WO2000019926A9

WO2000019926A9 - Large area thermal ablation

Info

Publication number: WO2000019926A9
Application number: PCT/US1999/023186
Authority: WO
Inventors: Robert J Crowley; Mark A Hamm
Original assignee: Scimed Life Systems Inc
Priority date: 1998-10-05
Filing date: 1999-10-05
Publication date: 2001-12-20
Also published as: US6394949B1; AU1442500A; US20130144287A1; US6932812B2; US20020120264A1; US7749159B2; US20100256632A1; WO2000019926A1; US20060020264A1

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.

Description

LARGE AREA THERMAL ABLATION

Cross-Reference to Related Case This application claims priority to and claims the benefit of U.S. provisional patent application serial number 60/103,060 filed October 5, 1998, which provisional application is incorporated herein by reference.

Technical Field

The invention relates to thermal ablation and, more particularly, to a thermal ablation

apparatus for use with an endoscope.

Background Information

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 ofthe working channel ofthe

endoscope. As a result, the electrode can only treat a small area ofthe tissue at a time.

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 ofthe ablative effect. The inability

to control sufficiently the depth ofthe ablation procedure can lead to charring or perforation of

the tissue or a failure to reduce significantly the number of precancerous cells to a sufficiently

low level.

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 ofthe accessory channel

of an endoscope.

Summary ofthe Invention

In general, the invention relates to ablating thermally a large tissue area in one procedure.

Thermal ablation apparatuses, according to the invention, are designed for use with an

endoscope.

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.

Embodiments of this aspect of the invention can include the following features.

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.

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.

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.

Embodiments of this aspect of the invention can include the following features.

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.

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.

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.

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.

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.

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.

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.

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.

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.

In another embodiment, the slurry is heated to remove the solution and to melt or reflow the conductive material.

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.

The foregoing and other objects, aspects, features, and advantages ofthe invention will

become more apparent from the following description and from the claims.

Brief Description ofthe Drawings

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 ofthe invention.

FIG. la is a side view of a thermal ablation apparatus for use with an endocsope

according to one embodiment ofthe invention.

FIG. lb is an end view ofthe thermal ablation apparatus of FIG. 1. FIG. 2 is a partial cross-sectional view ofthe thermal ablation apparatus of FIG. 1 mounted at the distal terminating end of an endoscope.

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.

FIG. 4 is a cross-sectional view of a thermal ablation apparatus according to another

embodiment ofthe invention.

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 ofthe invention.

FIG. 6a is a side view of a housing of a thermal ablation apparatus according to one

embodiment ofthe invention.

FIG. 6b illustrates a step in a method of manufacturing a thermal ablation apparatus

according to one embodiment ofthe invention.

FIG. 6c illustrates another step in a method of manufacturing a thermal ablation apparatus

according to one embodiment ofthe invention.

FIG. 6d illustrates another step in a method of manufacturing a thermal ablation

apparatus according to one embodiment ofthe invention.

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.

FIG. 8 is a detailed view ofthe light modulator assembly ofthe thermal ablation

apparatus of FIG. 7. Description

Referring to FIGs. la and lb, 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 ofthe housing 1 supports the electrodes 9. The proximal end 5

ofthe 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

ofthe 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 ofthe endoscope 21 itself. The housing 1 is not formed integrally with the distal

terminating end 28 ofthe endoscope 21 , but instead is placeable on and removable from the

distal terminating end 28 ofthe 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.

The distal end 3 ofthe 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 ofthe 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 ofthe 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 ofthe

endoscope 21. 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.

The proximal end 5 ofthe 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 ofthe housing 1 include, but are not limited to, silicone and rubber.

An outer diameter ofthe proximal end 5 can be similar to an outer diameter ofthe distal

end 3 so that the entire housing 1 has a generally uniform diameter. The distal end 3 and the

proximal end 5 ofthe 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 ofthe proximal end 5 to the distal end 3 ofthe housing 1. Alternatively, a filament can be tightly tied around the

lap joint 7 to provide a firm attachment ofthe proximal end 5 to the distal end 3 ofthe housing 1.

Referring to FIG. 2, the distal end 3 ofthe housing 1 can be relatively short in length to

minimize obstruction ofthe view provided by a typically wide-angle view ofthe endoscope 21.

In one embodiment, the housing 1 does not protrude significantly beyond the distal terminating end 28 ofthe endoscope 21. The distance between the distal end 3 ofthe housing 1 and the distal

terminating end 28 ofthe 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 ofthe 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 ofthe thermal ablation apparatus 10 and the

endoscope 21. Radial positioning ofthe 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 ofthe thermal ablation apparatus 10 in such a way as to be easily visible and

evident to an operator.

In another embodiment, an articulated housing 1 provides operating flexibility and

reduces the need for endoscope 21 manipulation. Articulation ofthe 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.

In the embodiment of FIGs. la and lb, an outer surface ofthe distal end 3 ofthe

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 reflown 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 ofthe housing 1 or at a distal end 3 ofthe 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 ofthe electrodes 9 can also vary as desired.

The thermal ablation apparatus 10 further includes an electrical conduit 11 connected to

the electrodes 9 at a distal end. Referring to FIG. lb, the electrodes 9 are placed radially from

the circumference ofthe 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 ofthe 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 ofthe 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.

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 ofthe housing 1 '. The

endoscope 21 ' is inserted inside the first channel 39 ofthe sheath 35, such that the distal

terminating end 28' ofthe endoscope 21 ' is positioned next to the housing 1 '.

In one embodiment, the sheath 35 is long enough to extend along the entire length ofthe

endoscope 21 '. Alternatively, the length ofthe sheath 35 can be shorter than the length ofthe

endoscope 21 ' such that the proximal end ofthe 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 ofthe

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' ofthe endoscope 21 '. Alternatively,

the proximal end ofthe housing 1 ' can be designed to fit over the distal terminating end 28' of

the endoscope 21 '.

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 ofthe sheath 35 near the housing 1 ' through

the entire length ofthe sheath 35 and terminate in a small opening near the proximal end ofthe

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.

The thermal ablation apparatus 30 includes a stop ring 37. The stop ring 37 controls the

position ofthe housing 1 ' relative to the endoscope 21 '. Changing the position ofthe stop ring

37 relative to the housing 1 ' changes the position ofthe housing 1' relative to the distal

terminating end 28' ofthe endoscope 21 '. Thus, the further away the stop ring 37 is from the

distal end ofthe housing 1 ', the further away the distal end ofthe housing 1 ' is from the distal terminating end 28' ofthe endoscope 21 '. Therefore, the stop ring 37 can prevent the housing 1 '

from slipping too far over the distal end ofthe endoscope 21 '. The stop ring 37 can be generally

circular in shape. Since the stop ring 37 allows the position ofthe housing 1 ' to be altered

relative to the distal terminating end 28' ofthe 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 ofthe body such as the oral and

gastrointestinal tract. The endoscopes can also be flexible or rigid.

FIG. 4 shows another embodiment of a thermal ablation apparatus ofthe 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 ofthe housing 1".

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 ofthe 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 ofthe housing 1" can be made foraminous by

providing pores or apertures 43 to the distal end 41 ofthe 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.

The electrodes 9" supported by the outer surface ofthe 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 ofthe 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

ofthe ablative energy into the tissue.

In the embodiment of FIG. 4, the electrodes 42, 44 are placed near the aperatures 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.

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.

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.

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 ofthe working channel 24 ofthe endoscope 21.

The electrical conduit 23^" is allowed to protrude out ofthe distal terminating end 28 ofthe

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 ofthe endoscope 21. The

connectors 15 and 25' are mated, and the electrical conduits 11, 23' are slid back into the working channel 24 ofthe endoscope 21. The housing 1 is fit over the distal terminating end 28

ofthe endoscope 21. The plugs 55 at the proximal end ofthe electrical conduit 23' are plugged

into the jacks 59 ofthe 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.

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.

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.

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.

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 ofthe housing 61.

In other embodiments, the slurry 65 is printed or dispensed over the grooves 63 ofthe

housing 61, eliminating the need for the subsequent machining step. Alternatively, the slurry 65 can be printed or dispensed over a smooth surface of a housing 61 , thereby creating conductive

regions that are raised above the general surface ofthe housing 61. An advantage of raising the

conductive material above the surface ofthe 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 ofthe 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.

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.

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 Serial No. 08/939,706 filed on September 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 ofthe

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 ofthe 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.

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 ofthe thermal ablation apparatus 70 with an adhesive. A metal

mounting block 99 provides a mounting surface for the individual components ofthe 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 ofthe endoscope. An electrical signal can be applied for the duration ofthe optical pulse from a flashtube in order

to momentarily shutter the optical channel.

An electrical signal applied to both sides ofthe electrodes 93 ofthe AOTF 83 changes the

refractive index ofthe 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.

Thermal ablation apparatuses and procedures ofthe 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.

The thermal ablation apparatus ofthe present invention provides several advantages. The

proximity ofthe thermal ablation apparatus to the distal end ofthe endoscope afforded by the

present invention allows for closer and more precise control ofthe 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.

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 ofthe

invention as claimed. Accordingly, the invention is to be defined not by the preceding

illustrative description but instead by the spirit and scope ofthe following claims.

What is claimed is:

Claims

Claims 1. An apparatus for use with an endoscope, comprising: a housing removably attachable to a distal terminating end ofthe endoscope, the housing comprising an outer surface and a cross-sectional area at least as large as a cross-sectional area ofthe distal terminating end ofthe endoscope; and at least one electrode supported by at least a portion ofthe outer surface ofthe housing and capable of delivering energy to a tissue region inside a body to ablate the tissue region.

2. The apparatus of claim 1 wherein the housing comprises an insulator.

3. The apparatus of claim 1 wherein the housing comprises at least one of a ceramic material, a glass, and a polymeric material.

4. The apparatus of claim 2 wherein the insulator comprises a thermal insulator.

5. The apparatus of claim 2 wherein the insulator comprises an electrical insulator.

6. The apparatus of claim 1 wherein at least a portion ofthe housing is transparent.

7. The apparatus of claim 1 wherein the housing comprises at least one groove and the electrode is positioned in the groove.

8. The apparatus of claim 1 wherein the housing is substantially ring-shaped.

9. The apparatus of claim 1 wherein the housing comprises a distal end and a proximal end, the proximal end comprising an elastomeric material and being sized and shaped to slip over the distal end ofthe endoscope.

10. The apparatus of claim 1 wherein the housing further comprises a stop ring.

11. The apparatus of claim 1 wherein at least one electrode comprises a pattern.

12. The apparatus of claim 11 wherein the pattern comprises a row of linear elements.

13. The apparatus of claim 11 wherein the pattern comprises a helical pattern.

14. The apparatus of claim 1 wherein the housing comprises a plurality of apertures.

15. The apparatus of claim 1 wherein the housing is foraminous.

16. The apparatus of claim 1 further comprising an electrical conduit in electrical communication with at least one electrode.

17. The apparatus of claim 16 wherein the electrical conduit comprises one of wire and coaxial conductor.

18. The apparatus of claim 17 wherein the wire comprises a twisted pair of wires.

19. The apparatus of claim 16 further comprising a connector in electrical communication with a proximal end ofthe electrical conduit.

20. The apparatus of claim 1 further comprising at least one light source disposed in the housing for emitting light and a light modulator disposed in the housing for modifying light emitted by the light source.

21. The apparatus of claim 1 wherein at least one electrode comprises a monopolar electrode.

22. The apparatus of claim 1 wherein at least one electrode comprises a bipolar electrode.

23. An apparatus for use with an endoscope, comprising: a sheath comprising a first channel for receiving the endoscope; a housing attached to a distal end of the sheath, the housing comprising 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; 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.

24. The apparatus of claim 23 wherein the sheath further comprises a second channel coextensive with the first channel and an electrical conduit disposed in the second channel, wherein the electrical conduit is in electrical communication with at least one electrode.

25. The apparatus of claim 23 wherein the sheath further comprises a second channel coextensive with the first channel for receiving a fluid.

26. The apparatus of claim 23 wherein the sheath comprises polyethylene.

27. The apparatus of claim 23 wherein the sheath has a thickness in the range from about 0.015 inches to about 0.085 inches.

28. The apparatus of claim 23 further comprising an adjustable stop ring for adjusting a position of the housing relative to the endoscope.

29. The apparatus of claim 23 wherein the housing comprises an insulator.

30. The apparatus of claim 23 wherein at least a portion of the housing is substantially transparent.

31. A medical apparatus, comprising: an endoscope terminating at a distal end; a housing removably attachable to the 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 ofthe distal terminating end ofthe endoscope; and at least one electrode supported by at least a portion ofthe outer surface ofthe housing and capable of delivering energy to a tissue region inside a body to ablate the tissue region.

32. A medical apparatus, comprising: an endoscope terminating at a distal end; a sheath comprising a channel for receiving the endoscope and a housing attached to a distal terminating end ofthe sheath, 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; 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.

33. A method of treating tissue in a body, comprising: a) attaching a housing to a distal terminating end of an endoscope, the housing removably attachable to the distal terminating end ofthe endoscope, the housing comprising an outer surface supporting at least one electrode on at least a portion ofthe outer surface and a cross-sectional area at least as large as a cross-sectional area ofthe distal terminating end ofthe endoscope; b) inserting the endoscope and the housing inside the body near a tissue region to be treated; and c) applying energy to at least one electrode to treat the tissue region.

34. The method of claim 33 further comprising connecting at least one electrode to a power source through an electrical conduit housed in a channel ofthe endoscope.

35. The method of claim 33 wherein step a) comprises attaching a housing comprising at least one aperture and further comprising providing a fluid to the tissue region through the aperture.

36. The method of claim 35 wherein the fluid comprises at least one of a cooling fluid, a flushing fluid and a conductive fluid.

37. The method of claim 33 wherein step a) comprises attaching a housing comprising an insulating material.

38. The method of claim 33 wherein step a) comprises attaching a housing comprising a substantially transparent material.

39. The method of claim 33 wherein step a) comprises attaching a housing supporting a bipolar electrode.

40. The method of claim 33 wherein step a) comprises attaching a housing supporting a monopolar electrode.

41. The method of claim 33 wherein step c) comprises applying RF energy.

42. The method of claim 33 wherein step c) comprises applying energy to ablate the tissue region.

43. The method of claim 33 further comprising illuminating the tissue region and detecting an optical property ofthe tissue region.

44. A method of treating tissue in a body, comprising: a) providing a sheath comprising a channel for receiving an endoscope and a housing attached to a distal end ofthe sheath, the housing comprising an outer surface supporting at least one electrode on at least a portion ofthe outer surface and a cross- sectional area at least as large as a cross-sectional area of a distal terminating end ofthe endoscope; b) inserting an endoscope inside the channel ofthe sheath such that the housing is positioned near the distal terminating end ofthe endoscope; c) inserting the sheath and the endoscope inside the body near a tissue region to be treated; and d) applying energy to at least one electrode to treat the tissue region.

45. The method of claim 44 further comprising connecting at least one electrode to a power source through an electrical conduit housed in a second channel ofthe sheath.

46. The method of claim 44 wherein step a) comprises providing a housing comprising at least one aperture and further comprising providing a fluid to the tissue region through the aperture.

47. The method of claim 46 wherein the fluid comprises at least one of a cooling fluid, a flushing fluid and a conductive fluid.

48. The method of claim 44 wherein step a) comprises providing a housing comprising an insulating material.

49. The method of claim 44 wherein step a) comprises providing a housing comprising a substantially transparent material.

50. The method of claim 44 wherein step a) comprises providing a housing supporting a bipolar electrode.

51. The method of claim 44 wherein step a) comprises providing a housing supporting a monopolar electrode.

52. The method of claim 44 wherein step d) comprises applying RF energy.

53. The method of claim 44 wherein step d) comprises applying energy to ablate the tissue region.

54. The method of claim 44 further comprising illuminating the tissue region and detecting an optical property of the tissue region.

55. A method of manufacturing an ablation apparatus comprising the steps of: a) providing a housing; b) providing a slurry comprising a conductive material and a solution; c) applying the slurry on at least a portion of a surface ofthe housing; and d) removing the solution applied on the surface ofthe housing to form an electrode comprising the conductive material on the surface ofthe housing.

56. The method of claim 55 wherein step c) comprises printing the slurry on the surface of the housing.

57. The method of claim 56 wherein step b) comprises providing a slurry comprising a sliver epoxy.

58. The method of claim 55 wherein step c) comprises applying the slurry by at least one of spraying, dipping, and brushing.

59. The method of claim 55 wherein step d) comprises heating the slurry to remove the solution and to melt the conductive material to form the electrode.

60. The method of claim 55 wherein step a) comprises providing a housing comprising at least one groove and step d) comprises removing at least a portion of the conductive material to form the electrode in the at least one groove.