U.S. patent application number 12/062516 was filed with the patent office on 2008-09-18 for electrocautery method and apparatus.
Invention is credited to Peter Seth Edelstein, Joseph Charles EDER, Mark Kane, Camran Nezhat, Benjamin Theodore Nordell.
Application Number | 20080228179 12/062516 |
Document ID | / |
Family ID | 39708348 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080228179 |
Kind Code |
A1 |
EDER; Joseph Charles ; et
al. |
September 18, 2008 |
ELECTROCAUTERY METHOD AND APPARATUS
Abstract
An electrode structure and a mechanism for automated or
user-selected operation or compensation of the electrodes, for
example to determine tissue coverage and/or prevent arcing between
bottom electrodes during electrocautery is disclosed.
Inventors: |
EDER; Joseph Charles; (Los
Altos, CA) ; Nordell; Benjamin Theodore; (San Mateo,
CA) ; Edelstein; Peter Seth; (Menlo Park, CA)
; Nezhat; Camran; (Woodside, CA) ; Kane; Mark;
(San Jose, CA) |
Correspondence
Address: |
GLENN PATENT GROUP
3475 EDISON WAY, SUITE L
MENLO PARK
CA
94025
US
|
Family ID: |
39708348 |
Appl. No.: |
12/062516 |
Filed: |
April 4, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11671891 |
Feb 6, 2007 |
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12062516 |
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11382635 |
May 10, 2006 |
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11671891 |
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11371988 |
Mar 8, 2006 |
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11382635 |
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11382635 |
May 10, 2006 |
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11371988 |
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60725720 |
Oct 11, 2005 |
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60680937 |
May 12, 2005 |
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Current U.S.
Class: |
606/33 |
Current CPC
Class: |
A61B 2018/00595
20130101; A61B 2018/00791 20130101; A61B 2018/00702 20130101; A61B
2018/0063 20130101; A61B 2018/00875 20130101; A61B 2018/00827
20130101; A61B 2018/165 20130101; A61B 18/1442 20130101; A61B
2018/00505 20130101; A61B 2018/00678 20130101 |
Class at
Publication: |
606/33 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. An electrocautery apparatus, comprising: a plurality of first
electrodes forming a first electrode array; at least one second
electrode; a power supply having multiple, independently adjustable
output channels for application of high frequency power to targeted
tissue via selective coupling of said high frequency power to said
first electrodes and to said at least one second electrode; at
least one sensor for sensing at least one parameter comprising any
of voltage, current, impedance, phase angle between applied voltage
and current, temperature, energy, and frequency and for producing
an output representative of a value or rate of change of said at
least one parameter; means, responsive to said at least one sensor,
for controlling at least one aspect of said high frequency power
provided by said power supply; and means for selectively applying
said high frequency power provided by said power supply between two
or more electrodes among any of the electrodes in the first
electrode array and said at least one second electrode; wherein
said high frequency power provided by said power supply cauterizes
or necroses tissue between surfaces of said first electrode array
and said at least one second electrode.
2. The apparatus of claim 1, wherein said power supply is
adjustable by any of real-time control, pre-set selection by a
user, default settings, or selection of a predetermined
profile.
3. The apparatus of claim 1, further comprising: means for
determining the area of tissue coverage of at least one of any of
said first electrodes and said at least one second electrode by
measuring phase-angle of RF voltage and current.
4. The apparatus of claim 1, said power generating high frequency
power in frequency bands comprising any of 100 kHz to 10 MHz or 200
kHz to 750 kHz.
5. The apparatus of claim 1, said power generating high frequency
power at power levels comprising any of 10 W to 500 W, or 25 W to
250 W, or 50 W to 200 W.
6. The apparatus of claim 1, said power supplying high frequency
power to said first electrodes and said at least one second
electrode at power levels comprising any of 1 W/cm.sup.2 to 500
W/cm.sup.2 or 10 W/cm.sup.2 to 100 W/cm.sup.2.
7. The apparatus of claim 1, said sensor comprising any of: a
voltmeter, analog-to-digital converter, thermistor, transducer, or
ammeter.
8. The apparatus of claim 1, said means for controlling said high
frequency power provided by said power supply further comprising:
means for selecting impedance to maintain an impedance match
between said power supply and said tissue to achieve maximum power
transfer and to make accurate power measurements; wherein impedance
matching is achieved when the phase-angle between applied voltage
and current is at or near zero.
9. The apparatus of claim 8, said means for controlling said high
frequency power provided by said power supply further comprising:
an inductive element that is adjustable to a near zero phase angle
to increase inductance and compensate for increased capacitive
reactance.
10. The apparatus of claim 1, said power supply comprising
adjustment means for any of: identifying individual electrodes to
be activated to focus energy of the individual electrodes on a
specific region of tissue; establishing a firing order for said
individual electrodes; assessing or measuring magnitude of
impedance to be used in compensating and/or impedance matching
between said power supply and said at least one of any of said
first electrodes and said at least one second electrode;
establishing at least one parameter of electrical power to be
applied in electrocautery, said parameters comprising voltage,
current, impedance, phase angle between applied voltage and
current, temperature, energy, frequency, and/or rate of change of
said at least one parameter.
11. The apparatus of claim 1, wherein said at least one sensor is
constructed to provide raw data to said means for controlling said
high frequency power provided by said power supply, said means for
controlling said high frequency power provided by said power supply
comprising means for analyzing whether and how to adjust impedance
by changing the frequency of RF energy delivered by said power
supply.
12. The apparatus of claim 1, said means for controlling said high
frequency power provided by said power supply, in conjunction with
said at least one sensor, further comprising: means for determining
whether or not tissue is present at each electrode at the beginning
of a cauterization cycle by measuring any of voltage, current,
impedance, phase angle between applied voltage and current,
temperature, energy, frequency, and/or rate of change of said at
least one parameter; wherein, if tissue is not present at any
electrode, then said electrode is idle; wherein said means for
controlling said high frequency power provided by said power supply
comprises means that deactivates firing of said idle electrode,
and/or provides a warning to an operator via a user interface.
13. The apparatus of claim 11, said means for controlling said high
frequency power provided by said power supply further comprising: a
status indicator for each electrode that indicates any of an idle,
active, or complete condition, once a cauterization cycle is
commenced with regard to each said electrode.
14. The apparatus of claim 1, wherein said at least one second
electrode comprises at least one return electrode.
15. The apparatus of claim 2, said power supply comprising: an RF
generator selectively operable by said means for selectively
applying a voltage from the power supply to insert a conjugate
impedance in the form of an inductance to cancel out capacitive
reactance with a fully covered electrode and to permit measurement
of phase-angle of RF voltage and current; wherein when an electrode
is only partially covered, capacitance changes; and wherein, as a
result, reactance and phase-angle of RF voltage and current
change.
16. The apparatus of claim 2, said means for selectively applying a
voltage from the power supply further comprising: an RF generator
control algorithm for changing RF generator frequency upon
detection of smaller electrode surface areas to maintain maximum
power transfer while minimizing electrical arcing and suboptimal
and/or excessive energy delivery.
17. The apparatus of claim 1, said means for selectively applying a
voltage from the power supply further comprising: means for
detecting electrical arcing and preventing suboptimal and/or
excessive energy delivery by determining rapid changes in phase
and/or impedance.
18. The apparatus of claim 3, means for detecting electrical arcing
and preventing suboptimal and/or excessive energy delivery further
comprising: means for using electrodes which are only partially
covered by tissue to signal said RF generator control algorithm to
shorten or change treatment parameters.
19. The apparatus of claim 15, said means for selectively applying
a voltage from the power supply further comprising: means for
maintaining an impedance match between said RF generator and
tissue; wherein impedance matching is achieved when a phase-angle
is about zero.
20. The apparatus of claim 19, said means for maintaining an
impedance match between said RF generator and tissue further
comprising: one or more reactive elements which compensate for
increased capacitive reactance.
21. The apparatus of claim 20, said means for maintaining an
impedance match between said RF generator and tissue further
comprising any of: means for insertion of a continuously variable
inductor with a finite range and nearly infinite resolution,
wherein said inductor adjustable to a near zero phase; means for
insertion of discrete elements to find a lowest phase; and means
for changing the frequency of said RF generator, wherein said RF
generator compensates for phase discrepancy by electronically
changing frequency.
22. The apparatus of claim 1, said power supply further comprising
a pulse width modulation mechanism for establishing a desired power
output.
23. An electrocautery method, comprising the steps of: forming a
first electrode array with a plurality of first electrodes;
providing at least one second electrode; selectively applying high
frequency power to targeted tissue by coupling high frequency power
to said first electrodes and to said at least one second electrode
from a power supply having multiple, independently adjustable
output channels; sensing at least one parameter comprising any of
voltage, current, impedance, phase angle between applied voltage
and current, temperature, energy, and frequency and for producing
an output representative of a value or rate of change of said at
least one parameter; and responsive to said output representative
of a value or rate of change of said at least one parameter,
controlling at least one aspect of said high frequency power
provided by said power supply; wherein said high frequency power
provided by said power supply cauterizes or necroses tissue between
surfaces of said first electrode array and said at least one second
electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/671,891, filed Feb. 6, 2007 (Attorney Docket No.:
ARAG0016), which is a continuation-in-part of U.S. application Ser.
Nos. 11/382,635 filed May 10, 2006 (Attorney Docket No.: ARAG002)
and 11/371,988 filed Mar. 8, 2006 (Attorney Docket No.: ARAG0003),
and claims the benefit thereof in accordance with 35 USC 120. U.S.
application Ser. No. 11/382,635 filed May 10, 2006 in turn, claims
the benefit of provisional applications 60/725,720 filed on Oct.
11, 2005 (Attorney Docket No. ARAG0001 PR) and 60/680,937 filed on
May 12, 2005 (Attorney Docket No. ARAG005PR). The entireties of the
foregoing applications are incorporated herein by this reference
thereto.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to tissue cauterization. More
particularly, the invention concerns an electrocautery system with
various electrodes and a mechanism for automated or user-selected
operation or compensation of the electrodes.
[0004] 2. Description of the Related Art
[0005] Various physiological conditions call for tissue and organ
removal. A major concern in all tissue removal procedures is
hemostasis, that is, cessation of bleeding. All blood vessels
supplying an organ or a tissue segment to be removed have to be
sealed, either by suturing or cauterization, to inhibit bleeding
when the tissue is removed. For example, when the uterus is removed
in a hysterectomy, bleeding must be inhibited in the cervical neck,
which must be resected along the certain vessels that supply blood
to the uterus. Similarly, blood vessels within the liver must be
individually sealed when a portion of the liver is resected in
connection with removal of a tumor or for other purposes. Achieving
hemostasis is necessary in open surgical procedures as well as
minimally invasive surgical procedures. In minimally invasive
surgical procedures, sealing of blood vessels can be especially
time consuming and problematic because there is limited access via
a cannula and other small passages.
[0006] Achieving hemostasis is particularly important in limited
access procedures, where the organ or other tissue must be
morcellated prior to removal. Most organs are too large to be
removed intact through a cannula or other limited access passage,
thus requiring that the tissue be morcellated, e.g. cut, ground, or
otherwise broken into smaller pieces, prior to removal.
[0007] In addition to the foregoing examples, there exist a variety
of other electrosurgical instruments to seal and divide living
tissue sheets, such as arteries, veins, lymphatics, nerves,
adipose, ligaments, and other soft tissue structures. A number of
known systems apply radio frequency (RF) energy to necrose bodily
tissue. Indeed, some of these provide significant advances and
enjoy widespread use today. Nevertheless, the inventors have sought
to identify and correct shortcomings of previous approaches, and to
research possible improvements, even when the known approaches are
adequate.
[0008] In this respect, one problem recognized by the inventors
concerns the small size of today's electrode structures. In
particular, many electrosurgical instrument manufacturers limit the
total length and surface area of electrodes to improve the
likelihood of completely covering the electrodes with tissue. This
small electrodes strategy results in the surgeon having to seal and
divide multiple times to seal and divide long tissue sheets
adequately. Such time consuming processes are also detrimental to
patients, increasing anesthetic time and potentially increasing the
risk of injury to surrounding structures, as the delivery of energy
and division of tissue is repeated again and again.
[0009] The consequences of partial electrode coverage can be
significant. This condition can cause electrical arcing, tissue
charring, and inadequate tissue sealing. Mechanical, e.g. blade, or
electrosurgical division of tissue is performed immediately
following tissue sealing, and the division of inadequately sealed
tissue can pose a risk to the patient because unsealed vessels may
hemorrhage. Arcing presents its own set of problems. If
electrocautery electrodes generate an arc between them, instead of
passing RF energy through targeted tissue, the tissue fails to
undergo the intended electrocautery. Furthermore, depending upon
the path of the arc, this might damage non-targeted tissue. Another
problem is that adjacent electrodes in a multiple electrode system
may generate electrical cross-talk or generate excessive thermal
effect in the transition zone between two adjacent electrodes that
fire sequentially. Previous designs prevented this by imposing a
mechanical standoff for the jaws that the electrodes were fastened
onto. However, this standoff prevented very thin tissue from making
contact with the opposing electrodes, preventing an optimal
electrical seal in these regions. These standoffs, if too shallow,
can also result in arcing between electrodes.
[0010] At typical radiofrequency energy (RF) frequencies in the 300
kHz to 10 MHz range, tissue impedance is largely resistive. Prior
to tissue desiccation, initial impedances can vary greatly
depending on the tissue type and location, vascularity, etc. Thus,
to ascertain the adequacy of tissue electrode coverage based solely
on local impedance is imprecise and impractical. A feasible and
dependable methodology for determining electrode coverage by tissue
would allow for the development of electrodes of greater length and
surface area for use in the safe and rapid sealing and division of
tissue sheets during surgical procedures. It would therefore be
advantageous to provide a methodology for determining the area of
tissue coverage of one or more electrodes.
SUMMARY
[0011] An electrode structure and a mechanism for automated or
user-selected operation or compensation of the electrodes, for
example to determine tissue coverage and/or prevent arcing between
bottom electrodes during electrocautery is disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a block diagram of the components and
interconnections of an electrocautery system according to the
invention;
[0013] FIG. 2 is a combination block and schematic diagram
illustrating an electrocautery device with a first embodiment of
compensating circuitry according to the invention;
[0014] FIG. 3 is a combination block and schematic diagram
illustrating an electrocautery device with a second embodiment of
compensating circuitry according to this invention;
[0015] FIG. 4 is a combination block and schematic diagram
illustrating an electrocautery device with a third embodiment of
compensating circuitry according to the invention;
[0016] FIG. 5 is a combination block and schematic diagram
illustrating an electrocautery device with circuitry for
selectively firing electrodes according to the invention; and
[0017] FIG. 6 is a block diagram showing an electrode having a
dielectric coating according to the invention.
DETAILED DESCRIPTION
[0018] In view of the problems of conventional technology that the
inventors have recognized (as discussed above), the inventors have
sought to improve the ability of a user to control electrocautery
electrodes after said electrode have been inserted into the body.
Further areas of their focus include improving the efficiency of
transferring power to electrode structures, and improving the
accuracy of measurements taken from the electrode structure in
situ. One benefit of implementing these improvements is the ability
to use larger electrode surfaces, with the advantageous
consequences discussed above.
[0019] FIG. 1 illustrates one embodiment of electrocautery system
100. The system 100 includes an electrode structure 102 that is
electrically driven by a power, electrode selector, and compensator
module 108. The module 108 is operated in accordance with user
input conveyed via one or more user interfaces 110.
[0020] As explained below in greater detail, certain components of
the system 100 may be implemented with digital data processing
features. These may be implemented in various forms.
[0021] Some examples include a general purpose processor, digital
signal processor (DSP), application specific integrated circuit
(ASIC), field programmable gate array (FPGA) or other programmable
logic device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the
functions described herein. A general purpose processor may be a
microprocessor, but in the alternative, the processor may be any
conventional processor, controller, microcontroller, or state
machine. A processor may also be implemented as a combination of
computing devices, e.g. a combination of a DSP and a
microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration.
[0022] As a more specific example, a digital data processing
includes a processor, such as a microprocessor, personal computer,
workstation, controller, microcontroller, state machine, or other
processing machine, coupled to digital data storage. In the present
example, the storage includes a fast-access storage, as well as
nonvolatile storage. The fast-access storage may be used, for
example, to store the programming instructions executed by the
processor. Storage may be implemented by various devices. Many
alternatives are possible. For instance, one of the components may
be eliminated. Furthermore, the storage may be provided on-board
the processor, or even provided externally to the apparatus.
[0023] The apparatus also includes an input/output, such as a
connector, line, bus, cable, buffer, electromagnetic link, antenna,
IR port, transducer, network, modem, or other means for the
processor to exchange data with other hardware external to the
apparatus.
[0024] As mentioned above, various instances of digital data
storage may be used, for example, to provide storage used by the
system 100 (FIG. 1), to embody the storage, etc. Depending upon its
application, this digital data storage may be used for various
functions, such as storing data, or to store machine-readable
instructions. These instructions may themselves aid in carrying out
various processing functions, or they may serve to install a
software program upon a computer, where such software program is
then executable to perform other functions related to this
disclosure.
[0025] An exemplary storage medium is coupled to a processor so the
processor can read information from, and write information to, the
storage medium. In the alternative, the storage medium may be
integral to the processor. In another example, the processor and
the storage medium may reside in an ASIC or other integrated
circuit.
[0026] In contrast to storage media that contain machine-executable
instructions (as described above), a different embodiment uses
logic circuitry to implement processing data processing features of
the system.
[0027] Depending upon the particular requirements of the
application in the areas of speed, expense, tooling costs, and the
like, this logic may be implemented by constructing an
application-specific integrated circuit (ASIC) having thousands of
tiny integrated transistors. Such an ASIC may be implemented with
CMOS, TTL, VLSI, or another suitable construction. Other
alternatives include a digital signal processing chip (DSP),
discrete circuitry (such as resistors, capacitors, diodes,
inductors, and transistors), field programmable gate array (FPGA),
programmable logic array (PLA), programmable logic device (PLD),
and the like.
Electrode Structure 102
[0028] Referring to FIG. 1, the electrode structure 102 includes
first and second electrode surfaces 103-104. The electrode surface
104 is formed by a group of electrodes, such as individual
electrodes 104a, 104b, etc. In one instance, the electrodes may be
substantially contiguous. The electrode surface 103, in one
instance, includes a single electrode, as illustrated. In another
instance, the surface 103 includes multiple electrodes, of the same
or different number than the electrodes 104.
[0029] In one embodiment the electrode surfaces 103-104 are
arranged to provide electrical power to a targeted tissue area
using opposed, bipolar electrodes. The use of opposed, bipolar
electrodes is advantageous because it concentrates energy flux
between the electrodes and limits the effect on adjacent tissue
that is not confined within the opposed electrodes.
[0030] In one case, the electrode structures 103-104 may have
generally similar geometries to contact tissue in a symmetric
fashion. Alternatively, the electrode structures 103-104 may have
dissimilar geometries. For example, one electrode structure may
comprise a probe for insertion into a natural body orifice with the
other electrode structure being structured to engage an exterior
tissue surface apart from the body orifice. In some instances, more
than two electrode structures may be employed, but at least two
electrode structures, or separate regions of a single structure,
are energized with opposite polarity to apply RF energy to the
targeted tissue. In some instances, the electrode structures may be
different regions formed as part of a single support structure,
e.g. a single elastic tube or shell which may be placed over an
organ or other tissue mass and which has two or more electrode
surfaces formed thereon.
[0031] The different electrode surfaces are isolated from each
other when high frequency energy of the same or opposite polarity
is applied to them. In still other instances, a single electrode
structure may have a plurality of electrically conductive or active
regions, where the electrically conductive regions may be energized
with the same or an opposite polarity.
[0032] In some instances, it may be desirable to provide additional
structure or components on the electrode structures to enhance or
increase the effective electrical contact area between the
electrode structure and the tissue. In particular, the electrode
structures may include tissue-penetrating elements to enhance
electrical contact i.e. reduce electrical impedance between the
electrode and the tissue and increase the total surface contact
area between the electrode and the tissue. Exemplary
tissue-penetrating elements include needles, pins, protrusions,
channels, or the like. A particular example includes pins having
sharpened distal tips so that they can penetrate through the tissue
surface and into the underlying tissue mass. The pins may have
depths in the range from 1 mm to 5 cm, or from 3 mm to 1 cm. The
diameters of the pins range from 0.1 mm to 5 mm, or from 0.5 mm to
3 mm. In one instance, the pins are evenly distributed over the
tissue-contact area of an electrode structure, with a pin density
in the range from 0.1 pin/cm.sup.2 to 10 pin/cm.sup.2, or from 0.5
pin/cm.sup.2 to 5 pin/cm.sup.2. When tissue-penetrating elements
are used, they may be dispersed in a general uniform matter over
the electrically active area of the electrode structure. The pins
or other tissue-penetrating elements may be provided in addition to
an electrically conductive conformable or rigid electrode surface,
but in some instances the pins may provide the total electrically
conductive or active area of an electrode structure.
[0033] In one example, the electrodes comprise a plurality of
different electrically conductive regions, where the regions may be
electrically isolated from each other or may be electrically
coupled to each other. Single electrode structures may include
three, four, five, and as many as ten or more discrete electrically
conductive regions thereon. Such electrically conductive regions
may be defined by electrically insulating regions or structure
between them.
[0034] One example of a multiple-electrode surface 104 is a
plurality of electrically conductive strips that are separated by a
gap which may be an air gap, a plastic member or other insulator.
The gap is preferably less than 0.5 mm. In addition, multiple
tissue-penetrating pins may be disposed along the length of each
electrically conductive strips. The electrically conductive strips
may be energized in an alternating polarity configuration. Most
simply, opposing strips are connected to opposite polls on a single
power supply. Electrical connections may be rearranged, however, to
power the strips in virtually any pattern. Moreover, it is also
possible to isolate different regions of each strip electrically to
permit powering those regions at different polarities; or to set
the electrodes to the same polarity but with various sequences of
firing pattern that can include firing every electrode, firing
specific electrode, or firing multiple electrodes
simultaneously.
[0035] Although shown as flat plates, the electrode structure 102
may be implemented in a variety of different shapes without
departing from the scope of the invention. For instance, the
electrode structures 103-104 may be generally curved to facilitate
placement over a tubular body structure or tissue mass. In one
case, electrode configurations are specifically configured to have
a geometry intended to engage a particular organ or tissue
geometry. In other cases, the electrode configurations are
conformable so that they can be engaged against and conform to
widely differing tissue surfaces. In this regard, electrode strips
may be constructed from such material as, for example, conformable
meshes, permitting the electrode structures to be flattened out or
to assume a wide variety of other configurations. Additionally, the
insulating structures may also be formed from a flexible or
conformable material, permitting further reconfiguration of the
electrode structures. The structure 102 may be implemented
according in any one, or a combination, of known shapes
configurations, which are familiar to the ordinarily skilled
artisan. Some exemplary shapes include opposing jaws, cylinder,
probe, flat pads, etc. In this regard, the electrodes may be
configured in any manner suitable for engaging a tissue
surface.
[0036] Thus, the electrodes can be rigid, flexible, elastic,
inelastic (non-distensible), planar, non-planar, or the like, and
may optionally employ tissue-penetrating elements to enhance
electrical contact between the electrode structure and the tissue,
as well as to increase the electrode area. Electrode configurations
may be conformable so that they can be engaged against and conform
to widely differing tissue surfaces, or they are specifically
configured to have a geometry intended to engage a particular organ
or tissue geometry. In both instances, the electrode structures may
further be provided with tissue-penetrating elements.
[0037] Optionally, electrode structures may include both a
conductive surface and a non-conductive surface. In some
embodiments this is accomplished by leaving one surface as an
exposed metallic face, while the other surface of the electrode is
covered or insulated with, for example, a dielectric material. In
the case of rigid electrodes, the insulation can be laminated,
coated, or otherwise applied directly to the opposed surface. In
the case of flexible and elastic electrodes, the insulating layer
is flexible so that it can be expanded and contracted together with
the electrode without loss or removal. In some cases, a separate,
expandable sheet of material covers the face for which insulation
is desired. In some embodiments, all electrode surfaces may be
coated with a dielectric material.
[0038] In one embodiment, the electrically active regions of the
electrode structures have an area ranging from one to fifty
cm.sup.2 or larger. Further details and examples of electrode
structures are explained in the U.S. patent applications as
identified incorporated herein by reference above.
Power Supply 106
[0039] The power supply 106 includes one or multiple power
supplies. Basically, the power supply 106 generates high frequency,
such as RF, power for application to targeted tissue through one or
more electrically active regions of the electrode structure 102. As
described below, the duration and magnitude of power cauterizes or
necroses tissue between the electrode surfaces 103-104.
[0040] Exemplary frequency bands include 100 kHz to 10 MHz or 200
kHz to 750 kHz. Power levels depend on the surface area and volume
of tissue being treated, with some examples including a range from
10 W to 500 W, or 25 W to 250 W, or 50 W to 200 W. Power may be
applied at a level of from 1 W/cm.sup.2 to 500 W/cm.sup.2, or 10
W/cm.sup.2 to 100 W/cm.sup.2, for example.
[0041] The power supply 106 may be implemented using various
conventional general purpose electrosurgical power supplies. The
power supply 106 may employ sinusoidal or non-sinusoidal wave forms
and may operate with fixed or controlled power levels. Suitable
power supplies are available from commercial suppliers.
[0042] In one embodiment, the power supply provides a constant
output power, with variable voltage and current, where power output
varies based upon load. Thus, if the system sees a very high
impedance load, the voltage is maintained at a reasonable level to
avoid arcing. With tissue electrocautery, impedance ranges from two
ohms to 1000 ohms, for example. By applying constant power, the
power supply 106 can provide significant current at low impedance
to achieve initial desiccation when the tissue is first being
cauterized and, as cauterization proceeds, to apply higher voltage
to complete the tissue sealing process. Thus, the power supply 106
can provide larger current and smaller voltage at the beginning of
the cauterization process and a higher voltage and lower current at
the sealing phase of the process. Control of such power generator
is based, at least in part, on the system 100 monitoring power.
[0043] In one embodiment, the power supply 106 includes a mechanism
for setting the desired power. This setting may occur by real-time
control, pre-set selection by a user, default settings, selection
of predetermined profile, etc. In one embodiment, pulse width
modulation is used in connection with a flyback transformer. The
system charges a primary of the flyback transformer and produces a
regulated output. The secondary may be regulated, for example, to
15 volts at a desired number of amperes to produce the desired
power output. Based upon the period, as determined by the width of
the pulse which charges the primary, the power curve is determined.
Thus, the invention establishes a certain level of power in the
primary of the flyback transformer and the same level of power is
provided by the secondary without regard to impedance of the load,
i.e. the tissue.
[0044] The power supply 106 may include digital data processing
equipment, such as mentioned above. This optional equipment, if
implemented, is used to establish and control features and
operation of the power supply 106.
[0045] As illustrated, the power supply 106 is a source of power
for multiple electrodes of the structure 102. Accordingly, the
power supply 106, or the module 108, provides multiple output
channels, each of which is independently adjustable. In this
embodiment, the system 100 includes a conductive supply path of
multiple conductors 108c to provide power to the electrodes, and a
return path 108b for providing a ground path and/or feedback to the
power supply or vice versa, depending on the direction of current
flow.
[0046] In a more particular embodiment, the module 108 has multiple
outputs 108c routed to the individual electrodes by a digital data
processor of the module 108. These multiple outputs are
independently operated by the processor and readily modulated and
assignable. Thus, the processor may assign an output to any one or
more of the electrode elements at a certain point in operation of a
cauterization cycle, and dynamically reassign them other points of
time. For example, if the power source were a four channel power
source and the electro-surgical device had sixteen electrodes, then
each channel may support four electrodes in electro-surgical
device. However, this arrangement may be varied so that some
channels support more electrodes than others.
User Interface 110
[0047] The user interface 110 comprises one or more devices for a
human to exchange information with the module 108, including the
power supply 106. There may be a common user interface, or separate
user interfaces for each component 106, 108. The user interface may
be implemented in various ways, with the following serving as some
examples. As for human-to-machine flow, some examples of the
interface 110 include buttons, dials, switches, keyboards, remote
control console, or other mechanical devices. Other examples
include pointing devices such as a mouse, trackball, etc. Still
other examples include digitizing pads, touch screens, voice input,
or any other example suitable for the purposes described herein. As
for the machine-to-human exchange, the interface 110 may employ a
video monitor, display screen, LEDs, mechanical indicators, audio
system, or other example suitable for the purposes described
herein.
[0048] User input is conveyed from the interface to the module 108
via the link 108a.
Sensors
[0049] The system 100 may also include various sensors attached to
various components of the system 100. The sensors, which are not
shown in FIG. 1 to avoid cluttering the diagram, may be attached to
components such as the electrodes 103-104, subparts of the module
108, equipment of the power supply 106, and the like. Examples of
these sensors include devices for sensing voltage, current,
impedance, phase angle between applied voltage and current,
temperature, energy, frequency, etc. More particular, some of these
devices include voltmeters, analog-to-digital converters,
thermistors, transducers, ammeters, etc.
Module 108
[0050] As shown above, the module 108 includes one or more power
supplies 106. Aside from this function, module 108 may be
implemented to perform some or all of automated or user-selected
operation or compensation of the electrodes in the manner shown
below. According to one aspect, the module 108 may be used to
target a specific region of tissue, or the control firing order of
electrodes, by selectively limiting power application to electrodes
whose selection is predetermined, machine-selected, or
user-selected. According to another aspect, the module 108 may
introduce impedance into the electrode circuitry to provide a
predetermined, machine-selected, or user-selected impedance
matching or compensation.
[0051] According to one optional aspect of the module 108, the
module 108 may target a specific region of tissue by selectively
limiting power application to electrodes whose selection is
predetermined, machine-selected, or user-selected. In this regard,
the module 108 has a variety of outputs 108b-108c individually
coupled to each of the electrodes 103-104. As one example, the
outputs 108b-108c may comprise wires, cables, busses, or other
electrical conductors. In the illustrated example, there are
multiple conductors 108c leading to the multiple electrodes 104a,
104b, etc.
[0052] The module 108 applies voltage from the power supply 106
across the first and second electrode surfaces 103-104, such that
the voltage is applied exclusively to selected ones of the
electrodes. These electrodes may be selected according to user
input from the interface 110, selected by a machine-implemented
analysis, and/or selected by a default state. In this regard, the
module 108 may include a switching network of electrical and/or
mechanical switches, relays, or other mechanism to provide power to
selected ones of the electrodes. As shown, the power supply 106 is
integrated into the module 108, and computer control selectively
activates selected output conductors.
[0053] Whether by independent switching network or computer
regulated activation of output conductors, the module 108 activates
electrodes according to input from user interface 110, or input
from a machine such as a digital data processing device as
discussed above. Depending upon the nature of the application, such
controlled application of power to electrodes may be performed in
accordance with a machine-selected criteria or analysis, default
state, or user input.
[0054] FIG. 5 illustrates a typical application of one example of a
processor-controlled switching network, shown in context of two
power supplies, electrode structures, and a targeted tissue region.
In this example, the electrode surfaces are configured as follows.
The electrode surfaces are substantially parallel during
performance of electrocautery, each electrode of one surface is
aligned with its counterpart in the other electrode surface. In
this example, there are two electrodes from the upper surface
corresponding to each electrode of the lower surface.
[0055] Significantly, the module 108 selectively limits power
application to certain electrodes, to target a specific region of
tissue. Electrodes may be selected for a different end, as well.
Namely, the module 108 may monitor or control the selection of
electrodes to prevent firing of adjacent electrodes of the same
electrode surface concurrently or sequentially. Ensuring that
electrode firing occurs in this spaced-apart fashion prevents
unintentional arcing between electrodes and improves the
effectiveness of electrocautery. In one embodiment, the controlled
firing order is implemented by computer control, and particularly,
by a digital data processing component of the module 108. As an
alternative to computer control, mechanical means may be used, such
as an electromechanical distributor or other device.
[0056] In another embodiment, the module 108 may introduce
impedance into the electrode circuitry to provide predetermined,
machine-selected, fixed, or user-selected impedance matching or
compensation. In other words, the module 108 contains a mechanism
to electrically introduce impedance into a circuit containing the
power supply, the outputs 108b-108c, and the electrodes
103-104.
[0057] More particularly, the module 108 includes capacitors,
inductors, and/or other impedance elements that can be adjusted or
selectively introduced to control the amount of impedance in the
circuit containing the power supply and electrodes 103-104. These
impedance elements may comprise discrete elements, integrated
circuit features, or other constructs suitable for the purposes
described herein. The module 108 establishes this impedance
matching or compensation according to directions from a user,
machine-implemented analysis, and/or default setting.
[0058] One example of an adjustable impedance is an adjustable
inductor that may comprise any known inductance, such as a coil of
conducting material wrapped around an adjustable ferromagnetic core
or discrete inductors. In this example, the overall inductance is
selectively increased by closing a switch that may be activated
manually, mechanically, electrically, or by any means suitable to
the purposes of this disclosure, for example, via the user
interface 110.
[0059] FIG. 2 illustrates an electrode arrangement having an
inductance in series with each electrode of an upper electrode
surface (as illustrated). FIG. 3 shows a different example,
including an inductance in series with each electrode of the lower
electrode surface (as illustrated). In a different example still,
FIG. 4 contains "T" type network where a capacitor is placed in
series with each electrode of the upper electrode surface.
Additionally, a different inductor is placed in parallel with each
pair of electrodes that are designed to be activated together. The
examples of FIGS. 2-4 may employ impedance elements that are fixed,
adjustable, or a combination of fixed and adjustable. Furthermore,
in connection with the electrodes having a dielectric coating on
their surface, a nearly limitless number of additional circuitry
configurations for impedance matching and/or compensation will be
apparent to ordinarily skilled artisans having the benefit of this
disclosure.
[0060] In addition to the arrangement for introducing impedance
into the electrode circuits, another consideration is the value of
such impedance elements. In one example, the impedance is selected
to achieve maximum power transfer and to make accurate power
measurements. In this regard, the impedance is chosen to maintain
an impedance match between the RF generator, namely, the power
supply 106, and the tissue. Impedance matching is achieved when the
phase-angle between applied voltage and current is zero. Namely,
additional inductance is increased to compensate for the increased
capacitive reactance. In one example, this is carried out with a
continuously variable inductor, with a finite range and nearly
infinite resolution. Such an inductor can be adjusted to a near
zero phase. In a different example, impedance matching is carried
out by using discrete inductive elements in an appropriate
arrangement, such as shown in FIGS. 2-4, to find the least possible
phase angle, though this may not be exactly zero.
[0061] Having described the structural features of the invention,
the operational aspects of the invention will be described. The
steps of any method, process, or algorithm described in connection
with the embodiments disclosed herein may be embodied directly in
hardware, in a software module executed by hardware,
human-performed steps, or a combination of these.
[0062] A sequence for performing an electrocautery procedure uses
an electrocautery system that includes an electrode structure and a
mechanism for automated or user-selected operation or compensation
of the electrodes. For ease of explanation, but without any
intended limitation, this example is described in the specific
context of the system 100 of FIG. 1.
[0063] In a first step, different parameters for operating the
system 100 are selected. In one example, one or more human users
select these parameters and convey them to the system 100 via the
user interface 110. In a different example, the parameters for
operating the system 100 are selected by digital data processing
equipment aboard the module 108. In this case, the parameters are
set according to user input, default values, measurements gathered
by the various sensors installed in the system 102, programming of
the module 108, etc.
[0064] Without any intended limitation, the following are some
non-exclusive examples of parameters that may be selected in the
first step: [0065] (1) Identity of individual electrodes to be
activated e.g., FIG. 5 in order to focus energy of the electrodes
103-104 on a specific region of tissue. [0066] (2) Firing order of
electrodes. [0067] (3) Assessment or measurement of magnitude of
impedance, e.g. FIGS. 2-4, to be used in compensating and/or
impedance matching between the power supply 106 and electrodes
103-104. [0068] (4) Parameters of electrical power to be applied in
electrocautery, such as magnitude, frequency, phase, or other
characteristics of voltage, current, power, etc. [0069] (5) Any
other parameter by which the operation of the system 100 can be
varied.
[0070] In a next step appropriately trained personnel apply the
electrodes 103-104 to a targeted tissue region to be
electrocauterized. The manner of applying the electrodes 103-104,
varies according to the construction of the electrodes 103-104, the
nature of the targeted body part, the procedure to be performed,
and other such factors. There may be circumstances where both
electrode structures 103-104 are used within the body, and other
embodiments where one electrode is inserted into the body and the
other electrode used externally, i.e. bipolar or monopolar
applications, as is know in the art.
[0071] In a specific example of this next step, there are multiple
electrodes of one surface, such as 104, corresponding to one
electrode of the other surface, such as 103. Optionally, personnel
arrange the first and second electrode surfaces 103-104 so that the
electrode surfaces are substantially parallel, and each one of the
second electrodes is aligned with its corresponding first
electrodes, although alignment is preferably obtained during
manufacture of the device. FIGS. 2-5 show examples of the final
arrangement.
[0072] In a further step, directions are given to begin
electrocautery. This occurs by user input submitted via the
interface 110. For example, a user may press a start button, utter
a start command, press a foot pedal, trip a lever, or perform other
action. In a different example, electronically occurs upon
expiration of a user-initiated timer.
[0073] In a still further step, the system 100 responds to the
start command and electrocautery is conducted. Here, the system 100
directs bipolar RF power at target tissue regions defined by
spaced-apart placement of the electrode structures 103-104. The use
of opposed, bipolar electrodes concentrates energy between the
electrodes and limits the effect on adjacent tissue that is not
confined within the opposed electrodes. In practice, power may be
applied for a time sufficient to raise the tissue temperature in
the tissue mass being treated to above a threshold level required
for cauterization or necrosis, such as 60-80.degree. C., or even
higher.
[0074] More specifically, electrocautery is conducted according to
the configuration set. For instance, the power supply 106 operates
according to the power settings established. Moreover, the module
108 acts to invoke individual ones of the electrodes according to
the electrode combination selected. In other words, the module 108
applies voltage from the power supply 106 across the first and
second electrode surfaces 103-104, such that voltage is applied
exclusively to the electrodes selected in. In the case of computer
control, this is achieved by the module 108 selectively applying
power to the selected electrodes.
[0075] As a further enhancement to the use of selected electrodes,
the electrodes may be activated using a selected firing order. In
this example, the module 108 applies voltage from the power supply
106 across the first and second electrode surfaces 103-104, such
that voltage is applied to one or more of the first electrodes 102
and one or more of the second electrodes 103 at any one time, and
the module 108 prevents firing of adjacent electrodes of the same
electrode surface concurrently or sequentially. The module 108 may
further implement a predetermined or user-selected firing
order.
[0076] For example, one way of preventing interaction, either
thermal or electrical, between two or more multiple electrodes in
an RF device with multiple electrodes is to alter the firing
sequence of electrodes so that adjacent electrodes are never
sequentially charged. For example, instead of sequential firing a
four electrode system, where the electrodes are sequentially
numbered 1,2,3,4, the invention fires them in an order such as
3,1,4,2, 4,2, 4,1,3,1,3, etc. so that adjacent electrodes are not
fired sequentially. Firing times may be different for each
electrode to balance the energy delivered in such a sequence where
some electrodes fire more frequently than others. This prevents
cross-talk during the transmission from one electrode to another as
well as cumulative effects of sequential heat build-up in the
transition area between the two electrodes. Additionally, rounded
electrodes can minimize the edge effect that occurs between
electrodes and at any transition surface.
[0077] Additionally, if one electrode surface or both opposing
surface of conductive, typically metal, electrodes are coated with
dielectric, non-conductive materials, RF energy may still be
transmitted through tissue between them via capacitive coupling.
FIG. 6 is a block diagram showing an electrode having a dielectric
coating according to the invention. However, due to the
non-conductive nature of the surface coating the electrode surfaces
does not create a short circuit if brought into close proximity or
contact. In this way, if a portion of an electrode pair only
partially captures tissue, i.e. there is a small, 5 mm air gap
between a portion of the electrodes, the RF energy still passes
through the tissue, as opposed to going around the tissue and
flowing directly between the close proximity electrodes. This is
especially important late in the sealing cycle as the tissue
impedance rises. When the tissue impedance is high the energy seeks
alternate pathways of lower resistance, such as between exposed
electrode sections. These dielectric layers can be thin coats of
polymers, such as Teflon, metal oxides, such as titanium, tungsten,
or tantalum or ceramics. To obtain adequate capacitance these
layers may be in the micron range of thickness.
[0078] In an alternative embodiment, a variety of different tissue
cauterization patterns can be achieved with the system 100 by
selectively energizing different ones of the electrode surfaces or
regions. By selectively energizing two adjacent electrodes, while
leaving all other electrodes non-energized, a limited tissue region
is cauterized. In contrast, by energizing other multiple electrode
surfaces, a larger region is cauterized. Slightly different
patterns are achieved depending on the precise pattern of electrode
surface polarity. In other embodiments, the electrode surfaces can
be energized in an alternating pattern of polarity to produce a
tissue cauterization pattern. Different patterns may also be used
to produce somewhat different patterns of cauterized tissue.
[0079] A different approach for selected firing is employed to
prevent local areas of high impedance from impacting the overall
system impedance along the entire electrode, and thus potentially
reducing the power output of the entire system as voltage reaches
its maximal capacity. Here, electrodes are activated to prevent one
area that has already been well sealed and has thus reached high
impedance value from affecting other regions in which the tissue is
not yet sealed, and is thus at a lower impedance. Optionally, the
module 108 may employ unique power and energy delivery profiles for
each electrode or electrode pair, based on the properties of the
tissue in a specific electrode location/position.
[0080] The performance of electrocautery employs the selected
impedance compensation and/or matching selected. As a result, power
delivered from the power supply 106 is delivered to the targeted
tissue region with less electrical loss.
[0081] The system 100 may further sense and automatically adjust
conjugate matching impedance. In response, the module 108 adjusts
the impedance applied to the conductive path containing the
electrode surfaces 103-104 and power supply 106. Alternatively, the
sensors may provide raw data to the module 108, which analyzes
whether and how to adjust impedance. In a different instance, the
module 108 may adjust impedance responsive to direction or data
from the sensors. This can be carried out by changing the frequency
of RF energy delivered by the power supply 106. For example, in one
embodiment the module 108 senses whether or not tissue is present
at each electrode at the beginning of a cauterization cycle by
measuring any of impedance, pressure, or any combination of these
and/or other parameters. If tissue is not present at any electrode,
then such electrode pair is idle; the module 108 deactivates firing
of this electrode, and/or provides a warning to an operator via the
user interface 110. The module 108 may also provide a status
indicator for each electrode pair that indicates whether the
sealing cycle is active or completed with regard to each electrode
pair. In this embodiment, each electrode pair may include a mode
status indicator, such as an LED for example, that indicates any of
an idle, active, or complete condition, once a cauterization cycle
is commenced.
[0082] The invention also addresses the problem of determining the
area of tissue coverage of one or more electrodes through the use
of dielectric coated electrode surfaces (See FIG. 6). With a
suitable RF generator and with electrode surfaces coated with a
dielectric coating, determination of tissue coverage may be
obtained by measuring phase-angle of RF voltage and current.
Because a dielectric coating essentially forms a capacitive
coupling to tissue, for a given dielectric material thickness, the
capacitance is a function of the area of coverage.
[0083] The basic formula for a capacitor is:
C=.di-elect cons..sub.0.di-elect cons..sub.rA/d [0084] Expressed in
Farads, where .di-elect cons..sub.0 is the permittivity of
free-space (8.854E-12), .di-elect cons..sub.r, is the relative
permittivity of the dielectric, A/d is the ratio of the area and
the dielectric thickness.
[0085] At a given frequency, the reactance is expressed as
Xc=1/.omega.C
where .omega. is 2*Pi*Frequency.
[0086] A suitable RF generator is required to insert a conjugate
impedance inductance in this case to cancel out the capacitive
reactance with a fully covered electrode and to measure the
phase-angle of RF voltage and current. When an electrode is only
partially covered, the capacitance changes i.e. becomes smaller,
because the effective area is smaller. As a result, the reactance
and, ultimately, the phase-angle of RF voltage and current change.
While the magnitude of change is affected in part by the tissue
resistance, it is believed that this methodology allows the
greatest degree of determination of electrode coverage by
tissue.
[0087] A further advantage of such a methodology may signal the RF
generator's control algorithm to change frequency, e.g. increase,
with smaller surface areas, thus maintaining maximum power transfer
while minimizing chances for electrical arcing and tissue charring.
Potential electrical arcing and tissue charring conditions may be
detected rapidly by rapid changes in phase and/or impedance and by
appreciating that electrodes which are only partially covered by
tissue may be used to signal the RF generator control algorithm to
shorten or change treatment parameters.
[0088] To achieve maximum power transfer and to make accurate power
measurements, it is desirable to maintain an impedance match
between the RF generator and the tissue. Impedance matching is
achieved when the phase-angle is zero. Several methodologies may be
used to attain near-zero phase. One such methodology uses
additional reactive elements e.g. greater inductance, to compensate
for the increased capacitive reactance. This approach can be
achieved in two different ways: [0089] (1) Via the insertion of a
continuously variable inductor with a finite range and nearly
infinite resolution, such an inductor can be adjusted to a near
zero phase; or [0090] (2) Via the insertion of discrete elements,
e.g. inductors to find the lowest phase, though this may not be
near-zero phase.
[0091] In both cases, electromechanical devices are required within
the RF generator.
[0092] Another methodology of achieving maximum power-transfer,
e.g. zero phase, is by changing the RF frequency. Given that the
reactance is frequency dependent, this methodology allows the RF
generator to compensate for phase discrepancy by electronically
changing frequency. This may not require any mechanical devices
such as relays, servos, etc. Further, the RF generator can change
frequency during operation rather than first interrupting RF power
to change elements. Thus, this may be the most desirable
methodology.
[0093] Although the invention is described herein with reference to
the preferred embodiment, one skilled in the art will readily
appreciate that other applications may be substituted for those set
forth herein without departing from the spirit and scope of the
present invention. Accordingly, the invention should only be
limited by the Claims included below.
* * * * *