U.S. patent application number 11/258916 was filed with the patent office on 2006-03-02 for electrical generator and system.
This patent application is currently assigned to Gyrus Medical Limited. Invention is credited to Colin C.O. Goble.
Application Number | 20060047275 11/258916 |
Document ID | / |
Family ID | 46150288 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060047275 |
Kind Code |
A1 |
Goble; Colin C.O. |
March 2, 2006 |
Electrical generator and system
Abstract
An electrosurgical system includes a generator for generating
radio frequency power, and an electrosurgical instrument including
at least three electrodes and. The generator includes a radio
frequency output stage having at least a pair of RF output lines,
and a power supply coupled to the output stage for supplying power
to the output stage. A controller is operable to limit the radio
frequency output voltage developed across the output lines to at
least a first predetermined threshold value to produce a cutting RF
waveform, and a second threshold value to produce a coagulating RF
waveform. In a combined mode, the controller delivers both cutting
and coagulating waveforms, either simultaneously or by alternating
constantly between the first and second threshold values to form a
blended signal. The system also includes means for feeding the
waveform to the three or more electrodes such that the cutting RF
waveform is delivered between a first pair of the electrodes, and
the coagulating waveform is delivered between a second pair of the
electrodes.
Inventors: |
Goble; Colin C.O.; (Surrey,
GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
Gyrus Medical Limited
Cardiff
GB
|
Family ID: |
46150288 |
Appl. No.: |
11/258916 |
Filed: |
October 27, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10378676 |
Mar 5, 2003 |
6966907 |
|
|
11258916 |
Oct 27, 2005 |
|
|
|
10228284 |
Aug 27, 2002 |
6984231 |
|
|
10378676 |
Mar 5, 2003 |
|
|
|
60314650 |
Aug 27, 2001 |
|
|
|
Current U.S.
Class: |
606/37 ; 606/42;
606/48; 606/51 |
Current CPC
Class: |
A61B 18/12 20130101;
A61B 2018/1273 20130101; A61B 18/1442 20130101; A61B 2018/124
20130101; A61B 2018/00666 20130101; A61B 18/1445 20130101; A61B
2018/0066 20130101; A61B 2018/00601 20130101; A61B 2017/00212
20130101; A61B 18/1206 20130101; A61B 2018/00892 20130101; A61B
2018/1467 20130101; A61B 2018/00607 20130101; A61B 2018/00404
20130101; A61B 2018/00678 20130101 |
Class at
Publication: |
606/037 ;
606/042; 606/048; 606/051 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2002 |
GB |
0212162.2 |
Claims
1.-20. (canceled)
21. An electrosurgical system including a generator for generating
radio frequency power, and an electrosurgical instrument including
at least two electrodes, the generator comprising: (i) a radio
frequency output stage having two or more output connections, each
in electrical connection with a respective one of the at least two
electrodes, (ii) a power supply coupled to the output stage for
supplying power to the output stage, (iii) a controller operable to
limit the radio frequency output voltage developed across the
output connections to at least a first predetermined threshold
value for cutting or vaporisation and a second threshold value for
coagulation and, in a blend mode, to alternate constantly between
the first and second threshold values, and (iv) adjustment means,
operable by a user of the electrosurgical system, for varying the
ratio of the blend mode so as to vary the part of the blend signal
that is limited to the first threshold value for cutting or
vaporisation, as compared with the part of the blend signal that is
limited to the second threshold value for coagulation.
22. The electrosurgical system according to claim 21 wherein the
adjustment means is carried by the electrosurgical instrument.
23. The electrosurgical system according to claim 21 wherein the
adjustment means is mounted on the generator.
24. An electrosurgical system including a generator for generating
radio frequency power and an electrosurgical instrument including
at least two electrodes, the generator comprising: a radio
frequency output stage having a plurality of output connections,
each output connections being in electrical connection with a
respective one of the at least two electrodes, a power supply
coupled to the output stage for supplying radio frequency power to
the output stage, a controller operable to limit the radio
frequency output voltage developed across the output connections to
at least a first predetermined threshold value for cutting or
vaporisation and a second threshold value for coagulation and, in a
blend mode, to alternate constantly between the first and second
threshold values, and a switching circuit comprising: three or more
output connections, a switching device for feeding the radio
frequency output voltage to the three or more output connections,
such that, in the blend mode, the cutting RF waveforms is delivered
between a first pair of the three or more electrodes, and the
coagulating RF waveform is delivered between a second pair of the
electrodes, and an adjustment device for adjusting the timing of
the switching device to alter the ratio between a first part of the
blended RF signal that is a cutting signal and a second part of the
blended RF signal that is a coagulating signal.
25. The electrosurgical system according to claim 24, wherein the
adjustment device is operable by a user of the system.
26. The electrosurgical system according to claim 24, wherein the
three or more output connections are comprised of a first output
connection connected to a cutting electrode of the electrosurgical
instrument and second and third output connections connected to
coagulation electrodes of the electrosurgical instrument, and
wherein the switching device is connected between the first and
second output connections so that the radio frequency cutting
signal is supplied between cutting electrode and one of the
coagulating electrodes when the switching device is open, and so
that the radio frequency coagulating voltage is supplied between
the two coagulation electrodes when the switching device is
closed.
27. An electrosurgical system including a generator for generating
radio frequency power and an electrosurgical instrument including a
cutting g electrode and first and second coagulation electrodes,
the generator comprising: an output stage having first, second and
third output connections, the first output connection being
connected to the cutting electrode of the electrosurgical
instrument, and the second and third output connections being
connected to the first and second coagulation electrodes of the
electrosurgical instrument, a power supply coupled to the output
stage for supplying radio frequency power to the output stage, a
controller operable to limit radio frequency output voltage
developed across the output connections to a first predetermined
threshold value for cutting or vaporisation and a second threshold
value for coagulation and, in a blend mode, to alternate constantly
between the first and second threshold values, and a switching
device for supplying the radio frequency cutting signal between the
cutting electrode and one of the coagulating electrodes when the
switching device is in a first state, and for supplying the radio
frequency coagulating voltage between the two coagulation
electrodes when the switching device is in a second state, and an
adjustment device for adjusting the timing of the switching device
to alter the ratio between a first part of the blended RF signal
that is a cutting signal and a second part of the blended RF signal
that is a coagulating signal.
28. The electrosurgical system according to claim 27, wherein, in
the first state, the switching device is open, and, in the second
state, the switching device is closed.
29. An electrosurgical system including a generator for generating
radio frequency power, and an electrosurgical instrument including
three or more electrodes, the generator comprising: means for
supplying radio frequency power, means for outputting the radio
frequency output power, the output means having a plurality of
output connections, each in electrical connection with a respective
one of the three or more electrodes, means for limiting radio
frequency output voltage developed across the output connections to
at least a first predetermined threshold value for cutting or
vaporisation and a second threshold value for coagulation and, in a
blend mode, to alternate constantly between the first and second
threshold values, switching means for delivering the radio
frequency output voltage to the plurality of output connections,
such that, in the blend mode, the cutting RF waveforms is delivered
between a first pair of the plurality of three or more electrodes,
and the coagulating RF waveform is delivered between a second pair
of the electrodes, and adjustment means, operable by a user of the
electrosurgical system, for varying the ratio of the blend mode so
as to vary the part of the blend signal that is limited to the
first threshold value for cutting or vaporisation, as compared with
the part of the blend signal that is limited to the second
threshold value for coagulation.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation-in-part of U.S. application Ser. No.
10/228,284 filed Aug. 27, 2002 which claims the benefit of U.S.
provisional application Ser. No. 60/314,650, filed Aug. 27, 2001,
the entire contents of both being incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to an electrosurgical generator, and
to an electrosurgical system comprising a generator and an
electrosurgical instrument with two or more treatment electrodes.
Such systems are commonly used for the cutting and/or coagulation
of tissue in surgical intervention, most commonly in "keyhole" or
minimally invasive surgery, but also in laparoscopic or "open"
surgery.
BACKGROUND OF THE INVENTION
[0003] It is known to provide electrosurgical generators which
provide different radio frequency signals for cutting and
coagulation, and also to provide a blended signal in which the
generator rapidly alternates between the signals for cutting and
coagulation. Our U.S. Pat. No. 6,416,509 and also U.S. Pat. No.
3,885,569 to Judson describe blended signals of this type.
SUMMARY OF THE INVENTION
[0004] The present invention provides an improvement to this type
of electrosurgical system, in that the cutting and coagulation
waveforms are delivered to different electrodes of the
electrosurgical instrument. Accordingly, there is provided an
electrosurgical system including a generator system for generating
radio frequency (RF) power, and an electrosurgical instrument
including at least three electrodes, the generator system
comprising one or more sources of RF output power, and a controller
operable to control the generator system such that it is capable of
delivering a first cutting RF waveform to the electrosurgical
instrument or a second coagulating RF waveform to the
electrosurgical instrument, and, in a combined mode, to deliver
both first and second RF waveforms, the system also including means
for feeding the waveform to the three or more electrodes such that,
in the combined mode, the cutting RF waveforms is delivered between
a first pair of the three or more electrodes, and the coagulating
RF waveform is delivered between a second pair of the
electrodes.
[0005] Our pending European patent application EP 02255826.6
describes an electrosurgical system in which the operator can
select between a cutting signal and a coagulation signal. When the
cutting signal is selected, it is supplied to one pair of
electrosurgical electrodes, and when the coagulation signal is
selected it is supplied to a different pair of electrosurgical
electrodes. The present invention is an improvement to this system,
in that it also provides a combined mode of operation, but with the
different components of the combined signal being supplied to
different sets of electrosurgical electrodes.
[0006] The "combined mode" of the generator can be provided in
different ways. In one arrangement, the generator system comprises
a single source of radio frequency power, and, in the combined
mode, the controller is operable to cause the generator system to
alternate constantly between delivering the first cutting RF
waveform and the second coagulating RF waveform. This is the more
traditional "blended" signal of U.S. Pat. Nos. 6,416,509 and U.S.
Pat. No. 3,885,569. Alternatively, the generator system comprises
at least first and second sources of radio frequency power,
operating at different frequencies, the first source of radio
frequency power being adapted to deliver the first cutting RF
waveform, and the second source of radio frequency power being
adapted to deliver the second coagulating RPF waveform, and, in the
combined mode, the controller is operable to cause the generator
system to deliver both the first and second RF waveforms
simultaneously. This is a different arrangement in which the output
of two RF sources is supplied to the instrument simultaneously.
Both arrangements have the effect, however, of supplying both
cutting and coagulating RF signals to the electrosurgical
instrument while the instrument is in use.
[0007] Where the alternating blended signal is employed, the means
for connecting the waveform conveniently comprises a switching
circuit for varying the connections between the source and the
three or more electrodes such that, in the combined mode, a first
part of the combined signal that is the cutting RF waveform is
delivered between a first pair of the three or more electrodes, and
a second part of the combined signal that is the coagulating RF
waveform is delivered between a second pair of the three or more
electrodes.
[0008] In a convenient arrangement, the switching circuit of the
generator is such that, in the combined mode, the connections
between the power supply and the electrodes are switched such that
the first part of the blend signal is delivered between the first
and second electrodes, and the second part of the blend signal is
delivered between the second and third electrodes. In this
arrangement, there is a common electrode which is used in both the
cutting and coagulation operations, but it is equally feasible to
have completely different pairs of electrodes for each
function.
[0009] Preferably, the switching circuit comprises first and second
input connections, first second and third output connections, and
an electronic switch connected between the first and second output
connections, and being adapted to open and close in order to
connect the first and second output connections periodically one to
the other. The electronic switch conveniently opens and closes at a
frequency of between 5 and 100 Hz. In this arrangement, the second
and third output connections are preferably connected one to the
other via a capacitor, typically one having a value of between 1
and 10 nF. The switching circuit is conveniently housed in the
electrosurgical instrument, although it can alternatively be housed
in the electrosurgical generator.
[0010] Conveniently, the controller within the generator is adapted
to determine the timing of the changes between the first and second
parts of the combined signal, and the switching circuit is
synchronised to operate in response thereto, so as to deliver the
first and second parts of the combined signal respectively to the
first and second pairs of electrodes. Alternatively, the switching
circuit is adapted to determine the timing of the changes between
the first and second parts of the combined signal, and the
controller is adapted to operate in response thereto.
[0011] Where the combined signal is provided by first and second RF
sources acting simultaneously, means for connecting the waveform
conveniently comprises one or more output stages arranged such that
the cutting RF waveform from the first RF source is delivered
between a first pair of the three or more electrodes, and the
coagulating waveform from the second RF source is delivered between
a second pair of the three or more electrodes. In this way the
first and second sources are "hard wired" to deliver their
respective waveforms to different output connections, and hence to
different pairs of electrodes. Thus the need for active switching
of the connections using a switching circuit is avoided, but the
power requirements needed for the operation of two RF sources may
make this construction unsuitable for some arrangements, such as
those in which the generator system is housed within the handpiece
of the electrosurgical instrument.
[0012] The invention further resides in an electrosurgical system
including a generator system for generating RF power, and an
electrosurgical instrument including at least three electrodes, the
generator system comprising at least one RF output stage, means for
supplying power to the at least one output stage, and a controller
operable to limit the radio frequency output voltage developed by
the at least one output stage to at least a first predetermined
threshold value for cutting or vaporisation and a second threshold
value for coagulation and, in a combined mode, to deliver waveforms
limited to both first and second threshold values, the
electrosurgical system also including means for coupling the
waveform to the three or more electrodes such that, in the combined
mode, a waveform limited to the first threshold value for cutting
or vaporisation is delivered between a first pair of the three or
more electrodes, and a waveform limited to the second threshold
value for coagulation is delivered between a second pair of the
three or more electrodes.
[0013] The invention further resides in an electrosurgical
generator for supplying RF power to an electrosurgical instrument,
the generator comprising at least one RF output stage, three more
output connections for the delivery of RF power to the
electrosurgical instrument, means for supplying power to the at
least one output stage, a controller operable to limit the RF
output voltage developed by the at least one output stage to at
least a first predetermined threshold value for cutting or
vaporisation and a second threshold value for coagulation and, in a
combined mode, to deliver waveforms limited to both first and
second threshold values, and means for feeding the waveforms to the
three or more output connections such that, in the combined mode,
the waveform that is limited to the first threshold value for
cutting or vaporisation is delivered between a first pair of the
three or more output connections, and the waveform that is limited
to the second threshold value for coagulation is delivered between
a second pair of the three or more output connections.
[0014] The invention further resides in an electrosurgical system
including a generator for generating RF power, and an
electrosurgical instrument including at least two electrodes, the
generator comprising a RF output stage having two or more output
connections, each in electrical connection with a respective one of
the at least two electrodes, a power supply coupled to the output
stage for supplying power to the output stage, a controller
operable to limit the RF output voltage developed across the output
connections to at least a first predetermined threshold value for
cutting or vaporisation and a second threshold value for
coagulation and, in a blend mode, to alternate constantly between
the first and second threshold values, and adjustment means,
operable by a user of the electrosurgical system, for varying the
ratio of the blend mode so as to vary the part of the blend signal
that is limited to the first threshold value for cutting or
vaporisation, as compared with the part of the blend signal that is
limited to the second threshold value for coagulation.
[0015] The electrosurgical system of U.S. Pat. No. 6,416,509 is
such that the frequency of the blended signal can be pre-set to
match the type of electrode intended for use. There is nothing in
U.S. Pat. No. 6,416,509 to suggest that the blend ratio (i.e. the
ratio of that part of the blended signal that is a cutting or
vaporisation signal, as compared with that part which is a
coagulation signal) can be pre-set, let alone easily adjusted by
the user of the system. Preferably the adjustment means is carried
by the electrosurgical instrument, but the adjustment means can
also conceivably be mounted on the generator.
[0016] The invention will be further described below, by way of
example only, with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
[0017] FIG. 1 is a schematic diagram of an electrosurgical system
in accordance with the present invention,
[0018] FIG. 2 is a block diagram of the generator of FIG. 1,
[0019] FIG. 3 is a schematic perspective view of an electrosurgical
instrument used as a part of the system of FIG. 1,
[0020] FIG. 4 is a schematic diagram of a switching circuit used in
the system of FIG. 1,
[0021] FIGS. 5A and 5B are circuit diagrams of two electronic
switching devices for the switching circuit of FIG. 4,
[0022] FIG. 6 is a schematic diagram of an alternative embodiment
of switching circuit which can be used in the system of FIG. 1,
[0023] FIG. 7 is a block diagram of a generator in accordance with
FIG. 2, incorporating a switching circuit in accordance with FIG.
4,
[0024] FIGS. 8A to 8C are diagrams illustrating techniques for
adjusting a blend switching ratio, FIGS. 8A and 8C being circuit
diagrams of alternative ratio adjusting devices and FIG. 8B being a
waveform diagram illustrating the operation of the device of FIG.
8A,
[0025] FIG. 9 is a block diagram of an alternative embodiment of
generator system in accordance with the present invention,
[0026] FIG. 10 is a block diagram of a further alternative system
in accordance with the invention, and
[0027] FIGS. 11A and 11B are yet further alternative systems for
feeding cut and coagulation outputs automatically to different
respective electrode pairs.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0028] Referring to FIG. 1, a generator 10 has an output socket 10S
providing a radio frequency (RF) output for an instrument 12 via a
connection cord 14. Activation of the generator may be performed
from the instrument 12 via a connection in cord 14 or by means of a
footswitch unit 16, as shown, connected to the rear of the
generator by a footswitch connection cord 18. In the illustrated
embodiment footswitch unit 16 has two footswitches 16A and 16B for
selecting a coagulation mode and a cutting mode of the generator
respectively. The generator front panel has push buttons 20 and 22
for respectively setting coagulation and cutting power levels,
which are indicated in a display 24. Push buttons 26 are provided
as an alternative means for selection between coagulation and
cutting modes.
[0029] Referring to FIG. 2, the generator comprises a radio
frequency (RF) power oscillator 60 having a pair of output lines
60C for coupling to the instrument 12. The instrument 12 is shown
in FIG. 2 in the form of an electrical load 64. Power is supplied
to the oscillator 60 by a switched mode power supply 66. In the
preferred embodiment, the RF oscillator 60 operates at about 400
kHz, with any frequency from 300 kHz upwards into the HF range
being feasible. The switched mode power supply typically operates
at a frequency in the range of from 25 to 50 kHz. Coupled across
the output lines 60C is a voltage threshold detector 68 having a
first output 68A coupled to the switched mode power supply 16 and a
second output 68B coupled to an "on" time control circuit 70. A
microprocessor controller 72 coupled to the operator controls and
display (shown in FIG. 1) is connected to a control input 66A of
the power supply 66 for adjusting the generator output power by
supply voltage variation and to a threshold-set input 68C of the
voltage threshold detector 68 for setting peak RF output voltage
limits.
[0030] In operation, the microprocessor controller 72 causes power
to be applied to the switched mode power supply 66 when
electrosurgical power is demanded by the surgeon operating an
activation switch arrangement which may be provided on a hand-piece
or footswitch (see FIG. 1). A constant output voltage threshold is
set independently on the supply voltage via input 68C according to
control settings on the front panel of the generator (see FIG. 1).
Typically, for desiccation or coagulation the threshold is set at a
desiccation threshold value between 150 volts and 200 volts. When a
cutting or vaporisation output is required the threshold is set to
a value in the range of from 250 or 300 volts to 600 volts. These
voltage values are peak values. Their being peak values means that
for desiccation at least it is preferable to have an output RF
waveform of low crest factor to give maximum power before the
voltage is clamped at the values given. Typically a crest factor of
1.5 or less is achieved. When a combined mode output is required,
the voltage output set via input 68C is constantly alternated
between the value for desiccation or coagulation and the value for
cutting or vaporisation, to form a blended signal.
[0031] When the generator is first activated, the status of the
control input 601 of the RF oscillator 60 (which is connected to
the "on" time control circuit 70) is "on", such that the power
switching device which forms the oscillating element of the
oscillator 60 is switched on for a maximum conduction period during
each oscillation cycle. The power delivered to the load 64 depends
partly on the supply voltage applied to the RF oscillator 60 from
the switched mode power supply 66 and partly on the load impedance
64. The voltage threshold for a desiccation output is set to cause
trigger signals to be sent to the "on" time control circuit 70 and
to the switched mode power supply 66 when the voltage threshold is
reached. The "on" time control circuit 70 has the effect of
virtually instantaneously reducing the "on" time of the RF
oscillator-switching device. Simultaneously, the switched mode
power supply is disabled so that the voltage supplied to oscillator
60 begins to fall. The operation of the generator in this way is
described in detail in our European Patent Application No. 0754437,
the disclosure of which is hereby incorporated by way of
reference.
[0032] FIG. 3 shows one possible design for the electrosurgical
instrument 12. The instrument 12 comprises an instrument shaft 5 at
the distal end of which is an electrode assembly shown generally at
8. The electrode assembly 8 comprises a central cutting electrode 2
disposed between two larger coagulation electrodes 3 and 40.
Insulating layer 4 separates the cutting electrode 2 from the first
coagulating electrode 3, while an insulating layer 41 separates the
cutting electrode 2 from the second coagulation electrode 40. The
cutting electrode 2 protrudes slightly beyond the two coagulating
electrodes.
[0033] When the user intends the instrument to cut tissue, the
generator applies a cutting RF signal between the cutting electrode
2 and one or both of the two coagulating electrodes 3 and 40.
Conversely, when the user intends the instrument to coagulate
tissue, the generator applies a coagulating RF signal between the
two coagulating electrodes 3 and 40. The application of the blended
RF signal will be described with reference to the switching circuit
shown in FIG. 4.
[0034] FIG. 4 shows a switching circuit shown generally at 45 and
comprising input connections 46 and 47 connected respectively to
the two output lines 60C of the generator 10. Switching circuit 45
has three output connections 48, 49 and 50. Output connection 48 is
connected to the cutting electrode 2 in the device of FIG. 3.
Output connections 49 and 50 are respectively connected to the
coagulating electrodes 3 and 40 in the device of FIG. 3. An
electronic switch device 51 is connected between output connections
48 and 49. The switch 51 is capable of rapidly making and breaking
the connection between the output lines 48 and 49. A capacitor 53
is connected between the output connections 49 and 50, the
capacitor typically having a value of between 1 and 10 nF.
[0035] When the user actuates the footswitches 16A or 16B to
operate the instrument 12 in the blended mode, the generator
supplies alternating bursts of the RF cutting and coagulating
signals to the input connections 46 and 47. The switch device 51
operates synchronised with the alternating RF signals such that
when that part of the signal containing the cutting signal is
received, the switch device is open such that there is open circuit
between the output connections 48 and 49. Thus the cutting RF
signal is supplied between cutting electrode 2 and coagulating
electrode 40, via output connections 48 and 50 respectively.
Conversely, when that part of the signal containing the coagulating
voltage is received across the input connections 46 and 47, the
switching device 51 is closed such that output connections 48 and
49 are in electrical communication one with the other. Thus, during
the coagulation part of the blended signal, the signal is supplied
between the two coagulation electrodes 3 and 40, via output
connections 49 and 50, with the capacitor 53 providing a potential
difference therebetween.
[0036] Switching device 51 mav comprise an AC opto-relay such as
the optically coupled dual FET arrangement shown in FIG. 5A.
Another switching device providing isolation between control
circuitry and the output lines is the combination of an AC bridge
and a single MOSFET switch controlled via an isolating driver, a
shown in FIG. 5B.
[0037] The above description is based upon the generator 10
controlling the blended mode signal, and the switching device 51
opening and closing synchronously therewith. However, this does not
have to be the case and the switching device can control the
generator in order to determine the changeover between the cutting
and coagulation RF signals.
[0038] Consider the switching circuit 45 as shown in FIG. 4. When
the switching device 51 is in its open condition, the cutting
signal is supplied across output connections 48 and 50. When the
switching device 51 closes, the cutting signal is initially
supplied between the output connections 49 and 50, separated by the
capacitor 53. This causes the current delivered by the generator to
rise rapidly such that the current limiting circuitry within the
generator operates to reduce the power being delivered, such that
the signal rapidly converts to an RF signal typical for
coagulation. The effect of the current limiting circuitry within
the generator is that the closing of the switching device 51 causes
the signal being delivered to be transformed, almost
instantaneously, from a cutting signal to a coagulating signal.
Conversely, when the switching device 51 opens again, the generator
ceases to be current limited, and the signal once again rapidly
reverts to being a cutting RF signal. In this way, the opening and
closing of the switching device 51 toggles the generator between
its cutting and coagulating modes, producing the blended signal
which is supplied to the electrodes of the instrument 12.
[0039] FIG. 6 shows an alternative embodiment of switching circuit,
which can be employed if the generator 10 is not a current limited
generator, or if it is desired not to use the current limiting
features of the generator. The switching circuit of FIG. 6 is
almost identical to that of FIG. 4, the main difference being the
addition of an additional capacitor 52 in series with the input
connection 46. The capacitor 52 typically has a value one half of
that of capacitor 53, such that the voltage delivered across output
connections 49 and 50 is divided down to a level typically used for
coagulation without reducing the power output of the generator 10.
In this way a cutting RF signal is delivered between output
connections 48 and 50 when the switching device 51 is open, and a
coagulating RF signal is delivered between output connections 49
and 50 when the switching device is closed.
[0040] Switching circuit 45 can be provided within the
electrosurgical instrument 12, or within the output stage of the
generator 10 as shown in FIG. 7. Wherever the switching circuit 45
is located, the switching device can be provided with an adjustment
device 55, (as shown in FIG. 6) operable by the user of the system
in order to adjust the timing of the switching device. By operating
the adjustment device 55, the user is able to alter the ratio
between that part of the blended RF signal which is a cutting
signal, and that part which is a coagulating signal. Whether the
adjustment device 55 is located on the instrument 12 or the
generator 10, the user of the system can vary the signal so as to
increase or decrease the coagulating component of the blended
signal with respect to the cutting component. and vice versa. This
gives considerable flexibility to the electrosurgical system in
terms of its use as a simultaneous cutting and coagulation device,
with user-operable control of how much coagulation is provided.
[0041] As in the arrangement described above in FIG. 4, the
switching device 51 of the alternative switching circuit of FIG. 6
may be as shown in FIG. 5A or FIG. 5B, the driving signal being
obtained from a source associated with the switching device itself
or from control circuitry within the generator which controls other
generator functions.
[0042] Various circuits for implementing the adjustment device 55
will be apparent to those skilled in the art. An example of a
circuit in which a blended mode signal is generated by elements
associated with the switching device and has a variable
mark-to-space ratio is shown in FIG. 8A. In this case, the output
of a triangular wave generator 56 is compared in a comparator 57
with a user-adjustable reference voltage to produce a square wave
of the switching device 51 (FIG. 6). Another circuit generating an
adjustable blended mode switching device control signal is shown in
FIG. 8C. Here, a user-operable potentiometer 58 is coupled with a
timer circuit 59 using a 555 i.c.
[0043] FIG. 9 shows an alternative generator system in which two RF
source circuits 74 and 74'' are employed. Source circuit 74
comprises RF oscillator 60 and its associated power supply and
control elements. The source circuit is as described with reference
to FIG. 2, and like elements are given the same reference numerals
as in FIG. 2. The second source circuit 74'' comprises a second RF
oscillator 60'', along with a second controller 72'', power supply
66'', voltage threshold detector 68'' and on time control circuit
70''. FIG. 9 shows the source circuit 74'' as having its own
dedicated version of each of these units, although it is feasible
that certain of them (such as the power supply 66'' and controller
72'') could be shared with the source circuit 74. The voltage
threshold detector 68 is set such that the output connections 60C
from source circuit 74 provide an output power signal having a
cutting RF waveform, while the voltage threshold detector 68'' is
set such that the output connections 60C'' from source circuit 74''
provide an output power signal having a coagulating RF waveform.
The second oscillator 60'' operates at a different frequency from
that of oscillator 60.
[0044] A common output stage 73 is provided for both source
circuits 74 and 74'' . Output connections 60C from source circuit
74 are connected to input connections 46 and 47 of the output stage
73, while output connections 60C'' from source circuit 74'' are
connected to input connections 46'' and 47'' of the output stage
respectively. Within the output stage 73, input connections 47 and
47'' are both connected to output connection 49, while input
connection 46 is connected to output connection 48, and input
connection 46'' to output connection 50. The result of this
arrangement is that the cutting RF signal from source circuit 74 is
delivered between output connections 48 and 49 and hence to one
pair of electrodes on the electrosurgical instrument 12.
Simultaneously, the coagulating RF signal from source circuit 74''
is delivered betVeen output connections 49 and 50 and hence to a
different pair of electrodes of the instrument 12. Thus the
electrosurgical instrument 12 is able simultaneously to cut and
coagulate tissue by virtue of the two different frequency signals.
As before, the advantage is that the cutting signal and the
coagulating signal, whether they be applied simultaneously or in an
alternating blended signal, are delivered to different pairs of
electrodes of the electrosurgical instrument. The design of these
electrodes can therefore be optimised, depending on whether they
are intended to cut or coagulate tissue.
[0045] Referring to FIG. 10, in an further alternative generator
and instrument combination, two RF power oscillators 60-1 and 60-2
are powered from a common power supply 62 and are controlled by a
common controller 72 to produce on respective output lines 60C an
RF power signal suitable for cutting and an RF power signal
suitable for coagulation. These signals may be fed to a switching
circuit 63 for selecting the power signal from one oscillator 60-1
or the other oscillator 60-2 according to inputs from, for
instance, foot switches, the selected power signal being
transmitted on output connections 80, 81. In a blended mode, the
switch is operated repeatedly at a predetermined rate to produce a
blended output power signal across connections 80, 81. The power
oscillators 60-1, 60-2 are operated at different frequencies, and
the respective cut and coagulation signals are fed to the required
electrodes by feeding the power signal on output connections 80, 81
to tuned circuits 82-1 and 82-2 tuned to the different frequencies.
The outputs of the tuned circuits are coupled via electrode lines
48, 49 and 50 to the respective electrodes of the electrosurgical
instrument. In this way, the cutting signal from oscillator 60-1 is
fed to a cutting electrode 48 and a common electrode 49, whereas
the coagulation signal from oscillator 60-2 is fed to a coagulation
electrode 50 and the common electrode 49.
[0046] In the embodiment shown in FIG. 10, the connection between
the electrosurgical generator and the electrosurgical instrument is
typically provided by output connections 80 and 81, but the
apportionment of circuit blocks between the generator and the
instrument may be varied.
[0047] Further embodiments are shown in FIGS. 11A and 11B. Like the
embodiment of FIG. 9, these embodiments dispense with the need for
a signal routing switch or switching circuit.
[0048] Referring to FIG. 11, there are provided two tuned circuits
82-1 and 82-2 (as in FIG. 10), tuned to different frequencies. Each
has a series-resonant inductor-capacitor pair 84 and a
parallel-resonant inductor-capacitor pair 86, the latter being
transformer coupled to output connections 46 and 47 on the one hand
and 46'' and 47'' on the other hand. As in the embodiment of FIG.
10, each tuned circuit has two inputs, one of which is connected to
a generator output connection 80 and the other of which is
connected to a generator output connection 81. In this embodiment,
the generator has an output stage comprising RF switches arranged
in two oppositely acting push-pull pairs 90A, 90B and 91A, 91B.
Typically these switches comprise power MOSFETS. Each switch 90A,
90B, 91A, 91B is connected to driver inputs 92, 93, as shown, which
receive an RF drive signal which, for producing on the output
connections 80, 81 an output having a cut waveform is at one RF
frequency, and for producing a coagulation output on the output
connections 80, 81, has a different RF frequency, these frequencies
being, respectively, the resonant frequency of, the resonant
combinations 84, 86 of the first tuned circuit 82-1 and, the
resonant frequency of the corresponding resonant combinations of
the other tuned circuit 82-2. As described above, the RF switches
90A, 90B, 91A and 91B of the generator output stage may be driven
according to, for instance, a footswitch control to produce a cut
output or a coagulation output. Again, additionally, a blended
output may be produced in which the RF frequency alternates
constantly between the two resonant frequencies of the tuned output
circuits.
[0049] The embodiment of FIG. 11B is a modification of that of FIG.
11A, in which the generator output stage has a single push-pull
pair of RF switches 90A, 90B and in which the tuned circuits each
have one input connected to the junction between the switches 90A,
90B and the other input connected to ground.
* * * * *