JPH0647028B2 - Electromagnetic wave heating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a medical electromagnetic wave heating device used for treatment of a malignant tumor or the like, and particularly to an electromagnetic wave heating device including an applicator to be inserted into a body cavity of a living body. Regarding the improvement of the device.

[Prior Art] Recently, as one of treatment methods for malignant tumors such as cancer, a method of irradiating a treatment site with electromagnetic waves and heating (hyper-samia) has been used. As a method of irradiating the treatment site with electromagnetic waves, a method of using an applicator that directly pierces the treatment site tissue with the electromagnetic wave irradiation unit, or a treatment site relatively close to the body cavity of the living body (eg, uterine cancer, esophageal cancer, etc.)
In this case, a method of inserting an applicator into a body cavity and emitting an electromagnetic wave is known. This body cavity insertion type applicator has an antenna section that radiates a heating electromagnetic wave supplied from an electromagnetic wave generator.

Conventionally, this type of electromagnetic wave warming device is as shown in FIG.
The base end of the linear antenna part 1 is used as a feeding point (excitation point) 1a, which is connected to the electromagnetic wave generator 2 via a feeding line (not shown). An electromagnetic wave having one resonance frequency is supplied. The linear antenna 1 has a sinusoidal current distribution in which the feeding point 1a has an antinode value and the terminal end 1b of the linear antenna part 1 has a node value, and the abruptly increases toward the terminal end 1a. Since the power pattern is attenuated and becomes zero at the terminal end 1b, the living tissue in the vicinity of the terminal end 1b is hardly heated, and uniform heating cannot be expected compared with the length of the antenna.

As a solution to this problem, there is a microwave heating device disclosed in Japanese Patent Laid-Open No. 60-246772 disclosed by the applicant. As shown in FIG. 4 (A), this device uses a helical monopole antenna 3 and a feeding point 3a at the base end.
Is excited by an electromagnetic wave of the nth high-order resonance frequency, the feeding point 3a has a current antinode value, and gradually decreases toward the terminal end 3b, but presents a current distribution having many irregularities, It was expected that a radiation power distribution suitable for heating could be obtained in the vicinity of the termination 3b as compared with that shown in FIG.

[Problems to be Solved] However, the electromagnetic wave warming device shown in FIG. 4 (A) has the following problems.

By exciting the helical monopole antenna 3 with an electromagnetic wave having a higher resonance frequency, the feeding point 3a to the terminal 3b are excited.
Even if a large number of uneven current distribution states are formed over, the current amplitude value of the semi-convex antinode part near the feeding point 3a is still the maximum, and the current amplitude value of the convex part 3b of the terminal end 3b is With such a current distribution, the applicator that should be inserted into the body cavity of the living body causes local heating near the feeding point 3a, especially when the size of the treatment site is large. As a result, it is still inconvenient, and a wide range and uniform heating is not realized yet.

Generally, a coaxial feed line of an unbalanced system line is used as a feed line for transmitting an electromagnetic wave from an electromagnetic wave generator, but since it is a monopole type antenna, it is shown in FIG. As shown in B), it is inevitable to connect the end of the outer conductor 4a of the coaxial feed line 4 to the sleeve-shaped choke 5 having a length of λ / 4 wavelength for matching.
Since the choke 5 also functions as a part of the antenna and emits electromagnetic waves, unnecessary heating is also performed on living tissues other than the treatment part, which is adversely affected. In addition, power loss is incurred.

[Object of the Invention] The present invention is to solve the above-mentioned problems, and an object of the present invention is to provide moderate heating in the vicinity of the end of the applicator and relatively low heating in the vicinity of the applicator base, and intermediate It is an object of the present invention to provide an electromagnetic wave heating device that can realize uniform heating over a wide range and reduce power loss by allocating so as to perform uniform heating.

[Means for Solving Problems] In order to solve the above problems, the configuration of the electromagnetic wave heating device according to the present invention has the following configuration requirements.

An applicator that has an antenna part that is excited by a heating electromagnetic wave of a higher resonance frequency supplied from an electromagnetic wave generator to a feeding point through a feeding line and that should be inserted into a body cavity of a living body.

The antenna part of the applicator must be a helical dipole type antenna.

For example, the "helical dipole structure" includes one in which one of the helical antenna parts is wound around the feeding line with respect to the feeding point.

[Operation of the Invention] In the electromagnetic wave warming device having such a configuration, central feeding is performed to the helical dipole antenna, and a current distribution having many irregularities appears over the entire length of the antenna part. The current amplitude value at both ends of the antenna part is smaller than that at the central feeding point, but it is not zero, and since it has a convex part with a finite value in the vicinity, it is unnecessary or excessively applied to living tissue near the base part. It does not become warm, it is heated moderately at the end, and the number of irregularities of the current amplitude that appears when the n-th higher-order resonance state in the helical monopole structure is the same In the dipole type structure described in (1), it can be realized in the n / 2-order higher-order resonance state, and in the case of the same higher-order resonance state, the number of irregularities is twice as dense as in the conventional case. Will allow more uniform and wide range heating. Further, unlike the conventional case, it is not necessary to intentionally mount a matching device at the base of the applicator, and the balanced feeder can be connected to the feeding point by interposing a matching device other than the applicator, so that the electric field does not leak at the base. As a result, unnecessary electromagnetic radiation that adversely affects the living body can be suppressed, and power loss can be reduced.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing an embodiment of an electromagnetic wave heating apparatus according to the present invention.

The electromagnetic wave warming device of the embodiment is roughly configured by an electromagnetic wave generator 10, a coaxial type power supply line 11, a matching device 12, a parallel two-wire type power supply line 13 and a body cavity insertion type applicator 14.

The electromagnetic wave generator 10 generates a heating electromagnetic wave, and its frequency is in the microwave region of about 100 to 3000 MHz.
Generally, the coaxial feed line 11 as an unbalanced feed line is directly connected to the electromagnetic wave generator 10, but in the present embodiment, the other end is connected to a matching device 12 such as a balun circuit. The matching device 12 is an unbalanced / balanced converter, and a parallel two-wire type feed line 13 is connected to the output side terminal thereof. The parallel two-wire type feed line 13 includes conductive wires 13a and 13b and an insulating jacket 13 that covers them.
It is a balanced feeder consisting of c and. The outer end of the parallel two-wire type power supply line 13 has a predetermined length, and the outer cover 13c is removed.
13a and 13b are exposed, and conductors 13a and 13b of this exposed portion are exposed.
A helical dipole antenna structure 15 having helical antenna portions 15a and 15b symmetrically with respect to the central feeding point P is formed by b. That is, the conductor
By winding the tip end side of 13a as it is, a helical antenna portion 15a that is linear in the axis line from the central feeding point P to the terminal end 16a is formed, and the tip end side of the conductor 13b is set from the central feeding point P to the end point side. By folding it back and winding it around the outer cover 13c as it is, the helical antenna part
A helical antenna portion 15b having a linear axis is formed from the end 15b in the direction opposite to 15a. The helical antenna parts 15a and 15b are wound in opposite directions to each other and have a symmetrical structure with respect to the central feeding point P, which contributes to stabilization of radiation characteristics. Both helical antenna parts 15a, 15b
Is integrally covered with a tube 17 made of a flexible low loss dielectric material (for example, Teflon (trade name), polypropylene, etc.), and the applicator 14 itself also has both helical antenna parts 15a, 15b and tube 17
It has flexibility or elasticity because of its flexibility.

The electromagnetic wave from the electromagnetic wave generator 10 is supplied to the central feeding point P via the coaxial feed line 11, the matching device 12, and the parallel two-wire feed line 13. The electromagnetic waves have second-order, third-order, ..., N-th higher-order resonance frequencies, and can be appropriately changed according to the part to which the applicator 14 is applied.

Next, the operation and effect of the above embodiment will be described. Since the antenna part is helical and is excited by the electromagnetic wave of the higher resonance frequency, the current distribution is equal to the entire length of both helical antenna parts 15a and 15b. Although it has a large number of irregularities (lobes) over the entire length, it also has a dipole type structure, and therefore, as shown in FIG. When the point P is maximum (main pole value), it vibrates toward the terminal end 16a of the helical antenna portion 15a and the terminal end 16b of the helical antenna portion 15b and gradually decreases. Termination of helical antenna part 15b
16b is located on the base side of the applicator 14 itself, but
Excessive heating of the base side as in the conventional applicator shown in FIG. Further, although the terminal end 16a of the helical antenna portion 15a is located on the tip end side of the applicator 14, there is a current convex portion (sub-extreme value) in the vicinity thereof, so it does not become zero steeply and moderate heating is performed. There is expected. Further, since it is a dipole type antenna, when it is excited by an electromagnetic wave of the same high-order resonance frequency as the conventional one, the number of irregularities (extreme value) twice that of the conventional one appears, so that both ends are terminated.
The adjacent convex portions are dense between 16a and 16b, and the state of heating the living tissue becomes more uniform and wide.

By the way, when the resonance frequency of the electromagnetic wave is set to an excessively high order, the electromagnetic wave absorbability in the living body is almost proportional to the frequency, and the heating in the depth direction of the living body tends to decrease. On the other hand, if the resonance frequency is too low, the number of irregularities in the current distribution is insufficient, and uniform heating cannot be expected. However, in the present embodiment, even when excited at a frequency of 1/2 of the conventional higher-order resonance frequency, the same number of irregularities as the conventional one appears, so that the degree of freedom in selecting the resonance frequency is doubled. Therefore, it is easy to select the resonance frequency suitable for the treatment site, and it becomes easy to adjust the heating in the deep direction.

Since no choke for matching is used at the central feeding point P and at the end of the applicator, the applicator 14 itself does not emit unnecessary electromagnetic waves. Because, when the coaxial feed line 11 is directly connected to the central feed point P, it becomes unbalanced and the central feed point P
It is necessary to install some matching device in the vicinity, but since it is a dipole type antenna, the conductor wire 13a, 13b on the tip side of the parallel two-wire type feed line 13 is used as it is, and a helical dipole antenna is used. As a result, it is not necessary to mount a matching device in the applicator 14, and the coaxial feed line 11 is parallel to the other than the applicator 14.
This is because the matching device 12 can be interposed between the linear power supply line 13 and the matching device 12. Since the parallel 2-wire type feed line 13 is used and the conductors 13a and 13b are used as they are as a helical dipole antenna, unnecessary radiation can be prevented not only in the transmission system but also in the applicator itself. Except for the helical antenna parts 15a and 15b, which radiate electromagnetic waves with a wide current distribution, almost no unnecessary radiation occurs. This made it possible to reduce power loss.

Further, since the one helical antenna portion 15b is configured by winding the conducting wire 13b exposing the feeding wire 13 around the folded outer jacket 13c, the helical antenna portion 15b is formed.
The axis line and the power supply line 13 coincide with each other, and in the natural state the antenna part becomes a straight rod shape in a natural state as a whole, and since there is no protruding part around it, it does not hinder the covering of the tube 17 and enters the body cavity. It is suitable as an applicator to be inserted.

[Effects of the Invention] As described above, the electromagnetic wave heating device according to the present invention is
Since the antenna part of the applicator is characterized by having a helical dipole structure, the following effects can be obtained.

The vicinity of the base of the applicator is not heated excessively or unnecessarily, and it is desirable as an applicator to be inserted into the body cavity, and even when it is excited at the same resonance frequency as before, uneven current distribution Because the number is twice as dense,
Since the power supply is finely distributed over the entire length of the antenna, more uniform and wide range heating is realized. If the resonance frequency is too high, the electromagnetic wave absorption in the living body is almost proportional to the frequency, and the heating in the deep direction of the living body tends to decrease, but the variable range of the number of unevenness of the current distribution is wide, and the deep distribution The degree of freedom in selecting the resonance frequency for heating is doubled. In particular, when excited at a high-order resonance frequency with a relatively small order, uniform and wide-range heating becomes remarkable,
It is very meaningful.

Since it is possible to effectively prevent the electric field from leaking and the emission of unnecessary electromagnetic waves in the vicinity of the power feeding point in the applicator, there is an advantage that the uniform and wide range heating can be further achieved in combination with the above effect, and the power loss is reduced. .

Further, in the helical dipole structure, when one helical antenna part is formed around the feeding line with respect to the feeding point, there is no need to additionally interpose an insulating member up to the feeding point. Moreover, since the entire antenna part has a flexible rod shape and no protruding part is formed around the antenna part, it is suitable as an applicator to be inserted into a body cavity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an electromagnetic wave heating apparatus according to the present invention. FIG. 2 is an explanatory view showing a current distribution of the antenna section in the embodiment. FIG. 3 is an explanatory view showing an example of a conventional electromagnetic wave heating device. FIG. 4 (A) is an explanatory view showing another example of the conventional electromagnetic wave heating device, and FIG. 4 (B) is a vertical cross-sectional view showing the vicinity of the feeding point of the antenna part. 10 ... Electromagnetic wave generator, 11 ... Coaxial feeder, 12 ... Matching device, 13 ... Parallel 2-wire feeder, 13a, 13b ... Conductor, 13c
...... Insulating jacket, 14 ...... Applicator for insertion into body cavity, 15
...... Helical dipole type structure, 15a, 15b ...... Helical antenna part, 16a, 16b ...... Termination of helical antenna part, 17 ...... Flexible low loss dielectric material tube, P
...... Central feeding point.

Claims (2)

[Claims] 1. An applicator to be inserted into a body cavity of a living body, the applicator having an antenna part excited by a heating electromagnetic wave having a higher resonance frequency supplied from an electromagnetic wave generator to a feeding point through a feeding line, The electromagnetic wave heating device, wherein the antenna section is an antenna having a helical dipole structure. 2. The helical dipole type structure, wherein one helical antenna portion with respect to the feeding point is wound around the feeding line. The electromagnetic wave heating device according to item 1.