U.S. patent application number 12/818077 was filed with the patent office on 2010-10-07 for large area thermal ablation.
This patent application is currently assigned to BOSTON SCIENTIFIC SCIMED, INC.. Invention is credited to Robert J. Crowley, Mark A. Hamm.
Application Number | 20100256632 12/818077 |
Document ID | / |
Family ID | 22293157 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100256632 |
Kind Code |
A1 |
Crowley; Robert J. ; et
al. |
October 7, 2010 |
LARGE AREA THERMAL ABLATION
Abstract
A large area thermal ablation apparatus for use with an
endoscope includes a housing and at least one electrode. The
housing is removably attachable to a distal terminating end of the
endoscope. The housing includes an outer surface and a
cross-sectional area that is at least as large as a cross-sectional
area of the distal terminating end of the endoscope. The electrode
is supported by the outer surface of the housing. The electrode is
capable of delivering energy to a tissue region inside a body to
ablate the tissue region.
Inventors: |
Crowley; Robert J.;
(Sudbury, MA) ; Hamm; Mark A.; (Lynnfield,
MA) |
Correspondence
Address: |
Vista IP Law Group LLP
2040 MAIN STREET, Suite 710
IRVINE
CA
92614
US
|
Assignee: |
BOSTON SCIENTIFIC SCIMED,
INC.
Maple Grove
MN
|
Family ID: |
22293157 |
Appl. No.: |
12/818077 |
Filed: |
June 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11158292 |
Jun 21, 2005 |
7749159 |
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12818077 |
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10134721 |
Apr 29, 2002 |
6932812 |
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11158292 |
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09410937 |
Oct 5, 1999 |
6394949 |
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10134721 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/00178
20130101; A61B 2018/1495 20130101; A61B 18/1492 20130101; A61B
2017/00526 20130101; A61B 2018/00988 20130101; Y10S 600/92
20130101; A61B 2018/1497 20130101; A61B 18/1482 20130101; A61B
2018/00482 20130101; A61B 2018/00494 20130101; A61B 2018/126
20130101; A61B 2017/00296 20130101; A61B 18/14 20130101; A61B
2018/00577 20130101; A61B 2018/00029 20130101; A61B 2018/143
20130101 |
Class at
Publication: |
606/41 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1-60. (canceled)
61. An apparatus for use with an endoscope comprising: an
articulating housing removably attachable to a distal terminating
end of the endoscope, the housing comprising an outer surface and a
cross-sectional area at least as large as a cross-sectional area of
the distal terminating end of the endoscope, the articulating
housing configured to articulate relative to the endoscope when
secured thereto; and at least one electrode supported by at least a
portion of the outer surface of the housing and capable of
delivering energy to a tissue region inside a body to ablate the
tissue region.
62. The apparatus of claim 1, wherein a plurality of electrodes are
supported by at least a portion of the outer surface of the housing
and capable of delivering energy to a tissue region inside a body
to ablate the tissue region.
63. The apparatus of claim 62, wherein the plurality of electrodes
are formed in a pattern.
64. The apparatus of claim 63, wherein the pattern comprises a row
of linear elements.
65. The apparatus of claim 63, wherein the pattern comprises a
helical pattern.
66. The apparatus of claim 62, wherein the plurality of electrodes
comprise a bipolar arrangement of interspersed electrodes.
67. The apparatus of claim 61, wherein the housing comprises an
insulator.
68. The apparatus of claim 61, wherein the housing comprises at
least one of a ceramic material, a glass, and a polymeric
material.
69. The apparatus of claim 67, wherein the insulator comprises a
thermal insulator.
70. The apparatus of claim 67, wherein the insulator comprises and
electrical insulator.
71. The apparatus of claim 61, wherein at least a portion of the
housing is transparent.
72. The apparatus of claim 61, wherein the housing comprises at
least one groove and a plurality of electrodes are positioned in
the groove.
73. The apparatus of claim 61, wherein the housing is substantially
ring-shaped.
74. The apparatus of claim 61, wherein the housing further
comprises a stop ring.
75. The apparatus of claim 61, further comprising an electrical
conduit extending proximally from the housing, the electrical
conduit having a connector in electrical communication with a
proximal end thereof.
76. An apparatus for use with an endoscope comprising: an
elastomeric housing removably attachable to a distal terminating
end of the endoscope, the housing comprising an outer surface and a
cross-sectional area at least as large as a cross-sectional area of
the distal terminating end of the endoscope, the elastomeric
housing configured for axial sliding movement along a length of the
endoscope in response to repositioning of the same; and at least
one electrode supported by at least a portion of the outer surface
of the housing and capable of delivering energy to a tissue region
inside a body to ablate the tissue region.
77. The apparatus of claim 76, wherein the elastomer comprises
silicone.
78. The apparatus of claim 76, wherein the elastomer comprises
rubber.
79. The apparatus of claim 76 wherein the elastomer is optically
transparent.
80. An apparatus for use with an endoscope comprising: a housing
removably attachable to a distal terminating end of the endoscope,
the housing comprising an outer surface and a cross-sectional area
at least as large as a cross-sectional area of the distal
terminating end of the endoscope, the housing having a plurality of
apertures dimensioned for fluid passage formed in a distal portion
of the housing; and a plurality of electrodes supported by at least
a portion of the outer surface of the housing and capable of
delivering energy to a tissue region inside a body to ablate the
tissue region.
Description
CROSS-REFERENCE TO RELATED CASE
[0001] This application claims priority to and claims the benefit
of U.S. provisional patent application Ser. No. 60/103,060 filed
Oct. 5, 1998, which provisional application is incorporated herein
by reference.
TECHNICAL FIELD
[0002] The invention relates to thermal ablation and, more
particularly, to thermal ablation apparatus for use with an
endoscope.
BACKGROUND INFORMATION
[0003] Thermal ablation of tissue can be performed to remove
diseased tissue, such as precancerous or cancerous tissue. For
example, thermal ablation has been used in the treatment of
Barrett's esophagus, which is a precancerous condition. Thermal
ablation can also be performed to remove old tissue and to provide
a new surface to support growth of new tissue. Typically, thermal
ablation is performed by passing an electrode through a working
channel of an endoscope, placing the electrode near the tissue
region to be treated and applying radio-frequency (RF) energy to
the electrode. An advantage of this technique is that the procedure
can be performed under direct visualization. A disadvantage of this
technique is that the diameter of the electrode is necessarily
limited by the small diameter of the working channel of the
endoscope. As a result, the electrode can only treat a small area
of the tissue at a time.
[0004] In some precancerous conditions that may be treatable via
thermal ablation, the area to be treated is relatively large with
respect to the electrode, resulting in very long procedure times,
irregular or incomplete ablation, and variations in the depth of
the ablative effect. The inability to control sufficiently the
depth of the ablation procedure can lead to charring or perforation
of the tissue or a failure to reduce significantly the number of
precancerous cells to sufficiently low level.
[0005] Attempts have been made to provide large electrodes to
overcome these limitations. For example, electrodes have been
provided on expandable surfaces such as balloons. These
apparatuses, however, have been limited to some extent by the
diameter of the accessory channel of an endoscope.
SUMMARY OF THE INVENTION
[0006] In general, the invention relates to thermal ablation of a
large tissue area. Thermal ablation apparatuses, according to the
invention, are designed for use with an endoscope.
[0007] In one aspect, the invention features an apparatus for use
with an endoscope which includes a housing and at least one
electrode. The housing is removably attachable to a distal
terminating end of the endoscope. The housing includes an outer
surface and a cross-sectional area that is at least as large as a
cross-sectional area of the distal terminating end of the
endoscope. The electrode is supported by at least a portion of the
outer surface of the housing. The electrode is capable of
delivering energy to a tissue region inside a body to ablate the
tissue region.
[0008] Embodiments of this aspect of the invention can include the
following features.
[0009] In one embodiment, the housing comprises an insulator. For
example, the housing can comprise a thermal insulator and/or an
electrical insulator. At least a portion of the housing can be
transparent. Examples of materials suitable for forming the housing
include, but are not limited to, a ceramic material, a glass, and a
polymeric material. The housing can be substantially ring-shaped.
In another embodiment, the housing includes a distal end and a
proximal end. The proximal end comprises an elastomeric material
and is sized and shaped to slip over the distal terminating end of
the endoscope.
[0010] In one embodiment, at least one electrode includes a
pattern. For example, the pattern can comprise a row of linear
elements or a helical pattern. The electrode can be monopolar or
bipolar. The housing can include at least one groove and the
electrode can be positioned in the groove. The apparatus can
further include an electrical conduit in electrical communication
with at least one electrode. For example, the electrical conduit
can be a wire, a pair of twisted wires, or a coaxial conductor.
[0011] In another aspect, the invention features an apparatus for
use with an endoscope which includes a sheath, a housing, and at
least one electrode. The sheath includes a first channel for
receiving the endoscope. The housing is attached to a distal end of
the sheath. The housing includes an outer surface and a
cross-sectional area at least as large as a cross-sectional area of
a distal terminating end of the endoscope. The electrode is
supported by at least a portion of the outer surface of the
housing. The electrode is capable of delivering energy to a tissue
region inside a body to ablate the tissue region.
[0012] Embodiments of this aspect of the invention can include the
following features.
[0013] In one embodiment, the sheath further includes a second
channel coextensive with the first channel. An electrical conduit
is disposed in the second channel. The electrical conduit is in
electrical communication with at least one electrode. In another
embodiment, the sheath further includes a second channel
coextensive with the first channel for receiving a fluid. The
sheath can comprise polyethylene. The sheath can have a thickness
in the range from about 0.015 inches to about 0.085 inches.
[0014] In another aspect, the invention features a medical
apparatus which includes an endoscope, a housing, and at least one
electrode. The endoscope terminates at a distal end. The housing is
removably attachable to the distal end of the endoscope. The
housing includes an outer surface and a cross-sectional area at
least as large as a cross-sectional area of the distal end of the
endoscope. The electrode is supported by at least a portion of the
outer surface of the housing. The housing is capable of delivering
energy to a tissue region inside a body to ablate the tissue
region.
[0015] In another aspect, the invention features a medical
apparatus which includes an endoscope, a sheath, and at least one
electrode. The endoscope terminates at a distal end. The sheath
comprises a channel for receiving the endoscope and a housing
attached to a distal end of the sheath. The housing includes an
outer surface and a cross-sectional area at least as large as a
cross-sectional area of the distal end of the endoscope. The
electrode is supported by at least a portion of the outer surface
of the housing. The electrode is capable of delivering energy to a
tissue region inside a body to ablate the tissue region.
[0016] In another aspect, the invention features a method of
treating tissue in a body which includes the following steps. A
housing is removably attached to a distal terminating end of an
endoscope. The housing is removably attachable to the distal
terminating end of an endoscope. The housing includes an outer
surface supporting at least one electrode on at least a portion of
the outer surface and a cross-sectional area at least as large as a
cross-sectional area of the distal terminating end of the
endoscope. The endoscope and the housing are inserted inside the
body near a tissue region to be treated. Energy is applied to at
least one electrode to treat the tissue region.
[0017] In one embodiment, at least one electrode is connected to a
power source through an electrical conduit housed in a channel of
the endoscope. In another embodiment, a housing comprising at least
one aperture is attached to the distal terminating end of the
endoscope and a fluid is provided to the tissue region through the
aperture. The fluid can be a cooling fluid, a flushing fluid and/or
a conductive fluid. In still another embodiment, the tissue region
is illuminated and an optical property of the tissue region is
detected.
[0018] In another aspect, the invention features a method of
treating tissue in a body including the following steps. A sheath
comprising a channel for receiving an endoscope and a housing
attached to a distal end of the sheath is provided. The housing
includes an outer surface supporting at least one electrode on at
least a portion of the outer surface and a cross-sectional area at
least as large as a cross-sectional area of a distal terminating
end of the endoscope. An endoscope is inserted inside the channel
of the sheath, such that the housing is positioned near the distal
terminating end of the endoscope. The sheath and the endoscope are
inserted inside the body near a tissue region to be treated. Energy
is applied to at least one electrode to treat the tissue
region.
[0019] In one embodiment, at least one electrode is connected to a
power source through an electrical conduit housed in a second
channel of the sheath. In another embodiment, energy is applied to
the tissue region to ablate the tissue region.
[0020] In another aspect, the invention features a method of
manufacturing an ablation apparatus including the following steps.
A housing is provided. A slurry comprising a conductive material
and a solution is also provided. The slurry is applied to at least
a portion of a surface of the housing. The solution is removed from
the slurry applied on the surface of the housing to form an
electrode comprising the conductive material on the surface of the
housing.
[0021] In one embodiment, a slurry including a conductive material
is printed on the surface of the housing. In another embodiment,
the slurry including a conductive material is applied to the
housing by spraying, brushing or dipping the housing into the
slurry.
[0022] In another embodiment, the slurry is heated to remove the
solution and to melt or reflow the conductive material.
[0023] In yet another embodiment, a housing comprising at least one
groove is provided. The solution in the slurry applied to the
surface of the housing is removed to form the electrode in the
groove of the housing.
[0024] The foregoing and other objects, aspects, features, and
advantages of the invention will become more apparent from the
following description and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the drawings, like reference characters generally refer
to the same parts throughout the different views. Also, the
drawings are not necessarily to scale; emphasis instead generally
being placed upon illustrating the principles of the invention.
[0026] FIG. 1a is a side view of a thermal ablation apparatus for
use with an endoscope according to one embodiment of the
invention.
[0027] FIG. 1b is an end view of the thermal ablation apparatus of
FIG. 1.
[0028] FIG. 2 is a partial cross-sectional view of the thermal
ablation apparatus of FIG. 1 mounted at the distal terminating end
of an endoscope.
[0029] FIG. 3 is a partial cross-sectional view of a thermal
ablation apparatus having a coextensive outer sheath arrangement
disposed over a typical endoscope, according to one embodiment of
the invention.
[0030] FIG. 4 is a cross-sectional view of a thermal ablation
apparatus according to another embodiment of the invention.
[0031] FIG. 5 is a perspective view of a power source and an
electrical conduit arrangement for mating with a thermal ablation
apparatus according to one embodiment of the invention.
[0032] FIG. 6a is a side view of a housing of a thermal ablation
apparatus according to one embodiment of the invention.
[0033] FIG. 6b illustrates a step in a method of manufacturing a
thermal ablation apparatus according to one embodiment of the
invention.
[0034] FIG. 6c illustrates another step in a method of
manufacturing a thermal ablation apparatus according to one
embodiment of the invention.
[0035] FIG. 6d illustrates another step in a method of
manufacturing a thermal ablation apparatus according to one
embodiment of the invention.
[0036] FIG. 7 is a schematic cross-sectional view of a thermal
ablation apparatus including a light assembly and a light modulator
disposed in a housing according to another embodiment of
invention.
[0037] FIG. 8 is a detailed view of the light modulator assembly of
the thermal ablation apparatus of FIG. 7.
DESCRIPTION
[0038] Referring to FIGS. 1a and 1b, a thermal ablation apparatus
10 includes a housing 1 and multiple electrodes 9 supported by the
housing 1. The housing 1 has a distal end 3 and a proximal end 5.
The distal end 3 of the housing 1 supports the electrodes 9. The
proximal end 5 of the housing 1 is designed to attach removably to
a distal terminating end 28 of an endoscope 21, as shown in FIG. 2.
The housing 1 is "removably attachable" to the distal terminating
end 28 of the endoscope 21 in that the housing 1 can be attached
and detached from the distal terminating end 28 of an endoscope 21
any number of times without affecting or changing the functionality
of the endoscope 21 itself. The housing 1 is not formed integrally
with the distal terminating end 28 of the endoscope 21, but instead
is placeable on and removable from the distal terminating end 28 of
the endoscope 21 as a separate piece. In one embodiment, the
housing 1 has a generally cylindrical shape. In another embodiment,
the housing 1 is a cap-like structure.
[0039] The distal end 3 of the housing 1 can be constructed of a
non-conductive material. A housing 1 made of a non-conductive
material provides electrical isolation between multiple electrodes
9 supported by the housing 1. The distal end 3 of the housing 1 can
also be constructed of a thermally insulating material. A housing 1
made of a thermally insulating material protects the endoscope 21
from heat generated by the electrodes 9 during an ablation
procedure. In some embodiments, the source of the thermal energy
can be very close to areas of the endoscope 21 that can be damaged
by the thermal energy. Therefore, in these situations, a housing 1
made of thermally insulating material can be essential to ensuring
the usefulness of the endoscope 21.
[0040] The housing 1 can further be made of an optically
transparent material, for example, glass tubing. A housing 1 made
of an optically transparent material allows an operator to observe
the ablation procedure through spaces between the electrodes 9.
Examples of materials suitable for forming the housing 1 include,
but are not limited to, ceramic material, glass, and plastic
material. In one embodiment, the housing 1 can be made of a ceramic
material that can be molded or machined into a suitable shape and
subsequently fired to form the housing 1. Advantages of a housing 1
comprising a ceramic material include low heat transfer, low cost
and good adhesion properties. In another embodiment, the housing 1
can made of glass that is generally shaped or molded by heat.
Advantages of a housing 1 comprising glass is that glass allows an
operator the opportunity to observe the ablation procedure. In yet
another embodiment, the housing 1 can be made of polymers such as
polyimide or polysulfone, or a high temperature, epoxy resin such
as phenol-formaldehyde resin. The advantage of using these
materials is that they can be made to be optically transparent.
[0041] The proximal end 5 of the housing 1 can be constructed of an
elastomeric material. The elastomeric material can be stretched to
slip over the distal terminating end 28 of the endoscope 21 and
provide a relatively secure mounting that can still allow flexure
between the housing 1 relative to the endoscope 21. Examples of
suitable elastomeric materials for constructing the proximal end 5
of the housing 1 include, but are not limited to silicone and
rubber.
[0042] An outer diameter of the proximal end 5 can be similar to an
outer diameter of the distal end 3 so that the entire housing 1 has
a generally uniform diameter. The distal end 3 and the proximal end
5 of the housing 1 can be connected via a lap joint 7. The lap
joint 7 provides an overlapping surface for placing an epoxy. The
epoxy provides a firm attachment of the proximal end 5 to the
distal end 3 of the housing 1. Alternatively, a filament can be
tightly tied around the lap joint 7 to provide a firm attachment of
the proximal end 5 to the distal end 3 of the housing 1.
[0043] Referring to FIG. 2, the distal end 3 of the housing 1 can
be relatively short in length to minimize obstruction of the view
provided by a typically wide-angle view of the endoscope 21. In one
embodiment, the housing 1 does not protrude significantly beyond
the distal terminating end 28 of the endoscope 21. The distance
between the distal end 3 of the housing 1 and the distal
terminating end 28 of the endoscope 21 can be easily adjusted due
to a generally cylindrical and coaxial configuration of the housing
1. The housing 1 can be slid into various axial positions along the
length of the distal end of the endoscope 21, and further be
repositioned as needed. Various types of stops, marks, location
dots or the like can be placed along the endoscope 21 or the
thermal ablation apparatus 10 to aid alignment of the thermal
ablation apparatus 10 and the endoscope 21. Radial positioning of
the thermal ablation apparatus 10 relative to the endoscope 21 can
also be accomplished by rotating the housing 1 relative to the
endoscope 21 with the aid of location marks, stops or other
reference points or indicia located on the housing 1 or other
portion of the thermal ablation apparatus 10 in such a way as to be
easily visible and evident to an operator.
[0044] In another embodiment, an articulated housing 1 provides
operating flexibility and reduces the need for endoscope 21
manipulation. Articulation of the housing 1 relative to the
endoscope 21 can be achieved through the use of a secondary force.
Examples of secondary forces include, but are not limited to, water
and air pressure. The secondary force can also be a guidewire.
[0045] In the embodiment of FIGS. 1a and 1b, an outer surface of
the distal end 3 of the housing 1 supports multiple electrodes 9
that are spaced apart and electrically connected to each other. The
electrodes 9 are constructed of a conductive material. Examples of
suitable conductive materials for forming the electrodes 9 include,
but are not limited to, copper foil, gold plating, and sintered or
renown metal and wires. In one embodiment, the electrodes 9 are
formed in a pattern for varying the application of energy to a
tissue region. For example, the electrodes 9 can form a helical
pattern or a dotted linear pattern. In another embodiment, the
patterns comprise a bipolar arrangement of interspersed electrodes.
The electrode patterns can be placed around the circumference of
the housing 1 or at a distal end 3 of the housing 1. Alternatively,
the electrodes 9 can be disposed over a more limited area, angle or
position on the housing 1. The shape and thickness of the
electrodes 9 can also vary as desired.
[0046] The thermal ablation apparatus 10 further includes an
electrical conduit 11 connected to the electrodes 9 at a distal
end. Referring to FIG. 1b, the electrodes 9 are placed radially
from the circumference of the housing 1. The electrodes 9 are
connected to the electrical conduit 11 via apertures 13. This
arrangement allows all the electrodes 9 to be connected to a power
source by an electrical conduit 11 that can be passed through the
working channel 24 of an endoscope 21. The electrical conduit 11
has a connector 15 at a proximal end. The electrical conduit 11 can
be a pair of wires. The pair of wires can be in the form of a
twisted pair such as pigtail wires, as shown in FIG. 1, or a
coaxial conductor. Alternatively, the electrical conduit 11 can be
a single wire. The wires can be insulated. The connector 15 can be
a single pin connector or a multi-pin connector. As shown in FIG.
2, the electrical conduit 11 of the thermal ablation apparatus 10
is coupled to a second electrical conduit 23 which extends from a
power source. The electrical conduit 11 and the second electrical
conduit 23 are mated through the connectors 15, 25. The electrical
conduits 11, 23 are positioned inside a working channel 24 of the
endoscope 21. A fluid sealing ring 47 can be provided at a junction
where the two connectors 15 and 25 mate. The fluid sealing ring 47
prevents any fluid from infiltrating the electrical conduits 11, 23
should the working channel 24 accommodate both the electrical
conduits 11, 23 and a fluid.
[0047] Referring to FIG. 3, a thermal ablation apparatus 30
includes a coextensive sheath 35 having a first channel 39 for
receiving an endoscope 21', a housing 1' attached to a distal end
of the sheath 35, and multiple electrodes 9' supported by the outer
surface of the housing 1'. The endoscope 21' is inserted inside the
first channel 39 of the sheath 35, such that the distal terminating
end 28' of the endoscope 21' is positioned next to the housing
1'.
[0048] In one embodiment, the sheath 35 is long enough to extend
along the entire length of the endoscope 21'. Alternatively, the
length of the sheath 35 can be shorter than the length of the
endoscope 21' such that the proximal end of the endoscope 21' is
exposed outside the sheath 35. The sheath 35 can be made of a
flexible material that permits some flexure between the sheath 35
and the housing 1', but still maintain a sufficiently fixed
relationship between the two. For example, the sheath 35 can be
constructed of polyethylene. A sheath 35 made of polyethylene with
a wall thickness of about 0.015'' to about 0.085'' provides
reasonable strength and flexibility. In addition, the sheath 35 can
be made to conform to the size and shape of the endoscope 21', thus
eliminating the need for the housing 1' to have a separate
elastomeric proximal end which fits over the distal terminating end
28' of the endoscope 21'. Alternatively, the proximal end of the
housing 1' can be designed to fit over the distal terminating end
28' of the endoscope 21'.
[0049] In the embodiment of FIG. 3, the sheath 35 has a coextensive
second channel 33. The second channel 33 can extend from the distal
end of the sheath 35 near the housing 1' through the entire length
of the sheath 35 and terminate in a small opening near the proximal
end of the sheath 35. The second channel 33 can be used to
accommodate an electrical conduit 31 connecting the electrodes 9'
to a power source. The second channel 33 can also be used to
deliver a fluid to a tissue region or to remove a bodily fluid from
a tissue region. Examples of fluids that can be delivered to the
tissue include, but are not limited to, cooling, cleaning,
flushing, and conducting fluids. The second channel 33 may be
formed onto the sheath 35 by coextrusion processes.
[0050] The thermal ablation apparatus 30 includes a stop ring 37.
The stop ring 37 controls the position of the housing 1' relative
to the endoscope 21'. Changing the position of the stop ring 37
relative to the housing 1' changes the position of the housing 1'
relative to the distal terminating end 28' of the endoscope 21'.
Thus, the further away the stop ring 37 is from the distal end of
the housing 1', the further away the distal end of the housing 1'
is from the distal terminating end 28' of the endoscope 21'.
Therefore, the stop ring 37 can prevent the housing 1' from
slipping too far over the distal end of the endoscope 21'. The stop
ring 37 can be generally circular in shape. Since the stop ring 37
allows the position of the housing 1' to be altered relative to the
distal terminating end 28' of the endoscope 21', the thermal
ablation apparatus 30 can be used with a large number of types and
various sizes of endoscopes. Different types of endoscopes usable
with the thermal ablation apparatus 30 include those used for
surgical procedures and for exploratory procedures in areas of the
body such as the oral and gastrointestinal tract. The endoscopes
can also be flexible or rigid.
[0051] FIG. 4 shows another embodiment of a thermal ablation
apparatus of the present invention. The thermal ablation apparatus
40 includes a housing 1'' having an array of apertures 43 and
multiple electrodes 9'' provided at the distal end 41 of the
housing 1''.
[0052] This embodiment is useful for thermal ablation procedures
performed with a fluid. Examples of fluids used in a thermal
ablation procedure include, but are not limited to, cooling,
cleaning, flushing and conducting fluids. These fluids can enhance
the thermal ablation procedure by cooling and/or cleaning the
treatment region by flushing or irrigating with a fluid.
Application of a conductive fluid can improve the electrical
contact between the electrode 9'' and the tissue during the thermal
ablation procedure. Saline is an example of a fluid that can be
used as a flushing as well as a conducting fluid. The apertures 43
permit the flow of the fluid to the tissue region. The apertures 43
can also permit a bodily fluid to be removed from the tissue
region. In one embodiment, the distal end 41 of the housing 1'' can
be made foraminous by providing pores or apertures 43 to the distal
end 41 of the housing 1''. For example, a porous ceramic can form
the housing 1''. Alternatively, plastic or a relatively transparent
material such as glass can be made foraminous by drilling
microapertures in the material.
[0053] The electrodes 9'' supported by the outer surface of the
housing 1'' are interdigitated with alternating electrodes 42, 44.
The electrodes 42 are connected to each other and to a wire 52. The
electrodes 44 are connected to each other and to a wire 54. The
electrodes 42 can be positively charged and the electrodes 44 can
be negatively charged. A positively charged electrode 42 is
positioned adjacent a negatively charged electrode 44 with an
insulator region separating the two electrodes 42, 44. The distance
between the electrodes 42, 44 determines the depth of penetration
of the ablative energy into a tissue region, since current flows
from a negative charged electrode 44 to an adjacent positively
charged electrode 42 through a tissue region near the two
electrodes 42, 44. The further apart the adjacent electrodes 42, 44
are, the greater the distance the current has to flow through the
tissue, thus causing a deeper penetration of the ablative energy
into the tissue.
[0054] In the embodiment of FIG. 4, the electrodes 42, 44 are
placed near the apertures 43, and a conductive fluid can be
delivered to a tissue region through the apertures 43. Placing the
electrodes 42, 44 near the apertures 43 allows the electrodes 42,
44 to be in close contact with the conducting fluid, permitting an
even and controlled application of RF energy to the tissue region.
The thermal ablation apparatus 40 includes an electrical conduit
11'' connected to electrodes 9'' at a distal end. The electrical
conduit 11'' has an electrical connector 15'' at a proximal end.
The electrical connector 15'' has a sealing ring 47'. The sealing
ring 47' prevents fluids such as saline from entering and possibly
interfering with the connections between the electrical connector
15'' to another electrical connector. The sealing ring 47' can be
made of rubber.
[0055] Referring to FIG. 5, an electrical conduit 23' is used for
connecting a thermal ablation apparatus (exemplary embodiments of
which are shown in FIGS. 1, 3, and 4) to a power source 57. The
electrical conduit 23' terminates with a pair of plugs 55 at a
proximal end and a connector 25 at a distal end. The plugs 55 can
be banana plugs. The electrical conduit 23' also includes a stopper
59 positioned along the electrical conduit 23'. The stopper 59
adjusts the length of electrical conduit 23' placed in the working
channel 24 of an endoscope 21, as shown in FIG. 2. The stopper 59
can be made of rubber.
[0056] The power source 57 can be a RF energy source. The power
source 57 includes jacks 59 to accept the plugs 55, a rheostat 61
to control the duration of the RF energy applied to the thermal
ablation apparatus and a floor foot pedal 63 for activating the
application of RF energy to the thermal ablation apparatus as
desired by the operator.
[0057] Prior to performing a thermal ablation procedure, an
electrical conduit 23' is passed through the working channel 24 of
an endoscope 21, as shown in FIG. 2, so that the distal end of the
conduit 23' protrudes from the distal end of the working channel 24
of the endoscope 21. The electrical conduit 23' is allowed to
protrude out of the distal terminating end 28 of the endoscope 21
to a length sufficient to allow a person's fingers to mate the
connectors 15, 25'. In one embodiment, a stopper 59 provided along
the electrical conduit 23' is adjusted prior to passing the
electrical conduit 23' through the working channel 24 to control
the amount of electrical conduit 23' that is allowed to protrude
out the distal end of the endoscope 21. The connectors 15 and 25
are mated, and the electrical conduits 11, 23' are slid back into
the working channel 24 of the endoscope 21. The housing 1 is fit
over the distal terminating end 28 of the endoscope 21. The plugs
55 at the proximal end of the electrical conduit 23' are plugged
into the jacks 59 of the power source 57, if it has not already
been done. Under endoscopic guidance, the endoscope 21 and the
housing 1 are inserted into a body and positioned near a tissue
region to be treated. The thermal ablation apparatus is positioned
near the tissue region and RF energy of a selected duration and
amplitude is applied to the electrodes 9 to ablate the tissue. In
one embodiment, the housing 1 is at least partially transparent and
the ablation procedure is monitored through the transparent spaces
between the electrodes 9.
[0058] FIGS. 6a-6d illustrate a method of fabricating an electrode
of a thermal ablation apparatus. A housing 61 having grooves 63 is
provided as shown in FIG. 6a. The housing 61 can be made of a
ceramic, polymeric, or glass material. The grooves 63 can be
machined in the housing 61. Alternatively, a base material for the
housing 61 can be molded to form the housing 61 with the grooves
63. The grooves 63 define a desired electrode pattern. In the
embodiment of FIGS. 6a-6d, the grooves 63 form a helical
pattern.
[0059] A slurry 65 comprising a conductive material is applied to
the outer surface of the housing 61 as shown in FIG. 6b. The slurry
65 can be applied through any appropriate means such as spraying,
dipping, and brushing. The slurry 65 can comprise a water-based
weak glue, such as a solution of glycerin and water, mixed with
powdered metal. For example, the slurry 65 can include powder made
from gold, silver, antimony, or tin. The slurry 65 can also be
silver bearing epoxy. In one embodiment, the conductive material
included in the slurry 65 has a melting temperature which is lower
than a melting temperature of a base material for the housing 61.
In another embodiment, the conductive material has low toxicity.
The slurry 65 applied to the housing 61 is dried to remove any
fluid, gas or other volatile substance contained in the slurry 65.
The slurry 65 can be dried at room temperature or at an elevated
temperature.
[0060] The housing 61 and the dried slurry 65 are heated. Heating
burns off any remaining volatile substance in the slurry 65 and
melts the conductive material. The molten conductive material flows
into the grooves 63 and covers at least a portion of the outer
surface of the housing 61. An appropriate duration and temperature
of the heating step depends on several factors including the
composition of the slurry 65. In one embodiment, heat is applied
slowly to reduce the generation of gas bubbles that can cause
pinholes or lifting of the conductive material from the housing 61.
Subsequent to the heating step, the housing 61 comprising the
conductive material is cooled. After cooling, the conductive
material is fused to the housing 61. In one embodiment, the housing
61 is cooled slowly or tempered to prevent the conductive material
from cracking, peeling, shattering or otherwise breaking away from
the housing 61.
[0061] Once the housing 61 has cooled, the fused conductive
material provided on the protruding surfaces 62 of the housing 61
is removed. The conducting material can be removed by machining.
For example, a hardened cutting tool 69 can be moved across the
protruding surfaces 62 of the housing 61, as the housing 61 is
simultaneously turned to remove the conductive material, as is
commonly done in lathe operations. Alternatively, a grinding
operation, such as centerless grinding, can be employed to remove
the conductive material on the protruding surface 62 of the housing
61.
[0062] In other embodiments, the slurry 65 is printed or dispensed
over the grooves 63 of the housing 61, eliminating the need for the
subsequent machining step. Alternatively, the slurry 65 can be
printed or dispensed over a smooth surface of the housing 61,
thereby creating conductive regions that are raised above the
general surface of the housing 61. An advantage of raising the
conductive material above the surface of the housing 61 is improved
electrode to tissue contact. A further advantage of using the
printing or dispensing method is that it can be a less expensive
method of fabrication. For example, the printing of a conductive
ink or epoxy, such as silver epoxy, can produce a low cost, albeit
somewhat less durable, pattern of conductive material on ceramic,
glass, and substrates that cannot withstand the application of very
high temperatures such as plastics. In still other embodiments,
electroplating conductive materials upon various substrates can be
employed in the construction of the thermal ablation apparatus, as
long as the electroplated layer is of sufficient conductivity to
carry the current and make contact with the subject tissue. The
electroplated electrodes on the housing 61 can be further modified
by chemical etchings.
[0063] The use of electrodes to apply RF energy in ablation
procedures is just one useful mode of operation. The housing of the
thermal ablation apparatus can also be equipped with spectroscopic,
light filtering and light emitting devices for performing tissue
spectroscopy.
[0064] Referring to FIG. 7, a thermal ablation apparatus 70
includes a housing 72 which can be removably attached to the distal
terminating end of an endoscope. The housing 72 includes a light
source 102 and a light modulator 104 disposed in the housing 72, as
substantially described in co-pending commonly-owned U.S. patent
application Ser. No. 08/939,706 filed on Sep. 9, 1997, the entire
contents of which are incorporated herein by reference. The housing
72 further includes at least one electrode 74 supported by the
outer surface of the housing 72. The light source 102 illuminates
tissue within the body. The light source 102 can include, without
limitation, a light emitting diode, a laser, a pulsed light source,
a source of ultraviolet energy, or a flashlamp. The light modulator
104 modifies the light emitted by the light source 102. The light
modulator 104 can include a filter providing a range of wavelengths
to the optical channel of the endoscope. The filter can include,
without limitation, an acousto-optic tunable filter, an
interference filter, a grating, a prism, a holographic filter, a
birefringent filter, or other component that provides a spectral
passband. The light modulator 104 can also include a shutter. The
shutter, for example, can comprise a liquid crystal device. This
embodiment allows the tissue to be characterized by tissue
spectroscopy prior to thermal ablation.
[0065] FIG. 8 shows a detailed light modulator assembly 75 disposed
within the housing 72 as shown in FIG. 7. A liquid crystal shutter
81 and an adjacent acousto-optic tunable filter (AOTF) 83 are
mounted on a surface of the thermal ablation apparatus 70 with an
adhesive. A metal mounting block 99 provides a mounting surface for
the individual components of the shutter 81 and the AOTF 83. The
AOTF control leads 101 and shutter control leads 103 extend through
recess channels (not shown). The liquid crystal shutter 81 includes
a liquid crystal 85 located between two electrodes 87. The
electrodes 87 can be metalization layers on glass covers 89. When
an electric field is applied between the electrodes 87, light
passing through the liquid crystal 85 becomes polarized. A
polarizing filter 91 is aligned for cross-polarization with the
liquid crystal 85 in its active state. Therefore, when an
electrical signal is applied to the electrodes 87, optical energy
is prevented from passing to the optical channel of the endoscope.
An electrical signal can be applied for the duration of the optical
pulse from a flashtube in order to momentarily shutter the optical
channel.
[0066] An electrical signal applied to both sides of the electrodes
93 of the AOTF 83 changes the refractive index of the AOTF crystal
95 and polarizes the transmitted optical energy. Attenuation or
selection of specific wavelengths is achieved when the AOTF crystal
95 is used in conjunction with polarizing filters 97. Voltage
applied to the electrodes 93 controls the selected wavelength,
allowing transmission of specific colors while rejecting other
colors.
[0067] Thermal ablation apparatuses and procedures of the present
invention can be imported to other procedures that can benefit from
the application of thermal energy, such as afforded by RF and
electrode contact. Procedures such as coagulation and tamponade
used to stop bleeding of esophageal varices, ulcerations, and
resected margins can also benefit from providing an apparatus which
can treat a large tissue region at a time. Other procedures that
currently use catheter devices that are small and may not apply
enough force over a sufficiently large area can also benefit from
the present invention.
[0068] The thermal ablation apparatus of the present invention
provides several advantages. The proximity of the thermal ablation
apparatus to the distal end of the endoscope afforded by the
present invention allows for closer and more precise control of the
thermal ablative procedure as compared to other procedures
performed with conventional methods. The present invention also
allows the endoscope to be manipulated by a user to apply firm,
even and well controlled pressure, tamponade and directional inputs
to the ablation apparatus at the tissue interface. In addition to
RF energy, light, heat, and cold (e.g. via cryogenic fluids) can be
delivered inside a body by providing appropriate compounds inside a
housing which is removably attached to a distal end of an
endoscope. A further advantage is that it provides the user the
ability to perform procedures quickly, easily and less expensively
with a wide variety of endoscopes.
[0069] Variations, modifications, and other implementations of what
is described herein will occur to those of ordinary skill in the
art without departing from the spirit and the scope of the
invention as claimed. Accordingly, the invention is to be defined
not by the preceding illustrative description but instead by the
spirit and scope of the following claims.
* * * * *