U.S. patent application number 12/581506 was filed with the patent office on 2013-06-27 for moisture transport system for contact electrocoagulation.
The applicant listed for this patent is Estela Hilario, Alfonso Lawrence Ramirez, Russel Mahlon Sampson, Stephanie Squarcia, Csaba Truckai. Invention is credited to Estela Hilario, Alfonso Lawrence Ramirez, Russel Mahlon Sampson, Stephanie Squarcia, Csaba Truckai.
Application Number | 20130165913 12/581506 |
Document ID | / |
Family ID | 46303026 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130165913 |
Kind Code |
A9 |
Truckai; Csaba ; et
al. |
June 27, 2013 |
MOISTURE TRANSPORT SYSTEM FOR CONTACT ELECTROCOAGULATION
Abstract
An apparatus and method for use in performing ablation or
coagulation of organs and other tissue includes a metallized fabric
electrode array which is substantially absorbent and/or permeable
to moisture and gases such as steam and conformable to the body
cavity. The array includes conductive regions separated by
insulated regions arranged to produce ablation to a predetermined
depth. Following placement of the ablation device into contact with
the tissue to be ablated, an RF generator is used to deliver RF
energy to the conductive regions and to thereby induce current flow
from the electrodes to tissue to be ablated. As the current heats
the tissue, moisture (such as steam or liquid) leaves the tissue
causing the tissue to dehydrate. Suction may be applied to
facilitate moisture removal. The moisture permeability and/or
absorbency of the electrode carrying member allows the moisture to
leave the ablation site so as to prevent the moisture from
providing a path of conductivity for the current.
Inventors: |
Truckai; Csaba; (Sunnyvale,
CA) ; Sampson; Russel Mahlon; (Mountain View, CA)
; Squarcia; Stephanie; (Palo Alto, CA) ; Ramirez;
Alfonso Lawrence; (San Jose, CA) ; Hilario;
Estela; (Los Altos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Truckai; Csaba
Sampson; Russel Mahlon
Squarcia; Stephanie
Ramirez; Alfonso Lawrence
Hilario; Estela |
Sunnyvale
Mountain View
Palo Alto
San Jose
Los Altos |
CA
CA
CA
CA
CA |
US
US
US
US
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20100036372 A1 |
February 11, 2010 |
|
|
Family ID: |
46303026 |
Appl. No.: |
12/581506 |
Filed: |
October 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10959771 |
Oct 6, 2004 |
7604633 |
|
|
12581506 |
|
|
|
|
09103072 |
Jun 23, 1998 |
6813520 |
|
|
10959771 |
|
|
|
|
08632516 |
Apr 12, 1996 |
5769880 |
|
|
09103072 |
|
|
|
|
60084791 |
May 8, 1998 |
|
|
|
Current U.S.
Class: |
606/33 ;
606/41 |
Current CPC
Class: |
A61B 2017/4216 20130101;
A61B 90/04 20160201; A61B 2018/00708 20130101; A61B 2090/0409
20160201; A61B 2017/22051 20130101; A61M 16/0427 20140204; A61B
2018/126 20130101; A61B 2018/00559 20130101; A61B 18/1485 20130101;
A61B 2018/00577 20130101; A61M 16/0463 20130101; A61B 18/18
20130101; A61B 18/1482 20130101; A61M 16/0481 20140204; A61B 17/42
20130101; A61B 18/14 20130101; A61B 2018/00291 20130101; A61B
2090/065 20160201 |
Class at
Publication: |
606/33 ;
606/41 |
International
Class: |
A61B 18/14 20060101
A61B018/14; A61B 18/18 20060101 A61B018/18 |
Claims
1. A method of ablating walls of a hollow body organ, comprising
the steps of: providing an ablation device comprising a tubular
member and a mesh electrode array carried by the tubular member;
positioning the array within a hollow body organ surrounded by
walls; applying suction through the tubular member and the mesh
array to pull interior surfaces of the walls into contact with the
array; and delivering ablation energy through the array to the
walls while continuing to apply suction through the tubular
member.
2. The method of claim 32, wherein the delivering step causes
moisture to be released from the tissue, and wherein the method
includes applying the suction during the delivering step to carry
released moisture away from the walls and through the tubular
member.
3. The method of claim 33, wherein the suction substantially
prevents the released moisture from creating a layer of liquid
which can provide an electrically conductive pathway between
electrodes in the array.
4. The method of claim 32, wherein the body organ includes an
opening, wherein the positioning step includes extending the
tubular member through the opening, and wherein the method further
comprises the step of substantially sealing the opening around the
tubular member.
5. The method of claim 35, wherein the body organ is a uterus and
wherein the opening is a cervical opening.
6. The method of claim 32, wherein the providing step further
provides the array to comprise a bipolar array of electrodes and
wherein the delivering step delivers RF energy to the bipolar
array.
7. The method of claim 32, wherein the applying step causes the
walls to at least partially collapse into contact with the array.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/084,791, filed May 8, 1998, and is a
Continuation in Part of copending U.S. application Ser. No.
08/632,516, filed Apr. 12, 1996, now U.S. Pat. No. 5,769,880,
issued Jun. 23, 1998.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
apparatuses and methods for ablating or coagulating the interior
surfaces of body organs. Specifically, it relates to an apparatus
and method for ablating the interior linings of body organs such as
the uterus and gallbladder.
BACKGROUND OF THE INVENTION
[0003] Ablation of the interior lining of a body organ is a
procedure which involves heating the organ lining to temperatures
which destroy the cells of the lining or coagulate tissue proteins
for hemostasis. Such a procedure may be performed as a treatment to
one of many conditions, such as chronic bleeding of the endometrial
layer of the uterus or abnormalities of the mucosal layer of the
gallbladder. Existing methods for effecting ablation include
circulation of heated fluid inside the organ (either directly or
inside a balloon), laser treatment of the organ lining, and
resistive heating using application of RF energy to the tissue to
be ablated.
[0004] U.S. Pat. No. 5,084,044 describes an apparatus for
endometrial ablation in which a bladder is inserted into the
uterus. Heated fluid is then circulated through the balloon to
expand the balloon into contact with the endometrium and to ablate
the endometrium thermally. U.S. Pat. No. 5,443,470 describes an
apparatus for endometrial ablation in which an expandable bladder
is provided with electrodes on its outer surface. After the
apparatus is positioned inside the uterus, a non-conductive gas or
liquid is used to fill the balloon, causing the balloon to push the
electrodes into contact with the endometrial surface. RF energy is
supplied to the electrodes to ablate the endometrial tissue using
resistive heating.
[0005] These ablation devices are satisfactory for carrying out
ablation procedures. However, because no data or feedback is
available to guide the physician as to how deep the tissue ablation
has progressed, controlling the ablation depth and ablation profile
with such devices can only be done by assumption.
[0006] For example, the heated fluid method is a very passive and
ineffective heating process which relies on the heat conductivity
of the tissue. This process does not account for variations in
factors such as the amount of contact between the balloon and the
underlying tissue, or cooling effects such as those of blood
circulating through the organ. RF ablation techniques can achieve
more effective ablation since it relies on active heating of the
tissue using RF energy, but presently the depth of ablation using
RF techniques can only be estimated by the physician since no
feedback can be provided as to actual ablation depth.
[0007] Both the heated fluid techniques and the latest RF
techniques must be performed using great care to prevent over
ablation. Monitoring of tissue surface temperature is normally
carried out during these ablation procedures to ensure the
temperature does not exceed 100.degree. C. If the temperature
exceeds 100.degree. C., the fluid within the tissue begins to boil
and to thereby produce steam. Because ablation is carried out
within a closed cavity within the body, the steam cannot escape and
may instead force itself deeply into the tissue, or it may pass
into areas adjacent to the area intended to be ablated, causing
embolism or unintended burning.
[0008] Moreover, in prior art RF devices the water drawn from the
tissue creates a path of conductivity through which current
traveling through the electrodes will flow. This can prevent the
current from traveling into the tissue to be ablated. Moreover, the
presence of this current path around the electrodes causes current
to be continuously drawn from the electrodes. The current heats the
liquid drawn from the tissue and thus turns the ablation process
into a passive heating method in which the heated liquid around the
electrodes causes thermal ablation to continue well beyond the
desired ablation depths.
[0009] Another problem with prior art ablation devices is that it
is difficult for a physician to find out when ablation has been
carried out to a desired depth within the tissue. Thus, it is often
the case that too much or too little tissue may be ablated during
an ablation procedure.
[0010] It is therefore desirable to provide an ablation device
which eliminates the above-described problem of steam and liquid
buildup at the ablation site. It is further desirable to provide an
ablation method and device which allows the depth of ablation to be
controlled and which automatically discontinues ablation once the
desired ablation depth has been reached.
SUMMARY OF THE INVENTION
[0011] The present invention is an apparatus and method of ablating
and/or coagulating tissue, such as that of the uterus or other
organ. An ablation device is provided which has an electrode array
carried by an elongate tubular member. The electrode array includes
a fluid permeable elastic member preferably formed of a metallized
fabric having insulating regions and conductive regions thereon.
During use, the electrode array is positioned in contact with
tissue to be ablated, ablation energy is delivered through the
array to the tissue to cause the tissue to dehydrate, and moisture
generated during dehydration is actively or passively drawn into
the array and away from the tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a front elevation view of a first embodiment of an
ablation device according to the present invention, with the handle
shown in cross-section and with the RF applicator head in a closed
condition.
[0013] FIG. 2 is a front elevation view of the ablation device of
FIG. 1, with the handle shown in cross-section and with the RF
applicator head in an open condition.
[0014] FIG. 3 is a side elevation view of the ablation device of
FIG. 2.
[0015] FIG. 4 is a top plan view of the ablation device of FIG.
2.
[0016] FIG. 5A is a front elevation view of the applicator head and
a portion of the main body of the ablation device of FIG. 2, with
the main body shown in cross-section.
[0017] FIG. 5B is a cross-section view of the main body taken along
the plane designated 5B-5B in FIG. 5A.
[0018] FIG. 6 is a schematic representation of a uterus showing the
ablation device of FIG. 1 following insertion of the device into
the uterus but prior to retraction of the introducer sheath and
activation of the spring members.
[0019] FIG. 7 is a schematic representation of a uterus showing the
ablation device of FIG. 1 following insertion of the device into
the uterus and following the retraction of the introducer sheath
and the expansion of the RF applicator head.
[0020] FIG. 8 is a cross-section view of the RF applicator head and
the distal portion of the main body of the apparatus of FIG. 1,
showing the RF applicator head in the closed condition.
[0021] FIG. 9 is a cross-section view of the RF applicator head and
the distal portion of the main body of the apparatus of FIG. 1,
showing the configuration of RF applicator head after the sheath
has been retracted but before the spring members have been released
by proximal movement of the shaft.
[0022] FIG. 10 is a cross-section view of the RF applicator head
and the distal portion of the main body of the apparatus of FIG. 1,
showing the configuration of RF applicator head after the sheath
has been retracted and after the spring members have been released
into the fully opened condition.
[0023] FIG. 11 is a cross-section view of a distal portion of an RF
ablation device similar to FIG. 1 which utilizes an alternative
spring member configuration for the RF applicator head.
[0024] FIG. 12 is a side elevation view of the distal end of an
alternate embodiment of an RF ablation device similar to that of
FIG. 1, which utilizes an RF applicator head having a modified
shape.
[0025] FIG. 13 is a top plan view of the ablation device of FIG.
12.
[0026] FIG. 14 is a representation of a bleeding vessel
illustrating use of the ablation device of FIG. 12 for general
bleeding control.
[0027] FIGS. 15 and 16 are representations of a uterus illustrating
use of the ablation device of FIG. 12 for endometrial ablation.
[0028] FIG. 17 is a representation of a prostate gland illustrating
use of the ablation device of FIG. 12 for prostate ablation.
[0029] FIG. 18 is a cross-section view of target tissue for
ablation, showing ablation electrodes in contact with the tissue
surface and illustrating energy fields generated during bi-polar
ablation.
[0030] FIGS. 19A-19C are cross-section views of target tissue for
ablation, showing electrodes in contact with the tissue surface and
illustrating how varying active electrode density may be used to
vary the ablation depth.
[0031] FIG. 20 is a side elevation view, similar to the view of
FIG. 2, showing an ablation device according to the present
invention in which the electrode carrying means includes inflatable
balloons. For purposes of clarity, the electrodes on the electrode
carrying means are not shown.
[0032] FIG. 21 is a side elevation view of a second exemplary
embodiment of an ablation device according to the present
invention, showing the array in the retracted state.
[0033] FIG. 22 is a side elevation view of the ablation device of
FIG. 21, showing the array in the deployed state.
[0034] FIG. 23 is a top plan view of the applicator head of the
apparatus of FIG. 21.
[0035] FIG. 24 is a cross-sectional top view of the encircled
region designated 24 in FIG. 23.
[0036] FIG. 25A is a perspective view of the electrode array of
FIG. 23.
[0037] FIG. 25B is a distal end view of the applicator head of FIG.
30A.
[0038] FIG. 26A is a plan view of a knit that may be used to form
the applicator head.
[0039] FIG. 26B is a perspective view of a strand of nylon-wrapped
spandex of the type that may be used to form the knit of FIG.
26A.
[0040] FIGS. 27A, 27B, 27C are top plan views illustrating
triangular, parabolic, and rectangular mesh shapes for use as
electrode arrays according to the present invention.
[0041] FIG. 28 is a perspective view showing the flexures and
hypotube of the deflecting mechanism of the applicator head of FIG.
23.
[0042] FIG. 29 is a cross-section view of a flexure taken along the
plane designated 29-29 in FIG. 23.
[0043] FIG. 30 is a top plan view illustrating the flexure and
spring arrangement of an alternative configuration of a deflecting
mechanism for an applicator head according to the present
invention.
[0044] FIG. 31 is a cross-sectional side view of the bobbin portion
of the apparatus of FIG. 21.
[0045] FIG. 32A is a side elevation view of the handle of the
ablation device of FIG. 21.
[0046] FIG. 32B is a top plan view of the handle of the ablation
device of FIG. 21. For clarity, portions of the proximal and distal
grips are not shown.
[0047] FIG. 33 illustrates placement of the applicator head
according to the present invention in a uterine cavity.
[0048] FIG. 34 is a side elevation view of the handle of the
ablation apparatus of FIG. 21, showing portions of the apparatus in
cross-section.
[0049] FIG. 35 is a front elevation view of the upper portion of
the proximal handle grip taken along the plane designated 35-35 in
FIG. 32B.
[0050] FIGS. 36A, 36B, and 36C are a series of side elevation views
illustrating the heel member as it becomes engaged with the
corresponding spring member.
[0051] FIGS. 37A and 37B are cross-sectional top views of the frame
member mounted on the proximal grip section, taken along the plane
designated 37-37 in FIG. 34 and illustrating one of the load
limiting features of the second embodiment. FIG. 37A shows the
condition of the compression spring before the heel member moves
into abutment with frame member, and FIG. 37B shows the condition
of the spring after the heel member moves into abutment with the
frame member.
DETAILED DESCRIPTION
[0052] The invention described in this application is an aspect of
a larger set of inventions described in the following co-pending
applications which are commonly owned by the assignee of the
present invention, and are hereby incorporated by reference: U.S.
Provisional Patent Application No. 60/084,724, filed May 8, 1998,
entitled "APPARATUS AND METHOD FOR INTRA-ORGAN MEASUREMENT AND
ABLATION" (attorney docket no. ENVS-400); and U.S. Provisional
Patent Application No. ______ filed May 8, 1998, entitled "A
RADIO-FREQUENCY GENERATOR FOR POWERING AN ABLATION DEVICE"
(attorney docket no. ENVS-500).
[0053] The ablation apparatus according to the present invention
will be described with respect to two exemplary embodiments.
First Exemplary Embodiment--Structure
[0054] Referring to FIGS. 1 and 2, an ablation device according to
the present invention is comprised generally of three major
components: RF applicator head 2, main body 4, and handle 6. Main
body 4 includes a shaft 10. The RF applicator head 2 includes an
electrode carrying means 12 mounted to the distal end of the shaft
10 and an array of electrodes 14 formed on the surface of the
electrode carrying means 12. An RF generator 16 is electrically
connected to the electrodes 14 to provide mono-polar or bipolar RF
energy to them.
[0055] Shaft 10 is an elongate member having a hollow interior.
Shaft 10 is preferably 12 inches long and has a preferred
cross-sectional diameter of approximately 4 mm. A collar 13 is
formed on the exterior of the shaft 10 at the proximal end. As best
shown in FIGS. 6 and 7, passive spring member 15 are attached to
the distal end of the shaft 10.
[0056] Extending through the shaft 10 is a suction/insufflation
tube 17 (FIGS. 6-9) having a plurality of holes 17a formed in its
distal end. An arched active spring member 19 is connected between
the distal ends of the passive spring members 15 and the distal end
of the suction/insufflation tube 17.
[0057] Referring to FIG. 2, electrode leads 18a and 18b extend
through the shaft 10 from distal end 20 to proximal end 22 of the
shaft 10. At the distal end 20 of the shaft 10, each of the leads
18a, 18b is coupled to a respective one of the electrodes 14. At
the proximal end 22 of the shaft 10, the leads 18a, 18b are
electrically connected to RF generator 16 via an electrical
connector 21. During use, the leads 18a, 18b carry RF energy from
the RF generator 16 to the electrodes. Each of the leads 18a, 18b
is insulated and carries energy of an opposite polarity than the
other lead.
[0058] Electrically insulated sensor leads 23a, 23b (FIGS. 5A and
5B) also extend through the shaft 10. Contact sensors 25a, 25b are
attached to the distal ends of the sensor leads 23a, 23b,
respectively and are mounted to the electrode carrying means 12.
During use, the sensor leads 23a, 23b are coupled by the connector
21 to a monitoring module in the RF generator 16 which measures
impedance between the sensors 25a, 25b. Alternatively, a reference
pad may be positioned in contact with the patient and the impedance
between one of the sensors and the reference pad measured.
[0059] Referring to FIG. 5B, electrode leads 18a, 18b and sensor
leads 23a, 23b extend through the shaft 10 between the external
walls of the tube 17 and the interior walls of the shaft 10 and
they are coupled to electrical connector 21 which is preferably
mounted to the collar 13 on the shaft 10. Connector 21, which is
connectable to the RF generator 16, includes at least four
electrical contact rings 21a-21d (FIGS. 1 and 2) which correspond
to each of the leads 18a, 18b, 23a, 23b. Rings 21a, 21b receive,
from the RF generator, RF energy of positive and negative polarity,
respectively. Rings 21c, 21d deliver signals from the right and
left sensors, respectively, to a monitoring module within the RF
generator 16.
[0060] Referring to FIG. 5A, the electrode carrying means 12 is
attached to the distal end 20 of the shaft 10. A plurality of holes
24 may be formed in the portion of the distal end 20 of the shaft
which lies within the electrode carrying means 12.
[0061] The electrode carrying means 12 preferably has a shape which
approximates the shape of the body organ which is to be ablated.
For example, the apparatus shown in FIGS. 1 through 11 has a
bicornual shape which is desirable for intrauterine ablation. The
electrode carrying means 12 shown in these figures includes horn
regions 26 which during use are positioned within the cornual
regions of the uterus and which therefore extend towards the
fallopian tubes.
[0062] Electrode carrying means 12 is preferably a sack formed of a
material which is non-conductive, which is permeable to moisture
and/or which has a tendency to absorb moisture, and which may be
compressed to a smaller volume and subsequently released to its
natural size upon elimination of compression. Examples of preferred
materials for the electrode carrying means include open cell
sponge, foam, cotton, fabric, or cotton-like material, or any other
material having the desired characteristics. Alternatively, the
electrode carrying means may be formed of a metallized fabric. For
convenience, the term "pad" may be used interchangeably with the
term electrode carrying means to refer to an electrode carrying
means formed of any of the above materials or having the listed
properties.
[0063] Electrodes 14 are preferably attached to the outer surface
of the electrode carrying means 12, such as by deposition or other
attachment mechanism. The electrodes are preferably made of lengths
of silver, gold, platinum, or any other conductive material. The
electrodes may be attached to the electrode carrying means 12 by
electron beam deposition, or they may be formed into coiled wires
and bonded to the electrode carrying member using a flexible
adhesive. Naturally, other means of attaching the electrodes, such
as sewing them onto the surface of the carrying member, may
alternatively be used. If the electrode carrying means 12 is formed
of a metallized fabric, an insulating layer may be etched onto the
fabric surface, leaving only the electrode regions exposed.
[0064] The spacing between the electrodes (i.e. the distance
between the centers of adjacent electrodes) and the widths of the
electrodes are selected so that ablation will reach predetermined
depths within the tissue, particularly when maximum power is
delivered through the electrodes (where maximum power is the level
at which low impedance, low voltage ablation can be achieved).
[0065] The depth of ablation is also effected by the electrode
density (i.e., the percentage of the target tissue area which is in
contact with active electrode surfaces) and may be regulated by
pre-selecting the amount of this active electrode coverage. For
example, the depth of ablation is much greater when the active
electrode surface covers more than 10% of the target tissue than it
is when the active electrode surfaces covers 1% of the target
tissue.
[0066] For example, by using 3-6 mm spacing and an electrode width
of approximately 0.5-2.5 mm, delivery of approximately 20-40 watts
over a 9-16 cm.sup.2 target tissue area will cause ablation to a
depth of approximately 5-7 millimeters when the active electrode
surface covers more than 10% of the target tissue area. After
reaching this ablation depth, the impedance of the tissue will
become so great that ablation will self-terminate as described with
respect to the operation of the invention.
[0067] By contrast, using the same power, spacing, electrode width,
and RF frequency will produce an ablation depth of only 2-3 mm when
the active electrode surfaces covers less than 1% of the target
tissue area. This can be better understood with reference to FIG.
19A, in which high surface density electrodes are designated 14a
and low surface density electrodes are designated 14b. For purposes
of this comparison between low and high surface density electrodes,
each bracketed group of low density electrodes is considered to be
a single electrode. Thus, the electrode widths W and spacings S
extend as shown in FIG. 19A.
[0068] As is apparent from FIG. 19A, the electrodes 14a, which have
more active area in contact with the underlying tissue T, produce a
region of ablation A1 that extends more deeply into the tissue T
than the ablation region A2 produced by the low density electrodes
14b, even though the electrode spacings and widths are the same for
the high and low density electrodes.
[0069] Some examples of electrode widths, having spacings with more
than 10% active electrode surface coverage, and their resultant
ablation depth, based on an ablation area of 6 cm.sup.2 and a power
of 20-40 watts, are given on the following table:
TABLE-US-00001 ELECTRODE WIDTH SPACING APPROX. DEPTH 1 mm 1-2 mm
1-3 mm 1-2.5 mm 3-6 mm 5-7 mm 1-4.5 mm 8-10 mm 8-10 mm
[0070] Examples of electrode widths, having spacings with less than
1% active electrode surface coverage, and their resultant ablation
depth, based on an ablation area of 6 cm.sup.2 and a power of 20-40
watts, are given on the following table:
TABLE-US-00002 ELECTRODE WIDTH SPACING APPROX. DEPTH 1 mm 1-2 mm
0.5-1 mm 1-2.5 mm 3-6 mm 2-3 mm 1-4.5 mm 8-10 mm 2-3 mm
[0071] Thus it can be seen that the depth of ablation is
significantly less when the active electrode surface coverage is
decreased.
[0072] In the preferred embodiment, the preferred electrode spacing
is approximately 8-10 mm in the horn regions 26 with the active
electrode surfaces covering approximately 1% of the target region.
Approximately 1-2 mm electrode spacing (with 10% active electrode
coverage) is preferred in the cervical region (designated 28) and
approximately 3-6 mm (with greater than 10% active electrode
surface coverage) is preferred in the main body region.
[0073] The RF generator 16 may be configured to include a
controller which gives the user a choice of which electrodes should
be energized during a particular application in order to give the
user control of ablation depth. For example, during an application
for which deep ablation is desired, the user may elect to have the
generator energize every other electrode, to thereby optimize the
effective spacing of the electrodes and to decrease the percentage
of active electrode surface coverage, as will be described below
with respect to FIG. 18.
[0074] Although the electrodes shown in the drawings are arranged
in a particular pattern, it should be appreciated that the
electrodes may be arranged in any pattern to provide ablation to
desired depths.
[0075] Referring to FIGS. 6 and 7, an introducer sheath 32
facilitates insertion of the apparatus into, and removal of the
apparatus from, the body organ to be ablated. The sheath 32 is a
tubular member which is telescopically slidable over the shaft 10.
The sheath 32 is slidable between a distal condition, shown in FIG.
6, in which the electrode carrying means 12 is compressed inside
the sheath, and a proximal condition in which the sheath 32 is
moved proximally to release the electrode carrying means from
inside it (FIG. 7). By compressing the electrode carrying means 12
to a small volume, the electrode carrying means and electrodes can
be easily inserted into the body cavity (such as into the uterus
via the vaginal opening).
[0076] A handle 34 attached to the sheath 32 provides finger holds
to allow for manipulation of the sheath 32. Handle 34 is slidably
mounted on a handle rail 35 which includes a sleeve 33, a finger
cutout 37, and a pair of spaced rails 35a, 35b extending between
the sleeve 33 and the finger cutout 37. The shaft 10 and sheath 32
slidably extend through the sleeve 33 and between the rails 35a,
35b. The tube 17 also extends through the sleeve 33 and between the
rails 35a, 35b, and its proximal end is fixed to the handle rail 35
near the finger cutout 37.
[0077] A compression spring 39 is disposed around the proximal most
portion of the suction/insufflation tube 17 which lies between the
rails 35a, 35b. One end of the compression spring 39 rests against
the collar 13 on the shaft 10, while the opposite end of the
compression spring rests against the handle rail 35. During use,
the sheath 32 is retracted from the electrode carrying means 12 by
squeezing the handle 34 towards the finger cutout 37 to slide the
sheath 32 in the distal direction. When the handle 34 advances
against the collar 13, the shaft 10 (which is attached to the
collar 13) is forced to slide in the proximal direction, causing
compression of the spring 39 against the handle rail 35. The
movement of the shaft 10 relative to the suction/insufflation tube
17 causes the shaft 10 to pull proximally on the passive spring
member 15. Proximal movement of the passive spring member 15 in
turn pulls against the active spring member 19, causing it to move
to the opened condition shown in FIG. 7. Unless the shaft is held
in this retracted condition, the compression spring 39 will push
the collar and thus the shaft distally, forcing the RF applicator
head to close. A locking mechanism (not shown) may be provided to
hold the shaft in the fully withdrawn condition to prevent
inadvertent closure of the spring members during the ablation
procedure.
[0078] The amount by which the springs 15, 19 are spread may be
controlled by manipulating the handle 34 to slide the shaft 10 (via
collar 13), proximally or distally. Such sliding movement of the
shaft 10 causes forceps-like movement of the spring members 15,
19.
[0079] A flow pathway 36 is formed in the handle rail 35 and is
fluidly coupled to a suction/insufflation port 38. The proximal end
of the suction/insufflation tube 17 is fluidly coupled to the flow
pathway so that gas fluid may be introduced into, or withdrawn from
the suction/insufflation tube 17 via the suction/insufflation port
38. For example, suction may be applied to the fluid port 38 using
a suction/insufflation unit 40. This causes water vapor within the
uterine cavity to pass through the permeable electrode carrying
means 12, into the suction/insufflation tube 17 via holes 17a,
through the tube 17, and through the suction/insufflation unit 40
via the port 38. If insufflation of the uterine cavity is desired,
insufflation gas, such as carbon dioxide, may be introduced into
the suction/insufflation tube 17 via the port 38. The insufflation
gas travels through the tube 17, through the holes 17a, and into
the uterine cavity through the permeable electrode carrying member
12.
[0080] If desirable, additional components may be provided for
endoscopic visualization purposes. For example, lumen 42, 44, and
46 may be formed in the walls of the introducer sheath 32 as shown
in FIG. 5B. An imaging conduit, such as a fiberoptic cable 48,
extends through lumen 42 and is coupled via a camera cable 43 to a
camera 45. Images taken from the camera may be displayed on a
monitor 56. An illumination fiber 50 extends through lumen 44 and
is coupled to an illumination source 54. The third lumen 46 is an
instrument channel through which surgical instruments may be
introduced into the uterine cavity, if necessary.
[0081] Because during use it is most desirable for the electrodes
14 on the surface of the electrode carrying means 12 to be held in
contact with the interior surface of the organ to be ablated, the
electrode carrying means 12 may be provide to have additional
components inside it that add structural integrity to the electrode
carrying means when it is deployed within the body.
[0082] For example, referring to FIG. 11, alternative spring
members 15a, 19a may be attached to the shaft 10 and biased such
that, when in a resting state, the spring members are positioned in
the fully resting condition shown in FIG. 11. Such spring members
would spring to the resting condition upon withdrawal of the sheath
32 from the RF applicator head 2.
[0083] Alternatively, a pair of inflatable balloons 52 may be
arranged inside the electrode carrying means 12 as shown in FIG. 20
and connected to a tube (not shown) extending through the shaft 10
and into the balloons 52. After insertion of the apparatus into the
organ and following retraction of the sheath 32, the balloons 52
would be inflated by introduction of an inflation medium such as
air into the balloons via a port similar to port 38 using an
apparatus similar to the suction/insufflation apparatus 40.
[0084] Structural integrity may also be added to the electrode
carrying means through the application of suction to the proximal
end 22 of the suction/insufflation tube 17. Application of suction
using the suction/insufflation device 40 would draw the organ
tissue towards the electrode carrying means 12 and thus into better
contact with the electrodes 14.
[0085] FIGS. 12 and 13 show an alternative embodiment of an
ablation device according to the present invention. In the
alternative embodiment, an electrode carrying means 12a is provided
which has a shape which is generally tubular and thus is not
specific to any particular organ shape. An ablation device having a
general shape such as this may be used anywhere within the body
where ablation or coagulation is needed. For example, the
alternative embodiment is useful for bleeding control during
laparoscopic surgery (FIG. 14), tissue ablation in the prostate
gland (FIG. 17), and also intrauterine ablation (FIGS. 15 and
16).
First Exemplary Embodiment--Operation
[0086] Operation of the first exemplary embodiment of an ablation
device according to the present invention will next be
described.
[0087] Referring to FIG. 1, the device is initially configured for
use by positioning the introducer sheath 32 distally along the
shaft 10, such that it compresses the electrode carrying means 12
within its walls.
[0088] At this time, the electrical connector 21 is connected to
the RF generator 16, and the fiberoptic cable 48 and the
illumination cable 50 are connected to the illumination source,
monitor, and camera, 54, 56, 45. The suction/insufflation unit 40
is attached to suction/insufflation port 38 on the handle rail 35.
The suction/insufflation unit 40 is preferably set to deliver
carbon dioxide at an insufflation pressure of 20-200 mmHg.
[0089] Next, the distal end of the apparatus is inserted through
the vaginal opening V and into the uterus U as shown in FIG. 6,
until the distal end of the introducer sheath 32 contacts the
fundus F of the uterus. At this point, carbon dioxide gas is
introduced into the tube 17 via the port 38, and it enters the
uterine cavity, thereby expanding the uterine cavity from a flat
triangular shape to a 1-2 cm high triangular cavity. The physician
may observe (using the camera 45 and monitor 56) the internal
cavities using images detected by a fiberoptic cable 48 inserted
through lumen 42. If, upon observation, the physician determines
that a tissue biopsy or other procedure is needed, the required
instruments may be inserted into the uterine cavity via the
instrument channel 46.
[0090] Following insertion, the handle 34 is withdrawn until it
abuts the collar 13. At this point, the sheath 32 exposes the
electrode carrying member 12 but the electrode carrying member 12
is not yet fully expanded (see FIG. 9), because the spring members
15, 19 have not yet been moved to their open condition. The handle
34 is withdrawn further, causing the shaft 10 to move proximally
relative to the suction/insufflation tube 17, causing the passive
spring members 15 to pull the active spring members 19, causing
them to open into the opened condition shown in FIG. 10.
[0091] The physician may confirm proper positioning of the
electrode carrying member 12 using the monitor 56, which displays
images from the fiberoptic cable 48.
[0092] Proper positioning of the device and sufficient contact
between the electrode carrying member 12 and the endometrium may
further be confirmed using the contact sensors 25a, 25b. The
monitoring module of the RF generator measures the impedance
between these sensors using conventional means. If there is good
contact between the sensors and the endometrium, the measured
impedance will be approximately 20-180 ohm, depending on the water
content of the endometrial lining.
[0093] The sensors are positioned on the distal portions of the
bicornual shaped electrode carrying member 12, which during use are
positioned in the regions within the uterus in which it is most
difficult to achieve good contact with the endometrium. Thus, an
indication from the sensors 25a, 25b that there is sound contact
between the sensors and the endometrial surface indicates that good
electrode contact has been made with the endometrium.
[0094] Next, insufflation is terminated. Approximately 1-5 cc of
saline may be introduced via suction/insufflation tube 17 to
initially wet the electrodes and to improve electrode electrical
contact with the tissue. After introduction of saline, the
suction/insufflation device 40 is switched to a suctioning mode. As
described above, the application of suction to the RF applicator
head 2 via the suction/insufflation tube 17 collapses the uterine
cavity onto the RF applicator head 2 and thus assures better
contact between the electrodes and the endometrial tissue.
[0095] If the generally tubular apparatus of FIGS. 12 and 13 is
used, the device is angled into contact with one side of the uterus
during the ablation procedure. Once ablation is completed, the
device (or a new device) is repositioned in contact with the
opposite side and the procedure is repeated. See. FIGS. 15 and
16.
[0096] Next, RF energy at preferably about 500 kHz and at a
constant power of approximately 30 W is applied to the electrodes.
As shown in FIG. 5a, it is preferable that each electrode be
energized at a polarity opposite from that of its neighboring
electrodes. By doing so, energy field patterns, designated F1, F2
and F4 in FIG. 18, are generated between the electrode sites and
thus help to direct the flow of current through the tissue T to
form a region of ablation A. As can be seen in FIG. 18, if
electrode spacing is increased such by energizing, for example
every third or fifth electrode rather than all electrodes, the
energy patterns will extend more deeply into the tissue. (See, for
example, pattern F2 which results from energization of electrodes
having a non-energized electrode between them, or pattern F4 which
results from energization of electrodes having two non-energized
electrodes between them).
[0097] Moreover, ablation depth may be controlled as described
above by providing low surface density electrodes on areas of the
electrode carrying member which will contact tissue areas at which
a smaller ablation depth is required (see FIG. 19A). Referring to
FIG. 19B, if multiple, closely spaced, electrodes 14 are provided
on the electrode carrying member, a user may set the RF generator
to energize electrodes which will produce a desired electrode
spacing and active electrode area. For example, alternate
electrodes may be energized as shown in FIG. 19B, with the first
three energized electrodes having positive polarity, the second
three having negative polarity, etc.
[0098] As another example, shown in FIG. 19C, if greater ablation
depth is desired the first five electrodes may be positively
energized, and the seventh through eleventh electrodes negatively
energized, with the sixth electrode remaining inactivated to
provide adequate electrode spacing.
[0099] As the endometrial tissue heats, moisture begins to be
released from the tissue. The moisture permeates the electrode
carrying member 12 and is thereby drawn away from the electrodes.
The moisture may pass through the holes 17a in the
suction/insufflation tube 17 and leave the suction/insufflation
tube 17 at its proximal end via port 38 as shown in FIG. 7.
Moisture removal from the ablation site may be further facilitated
by the application of suction to the shaft 10 using the
suction/insufflation unit 40.
[0100] Removal of the moisture from the ablation site prevents
formation of a liquid layer around the electrodes. As described
above, liquid build-up at the ablation site is detrimental in that
provides a conductive layer that carries current from the
electrodes even when ablation has reached the desired depth. This
continued current flow heats the liquid and surrounding tissue, and
thus causes ablation to continue by unpredictable thermal
conduction means.
[0101] Tissue which has been ablated becomes dehydrated and thus
decreases in conductivity. By shunting moisture away from the
ablation site and thus preventing liquid build-up, there is no
liquid conductor at the ablation area during use of the ablation
device of the present invention. Thus, when ablation has reached
the desired depth, the impedance at the tissue surface becomes
sufficiently high to stop or nearly stop the flow of current into
the tissue. RF ablation thereby stops and thermal ablation does not
occur in significant amounts. If the RF generator is equipped with
an impedance monitor, a physician utilizing the ablation device can
monitor the impedance at the electrodes and will know that ablation
has self-terminated once the impedance rises to a certain level and
then remains fairly constant. By contrast, if a prior art bipolar
RF ablation device was used together with an impedance monitor, the
presence of liquid around the electrodes would cause the impedance
monitor to give a low impedance reading regardless of the depth of
ablation which had already been carried out, since current would
continue to travel through the low-impedance liquid layer.
[0102] Other means for monitoring and terminating ablation may also
be provided. For example, a thermocouple or other temperature
sensor may be inserted to a predetermined depth in the tissue to
monitor the temperature of the tissue and terminate the delivery of
RF energy or otherwise signal the user when the tissue has reached
a desired ablation temperature.
[0103] Once the process has self terminated, 1-5 cc of saline can
be introduced via suction/insufflation tube 17 and allowed to sit
for a short time to aid separation of the electrode from the tissue
surface. The suction insufflation device 40 is then switched to
provide insufflation of carbon dioxide at a pressure of 20-200
mmHg. The insufflation pressure helps to lift the ablated tissue
away from the RF applicator head 2 and to thus ease the closing of
the RF applicator head. The RF applicator head 2 is moved to the
closed position by sliding the handle 34 in a distal direction to
fold the spring members 15, 19 along the axis of the device and to
cause the introducer sheath 32 to slide over the folded RF
applicator head. The physician may visually confirm the sufficiency
of the ablation using the monitor 56. Finally, the apparatus is
removed from the uterine cavity.
Second Exemplary Embodiment--Structure
[0104] A second embodiment of an ablation device 100 in accordance
with the present invention is shown in FIGS. 21-37B. The second
embodiment differs from the first embodiment primarily in its
electrode pattern and in the mechanism used to deploy the electrode
applicator head or array. Naturally, aspects of the first and
second exemplary embodiments and their methods of operation may be
combined without departing from the scope of the present
invention.
[0105] Referring to FIGS. 21 and 22, the second embodiment includes
an RF applicator head 102, a sheath 104, and a handle 106. As with
the first embodiment, the applicator head 102 is slidably disposed
within the sheath 104 (FIG. 21) during insertion of the device into
the uterine cavity, and the handle 106 is subsequently manipulated
to cause the applicator head 102 to extend from the distal end of
the sheath 104 (FIG. 22) and to expand into contact with body
tissue (FIG. 33).
[0106] RF Applicator Head
[0107] Referring to FIG. 23, in which the sheath 104 is not shown
for clarity, applicator head 102 extends from the distal end of a
length of tubing 108 which is slidably disposed within the sheath
104. Applicator head 102 includes an external electrode array 102a
and an internal deflecting mechanism 102b used to expand and
tension the array for positioning into contact with the tissue.
[0108] Referring to FIGS. 25A and 25B, the array 102a of applicator
head 102 is formed of a stretchable metallized fabric mesh which is
preferably knitted from a nylon and spandex knit plated with gold
or other conductive material. In one array design, the knit (shown
in FIGS. 26A and 26B) is formed of three monofilaments of nylon
109a knitted together with single yarns of spandex 19b. Each yarn
of spandex 109b has a double helix 109c of five nylon monofilaments
coiled around it.
[0109] This knit of elastic (spandex) and inelastic (nylon) yarns
is beneficial for a number of reasons. For example, knitting
elastic and relatively inelastic yarns allows the overall
deformability of the array to be pre-selected.
[0110] The mesh is preferably constructed so as to have greater
elasticity in the transverse direction (T) than in the longitudinal
direction (L). In a preferred mesh design, the transverse
elasticity is on the order of approximately 300% whereas the
longitudinal elasticity is on the order of approximately 100%. The
large transverse elasticity of the array allows it to be used in a
wide range of uterine sizes.
[0111] Another advantage provided by the combination of elastic and
relatively inelastic yarns is that the elastic yarns provide the
needed elasticity to the array while the relatively inelastic yarns
provide relatively non-stretchable members to which the
metallization can adhere without cracking during expansion of the
array. In the knit configuration described above, the metallization
adheres to the nylon coiled around the spandex. During expansion of
the array, the spandex elongates and the nylon double helix at
least partially elongates from its coiled configuration.
[0112] One process which may be used to apply the gold to the
nylon/spandex knit involves plating the knit with silver using
known processes which involve application of other materials as
base layers prior to application of the silver to ensure that the
silver will adhere. Next, the insulating regions 110 (described
below) are etched onto the silver, and afterwards the gold is
plated onto the silver. Gold is desirable for the array because of
it has a relatively smooth surface, is a very inert material, and
has sufficient ductility that it will not crack as the nylon coil
elongates during use.
[0113] The mesh may be configured in a variety of shapes, including
but not limited to the triangular shape S1, parabolic S2, and
rectangular S3 shapes shown in FIGS. 27A, 27B and 27C,
respectively.
[0114] Turning again to FIGS. 25A and 25B, when in its expanded
state, the array 102a includes a pair of broad faces 112 spaced
apart from one another. Narrower side faces 114 extend between the
broad faces 112 along the sides of the applicator head 102, and a
distal face 116 extends between the broad faces 112 at the distal
end of the applicator head 102.
[0115] Insulating regions 110 are formed on the applicator head to
divide the mesh into electrode regions. The insulated regions 110
are preferably formed using etching techniques to remove the
conductive metal from the mesh, although alternate methods may also
be used, such as by knitting conductive and non-conductive
materials together to form the array.
[0116] The array may be divided by the insulated regions 110 into a
variety of electrode configurations. In a preferred configuration
the insulating regions 110 divide the applicator head into four
electrodes 118a-118d by creating two electrodes on each of the
broad faces 112. To create this four-electrode pattern, insulating
regions 110 are placed longitudinally along each of the broad faces
112 as well as along the length of each of the faces 114, 116. The
electrodes 118a-118d are used for ablation and, if desired, to
measure tissue impedance during use.
[0117] Deflecting mechanism 102b and its deployment structure is
enclosed within electrode array 102a. Referring to FIG. 23,
external hypotube 120 extends from tubing 108 and an internal
hypotube 122 is slidably and co-axially disposed within hypotube
120. Flexures 124 extend from the tubing 108 on opposite sides of
external hypotube 120. A plurality of longitudinally spaced
apertures 126 (FIG. 28) are formed in each flexure 124. During use,
apertures 126 allow moisture to pass through the flexures and to be
drawn into exposed distal end of hypotube 120 using a vacuum source
fluidly coupled to hypotube 120.
[0118] Each flexure 124 preferably includes conductive regions that
are electrically coupled to the array 102a for delivery of RF
energy to the body tissue. Referring to FIG. 29, strips 128 of
copper tape or other conductive material extend along opposite
surfaces of each flexure 124. Each strip 128 is electrically
insulated from the other strip 128 by a non-conductive coating on
the flexure. Conductor leads (not shown) are electrically coupled
to the strips 128 and extend through tubing 108 (FIG. 23) to an
electrical cord 130 (FIG. 21) which is attachable to the RF
generator.
[0119] During use, one strip 128 on each conductor is electrically
coupled via the conductor leads to one terminal on the RF generator
while the other strip is electrically coupled to the opposite
terminal, thus causing the array on the applicator head to have
regions of alternating positive and negative polarity.
[0120] The flexures may alternatively be formed using a conductive
material or a conductively coated material having insulating
regions formed thereon to divide the flexure surfaces into multiple
conductive regions. Moreover, alternative methods such as electrode
leads independent of the flexures 124 may instead be used for
electrically connecting the electrode array to the source of RF
energy.
[0121] It is important to ensure proper alignment between the
conductive regions of the flexures 124 (e.g. copper strips 128) and
the electrodes 118a-118d in order to maintain electrical contact
between the two. Strands of thread 134 (which may be nylon) (FIG.
23) are preferably sewn through the array 102a and around the
flexures 124 in order to prevent the conductive regions 128 from
slipping out of alignment with the electrodes 118a-118d. Alternate
methods for maintaining contact between the array 102a and the
conductive regions 128 include using tiny bendable barbs extending
between the flexures 124 and the array 102a to hook the array to
the conductive regions 128, or bonding the array to the flexures
using an adhesive applied along the insulating regions of the
flexures.
[0122] Referring again to FIG. 23, internal flexures 136 extend
laterally and longitudinally from the exterior surface of hypotube
122. Each internal flexure 136 is connected at its distal end to
one of the flexures 124 and a transverse ribbon 138 extends between
the distal portions of the internal flexures 136. Transverse ribbon
138 is preferably pre-shaped such that when in the relaxed
condition the ribbon assumes the corrugated configuration shown in
FIG. 23 and such that when in a compressed condition it is folded
along the plurality of creases 140 that extend along its length.
Flexures 124, 136 and ribbon 138 are preferably an insulated spring
material such as heat treated 17-7 PH stainless steel.
[0123] The deflecting mechanism is preferably configured such that
the distal tips of the flexures 124 are sufficiently flexible to
prevent tissue puncture during deployment and/or use. Such an
atraumatic tip design may be carried out in a number of ways, such
as by manufacturing the distal sections 124a (FIG. 28) of the
flexures from a material that is more flexible than the proximal
sections 124b. For example, flexures 124 may be provided to have
proximal sections formed of a material having a modulus of
approximately 28.times.10.sup.6 psi and distal sections having a
durometer of approximately 72 D.
[0124] Alternatively, referring to FIG. 30, the flexures 124 may be
joined to the internal flexures 136 at a location more proximal
than the distal tips of the flexures 124, allowing them to move
more freely and to adapt to the contour of the surface against
which they are positioned (see dashed lines in FIG. 30). Given that
uterine sizes and shapes vary widely between women, the atraumatic
tip design is further beneficial in that it allows the device to
more accurately conform to the shape of the uterus in which it is
deployed while minimizing the chance of injury.
[0125] The deflecting mechanism formed by the flexures 124, 136,
and ribbon 138 forms the array into the substantially triangular
shape shown in FIG. 23, which is particularly adaptable to most
uterine shapes. As set forth in detail below, during use distal and
proximal grips 142, 144 forming handle 106 are squeezed towards one
another to withdraw the sheath and deploy the applicator head. This
action results in relative rearward motion of the hypotube 120 and
relative forward motion of the hypotube 122. The relative motion
between the hypotubes causes deflection in flexures 124, 136 which
deploys and tensions the electrode array 102a.
[0126] Measurement Device
[0127] The ablation device according to the second embodiment
includes a measurement device for easily measuring the uterine
width and for displaying the measured width on a gauge 146 (FIG.
21). The measurement device utilizes non-conductive (e.g. nylon)
suturing threads 148 that extend from the hypotube 122 and that
have distal ends attached to the distal portion of the deflecting
mechanism (FIG. 23). As shown in FIG. 24, threads 148 are
preferably formed of a single strand 150 threaded through a wire
loop 152 and folded over on itself. Wire loop 152 forms the distal
end of an elongate wire 154 which may be formed of stainless steel
or other wire.
[0128] Referring to FIG. 31, wire 154 extends through the hypotube
122 and is secured to a rotatable bobbin 156. The rotatable bobbin
156 includes a dial face 158 preferably covered in a clear plastic.
As can be seen in FIG. 32, dial face 158 includes calibration
markings corresponding to an appropriate range of uterine widths.
The bobbin is disposed within a gauge housing 160 and a
corresponding marker line 162 is printed on the gauge housing. A
torsion spring 164 provides rotational resistance to the bobbin
156.
[0129] Expansion of the applicator head 102 during use pulls
threads 148 (FIG. 23) and thus wire 154 (FIG. 24) in a distal
direction. Wire 154 pulls against the bobbin 156 (FIG. 31), causing
it to rotate. Rotation of the bobbin positions one of the
calibration markings on dial face 158 into alignment with the
marker line 162 (FIG. 32B) to indicate the distance between the
distal tips of flexures 124 and thus the uterine width.
[0130] The uterine width and length (as determined using a
conventional sound or other means) are preferably input into an RF
generator system and used by the system to calculate an appropriate
ablation power as will be described below. Alternately, the width
as measured by the apparatus of the invention and length as
measured by other means may be used by the user to calculate the
power to be supplied to the array to achieve the desired ablation
depth.
[0131] The uterine width may alternatively be measured using other
means, including by using a strain gauge in combination with an A/D
converter to transduce the separation distance of the flexures 124
and to electronically transmit the uterine width to the RF
generator.
[0132] Control of Ablation Depth
[0133] The most optimal electrocoagulation occurs when relatively
deep ablation is carried out in the regions of the uterus at which
the endometrium is thickest, and when relatively shallower ablation
is carried out in areas in which the endometrium is shallower. A
desirable range of ablation depths includes approximately 2-3 mm
for the cervical os and the cornual regions, and approximately 7-8
mm in the main body of the uterus where the endometrium is
substantially thicker.
[0134] As discussed with respect to the first embodiment, a number
of factors influence the ablation depth that can be achieved using
a given power applied to a bipolar electrode array. These include
the power supplied by the RF generator, the distance between the
centers of adjacent electrodes ("center-to-center distance"), the
electrode density (i.e., the porosity of the array fabric or the
percent of the array surface that is metallic), the edge gap (i.e.
the distance between the edges of adjacent electrode poles), and
the electrode surface area. Other factors include blood flow (which
in slower-ablating systems can dissipate the RF) and the impedance
limit.
[0135] Certain of these factors may be utilized in the present
invention to control ablation depth and to provide deeper ablation
at areas requiring deeper ablation and to provide shallower regions
in areas where deep ablation is not needed. For example, as
center-to-center distance increases, the depth of ablation
increases until a point where the center to center distance is so
great that the strength of the RF field is too diffuse to excite
the tissue. It can been seen with reference to FIG. 33 that the
center to center distance d1 between the electrodes 118a, 118b is
larger within the region of the array that lies in the main body of
the uterus and thus contributes to deeper ablation. The center to
center distance d2 between electrodes 118a, 118b is smaller towards
the cervical canal where it contributes to shallower ablation. At
the distal end of the device, the shorter center to center
distances d3 extend between top and bottom electrodes 118b, 118c
and 118a, 118d and again contribute to shallower ablation.
[0136] Naturally, because the array 102a expands to accommodate the
size of the uterus in which it is deployed, the dimensions of the
array 102a vary. One embodiment of the array 102a includes a range
of widths of at least approximately 2.5-4.5 cm, a range of lengths
of at least approximately 4-6 cm, and a density of approximately
35%-45%.
[0137] The power supplied to the array by the RF generator is
calculated by the RF generator system to accommodate the electrode
area required for a particular patient. As discussed above, the
uterine width is measured by the applicator head 102 and displayed
on gauge 146. The uterine length is measured using a sound, which
is an instrument conventionally used for that purpose. It should be
noted that calibration markings of the type used on a conventional
sound device, or other structure for length measurement, may be
included on the present invention to allow it to be used for length
measurement as well.
[0138] The user enters the measured dimensions into the RF
generator system using an input device, and the RF generator system
calculates or obtains the appropriate set power from a stored
look-up table using the uterine width and length as entered by the
user. An EPROM within the RF generator system converts the length
and width to a set power level according to the following
relationship:
P=L.times.W.times.5.5
Where P is the power level in watts, L is the length in
centimeters, W is the width in centimeters, and 5.5 is a constant
having units of watts per square centimeter.
[0139] Alternatively, the user may manually calculate the power
setting from the length and width, or s/he may be provided with a
table of suggested power settings for various electrode areas (as
determined by the measured length and width) and will manually set
the power on the RF generator accordingly.
[0140] Handle
[0141] Referring again to FIGS. 21 and 22, the handle 106 of the RF
ablation device according to the second embodiment includes a
distal grip section 142 and a proximal grip section 144 that are
pivotally attached to one another at pivot pin 166.
[0142] The proximal grip section 144 is coupled to the hypotube 122
(FIG. 23) via yoke 168, overload spring 170 and spring stop 172,
each of which is shown in the section view of FIG. 34. The distal
grip section 142 is coupled to the external hypotube 120 via male
and female couplers 174, 176 (see FIGS. 32A and 32B). Squeezing the
grip sections 142, 144 towards one another thus causes relative
movement between the external hypotube 120 and the internal
hypotube 122. This relative sliding movement results in deployment
of the deflecting mechanism 102b from the distal end of the sheath
and expansion of the array 102a to its expanded state.
[0143] Referring to FIGS. 32A and B, rack 180 is formed on male
coupler 174 and calibration markings 182 are printed adjacent the
rack 180. The calibration markings 182 correspond to a variety of
uterine lengths and may include lengths ranging from, for example,
4.0 to 6.0 cm in 0.5 cm increments.
[0144] A sliding collar 184 is slidably disposed on the tubing 108
and is slidable over male coupler 174. Sliding collar 184 includes
a rotating collar 186 and a female coupler 176 that includes a
wedge-shaped heel 188. A locking spring member 190 (FIGS. 32B and
35) extends across an aperture 192 formed in the proximal grip 144
in alignment with the heel 188. When the distal and proximal handle
sections are squeezed together to deploy the array, the heel 188
passes into the aperture 192. Its inclined lower surface gradually
depresses the spring member 190 as the heel moves further into the
aperture 192. See FIGS. 36A and 36B. After passing completely over
the spring member, the heel moves out of contact with the spring
member. The spring member snaps upwardly thereby engaging the heel
in the locked position. See FIG. 36C.
[0145] A release lever 194 (FIG. 35) is attached to the free end of
the spring member 190. To disengage the spring lock, release lever
194 is depressed to lower spring member 190 so that the inclined
heel can pass over the spring member and thus out of the aperture
192.
[0146] Referring again to FIGS. 32A and 32B, sliding collar 184 is
configured to allow the user to limit longitudinal extension of the
array 102a to a distance commensurate with a patient's
predetermined uterine length. It does so by allowing the user to
adjust the relative longitudinal position of male coupler 174
relative to the female coupler 176 using the rotating collar 186 to
lock and unlock the female coupler from the rack 180 and the male
coupler 174. Locking the female coupler to the rack 180 and male
coupler 174 will limit extension of the array to approximately the
predetermined uterine length, as shown on the calibration markings
182.
[0147] Once the uterine length has been measured using a
conventional sound, the user positions sliding collar 184 adjacent
to calibration marks 182 corresponding to the measured uterine
length (e.g. 4.5 cm). Afterwards, the user rotates the collar
section 186 to engage its internally positioned teeth with the rack
180. This locks the longitudinal position of the heel 188 such that
it will engage with the spring member 190 on the proximal grip when
the array has been exposed to the length set by the sliding
collar.
[0148] The handle 106 includes a pair of spring assemblies which
facilitate controlled deployment and stowage of the array 102a. One
of the spring assemblies controls movement of the grips 142, 144 to
automatically stow the array 102a into the sheath 104 when the user
stops squeezing the grips 142, 144 towards one another. The other
of the spring assemblies controls the transverse movement of the
spring flexures 124 to the expanded condition by limiting the
maximum load that can be applied to the deployment mechanism
102b.
[0149] FIG. 34 shows the distal and proximal grips 142 and 144 in
partial cross-section. The first spring assembly for controlled
stowage includes a handle return mandrel 196 that is slidably
disposed within the proximal grip 144. A compression spring 198
surrounds a portion of the return mandrel 196, and a retaining ring
200 is attached to the mandrel 196 above the spring 198. A spring
stop 202 is disposed between the spring 198 and the retaining
ring.
[0150] The lowermost end of the return mandrel 196 is pivotally
engaged by a coupling member 204 on distal grip 142. Relative
movement of the grips 142, 144 towards one another causes the
coupling member 204 to pull the return member downwardly with the
proximal grip 144 as indicated by arrows. Downward movement of the
mandrel 196 causes its retaining ring 200 and spring stop 202 to
bear downwardly against the compression spring 198, thereby
providing a movement which acts to rotate the grips 142, 144 away
from one another. When tension against the grips 142, 144 is
released (assuming that heel 188 is not locked into engagement with
spring member 190) the grips rotate apart into the opened position
as the compression spring 198 returns to the initial state, stowing
the applicator head inside the sheath.
[0151] The second spring assembly for controlling array deployment
is designed to control separation of the flexures. It includes a
frame member 178 disposed over yoke 168, Which is pivotally
attached to proximal grip 144. Tubing 108 extends from the array
102a (see FIG. 23), through the sheath 104 and is fixed at its
proximal end to the frame member 178. Hypotube 122 does not
terminate at this point but instead extends beyond the proximal end
of tubing 108 and through a window 206 in the frame member. Its
proximal end 208 is slidably located within frame member 178
proximally of the window 206 and is fluidly coupled to a vacuum
port 210 by fluid channel 212. Hypotube 120 terminates within the
frame. Its proximal end is fixed within the distal end of the
frame.
[0152] A spring stop 214 is fixed to a section of the hypotube
within the window 206, and a compression spring 170 is disposed
around the hypotube between the spring stop 172 and yoke 168. See
FIGS. 32B and 34.
[0153] When the distal and proximal grips are moved towards one
another, the relative rearward motion of the distal grip causes the
distal grip to withdraw the sheath 104 from the array 102a.
Referring to FIGS. 37A and 37B, this motion continues until female
coupler 176 contacts and bears against frame member 178. Continued
motion between the grips causes a relative rearward motion in the
frame which causes the same rearward relative motion in external
hypotube 120. An opposing force is developed in yoke 168, which
causes a relative forward motion in hypotube 122. The relative
motion between the hypotubes causes deflection in flexures 124, 136
which deflect in a manner that deploys and tensions the electrode
array. Compression spring 170 acts to limit the force developed by
the operator against hypotubes 120, 122, thus limiting the force of
flexures 124, 136 acting on the array and the target tissue
surrounding the array.
[0154] Referring to FIG. 21, collar 214 is slidably mounted on
sheath 104. Before the device is inserted into the uterus, collar
214 can be positioned along sheath 104 to the position measured by
the uterine sound. Once in position, the collar provides visual and
tactile feedback to the user to assure the device has been inserted
the proper distance. In addition, after the applicator head 102 has
been deployed, if the patient's cervical canal diameter is larger
than the sheath dimensions, the collar 214 can be moved distally
towards the cervix, making contact with it and creating a pneumatic
seal between the sheath and cervix.
Second Exemplary Embodiment--Operation
[0155] In preparation for ablating the uterus utilizing the second
exemplary embodiment, the user measures the uterine length using a
uterine sound device. The user next positions sliding collar 184
(FIG. 32B) adjacent to calibration marks 182 corresponding to the
measured uterine length (e.g. 4.5 cm) and rotates the collar
section 186 to engage its internally positioned teeth with the rack
180. This locks the longitudinal position of the heel 188 (FIG.
32A) such that it will engage with the spring member 190 when the
array has been exposed to the length set by the sliding collar.
[0156] Next, with the grips 142, 144 in their resting positions to
keep the applicator head 102 covered by sheath 104, the distal end
of the device 100 is inserted into the uterus. Once the distal end
of the sheath 104 is within the uterus, grips 142, 144 are squeezed
together to deploy the applicator head 102 from sheath 104. Grips
142, 144 are squeezed until heel 188 engages with locking spring
member 190 as described with respect to FIGS. 3BA through 36C.
[0157] At this point, deflecting mechanism 102b has deployed the
array 102a into contact with the uterine walls. The user reads the
uterine width, which as described above is transduced from the
separation of the spring flexures, from gauge 146. The measured
length and width are entered into the RF generator system 250 (FIG.
21) and used to calculate the ablation power.
[0158] Vacuum source 252 (FIG. 21) is activated, causing
application of suction to hypotube 122 via suction port 210.
Suction helps to draw uterine tissue into contact with the array
102.
[0159] Ablation power is supplied to the electrode array 102a by
the RF generator system 250. The tissue is heated as the RF energy
passes from electrodes 118a-d to the tissue, causing moisture to be
released from the tissue. The vacuum source helps to draw moisture
from the uterine cavity into the hypotube 122. Moisture withdrawal
is facilitated by the apertures 126 formed in flexures 124 by
preventing moisture from being trapped between the flexures 124 and
the lateral walls of the uterus.
[0160] If the RF generator 250 includes an impedance monitoring
module, impedance may be monitored at the electrodes 118a-d and the
generator may be programmed to terminate RF delivery automatically
once the impedance rises to a certain level. The generator system
may also or alternatively display the measured impedance and allow
the user to terminate RF delivery when desired.
[0161] When RF delivery is terminated, the user depresses release
lever 194 to disengage heel 188 from locking spring member 190 and
to thereby allow grips 142, 144 to move to their expanded (resting
condition). Release of grips 142, 144 causes applicator head 102 to
retract to its unexpanded condition and further causes applicator
head 102 to be withdrawn into the sheath 104. Finally, the distal
end of the device 100 is withdrawn from the uterus.
[0162] Two embodiments of ablation devices in accordance with the
present invention have been described herein. These embodiments
have been shown for illustrative purposes only. It should be
understood, however, that the invention is not intended to be
limited to the specifics of the illustrated embodiments but is
defined only in terms of the following claims.
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