Temperature Measurement Device and Temperature Measurement Method

Abstract

An embodiment a temperature measuring device including a blood flow meter configured to measure a first blood flow near a skin surface of a subject, a sensor configured to measure a first temperature and a first heat flux of the skin surface of the subject, a storage device configured to store a second blood flow of the subject, the second blood flow being measured before the first blood flow, a thermal resistance deriver configured to derive a first thermal resistance of the subject based on an amount of change between the first and second blood flows, and a temperature calculator configured to calculate an internal temperature of the subject based on the first temperature, the first heat flux, and the first thermal resistance.

Claims

1-4. (canceled)

5. A temperature measuring device comprising: a blood flow meter configured to measure a first blood flow near a skin surface of a subject; a sensor configured to measure a first temperature and a first heat flux of the skin surface of the subject; a storage device configured to store a second blood flow of the subject, the second blood flow being measured before the first blood flow; a thermal resistance deriver configured to derive a first thermal resistance of the subject based on an amount of change between the first and second blood flows; and a temperature calculator configured to calculate an internal temperature of the subject based on the first temperature, the first heat flux, and the first thermal resistance.

6. The temperature measuring device according to claim 5, wherein the storage device stores in advance a conversion table in which a thermal resistance is registered for each amount of change in blood flow.

7. The temperature measuring device according to claim 6, wherein the thermal resistance deriver derives the first thermal resistance by acquiring, from the conversion table, a value of thermal resistance corresponding to the amount of change between the first and second blood flows.

8. The temperature measuring device according to claim 5, further comprising: the blood flow meter configured to measure the second blood flow near the skin surface of the subject.

9. The temperature measuring device of claim 5, further comprising: a display device to display the calculated internal temperature.

10. A temperature measuring method comprising: measuring a first blood flow near a skin surface of a subject; deriving a first thermal resistance of the subject based on an amount of change between the first blood flow and a second blood flow measured in advance; measuring a first temperature and a first heat flux of the skin surface of the subject; and calculating an internal temperature of the subject based on first temperature, the first heat flux, and the derived thermal resistance.

11. The temperature measuring method according to claim 10, further comprising: storing in advance a calibration table in which thermal resistance corresponding to the amount of change between the first and second blood flows.

12. The temperature measuring method according to claim 10, wherein the first thermal resistance is derived by acquiring, from a conversion table stored in advance, a value of thermal resistance corresponding to the amount of change in blood flow.

13. The temperature measuring method according to claim 10, further comprising: outputting the calculated internal temperature to a display device.

14. The temperature measuring method according to claim 10, further comprising: sending the calculated internal temperature to a communication device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a block diagram illustrating the configuration of a temperature measuring device according to an embodiment of the present invention.

[0013] FIG. 2 is a diagram illustrating a thermal equivalent circuit model of a sensor and a living body according to the embodiment of the present invention.

[0014] FIG. 3 is a flowchart for explaining operations of the temperature measuring device according to the embodiment of the present invention.

[0015] FIG. 4 is a diagram for explaining operations of the temperature measuring device according to the embodiment of the present invention.

[0016] FIG. 5 is a block diagram illustrating an example of the configuration of a computer that implements the temperature measuring device according to the embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of a temperature measuring device according to an embodiment of the present invention. The temperature measuring device includes a sensor 1 that measures a temperature T.sub.Skin of a skin surface of a living body 10 (subject) and a heat flux H.sub.Skin on the skin surface, a laser Doppler blood flow meter 2 that measures a blood flow v.sub.Blood near the skin surface of the living body 10, a storage unit 3 that stores an initial value v.sub.Blood (o) of the blood flow v.sub.Blood in advance, a thermal resistance derivation unit 4 that derives thermal resistance R.sub.Combined of the living body 10 on the basis of the amount Δv.sub.Blood of change with respect to the initial value v.sub.Blood (o) of the blood flow v.sub.Blood, a temperature calculation unit 5 that calculates a deep body temperature T (internal temperature) of the living body 10 on the basis of the temperature T.sub.Skin, the heat flux H.sub.Skin, and the thermal resistance R.sub.Combined, and a calculation result output unit 6 that outputs the calculation result of the deep body temperature T.sub.Core.

[0018] The sensor 1 includes a thermal insulation member wo, a temperature sensor 101 disposed on a surface of the thermal insulation member wo in contact with the skin of the living body 10, and a temperature sensor 102 disposed on a surface of the thermal insulation member wo on a side opposite to the surface in contact with the skin. By the temperature sensor 101, it is possible to measure the temperature T.sub.Skin of the skin surface of the living body 10. Furthermore, it is possible to derive the heat flux H.sub.Skin of the skin surface on the basis of a difference between the temperature T.sub.Skin of the skin surface and a temperature T.sub.Upper measured by the temperature sensor 102. The sensor 1 is attached to the skin surface of the living body 10 by, for example, a thermally conductive double-sided tape. The configuration illustrated in FIG. 1 is an example, and the sensor 1 may have a configuration different from that illustrated in FIG. 1.

[0019] The laser Doppler blood flow meter 2 includes a sensor probe 200 and a blood flow calculation unit 203. The sensor probe 200 is provided with a semiconductor laser 201 that irradiates the living body 10 with a laser beam and a photodiode 202 that receives reflected light from the living body 10. The blood flow calculation unit 203 calculates the blood flow v.sub.Blood of the living body 10 on the basis of an electric signal output from the photodiode 202. Since the laser Doppler blood flow meter 2 is a well-known technology, detailed description thereof will be omitted.

[0020] FIG. 2 is a diagram illustrating a thermal equivalent circuit model of the sensor 1 and the living body 10. In the present invention, not only the thermal resistance R.sub.Body of the living body 10 is modeled, but also thermal energy transferred by blood flow is modeled. In FIG. 2, 11 denotes a blood vessel, T.sub.Upper denotes the temperature of an upper surface of the sensor 1 on a side opposite to the surface in contact with the skin of the living body 10, R.sub.Sensor denotes the thermal resistance of the sensor 1, R.sub.Blood denotes heat resistance due to the blood flow, and H.sub.Blood denotes a heat flux due to the blood flow.

[0021] Thermal resistance given by initial calibration is the combined resistance R.sub.Combined of the thermal resistance R.sub.Body of tissues (skin, fat, muscle, nerve, internal organs, bone, etc.), other than the blood of the living body 10, and the thermal resistance R.sub.Blood due to the blood flow of the living body 10.

T.sub.Core=T.sub.Skin+R.sub.CombinedH.sub.Skin  (2)

[0022] In the initial calibration, when the initial value of the deep body temperature T.sub.core of the living body 10, whose deep body temperature T.sub.Core is to be measured, at a part around the sensor 1 is measured by, for example, a heat flow compensation method or an eardrum thermometer and at the same time, the skin surface temperature T.sub.Skin and the skin surface heat flux H.sub.Skin are measured by the sensor 1, the initial value R.sub.Combined (o) of the combined resistance R.sub.Combined can be obtained by Equation 2 above.

[0023] The thermal resistance R.sub.Body is a constant, and the thermal resistance R.sub.Blood is expressed as a function of the blood flow v.sub.Blood. Consequently, the combined resistance R.sub.Combined is a function of blood flow v.sub.Blood as expressed by the equation below.

[00001]$\begin{array}{cc}\left[\mathrm{Math}.1\right]& \\ R_{\mathrm{Combined}}=\frac{R_{\mathrm{Body}}{R}_{\mathrm{Blood}}}{R_{\mathrm{Body}}+R_{\mathrm{Blood}}}=f\left(v_{Blood}\right)& \left(3\right)\end{array}$

[0024] Therefore, a conversion table for the amount of change in the combined resistance R.sub.Combined and the blood flow v.sub.Blood is prepared in advance, and the initial value R.sub.Combined (o) of the combined resistance R.sub.Combined is updated from the amount of change in the blood flow v.sub.Blood measured by a laser Doppler blood flow meter or the like, as expressed by the equation below.

[00002]$\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ R_{\mathrm{Combined}}=R_{\mathrm{Combined}}\left(0\right)f\left(\frac{v_{\mathrm{Blood}}}{v_{\mathrm{Blood}}\left(0\right)}\right)& \left(4\right)\end{array}$

[0025] In this way, in the present embodiment, it is possible to reduce an error in the estimated value of the deep body temperature T.sub.Core that occurs when the blood flow changes. FIG. 3 is a flowchart for explaining operations of the temperature measuring device of the present embodiment. The storage unit 3 of the temperature measuring device stores in advance a conversion table, in which the combined resistance R.sub.Combined of the living body 10 is registered for each amount Δv.sub.Blood of change in the blood flow v.sub.Blood, and the initial value v.sub.Blood (o) of the blood flow v.sub.Blood measured by the laser Doppler blood flow meter 2 at the time of the initial calibration.

[0026] In order to generate the conversion table, the deep body temperature T.sub.Core of the living body 10, whose deep body temperature T.sub.Core, is to be measured, at the part around the sensor 1 is measured by, for example, a heat flow compensation method or an eardrum thermometer while monitoring the blood flow v.sub.Blood at the part around the sensor 1 by the laser Doppler blood flow meter 2, and the skin surface temperature T.sub.Skin and the skin surface heat flux H.sub.Skin are measured by the sensor 1. Then, in a case where there is a change in the blood flow v.sub.Blood, when the combined resistance R.sub.Combined is calculated by Equation 2 above from the deep body temperature T.sub.Core, the skin surface temperature T.sub.Skin, and the skin surface heat flux H.sub.Skin when the blood flow v.sub.Blood changes from a non-steady state to a steady state, it is possible to obtain the value of the combined resistance R.sub.Combined corresponding to the amount Δv.sub.Blood of change in the blood flow v.sub.Blood. Such measurement is performed for each amount Δv.sub.Blood of change. The above R.sub.Combined (o) is registered in the conversion table as the combined resistance R.sub.Combined when the amount Δv.sub.Blood of change in the blood flow v.sub.Blood is o.

[0027] The laser Doppler blood flow meter 2 of the temperature measuring device constantly measures the blood flow v.sub.Blood of the living body 10 at the part around the sensor 1 (step S100 in FIG. 3).

[0028] The thermal resistance derivation unit 4 of the temperature measuring device derives the combined resistance R.sub.Combined by acquiring, from the conversion table of the storage unit 3, the value of combined resistance R.sub.Combined corresponding to the amount Δv.sub.Blood of change (=v.sub.Blood−v.sub.Blood (o)) of the blood flow v.sub.Blood measured by the laser Doppler blood flow meter 2 (step S101 in FIG. 3).

[0029] When the blood flow v.sub.Blood is within a predetermined threshold range centered on the initial value v.sub.Blood (o), the thermal resistance derivation unit 4 determines that there is no change in the blood flow v.sub.Blood (the amount Δv.sub.Blood of change is o), and when the blood flow v.sub.Blood is out of the threshold range, the thermal resistance derivation unit 4 determines that there is a change in the blood flow v.sub.Blood (absolute value of the amount Δv.sub.Blood of change is larger than o).

[0030] The temperature calculation unit 5 of the temperature measuring device calculates the deep body temperature T.sub.Core of the living body 10 by Equation 2 above on the basis of the of result of the measurement (step S102 in FIG. 3) of the skin surface temperature Tam and the skin surface heat flux Hain by the sensor 1 and the combined resistance R.sub.Combined derived by the thermal resistance deriving part 4 (step S103 in FIG. 3).

[0031] The calculation result output unit 6 of the temperature measuring device outputs the calculation result of the temperature calculation unit 5 (step S104 in FIG. 3). Examples of the output method include the display of the calculation result, the transmission of the calculation result to the outside, or the like.

[0032] FIG. 4 is a flowchart for explaining operations of the temperature measuring device of the present embodiment. FIG. 4 illustrates an example in which the initial calibration is performed at time t=o and a person (the living body 10) wearing the sensor 1 and the sensor probe 200 starts taking a warm bath at time t=t1. In FIG. 4, 400 denotes the true value of a deep body temperature T.sub.Core, 401 denotes a deep body temperature T.sub.Core calculated by the method of the related art, and 402 denotes the deep body temperature T.sub.Core calculated by the temperature measuring device of the present embodiment.

[0033] According to FIG. 4, it can be seen that when there is a change in the blood flow v.sub.Blood, the combined resistance R.sub.Combined is updated by the thermal resistance derivation unit 4 of the present embodiment from the initial value R.sub.Combined (o) to a value corresponding to the amount Δv.sub.Blood of change in the blood flow v.sub.Blood. On the other hand, the thermal resistance R.sub.Body used in the related art remains constant. Consequently, it can be seen that in the related art, an error occurs in the estimated value of the deep body temperature but in the present embodiment, the deep body temperature T.sub.Core approximately equal to the true value can be estimated.

[0034] As described above, in the present embodiment, the combined resistance R.sub.Combined of the living body 10 is derived on the basis of the amount Δv.sub.Blood of change in the blood flow v.sub.Blood, so that it is possible to reduce an error in the estimated value of the deep body temperature T.sub.Core caused by a change in the blood flow v.sub.Blood. In the present embodiment, the laser Doppler blood flow meter 2 is used as a blood flow meter, but other blood flow meters may be used.

[0035] The storage unit 3, the thermal resistance derivation unit 4, the temperature calculation unit 5, and the calculation result output unit 6 described in the present embodiment can be implemented by a computer including a central processing unit (CPU), a storage apparatus, and an interface, and a program that controls these hardware resources. An example of the configuration of the computer is illustrated in FIG. 5.

[0036] The computer includes a CPU 500, a storage device 501, and an interface device (hereinafter simply referred to as I/F) 502. The sensor 1, the laser Doppler blood flow meter 2, a display device, a communication device, or the like are connected to the I/F 502. In such a computer, a program for implementing the temperature measuring method of the present invention is stored in the storage apparatus 501. The CPU 500 executes the processing described in the present embodiment in accordance with the program stored in the storage device 501.

INDUSTRIAL APPLICABILITY

[0037] The embodiments of the present invention can be applied to a technology for measuring the internal temperature of a subject such as a living body.

REFERENCE SIGNS LIST

[0038] 1 Sensor [0039] 2 Laser Doppler blood flow meter [0040] 3 Storage unit [0041] 4 Thermal resistance derivation unit [0042] 5 Temperature calculation unit [0043] 6 Calculation result output unit [0044] 10 Living body [0045] 100 Thermal insulation member [0046] 101, 102 Temperature sensor [0047] 200 Sensor probe [0048] 201 Semiconductor laser [0049] 202 Photodiode [0050] 203 Blood flow calculation unit