CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date of provisional U.S. Patent Application No. 62/788,201, filed January 4, 2019.

FIELD

[0002] The present disclosure relates to electrosurgical devices suitable for use in tissue ablation applications and, more particularly, to electrosurgical devices with a fluid filled balun structure galvanically isolated from microwave delivery components and methods of directing energy to tissue using the same.

BACKGROUND

[0003] Treatment of certain diseases requires the destruction of malignant tissue growths, e.g., tumors. Electromagnetic radiation can be used to heat and destroy tumor cells. Treatment may involve inserting ablation antennas into tissues where cancerous tumors have been identified. Once the antennas are positioned, electromagnetic energy is passed through the antennas into surrounding tissue.

[0004] In the treatment of diseases such as cancer, certain types of tumor cells have been found to denature at elevated temperatures that are slightly lower than temperatures normally injurious to healthy cells. Known treatment methods, such as hyperthermia therapy, heat diseased cells to temperatures above 41°C while maintaining adjacent healthy cells below the temperature at which irreversible cell destruction occurs. These methods involve applying electromagnetic radiation to heat, ablate and/or coagulate tissue. Microwave energy is sometimes utilized to perform these methods. Other procedures utilizing electromagnetic radiation to heat tissue also include coagulation, cutting and/or ablation of tissue.

[0005] Electrosurgical devices utilizing electromagnetic radiation have been developed for a variety of uses and applications. A number of devices are available that can be used to provide high bursts of energy for short periods of time to achieve cutting and coagulative effects on various tissues. There are a number of different types of apparatus that can be used to perform ablation procedures. Typically, microwave apparatus for use in ablation procedures include a microwave generator that functions as an energy source, and a microwave surgical instrument (e.g., microwave ablation antenna) having an antenna assembly for directing the energy to the target tissue. The microwave generator and surgical instrument are typically operatively coupled by a cable assembly having a plurality of conductors for transmitting microwave energy from the generator to the instrument, and for communicating control, feedback and identification signals between the instrument and the generator.

[0006] There are several types of microwave antennas in use, e.g., monopole, dipole and helical, which may be used in tissue ablation applications. In monopole and dipole antenna assemblies, microwave energy generally radiates perpendicularly away from the axis of the conductor. Monopole antenna assemblies typically include a single, elongated conductor. A typical dipole antenna assembly includes two elongated conductors that are linearly aligned and positioned end-to-end relative to one another with an electrical dielectric placed therebetween. Helical antenna assemblies include helically-shaped conductor configurations of various dimensions, e.g., diameter and length. The main modes of operation of a helical antenna assembly are normal mode (broadside), in which the field radiated by the helix is maximum in a perpendicular plane to the helix axis, and axial mode (end fire), in which maximum radiation is along the helix axis.

[0007] Microwave antennas are generally inserted into a patient’s body in order to apply microwave energy to the treatment site, such as a cancerous tumor. In order to reach the treatment site, the microwave antenna is passed through either an incision, a trocar, or an access port that holds open an incision. Additional medical devices may also be passed through the incision at the same time as the microwave antenna to aid in performance of a medical procedure, reducing the space with which the medical devices may be operated or requiring an increase in the size of the incision. Physicians generally aim to limit the size of the incision as much as possible in order to minimize a required recovery time for the patient. Accordingly, there is a need for a microwave antenna with a reduced size that can safely apply microwave energy. SUMMARY

[0008] Provided in accordance with the present disclosure is an energy applicator for directing electromagnetic energy to tissue. The energy applicator includes a feedline, an antenna, and a balun structure. The feedline includes an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a first dielectric material disposed

therebetween. The antenna includes a radiating section operably coupled to the feedline. The balun structure is coaxially disposed around the outer conductor of the feedline with a medium disposed therebetween, and is galvanically isolated from the feedline.

[0009] In an aspect of the present disclosure, the medium is a second dielectric material.

[0010] In a further aspect of the present disclosure, the medium is air, de-ionized water, saline, or a coolant fluid.

[0011] In another aspect of the present disclosure, the energy applicator further includes a tube coaxially disposed around the outer conductor.

[0012] In yet another aspect of the present disclosure, the balun structure is composed of a metal coating on at least one of an inner surface of the tube or an outer surface of the tube.

[0013] In a further aspect of the present disclosure, a length of the balun is approximately equal to half of a wavelength of the energy

[0014] Further provided in accordance with the present disclosure is an energy application system for directing energy to tissue. The energy application system includes an energy generator, a feedline, an antenna, and a balun structure. The feedline is configured to transmit energy between the energy generator and the antenna, and includes an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a first dielectric material disposed therebetween. The antenna includes a radiating section operably coupled to the feedline. The balun structure is coaxially disposed around the outer conductor of the feedline with a medium disposed therebetween, and is galvanically isolated from the feedline.

[0015] As it is used in this description, "energy applicator" generally refers to any device that can be used to transfer energy from a power generating source, such as a microwave or RF electro surgical generator, to tissue. For the purposes herein, the term "energy applicator" is interchangeable with the term "energy-delivery device". As it is used in this description, "transmission line" generally refers to any transmission medium that can be used for the propagation of signals from one point to another. As it is used in this description, "fluid" generally refers to a liquid, a gas or both.

[0016] As it is used in this description, "length" may refer to electrical length or physical length. In general, electrical length is an expression of the length of a transmission medium in terms of the wavelength of a signal propagating within the medium. Electrical length is normally expressed in terms of wavelength, radians or degrees. For example, electrical length may be expressed as a multiple or sub-multiple of the wavelength of an electromagnetic wave or electrical signal propagating within a transmission medium. The wavelength may be expressed in radians or in artificial units of angular measure, such as degrees. The electrical length is in general different from the physical length. By the addition of an appropriate reactive element (capacitive or inductive), the electrical length may be made significantly shorter or longer than the physical length.

[0017] Hereinafter, embodiments of energy-delivery devices (also referred to as energy applicators) with a fluid filled antenna assembly, and systems including the same, of the present disclosure are described with reference to the accompanying drawings. Like reference numerals may refer to similar or identical elements throughout the description of the figures. As shown in the drawings and as used in this description, and as is traditional when referring to relative positioning on an object, the term "proximal" refers to that portion of the apparatus, or component thereof, closer to the user and the term "distal" refers to that portion of the apparatus, or component thereof, farther from the user.

[0018] This description may use the phrases "in an embodiment," "in embodiments," "in some embodiments," or "in other embodiments," which may each refer to one or more of the same or different embodiments in accordance with the present disclosure.

[0019] Electromagnetic energy is generally classified by increasing energy or decreasing wavelength into radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma- rays. As it is used in this description, "microwave" generally refers to electromagnetic waves in the frequency range of 300 megahertz (MHz) (3. times.10. sup.8 cycles/second) to 300 gigahertz (GHz) (3. times.10. sup.11 cycles/second). As it is used in this description, "ablation procedure" generally refers to any ablation procedure, such as, for example, microwave ablation, radiofrequency (RF) ablation, or microwave or RF ablation-assisted resection. [0020] Any of the above aspects and embodiments of the present disclosure may be combined without departing from the scope of the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

[0021] Objects and features of the presently disclosed energy-delivery devices with a fluid filled antenna assembly and systems including the same will become apparent to those of ordinary skill in the art when descriptions of various embodiments thereof are read with reference to the accompanying drawings, of which:

[0022] FIG. 1 is an exploded perspective view, with parts separated, of a medical device in accordance with an embodiment of the present disclosure;

[0023] FIG. 2A is a schematic diagram of a medical device including an antenna, a hub assembly, and a generator connector assembly in accordance with an embodiment of the present disclosure;

[0024] FIG. 2B is cross-sectional view of the indicated area of detail of FIG. 2A in accordance with an embodiment of the present disclosure;

[0025] FIG. 3 A is a longitudinal cross-sectional view of the antenna and hub assembly in accordance with an embodiment of the present disclosure;

[0026] FIG. 3B is an enlarged view of the indicated area of detail of FIG. 3 A, in accordance with an embodiment of the present disclosure;

[0027] FIG. 4 is a longitudinal cross-sectional view of a distal portion of an antenna assembly in accordance with an embodiment of the present disclosure; and

[0028] FIG. 5 is a longitudinal cross-sectional view of a distal portion of another antenna assembly in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0029] The present disclosure is generally directed to a microwave ablation antenna including a fluid filled balun structure. The balun is isolated from microwave delivery components, e.g. the inner and outer conductors of a feedline, and therefore allows for a simplified balun structure. A simplified balun structure enables lower cost production with a reduced size enabling better access to treatment targets. The balun structure may be added to fluid inflow tubes or outflow tubes (used to bathe the antenna) through a process of

metallization. Moreover, an external dielectric and a metallic balun material may individually be added to existing microwave delivery components to achieve a similar effect. Thus, there is no need for a separate, expensive, and complicated balun structure to be manufactured attached to any part of the feedline.

[0030] The following device may be designed to operate at a first operating frequency of about 915 MHz, and a second operating frequency of about 2.45 GHz or about 5.8 GHz, or any other applicable frequencies. In some embodiments, the presently disclosed ablation devices include a first balun structure adapted to allow for operation at a first frequency and a second balun structure adapted to allow for operation at a second frequency, and electrosurgical systems including the same may be operated at a first frequency, e.g., about 915 MHz, wherein the distal radiating section has a first length, e.g., about 4 cm, and a second frequency, e.g., about 2.45 GHz, wherein the distal radiating section is adjusted to have a second length, e.g., about 2 cm. In some embodiments, the second balun structure may be adapted to allow for operation at a second frequency of about 5.8 GHz, wherein the distal radiating section is adjusted to have a length of about 1 cm.

[0031] Various embodiments of the present disclosure provide an energy-delivery device with a fluid filled antenna assembly including a balun. Embodiments may be suitable for utilization in open surgical applications. Embodiments may be suitable for utilization with hand- assisted, endoscopic and laparoscopic surgical procedures such as Video Assisted Thoracic Surgery. Embodiments may be implemented using electromagnetic radiation at microwave frequencies, RF frequencies or at other frequencies. An electrosurgical system including the presently disclosed energy-delivery device with a fluid filled antenna assembly disposed in fluid communication with a fluid supply system via a hub 40 according to various embodiments is configured to operate at frequencies between about 300 MHz and about 10 GHz. During operation, the antenna assembly may enhance the overall heating pattern of the antenna assembly, prevent damage to the antenna assembly, and/or prevent harm to the clinician or patient.

[0032] Various embodiments of the presently disclosed energy-delivery device with a fluid filled antenna assembly including a balun are suitable for microwave or RF ablation, pre coagulation, and ablation-assisted surgical resection. Although various methods described herein below are targeted toward microwave ablation and the complete destruction of target tissue, it is to be understood that methods for directing electromagnetic radiation may be used with other therapies in which the target tissue is partially destroyed or damaged, such as, for example, to prevent the conduction of electrical impulses within heart tissue. In addition, although the following description describes the use of a dipole microwave antenna, the teachings of the present disclosure may also apply to a monopole, helical, or other suitable type of microwave antenna or RF electrode.

[0033] FIG. 1 shows energy applicator 10. In some embodiments, energy applicator 10 is a microwave antenna. Energy applicator 10 includes an outer tubular member 30, an inner tubular member 35, a feedline 14, an antenna 12, and a tip 19, which, when assembled, form an antenna assembly 20, or portions thereof. Energy applicator 10 generally includes two housing halves 21 and 22, which, when assembled, form a handle body 23. Handle body 23 defines a handle-body chamber 26 therein. Energy applicator 10 includes a hub 40 (as well as other components described herein) disposed, at least in part, within the handle-body chamber 26.

[0034] Hub 40 includes a hub body 43 defining a hub-body chamber 46 therein. Energy applicator 10 includes a hub cap 150 and a hub divider 160, which are configured to be receivable within the hub-body chamber 46 in sealing engagement with the inner walls of the hub body 43. Outer tubular member 30, the inner tubular member 35, the hub 40, and the components cooperative therewith (e.g., hub cap 150 and hub divider 160) are adapted to maintain fluid flow to the antenna 12. Hub body 43 generally includes a first port 41 and a second port 42, e.g., to allow fluid communication with a fluid supply system (e.g., fluid supply system 50 shown in FIG. 2A) via one or more fluid paths (e.g., first fluid path 16 and second fluid path 18 shown in FIG. 2A). First port 41 and the second port 42 may be of any suitable shape, e.g., rectangular, cylindrical, etc., and may include a groove adapted to receive an o-ring or other suitable sealing element.

[0035] In some embodiments, the hub body 43 may include one or more mechanical interfaces, e.g., recess 45, adapted to engage with one or more corresponding mechanical interfaces (e.g., tab 70 shown in FIG. 2A) associated with the handle body 23, e.g., to align the hub 40 within the handle body 23 and/or to fixedly secure the hub 40 within the handle-body chamber 26. Similarly, each of the housing halves 21, 22 may include a series of mechanical interfacing components, e.g., alignment pins 74, 76, and 78, configured to mating engage with a corresponding series of mechanical interfaces (not shown), e.g., to align the two housing halves 21, 22 about the components and assemblies of the energy applicator 10. It is contemplated that the housing halves (as well as other components described herein) may be assembled together with the aid of alignment pins, snap-like interfaces, tongue and groove interfaces, locking tabs, adhesive ports, etc., utilized either alone or in combination for assembly purposes.

[0036] Hub divider 160 is configured and utilized to divide the hub-body chamber 46 into a first chamber, e.g., disposed in fluid communication with the first port 41, and a second chamber, e.g., disposed in fluid communication with the second port 42. The first chamber (e.g., first chamber 147 shown in FIG. 3A) generally fluidly connects the first port 41 to the inner tubular member 35. The second chamber (e.g., second chamber 143 shown in FIG. 3A) generally fluidly connects the second port 42 to the inner tubular member 35.

[0037] In some embodiments, the inner walls of the hub body 43 may include a

configuration of engagement portions adapted to provide sealing engagement with the hub cap 150 and/or the hub divider 160. In some embodiments, as shown in FIG. 1, an o-ring 157 is provided for engagement with the hub cap 150. O-ring 157 may provide sealing force that permits flexing and/or other slight movement of the hub cap 150 relative to the hub 40 under fluid- pressure conditions. Hub cap 150 and the hub divider 160 are described in more detail later in this disclosure with reference to FIG. 3 A.

[0038] Outer tubular member 30 and the inner tubular member 35 may be formed of any suitable non-electrically-conductive material, such as, for example, polymeric or ceramic materials. In some embodiments, as shown in FIGS. 3A and 3B, the inner tubular member 35 is coaxially disposed around the feedline 14 and defines a first lumen 37 therebetween, and the outer tubular member 30 is coaxially disposed around the inner tubular member 35 and defines a second lumen 33 therebetween.

[0039] Antenna assembly 20 generally includes an antenna 12 having a first radiating portion (e.g., distal radiating section 318 shown in FIGS. 4 and 5) and a second radiating portion.

Antenna 12, which is described in more detail later in this disclosure, is operably coupled by the feedline 14 to a transition assembly 80 shown in FIG. 1, which is adapted to transmit the microwave energy, from the cable assembly 15 to the feedline 14. A connector assembly 17 shown in FIG. 1 is adapted to further operably connect the energy applicator 10 to a microwave generator 28 (shown in FIG. 2A).

[0040] Antenna assembly 20 further includes balun 90. Baiun 90 is shown, in Fig. 1, disposed on an outer surface of inner tubular member 35. Balun 90 may also be position on an inner surface of inner tubular member 35 ( see FIGS. 4 and 5) or an inner or outer surface of outer tubular member 30 (not shown). Baiun 90 is composed of a material with high electromagnetic permeability such as, for example, iron, steel, ferrite, mu-metal, or any other suitable material. Baiun 90 may also be composed of a material with high electrical conductivity such as, for example, copper, silver, gold, or any other suitable material. Baiun 90 may be coupled to inner tubular member 35 (or outer tubular member 30) using any appropriate means. For example, a process of metallization may be used to apply a metal (or ferromagnetic) layer 92 (see FIGS. 4 and 5) to inner tubular member 35 or outer tubular member 30 to generate balun 90. The metallization process describes a technique for coating metal on the surface of an object and typically includes applying a metal powder, a binder, and a hardener. In the alternative, metal layer 92 (or ferromagnetic layer) may be manufactured separately and fastened or bonded to inner tubular member 35 or outer tubular member 30. In an aspect, antenna assembly 20 may include a plurality of baluns 90 formed of a plurality of metal layers 92, each of which being disposed or coupled to different portions of the antenna assembly 20. Each of the baluns 92, or specifically metal layers 92 may be galvanically isolated.

[0041] Feedline 14 may be any suitable transmission line, e.g., a coaxial cable. In some embodiments, as shown in FIGS. 3A and 3B, the feedline includes an inner conductor 220, an outer conductor 224 coaxially disposed around the inner conductor 220, and a dielectric material 222 disposed therebetween. Dielectric material 222 may be formed from any suitable dielectric material, e.g., polyethylene, polyethylene terephthalate, polyimide, or polytetrafluoroethylene (PTFE). Inner conductor 220 and the outer conductor 224 may be formed from any suitable electrically-conductive material. In some embodiments, the inner conductor 220 is formed from a first electrically-conductive material (e.g., stainless steel) and the outer conductor 224 is formed from a second electrically-conductive material (e.g., copper). Electrically-conductive materials used to form the feedline 14 may be plated with other materials, e.g., other conductive materials, such as gold or silver, to improve their properties, e.g., to improve conductivity, decrease energy loss, etc. Feedline 14 may have any suitable length defined between its proximal and distal ends. In accordance with various embodiments of the present disclosure, the feedline 14 is coupled at its proximal end to a transition assembly 80 and coupled at its distal end to the antenna 12.

Feedline 14 is disposed at least in part within the inner tubular member 35. [0042] FIG. 2 A shows energy applicator 10 incorporated into an operational system including a microwave generator 28 and a fluid supply system 50. Energy applicator 10 includes an antenna assembly 20 and a handle assembly 60. Antenna assembly 20 generally includes the outer tubular member 30, the inner tubular member 35, the feedline 14, the antenna 12, and the tip 19 shown in FIG. 1. Handle assembly 60 generally includes a handle body 23 defining a handle- body chamber 26 therein. Energy applicator 10 also includes the hub 40 shown in FIG. 1 (as well as other components described herein) disposed, at least in part, within the handle-body chamber 26.

[0043] Antenna assembly 20 may include a balun 90 (shown in FIGS. 1 and 7) disposed proximal to and spaced apart a suitable length from the feed point 322. In aspects, the distal edge of the balun 90 may overlap the feed point 322 and extend over the electrically-conductive element 320. Additionally, or alternatively, two or more balun 90 structures of various lengths may be situated about the radiating elements of inner conductor 220, dielectric material 222, and/or outer coating or sleeve 226, or any other portion of antenna assembly 20. The balun 90, which is described in more detail later in this disclosure, generally includes a balun insulator, and an electrically-conductive layer disposed around the outer peripheral surface of the balun insulator, or portions thereof. In some embodiments, the antenna assembly 20 includes a temperature sensor 102 disposed in association with the balun 90.

[0044] As shown in FIG. 2A, the antenna assembly 20 is operably coupled by a cable assembly 15 to a connector assembly 17. Connector assembly 17 is a cable connector suitable to operably connect the energy applicator 10 to a microwave generator 28. The connector may house a memory (e.g., an EEPROM) storing a variety of information regarding the cable assembly 15 and the energy applicator 10. For example, the memory may include identification information that can be used by the microwave generator 28 to ensure that only properly identified energy applicators 10 are connected thereto. In addition, the memory may store operating parameters of the energy applicator 10 (e.g., time, power, and dosage limits), cable compensation parameters of the cable assembly 15, and information regarding the usage of the energy applicator 10 or the cable assembly 15. Usage monitoring may enable limiting re-use of the energy applicator 10 beyond a certain number of energizations or a single use of the device. Such usage limitations may optionally be reset via reprocessing as is commonly understood in the art. Still further, the connector assembly 17 may include sensor electronics related to radiometry and temperature sensing as described elsewhere herein. Cable assembly 15 may be any suitable, flexible transmission line, and particularly a coaxial cable as shown in Fig. 2B, including an inner conductor 220, a dielectric material 222 coaxially surrounding the inner conductor 220, and an outer conductor 224 coaxially surrounding the dielectric material 222. Cable assembly 15 may be provided with an outer coating or sleeve 226 disposed about the outer conductor 224. Sleeve 226 may be formed of any suitable insulative material, and may be may be applied by any suitable method, e.g., heat shrinking, over-molding, coating, spraying, dipping, powder coating, and/or film deposition.

[0045] During microwave ablation the antenna assembly 20 is inserted into or placed adjacent to tissue and microwave energy is supplied thereto. One or more visualization techniques including Ultrasound, computed tomography (CT), fluoroscopy, and direct visualization may be used to accurately guide the antenna 100 into the area of tissue to be treated, as will be described in detail below. Antenna assembly 20 may be placed percutaneously or surgically, e.g., using conventional surgical techniques by surgical staff. A clinician may pre-determine the length of time that microwave energy is to be applied. Application duration may depend on many factors such as tumor size and location and whether the tumor was a secondary or primary cancer. The duration of microwave energy application using the antenna assembly 20 may depend on the progress of the heat distribution within the tissue area that is to be destroyed and/or the surrounding tissue.

[0046] According to various embodiments, the antenna assembly 20 is configured to circulate coolant fluid "F", e.g., saline, water or coolant fluid, which may, at least in part, remove heat generated by the antenna 12 and/or heat that may be generated along the length of the feedline 14, or portions thereof, during the delivery of energy.

[0047] In some embodiments, as shown in FIG. 3B, the first lumen 37 is utilized as a fluid inflow conduit and the second lumen 33 is utilized as a fluid outflow conduit. In other

embodiments, the first lumen 37 may serve as a fluid outflow conduit and the second lumen 33 may serve as a fluid inflow conduit. Outer tubular member 30 and/or the inner tubular member 35 may be adapted to circulate fluid therethrough, and may include baffles, multiple lumens, flow restricting devices, or other structures that may redirect, concentrate, or disperse flow depending on their shape. The size and shape of the inner tubular member 35, the outer tubular member 30, the first lumen 37, and the second lumen 33 may be varied from the configuration depicted in FIGS. 3A and 3B.

[0048] In some embodiments, at least a portion of the inner tubular member 35 and/or at least a portion of the outer tubular member 30 (e.g., a distal portion) may include an integrated, spiraling metallic wire to add shape-memory properties to the antenna assembly 20 to aid in placement. In some embodiments, the inner tubular member 35 and/or the outer tubular member 30 may increase in stiffness and exhibit increased shape-memory properties along their length distally toward the antenna 12.

[0049] In some embodiments, the first port 41 and the second port 42 are coupled in fluid communication with a fluid supply system 50 via one or more fluid paths 16 and 18, as shown in FIG. 2 A. Fluid paths 16 and 18 may be coupled to and in fluid communication with the antenna assembly 20 via first and second chambers, 147 and 143, as shown in FIG. 3A. Fluid supply system 50 may be adapted to circulate fluid "F" into and out of the antenna assembly 20. Fluid source 52 may be any suitable housing containing a reservoir of fluid "F", and may maintain fluid "F" at a predetermined temperature. For example, the fluid source 52 may include a cooling unit (not shown) capable of cooling the returning fluid "F" from the antenna 12 via the hub 40.

[0050] Fluid "F" may be any suitable fluid that can be used for cooling or buffering the antenna assembly 20, e.g., deionized water, or other suitable cooling medium. Fluid "F" may have dielectric properties and may provide dielectric impedance buffering for the antenna 12 (e.g., distal radiating section 318). Fluid "F" composition may vary depending upon desired cooling rates and the desired tissue impedance matching properties. Various fluids may be used, e.g., liquids including, but not limited to, water, saline, perfluorocarbon, such as the commercially available Fluorinert® perfluorocarbon liquid offered by Minnesota Mining and Manufacturing Company (3M), liquid chlorodifluoromethane, etc. In other variations, gases (such as nitrous oxide, nitrogen, carbon dioxide, etc.) may also be utilized as the cooling fluid. In yet another variation, a combination of liquids and/or gases, including, for example, those mentioned above, may be utilized as the fluid "F".

[0051] Fluid supply system 50 generally includes a first fluid path 16 leading from the fluid source 52 to the first port 41 (also referred to herein as the fluid inlet port), and a second fluid path 18 leading from the second port 42 (also referred to herein as the fluid outlet port) to the fluid source 52. In some embodiments, the first fluid path 16 includes a fluid supply line 31, e.g., leading from the fluid source 118 to the fluid inlet port 41, and the second fluid path 18 includes a fluid supply line 32, e.g., leading from the fluid source 52 to fluid outlet port 42. In some embodiments, the first fluid path 16 includes a fluid-movement device (not shown) configured to move fluid "F" through the first fluid path 16. Second fluid path 18 may additionally, or alternatively, include a fluid-movement device (not shown) configured to move fluid "F" through the second fluid path 18. Examples of fluid supply system embodiments are disclosed in commonly assigned U.S. Patent Application Serial No. 12/566,299 filed on September 24, 2009, entitled "OPTICAL DETECTION OF INTERRUPTED FLUID FLOW TO ABLATION

ANTENNA", and U.S. Application Serial No. 13/835,625 filed on March 15, 2013 (Attorney Docket No. H-IL -00083 (1988-83) entitled“RECIRCULATING COOLING SYSTEM FOR ENERGY DELIVERY DEVICE” the disclosure of which is incorporated herein by reference.

[0052] FIG. 3 A shows the antenna assembly 20 disposed in part within the hub 40, wherein the hub cap 150 and the hub divider 160 are disposed in sealing engagement with the inner walls of the hub body 43, and a proximal portion of the antenna assembly 20 is disposed in association with the hub cap 150 and hub divider 160. Hub divider 160 generally divides the hub-body chamber 46 (shown in FIG. 1) into a first chamber 147 a second chamber 143, respectively. First chamber 147 is disposed in fluid communication with the first port 41. Second chamber 143 is disposed in fluid communication with the second port 42. In some embodiments, as shown in FIG. 3 A, the proximal end of the inner tubular member 35 is disposed within the first chamber 147, wherein the first lumen 37 is disposed in fluid communication with the first port 41, and the proximal end of the outer tubular member 30 is disposed within the second chamber 143, wherein the second lumen 33 is disposed in fluid communication with the second port 42.

[0053] In some embodiments, as shown in FIG. 3 A, the inner tubular member 35 includes a first portion having a first outer diameter, a second portion having a second outer diameter greater than the first outer diameter, and a neck portion 36 disposed therebetween. In some embodiments, the opening in the hub divider 160 is configured for sealing engagement with the second portion of inner tubular member 35 having the second outer diameter. In some embodiments, located within the interior of the second portion of the inner tubular member 35 is a high hoop strength metal cylinder 38. The metal cylinder 38 engages the inner diameter of the inner tubular member 35. The hub divider 160 is formed of an elastomeric material and when forced into place within the hub 40, as shown in FIG. 3 A, the elastomeric material of the hub divider 160 creates an improved water tight seal separating the first hub chamber 147 from the second hub chamber 143. The metal cylinder 38 improves this seal by ensuring better contact between the elastomeric material of the hub divider 160 and the inner tubular member 35 upon application of lateral forces to the hub divider 160.

[0054] Hub body 43 may be configured to engage the coolant supply lines forming coolant paths 16 and 18 to fluid inlet port 41 and fluid outlet port 42. Fluid inlet port 41 and the fluid outlet port 42 may have any suitable configuration, including without limitation nipple-type inlet fittings, compression fittings, and recesses, and may include an o-ring type elastomeric seal.

[0055] FIG. 3B shows a portion of the antenna assembly 20 of FIG. 3 A including the first lumen 37, shown disposed between the outer tubular member 30 and inner tubular member 35, the second lumen 33, shown disposed between the inner tubular member 35 and the feedline 14, and a transmission line 11 extending longitudinally within the second lumen 33. As indicated by the direction of the arrow-headed lines in FIG. 3B, the first lumen 37 serves as an inflow conduit for fluid "F" and the second lumen 33 serves as an outflow conduit for fluid "F," however as noted above these could be reversed without departing from the scope of the present disclosure.

[0056] In FIGS. 4 and 5, there is shown two configurations of a portion of the antenna assembly 20 including balun 90, which is composed of metal layer 92. Baiun 90 is shown, in FIGS. 4 and 5, applied or coupled to an inner surface, of inner tubular member 35. Fluid "F" fills the space between balun 90 and outer conductor 224 through feedline 14. As fluid“F” flows through feedline 14, it acts as a balun insulator or dielectric fill, serving to aid in galvanically isolating balun 90 from outer conductor 224 (as well as inner conductor 220). The fluid“F” also prevents electromagnetic wavelength change on the radiating elements of the antenna 12, such as electrically-conductive element 320, which would otherwise occur with the dielectric constant drop in the surrounding dessicating tissues over the course of creating an ablation.

[0057] Length“L” of balun 90 is determined in order to balance radiator 120. In other words, length“L” is established to prevent flow of current proximally behind the distal portion of the feed line, inner conductor and outer conductor, and the radiator. In order to ensure that radiator 120 is balanced, the value of“L” will be approximately given according to an open-circuit termination at the proximal end of balun 90. For such an open-circuit termination condition at the proximal end of balun 90,“L” spans approximately l/2, where l is the wavelength of the energy being delivered to the tissue. [0058] Alternatively, in other embodiments, length“L” of balun 90 may also be equal to, for example, ¼ l, ¾ l, or any other suitable length as compared to the wavelength or otherwise established. Odd harmonics (e.g., ¼ l, ¾ l, etc.) may cause a current null at the balun entrance, which helps maintain a desired radiation pattern. The length of the balun 90 is selected to create a favorable phase cancellation of electromagnetic energy, specifically, the length and position of the balun 90 is selected to prevent electromagnetic energy from traveling proximally away from the radiating section 318 of the antenna 12.

[0059] FIGS. 4 and 5 further show antenna 12 which includes a distal radiating section 318 including an electrically-conductive element 320, and a feed point 322 disposed therebetween. Electrically-conductive element 320 may be formed of any suitable electrically-conductive material, e.g., metal such as stainless steel, aluminum, titanium, copper, or the like. In some embodiments, the electrically-conductive element 320 is dielectrically buffered by fluid "F", preventing electromagnetic wavelength change on the radiating portions of the antenna 12, such as electrically-conductive element 320, which would otherwise occur with the dielectric constant drop in the surrounding dessicating tissues over the course of creating an ablation.

[0060] As shown in FIG. 5 electrically-conductive element 320 has a stepped configuration, such that the outer diameter of the distal portion 324 is less than the outer diameter of the proximal portion 326. Further, the inner conductor 220 of the feedline 14 is arranged such that it extends past the distal end of the insulator 222 and into the proximal portion 326 of the electrically-conductive element 320. A hole 328, formed in the proximal portion 326

approximately at 90 degrees to the inner conductor 220 allows for solder, a set screw, or other securing mechanisms to physically secure the electrically-conductive element 320 to the inner conductor 220 and therewith the feedline 14 of the antenna assembly 20.

[0061] Although embodiments have been described in detail with reference to the accompanying drawings for the purpose of illustration and description, it is to be understood that the inventive processes and apparatus are not to be construed as limited thereby. It will be apparent to those of ordinary skill in the art that various modifications to the foregoing embodiments may be made without departing from the scope of the disclosure.