JPH06347329A - Noninvasive temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To enable accurate measurement of temperature ensuring sufficient heating effect by arranging first and second judging means and the like following respective specified procedures. CONSTITUTION:Noise temperature of a control noise source is adjusted in the direction in which an output voltage of a radio meter 6 is down to zero. In a fixed time after the start of the adjustment, it is judged whether the output voltage of the meter 6 is within a specified value centered on zero or not (first judging means). When the judgment is satisfied, it is judged whether the output voltage of the meter 6 is held within a fixed value centered on zero or not in a fixed time thereafter (second judging means). When the second judgment is satisfied, the temperature of the noise source is taken in as measuring temperature of the meter 6 and a temperature distribution of a coaxial cable 4 detected with a thermometer 15, a probe data or the like stored in the memory 12 are read into correct the measuring temperature of the meter 6 by computing these various data. The results are shown on a display section 13 as luminance temperature of an organism 1. If the judgments of the first and second judging means are not satisfied, the adjustment of the noise temperature is executed again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-invasive temperature measuring device used for measuring a living body temperature when diagnosing hyperthermia or a lesion.

[0002]

2. Description of the Related Art Temperature measurement techniques include contact-type temperature measurement and non-contact-type non-invasive temperature measurement. Examples of contact type temperature measurement include thermocouples, platinum elements, thermistors, optical fiber thermometers, etc., but these measure the temperature of the contacting part, It is difficult to use it in a body cavity or when it is necessary to insert it.

As an example of non-invasive temperature measurement, there is a radiometric method in which a microwave emitted from an object to be measured is received for measurement, and a microwave is radiated to a living body to scatter or absorb the microwave. There are various methods in the world such as a method using microwave CT for forming an image and a method using MRI. In the rageometry method,
There is one shown in 59-192925.

A problem in the case of measuring the temperature of a living body using the radiography method is a reflection coefficient at the interface between the antenna and the living body, and a balance method radio is used as a measurement method for eliminating an error based on the reflection coefficient. I have a metric. This is shown in Elect. Leters, 14, 194-196 and Hyperthermia Vol.

When this balance method radius geometry is used for temperature measurement in hyperthermia or other hyperthermia treatment, it is necessary to turn off the heating output at the time of measurement because it is necessary to capture the weak microwave radiated from the object to be measured. There is. A technique concerning this is disclosed in Japanese Patent Publication No. 57-53110. In addition, Japanese Patent Application No. 4-96648 and Japanese Patent Application No. 4-302158 disclose a technique for shortening the measurement time in the combination of the balance method radius geometry and hyperthermia.

In the balance method radius,
A technique for correcting an error due to power attenuation in a transmission line between the antenna and the antenna is disclosed in Japanese Patent Laid-Open No. 3-293526. In general, a radiometer for measuring temperature using the balance method radiometer generates a microwave from a reference noise source, radiates it from an antenna to an object to be measured, and emits and reflects microwaves from the object to be measured. Is received by the above antenna, the noise temperature of the reference noise source (reference noise temperature) is adjusted so that the difference between the received microwave power and the microwave power of the reference noise source becomes zero, and the power difference becomes zero. When it becomes, the noise temperature of the reference noise source is captured as it is as the temperature of the measuring object. That is,
Highly accurate measurement is possible without being affected by the power reflection coefficient at the interface between the antenna and the living body.

[0007]

In the radiometer, the power difference does not easily reach zero with only one adjustment of the reference noise temperature, and several adjustments are repeated before reaching the zero. Moreover, since the reference noise temperature is not stable immediately, it is necessary to wait for each adjustment. A reference noise source of the type using a 50 Ω resistor, which is particularly long.

Therefore, the time required for temperature measurement tends to be long. If the measurement time is long, the heating effect will be impaired during the hyperthermia treatment in which the heating output must be turned off during the measurement.

Although the measurement time can be shortened by eliminating the zero determination of the power difference, the measurement accuracy is deteriorated. The present invention has taken the above circumstances into consideration, and an object thereof is to enable measurement in a short time while ensuring the effect of improving the measurement accuracy by the balance method radius geometry, and to provide a sufficient heating effect during hyperthermia treatment. The object of the present invention is to provide a highly reliable non-invasive temperature measuring device that enables reliable temperature measurement while ensuring the above.

[0010]

A non-invasive temperature measuring device according to the present invention includes a reference noise source for generating a microwave corresponding to a set noise temperature, and a microwave emitted from the reference noise source for an object to be measured. In which the difference between the power of the microwave received by this antenna and the power of the microwave of the reference noise source becomes zero. Means for adjusting the noise temperature of the reference noise source, first judging means for judging whether or not the difference is within a predetermined value after a lapse of a certain time T ₁ from the start of the adjustment, and judgment by the first judging means. Is satisfied when a predetermined time T ₂ has passed and then a second judging means for judging whether or not the difference is within a constant value, and when the judgment of the second judging means is satisfied, the noise of the reference noise source is satisfied. Means for obtaining the temperature of the object to be measured from temperature, and means for re-performing the adjustment when the judgments of the first and second judgment means are not satisfied.

[0011]

The microwave emitted from the reference noise source is radiated from the antenna to the object to be measured, the microwaves emitted and reflected from the object to be measured are received by the same antenna, and the power of the received microwave and the reference noise source are received. The noise temperature of the reference noise source is adjusted so that the difference from the microwave power of is within a predetermined value. After a lapse of a predetermined time T ₁ from the start of this adjustment, it is determined whether or not the power difference is within a predetermined value.
If this determination is satisfied, after a lapse of a fixed time T _{2 from that} time, it is again judged whether or not the power difference is within a fixed value. If this determination is satisfied, the temperature of the measurement object is obtained from the noise temperature of the reference noise source at that time. When none of the judgments are satisfied, the above adjustment is performed again.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a living body (inside a body cavity) which is an object to be measured, and a balloon 2 is brought into contact with an arbitrary portion of the living body 1. The balloon 2 accommodates the antenna 3 for the inside of the body cavity therein, and functions to hold the antenna 2 inside the living body 1 by being inflated by injecting a liquid from the outside by a water supply tube and a water supply pump (not shown).

The antenna 3 is for receiving (and transmitting) thermal noise radio waves (microwaves) emitted from the living body 1, and forms a probe together with the coaxial cable 4, and the coaxial cable 4 is connected to the radiometer by the connector 5. 6 is connected.

In the coaxial cable 4, a plurality of temperature sensors 7a, 7b, ... 7 are arranged at predetermined intervals along the axial direction.
n is attached. Here, a specific example of the radiometer 6 is shown in FIG.

A port of a circulator 22 is connected to the coaxial cable 4 via a Dicky switch 21. The Dickie switch 21 is a synchronization signal oscillator 23.
It is turned on / off by a rectangular-wave-shaped synchronizing signal emitted from the device, and when the switch is turned on, the coaxial cable 4 and the port of the circulator 22 are conducted, and when the switch is turned off, the coaxial cable 4 and the port of the circulator 22 are shut off.

The circulator 22 has three ports, and the Dicky switch 21, the isolator 24, and the reference noise source 25 are connected to each port in the order of signal transmission. Dicky switch 2
The thermal noise signal input via the circulator 22
Is amplified by the RF amplifier 26 via the isolator 24 and input to the RF terminal of the mixer 27. The isolator 24 functions to absorb the signal reflected by the RF amplifier 26 and the subsequent components.

The reference noise source 25 has a set noise temperature T
It generates microwaves of electric power according to ref, and uses a 50Ω resistor that can control the physical temperature with a Peltier element from the viewpoint of accurately measuring the brightness temperature at room temperature. The characteristics of this 50Ω resistor are shown in FIG.

A local oscillator 29 is connected to the LO terminal of the mixer 27 via an attenuator 28 for sensitivity adjustment. The signal emitted from the local oscillator 29 is input to the mixer 27 via the attenuator 28, where it is subjected to frequency conversion by multiplication with the output of the RF amplifier 26.

The output of the mixer 27 is amplified by the IF amplifier 30 and sent to the detector 31, where the DC component of the signal is extracted. This signal is sent to the lock-in amplifier 32. The lock-in amplifier 32 includes the synchronization signal oscillator 23.
The Dicky switch 21 is synchronized with ON / OFF of the Dicky switch 21 based on the sync signal of the Dicky switch 21.
The voltage signal having a level proportional to the difference between the voltage level of the signal input when the switch is turned on and the voltage level of the signal input when the switch is turned off is output as Vlock.

That is, the output voltage Vlock of the lock-in amplifier 32 corresponds to the difference between the microwave power received by the antenna 3 and the microwave power of the reference noise source 25. This output voltage Vlock is sent to the control unit 10 of FIG. 1 as the output of the radiometer 6.

The control unit 10 controls the entire apparatus, and includes a microcomputer and its peripheral circuits. In addition to the microwave receiver 6, an input unit 11, a memory 12, a display unit 13, a calibration constant temperature bath 14, and a thermometer 15 are connected to the control unit 10.

The input unit 11 is provided with a switch and a keyboard, and is used for setting an operation mode and inputting probe data and the like regarding the probe.
The memory 12 is also connected to the radiometer 6, the input unit 11, and the thermometer 15, and the noise temperature Tref of the reference noise source 25, the probe data input from the input unit 11,
And the temperature detected by the thermometer 15 is sequentially stored. Further, the memory 12 stores the power reflectance Rw between the antenna 3 and the liquid in the calibration constant temperature bath 14 and the length L of the coaxial cable 4 as probe data relating to the probe.
The power attenuation rate α is stored.

The display unit 13 displays the calculation result of the control unit 10 (corrected measured temperature). The calibration constant temperature bath 14 contains a liquid (electrolyte such as physiological saline) having a large attenuation effect on microwaves therein, and controls the temperature of the liquid according to a command from the control unit 10.

The thermometer 15 detects the temperature Tw of the liquid in the calibration constant temperature bath 14 using the temperature sensor 16 and also takes in the temperature detected by the temperature sensors 7a, 7b, ... Temperature distribution Tc in the axial direction
(Z) is detected.

Then, the control unit 10 executes the following [1] to [1
[0] functional means. [1] A means for setting the preliminary measurement mode and the main measurement mode according to the operation of the input unit 11.

[2] In the preliminary measurement mode, the operation of the calibration thermostat 14 is controlled while monitoring the temperature detected by the thermometer 15 (the temperature of the liquid in the calibration thermostat 14) Tw ', and the detected temperature Tw A means for maintaining ´ at a predetermined value.

[3] Radiometer 6 in the preliminary measurement mode
The noise temperature Tref of the reference noise source 25 is adjusted so that the output voltage Vlock of the reference noise source becomes zero, and the noise temperature Tref when it becomes zero.
As the measured temperature Tref 'of the radiometer 6 in the memory 12
Means to store in.

[4] In the preliminary measurement mode, the liquid temperature Tw ′ detected by the thermometer 15 and the axial temperature distribution Tc (z) ′ of the coaxial cable 4 detected by the thermometer 15 are stored in the memory 12. Functional means to make.

[5] Means for adjusting the noise temperature Tref of the reference noise source 25 so that the output voltage Vlock of the radiometer 6 becomes zero in the main measurement mode. [6] T _{1 for a} fixed time from the start of adjusting the noise temperature Tref
After that, it is determined whether or not the output voltage Vlock of the radiometer 6 is within a predetermined range ± Vrange1 centered around zero (the difference between the received microwave power and the microwave power of the reference noise source 25 is within a predetermined value). First determination means.

[7] When the judgment of the first judging means is satisfied, after a lapse of a predetermined time T ₂ from then, the output voltage Vlock of the radiometer 6 is within a predetermined range ± Vrange 2 centered at zero (refer to the received microwave power). Second determination means for determining whether or not the difference from the microwave power of the noise source 25 is within a fixed value. Here, the constant range ± Vrange2 is smaller than the predetermined range ± Vrange1 used in the first determination, and is a value that can be recognized as almost zero.

[8] When the determination by the second determining means is satisfied, the noise temperature Tref of the reference noise source 25 at that time is taken in as the measurement temperature of the radiometer 6 and the coaxial cable 4 detected by the thermometer 15 Temperature distribution Tc in the axial direction of
(Z) is taken in, and T stored in the memory 12 is further stored.
A means for correcting the measured temperature Tref of the radiometer 6 by reading w ', Tref', Tc (z) 'and the probe data and executing an operation using these various data.

[9] A means for displaying the temperature Tobj obtained by the correction on the display unit 13 as the brightness temperature of the living body 1. [10] Means for re-adjusting the noise temperature Tref from the beginning when the judgment of the first judging means is not satisfied and when the judgment of the second judging means is not satisfied.

Next, the operation of the above configuration will be described. First, the processing of the radiometer 6 will be described. The Dicky switch 21 is turned on and off, and when the Dicky switch 21 is turned on, the microwave emitted from the reference noise source 25 is generated by the circulator 2.
2, Dickie switch 21, and coaxial cable 4
Is sent to the antenna 3 via. This microwave is radiated from the antenna 3 toward the living body 1.

The radiated microwave is absorbed by the living body 1 and is partially reflected by the boundary surface between the antenna 3 and the living body 1. This reflected microwave is received by the antenna 3 together with the microwave emitted from the living body 1, and the received signal is taken in via the coaxial cable 4 and the Dickie switch 21.

When the Dicky switch 21 is off, the microwave generated from the reference noise source 25 is sent to the Dicky switch 21 via the circulator 22 and is totally reflected there. The totally reflected microwaves pass through the circulator 22 again and are taken into the isolator 24 side.

Therefore, the brightness temperature of the living body 1 is Tobj,
Assuming that the power reflection coefficient at the interface between the antenna 3 and the living body 1 is R and the noise temperature emitted from the reference noise source 25 is Tref, the amount of microwave energy emitted from the living body 1 and entering the antenna 3 is Is reflected by the living body 1 (T
obj.R), and Tobj-Tobj.R. That is, it is (1-R) · Tobj.

The amount of microwave energy emitted from the antenna 3 and reflected at the boundary surface and entering the antenna 3 again is
Tref · R.

From this, the Dicky switch 21
The voltage Von output from the detector 31 at the time of turning on is as follows. Von = k * G * Cd * (1-R) * Tobj * B + k * G * Cd * Tref * RB * B Moreover, the detector 31 when the Dickie switch 21 is off.
The voltage Voff output from is as follows.

Voff = k * G * Cd * Tref * B where k is Boltzmann's constant. G is the system gain up to the IF amplifier 30. Cd is the sensitivity constant of the detector 31. B is the bandwidth.

The output voltage Vlock of the lock-in amplifier 32 to which the output voltages Von and Voff of the detector 31 are input is
It corresponds to the difference between the two input voltages Von and Voff. Vlock = k * Gsys * B * (1-R) * (Tobj-Tre
f) Note that Gsys is the gain of the entire system.

If the reference noise temperature Tref of the reference noise source 25 is adjusted so that Vlock becomes zero, Tobj = Tref if the power reflection coefficient R is not "1", and the measurement is performed regardless of the power reflection coefficient R. The temperature of the object can be measured directly. This is the principle of the conventional balance method radius geometry.

Next, the overall operation will be described. The preliminary measurement mode is set by the input unit 11, and the starting operation is performed. Then, the control unit 10 starts the heating operation of the calibration constant temperature bath 14 and controls the heating while monitoring the detection temperature Tw of the thermometer 15 to control the temperature of the liquid in the calibration constant temperature bath 14 to a predetermined value. To maintain.

In this state, when the antenna 3 is submerged in the calibration thermostat 14 together with the balloon 2 filled with the liquid,
The temperature of the liquid is measured by the radiometer 6. At this time,
The temperature of the liquid in the balloon 2 is adjusted so as to match the temperature of the liquid in the calibration constant temperature bath 14.

Here, according to a storage command issued from the input section 11 or the control section 10, the measured temperature Tref 'of the radiometer 6, the liquid temperature Tw' detected by the thermometer 15, and the thermometer 15 are also detected. The temperature distribution Tc (z) 'in the axial direction of the coaxial cable 4 is stored in the memory 12, respectively. Note that z is the axial position of the coaxial cable 4 as indicated by the arrow in FIG.

By executing this measurement while changing the liquid temperature Tw 'in a certain temperature range,
Correlation between liquid temperature Tw 'and measured temperature Tref', and further liquid temperature Tw 'or measured temperature Tref' and internal temperature distribution T
Correlation with c (z) 'is retained, respectively.

After that, the balloon 2 is inflated at an arbitrary position of the living body 1 to hold the antenna 3. Then, the main measurement mode is set by the input unit 11, and the start operation is performed. Then, the thermal noise emitted from the living body 1 is transmitted to the antenna 3
Then, the next temperature measurement by the radiometer 6 is started. The operation from here is shown in FIG.

First, the noise temperature Tref of the reference noise source 25 is adjusted so that the output voltage Vlock of the radiometer 6 becomes zero. In this adjustment, considering that it takes time for the noise temperature Tref to change, as can be seen from the characteristics of FIG. 3, the output voltage Vlock of the radiometer 6 is centered at zero when the _first fixed time T ₁ elapses. Given range ± Vra
It is determined whether it is within nge1 (the difference between the received microwave power and the microwave power of the reference noise source 25 is within a predetermined value).

If this judgment is not satisfied, that is, Vlo
If ck is out of ± Vrange1, the noise temperature T
Readjust to change ref to another value.

When the determination is satisfied, that is, Vlock is ±
If falls within Vrange1, then after a predetermined time T _2,
The output voltage Vlock of the radiometer 6 is within a certain range ± Vrange2 around zero (received microwave power and reference noise source 2
It is determined whether or not the difference from the microwave power of 5 is within a fixed value).

If this judgment is not satisfied, that is, Vlo
If ck is out of ± Vrange2, the noise temperature T
Readjust to change ref to another value.

When the determination is satisfied, that is, Vlock is ±
When the value is within Vrange2 and is recognized as almost zero, the noise temperature Tref at that time is taken in as the measurement temperature of the radiometer 6.

The fixed times T ₁ and T ₂ differ depending on how much the noise temperature Tref is changed, but the correlation between the amount of change and time may be measured and determined in advance. For example, the noise temperature Tref is ± 0 of the actual temperature.
The time until the noise temperature Tref falls within the range of ± 0.03 ° C of the actual temperature may be set as T ₂ , and the time until the noise temperature Tref falls within the range of 1 ° C may be set as T ₁ . Incidentally, there is no practical problem even if T ₁ is set to about 4 seconds.

As described above, by dividing the adjustment of the noise temperature Tref into the two stages of the former stage and the latter stage, the measurement time is T ₁ ,
It can be shortened for T ₂ of the time difference (= T ₂ -T _1).

In this method, the lock-in amplifier 3 is used at the time of measurement.
This is especially effective when 2 is overrange.
Since the temperature difference between the measured brightness temperature and the noise temperature cannot be predicted from the lock-in amplifier output when the range is over, it is very unlikely that the output voltage Vlock of the lock-in amplifier 32 has not approached zero even after the change. This is because.

The obtained measured temperature Tref is the temperature distribution Tc (z) in the axial direction of the coaxial cable 4 detected by the thermometer 15 and Tw ', Tref', Tc in the memory 12.
It is corrected by the following equation using the correlation data of (z) ′ and the probe data (power reflectance Rw, coaxial cable length L, power attenuation rate α) in the memory 12. By this correction, the influence of power attenuation and thermal noise of the coaxial cable 4 is removed, and the correct brightness temperature Tobj of the living body 1 is obtained.

[0056]

[Equation 1]

[Delta] Tc (z) = Tc (z) -Tc
(Z) '. This formula is based on the Institute of Electronics, Information and Communication Engineers EMCJ
88-71, which corresponds to the equation (10) described in the document "Method for reducing error in measuring luminance temperature of medical radiometer".

The obtained brightness temperature Tobj of the living body 1 is displayed on the display unit 13 and notified to the user. That is,
One of the factors that greatly affects the measurement error is the temperature change of the coaxial cable. This is due to the influence of power attenuation and thermal noise in the coaxial cable, and especially the heat radiation component corresponding to the power attenuation is generated from the coaxial cable. Therefore, when the temperature of the coaxial cable changes, the thermal radiation power from the coaxial cable changes, and that amount appears as a measurement error. In order to deal with this, the above correction is performed. This correction is also disclosed in JP-A-3-293526.

By the way, the noise temperature Tre of the reference noise source 25
The actual adjustment of f, that is, the so-called balance operation is performed by calculating the operation amount S of the temperature change from the output Vlock of the lock-in amplifier 32 of the radiometer 6 and performing only the operation amount S. Vlock
Let k be the correlation coefficient between S and S. If the object is stable, it is possible to operate by always using the correlation coefficient k obtained by measuring in advance, but if the temperature of the object to be measured is slightly fluctuating or the reflection coefficient R When there is a possibility that there is a change, or when there is a variation in the correlation between the amount of change in the noise temperature and the amount of operation, the balance operation can be performed faster by changing the correlation coefficient k at any time. When used as a temperature measuring device during hyperthermia, the temperature of the object to be measured is gradually decreased because the heating output is turned off during the measurement, and this operation is particularly necessary. Three examples of the device in this case are shown below.

[First Method] The output of the lock-in amplifier 32 before the initial balance operation is Vlock ₁ , the initial operation amount (for example, the stepping motor rotation step number or the change voltage) is S ₁ , and the initial operation amount S ₁ is calculated. K ₁ for the correlation coefficient, and lock-in amplifier 3 after the initial balance operation
The output of ₂ is Vlock ₂ , and the correlation coefficient in the second balance operation is k ₂ .

The correlation coefficient is used as S ₁ = k ₁ · Vlock ₁ . Originally, if this correlation coefficient is just a value, Vlock ₂ = 0, but the correlation coefficient changes due to changes in the object temperature, changes in the reflection coefficient, and the like. Therefore, after the first operation, when Vlock ₁ · Vlock ₂ <0, when k ₂ = 0.9 · k ₁ Vlock ₁ · Vlock ₂ > 0, k ₂ = 1.1 · k ₁ is adjusted to the correlation coefficient k _2. Do it. From the second time onward, the correlation coefficient is changed in the same way by simply changing the values of Vlock ₁ and Vlock ₂ . By this, even if a change in state occurs during measurement, the correlation coefficient tracks it, and a quick balance operation can be performed.

Further, even in the temperature measurement of the object after heating, the tracking is always performed for the object whose temperature is decreasing, and the correlation coefficient is higher than that in the measurement of the object having the stable temperature. A large value will be shown, and a quick measurement will be performed.

[0063] Vlock ₁ the output of the second method] First balance operations before the lock-in amplifier 32, the first manipulated variable (e.g. stepping motor step number and changes the voltage etc.) S _1, calculate the first operation amount S ₁ Let k _{1 be} the correlation coefficient for this purpose, V lock _{2 be} the output of the lock-in amplifier 32 after the first balancing operation, and k ₂ be the reference correlation coefficient in the second balancing operation.

The manipulated variable is determined as follows. Vlo
When ck ₁ indicates that the noise temperature Tref is too high, S ₁ = 1.1 · k ₁ · Vlock _{1 When} Vlock ₁ indicates that the noise temperature Tref is too low, S ₁ = 0.9 · k ₁ · Vlock _1, and before entering the second balancing operation, the reference correlation coefficient k ₂ is changed as follows.

When Vlock ₁ · Vlock ₂ <0, k ₂ = 0.9 · k ₁ Vlock ₁ · Vlock ₂ > 0, k ₂ = 1.1 · k ₁ The values of Vlock ₁ and Vlock ₂ are exchanged after the second time The correlation coefficient will be changed according to the same idea. This not only has the advantage of the first method in that the reference correlation coefficient can be changed in response to changes in the reflection coefficient and the like due to changes in the state of the target object, etc., and quick balance operation can be performed. The latter one can positively perform a quick balance operation while the temperature is decreasing.

[Third Method] The output of the lock-in amplifier 32 before the initial balance operation is Vlock ₁ , the initial operation amount (for example, the stepping motor rotation step number or the change voltage) is S ₁ , and the initial operation amount S ₁ is calculated. Let k be the correlation coefficient, Vlock _{2 be} the output of the lock-in amplifier 32 after the initial balance operation, and S _{2 be} the operation amount for the _second balance operation.
Define lock _n and Sn.

S ₁ is calculated as S ₁ = k · Vlock ₁ as in the first method. Originally, Vlock ₂ should be set to 0 by this operation, but when the temperature of the object to be measured changes, that amount is shifted and Vlock ₂ does not become zero. Therefore, in the calculation of the operation amount for the second time, the calculation is performed on the assumption that the temperature of the measurement target changes by Vlock ₂ during the time required for the measurement.

S ₂ = k (Vlock ₂ + Vlock ₂ ) The measurement after S ₃ is carried out while considering the difference between the previously predicted temperature change and the actual value.

Sn = k · {Vlockn + (Vlock ₁ + Vlo
ck ₂ + ... + Vlock _n )} When this calculation method is used, the advance control is not performed by multiplying the coefficient as is the case with the second method, but the advance control is firmly based on the data at the time of measurement. .
In addition, this method can universally cope not only with the temperature of the measurement object being lowered but also with the temperature thereof being rising. Also, when the balance waiting time differs depending on the operation amount, the time is corrected by multiplying the temperature change predicted amount.

On the other hand, as described above, the lock-in amplifier 3
If the output of 2 is overranged, the balance operation may not be performed smoothly, which may cause a long measurement time. Especially in combination with hyperthermia,
When the heating output is on, there is a high possibility of overrange due to noise, which comes mainly from the antenna and cable.

This can be dealt with by providing a coaxial switch in the radiometer 6 and setting a mode (open mode) in which the input side is not connected to components after the coaxial switch when the heating output is on. An example in which this is applied to a single frequency radiometer 6 is shown in FIG.

The coaxial switch 40 is inserted and connected between the Dicky switch 21 and the circulator 22. First, the coaxial switch 4 is instructed by the control circuit 10 during heating.
Keep 0 open. As a result, no excessive input is applied to each element in the heterodyne receiver, that is, the components after the coaxial switch 40, and the fear of component destruction is eliminated.
Also, there is no fear that the lock-in amplifier 32 will be overranged and saturated.

Next, the heating output is turned off, and the coaxial switch 40
Close. Since the lock-in amplifier 32 is not saturated, the lock-in amplifier 32 reacts to the input obediently, and quick luminance temperature measurement becomes possible.

In a multi-frequency radiometer, SPS
Use a multi-channel coaxial switch instead of the T coaxial switch, set the open mode in which the common terminal of the coaxial switch is not connected to any channel during heating, and set the coaxial switch to the channel you want to measure during the heating off period. Connect the common terminal and measure the brightness temperature.

By the way, although the measurement error due to the power attenuation in the coaxial cable has been described above, it is possible that the power attenuation comparable to that can occur in the Dicky switch 21.
Is. As a countermeasure, it is common to control the temperature of the exterior of the Dicky switch 21 with a Peltier element, but the internal semiconductor switch part is still connected to the coaxial cable 4, the coaxial switch 40 in the subsequent stage, and the circulator 22. The temperature changes due to the heat conduction of. For this reason, reliable temperature control cannot be performed, and if it is trusted, a measurement error may occur by the actual temperature change.

Therefore, a temperature sensor is mounted on the connector part of the switch line of the Dicky switch 21, and the average value of the detected temperature of the temperature sensor and the original control temperature of the exterior part is the semiconductor switch inside the Dicky switch 21. Capture as the temperature of the part. By using this temperature data, the temperature change of the Dicky switch 21 can be corrected. The effect of controlling the temperature of the exterior is added to this.

When the temperature control is also applied to the subsequent components such as the RF amplifier 26, the control value is set to the Dickie
By maintaining the same temperature as the control temperature of the exterior part of the switch 21, the temperature of the connector part and the temperature of the exterior part become substantially equal, and the temperature stability of the Dicky switch 21 is further improved.

For correction, the condition of a cable having a length of 0 cm and power attenuation may be added to a conventional correction formula. Assuming that there is no power reflection between the coaxial cable 4 and the Dicky switch 21, a new correction equation can be easily obtained by expanding the equation of [Equation 1].

Further, one of the major causes of the temperature fluctuation of the Dicky switch 21 is that it is affected by the room temperature fluctuation due to the heat conduction from the coaxial cable 4.
Therefore, by adopting the configuration shown in FIGS. 6 and 7 and suppressing the temperature fluctuation of the coaxial cable 4 near the Dicky switch 21, the accuracy of the measurement temperature can be improved.

That is, a predetermined portion of the coaxial cable 4 is surrounded by the aluminum block 50. The aluminum block 50 is composed of a pair of blocks 50a and 50b, and is attached to the coaxial cable 4 in a state of being sandwiched by both blocks from above and below. This mounting location is near the connector 5 for connecting the coaxial cable 4 and the Dickie switch 21.

The thermo module 7 is attached to the aluminum block 50, and the temperature of the aluminum block 50 is controlled by the thermo module 7. Further, a heat sink 8 for releasing heat is attached to the thermo module 7.

According to this structure, the temperature of the coaxial cable 4 near the Dicky switch 21 is kept constant, so that the coaxial cable 4 is connected to the Dicky switch 2 at a constant temperature.
The heat conduction to 1 is neglected, and the temperature of the Dicky switch 21 is remarkably stable. Therefore, it is not necessary to correct the temperature of the Dicky switch 21. Moreover, the temperature control value of the aluminum block 50 is Dickie
If the outer temperature of the switch 21 is set to the same value, the temperature stability of the Dicky switch 21 is further improved.

In the above embodiment, the temperature sensors 7a,
Although thermocouples are used as the detection elements 7b, ... 7n, the invention is not limited to this, and platinum elements or thermistors may be used, and an optical fiber temperature sensor can also be used. In the case of this optical fiber temperature sensor, an electrically insulating coating is unnecessary.

[0084]

As described above, according to the present invention, the noise temperature of the reference noise source is adjusted so that the difference between the received microwave power and the microwave power of the reference noise source falls within a predetermined value. After a certain time T ₁ from the start of this adjustment, it is determined whether or not the power difference is within a predetermined value. If this determination is satisfied, a certain time T ₂ hours later, the power difference is within a certain value. If the judgment is satisfied, the temperature of the measuring object is obtained from the noise temperature of the reference noise source at that time, and if none of the judgments is satisfied, the above adjustment is executed again. Since it is configured, it is possible to measure in a short time while securing the effect of improving the measurement accuracy by the balance method radius geometry,
It is possible to provide a highly reliable non-invasive temperature measuring device that enables reliable temperature measurement while ensuring a sufficient heating effect during hyperthermia treatment.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a specific configuration diagram of a radiometer in the same embodiment.

FIG. 3 is a characteristic diagram of a temperature change of a reference noise source in the example.

FIG. 4 is a flowchart for explaining the operation of the embodiment.

FIG. 5 is a configuration diagram of a modified example of the radiometer in the same embodiment.

FIG. 6 is a configuration diagram of a modified example of the coaxial cable peripheral portion of the radiometer according to the embodiment.

FIG. 7 is a view of FIG. 6 viewed from the side.

[Explanation of symbols]

1 ... Living body (measurement target), 3 ... Antenna, 4 ... Coaxial cable, 6 ... Radiometer, 10 ... Control part, 12 ... Memory, 14 ... Calibration thermostat, 15 ... Thermometer.

Claims (1)

[Claims] 1. A reference noise source that generates a microwave corresponding to a set noise temperature, and a microwave emitted from this reference noise source is emitted to a measurement target and is emitted and reflected from the measurement target. An antenna for receiving microwaves, a means for adjusting the noise temperature of the reference noise source in a direction in which the difference between the microwave power received by the antenna and the microwave power of the reference noise source becomes zero, and the difference is a first determination means for determining whether or not within a predetermined value after a predetermined time T ₁ from the start of the adjustment, the difference after a predetermined time T ₂ hours therefrom when the determination of the first determining means is satisfied Second determining means for determining whether or not is within a fixed value, and means for determining the temperature of the measurement object from the noise temperature of the reference noise source when the determination of the second determining means is satisfied, Non-invasive temperature measurement apparatus comprising the means for performing the adjustment again when the determination of the first and second judging means is not satisfied.