U.S. patent application number 14/264172 was filed with the patent office on 2014-08-21 for method and system of reduction of low frequency muscle stimulation during electrosurgical procedures.
This patent application is currently assigned to ArthroCare Corporation. The applicant listed for this patent is ArthroCare Corporation. Invention is credited to Duane W. Marion, Jean Woloszko.
Application Number | 20140236141 14/264172 |
Document ID | / |
Family ID | 44710512 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140236141 |
Kind Code |
A1 |
Woloszko; Jean ; et
al. |
August 21, 2014 |
METHOD AND SYSTEM OF REDUCTION OF LOW FREQUENCY MUSCLE STIMULATION
DURING ELECTROSURGICAL PROCEDURES
Abstract
Reduction of low frequency muscle stimulation during
electrosurgical procedures. At least some of the illustrative
embodiments are methods including: treating a target tissue with an
electrosurgical wand comprising a plurality of active electrodes
intermittently exposed to a rectifying electrical phenomenon;
charging a first capacitance in series with a first electrode of
the plurality of active electrodes, the charging during periods of
time when the rectifying electrical phenomenon proximate the first
electrode; charging a second capacitance in series with a second
electrode of the plurality of active electrodes, the charging
during periods of time when the rectifying electrical phenomenon is
proximate the second electrode; charging a third capacitance in
series with a third electrode of the plurality of active
electrodes, the charging during periods of time when the rectifying
electrical phenomenon is proximate the third electrode; and
discharging, through the first electrode, the first capacitance,
while simultaneously charging the second capacitance.
Inventors: |
Woloszko; Jean; (Austin,
TX) ; Marion; Duane W.; (Santa Clara, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ArthroCare Corporation |
Austin |
TX |
US |
|
|
Assignee: |
ArthroCare Corporation
Austin
TX
|
Family ID: |
44710512 |
Appl. No.: |
14/264172 |
Filed: |
April 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12754727 |
Apr 6, 2010 |
8747399 |
|
|
14264172 |
|
|
|
|
Current U.S.
Class: |
606/34 |
Current CPC
Class: |
A61B 2018/1467 20130101;
A61B 18/1233 20130101; A61B 18/14 20130101; A61B 2018/1213
20130101; A61B 2018/147 20130101; A61B 18/1206 20130101; A61B
2018/00625 20130101 |
Class at
Publication: |
606/34 |
International
Class: |
A61B 18/12 20060101
A61B018/12; A61B 18/14 20060101 A61B018/14 |
Claims
1. A system comprising: a wand comprising: a non-conductive outer
surface; a plurality of active electrodes disposed on a distal end
of the wand; a plurality of electrical leads, the electrical leads
electrically coupled one each to a respective active electrode of
the plurality of active electrodes; a controller comprising: a
voltage generator configured to generate voltage of varying
amplitude, the voltage generator has an active terminal and a
return terminal; and the active terminal coupled to each of the
plurality of electrical leads; a plurality of capacitors, the
capacitors electrically coupled one each in series with a
respective electrical lead of the plurality of electrical
leads.
2. The system of claim 1 wherein the controller further comprises:
an enclosure that encloses the voltage generator; wherein at least
one capacitor of the plurality of capacitors is disposed within the
enclosure.
3. The system of claim 2 wherein the plurality of capacitors is
disposed within the enclosure.
4. The system of claim 1 wherein the wand further comprises: a
handle and an elongate shaft coupled to the handle; and wherein at
least one capacitor of the plurality of capacitors is disposed
within the wand.
5. The system of claim 4 wherein the plurality of capacitors is
disposed within the wand.
6. The system of claim 1 further comprising the plurality of
electrical leads form a multi-conductor cable electrically coupled
between the controller and the plurality of active electrodes, and
wherein at least one capacitor of the plurality of capacitors
disposed within the multi-conductor cable.
7. The system of claim 6 wherein the plurality of capacitors is
disposed within the multi-conductor cable.
8. The system of claim 1 further comprising: wherein the plurality
of active electrodes further comprises at least twenty active
electrodes; and wherein the plurality of electrical leads further
comprises at least twenty electrical leads; and wherein the
plurality of capacitors further comprises at least twenty
capacitors.
9. An electrosurgical wand comprising: an elongate shaft that
defines a proximal end and a distal end, at least a portion of the
exterior surface comprising non-conductive material; a connector
comprising a plurality of pins; a first active electrode disposed
on the distal end of the elongate shaft, and a first electrical
lead electrically coupled to the first electrode and a first pin of
the connector; a second active electrode disposed on the distal end
of the elongate shaft, and a second electrical lead electrically
coupled to the second electrode and a second pin of the connector;
and a third active electrode disposed on the distal end of the
elongate shaft, and a third electrical lead electrically coupled to
the third electrode and a third pin of the connector; a first
capacitor electrically coupled in series between the first pin and
the first active electrode; a second capacitor electrically coupled
in series between the second pin and the second active electrode;
and a third capacitor electrically coupled in series between the
third pin and the third active electrode.
10. The electrosurgical wand of claim 9 further comprising at least
one of the capacitors disposed between the connector and the
proximal end of the elongate shaft.
11. The electrosurgical wand of claim 9 further comprising: the
first capacitor disposed between the connector and the proximal end
of the elongate shaft; the second capacitor disposed between the
connector and the proximal end of the elongate shaft; and the third
capacitor disposed between the connector and the proximal end of
the elongate shaft.
12. The electrosurgical wand of claim 9 further comprising at least
one of the capacitors disposed within the elongate shaft.
13. The electrosurgical wand of claim 9 further comprising: the
first capacitor disposed within the elongate shaft; the second
capacitor disposed within the elongate shaft; and the third
capacitor disposed within the elongate shaft.
14. An electrosurgical controller comprising: an enclosure that
defines an outer surface; a voltage generator disposed within the
enclosure, the voltage generator configured to generate an
alternating current (AC) output voltage, the voltage generator has
an active terminal and a return terminal; a first connector
disposed on the outer surface, the first connector configured to
couple to a connector of an electrosurgical wand, and the first
connector comprising a first, second and third electrical pins; a
first capacitor electrically coupled in series between the active
terminal and the first electrical pin; a second capacitor
electrically coupled in series between the active terminal and the
second electrical pin; and a third capacitor electrically coupled
in series between the active terminal and the third electrical
pin.
15. The electrosurgical controller of claim 14 wherein the
connector is further configured to couple to the connector of an
electrosurgical wand in only one orientation.
16. The electrosurgical controller of claim 14 wherein the
connector comprises at least one selected from the group consisting
of: a tab configured to mechanically couple to a slot of the
connector of the electrosurgical wand; and a slot configured to
mechanically couple to a tab of the connector of the
electrosurgical wand.
17. The electrosurgical controller of claim 14 further comprising:
the first connector further comprising a third through twentieth
electrical pins; and a third through twentieth capacitors coupled
one each in series between the active terminal and a respective
third through twentieth electrical pin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 12/754,727 filed Apr. 6, 2010, the complete disclosure of which
is hereby incorporated by reference in its entirety for all
purposes.
BACKGROUND
[0002] Electrosurgical systems are used by physicians to perform
specific functions during surgical procedures. For example, in an
ablation mode electrosurgical systems use high frequency electrical
energy to remove soft tissue such as sinus tissue, adipose tissue
or meniscus, cartilage and/or sinovial tissue in a joint. In a
coagulation mode, the electrosurgical device may aid the surgeon in
reducing internal bleeding by assisting in the coagulation and/or
sealing of vessels.
[0003] The electrosurgical procedures are performed using high
frequency signals, as such high frequency signals provide the
desired electrosurgical effect and in theory should not result in
muscle or nerve stimulation of the patient. Stated another way,
unwanted muscle and nerve stimulation is induced by low frequency
and/or direct current (DC) signals flowing across or through muscle
or nerve. Equipment constructed in accordance with the
International Electrotechnical Commission (IEC) standards use DC
blocking capacitance between the voltage generator of the
electrosurgical controller and the patient to block DC signals
flowing to or from the voltage generator.
[0004] However, in spite of being constructed in accordance with
IEC standards, muscle and/or nerve stimulation is still noted in
some patients.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] For a detailed description of exemplary embodiments,
reference will now be made to the accompanying drawings in
which:
[0006] FIG. 1A shows charging of a lumped blocking capacitance in
an electrosurgical procedure;
[0007] FIG. 1B shows a discharging of a lumped blocking capacitance
in an electrosurgical procedure;
[0008] FIG. 2 shows discrete capacitances in accordance with at
least some embodiments;
[0009] FIG. 3 shows an electrosurgical system in accordance with at
least some embodiments;
[0010] FIG. 4 shows a perspective view a portion of a wand in
accordance with at least some embodiments;
[0011] FIG. 5 shows a cross-sectional view of a wand in accordance
with at least some embodiments;
[0012] FIG. 6 shows both an elevation end-view (left) and a
cross-sectional view (right) of a wand connector in accordance with
at least some embodiments;
[0013] FIG. 7 shows both an elevation end-view (left) and a
cross-sectional view (right) of a controller connector in
accordance with at least some embodiments;
[0014] FIG. 8 shows an electrical block diagram of an
electrosurgical controller in accordance with at least some
embodiments; and
[0015] FIG. 9 shows a method in accordance with at least some
embodiments.
NOTATION AND NOMENCLATURE
[0016] Certain terms are used throughout the following description
and claims to refer to particular system components. As one skilled
in the art will appreciate, companies that design and manufacture
electrosurgical systems may refer to a component by different
names. This document does not intend to distinguish between
components that differ in name but not function.
[0017] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . " Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection or through an indirect electrical connection via other
devices and connections.
[0018] Reference to a singular item includes the possibility that
there are plural of the same items present. More specifically, as
used herein and in the appended claims, the singular forms "a,"
"an," "said" and "the" include plural references unless the context
clearly dictates otherwise. It is further noted that the claims may
be drafted to exclude any optional element. As such, this statement
serves as antecedent basis for use of such exclusive terminology as
"solely," "only" and the like in connection with the recitation of
claim elements, or use of a "negative" limitation. Lastly, it is to
be appreciated that unless defined otherwise, all technical and
scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs.
[0019] "Active electrode" shall mean an electrode of an
electrosurgical wand which produces an electrically-induced
tissue-altering effect when brought into contact with, or close
proximity to, a tissue targeted for treatment, and/or an electrode
having a voltage induced thereon by a voltage generator.
[0020] "Return electrode" shall mean an electrode of an
electrosurgical wand which serves to provide a current flow path
for electrons with respect to an active electrode, and/or an
electrode of an electrical surgical wand which does not itself
produce an electrically-induced tissue-altering effect on tissue
targeted for treatment.
[0021] "Rectifying electrical phenomenon" shall mean arcing,
ionization or plasma creation proximate to an active electrode
where the arcing, ionization or plasma has at least a slight
electrical rectifying property.
[0022] Where a range of values is provided, it is understood that
every intervening value, between the upper and lower limit of that
range and any other stated or intervening value in that stated
range is encompassed within the invention. Also, it is contemplated
that any optional feature of the inventive variations described may
be set forth and claimed independently, or in combination with any
one or more of the features described herein.
[0023] All existing subject matter mentioned herein (e.g.,
publications, patents, patent applications and hardware) is
incorporated by reference herein in its entirety except insofar as
the subject matter may conflict with that of the present invention
(in which case what is present herein shall prevail). The
referenced items are provided solely for their disclosure prior to
the filing date of the present application. Nothing herein is to be
construed as an admission that the present invention is not
entitled to antedate such material by virtue of prior
invention.
DETAILED DESCRIPTION
[0024] Before the various embodiments are described in detail, it
is to be understood that this invention is not limited to
particular variations set forth herein as various changes or
modifications may be made, and equivalents may be substituted,
without departing from the spirit and scope of the invention. As
will be apparent to those of skill in the art upon reading this
disclosure, each of the individual embodiments described and
illustrated herein has discrete components and features which may
be readily separated from or combined with the features of any of
the other several embodiments without departing from the scope or
spirit of the present invention. In addition, many modifications
may be made to adapt a particular situation, material, composition
of matter, process, process act(s) or step(s) to the objective(s),
spirit or scope of the present invention. All such modifications
are intended to be within the scope of the claims made herein.
[0025] The inventors of the present specification have uncovered a
reason for parasitic stimulation of muscle and nerves of a patient
by DC and/or low frequency signals in spite of electrosurgical
systems using high frequency signals and a lumped blocking
capacitance in accordance with IEC Standards. FIG. 1A illustrates a
simplified system in order to explain the presence of parasitic DC
and low frequency signals. In particular, FIG. 1A illustrates a
voltage generator 100 having an active terminal 102 and a return
terminal 104. The voltage generator is coupled to a plurality of
active electrodes 106, 108 and 110, and as illustrated a single
return electrode 112. In accordance with IEC standards the
illustrative system of FIG. 1A has a direct current (DC) blocking
capacitance in the form of a single DC blocking capacitor 114
coupled between the active terminal 102 and the various active
electrodes.
[0026] In operation, each active electrode 106, 108 and 110 creates
an electrical phenomenon 116 proximate to the active electrodes.
The electrical phenomenon is in most cases an electrical arcing,
ionization and/or plasma. Regardless of the precise nature of the
electrical phenomenon, the electrical phenomenon has an inherent
electrical rectifying characteristic, and thus is termed herein a
"rectifying electrical phenomenon." The rectifying nature of the
electrical phenomenon is illustrated by the diode 118 shown within
the electrical phenomenon 116; however, it is to be understood that
the rectifying electrical phenomenon produces a rectifying effect
associated with each active electrode when the rectifying
electrical phenomenon is proximate to each active electrode.
Moreover, the rectifying electrical phenomenon is neither itself a
diode, nor is the rectifying electrical phenomenon as efficient at
rectification as a diode coupled between the electrodes. Rather,
the rectifying effect is slight, and although shown to favor
electrical current flow from the return electrode 112 to the active
electrode 110, in some situations rectifying electrical phenomenon
favors current flow from the active electrode(s) to the return
electrode(s) 112. The rectifying electrical phenomenon results in a
charging of the DC blocking capacitor 114. In particular, the
rectifying electrical phenomenon, when present, builds a DC bias on
the capacitor 114, as illustrated by the line 120 and "plus" symbol
on the capacitor 114 plate. The charge continues to accumulate
through each active electrode 106, 108 and 110 during periods of
time when the rectifying electrical phenomenon is proximate each
active electrode, and thus may build for extended periods (relative
to the period of the AC signal generated by the voltage
generator).
[0027] However, the rectifying electrical phenomenon is not
continuous during electrosurgical procedures. That is, the
rectifying electrical phenomenon is present for a time, and then
may cease for a time, depending on factors such as proximity of the
active electrodes to bodily tissue, and the amount and location of
conductive fluid relative to the active electrode, just to name a
few. The inventors have found that during periods of time when the
rectifying electrical phenomenon is absent, if an active electrode
physically contacts the patient, an electrical circuit is created
which discharges the charge stored on the blocking capacitor 114
through the patient. FIG. 1B illustrates such a situation. In
particular, FIG. 1B illustrates the situation where the rectifying
electrical phenomenon has ceased proximate to active electrodes
106, 108 and 110, and further that active electrode 108 contacts
the patient 122. Having active electrode 108 complete the
electrical circuit is merely illustrative, as any one active
electrode singly, or two more active electrodes together, may
complete the electrical circuit by contacting the tissue and/or
fluid of the patient. In contacting the patient 122, a completed
electrical circuit is created such that the charge stored on the DC
blocking capacitor 114 is discharged through the patient, as shown
by line 124. The charge stored on the DC blocking capacitor 114 is
a DC charge, and thus discharging the DC blocking capacitor can be
considered a DC current flow. Moreover, if the electrical circuit
through the patient is created periodically (e.g., 100 times a
second or less), then the discharging of the DC blocking capacitor
appears as a low frequency (e.g., 100 Hertz) parasitic
stimulation.
[0028] Thus, having the DC blocking capacitance lumped as shown in
FIGS. 1A and 1B results in large energy storage capability for the
DC blocking capacitance, and further results in each and every
active electrode that is involved in completing and electrical
circuit discharging the energy through the patient.
[0029] In order to at least partially address these issues,
electrosurgical systems in accordance with the various embodiments
distribute the DC blocking capacitance across active electrodes.
FIG. 2 illustrates such a system. In particular, rather than
lumping the DC blocking capacitance, the system comprises a
plurality of capacitors 200, 202 and 204, and wherein the plurality
of capacitors are electrically coupled one each in series with a
respective electrical lead and active electrode 106, 108, and 110
as illustrated by FIG. 2. While FIG. 2 shows only three electrical
leads coupled to active electrodes, two or more active electrodes
are contemplated, and in some cases 23 active electrodes each
having a 2.2 nano-Farad (nF) capacitor in series therewith. While
at first blush the circuit of FIG. 2 may seem electrically
equivalent to the lumped DC blocking capacitance 114 of FIGS. 1A
and 1B, a surprising result is obtained in embodiments constructed
as in FIG. 2.
[0030] In particular, the inventors of the present specification
have found that the rectifying electrical phenomenon is
discontinuous during electrosurgical procedures with respect to
each active electrode considered individually. That is, for a
particular active electrode the rectifying electrical phenomenon
randomly is present for a time, then ceases for a time, and then
again present. During periods of time when the rectifying
electrical phenomenon has ceased for the particular active
electrode, other active electrodes may continue to have their
respective rectifying electrical phenomenon present. For example,
active electrode 110 may have its respective rectifying electrical
phenomenon 206 present, but active electrodes 106 and 108 may not.
Thus, in the illustrative situation capacitor 204 may be being
charged with a DC bias voltage, while capacitors 200 and 202 retain
their charge and/or discharge through the patient. The
randomization of the discharge states of the capacitors 200, 202
and 204 surprisingly results in an effective capacitance seen by
the patient during electrosurgical procedures lower than the sum of
the capacitances in parallel, and thus lower than the
electrosurgical systems in FIGS. 1A and 1B.
[0031] Although the inventors do not wish to be tied to any
particular physical interpretation that results in the lower
effective capacitance, it is believed that a portion of the lower
effective capacitance is based on the lower amount of energy that
can be discharged through each active electrode. While in the
systems of FIGS. 1A and 1B any active electrode could discharge the
full energy storage of the DC blocking capacitor 114, in the
embodiments of FIG. 2 each electrode can only discharges its
respective capacitor (e.g., the energy stored on capacitor 200 can
only be discharged through active electrode 106). Moreover, with
lower energy stored on each capacitor, a capacitor may discharge
more quickly, rather than partial discharges that may occur for a
lumped DC blocking capacitance. Relatedly, another physical aspect
that may result in the lower effective capacitance is limited
charging pathways for each capacitor 200, 202 and 204. In
particular, the DC current flowing through an active electrode
caused by the rectifying electrical phenomenon can only charge the
respective capacitor of the active electrode. Thus, the amount of
charge accumulated on a capacitor during periods of time when the
rectifying electrical phenomenon associated with a particular
active electrode may be lower than if electrical current through
any or all active electrodes can contribute to the stored
charge.
[0032] The embodiments of FIG. 2 do not intimate any particular
physical location of the capacitors coupled one each in series with
a respective electrical lead (or respective active electrode), and
the physical placement may vary from embodiment-to-embodiment. The
specification now turns to various embodiments of the
electrosurgical controllers and wands, and various illustrative
locations for physical placement of the respective capacitors.
[0033] FIG. 3 illustrates an electrosurgical system 300 in
accordance with at least some embodiments. In particular, the
electrosurgical system comprises an electrosurgical wand 302
(hereinafter "wand") coupled to an electrosurgical controller 304
(hereinafter "controller"). The wand 302 comprises an elongate
shaft 306 that defines distal end 308 where at least some
electrodes are disposed. The elongate shaft 306 further defines a
handle or proximal end 310, where a physician grips the wand 302
during surgical procedures. The wand 302 further comprises a
flexible multi-conductor cable 312 housing a plurality of
electrical leads (not specifically shown in FIG. 3), and the
flexible multi-conductor cable 312 terminates in a wand connector
314. Though not visible in the FIG. 3, in some embodiments the wand
302 has an internal passage fluidly coupled to a flexible tubular
member 316. The internal passage and flexible tubular member 316
may be used as a conduit to supply conductive fluid proximate to
the distal end 308, or the internal passage and flexible tubular
member may be used to aspirate the area proximate to the distal end
308 of the wand 302.
[0034] As shown in FIG. 3, the wand 302 couples to the controller
304, such as by a controller connector 320, on an outer surface of
an enclosure 322 (in the illustrative case of FIG. 3 the controller
connector 320 is on a front surface). A display device or interface
panel 324 is visible through the enclosure 322, and in some
embodiments a user may select operational modes of the controller
304 by way of the interface device 324 and related buttons 326.
[0035] Still referring to FIG. 3, in some embodiments the
electrosurgical system 300 also comprises a foot pedal assembly
330. The foot pedal assembly 330 may comprise one or more pedal
devices 332 and 334, a flexible multi-conductor cable 336 and a
pedal connector 338. While only two pedal devices 332, 334 are
shown, any number of pedal devices may be implemented. The
enclosure 322 of the controller 304 may comprise a corresponding
connector 340 that couples to the pedal connector 338. A physician
may use the foot pedal assembly 330 to control various aspects of
the controller 304, such as the operational mode. For example, a
pedal device, such as pedal device 332, may be used for on-off
control of the application of radio frequency (RF) energy to the
wand 302, and more specifically for control of energy in an
ablation mode. A second pedal device, such as pedal device 334, may
be used to control and/or set the operational mode of the
electrosurgical system. For example, actuation of pedal device 334
may switch between ablation mode and a coagulation mode.
Alternatively, pedal device 334 may be used to control the
application of RF energy to wand 302 in a coagulation mode. The
pedal devices may also be used to change the voltage level
delivered to wand 302.
[0036] The electrosurgical system 300 of the various embodiments
may have a variety of operational modes. One such mode employs
Coblation.RTM. technology. In particular, the assignee of the
present disclosure is the owner of Coblation.RTM. technology.
Coblation.RTM. technology involves the application of a RF signal
between one or more active electrodes and one or more return
electrodes of the wand 302 to develop high electric field
intensities in the vicinity of the target tissue. The electric
field intensities may be sufficient to vaporize an electrically
conductive fluid over at least a portion of the one or more active
electrodes in the region between the one or more active electrodes
and the target tissue. The electrically conductive fluid may be
inherently present in the body, such as blood, or in some cases
extracelluar or intracellular fluid. In other embodiments, the
electrically conductive fluid may be a liquid or gas, such as
isotonic saline. In some embodiments the electrically conductive
fluid is delivered in the vicinity of the active electrodes and/or
to the target site by the wand 302, such as by way of the internal
passage and flexible tubular member 316.
[0037] When the electrically conductive fluid is heated to the
point that the atoms of the fluid vaporize faster than the atoms
recondense, a gas is formed. When sufficient energy is applied to
the gas, the atoms collide with each other causing a release of
electrons in the process, and an ionized gas or plasma is formed
(the so-called "fourth state of matter"). Stated otherwise, plasmas
may be formed by heating a gas and ionizing the gas by driving an
electric current through the gas, or by directing electromagnetic
waves into the gas. The methods of plasma formation give energy to
free electrons in the plasma directly, electron-atom collisions
liberate more electrons, and the process cascades until the desired
degree of ionization is achieved. A more complete description of
plasma can be found in Plasma Physics, by R. J. Goldston and P. H.
Rutherford of the Plasma Physics Laboratory of Princeton University
(1995), the complete disclosure of which is incorporated herein by
reference.
[0038] As the density of the plasma becomes sufficiently low (i.e.,
less than approximately 1020 atoms/cm.sup.3 for aqueous solutions),
the electron mean free path increases such that subsequently
injected electrons cause impact ionization within the plasma. When
the ionic particles in the plasma layer have sufficient energy
(e.g., 3.5 electron-Volt (eV) to 5 eV), collisions of the ionic
particles with molecules that make up the target tissue break
molecular bonds of the target tissue, dissociating molecules into
free radicals which then combine into gaseous or liquid species.
Often, the electrons in the plasma carry the electrical current or
absorb the electromagnetic waves and, therefore, are hotter than
the ionic particles. Thus, the electrons, which are carried away
from the target tissue toward the active or return electrodes,
carry most of the plasma's heat, enabling the ionic particles to
break apart the target tissue molecules in a substantially
non-thermal manner.
[0039] By means of the molecular dissociation (as opposed to
thermal evaporation or carbonization), the target tissue is
volumetrically removed through molecular dissociation of larger
organic molecules into smaller molecules and/or atoms, such as
hydrogen, oxygen, oxides of carbon, hydrocarbons and nitrogen
compounds. The molecular dissociation completely removes the tissue
structure, as opposed to dehydrating the tissue material by the
removal of liquid within the cells of the tissue and extracellular
fluids, as occurs in related art electrosurgical desiccation and
vaporization. A more detailed description of the molecular
dissociation can be found in commonly assigned U.S. Pat. No.
5,697,882, the complete disclosure of which is incorporated herein
by reference.
[0040] In addition to the Coblation.RTM. mode, the electrosurgical
system 300 of FIG. 3 is also useful for sealing larger arterial
vessels (e.g., on the order of about 1 mm in diameter), when used
in what is known as a coagulation mode. Thus, the system of FIG. 3
may have an ablation mode where RF energy at a first voltage is
applied to one or more active electrodes sufficient to effect
molecular dissociation or disintegration of the tissue, and the
system of FIG. 3 has a coagulation mode where RF energy at a
second, lower voltage is applied to one or more active electrodes
(either the same or different electrode(s) as the ablation mode)
sufficient to heat, shrink, seal, fuse, and/or achieve homeostasis
of severed vessels within the tissue.
[0041] The energy density produced by electrosurgical system 300 at
the distal end 308 of the wand 302 may be varied by adjusting a
variety of factors, such as: the number of active electrodes;
electrode size and spacing; electrode surface area; asperities
and/or sharp edges on the electrode surfaces; electrode materials;
applied voltage; electrical conductivity of the fluid in contact
with the electrodes; density of the conductive fluid; and other
factors. Accordingly, these factors can be manipulated to control
the energy level of the excited electrons. Since different tissue
structures have different molecular bonds, the electrosurgical
system 300 may be configured to produce energy sufficient to break
the molecular bonds of certain tissue but insufficient to break the
molecular bonds of other tissue. For example, fatty tissue (e.g.,
adipose) has double bonds that require an energy level higher than
4 eV to 5 eV (i.e., on the order of about 8 eV) to break.
Accordingly, the Coblation.RTM. technology in some operational
modes does not ablate such fatty tissue; however, the
Coblation.RTM. technology at the lower energy levels may be used to
effectively ablate cells to release the inner fat content in a
liquid form. Other modes may have increased energy such that the
double bonds can also be broken in a similar fashion as the single
bonds (e.g., increasing voltage or changing the electrode
configuration to increase the current density at the electrodes). A
more complete description of the various phenomena can be found in
commonly assigned U.S. Pat. Nos. 6,355,032, 6,149,120 and
6,296,136, the complete disclosures of which are incorporated
herein by reference.
[0042] FIG. 4 illustrates the distal end 308 of illustrative wand
302. In particular, in some embodiments the elongate shaft 306 is
made of an inorganic insulating (i.e., non-conductive) material. In
other embodiments, the elongate shaft 306 comprises a conductive
material, but is covered with an insulating material. The distal
end 308 further comprises a plurality of electrodes. For example,
in the illustrative case of FIG. 4, seven electrodes 402, 404, 406,
408, 410, 412 and 414 are shown; however, three or more electrodes
may be equivalently used. As illustrated in FIG. 4, the electrodes
may take many forms. Electrodes 402, 404 and 406 are illustrative
of wire-type electrodes that protrude slightly from the end 416 of
the elongate shaft 306. The wire-type electrodes 402, 404 and 406
may be used, for example, singly or in combination to be the
electrodes to which the RF energy is applied in the ablation mode.
Electrodes 408, 410 are disposed on a surface 418 of the distal end
308, and the electrodes 408, 410 span a certain circumferential
distance. Electrodes 412, 414 are similar to electrodes 408, 410,
but span a smaller circumferential distance. Other electrode types,
such as button electrodes (i.e., round electrodes), arrays of
button electrodes, or screen electrodes, may be equivalently
used.
[0043] Still referring to FIG. 4, in some embodiments the wand 302
has an internal lumen 450 that fluidly couples to the flexible
tubular member 316 (FIG. 1). In some modes of operation, the
internal lumen 450 is used to supply conductive fluid to the target
area to aid in implementing the Coblation.RTM. technology. In other
modes of operation, the internal lumen 450 may be used to aspirate
the area near the distal end 308 of the wand 302, such as when
sufficient conductive fluid is already present at the target
location and ablation is taking place, or to remove byproducts of
the ablation process.
[0044] FIG. 5 shows a cross-sectional view of wand 302 in
accordance with at least some embodiments. In particular, FIG. 5
illustrates the elongate shaft 306 comprising distal end 308 and
proximal end 310. Distal end 308 comprises a plurality of
electrodes 500, and while the electrodes 500 are similar to the
electrodes of FIG. 4, electrodes 500 are not necessarily the same
as those of FIG. 4. Each electrode 500 has an electrical lead
associated therewith that runs through the elongate shaft 306 to
the flexible multi-conductor cable 312. In particular, electrode
500A has dedicated electrical lead 502A which runs within the
elongate shaft to the become part of cable 312. Similarly,
electrode 500B has dedicated electrical lead 502B which runs within
the elongate shaft 306 to become part of cable 312. Illustrative
electrodes 500C and 500D likewise have dedicated electrical leads
502C and 502D which run within the elongate shaft 306 to become
part of cable 312. In some embodiments, the elongate shaft 306 has
dedicated internal passages (in addition to internal lumen 450)
through which the electrical leads 502 run. In other embodiments,
the electrical leads 502 are cast within the material that makes up
the elongate shaft.
[0045] FIG. 5 also illustrates internal lumen 450 having an
aperture 504 fluidly coupled to the flexible tubular member 316 on
the proximal end 310. In other embodiments, the fluid coupling of
the internal lumen 450 to the flexible tubular member 316 may be
between the distal end 308 and proximal end 310. The internal lumen
450 is used in some embodiments to supply conductive fluid through
the aperture 504 to the target area, and in other embodiments the
internal lumen 450 is used for aspiration of ablated tissue
fragments and/or molecules. In some embodiments, an electrode 502D
may be disposed within the internal lumen 450 proximate to the
aperture 504. An electrode 500D within the internal lumen 450 may,
for example, be selected as either an active or return electrode in
an ablation mode, and may aid in disassociation of tissue pieces
into smaller pieces during ablation and aspiration procedures.
[0046] In accordance with at least some embodiments, the plurality
of capacitors coupled one each in series with a respective
electrical lead may be disposed within the wand 302 as shown in
FIG. 5. In particular, for the illustrative four active electrodes
500A-500D, there may be a respective four capacitors 510A-510D
disposed within wand 302 (and as illustrated in the handle 310). In
other embodiments the capacitors may be disposed within the
elongate shaft 306.
[0047] FIG. 5 also illustrates embodiments where the plurality of
capacitors coupled one each in series with a respective electrical
lead may be disposed within the multi-conductor cable 312. In
particular, for the illustrative four active electrodes 500A-500D,
there may be a respective four capacitors 512A-512D disposed within
multi-conductor cable 312. While FIG. 5 shows capacitors both in
the multi-conductor cable 312 and in the wand 302, and an
electrosurgical system would be operational as illustrated in FIG.
5, when disposing the plurality of capacitors outside the
controller 304 either location alone will suffice.
[0048] In addition to the distributed capacitors, current-limiting
resistors may be selected. The current-limiting resistors will have
a large positive temperature coefficient of resistance so that, as
the current level begins to rise for any individual active
electrode in contact with a low resistance medium (e.g., saline or
blood), the resistance of the current limiting resistor increases
significantly, thereby reducing the power delivery from the active
electrode into the low resistance medium. In some embodiments, the
current limited devices may reside within the elongate shaft 306,
or may reside within the cable 312.
[0049] As illustrated in FIG. 3, flexible multi-conductor cable 312
(and more particularly its constituent electrical leads 502) couple
to the wand connector 314. Wand connector 314 couples the
controller 304, and more particularly the controller connector 320.
FIG. 6 shows both a cross-sectional view (right) and an end
elevation view (left) of wand connector 314 in accordance with at
least some embodiments. In particular, wand connector 314 comprises
a tab 600. Tab 600 works in conjunction with a slot on controller
connector 320 (shown in FIG. 6) to ensure that the wand connector
314 and controller connector 320 only couple in one relative
orientation. The illustrative wand connector 314 further comprises
a plurality of electrical pins 602 protruding from wand connector
114. The electrical pins 402 are coupled one each to a single
electrical lead 502. Stated otherwise, each electrical pin 602
couples to a single electrical lead 502, and thus each illustrative
electrical pin 602 couples to a single electrode 500 (FIG. 5).
While FIG. 6 shows only four illustrative electrical pins, in some
embodiments 26 or more electrical pins may be present in the wand
connector 314.
[0050] FIG. 7 shows both a cross-sectional view (right) and an end
elevation view (left) of controller connector 320 in accordance
with at least some embodiments. In particular, controller connector
320 comprises a slot 700. Slot 700 works in conjunction with a tab
600 on wand connector 314 (shown in FIG. 6) to ensure that the wand
connector 314 and controller connector 320 only couple in one
orientation. The illustrative controller connector 320 further
comprises a plurality of electrical pins 702 residing with
respective holes of controller connector 320. The electrical pins
702 may be individually coupled to a relay within the controller
304 (discussed more thoroughly below). When wand connector 314 and
controller connector 320 are coupled, each electrical pin 702
couples to a single electrical pin 602, and thus each illustrative
electrical pin 702 couples to a single electrode 500 (FIG. 5).
While FIG. 7 shows only four illustrative electrical pins, in some
embodiments 26 or more electrical pins may be present in the wand
connector 120.
[0051] While illustrative wand connector 314 is shown to have the
tab 600 and male electrical pins 602, and controller connector 320
is shown to have the slot 700 and female electrical pins 702, in
alternative embodiments the wand connector has the female
electrical pins and slot, and the controller connector 120 has the
tab and male electrical pins. In other embodiments, the arrangement
of the pins within the connectors may enable only a single
orientation for connection of the connectors, and thus the tab and
slot arrangement may be omitted. In yet still other embodiments,
other mechanical arrangements to ensure the wand connector and
controller connector couple in only one orientation may be
equivalently used.
[0052] FIG. 8 illustrates a controller 304 in accordance with at
least some embodiments. In particular, the controller 304 in
accordance with at least some embodiments comprises a processor
800. The processor 800 may be a microcontroller, and therefore the
microcontroller may be integral with read-only memory (ROM) 802,
random access memory (RAM) 804, digital-to-analog converter (D/A)
806, digital outputs (D/O) and digital inputs (D/I) 810. The
processor 800 may further provide one or more externally available
peripheral busses, such as a serial bus (e.g., I.sup.2C), parallel
bus, or other bus and corresponding communication mode. The
processor 800 may further be integral with a communication logic
812 to enable the processor 800 to communicate with external
devices, as well as internal devices, such as display device 324.
Although in some embodiments the controller 304 may implement a
microcontroller, in yet other embodiments the processor 800 may be
implemented as a standalone central processing unit in combination
with individual RAM, ROM, communication, D/A, D/O and D/I devices,
as well as communication port hardware for communication to
peripheral components.
[0053] ROM 802 stores instructions executable by the processor 800.
In particular, the ROM 802 may comprise a software program that
implements various operation modes, as well as interfacing with the
user by way of the display device 324, the foot pedal assembly 330
(FIG. 1), and/or a speaker assembly 870. The RAM 804 may be the
working memory for the processor 800, where data may be temporarily
stored and from which instructions may be executed. Processor 800
couples to other devices within the controller 304 by way of the
D/A converter 806 (e.g., the voltage generator 816), digital
outputs 808 (e.g., electrically controlled switches 820), digital
inputs 810 (e.g., push button switches 326, and the foot pedal
assembly 330 (FIG. 1)), communication device 812 (e.g., display
device 324), and other peripheral devices. The other peripheral
devices may comprise electrode relays and/or switches, devices to
set desired voltage generator 816 output voltage, and other
secondary devices internal to the generator.
[0054] Voltage generator 816 generates selectable alternating
current (AC) voltages that are applied to the electrodes of the
wand 302. In some embodiments, the voltage generator defines an
active terminal 824 and a return terminal 826. The active terminal
824 is the terminal upon which the voltages and electrical currents
are induced by the voltage generator 816, and the return terminal
826 provides a return path for electrical currents. In some
embodiments, the return terminal 826 may provide a common or ground
being the same as the common or ground within the balance of the
controller 304 (e.g., the common 828 used on push-buttons 826), but
in other embodiments the voltage generator 816 may be electrically
"floated" from the balance of the supply power in the controller
304, and thus the return terminal 826, when measured with respect
to the common (e.g., common 828) within the controller 304, may
show a voltage difference; however, an electrically floated voltage
generator 816 and thus the potential for voltage readings on the
return terminal 816 does not negate the return terminal status of
the terminal 826 relative to the active terminal 824.
[0055] The voltage generated and applied between the active
terminal 824 and return terminal 826 by the voltage generator 616
is a RF signal that, in some embodiments, has a frequency of
between about 5 kilo-Hertz (kHz) and 20 Mega-Hertz (MHz), in some
cases being between about 30 kHz and 2.5 MHz, preferably being
between about 50 kHz and 500 kHz, often less than 350 kHz, and
often between about 100 kHz and 200 kHz. In some applications, a
frequency of about 100 kHz is useful because target tissue
impedance is much greater at 100 kHz. In other applications, such
as procedures in or around the heart or head and neck, higher
frequencies may be desirable (e.g., 400-600 kHz).
[0056] The RMS (root mean square) voltage generated by the voltage
generator 816 may be in the range from about 5 Volts (V) to 1000 V,
preferably being in the range from about 10 V to 500 V, often
between about 10 V to 400 V depending on the active electrode size,
the operating frequency and the operation mode of the particular
procedure or desired effect on the tissue (i.e., contraction,
coagulation, cutting or ablation). The peak-to-peak voltage
generated by the voltage generator 816 for ablation or cutting in
some embodiments is a square wave form in the range of 10 V to 2000
V and in some cases in the range of 100 V to 1800 V and in other
cases in the range of about 28 V to 1200 V, often in the range of
about 100 V to 320V peak-to-peak (again, depending on the electrode
size, number of electrodes the operating frequency and the
operation mode). Lower peak-to-peak voltage is used for tissue
coagulation, thermal heating of tissue, or collagen contraction and
may be in the range from 50 V to 1500V, preferably 100 V to 1000 V
and more preferably 60 V to 130 V peak-to-peak (again, these values
are computed using a square wave form).
[0057] The voltage and current generated by the voltage generator
816 may be delivered in a series of voltage pulses or AC voltage
with a sufficiently high frequency (e.g., on the order of 5 kHz to
20 MHz) such that the voltage is effectively applied continuously
(as compared with, e.g., lasers claiming small depths of necrosis,
which are pulsed about 10 Hz to 20 Hz). In addition, the duty cycle
(i.e., cumulative time in any one-second interval that energy is
applied) of the square wave voltage produced by the voltage
generator 816 is on the order of about 50% for some embodiments as
compared with pulsed lasers which may have a duty cycle of about
0.0001%. Although square waves are generated and provided in some
embodiments, the various embodiments may be equivalently
implemented with many applied voltage waveforms (e.g., sinusoidal,
triangular).
[0058] Still referring to the voltage generator 816, the voltage
generator 816 delivers average power levels ranging from several
milliwatts to hundreds of watts per electrode, depending on the
voltage applied to the target electrode for the target tissue being
treated, and/or the maximum allowed temperature selected for the
wand 102. The voltage generator 816 is configured to enable a user
to select the voltage level according to the specific requirements
of a particular neurosurgery procedure, cardiac surgery,
arthroscopic surgery, dermatological procedure, ophthalmic
procedures, open surgery or other endoscopic surgery procedure. For
cardiac procedures and potentially for neurosurgery, the voltage
generator 816 may have a filter that filters leakage voltages at
frequencies below 100 kHz, particularly voltages around 60 kHz.
Alternatively, a voltage generator 816 configured for higher
operating frequencies (e.g., 300 kHz to 600 kHz) may be used in
certain procedures in which stray low frequency currents may be
problematic. A description of one suitable voltage generator 616
can be found in commonly assigned U.S. Pat. Nos. 6,142,992 and
6,235,020, the complete disclosure of both patents are incorporated
herein by reference for all purposes.
[0059] In accordance with at least some embodiments, the voltage
generated 816 is configured to limit or interrupt current flow when
low resistivity material (e.g., blood, saline or electrically
conductive gel) causes a lower impedance path between the return
electrode(s) and the active electrode(s). Further still, in some
embodiments the voltage generator 816 is configured by the user to
be a constant current source (i.e., the output voltage changes as
function of the impedance encountered at the wand 302).
[0060] In some embodiments, the various operational modes of the
voltage generator 816 may be controlled by way of digital-to-analog
converter 806. That is, for example, the processor 800 may control
the output voltage by providing a variable voltage to the voltage
generator 816, where the voltage provided is proportional to the
voltage generated by the voltage generator 816. In other
embodiments, the processor 800 may communicate with the voltage
generator by way of one or more digital output signals from the
digital output 808 device, or by way of packet based communications
using the communication 812 device (the alternative embodiments not
specifically shown so as not to unduly complicate FIG. 8).
[0061] In addition to controlling the output of the voltage
generator 816, in accordance with at least some embodiments the
controller 304 is also configured to selectively electrically
couple the active terminal 824 singly or in combination to the
electrodes of the wand (by way of the electrical pins of the
controller connector 320). Likewise, in the various embodiments,
the controller 304 is also configured to selectively electrically
couple the return terminal 826 singly or in combination to the
electrodes of the wand (again by way of the electrical pins of the
controller connector 320). In order to perform the selective
coupling, the controller 304 implements a control circuit 830,
shown in dashed lines in FIG. 8. For convenience of the figure the
control circuit has two parts, 830A and 830B, but the two parts
nevertheless comprise the control circuit 830. In particular, the
control circuit 830 comprises the processor 800, voltage controlled
switches 820 and mechanic relays K1-K6. The coils of relays K1-K6
are shown within portion 830A, while the contacts for each
mechanical relay are shown within portion 830B. The correlation
between the coils for mechanical relays K5 and K6 and the contacts
for mechanical relays K5 and K6 are shown by dashed arrow-headed
lines 850 and 852 respectively. The correlation between the
remaining coils and contacts is not specifically shown with
arrow-headed lines so as not to unduly complicate the figure;
however, the correlation is noted by way of corresponding
references.
[0062] In accordance with at least some embodiments, at least three
electrodes of the wand 302 are separately electrically coupled to
the controller 304. Thus, the description of FIG. 8 is based on
three separately electrically coupled electrodes, but it will be
understood that three or more separately electrically coupled
electrodes may be used. The electrical pin of the controller
connector 320 for each electrode is configured to be selectively
coupled to either the active terminal 824 or the return terminal
826. For example, the electrical lead configured to couple
illustrative electrode 1 of FIG. 8 couples to the normally open
(NO) contact terminals for the mechanical relays K1 and K2. The
other side of the normally open contact for mechanical relay K1
couples to the active terminal 824 by way of capacitor 880A, while
the other side of the normally open contact for the mechanical
relay K2 couples to the return terminal 626. Thus, by selectively
activating mechanical relay K1 or mechanical relay K2, electrode 1
can be either an active or return electrode in the surgical
procedure. Alternatively, both relays can remain inactivated, and
thus electrode 1 may remain unconnected.
[0063] Similarly, the electrical lead configured to couple
illustrative electrode 2 couples to the normally open contact
terminals for the mechanical relays K3 and K4. The other side of
the normally open contact for mechanical relay K3 couples to the
active terminal 824 by way of capacitor 880B, while the other side
of the normally open contact for the mechanical relay K4 couples to
the return terminal 826. Thus, by selectively activating mechanical
relay K3 or mechanical relay K4, electrode 2 can be either an
active or return electrode in the surgical procedure.
Alternatively, both relays K3 and K4 can remain inactivated, and
thus electrode 2 may remain unconnected. Finally with respect to
the illustrative electrode 3, the electrical lead configured to
couple to illustrative electrode 3 couples to the normally open
contact terminals for the mechanical relays K5 and K6. The other
side of the normally open contact for mechanical relay K5 couples
to the active terminal 824 by way of capacitor 880C, while the
opposite side of the normally open contact for the mechanical relay
K6 couples to the return terminal 826. Thus, by selectively
activating mechanical relay K5 or mechanical relay K6, electrode 3
can be either an active or return electrode in the surgical
procedure. Alternatively, both relays can remain inactivated, and
thus electrode 3 may remain unconnected.
[0064] In accordance with at least some embodiments, mechanical
relays K1-K6 are selectively activated (by way of their respective
coils 834) by voltage controlled switches 820. For example, when
the control circuit 830 desires to couple the active terminal to
electrode 1, the voltage controlled switch 820A is activated, which
allows current to flow through the coil 834A of mechanical relay
K1. Current flow through the coil 834 activates the relay, thus
closing (making conductive) the normally open contacts. Similarly,
the control circuit 830 may selectively activate any of the voltage
controlled switches 820, which in turn activate respective
mechanical relays K1-K6. In accordance with at least some
embodiments, each mechanical relay is a part number JW1FSN-DC 12V
relay available from Panasonic Corporation of Secaucus, N.J.;
however, other relays may be equivalently used. Moreover, while
FIG. 8 illustrates the use of field effect transistors as the
voltage controlled switches 820 to control the current flow through
coils of the mechanical relays, other devices (e.g., transistors,
or if coils use AC driving current, triacs) may be equivalently
used. Further still, in embodiments where the digital outputs 808
have sufficient current carrying capability, the voltage controlled
switches may be omitted.
[0065] FIG. 8 also illustrates that the capacitors for each
electrode may reside within the controller 304. In particular,
capacitors 880 are representative of capacitors coupled one each in
series with each electrode. It is noted that if the capacitors
reside within the controller as shown in FIG. 8, the capacitors in
the multi-conductor cable 312 and/or the capacitors in wand 302 may
be omitted. While FIG. 8 shows the capacitors as residing between
the active electrode 824 and the respective relay contacts, in
other embodiments the capacitors may reside between the relay
contacts and the connector 320.
[0066] FIG. 9 illustrates a method in accordance with at least some
embodiments. In particular, the method starts (block 900) and
proceeds to treating a target tissue with an electrosurgical wand
comprising a plurality of active electrodes on a distal end of the
electrosurgical wand, each of the plurality of active electrodes
intermittently exposed to a rectifying electrical phenomenon (block
902). The method further comprises charging a first capacitance in
series with a first electrode of the plurality of active electrodes
(the charging during periods of time when the rectifying electrical
phenomenon proximate the first electrode) (block 904), charging a
second capacitance in series with a second electrode of the
plurality of active electrodes (the charging during periods of time
when the rectifying electrical phenomenon is proximate the second
electrode) (block 906), and charging a third capacitance in series
with a third electrode of the plurality of active electrodes (the
charging during periods of time when the rectifying electrical
phenomenon is proximate the third electrode) (block 908). And then,
the method comprises discharging, through the first electrode, the
first capacitance while simultaneously charging the second
capacitance (block 910), and the illustrative method ends (block
912).
[0067] In vivo experiments prove that the change in capacitor
configuration from a single lumped capacitance (as in FIG. 1A) to a
set of discrete capacitances associated one each with each
electrode (as in FIG. 1B) results in a noticeable reduction in low
frequency stimulation in the animal analogue (e.g., chicken) as the
number of discrete capacitances increases. For example, the most
significant effect was observed when the single 50 nano-Farard (nF)
capacitance was replaced with 23 discrete 2.2 nF capacitors.
Experiments with three discrete capacitors (on 10 nF and two 20 nF)
shows improvement over the single 50 nF capacitor set-up, but with
the results less pronounced than the 23 discrete 2.2 nF capacitor
set up.
[0068] While preferred embodiments of this disclosure have been
shown and described, modifications thereof can be made by one
skilled in the art without departing from the scope or teaching
herein. The embodiments described herein are exemplary only and are
not limiting. Because many varying and different embodiments may be
made within the scope of the present inventive concept, including
equivalent structures, materials, or methods hereafter though of,
and because many modifications may be made in the embodiments
herein detailed in accordance with the descriptive requirements of
the law, it is to be understood that the details herein are to be
interpreted as illustrative and not in a limiting sense.
* * * * *