U.S. patent number 3,875,945 [Application Number 05/412,292] was granted by the patent office on 1975-04-08 for electrosurgery instrument.
This patent grant is currently assigned to Demetron Corporation. Invention is credited to Joshua Friedman.
United States Patent |
3,875,945 |
Friedman |
April 8, 1975 |
Electrosurgery instrument
Abstract
An electrosurgery instrument having a radio frequency oscillator
energized from a power supply controlled by a switching arrangement
to produce either dc, full wave rectified ac, or half-wave
rectified ac at its output, depending upon whether it is desired to
operate in the cut, coagulate, or fulgurate modes, respectively.
The level of output voltage of the power supply may be set to any
value within a range and thereafter increased by a fixed percentage
upon the operation of a remote control switch. The level of output
voltage in any mode of operation, once set, is regulated by a
feedback control circuit to minimize sparking at the electrode tip.
The oscillator output is coupled to an operating probe through an
impedance transformer and coaxial cable designed to deliver maximum
radio frequency power to the patient without the use of a ground
plate. An indicating lamp is connected to points of different
potential in the cable and within the probe in order to give a
positive indication of the presence of radio frequency power at the
probe tip.
Inventors: |
Friedman; Joshua (Ridgefield,
CT) |
Assignee: |
Demetron Corporation
(Ridgefield, CT)
|
Family
ID: |
23632415 |
Appl.
No.: |
05/412,292 |
Filed: |
November 2, 1973 |
Current U.S.
Class: |
606/45; 606/38;
606/49 |
Current CPC
Class: |
A61B
18/1206 (20130101); A61B 2018/1253 (20130101) |
Current International
Class: |
A61B
18/12 (20060101); A61b 017/36 (); A61n
003/02 () |
Field of
Search: |
;128/303.14,303.13,303.17,303.18,303.19,412R,420 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Cohen; Lee S.
Claims
What I claim is:
1. An electrosurgery instrument connected to a source of ac power
comprising a power supply including a switching means for
selectively producing a full wave rectified output voltage, a half
wave rectified output voltage and a substantially ripple-free dc
output voltage from said source of ac power; and ac oscillator
having input terminals and output terminals; an operating probe
containing a cutting tip, means for coupling said oscillator output
terminals to said cutting tip; and regulator means for connecting a
selected one of said output voltages to said oscillator input
terminals including feedback means connected to said coupling means
for maintaining a substantially constant voltage at said oscillator
output terminals independent of variations in load impedance and
power line voltage.
2. An electrosurgery instrument in accordance with claim 1 wherein
said regulator means includes means for selectively adjusting the
magnitude of output voltage from said power supply independent from
said switching means.
3. An electrosurgery instrument in accordance with claim 2 wherein
said regulator means further includes a feedback circuit comprising
a rectifier connected to a portion of said oscillator output
voltage, a filter network including a potentiometer connected to
said rectifier, an inverting amplifier connected to the slide of
said potentiometer and amplifier means controlled by said inverting
amplifier for connecting a selected one of said power supply output
voltages to said oscillator input terminals.
4. An electrosurgery instrument in accordance with claim 1 wherein
said switching means includes a primary switch for selectively
producing one of said output voltages at the output of said power
supply and a remotely situated control switch having a first stage
for energizing said oscillator input terminals with a selected one
of said power supply output voltages and a second stage for
simultaneously increasing the magnitude of said selected output
voltage and for overriding said primary switch to produce said full
wave rectified voltage at said output of said power supply when
said primary switching means is arranged to select said ripple-free
dc output voltage for application to said output of said power
supply.
5. An electrosurgery instrument in accordance with claim 4 wherein
said oscillator produces a voltage having a frequency in the range
of 1 to 4 megacycles.
6. An electrosurgery instrument in accordance with claim 1 wherein
said means for coupling said oscillator to said cutting tip
includes an impedance transformer to effect a substantial match
between the operating impedance seen by said cutting tip and the
output impedance of said oscillator, a coaxial cable having a
length less than one-quarter the wave length of said oscillator
voltage connected between said cutting tip and said impedance
transformer and an inductance having a magnitude in the range of
10-40 microhenrys serially connected between the terminal of said
cable within said probe and said cutting tip.
7. An electrosurgery instrument in accordance with claim 1 wherein
said operating probe comprises a hollow tubular housing fabricated
from an electrical insulator material having a translucent band
running circumferentially over a portion of its length and an
interior lamp adjacent to said band having two terminals connected
to points of different potential on said cable.
Description
The present invention relates to electrosurgery instruments and,
more particularly, to an electrosurgery instrument capable of
efficiently delivering an adjustable quantity of radio frequency
power for use in a selected one of three modes of operation.
For many years various types of surgical tools using electrical
energy have been used to carry out various medical and dental
operations. Early instruments utilized spark gap current to burn
tissue and, while this was satisfactory for operations where the
purpose was destruction of tissue, it was unsatisfactory where it
was used to make an incision or for hemostasis with a minimum of
necrosis and other undesirable histological changes in adjacent
tissue.
Improved instruments, utilizing radio frequency electromagnetic or
diathermy energy, overcome some of these limitations but
nevertheless suffer from certain disadvantages which have limited
their utility. For example, a number of existing radio frequency
electrosurgical devices utilize vacuum tubes with their concomitant
bulk, delay for warm up time, excessive heat generation and poor
reliability. Other such units are hazardous to the patient and
operator in that they require ground plates to minimize the patient
to ground impedance and to complete the radio frequency circuit, or
they lack effective means for accurately indicating a "hot"
electrode tip. Illustratively, units requiring a ground plate may
not only hinder the operator and present a psychological deterrent
to an already apprehensive patient, but they also suffer the
disadvantage of subjecting the patient to the possibility of raio
frequency burn where non uniform contact is made between the ground
plate and the patient's skin, or where, by reason of an unsuspected
intermittent break in the plate-connecting wire, the operator finds
it necessary to increase the output power level only to find that
the output increases still further when the break is reconnected.
Still other radio frequency electro-surgery units lack effective
means for giving a true indication that the tip is energized and
thus give rise to the possibility of severe burns if the "hot" tip
is inadvertently touched or wiped to remove tissue therefrom.
Another significant disadvantage in existing electrosurgery units
is the lack of versatility where there are but two output wave
forms to choose from, for it is often desireable to have available
an intermediate operational mode for coagulation as well as a
cutting mode, designed for incision with a minimum of tissue
destruction, and a fulguration mode, designed primarily for tissue
destruction. Other such instruments fail to provide the operator
with means enabling him to switch from one operational mode to
another without taking his eyes from the site of surgery.
Accordingly, it is an object of my invention to provide a compact,
efficient, reliable and versatile electro-surgery unit which
utilizes radio frequency power and overcomes the shortcomings of
the prior art.
It is still another object of my invention to provide a radio
frequency electrosurgery instrument which operates efficiently
without the need for a ground plate.
It is another object of my invention to provide a radio frequency
electrosurgery instrument which affords the operator an opportunity
to select from amongst three modes of operation designed primarily
for cutting, coagulation, and fulguration, respectively.
It is still another object of my invention to provide a radio
frequency electrosurgery instrument in which the operator may
quickly switch from one mode of operation to another without
diverting his attention from the site of surgery, or removing his
hands from the electrode handpiece.
It is yet another object of my invention to provide an
electrosurgery instrument in which there is a positive indication
of a "hot" tip to prevent inadvertent injury to the patient,
operator, or operator's assistant.
In most existing radio frequency electrosurgery instruments the
operating voltage at the cutting tip varies markedly as contact is
made and broken between the cutting tip and the tissue being cut.
When this occurs sparking takes place, causing undesireable damage
to the tissue.
Accordingly, it is another object of my invention to provide an
electrosurgery instrument in which the radio frequency voltage
applied to the cutting tip is kept constant, independent of the
probe tip to ground impedance.
In accordance with the foregoing and other objects and features of
the invention, I have provided an electro-surgery instrument in
which a power supply connected to a radio frequency oscillator
delivers power over a coaxial cable to a probe containing a
surgical tip held in place by a spring loaded or other chuck. The
instrument is designed to permit the operator to select from
amongst three modes of operation by means of a switching
arrangement that causes the power supply to deliver either a dc
voltage, a full wave rectified ac, or a half-wave rectified ac as
the supply voltage to an r.f. oscillator. The electrode tip coupled
to the output of the oscillators is thus energized with a radio
frequency voltage which is either unmodulated for operation in the
cut mode, or modulated with a 60cps signal for operation in the
coagulate mode, or modulated with a 120cps signal for operation in
the fulgurate mode.
After the unit is turned on, the particular mode of operation is
selected by first actuating a corresponding switch on a console
control panel and thereafter enabling the first stage of a two
position control switch remotely located from the console in the
area of the patient. This switch may be foot operated or be mounted
within the hand probe proximate to the cutting tip. The operator
may, by increasing the pressure on the control switch, enable the
second stage of the switch to increase the level of output voltage
from the power supply and consequently the peak level of radio
frequency output power. And when the instrument is being operated
in the cut mode, engagement of the second stage of the control
switch also causes operation to switch into the coagulation
mode.
The instrument also incorporates an impedance transformer, for
matching the oscillator low output impedance to the higher patient
to ground impedance for the efficient transmission of power without
the need of a ground plate, and an indicating lamp, connected
within the probe to give positive, reliable indications of a "hot"
tip.
These and other objectives and features of my invention will be
better understood if reference is had to the following detailed
description and accompanying drawing depicting a schematic circuit
and probe construction used in my invention.
Referring now to the drawing, the electrosurgery instrument
includes a power supply 10 driving an oscillator 20 which is
coupled by means of an impedance tranformer 30 to a coaxial cable
40 terminated in a surgical probe 50 containing a cutting tip
60.
The basic components of power supply 10 include a step down
transformer, a bridge rectifier and filter and a voltage regulator
circuit. Also connected to control the power supply is a remote
control two stage switch 108 and 108'.
Step down transformer 1 is arranged so that its primary winding is
connected through a normally open switch 2 and a fuse 3 to the 110
volt source of power. The secondary of transformer 1 is connected
to a full wave bridge rectifier comprising diodes 4, 5, 6 and 7. A
filter circuit, consisting of resistor 8 and electrolytic capacitor
9, is connected between the positive output terminal of the bridge
circuit and ground. An output voltage regulating circuit 11 is
connected between the positive output terminal of the bridge
circuit and the output of the power supply.
Power supply 10, oscillator 20 and impedance transformer 30 may all
be included within a console containing on-off switch 2 and mode
switches 105, 105', 106, 107 and 107' as well as indicating lamps
117, 119 and 121. Switches 105 and 105' are mechanically coupled as
are 107 and 107', and switches 105, 106 and 107 are mechanically
interlocked so that only one may be actuated at a time. A two stage
spring loaded control switch 108 and 108', remotely situated from
the console in the area of the patient, also forms part of the
circuit for the electrosurgical instrument.
The drawing depicts the circuit as it exists when line power is
applied to the instrument, the cut mode of operation is selected at
the console and the first stage only of the control switch is
actuated. Under these circumstances on-off switch 2 is closed, cut
switch contacts 105' are closed to deliver ac power from the
secondary of transformer 1 through limiting resistor 116 to lamp
117 located under the cut mode switch button, the normally open
contacts 108 in the first stage of the control switch are closed
and the single pole double throw contacts of switch 108' are as
shown to connect resistor 111 through the closed contacts of
switches 108, 108' and 105 to the positive terminal of capacitor 9.
At the same time resistor 8 is shorted through switches 108' and
105.
When the pressure on the control switch is increased sufficiently
to actuate the second stage of the control switch, contacts 108
remain closed and the position of contacts 108' are changed to
remove the short across resistor 8 and connect the emitter of
transistor 104 through resistor 110 to the positive output terminal
of the bridge rectifier circuit. Now resistor 8 is connected in
series between the positive terminal of the bridge rectifier and
capacitor 9. Resistor 111 remains connected to the positive
terminal of the bridge rectifier.
When normally open switch 105 is actuated for the cut mode of
operation, the contacts of coagulate mode switch 106 are open and
the contacts of the fulgurate mode switch 107 and 107' are as shown
with ground connected to the negative output terminal of the bridge
circuit. With the first stage of the control switch actuated as
shown, a full wave rectified ac voltage is produced at the output
terminals of the bridge circuit and thereafter filtered to deliver
dc power to the input of the oscillator which in turn produces an
unmodulated radio frequency signal at its output. The filter
circuit consists of capacitor 9 connected directly across the
output terminals of the bridge circuit inasmuch as resistor 8 is
shorted through the contacts of switches 105 and 108'. Capacitor 9
must be large enough to provide a relatively smooth, ripple free dc
voltage across its terminals.
A feedback circuit is provided to regulate the voltage at the
cutting tip in order to keep it constant at a selected value in the
face of varying load impedance. A portion of the radio frequency
voltage at the output of oscillator 20 -- e.g., the voltage drop
between the input and first tap in inductance 32 of impedance
tranformer 30 -- is rectified by diode 114 and thereafter filtered
by capacitor 115 connected in parallel with potentiometer 109. A
portion of this rectified and filtered voltage is picked off by the
wiper of potentiometer 109 and impressed upon the base of
transistor 104 which is connected as an inverting amplifier.
Transistors 102 and 101 connected as Darlington emitter followers
are connected between the collector-output of transistor 104 and
the output of power supply 10. The emitter voltage of transistor
101 follows the base voltage of transistor 102. Since the collector
of transistor 104 is connected to the base of transistor 102, the
emitter voltage of transistor 101, which is the dc supply voltage
for oscillator 20, follows the collector voltage of transistor
104.
Thus, if the wiper of potentiometer 109 is set closer to its
grounded end, a smaller voltage is applied to the base of
transistor 104 causing its collector voltage to increase. This, in
turn, causes the emitter voltage at transistor 101, and thus the
output voltage of power supply 10, to increase. Since the output
voltage of rf oscillator 20 is proportional to its dc input
voltage, it is controlled by the dc voltage at the emitter of
transistor 101. Accordingly, the rf output voltage at the tip of
probe 60 is adjusted by moving the wiper of potentiometer 109 --
the closer the wiper is to ground, the higher the output rf voltage
applied to cutting tip 60.
As is well known in the art, the tip to ground impedance varies
considerably during operation. Thus, for example, tip to ground
impedance when the tip is not in contact with the patient's tissue
is substantially greater than when contact is made. Unless this
variation in impedance is compensated for, the rf voltage at the
probe tip will vary during operation, producing a high voltage when
the tip is separated from the tissue being cut and a much lower
voltage when the tip is in contact with the tissue. And when the
voltage increases as described, sparking occurs between the tip and
the tissue being cut, causing undesireable tissue damage. It is a
prevent this, as well as to make the output independent of power
line variations, that I have provided the voltage regulating
circuit 11.
By means of the negative feedback arrangement described, any rf
voltage increase at the tip of the probe above the level set by
potentiometer 109, is detected by diode 114. After passing through
the wiper of potentiometer 109 and transistor inverting amplifier
104, the probe tip voltage increase causes a voltage decrease at
the collector of transistor 104. This, in turn, causes the dc
supply voltage to the oscillator to decrease and thus produces a
decrease in the oscillator output voltage applied to the cutting
tip. In this fashion the rf voltage at cutting tip 60, selected by
the position of the slide on potentiometer 109, is maintained at a
relatively constant level despite variations in load impedance seen
by the cutting tip.
Also shown in the drawing are three lamp circuits connected in
parallel across the secondary of transformer 1 to provide an
indication of the mode of operation selected. As described above,
when switch 105 is actuated for operation in the cut mode, normally
open switch contacts 105' are closed to deliver ac power from the
secondary of transformer 1 through limiting resistor 116 to lamp
117 located under the cut mode switch button. Similar arrangements
are provided for the coagulate mode and the fulgurate mode in the
form of switches 106 and 107', respectively.
If, while in the cut mode of operation, the operator desires to
switch to the coagulate mode, he will increase his pressure on the
control switch and thereby actuate the second stage contacts 108'
to simultaneously remove the short across resistor 8 and connect
resistor 110 between the emitter of transistor 104 and the output
of the bridge circuit. This puts resistor 8 in series with
capacitor 9, and since resistor 8 is substantially larger than the
bridge circuit impedance, a substantially unfiltered full wave
rectified ac appears across the positive output terminal of the
bridge circuit and thus across resistor 110 in series with resistor
103. Resistor 110 and resistor 103 form a voltage divider with the
portion of the unfiltered full wave ac voltage across resistor 103
applied to emitter of transistor 104 to increase its collector
voltage by a fixed amount. This, of course, also increases the rf
output voltage of the oscillator by a fixed amount. The voltage
regulating circuit 11 continues to function as before, only now a
full wave rectified ac voltage is produced at the output of power
supply 10 and connected to oscillator 20 as a modulating signal. It
can be shown histologically that by selecting a value for resistor
110 which permits an increase of approximately 50 percent in the
ratio of peak to average output voltage, more effective in vivo
operation in the coagulate mode results.
It can be seen that the two stage switch circuit arrangement
produces certain desirable advantages. Often, during operation in
the cut mode, the operator wishes to quickly and effectively
coagulate blood without removing his eyes from the surgical site.
He may do this by actuating the second stage of the control switch.
If, thereafter, he reduces his pressure on the control switch, the
second stage will disengage and operation in the cut mode is
resumed. When this is done switch contacts 108' return to their
original state to again short out resistor 8 and disconnect
resistor 110 from the emitter of transistor 104.
When the operator selects the coagulate mode of operation by
actuating switch 106 at the console, switch 105 opens to remove the
short from across resistor 8 which is then connected in series
between the positive output terminal of the bridge circuit and
capacitor 9. When the first stage of the control switch is
actuated, contacts 108 are closed and the resistor 111 is connected
to the positive output terminal of the bridge rectifier circuit to
energize transistor 104. As before a full wave rectified ac voltage
is produced at the output of power supply 10. If, now, the operator
wishes to momentarily actuate the second stage of the control
switch -- i.e., contacts 108' -- resistor 110 is connected to the
emitter of transistor 104 to increase the peak to average output
voltage as before.
If it is desired to operate the instrument in the fulgurate mode,
the operator actuates switch 107, which, by reason of its
mechanical interconnection, causes switches 105 and 106 to open.
When this occurs the ground is removed from the negative terminal
of the bridge circuit and applied instead to one side of the
secondary winding of transformer 1. Of course, switch 105 is opened
and the short is removed from across resistor 8. The effect of this
is to convert the full-wave bridge rectifier circuit into a
half-wave rectifier circuit, utilizing only rectifier 5 to produce
a half-wave rectified ac voltage at the positive terminal of the
bridge circuit. And since resistor 8 is now connected in series
with capacitor 9, the half wave output voltage, in substantially
unfiltered form, is applied to the collector of transistor 104
through resistor 111 and the terminals of contacts 108 of the first
stage of the foot switch. As before, the unfiltered voltage appears
at the output of power supply 10. Once again, if the operator
desires to momentarily increase the output power, he will engage
the second stage of the control switch and actuate contacts 108' to
connect resistor 110 between the emitter of transistor 104 and the
positive terminal of the rectifier circuit to deliver an increased
peak to average voltage at the output of power supply 10.
In each mode of operation the power supply produces the direct
current power to operate and modulate oscillator 20. While a common
emitter feedback type oscillator circuit is shown, it has been
found that any oscillator producing a radio frequency in the range
of 1 to 4 megacycles will enable the instrument to perform
satisfactorily.
Typically, the collector impedance of transistor power oscillators
such as oscillator 20 is small compared to the impedance between
the cutting tip and ground -- e.g., the power oscillator collector
impedance is resistive and on the order of 5 ohms, while the tip to
ground impedance, consisting of the patient body resistance in
series with the patient to ground capacitance, can be as high as
1,500 ohms. In conventional electrosurgery instruments this
mismatch is compensated for by reducing the tip to ground impedance
with a ground plate with its concomitant disadvantage.
In my invention, I have eliminated the need for a ground plate and
simultaneously avoided the problems of radiation interference and
the possibility of radio frequency burns (where insulation becomes
defective) associated with the common usage of an insulated
conductor connecting the oscillator to the probe.
In my invention, coaxial cable 40 is connected between the probe 50
and an impedance transformer 30 to match the load impedance to the
oscillator output impedance for efficient and safe power transfer.
By choosing a length for cable 40 which is less than one quarter
wavelength, the impedance seen looking into the cable at the
junction with impedance transformer 30 is approximately the
capacitance of cable 40 in parallel with the patient-body
impedance. As will be understood by those versed in the art, the
cable capacitance adds to the capacitance of capacitor 31 in
impedance tranformer 30, and this augmented capacitance is
connected in a .pi. network, including capacitor 33 and the portion
of inductor 32 between capacitor 31 and capacitor 33, to transform
the high patient impedance into a lower impedance approximating the
output impedance of oscillator 20.
An inductance 56 may be connected between the end of the cable 40
and a terminal post 55 that is electrically connected to a chuck
fitted within the hollow of probe 50, which may be fashioned from
cylindrically shaped insulation material. The inductance will then
be in series with the patient to ground circuit. This inductance 56
is selected to have a value so that its positive reactance equals
the negative reactance of an average patient to ground capacitance
to further increase the effective rf power delivered to the cutting
site.
The shield of coaxial cable 40 is grounded at a jack terminal at
the impedance transformer 30 within the console. Insulation is
stripped away from a portion of cable 40 within probe 50 some
distance from terminal post 55 to expose a shield segment 51. A
series circuit consisting of resistor 54 and lamp 53 is connected
between the end of the center conductor of cable 40 and the exposed
shield segment 51 to provide a means for indicating when radio
frequency power is present at the cutting tip 60. Probe 50 is
constructed with a translucent circumferential band forming a
window 57 that permits the light from lamp 53 to be seen over a
360.degree. viewing angle.
A series circuit consisting of resistor 41 and a lamp 42 may be
connected at the console between the output of impedance
transformer 30 and ground to indicate when oscillator 20 is
energized. Lamps 53 and 42 may be neon bulbs or any other
indicators that can be energized directly by rf voltage.
Finally, the chuck may be any of a variety of convenient devices
which enable cutting tip 60 to be inserted and removed with
facility. Thus, for example, the chuck may be a friction device or,
as shown in the drawing and as more fully described in U.S. Pat.
No. 2,801,613, a device having 3 or 4 normally open jaws 71 made
from spring brass or other conductive metal which are closed by a
spring loaded collar 72. Cap 73 is press fitted over a retainer
bushing 74 fitted over collar 72, which in turn acts against spring
75. Jaws 71 are fitted within collar 72 so that their shaft extends
through spring 75 into a tapped portion of terminal post 55 so an
electrical connection is made therebetween. When cap 73 is pushed
to compress spring 75, the jaws of the chuck extend from collar 72
to expand and permit the insertion or removal of cutting tip 60.
This extension of jaws 71 takes place entirely within cap 73, which
has a small opening 76 at its end to admit tip 60. With this
arrangement, the chuck is made to accept various diameter cutting
tips.
It is to be understood that the above-described arrangements are
illustrative of the application of the principles of the invention.
Numerous other arrangements may be devised by those skilled in the
art without departing from the spirit and scope of the
invention.
* * * * *