AU2014253563B2 - Modified wet tip antenna design - Google Patents

Abstract

MODIFIED WET TIP ANTENNA DESIGN A microwave antenna comprises a feedline (20) including a coaxial cable (16) having an inner conductor (50), an outer conductor (56), and a dielectric (52) disposed therebetween. The antenna further comprises a radiating section (18) coupled to the feedline (20), the radiating section (18) includes a choke. The antenna also comprises an inflow tube disposed around the outer conductor (56), the inflow tube defines an inlet flow path configured to supply a fluid to the radiating section (18); and a transition collar (53) formed from a dielectric material.

Description

1 MODIFIED WET TIP ANTENNA DESIGN TECHNICAL FIELD [0001] The present disclosure relates generally to microwave applicators used in tissue ablation procedures. More particularly, the present disclosure is directed to a modified version of a choked wet-tip ablation antenna. BACKGROUND [0002] Treatment of certain diseases requires destruction of malignant tissue growths (e.g., tumors). It is known that tumor cells denature at elevated temperatures that are slightly lower than temperatures injurious to surrounding healthy cells. Therefore, known treatment methods, such as hyperthermia therapy, heat tumor cells to temperatures above 410 C, while maintaining adjacent healthy cells at lower temperatures to avoid irreversible cell damage. Such methods involve applying electromagnetic radiation to heat tissue and include ablation and coagulation of tissue. In particular, microwave energy is used to coagulate and/or ablate tissue to denature or kill the cancerous cells. [0003] Microwave energy is applied via microwave ablation antennas that penetrate tissue to reach tumors. There are several types of microwave antennas, such as monopole and dipole. In monopole and dipole antennas, microwave energy radiates perpendicularly from the axis of the conductor. A monopole antenna includes a single, elongated microwave conductor. Dipole antennas typically have a coaxial construction including an inner conductor and an outer conductor separated by a dielectric portion. More specifically, dipole microwave antennas include a long, thin inner conductor that extends along a longitudinal axis of the antenna and is surrounded by an outer conductor. In certain variations, a portion or portions of the outer conductor may be selectively removed to provide for more effective outward radiation of energy. This type of microwave antenna construction is typically referred to as a "leaky waveguide" or "leaky coaxial" antenna. [0004] A typical tissue-penetrating (i.e., percutaneously inserted) microwave energy delivery device includes a transmission portion formed by a long, thin inner conductor that extends along the axis of the device. The inner conductor is surrounded by a dielectric material and the outer 2 conductor is radially-disposed relative to the dielectric material and forms a coaxial waveguide for transmitting a microwave signal. The distal end of the transmission portion of the outer conductor connects to a microwave antenna configured to receive the microwave signal from the transmission portion and to radiate the microwave energy signal to tissue. [0005] Structural strength is provided to the microwave energy delivery device by surrounding at least part of the transmission portion and/or the microwave antenna with a high-strength jacket. The distal end of the high-strength jacket may connect to, or form, a sharpened tip for piercing tissue. [0006] Invasive procedures have been developed in which the microwave antenna delivery device is inserted directly into a point of treatment via percutaneous insertion. Such invasive procedures potentially provide better temperature control of the tissue being treated. Because of the small difference between the temperature required for denaturing malignant cells and the temperature injurious to healthy cells, a known heating pattern and predictable temperature control is important so that heating is confined to the tissue to be treated. For instance, hyperthermia treatment at the threshold temperature of about 41.50 C. generally has little effect on most malignant growths of cells. However, at slightly elevated temperatures above the approximate range of 430 C. to 450 C., thermal damage to most types of normal cells is routinely observed; accordingly, great care must be taken not to exceed these temperatures in healthy tissue. [0007] Systems and methods developed to control heating and prevent elevated temperatures to surrounding tissue typically include cooling fluid that circulates around at least a portion of the microwave energy delivery device. For example, in one system cooling fluid is provided to the distal end of the microwave energy delivery device via a thin-walled tube. The thin-walled tube deposits the cooling fluid near the microwave antenna and the cooling fluid flows proximally through a return path in the microwave energy deliver device. [0008] There are several challenges to providing cooling to a microwave energy delivery device. The first challenge is providing suitable supply and return fluid pathways in the microwave energy delivery device without increasing the overall diameter of the microwave energy delivery device. Another challenge is providing suitable supply and return fluid pathways while maintaining a concentric configuration throughout the microwave energy 3 delivery device. Yet another challenge is providing a suitable configuration that simplifies assembly and manufacturing. OBJECT [0009] It is the object of the present invention to substantially overcome or ameliorate one or more of the disadvantages of the prior art, or at least provide a useful alternative. SUMMARY [0010] The microwave energy delivery devices described hereinbelow includes an assembly that forms a fluid-cooled device with a substantially concentric geometry along the length of the device without increasing in the overall diameter of the microwave energy delivery device. [0011] An apparatus and method of fabricating a microwave energy delivery device, which is structurally robust enough for unaided direct insertion into tissue is described herein. The microwave antenna is generally comprised of a radiating portion which may be connected to a feedline (or shaft), which in turn, may be connected by a cable to a power generating source such as a generator. The microwave assembly may be a monopole microwave energy delivery device but is preferably a dipole assembly. The distal portion of the radiating portion preferably has a tapered end which terminates at a tip to allow for the direct insertion into tissue with minimal resistance. The proximal portion is located proximally of the distal portion. [0012] The adequate rigidity necessary for unaided direct insertion of the antenna assembly into tissue, e.g., percutaneously, while maintaining a minimal wall thickness of less than 0.010 inches of an outer jacket, comes in part by a variety of different designs. An embodiment of a microwave design includes a coaxial cable. The coaxial cable includes an inner conductor, an outer conductor, and a dielectric insulator disposed therebetween. The radiating section includes a dipole antenna that is coupled to the feedline and a trocar coupled to the dipole antenna at a distal end thereof. The microwave antenna further includes an inflow hypotube disposed around the outer conductor. The inflow hypotube supplies fluid to the radiating portion. The inflow hypotube enables the increased in strength thereby allowing for a smaller wall thickness requirement of the outer jacket of a microwave antenna.

4 [0013] In one aspect, there is provided a microwave antenna, comprising: a feedline including a coaxial cable including an inner conductor, an outer conductor, and a dielectric disposed therebetween; a radiating section coupled to the feedline, the radiating section including a choke; an inflow tube disposed around the outer conductor, the inflow tube defining an inlet flow path configured to supply a fluid to the radiating section; and a transition collar formed from a dielectric material, the transition collar having a proximal end and a distal end, the proximal end coupled to a distal end of the inflow tube and forming a portion of the choke, the transition collar further including at least one outflow slot at the proximal end thereof configured to receive the fluid from the distal end of the inflow tube and transition the fluid from the at least one outflow slot to a distal end of the radiating section. [0014] The sleeve may be a polyimide sleeve. The microwave antenna may further include an outer jacket that surrounds the proximal to distal end of the feedline and an outer hypotube. The outer jacket forms a fluid-tight seal with the trocar and/or the distal end of radiating section and defines a second gap for receiving fluid from the first gap. The outer hypotube surrounds the inflow hypotube at the proximal end of the feedline and defines a third gap positioned relative to the inflow hypotube. The outer hypotube includes one or more slots defined therein and forms a fluid-tight seal with the outerjacket proximal one or more slots. The one or more slots are configured to enable the fluid to flow proximally from the second gap into the third gap and through the microwave antenna. [0015] In another embodiment, the inflow hypotube and/or the outer hypotube are made from stainless steel or from a non-metallic composite such as PolyMed@ made by Polygon. The wall thickness of the outer hypotube and the inflow hypotube may be less than about 0.010 inches. The microwave antenna may further include a choke configured to partially surround a proximate portion of the feedline [0016] In yet another embodiment, the puck is injection molded during the manufacturing process to form a water-tight seal around the outer conductor. The transition collar may be press-fit over the inflow hypotube to form a fluid-tight seal therebetween.

5 [0017] In a further embodiment, the microwave antenna may included a connection hub with a cable connector coupled to the feedline, an inlet fluid port and an outlet fluid port defined therein and a bypass tube configured to transition fluid proximate the cable connector to the outlet fluid port. An inflow tube may be coupled to the inlet fluid port for supplying the fluid thereto and an outflow tube may be coupled to the outlet fluid port and in fluid communication with the inflow hypotube for withdrawing fluid therefrom. [0018] A method for manufacturing a microwave antenna in accordance with an embodiment may include the steps of: providing a feedline including a coaxial cable including an inner conductor, an outer conductor, and a dielectric disposed therebetween; coupling a radiating section to the distal end of the feedline, the radiating section including a dipole antenna; coupling a trocar to the distal end of the dipole antenna; disposing an inflow hypotube around the outer conductor, the inflow hypotube configured to supply fluid to the radiating section; disposing a puck around at least a portion of the radiating section having a distal end and a proximal end, the puck including two or more longitudinal ribs for providing mechanical strength to the microwave antenna, the two or more ribs extending from the distal end to the proximal end to define inflow slots between two adjacent ribs; disposing a transition collar between a distal end of the inflow hypotube and a proximal end of the puck, the transition collar including at least two outflow slots configured to receive fluid from a distal end of the inflow hypotube and transition the fluid from the at least two outflow slots to a distal end of the radiating section; and disposing a sleeve to overlay the at least two outflow slots of the transition collar, the puck and at least the distal portion of the radiating section, the sleeve forming a fluid tight seal with the transition collar proximal the at least two outflow slots and defining a first gap for transitioning the fluid to exit the at least two outflow slots of the transition collar to the distal end of the radiating section. [0019] The method for manufacture may further include the steps of: disposing an outerjacket radially outward of the distal end of the feedline, the outerjacket forming a fluid-tight seal with one of the trocar and a distal end of the radiating section, the outerjacket defining a second gap for receiving fluid from the first gap; and disposing an outer hypotube radially outward of the inflow hypotube and defining a third gap positioned relative to the inflow hypotube, the outer hypotube including at least one slot defined therein and forming a fluid-tight seal with the outer jacket proximal the at least one slot, the at least one slot configured to enable the fluid to flow proximally from the second gap into the third gap and through the microwave antenna.

6 BRIEF DESCRIPTION OF THE DRAWINGS [0020] Preferred embodiments of the invention will be described hereinafter, by way of examples only, with reference to the accompanying drawings, in which: [0021] FIG. 1 is a schematic diagram of a microwave ablation system according to an embodiment of the present disclosure; [0022] FIG. 2 is an isometric view of a distal portion of the microwave energy delivery device according to one embodiment of the present disclosure; [0023] FIG. 3A is a longitudinal cross-sectional view of the feedline portion of the microwave energy delivery device of FIG. 2; [0024] FIG. 3B is a traverse, cross-sectional view taken along line 3B - 3B of FIG. 2; [0025] FIG. 4 is a perspective view of the distal portion of the microwave energy delivery device illustrating the coaxial inflow and outflow channels according to the present disclosure; [0026] FIG. 5 is an exploded view of the distal portion of the microwave energy delivery device illustrated in FIG. 4; [0027] FIG. 6 is a longitudinal cross-sectional view of the distal tip of the microwave energy delivery device; [0028] FIG. 7A is a transverse, cross-sectional view of the distal tip of the microwave energy delivery device according to one embodiment of the present disclosure; [0029] FIG. 7B is a transverse, cross-sectional view of the distal tip of the microwave energy delivery device according to another embodiment of the present disclosure; and [0030] FIG. 8 is a perspective view of the distal portion of the microwave energy delivery device illustrating the coaxial outflow channel according to the present disclosure; 7 DETAILED DESCRIPTION [0031] Particular embodiments of the present disclosure are described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. [0032] FIG. 1 illustrates a microwave ablation system 10 that includes a microwave energy delivery device 12, a microwave generator 14 and a cooling fluid supply 33. The microwave energy delivery device 12 is coupled to a microwave generator 14 via a flexible coaxial cable 16 and coupled to the cooling fluid supply 33 via cooling fluid supply lines 86 and 88. Cooling fluid exits the microwave energy delivery device 12 through a cooling fluid return line 88 and is discharged in a suitable drain. In a closed-loop cooling fluid system the microwave energy delivery device 12 couples to the cooling fluid supply 33 via a cooling fluid return line 88 and cooling fluid is cycled through the cooling fluid supply 33. In an opened-loop cooling fluid system the cooling fluid return line 88 deposits the cooling fluid in a drain or other suitable disposable receptacle and new cooling fluid is provided to the cooling fluids supply from a cooling fluid reservoir 36 or other suitable source of cooling fluid. [0033] Microwave energy delivery device 12 generally includes a connection hub 22, a feedline 20 and a radiating portion 18. Connection hub 22 connects the microwave generator 14 and the cooling fluid supply 33 to the microwave energy delivery device 12. The microwave signal is produced by the microwave generator 14, transmitted through the flexible coaxial cable 16, which connects to the connection hub 22, and the connection hub 22 facilitates the transfer of the microwave energy signal to the feedline 20. Connection hub 22 further facilitates the transfer of cooling fluid to and from the feedline 20. Cooling fluid, provided from the pump 34 of the cooling fluid supply 33, is provided to the connection hub 22 through the cooling fluid supply line 86. Connection hub 22 transfers the cooling fluid from the cooling fluid supply line 86 to the cooling fluid supply lumen (not explicitly shown) of the feedline 20. Cooling fluid, after being circulated through the feedline 20 and radiating portion 18 of the microwave energy delivery device 12, is returned to the connection hub 22 through the return lumen (not explicitly shown) of the feedline 20. Connection hub 22 facilitates the transfer of the cooling fluid from the return lumen (not explicitly shown) to the cooling fluid return line 88.

8 [0034] In one embodiment, the microwave ablation system 10 includes a closed-loop cooling system wherein the cooling fluid return line 88 returns the cooling fluid to the pump 34 of the cooling fluid supply 33. The cooling fluid supply 33 cools the returned cooling fluid from the cooling fluid return line 88 before recirculating at least a portion of the returned cooling fluid through the Microwave ablation system 10. [0035] In another embodiment, the cooling fluid return line 88 connects to a suitable drain and/or reservoir (e.g., cooling fluid from the microwave energy delivery device 12 is not returned to the cooling fluid supply 33). Cooling fluid reservoir 36 of the cooling fluid supply 33 provides a continuous supply of cooling fluid to the pump 34. Cooling fluid reservoir 36 may also include a temperature control system configured to maintain the cooling fluid at a predetermined temperature. Coolant fluid may include any suitable liquid or gas, including air, or any combination thereof [0036] The microwave energy delivery device 12 may include any suitable microwave antenna 40 such as, for example, a dipole antenna, a monopole antenna and/or a helical antenna. The microwave generator 14 may be configured to provide any suitable microwave energy signal within an operational frequency from about 300 MHz to about1O GHz. The physical length of the microwave antenna 40 is dependant on the frequency of the microwave energy signal generated by the microwave generator 14. For example, in one embodiment, a microwave generator 14 providing a microwave energy signal at about 915 MHz drives a microwave energy delivery device 12 that includes a microwave antenna 40 with a physical length of about 1.6 cm to about 4.0 cm. [0037] FIG. 2 is an enlarged view of the distal portion of the microwave energy delivery device 12 of FIG. 1 and includes a feedline 20, a proximal radiating portion 42 and a distal radiating portion 44. The proximal radiating portion 42 and the distal radiating portion 44 form a dipole microwave antenna 40. As illustrated in FIG. 2, proximal radiating portion 42 and the distal radiating portion 44 are unequal thereby forming an unbalanced dipole antenna 40. The microwave energy delivery device 12 includes a sharpened tip 48 having a tapered end 24 that terminates, in one embodiment, at a pointed end 26 to allow for insertion into tissue with minimal resistance at a distal end of the radiating portion 18. In another embodiment the radiating portion 18 is inserted into a pre-existing opening or catheter and the tip may be rounded or flat.

9 [0038] Sharpened tip 48 may be machined from various stock rods to obtain a desired shape. The sharpened tip 48 may be attached to the distal radiating portion 44 using various adhesives or bonding agents, such as an epoxy sealant. If the sharpened tip 48 is metal, the sharpened tip 48 may be soldered to the distal radiating portion 44 and may radiate electrosurgical energy. In another embodiment, the sharpened tip 48 and a distal radiating portion 44 may be machined as one piece. The sharpened tip 48 may be formed from a variety of heat-resistant materials suitable for penetrating tissue, such as ceramic, metals (e.g., stainless steel) and various thermoplastic materials, such as polyetherimide, polyimide thermoplastic resins, an example of which is Ultem® sold by General Electric Co. of Fairfield, CT. [0039] FIG. 3A is a longitudinal cross-sectional view of a section of the feedline 20 of the microwave energy delivery device 12 of FIG. 1 and FIG. 3B is a transverse, cross-sectional view of the feedline 20 of the microwave energy delivery device 12 of FIG. 3A. Feedline 20 is coaxially formed with an inner conductor 50 at the radial center surrounded by a dielectric layer 52 and an outer conductor 56. Inflow hypotube 55 is spaced apart and disposed radially outward from the outer conductor 56. The outer surface of the outer conductor 56b and the inner surface of the inflow hypotube 55a form an inflow channel 17i allowing cooling fluid to flow distally through the feedline 20 of the microwave energy delivery device 12 as indicated by cooling fluid inflow arrows 17i. The inflow hypotube 55 may be formed from a variety of heat-resistant materials, such as ceramic, metals (e.g., stainless steel), various thermoplastic materials, such as polyetherimide, polyimide thermoplastic resins, an example of which is Ultem® sold by General Electric Co. of Fairfield, CT, or composite medical tubing, an example of which is PolyMed® sold by Polygon of Walkerton, Indiana. In one embodiment, the inflow hypotube 55 may have a wall thickness less than about 0.010 inches. In another embodiment, the inflow hypotube 55 may have a wall thickness less than about 0.001 inches. [0040] The outer hypotube 57 is spaced apart from, and radially outward from, the inflow hypotube 55. The outer surface of the inflow hypotube 55b and the inner surface of the outer hypotube 57a form an outflow channel 17o that allows cooling fluid to flow proximately through the feedline 20 of the microwave energy delivery device 12 as indicated by cooling fluid outflow arrows 17o. The outer hypotube 57 may be formed from a variety of heat-resistant materials, such as ceramic, metals (e.g., stainless steel), various thermoplastic materials, such as polyetherimide, polyimide thermoplastic resins, an example of which is Ultem® sold by General Electric Co. of Fairfield, CT, or composite medical tubing, an example of which is 10 PolyMed@ sold by Polygon of Walkerton, Indiana. In one embodiment, the outer hypotube 57 may have a wall thickness less than about 0.010 inches. In another embodiment, the outer hypotube 57 may have a wall thickness less than about 0.001 inches. [0041] The substantially radially concentric cross-sectional profile, as illustrated in FIG. 3B, provides uniform flow of fluid in both the inflow channel 17i and the outflow channel 17o. For example, an inflow channel gap GI defined between the outer surface of the outer conductor 56b and the inner surface of the inflow hypotube 55a is substantially uniform around the circumference of the outer conductor 56. Similarly, an outflow channel gap G2 defined between the outer surface of the inflow hypotube 55b and the inner surface of the outer hypotube 57 is substantially uniform around the circumference of the inflow hypotube 55. [0042] In addition, the cross-sectional area of the inflow channel 17i and the outflow channel 17o (i.e., the effective area of each channel in which fluid flows) is the difference between the area at the outer surface of each channels 17i, 17o (i.e., the area at the inner diameter of the inflow hypotube 55 and the area at the inner diameter of the outer hypotube 57, respectively) and the area at the inner surface of the each channels 17i, 17o (i.e, the area at the outer diameter of the outer conductor 56 and the area at the outer diameter of the inflow hypotube 55). The cross-sectional area of the inflow channel 17i and the outflow channel 17o is substantially uniform along the longitudinal length of the feedline 20. In addition, transverse shifting of the inflow hypotube 55 within the outer hypotube 57 or transverse shifting of the outer conductor 56 within the inflow hypotube 55, may create a non-uniform inflow or outflow channel gap GI, G2, but will not affect the cross-sectional area of either inflow channel 17i and/or outflow channel 17o. [0043] FIG. 4 (illustrating in partial assembly the radiating portion 18 of FIG. 1) further illustrates the inflow fluid flow pathways. The radiating portion 18 is formed by inserting the distal portion of the feedline 20 into the microwave antenna 40. [0044] The feedline 20 is configured to provide cooling fluid and a microwave energy signal to the microwave antenna 40. As discussed hereinabove, the feedline 20 provides cooling fluid through the inflow channel 17i formed between the inflow hypotube 55 and the outer conductor 56 of the feedline 20. The feedline 20 also provides a microwave energy signal between the inner conductor 50 and the outer conductor 56.

11 [0045] The microwave antenna 40 includes a tapered inflow transition collar 53, a channeled puck 46, a distal radiating portion 44, including a plurality of antenna sleeve stops 68a - 68d, and a sharpened tip 48. The feedline 20, when inserted into the microwave antenna 40, connects the outer conductor 56 to the tapered inflow transition collar 53 and the inner conductor 50 to the distal radiating portion 44. [0046] FIG. 5 is an exploded view of the microwave antenna 40 of FIG. 4 that further illustrates the components of the microwave assembly. The tapered inflow transition collar 53 includes an outer taper 60a, a middle taper 60b and an inner taper 60c and is configured to transition the cooling fluid from the inflow channel 17i to various fluid channels formed in the microwave antenna 40 as discussed hereinbelow. During assembly, and as illustrated in FIG. 4 and discussed hereinbelow, the distal end of the feedline 20 is inserted into the proximal end of the tapered inflow transition collar 53. Each component 50, 52, 55, 56 of the feedline 20 is cut to a specific length such that when the feedline 20 is inserted each component ends at a predetermined position within the microwave antenna assembly 40. [0047] Starting with the radially-outward component of the distal end of the feedline 20, the inflow hypotube 55 (See FIG. 4) is inserted into the proximal end of the outer taper 60a portion of the tapered inflow transition collar 53. The transition between the outer taper 60a and the middle taper 60b forms a mechanical stop for the inflow hypotube 55. Outer taper 60a and inflow hypotube 55 forms a fluid-tight seal therebetween thereby limiting cooling fluid to the middle taper 60b of the tapered inflow transition collar 53. The fluid-tight seal between the inflow hypotube 55 and the outer taper 60a may be formed by adhesive, epoxy, or a polytetrafluoroethylene or other suitable sealant, or fluid-tight seal may be formed by a tight mechanical connection between the inflow hypotube 55 and the outer taper 60a. [0048] In one embodiment, the inflow hypotube 55 is formed of a conductive metal such as, for example, stainless steel, steel, copper or any other suitable metal, and the fluid-tight seal insulates the inflow hypotube 55 and the inner surface of the tapered inflow transition collar 53. In another embodiment, the fluid tight seal may include one or more insulating materials that forms a dielectric barrier between the inflow hypotube 55 and tapered inflow transition collar 53.

12 [0049] The outer conductor 56 when inserted into the proximal end of the outer taper 60a extends through the middle taper 60b with at least a portion of the outer conductor 56 connecting to the inner taper 60c. The outer conductor 56 and inner taper 60c form an electrical connection therebetween such that microwave energy signal provided by the outer conductor 56 conducts to the tapered inflow transition collar 53 such that the tapered inflow transition collar 53 forms at least a portion of the proximal radiating portion 42 of the microwave antenna 40. [0050] The outer surface of the inflow hypotube 55 and the inner surface of the outer taper 60a form a fluid-tight seal therebetween. Fluid exits the inflow channel 17i and is deposited in the open area formed within the middle taper 60b. The outer surface of the outer conductor 56 and inner surface of the inner taper 60c form a fluid-tight seal therebetween, thereby preventing the cooling fluid from traveling distal of the middle taper 60b within the tapered inflow transition collar 53. [0051] In one embodiment, an electrical connection is formed between the outer conductor 56 and the inner taper 60c of the tapered inflow transition collar 53. As such, tapered inflow transition collar 53 forms at least a portion of the proximal radiating portion 42 of the radiating portion 18, wherein the radiating portion 18 is a dipole antenna. The electrical connection between the outer conductor 56 and the inner taper 60c may include all of the contact surface therebetween or the electrical connection may include only a portion thereof. For example, in one embodiment the electrical connection between the outer conductor 56 and the inner taper 60c is formed circumferentially along the distal portion of the inner taper 60c and the remaining portion of the contact surface insulates the outer conductor 56 and the inner taper 60c. [0052] In another embodiment, the fluid-tight seal between the outer conductor 56 and the inner taper 60c forms an insulating barrier therebetween and the tapered inflow transition collar 53 does not form a portion of the radiating portion 18, wherein the radiating portion 18 is a monopolar antenna. [0053] In yet another embodiment, the fluid-tight seal between the outer conductor 56 and the inner taper 60c forms an insulating barrier therebetween. An electrical connection between the outer conductor 56 and the inner taper 60c is formed by connecting a distal end of the outer conductor 56 or the inner taper 60c to one another.

13 [0054] The fluid-tight seal between the inflow hypotube 55 and the outer taper 60a and the fluid-tight seal between the outer conductor 56 and the inner taper 60c isolates the cooling fluid discharged from the inflow channel 17i to the middle taper 60b of the tapered inflow transition collar 53. As additional fluid is deposited in the middle taper 60b, pressure builds and the cooling fluid exits the middle taper 60b through one of the plurality of cooling fluid transition apertures 53a - 53d formed in the tapered inflow transition collar 53. [0055] After the cooling fluid flows radially outward through one of the plurality of cooling fluid transition apertures 53a - 53d formed in the middle taper 60b, the cooling fluid flows distally along the outer surface of the middle taper 60b between the tapered inflow transition collar 53 and the antenna sleeve 2. Antenna sleeve 2 forms a fluid-tight seal with the outer taper 60a of the tapered inflow transition collar 53 thereby requiring fluid to flow distally toward the channeled puck 46. In one embodiment, the antenna sleeve 2 is a thin polyimide sleeve, or other suitable non-conductive material that has little or no impact on the transmission and/or delivery of microwave radiation. [0056] With reference to FIG. 4, cooling fluid exiting one of the plurality of cooling fluid transition apertures 53a - 53d flows distally along the outer surface of the tapered inflow transition collar 53, the outer surface of the channeled puck 46 and the outer surface of the distal radiating portion 44 and along the inner surface of the antenna sleeve 2. Proximal end of antenna sleeve 2 forms a fluid-tight seal with the outer taper 60a of the tapered inflow transition collar 53. In one embodiment, the proximal end 2a of the antenna sleeve 2 mates with a proximal antenna sleeve stop 53s formed in the outer taper 60a such that the outer diameter of the antenna sleeve 2 and the outer diameter of the outer taper 60a are substantially identical. [0057] A channel 67a, 67b, 67c, 67d is formed between each of the adjacent raised portions 66a-66d wherein the radial outer surface of the channeled puck 46 at the raised portion 66a-66d is radially outward from the outer surface of the channeled puck 46 at each of the channels 67a 67d. Channels 67a - 67d are configured to form a cooling fluid pathway between the outer surface of the channeled puck 46 and the inner surface of the antenna sleeve 2. [0058] As illustrated in FIG. 4, cooling fluid exits the middle taper 60b of the tapered inflow transition collar 53, flows distal through the plurality of channels 67a-67d formed between the raised portions 66a-66d of the channeled puck 46 and the antenna sleeve 2 and is deposited on 14 the outer surface of the distal radiating portion 44. The cooling fluid is deposited into a gap formed between the outer surface of the proximal end 2a of the distal radiating portion 44 and the inner surface of the antenna sleeve 2. [0059] Distal end 2b of the distal radiating portion 44 includes a plurality of antenna sleeve stops 68a - 68d. Adjacent antenna sleeve stops 68a - 68d are spaced apart from each other and form a plurality of distal flow channels 70a - 70d therebetween. Distal end 2b of antenna sleeve 2 is configured to abut a distal lip 69a - 69d formed on the distal end of each of the respective antenna sleeve stops 68a - 68d. [0060] Fully assembled, the distal end of the outer jacket 43 forms a fluid tight seal with a proximal portion of the sharpened tip 48. As illustrated in FIG. 6, a fluid-tight seal is formed between the outerjacket 43 and the sharpened tip 48, wherein the fluid-tight seal is distal the distal end 2b of the antenna sleeve 2. As such, the antenna sleeve 2 is contained within the outer jacket 43 and at least a portion of the outflow channel 17o is formed between the inner surface of the outer jacket 43 and the outer surface of the antenna sleeve 2. [0061] In one embodiment, the distal lip 69a - 69d of the respective antenna sleeve stops 68a 68d extend radially outward from the outer surface of the antenna sleeve 2 and space the outer jacket 43 from the outer surface of the antenna sleeve 2. A gap is formed between the antenna sleeve 2 and the outer jacket 43 that forms at least a portion of the outflow channel 17o. The plurality of circumferentially-spaced sleeve stops 68a - 68d uniformly position the outerjacket 43 with respect to the antenna sleeve 2. [0062] FIG. 5 is an exploded view of a portion of the radiating portion 18 illustrated in FIG. 4 including the tapered inflow transition collar 53, the channeled puck 46, the distal radiating portion 44, the antenna sleeve 2 and the sharpened tip 48. Assembled, the channeled puck 46 is positioned between the tapered inflow transition collar 53 and the distal radiating portion 44. Similarly, the antenna sleeve 2 is also positioned between a portion of the tapered inflow transition collar 53 and the distal radiating portion 44; the antenna sleeve 2 being spaced radially outward from the channeled puck 46.

15 [0063] As discussed hereinabove, the tapered inflow transition collar 53 includes an outer taper 60a, a middle taper 60b and an inner taper 60c. A portion of the outer surface of the outer taper 60a may form a proximal antenna sleeve stop 53s configured to receive the proximal end of the antenna sleeve 2. Outer taper 60a is configured to slide over the distal end of the inflow hypotube 55. Inflow hypotube 55 may abut the transition portion between the outer taper 60a and the middle taper 60b. Fluid-tight seals, formed between the inflow hypotube 55 and the outer taper 60a and between the outer conductor 56 and the inner taper 60c, force the cooling fluid traveling distally through in inflow channel 17i (formed between outer surface of the outer conductor 56 and the inner surface of the inflow hypotube 55, see FIG. 3A) to be deposited into the middle taper 60b of the tapered inflow transition collar 53. [0064] In one embodiment the fluid-tight seal between the tapered inflow transition collar 53 and the inflow hypotube 55 is formed by a press-fit connection therebetween. The inflow hypotube 55 may be press-fit over the tapered inflow transition collar 53 or the tapered inflow transition collar 53 may be press-fit over the inflow hypotube 55, as illustrated in FIGS. 2, 4 and 8. [0065] The outer diameters of the outer taper 60a, a middle taper 60b and an inner taper 60c, D1, D2, D3, respectively, and the thickness of each taper 60a-60c are configured to facilitate the assembly of components that form the microwave energy delivery device 12. For example, the diameter D1 and thickness of the outer taper 60a is selected such that the inflow hypotube 55 forms a fluid-tight seal with the inner surface of the outer taper 60a and the antenna sleeve 2 forms a fluid-tight seal with the outer diameter of the outer taper 60a. The diameter D2 of the middle taper 60b is selected to provide an adequate gap between the outer conductor 56 and the antenna sleeve 2 and to facilitate fluid flow through the middle taper 60b. The diameter D3 and thickness of the inner taper 60c is selected such that the outer conductor 56 forms a fluid tight seal with the inner surface of the inner taper 60c and the channeled puck 46 forms a fluid-tight seal with the outer diameter of the inner taper 60c. [0066] The three tiers of the tapered inflow transition collar 53 are configured to facilitate the transition of cooling fluid between a first portion of the inflow channel 17i (radially formed in a first portion of the coaxially configured structure) and a second channel portion of the inflow channel 17i (radially formed in a second portion of the coaxially configured structure). For example (proximal to the tapered inflow transition collar 53), a first portion of the inflow 16 channel 17i is formed between the outer surface of the outer conductor 56 and the inner surface of the inflow hypotube 55 and at a point distal to the tapered inflow transition collar 53, a second portion of the inflow channel 17i is formed between the antenna sleeve 2 and the channeled puck 46. [0067] In another embodiment, the tapered inflow transition collar 53 facilitates the transition of fluid from a first portion of the inflow channel 17i formed at a first radial distance from the radial center of the microwave energy delivery device 12 to a second portion of the inflow channel 17i formed at a second radial distance from the radial center of the microwave energy delivery device 12. The first and second radial distances from the radial center of the microwave energy delivery device 12 may or may not be equal. [0068] The proximal end of the channeled puck 46 is configured to receive at least a portion of the inner taper 60c of the tapered inflow transition collar 53 and forms a fluid-tight seal therebetween and the distal end of the channeled puck 46 is configured to receive at least a portion of the distal radiating portion 44. The inner conductor (not explicitly shown) extends through the radial center of the channeled puck 46 and is received by the distal radiating portion 44. [0069] In one embodiment the channeled puck 46 is injection molded during the manufacturing process to form a water-tight seal around a portion of the outer conductor 56 and/or a portion of the tapered inflow transition collar 53. In another embodiment, the channeled puck 46 is press-fit over a portion of the outer conductor and/or a portion of the tapered inflow transition collar 53 and forms a fluid-tight seal therebetween. [0070] The distal radiating portion 44 includes a conductive member that may be formed from any type of conductive material, such as metals (e.g., copper, stainless steel, tin, and various alloys thereof). The distal radiating portion 44 may have a solid structure and may be formed from solid wire (e.g., 10 AWG). In another embodiment, the distal radiating portion 44 may be formed from a hollow sleeve of an outer conductor 56 of the coaxial cable or another cylindrical conductor. The cylindrical conductor may then be filled with solder to convert the cylinder into a solid shaft. More specifically, the solder may be heated to a temperature sufficient to liquefy the solder within the cylindrical conductor (e.g., 5000 F) thereby creating a solid shaft.

17 [0071] The radially-outward surface of the channeled puck 46 includes a plurality of raised portions 66a-66d and/or a plurality of recessed portions that form the channels 67a-67d. The plurality of raised portions 66a-66d are configured to slideably engage the antenna sleeve 2 and form a plurality of inflow channels 17i defined between the recessed portions and the inner surface of the antenna sleeve 2. [0072] Antenna sleeve 2 is configured to surround the channeled puck 46 and surround at least a portion of the distal radiating portion 44. As discussed hereinabove, the proximal end portion of the antenna sleeve 2 connects to the proximal antenna sleeve stop 53s (formed in a portion of the outer taper 60a) and the distal end portion of the antenna sleeve 2 connects to the distal antenna sleeve stops 68a - 68d formed in the distal radiating portion 44. A electrical connection between the distal radiating portion 44 and the inner conductor (not explicitly shown) may be formed through access slot 70. The access slot 70 may be filled with a suitable electrically conductive material and an electrical connection may be formed between the distal radiating portion 44 and the inner conductor (not explicitly shown). Distal end of the distal radiating portion 44 may connect to sharpened tip 48 or may form the sharpened tip 48. [0073] The inflow channel 17i and the outflow channel 17o (i.e., the paths of the cooling fluid as it flows through the distal end of the microwave energy delivery device 12) are illustrated in FIGS. 4 and 6. Cooling fluid flows distally through the distal flow channels 70a - 70d formed between adjacent antenna sleeve stops 68a- 68d. After the cooling fluid flows distal of the distal end 2b of the antenna sleeve 2, the fluid is deposited in a fluid transition chamber 117 formed between the distal radiating portion 44 and the outer jacket 43. A fluid-tight seal, formed between the outerjacket 43 and the sharpened tip 48, prevents fluid from flowing distal the fluid transition chamber 117. As indicated by the transition arrows cooling fluid in the fluid transition chamber 117 exits the fluid transition chamber 117 and flows proximally and into the outflow channel 17o formed between the outer surface of the antenna sleeve 2 and the inner surface of the outer jacket 43. [0074] In another embodiment and as illustrated in FIGS. 7A - 7B, the radially outward portion of the distal lip 69a - 69d formed on the distal end of each of the respective antenna sleeve stops 68a - 68d (i.e., the portion of the distal lips 69a - 69d that contact the outer jacket 43) may form additional channels between the distal lips 69a - 69d and the outerjacket 43 to allow the cooling fluid to flow proximally from the fluid transition chamber 117.

18 [0075] The distal portion of the outflow channel 17o is illustrated in FIG. 8. The outerjacket 43 forms the outer boundary of the outflow channel 17o in the distal portion of the microwave energy delivery device 12. The distal end of the outer jacket 43 forms a fluid tight seal with the sharpened tip 48 and/or the distal radiating portion 44 and the proximal end forms a fluid tight seal with a portion of the outer hypotube 57 proximal the fluid outflow slots 57a, 57b (57c, 57d not shown). Outer hypotube 57 may further include a proximal outerjacket stop 57s that provides a smooth transition on the outer surface of the microwave energy delivery device 12 between the outer hypotube 57 and the outerjacket. [0076] A portion of the outflow channel 17o is formed between the interior surface of the outer jacket 43 and at least a portion of the antenna sleeve 2, a portion of the tapered inflow transition collar 53, a portion of the choke dielectric 19, a portion of the EMF shield 28 that covers the core choke (not shown) and a portion of the outer hypotube 57. The coaxial arrangement of the outflow channel 17o provides for the uniform application of cooling fluid to the distal portion of the microwave energy delivery device 12. [0077] On the proximal end of the outer jacket 43 the fluid-tight seal between the outer jacket 43 and the outer hypotube 57 directs the cooling fluid to travel through the fluid outflow slots 57a, 57b (57c, 57d not explicitly shown) and into the portion of the outflow channel 17o formed between the interior surface of the outer hypotube 57 and the outer surface of the inflow hypotube 55, as illustrated in FIG. 3A and described hereinabove. [0078] As illustrated in FIGS. 1 - 8 and described hereinabove, the microwave energy delivery devices 12 includes a substantially coaxially arrangement through the length. Various layers of the microwave energy delivery device 12 form a substantially coaxial arrangement of the inflow channel 17i and a substantially coaxial arrangement of the outflow channel 17o between two (or more) of the coaxial layers. The substantially coaxial inflow and outflow channels 17i, 17o coaxially distribute the cooling fluid and thereby provides even cooling throughout the microwave energy delivery device 12. [0079] Various structures in the microwave energy delivery device 12 facilitate the transition of the cooling fluid between the various sections of the inflow and outflow channels 17i, 17o respectively, while maintaining a substantially coaxial arrangement throughout the device. The tapered inflow transition collar 53 transitions the cooling fluid from inflow channel 17i formed 19 between the outer conductor 56 and inflow hypotube 55 and an inflow channel 17i formed between the antenna sleeve 2 and the tapered inflow transition collar 53, the channeled puck 46 and the distal radiating portion 44. The distal flow channels 70a - 70d formed by the arrangement of the antenna sleeve stops 68a - 68d transition the cooling fluid from the inflow channel 17i formed between the antenna sleeve 2 and the distal radiating portion 44 to the outflow channel 17o formed between the outer surface of the antenna sleeve 2 and the inner surface of the outerjacket 43. Finally, the fluid outflow slots 57a - 57d formed in the outer hypotube 57 directs the cooling fluid from outflow channel 17o formed between the EMF shield 28 and the outerjacket 43 and an outflow channel 17o formed between the inflow hypotube 55 and the outer hypotube 57. As such, the cooling fluid maintains a substantially coaxial arrangement along the length of the microwave energy delivery device 12. [0080] Various structures of the microwave energy delivery device 12 facilitate the substantially coaxial fluid flow while supporting the coaxial arrangement. For example, the raised portions 66a of the channeled puck 46, the outer taper 60a of the tapered inflow transition collar 53 and the distal portions of the antenna sleeve stops 68a - 68d position the antenna sleeve 2 in substantially coaxial arrangement while forming a portion of the inflow channel 17i therebetween. Similarly, the sharpened tip 48, the distal portions of the antenna sleeve stops 68a - 68d and the inflow hypotube 55 position the outerjacket 43 in substantially coaxial arrangement while forming a portion of the outflow channel 17o therebetween. [0081] 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. Various modifications and variations can be made without departing from the spirit or scope of the disclosure herein.

Claims (11)

1. A microwave antenna, comprising: a feedline including a coaxial cable including an inner conductor, an outer conductor, and a dielectric disposed therebetween; a radiating section coupled to the feedline, the radiating section including a choke; an inflow tube disposed around the outer conductor, the inflow tube defining an inlet flow path configured to supply a fluid to the radiating section; and a transition collar formed from a dielectric material, the transition collar having a proximal end and a distal end, the proximal end coupled to a distal end of the inflow tube and forming a portion of the choke, the transition collar further including at least one outflow slot at the proximal end thereof configured to receive the fluid from the distal end of the inflow tube and transition the fluid from the at least one outflow slot to a distal end of the radiating section.

2. The microwave antenna according to claim 1, further comprising an outer tube surrounding the inflow tube and coupled to the distal end of the radiating section, the outer tube defining a first gap configured to receive the fluid from the distal end of the radiating section.

3. The microwave antenna according to claim 1, further comprising a sleeve disposed over the at least one outflow slot and at least a portion of the distal end of the radiating section, the sleeve defining a second gap configured to transition the fluid to the at least one outflow slot to the distal end of the radiating section.

4. The microwave antenna according to claim 2, wherein the inflow tube and the outer tube are formed from a conductive material.

5. The microwave antenna according to claim 3, wherein the sleeve is formed from a dielectric material.

6. The microwave antenna according to claim 3, wherein the sleeve has a wall thickness less than about 0.010 inches.

7. The microwave antenna according to claim 3, wherein the dielectric material is a polyimide. 21

8. The microwave antenna according to claim 1, further comprising a puck having a proximal end and a distal end, the puck including a plurality of ribs extending from the proximal end to the distal end defining inflow slots between two adjacent ribs, wherein the distal end of the transition collar is coupled to the proximal end of the puck.

9. The microwave antenna according to claim 8, wherein the puck is formed by injection molding to form a water-tight seal around the outer conductor.

10. The microwave antenna according to claim 1, wherein the transition collar is press-fit over the inflow tube thereby forming a fluid-tight seal therebetween.

11. The microwave antenna according to claim 1, wherein the radiating section further includes an electromagnetic field (EMF) shield disposed about a portion of the radiating section. Covidien LP Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON