U.S. patent application number 15/880958 was filed with the patent office on 2018-05-31 for medical ablation system and method of making.
The applicant listed for this patent is Hermes Innovations LLC. Invention is credited to Aaron GERMAIN, Benedek ORCZY-TIMKO, John SHADDUCK, Csaba TRUCKAI.
Application Number | 20180147003 15/880958 |
Document ID | / |
Family ID | 51654970 |
Filed Date | 2018-05-31 |
United States Patent
Application |
20180147003 |
Kind Code |
A1 |
SHADDUCK; John ; et
al. |
May 31, 2018 |
MEDICAL ABLATION SYSTEM AND METHOD OF MAKING
Abstract
An electrosurgical device comprises an elongated shaft having an
axis with an interior channel extending along the axis to an
opening in a distal end of the shaft. The channel is configured to
be coupled to a negative pressure source, and an electrode with a
conductive, usually hook-shaped, distal portion is coupled to the
shaft and moveable between a first position in which a distal tip
of the electrode is disposed proximate to a periphery of the
opening of and a second position in which the distal electrode tip
is exposed and spaced apart from the opening.
Inventors: |
SHADDUCK; John; (Menlo Park,
CA) ; ORCZY-TIMKO; Benedek; (Budapest, HU) ;
GERMAIN; Aaron; (San Jose, CA) ; TRUCKAI; Csaba;
(Saratoga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hermes Innovations LLC |
Cupertino |
CA |
US |
|
|
Family ID: |
51654970 |
Appl. No.: |
15/880958 |
Filed: |
January 26, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13857068 |
Apr 4, 2013 |
9901394 |
|
|
15880958 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2018/00875
20130101; A61B 2218/007 20130101; A61B 2018/00202 20130101; A61B
2018/00791 20130101; A61B 2018/1422 20130101; A61B 2018/1475
20130101; A61B 2218/002 20130101; A61B 18/148 20130101 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. An electrosurgical device, comprising: an elongated shaft having
a longitudinal axis with an interior channel extending along the
axis to an opening in a distal surface of the shaft, said channel
being configured to be coupled to a negative pressure source,
wherein the distal surface is sloped relative to the longitudinal
axis; an electrode with a hook-shaped distal tip, said electrode
being moveable between a first position in which the distal tip is
positioned within the opening in the distal surface and a second
position in which the distal tip is spaced distally from a
distal-most edge of the opening, wherein the electrode is mounted
to axially translate between the first and second positions; and a
rotator coupled to the electrode which causes the electrode to
rotate as it is being axially translated.
2. The electrosurgical device of claim 1, wherein the electrode is
mounted to axially translate and/or rotate about the axis between
the first and second positions.
3. The electrosurgical device of claim 1, further comprising a
valve in the interior channel for controlling fluid flow
therethrough.
4. The electrosurgical device of claim 1, wherein an exterior of
the shaft comprises a second electrode.
5. The electrosurgical device of claim 1, wherein a notch is formed
in a periphery of the opening and the notch is configured to
receive the hook-shaped distal tip of electrode when the electrode
is in the first position.
6. The electrosurgical device of claim 1, further comprising a
temperature sensor near a distal end of the shaft.
7. The electrosurgical device of claim 1, further comprising
impedance sensing electrodes near a distal end of the shaft.
8. The electrosurgical device of claim 1, further comprising a
temperature-response current limiting element in series with the
electrode.
9. An electrosurgical device, comprising: an electrically
non-conductive elongated shaft extending along a longitudinal axis;
an electrically conductive distal housing coupled to a distal end
of the elongated shaft and having an opening in a distal surface
thereof; a moveable hook-shaped electrode having a conductive
portion with a proximal end and a distal end, wherein the distal
end of the conductive portion is disposed within the opening of the
housing when the electrode is in a non-extended position and the
distal end extends distally beyond the periphery when the electrode
is in an extended position, wherein the electrode is mounted to
axially translate between the first and second positions, wherein
the hook portion the electrode is turned so that a back of the hook
extends outwardly from the opening when the electrode is in the
first position; and a rotator coupled to the electrode which causes
the electrode to rotate as it is being axially translated.
10. The electrosurgical device of claim 9, wherein the electrode is
mounted to rotate about the axis between the first and second
positions.
11. The electrosurgical device of claim 9, wherein the electrode is
mounted to axially translate and/or rotate about the axis between
the first and second positions.
12. The electrosurgical device of claim 9, further comprising a
valve in the interior channel for controlling fluid flow
therethrough.
13. The electrosurgical device of claim 9, wherein an exterior of
the shaft comprises a second electrode.
14. The electrosurgical device of claim 9, wherein a notch is
formed in a periphery of the opening and the notch is configured to
receive a distal tip of the hook-shaped of electrode when the
electrode is in the first position and to receive a back portion of
the electrode when the electrode is in its second position.
15. The electrosurgical device of claim 9, further comprising a
temperature sensor near a distal end of the shaft.
16. The electrosurgical device of claim 9, further comprising
impedance sensing electrodes near a distal end of the shaft.
17. The electrosurgical device of claim 9, further comprising a
temperature-response current limiting element in series with the
electrode.
18. An electrosurgical device, comprising: an elongated member
having a central axis with an interior channel and a passage
extending axially in the member, said interior channel extending to
an opening in a distal surface of the member and being configured
to be coupled to a negative pressure source, wherein the distal
surface is sloped relative to the central axis; an electrode having
a shaft portion with a centerline and a distal spine portion with a
length radially offset from said centerline, said distal spine
portion extending across an axial length of the opening and said
shaft portion rotatable within the passage to move the offset
length of the spine portion in and out of the opening; and a
rotator coupled to the electrode shaft which causes the electrode
to rotate.
19. The electrosurgical device of claim 18, wherein the electrode
shaft is mounted to axially translate in the passage.
20. The electrosurgical device of claim 18, further comprising a
actuator for controlling fluid flow through the interior
channel.
21. The electrosurgical device of claim 18, wherein an exterior of
the shaft comprises a second electrode.
22. The electrosurgical device of claim 18, wherein a notch is
formed in a periphery of the opening and the notch is configured to
receive a distal tip of the electrode.
23. The electrosurgical device of claim 18, wherein the passage
comprises a bore in the elongated member.
24. An electrosurgical device, comprising: an elongated member
having a central axis with an interior channel extending to an
opening in a distal surface of the member and being configured to
be coupled to a negative pressure source, wherein the distal
surface is sloped relative to the central axis; and an electrode
having a shaft portion with a centerline and a distal spine portion
with a length radially offset from said centerline, said shaft
portion rotatable within the interior channel in the elongate
member wherein the offset length of the spine portion can be moved
laterally back and forth across the opening; wherein the
hook-shaped distal tip the electrode is configured to be turned so
that a back of the hook-shaped distal tip extends laterally beyond
the distal surface when the electrode is in the first position.
25. The electrosurgical device of claim 1, wherein a notch is
formed in a periphery of the opening and the notch is configured to
receive a distal tip of the electrode and to allow the offset
length of the spine portion to be moved laterally back and forth
across the opening
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/857,068 (Attorney Docket No.
37644-708.201), filed Apr. 4, 2013, now U.S. Pat. No. ______, the
entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to medical instruments and systems
for applying energy to tissue, and more particularly relates to an
electrosurgical probe adapted for ablating, cutting and treating
tissue in an endoscopic procedure.
BACKGROUND OF THE INVENTION
[0003] Various types of medical instruments utilizing
radiofrequency (RF) energy, laser energy and the like have been
developed for delivering thermal energy to tissue, for example to
ablate tissue and to cut tissue. Arthroscopic and other endoscopic
electrosurgical tools often comprise treatment electrodes of
different configurations where the tools may optionally be combined
with irrigation and/or aspiration tools for performing particular
minimally invasive procedures. Often the nature of the electrode
limits use of a particular tool, and tools must be exchanged during
a procedure to perform different tasks. For these reasons, it would
be desirable to provide new and different designs for
electrosurgical tools that allow the tools to be re-configured
during a procedure to perform different tasks. At least some of
these objectives will be met by the inventions described below.
SUMMARY OF THE INVENTION
[0004] In a first aspect of the present invention, an
electrosurgical device comprises an elongated shaft having an axis
with an interior channel extending along the axis to an opening in
a distal end of the shaft. The channel is configured to be coupled
to a negative pressure source, and an electrode with a hook-shaped
distal portion is coupled to the shaft and moveable between a first
position in which a distal tip of the electrode is disposed at a
periphery of the opening and a second position in which the distal
tip extends distally beyond the opening. With the distal portion of
the electrode in the first position, the tool is particularly
useful for surface ablation of tissue such as cartilage. With the
distal portion of the electrode in the second position, the tool is
particularly useful for cutting tissue structures. In one
application, the hook-shaped electrode can be used in a lateral
release, which is an arthroscopic procedure for releasing tight
capsular structures, e.g., the lateral retinaculum, on the outer or
lateral aspect of the kneecap. Such a procedure is performed due to
pain related to the kneecap being pulled over to the outer
(lateral) side and not being able to move properly in a groove of
the femur bone as the knee bends and straightens. In a second
aspect of the present invention, an electrosurgical device
comprises an elongated shaft extending along an axis with an
interior channel extending to an opening with a periphery in a
working end. The channel is adapted to be coupled to a negative
pressure source. A moveable electrode having a conductive portion
with a proximal end and a distal end is coupled to the shaft so
that the distal end of the conductive portion is located proximate
the periphery of the opening when the electrode is in a proximally
retracted position and the distal end of the electrode extends
distally beyond the periphery when the electrode is in a distally
extended position. With the conductive portion of the electrode in
the first position, the tool is particularly useful for surface
ablation of tissue and cautery. With the conductive portion of the
electrode in the second position, the tool is particularly useful
for capturing and cutting tissue structures.
[0005] Usually, in both aspects, the electrode of the
electrosurgical device is mounted to axially translate between the
first and second positions. Optionally, the electrode is mounted to
rotate about the axis between the first and second positions. In
another variation, the electrode of the electrosurgical device of
is mounted to axially translate and/or rotate about the axis
between the first and second positions.
[0006] In specific embodiments, the electrosurgical device may
further comprise a valve in the interior channel for controlling
fluid flow therethrough. An exterior of the electrosurgical shaft
may comprise a second electrode. The electrosurgical device may
further comprise a rotator coupled to the electrode, where the
rotator causes the electrode to rotate as it is being axially
translated. The opening of the electrosurgical device may define a
plane which is angled relative to the axis of the shaft, and the
hook-shaped portion of the electrode may be turned so that a back
of the hook portion extends outwardly above the plane when the
electrode is in the first position. The electrosurgical device may
still further comprise a temperature sensor and/or impedance
sensing electrodes near a distal end of the shaft. Alternatively,
or in addition to the sensors, the electrosurgical device may
further comprise a temperature-responsive current limiting element
in series with the electrode in order to inhibit or prevent
overheating of distention fluid in a treatment site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1A is side view of an electrosurgical probe
corresponding to the invention that includes an elongated shaft
extending along an axis to a working end with a re-configurable
electrode.
[0008] FIGS. 1B and 1C illustrate various embodiments of the
re-configurable electrode of FIG. 1.
[0009] FIG. 2A is a perspective view of the working end of FIG. 1
with the moveable electrode in a first position.
[0010] FIG. 2B is a perspective view of the working end of FIG. 1
with the moveable electrode in a second position.
[0011] FIG. 2C is a perspective view of the working end of FIG. 1
with the moveable electrode in a third position.
[0012] FIG. 3 is an exploded view of the components of the working
end of FIG. 1.
[0013] FIG. 4 is a perspective view of a working end of an
electrosurgical device similar to that of FIG. 1 with temperature
sensor for measuring the temperature of distention fluid in a joint
and a controller that can signal an LED to illuminate as a high
temperature alert to the physician.
[0014] FIG. 5 is a perspective view of the working end of an
electrosurgical device similar to that of FIG. 1 with a second
electrode arrangement configured to measure impedance in distention
fluid in a joint in order to determine the temperature of the
fluid.
[0015] FIG. 6A is a cut-away perspective view of the working end of
an ablation device similar to that of FIG. 1 with a PTCR (positive
temperature coefficient of resistance) material in the return
electrode assembly which can sense distention fluid temperature to
de-activate the electrical path from the return electrode to the RF
source.
[0016] FIG. 6B is another cut-away view of the working end of FIG.
7A showing an inner sleeve that carries the working end
assembly.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring now to the drawings and the reference numbers
marked thereon, FIGS. 1A and 2A-2C illustrate one embodiment of
electrosurgical probe 100 that includes handle portion 104 and
elongated shaft 105 that extends about longitudinal axis 108. FIG.
1 is a schematic view of the probe in which the shaft 105 consists
of an assembly further described below having a diameter ranging
from about 3.0 mm to 6.0 mm and any suitable length for arthroscopy
or another endoscopic procedure. The working end 110 carries an
electrode arrangement including a moveable first polarity or active
electrode 120 and a second polarity or return electrode 122
operatively coupled to an RF source 125 and controller 130. As can
be seen in FIG. 1A, the shaft 105 has a fluid extraction channel
132 in communication with a negative pressure source 135 that can
be a wall suction source in an operating room or a pump system in
controller 130. In FIG. 2A, it can be seen that fluid channel 132
extends distally to an opening 140 in the working end 110 which is
proximate the electrode 120.
[0018] In one embodiment in FIGS. 1A and 2A-2C, the first polarity
electrode 120 has an elongated medial portion 142 that extends
through a passageway 144 (or channel 132) in shaft 105 to an
acutator mechanism 146 in the handle 104. The electrode 120
terminates in an electrically conductive portion free from
insulation, with the conductive portion typically being hook-shaped
as described in more detail below. In FIG. 1A, it can be seen that
actuator 146 is adapted to slide from position A to position B to
position C to thereby move the electrode 120 from the non-extended
position of FIG. 2A to the extended position of FIG. 2B and then to
the extended and rotated position of FIG. 2C. Any suitable actuator
mechanism known in the art can be used to move the electrode 120
axially and rotationally, and in one variation shown in FIG. 1, a
barrel 148 with a spiral groove 152 therein can translate linear
motion of the actuator mechanism 146 to rotational motion. In
another embodiment, the actuator 146 can be fixed to the proximal
end 149 of electrode 120 and adapted to move both axially and
rotationally to move the electrode 120 between the various
positions shown in FIGS. 2A-2C. The moveable actuator 146 can be
configured with detents that engages a portion of handle 104 to
releaseably maintain the electrode 120 in one of the selected
positions of FIGS. 2A-2C.
[0019] Referring again to FIG. 1A, a second actuator 160 in handle
104 is adapted to modulate outflows in fluid extraction channel
132. FIG. 1A shows the extraction channel portion 132' in handle
104 extends to a quick-connect 162 on handle 104 to which an
outflow tubing 164 is coupled that extends to the negative pressure
source 135. The actuator 160 can operate any type of suitable valve
165 to control the amount of outflow from a treatment site, such as
a knee or shoulder. In such an arthroscopic procedure, the fluid
inflows are provided through an independent inflow path which can
be through a fluid channel in an endoscope or through another
independent cannula accessing the treatment site.
[0020] Still referring to FIG. 1A, an electrical cable 166 extends
from RF source 125 and controller 130 to the handle 104 with leads
in the handle coupled to the first and second electrodes. The
system can include a footswitch 168 operatively connected to
controller 130 for ON-OFF actuation of RF energy to the electrode
arrangement. In another variation, the switch for actuation of RF
energy can be positioned in the probe handle 104. The RF source and
controller can provide for various power setting as is known in the
art, and can use any radiofrequency known in the art for creating a
plasma about the electrode 120 for cutting tissue.
[0021] Referring to FIGS. 1B and 1C, the active electrode 120 which
includes the conductive portion of the electrode extending distally
from the medial portion 142 is typically hook-shaped and may have
an a square or trapezoidal profile, as shown in FIG. 1B, or may
have a curved or arcuate profile, as shown in FIG. 1C. The hook
portion will typically have a length L in the range from 3 mm to 10
mm and a depth X in the range from 2 mm to 6 mm. The hook-shaped
active electrode will also include a back or a spine region 121
that remains exposed over a plane defined by the opening 140 when
the electrode is proximally retracted and a distal tip 190 of the
electrode engages or lies proximate to the periphery or perimeter
192 surrounding the opening 140. The distal tip 190 may terminate
at, above, or below a centerline 123 of the electrode, as shown in
full line and broken lines in FIGS. 1B and 1C.
[0022] The exploded view of a portion of the probe of FIG. 3
illustrates the components and assembly of the working end 110. In
one variation shown in FIG. 3, the shaft 105 includes an elongate
metal sleeve 170 (e.g., stainless steel) that is coupled to handle
104 which provides structural strength to the shaft 105 and further
serves an electrical conductor to function as, or connect to, the
return electrode 122. The proximal end of sleeve 170 is fixed to
handle 104 with an electrical connector (not shown) within the
handle coupling the sleeve 170 to cable 166 and a pole of the RF
source 125 (see FIG. 1).
[0023] In FIG. 3, it can be seen that the distal end 174 of sleeve
170 couples with non-conductive ceramic body 175, which can be
zirconium oxide, aluminum oxide or a similar material. In one
variation, a reduced diameter proximal end 177 of ceramic body 175
can mate with bore 180 in sleeve 170. FIG. 3 further shows a metal
distal body or housing 185 that is configured to slide over ceramic
body 175 and then is welded to the distal end 174 of sleeve 170 to
thus provide the assembled working end of FIG. 2A-2C. The metal
distal body or housing 185 then functions as second polarity
electrode 122 as can be understood from FIG. 2A-2C. In one
variation, a thin-wall dielectric material 186 such a heat shrink
material (PFA, FEP or the like) covers the sleeve 170 proximally
from the distal metal housing 185 to the handle 104.
[0024] In FIG. 3, it can be seen that first polarity electrode 120
and more particularly its medial portion 142 extends through a bore
189 in ceramic body 175. The elongated portion of electrode 120 is
covered by a heat-shrink insulator 187 of a material such as FEP or
PFA. The distal portion of electrode 120 is configured with bends
or curvature to provide a hook-shaped electrode with an outermost
electrode surface 188 that is approximately within an envelope
defined by the cylindrical periphery of shaft 105 in the position
of FIG. 2A. This configuration permits the physician to paint the
outermost surface 188 of electrode 120 across a tissue surface to
perform an electrosurgical surface ablation of such tissue.
Referring to FIGS. 2A and 3, the distal tip 190 of electrode 120 in
the position shown in FIG. 2A is configured to be disposed within
or adjacent a periphery or perimeter 192 of opening 140 in the
working end. More particularly, distal tip 190 in the position of
FIG. 2A is configured to rest in a notch 194 in ceramic body 175.
When the distal tip 190 is in the position of FIG. 2A, the tip 190
is distance D of at least 0.010'' (see FIG. 2A) from the closest
edge of window 195 of the metal body 185. As can be seen in FIGS.
2A-2C, the window edge 195 of metal body 185 is configured to have
notch 200 that is larger than the notch 194 in ceramic body 175 to
insure that the first and second electrodes, 120 and 122, are not
in close proximity in the electrode position shown in FIG. 2A.
[0025] As can be seen in FIGS. 2B and 2C, the hook-shaped distal
portion of electrode 120 can be extended axially and optionally
rotationally to orient the distal tip 190 and terminal hook portion
196 for electrosurgical cutting of tissue as is known in the art
using hook electrode tools. Thus, the electrode 120 is
re-configurable to perform electrosurgical surface ablation
treatments or electrosurgical cutting treatments. The electrode 120
can be a wire formed of tungsten, stainless steel or any other
suitable material having a round, oval or polygonal cross
section.
[0026] Referring again to FIG. 3, in one variation, it can be seen
that the bore 180 in sleeve 170 is lined with a thin-wall
dielectric material 198 such a Teflon.RTM., Nylon, PFA, FEP,
polyethylene or the like which prevents the inner wall of sleeve
170 from functioning as an electrode. In another aspect of the
invention, FIG. 4 illustrates a temperature sensing and signaling
system that is carried within the working end 220 of a probe
similar to that of FIGS. 1-3. Temperature sensing of distention
fluid in an arthroscopic procedure is important as the fluid can be
heated during any electrosurgical ablation procedure. If the
distention fluid is at an elevated temperature for an excessive
time period, tissue throughout the joint can be damaged. In FIG. 4,
it can be seen a temperature sensor 225 is provided in a surface of
the working end which can comprise any form of thermocouple,
thermistor or other type of sensor. The sensor 225 is configured to
send temperature signals to the controller 130 which can signal the
operator of elevated temperature and/or terminate energy delivery
from the RF source to the working end 220. In one variation shown
in FIG. 5, the controller 130 can signal the physician of a high
temperature signal from sensor 225 by illuminating LED lights 240a
and 240b coupled to electrical source 245 on either side of the
working end 220. In such an embodiment, the controller 130 may have
algorithms for blinking the LEDs at increasing rates that increase
with temperature of the distention fluid. Any combination of
visual, aural and tactile signals may be used to alert the
physician of elevated temperatures in the distention fluid. In
another embodiment (not shown), the temperature sensor 225 can
actuate at least one light source in the controller that is coupled
to optical fibers to carry light to light emitters in the working
end. In another variation, a plurality of different wavelength
light sources in the controller can send different wavelengths to
the emitter(s) in the working end to indicate different
temperatures of the distention fluid.
[0027] FIG. 5 illustrates another temperature sensing system that
can be carried by the working end 220 as in FIG. 5. In FIG. 5,
spaced apart first and second electrodes, 252a and 252b are
provided in insulated surface 254 of the probe shaft 255. The
electrodes 252a and 252b are coupled to an electrical source 255
and controller 130 which is configured to measure an electrical
parameter of the distention fluid, for example impedance or
capacitance of a saline distention fluid. The measured electrical
parameter then can be compared to known values of saline at various
temperatures in a look-up table to determine fluid temperature. The
calculated temperature then can actuate any visual, aural or
tactile signal to alert the physician of elevated temperatures in
the saline.
[0028] FIGS. 6A-6B illustrate another system embodiment that
integrates a temperature sensing mechanism with the return
electrode to control energy delivery to tissue. As can be seen in
FIG. 6A, the working 260 of a probe is similar to that of FIGS.
1-3. However, the distal metal housing 265 does not function as a
return electrode. The metal housing 265 is not welded to elongated
sleeve 270 which is electrically coupled to RF source 125 and
controller 130. Rather, an independent return electrode sleeve 275
with a short length is positioned proximally from the distal metal
housing 265. In one variation, an insulative ceramic collar 277
separates the distal metal housing 265 from the return electrode
sleeve 275. The temperature-sensing component of the working end
260 comprises a polymer PTCR (positive temperature coefficient of
resistance) sleeve 280 forms an intermediate electrical connector
between the return electrode sleeve 275 and sleeve 270 which is
electrically coupled to RF source 125 (see FIG. 1). The return
electrode sleeve 275, the PTCR sleeve 280 and sleeve 270 can be
mounted over insulated support sleeve 285 shown in FIG. 6B. The
PTCR material of sleeve 280 allows conduction of RF current
therethrough within a selected low temperature range, but can
prevent current flow through the sleeve at a selected elevated
temperature. As can be seen in FIGS. 6A-6B, the proximal end 282 of
the return electrode 275, the PTCR sleeve 280 and the elongated
sleeve 270 is covered with a thin-wall insulator 288 to thus
prevent conductive saline contact with this portion of the probe.
As can be understood in FIGS. 6A-6B, the thin-wall insulator 288
allows heat transfer from the distention fluid through the
insulator 288 to the PTCR sleeve 280 which then can cause the PTCR
sleeve to become non-conductive to terminate current flow from the
return electrode 275 to the RF source 125. By this means, the PTCR
mechanism can terminate RF energy delivery in response to elevated
temperatures in the distention fluid. The PTCR material can be
selected to have a any suitable switching temperature, for example
any temperature between about 40.degree. C. and 45.degree. C.
Suitable polymer PTCR materials can be fabricated by Bourns, Inc.
3910 Freedom Circle, Ste. 102, Santa Clara, Calif. 95954.
[0029] Although particular embodiments of the present invention
have been described above in detail, it will be understood that
this description is merely for purposes of illustration and the
above description of the invention is not exhaustive. Specific
features of the invention are shown in some drawings and not in
others, and this is for convenience only and any feature may be
combined with another in accordance with the invention. A number of
variations and alternatives will be apparent to one having ordinary
skills in the art. Such alternatives and variations are intended to
be included within the scope of the claims. Particular features
that are presented in dependent claims can be combined and fall
within the scope of the invention. The invention also encompasses
embodiments as if dependent claims were alternatively written in a
multiple dependent claim format with reference to other independent
claims.
* * * * *