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BACKGROUND OF THE INVENTION
Field of the Invention and Related Art Statement
The present invention relates to a hyperthermia apparatus for use in a
thermotherapy in which malignant body tissues, particularly cancer tissues
are necrosed by selectively heating them with electric fields at high
frequencies.
The hyperthermia apparatus has been developed to necrose cancer tissues by
heating them above a temperature higher than 45.degree..about.43.degree.
C. due to the fact that the cancer tissues are liable to be damaged by
heat rather than normal tissues. There have been proposed various types of
hyperthermia apparatuses.
For instance, in Japanese Patent Publication Kokai No. 59-135,066, there is
disclosed a hyperthermia device comprising a single inside-body electrode
and a single outside-body electrode. This type of hyperthermia apparatus
has been manufactured and sold by Kureha Kagaku Kogyo Co., Ltd. in Japan
under the trade name of Endoradiotherm 100A. In U.S. Pat. No. 1,350,168
and Japanese Utility Model Publication No. 58-8,254, there is described
another type of hyperthermia apparatus comprising a plurality of
outside-body electrodes which are arranged around the patient's body and a
switching means for selectively using a pair of electrodes which are faced
to each other via the body of the patient.
FIG. 1 is a schematic view illustrating the known hyperthermia apparatus
disclosed in said Japanese Patent Publication Kokai No. 59-135,066. In
this known hyperthermia apparatus an inside-body electrode 4 is inserted
into a cavity 2 of a patient's body 1 and an outside-body electrode 5 is
placed on the outer surface of the body such that these electrodes are
faced to each other via a cancer 3. Across the inside-body electrode 4 and
outside-body electrode 5 is applied an RF electric power from an RF
oscillator 6 to generate an electric field at a high frequency within the
patient's body 1, and then a portion of the body 1 between these
electrodes is heated by the electromagnetic induction. The electrode 4 is
inserted into the cavity 2, so that its surface area is much smaller than
that of the electrode 5. Therefore, the density of the high frequency
electric field becomes higher toward the inside-body electrode 4.
FIG. 2 is a schematic view illustrating another known hyperthermia
apparatus including a plurality of outside-body electrodes. This type of
apparatus is disclosed in the above mentioned Japanese Utility Model
Publication No. 58-8,254. In this known hyperthermia apparatus, on an
outer surface of a patient's body 1, there are arranged outside-body
electrodes 7 and 8 such that a cancer 3 is sandwiched by these electrodes.
Then, an RF electric power is applied across the electrodes 7 and 8 from
an RF oscillator 9 to generate an electric field of high frequency so that
a portion of the body 1 between the electrodes 7 and 8 is selectively
heated by the electromagnetic induction.
In the known hyperthermia apparatus illustrated in FIG. 1, since the
density of the higy frequency electric field is increased toward the
inside-body electrode 4, the body is preferably heated locally. However,
this local heating has a demerit in some applications and a part of the
cancer 3 may not be heated due to an error in the positioning of the
electrodes or due to the size of the cancer 3. For instance, in the
esophagus where a long cancer is liable to from in a longitudinal
direction of the esophagus, it is practically impossible to heat the whole
cancer to a predetermined temperature, and a part of the cancer is
therefore not sufficiently heated. Then, this part of the cancer may not
be necrosed, and grows. Moreover, since there is provided only one
outside-body electrode 4, when a plurality of cancers are existent around
the patent body 1, it is necessary to rearrange the electrode 4, which
makes the operation cumbersome.
In the known hyperthermia apparatus depicted in FIG. 2, the outside-body
electrodes 7 and 8 may have a relatively large surface area, so that the
cancer 3 having a large area can be heated to the effective temperature.
However, the high frequency electric field is spread widely between the
large electrodes, and thus the normal tissues surrounding the cancer
tissues might be heated to a higher temperature. Therefore, the
hyperthermia apparatus could not be used for a long time period. As is
well known in the art, the effect of the thermotherapy depends on not only
the temperatures to which the tissues are heated, but also upon the time
period for which the tissues are held at such temperatures. In this known
hyperthermia apparatus, in order not to heat the normal tissues
excessively, there is provided a cooling means of a large scale at the
electrode. This results in the whole electrode becoming complicated in
construction and large in size.
In the known hyperthermia apparatus described in the above mentioned U.S.
Pat. No. 4,350,168, there is provided a cooling means beside an electrode
in order to cool the patient body near the electrode. The coolimg means
includes a balloon and a device for circulating cooling water through the
balloon.
In the U.S. Pat. No. 4,350,168, there is also shown another hyperthermia
apparatus including three pairs of outside-body electrodes and high
frequency powers having mutual phase difference of 123.degree. being
applied to respective pairs of electrodes. In this known appartus, three
pairs of electrodes would operate just like a single pair of electrodes,
so that the normal tissues near the electrodes might be heated to
undesired high temperatures. Further, if more than three pairs of
electrodes are provided the mutual phase difference of the driving signals
becomes smaller, and a high frequency current might flow into adjacent
electrodes so that all the electrodes would operate as a single pair of
electrodes.
In Japanese Patent Publication Kokai 60-119,962, there is disclosed
inside-body and outside-body applicators each including an electrode, a
balloon surrounding the electrode and a device for circulating a cooling
medium through the balloon. By using such applicators, the normal tissues
can be prevented from being heated excessively. In this known hyperthermia
apparatus, the cooling medium circulating device is commonly used for the
balloons of both the inside-body and outside-body applicators. In this
apparatus, in order to prevent the electrodes from being short-circuited,
the cooling medium has to be made of an electrically insulating substance.
However, if the electrode is surrounded by the insulating medium, the
impedance between the electrodes is increased and the high frequency
electric field may not be produced in the living body at a high efficiency
and the tissues may not be heated to the desired high temperature.
Therefore, an electrically conductive substance has to be used as the
cooling medium, and thus there are provided separate devices for
circulating the cooling mediums through respective balloons in order to
avoid the short-circuiting. However, in the known hyperthermia apparatus
these devices are not completely isolated from each other. For example,
even if pipes connected to the balloons and pumps for circulating the
cooling mediums through the balloons are provided separately, when the
pumps and cooling devices are connected commonly to a power supply line,
the cooling mediums might be electrically connected to each other by means
of the power supply line, and the patient may not be protected against
danger.
In Japanese Patent Publication No. 56-38,230, there is described still
another known hyperthermia apparatus. In this known apparatus, there is
arranged an automatic impedance matching circuit for matching an output
impedance of a high frequency oscillator and an input impedance of a load
circuit including electrodes to which is supplied high frequency electric
power from the oscillator and the living body, so that the high frequency
electric field can be generated efficiently in the living body.
Howwver, in such a known hyperthermia apparatus, there is not provided a
protection means for the impedance mismatching at the start of applying
the high frequency electric power, so that the electric device might be
damaged by the high electric power reflected from the load due to the
mismatching.
Moreover, in the known hyperthermia apparatus in which the electrodes are
selectively switched into and out of the circuit, after switching the
electrodes, the high frequency electric power is adjusted to have a
desired amplitude and then is applied to the electrodes. However, the
impedance of the load including the selected electrodes might vary due to
various factors such as condition of the living body, contact condition of
the electrodes to the body and connecting condition of the electrodes to
connectors. Therefore, the impedance mismatching might be produced and the
instrument might be damaged by the reflected high power. Further, the
patient might be subjected to an electrical shock.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a novel and useful
hyperthermia apparatus in which malignant tissues can be wholly heated to
a desired temperature for a desired time period, while normal tissues can
be effectively prevented from being heated excessively.
It is another object of the invention to provide a hyperthermia apparatus
which can be utilized in a highly safe manner by separating electrically
cooling mediums each being circulated through balloons surrounding
respective electrodes in a complete manner.
It is still another object of the invention to provide a hyperthermia
apparatus which does not require a complicated means for cooling an
electrode.
It is still another object of the present invention to provide a
hyperthermia apparatus in which the damage to the apparatus and living
body due to the impedance mismatching when a high frequency electric power
is applied to electrodes or electrodes are selectively switched into a
circuit.
In order to attain the above object, according to the invention, a
hyperthermia apparatus comprises
inside-body electrode means including at least one inside-body electrode to
be inserted into a cavity of a living body;
outside-body electrode means including at least two outside-body electrodes
to be applied on an outer surface of the living body;
selection means for selecting two electrodes including at least one
outside-body electrode among said outside-body and inside-body electrodes;
and
power source means for applying a high frequency electric power across the
two electrodes selected by said selection means to heat a cancer in the
living body to a desired temperature.
In a preferred embodiment of the hyperthermia apparatus according to the
invention, each of said electrodes is formed as an applicator including a
balloon which surrounds the electrode, and there are provided devices for
circulating cooling mediums through respective balloons, said devices are
electrically isolated from each other in a complete fashion. In such a
hyperthermia apparatus, although use are made of electrically conductive
cooling mediums circulating through respective balloons, these mediums are
completely isolated from each other, any accident of short-circuiting can
be removed to improve safety. Moreover, various electrical instruments of
the cooling means may be connected commonly to the same power supply line
without causing any trouble, so that the consturction becomes much
simpler.
In another preferred embodiment of the hyperthermia apparatus according to
the invention, inside-body electrodes and/or outside-body electrodes are
divided into plurality of sections and a high frequency electric power is
successively supplied to these electrode sections at a given period. Then
the electrode sections can be effectively prevented from being locally
heated to a high temperature and the heat can be efficiently radiated or
diffused, so that normal tissues are effectively protected against the
damage.
In still another preferred embodiment of the hyperthermia apparatus
according to the invention, there are provided an automatic impedance
matching circuit for matching an output impedance of the high frequency
electric power supply means with respect to an impedance of a load, and a
control circuit for controlling the high frequency electric power
supplying means such that the output power of the supplying means is set
to a low level at the start of the power supply and is changed to a
desired high level after the impedance matching has been substantially
attained by said automatic impedance matching circuit. In this embodiment,
before connecting electrodes selected by said selection means to the high
frequency power supplying means, the output level of the power supplying
means is changed to a low or zero level, and after the impedance matching
is performed by the impedance matching circuit, the output level of the
power supplying means is changed to the desired high level.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing a known hyperthermia apparatus including
an outside-body electrode and an inside-body electrode;
FIG. 2 is a schematic view illustrating a known hyperthermia apparatus
comprising two outside-body electrodes;
FIG. 3 is a schematic view depicting the construction of an embodiment of
the hyperthermia apparatus according to the invention;
FIG. 4 is a schematic view explaining the heating operation with the aid of
the apparatus shown in FIG. 3;
FIG. 5 is a schematic view showing the construction of another embodiment
of the hyperthermia apparatus according to the invention;
FIG. 6 is a circuit diagram depicting the detailed construction of an RF
electric power generating device of the hyperthermia apparatus according
to the invention;
FIG. 7 is a schematic view illustrating the construction of another
embodiment of the hyperthermia apparatus according to the invention;
FIG. 8 is a schematic view showing the detailed construction of the
apparatus shown in FIG. 7;
FIGS. 9 and 10 are cross sectional views showing two embodiments of a heat
exchanger of the apparatus shown in FIG. 8;
FIG. 11 is a schematic view illustrating still another embodiment of the
hyperthermia apparatus according to the invention in which an electrode is
divided into a plurality of sections; and
FIG. 12 is a schematic view depicting a modified embodiment of the
hyperthermia apparatus of FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 3 is a schematic view showing an embodiment of the hyperthermia
apparatus according to the invention. In the present embodiment, there are
provided a single inside-body electrode 11 (hereinafter referred to as
first electrode), two outside-body electrodes 12 and 13 (referred to as
second and third electrodes, respectively), and a selection switch 14. The
selection switch 14 serves to connect a first combination of the first and
second electrodes 11 and 12 or a second combination of the second and
third electrodes 12 and 13 to a high frequency power supply source 15 so
that an electric field of a Radio Frequency can be applied across the
electrodes 11 and 12 or the electrodes 12 and 13.
The first electrode 11 is arranged at a distal end of a flexible thin tube
19 and is inserted into a cavity 2 of a patient's body 1 at such a
position that the first electrode is faced to a cancer 3. In FIG. 3, the
apparatus is utilized to destroy the cancer 3 formed in an esophagus 2a.
The first electrode 11 is surrounded by a balloon 16. Through the balloon
16, an electrically conductive liquid medium such as physiological saline
solution is circulated via tubes 20a inserted into the insertion tube 19
and a heat exchanger (not shown to) heat or cool a cavity wall against
which the balloon 16 is urged.
The second electrode 12 is placed on a front surface of the body 1 such
that it is faced to the first electrode 11 via the cancer 3. Further, the
third electrode 13 is arranged on a rear surface of the body 1 at such a
position that it is faced to the second electrode 12. Similar to the first
electrode 11, the second and third electrodes 12 and 13 are surrounded by
balloons 17 and 18, respectively. An electrically conductive liquid medium
such as physiological saline solution is circulated through the balloons
17 and 18 by means of tubes 20b and 20c and a heat exchanger (not shown),
so that parts of the body 1 contacting the balloons 17 and 18 are cooled.
It should be noted that the heating or cooling system for the first
electrode 11 and the cooling systems for the second and third electrodes
12 and 13 are electrically isolated from each other as will be explained
later.
The RF power supply device 15 has two output termianls, one of which is
directly connected to the second electrode 12 and the other of which is
connected to a switching contact 14a of the selection switch 14 whose
fixed contacts 14b and 14c are connected to the first and third electrodes
11 and 13, respectively. Therefore, in the present embodiment, the second
outside-body electrode 12 is always connected to the RF power supply
device 15.
When a switching arm of the switch 14 is connected to the fixed contact
14b, the first and second electrodes 11 and 12 are selected and the RF
electric field is selectively generated across these electrodes. When the
switching arm of the switch 14 is changed to the fixed contact 14c, the
second and third electrodes 12 and 13 are selected and the RF electric
field is produced thereacross. Therefore, by changing the switching arm
periodically, the first pair of electrodes 11, 12 and the second pair of
electrodes 12, 13 are alternatively selected. The switching arm of the
switch 14 may be driven manually or automatically in accordance with a
program which has been set on the basis of the dimension and position of
the cancer 3. Further, the application of the RF electric power to the
electrodes can be automatically controlled by means of temperature sensors
such as thermo-couples arranged on the outer surfaces of the balloons 16
to 18 in such a manner that when sensed temperatures exceed predetermined
temperatures, the application of the RF power is interrupted until the
sensed temperatures become lower than the predetermined temperatures. In
this manner, the cancer 3 can be maintained substantially at the desired
temperature.
In the present embodiment, when the first and second electrodes 11 and 12
are selected, a restricted portion in the body 1 can be locally heated as
shown by solid lines in FIG. 4, whilst when the second and third
electrodes 12 and 13 are selected, a wider portion of the body is heated
as illustrated by broken lines in FIG. 4. Therefore, the cancer 3 can be
wholly heated substantially uniformly to a desired temperature at which
the malignant tissues are selectively necrosed substantially regardless of
the size and position of the cancer and any error in positioning the
electrodes. Moreover, since the first pair of electrodes 11, 12 and the
second pair of electrodes 12, 13 are alternately connected to the electric
power supply device 15, the normal tissues can be effectively prevented
from being heated excessively, and thus the hyperthermia apparatus can be
continuously utilized for a long time period necessary for an optimum
thermotherapy.
FIG. 5 is a schematic view illustrating another embodiment of the
hyperthermia apparatus according to the invention. In this embodiment,
portions similar to those of the previous embodiment are denoted by the
same reference numerals as those used in FIG. 3. The present embodiment
differs from the previous embodiment only in the point that a first
inside-body electrode 11 is directly connected to one output of an RF
power supply device 15, and second and third outside-body electrodes 12
and 13 are connected to fixed contacts 14b and 14c of a switch 14, whose
switching contact is connected to the other output of the power supply
device 15. When a first pair of electrodes 11 and 12 is selectively
connected to the power supply device 15, there is generated within a
patient's body 1 an electric field illustrated by solid lines, while when
a second pair of electrodes 11 and 13 are selected, an electric field
shown by broken lines is generated across these electrodes.
In the present embodiment, since the first inside-body electrode 11 is
always selected, the cancer 3 which is formed around the cavity 2 can be
efficiently heated to a desired temperature. It should be noted that if
cancers are existent in cavity wall portions opposing each other, it would
be preferable to constitute a mode in which the second and third
electrodes are selected.
As explained above, in the hyperthermia apparatus according to the
invention, two electrodes including at least one outside-body electrode
are selectively connected to the RF power supply device and the high
frequency electric field is applied across the selected electrodes, so
that the malignant tissues of the cancer can be wholly heated to the
desired temperature, while the normal tissues can be effectively prevented
from being heated to excessively high temperatures.
FIG. 6 is a block diagram showing the detailed construction of an
embodiment of the RF power supply device 15. In the present embodiment, an
RF signal generated from an RF oscillator 21 is supplied via high
frequency amplifier 22 and impedance matching (IM) circuit 23 to a
co-axial cable 24. The impedance matching circuit 23 serves to attain the
impedance matching with respect to the co-axial cable 24 and an output end
of the co-axial cable is connected to an interface 25 which is arranged
near the patient. The interface 25 comprises variable impedance matching
(VIM) circuit 26, selection switch 14 and connectors 31, 32 and 33 to
which connectors the first, second and third electrodes 11, 12 and 13 are
connected via condutors, respectively. As explained above, two electrodes
are selected among these three electrodes with the aid of the switch 14
and the RF power is supplied to the selected electrodes via the co-axial
cable 24, variable impedance matching circuit 26 and switch 24. In the
present embodiment, the electrode selecting operation of the switch 14 is
controlled by a main controller 34 in accordance with a predetermined
program. The interface 25 further comprises connectors 35, 36 and 37 to
which temperature sensors arranged near respective electrodes 11, 12 and
13 are connected via conductors, respectively. Output signals supplied
from the temperature sensors via the connectors 35, 36 and 37 are sent to
the main controller 34. It should be noted that the switch 14 may be
controlled in accordance with a program which uses the sensed temperatures
as parameters.
Between the high frequency amplifier 22 and the impedance matching circuit
23, there are connected phase detector 38 for detecting a phase shift of
the RF signal and wattmeter 39 of transmission type for measuring incident
power and reflected power. Outputs of the phase detector 38 and wattmeter
39 are supplied to the main controller 34 as well as to an automatic
impedance matching controller 40. This controller 40 supplies a control
signal to the variable impedance matching circuit 26 such that the input
impedance of the load circuit including two electrodes selected by the
switch 14 is matched to the output impedance of the RF power supply device
15 including the co-axial cable 24.
The high frequency amplifier 22 is energized by a power source 41. The
power source 41 is controlled by an ON/OFF controller 42 under the control
of the main controller 34 such that the output power from the amplifier 22
is returned ON and OFF. For instance, when the electrodes are switched
into or out of the circuit by the switch 14, the RF power is decreased to
zero, and when the sensed temperatures increase or above decrease blow the
predetermined values, the RF power is switched OFF or ON.
The reflected power measured by the wattmeter 39 is supplied also to an
excessive reflection monitor 43. In the monitor 43, the measured
reflection power is compared with a given freference value, and when the
reflection power exceeds the reference value, a signal is supplied to an
over-reflection display 44 to display the excessive reflection of the RF
power. The monitor 43 supplies the signal also to the main controller 34
and a forcedly OFF controller 45, and the output power of the high
frequency amplifier 22 is made OFF via the ON/OFF controller 42 and power
source 41. Therefore, even if there occurs sudden impedance mismatching
due to the disconnection of one or more electrodes from relevant
connectors 31, 32 and 33, the excessive large reflection power which might
damage the apparatus could never be produced.
Further, in the present embodiment, the amplification factor of the high
frequency amplifier 22 is adjusted by the main controller 34 such that the
output power of the amplifier 22 is decreased to a safe low level when the
impedance matching becomes worse at a time of switching the electrodes and
during the application of the RF power to the electrodes. Then, the
automatic impedance matching is carried out at said safe low level, and
after the impedance matching has been attained, the output power of the
high frequency amplifier 22 is increased to the desired high level. In
this manner, the apparatus can be protected against damage due to the
impedance mismatching at the start time and during the application of the
RF power to the electrodes, and at the same time, the patient is
effectively prevented from being subjected to the dangerous electric
shock.
In the above mentioned embodiment, after the output power of the high
frequency amplifier 22 has been decreased to the lower level, the
switching operation of electrodes is effected, but it is also possible to
make the output power OFF from the low level or directly from the desired
high level without interleaving the low level, and after the electrodes
have been switched, the output power is slightly increased to the low
level and the impedance matching is effected under this low level.
Further, the switching of electrodes may be carried out manually instead
of automatically. In this case, it is preferable to provide a manual
switch for changing the output power of the high frequency amplifier 22
among the desired high level, safe low level and zero level, and prior to
the selection of electrodes, the output power is manually set to the low
level or zero level. After the selection of electrodes has been effected,
the impedance matching is carried out automatically or manually under the
low output power. When the impedance matching has been confirmed by an
indicator such as meter, lamp or buzzer, the output power is increased to
the high level by operating the manual switch. It should be noted that
when using the manual selection switch 14, there may be provided a lock
mechanism for inhibiting the operation of the switch as long as the high
level power is generated from the high frequency amplifier 22. Moreover,
there may be provided a photosensor or contact sensor for detecting the
operation of the manual switch 14, and an alarm for producing an alarm
sound or light when the switch is to be operated under the high output
condition.
By utilizing the RF power supply device just explained above, the output
power is switched into the low or zero level prior to the switching of
electrodes, and after the electrodes have been switched, the impedance
matching is carried out under the low level power and then the output
power is increased to the high level for heating the body. Therefore, the
apparatus is effectively protected against damage due to the impedance
mismatching and further the patient can be prevented from being subjected
to the electric shock, so that the thermotherapy can be performed safely.
In the embodiments so far explained, there are arranged one inside-body
electrode and two outside-body electrodes, but the present invention is
not restricted to such a construction. For instance, a plurality of
inside-body electrodes may be inserted into the cavity of a patient's body
extending in the longitudinal direction thereof and a corresponding number
of outside-body electrodes may be arranged on the outer surface of the
patient's body. Further, in the apparatus according to present invention
the microwave power can be effectively used instead of the RF power.
FIG. 7 is a schematic view illustrating the construction of another
embodiment of the hyperthermia apparatus according to the invention, and
FIG. 8 is a view showing its fluid system in detail. The hyperthermia
apparatus comprises an RF supply unit 51 and a cooling unit 52. The RF
power supply unit 51 is coupled with an electrode of an inside-body
applicator 54 by means of an RF cable 53 as well as to electrodes of two
outside-body applicators 56a and 56b via RF cables 55a and 55b,
respectively. The cooling unit 52 is connected to a balloon of the
inside-body applicator 54 through water supply and discharge pipes 57 and
58 as well as to balloons of the outside-body applicators 56a and 56b by
means of water supply and discharge pipes 59a, 59b, 59c and 60a, 60b, 60c.
The inside-body applicator 54 has a suitable size, shape and construction
for easy insertion into the cavity of the body 61.
As illustrated in FIG. 8, the inside-body applicator 54 comprises a
flexible rod 62 made of electrically insulating material, an inside-body
electrode 63 arranged on a distal end of the rod and a balloon 64 made of
electrically insulating material, the electrode being wholly surrounded by
the balloon. In the rod 62 there are formed a duct 65 which is connected
to the electrically insulating water supply pipe 57 and a duct 66 which is
coupled with the water discharge pipe 58 made of electrically insulating
material, these ducts being open within the balloon 64. On the outer
surface of rod 62 there is applied a conductive strip 67 which is
connected to the RF cable 53 and extends up to the electrode 63. On the
outer surface of balloon 64 there is provided a thermocouple 68 which is
connected via a conductor 69 to a temperature measuring device (TM) 70
arranged in the RF power supply unit 51.
The two outside-body applicators 56a and 56b have the same construction and
comprise outside-body electrodes 71a and 71b connected the RF cables 55a
and 55b, and balloons 72a, 72b made of electrically insulating material,
the electrodes being separated from the body 61 by the balloons. To the
balloon 72a are connected water supply and discharge pipes 59b and 60b,
and to the balloon 72b are coupled water supply and discharge pipes 59c
and 60c, said pipes being made of electrically insulating material. On the
other surfaces of balloons 72a and 72b, there are provided thermocouples
73a and 73b which are connected via conductors 74a and 74b to a
temperature measuring circuit 75 provided in the RF power supply unit 51.
The temperature measuring circuits 70 and 75 detect temperatures at
positions of the applicators 54, 56a and 56b, and supply signals to a
power source controller 76 which then supplies a control signal to an RF
signal source 77a. The output power of the RF signal generator 77a is
supplied to electrodes via a selection switch 77b.
The cooling unit 52 comprises a heating/cooling device 78 and a heat
exchanger 79 connected thereto, so that a liquid medium 80, for instance,
water heated or cooled by the heating/cooling device is circulated through
the heat exchanger 79. In the heat exchanger 79 there is arranged a coiled
pipe 81 which is connected to the supply and discharge pipes 57 and 58.
The coiled pipe 81 is made of electrically insulating material. In the
supply pipe 57 is inserted a roller pump 82 for circulating an
electrically conductive medium, i.e. saline solution 83 through pump
82--pipe 57--duct 65--balloon 64--duct 66--pipe 68--coiled pipe 81--pipe
57--pump 82. In the heat exchanger 79, the heat exchange is carried out
between the water 80 and the medium 83 flowing through the coiled pipe 81,
and thus the temperature of the medium 83 is controlled. It should be
noted that the liquid medium 83 circulated through the balloon 64 of the
inside-body applicator 54 serves not only to cool the living body, but
also to heat the body. In the thermotherapy, it is necessary to heat the
malignant tissues of cancer to a high temperature higher than 42.degree.
to 43.degree. C. Therefore, during a start period of the thermotherapy, it
is preferable to heat the body with the aid of the medium 83. In order to
avoid the death or damage of normal tissues, it is necessary to keep the
normal tissues at temperatures below 43.degree. to 44.degree. C., so that
the medium 83 must have the function to cool the body. In this manner, the
temperature of the medium 83 has to be controlled in accordance with
temperatures of the part of the body at which the applicator 54 is
arranged.
The outside-body applicators 56a and 56b must have the function for cooling
the body, so that a cooling device 84 and a heat exchanger 85 coupled
therewith are provided in the cooling unit 52. In the heat exchanger 85,
there is arranged a coiled pipe 86 connected to the pipes 59a and 60a made
of electrically insulating material. In the pipe 59a there is inserted a
roller pump 87 for circulating a cooling medium 88 made of saline solution
through pump 87--pipes 59a, 59b--balloon 72a--pipes 60b, 60a--coiled pipe
86--pipe 59a--pump 87 as well as pump 87--pipes 59a, 59c--balloon
72b--pipes 60c, 60a--coiled pipe 86--pipe 59--pump 87. The cooling device
84 is controlled by the temperature measuring circuit 75 to adjust the
temperature of the saline solution 88.
In the present embodiment, the saline solutions 83 and 88 circulate through
the balloons 64 and 72a, 72b and the waters 80 and 89 circulate via the
heating/cooling devices 78 and 84 such that these devices are electrically
isolated from each other, and therefore the saline solutions 83 and 88 are
never short-circuited although the heating/cooling devices 78 and 84 are
connected to the common power supply line. Further, the roller pumps 82
and 87 do not contact the saline solutions 83 and 88 and feed the
solutions by squeezing the flexible tubes, so that although motors for
rotating rollers of the roller pumps are commonly connected to the same
power supply line, the solutions are not short-circuited at all through
the roller pumps.
FIG. 9 is a partially cross sectional schematic view showing another
embodiment of the cooling unit for controlling the temperature of the
liquid mediums. This embodiment is applicable to the hyperthermia
apparatus including two outside-body electrodes. In this embodiment, the
cooling unit comprises a cooling device 84 and a heat exchanger 85 coupled
therewith. In th | | |
