FLUID COOLED CHOKE DIELECTRIC AND COAXIAL CABLE DIELECTRIC
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.
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.
BACKGROUND1. Technical Field
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.
2. Background of Related Art
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° 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.
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.
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.
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.
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.
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.
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.
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.
SUMMARYThe 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.
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.
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.
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.
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.
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.
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.
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.
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:
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.
In the monopole antenna of
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.
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® FR3™ 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® and ECO-FR Fluid® 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.
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.
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.
In another embodiment, as illustrated in
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).
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.
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.
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.
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.
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
With reference to
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”.
With reference to
With continued reference to
In another embodiment, the fluid supply lumen 236 and the fluid return lumen 237 extend through the distal radiating portion 205. As illustrated in
Turning now to
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.
Referring to
With reference to
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.
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.
Type: Application
Filed: Nov 4, 2014
Publication Date: Feb 26, 2015
Inventor: Kenlyn S. Bonn (Lakewood, CO)
Application Number: 14/532,337
International Classification: A61B 18/18 (20060101);