JPH0151270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic wave generator used in thermotherapy, which irradiates cancerous tissue in the human body with electromagnetic waves and heats it to a predetermined temperature, thereby stopping the regenerative function of cancer cells and causing death. .

In recent years, attention has been paid to the extremely effective thermal treatment for cancer treatment, and progress is being made in the development of hyperthermia therapy that heats malignant tumors to a temperature of around 43°C for the required time.

For this kind of thermal treatment, there are generally electric field heating methods in which the human body is heated by sandwiching the human body between a pair of electrode plates, induction heating methods in which the human body is placed inside an electromagnetic coil and heated, and further heating by radiating electromagnetic waves to the human body. There is an electromagnetic wave heating method that heats a large area of the human body, and electric field and induction heating methods are used to heat a fairly wide area of the human body because it is difficult to perform spot heating that intensively heats only the cancerous tissue within the body. On the other hand, in the case of the electromagnetic wave method, since it is possible to focus the electromagnetic waves into a beam, it is considered to be used for local heating in which only the very vicinity of cancer tissue is heated.

By the way, when performing thermotherapy using electromagnetic waves, the most important component is an electromagnetic wave generator, which is an element for applying microwave energy to the living body, and this is also generally called an applicator.

As this electromagnetic wave generator, an electromagnetic horn shown in FIG. 1 has conventionally been used. In FIG. 1, an electromagnetic horn 1 is connected to a power feeding section 3 provided with a waveguide connector
and a horn 2 that emits microwave energy, and a high dielectric material 5 is loaded inside the horn 2 to ensure alignment with the human body, as shown in FIG.

This high dielectric material 5 is made of a high dielectric material having a dielectric constant approximately equal to that of the human body.
Matching with the waveguide provided in the power feeding section 3 is achieved by forming the high dielectric material 5 into a tapered shape as shown.

FIG. 3 is an explanatory diagram of thermotherapy using a conventional electromagnetic horn 1, in which microwaves are irradiated toward cancer tissue 8 with a cooling water film 7 interposed between the electromagnetic horn 1 and the human body 6. Then, the cancer tissue 8 was incubated at 43°C for the required time.
When heated in the vicinity, cancer cells lose their regenerative function,
A cell-killing effect can be obtained.

However, conventional electromagnetic wave generators using electromagnetic horns have the drawback that unless the operating frequency is 2 GHz or higher, the electromagnetic horn becomes too large to inject electromagnetic waves into the human body. Miniaturization is achieved by using the 2.45GHz frequency, which is permitted for commercial use. However, the higher the frequency, the shallower the penetration of electromagnetic waves into the human body, and at 2.45 GHz, the attenuation at the surface layer of the human body is large and it is only possible to heat the human body to a depth of about 2 cm.

Of course, if you lower the frequency used, for example 434M
It is possible to increase the heating depth to about 5 cm in Hz, but as mentioned above, in the megahertz order, the electromagnetic horn becomes extremely large, making it difficult to put it to practical use as a medical device that injects electromagnetic waves into the human body. Ta.

The present invention was made in view of these conventional problems, and provides an electromagnetic wave generator for thermotherapy that can be used at a frequency on the megahertz order that allows electromagnetic waves to sufficiently penetrate the human body, and that is sufficiently miniaturized for medical use. The purpose is to provide

In order to achieve this objective, the present invention utilizes the dielectric antenna used in communication in the opposite way, that is, the radiation efficiency of electromagnetic waves to the outside is reduced as much as possible, contrary to that for communication, and the radiated energy is transferred to the dielectric antenna. Based on the internal containment method, the excitation antenna is enclosed inside a columnar dielectric material with a dielectric constant approximately equal to that of the human body, with a radiation surface formed at one end, and a feeder antenna is drawn out to the outside of the columnar dielectric material. 500M by electric wire
It is designed to concentrate and radiate electromagnetic energy to the human body by exciting it at frequencies below Hz. below,
Embodiments of the present invention will be described based on the drawings.

FIG. 4 is a perspective view showing an embodiment of the present invention.

First, to explain the configuration, reference numeral 10 is a columnar dielectric body with a circular cross section, and one end forms a radiation surface 12 for radiating electromagnetic wave energy to the human body, and the opposite side to the radiation surface 12 has a loop. An antenna 14 is enclosed within the columnar dielectric 10 as an excitation antenna, and a pair of feed lines 16 are drawn out from the loop antenna 14.
Here, the columnar dielectric body 10 is made of a dielectric material having a relative permittivity εr that is approximately the same as that of human tissue, and the effective relative permittivity of human tissue is extremely high, ε=80.
Since the dielectric constant is approximately 100, the columnar dielectric body 10 is made of a dielectric material having a dielectric constant of approximately equal to the relative permittivity of human tissue, for example, εr=80.

Of course, the columnar dielectric 10 is made of a dielectric material that has a dielectric constant approximately equal to that of human tissue and has low dielectric loss.

On the other hand, the loop antenna 14 enclosed in the columnar dielectric 10 has an excitation characteristic that efficiently propagates electromagnetic waves of 500 MHz or less to the human body by using the columnar dielectric 10 as a dielectric waveguide. is determined by the dielectric constant εr of the columnar dielectric 10, which is 1/√, that is, εr=80, for the size of a communication loop antenna installed in the atmosphere that is used in a frequency band of 500 MHz or less. Approximately 1/
This can be achieved with a size of 9. Also loop antenna 14
Since the frequency used is 500 MHz or less, the excitation signal is supplied by the feed line 16 to the feed line 16 by connecting a coaxial cable to the feed line 16 via a matching circuit.

Next, the operation of the present invention will be explained.

The electromagnetic waves radiated by the excitation of the loop antenna 14 enclosed in the columnar dielectric 10 are composed of electromagnetic energy that propagates within the columnar dielectric 10 and enters the human body, and electromagnetic energy that is radiated to the outside from the dielectric 10. The relationship between the two is shown in the characteristic graph of FIG. 5.

That is, Figure 5 shows the ratio of the radiated power Wi inside the dielectric and the radiated power Wo radiated to the outside of the dielectric with respect to the dielectric constant εr, with the diameter of the columnar dielectric as the horizontal axis. In the case of a dielectric antenna for communication, the radiation power ratio Wi/Wo is made less than 1 by reducing the relative permittivity εr of the dielectric used, but in the present invention, the relative permittivity of the columnar dielectric 10 is Since the ratio εr is extremely high as εr=80, even if the diameter of the columnar dielectric body is the same, a radiated power ratio Wi/Wo of approximately 10 to 20 can be obtained. The radiated power Wo radiated into the atmosphere from 10 is suppressed to a very small radiated power of about 1/10 to 1/20, and most of the radiated energy from the loop antenna 14 propagates within the columnar dielectric 10. and enters the human body from the radiation surface 12.

To explain in more detail, the incident power of the electromagnetic wave that is incident perpendicularly to the interface between the columnar dielectric 10 and the air from the loop antenna 14 enclosed in the columnar dielectric 10 is Pi, and the incident power of the electromagnetic wave that enters the atmosphere from the columnar dielectric 10 is Pi. When the radiated transmitted power is Pt and the reflected power reflected at the interface and returned into the columnar dielectric 10 is Pr, the following relational expression holds true.

Pi/Pt={(√−√)/(√+√)} ² (However, εa is the relative permittivity of air and ε=1) In other words, assuming the relative permittivity of the columnar dielectric 10 is εr=80, Pi /Pt=0.7988, and the columnar dielectric 10 is smaller than the loop antenna 14.
Even if an electromagnetic wave is incident perpendicularly to the interface between
Only a fraction is radiated to the outside, and the remaining 80% is reflected inside the columnar dielectric 10, and moreover, only a small portion of the electromagnetic waves from the loop antenna 14 is incident perpendicularly to the interface between the columnar dielectric 10 and the air. Since the other parts are incident at an angle of incidence of 90 degrees or less, the radiation power to the outside of the columnar dielectric 10 is even smaller, and the loop antenna 1
Approximately 90% or more of the electromagnetic wave energy radiated from the columnar dielectric body 10 can be contained within the columnar dielectric body 10.

On the other hand, when performing thermal treatment on a human body using the electromagnetic wave generator of the present invention shown in FIG. 4, a cooling water film is interposed between the radiation surface 12 of the columnar dielectric 10 and the human body, as shown in FIG. This causes electromagnetic waves to enter the human body, but the dielectric constant of water, εw, is εw=80.7.
Since this is approximately equal to the dielectric constant εr of the columnar dielectric 10, there is almost no reflection loss due to the interposition of the water film, and it is possible to concentrate the electromagnetic wave energy radiated from the loop antenna 14 into the human body. Moreover, since the excitation frequency is set to 500 MHz or less, electromagnetic wave energy can penetrate deep enough into the human body to heat cancer tissue. In addition, the electromagnetic wave energy that enters the human body Since the beam has characteristics determined by the shape of the radiation surface 12 of the body 10, it is possible to spot-heat cancer tissue that requires heating.

6, 7, and 8 are cross-sectional views showing other embodiments of the columnar dielectric 10 used in the electromagnetic wave generator of the present invention, and correspond to the columnar dielectric 10 having a circular cross section shown in FIG. Since the electromagnetic waves radiated from the loop antenna 14 are likely to propagate in multiple modes and cause mode loss, in order to reduce the propagation mode of the electromagnetic waves propagating through the columnar dielectric 10,
A columnar dielectric body 10 having an oval cross-sectional shape as shown in FIG. 6, a columnar dielectric body 10 having an elliptical cross-sectional shape as shown in FIG. 7, or a polygon such as a regular octagon as shown in FIG. It is desirable that the columnar dielectric body 10 has a cross section.

In addition to the loop antenna 14 shown in FIG. 4, the dipole antenna 18 shown in FIG.
A plate-shaped antenna in which a pair of electrode plates 20 are enclosed as shown in Fig. 0, a corner reflector antenna in which a dipole antenna 18 is combined with a corner reflector 22 in the form of a flat reflector bent in two as shown in Fig. 11, and a corner reflector antenna shown in Fig. 12. Either the folded antenna 24 shown in FIG. 13 or the helical antenna 26 shown in FIG. It is confined inside the columnar dielectric 10 with a size of .

In addition, the excitation antenna is not limited to the antennas shown in Figures 9 to 13, and can range from 100 to 1000MHz.
Any suitable antenna that can be used in the VHF and UHF bands can be used. Furthermore, since the columnar dielectric 10 is made of a high dielectric material, the radiated electromagnetic waves can be sufficiently confined within the columnar dielectric 10 even if the antenna is omnidirectional. However, it is preferable to use a directional excitation antenna that radiates electromagnetic waves in a predetermined direction in a concentrated manner.

Next, the effect of the present invention will be explained. Since electromagnetic waves having a frequency of 500 MHz or less are emitted, the electromagnetic waves can penetrate deep cancerous tissues in the human body and heat them.

In addition, since the excitation antenna is sealed inside a columnar dielectric material that has a dielectric constant almost equal to that of the human body as an electromagnetic waveguide, the size of the excitation antenna is 1/√ of the size in the atmosphere. The size can be changed to 500MHz.
Since the excitation antenna can be made sufficiently small even if it is lowered to below, the size of the columnar dielectric body, which is determined by the size of the excitation antenna, can also be made sufficiently small, making it a compact electromagnetic wave generator that is extremely easy to handle as a medical electromagnetic wave generator. has been realized.

Furthermore, the columnar dielectric material through which the electromagnetic waves from the excitation antenna propagate is made of a dielectric material with a dielectric constant that is almost the same as that of human tissue, so the reflection loss at the surface in contact with the human body is extremely small. , most of the radiation energy from the excitation antenna can be directed into the human body in the form of a beam, achieving extremely high radiation efficiency.

Furthermore, since the dielectric constant of the columnar dielectric is extremely high compared to that of air, the electromagnetic waves incident on the interface between the columnar dielectric and air are not radiated into the air but are transmitted inside the columnar dielectric. Although the frequency band below 500 MHz has not been approved for medical use, the electromagnetic wave energy leaked to the outside from the electromagnetic wave generator of the present invention is extremely small, so electromagnetic wave leakage is prevented. The shielding equipment required to prevent communication interference due to radio transmission is also minimal, and it is possible to sufficiently suppress the occurrence of radio wave interference in equipment for medical facilities.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing a conventional electromagnetic wave generator, FIG. 3 is an explanatory diagram of thermotherapy using a conventional electromagnetic wave generator, and FIG. 4 is a perspective view showing an embodiment of the present invention. Figure 5 shows the radiation power ratio of a dielectric antenna.
Graphs showing Wi/Wo, Figures 6, 7 and 8 are cross-sectional views showing other embodiments of the columnar dielectric in the present invention, and Figures 9, 10, 11, 12 and 13 are used in the present invention. It is an explanatory view showing other examples of an excitation antenna. 10... Column dielectric, 12... Radiation surface, 14...
... Loop antenna, 16 ... Feed line, 18 ... Dipole antenna, 20 ... Electrode plate, 22 ... Corner reflector, 24 ... Folded antenna, 26
...Helical antenna.

Claims (1)

[Scope of Claims] 1. A columnar dielectric having a dielectric constant substantially equal to that of human tissue and having an electromagnetic wave radiation surface formed at one end; an excitation antenna sealed inside the columnar dielectric; 1. An electromagnetic wave generator for thermotherapy, characterized in that the electromagnetic wave generator comprises a feed line for the excitation antenna that is drawn out of a columnar dielectric body. 2 The columnar dielectric has a circular shape, an oval shape, an elliptical shape,
The electromagnetic wave generator for thermotherapy according to claim 1, which has a polygonal cross-sectional shape. 3. The electromagnetic wave generator for hyperthermia therapy according to claim 1, wherein the excitation antenna is an antenna excited by ultra-high frequency waves and/or ultra-high frequency waves. 4. The electromagnetic wave generator for thermotherapy according to claim 1, wherein the excitation antenna is an antenna excited at a frequency of 500 MHz or less. 5. The excitation antenna is a linear antenna such as a dipole, loop, or helical antenna, or a plate antenna using a pair of electrodes.
Electromagnetic wave generator for thermotherapy as described in .