JPH0216150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for warming a living body using electromagnetic waves, and more particularly to a device for controlling temperature distribution in a living body.

The method of heating a living body using electromagnetic waves utilizes the heat generation phenomenon that occurs when electromagnetic waves incident on a living body are absorbed by various parts of the living body, and many reports have been made in recent years regarding its effectiveness in treating malignant tumors.

When treating the above-mentioned malignant tumors, etc., it is necessary to manage or control the temperature of the affected area, and temperature control is generally performed using invasive methods, that is, by inserting a temperature sensor into the living body and measuring the temperature. The method is adopted. however,
There are concerns that the above method may cause pain to the patient and may stimulate tumor cells to promote their proliferation, so a non-invasive temperature measurement method is desired.

Furthermore, the method of warming a living body using electromagnetic waves has a problem in that it gives the patient a sensation of heat due to local heating. Electromagnetic waves incident on a living body propagate while being absorbed by various parts of the living body, attenuating exponentially, and only propagating over a distance several times the wavelength.

Therefore, the temperature inside a living body is high at the surface of the living body and decreases as it goes deeper.
On the other hand, each tissue in a living body absorbs electromagnetic waves differently; for example, in the case of extremely high frequency waves, the absorption mainly occurs in the skin and muscle layers. Therefore, in combination with the above-mentioned temperature distribution, the temperature of the skin increases significantly, giving the patient a sensation of heat. In the case of electromagnetic waves in the high frequency range, heat generation in the fat layer is large and subcutaneous fat becomes high temperature. Usually, to eliminate the above-mentioned heat sensation, a method is adopted in which a probe including a heating antenna that is brought into contact with a predetermined living body surface is cooled to suppress the rise in temperature of the skin. However, with the above method, there is no guarantee that the affected area is being effectively heated because it cools the area more than necessary.

Therefore, there is a current need for the development of a method and device that can warm the affected area under quantitative control without causing heat sensation or pain to the patient when heating the body using electromagnetic waves.

In view of the above-mentioned current situation, the present inventors not only eliminate the patient's sensation of heat and pain by actively utilizing the cooling effect using a probe, but also improve the temperature distribution in the living body.
In other words, the device of the present invention has been achieved which allows the location of the highest temperature and its temperature to be controlled.

The present invention, based on the above findings, provides a heating means configured to inject high-frequency waves for heating from the surface of a living body, a cooling means configured to cool the living body from the surface side, and a heating device configured to apply high frequency waves to the living body from the heating means. a means for measuring the amount of heat per unit time removed from the living body by the cooling means; a calculating means for calculating the temperature distribution in the living body based on these measured values; and control means for controlling either or both of the electric power and the amount of heat to a predetermined value so that the temperature distribution obtained coincides with a given target temperature distribution.

As the heating means, a high frequency oscillator and a pair of electrodes are used, and as the cooling means, preferably, a probe covered with a rubber balloon configured to allow cooling water to flow therein is used.

The control means includes means for measuring the amount of heating heat;
and means for controlling the amount of heating heat, means for measuring the amount of cooling heat, and means for controlling the amount of cooling heat.

The means for measuring the amount of heating heat is substantially configured to measure the energy given to the living body, and the means for controlling the amount of heating heat is configured to control the level of energy given to the living body from the electrodes, or to control the level of energy given to the living body from the electrodes. The configuration is such that intermittent radio frequency radiation can be controlled by turning it off.

The means for measuring the amount of cooling heat preferably consists of a heat flow meter that utilizes the thermal resistance of the rubber membrane of the rubber balloon. =K(Tp
−Tw) to measure the cooling heat flow rate. Here, K is a parameter determined based on the difference between the temperature Ti of the cooling water flowing into the balloon and the temperature Tf of the cooling water flowing out from the balloon, and the flow rate of the cooling water flowing through the balloon.

The means for controlling the amount of cooling heat is configured to maintain the temperature and flow rate of the cooling water at a constant level and to be able to independently adjust the level.

According to a preferred embodiment of the present invention, the temperature distribution control device in a living body of the present invention uses a living body warming device consisting of a high frequency oscillator, a cable, a probe, a cooling water circulation device, and a temperature sensor, and uses a high frequency oscillator output and cooling. It is configured to control the temperature distribution in the living body by circulating water, and measures the electric power incident on the living body and the amount of heat removed from the living body by cooling water, and calculates the temperature distribution inside the living body by measuring these measured values (parameters). It is configured to calculate the relationship with the resulting temperature distribution, then compare it with the target temperature distribution, and select the oscillator output and cooling water temperature and flow rate to match the target temperature distribution. .
According to the present invention, when heating a relatively shallow part near the biological surface, the incident power by the heating means is made relatively small and the amount of heat removed by the cooling means (heat flow) is reduced.
By reducing the temperature, it is possible to create a gentle distribution of heat generation in the living body and to slightly cool the area close to the surface, and to manage or control the temperature so that the maximum temperature is in the range of 42 to 45°C. In addition, when heating the deep part of a living body, by increasing the incident power by the heating means and increasing the amount of heat removed by the cooling means, it is possible to create a temperature distribution that reaches quickly and deeply into the living body, and also to create a temperature distribution that reaches deep inside the living body. It is possible to achieve more sufficient cooling and to create the region where the highest temperature occurs deep inside.

This temperature distribution in the living body is calculated using the following formula.

C〓∂T／∂t＝K∂ ² T／∂x ² +Qe ^- 〓 ^x −RT Here, C is the comparison of heated objects, ρ is the density, K is the thermal conductivity, and Q is the high frequency input per unit time. energy, λ is the absorption rate of high frequency, R is the cooling coefficient due to blood flow, T is the temperature based on the biological temperature,
t is time, x is the length measured in the depth direction with the biological surface as zero, and the following boundary condition must be satisfied: (K∂T/∂X−hT)x=0=−hTw. Here, h represents the film heat transfer coefficient, and Tw represents the cooling water temperature measured based on the biological temperature. If there is no temperature sensor to measure Tw, Tw may be calculated from the cooling water temperature at the inlet and outlet.

Measure in advance the amount of heat per unit time (heat flow) removed from the living body by the electric power and cooling water incident on the living body, and calculate the relationship between this measurement parameter and the temperature distribution occurring in the living body from the above calculation formula. As a result, the temperature distribution in the living body can be quantitatively understood, so if the oscillator output and cooling water temperature and flow rate are selected to match the given target temperature distribution, the affected area can be heated extremely effectively. obtain.

In order to carry out the present invention, the following devices are required for the device. That is, it is necessary to be able to measure or adjust the power incident on the living body, and also to be able to measure the amount of heat removed by the cooling water per unit time. A block diagram of a device for this purpose is shown in FIG.

In the figure, 1 is a high frequency oscillator, and the oscillator 1 has a wattmeter 2 for measuring output power and is configured to be able to control the output power.

The output power can be controlled by adjusting the level of the constant output from the oscillator 1, or by turning on and off a switch; Calculate the time average output by multiplying the ratios. The output of the oscillator 1 is led to the probe 5 including the electrode 4 via the cable 3, and is incident on the living body 8 as a high frequency wave through the cooling water 6 in the probe 5 and the diaphragm 7 defining the surface of the probe 5, where it is absorbed. be done. The energy incident on the living body can be measured using a phantom instead of the living body and from the energy absorbed by the phantom, and the power meter can be calibrated in advance based on the measurement results. The probe 5 has on its surface a thermocouple 9 for measuring the temperature Tp corresponding to the biological surface temperature and a thermocouple 10 for measuring the temperature Tw of the cooling water 6. With the high frequency stopped, the amount of heat flowing from the phantom toward the cooling water 6 was measured using thermocouples 11 and 12, and the difference between the temperatures Ti and Tf at the entrance and exit of the cooling water 6 and the cooling water flow rate temperature controller 13
If the amount of heat is obtained from the product of the amount of cooling water measured in The amount of heat flowing from the cooling water 6 to the cooling water 6 can be determined from the temperature difference between thermocouples 9 and 10 that function as thermometers. Note that 13a is a pump.

Here, the cooling water flow rate temperature controller 13 may be omitted if a calibrated metering pump is used, and the cooling water temperature Tw is calculated from the readings of thermocouples 11 and 12 that function as cooling water inlet and outlet thermometers. Thermocouple 10 to function as a cooling water thermometer
You can also brush it off. The temperature distribution can be easily calculated from the incident power and the amount of heat removed from the cooling water by using the calculator 14.

Of course, the average output signal from wattmeter 2, thermocouple 9
Temperature signals from ~12 and flow rate temperature controller 13
The temperature distribution estimated to be generated in the living body is automatically calculated using an appropriate combination of the flow rate signals from the flow rate detection unit as described above, and the calculated temperature distribution is set as the target temperature. Automatically find the difference by comparing it with the distribution, and in order to eliminate this difference,
While automatically controlling the oscillation output of the oscillator 1,
Adjust the cooling water flow rate temperature controller 13 to reduce the cooling water 6.
The computer 14 may be provided with a control mechanism that automatically controls the temperature and flow rate.

When estimating temperature using this method, it is desirable that the electromagnetic waves from the electrode 4 be incident on the living body without attenuation on the way, and when using high frequencies in a relatively low frequency range, the cooling water should be conductive. It is better to use normal saline.

FIG. 2 shows the temperature distribution expected by the present invention. Curve 15 shows an example in which the oscillator output Q is reduced to keep the cooling water temperature Tw high so that the maximum temperature is almost constant, and on the other hand, an example in which the oscillator output Q is increased to lower the cooling water temperature Tw. is shown in curve 16.

The vertical axis shows the temperature T, the horizontal axis shows the depth X from the surface, and the horizontal line 17 shows the temperature distribution before the start of heating. 18,
19 indicates the water temperature Tw.

As described above, by controlling the oscillator output Q and the cooling water temperature Tw, it is possible to adjust the temperature distribution in the living body, that is, the maximum temperature and the position at which the maximum temperature occurs.

Hereinafter, the present invention will be explained in detail with reference to Examples.

In the device shown in FIG. 1, the probe 5 has a frame around the electrode 4 with internal dimensions of 2.21 cm x 4.75 cm.
1/100mm diaphragm 7, for example, with a rubber sheet,
A thermocouple 9, for example a chromel alumel (CA) thermocouple, is glued to its surface. Cooling water is circulated between the electrode 4 and the diaphragm 7 at a rate of 10/min by a pump 13a, for example a peristaltic pump.The cooling water temperature Tw is determined by a thermocouple 10, for example a CA thermocouple, between the electrode 4 and the diaphragm 7. It was inserted and measured. As the living body 8, a phantom was created by kneading Super Stuff (registered trademark) with physiological saline and molding it to a thickness of 10 mm.One side of the phantom was brought into contact with the probe 5, and a 10 cm x 10 cm electrode was placed on the other side. The surface was cooled with 37°C water. The temperature of the phantom was measured by inserting the CA thermocouples at positions 3 mm and 6 mm from the surface of the diaphragm 7 of the probe 5, and the temperature at the position 3 mm was measured.
When the temperature exceeded 44℃, the high frequency was turned off, and when the temperature dropped to 43℃, the high frequency was controlled to be input.

Figure 3 shows the change in temperature of the phantom over time when the incident high-frequency energy (power) is 0.82W/cm ² and the cooling water temperature Tw is 37℃.The incident power is 0.5W/cm ² and the cooling water temperature Tw is 42℃. Figure 4 shows the change in temperature over time. Further, the calculated values of the temperature distribution T(X) using the above calculation formula at this time are shown in FIGS. 5 and 6. However, when calculating the temperature distribution T(X), the time average power was taken as the incident power Q, and it was set as 0.82×1.3/1.6=0.67W/cm ² and 0.50×1.1/1.6=0.34W/cm ² respectively. . According to Figure 5, which corresponds to the conditions where the cooling water temperature is 37℃ and the average power is 0.67W/cm ² (power 0.82W/cm ² ), the maximum Tmax occurs at a position of 4 to 5 mm from the surface, and the cooling water temperature is 42℃ and the average power is 0.82W/cm 2 . Average power 0.34W/cm ² (power 0.5
In Fig. 6, which corresponds to the condition of W/cm ² ), it is 2 to 4 mm.
shows the highest value Tmax, indicating that the heating pattern can be selected.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a control device for temperature distribution in a living body according to a preferred embodiment of the present invention, and Fig. 2 shows the temperature distribution when the oscillator output is small and the cooling water temperature is high, and when the oscillator output is large and the cooling water temperature is low. Graphs showing the differences, FIGS. 3 to 6, are graphs based on experimental results for explaining the temperature distribution obtained by the apparatus of the present invention. 1... Oscillator, 2... Power meter, 3... Cable, 4...
Electrode, 5... Probe, 6... Cooling water, 7... Diaphragm, 8
...Living body (phantom), 9, 10, 11, 12...
Thermocouple, 13...Cooling water flow rate temperature controller, 13a
...pump, 14...calculator, 15,16,17...temperature distribution curve.

Claims (1)

[Claims] 1. A heating means configured to inject high frequency heating waves from the surface of a living body, a cooling means configured to cool the living body from the surface side, and a means for measuring high frequency power given to the living body from the heating means. ,
means for measuring the amount of heat per unit time removed from the living body by the cooling means; calculating means for calculating the temperature distribution in the living body based on these measured values; and calculating means for calculating the temperature distribution in the living body based on these measured values; A control device for controlling temperature distribution in a living body, comprising a control means for controlling either or both of the electric power and the amount of heat to a predetermined value so as to match the temperature distribution.