U.S. patent number 3,838,242 [Application Number 05/256,714] was granted by the patent office on 1974-09-24 for surgical instrument employing electrically neutral, d.c. induced cold plasma.
This patent grant is currently assigned to Hogle-Kearns International. Invention is credited to Robert G. Goucher.
United States Patent |
3,838,242 |
Goucher |
September 24, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
SURGICAL INSTRUMENT EMPLOYING ELECTRICALLY NEUTRAL, D.C. INDUCED
COLD PLASMA
Abstract
A surgical instrument (plasma scalpel) generates an electric
field plasma in a carrier gas for cutting and/or cauterizing
tissue. The instrument includes a tubular conductor for carrying
both current and gas to an anode. The gas flows from the tubular
conductor, around the surface of an anode, and thence through an
annular cathode. The electric field between the anode and cathode
excites the gas to a plasma state, and the excited gas then flows
in a directed stream through the cathode and out the end of the
instrument. The tubular conductor is surrounded by a cooling jacket
which concomitantly serves as an electrical conductor to the
cathode. A dielectric sheath may be provided over the cooling
jacket. This sheath may be overlaid with a conductive skin
connected to earth ground to prevent an excessive electric charge
from accumulating thereon. The conductive skin is preferably
grounded through a circuit breaking device to cut off all power to
the instrument if the potential of the skin differs greatly from
the potential of the cathode.
Inventors: |
Goucher; Robert G. (Salt Lake
City, UT) |
Assignee: |
Hogle-Kearns International
(Salt Lake City, UT)
|
Family
ID: |
22973305 |
Appl.
No.: |
05/256,714 |
Filed: |
May 25, 1972 |
Current U.S.
Class: |
219/121.36;
128/908; 219/69.19; 219/75; 219/121.54; 313/231.01; 606/22; 606/27;
606/40 |
Current CPC
Class: |
H05H
1/32 (20130101); A61B 18/042 (20130101); Y10S
128/908 (20130101) |
Current International
Class: |
A61B
18/00 (20060101); H05H 1/32 (20060101); H05H
1/26 (20060101); B23k 009/04 () |
Field of
Search: |
;219/121P,75,69S
;128/303.1,303.14 ;315/111 ;313/231 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reynolds; Bruce A.
Attorney, Agent or Firm: Trask; David V. Bojanowski; Richard
F.
Claims
I claim:
1. A surgical instrument for generating an electrically neutral,
D.C.-induced, cold plasma, comprising:
an elongate body member with a hollow interior;
nozzle means contained within and at the forward end of said body
member, said nozzle means including a nonconductive entry portion,
a nonconductive throat portion and a conductive exit portion formed
as an annular cathode element;
conductor means for connecting said cathode element to the negative
side of a D.C. power supply;
gas supply means extending from communication with said entry
portion of said nozzle, through said hollow interior and out the
rearward end of said body member for connection to a source of
gas;
anode means fixed to the forward end of said gas supply means and
disposed within said entry portion of said nozzle in coaxial
arrangement with said cathode such that gas delivered to the gas
supply means flows around said anode, through the nozzle, and out
through the cathode; and
conductor means for connecting said anode to the positive side of a
D.C. power supply.
2. An instrument according to claim 1, wherein said gas supply
means includes a tube made of electrically conductive material,
means are provided to electrically insulate said tube from said
body, and the wall of said tube serves as the conductor means for
connecting said anode to said power supply.
3. An instrument according to claim 1, wherein said body comprises
an annular cooling jacket and including means for delivering cool
liquid thereinto and for removing warmed liquid therefrom.
4. An instrument according to claim 3, wherein said cooling jacket
is made of electrically conductive material and serves as conductor
means for connecting said cathode to said power supply.
5. An instrument according to claim 4, wherein said gas supply
means includes a tube made of electrically conductive material,
means are provided to electrically insulate said tube from said
body, and the wall of said tube serves as the conductor means for
connecting said anode to said power supply.
6. An instrument according to claim 5, wherein said anode forms a
closure at the end of said tube and perforations are formed through
the wall of said tube behind said anode so that carrier gas is
forced through said perforations and said perforations are disposed
within a gas entry element abutting the entry portion of said
nozzle and openly communicating therewith.
7. An instrument according to claim 6, wherein the gas entry
element includes a plenum chamber in open communication with said
perforations and longitudinal parts openly connecting said plenum
chamber with said entry portion of said nozzle.
8. An instrument according to claim 5, wherein a protective sheath
is provided about said electrically conductive cooling jacket and
said sheath includes a lining of dielectric material.
9. An instrument according to claim 8, wherein said protective
sheath further comprises a metallic skin which is fixed over said
dielectric lining and is insulated thereby from said jacket.
10. An instrument according to claim 9, wherein said skin is
connected to earth ground.
11. An instrument according to claim 10, wherein said skin is
connected to ground through a safety circuit, the elements of said
circuit being actuated by differences in potential between earth
ground and the cathode to cut the supply of electric power to said
instrument.
Description
RELATED APPLICATIONS
Commonly assigned, copending application Ser. No. 79,840, filed
Oct. 12, 1970, now abandoned, discloses and claims methods and
apparatus for plasma surgery. According to that application, a cold
plasma is established and attenuated to a small cross section. This
plasma is applied to tissue to produce an incision. Commonly
assigned, copending application Ser. No. 253,494, filed May 15,
1972, claims the additional discovery that an electrically neutral,
D.C.-induced cold plasma is especially useful for surgical
applications, and discloses surgical apparatus suitable for
producing such a plasma. The present application discloses such
apparatus more fully and claims the same.
BACKGROUND OF THE INVENTION
1. Field
This invention relates generally to plasma scalpel devices which
emit a flow of plasma for cutting or cauterizing tissue. It is
specifically directed to such a device particularly useful for
producing electrically neutral, D.C.-induced plasmas.
2. State of the Art
The use of D.C. arc plasma for surgery is suggested by U.S. Pat.
No. 3,434,476, which discloses and claims apparatus intended for
use as a surgical scalpel. The apparatus thus disclosed is
apparently incapable of producing plasmas which are not
substantially at thermal equilibrium. This instrument is reported
to be unsafe for actual clinical use because it tends to char
tissue. It is recognized in the disclosure of the aforementioned
application Ser. No. 79,840 that plasmas of metastable noble gas
are preferred for surgical applications. The apparatus there
disclosed produces rf-induced plasmas which, although cold, are not
electrically neutral.
As used hereinafter, the term "cold plasma" includes all plasmas
which evidence a low wall-heating effect, whether or not such
plasmas exhibit the appearance and/or other physical
characteristics normally associated with the specific cold plasmas
and glow discharge phenomena heretofore recognized in the art. The
term refers generally to plasmas in substantial thermal
nonequilibrium; i.e., those which exhibit a much lower tactile or
gas temperature than the temperature equivalent of the energy level
of the free electrons in the plasma.
SUMMARY OF THE INVENTION
The present invention provides a surgical instrument capable of
producing electrically neutral, D.C.-induced cold plasmas in a form
suitable for surgical applications. The instrument includes, inter
alia, an elongate body in which is disposed a conduit made of
electrically conductive material. The conduit concurrently serves
to carry an electric current and a stream of surgical gas to an
anode near the forward end of the instrument. The carrier gas
passes around the anode, through a constrictor nozzle and then
through an annular cathode which is fixed coaxially with respect to
the anode to the forward end of the instrument. The electric field
established between the anode and cathode generates plasma in the
carrier gas which leaves the annular cathode in a directed stream.
A cooling jacket surrounds the conduit and serves concomitantly as
an electrical conductor to the cathode. Means are provided to
convey cooling liquid into and from the jacket. In one embodiment
of the invention, a sheath which includes a dielectric lining
overlaid by a metallic skin is provided over the cooling jacket. A
safety circuit may be connected to the skin to prevent the
development of excessive potential differences between the cathode
and the outer skin.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be better understood by referring to the
following description and appended drawings which are offered by
way of illustration and not in limitation of the invention, the
scope of which is defined by the appended claims and equivalents.
Specific reference herein to details of the illustrated embodiment
is thus not intended to restrict the scope of the claims, which
themselves recite those features regarded as essential to the
invention.
In the drawings:
FIG. 1 is a pictorial view, partially cut away and in section, of a
preferred embodiment of the plasma scalpels of the invention;
FIG. 2 is a pictorial view of the scalpel of FIG. 1 slightly
modified;
FIG. 3 is a side view in section of the scalpel shown in FIG.
2;
FIG. 4 is an exploded detail, in section, of structure at the
forward end of the scalpel of FIGS. 1, 2 and 3;
FIG. 5 is a schematic diagram of a safety circuit for use with the
scalpel of FIGS. 2 and 3; and
FIG. 6 is a detail in cross section of a connector for use with the
illustrated instruments.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The illustrated instrument 10 has an elongate body comprising a
cooling jacket generally designated 12 in which water or other
cooling liquid is circulated. The illustrated jacket 12 is a
tube-within-a-tube arrangement having a cylindrical inner wall 14
spaced coaxially from a cylindrical outer wall 16 by respective,
radially extending end walls 17 and 18. Together, the walls define
an enclosed annular space. Preferably, the walls of the jacket are
made of an electrically conductive material.
An inlet conduit 21 connects into the jacket at an aperture 23
formed through the outer wall 16 near the forward end of the
instrument, and an outlet conduit 24 connects into the jacket
through an aperture 26 near the rear of the instrument. Cooling
liquid flows through the inlet conduit 21 into the jacket, thence
circulates the length of the jacket before exiting therefrom via
outlet conduit 24. The flow direction is indicated by the arrows in
FIG. 1. Preferably, the conduits 21, 22 are rigid. Flexible tubes
26 (shown in FIG. 2) may be connected to the distal ends of the
conduits so that the instrument can be freely moved about.
FIGS. 2 and 3 illustrate a configuration of the instrument with an
insulating sheath 30 secured about the cooling jacket 12. The
sheath is connected to chassis or earth ground and is isolated from
the cathode which is normally at D.C. ground potential. Such
isolation is desirable because it is possible for the D.C. ground
potential to shift significantly from chassis ground potential. The
most likely discharge path in that event would be through the body
of either the surgeon or the patient. Aside from the sheath, the
instrument shown in FIGS. 2 and 3 is identical to that shown in
FIG. 1. The sheath 30 may include a dielectric lining 31 overlaid
with a metallic skin 32. The skin 32 provides a protective cover
which is readily sterilized for antiseptic use. The dielectric
lining 31 may be heat-shrinkable plastic fitted to the cooling
jacket as shown. The metallic skin 32 may comprise one or more
coatings of metal applied by well-known dipping, spraying or
electroplating techniques. The outer surface of the skin is
desirably of nickel or similar metal acceptable for hospital
use.
Ordinarily, the grounded metallic skin of the sheath provides
adequate protection against accidental discharges. Nevertheless,
the safety circuit of FIG. 5 is desirably incorporated in the power
supply for the scapel. This circuit automatically shuts off the
power supply and connects the D.C. and chassis grounds in response
to shifts in their relative potentials. The hazards of sparking and
shocking are thereby eliminated.
The particular configuration of the sheath is of no consequence so
long as the instrument can be firmly held. However, the overall
shape and dimensions of the instrument are important. The utility
and acceptance of any surgical instrument depends largely upon the
facility with which it can be manipulated by a surgeon. An
important aspect of the presently claimed instrument is that it can
be constructed on a scale comparable to an ordinary scalpel, yet
generate a reliable and controllable plasma suitable for surgical
use.
Preferably, both cylindrical walls of the cooling jacket 12 serve
as conductors for carrying an electric current to the cathode 86 of
the instrument. However, the term "cathode conductor" as used
hereinafter particularly refers to the inner cylindrical wall 14.
This cathode conductor, in turn, coaxially surrounds a metallic
tube 33 which carries an electric current to the anode 75 of the
instrument. This metallic tube 33 is referred to hereinafter as the
anode tube or anode conductor. The cathode conductor is insulated
from the anode conductor, and together the two conductors comprise
a coaxial electrical line. In the illustrated embodiment, the
conductors are finitely spaced apart and air therebetween effects
an electrical insulation.
A bushing-like insulator member 37 made of dielectric material is
fitted around the anode tube 33 and spaces it from the cathode
conductor 14 at the rear of the instrument. The bushing 37 has a
circumferential shoulder 38 of greater diameter than the cathode
conductor 14 abut the end of that conductor. The anode tube
includes an integral collar 41 which abuts the forward end of the
bushing 37. A cap 39 is threaded or otherwise releasably fixed over
the rear of the jacket 12 and has a central aperture 43 formed
therethrough which is of such size as to allow the end of the anode
conductor and a portion of the bushing 37 to extend therethrough.
The shoulder 38 of the bushing is, however, clamped between the
rear of the jacket 12 and the cap 39. Consequently, the cap secures
in position the bushing, which in turn abuts the collar 41 to
prevent the anode conductor from slipping rearward.
The cap 39 is made of an electrically conductive material and
serves as a lead to the cathode conductor. An electrical wire, not
shown, connects the cap to D.C. ground potential. The cap 39 is
insulated from the anode conductor by the bushing 37.
While the wall of the anode tube 33 conducts an electric current to
the anode of the instrument, the interior of the tube provides a
closed channel for carrying a stream of gas to the tip of the
instrument. The gas is supplied to the tube through a flexible hose
51 fitted to its rearwardly protruding end, entering through side
ports 54. The hose houses a current-carrying wire 53 which may or
may not be insulated. The wire 53 is connected, e.g., by soldering,
to the wall of the anode tube 33.
The emote end 51a of the hose 51 is connected to a gas supply
source (not shown) by connector assembly generally designated 57 in
FIG. 6. THe connector includes a rigid block 59 having intersecting
channels 61 and 62 formed therein. The end of the hose 51 is
connected into channel 61 by a threaded adapter 64. The wire 53
extends through the channel 61 to another adapter 66 for connection
to a power source (not shown) through an insulated wire 68. A
fitting 69 leads from the connector block 59 to the gas source. The
connector block may, of course, be electrically insulated from both
the power source and the gas source.
Referring to the instrument proper 30, the forward end of the anode
tube 33 is spaced from the inner wall of the jacket by an annular
spacer 71 (see especially FIG. 3) made of insulating material. The
spacer lies wholly somewhat behind the forward end of the anode
tube and effects a seal between the anode tube and the inner wall
of the jacket 12 to prevent gas which leaves the anode tube from
flowing back into the instrument. The spacer may be epoxied or
otherwise fixed to the anode tube. Ahead of the spacer 71, the wall
of the anode tube is perforated and gas carried inside the tube can
escape therefrom through the perforations 72.
An electrically conducting tip 75 is secured to the forward end of
the anode tube and is, in fact, the anode of the instrument.
Preferably, this tip prevents gas from exiting out the anode tube
end and, consequently, the total gas flow is out the perforations
72 in the tube wall.
A cylindrical, gas entry member 76, which is formed of a dielectric
material, is fitted around the anode 75. The gas entry member 76
insulates the carrier gas from the inner wall of the jacket, and
holds the anode in proper position with respect to the flowing gas.
Accordingly, the member 76 has an enlarged central recess 77 formed
in its rearward end; an axial channel extends from the recess to
the forward end of the member and closely surrounds the anode 75.
With the instrument assembled, the rearward end of the member 76
abuts the forward end of the spacer and the recess 77 forms a small
plenum for the gas flowing out of the anode tube 33. A plurality of
gas ports 79 extend from the recess to the forward face of the
member 76 and carry substantially all of the gas to the tip of the
anode 75. These gas ports 79 are desirably formed to impart a
helical movement to the gas exiting therefrom.
Ahead of the member 76, but still within the jacket, is a
cylindrical constrictor or nozzle entry section 81. The constrictor
is preferably made of dielectric material, such as boron nitride,
and includes a converging axial channel 82. This channel surrounds
the tip of the anode, and communicates, at its enlarged end, with
the gas ports in the cylindrical member 76. The wall of the
converging channel maintains the gas which flows from the ports
insulated from the inner wall 14 of the cooling jacket. The anode
extends into, but not all the way through, the channel 82. Gas
passing the anode 75 enters a nozzle throat portion 83 of the
constrictor section 81.
Abutting the forward end of the constrictor is the cathode 86 of
the instrument. The cathode is annular and fits within (i.e., is
surrounded by) the inner wall 14 of the cooling jacket 12. The
cathode may be brazed or otherwise fixed to the jacket to make a
good electrical connection therewith. The orifice diameter 86 of
the cathode is somewhat larger than the throat 83 of the
constrictor member 81 and functions as a nozzle exit. As shown, the
cathode 86 desirably terminates at the end wall 17 of the cooling
jacket.
The anode tube 33 is prevented from slipping forward in the
instrument by the above-described structure. That is, the spacer 71
is fixed to the anode tube and presses, via member 76 and
constrictor 81, against the cathode 86 which is fixed to the
cooling jacket. As previously described, however, the anode tube is
readily removable from the rear of the instrument by releasing the
cap 39.
In operation, a direct current (D.C.) voltage source (not shown) is
connected to the instrument. The positive terminal of the source is
connected to the anode lead wire 53 and the negative terminal (or
ground) is connected to the cap 39. Initially, a current flows to
the anode 75 and away from the cathode 86, but because the anode is
spaced apart from the cathode, the current flow stops once the
potential drop across these electrodes equals the potential of the
D.C. source. Concurrently, gas is delivered to the instrument
through the hose 51. A typical gas flow is 1.0 CFH (STP). The gas
flows through the anode tube 33 to its forward end thence escapes
through the perforations into the plenum 77. From the plenum the
gas flows through the gas ports 79 into the entry section 82 of the
nozzle (81 and 86).
The voltage of the source is increased until the ionization
potential of the gas is exceeded. The gas then "ignites;" i.e., it
is transformed into a plasma state under the influence of the
potential difference between the anode and the cathode. The plasma
exits the orifice 87 of the cathode 86 in a directed jet stream.
The characteristics of the plasma produced by the claimed
instrument depend upon the amount of current available to it from
the source. Increasing the power applied to the gas results in very
small increases in the voltage drop across the plasma but
correspondingly large increases in the current carried by plasma
until the critical arcing level is exceeded; i.e., the power level
at which the plasma converts to a "hot" plasma (at substantial
thermal equilibrium). A notable characteristic of the claimed
instrument is the ease with which the character of the plasma may
be controlled. The arrangement of the annular cathode with respect
to the anode assures an electrically neutral plasma, which is
beneficial for surgical use. Cathodes of copper, tungsten or alloys
thereof are generally satisfactory. A satisfactory anode material
is nichrome wire.
The electric field between the anode and cathode produces a certain
amount of heat. The cooling liquid which circulates through the
jacket 12 as previously described effectively removes such heat.
Accordingly, the instrument is at all times comfortable to touch.
Usually, the cooling liquid is ordinary tap water.
The safety circuit of FIG. 5 prevents a large net electric charge
with respect to D.C. ground potential from building on the metal
skin of the sheath of the instrument. Lines 101 and 102 are the
usual 120 volt A.C. lines leading to a conventional transformer
(not shown) which generates the voltage supplied to the instrument.
A connection is made by line 106 from line 101 to line 102 through
the periphery winding 107 of a conventional transformer 108. The
secondary winding of the transformer 108 is connected to chassis
ground at 109 by center tap line 111, and to D.C. ground return 110
through a high value resistor 112. The output lines 116 and 117 of
the secondary winding are connected to a conventional full wave
bridge rectifier 118 which converts the alternating current in the
secondary to a direct current across the bridge output lines 121
and 122. Preferably, the potential across the lines 121 and 122 is
about 16 volts. Grounded capacitors 124 and 125 may be connected to
the output lines 121 and 122, repsectively, to smooth the output
voltage.
Each of the lines 121 and 122 lead to ordinary solenoids (126 and
127) respectively; when the voltage is held constant, the solenoids
are inactive. Line 121 leads from solenoid 126 to the collector of
an ordinary PNP transistor 131. The emitter of that transistor is
common to chassis ground (via line 135) and to the emitter of an
ordinary NPN transistor 137. The collector of this second
transistor 137 connects to the output line 122 coming from the
solenoid 127. The two transistors are connected in common-emitter,
base-input arrangement so that the current which the transistors
conduct is readily controlled by the potential applied between the
transistors' common base and emitter leads 134, 135.
The emitter lead 135 is at chassis potential. The base lead 141 is
ordinarily at ground or zero potential; it connects through series
opposed zener diodes 144 and 146 (having, for example, about 5 volt
values) to a relatively small resistor, which is connected in
series with the D.C. ground return 110. Ordinarily, the series
opposed zener diodes do not conduct current in either direction.
However, if the potential difference between chassis ground and
D.C. ground exceeds the zener breakdown point, as when a large net
charge accumulates on the skin of the sheath, a current flows
through the diodes. When such a current flows, it causes the
transistor output to vary considerably. Accordingly, the current
through the respective solenoids 126 or 127, depending upon the
polarity of the accumulated charge, changes and one or the other of
the solenoids acts to break the power supply circuit, as
hereinafter explained.
A line 151 is connected across the 120 volt A.C. lines 101 and 102
to control solenoid 153. That solenoid, in turn, can move to
actuate a switch 154 in the main line 101. Ordinarily, the solenoid
153 retains the switch closed so that current flows through line
101. Two switches 161 and 162 are connected along line 151 (as
indicated by the dotted lines) to the solenoids 126 and 127.
Ordinarily, those solenoids allow the switches 161 and 162 to
remain closed so that current flows through line 151. However, when
the output current of the transistors changes due to a base current
in the transistors 131 and 137, at least one of the solenoids is
activated and opens the switch to which it is connected. In that
event, line 151 becomes an open circuit and solenoid 153 is
released and opens the switch 154 whereupon the source of power for
the power supply 163 is cut.
To reset the safety circuit, a button or switch 164 is closed which
short-circuits the two switches 126 and 127. Solenoid 154 is thus
energized to close switch 154. A manual switch 167 may also be
provided in line 151 to selectively manually cut the current in the
line 101.
* * * * *