U.S. patent application number 12/476871 was filed with the patent office on 2009-09-24 for systems and methods for performing simultaneous ablation.
This patent application is currently assigned to BOSTON SCIENTIFIC SCIMED, INC.. Invention is credited to Robert Garabedian, Jerry Jarrard, Robert F. Rioux.
Application Number | 20090240247 12/476871 |
Document ID | / |
Family ID | 34573694 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090240247 |
Kind Code |
A1 |
Rioux; Robert F. ; et
al. |
September 24, 2009 |
SYSTEMS AND METHODS FOR PERFORMING SIMULTANEOUS ABLATION
Abstract
A system for treating tissue includes first and second ablation
devices each including a plurality of wire electrodes and coupled
to a generator in parallel. In one embodiment, the generator
includes first and second terminals coupled in parallel to one
another, and the first and second ablation devices are connected to
the first and second terminals, respectively. Alternatively, the
first and second ablation devices are coupled to a single terminal
of the generator using a "Y" cable. A ground electrode is coupled
to the generator opposite the first and second ablation devices for
monopolar operation. The first and second arrays of electrodes are
inserted into first and second sites adjacent one another within a
tissue region. Energy is simultaneously delivered to the first and
second arrays to generate lesions at the first and second sites
preferably such that the first and second lesions overlap.
Inventors: |
Rioux; Robert F.; (Ashland,
MA) ; Garabedian; Robert; (Tyngsboro, MA) ;
Jarrard; Jerry; (Sunnyvale, CA) |
Correspondence
Address: |
Vista IP Law Group LLP
2040 MAIN STREET, 9TH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
BOSTON SCIENTIFIC SCIMED,
INC.
Maple Grove
MN
|
Family ID: |
34573694 |
Appl. No.: |
12/476871 |
Filed: |
June 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12033262 |
Feb 19, 2008 |
7549986 |
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12476871 |
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11238403 |
Sep 28, 2005 |
7354436 |
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12033262 |
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10713357 |
Nov 14, 2003 |
6958064 |
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11238403 |
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Current U.S.
Class: |
606/33 ;
606/41 |
Current CPC
Class: |
A61B 18/1206 20130101;
A61B 2018/143 20130101; A61B 2018/1475 20130101; A61B 2018/00702
20130101; A61B 2018/00875 20130101; A61B 18/148 20130101 |
Class at
Publication: |
606/33 ;
606/41 |
International
Class: |
A61B 18/18 20060101
A61B018/18; A61B 18/14 20060101 A61B018/14 |
Claims
1-42. (canceled)
43. A system for treating tissue within a tissue region using two
different energy types, comprising: a first ablation device
comprising a first structure configured to deliver energy of a
first type; a second ablation device comprising a second structure
configured to delivery energy of a second type different from the
first type, wherein the first ablation device and the second
ablation device are configured for creating first and second
lesions at first and second sites, respectively, within the tissue
region, and wherein the first structure and the second structure
are independently moveable relative to each other.
44. The system of claim 43, wherein the first ablation device is
configured to delivery ultrasound energy while the second ablation
device is configured to delivery radio frequency energy.
45. The system of claim 44, wherein the second ablation device
comprises an elongate member carrying at least one electrode.
46. The system of claim 45, wherein the at least one electrode
comprises a single electrode disposed at a distal tip of the
elongate member.
47. The system of claim 45, wherein the at least one electrode
comprises a plurality of electrodes disposed at a distal tip of the
elongate member.
48. The system of claim 47, wherein the plurality of electrodes
comprise wires.
49. The system of claim 44, further comprising a source of
ultrasound energy operatively coupled to the first ablation
device.
50. The system of claim 44, further comprising a source of
electrical energy operatively coupled to the second ablation
device.
51. The system of claim 50, wherein the source of electrical energy
comprises a radio frequency (RF) generator.
52. The system of claim 44, wherein the first structure and the
second structure are laterally moveable relative to each other.
53. The system of claim 44, wherein the first structure comprises a
cannula having a lumen and a shaft disposed within the lumen.
54. The system of claim 44, wherein the second structure comprises
a cannula having a lumen and a shaft disposed within the lumen.
55. The system of claim 44, wherein the first ablation device and
the second ablation device are configured for creating first and
second lesions substantially simultaneously.
56. A method for creating a lesion within a tissue region, the
method comprising: inserting a first ablation device configured to
deliver energy of a first type into a first site within the tissue
region; inserting a second ablation device configured to deliver
energy of a second type into a second site within the tissue
region, wherein the first ablation device and the second ablation
device are independently moveable relative to each other; and
delivering energy from the first ablation device and the second
ablation device to generate lesions at the first and second sites
within the tissue region.
57. The method of claim 56, wherein the first ablation device and
the second ablation are laterally moveable relative to each
other.
58. The method of claim 56, wherein the first ablation device is
configured to delivery ultrasound energy while the second ablation
device is configured to delivery radio frequency energy.
59. The method of claim 56, wherein the first ablation device and
the second ablation device are configured for percutaneous
introduction into the tissue region.
60. The method of claim 56, wherein the tissue region comprises a
liver.
61. The method of claim 56, wherein the lesions at the first and
second site at least partially overlap.
62. The method of claim 56, wherein insertion of the first ablation
device comprises inserting a cannula having a lumen into tissue and
inserting a shaft into the first site within the tissue region.
63. The method of claim 56, wherein insertion of the second
ablation device comprises inserting a cannula having a lumen into
tissue and inserting a shaft into the second site within the tissue
region.
64. The method of claim 56, wherein the energy from the first
ablation device and the second ablation device are delivered
substantially simultaneously.
65. A system for treating tissue within a tissue region using two
different energy types, comprising: a first ablation device having
at least one electrode configured to deliver radio frequency
energy; a second ablation device configured to delivery ultrasound
energy, wherein the first ablation device and the second ablation
device are configured for creating first and second lesions at
first and second sites, respectively, within the tissue region, and
wherein the first structure and the second structure are
independently moveable relative to each other; and a source of
electrical energy operatively coupled to the at least one
electrode.
66. The system of claim 65, wherein the first ablation device and
the second ablation device are configured for creating first and
second lesions substantially simultaneously.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S.
application Ser. No. 10/713,357, filed on Nov. 14, 2003, the
disclosures of which is hereby incorporated herein by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The field of the invention relates to medical devices, and
more particularly, to systems and methods for ablating or otherwise
treating tissue using electrical energy.
[0004] 2. Background of the Invention
[0005] Tissue may be destroyed, ablated, or otherwise treated using
thermal energy during various therapeutic procedures. Many forms of
thermal energy may be imparted to tissue, such as radio frequency
electrical energy, microwave electromagnetic energy, laser energy,
acoustic energy, or thermal conduction.
[0006] In particular, radio frequency ablation (RFA) may be used to
treat patients with tissue anomalies, such as liver anomalies and
many primary cancers, such as cancers of the stomach, bowel,
pancreas, kidney and lung. RFA treatment involves the destroying
undesirable cells by generating heat through agitation caused by
the application of alternating electrical current (radio frequency
energy) through the tissue.
[0007] Various RF ablation devices have been suggested for this
purpose. For example, U.S. Pat. No. 5,855,576 describes an ablation
apparatus that includes a plurality of wire electrodes deployable
from a cannula or catheter. Each of the wires includes a proximal
end that is coupled to a generator, and a distal end that may
project from a distal end of the cannula. The wires are arranged in
an array with the distal ends located generally radially and
uniformly spaced apart from the catheter distal end. The wires may
be energized in a monopolar or bipolar configuration to heat and
necrose tissue within a precisely defined volumetric region of
target tissue. The current may flow between closely spaced wire
electrodes (bipolar mode) or between one or more wire electrodes
and a larger, common electrode (monopolar mode) located remotely
from the tissue to be heated. To assure that the target tissue is
adequately treated and/or to limit damaging adjacent healthy
tissues, the array of wires may be arranged uniformly, e.g.,
substantially evenly and symmetrically spaced-apart so that heat is
generated uniformly within the desired target tissue volume. Such
devices may be used either in open surgical settings, in
laparoscopic procedures, and/or in percutaneous interventions.
[0008] During tissue ablation, the maximum heating often occurs in
the tissue immediately adjacent the emitting electrodes. In
general, the level of tissue heating is proportional to the square
of the electrical current density, and the electrical current
density in tissue generally falls rapidly with increasing distance
from the electrode. The decrease of a current density depends upon
a geometry of the electrode. For example, if the electrode has a
spherical shape, the current density will generally fall as the
second power of distance from the electrode. On the other hand, if
the electrode has an elongate shape (e.g., a wire), the current
density will generally fall with distance from the electrode, and
the associated power will fall as the second power of distance from
the electrode. For the case of spherical electrode, the heating in
tissue generally falls as the fourth power of distance from the
electrode, and the resulting tissue temperature therefore decreases
rapidly as the distance from the electrode increases. This causes a
lesion to form first around the electrodes, and then to expand into
tissue disposed further away from the electrodes.
[0009] Due to physical changes within the tissue during the
ablation process, the size of the lesion created may be limited.
For example, the concentration of heat adjacent to wires often
causes the local tissue to desiccate, thereby reducing its
electrical conductivity. As the tissue conductivity decreases, the
impedance to current passing from the electrode to the tissue
increases so that more voltage must be supplied to the electrodes
to affect the surrounding, more distant tissue. The tissue
temperature proximate to the electrode may approach 100.degree. C.,
so that water within the tissue boils to become water vapor. As
this desiccation and/or vaporization process continues, the
impedance of the local tissue may rise to the point where a
therapeutic level of current can no longer pass through the local
tissue into the surrounding tissue.
[0010] Thus, the rapid fall-off in current density may limit the
volume of tissue that can be treated by the wire electrodes. As
such, depending upon the rate of heating and the size of the wire
electrodes, existing ablation devices may not be able to create
lesions that are relatively large in size. Longer wire electrodes
and/or larger arrays have been suggested for creating larger
lesions. The effectiveness of such devices, however, may be limited
by the desiccation and/or vaporization process discussed
previously. While wire electrodes can be deployed, activated,
retracted, and repositioned sequentially to treat multiple
locations within a tissue region, such an approach may increase the
length of time of a procedure, and precise positioning to ensure
that an entire tissue region is treated may be difficult to
accomplish.
[0011] Accordingly, improved systems and methods for tissue
ablation would be useful.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to systems and methods for
delivering energy to tissue, and more particularly to systems and
methods for delivering energy substantially simultaneously to
multiple electrode arrays to increase a volume of tissue being
treated.
[0013] In accordance with a first aspect of the present invention,
a system for treating tissue within a tissue region is provided
that includes a source of energy, a first ablation device including
a plurality of wires coupled to the source of energy, and a second
ablation device including a plurality of wires coupled to the
source of energy in parallel with the first ablation device,
whereby the first and second ablation devices can substantially
simultaneously create first and second lesions, respectively,
within a tissue region.
[0014] In a preferred embodiment, the wires of the first and second
ablation devices are electrodes and the source of energy is a
source of electrical energy, e.g., a radio frequency (RF)
generator. Preferably, the first and second ablation devices
include an array of wires deployable from a cannula.
[0015] The source of electrical energy may include first and second
terminals coupled in parallel to one another. The first ablation
device may be coupled to the first terminal and the second ablation
device may be coupled to the second terminal. Alternatively, the
source of electrical energy may include a terminal, and a "Y" cable
or other connector may be coupled between the first and second
ablation devices and the terminal to couple the first and second
ablation devices in parallel. Optionally, a ground electrode may be
coupled to the source of energy opposite the first and second
ablation devices, e.g., to provide a return path for electrical
energy delivered to the tissue from the electrodes.
[0016] In accordance with another aspect of the present invention,
a method is provided for creating a lesion within a tissue region,
e.g., a benign or cancerous tumor within a liver or other tissue
structure. A first array of electrodes may be inserted into a first
site within the tissue region, and a second array of electrodes may
be inserted into a second site within the tissue region.
Preferably, the second array of electrodes is coupled in parallel
with the first array of electrodes, e.g., to a RF generator or
other source of energy.
[0017] In one embodiment, the first and second arrays of electrodes
may be introduced into the first and second sites from first and
second cannulas, respectively. Preferably, the first and second
cannulas are introduced into the tissue region until distal ends of
the first and second cannulas are disposed adjacent the first and
second sites, respectively. The first and second arrays of
electrodes may then be deployed from the distal ends of the first
and second cannulas into the first and second sites,
respectively.
[0018] Energy may be substantially simultaneously delivered to the
first and second arrays of electrodes to generate lesions at the
first and second sites within the tissue region. Preferably, the
first and second sites are disposed adjacent to one another within
the tissue region such that the first and second lesions at least
partially overlap. Optionally, at least one or both of the first
and second arrays of electrodes may be removed from the tissue
region and introduced into a third (and fourth) site within the
tissue region, and activated to increase the size of the lesion
created. In other embodiments, the first and second arrays of
electrodes can be placed at different sites, each of which is
associated with a treatment region. In such arrangement, separate
tissues at different treatment sites can be ablated
simultaneously.
[0019] Other aspects and features of the invention will be evident
from reading the following detailed description of the preferred
embodiments, which are intended to illustrate, not limit, the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The drawings illustrate the design and utility of preferred
embodiments of the present invention, in which similar elements are
referred to by common reference numerals. In order to better
appreciate how advantages and objects of the present inventions are
obtained, a more particular description of the present inventions
briefly described above will be rendered by reference to specific
embodiments thereof, which are illustrated in the accompanying
drawings. Understanding that these drawings depict only typical
embodiments of the invention and are not therefore to be considered
limiting its scope, the invention will be described and explained
with additional specificity and detail through the use of the
accompanying drawings.
[0021] FIG. 1 illustrates a system for delivering electrical energy
to tissue, in accordance with a preferred embodiment of the present
invention.
[0022] FIG. 2 illustrates a variation of the ablation system of
FIG. 1, showing the power supply having a plurality of output
terminals.
[0023] FIG. 3 is a cross-sectional side view of an embodiment of an
ablation device, showing electrode wires constrained within a
cannula.
[0024] FIG. 4 is a cross-sectional side view of the ablation device
of FIG. 3, showing the wires deployed from the cannula.
[0025] FIGS. 5A-5D are cross-sectional views, showing a method for
treating tissue, in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Referring now to the drawings, in which similar or
corresponding parts are identified with the same reference numeral,
FIG. 1 shows a preferred embodiment of an ablation system 10, in
accordance with the present invention. The ablation system 10
includes a source of energy 12, e.g., a radio frequency (RF)
generator, having an output terminal 14, a connector 16, a first
ablation device 18, and a second ablation device 20. One or both of
the first and the second ablation devices 18, 20 may be capable of
being coupled to the generator 12.
[0027] The generator 12 is preferably capable of operating with a
fixed or controlled voltage so that power and current diminish as
impedance of the tissue being ablated increases. Exemplary
generators are described in U.S. Pat. No. 6,080,149, the disclosure
of which is expressly incorporated by reference herein. The
preferred generator 12 may operate at relatively low fixed
voltages, typically below one hundred fifty volts (150 V)
peak-to-peak, and preferably between about fifty and one hundred
volts (50-100 V). Such radio frequency generators are available
from Boston Scientific Corporation, assignee of the present
application, as well as from other commercial suppliers. It should
be noted that the generator 12 is not limited to those that operate
at the range of voltages discussed previously, and that generators
capable of operating at other ranges of voltages may also be
used.
[0028] The connector 16 includes an input terminal 22, a first
output terminal 24, and a second output terminal 26 that is
connected in parallel with the first output terminal 24. The first
and second output terminals 24 and 26 of the connector 16 are
configured for coupling to the first and second ablation devices
18, 20, respectively, while the input terminal 22 of the connector
16 is configured for coupling to the output terminal 14 of the
generator 12. Optionally, the ablation system 10 may include one or
more cables 28, e.g., extension cables or cables that extend from
the first and second ablation devices 18, 20. If cables 28 are not
provided, the first and second ablation devices 18, 20 may be
coupled directly to the output terminals 24 and 26, respectively,
of the connector 16. In the illustrated embodiment, the connector
16 may deliver power from the generator 12 simultaneously to the
first and second ablation devices 18, 20. If it is desired to
deliver power to more than two ablation devices, the connector 16
may have more than two output terminals connected in parallel to
one another (not shown).
[0029] Alternatively, as shown in FIG. 2, instead of the "Y"
connector 16, a generator 12' may be provided that includes two (or
optionally more) output terminals 14' coupled in parallel with one
another. In this case, first and second ablation devices 18,' 20'
may be coupled to separate output terminals 14' of the generator
12' without requiring a connector 16 (not shown, see FIG. 1).
However, if the generator 12' does not provide an adequate number
of output terminals 14 for the number of ablation devices desired,
one or more connectors 16 (not shown) may be used to couple two or
more ablation devices to a single output terminal of the generator
12.'
[0030] The output terminals 14' of the generator 12' may be coupled
to common control circuits (not shown) within the generator 12.'
Alternatively, the generator 12' may include separate control
circuits coupled to each of the output terminals 14.' The control
circuits may be connected in parallel with one another, yet may
include separate impedance feedback to control energy delivery to
the respective output terminals 14.' Thus, the output terminals 14'
may be connected in parallel to an active terminal of the generator
12' such that the ablation devices 18,' 20' deliver energy to a
common ground pad electrode (not shown) in a monopolar mode.
Alternatively, the output terminals 14' may be connected to
opposite terminals of the generator 12' for delivering energy
between the ablation devices 18,' 20' in a bipolar mode.
[0031] Turning to FIGS. 3 and 4, in a preferred embodiment, each of
the ablation devices 18, 20 of FIG. 1 (or alternatively, the
ablation devices 18,' 20' of FIG. 2) may be a probe assembly 50.
The probe assembly 50 may include a cannula 52 having a lumen 54, a
shaft 56 having a proximal end 58 and a distal end 60, and a
plurality of electrode wires 62 secured to the distal end 60 of the
shaft 56. The proximal end 58 of the shaft 56 may include a
connector 63 for coupling to the generator 12. For example, the
connector 62 may be used to connect the probe assembly 50 to a
cable 66, which may be part of the connector 16 (not shown, see
FIG. 1), an extension cable, or a cable that extends from the
output terminal 14 of the generator 12. Alternatively, the probe
assembly 50 may itself include a cable (not shown) on the proximal
end 58 of the shaft 56, and a connector may be provided on the
proximal end of the cable (not shown).
[0032] The cannula 52 may have a length between about five and
thirty centimeters (5-30 cm), and/or an outer diameter or cross
sectional dimension between about one and five millimeters (1-5
mm). However, the cannula 52 may also have other lengths and outer
cross sectional dimensions, depending upon the application. The
cannula 52 may be formed from metal, plastic, and the like, and/or
may be electrically active or inactive within the probe assembly
50, depending upon the manner in which electrical energy is to be
applied.
[0033] The cannula 52 may coaxially surround the shaft 56 such that
the shaft 56 may be advanced axially from or retracted axially into
the lumen 54 of the cannula 52. Optionally, a handle 64 may be
provided on the proximal end 58 of the shaft 56 to facilitate
manipulating the shaft 56. The wires 62 may be compressed into a
low profile when disposed within the lumen 54 of the cannula 52, as
shown in FIG. 3. As shown in FIG. 4, the proximal end 58 of the
shaft 56 or the handle 64 (if one is provided) may be advanced to
deploy the wires from the lumen 54 of the cannula 52. When the
wires 62 are unconfined outside the lumen 54 of the cannula 52,
they may assume a relaxed expanded configuration. FIG. 4 shows an
exemplary two-wire array including wires 62 biased towards a
generally "U" shape and substantially uniformly separated from one
another about a longitudinal axis of the shaft 56. Alternatively,
each wire 62 may have other shapes, such as a "J" shape, and/or the
array may have one wire 62 or more than two wires 62. The array may
also have non-uniform spacing to produce an asymmetrical lesion.
The wires 62 are preferably formed from spring wire, superelastic
material, or other material, such as Nitinol, that may retain a
shape memory. During use of the probe assembly 50, the wires 62 may
be deployed into a target tissue region to deliver energy to the
tissue to create a lesion.
[0034] Optionally, a marker (not shown) may be placed on the handle
64 and/or on the proximal end 58 of the shaft 56 for indicating a
rotational orientation of the shaft 56 during use. The probe
assembly 50 may also carry one or more radio-opaque markers (not
shown) to assist positioning the probe assembly 50 during a
procedure, as is known in the art. Optionally, the probe assembly
50 may also include a sensor, e.g., a temperature sensor and/or an
impedance sensor (not shown), carried by the distal end of the
shaft 56 and/or one or more of the wires 62.
[0035] Exemplary ablation devices having a spreading array of wires
have been described in U.S. Pat. No. 5,855,576, the disclosure of
which is expressly incorporated by reference herein.
[0036] It should be noted that the ablation devices 18, 20 are not
necessarily limited to the probe assembly 50 shown in FIGS. 3 and
4, and that either or both of the ablation devices 18, 20 may be
selected from a variety of devices that are capable of delivering
ablation energy. For example, medical devices may also be used that
are configured for delivering ultrasound energy, microwave energy,
and/or other forms of energy for the purpose of ablation, which are
well known in the art. Furthermore, the first and second ablation
devices 18, 20 are not necessarily limited to the same type of
devices. For example, the first ablation device 18 may deliver
ultrasound energy while the second ablation device 20 may deliver
radio-frequency energy. Also, the first and second ablation devices
18, 20 may have different sizes of arrays of wires 62, and/or
different types or numbers of electrodes. For example, either of
the first and second ablation devices 18, 20 may be an elongate
member carrying a single electrode tip.
[0037] Referring now to FIGS. 5A-5D, the ablation system 10 may be
used to treat a treatment region TR within tissue located beneath
skin or an organ surface S of a patient. The tissue TR before
treatment is shown in FIG. 5A. As shown in FIG. 5B, the cannulas 52
of the first and second ablation devices 18, 20 may be introduced
into the treatment region TR, so that the respective distal ends of
the cannulas 52 of the first and second ablation devices 18, 20 are
located at first and second target sites TS1, TS2. This may be
accomplished using any of a variety of techniques. In some cases,
the cannulas 52 and shafts 56 of the respective ablation devices
18, 20 may be introduced into the target site TS percutaneously,
i.e., directly through the patient's skin, or through an open
surgical incision. In this case, the cannulas 52 may have a
sharpened tip, e.g., a beveled or pointed tip, to facilitate
introduction into the treatment region. In such cases, it is
desirable that the cannulas 52 be sufficiently rigid, i.e., have
sufficient column strength, so that the cannulas 52 may be
accurately advanced through tissue.
[0038] In an alternative embodiment, the cannulas 52 may be
introduced without the shafts 56 using internal stylets (not
shown). Once the cannulas 52 are positioned as desired, the stylets
may be exchanged for the shafts 56 that carry the wires 62. In this
case, each of the cannulas 52 may be substantially flexible or
semi-rigid, since the initial column strength of the apparatus 10
may be provided by the stylets. Various methods known in the art
may be utilized to position the probe 50 before deploying the
wires.
[0039] In a further alternative, one or more components or elements
may be provided for introducing each of the cannulas 52 to the
treatment region. For example, a conventional sheath and sharpened
obturator (stylet) assembly (not shown) may be used to access the
target site(s). The assembly may be positioned using ultrasonic or
other conventional imaging. Once properly positioned, the
obturator/stylet may be removed, providing an access lumen through
the sheath. The cannula 52 and shaft 56 of each of the ablation
devices 18, 20 may then be introduced through the respective sheath
lumens so that the distal ends of the cannulas 52 of the first and
second ablation devices 18, 20 advance from the sheaths into the
target sites TS1, TS2.
[0040] Turning to FIG. 5C, after the cannulas 52 of the ablation
devices 18, 20 are properly placed, the shafts 56 of the respective
ablation devices 18, 20 may be advanced distally, thereby deploying
the arrays of wires 62 from the distal ends of the respective
cannulas 52 into the target sites TS1, TS2. Preferably, the wires
62 are biased to curve radially outwardly as they are deployed from
the cannulas 52. The shaft 56 of each of the ablation devices 18,
20 may be advanced sufficiently such that the wires 62 fully deploy
to circumscribe substantially tissue within the target sites TS1,
TS2 of the treatment region TR, as shown in FIG. 5D. Alternatively,
the wires 62 may be only partially deployed or deployed
incrementally in stages during a procedure.
[0041] If the generator 12 of the ablation system 10 includes only
one output terminal 14, one or more connectors 16, described
previously, may be used to couple the ablation devices 18, 20 to
the output terminal 14. If the generator 12 includes more than one
output terminals 14, the ablation devices 18, 20 may be coupled
directly to the generator 12 without using the connector 16.
Extension cables 28 may also be used to couple the ablation devices
18, 20 to the connector 16 or to the generator 12. The ablation
devices 18, 20 may be coupled to the generator 12 in parallel with
one another after the wires 62 of the respective ablation devices
18, 20 have been deployed. Alternatively, the wires 62 may be
coupled to the generator 12 before the cannulas 52 are introduced
to the treatment region, or at any time before the tissue is
ablated. A neutral or ground electrode, e.g., an external electrode
pad, may be coupled to the opposite terminal (not shown) of the
generator 12 and coupled to the patient, e.g., the patient's skin,
in a conventional manner.
[0042] Next, energy, preferably RF electrical energy, may be
delivered from the generator 12 to the wires 62 of the respective
ablation devices 18, 20, thereby substantially simultaneously
creating lesions at the first and second target sites TS1, TS2 of
the treatment region TR, respectively. Because the ablation devices
18, 20 are connected in parallel to the generator 12, as the
impedance of tissue at one of the target sites TS1, TS2 increases,
e.g., as the tissue is desiccated or otherwise treated, current may
continue to flow to the other target site(s) to complete treatment
of both target sites.
[0043] Simultaneously creating two or more lesions within a
treatment region may substantially reduce the duration of an
ablation procedure. In addition, using only a single generator 12
(or fewer generators than deployed ablation devices) may reduce the
cost of equipment necessary to complete a procedure. When desired
lesions at the first and second target sites TS1, TS2 of the
treatment region TR have been created, the wires 62 of each of the
ablation devices 18, 20 may be retracted into the respective lumens
54 of the cannulas 52, and the ablation devices 18, 20 may be
removed from the treatment region TR. In many cases, two ablation
devices 18, 20 may be sufficient to create a desired lesion.
However, if it is desired to perform further ablation to increase
the lesion size or to create lesions at different site(s) within
the treatment region TR or elsewhere, the wires 62 of either or
both of the ablation devices 18, 20 may be introduced and deployed
at different target site(s), and the same steps discussed
previously may be repeated.
[0044] Although an embodiment has been described with reference to
placing ablation devices at different sites that are within a
treatment region, the scope of the invention should not be so
limited. In alternative embodiments, the ablation devices 18, 20
are disposed at different sites, each of which is associated with a
treatment region. In such arrangement, separate tissues at
different sites can be ablated simultaneously. In addition, it
should be noted that the scope of the invention should not be
limited to the ablation system 10 having two ablation devices. In
alternative embodiments, the ablation system 10 can have more than
two ablation devices.
[0045] Thus, although several preferred embodiments have been shown
and described, it would be apparent to those skilled in the art
that many changes and modifications may be made thereunto without
the departing from the scope of the invention, which is defined by
the following claims and their equivalents.
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