JPS6215235B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention enables non-invasive, easy and accurate heating of the affected area from outside the living body in heating therapy targeting the affected area located deep inside the living body. This invention relates to a heating device for warming up the body.

By the way, in order to cure cancer or other tumors, that is, the affected area composed of abnormal cell tissue of the living body, one of the treatments is to treat the affected area with 43~
In recent years, it has been revealed that so-called hyperthermia therapy, which involves heating the body within a temperature range of 45°C for several tens of minutes, is effective and has been clinically confirmed.

Various proposals have been made in the past as heating methods to enable such heating therapy;
A heating source that directly contacts or approaches an affected area is not appropriate when targeting an affected area deep inside a living body, unless the affected area is within a certain type of body cavity.

Therefore, when targeting deep affected areas, the following high-frequency heating has been mainly attempted.

A well-known method is a heating method that utilizes dielectric heat generation within a high-frequency electric field. In this method, high-frequency energy of, for example, 13.56 MHz is supplied between a pair of opposing heating electrode bodies that are attached to the biological surface so as to sandwich a deep affected area, and the affected area is heated by dielectric heat generation. Therefore, even if the affected area is deep, it can be heated sufficiently. However, this method tends to involve complicated problems in impedance matching between the heating electrode body connected to the high-frequency generation source and the living body to be heated, and the electrodes are Since the body must be brought into close contact with the living body surface, handling of the electrode body is surprisingly troublesome.

In addition, heating methods that utilize induction heat generation based on the electromagnetic induction effect of high-frequency coils approach zero as the amount of heat generated moves toward the center of the coil, so generally speaking, it is difficult to target deep affected areas. Although unsuitable, the improved method and heating applicator disclosed in Japanese Patent Publication No. 59-2501 make it possible to warm even deep affected areas. However, although this improved heating method is in many respects superior to the method using dielectric heat generation described above, the amount of heat generated tends to gradually decrease as the distance from the heating surface of the applicator to the affected area increases. Therefore, as the position of the affected area becomes deeper, more of the applied high-frequency energy is wasted, and the risk of excessive heating of normal tissue in the superficial layer than the affected area increases.

On the other hand, high-frequency heating methods that work more directly on deep affected areas include:
A needle-shaped electrode is inserted from the surface of the living body to the affected area, and a 300KHz high-frequency current is passed from the electrode to the affected area to warm the affected area, or the affected area has a small electrically conductive material embedded in advance.
It is known that the device is placed in an induction coil through which a high-frequency current of 13.56 MHz flows, and the affected area is heated by the heat generated by the electromagnetic induction of the good conductor. However, these heating methods all require the insertion of an electrode or the implantation of a good conductor as described above, so the applicable affected areas are limited, and the area that can be heated is limited to the very vicinity around the electrode or good conductor. However, there is a high risk of excessive heating.

Although it is slightly different from the high-frequency heating described above, it is a heating method that also aims to warm the affected area, but uses a directional antenna to irradiate 2450MHz microwaves to the affected area. It has been known. However, with this method, it is possible to heat the body to the required temperature only to a depth of several centimeters from the surface of the body, so it is not effective for affected areas deeper than that.

The heating device according to the present invention addresses the above-mentioned problems with various conventionally known heating methods, and non-invasively treats the affected area deep inside the living body from outside the living body. However, in order to easily and accurately heat the body, we utilize resistance heat generation when high-frequency current flows inside the body, and while flowing the high-frequency current in parallel, we deflect and focus it on the affected area using a high-frequency induced electric field from the outside. Therefore, the structure is such that only the amount of heat generated at the affected area increases. Details of this will be explained below in sequence according to the drawings.

First, to explain the principle of the heating method applied in the device of the present invention, in FIG. 1, two electrodes 2 ₁ and 2 ₂ each having a certain area are attached to both ends of a certain conductor 1 Attach so that they are facing each other,
When a high frequency voltage is applied between each of the electrodes 2 ₁ , 2 ₂ and the conductor 1 while taking care to maintain good conductivity between the electrodes 2 1 , 2 2 and the conductor 1, the inside of the conductor 1 as shown in FIG. A parallel current I ₁ flows.

Further, in FIG. 2, two induction coils 3 ₁ and 3 ₂ each having one turn are placed on both sides of the conductor 1 so as to face each other, and each of these coils 3
When a high frequency current is passed through _the conductor ₁ , an induced electric field generated in each coil acts within the conductor 1, and an eddy current _I2 as shown is induced in each coil.

Note that 4 in FIGS. 1 and 2 is a high frequency generation source.

Next, a parallel current I ₁ is caused to flow into the conductor 1, and at the same time an eddy current I ₂ is induced. That is, the third
In the figure, the above-mentioned electrodes 2 are attached to both ends of the conductor 1.
₁ , 2 ₂ are attached, and induction coils 3 ₁ , 2 are installed on both sides.
3 ₂ is arranged, and while applying a high frequency voltage between the electrodes 2 ₁ and 2 ₂ of the former, a high frequency current is passed through each of the coils 3 ₁ and 3 ₂ of the latter. Note that the current and electric field induced by the induction coil are delayed in phase by 90° from the high frequency current supplied to the coil. Therefore, when the electrodes 2 ₁ , 2 ₂ and the induction coils 3 ₁ , 3 ₂ share the same high frequency generation source 4 as shown in the figure,
It is necessary to interpose a 90° phase delay circuit 5 between this generation source 4 and each electrode 2 ₁ , 2 ₂ .

In this way, the conductor 1 between the electrodes 2 ₁ and 2 ₂
The parallel current I ₁ flowing inside the induction coils 3 ₁ , 3 ₂
When passing through the portion sandwiched by the conductor 1, the current I ₁ ' is deflected away from the respective coils and is focused at the central portion of the conductor 1. In other words, when a parallel current I ₁ passes through the part sandwiched between the induction coils 3 ₁ and 3 ₂ in the conductor 1, the parallel current I ₁ is , is canceled out by the eddy current I ₂ flowing in the opposite direction, but in a place far from the coil, that is, inside the conductor 1, the parallel current I ₁ is offset by the eddy current I ₂ flowing in the same direction. As a result, the deflection and focusing described above will occur.

However, if there are only two induction coils as shown in FIG. 3, the above-mentioned deflection and focusing of the parallel current _I1 will not occur in the direction perpendicular to the plane of the paper. In practice, therefore, at least four or more induction coils 3 ₁ are arranged around the conductor 1, as schematically shown in FIG.
It is necessary to arrange 3 ₂ , 3 _{3 ,} . . . and surround the conductor with these coils.

However, when current flows through a conductor, resistance heat generation occurs within the conductor, as is well known. The amount of heat generated W ₁ at this time can generally be determined by the formula W ₁ =ρI ² (1), where I is the density of the current flowing in the conductor and ρ is the specific resistance of the conductor. That is, the amount of heat generated in this case increases in proportion to the square of the current density.

Such heat generation is caused by the parallel current I ₁ in FIGS. 3 and 4.
However, the amount of heat generated differs depending on the location in relation to the above-mentioned current convergence. That is, when the parallel current I ₁ flowing in the conductor 1 is focused in a portion surrounded by the induction coils 3 ₁ , 3 ₂ , 3 ₃ , . . . , the current density increases in that portion as a natural result. Therefore, even if the current density is so small that the amount of heat generated is negligible in the part of the conductor 1 where the parallel current I ₁ flows, in the part where the focused current I ₁ ' flows, the current Since the density is increasing, the calorific value also increases by a factor of two according to the above equation (1).

On the other hand, such heat generation can also be explained using the concept of an electric field. As is known, when a conductor is placed in an electric field, it generates heat. This is the same even when an electric field is formed within a conductor, and the portion of the conductor that exists within the electric field generates heat. The amount of heat generation W ₂ at this time is given by E, the electric field strength, and σ, the electrical conductivity of the conductor.
In general, it can be determined by the following formula: W ₂ =σE ² (2). That is, the amount of heat generated increases in proportion to the square of the electric field strength.

When considering the configuration shown in FIGS. 3 and 4, heat generation within such an electric field is as follows. That is, in this example, the parallel electric field created by flowing the parallel current I ₁ and the circular electric field created by inducing the eddy current I ₂ overlap. In the area where these two electric fields overlap, the two electric fields cancel each other out and strengthen each other based on the direction of the currents I ₁ and I ₂ flowing for each electric field, changing the electric field strength. That is, near the surface of the conductor 1, the electric field strength decreases as the two electric fields cancel each other out, and inside the conductor, the electric field strength increases as the two electric fields strengthen each other. Therefore, even if the electric field strength is small in the part of the conductor 1 where the parallel current I ₁ flows and the amount of heat generated is negligible, in the part where the focused current I ₁ ' flows, Since the electric field strength is increasing, the amount of heat generated also increases by a factor of two according to equation (2) above.

Note that heat generation within this electric field is nothing but resistance heat generation. Therefore, both equations (1) and (2) above simply capture the same heat generation phenomenon in a conductor from different viewpoints, and both equations are equivalent, that is, W ₁ =
_W2 .

By the way, in the configuration shown in Figures 3 and 4 above,
How densely is the parallel current I ₁ focused?
It depends on the strength of the induced eddy current I ₂ but also on the distance of the induction coils 3 ₁ , 3 ₂ , 3 ₃ , . . . from the conductor 1. Therefore, the current density in the part where the focused current I ₁ ' flows, and therefore the amount of heat generated in that part, can be determined by changing the strength of the high-frequency current flowing through each of the induction coils, or by changing the intensity of the high-frequency current flowing through each of the induction coils, or by It can be easily controlled by changing the distance between. In addition, where in the cross section perpendicular to the parallel current I ₁ inside the conductor the current is focused can be determined by individually varying the strength of the high frequency current or the distance from the conductor 1 for each coil. It can be freely controlled, and can also be controlled by changing the phase of the current flowing through either coil.

Next, a specific example of the heating device of the present invention to which the above principle is applied will be explained with reference to FIG.
Reference numeral 11 in this figure is a patient and corresponds to the conductor 1 described above. In this embodiment, one of the opposing electrodes ₂₁ is shaped so that it can be attached around the neck and shoulders of the patient 11, and the other electrode ₂₂ can be wrapped around one thigh. It is said to be shaped like this. However, these two electrodes
₁ and 2 ₂ may be attached so as to sandwich at least a region including the affected area of the patient 11, and are not necessarily limited to the locations shown in the drawings. In addition, each induction coil 3 ₁ , 3 ₂ , 3 ₃ ,...
It exists deep inside the torso portion of the first person and is arranged around the torso portion so as to surround the affected area.

In the above state, both electrodes 2 ₁ , 2
While applying a high frequency voltage between the _two induction coils 3 ₁ ,
When a high frequency current is passed through 3 ₂ , 3 ₃ ,..., this fifth
Although not shown in the figure, as in the example shown in _FIG .
An eddy current I ₂ is induced by the induced electric field acting on the portion. Of course, it is inevitable that the parallel current flowing in the body at this time will be slightly biased because the electrical conductivity of the patient 11 differs locally within the body, but this bias is to the extent that it does not cause any practical problems. Therefore, it can be considered that the flow is approximately parallel as a whole.

In this way, the parallel current I ₁ flowing inside the body of the patient 11 is focused under the influence of the eddy current I ₂ induced near the torso. Therefore, each induction coil 3 ₁ ,
By adjusting the strength and phase of the current flowing through 3 ₂ , 3 ₃ , ... or the distance from the body of each coil as described above, to what extent the parallel current I ₁ is focused?
And where it is focused is adjusted so that the current I ₁ ' focused at the required current density flows only to the affected area. In this way, even if the amount of resistance heat generated by passing an electric current into the body is extremely small in areas other than the affected area, it becomes considerably large in the affected area. For example, if the cross-sectional area through which the parallel current _I1 flows is focused to 1/5 at the affected area, the current density will increase five times in that affected area, and the electric field strength will also increase accordingly. The calorific value of
Increased by the above formula (1) or (2), 25 elsewhere
It will be doubled. Therefore, even if the temperature rise inside the patient's body due to the above-mentioned calorific value is about 0.5°C outside the affected area, it reaches up to 12.5°C in the affected area, so the affected area can be sufficiently warmed.

The frequency of the high-frequency current supplied in the embodiment shown in FIG. 5, that is, the parallel current flowing inside the body and the current flowing through the induction coil, is several tens of K.
If it is below Hz, it will cause irritating pain to patient 11,
It is desirable that it be higher than that. However, the frequency may be much lower than the frequency in conventional microwave irradiation, and even lower than the frequency in high frequency heating using dielectric heat generation or induction heat generation. Therefore, even if heat generation efficiency is taken into account, the frequency is
It may be 10MHz or less, for example about 6MHz is sufficient.

As described above, the present invention utilizes resistance heat generation when a high-frequency current flows inside a living body, flows the high-frequency current into the body in parallel, and deflects and focuses the current with a plurality of high-frequency induced electric fields. The heat is concentrated on the deep affected area, so that only the amount of resistance heat generated in the affected area is greater than in the other areas. Therefore, the heating device of the present invention does not have complicated problems associated with impedance matching or troublesome electrode handling, compared to the conventional heating device using dielectric heat generation.
Compared to those that use induction heating, there is less wastage of high-frequency energy, there is no risk of excessive heating of the surface of the body, and there is no pain to the patient compared to those that require insertion of electrodes or implantation of good conductors. It does not involve excessive local heating and can target deeper areas than microwave irradiation.
In addition, in the device of the present invention, the heating temperature and heating range can be easily controlled, and the required frequency is relatively low, so the electrical drive system can be simplified and the heating operation can be performed easily. Therefore, according to the present invention, it is possible to non-invasively and easily and accurately warm an affected area located deep within a living body, and therefore the range of application of heating therapy can be further expanded. You can expect good results.

[Brief explanation of the drawing]

1 to 4 are explanatory diagrams for explaining the principle of the heating method to which the apparatus of the present invention is applied. FIG. 5 is a perspective view showing a specific configuration of an embodiment of the present invention. 1... Conductor, 2 ₁ , 2 ₂ ... Electrode, 3 ₁ , 3
₂ , 3 ₃ , 3 ₄ ... induction coil, 4 ... high frequency generation source, 5 ... phase delay circuit, 11 ... patient, I ₁ ...
...parallel current, I ₁ ′ ... focused current, I ₂ ... eddy current.

Claims (1)

[Claims] 1. A heating device that targets an affected area that exists deep inside a living body, which includes a pair of electrodes that flow a high-frequency current in parallel into the area of the living body that includes at least the above-mentioned affected area, and a heating device that flows from outside the living body around the affected area. applying multiple high-frequency induced electric fields to surround the affected area,
A device for warming a deep affected area in heating therapy, comprising a plurality of induction coils that deflect the parallel currents using these induced electric fields and focus them on the affected area.