JP7591766B2 - Deep temperature measurement method and deep thermometer - Google Patents

Description

The present invention relates to a deep temperature measurement method and a deep thermometer for measuring the internal temperature of various objects and living things such as humans and animals.

Elderly people and patients with spinal cord injuries have a reduced ability to regulate their body temperature, which increases the risk of heatstroke and hypothermia. Therefore, an environment where body temperature can be measured at all times is desirable. However, with ordinary thermometers, the measured values tend to vary depending on the part of the body where the temperature is measured. On the other hand, the temperature of deep parts of the body is less affected by the outside air temperature. For this reason, various deep body thermometers have been developed (Patent Documents 1 to 4).

JP2006-308538A Patent Publication 2007-212407 Patent No. 6395176 Tokuho 5-65090

The known prior art has the following problems to be solved.
Conventional deep body thermometers may have measurement errors due to various factors that will be described later. The above-mentioned patent documents also describe methods for solving the problem. The present invention aims to provide a method for measuring deep body temperature with higher accuracy and a practical deep body thermometer that operates by the method. In addition, the present invention aims to provide a deep body thermometer that can be used to measure not only human body temperature but also the internal temperatures of living organisms such as animals and various objects.

The following configurations are each a means for solving the above problems.
<Configuration 1>
A theoretical formula is generated that shows a relationship between a temperature measured by a temperature sensor on the upstream side of a plurality of heat flows arranged on the side of the object to be measured, a temperature measured by a temperature sensor on the downstream side of the plurality of heat flows arranged at a position away from the object to be measured, a temperature measured by an environmental temperature sensor, and a ratio of thermal resistances of a plurality of heat flow paths between any of the upstream temperature sensors and any of the downstream temperature sensors;
A method for measuring deep temperature, characterized in that when the deep temperature is known, this deep temperature and the temperature measured by the temperature sensor are substituted into the theoretical formula to perform a calculation to back-calculate a parameter K indicating the ratio of the thermal resistance of the multiple heat flow paths, and this newly obtained parameter K is then used in the calculation formula for measuring the deep temperature.

<Configuration 2>
A method for measuring deep temperature by bringing a heat transfer body into close contact with a surface of a measurement object, comprising:
A first temperature sensor and a second temperature sensor are disposed at two locations on a surface of the measurement object covered with the heat transfer body;
a third temperature sensor is disposed at a point on a first heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the first temperature sensor in a direction perpendicular to the surface of the object to be measured;
a fourth temperature sensor is disposed at a point on a second heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the second temperature sensor in a direction perpendicular to the surface of the object to be measured;
A probe is used in which the thermal resistance of the first heat flow route is set to Ra and the thermal resistance of the second heat flow route is set to Rb,
The heat conductor of this probe is brought into close contact with the surface of the object to be measured, and the detected temperatures T1, T2, T3, and T4 of the first, second, third, and fourth temperature sensors are obtained after the detected temperatures of the temperature sensors have reached a steady state. A theoretical formula is then generated to determine the deep temperature Tc when the ratio of the thermal resistance Ra of the first heat flow route to the thermal resistance Rb of the second heat flow route is set as a parameter K,
When the deep temperature is a known value Tc, this Tc and the above-mentioned T1, T2, T3, and T4 obtained by actual measurement are substituted into a theoretical formula for calculating the deep temperature Tc, the above-mentioned parameter K is calculated backwards, and this newly calculated parameter K is used in an arithmetic formula for measuring the deep temperature.

<Configuration 3>
A method for measuring deep temperature by bringing a heat transfer body into close contact with a surface of a measurement object, comprising:
A first temperature sensor and a second temperature sensor are disposed at two locations on a surface of the measurement object covered with the heat transfer body;
a third temperature sensor is disposed at a point on a first heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the first temperature sensor in a direction perpendicular to the surface of the object to be measured;
a fourth temperature sensor is disposed at a point on a second heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the second temperature sensor in a direction perpendicular to the surface of the object to be measured;
A probe is used in which the thermal resistance of the first heat flow route is set to Ra and the thermal resistance of the second heat flow route is set to Rb,
The heat conductor of this probe is brought into close contact with the surface of the object to be measured, and the detected temperatures of the first temperature sensor, the detected temperatures T1, T2, T3, and T4 of the third temperature sensor, and the fourth temperature sensor are obtained after the detected temperatures of the temperature sensors reach a steady state. When the ratio of the thermal resistance Ra of the first heat flow route to the thermal resistance Rb of the second heat flow route is set as a parameter K, the theoretical formula for calculating the deep temperature Tc is given by the following formula (A):
A method for measuring deep temperature, characterized in that when the deep temperature is a known value Tc, this Tc and the above-mentioned T1, T2, T3, and T4 obtained by actual measurements are substituted into the above-mentioned theoretical formula, the above-mentioned parameter K is calculated backwards using the following formula (B), and this newly obtained parameter K is used in an arithmetic formula for measuring the deep temperature.

<Configuration 4>
A method for measuring deep temperature described in any one of configurations 1 to 3, characterized in that a parameter K is calculated for each environmental temperature Te, and the parameter K selected according to the environmental temperature is used in an arithmetic equation for measuring deep temperature.

<Configuration 5>
A deep body thermometer comprising: a means for determining a parameter K by the method according to any one of configurations 1 to 3; and a means for executing a calculation for measuring a deep body temperature using the parameter K.

<Configuration 6>
A deep thermometer comprising a temperature sensor for measuring an environmental temperature Te, a means for determining a plurality of types of parameters K by the method described in configuration 5, and a means for using the parameters K to perform calculations for measuring a deep temperature according to the environmental temperature.

<Configuration 7>
A computer program that causes a computer of a deep body thermometer to function as the means described in configuration 5 or 6.

<Configuration 8>
A computer-readable recording medium having the computer program according to configuration 7 recorded thereon.

By rewriting the value of parameter K in the theoretical formula that calculates the deep temperature Tc when the ratio of the thermal resistance Ra of the first heat flow route to the thermal resistance Rb of the second heat flow route is set as parameter K, the deep temperature can be measured with high accuracy.

FIG. 1 is an explanatory diagram of the principle and problems of a known deep body thermometer. FIG. 2 is an explanatory diagram of a theoretical method for calculating deep temperature. FIG. 3 is an explanatory diagram showing a calculation formula for the parameter K. FIG. 4 is a perspective view of an example of a thermometer probe. FIG. 5 is a block diagram of the device for actual measurement and the arithmetic unit of the thermometer. FIG. 6 is a data explanatory diagram showing an example of the actual measurement results. FIG. 7 is another data explanatory diagram showing an example of actual measurement results.

In the present invention, for example, a probe 10 having a shape as shown in FIG. 1(a) is used to measure deep temperature. As shown in FIG. 1, the probe 10 is brought into close contact with a body surface 12, such as the patient's forehead, to measure deep temperature. A material such as sponge that has a lower thermal conductivity than skin is used for the heat transfer body 14 that is brought into close contact with the body surface 12. The upper surface of the probe 10 is covered with, for example, an aluminum plate that has a higher thermal conductivity than the heat transfer body 14. The overall shape is shown in FIG. 4(a), which will be explained later.

A first temperature sensor 16 and a second temperature sensor 18 are placed at two locations on the body surface 12 covered by the heat transfer body 14. The distance between the first temperature sensor 16 and the second temperature sensor 18 is, for example, about a few millimeters. In this heat transfer body 14, a temperature difference in the vertical direction (perpendicular to the body surface) generates heat flows in the direction of arrow A (first heat flow route) and in the direction of arrow B (second heat flow route).

The third temperature sensor 20 is placed in the heat transfer body 14 at the first arrival point when heat flow is transmitted from the first temperature sensor 16 to the body surface 12 in the direction of arrow A.

The heat flow in the direction of arrow B is a circular heat flow around arrow A. A fourth temperature sensor 22 is placed in this heat transfer body 14 at the second arrival point when the heat flow is transmitted from the second temperature sensor 18 to the body surface 12 in the direction of arrow B.

After starting to measure the deep temperature, wait in this state until the temperature detected by each temperature sensor reaches a steady state. As time passes, the temperature of each part rises, and the temperature distribution along arrow A and the temperature distribution along arrow B become as shown in Figure 1 (b).

At this time, the magnitude relationship between the detected temperature T1 of the first temperature sensor 16, the detected temperature T2 of the second temperature sensor 18, the detected temperature T3 of the third temperature sensor 20, and the detected temperature T4 of the fourth temperature sensor 22 is Tc>T1>T3, Tc>T2>T4.

Figure 2 shows the procedure for theoretically calculating the deep temperature when using this deep thermometer. When the heat flow on the first heat flow route is Ia, the heat flow on the second heat flow route is Ib, the thermal resistance of the subcutaneous tissue is Rm, the thermal resistance of the first heat flow route is Ra, and the thermal resistance of the second heat flow route is Rb, the relationship between the heat flow on the first heat flow route and the temperature of each part, and the relationship between the heat flow on the second heat flow route and the temperature of each part are as shown in Figure 2.

As a result, as shown in Figure 2, two types of relational expressions (1) and (2) can be obtained to calculate the thermal resistance Rm of the subcutaneous tissue. Here, the ratio of the thermal resistance Ra of the heat transfer body 14 from the first temperature sensor 16 to the third temperature sensor 20 to the thermal resistance Rb of the heat transfer body 14 from the second temperature sensor 18 to the fourth temperature sensor 22 is K = Ra/Rb (relational expression (3)). From the above relational expressions (1), (2), and (3), the relational expression (4) for calculating the deep temperature Tc can be obtained.

Conventionally, deep temperature has been theoretically calculated using this relationship. However, as shown in Figure 1(b), the relationship between the temperature distribution along arrow A and the temperature distribution along arrow B results in a lateral heat flow corresponding to the lateral temperature difference, as shown in Figure 1(c), which can cause measurement errors depending on the material and structure of the probe.

Therefore, in the present invention, we first create a relational equation (A) for calculating the deep temperature Tc, as shown in Figure 3. This relational equation (A) replaces the term (T1-T3) in relational equation (4) in Figure 2 with (T1-T2). This is a modification of the theoretical equation so that the temperature difference between T1 and T2 is strongly reflected in the calculation results, minimizing errors due to heat flows in the directions of the arrows X and Y shown in Figure 3.

In addition, by taking into account the lateral heat flow, a modified equation can be created to theoretically calculate the deep temperature Tc using the above T1, T2, T3, T4, and parameter K. The above equation (A) has been found to be particularly effective in application to the present invention, so an example using this equation is shown below.

First, create relational equation (B) to calculate parameter K backward from relational equation (A). Using a test device with a known deep temperature Tc, this Tc and the above values of T1, T2, T3, and T4 obtained by actual measurements are used to find a new parameter K from relational equation (B). In other words, parameter K is replaced with a new value regardless of the content of relational equation (3) above.

Figures 4(a) and (b) show perspective views of two types of probes. (a) has a structure in which a large-diameter disk and a small-diameter disk are stacked on top of each other, and is equipped with a cylindrical pillar 28 and a flange-like portion 30. (b) has a cylindrical pillar 28 and a protruding portion 31, with only a portion of the flange-like portion 30 remaining. Both are designed to have the same ratio of thermal resistance Ra to thermal resistance Rb. When the deep temperature is theoretically calculated using the above relational equation (4), the same result is obtained in both cases. However, these probes can measure deep temperatures with even higher accuracy. This is explained in the following example.

First, a test device for measuring deep body temperature was prepared as shown in Figure 5. This assumes that a probe will be placed on the forehead to measure the body temperature inside the skull. First, a thermostatic chamber is filled with warm water, and an aluminum plate and a plaster plate are placed on top of the water surface. A probe with the above structure is placed on top of the plaster plate. As described above, this probe has a sponge structure with an aluminum plate covering the top surface.

The temperature Tc of the warm water is the deep temperature. It was set to 37 degrees Celsius. An aluminum plate with good thermal conductivity was placed in contact with the warm water, and a plaster plate simulating the bones and skin of the head was placed. The thickness of the plaster plate was also adjusted to match an actual living body. These should be shaped to match the part of the body where they are to be worn. A plaster plate was used as it has a thermal conductivity close to that of human skin and skull. An electric heater or other heat source may be used instead of warm water. The plaster plate simulating the head may be made of another material, for example, to match the part of the body where it is to be worn.

As shown in (a), two temperature sensors are placed on the part corresponding to the body surface (on the plaster board). In addition, two temperature sensors are placed at a certain distance vertically away from the body surface. These are used to measure temperatures T1, T2, T3, and T4 as described above. The ratio of the thermal resistance Ra to the thermal resistance Rb is set to 2.

Figure 5 (b) shows a block diagram of an embodiment of the deep body thermometer of the present invention. The detection signals of the four temperature sensors 16, 18, 20, 22 are input to the calculation processing unit 34 via the interface 32. Furthermore, an environmental temperature sensor 38 is connected to this interface 32, and its output signal is also input to the calculation processing unit 34. The calculation processing unit 34 executes calculation processing, which will be described later, and the calculation processing result is output to the display unit 36. The deep body temperature Tc and the parameter K are displayed on the display unit 36. That is, the detection signal of the probe is automatically calculated by the computer, and the parameter K is stored and set, which becomes the initial setting processing. Thereafter, the deep body temperature is calculated using this parameter K and displayed as the measurement result.

Figure 6 shows the actual measured values of a deep thermometer using a probe with the structure shown in Figure 4(a). Using the test equipment shown in Figure 5(a), the deep temperature was set to 37 degrees Celsius, and tests were conducted while varying the outside air temperature Te from approximately 15 degrees Celsius to approximately 40 degrees Celsius. At each outside air temperature, the measured values were obtained after the temperatures measured by all the temperature sensors had stabilized. Data was obtained 60 times every 10 seconds over a period of approximately 10 minutes, and the average values were recorded, as shown in the table in Figure 6(a).

The parameter K was calculated by substituting the deep temperature Tc and the measured values T1, T2, T3, and T4 of each temperature sensor into the relational expression (B) shown in Figure 3. As a result, it was found that the value of parameter K is in the range of 1.42 to 1.46 when the outside air temperature is in the range of 15 degrees Celsius to 40 degrees Celsius. The theoretically calculated value of parameter K is 2.

Figure 6 (b) is a graph showing the error from the true value of deep temperature on the vertical axis in the range of -1.2 to +1.2, and the environmental temperature on the horizontal axis. When deep temperature was calculated with the parameter K set to 1.44, the error was minimal regardless of the environmental temperature. On the other hand, when the parameter K was set to 2, deep temperature could be calculated with high accuracy when the environmental temperature was around 35 degrees Celsius, but the error became larger as the environmental temperature became lower.

In other words, when the deep temperature is a known value Tc, this Tc and the above-mentioned T1, T2, T3, and T4 obtained by actual measurement can be used to back-calculate the parameter K from the above relational equation, and this newly calculated parameter K can be used in the calculation equation for measuring the deep temperature, thereby making it possible to measure the deep temperature with high accuracy.

For this reason, if the calculation processing unit 34 shown in Figure 5(b) waits for a predetermined time when the probe is set in the test device, acquires Tc, T1, T2, T3, and T4, and automatically uses the relational equation shown in Figure 3(b) to back-calculate parameter K, and executes a process to incorporate the parameter K into the calculation equation for measuring deep body temperature, the deep body thermometer can be automatically calibrated. During actual use, the deep body temperature is calculated using the relational equation shown in Figure 3(A) using that parameter K.

Next, a similar test was performed using a probe with the structure shown in Figure 4(b). The results are shown in the table in Figure 7(a). What was learned here is that when the probe structure is different, the environmental temperature dependency can become significant, as shown in the test results.

The relational equation taking into account this temperature dependency is as follows:
K=-0.0043Te+1.0568
This is an arithmetic formula in which the parameter K is calculated using the relational expression shown in Fig. 3(b) and a correction term dependent on the environmental temperature Te is added. The graph in Fig. 7(b) has the parameter K on the vertical axis and the environmental temperature Te on the horizontal axis. Using this relational expression, the above parameter K is recalculated for each environmental temperature Te, and the recalculated parameter K selected according to the environmental temperature is used in the arithmetic formula for measuring the deep temperature. The result is shown in Fig. 7(c).

The graph in FIG. 7(c) is similar to the graph in FIG. 6(b), with the vertical axis showing the error from the true value of deep temperature in the range of -1.2 to +1.2, and the horizontal axis showing the environmental temperature. Deep temperatures can be calculated with high accuracy over a wide temperature range. As shown in FIG. 5(b), a temperature sensor 38 for measuring environmental temperature is provided at a specified location on the deep thermometer, and the calculation processing unit 34 uses the above relational equation to determine parameter K for each environmental temperature, and executes calculations for measuring deep temperatures according to the environmental temperature, thereby making it possible to measure deep temperatures with high accuracy regardless of the environmental temperature.

Note that if any of the four temperature sensors 16, 18, 20, and 22 can measure a temperature close to the ambient temperature, that temperature sensor may also serve as the ambient temperature sensor.

The first and second temperature sensors may be placed on the side of the object to be measured. The third and fourth temperature sensors may also be placed away from the object to be measured. It is sufficient to obtain the temperatures measured by the upstream temperature sensor and the downstream temperature sensor on multiple heat flows. Two or more heat flows may be provided, but if there are three or more heat flows, two heat flows that show appropriate measurement values may be selected each time to obtain a theoretical formula. If there are heat flows that are physically similar, the average value of the temperature measurements by the temperature sensors may be used to obtain the temperature measurement value on one heat flow. In either case, it is preferable to select two heat flows and obtain a theoretical formula for calculating the environmental temperature by setting the ratio of thermal resistance between the upstream temperature sensor and the downstream temperature sensor as K.

For example, by changing the theoretical formula for each heat flow path, multiple types of relational equations for calculating the above K can be generated. These relational equations can be used to calculate different parameters K, and the average value can be used or one of them can be selected. Even if the same relational equation is used, the measured values of the temperature sensor differ for each heat flow path, so, for example, a combination of two heat flow paths from three or more heat flow paths can be selected and multiple types of parameters K can be calculated for each combination. In this case, too, it is advisable to adopt the average value of the parameter K or one of them.

As can be seen from the above test device, the deep body temperature measurement method and deep body thermometer of the present invention can be widely used for indirectly measuring the deep body temperature of various objects, including not only human body temperature but also various living creatures such as pets and livestock.

10 Probe 12 Body surface 14 Heat transfer body 16 First temperature sensor 18 Second temperature sensor 20 Third temperature sensor 22 Fourth temperature sensor 24 Thermal resistance R1
26 Thermal resistance R2
28 Cylindrical column 30 Flange 31 Projection 32 Interface 34 Processing unit 36 Display unit 38 Environmental temperature sensor

Claims (6)

A method for measuring deep temperature by bringing a heat transfer body into close contact with a surface of a measurement object, comprising:
A first temperature sensor and a second temperature sensor are disposed at two locations on a surface of the measurement object covered with the heat transfer body;
a third temperature sensor is disposed at a point on a first heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the first temperature sensor in a direction perpendicular to the surface of the object to be measured;
a fourth temperature sensor is disposed at a point on a second heat flow route where a heat flow reaches when the heat flow travels through the heat transfer body from the second temperature sensor in a direction perpendicular to the surface of the object to be measured;
A probe is used in which the thermal resistance of the first heat flow route is set to Ra and the thermal resistance of the second heat flow route is set to Rb,
The heat conductor of this probe is brought into close contact with the surface of the object to be measured, and the detected temperatures of the first temperature sensor, the detected temperatures T1, T2, T3, and T4 of the third temperature sensor, and the fourth temperature sensor are obtained after the detected temperatures of the temperature sensors reach a steady state. When the ratio of the thermal resistance Ra of the first heat flow route to the thermal resistance Rb of the second heat flow route is set as a parameter K, the theoretical formula for calculating the deep temperature Tc is given by the following formula (A):
A method for measuring deep temperature, characterized in that when the deep temperature is a known value Tc, this Tc and the above-mentioned T1, T2, T3, and T4 obtained by actual measurements are substituted into the above-mentioned theoretical formula, the above-mentioned parameter K is calculated backwards using the following formula (B), and this newly obtained parameter K is used in an arithmetic formula for measuring the deep temperature.

A method for measuring deep body temperature according to claim 1 , characterized in that a parameter K is calculated for each environmental temperature Te, and the parameter K selected according to the environmental temperature is used in an arithmetic equation for measuring the deep body temperature. 2. A deep body thermometer comprising: a means for determining a parameter K by the method according to claim 1 ; and a means for executing a calculation for measuring a deep body temperature using the parameter K. A deep thermometer comprising a temperature sensor for measuring an environmental temperature Te, a means for determining a plurality of types of parameters K by the method described in claim 2 , and a means for using those parameters K to perform calculations for measuring a deep temperature according to the environmental temperature. A computer program that causes a computer of a deep body thermometer to function as the means for determining the parameter K according to claim 3 or 4 and as the means for executing a calculation for measurement . A computer-readable recording medium having the computer program according to claim 5 recorded thereon.

Images