U.S. patent application number 13/771314 was filed with the patent office on 2013-06-27 for surgical clamp having treatment elements.
This patent application is currently assigned to MEDTRONIC CRYOCATH LP. The applicant listed for this patent is Medtronic Cryocath LP. Invention is credited to Sean CARROLL, Alan H. MENKIS, Daniel NAHON, Cristian PETRE, Allan SKANES, Real STE-MARIE, Dan WITTENBERGER.
Application Number | 20130165927 13/771314 |
Document ID | / |
Family ID | 43706286 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130165927 |
Kind Code |
A1 |
NAHON; Daniel ; et
al. |
June 27, 2013 |
SURGICAL CLAMP HAVING TREATMENT ELEMENTS
Abstract
A medical device is provided having a means for actuating a pair
of opposing jaw members. The jaw members are movable relative to
one another from a first position, wherein the jaw members are
disposed in a spaced apart relation relative to one another, to a
second position, wherein the jaw members cooperate to grasp tissue
therebetween. An ablation tool is connected to at least one of the
jaws members, such that the jaw members are capable of conducting
ablation energy through the tissue grasped therebetween.
Inventors: |
NAHON; Daniel; (Ottawa,
CA) ; CARROLL; Sean; (Rancho Cucamonga, CA) ;
WITTENBERGER; Dan; (L'lle-Bizard, CA) ; PETRE;
Cristian; (Fabreville, CA) ; SKANES; Allan;
(London, CA) ; MENKIS; Alan H.; (London, CA)
; STE-MARIE; Real; (Notre-Dame-de-L'lle-Perrot,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic Cryocath LP; |
Toronto |
|
CA |
|
|
Assignee: |
MEDTRONIC CRYOCATH LP
Toronto
CA
|
Family ID: |
43706286 |
Appl. No.: |
13/771314 |
Filed: |
February 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11375231 |
Mar 14, 2006 |
8398632 |
|
|
13771314 |
|
|
|
|
10458745 |
Jun 10, 2003 |
7044946 |
|
|
11375231 |
|
|
|
|
Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/1465 20130101;
A61B 2018/0212 20130101; A61B 2017/00026 20130101; A61B 2018/00875
20130101; A61B 2018/0225 20130101; A61B 2018/0262 20130101; A61B
2018/00839 20130101; A61B 18/02 20130101; A61B 2018/00791
20130101 |
Class at
Publication: |
606/41 |
International
Class: |
A61B 18/08 20060101
A61B018/08 |
Claims
1. A medical device comprising an elongate shaft, a cooling
element, and a second element movable with respect to the cooling
element to define a clamp, wherein the movable element is
selectively detachable from the shaft.
2. The medical device of claim 1, wherein at least a portion of
each of the elongate shaft, cooling element, and second element are
thermally insulated.
3. The medical device of claim 1, wherein the elongate shaft
defines a coolant flow path.
4. The medical device of claim 3, wherein at least one of the
cooling element and second element defines a coolant flow path that
is in fluid communication with the coolant flow path defined by the
elongate shaft.
5. The medical device of claim 4, wherein both the cooling element
and second element each define a coolant flow path.
6. The medical device of claim 1, wherein at least one of the
cooling element and the second element includes a temperature
measurement device.
7. The medical device of claim 6, wherein at least one of the
cooling element and the second element includes an impedance
measurement device.
8. The medical device of claim 1, wherein the second element
includes a temperature sensor.
9. The medical device of claim 1, wherein the device is operable to
clamp an area of target tissue when the second element is attached
to the shaft, and the device is operable to ablate the target
tissue area when the second element is either attached to the shaft
or detached from the shaft.
10. A method for evaluating transmurality of a lesion comprising:
positioning a first and a second jaw of an ablating device about
tissue to be treated; applying a cooling element to at least the
first jaw of the ablating device; and measuring temperature from a
temperature sensor associated with the second jaw of the ablating
device.
11. The method of claim 10, wherein at least a portion of each of
the first jaw and the second jaw are thermally insulated.
12. The method of claim 10, wherein the device further includes an
elongate shaft, at least a portion of which is thermally
insulated.
13. The method of claim 13, wherein the elongate shaft defines a
coolant flow path.
14. The method of claim 14, wherein the cooling element is in fluid
communication with the coolant flow path defined by the elongate
shaft.
15. The method of claim 10, wherein the step of applying a cooling
element to at least the first jaw of the ablating device ablates
the tissue between the first jaw and second jaw to create a
lesion.
16. The method of claim 15, further comprising determining the
transmurality of the lesion.
17. The method of claim 16, wherein the transmurality of the lesion
is determined by measuring the temperature from the temperature
sensor associated with the second jaw of the ablating device.
18. The method of claim 17, wherein the lesion is determined to be
transmural when the temperature sensor associated with the second
jaw of the ablating device measures a temperature of between
approximately -60.degree. C. and approximately -20.degree. C.
19. The method of claim 18, wherein the lesion is determined to be
transmural when the temperature sensor associated with the second
jaw of the ablating device measures a temperature of approximately
-40.degree. C.
20. The method of claim 19, wherein the lesion is determined to be
transmural when the temperature sensor associated with the second
jaw of the ablating device measures a temperature of approximately
-40.degree. C. for a time duration of approximately two minutes.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation of patent application
Ser. No. 11375231, filed Mar. 14, 2006, entitled SURGICAL CLAMP
HAVING TREATMENT ELEMENTS, which application is a Divisional of
patent application Ser. No. 10458745, entitled SURGICAL CLAMP
HAVING TREATMENT ELEMENTS, now issued U.S. Pat. No. 7,044,946,
issued May 16, 2006, the entirety of which is incorporated herein
by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] n/a
FIELD OF THE INVENTION
[0003] The present invention relates to a method and system for
ablating tissue, and more particularly to a medical device having a
pair of opposing jaws used for tissue ablation.
BACKGROUND OF THE INVENTION
[0004] It is well documented that atrial fibrillation (AF), either
alone or as a consequence of other cardiac disease, continues to
persist as the most common type of cardiac arrhythmia. In the
United States, AF currently affects an estimated two million
people, with approximately 160,000 new cases being diagnosed each
year. The cost of treatment for AF alone is estimated to be in
excess of $400 million worldwide each year.
[0005] Although pharmacological treatment is available for AF, the
treatment is far from perfect. For example, certain antiarrhythmic
drugs, like quinidine and procainamide, can reduce both the
incidence and the duration of AF episodes. Yet, these drugs often
fail to maintain sinus rhythm in the patient. Cardioactive drugs,
like digitalis, Beta blockers, and calcium channel blockers, can
also be given to control AF by restoring the heart's natural rhythm
and limiting the natural clotting mechanism of the blood. However,
antiarrhythmic drug therapy often becomes less effective over time.
In addition, antiarrhythmic drug can have severe side effects,
including pulmonary fibrosis and impaired liver function.
[0006] Another therapy for AF is surgery. In a technique known as
the "Maze" procedure, a surgeon makes several incisions through the
wall of the atrium with a scalpel and then sews the cuts back
together, creating a scar pattern. The scars isolate and contain
the chaotic electrical impulses to control and channel the
electrical signals. The Maze procedure is expensive, complicated to
perform, and associated with long hospital stays and high
morbidity.
[0007] An alternative to open heart or open chest surgery is a
minimally invasive treatment in which ablation devices are used to
form scars in various locations in the atrial tissue. Ablation
devices that apply heat or cold to body tissue are known.
Typically, these devices have an elongate, highly-flexible shaft
with a steerable distal end for negotiating a path through the body
of a patient. Rigid shaft devices are used in more invasive
procedures where a more local opening or direct access to a
treatment site is available or created.
[0008] It is important to note that these devices are used in an
attempt to ablate tissue through the full thickness of the cardiac
wall, and thus create a risk associated with damaging structures
within or on the outer surface of the cardiac wall. Accordingly
ablation devices have been developed which include opposing jaw
members to ablate tissue from both sides of the cardiac wall. For
example, U.S. Pat. No. 6,161,543 to Cox; U.S. Pat. No. 5,733,280 to
Avitall; and U.S. Pat. No. 6,517,536 to Hooven describe techniques
for ablating tissue of organs or vessels having opposing walls and
disclose ablation devices having clamping members to clamp a
treatment site therebetween. Such devices include rigid
members/shafts to facilitate reaching the tissue treatment
site.
[0009] While rigid shafts may be useful in some applications, they
have certain limitations as well. For example, without a preset
shape for reaching a particular location in the body of a patient,
the rigid nature of the shaft limits the area of tissue that can be
reached and treated. Even where a relatively large incision is
provided, tissue areas that are not at least somewhat directly
accessible cannot be reached.
[0010] Although a rigid shaft can be provided with a predetermined
shape, one must select a device with a rigid shaft that has the
most appropriate shape for positioning the working portion of the
device in contact with the treatment site in view of the particular
anatomical pathway to be followed in the patient. It will be
appreciated that a large inventory of devices having rigid shafts
may be required to accommodate the various treatment sites and
patient anatomies. As an example, U.S. Pat No. 6,161,543 to Cox el
al. describes a variety of rigid probe shapes. Further, for a
patient having a relatively uncommon anatomic configuration and/or
a difficult to reach treatment site, all rigid devices of an
existing set may have less than optimal shapes for positioning.
This may impair the prospects of successfully carrying out the
treatment procedure. For an ablation device which must bear against
tissue at the remote region to create lesions, the contour followed
by the device in reaching the target site will in general further
restrict the direction and magnitude of the movement and forces
which may be applied or exerted on the working portion of the
device to effect tissue contact and treatment.
SUMMARY OF THE INVENTION
[0011] The present invention advantageously provides a medical
device for ablating tissue including a pair of opposing jaws
positionable from a first position to a second position. The pair
of opposing jaws includes at least one an ablation tool disposed
thereon, such that the opposing jaws are capable of conducting
ablation energy through the tissue grasped therebetween. A shaft
assembly is operably connected to the opposing jaws, wherein the
shaft assembly has a malleability such that the shaft assembly
retains a first shape until manipulated to a second shape.
[0012] A handle assembly is attached to the shaft assembly opposite
the opposing jaws. The handle assembly is operably connected to the
opposing jaws such that the handle assembly moves the opposing jaws
from a first position, wherein the opposing jaws are in a spaced
apart relation, to a second position, wherein the opposing jaws
grasp the tissue to be treated.
[0013] The present invention advantageously provides a method of
ablating tissue using the above medical device. The shaft assembly
is manipulated from the first shape to the second shape, wherein
the second shape is determined by the anatomy of the patient. The
opposing jaws are positioned in the first position, such that the
opposing jaws are in a spaced apart relation. The medical device is
placed about the tissue treatment site, such that the opposing jaws
are about the tissue to be treated. The opposing jaws are
positioned in the second position, wherein the opposing jaws grasp
the tissue to be treated, and the ablation tool is in contact with
the tissue treatment site. The tissue is treated by providing
ablating energy to the ablating tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A more complete understanding of the present invention, and
the attendant advantages and features thereof, will be more readily
understood by reference to the following detailed description when
considered in conjunction with the accompanying drawings
wherein:
[0015] FIG. 1 is a plan view of a surgical clamp in accordance with
the present invention;
[0016] FIG. 2 is a sectional view of an ablation segment of the
surgical clamp of FIG. 1;
[0017] FIG. 3 is a sectional view of an ablation segment including
multiple injection tubes of the surgical clamp of FIG. 1;
[0018] FIG. 4 is a sectional view of an ablation segment including
orifices of the surgical clamp of FIG. 1;
[0019] FIG. 5 is a plan view of an alternative embodiment of the
surgical clamp of FIG. 1;
[0020] FIG. 6 is a plan view of the surgical clamp of FIG. 1
including curved jaws;
[0021] FIG. 7 is a sectional view of an ablation segment including
insulation sleeve of the surgical clamp of FIG; 1
[0022] FIG. 8 is a plan view of the surgical clamp of FIG. 1
including elongated shafts;
[0023] FIG. 9 is a sectional view of the elongated shaft and
ablation segment of the surgical clamp of FIG. 8;
[0024] FIG. 10 is a surgical system for operating the surgical
clamp in accordance with the present invention;
[0025] FIG. 11 a plan view of an alternative surgical clamp in
accordance with the present invention;
[0026] FIG. 12 is a sectional view of an elongated shaft and
ablation segment of the surgical clamp of FIG. 11;
[0027] FIGS. 13-17 illustrate additional configurations of a
surgical clamp;
[0028] FIG. 18 illustrates still another surgical clamp
configuration;
[0029] FIGS. 19 and 20 illustrate additional details of the jaw
elements shown in FIG. 18; and
[0030] FIGS. 21 and 22 show additional clamp configurations.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention provides a medical device having a
handle assembly for actuating a pair of opposing jaw members. The
jaw members are movable relative to one another from a first
position, wherein the jaw members are disposed in a spaced apart
relation relative to one another, to a second position, wherein the
jaw members cooperate to grasp tissue therebetween. An ablation
tool is connected to at least one of the jaw members, such that the
jaw members are capable of conducting ablation energy through the
tissue grasped therebetween.
[0032] Referring now to the figures in which like reference
designators refer to like elements, there is shown in FIG. 1 a plan
view of an exemplary embodiment of the medical device constructed
in accordance with the principles of the present invention and
designated generally as surgical clamp 10. The surgical clamp 10
includes a handle assembly having elongated handles 12 and 14 and
may optionally include a lock mechanism 16, similar to a
conventional surgical hemostat. The elongated handles 12, 14 are
connected to one another by pivot or hinge 18, and continue
distally in the form of a first elongated jaw 20 and a second
elongated jaw 22. At least one of the elongated jaws 20, 22
includes an ablation tool. For example, the first elongated jaw 20
includes an ablation tool 24 positioned on the inner surface 26 of
the first elongated jaw 20.
[0033] Referring to FIGS. 2-3, the ablation tool 24 includes an
ablation segment 28 having a thermally-transmissive region 30, and
defining a fluid path having at least one fluid inlet 32 and a
fluid outlet 34 through the ablation tool 24 to the ablation
segment 28, wherein the fluid inlet 32 is in fluid communication
with a cryogenic fluid source. Also, even though many materials and
structures can be thermally conductive or thermally transmissive if
chilled to a very low temperature and/or cold soaked, as used
herein, a "thermally-transmissive region" is intended to broadly
encompass any structure or region of the ablation tool 24 that
readily conducts heat.
[0034] For example, a metal structure exposed (directly or
indirectly) to the cryogenic fluid path is considered a
thermally-transmissive region 30 even if an adjacent polymeric or
latex portion also permits heat transfer, but to a much lesser
extent than the metal. Thus, the thermally-transmissive region 30
can be viewed as a relative term to compare the heat transfer
characteristics of different catheter regions or structures,
regardless of the material.
[0035] Furthermore, while the thermally-transmissive region 30 can
include a single, continuous, and uninterrupted surface or
structure, it can also include multiple, discrete,
thermally-transmissive structures that collectively define a
thermally-transmissive region that is elongate or linear. Depending
on the ability of the cryogenic system, or portions thereof, to
handle given thermal loads, the ablation of an elongate tissue path
can be performed in a single or multiple cycle process without
having to relocate the catheter one or more times or drag it across
tissue.
[0036] In an exemplary embodiment, as shown in FIG. 4, the ablation
segment 28 includes one or more orifices 34, where the orifices 34
define the thermally-transmissive region 30. The orifices 34 enable
the application of cryogenic fluid directly onto the tissue to be
treated.
[0037] Additionally, the second elongated jaw 22 can include an
ablation tool 42 positioned on the inner surface 44 of the second
elongated jaw 22. The ablation tool 42 includes an ablation segment
46 having a thermally-transmissive region 30, and defines a fluid
path having at least one fluid inlet 48 and a fluid outlet 50
through the ablation tool 42 to the ablation segment 46, wherein
the fluid inlet 48 is in fluid communication with a cryogenic fluid
source.
[0038] In an exemplary embodiment, as shown in FIG. 5, the
handles12 and 14 are at an acute angle to the first elongated jaw
20 and the second elongated jaw 22. Furthermore, as shown in FIG.
6, the first elongated jaw 20 and the second elongated jaw 22
include a curved portion.
[0039] Additionally, the first elongated jaw 20 and the second
elongated jaw 22 are malleable, each have a shape-holding
deformability, that is, they have rigidity such that the first
elongated jaw 20 and the second elongated jaw 22 each retain a
first shape until manipulated to a further shape with the
application of moderate pressure, and until reshaped. The first
elongated jaw 20 and the second elongated jaw 22 retain their shape
with sufficient rigidity to manipulate the ablation segment 28
against tissue, and push it past intervening tissue to a desired
position.
[0040] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the first elongated jaw 20 and the second elongated jaw
22 for positioning the active or distal portion of the ablation
tool 24, and may include successive bends or segments having more
than one curve, angle, deformation or other non-linear
configuration. The shape-retaining feature of the first elongated
jaw 20 and the second elongated jaw 22 allows an operator to bend
the first elongated jaw 20 and the second elongated jaw 22 to a
shape or contour, for example around an organ or tissue structure,
and have an optimal configuration for positioning and or orienting
the active or distal region of the first elongated jaw 20 and the
second elongated jaw 22 based upon the particular anatomy of a
patient and the location of the treatment site.
[0041] Further, the stiffness of first elongated jaw 20 and the
second elongated jaw 22 is such that the surgeon can form the first
elongated jaw 20 and the second elongated jaw 22 by hand to a
desired shape without undue effort, and yet the first elongated jaw
20 and the second elongated jaw 22 retain the set shape as the
surgical clamp 10 is maneuvered to and held in position at the
treatment site. The first elongated jaw 20 and the second elongated
jaw 22 should also be sufficiently rigid such that the surgeon can
place the ablation segment 28 of the ablation tool 24 in pressured
contact with the tissue treatment site. That is, the first
elongated jaw 20 and the second elongated jaw 22 are sufficiently
stiff to enable the surgeon to press the ablation segment 28
against the tissue to be treated without inducing a further
deformation in the shape of the first elongated jaw 20 and the
second elongated jaw 22. The first elongated jaw 20 and the second
elongated jaw 22 may in some embodiments deflect slightly, and yet
have sufficient stiffness to transfer an effective level of lateral
force at their distal end.
[0042] In an exemplary embodiment, the first elongated jaw 20 and
the second elongated jaw 22 are configured so that they are
deformable in a single plane, where the first elongated jaw 20 and
the second elongated jaw 22 remain substantially rigid in all other
planes. For example, the first elongated jaw 20 and the second
elongated jaw 22 can be manipulated in a first plane "P1" from a
first shape to a second shape, wherein the first elongated jaw 20
and the second elongated jaw 22 are sufficiently rigid to retain
the second shape. The first elongated jaw 20 and the second
elongated jaw 22 also have sufficient rigidity such that the first
elongated jaw 20 and the second elongated jaw 22 cannot be
manipulated in a second plane "P2" orthogonal to the first plane,
such that the first elongated jaw 20 and the second elongated jaw
22 are deformable only in the first plane "P1." As such, the first
elongated jaw 20 and the second elongated jaw 22 are deformable in
only one plane.
[0043] In accordance with yet another aspect of the invention, as
shown in FIG. 7, particularly directed to the ablative properties
of ablation segments 28, 44, the energy distribution during
treatment of tissue is further controlled by an adjustable
insulation sleeve 52, wherein one each extends over and partially
envelops the ablation segments 28, 44. A slotted segment 54 in the
insulation sleeve 52 forms a partial circumferential blanket or
insulating sleeve which prevents the ablation segments 28,44 from
affecting tissue on one side of the ablation segments 28, 44, while
leaving the other side of the ablation segments 28, 44 exposed for
contact with tissue.
[0044] In a further exemplary embodiment, as shown in FIG. 8, the
surgical clamp 10 includes a shaft assembly having a first shaft 56
and a second shaft 58 interposed between the handles 12 and 14 and
the first elongated jaw 20 and the second elongated jaw 22. The
first shaft 56 and a second shaft 58 operably connect the first
elongated jaw 20 and the second elongated jaw 22 to the handles 12
and 14 such that the first elongated jaw 20 and the second
elongated jaw 22 are movable relative to one another from a first
position, wherein the first elongated jaw 22 and the second
elongated jaw 20 are disposed in a spaced apart relation relative
to one another, to a second position, wherein the first elongated
jaw 20 and the second elongated jaw 22 cooperate to grasp tissue
therebetween.
[0045] Referring to FIG. 9, the first shaft 56 is substantially
hollow, defining a first lumen 60 having at least one input lumen
62 positioned therein, wherein the first lumen 60 and the at least
one lumen 62 define a fluid path to the ablation tool 24 on the
first elongated jaw 20. The first lumen 60 and the at least one
lumen 62 are in fluid communication with the ablation fluid outlet
34 and the ablation fluid inlet 32.
[0046] Additionally, similar to the first shaft 56, the second
shaft 58 can be substantially hollow, defining a first lumen having
at least one input lumen positioned therein, wherein the first
lumen 60 and the at least one lumen 62 define a fluid path to the
ablation tool 42 on the second elongated jaw 22. The first lumen
and the at least one lumen 62 are in fluid communication with the
ablation fluid outlet 48 and the ablation fluid inlet 50.
[0047] The first shaft 56 and the second shaft 58 are malleable,
each have a shape-holding deformability, that is, they have a
rigidity such that the first shaft 56 and the second shaft 58 each
retain a first shape until manipulated to a further shape with the
application of moderate pressure, and until reshaped. The first
shaft 56 and the second shaft 58 retain their shape with sufficient
rigidity to close the first elongated jaw 20 and the second
elongated jaw 22 to grasp the tissue, and push it past intervening
tissue to a desired position.
[0048] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the surgical clamp 10 for positioning the active or
distal portion of the ablation tool 24, and may include successive
bends or segments having more than one curve, angle, deformation or
other non-linear configuration. The shape-retaining feature of the
first shaft 56 and the second shaft 58 allows an operator to bend
the first shaft 56 and the second shaft 58 to a shape or contour,
for example around an organ or tissue structure, and have an
optimal configuration for positioning and or orienting the active
or distal region of the surgical clamp 10 based upon the particular
anatomy of a patient and the location of the treatment site.
[0049] Further, the stiffness of the first shaft 56 and the second
shaft 58 is such that the surgeon can form the first shaft 56 and
the second shaft 58 by hand to a desired shape without undue
effort, and yet the first shaft 56 and the second shaft 58 retain
the set shape as the surgical clamp 10 is maneuvered to and held in
position at the treatment site. The first shaft 56 and the second
shaft 58 should also be sufficiently rigid such that the surgeon
can place the ablation segment 28 of the ablation tool 24 in
pressured contact with the tissue treatment site. That is, the
first shaft 56 and the second shaft 58 are sufficiently stiff to
enable the surgeon to press the ablation segment 28 against the
tissue to be treated without inducing a further deformation in the
shape of the first shaft 56 and the second shaft 58. The first
shaft 56 and the second shaft 58 may in some embodiments deflect
slightly, and yet have sufficient stiffness to transfer an
effective level of lateral force at their distal end.
[0050] In an embodiment, the first shaft 56 and the second shaft 58
are configured so that they are deformable in a single plane, where
the first shaft 56 and the second shaft 58 remain substantially
rigid in all other planes. For example, the first shaft 56 and the
second shaft 58 can be manipulated in a first plane "P1" from a
first shape to a second shape, wherein the first shaft 48 and the
second shaft 56 are sufficiently rigid to retain the second shape.
The first shaft 56 and the second shaft 58 also have sufficient
rigidity such that the first shaft 56 and the second shaft 58
cannot be manipulated in a second plane "P2" orthogonal to the
first plane, such that the first shaft 56 and the second shaft 58
are deformable only in the first plane "P1." As such the first
shaft 56 and the second shaft 58 are deformable in only one
plane.
[0051] In an exemplary embodiment, as shown in FIG. 10, the present
invention includes an ablation control system 64. The ablation
control system 64 includes a supply of cryogenic or cooling fluid
66 in communication with the surgical clamp 10. A fluid controller
68 is interposed or is in-line between the cryogenic fluid supply
66 and the surgical clamp 10 for regulating the flow of cryogenic
fluid 66 into the surgical clamp 10 in response to a controller
command. Controller commands can include programmed instructions,
sensor signals, and manual user input. For example, the fluid
controller 68 can be programmed or configured to increase and
decrease the pressure of the fluid by predetermined pressure
increments over predetermined time intervals.
[0052] In another exemplary embodiment, the fluid controller 68 can
be responsive to input from a user input device to permit flow of
the cryogenic fluid 66 into the surgical clamp 10. As also shown in
FIG. 1, one or more temperature sensors 40 in electrical
communication with the fluid controller 68 can be provided to
regulate or terminate the flow of cryogenic fluid 66 into the
surgical clamp 10 when a predetermined temperature at a selected
point or points on or within the ablation segment 28 is/are
obtained. For example a temperature sensor 40 can be placed at a
point proximate the ablation tool 24 distal end and other
temperature sensors 40 can be placed at spaced intervals between
the ablation tool 24 distal end and another point that is between
the distal end and the proximal end.
[0053] In another exemplary embodiment, one or more sensors 70,
such as a ECG leads, in electrical communication with the
controller can be provided to regulate or terminate the flow of
cryogenic fluid 66 into the ablation tool 24 depending on the
electrical activity in the tissue being treated. For example, the
first elongated jaw 20 and second elongated jaw 22 may provide
feedback that permits a user to gauge the completeness of the
ablation. Specifically, a lesion blocks electrical signals because
it is non-conductive scar tissue. The first elongated jaw 20 and
second elongated jaw 22 can be used to measure the ability of the
lesion to block an electrical signal. Referring to FIG. 1, an
electrode 70 is affixed one each to the distal ends of the first
elongated jaw 20 and second elongated jaw 22. In an exemplary use,
the electrodes 70 are used to verify electrical isolation of the
lesion created by the ablation tool 24. For example, the first
elongated jaw 20 and the second elongated jaw 22 are opened to
position an electrode 70 on each side of the lesion. An electrical
signal is transmitted from one electrode, through the lesion, to
the opposite electrode. The lesion is considered electrically
isolated if the receiving electrode is electrically silent to the
signal.
[0054] Alternatively, the electrical sensors can be replaced or
supplemented with pressure sensors. The pressure sensors can be
used to determine when the ablation segment is in physical contact
with the tissue to be treated.
[0055] The cryogenic fluid can be in a liquid or a gas state, or
combination thereof. An extremely low temperature can be achieved
within the medical device, and more particularly at the ablation
segment by cooling the fluid to a predetermined temperature prior
to its introduction into the medical device, by allowing a liquid
state cryogenic fluid to boil or vaporize, or by allowing a gas
state cryogenic fluid to expand. Exemplary liquids include
chlorodifluoromethane, polydimethylsiloxane, ethyl alcohol, HFC's
such as AZ-20 (a 50-50 mixture of difluoromethane &
pentafluoroethane sold by Allied Signal), and CFC's such as
DuPont's Freon. Exemplary gasses include argon, nitrous oxide, and
carbon dioxide.
[0056] Referring now to FIG. 11, there is shown a plan view of an
exemplary embodiment of a medical device constructed in accordance
with the principles of the present invention and designated
generally as surgical clamp 100. The surgical clamp 100 includes a
shaft assembly having opposing jaw assemblies 102, 104 with jaw
assembly 102 being fixed and jaw assembly 104 being movable between
a first position, wherein the jaw assemblies 102 and 104 are
disposed in a spaced apart relation relative to one another, to a
second position, wherein the jaw assemblies 102 and 104 cooperate
to grasp tissue therebetween.
[0057] The fixed jaw assembly 102 includes a fixed extension shaft
106 and an ablation tool 108 disposed on the distal end of the
fixed extension shaft 106, at an acute angle to the fixed extension
shaft 106. As shown in FIG. 12, the fixed extension shaft 106
defines a first lumen 110 having at least one input lumen 112
positioned therein, wherein the first lumen 110 and the at least
one input lumen 112 define a fluid path to the ablation tool 108,
wherein the at least one input lumen 112 is in fluid communication
with a cryogenic fluid source. The ablation tool 108 includes an
ablation segment 114 with a thermally-transmissive region 116,
defines a fluid path through the ablation tool 108 to the ablation
segment 112, wherein the fluid path is in fluid communication with
the first lumen 110 and the at least one input lumen 112.
[0058] The moveable jaw assembly 104 includes a movable extension
shaft 118 and a moveable jaw 120 disposed on the distal end of the
moveable extension shaft 118 at an acute angle to the moveable
extension shaft 118. The moveable extension shaft 118 is operably
connected to the fixed extension shaft 106, such that the moveable
extension shaft 118 slides along the fixed extension shaft 106 to
move the moveable jaw 120 between a first position, wherein the
moveable jaw 120 and the ablation tool 108 are disposed in a spaced
apart relation relative to one another, to a second position,
wherein the moveable jaw 120 and the ablation tool 108 cooperate to
grasp tissue therebetween.
[0059] In an exemplary embodiment, the ablation tool 108 and the
moveable jaw 120 are malleable, each having a shape-holding
deformability, that is, they have rigidity such that the ablation
tool 108 and the moveable jaw 120 each retain a first shape until
manipulated to a further shape with the application of moderate
pressure, and until reshaped. The ablation tool 108 and the
moveable jaw 120 retain their shape with sufficient rigidity to
manipulate the ablation segment 114 against the tissue, and push it
past intervening tissue to a desired position.
[0060] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the ablation tool 108 and the moveable jaw 120 for
positioning the active or distal portion of the ablation tool 104,
and may include successive bends or segments having more than one
curve, angle, deformation or other non-linear configuration. The
shape-retaining feature of the ablation tool 108 and the moveable
jaw 120 allows an operator to bend the ablation tool 108 and the
moveable jaw 120 to a shape or contour, for example around an organ
or tissue structure, and have an optimal configuration for
positioning and or orienting the active or distal region of the
ablation tool 108 and the moveable jaw 120 based upon the
particular anatomy of a patient and the location of the treatment
site.
[0061] Further, the stiffness of the ablation tool 108 and the
moveable jaw 120 is such that the surgeon can form the ablation
tool 108 and the moveable jaw 120 by hand to a desired shape
without undue effort, and yet the ablation tool 108 and the
moveable jaw 120 retain the set shape as the surgical clamp 100 is
maneuvered to and held in position at the treatment site. The
ablation tool 108 and the moveable jaw 120 should also be
sufficiently rigid such that the surgeon can place the ablation
tool 108 and the moveable jaw 120 in pressured contact with the
tissue treatment site. That is, the ablation tool 108 and the
moveable jaw 120 are sufficiently stiff to enable the surgeon to
press the ablation segment 114 against the tissue to be treated
without inducing a further deformation in the shape of the ablation
tool 108 and the moveable jaw 120. The ablation tool 108 and the
moveable jaw 120 may in some embodiments deflect slightly, and yet
has sufficient stiffness to transfer an effective level of lateral
force at its distal end.
[0062] In an exemplary embodiment, the ablation tool 108 and the
moveable jaw 120 are configured so that they are deformable in a
single plane, where the ablation tool 108 and the moveable jaw 120
remain substantially rigid in all other planes. For example, the
ablation tool 108 and the moveable jaw 120 can be manipulated in a
first plane "P1" from a first shape to a second shape, wherein the
ablation tool 108 and the moveable jaw 120 are sufficiently rigid
to retain the second shape. The ablation tool 108 and the moveable
jaw 120 also have sufficient rigidity such that the ablation tool
108 and the moveable jaw 120 cannot be manipulated in a second
plane "P2" orthogonal to the first plane, such that the ablation
tool 108 and the moveable jaw 120 are deformable only in the first
plane "P1." As such the ablation tool 108 and the moveable jaw 120
are deformable in only one plane.
[0063] In an exemplary embodiment, the fixed extension shaft 106
and the moveable extension shaft 118 are malleable, each have a
shape-holding deformability, that is, they have a rigidity such
that the fixed extension shaft 106 and the moveable extension shaft
118 shaft each retain a first shape until manipulated to a further
shape with the application of moderate pressure, and until
reshaped. The fixed extension shaft 106 and the moveable extension
shaft 118 retain their shape with sufficient rigidity to close the
ablation tool 108 and the moveable jaw 120 to grasp the tissue, and
push it past intervening tissue to a desired position. The
shape-retaining feature of the fixed extension shaft 106 and the
moveable extension shaft 118 allows an operator to bend the fixed
extension shaft 106 and the moveable extension shaft 118 to a shape
or contour, for example around an organ or tissue structure, and
have an optimal configuration for positioning and or orienting the
active or distal region of the surgical clamp 100 based upon the
particular anatomy of a patient and the location of the treatment
site.
[0064] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the fixed extension shaft 106 and the moveable extension
shaft 118 for positioning the active or distal portion of the
ablation tool 104, and may include successive bends or segments
having more than one curve, angle, deformation or other non-linear
configuration. The shape-retaining feature of the fixed extension
shaft 106 and the moveable extension shaft 118 allows an operator
to bend the fixed extension shaft 106 and the moveable extension
shaft 118 to a shape or contour, for example around an organ or
tissue structure, and have an optimal configuration for positioning
and or orienting the active or distal region of the fixed extension
shaft 106 and the moveable extension shaft 118 based upon the
particular anatomy of a patient and the location of the treatment
site.
[0065] Further, the stiffness of the fixed extension shaft 106 and
the moveable extension shaft 118 is such that the surgeon can form
the fixed extension shaft 106 and the moveable extension shaft 118
by hand to a desired shape without undue effort, and yet the fixed
extension shaft and the moveable extension shaft retains the set
shape as the surgical clamp 100 is maneuvered to and held in
position at the treatment site. The fixed extension shaft 106 and
the moveable extension shaft 118 should also be sufficiently rigid
such that the surgeon can place the ablation segment of the
ablation segment 114 in pressured contact with the tissue treatment
site. That is, the fixed extension shaft 106 and the moveable
extension shaft 118 are sufficiently stiff to enable the surgeon to
press the ablation segment 114 against the tissue to be treated
without inducing a further deformation in the shape of the fixed
extension shaft 106 and the moveable extension shaft 118. The fixed
extension shaft 106 and the moveable extension shaft 118 may in
some embodiments deflect slightly, and yet haves sufficient
stiffness to transfer an effective level of lateral force at its
distal end.
[0066] In an embodiment, the fixed extension shaft 106 and the
moveable extension shaft 118 are configured so that they are
deformable in a single plane, where the fixed extension shaft 106
and the moveable extension shaft 118 remain substantially rigid in
all other planes. For example, the fixed extension shaft 106 and
the moveable extension shaft 118 can be manipulated in a first
plane "P1" from a first shape to a second shape, wherein the fixed
extension shaft 106 and the moveable extension shaft 118 are
sufficiently rigid to retain the second shape. The fixed extension
shaft 106 and the moveable extension shaft 118 also have sufficient
rigidity such that the fixed extension shaft 106 and the moveable
extension shaft 118 cannot be manipulated in a second plane "P2"
orthogonal to the first plane, such that the fixed extension shaft
106 and the moveable extension shaft 118 are deformable only in the
first plane "P1." As such the fixed extension shaft 106 and the
moveable extension shaft 118 are deformable in only one plane.
[0067] Referring to FIG. 12, the moveable extension shaft 118
defines a first lumen 122 having at least one input lumen 124
positioned therein, the first lumen 122 and the at least one input
lumen 124 defining a fluid path to the moveable jaw 120, wherein
the at least one fluid input lumen 124 is in fluid communication
with a cryogenic fluid source. The moveable jaw 120 is an ablation
tool including an ablation segment 126 with a
thermally-transmissive region 128, and defining a fluid path
through the moveable jaw 120 to the ablation segment 126, wherein
the fluid path is in fluid communication with the first lumen 122
and the at least one input lumen 124.
[0068] The fixed jaw assembly 102 and the moveable jaw 104 assembly
are operably connected to a handle assembly 103. The handle
assembly 130 includes a fixed handle 132 attached to the fixed
extension shaft 106 and a lever arm 134 pivotally connected to the
fixed handle 132. The lever arm 134 is attached to the movable
extension shaft, 118 such that as the lever arm 134 pivots about
the fixed handle 132 from a start position, the moveable jaw 120
moves from a first position to a second position.
[0069] Referring now to FIG. 13, there is shown a plan view of an
exemplary embodiment of a medical device constructed in accordance
with the principles of the present invention and designated
generally as surgical clamp 200. The surgical clamp 200 includes a
jaw assembly having a first jaw 202, and a second jaw 204 in
opposing relation. The first jaw 202 and the second jaw 204 are
movable between a first position, wherein the first jaw 202 and the
second jaw 204 are disposed in a spaced apart relation relative to
one another, to a second position, wherein the first jaw 202 and
the second jaw 204 cooperate to grasp tissue therebetween. The
first jaw 202 and the second jaw 204 are connected to an elongated
shaft assembly 206, wherein a handle assembly 208 is connected to
the elongated shaft assembly 206 opposite the first jaw 202 and the
second jaw 204. At least one of the first jaw 202 and the second
jaw 204 includes an ablation tool. For example, the first jaw 202
includes an ablation tool 210 positioned on the inner surface 212
of the first jaw 202.
[0070] The elongated shaft assembly 206 defines a first lumen 212
having at least one input lumen 214 positioned therein. The first
lumen 212 and the at least one input lumen 214 define a fluid path
to the ablation tool 210, wherein the at least one input lumen 214
is in fluid communication with a cryogenic fluid source. The
ablation tool 201 includes an ablation segment 216 with a
thermally-transmissive region 218, and defines a fluid path through
the ablation tool to the ablation segment 218, wherein the fluid
path is in fluid communication with the first lumen 212 and the at
least one input lumen 214.
[0071] Additionally, the second jaw 204 can include an ablation
tool 220 having an ablation segment 222 with a
thermally-transmissive region 224, and defining a fluid path
through the ablation tool 220 to the ablation segment 222, wherein
the fluid path is in fluid communication with the first lumen 212
and the at least one input lumen 214.
[0072] In an exemplary embodiment, the first jaw 202 and the second
jaw 204 are malleable, each have a shape-holding deformability,
that is, they have rigidity such that the first jaw 202 and the
second jaw 204 each retain a first shape until manipulated to a
further shape with the application of moderate pressure, and until
reshaped. The first jaw 202 and the second jaw 204 retain their
shape with sufficient rigidity to manipulate the ablation segment
216 against tissue, and push it past intervening tissue to a
desired position.
[0073] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the first jaw 202 and the second jaw 204 for positioning
the active or distal portion of the ablation tool, and may include
successive bends or segments having more than one curve, angle,
deformation or other non-linear configuration. The shape-retaining
feature of the first jaw 202 and the second jaw 204 allows an
operator to bend the first jaw 202 and the second jaw 204 to a
shape or contour, for example around an organ or tissue structure,
and have an optimal configuration for positioning and or orienting
the active or distal region of the first jaw 202 and the second jaw
204 based upon the particular anatomy of a patient and the location
of the treatment site.
[0074] Further, the stiffness of the first jaw 202 and the second
jaw 204 is such that the surgeon can form the first jaw 202 and the
second jaw 204 by hand to a desired shape without undue effort, and
yet the first jaw 202 and the second jaw 204 retain the set shape
as the surgical clamp 200 is maneuvered to and held in position at
the treatment site. The first jaw 202 and the second jaw 204 should
also be sufficiently rigid such that the surgeon can place the
ablation segment of the ablation tool in pressured contact with the
tissue treatment site. That is, the first jaw 202 and the second
jaw 204 are sufficiently stiff to enable the surgeon to press the
ablation segment against the tissue to be treated without inducing
a further deformation in the shape of the first jaw 202 and the
second jaw 204. The first jaw 202 and the second jaw 204 may in
some embodiments deflect slightly, and yet have sufficient
stiffness to transfer an effective level of lateral force at its
distal end.
[0075] In an exemplary embodiment, the first jaw 202 and the second
jaw 204 are configured so that they are deformable in a single
plane, where the first jaw 202 and the second jaw 204 remain
substantially rigid in all other planes. For example, the first jaw
202 and the second jaw 204 can be manipulated in a first plane "P1"
from a first shape to a second shape, wherein the first jaw 202 and
the second jaw 204 are sufficiently rigid to retain the second
shape. The first jaw 202 and the second jaw 204 also have
sufficient rigidity such that the f first jaw 202 and the second
jaw 204 cannot be manipulated in a second plane "P2" orthogonal to
the first plane, such that the first jaw 202 and the second jaw 204
are deformable only in the first plane "P1." As such the first jaw
202 and the second jaw 204 are deformable in only one plane.
[0076] In an exemplary embodiment, the elongated shaft assembly 206
is malleable, having a shape-holding deformability, that is, it has
rigidity such that the elongated shaft assembly 206 retains a first
shape until manipulated to a further shape with the application of
moderate pressure, and until reshaped. The elongated shaft assembly
206 retains its shape with sufficient rigidity to close the first
jaw 202 and the second jaw 204 to grasp the tissue, and push it
past intervening tissue to a desired position.
[0077] It is understood that shape, as used herein, is to be
construed broadly to include any contour which is needed to
configure the surgical clamp 200 for positioning the active or
distal portion of the ablation tool, and may include successive
bends or segments having more than one curve, angle, deformation or
other non-linear configuration. The shape-retaining feature of the
elongated shaft assembly 206 allows an operator to bend the
elongated shaft assembly 206 to a shape or contour, for example
around an organ or tissue structure, and have an optimal
configuration for positioning and or orienting the active or distal
region of the surgical clamp 200 based upon the particular anatomy
of a patient and the location of the treatment site.
[0078] Further, the stiffness of the elongated shaft assembly 206
is such that the surgeon can form the elongated shaft assembly 206
by hand to a desired shape without undue effort, and yet the
elongated shaft assembly 206 retains the set shape as the surgical
clamp 200 is maneuvered to and held in position at the treatment
site. The elongated shaft assembly 206 should also be sufficiently
rigid such that the surgeon can place the ablation segment of the
ablation tool in pressured contact with the tissue treatment site.
That is, the elongated shaft assembly 206 is sufficiently stiff to
enable the surgeon to press the ablation segment against the tissue
to be treated without inducing a further deformation in the shape
of the elongated shaft assembly 206. The elongated shaft assembly
206 may in some embodiments deflect slightly, and yet has
sufficient stiffness to transfer an effective level of lateral
force at its distal end.
[0079] In an embodiment, the elongated shaft assembly 206 is
configured so that it is deformable in a single plane, where the
elongated shaft assembly 206 remains substantially rigid in all
other planes. For example, the elongated shaft assembly 206 can be
manipulated in a first plane "P1" from a first shape to a second
shape, wherein the elongated shaft assembly 206 is sufficiently
rigid to retain the second shape. The elongated shaft assembly 206
also has sufficient rigidity such that the elongated shaft assembly
206 cannot be manipulated in a second plane "P2" orthogonal to the
first plane, such that the elongated shaft assembly 206 is
deformable only in the first plane "P1." As such the elongated
shaft assembly 206 are deformable in only one plane.
[0080] Referring now to FIG. 14, an exemplary tool is shown having
a handle portion 208 from which extends a probe 210 having a
cooling segment 212. As will all disclosed embodiments, the cooing
segment 212 can be provided with a smooth or textured tissue
engaging surface 214. In FIG. 14, the tissue-engaging surface 214
is textures to have "teeth." A second element 216 is movable
relative to the probe to define a tissue capture zone 218. A distal
region 220 of the second element 216 can have a complementary shape
to the cooling segment 212 and be smooth (as shown) or textured. As
the probe 210 and the second element 216 are moved axially with
respect to each other, the tissue capture zone 218 increases or
decreases in size. In the illustrated embodiment, the second
element 216 is secured to the probe 210 and is axially slidable
with respect thereto by axially moving a proximal portion 222 of
the second element.
[0081] With respect to FIG. 15, a different actuating mechanism is
shown in an exemplary tool having a handle portion 224 from which
extends a probe 226 having a cooling segment 228. A second element
230 is movable relative to the probe 226 to define a tissue capture
zone 232. As the probe 226 and the second element 230 are moved
axially with respect to each other, the tissue capture zone 232
increases or decreases in size. In the illustrated embodiment, the
second element 230 is secured to the probe 226 and is axially
slidable with respect thereto by axially moving a proximal portion
234 of the second element by pulling a handle, lever, or trigger
236 that is engaged with the proximal portion of the second
element. A spring 238 or other bias means can be provided to either
urge the second element 230 in either the distal or proximal
direction.
[0082] FIG. 16 shows yet another configuration wherein a cooling
element 240 is juxtaposed a second element 242 and wherein the
elements are biased apart. A sleeve or handle element is slidable
with respect to the elements so that as it is moved distally it
urges the elements together.
[0083] Referring to FIG. 17 another clamping tool is disclosed that
includes a handle portion 246 having an actuator 248 that pivots or
rotates fore and aft. The actuator 248 is coupled to a pull or push
wire 250 that is secured to a distal portion of an elongate shaft
structure 252 to cause the shaft structure to clamp tissue 254. As
shown, the shaft structure 252 includes an insulating distal
portion 256, a bellows or coil portion 258 that provides a clamping
effect, and a cooling segment 260. A coolant injection tube 262
introduces coolant into the cooling segment 260. The elongate shaft
structure 252 can be transitioned from a substantially linear
configuration to the configuration shown or it can be preformed to
substantially the configuration shown and actuated to tighten the
space between the insulating distal portion 256 and the cooling
segment 260 which can further be insulated on its outward face. As
shown, the wire 250 is secured at its distal end to a shim 264.
[0084] FIG. 18 illustrates yet another configuration of a tool
including a handle 266, actuator 268, insulated shaft 270, first
jaw 272, and second jaw 274, wherein manipulation of the actuator
268 causes the jaws to open and close or move relative to each
other. The figure depicts the jaws in both the open and clamped
state. Coolant can flow to and/or through one or both jaws and both
jaws can be insulated except at the point where they meet. One or
both jaws can be provided with temperature and/or impedance
measurement devices to monitor and evaluate lesion formation and
characteristics. In an embodiment a temperature sensor is
associated with a jaw that does not have a cooling element. The
jaws are clamped together with tissue therebetween. The
transmurality of a lesion could be ascertained when the temperature
sensor detects a temperature of -40 degrees Centigrade for two
minutes. Of course time and temperature may be different for
different types, conditions and thickness of tissue.
[0085] FIGS. 19 and 20 show additional details of the first jaw 272
and the second jaw 274, respectively; wherein the first jaw made of
an insulating material defines a recess 276 shaped to receive an
elongate cooling element 278 affixed to insulating material.
[0086] Although the device of FIG. 18 may include two jaws, one jaw
can be removable so that a single jaw with a cooling segment is
provided. Thus, the device can be convertible from a clamping tool
to a "wand" type device for use in procedures not requiring
clamping.
[0087] FIG. 21 illustrates yet another configuration for the
clamping device. Here, cooling segment 260 can be deflected from
its normal position to a variety of deflection positions via use of
actuator 248 (not shown). Cooling segment 260 may be deflected to
an angle of choice my manipulation of the actuator. Coolant can
then be introduced to cooling segment 260 via the internal
injection tube (not shown).
[0088] FIG. 22 illustrated yet another configuration for a clamping
device wherein a cooling element 280 is slidably disposed within an
insulating sheath 282. The distal portion of the cooling element
281 and the distal portion of the sheath 283 are angled with
respect to their proximal portion so that extension and retraction
of the cooling element with respect to the sheath opens and closes
a tissue-clamping zone 284.
[0089] Although generally shown as a cryogenic ablation tool, it is
understood that in other embodiments the ablation segment applies
other types of energy or combination of energies, to the tissue to
be treated, including, but not limited to, cryogenic energy, radio
frequency (RF) energy, microwave energy, ultrasound energy, laser
energy, and contact heating energy. It is further understood that
other devices can be coupled to the guide distal end, for example,
cameras, video devices, probes and other components can be affixed
to the guide for various applications For example, pacing/sensing
electrodes can be affixed to points on ton the slotted segment.
[0090] The medical device of the present invention is well suited
for treating tissue in a variety of locations in the body during
invasive surgical procedures. Illustrative applications include
open thoracic and peritoneal surgery as well as endoscopic
procedures, e.g., treating tissue located at or near the heart,
intestines, uterus, and other regions for which surgical or
endoscope assisted surgical access and topical tissue treatment, or
cauterization or ablation is appropriate, as well as ophthalmic
surgery, and tumor ablation and various applications preparatory to
further surgical steps.
[0091] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. In addition, unless mention was
made above to the contrary, it should be noted that all of the
accompanying drawings are not to scale. A variety of modifications
and variations are possible in light of the above teachings without
departing from the scope and spirit of the invention, which is
limited only by the following claims.
* * * * *