to the center of the body.

The radiant energy intensity Tb, measured by the electromagnetic wave sensor 2 and the receiver 3, is expressed as a function of the electrical characteristic values of the measuring body tissue, that is, the relative dielectric constant ε, the conductivity σ and ΔT, b, as Tb1=f(ε, Q, ΔT, b) (
2). However, i=1.2. ..., n. By measuring the radiant energy intensity Tbi of the measurement site using a plurality of frequencies, the core body temperature can be measured with extremely high accuracy from equation (2).

All objects, including living organisms, radiate thermal noise electromagnetic waves based on Blank's radiation law unless their temperature is absolute zero. This radiant energy has a maximum value at a wavelength of about 9.7 micrometers for humans, and decreases as the frequency becomes higher or lower than this maximum value. As the measurement frequency is lowered, the radiant energy decreases if the temperature is constant, but the thickness through which electromagnetic waves penetrate the living body increases, so thermal noise electromagnetic waves emitted from each point inside the living body can be directly measured even from the body surface. be able to. It is also known that the thickness of living tissue through which electromagnetic waves can penetrate decreases monotonically as the frequency of electromagnetic waves increases, and the electrical characteristic values of main living tissues are also known. Therefore, assuming the temperature distribution of equation (1) at parts of the living body with little individual difference, Ts
Also, if you measure the radiant energy intensity in multiple ways,
The deep temperature can be calculated from equation (2) as T=Ts+ΔT.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a block diagram showing an example of the configuration of an apparatus to which the present invention is applied. In FIG. 3, electromagnetic waves emitted from various points inside a living body 1 are captured by an electromagnetic wave sensor 2 placed on the body surface, and their intensity is measured by a receiver 3. Using the sensor temperature control device 7, the temperature of the electromagnetic wave sensor 2 integrated with the thermometer 5 is controlled so as to be maintained at approximately the same temperature as the average skin surface temperature of the measurement site 8. The reason for this is that the measurement of the radiant energy intensity takes a short time, so there is practically no problem in measuring the biological temperature distribution. This is to prevent it from being significantly disturbed. In this embodiment, a contact type electromagnetic wave sensor 2 is used. One octave is sufficient for the measurable band of the electromagnetic wave sensor 2. Here, it is assumed that the bandwidth is 2 to 4 GHz. Of course, the measurement bandwidth of the receiver 3 needs to be equal to or greater than the bandwidth of the electromagnetic wave sensor 2. At this time, the electromagnetic wave sensor 2
Since it is necessary to efficiently capture weak electromagnetic waves emitted from a living body, it is desirable to suppress the voltage standing wave ratio to about 2 or less as an impedance matching condition with the living body.

First, the skin surface temperature of the measurement site 8 is measured in a non-contact manner using the thermometer 5 while bringing the electromagnetic wave sensor 2 close. If there is a certain positional difference between the temperature of the electromagnetic wave sensor 2 whose temperature is kept constant in advance and the skin surface temperature of the measurement site 8, the contact type electromagnetic wave sensor 2 as in this embodiment , the set temperature of the electromagnetic wave sensor 2 is adjusted until it reaches equilibrium with the temperature of the measurement site 8. In this way, when the temperatures of the living body 1 and the electromagnetic wave sensor 2 become almost equal, the electromagnetic wave sensor 2
is brought into contact with the surface of the living body 1, and the radiant energy intensity is measured at two or more measurement frequencies.

Two or more radiant energy intensities measured by the electromagnetic wave sensor 2 are sent to the receiver 3 and then to the temperature calculation device 6. The temperature calculation device 6 calculates the temperature according to equation (2) from the radiant energy intensity measured by the electromagnetic wave sensor 2, the skin surface temperature measured by the thermometer 5, the electrical characteristic values of the living tissue, and the subcutaneous structure of the measurement site. Find ΔT, T=
The deep temperature is determined by Ts+ΔT.

At least two measurement frequencies are required, but when there are two measurement frequencies, it is desirable that they are appropriately separated so that b and 6 in equation (1) can be estimated with high accuracy. If the measurement frequencies are too close to each other, independence of data is not guaranteed and errors in the estimated values of b and ΔT become large. However, if the measurement frequencies are too far apart, especially if one frequency becomes too high, the accuracy of estimating b and 6 in equation (1) will decrease and broadband components will be required, which will inevitably be expensive. It becomes a measuring device. Furthermore, picking up signals from deeper parts does not necessarily contribute to improving measurement accuracy, and may sometimes cause larger errors. In other words, when we try to lower the frequency to pick up signals from deep inside the body, the radiant energy intensity distribution measured at that time will be different from what would be expected in the body if these influencing factors are not taken into consideration due to the presence of gas deep inside the body and the influence of bones. deviates from the radiant energy intensity distribution. As far as I have tested, the measurement frequency is 2 to 4 G.
For humans, it is appropriate to measure in the Hz band.

[Effects of the Invention] As explained above, according to the present invention, instantaneous non-invasive measurement of core body temperature can be performed, and the body temperature of infants and critically injured patients can be measured instantaneously and with high precision. Therefore, it will be of great benefit in actual clinical practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a device to which the present invention is applied, FIG. 2 is an internal temperature distribution diagram, and FIG. 3 is a block diagram of an example configuration of a device to which the present invention is applied. DESCRIPTION OF SYMBOLS 1... Living body, 2... Electromagnetic wave sensor, 3... Receiver, 4... Measurement area, 5... Thermometer, 6... Temperature calculation device, 7... Sensor temperature control device , 8...Measurement site. Figure 1: 1st surface is 5C ridge

Claims (1)

[Claims] 1) Measure the radiant energy intensity of electromagnetic waves emitted from a living body at two or more different frequencies, measure the temperature of the skin surface of the living body, and compare the data of the radiant energy and the temperature of the skin surface. A method for measuring body temperature, characterized in that the deep temperature inside the living body is calculated by analyzing data.