U.S. patent application number 14/532337 was filed with the patent office on 2015-02-26 for fluid cooled choke dielectric and coaxial cable dielectric.
The applicant listed for this patent is COVIDIEN LP. Invention is credited to Kenlyn S. Bonn.
Application Number | 20150057651 14/532337 |
Document ID | / |
Family ID | 43781154 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150057651 |
Kind Code |
A1 |
Bonn; Kenlyn S. |
February 26, 2015 |
FLUID COOLED CHOKE DIELECTRIC AND COAXIAL CABLE DIELECTRIC
Abstract
The microwave antenna assembly includes a feedline electrically
connected to an elongated shaft by a choke electrical connector.
The feedline includes an inner conductor, an outer conductor, an
elongated shaft and a choke electrical connector. The inner
conductor is disposed in coaxial arrangement with the inner
conductor and forms a dielectric supply lumen therebetween. The
elongated shaft at least partially surrounding the feedline and
form a dielectric return lumen therebetween. The choke electrical
connector surrounds at least a portion of the feedline and
electrically connects the feedline outer conductor to the elongated
shaft. A low-loss dielectric fluid is supplied between the inner
conductor and the outer conductor of the feedline and forms a
dielectric barrier therebetween. The low-loss dielectric fluid also
forms a dielectric barrier between the outer conductor of the
feedline and the elongated shaft and the choke electrical connector
forms a plurality of apertures extending therethrough, the
apertures forming at least a portion of the dielectric return
lumen.
Inventors: |
Bonn; Kenlyn S.; (Lakewood,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COVIDIEN LP |
Mansfield |
MA |
US |
|
|
Family ID: |
43781154 |
Appl. No.: |
14/532337 |
Filed: |
November 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12568777 |
Sep 29, 2009 |
8876814 |
|
|
14532337 |
|
|
|
|
Current U.S.
Class: |
606/33 |
Current CPC
Class: |
A61B 2018/00023
20130101; H01Q 1/27 20130101; A61B 2018/00791 20130101; A61B
2018/00875 20130101; A61B 2018/00577 20130101; A61B 2018/00166
20130101; A61B 18/18 20130101; H01Q 9/16 20130101; A61B 2018/1892
20130101; A61B 18/1815 20130101 |
Class at
Publication: |
606/33 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1-17. (canceled)
18. A microwave ablation system, comprising: a power generating
source configured to supply microwave energy to a microwave antenna
assembly, the microwave antenna assembly including: a feedline
having a length, the feedline including: an inner conductor; an
outer conductor in a coaxial arrangement with the inner conductor,
the inner conductor and outer conductor forming a supply lumen
therebetween; an elongated shaft at least partially surrounding the
feedline, the elongated shaft and the feedline forming a return
lumen therebetween in fluid communication with the supply lumen;
and a choke including a substantially cylindrical inner surface
surrounding at least a portion of the length of the feedline and
configured to electrically connect the outer conductor to the
elongated shaft; and a fluid supply configured to supply a low-loss
dielectric fluid to the supply lumen, wherein a first dielectric
barrier is formed between the inner conductor and the outer
conductor, and to receive the low-loss dielectric fluid from the
return lumen, wherein a second dielectric barrier is formed between
the outer conductor and the elongated shaft.
19. The system of claim 18, wherein the fluid supply includes a
fluid analyzer configured to determine at least one characteristic
of the low-loss dielectric fluid.
20. The system of claim 19, wherein the fluid analyzer is
configured to determine a strength of at least one of the first
dielectric barrier or the second dielectric barrier based on the at
least one characteristic of the low-loss dielectric fluid.
21. The system of claim 19, wherein the at least one characteristic
of the low-loss dielectric fluid is selected from the group
consisting of impedance and temperature.
22. The system of claim 18, wherein the microwave antenna assembly
includes a radiating section connected to a distal end of the
feedline, the radiating section configured to radiate microwave
energy supplied from the power generating source.
23. The system of claim 19, wherein the power generating source is
configured to adjust energy delivered to the radiating section
based on the at least one characteristic of the low-loss dielectric
fluid.
24. The system of claim 18, wherein the fluid supply includes a
fluid cooler configured to remove thermal energy from the low-loss
dielectric fluid received from the return lumen.
25. The system of claim 18, wherein the low-loss dielectric fluid
is configured to absorb thermal energy from at least one of the
inner conductor or the outer conductor.
26. The system of claim 18, wherein the choke includes a plurality
of apertures disposed therethrough, the plurality of apertures
forming at least a portion of the return lumen.
27. A microwave ablation system, comprising: a power generating
source configured to supply microwave energy to a microwave antenna
assembly, the microwave antenna assembly including: a feedline
having a length, the feedline including: an inner conductor; and an
outer conductor in a coaxial arrangement with the inner conductor,
the inner conductor and outer conductor forming a supply lumen
therebetween; an elongated shaft at least partially surrounding the
feedline, the elongated shaft and the feedline forming a return
lumen therebetween in fluid communication with the supply lumen; a
choke including a substantially cylindrical inner surface
surrounding at least a portion of the length of the feedline and
configured to electrically connect the outer conductor to the
elongated shaft; and a radiating section connected to a distal end
of the feedline and configured to radiate microwave energy supplied
from the power generating source; and a fluid supply including a
fluid analyzer, the fluid supply configured to supply a low-loss
dielectric fluid to the supply lumen and to receive the low-loss
dielectric fluid from the return lumen, wherein a first dielectric
barrier is formed between the inner conductor and the outer
conductor and a second dielectric barrier is formed between the
outer conductor and the elongated shaft, the fluid analyzer
configured to determine a strength of at least one of the first
dielectric barrier or the second dielectric barrier based on at
least one characteristic of the low-loss dielectric fluid received
from the return lumen.
28. The system of claim 27, wherein the at least one characteristic
of the low-loss dielectric fluid is selected from the group
consisting of impedance and temperature.
29. The system of claim 27, wherein the power generating source is
configured to adjust energy supplied to the radiating section based
on the at least one characteristic of the low-loss dielectric
fluid.
30. The system of claim 27, wherein the fluid supply includes a
fluid cooler configured to remove thermal energy from the low-loss
dielectric fluid.
31. A microwave antenna assembly, comprising: a feedline having a
length, the feedline including: an inner conductor; and an outer
conductor in a coaxial arrangement with the inner conductor, the
inner conductor and outer conductor forming a supply lumen
therebetween; an elongated shaft, at least partially surrounding
the feedline, the elongated shaft and the feedline forming a return
lumen therebetween in fluid communication with the supply lumen,
wherein the supply lumen is configured to receive a low-loss
dielectric fluid from a fluid supply such that a first dielectric
barrier is formed between the inner conductor and the outer
conductor, and the return lumen is configured to return the
low-loss dielectric fluid to a fluid supply such that a second
dielectric barrier is formed between the outer conductor and the
elongated shaft; and a choke including a substantially cylindrical
inner surface surrounding at least a portion of the length of the
feedline and configured to electrically connect the outer conductor
to the elongated shaft.
32. The assembly of claim 31, further comprising: a radiating
section connected to the distal end of the feedline and configured
to radiate microwave energy supplied from a power generating
source.
33. The assembly of claim 31, wherein the low-loss dielectric fluid
is configured to absorb thermal energy from at least one of the
inner conductor or the outer conductor.
34. The assembly of claim 31, wherein the choke includes a
plurality of apertures disposed therethrough, the plurality of
apertures forming at least a portion of the return lumen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 12/568,777, filed on Sep. 29, 2009, the entire
contents of which is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates generally to microwave
surgical devices having a microwave antenna which may be inserted
directly into tissue for diagnosis and treatment of diseases. More
particularly, the present disclosure is directed to a microwave
antenna having a cooled coaxial feed, radiating section and balun
choke dielectric and a method of manufacturing the same.
[0004] 2. Background of Related Art
[0005] In the treatment of diseases such as cancer, certain types
of cancer cells have been found to denature at elevated
temperatures (which are slightly lower than temperatures normally
injurious to healthy cells.) These types of treatments, known
generally as hyperthermia therapy, typically utilize
electromagnetic radiation to heat diseased cells to temperatures
above 41.degree. C., while maintaining adjacent healthy cells at
lower temperatures where irreversible cell destruction will not
occur. Other procedures utilizing electromagnetic radiation to heat
tissue also include ablation and coagulation of the tissue. Such
microwave ablation procedures, e.g., such as those performed for
menorrhagia, are typically done to ablate and coagulate the
targeted tissue to denature or kill the tissue. Many procedures and
types of devices utilizing electromagnetic radiation therapy are
known in the art. Such microwave therapy is typically used in the
treatment of tissue and organs such as the prostate, heart, liver,
lung, kidney, and breast.
[0006] One non-invasive procedure generally involves the treatment
of tissue (e.g., a tumor) underlying the skin via the use of
microwave energy. The microwave energy is able to non-invasively
penetrate the skin to reach the underlying tissue. However, this
non-invasive procedure may result in the unwanted heating of
healthy tissue. Thus, the non-invasive use of microwave energy
requires a great deal of control.
[0007] Presently, there are several types of microwave probes in
use, e.g., monopole, dipole, and helical. One type is a monopole
antenna probe, which consists of a single, elongated microwave
conductor exposed at the end of the probe. The probe is typically
surrounded by a dielectric sleeve. The second type of microwave
probe commonly used is a dipole antenna, which consists of a
coaxial construction having an inner conductor and an outer
conductor with a dielectric junction separating a portion of the
inner conductor. The inner conductor may be coupled to a portion
corresponding to a first dipole radiating portion, and a portion of
the outer conductor may be coupled to a second dipole radiating
portion. The dipole radiating portions may be configured such that
one radiating portion is located proximally of the dielectric
junction, and the other portion is located distally of the
dielectric junction. In the monopole and dipole antenna probe,
microwave energy generally radiates perpendicularly from the axis
of the conductor.
[0008] A typical microwave ablation probe includes a transmission
line that provides a microwave energy signal to the microwave
antenna. The transmission line is enclosed in an elongated shaft
and includes a long, thin inner conductor that extends along the
axis of the probe and is surrounded by a dielectric material and is
further surrounded by an outer conductor around the dielectric
material such that the outer conductor also extends along the axis
of the probe.
[0009] A cooling system may also be enclosed in the elongated shaft
of the microwave ablation probe. For example, cooling fluid may be
supplied to the distal end of the microwave ablation probe through
one or more cooling supply lumens. After being deposited at the
distal end of the elongated shaft the cooling fluid flows
proximally through the elongated shaft through a return lumen,
typically a chamber between the outer surface of the transmission
line and the inner surface of the elongated shaft. In addition to
providing cooling for the elongated shaft portion of the microwave
ablation probe, the cooling fluid also at least partially insulates
the transmission line from the outer surface of the elongated
shaft.
[0010] The coaxial construction of the monopole antenna, the dipole
microwave antennas and the transmission line that provides a
microwave signal thereto, include a dielectric sleeve that provides
a dielectric junction between the inner and outer conductors.
[0011] Development of structurally stronger invasive probes have
resulted in long, narrow, needle-like antenna probes which may be
inserted directly into the body tissue to directly access a site of
a tumor or other malignancy. Such rigid probes generally have small
diameters that aid not only in ease of use but also reduce the
resulting trauma to the patient.
[0012] Further improvements (i.e., a reduction in diameter,
improved temperature management along the shaft and choke, and/or
an improvement in strength) may be accomplished by combining the
cooling system and the dielectric portions of the transmission line
and/or the antenna, as disclosed in the present application.
SUMMARY
[0013] The present disclosure provides a surgical microwave antenna
assembly and a surgical microwave ablation system. The microwave
antenna assembly includes a feedline electrically connected to an
elongated shaft by a choke electrical connector. The feedline
includes an inner conductor in coaxial arrangement with an outer
conductor and forming a dielectric supply lumen therebetween. The
elongated shaft at least partially surrounds the feedline and forms
a dielectric return lumen therebetween. The choke electrical
connector surrounds at least a portion of the feedline and
electrically connects the feedline outer conductor to the elongated
shaft. A low-loss dielectric fluid is supplied between the inner
conductor and the outer conductor of the feedline and forms a
dielectric barrier therebetween. The low-loss dielectric fluid also
forms a dielectric barrier between the outer conductor of the
feedline and the elongated shaft. The choke electrical connector
forms a plurality of apertures extending therethrough, the
apertures forming at least a portion of the dielectric return
lumen.
[0014] The dielectric supply lumen and a dielectric return lumen
are disposed in fluid communication with each other. The low-loss
dielectric fluid, supplied to the dielectric supply lumen and the
dielectric return lumen, is configured to absorb thermal energy
from the inner conductor and/or the outer conductor.
[0015] In one embodiment, the assembly includes an antenna,
connected to the distal end of the feedline, configured to radiate
microwave energy at a predetermined microwave frequency. The
antenna may be at least partially surrounded by a high-dielectric
jacket.
[0016] In another embodiment, the choke electrical connector forms
a Faraday shield to shunt electromagnetic energy radiating
proximally from the antenna at the predetermined microwave
frequency. The predetermined microwave frequency may be in the
range of about 915 MHz to about 2.54 GHz.
[0017] The present disclosure further relates to a surgical
microwave ablation system, including a microwave signal generator,
a low-loss dielectric fluid supply, and a surgical microwave
antenna assembly. The surgical microwave antenna assembly includes
a feedline, an elongated shaft, a choke electrical connector and a
low-loss dielectric fluid. The feedline includes an inner conductor
in coaxial arrangement with an outer conductor, the inner conductor
and outer conductor forming a dielectric supply lumen therebetween.
The elongated shaft at least partially surrounds the feedline, the
elongated shaft and the feedline forming a dielectric return lumen
therebetween. A choke electrical connector surrounds at least a
portion of the feedline and electrically connects the feedline
outer conductor to at least a portion of the elongated shaft. A
low-loss dielectric fluid is supplied between the inner conductor
and the outer conductor of the feedline and forms a dielectric
barrier therebetween. The low-loss dielectric fluid also forms a
dielectric barrier between the outer conductor of the feedline and
the elongated shaft. The low-loss dielectric fluid supply provides
the low-loss dielectric cooling fluid to the dielectric supply
lumen.
[0018] In one embodiment the choke electrical connector of the
surgical microwave antenna assembly forms a plurality of apertures
extending therethrough, the apertures forming at least a portion of
the dielectric return lumen. The low-loss dielectric fluid supply
and the dielectric return lumen are in fluid communication through
the dielectric supply lumen.
[0019] In yet another embodiment, the system further includes an
antenna, connected to the distal end of the feedline, configured to
radiate microwave energy at a predetermined microwave frequency.
The microwave signal generator generates the microwave energy
signal and the feedline electrically connects the microwave signal
generator to the antenna.
[0020] The choke electrical connector of the surgical microwave
antenna assembly forms a Faraday shield and is configured to shunt
electromagnetic energy radiating proximally from the antenna. The
antenna of the surgical microwave antenna assembly is at least
partially surrounded by a high-dielectric jacket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The above and other aspects, features, and advantages of the
present disclosure will become more apparent in light of the
following detailed description when taken in conjunction with the
accompanying drawings in which:
[0022] FIG. 1 shows a representative diagram of a variation of a
microwave antenna assembly in accordance with an embodiment of the
present disclosure;
[0023] FIG. 2A shows a cross-sectional view of a representative
variation of a distal end of microwave antenna assembly of FIG. 1
in accordance with an embodiment of the present disclosure;
[0024] FIG. 2B is a sectional view of the distal radiating section
in accordance with another embodiment of the present
disclosure;
[0025] FIG. 3 shows a cross-sectional view of a representative
variation of the choked portion of the microwave antenna assembly
in accordance with an embodiment of the present disclosure;
[0026] FIG. 4A is an end view of the choke electrical connector
from FIG. 3 in accordance with an embodiment of the present
disclosure, and
[0027] FIG. 4B is an end view of a variation of the choke
electrical connector from FIG. 3 in accordance with another
embodiment of the present disclosure.
DETAILED DESCRIPTION
[0028] Particular embodiments of the present disclosure will be
described herein with reference to the accompanying drawings. As
shown in the drawings and as described throughout the following
description, and as is traditional when referring to relative
positioning on an object, the term "proximal" refers to the end of
the apparatus that is closer to the user and the term "distal"
refers to the end of the apparatus that is further from the user.
In the following description, well-known functions or constructions
are not described in detail to avoid obscuring the present
disclosure in unnecessary detail.
[0029] FIG. 1 shows an embodiment of a microwave antenna assembly
100 in accordance with the present disclosure. The antenna assembly
100 includes a radiating portion 12 that is connected by elongated
shaft 110 via cable 15 to connector 16, which may further connect
the assembly 100 to a power generating source 28 (e.g., a microwave
or RF electrosurgical generator) and a dielectric cooling fluid
supply 70. Assembly 100, as shown, is a monopole microwave antenna
assembly, but other antenna assemblies, e.g., dipole or leaky wave
antenna assemblies, may also utilize the principles set forth
herein. Distal radiating portion 105 of the radiating section 12
includes a tapered end 120 which terminates at a tip 123 to allow
for insertion into tissue with minimal resistance. It is to be
understood, however, that tapered end 120 may include other shapes,
such as without limitation, a tip 123 that is rounded, flat,
square, hexagonal, or cylindroconical. Antenna may be positioned
using an insertion assistance device such as a catheter, an
introducer, an insertion jacket or any other suitable device
configured to aid in the positioning of a microwave antenna
assembly in tissue.
[0030] In the monopole antenna of FIG. 1, the feed point 130 is the
portion between the distal end of the feedline (i.e., coaxial
cable--not explicitly shown) within the elongated shaft 110 and the
distal radiating portion 105. In a dipole antenna, the feed point
is the portion between the distal radiating portion and the
proximal radiating portion.
[0031] Power generating source 28 is configured to generate and
provide an electrosurgical signal to the assembly 100. The
electrosurgical signal may include a microwave frequency component
at 915 MHz, 2.45 GHz or any other suitable frequency.
[0032] Dielectric cooling fluid supply 70 is configured to supply a
low-loss dielectric cooling solution that does not conduct an
electric current at the frequency provided from the power
generating source 28. Dielectric cooling fluid may include mineral
oil or mineral oil derivatives, soybean oil or a soybean oil
derivative, a natural ester-based fluid formulation made from
seeds, such as the ester-based fluid sold under the trademark
Envirotemp.RTM. FR3.TM. and manufactured and sold by Cooper Power
Systems of Waukesha, Wis., a synthetic hydrocarbon fluid such as
the synthetic hydrocarbon fluid sold under the trademarks ECO
Fluid.RTM. and ECO-FR Fluid.RTM. manufactured and sold by DSI
Ventures, Inc. of Tyler, Tex. Dielectric cooling fluid is selected
based on a high degree of biodegradation, environmental
compatibility and low toxicity.
[0033] The dielectric cooling fluids described in the present
disclosure are configured to replace the dielectric materials
traditionally provided in microwave antenna assemblies and the
feedline that provide the microwave signal to the microwave antenna
portion of the microwave antenna assemblies.
[0034] In one embodiment, the low-loss dielectric cooling fluid
provided to the microwave antenna assembly 100 by the dielectric
cooling fluid supply 70 is supplied from the pump 75. Pump 75 draws
low-loss dielectric cooling fluid from a supply reservoir (not
explicitly shown) and supplies the fluid to the fluid supply 71a.
The low-loss dielectric cooling fluid returns from the microwave
antenna assembly 100 via the fluid return 71b and is deposited into
a return reservoir. The supply reservoir and the return reservoir
may or may not circulate fluid therebetween.
[0035] In another embodiment, as illustrated in FIG. 1, the
dielectric cooling fluid supply 70 is configured to circulate and
re-circulate the low-loss dielectric cooling solution through the
microwave antenna assembly 100. Fluid supply 71a provides a cooled
low-loss dielectric cooling fluid to the connector 16 of the
microwave antenna assembly 100. The cooled low-loss dielectric
cooling fluid is circulated through the microwave antenna assembly
100 wherein the low-loss dielectric cooling fluid absorbs thermal
energy from the microwave antenna assembly. Thermally heated fluid
is returned to the dielectric cooling fluid supply 70 through the
fluid return 71b. The circulation path of the low-loss dielectric
cooling fluid through the distal portion of the microwave antenna
assembly 100 is further described hereinbelow and illustrated in
FIGS. 2A-4.
[0036] Dielectric cooling fluid supply 70 may include a fluid
cooling module 73 configured to remove thermal energy from the
low-loss dielectric cooling fluid. Fluid cooling module 73 may
include active or a passive cooling. Passive cooling may include
passing the low-loss dielectric cooling fluid over a thermal energy
absorbing material with a high thermal mass or through a thermal
energy exchanging module as is known in the art. Active cooling may
include a thermoelectric cooling system that uses the Peltier
effect to create a heat flux between the junction of two different
types of materials. For example, a Peltier cooler or thermoelectric
heat pump may transfer heat energy absorbed from the low-loss
dielectric cooling fluid by the fluid cooling module 73 to maintain
a desirable temperature in the recirculation system. Various
devices are know in the art as a Peltier device, a Peltier diode, a
Peltier heat pump, a solid state refrigerator, and a thermoelectric
cooler (TEC).
[0037] Dielectric cooling fluid supply 70 may include a fluid
analyzer 77 configured to analyze at least one physical property of
the low-loss dielectric cooling fluid. The fluid analyzer 77 may
provide an alert, alarm or warning if the analyzed physical
property is outside a predetermined range or exceeds a
predetermined limit or threshold. For example, fluid analyzer 77
may be configured to sample the impedance of the low-loss
dielectric cooling fluid that is returned and/or circulated through
the microwave antenna assembly. The analyzer may determine, based
on the sampled impedance that a change in impedance of the low-loss
dielectric cooling fluid has occurred.
[0038] In one embodiment, the fluid analyzer 77 determines if the
impedance of the low-loss dielectric cooling fluid is such that a
sufficient dielectric barrier in the microwave antenna assembly 100
cannot be maintained. Based on the measured parameter the
dielectric cooling fluid supply 70 may take a preventative action
such as, for example, alerting the clinician with an audio or
visual alarm or alert, providing an alarm to the power generating
source 28 that results in the termination of energy delivery and/or
providing an alarm to the microwave antenna assembly 100 that may
result in the termination of energy delivery to the distal
radiating portion 105. Alternatively, the dielectric cooling fluid
supply 70 may perform a corrective action such as terminating or
diverting the circulation of the low-loss dielectric cooling fluid
and introducing a fresh supply of low-loss dielectric cooling fluid
from a fluid reservoir into the recirculation path.
[0039] In another embodiment, the dielectric cooling fluid supply
70 and power generating source 28 share information via a
communication line 78. Information may be shared as one or more
analog signals or shared as a digital signal over the communication
line 78 by any suitable unidirectional or bidirectional
communication protocol. The shared information may include a
property of the low-loss, dielectric cooling fluid, a fluid-flow
parameter and/or a parameter related to energy delivery.
[0040] In one embodiment, the fluid analyzer provides a real-time
measurement of the low-loss, dielectric cooling fluid to the power
generating source 28 and the power generating source 28 may adjust
one or more parameters related to energy delivery. In another
embodiment, the power generating source provides a real-time
measurement of the impendence or temperature of the distal
radiating portion 105 and the dielectric cooling fluid supply 70
may adjust one or more parameters related to fluid flow or fluid
supply. For example, a rise in temperature at the distal radiating
portion 105 may be corrected by the dielectric cooling fluid supply
70 increasing the flow rate or an impedance change in the fluid or
the distal radiating portion 105 may be corrected by adjusting the
impedance of the low-loss, dielectric cooling fluid or the output
impedance of the power generating source 28.
[0041] FIG. 2A is a cross-sectional view of the distal end of
microwave antenna assembly 100 shown as 200. Distal end 200
includes at least a portion of the elongated shaft 210 and the
distal radiating section. The elongated shaft includes a feedline
226 and a choke jacket 260. Feedline 226 includes an inner
conductor 250 separated from an outer conductor 234 by low-loss
dielectric cooling fluid, thereby forming fluid supply lumen 236
therebetween. Inner conductor 250 and outer conductor 234 may be
formed from any suitable electrically conductive material. In some
embodiments, inner conductor 250 is formed from stainless steel and
outer conductor 234 is formed from copper. In one embodiment, the
low-loss dielectric cooling fluid forms a dielectric barrier
between the inner conductor 250 and the outer conductor 234 such
that feedline 226 has an impedance of about 50 ohms.
[0042] Choke jacket 260 may be formed from a variety of
biocompatible heat resistant, electrically conductive material
suitable for penetrating tissue, such as without limitation,
stainless steel. Metal jacket of the elongated shaft 110 (see FIG.
1) is proximal the choke jacket 260 and extends the length of the
shaft to provide strength and reduce assembly steps. Metal jacket
may be formed of stainless steel, a carbon fiber composite or high
strength plastic with a conductive surface (i.e., copper, silver,
gold or brass) or a silver plated brass. Choke jacket 260
electrically connects to the outer conductor of the feedline 226
and is configured to prevent the proximal propagation of microwave
energy. At least a portion of the outer surface 260b of the choke
jacket 260 may be coated or covered by a dielectric layer or
no-stick layer (not explicitly shown). Coating may include any
suitable dielectric material, such as without limitation, ceramic
material. In some embodiments, coating may be formed from titanium
dioxide and/or zirconium dioxide. Dielectric coating may be applied
to choke jacket 260 or may be applied as an additional dielectric
coating over the high dielectric jacket 265 of the distal radiating
portion 205. Coating may be applied by any suitable process, for
example without limitation, plasma spraying or flame spraying.
Coating may have a thickness in the range of about 0.005 inches to
about 0.015 inches. During an ablation procedure, the dielectric
coating may provide improved dielectric matching and/or improved
dielectric buffering between the antenna and tissue, which may
enable the use of higher power levels, which, in turn, may enable a
surgeon to achieve greater ablation rates resulting in increased
ablation size, reduced operative times, and/or improved operative
outcomes.
[0043] With reference to FIGS. 1 and 2A, the fluid supply lumen
extends proximally through the length of the elongated shaft 110,
the cable 15 and fluidly connects to the fluid supply 71a through
connector 16. Pump 75 in dielectric cooling fluid supply 70
pressurizes the fluid supply 71a and the low-loss dielectric
cooling fluid flows distally through the fluid supply lumen 236 as
indicated by supply flow arrows "A". Low-loss dielectric cooling
fluid exits the fluid supply lumen 236 from the distal end of the
feedline 226 and is deposited into the feedpoint 230. At least a
portion of the low-loss dielectric cooling fluid flows distally
into the distal radiating portion 205, as indicated by the distal
radiating portion flow arrows "AA", and absorbs thermal energy
therefrom.
[0044] A fluid return lumen 237 is formed between the outer surface
226a of the feedline 226 and the inner surface 260a of the choke
jacket 260. Fluid deposited into the feedpoint 230 and distal
radiating portion 205 flows proximally through the fluid return
lumen 237 as indicated by return flow arrows "AAA".
[0045] With reference to FIGS. 1 and 2, the fluid return lumen 237
extends proximally through the length of the elongated shaft 110,
the cable 15 and fluidly connects to the fluid return 71b through
connector 16.
[0046] With continued reference to FIG. 2A, distal end 200 includes
the distal radiating portion 205 at least partially surrounded by a
high dielectric jacket 265 that forms a tapered end at the distal
portion thereof. Inner conductor 250 is electrically coupled with
distal radiating portion 205. High dielectric jacket 265 may be
formed from any suitable material, including without limitation
polymeric or ceramic materials. In some embodiments, outer jacket
265 is coated with a non-stick coating like a
polytetrafluoroethylene (PTFE). a fluorinated ethylene propylene
(FEP) or coated with a lubricous spray coat. In another embodiment,
the outer jacket 265 is formed of a composite tubing or formed from
any suitable non-conductive material.
[0047] In another embodiment, the fluid supply lumen 236 and the
fluid return lumen 237 extend through the distal radiating portion
205. As illustrated in FIG. 2B, spacers 241a, 241b connect distal
radiating portion 205 to the high dielectric jacket 265 thereby
dividing the lumen formed therebetween into a portion of the fluid
supply lumen 236 and a portion of the fluid return lumen 237. As
such, the low-loss dielectric cooling fluid flows distally relative
to the distal radiating portion 205 and exits the fluid supply
lumen 236 formed between the distal radiating portion 205 and the
high dielectric jacket 265. The low-loss dielectric cooling fluid
then flows proximally through the fluid return lumen 237 formed
between the distal radiating portion 205 and the high dielectric
cooling jacket 265.
[0048] Turning now to FIG. 3, a cross sectional view of the choked
portion of the distal end of a microwave antenna assembly 100 of
FIG. 1, in accordance with an embodiment of the present disclosure
is shown as 300. Choked portion includes a feedline 326 separated
from a choke jacket 360 by the choke electrical connector 390. A
fluid supply lumen (not explicitly shown) is formed within the
feedline 326 as discussed hereinabove and the fluid return lumen
337 is formed between the outer surface of the feedline 326 and the
inner surface of the choke jacket 360 and at least a portion of the
inner surface of the high dielectric jacket 365.
[0049] Choke electrical connector 390 electrically connects the
outer conductor (not explicitly shown) of the feedline 326 to the
choke jacket 360. Connection may be a weld, solder joint or a
press-fit connection or any other suitable connection that provides
suitable continuity between the outer conductor of the feedline 326
and the choke jacket 360.
[0050] Referring to FIGS. 4A and 4B choke electrical connector 390
also provides a plurality of fluid pathways P1, P2 for fluid to
flow distally therethrough the choke electrical connector 390, the
fluid pathways P1, P2 forming at least a portion of the fluid
return lumen 337. As illustrated in FIGS. 4A and 4B, the fluid
pathways P1, P2 are formed through the plurality of apertures 491a,
492b thereby providing a flow path for the low-loss dielectric
cooling fluid to flow through the choke electrical connectors 390,
490a, 490b.
[0051] With reference to FIGS. 3, 4A and 4B, apertures 491a, 491b
of the choke electrical connector 390, 490a, 490b form a Faraday
shield configured to shunt any microwave energy that propagates
distally from the distal radiating section 305. The effectiveness
of the Faraday cage (or shield) is dependent upon the wavelength of
the electric or electromagnetic fields produced by the distal
radiating section 305 and the geometry of the choke electrical
connector 390, 490a, 490b. The thickness T1 of the choke electrical
connector 390, the diameter D1, D2 of the apertures 490a, 490b,
respectively, and/or the spacing D1, D2 between apertures 490a,
490b, respectively, determine the frequencies that are effectively
shunted by the choke electrical connector. For example, the
diameter D1, D2 of the apertures 490a, 490b, respectively, must be
significantly smaller than the wavelength of the microwave signal
radiated by the distal radiating section 305. Similarly, the
thickness T1 must be sufficiently thick to effectively shunt the
electromagnetic fields generated by the distal radiating section
305.
[0052] The described embodiments of the present disclosure are
intended to be illustrative rather than restrictive, and are not
intended to represent every embodiment of the present disclosure.
Further variations of the above-disclosed embodiments and other
features and functions, or alternatives thereof, may be made or
desirably combined into many other different systems or
applications without departing from the spirit or scope of the
disclosure as set forth in the following claims both literally and
in equivalents recognized in law.
* * * * *