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BACKGROUND OF THE INVENTION
Extensive research has been conducted on the unique characteristics of
tumor bearing tissue and the treatment thereof by various techniques. One
discovered characteristic of tumor bearing tissue is that blood flow
through the tumor is substantially less; for example, 2% to 15%, than
blood flow through surrounding normal tissue (Radio Frequency Therapy JAMA
5/17/76, Volume 235, No. 20, LeVeen et al). Because of this vascularity of
tumor tissue, under heat therapy such tumor tissue acted as a heat
reservoir, was unable to dissipate heat at the same rate as surrounding
normal tissue, and therefore reached temperatures from 5.degree. C. to
10.degree. C. higher than normal tissue under certain treatment
procedures. Such temperature differential suggested bringing tumorous
tissue to temperatures in the range of 45.degree. C. to 50.degree. C., at
which the tumorous tissue would be destroyed or subject to substantial
regression, with preservation of normal tissue at physiologic
temperatures. Substantial regression of the tumorous tissue may be a
beneficial adjunct to other forms of treatment of tumors, such as surgery,
radiation, chemotherapy, and immunotherapy.
Medical diathermy, used for decades in musculo-skeletal disorders, has
limitations to deep heating imposed by the inability to provide for
surface tissue protection by cooling. Provision of surface tissue at
physiologic temperatures, while causing deep musculo-skeletal heating,
would broaden the applications for medical diathermy in varied disease
states (sprains, strains, arthritis, etc.).
Various ways of heating body tissue have been proposed. Localized
application of heat by use of electromagnetic energy derived from radio
frequency generators has been conducted in the ranges of ultrasonic
frequencies 0.8-1.0 MHz, shortwave frequencies 13-27 MHz and microwave
frequencies 915-2450 MHz. Most relevant to (but not a limitation of) the
present invention is the shortwave frequency, which is described in said
publication on Radio Frequency Therapy. Shortwave generates less heat in
fat with deep penetration and is the longest band width (13.56 MHz)
approved by the Federal Communications Commission for medical use.
One of the problems encountered in localized application of radio frequency
waves to tissue is that of severe burning of skin and subcutaneous
tissues. Surface cooling in a microwave field at 915 MHz has been proposed
by using a microwave antenna in non-surface contact with the skin and
blowing cooled air onto the skin through the space between the radio
frequency emitter and the skin. Another cooling method is described in
application of heat to muscle in human subjects with a 915 MHz microwave
contact applicator in which coolant was circulated through a dielectric
cooling plate of a microwave applicator in which the emitter was an
antenna in a tuned cavity type applicator, the emitter antenna being
relatively widely spaced from the dielectric cooling contact plate.
(Archives of Physical Medicine and Rehabilitation, March 1970, pages
143-151, "Evaluation of a Microwave Contact Applicator," Lehman et al and
"Muscle Heating in Human Subjects With 915 MHz Microwave Contact
Applicator," LeLateur et al.)
SUMMARY OF THE INVENTION
The present invention relates to a novel electrode means for use in the
localized application of heat to tissue without damage to living tissue.
The invention contemplates an electrode means so constructed and operable
to provide deep heating, where necessary, by emitting shortwave or
microwave frequencies to establish an electromagnetic field with the tumor
bearing tissue therein and to provide adequate cooling of skin and
subcutaneous tissues surrounding the tumor bearing tissue, or to establish
an electromagnetic field to provide for deep heating in musculoskeletal
disease states or conditions.
This invention particularly contemplates an electrode means for interfacial
contact or close proximity with the skin surface of a body having a
cancerous tumor wherein a shortwave radio frequency is generated in the
nature of 13.56 MHz, and wherein the electromagnetic field is generated
between two opposed electrodes embodying this invention disposed on
opposite sides of the body with the tumor bearing tissue therebetween. An
impedance matching circuit is connected with the electrode means and the
radio frequency generator so that the impedance of the body portion lying
between the electrodes and the impedance of the generator may be suitably
matched. An electrode acting as a microwave antenna could impart a
directional electromagnetic field from a single electrode directed at the
body part. Each electrode means is provided with a chamber through which
cooling fluid is circulated at a selected rate of flow to maintain the
wall of the chamber in contact with the skin of the patient at a selected
temperature. The proximity and, sometimes preferred, direct contact of the
electrode wall with the skin surface minimizes possible changes in the
impedance of the body portion caused by changes in the electromagnetic
field and also acts as a heat transfer means for maintaining the skin and
subcutaneous tissue therebeneath in a suitably relatively cooled state
while a selected dosage of heat is being applied to tumor bearing or deep
musculo-skeletal tissue. The invention contemplates that the wall of the
electrode means may be suitably configured to closely fit to the contour
configuration of the body member against which it is placed.
In another example of the electrode means, one wall is made of a flexible
compliant metallized conductive material so that the wall may be readily
adjusted to the surface configuration of the body member under pressure of
the circulating cooling fluid. When the electrode means includes a
relatively non-compliant, thin section metal wall, the electrode means may
be pressed against the surface of the body member to conform the skin to
the configuration of the electrode wall.
In a further example, virtually all portions of the electrode means are
flexible, cooling being provided by a spiral of flexible tubing in which
coolant is circulated and which overlays flexible metallized material.
Both tubing and flexible material make close surface contact and conform
and yield to body surface contour.
To increase surface contact on very irregular skin surfaces, another
example of the invention contemplates use of a thin flexible pliant bag
filled with electrolyte solution and placed between the surface and an
electrode means of this invention. The electrolyte solution then becomes
an effective extension of the electrode means and itself emits
electromagnetic waves. The thin bag filled with static electrolyte
solution is cooled by contact with the electrode means.
In all examples, means are provided for a second and peripheral cooling
chamber of non-metallic material to provide for surface cooling of tissue
peripherally adjacent to, but not contacted by, the electrode emitting
surface. This provides cooling of adjacent peripheral tissue heated by the
near electrode field which spreads peripherally outwardly from the
emitting electrode edge.
The primary object of the present invention therefore is to provide a novel
electrode means for localized application of heat by electromagnetic
energy to tumor bearing and deep musculo-skeletal tissue.
An object of the present invention is to provide an electrode means adapted
to be secured in direct interfacial contact with the surface of the body
being treated to minimize changes in impedance between the electrode
means.
Another object of the invention is to provide a novel electrode means
including cooling means for control of tissue temperature in the
electromagnetic field.
A further object of the present invention is to provide an electrode means
having a surface for direct uniform contact with the surface of the skin
of a body and wherein the surfaces in contact are substantially conformed
one to the other.
A still further object of the present invention is to provide an electrode
means wherein a cooling chamber is formed, and cooling fluid is circulated
through the cooling chamber or tubing to provide transfer of heat through
a wall of the chamber to adjacent tissue of a body for maintaining a
selected temperature of said adjacent tissue during localized heating of
an internal tumor bearing tissue or the treatment of musculo-skeletal
disease conditions.
Still another object of the present invention is to provide an electrode
means having a flexible electrode wall or a completely flexible electrode
means readily conformable to the configuration of the surface of skin of a
patient to which the electrode is applied.
Still another object of the invention is to provide an electrode means
having a flexible electrode wall as mentioned above wherein said wall
forms part of a cooling chamber and wherein cooling fluid in said chamber
imposes fluid pressure on said wall to conform said wall to the
configuration of the skin surface of the patient.
Still another object of the invention is to provide for means of cooling
tissue adjacent to the electrode, not contacted by the electrode but
subjected to heating by the effects of the near electromagnetic field.
A general object of the invention is to provide a novel electrode means
including circulating cooling means whereby the skin and subcutaneous
tissue of a body are preferentially cooled in the presence of heating
effect of coincident radio frequency waves while said radio frequency
waves heat tumor bearing tissue to a sufficient temperature to cause
necrosis or regression of the tumor tissue, or heat deep musculo-skeletal
tissue for its theraputic benefit in disease states or conditions.
The invention further contemplates electromagnetic heating of tissue at
relatively great depths with control of superficial heating of living
tissue and for the non-invasive treatment of relatively deeply located
tumor or otherwise diseased tissue.
The invention specifically contemplates an electrode construction for
transmitting electromagnetic energy and adapted to be connected to a power
source in which the electrode construction includes an electrode body
having an emitting surface adapted to be placed in at least close
proximity, if not direct contact, with a surface of a body being treated
and means for cooling the emitting surface and adjacent body surfaces. The
cooling means includes means for circulating cooling fluid in heat
transfer relation to the emitting surface and to the body surface.
The invention further contemplates another embodiment wherein a flexible
emitting surface is contained within a flexible bag having inlet and
outlet fittings for cooling fluid and also containing porous flexible
material within the bag to position and hold the flexible emitting surface
in contact with the wall of the bag positionable against a skin surface.
Many and other objects and advantages of the present invention will be
readily apparent from the following description in which the drawings
illustrate exemplary embodiments of an electrode means of this invention.
IN THE DRAWINGS
FIG. 1 is a schematic view of a patient having electrode means of this
invention applied to his body, the electrode means being schematically
connected to an impedance matching circuit and power source for emitting
radio frequency waves through the electrode means to create an
electromagnetic field between the electrode means, and also being
connected to a controllable cooling means.
FIG. 2 is a fragmentary schematic view similar to FIG. 1 showing an
electrode means of this invention used to emit waves of microwave
frequency for particular use in muscular skeletal heating.
FIG. 3 is an end view of an electrode means shown in FIG. 1, the view
partly in section and fragmentarily showing strap securing means.
FIG. 4 is a top view of FIG. 3 taken in the plane indicated by FIG. IV--IV
of FIG. 3, the view being partly in section to show circulation of cooling
fluid through the electrode means.
FIG. 5 is an end view similar to FIG. 3 of an electrode means of the
invention as shown in FIGS. 3 and 4 used with a separate bag containing
electrolyte solution.
FIG. 6 is a top plan view similar to FIG. 4 showing a modification of the
electrode means of the invention shown in FIGS. 3 and 4.
FIG. 7 is a fragmentary enlarged vertical sectional view taken in the plane
indicated by line VII--VII of FIG. 6.
FIG. 8 is a vertical sectional view of an electrode means embodying a
modification of the invention showing a flexible wall and flexible
emitting surface.
FIG. 9 is a sectional view similar to FIG. 8 and shows a modification of
the invention in which two flexible walls define inner and outer separate
cooling chambers, the emitting surface being on the wall of the inner
chamber.
FIG. 10 is a top plan view of a still further modification of the electrode
means of this invention embodying a spiral tube for cooling fluid.
FIG. 11 is a vertical transverse sectional view of FIG. 10, the section
being taken in the plane indicated by line XI--XI of FIG. 10.
FIG. 12 is a top plan view of an electrode means embodying a still further
modification of this invention in which additional outer turns of tubing
providing cooling fluid are provided.
FIG. 13 is a sectional view taken in the vertical transverse plane
indicated by line XIII--XIII of FIG. 12.
FIG. 14 is a sectional view similar to FIGS. 11 and 13 and illustrates a
further modification of the flexible wall of the emitting surface, in this
example a flexible screen.
FIG. 15 is a vertical transverse sectional view of another embodiment of
this invention in which the emitting surface is contained within a
flexible bag through which cooling fluid is circulated.
FIG. 16 is a chart illustrating internal heating of an animal lung tumor
while maintaining skin and subcutaneous tissue at substantially cooler
temperatures, the chart being illustrative of heating and cooling effects
obtained by electrode means of this invention.
FIG. 17 discloses two charts showing the effect of electrode heating with
and without surface cooling means, the chart at the left being without
cooling means and the chart at the right being with surface cooling means.
FIG. 18 is a chart illustrating internal heating of a human tumor while
maintaining skin and subcutaneous tissue at substantially cooler
temperatures.
Referring generally to FIG. 1, a patient is illustrated having a body 10
with a leg 11 to which is externally applied electrode means 12 embodying
this invention. In the illustration, it is assumed that the thigh of leg
11 has an internal body portion, indicated in dotted lines 14, which
comprises tumor bearing tissue or diseased musculo-skeletal tissue.
Surrounding body portions of non-tumor bearing tissue or normal tissue
include subcutaneous tissue 16 (FIG. 3) and skin 15 having external skin
surfaces. As noted hereinabove, blood flow within tumor bearing tissue 14
is substantially less than blood flow through surrounding normal tissue
17. The effect of heating normal tissue increases blood flow through
normal tissue and protects against the effects of the heat. Blood flow is
substantially less in the tumor bearing tissue 14 which acts as a heat
reservoir and therefore the temperature of the tumor bearing tissue will
more rapidly rise than that of the surrounding normal tissue. This
characteristic of tumor bearing tissue is fully described in the article
by H. H. Leveen, "Journal of the American Medical Association" 235; 2198,
1976, noted above. LeVeen found that tumor blood flow under heat
conditions was only 2-15% that of surrounding tissue. In musculo-skeletal
disease states, the direct effect of deep heat on diseased tissue may
augment healing.
The tolerance of normal tissue (fat, muscle, skin) to heat depends upon the
amount of heat, the time during which the tissue is subjected to heat, as
well as the amount of power used to generate the radio frequency.
In the apparatus of the present invention, a power source 18 may comprise a
suitable known shortwave or microwave transmitter or generator capable of
emitting radio frequencies in the order of 13.56 Mhz to 2450 MHz and
having a power rating of up to 3 kilowatts. Power source 18 is suitably
electrically connected to the electrodes 12 through electrical circuitry
which includes an impedance matching circuit 19 in order to precisely and
closely match the impedance of the material of the body portion between
the electrodes with the generator. The conductivity of the material of the
body portions will vary depending upon whether such body materials have
high or low water content, and the amount of skin, muscle or fat which are
in the body portions. For example, Geddes and Baker (Medical and Biology,
Volume 5, pages 271-293, 1967) describes the following conductivity or
resistance of materials comprising human skin to be 289 ohms per
centimeter, and human fat to be in the range of 2000 to 5000 ohms per
centimeter.
In the example of electrode means 12 shown in FIGS. 1, 3, 4 electrode means
12 comprises a top wall 20, a bottom wall 21 and side or edge walls 22
which extend peripherally around the electrode means. The walls may be
made of thin metal having characteristics of effective and efficient
transfer of heat and also electrical conductivity. Examples of thin metal
having such characteristics are phosphor bronze and beryllium copper,
which may be obtained in wall thicknesses of from 0.005 to 0.25 inches.
Such walls of thin metal may be readily formed in a curved shape for
general correspondence with the configuration of the external surface of a
body with which the bottom wall 21 may be placed in contact.
The top, bottom and side walls form a hollow chamber for circulation of
cooling fluid. The spacing of the top and bottom walls may be 0.25 inches.
The spacing may be more or less depending upon the design criteria for the
electrodes and its specific use.
Bottom wall 21 has a surface generally contoured to the skin surface to
provide uniform interfacial direct contact with the skin surface 15 over
the entire surface area of wall 21. The surface area of wall 21 may vary
between 50-500 square centimeters and it is understood that such surface
area variation will also depend upon the configuration of the body portion
and external skin surface to which the electrode means is directly
applied. Direct skin contact by securing electrodes 12 on opposite sides
of the internal body portion 14 to be treated with a non-conductive strap
25 applied over the electrodes. Such non-conductive or dielectric strap is
fragmentarily shown in FIG. 2 and not only secures the electrodes in fixed
position on the body, but also may be sufficiently tightened to press the
bottom walls 21 of the electrode means into intimate direct contact with
the skin surface 15 and to cause uniform contact of the entire surface
area of wall 21 with the skin. Such fixed, uniform contact of a
predetermined area of bottom wall 21 with the skin surface is of
importance in maintaining balanced electromagnetic fields at each
electrode as later described.
Means for uniform cooling of the electrode means 12 includes suitably
arranged partitions 24 in chamber 23 to cause cooling fluid to circulate
in heat transfer relation with the bottom wall 21 of the electrode means
12. The cooling means includes an inlet fitting 26 and an outlet fitting
27 which are adapted to be connected to suitable tubes or conduits 28 and
29 for conducting and circulating cooling fluid into and out of the
electrode means 12. The inlet fitting 26 may be connected to a water line
readily available in hospitals, clinics and elsewhere, or to a suitable
closed circuit refrigeration unit to provide selected cooling, for
example, (0.degree. C.) as required. The discharge outlet 27 and conduit
29 may be connected to a suitable drain or to a suitable reservoir for
conserving water circulated through the electrodes. It will also be
understood that the cooling fluid may be provided by any suitably cooling
fluid supply source at a preselected temperature and may be circulated by
a suitable pump means (not shown) for causing sufficient flow of the
cooling fluid to produce the desired cooling effect on the body portions.
The selected rate of flow of cooling fluid will depend upon the
temperature of the cooling fluid available, on the desired temperature of
the skin and subcutaneous tissue, the depth of penetration of the heat
applied to the internal body portions by the radio frequency waves, and
the length of time of the treatment.
Control of the circulation of the cooling fluid may also be dependent upon
the observation of precisely located needle-type thermometers placed in
the body at critical locations and depth to determine internal
temperatures of the normal tissue and tumor bearing tissues. Such
needle-type thermometers may be of any suitable manufacture and are
accurate to 0.1.degree. C. and may be applied by using standard medical
catheters.
The cooling fluid has been exemplified above as being tap water. For
precise control and under certain circumstances, it may be desirable to
use other types of liquid or gas which would permit effective efficient
regulation of the transfer of heat from the skin surfaces and subcutaneous
tissue to the cooling fluid through the bottom wall 21 of the electrode
means. The type of cooling fluid used may also depend upon the length of
time of the treatment, to the amount of power used during treatment, and
to the surface temperature required.
The circuitry illustrated in FIG. 1 is exemplary only since the impedance
matching circuit may be a conventional circuit. It is important to note
that the impedance of the material of the body portions between the
electrodes 12 may be determined and matched by placing the electrode means
on the skin surfaces in opposed relation with the tumor bearing tissue
therebetween and applying a suitable minimum amount of power; for example,
50 watts to the circuit. A pair of directional power meters are employed
in the circuit, one of which reads the reflected power and the other of
which reads the incident power. The circuit includes means for adjusting
the circuit to minimize reflection and then to further adjust the circuit
to bring it into a resonance condition. It is important that the
electromagnetic field for each electrode means 12 should be equalized and
such fields are measured and adjusted to provide the desired balance. It
will thus be apparent that while the impedance matching circuitry may be
conventional, the direct interfacial contact between the skin 15 and the
surface of bottom wall 21 remains unchanged during treatment and therefore
the physical conditions minimize chances of unbalancing of the matched
impedances which might create a condition causing burning of the skin
surface or unwarranted heating of subcutaneous tissue.
Similar advantages of a cooled, surface electrode would apply to microwave
frequencies, where a single electrode means 12a (FIG. 2) might be used as
a microwave antenna. In such use the power generator, impedance matching
circuit, and other parts would be modified and changed for the effective
emission of microwaves.
In treatment of a tumor bearing tissue such as internal body portions 14,
the location of the tumor bearing or otherwise diseased tissue is
determined by known procedures. Electrode means 12 are placed on opposite
side of the internal body portion 14 and the circuitry is placed in
balance as above described so that the material of the body portions
between the electrode means and its impedance is balanced with the
impedance of the generator and the electrical fields at the electrodes are
in balance. When the radio frequency waves are generated by the power
source and transmitted by the electrode means 12 into the body portions
between the electrode means, internal heating of the body portions will
occur in a manner similar to well-known diathermy, shortwave and microwave
processes. The amount of power used in such treatment depends upon the
emitting area of the electrode means and the power of the generator.
Heating of the tumor bearing or otherwise diseased tissue and the normal
tissue surrounding the tumor bearing tissue is monitored by the use of a
plurality of needle-like thermometers, as above-described. The cooling
fluid is controlled so that sufficient flow of cooling fluid is provided
through the chambers of the electode means 12 to maintain the skin and
subcutaneous tissue at selected temperatures. The length of application of
shortwaves to the tumor bearing or otherwise diseased tissue and the
dosage thereof may be selected in accordance with the specific conditions
of the patient.
It will be understood that the construction of electrode means 12, as
described above, together with the control of cooling fluid and the use of
a 3 kilowatt generator or a generator of selected power, provides deep
penetration with heat, up to 9 centimeters, such as internal body portion
14, while maintaining the skin surface and subcutaneous tissue at a
substantially lower temperature to prevent damage thereto or burning of
the skin surfaces.
Experiments on animals and humans have been conducted and an example of
such temperature differential using the electrode means of this invention
is illustrated in the chart of FIG. 15. The chart illustrated on FIG. 15
was evolved from treatment of a lung tumor in a dog by electrode means and
apparatus embodying the present invention as described above. It is known
and it will be understood that tests have indicated that certain portions
of the body protectively adapt themselves to heat more than other portions
of the body, such portions being in the case of an animal, such as a dog,
the heart, lung and liver.
With reference to the chart shown in FIG. 16, the temperature in degrees
centigrade is shown on the Y axis, and the time of dosage or treatment on
the X axis. Before treatment it will be noted that the temperature of the
skin is about 29.degree. C., that of the subcutaneous tissue about
30.degree. C., and that of the lung, including lung tumor, about
36.degree. C. Upon commencing treatment, which begins with the circulation
of the cooling fluid, the temperature of the skin and subcutaneous tissue
dropped to 20.degree. C. and 24.degree. C., respectively, as a result of
the circulation of the cooling fluid. After one minute, the generator was
started with only partial power and for the next three minutes the
temperature of the skin and the subcutaneous tissue increased as shown on
the chart. At four minutes additional power was introduced whereby the
temperature of the lung and lung tumor increased substantially. It should
be noted that after seven minutes the lung tumor reached 51.degree. C. and
maintained this temperature until 13 minutes had elapsed and then for the
next three minutes while power was on, only decreased by a half a degree
centigrade. Power was turned off at 16 minutes, and from that point on the
temperature of the lung tumor decreased as shown on the chart. The area of
the chart sectioned under the line illustrating the temperature and time
during which the temperature is sufficiently high to destroy the cancerous
tissue. The chart also indicates that the lung reaches a temperature of
only 42.5.degree. C., at which temperature the lung can survive because of
its protective heat adaptive characteristic. Of significant importance is
the cooling effect of the cooling fluid on the skin and subcutaneous
tissue in which the subcutaneous tissue reaches a top temperature of only
36.degree. C. and the skin of only 30.5.degree. C., both of which
temperatures are substantially below temperatures at which normal living
tissue would be damaged or destroyed. It will be understood that the
illustration of FIG. 16 shows the results of the application of the
electrode means of this invention on an animal; that is, a dog, in order
to illustrate the temperature results achieved by the electrode means of
the present invention.
The two charts of FIG. 17 compare the degree of surface temperature
comprised of skin and subcutaneous tissue with the degree of deep muscle
heating, without and with surface cooling provided. The small chart at the
left of FIG. 17 shows that without surface cooling the skin reaches an
injurious level of surface heat indicated as well over 50.degree. C. The
subcutaneous tissue reaches an injurious level of heat of about 45.degree.
C. Meanwhile, the deep muscle portion of the body at 5 centimeters depth
shows heating only to about 41.degree., 42.degree. C.
In the chart on the right part of FIG. 17, the beneficial effect of surface
cooling is clearly indicated and even greater deep heat to 9 centimeters
is accomplished with the surface at physiologic temperatures. As shown in
this chart, with surface cooling the skin is maintained at a fairly
uniform temperature of below 20.degree. C.; the subcutaneous tissue is at
first cooled and then gradually rises to about 40.degree. C. after 30
minutes, and the deep (9 centimeters) muscle heat gradually rises after 10
minutes to about 41.degree., 42.degree. C.; the deep muscle temperature
recedes slightly and then increases to about 42.degree. to 43.degree. C.
after 30 minutes. This chart indicates that surface cooling and deep
heating is applicable to deep musclo-skeletal disease states.
The chart of FIG. 18 discloses heating and cooling effects of an electrode
means of this invention during treatment of a 15.times.15.times.15
centimeter human chest muscle tumor and overlying skin and subcutaneou
tissue, with pretreatment ambient temperatures of 41.degree. C. Prior to
treatment with radio frequency waves the body was subjected to cooling for
about 10 minutes during which the temperature of the skin was reduced to
about 17.degree. C. and temperature of the subcutaneous tissue reduced to
about 32.degree. C. The temperature of the tumor during this period
remained at about 41.degree. C. Upon initiation of treatment of energizing
the electrode means of this invention, the chart indicates for a period of
35 minutes of exposure to electromagnetic energy, the temperature of the
skin increased slightly to 20.degree. C. and that of the subcutaneous
tissue did not exceed 38.degree. C., these temperatures being relatively
low and physiologic temperatures. Meanwhile the human tumor was heated to
greater than 45.degree. C. for 30 minutes and as the chart indicates the
tumor reached 63.degree. C. at the end of 35 minutes of treatment. Such an
effective degree of tumor heating with preservation of normal tissue at
relatively low physiologic temperatures (less than 40.degree. C.) has, to
my knowledge, never been achieved.
In FIG. 6, a modification of the electrode means 12 is illustrated. The
central portion of FIG. 6 includes an electrode construction identical to
that described in FIGS. 3 and 4, and wherein chamber 23 has a bottom wall
21, partition walls 24, a top wall 20 and edge walls 22; inlet and outlet
fittings 26 and 27 are similarly provided and connected to suitable fluid
conducting lines. Inlet fitting 26 may be connected to a fluid source 26a.
To provide surface c | | |
