US20140052125A1 - Flexible microwave catheters for natural or artificial lumens - Google Patents

Abstract

A method for implementing a microwave ablation waveguide, that includes selecting a lumen adapted to convey a fluid and formed from living biological tissue, introducing an elongate inner conductor into the lumen, positioning at least a portion of the elongate inner conductor within the lumen such that a longitudinal axis of the elongate inner conductor is positioned substantially parallel to and at a desired distance from a longitudinal axis of the lumen and proximate an anatomical feature of interest, and transferring microwave energy along the elongate inner conductor such that the lumen shields the inner conductor and allows a pre-determined amount of microwave energy to propagate through the anatomical feature of interest.

Description

BACKGROUND
• 1. Technical Field
• The present disclosure relates generally to flexible microwave catheters for natural or artificial lumens, and related methods of assembly and use.
• 2. Background of Related Art
• Energy-based tissue treatment is known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal, laser, and so forth) are applied to tissue to achieve a desired result. Disclosed are microwave catheters that enable microwave energy to be effectively delivered within a natural lumen within a body, to a location accessible through a natural or artificial lumen within a body, and/or a body structure such as, for example, an internal organ or body structure.
• One such family of natural lumens includes lumens related to the gastrointestinal system (e.g., mouth, pharynx, esophagus, stomach, pancreatic structures, small and large bowel, bile duct, rectum and anus). Another such family of natural lumens includes lumens related to the auditory system (e.g., auditory canal and Eustachian tube). Yet another such family of natural lumens includes lumens related to the respiratory system (e.g., nasal vestibules, nasal cavity, sinus, trachea and the main and lobar bronchus). Another such family of natural lumens includes lumens related to the urinary system (e.g., urethra, bladder, ureter, prostate, and kidney). Another such family of natural lumens includes lumens related to the female reproductive system (e.g., vagina, cervix, uterus, fallopian tubes, and ovaries). Another such family of natural lumens includes lumens related to the male reproductive system (e.g., urethra, ejaculatory duct, vas deferens, and testis). Other natural lumens may require access via other means, such as common intravascular procedures to gain access to the lumens associated with the vascular system (aorta, arteries, veins, chambers of the heart). Additionally, the lumens associated with the vascular system may provide a pathway and/or access to all internal organs/body structures (e.g., access to the heart, lungs, kidneys, liver, stomach, intestine, colon, spleen, gall bladder and appendix).
• It is believed that renal sympathetic nerve activity initiates, and sustains, the elevation of blood pressure. Chronic elevated blood pressure, or hypertension, is a significant cause of heart disease and death and afflicts millions worldwide. Generally, one having chronic blood pressure of over 140 mm Hg systolic and 90 mm Hg diastolic is classified as suffering from hypertension. Renal denervation has been found to reduce blood pressure. The renal nerves are bundled around the renal artery, which is readily accessible via the femoral artery. Targeting the renal nerves result in additional beneficial outcomes beyond blood pressure reduction which may become primary motivations for the procedure such as metabolic syndrome, heart failure, sleep apnea syndrome, renal insufficiency and diabetic nephropathy
SUMMARY
• In an aspect of the present disclosure, a flexible microwave catheter is provided. The disclosed flexible microwave catheter includes a flexible coaxial cable having an inner conductor, an inner dielectric coaxially disposed about the inner conductor, and an outer conductor coaxially disposed about the inner dielectric. The disclosed flexible microwave catheter includes at least one feedpoint defining a microwave radiating portion of the flexible coaxial cable. A mesh structure having a collapsed configuration and an expanded configuration and disposed about the microwave radiating portion of the flexible coaxial cable is provided, wherein the mesh structure expands radially outward from the flexible microwave catheter thereby positioning the at least one feedpoint at the radial center of the mesh structure. In some aspects, the mesh structure of the flexible microwave catheter includes a conductive material that reduces propagation of denervation energy from the microwave radiating portion in an axial direction.
• In some aspects, the mesh structure comprises an elastomeric balloon having a conductive pattern disposed on an inner surface thereof. In some aspects, the elastomeric balloon in an expanded configuration positions the at least one feed point at the radial center of the mesh structure. In some aspects, the conductive pattern defines a window on the inner surface of the elastomeric balloon, wherein the window is characterized by a lack of the conductive pattern. In some aspects, the mesh structure and the at least one feed point form a circumferentially balanced resonating structure. In some aspects, the mesh structure further includes a distal conductive end-cap mesh, a proximal conductive end-cap mesh, and a tubular mesh body formed between the distal end-cap mesh and the proximal end-cap mesh, wherein the distal conductive end-cap mesh and proximal conductive end-cap mesh reduce propagation of microwave energy from the microwave radiating portion in an axial direction. In some aspects, the tubular mesh body defines a window that radiates energy over 360 degrees along a longitudinal span of about 2 cm to about 3 cm.
• In another aspect of the present disclosure, a flexible microwave catheter is provided having a flexible coaxial cable having an inner conductor, an inner dielectric coaxially disposed about the inner conductor, and an outer conductor coaxially disposed about the inner dielectric. At least one feed gap defines a microwave radiating portion of the flexible coaxial cable. A centering structure is disposed adjacent to the microwave radiating portion of the flexible coaxial cable and has a collapsed configuration and an expanded configuration wherein the centering structure extends radially outward from the flexible microwave catheter thereby positioning the at least one feedpoint at the radial center of the centering structure.
• In some aspects, the centering structure of the flexible microwave catheter includes a stent-like expandable element that expands to a tubular shape when distally advanced from the confides of an outer sheath of the flexible microwave catheter. In some aspects, the stent-like expandable element defines a plurality of windows that radiate energy over 360 degrees along a longitudinal span. In some aspects, the centering structure includes a plurality of centering devices, at least one of the plurality of centering devices being disposed distal each of the at least one feed gaps and at least one of the plurality of centering devices being disposed proximal each of the at least one feed gaps. In some aspects, the plurality of centering devices reduces propagation of microwave energy from each of the at least one feed gaps in an axial direction. In some aspects, the at least one feed gap includes a first feed gap and a second feed gap and the centering structure further includes a first centering device operably associated with the first feed gap, and a second centering device operably associated with the second feed gap, wherein in the expanded configuration the first feed gap is at the radial center of the first centering device and the second feed gap is at the radial center of the second centering device. In some aspects, the first centering device and the second centering device each define a window therein that radiates microwave energy therethrough.
• In some aspects, the centering structure includes an inflatable balloon housing, and a plurality of lobes formed on the inflatable balloon housing, wherein in an expanded configuration, a channel is formed between adjacent lobes of the plurality of lobes. In some aspects, the centering structure includes a plurality of fins equally spaced about the circumference of the flexible microwave catheter, wherein in a collapsed configuration the plurality of fins is restrained within an outer sheath of the flexible microwave catheter and in an expanded configuration the plurality of fins extends radially outward from the flexible microwave catheter. In some aspects, the plurality of fins is dimensioned to self-center the flexible microwave catheter in a fluid flow lumen via fluid/hydrodynamic forces generated by fluid flowing through the fluid flow lumen.
• [In some aspects, the centering structure includes a centering basket. The centering basket includes a first receiver for engaging the flexible microwave catheter, a second receiver for engaging the flexible microwave catheter, and a plurality of bands extending between the first receiver and the second receiver, each of the plurality of bands bowing outwardly and forming an arcuate path between the first receiver and the second receiver. In the collapsed configuration, the plurality of bands is compressed radially inwardly thereby elongating the centering basket. In an expanded configuration, the plurality of bands is uncompressed and extends radially outwardly. In some aspects, the first receiver fixedly engages the flexible microwave catheter and the second receiver slidably engages the flexible microwave catheter.
• In some aspects, the centering structure includes at least two centering baskets. Each of the at least two centering baskets includes a first receiver for engaging the flexible microwave catheter, a second receiver for engaging the flexible microwave catheter, and a plurality of bands extending between the first receiver and the second receiver, each of the plurality of bands bowing outwardly and forming an arcuate path between the first receiver and the second receiver. In the collapsed configuration, the plurality of bands is compressed radially inwardly thereby elongating the centering basket and in an expanded configuration the plurality of bands is uncompressed and extends radially outwardly. In some aspects, the first receiver fixedly engages the flexible microwave catheter and the second receiver slidably engages the flexible microwave catheter. In some aspects, one of the at least one feed gaps is located between a first and a second of the at least two centering baskets.
• In some aspects, the centering structure includes a plurality of paddles equally spaced about the circumference of the flexible microwave catheter. Each of the plurality of paddles is hingedly attached to the flexible microwave catheter, wherein in a collapsed configuration the plurality of paddles is adjacent and parallel the flexible microwave catheter and in expanded configuration the plurality of paddles extends perpendicular to, and extending radially outwardly from, the flexible microwave catheter.
• In some aspects, the centering structure includes a plurality of helical ribs connected to the outer surface of the flexible microwave catheter an extending about the outer surface of the flexible microwave catheter in a helical-like fashion, wherein in collapsed configuration the plurality of helical ribs is compressed between the flexible coaxial cable and an inner surface of the outer sheath of the flexible microwave catheter and in an expanded configuration, the plurality of helical ribs extends radially from the flexible coaxial cable.
• In yet another aspect of the present disclosure, a coupler for coupling a coaxial flexible cable, a fluid cooling system, and the outer sheath of a catheter, is provided. The coupler includes a fluid coupler body having a fluid inlet formed in the fluid coupler body and configured to operably couple to a source of cooling fluid and receive fluid therefrom, a fluid outlet formed in the fluid coupler body and configured to operably couple to a fluid discharge, a bypass bulb forming an aperture for slidably coupling with a coaxial cable, and an outer sheath coupler forming an aperture for coupling with an outer sheath of a catheter while forming a fluid-tight seal therewith. The coupler includes a fluid sealing system housed in the fluid coupler body having a distal sealing diaphragm configured to form a fluid-tight seal about an outer surface of an inflow lumen and a fluid-tight seal with an interior surface of the fluid coupler body defining an outflow plenum in fluid communication with the fluid outlet, the outflow plenum formed between a distal interior surface of the fluid coupler body, the outer surface of the inflow lumen, a distal side of the distal sealing diaphragm and the outer sheath coupler. The coupler includes a proximal sealing diaphragm configured to form a fluid-tight seal about an outer surface of the coaxial cable and a fluid-tight seal with an interior surface of the fluid coupler body thereby forming an inflow plenum in fluid communication with the fluid inlet, the outflow plenum formed between a proximal interior surface of the fluid coupler body, and a proximal side of the distal sealing diaphragm, a proximal side of the proximal sealing diaphragm.
• In some aspects, the catheter is coaxially formed about the inner lumen, the inner lumen is coaxially formed about the coaxial cable, and the inflow plenum is in fluid communication with a fluid passageway formed between the outer surface of the coaxial cable and the inner surface of the inflow lumen. In some aspects, the catheter is coaxially formed about the inner lumen, the inner lumen is coaxially formed about the coaxial cable, the outflow plenum is in fluid communication with a fluid passageway formed between the outer surface of the inflow lumen and the inner surface of the outer sheath.
• In some aspects, the catheter is coaxially formed about the inner lumen, the inner lumen is coaxially formed about the coaxial cable, the inflow plenum is in fluid communication with a fluid passageway formed between the outer surface of the coaxial cable and the inner surface of the inflow lumen, and the outflow plenum is in fluid communication with a fluid passageway formed between the outer surface of the inflow lumen and the inner surface of the outer sheath. In some aspects, the fluid coupler body slidably engages the coaxial cable.
• In yet another aspect of the present disclosure, a microwave energy delivery device is provided. The microwave energy delivery device includes a coaxial feedline having an inner conductor, an inner dielectric insulator coaxially disposed about the inner conductor, and an outer conductor coaxially disposed about the inner dielectric. The microwave energy delivery device includes a radiating portion operably coupled to a distal end of the coaxial feedline. The radiating portion includes a radiating portion inner conductor operably coupled to and extending from a distal end of the coaxial feedline inner conductor; a shielding outer conductor helically wrapped about the radiating portion inner conductor and operably coupled to the coaxial feedline outer conductor, and a shielding dielectric positioned between the radiating portion inner conductor and the shielding outer conductor. The width of the shielding outer conductor varies according to the longitudinal position thereof along the coaxial feedline inner conductor. A cap operably couples to a distal end of the radiating portion inner conductor and the shielding outer conductor, and provides an electrical connection therebetween.
• In some aspects, the microwave energy delivery device includes a temperature sensor disposed at a distal end thereof. In some aspects, a radiation pattern generated by the radiating portion is related to at least one of the variable width of the shielding outer conductor, or a variable helix angle of the shielding outer conductor.
• In some aspects, the microwave energy delivery device includes a feed gap defined by a void formed between adjacent wraps of the shielding outer conductor. In some aspects, a feed gap ratio, defined by the ratio of a feed gap circumference and a shielding outer conductor circumference along a cross section, changes linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio changes non-linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio varies between 0% at the proximal end of the radiating portion and about 50% at the distal end of the radiating portion. In some aspects, the feed gap ratio varies between 0% on the proximal end of the radiating portion and about 100% on the distal end of the radiating portion.
• In some aspects, the microwave energy delivery device generates a helical-shaped electromagnetic field that extends along the longitudinal length of the radiating portion. In some aspects, the helical-shaped electromagnetic field is related to a void formed between the individual wraps of the shielding outer conductor. In some aspects, the shielding outer conductor includes at least two helix turns. In some aspects, the cap provides an electrical connection between the radiating portion inner conductor and the shielding outer conductor.
• In yet another aspect of the present disclosure, a microwave energy delivery device is provided that includes a coaxial feedline having an inner conductor, an inner dielectric insulator coaxially disposed about the inner conductor, and an outer conductor coaxially disposed about the inner dielectric. The microwave energy delivery device includes a radiating portion operably coupled to a distal end of the coaxial feedline that includes a radiating portion inner conductor operably coupled to and extending from a distal end of the coaxial feedline inner conductor, a shielding outer conductor helically wrapped about the radiating portion inner conductor and operably coupled to the coaxial feedline outer conductor, a shielding dielectric positioned between the radiating portion inner conductor and the shielding outer conductor. The helix angle of the shielding outer conductor varies according to the longitudinal position thereof along the coaxial feedline inner conductor. A cap operably couples to a distal end of at least one of the radiating portion inner conductor and the shielding outer conductor.
• In some aspects, the microwave energy delivery device includes a feed gap defined by a void formed between adjacent wraps of the shielding outer conductor. In some aspects, a feed gap ratio, defined by the ratio of a feed gap circumference and a shielding outer conductor circumference along a cross section, change linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio changes non-linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio varies between 0% at the proximal end of the radiating portion and about 50% at the distal end of the radiating portion. In some aspects, the microwave energy delivery device generates a helical-shaped electromagnetic field that extends along the longitudinal length of the radiating portion. In some aspects, the helical-shaped electromagnetic field is related to a void formed between the individual wraps of the shielding outer conductor. In some aspects, a cap provides an electrical connection between the radiating portion inner conductor and the shielding outer conductor.
• In still another aspect of the present disclosure, a microwave energy delivery device is provided that includes a coaxial feedline having an inner conductor, an inner dielectric insulator coaxially disposed about the inner conductor, and an outer conductor coaxially disposed about the inner dielectric. The disclosed microwave energy delivery device includes a radiating portion operably coupled to a distal end of the coaxial feedline. The radiating portion includes a radiating portion inner conductor operably coupled to and extending from a distal end of the coaxial feedline inner conductor, a shielding outer conductor helically wrapped about the radiating portion inner conductor and operably coupled to the coaxial feedline outer conductor, and a shielding dielectric positioned between the radiating portion inner conductor and the shielding outer conductor. The pitch of the helix angle of the shielding outer conductor varies according to the longitudinal position thereof along the coaxial feedline inner conductor. A cap is operably coupled to a distal end of at least one of the radiating portion inner conductor and the shielding outer conductor.
• In some aspects, the microwave energy delivery includes a feed gap defined by a void formed between adjacent wraps of the shielding outer conductor. In some aspects, a feed gap ratio, defined by the ratio of a feed gap circumference and a shielding outer conductor circumference along a cross section, changes linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio changes non-linearly from a proximal end of the shielding outer conductor to a distal end of the shielding outer conductor. In some aspects, the feed gap ratio varies between 0% at the proximal end of the radiating portion and about 50% at the distal end of the radiating portion. In some aspects, the microwave energy delivery device generates a helical-shaped electromagnetic field that extends along the longitudinal length of the radiating portion. In some aspects, the helical-shaped electromagnetic field is related to a void formed between the individual wraps of the shielding outer conductor. In some aspects, the cap provides an electrical connection between the radiating portion inner conductor and the shielding outer conductor.
• In yet another aspect of the present disclosure, a method for forming a resonating structure within a body lumen is provided. The method includes advancing a flexible microwave catheter with a body lumen of a patient, the flexible microwave catheter including a radiating portion on the distal end of the flexible microwave catheter, the radiating portion configured to receive a microwave energy signal at a microwave frequency, and at least one centering device adjacent the radiating portion and configured to deploy radially outward from the flexible microwave catheter. The radiating portion is positioning adjacent a targeted tissue. At least one centering device is deployed radially outward from the flexible microwave catheter and within the body lumen to position the radiating portion at the radial center of the body lumen. A circumferentially balanced resonating structure is formed within the body lumen via the radiating portion, and a microwave energy signal at the microwave frequency is delivered from the radiating portion, and resonates the body lumen at the microwave frequency.
• In some aspects, the circumferentially balanced resonating structure radiates energy over 360 degrees along a longitudinal span of about 2 cm to about 3 cm. In some aspects, body lumen is the renal artery. In some aspects, the targeted tissue is the renal nerve and the circumferentially balanced resonating structure generates an electromagnetic field that denervates the targeted tissue.
• In some aspects, the method further including the steps of providing a continuous fluid flow with the body lumen, and cooling at least a portion of the body lumen. In some aspects, the method further includes the step of continuing the delivery of the microwave energy signal until a sufficient amount of energy has been delivered to effectively damage the targeted tissue while preserving the critical structure of the body lumen.
• In some aspects, the method further includes the steps of monitoring the temperature of the continuous fluid flow, and terminating the delivery of microwave energy if the monitored temperature exceeds a threshold temperature.
• In some aspects, the body lumen is selected from at least one of a gastrointestinal lumen, an auditory lumen, a respiratory system lumen, urinary system lumen, a female reproductive system lumen, a male reproductive system lumen, a vascular system lumen, and an internal organ.
• [In some aspects, the method further includes expanding the body lumen to form a structure related to the microwave frequency.
• In some aspects, the method further includes selecting the microwave frequency to resonate the body lumen based on the anatomical structure of the body lumen.
• In some aspects, the method further includes monitoring a temperature within the body lumen, and terminating the delivery of the microwave energy signal when the temperature exceeds a threshold temperature.
• In some aspects, the radiating portion includes a feed gap forming an open circuit in the flexible microwave catheter. In some aspects, the radiating portion includes a first feed gap and a second feed gap wherein the first and second feed gaps each form open circuits in the flexible microwave catheter.
• In still another aspect of the present disclosure, a method for forming a resonating structure within a body lumen is presented. The presented method includes advancing a flexible microwave catheter with a body lumen of a patient. The flexible microwave catheter includes a radiating portion on the distal end of the flexible microwave catheter that is configured to receive a microwave energy signal at a microwave frequency, an electrically conductive mesh adjacent the radiating portion, and a retractable sheath configured to deploy the electrically conductive mesh about the radiating portion. The method includes positioning the radiating portion adjacent a targeted tissue, retracting the retractable sheath, deploying the electrically conductive mesh radially outward from the flexible microwave catheter and within the body lumen thereby centering the radiating portion at the radial center of the body lumen, forming a circumferentially balanced resonating structure within the body lumen via the radiating portion, and delivering the microwave energy signal at the microwave frequency to resonate the body lumen at the microwave frequency.
• In some aspects, the method includes forming a window in the electrically conductive mesh, the window being characterized by a lack of material, and heating a region of the body lumen related to the window. In some aspects, the body lumen is a renal artery, the targeted tissue is a renal nerve, and heating the region of the body lumen related to the window at least partially denervates the kidney.
• In some aspects, the method includes the step of cooling at least a portion of the renal artery.
• In some aspects, the method includes the steps of providing a fluid cooling structure to enhance energy delivery and reduce heating of a least a portion of the flexible microwave catheter. The body lumen may be selected from at least one of a gastrointestinal lumen, an auditory lumen, a respiratory system lumen, urinary system lumen, a female reproductive system lumen, a male reproductive system lumen, a vascular system lumen, and an internal organ. In some aspects, the circumferentially balanced resonating structure radiates energy over 360 degrees along a longitudinal span of about 2 cm to about 3 cm.
• In yet another aspect of the present disclosure, a method for implementing a microwave ablation waveguide is provided. The method includes the steps of selecting a lumen adapted to convey a fluid and formed from living biological tissue, longitudinally introducing an elongate inner conductor into the lumen, positioning a distal end of the elongate inner conductor at a location within the lumen adjacent to an anatomical feature of interest, centering at least a portion of the elongate inner conductor along the longitudinal axis of the lumen, energizing the elongate inner conductor with microwave ablation energy, and electrically shielding, with the lumen, the elongate inner conductor to reduce propagation of microwave ablation energy proximally of the anatomical feature of interest. In some aspects, the lumen is selected in accordance with a dielectric property of the fluid conveyed therein.
• In some aspects, the centering step includes providing a centering member which facilitates the flow of the conveyed fluid therethrough. In some aspects, the method further includes the step of altering a dielectric property of the conveyed fluid. In some aspects, the method further includes the step of introducing a fluid amendment into the conveyed fluid. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter. The sensed electrical parameter may be selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter. The sensed biological parameter may be selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response. In some aspects, the fluid amendment may be introduced into the conveyed fluid at continuous rate. In some aspects, the fluid amendment is introduced into the conveyed fluid at variable rate. The fluid amendment may be introduced into the conveyed fluid at a rate selected in response to a sensed electrical parameter and/or a sensed biological parameter.
• In still another aspect of the present disclosure, a method of using a microwave ablation instrument having a radiation pattern is provided. The method includes selecting a lumen adapted to convey a fluid and formed from living biological tissue, longitudinally introducing the microwave ablation pattern into the lumen, positioning the radiation pattern of the microwave ablation instrument at a location adjacent to an anatomical feature of interest, energizing the microwave ablation instrument with microwave ablation energy, and electrically shielding, with the lumen, the microwave ablation instrument to reduce propagation of microwave ablation energy along the lumen proximally of the anatomical feature of interest.
• In some aspects of the method, the lumen is selected in accordance with a dielectric property of the fluid conveyed therein. In some aspects, the method includes altering a dielectric property of the conveyed fluid. In some aspects, the method includes introducing a fluid amendment into the conveyed fluid. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter. In some aspects the sensed electrical parameter is selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter. In some aspects, the sensed biological parameter is selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response.
• In yet another aspect of the present disclosure, a method for implementing a microwave ablation waveguide is provided. The method includes the steps of selecting a lumen adapted to convey a fluid and formed from living biological tissue, introducing an elongate inner conductor into the lumen, positioning at least a portion of the elongate inner conductor within the lumen such that a longitudinal axis of the elongate inner conductor is positioned substantially parallel to and at a desired distance from a longitudinal axis of the lumen and proximate an anatomical feature of interest, and transferring microwave energy along the elongate inner conductor such that the lumen shields the inner conductor and allows a predetermined amount of microwave energy to propagate through the anatomical feature of interest. In some aspects of the method, the lumen is selected in accordance with a dielectric property of the fluid conveyed therein. In some aspects, the method includes altering a dielectric property of the conveyed fluid. In some aspects, the method includes introducing a fluid amendment into the conveyed fluid. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter. In some aspects the sensed electrical parameter is selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter. In some aspects, the sensed biological parameter is selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response.
• In still another aspect of the present disclosure, a method of using a microwave ablation instrument is provided. The method includes selecting a lumen adapted to convey a fluid and formed from living biological tissue, introducing a microwave antenna having an outer conductor with a structure capable of producing a predefined radiation pattern into the lumen, positioning the microwave antenna at a location proximate an anatomical feature of interest, and energizing the microwave antenna with microwave energy such that as the microwave energy emanates from the microwave antenna in the predetermined radiation pattern, the lumen controls the amount of microwave energy allowed to propagate therethrough. In some aspects of the method, the lumen is selected in accordance with a dielectric property of the fluid conveyed therein. In some aspects, the method includes altering a dielectric property of the conveyed fluid. In some aspects, the method includes introducing a fluid amendment into the conveyed fluid. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter. In some aspects the sensed electrical parameter is selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance. In some aspects, the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter. In some aspects, the sensed biological parameter is selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response.
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings, which are incorporated in, and constitute a part of this specification, illustrate various example embodiments of the present disclosure. Together with the general description given above, and the detailed description of the embodiments given below, the accompanying drawings serve to explain the principles of the system, apparatus and methods disclosed herein.
• FIG. 1 is a partial cross-sectional view of a flexible microwave catheter accessing the renal artery via the vascular system according to some embodiments of the present disclosure;
• FIG. 2 is a system diagram of a microwave energy delivery system having a flexible microwave catheter according to some embodiments of the present disclosure;
• FIG. 3 is a partial cross-sectional view of a flexible microwave catheter accessing the renal artery via the vascular system in accordance with some embodiments of the present disclosure;
• FIG. 4A is a transverse cross-sectional view of the anatomical structure of a renal artery;
• FIG. 4B is a transverse cross-sectional view of an embodiment of a flexible coaxial cable in accordance with some embodiments of the present disclosure;
• FIG. 4C is a transverse cross-sectional view of an embodiment of a microwave waveguide structure within a natural body lumen in accordance with some embodiments of the present disclosure;
• FIG. 5 is a longitudinal cross-section of an embodiment of a microwave waveguide structure in accordance with some embodiments of the present disclosure;
• FIG. 6A is a block diagram of a catheter hub according to some embodiments of the present disclosure;
• FIG. 6B is a transverse cross-section of an embodiment of a flexible microwave catheter according to some embodiments of the present disclosure;
• FIG. 7 is a system diagram of an embodiment of a microwave energy delivery system in accordance with some embodiments of the present disclosure having a flexible microwave catheter with at least a part of the radiating portion housed in the outer sheath of the flexible microwave catheter;
• FIGS. 8A-8C illustrate embodiments of longitudinal cross-sections of catheter hub couplers according to some embodiments of the present disclosure;
• FIG. 9A is a side view of an embodiment of a flexible microwave catheter guide wire system according to some embodiments of the present disclosure;
• FIGS. 9B-9C are longitudinal cross-sectional diagrams of the guide wire system ofFIG. 9A;
• FIGS. 10A-10B are longitudinal and transverse cross-sections, respectively, of an embodiment of a flexible microwave catheter centered in a renal artery in accordance with some embodiments of the present disclosure;
• FIGS. 11A-11B are longitudinal and transverse cross-sections, respectively, of a flexible microwave catheter in an off-center position within a renal artery;
• FIGS. 12A-12B are longitudinal and transverse cross-sections, respectively, of a flexible microwave catheter in an off-center position within a renal artery;
• FIG. 13 illustrates a relationship between temperatures measured inside and outside the renal artery and power measured during an experimental procedure;
• FIGS. 14A-14F illustrates steps of a manufacturing process for assembling some of the embodiments of the present disclosure;
• FIG. 15A is a longitudinal, cross-sectional view of an embodiment of a radiating portion cap in accordance with the present disclosure for returning circulating fluid from an inflow fluid passageway to an outflow fluid passageway;
• FIG. 15B is a perspective view with partial cross-section of the cap ofFIG. 15A;
• FIGS. 16A-16B are longitudinal, cross-sectional views of embodiments of stent-like expandable elements associated with a radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 16C is a side view of an embodiment of a stent-like expandable element associated with a radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 17A is a perspective view of an embodiment of a conductive mesh structure that defines a plurality of windows for selectively delivering denervation energy to tissue in accordance with some embodiments of the present disclosure;
• FIG. 17B is a perspective view of a portion of a renal artery after receiving the selectively delivered denervation energy from the conductive mesh structure ofFIG. 17A;
• FIG. 18A is a perspective view of an embodiment of a conductive mesh structure that defines a window for selectively delivering denervation energy to tissue in accordance with some embodiments of the present disclosure;
• FIGS. 18B-18G are perspective views illustrating steps of a surgical procedure in accordance with some embodiments of the present disclosure utilizing the conductive mesh structure ofFIG. 18A;
• FIG. 19A is a perspective view of an embodiment of a conductive mesh structure that defines a plurality of windows for selectively delivering denervation energy to tissue in accordance with some embodiments of the present disclosure;
• FIG. 19B is a perspective view of a portion of a renal artery after receiving selectively delivered denervation energy from the conductive mesh structure ofFIG. 19A;
• FIG. 20 is a side view of an embodiment of a radiating portion in accordance with some embodiments of the present disclosure having a plurality of conductive mesh structures each defining a window for selectively delivering denervation energy to tissue;
• FIG. 21 is a side view of an embodiment of a radiating portion in accordance with some embodiments of the present disclosure having a plurality of conductive mesh structures that define a plurality of radiating portions;
• FIG. 22A is a side view of an embodiment of a radiating portion in accordance with some embodiments of the present disclosure having a distal mesh basket structure and a proximal mesh structure;
• InFIG. 22B is a side view of an embodiment of a radiating portion in accordance with some embodiments of the present disclosure having a proximal mesh structure and a distal mesh basket structure operably coupled to the cap via a tether;
• FIG. 23 is a perspective view of an embodiment of a stepped flexible microwave catheter with a stepped diameter in accordance with some embodiments of the present disclosure;
• FIG. 24 is a side view of a radiating portion of an embodiment of a flexible microwave catheter that includes an inflatable centering balloon in accordance with some embodiments of the present disclosure;
• FIG. 25A is a longitudinal, cross-sectional view of an embodiment of a microwave energy delivery system having a distal radiating portion within an inflatable balloon in accordance with some embodiments of the present disclosure;
• FIG. 25B is a transverse, cross-sectional view of an embodiment of the distal radiating portion of the microwave energy delivery system ofFIG. 25A;
• FIG. 26A is a perspective view of an embodiment of an inflatable balloon having a plurality of lobes for centering a radiating portion in a body lumen in accordance with some embodiments of the present disclosure;
• FIG. 26B is a transverse, cross-sectional view of the inflatable balloon ofFIG. 26A;
• FIG. 26C is a perspective view of the housing of the inflatable balloon ofFIG. 26A;
• FIGS. 27A-27B are longitudinal and transverse cross-sectional views, respectively, of a centering device housed in the outer sheath of the flexible microwave catheter in accordance with some embodiments of the present disclosure;
• FIG. 27C is a longitudinal cross-sectional view of an embodiment of a centering device deployed from the outer sheath of a flexible microwave catheter in accordance with some embodiments of the present disclosure;
• FIG. 27D is a perspective view of the centering device ofFIGS. 27A-27C in a deployed position;
• FIG. 28 is a perspective view of an embodiment of a four-prong centering device in accordance with some embodiments of the present disclosure;
• FIG. 29 is perspective view of an embodiment of a centering basket adapted to center a radiating portion of a distal portion of a flexible microwave catheter in accordance with some embodiments of the present disclosure;
• FIG. 30 is perspective view of an embodiment of a centering basket adapted to center a radiating portion of a flexible microwave catheter proximal the radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 31 is perspective view of an embodiment of a centering basket adapted to center a radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 32A is a perspective view of an embodiment of a proximal centering basket and a distal centering basket operably coupled to the distal end of a flexible microwave catheter in accordance with some embodiments of the present disclosure;
• FIG. 32B is a perspective view of an embodiment of a proximal centering basket and a distal centering basket operably coupled to the distal end of a flexible microwave catheter in accordance with some embodiments of the present disclosure;
• FIG. 33 is a perspective view of an embodiment of a dual-band centering device centered on the radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 34 is a perspective view of an embodiment of a clover-leaf centering device including a plurality of petals for centering a radiating portion in accordance with some embodiments of the present disclosure;
• FIG. 35 is a perspective view of an embodiment of the distal end of a flexible microwave catheter including a clover-leaf centering device and a centering basket in accordance with some embodiments of the present disclosure;
• FIGS. 36A and 36B are perspective views of an embodiment of a deployable paddle centering device in accordance with some embodiments of the present disclosure;
• FIGS. 37A and 37B are perspective views of an embodiment of a deployable dual paddle centering device in accordance with some embodiments of the present disclosure;
• FIGS. 38A and 38B are perspective views of an embodiment of a deployable paddle centering device in accordance with some embodiments of the present disclosure;
• FIGS. 39A and 39B are perspective views of an embodiment of deployable dual paddle centering device in accordance with some embodiments of the present disclosure;
• FIGS. 40A and 40B are perspective views of an embodiment of a deployable centering device with a plurality of tines in accordance with some embodiments of the present disclosure;
• FIGS. 41A and 41B are perspective views of an embodiment of a helical centering devices in accordance with some embodiments of the present disclosure;
• FIG. 42 is a side view of a distal portion of theFIG. 7 embodiment of a microwave energy radiating device having a portion of the outer sheath removed and having a configurable portion in a fully retracted position;
• FIG. 43 is a side view of a distal portion of theFIG. 7 embodiment of a microwave energy radiating device having a portion of the outer sheath removed and having a configurable portion in a partially deployed position;
• FIG. 44 is a side view of the distal portion of theFIG. 7 embodiment of a microwave energy radiating device having a portion of the outer sheath removed and having a configurable portion in a fully deployed position;
• FIG. 45 is a side, perspective view of an embodiment of a microwave energy radiating device having a non-linear wrap pattern in accordance with some embodiments of the present disclosure;
• FIG. 46 is a top, perspective view of the outer conductor of theFIG. 45 embodiment having been removed therefrom;
• FIG. 47 is a side, perspective view of an embodiment of a microwave energy radiating device having a non-linear wrap pattern according to another embodiment of the present disclosure;
• FIG. 48 is a top, perspective view of the outer cover of theFIG. 47 embodiment having been removed therefrom;
• FIG. 49 is a graph illustrating a ratio of a radiating portion to a non-radiating portion of the microwave energy radiating devices ofFIGS. 44,45 and47;
• FIG. 50 is an electrical circuit diagram of an embodiment of a leaky waveguide according to the present disclosure;
• FIG. 51 illustrates an embodiment of a leaky waveguide having a varying slot width according to the present disclosure;
• FIG. 52 is an electrical diagram of an embodiment of a ten-slot waveguide in accordance with the present disclosure illustrating the available energy for each slot and the percentage of the available energy transmitted from each slot;
• FIG. 53 is a side view of an embodiment of a ten-slot waveguide in accordance with the present disclosure wherein each slot transmits a substantially similar amount of energy,
• FIG. 54 is a side view of an embodiment of a helix waveguide with ten helix wraps according to embodiments of the present disclosure,
• FIG. 55 is a perspective view of a five-slot waveguide according to embodiments of the present disclosure;
• FIG. 56 is a perspective view of a helix waveguide with five helix wraps according to embodiments of the present disclosure;
• FIG. 57 is a side-by-side comparison of a five-slot waveguide and a helix waveguide with five helix wraps according to embodiments of the present disclosure.
• FIG. 58A is a perspective view of an embodiment of a balloon centering device in a deflated configuration with a spiral window formed therein in accordance with some embodiments of the present disclosure;
• FIG. 58B is a perspective view in partial cross-section of the balloon centering device ofFIG. 58A in a fully inflated configuration and positioned in the renal artery via the vascular system; and
• FIG. 58C is a perspective view of a portion of a renal artery after receiving selectively delivered denervation energy from the balloon catheter ofFIGS. 58A-58C.
DETAILED DESCRIPTION
• Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Well-known and/or repetitive functions and constructions are not described in detail to avoid obscuring the present disclosure in unnecessary or redundant detail. Therefore, the terminology used herein for the purpose of describing particular embodiments, specific structural and functional details disclosed herein, as well as the specific use disclosed herein, are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. In this description, as well as the drawings, like-referenced numbers represent elements which may perform the same, similar, or equivalent functions.
• As used herein, the term “proximal,” as is traditional, shall refer to the end of the instrument that is closer to the user, while the term “distal” shall refer to the end that is farther from the user. As used herein, terms referencing orientation, e.g., “top”, “bottom”, “up”, “down”, “left”, “right”, “o'clock”, and the like, are used for illustrative purposes with reference to the figures and corresponding axes and features shown therein. It is to be understood that embodiments in accordance with the present disclosure may be practiced in any orientation without limitation.
• As discussed hereinabove, a flexible microwave catheter may be used to perform a procedure by utilizing a natural or artificial lumen. One particular procedure discussed herein is a denervation procedure that utilizes the vascular system to access a kidney. Embodiments are disclosed herein whereby the energy and antenna characteristics are designed to enable application of microwave denervation energy to a targeted neurological structure, such as without limitation, a sympathetic nerve bundle surrounding a renal artery, although the devices and methods may be utilized in any other procedure and on any other body lumen, organ or bodily structure. This particular procedure is only used to demonstrate general concepts and the use of some embodiments in accordance with the present disclosure. For example, embodiments of the flexible microwave catheter disclosed herein may also be used to perform procedures in the respiratory system, e.g., to treat tumors in the upper respiratory tract and the lungs, as well as to treat asthma, chronic obstructive pulmonary disease (COPD) emphysema, etc.
• As illustrated inFIG. 1, the disclosedflexible microwave catheter30 is percutaneously introduced into the femoral artery FA through anarterial catheter110 and positioned within the right renal artery RRA and adjacent to the right renal nerve bundle RRN. Theflexible microwave catheter30 includes a radiatingportion100 that cooperates advantageously with the right and/or left renal artery RRA, LRA (hereinafter, “renal artery RA”) physiology to deliver denervation energy to the respective right and/or left renal nerve bundles RRN, LRN (hereinafter “renal nerve RN”) while minimizing collateral damage to the respective arterial vessel and related anatomical structures. In the discussion to follow, the renal nerve RN and the renal artery RA are used to illustrate embodiments in accordance with the present disclosure however it is to be understood the disclosed embodiments may be used with either the right renal artery RRA or the left renal artery LRA to deliver denervation energy to the respective right renal nerve bundle RRN and left renal nerve bundle LRN.
• Elevated sympathetic nerve activity initiates and sustains the elevation of blood pressure. The renal nerve bundle RN include the renal sympathetic nerves (efferent and afferent) that are bundled around the renal artery RA. As such, the renal artery RA facilitates access to the renal nerve bundles RN through the femoral artery FA and/or the abdominal aorta A. Theflexible microwave catheter30 places the radiatingportion100 of a microwave energy applicator in close proximity to the renal nerve bundles RN. Once positioned in the renal artery RA, the radiatingportion100 can focus energy from within the renal artery RA toward the respective renal nerves bundle RN surrounding the renal artery RA in an effort to denervate the kidneys and ultimately reduce blood pressure.
• As discussed in greater detail hereinbelow, the various embodiments include structures that allow for the application of electrosurgical energy to one or more locations within the renal artery RA (or other lumen or body structure) without compromising the overall integrity of the vessel wall. In some embodiments, the energy delivery structure does not mechanically contact the vessel wall, thereby reducing complications from perforation or stenosis as a result of mechanical damage. In some embodiments, the energy delivery structure directs energy to a particular portion of one or more layers of the body lumen/body structure thereby maintaining the overall viability of the body lumen/body structure. In some embodiments blood or fluid flow with the vessel contributes to cooling of inner layers of the vessel wall, thereby reducing unwanted heating and collateral damage to the vessel wall while enabling energy delivery to the outer layer proximate the renal nerves.
• The systems, devices and methods described herein provide spatial energy control of microwave energy. Spatial energy control incorporates three factors, namely, repeatability of energy delivery, precise control of the delivered energy, and efficient delivery of energy. The factors that contribute to spatial energy control include thermal management, dielectric management, buffering, and electrical current control. These factors can be controlled through systems, devices and methods that operate in tandem with the surrounding anatomical structure, effectively incorporating the surrounding tissue as part of the microwave device.
• Microwave energy systems and devices exhibit behaviors that are fundamentally different than behaviors of systems and devices using lower frequency RF signals. For example, the operation and functionality of a RF system, using low frequency “RF” signals, requires an electrical circuit that includes a closed-loop connection of conductive materials, e.g., a completed electrical circuit. The behavior of the circuit is directly dependant on the electrical properties of the closed connection of conductive materials. The most obvious behavior and example being that in a RF circuit, a break in the closed-loop connection of conductive materials, e.g., an open circuit, renders the system inoperable.
• Microwave systems, on the other hand, transmit microwave energy signals through waveguides. The most common example of a waveguide being a coaxial cable that consists of an inner conductor positioned coaxially within an outer conductor by a dielectric. Unlike a RF circuit, creating an open circuit (e.g., slot) in the coaxial outer conductor does not render the system inoperable. Instead, the waveguide continues to convey the microwave signal, and the slot radiates a portion of the energy being transmitted by the waveguide.
• As such, some embodiments of the systems, devices and methods described herein incorporate a portion of the anatomical structure into the design of the microwave energy delivery system. More specifically, the cylindrical structure of natural body lumens and other body structures that are concentric in nature can be utilized to operate in conjunction with, and become part of, a waveguide used by the devices described herein to transmit microwave energy.
• The use of the natural lumen structure and/or body structure as a component of the radiating structure enables enhanced energy delivery techniques, such as focusing microwave energy-induced thermal therapy to a targeted anatomy. For example, as noted above structures described herein are capable of targeting the smooth muscle layer within the bronchus of the lungs, and are capable of targeting the renal nerves within the adventitia layer of the renal nerve. Additionally, the use of the devices described herein within the lumen structures enables the formation of a directional radiating pattern to specific sections of the lumen.
• In some embodiments, the devices described herein also utilize the fluids present in the natural body lumens to perform dielectric loading of the anatomical radiating structure. The properties of the fluid are incorporated into the design of the microwave radiator as a design component. For example, bodily fluids may form a dielectric layer and/or a conductive layer of an anatomical waveguide and the properties of the fluid are utilized in the design, such as, for example, for impedance matching, energy efficiency, wavelength buffering, and radiation pattern control and shaping.
• The fluid's dielectric properties may be externally manipulated and/or adjusted by introducing (and/or eliminating) one or more elements into the fluid. For example, fluids high in water content exhibit a high dielectric constant that enable shaping of microwave fields around radiation structures. As such, the dielectric properties of blood may be adjusted by modifying the plasma composition and adjusting the ratio of water, protein, inorganic salts, and organic substances. Similarly, the dielectric properties of blood may be adjusted by changing the glucose levels. In this manner, changing the dielectric property of the fluids may effectuate changes in the performance of the devices described herein, since the bodily fluids can be used as the dielectric layer in the anatomical waveguides discussed herein.
• The systems, devices, and methods described herein also utilize fluids (e.g., natural or externally introduced) within the natural body lumens for thermal management of one or more layers of the anatomical waveguide and/or one or more components of the devices described herein. Fluids mitigate thermal damage through fluid cooling of non-target anatomy within the heating profile of the devices. Additionally, the fluid flow may be manipulated by adjusting the device(s) (e.g., increasing or decreasing a blockage thereby decreasing or increasing fluid flow), adjusting the natural flow rate (e.g., directing fluid flow to a particular body portion by restricting flow at another body portion) and/or adjusting a body function (e.g., elevating the heart rate thereby increasing the rate of blood flow through the body). Fluid temperature may also be manipulated by providing an external or an internal heat sink.
• Centering of the devices described herein increases the predictability and repeatability of energy delivery to the targeted anatomical structures. The centering devices described herein include passive centering devices (e.g., utilizing the natural flow of fluid in a lumen for centering) or active devices that actively and/or positively position the radiating portion in the lumen.
• In embodiments in accordance with the present disclosure, a microwaveenergy delivery system12 with aflexible microwave catheter30 is provided and illustrated inFIG. 2.Microwave system12 includes amicrowave generator22,transmission line14, afluid cooling system40,catheter hub18 and aflexible microwave catheter30. Some embodiments may include aguide wire47 for guiding and/or positioning the radiatingportion100 of theflexible microwave catheter30 to a desirable position.
• Flexible microwave catheter30, in accordance with the present disclosure, includes a flexiblecoaxial cable32, or feedline, that is operably connectable to the microwave generator22 (e.g., through thecatheter hub18 and transmission line14).Flexible microwave catheter30 includes a radiatingportion100 positioned on a distal-most end thereof. In some embodiments, as discussed hereinbelow and illustrated in the accompanying drawings, the radiatingportion100 is deployable from theouter sheath35 offlexible microwave catheter30 and includes an exposedcap33 on the distal-most end thereof.
• One or more parameters of the microwave energy signal may be related to the targeted tissue. In some embodiments, the frequency of the microwave energy signal generated by themicrowave generator22 is related to the diameter of the body lumen. For example, the diameter of the renal artery may require a microwave signal at first frequency, the diameter of the esophagus may require a microwave signal at a second frequency and the diameter of the vaginal cavity may require a microwave signal at a third frequency. Some applications, such as providing treatment to the respiratory system, may require the frequency to vary with the position of the radiating portion within the body lumen due to the varying diameter along the body lumen (e.g., airways).
• Catheter hub18 is disposed at a proximal end offlexible microwave catheter30 and is configured to enable the operable coupling of a source of denervating energy (e.g., a microwave generator22) to thetransmission line14.Catheter hub18 provides an exchange of cooling fluid between theflexible microwave catheter30 and thefluid cooling system40.Fluid cooling system40 provides a source of coolant to theinflow conduit42 and receives coolant evacuated from thecatheter hub18 through anoutflow conduit43 connected to a fluid receiving destination (e.g., a receptacle, reservoir, or drain).
• FIG. 3 illustrates aflexible microwave catheter30 in accordance with the present disclosure positioned in a renal artery RA. In some embodiments, theflexible microwave catheter30 is maneuvered through along sheath31 initially positioned in the femoral artery and/or the aorta. A distal end of thelong sheath31 is positioned at a proximal end of the renal artery RA.Flexible microwave catheter30 is guided through thelong sheath31 and into the renal artery RA, e.g., extended past the distal end of thelong sheath31 and positioned within the renal artery RA. In some embodiments, aguide wire47 may be utilized to guide and/or position thelong sheath31 or theflexible microwave catheter30 as described herein.
• The radiatingportion100 of theflexible microwave catheter30 is positioned within the renal artery RA and receives a microwave energy signal from the microwave generator22 (seeFIG. 2). At least a portion of the microwave energy signal is selectively delivered to at least a portion of the renal artery RA. Some embodiments described herein, and illustrated in the accompanying figures, advantageously utilize the renal artery physiology in the application of microwave energy, thereby inducing modification of the target tissue. With respect to a renal denervation procedure, the target tissue for treating hypertension includes at least a portion of the renal nerves RRN, LRN.
• The anatomical structure of a natural body lumen (e.g., a renal artery RA), is illustrated inFIG. 4A. The innermost layer and/or core of the lumen that forms the fluid pathway of the lumen (e.g., the hollow body formed by the lumen). Thefluid1 contained in an artery is typically a bodily fluid (e.g., blood) although a non-bodily fluid (e.g., saline, air, or any other suitable fluid) may be utilized and/or introduced. Other natural body lumens may contain other body fluids (e.g., blood, mucus, urine, bile, air, and any combination thereof) or the lumen may contain an externally-introduced fluid (e.g., air, saline, and water), or any combination thereof.
• The first layer of the body lumen (e.g., renal artery RA) is theintima layer2 formed of about 50% elastin and about 50% cartilage. Other natural lumens may include a similar elastin and/or cartilage-like layer such, as for example, a mucus layer, a mucus membrane layer or the stratum corneum. The second layer of the body lumen (e.g., renal artery RA) is asmooth muscle layer3. Examples of other natural lumens that include a layer of smooth muscle are the esophagus, stomach, intestines, brochi, uterus, urethra and the bladder. The third layer in a body lumen (e.g., renal artery RA) is the adventitia layer4 (a.k.a., the tunica externa).Adventitia layer4 is the outermost connective tissue covering most organs, vessels and other body structures. Theoutermost adventitia layer4, as with many body lumens, is covered with anoutermost fat layer5.
• While each body lumen and bodily structure is functionally different, the general structures of body lumens and many bodily structures have structural similarities. For example, the first layer of the esophageal wall is the mucosa (e.g., mucus membrane), the second layer is the submucosa which includes esophageal glands, the third layer is the muscularis (e.g., smooth muscle), and the outermost layer is the adventitia layer which is covered by fat. Variations in the natural body lumens and body structures do not change the general operation of the devices, systems, and methods described herein, and may only require slight variations in one or more operational parameters thereof.
• FIG. 4B illustrates the coaxial arrangement of a flexiblecoaxial cable32 that includes aninner conductor20, adielectric layer22 and anouter conductor24. Drawing an analogy between the structures that form a natural body lumen inFIG. 4A and the structures that form a flexiblecoaxial cable32 inFIG. 4B, theouter conductor24 is analogous to theadventitia layer4 and/or theoutermost fat layer5 and thedielectric layer22 is analogous to thefluid1 in the hollow body.
• FIG. 4C illustrates the formation of a microwave waveguide structure RA/32 within a body lumen (e.g., renal artery RA) wherein the microwave structure RA/32 includes an inner conductor20 (e.g., conductor positioned in the hollow body1), a dielectric (e.g., fluid in thehollow body1/22) and an outer conductor (e.g., formed from theoutermost fat layer5/24). As such, when applied with a microwave energy signal, the anatomy becomes part of the microwave waveguide structure wherein the dielectric constant and loss factors are related to the physiology and composition of the natural body lumen and/or bodily structure.
• Energy losses in any waveguide structure include dielectric losses (e.g., loss through the dielectric material) and conductor losses (e.g., losses in the conductors forming the waveguide). As such, the dielectric losses are losses in the anatomy that forms the dielectric (e.g.,fluid1 in the hollow body) and conductor losses are losses in the structures and/or anatomy that form theinner conductor20 and theouter conductor4/24 and5/24.
• In some embodiments, forming a resonating microwave waveguide structure with the layers that form the anatomical structure of the renal artery creates an inefficient waveguide through which the losses in the anatomical structure can heat target tissue to damaging temperature levels. For example, the renal nerves LRN, RRN (e.g., renal efferent nerves and the renal afferent nerves) reside within theadventitia layer4 that is surrounded by thefat layer5. Theadventitia layer4 and thefat layer5 exhibit properties that resemble that of a conductive material and properties that resemble that of a dielectric material. As such, microwave currents generated by an electromagnetic field in theadventitia layer4 and the fat layer travel on the surface of each layer (conductive property) and travel through each layer (dielectric properties). As such, losses in theadventitia layer4 and thefat layer5 include conductive and dielectric losses.
• In some embodiments, as illustrated inFIG. 5, theadventitia layer4 may be viewed as being analogous to a lossy dielectric film (LDF) formed on an inner surface of a coaxial cable outer conductor24 (e.g., formed on an inner surface of the fat layer5). High energy absorption rates can therefore target theadventitia layer4 and damage the nerves contained therewithin and/or adjacent thereto. Due to the rate of blood flow through the renal artery RA, the microwave thermal energy that may induce tissue damage may be tempered in the body structure (e.g., renal artery RA) thereby resulting in the preservation of theintima layer2 andsmooth muscle layer3 and maintaining a viable arterial structure.
• FIG. 6A illustrates a block diagram of thecatheter hub18 in accordance with some embodiments of the present disclosure. Thecatheter hub18 may include five-ports and may be disposed at a proximal end of amulti-lumen tube630, as illustrated inFIG. 6B.Catheter hub18 may include connectors to facilitate operable coupling of the five lumens with corresponding elements of the generator, coolant source and return, and so forth.Catheter hub18 is disposed at a proximal end of theflexible microwave catheter30 and configured to enable the operable coupling of various systems that may connect to theflexible microwave catheter30. Thecatheter hub18 connects to atransmission line14 and receives denervating energy, generated by a source of denervation energy (e.g., a microwave generator22), therefrom. Thecatheter hub18 may connect to afluid cooling system40 and may provide an exchange of cooling fluid between theflexible microwave catheter30 and thefluid cooling system40. Thefluid cooling system40 provides a source of coolant to theinflow conduit42, receives coolant evacuated from thecatheter hub18 through anoutflow conduit43, and deposits the evacuated coolant to a receiving destination (e.g., a receptacle, reservoir, or drain). Thecatheter hub18 may connect to aguide wire47 for guiding and positioning theflexible microwave catheter30. Thecatheter hub18 may also connect to one or more sensor leads34athat operably couple one or more sensors1534 (seeFIG. 15A) on theflexible microwave catheter30 to a control system or sensor monitoring system housed in themicrowave generator22.
• As illustrated inFIG. 6B, theflexible microwave catheter30 in accordance with the present disclosure includes amulti-lumen tube630 having amulti-port catheter hub18 at a proximal end thereof (seeFIG. 2). Themulti-lumen tube630 has a generally elongated cylindrical outer surface having formed therein a plurality of conduits, passageways and/or lumens disposed longitudinally therein. Themulti-lumen tube630 may be formed by any suitable manner of manufacture, such as without limitation, extrusion. Themulti-lumen tube630 may include a central lumen (e.g., flexible coaxial cable lumen32a) having a generally circular cross-section extending axially therethrough and dimensioned to accommodate a flexible coaxial feedline32 (seeFIG. 2). A first pair of lumens (e.g., guidewire tracking lumen30bandsensor lead lumen30c) having a generally a circular cross-section may be positioned on opposing sides of the central lumen (e.g., at a 12 o'clock and 6 o'clock position) that are adapted to accommodate, e.g., aguidewire47 and asensor conductor34a(seeFIG. 8A), respectively. A second pair of lumens (e.g.,inflow fluid passageway44aandoutflow fluid passageway44b) having a generally arcuate cross-section may be positioned on opposing sides of the central lumen, between the first pair of lumens (e.g., at 9 o'clock and 3 o'clock, respectively), to accommodate coolant inflow and coolant outflow, respectively.
• Theouter sheath35 of theflexible microwave catheter30 may include braiding and/or windings to improve strength, to resist kinking, and/or to provide flexibility while maintaining sufficient stiffness.Outer sheath35 may include one or more steering wires (not shown) to facilitate steering and manipulation of theflexible microwave catheter30 to a desirable position.Outer sheath35 may include a dielectric coating, such as, for example, Parylene, on theouter surface35cof the outer lumen to reduce blood clotting
• As illustrated inFIG. 7, in some embodiments the flexiblecoaxial cable32 and at least part of the radiating portion are housed in theouter sheath35 of theflexible microwave catheter30.Catheter hub18 includes anactuator15 housed in thecatheter hub18 and coupled to the radiatingportion100.Actuator15 is configured to deploy the radiatingportion100 andcap33 distally from theouter sheath35, as discussed in detail hereinbelow.
• Thecatheter hub18 includes acoupler45 or anadjustable fluid coupler845 as illustrated inFIGS. 8A-8B andFIG. 8C, respectively.Coupler45 and adjustablefluid coupler845 provide connections to the one ormore lumens30a-30c,44aand44bformed in theflexible microwave catheter30FIG. 8A illustrates a cross-section of acoupler45 that provides connections to a flexiblecoaxial cable lumen30a, a guidewire tracking lumen30band asensor lead lumen30c.FIG. 8B illustrates a cross-section of acoupler45 that provides connections to a flexiblecoaxial cable lumen30aand inflow andoutflow fluid passageways44a,44b.FIG. 8C illustrates anadjustable coupler845 that provides adjustable connections to a flexiblecoaxial cable lumen30aand inflow andoutflow fluid passageways44a,44b.Catheter hub18 andcoupler45 andadjustable coupler845 may include any number and combinations of lumens, pathways and electrical conduits required to facilitate the various connections to theflexible microwave catheter30.
• InFIG. 8A, aguide wire47 is introduced into the guidewire tracking lumen30bthrough an opening (not shown) formed between thecoupler body45aand theproximal stain relief45cand one or more sensor leads34aare introduced into thesensor lead lumen30cthrough another opening formed between thecoupler body45aand theproximal strain relief45c.
• InFIG. 8B, aninflow conduit42 connects toinflow port42aand provides cooling fluid toinflow plenum42b. Cooling fluid ininflow plenum42bflows distally through theinflow fluid passageway44aproviding cooling to the distal end of theflexible microwave catheter30.Inflow fluid passageway44ais in fluid communication withoutflow fluid passageway44bof the distal end of the flexible microwave catheter30 (seeFIGS. 15A-15B) such that cooling fluid travels proximally through theoutflow fluid passageway44bto theoutflow plenum43bof theoutflow port43a.Outflow conduit43 connects theoutflow port43aand returns cooling fluid tofluid cooling system40.Inflow port43aandoutflow port43aare formed in thecoupler45 between thecoupler body45aand theproximal strain relief45calthough connections to any one or more of the lumens of the flexible microwave catheter30 (e.g. flexiblecoaxial cable lumen30a, guidewire tracking lumen30b,sensor lead lumen30c,inflow fluid passageway44aandoutflow fluid passageway44b) may be formed in any portion of thecoupler45.
• In some embodiments,catheter hub18 includes anadjustable fluid coupler845, as illustrated inFIG. 8C. Adjustablefluid coupler845 includes afluid coupler body845aforming aninflow plenum842band anoutflow plenum843bwithin thefluid coupler body845a. Theinflow plenum842bis in fluid communication with the inflow conduit842 and theoutflow plenum843bin fluid communication with the outflow conduit843.
• Adjustablefluid coupler845 may also include a distal and/or proximal strain relief (not explicitly shown) that supports the flexible microwave catheter30 (e.g., the assemblage and connections to the flexible coaxial cable32) and thetransmission line14. Additional strain reliefs may be provided to support the inflow conduit41a, the outflow conduit41band other elements that connect to thecoupler45 and adjustablefluid coupler845 described herein.
• Adjustablefluid coupler845 is configured to adjustably couple a coaxial cable (e.g.,transmission line14 or the coaxial flexible cable32), thefluid cooling system30 and theouter sheath35 of theflexible microwave catheter30.Fluid coupler body845ahouses afluid sealing system819 and forms anouter sheath coupler845bon the distal end.Fluid sealing system819 includes adistal sealing diaphragm819a, aproximal sealing diaphragm819band abypass bulb819con the proximal end of thefluid coupler body845a. Thedistal sealing diaphragm819aandproximal sealing diaphragm819bmay each include one or more o-rings.
• When discussing deployment herein, two approaches may be utilized. In the first approach, the distal end of theflexible microwave catheter30 is placed proximal the targeted tissue and the radiatingportion100 is eased out distally from theouter sheath35 of the flexible microwave catheter30 (see at leastFIGS. 42-44). In a second approach, the distal end of theflexible microwave catheter30 is placed adjacent the targeted tissue and theouter sheath35 is pulled back proximally thereby deploying the radiating portion100 (see at leastFIGS. 18B-18G).
• Thedistal sealing diaphragm819ais disposed between afluid flow lumen37 and the interior surface of thefluid coupler body845athereby forming anoutflow plenum843bbetween the distal inner surface of thefluid coupler body845a, the outer surface of thefluid flow lumen37, thedistal sealing diaphragm819aand theouter sheath coupler845b. Theoutflow plenum843breceives fluid circulated through theflexible microwave catheter30 and provides the circulated fluid to theoutflow port843a.
• Proximal sealing diaphragm819bis disposed between thefluid coupler body845aand the flexiblecoaxial cable32 thereby forming aninflow plenum842bbetween the inner surface of thefluid coupler body845a, the outer surface of the flexible coaxial cable832, thedistal sealing diaphragm819aand theproximal sealing diaphragm819b. Theinflow plenum842breceives cooling fluid from theinflow port842a. The cooling fluid provided to theinflow plenum842bfrom theinflow port842aflows through theflexible microwave catheter30 in aninflow fluid passageway44aformed between the outer surface of the flexiblecoaxial cable32 and the inner surface of thefluid flow lumen37.
• Bypass bulb819cprovides a secondary seal between thefluid coupler body845aand the flexiblecoaxial cable32.Bypass bulb819cis configured to catch fluid which may pass through theproximal sealing diaphragm819b.Bypass bulb819cmay also provide strain relief to the flexiblecoaxial cable32 that extends into and through thefluid coupler body845a.
• During use, coolant flows through theinflow port842aand into theinflow plenum842b. Fluid pressure in theinflow plenum842bforces the coolant into the inflow fluid passageway844aformed between the outer surface of the flexiblecoaxial cable32 and the inner surface of thefluid flow lumen37. Coolant continues to the distal end of theflexible microwave catheter30, through the assembly (e.g., radiating portion100) on the distal end thereof, and into anoutflow fluid passageway44b. Theoutflow fluid passageway44bis formed between the outer surface of thefluid flow lumen37 and the inner surface of theouter sheath35. Fluid from theoutflow fluid passageway44bis deposited in theoutflow plenum843a, flows through theoutflow port843aand to a coolant destination (e.g., storage container for re-use and/or drainage system).
• Thefluid flow lumen37 is positioned coaxially around the flexiblecoaxial cable32, and theouter sheath35 is positioned coaxially around thefluid flow lumen37. A clearance between the outer diameter of the flexiblecoaxial cable32 and inner diameter of thefluid flow lumen37 defines a first fluid conduit (e.g.,inflow fluid passageway44a). A clearance between the outer diameter of thefluid flow lumen37 and an inner diameter of theouter sheath35 defines a second fluid conduit (e.g.,outflow fluid passageway44b. During use, a coolant, e.g., carbon dioxide, air, saline, water, or other coolant media, may include a desirable dielectric property and may be supplied to theflexible microwave catheter30 and/orradiation portion100 on the distal end thereof by one coolant conduit, and evacuated from theflexible microwave catheter30 by the other coolant conduit. That is, in some embodiments, the first fluid conduit (e.g.,inflow fluid passageway44a) supplies coolant and the second fluid conduit (e.g.,outflow fluid passageway44b) evacuates coolant. In other embodiments, the direction of fluid flow may be opposite. One or more longitudinally-oriented fins or struts (not explicitly shown) may be positioned within theinflow fluid passageway44a, theoutflow fluid passageway44band/or theouter sheath35 to achieve and maintain coaxial centering among theouter sheath35,fluid flow lumen37, and/or the flexiblecoaxial cable32.
• In some embodiments,actuator arm15bprovides a linkage between the flexiblecoaxial cable32 and theactuator15.Actuator15 andactuator arm15bare configured to impart movement of the flexiblecoaxial cable32 through theadjustable fluid coupler845. Movement of the flexiblecoaxial cable32 deploys the radiatingportion100 as discussed in detail hereinbelow. During movement of the flexiblecoaxial cable32, a fluid-tight seal is maintained about the flexible coaxial cable by theproximal sealing diaphragm819b.
• In some embodiments,coupler actuator arm15cprovides a linkage between theadjustable fluid coupler845 and theactuator15.Actuator15 andcoupler actuator arm15care configured to impart movement to theadjustable fluid coupler845, which, in turn, imparts movement to the inflow lumen837 andouter sheath35 about the flexiblecoaxial cable32 which is fixed in position within thehub18. As such, in some embodiments, the flexiblecoaxial cable32 is moved longitudinally through the stationary adjustablefluid coupler845, thereby deploying a distally-positionedradiating portion100. In some embodiments, the flexiblecoaxial cable32 is stationary and theadjustable fluid coupler845,outer sheath35 andfluid flow lumen37 are moved longitudinally about the flexiblecoaxial cable32 thereby retracting theouter sheath35 from the distally positionedradiation portion100.
• In use, theflexible microwave catheter30 is fed through a lumen to a target tissue adjacent a natural body lumen and/or body structure. In certain instances, the vascular system presents a serpentine route through the body to various natural body lumens and/or body structures. For example, the femoral artery provides access to the renal artery. The various elements that form theflexible microwave catheter30 may be subject to shifting and/or displacement forces arising from the differing radii of theflexible microwave catheter30 elements, which can cause undesirable effects such as kinking, twisting, etc. Advantageously, the various components that form theflexible microwave catheter30 and the connections to thefluid sealing system819 are formed from material having resilient and lubricious qualities, that enables the elements to move independently longitudinally (e.g., proximally and/or distally) within thefluid coupler body845aand/or thecatheter hub18. In this manner, the elements can shift in position as theflexible microwave catheter30 is guided into place while the fluidic integrity of the cooling elements are maintained.
• The disclosedflexible microwave catheter30 may be percutaneously introduced into the femoral artery and positioned within the renal artery adjacent to the renal nerve bundle. Placement of theflexible microwave catheter30 may be intravascularly introduced and positioned adjacent to any desired target tissue. The configurable length microwaveenergy radiating device100 includes a radiating portion that cooperates advantageously with the renal artery physiology to deliver denervation energy to the renal nerve bundle while minimizing collateral damage to the arterial vessel and related anatomical structures.
• A catheter system in accordance with the present disclosure may include a guidewire having a knob or ball disposed at a distal end thereof. The knob or ball may be radiopaque to enable positioning of the guidewire, and more particularly, the distal end thereof, using imaging (fluoroscopy, MRI, etc.). During use, a distal end of the guidewire may be introduced into a body lumen and advanced into position, optionally using imaging as described above. A proximal end of the guidewire may then be inserted into a corresponding port on the catheter that is in communication with the guidewire lumen. The catheter is then advanced into the body lumen to the desired location. As the catheter is advanced to the desired location, an indentation or other feature of the knob, ball, and/or catheter provides tactile feedback and/or a positive stop to facilitate correct positioning of the catheter.
• In some embodiments, the distal end of the guidewire tracking lumen30bterminates proximal from the radiatingportion100, as illustrated inFIGS. 9A-9C.Distal end30bdof guidewire tracking lumen30bforms a guide wire ball receiver47bin theouter sheath35 of theflexible microwave catheter30. Guide wire ball receiver47bis configured to receive the proximal end ofguide wire47 as illustrated inFIG. 9A.
• In use,guide wire47 and distal guide wire ball47aare inserted into the body, and distal guide wire ball47ais positioned adjacent to targeted tissue using a guidance system (e.g., imaging system or any suitable guidance and positioning system). After positioning the distal guide wire ball47aat a desired location, the proximal end (not explicitly shown) of theguide wire47 is inserted into the guide wire ball receiver47b, passed through the guidewire tracking lumen30band through the catheter hub18 (seeFIGS. 2,6A, and7B).
• Flexible microwave catheter30 is guided to the target tissue via theguide wire47. As illustrated inFIGS. 9B and 9C, distal guide wire ball47ais received by the guide wire ball receiver47bsuch that the guide wire ball47ais proximal to the radiatingportion100.
• Some embodiments and structures discussed herein follow the coaxial structure analogy described hereinabove and illustrated inFIGS. 4A-4C and5 wherein the coaxial structure incorporates one or more layers of a natural body lumen to form a coaxial feedline structure. Like any other coaxial structure, the coaxial-positioning of structures that form the waveguide are directly related to the operation and/or efficiency of the waveguide.
• FIGS. 10A-12A each illustrate aflexible microwave catheter30 positioned in a renal artery RA andFIGS. 10B-12B illustrate the respective cross-section thereof. InFIGS. 10A and 10B, theflexible microwave catheter30 anddistal radiating portion100 are centered in the renal artery RA. InFIGS. 11A and 11B, theflexible microwave catheter30 anddistal radiating portion100 are offset from dead center by 0.5 mm and inFIGS. 12A and 12B, theflexible microwave catheter30 anddistal radiating portion100 are offset from dead center by 1 mm. Each ofFIGS. 10A-12A and10B-12B illustrate a distribution of thermal energy in and around the renal artery from the application of 25 W of microwave energy to theflexible microwave catheter30 for about 2 minutes.
• In each ofFIGS. 10A-12A, theflexible microwave catheter30 includes a first proximal waveguide, formed by the flexiblecoaxial cable32, and a second distal waveguide, formed by theinner conductor20 and a portion of the anatomical structure. The flexiblecoaxial cable32 that forms the first proximal waveguide includes aninner conductor20 centered and coaxially offset from anouter conductor24 by adielectric layer22. The second distal waveguide is an anatomicalresonant structure1032,1132, and1232 that includes a portion of theinner conductor1020,1120,1220, respectively, extending distally from the flexiblecoaxial cable32, a portion of the renal artery RA coaxially offset from the inner conductor by atransitional dielectric1026,1126,1226 andfluid1 contained in the renal artery.
• A radiatingportion100 of theflexible microwave catheter30 is formed at a distal end of the flexiblecoaxial cable32. In embodiments according to the present disclosure, and of a manufacturing process therefor, a portion of theouter conductor24 is removed to expose theinner conductor20 thereby forming afeed gap1050,1150,1250 (e.g., feed point) that facilitates the propagation of denervation energy, such as microwave energy. Optionally or alternatively, a transitional dielectric26 is disposed in thefeed gap1050,1150,1250. Thetransitional dielectric1026,1126,1226 corresponds generally and/or geometrically to the portion of theouter conductor24 removed therefrom.
• The transitional dielectric26 may have dielectric properties between that of theinner dielectric22 and that of the expected or average dielectric properties of the targeted anatomical structures (e.g., the renal artery RA, body lumen and/or other body structure). Use of a transitional dielectric26 in this manner may improve coupling between the radiatingportion100 and the targeted tissue, by, e.g., reducing reflections, reducing standing waves (e.g., VSWR), and by providing impedance matching between the radiatingportion100 and targeted tissue.
• InFIGS. 10A and 10B, theinner conductor20 is coaxially centered in the renal artery RA. As such, the anatomicalresonant structure1032 is substantially coaxial thereby generating a substantially balanced resonating structure. The balanced anatomicalresonant structure1032 generates heating, due to dielectric losses and/or conductive losses, in the anatomical portions of the renal artery structure (e.g., one or more layers of the renal artery as discussed hereinabove). As illustrated inFIG. 10B, centering of theinner conductor20 within the renal artery RA generates substantiallyuniform heating1000aabout the renal artery RA.
• Centering theinner conductor1020 in the renal artery RA, in addition to forming a balanced anatomicalresonant structure1032, generates substantiallyuniform heating1000aand even distribution of the generated thermal energy about the renal artery RA. Additionally, heating of the distal end of the flexiblecoaxial cable32 and heating of the exposedinner conductor1020 in the anatomicalresonant structure1032 are maintained to acceptable temperatures.
• As illustrated inFIGS. 11A-12A, offsetting theinner conductor20, as illustrated inFIGS. 11A-12A and11B-12B, with respect to the anatomical structure (e.g., the renal artery RA) that forms the anatomicalresonant structure1132 and1232 results in the generation ofnon-uniform heating1100a,1200aabout the renal artery RA.
• InFIGS. 11A and 11B, theinner conductor20 is offset from the center of the renal artery RA by 0.5 mm and inFIGS. 12A and 12B theinner conductor20 is offset from the center of the renal artery RA by 1 mm, in each instance an unbalanced anatomicalresonant structure1132 and1232 is formed. The unbalanced anatomicalresonant structure1132,1232 generatesnon-uniformed heating1100a,1200aabout the renal artery RA forming a hot-spot adjacent the renal artery RA. The hot-spot may result in raising the temperatures of the portion of the renal artery RA adjacent the hot spot and may result in irreversible tissue damage. Additionally, offsetting theinner conductor20 may also heat the distal end of the flexiblecoaxial cable32 and/or a portion of the exposedinner conductor20 to unacceptable temperatures.
• As illustrated inFIGS. 10A-12A, each anatomicalresonant structure1032,1132,1232 generates a large delta between the inside temperature and the outside temperature of the renal artery RA.FIG. 13 illustrates experimental data showing the temperature inside and outside of the renal artery RA plotted against the power measured at the beginning of the flexible coaxial cable32 (seeFIG. 7). The linear representation of the maximum temperature inside therenal artery1334aand the linear representation of the maximum temperature outside therenal artery1334bdemonstrates that the anatomicalresonant structures1032,1132,1232 generate temperatures outside of the renal artery RA that will achieve a cytotoxic temperature (e.g., a quality of thermal energy toxic to cells) in the outer layers of the vessel while maintaining less than lethal temperatures inside the renal artery RA.
• As discussed hereinbelow, theflexible microwave catheter20 may include a centering device configured to coaxially center the radiatingportion100 in a natural body lumen or in a natural body structure thereby forming a balanced anatomical resonant structure as discussed hereinabove. Centering device described herein includes stent-like expandable members (seeFIGS. 16A-16C,17A-17B,18A,19A,20,21 and22A-22B), balloon-like inflatable members (seeFIGS. 24,25a-25B,26A-26C and58A-58D), compressible expandable members (seeFIGS. 27A-35), repositionable expandable members (seeFIG. 18A), a centering device with a plurality of members (seeFIGS. 32A-32B,35,37A-37B,39A-39B,40A-41B), two or more fin expandable members (seeFIGS. 27A-27D and28), expandable basket members (seeFIGS. 29-35), clover leaf expandable members (seeFIG. 34-35), expandable single and double paddle members (seeFIGS. 36A-39B), expandable single and double propeller members (seeFIG. 36A-39B), expandable tines (seeFIGS. 40A-40B), expandable fin members and expandable helical fin members (seeFIG. 41A-41B), and any combination thereof.
• The centering structures described herein provide minimal resistance to blood flow along the structure, which enables the flowing blood to cool the structure and tissues not targeted for ablation.
• In some embodiments, the centering device (or devices) are restrained in an outer sheath and self-deploy (e.g., expand), and thereby center theradiation portion100, when released from the outer sheath. Similarly, the centering device self-retracts when retracted into the outer sheath.
• Centering structures described herein may be formed from conductive materials, non-conductive materials, dielectric materials or any combination thereof. In some embodiments, a conductive centering structure includes a shaped memory material such as, for example, a nickel-titanium alloy (e.g., nitinol), or a ferromagnetic shape-memory alloy.
• In some embodiments, a non-conductive centering structure includes a shaped-memory polymer. The shaped-memory polymer may be triggered to expand to a shape-memory position by an electromagnetic field generated by the delivery of microwave energy. As such, the centering device centers the radiatingportion100 within the body lumen while the radiatingportion100 delivers microwave energy.
• In some embodiments, the centering device may be used to anchor the radiating portion of the flexible medical catheter into tissue or adjacent targeted tissue. Alternatively, the centering device may be self-centering via fluid/hydrodynamic, and/or mechanical forces within the body lumen BL.
• In some embodiments, centering devices may also be configured to dielectrically buffer the microwave currents from the surrounding physiology.
• Embodiments and features described herein may be selected and combined with other embodiments and features described herein in any combination. For example, radiating portion may be selected from a radiating portion with a monopole antenna (seeFIG. 5), one or more slotted feed gaps (seeFIGS. 10A-12A,14F,16A-C,19A-F,20-22B,50-53,55 and57), a dipole antenna (seeFIG. 17A), a radiating portion with a helical fed gap (seeFIGS. 42-45,47,54,56 and57), or any combination thereof. The selected radiating portion may be combined with a fluid cooled flexible microwave catheter that connects and combined with a catheter with a fluid coupler or a adjustable fluid coupler for deploying the radiating portion from the outer sheath of the flexible microwave catheter. Further, any of the above named combinations may include a centering device or structure. The centering device or structure may connect to the catheter hub that facilitates the actuation and/or deployment of the centering device.
• Centering devices may provide additional functionality in addition to positioning the device. For example, in some embodiments the centering device may form a choke or balun that defines and/or limits the derivation region and/or defines and/or limits the anatomical resonant structure. In some embodiments, the centering device may include one or more structures wherein the structure(s) defines a pattern of applied denervation energy.
• One embodiment of a radiatingportion100 according to the present disclosure, and of a manufacturing process therefor, is illustrated inFIGS. 14A-14E. In the first step of the manufacturing process, a flexiblecoaxial cable32 is provided as illustrated inFIG. 14A. A cylindrical or semi-cylindrical portion of theouter conductor1424 and dielectric1422 is removed to expose the inner conductor thereby forming a feed gap1450 (e.g., feedpoint).Feed gap1450 facilitates the propagation of denervation energy, such as microwave energy.
• The portion of theouter conductor1424 may be removed by etching, cutting, or stripping the outer conductor off the cable in a ring with length of approximately 0.01″ leaving approximately ¼ wavelength of coaxial cable distal to this location.
• Optionally, atransitional dielectric1426 may be disposed in thefeed gap1450, corresponding generally to the cylindrical section of theouter conductor1424 that is removed, as illustrated inFIG. 14B. Thetransitional dielectric1426 has dielectric properties between that of theinner dielectric1422, and that of the expected or average dielectric properties of the anatomical structures with which the antenna is to be used, e.g., the renal artery and/or blood in the renal artery.Transitional dialectic1426 may be a formed from any suitable dielectric material and/or dielectric fluid. Use of a transitional dielectric1426 in this manner may improve coupling between the radiatingportion100 and targeted tissue, by, e.g., reducing reflections, reducing standing waves (e.g., VSWR), and by providing impedance matching between the radiatingportion100 and tissue.
• As further illustrated inFIG. 14B, a distal-most end of the flexiblecoaxial cable32, a portion of theouter conductor1424 and inner dielectric1422 are removed thus exposing a portion of theinner conductor1420. As illustrated inFIG. 14C, a short conductive (e.g., metallic) cylinder, disc, orcap1433 having an opening defined at the center thereof, the opening being dimensioned to accept theinner conductor1420, is joined at the opening to the exposed end of theinner conductor1420 and at the perimeter thereof to theouter conductor1424. This distal “cap”1433 shorts theinner conductor1420 to theouter conductor1424, which, in turn, may optimize, control, focus, and/or direct the general distal radiating pattern of the radiatingportion100, e.g., reduce, focus, shape and/or enhance the propagation of denervation energy beyond the distal end of the radiatingportion100.
• In some embodiments,cap1433 is formed from a high-temperature dielectric such as a plastic, ceramic, or other suitable dielectric material.Cap1433 may include a high-temperature dielectric and a conductive portion formed therein that provides a short or low impedance path between theinner conductor1420 and theouter conductor1424. In some embodiments, the distal portion of thecap1433 is formed from a non-conducting material, such as, for example, a polymer.
• In some embodiments, a choke orbalun1408 short may be fixed to theouter conductor1424 at a position proximal of thefeed gap1450, as illustrated inFIG. 14D. Thebalun1408 may include a short conductive (“metallic”)ring1408ahaving an inner diameter dimensioned to accept theouter conductor1424. Thebalun ring1408ais electrically bonded (e.g., soldered, welded, and/or mechanically connected) to theouter conductor1424. Thebalun ring1408ais positioned a distance from thefeed gap1450 of about 180 degrees in phase length. Thisbalun ring1408aaffects a microwave short which, in turn, may optimize, control, focus, and/or direct the general radiating pattern of the radiatingportion100, e.g., reduce the propagation of denervation energy beyond the proximal end of the radiatingportion100 and/or thebalun1408.Balun ring1408amay improve impedance matching, reduce reflections and/or standing waves, improve efficiency, and reduce the risk of embolism (e.g., clotting).
• Thebalun1408 may further include abalun dielectric sleeve1408b, which may be formed from extruded polytetrafluoroethylene (PTFE, e.g., Teflon®), from extruded polyethylene terephthalate (PET) and/or from extruded fluorinated ethylene propylene (FEP). Thebalun dielectric sleeve1408bmay be positioned over the radiatingportion100 of the assembly and mated to thebalun ring1408a. Thebalun dielectric sleeve1408bmay further include a length ofheat shrink tubing1408c, having a conductive material on a surface thereof, preferably an inner surface, that may be positioned over the PTFEbalun dielectric sleeve1408cto change a dielectric property and/or to improve the performance of thebalun1408 and thus, improve the radiating pattern of denervation energy. A silver ink may be disposed on the inner surface of theheat shrink tubing1408c, whereupon shrinking theheat shrink1408cover thebalun ring1408aand balun dielectric1408bforms a resonant microwave structure that improves the performance of thebalun1408 and, in turn, improves the radiating pattern of the denervation energy.
• In some embodiments, thebalun dielectric sleeve1408bandmetal ring1408aare then covered from the proximal end to near the distal end with a heat shrink coated in conductive ink (e.g., a balun outer conductor). In some embodiments, the distal end of thebalun dielectric sleeve1408bis not coated with the conductive heat shrink, and thus forms a balun extended dielectric that improves balun performance.
• As illustrated inFIGS. 15A-15B, thecap1533 connects to the distal end of the flexiblecoaxial cable1532, the distal end of thefluid flow lumen1537 and the distal end of theouter sheath1535. A distal end of thefluid flow lumen37 is sealably joined to the proximal face of thecap1533 to achieve and maintain concentric alignment among the radiatingportion100 elements. One or morecap coolant passageways1533a,1533bformed within thecap1533 enables coolant to circulate from theinflow fluid passageway1544ato theoutflow fluid passageway1544b, which facilitates the flow of coolant through the radiatingportion100, and may advantageously provide cooling of the radiatingportion100 andcap1533.
• Cap1533 may receive theinner conductor1520 via the proximalinner conductor receiver1533cand connect to theouter conductor1524 thereby providing a short or low resistance connection between theinner conductor1520 and theouter conductor1524.
• Cap1533 connects toouter sheath1535 and forms a fluid-tight seal therebetween.Cap1533 may be bonded to theouter sheath1535 by welding, bonding, adhesive, or any other suitable manner of connection. Cooling fluid enterscap fluid chamber1533dthrough capinflow coolant passageways1533aand flows out of thecap fluid chamber1533dthrough capoutflow coolant passageways1533b.
• Atemperature sensor1534 may be operatively associated with the radiatingportion100 and/orcap1533 in accordance with the present disclosure. For example, and without limitation, one or more thermoprobes, pressure sensors, flow sensors, or any other suitable sensor may be included within the radiatingportion100,cap1533,outer sheath1535, the flexiblecoaxial cable1532, the inflow and/oroutflow fluid passageway1544a,1544b, acap fluid chamber1533dor any other conduit and/or structure (e.g., a mesh, balloon, expandable and/or deployable member,) described herein. In some embodiments,temperature sensor1534 may be positioned on the distal end of thecap1533. One or more thermoprobes may be included within the flexible microwave catheter1530 (e.g., outer sheath, flexiblecoaxial cable32, one or more fluid chambers or conduits, outer dielectric insulatinglayer128, shieldingouter conductor124a, and/or any other structure described herein).
• Temperature sensor1534 may be positioned distal to the active heating zone of the radiatingportion100. The microwaveenergy delivery system12 thereby monitors the temperature of the fluid passing through the hottest location. If thetemperature sensor1534 measures a temperature above a clotting temperature threshold, thesystem12 may temporarily or permanently halt power delivery. In some embodiments, one ormore temperature sensors1534 may be positioned at the discharge of a fluid passageway formed in, thorough, or around a centering device as discussed hereinbelow.
• In some embodiments,cap1533 or any portion of the distal tip of theflexible microwave catheter30 may include a radiopaque material (such as barium) to enhance the visibility thereof during fluoroscopy.
• As discussed hereinabove with respect to FIGS.6A and8A-8C, acatheter hub18 at a proximal end of theflexible microwave catheter30 enables the operable coupling of a source of denervating energy (e.g., a microwave generator22) to the flexiblecoaxial cable32, afluid cooling system19 to theinflow fluid passageway44a, and a receiving destination (e.g., a receptacle, reservoir, or drain) for coolant evacuated from theoutflow fluid passageway44b.
• As illustrated inFIGS. 16A-16C, aflexible microwave catheter1630 in accordance with the present disclosure may include one or more stent-likeexpandable elements1670 associated with the radiatingportion100. As illustrated inFIG. 16A, the stent-like expandable elements may be maintained in a compressed state while guiding theflexible microwave catheter1630 through the vascular system to a position adjacent the target tissue. In some embodiment, the stent-likeexpandable element1670 is maintained in a compressed state by the distal portion of theouter sheath1635. In other embodiments, the stent-likeexpandable element1670 is stowed in a compressed state within theouter sheath1635.
• During use, and as illustrated inFIG. 16B, theouter sheath1635 may be retracted proximally and/or the stent-likeexpandable element1670 may be advanced distally, causing the stent-likeexpandable element1670 to extend from the confines of theouter sheath1635 and to expand into a generally tubular, cylindrical and/or balloon-like shape around the radiatingportion100 thereby centering the radiatingportion100 of theflexible microwave catheter1630 within the lumen (not specifically shown). The stent-likeexpandable element1670 may be positioned such that the center of the stent-likeexpandable element1670 is generally coincident with a feedpoint (e.g., feed gap1650) of the radiatingportion100.Feed gap1650, as illustrated inFIGS. 16A-16C, may include an exposed slotted portion of theinner conductor1620 wherein a portion of theouter conductor1624 has been removed. An exposed portion of theinner conductor1620 may also include a transitional dielectric1650 that covers theinner conductor1620.
• At least a portion of the stent-likeexpandable element1670 may be positioned distal to the radiatingportion100, positioned proximally to the radiatingportion100, may generally surround the radiatingportion100, or any combination thereof. The stent-likeexpandable element1670 may be formed from, e.g., wire mesh, wire members, stamped metal, and/or may be formed from any suitable electrically conductive material, including without limitation, stainless steel, copper, silver, platinum, gold, shape memory allow (e.g., Nitinol) and the like. In some embodiments, stent-likeexpandable element1670 may also be formed from, and/or may include, a polymer or composite material with low electrical conductive such as a polyurethane, polyimide, FEP, PET, and/or PTFE.
• FIG. 16C illustrates a stent-likeexpandable mesh element1672. In some embodiments, the stent-likeexpandable mesh element1672 includes a distal and a proximal end-cap mesh1672ajoined by atubular body mesh1672b. At least a portion of thetubular body mesh1672bextends radially outward from the radiatingportion100 including the feed gap1650 (e.g.,inner conductor1620 and transitional dielectric1650).
• In some embodiments, at least a portion of theendcap mesh1672aincludes a variable mesh density wherein the mesh density is greater at the distal and/or proximal ends, and less dense along the length of thetubular body mesh1672b. The mesh structures described herein provide minimal impedance to blood flow distally along the structure, which enables the flowing blood to cool structures and tissues not targeted for ablation (blood, intima, and media of renal artery).
• In some embodiments, the stent-likeexpandable element1670 may be left in place within the renal artery RA as a stent to reduce complications from a potential stenosis. The stent-likeexpandable element1670 may detach from theflexible microwave catheter1630 after energy application and be left in place to mechanically support the renal artery RA.
• In some embodiments, the stent-likeexpandable element1670, or other expandable device described herein, may include three positions. In a first position, the stent-likeexpandable element1670 is fully expanded/extended for initial placement. In a second position, the stent-likeexpandable element1670 is retracted proximally to allow for deployment while maintaining the stent-likeexpandable element1670 in place about theradiating section100. In a third position, the stent-likeexpandable element1670 is fully retracted such that the final proximal portion of the stent-likeexpandable element1670 is released. The far distal portion of the stent-likeexpandable element1670 may be released from theflexible microwave catheter30 when thecatheter30 is pulled proximally out the renal artery RA. For example, it may fit into a slot which faces in the distal direction and therefore hold the mesh when the catheter is advanced distally, but releases only when the device is pulled proximally and the sheath is fully retracted.
• InFIGS. 16A-16C,cap1633 connects to the distal end of the radiatingportion100 and provides an electrical short between theinner conductor1620 andouter conductor1624,1624a.Temperature sensor1634 may be housed in thecap1633 or housed in any other portion of the radiatingportion100, stent-likeexpandable element1670, stent-likeexpandable mesh element1672, flexible coaxial cable1632 orouter sheath1635.
• In some embodiments, the proximal and/or distal portion of the stent-likeexpandable element1670 and/or the proximal and/or distal portion of the stent-likeexpandable mesh element1672aform a choke or balun short. The choke or balun short substantially confines the electromagnetic field to an electromagnetic boundary defined by the choke or balun short. As such, thermal heat generation is substantially limited to the portion radially outward from the feed gap.
• In some embodiments, the centering structure forms a Faraday cage that is substantially opaque to microwave energy at the distal and proximal ends while remaining substantially transparent to microwave energy along at least a portion of the length thereof. Such an arrangement may have advantages, since it enables the device to target delivery of denervation energy radially (e.g., circumferentially to the renal artery) while reducing or eliminating the delivery of denervation energy axially (e.g., distally and proximally along the renal artery). A flexible medical catheter in accordance with the present disclosure may improve operative outcomes by enabling a surgeon to precisely deliver energy to targeted tissue while reducing or eliminating complications arising from collateral tissue effects.
• The mesh forming the proximal portion and distal portions of the Faraday cage may form a choke or balun short that confines a substantial portion of the anatomical resonant structure to the anatomical structures between the proximal portion and distal portion of the Faraday cage.
• In some embodiments, the mesh may be configured to accommodate specific wavelengths, or ranges of wavelengths, of denervation energy that may be utilized during denervation procedures. For example, and without limitation, to provide the desired microwave radiation pattern the mesh spacing (e.g., space between adjacent mesh elements) may be less than about 1/10λ (e.g., one-tenth the wavelength of the intended microwave signal) at the distal and proximal ends of the mesh structure to create an effective microwave boundary. Along the length of the mesh, the mesh spacing may be greater than about 1/10λ to avoid creating a microwave boundary thereby allowing for radiation of denervation energy.
• Advantageously, the open mesh structure of the disclosed device enables blood to continue to flow along the surgical site during a denervation procedure, thereby increasing the time window available to the surgeon for completion of the procedure. Maintaining blood flow provides thermal management of theflexible microwave catheter30 and the radiatingportion100, while providing cooling of the inner structure of the vessel walls.
• Some embodiments according to the present disclosure include a radiating portion having a plurality of feed gaps. The radiating portion of a flexible microwave catheter in accordance with the present disclosure may include a mesh structure having a plurality of windows defined therein. Windows may include one or more materials with properties that are different than the body of the mesh structure. Alternatively, a window may be an open structure characterized by the absence of material (e.g., an aperture). As discussed herein, a window in a structure formed from a different material and a window in a structure characterized by the absence of material (e.g., an aperture) are used interchangeably. The material property may include a mechanical property, a material property, an electrical property, or any combination thereof. The window material properties may include a mechanical difference such as, for example, mesh spacing, mesh gauge, mesh formation, mesh thickness or any combination thereof. The window material property may include a physical difference such as, for example, material type, composition, material construction or any combination thereof. The window property may include an electrical difference such as, for example, conductivity, resistivity or any combination thereof.
• The position of the windows may be distributed laterally along the mesh structure, and may be indexed radially and/or may be distributed radially. In some embodiments, three windowed slots are indexed radially 60° apart and distributed longitudinally along the mesh structure. The windows correspond to defined treatment zones (e.g., kill zones) that enable a surgeon to select with precision the tissue regions targeted for denervation. A multi-window mesh structure, as describe herein, may also be utilized with a single feed gap design. A multi-window design may have advantages in that during denervation only a portion of the vessel wall is subjected to energy delivery, while still ensuring the renal nerve bundle is treated effectively.
• Mesh structures may be configured to center the radiatingportion100 of theflexible microwave catheter30 in a body lumen and/or a body structure.
• Mesh structures may include conductive materials, non-conductive materials or a combination of conductive and non-conductive materials. Conductive mesh structures are configured to interact with the radiating portion of the flexible microwave catheter. For example, a conductive mesh structure may form part of a resonance structure. In some embodiments, the conductive mesh structure forms part of an anatomical resonant structure that includes at least a portion of the tissue surrounding the mesh structure.
• At least a portion of a mesh structure may include a conductive portion configured to form a microwave choke or balun. For example, a distal and/or proximal portion of the mesh structure may include a conductive mesh structure configured to shunt the microwave energy signal thereby preventing at least a portion of the microwave energy signal from propagating proximally and/or distally of the conductive mesh structure.
• In some embodiments, the stent-likeexpandable element1670 is coupled to an actuator (e.g.,actuator15 and/or rotatingactuator15g). Actuator may be configured to mechanically expand the stent-like expandable element1670 (or configured to expand, deploy or open a centering device described herein). Distal or proximal end-cap mesh1672amay be coupled toactuator15 and expanded and/or contracted by varying the position of theactuator15.
• Actuation of the centering device (e.g., stent-like expandable element or other centering device described herein) may vary the amount of force exerted to the inner surface of the body lumen thereby shaping the anatomy to a desirable structure and/or geometry. The body lumen may be shaped to form a particular shape, diameter and/or cylindrical structure to facilitate delivery of energy to the targeted tissue.
• As illustrated inFIGS. 17A-17B, theconductive mesh structure1772 includes a plurality of windows1773a-1773edefined in at least a portion of the lengthwise section. Theconductive mesh structure1772 is configured to enable the delivery of denervation energy to tissue through the windows1773a-1773e, while attenuating or eliminating the delivery of denervation energy to tissue from the remainder of themesh structure1772. Proximal and distal mesh end-caps1772a,1772bmay be configured to substantially limit the resonant structure to the confines of themesh structure1772.
• In some embodiments, theconductive mesh structure1772 has density sufficient to limit radiation of microwave energy therethrough, except for one or more of the windows1773a-1773ewhere the structure has a density of about zero. The clinical effect is therefore ablation of the renal artery in a pattern corresponding to the windows1773a-1773e.
• In some embodiments, the window region of themesh1772 may have a mesh density of greater than about 1/10λ (e.g., mesh elements spaced greater than 1/10λ apart), while the non-window region of the mesh may have a mesh density of less than about 1/10λ (e.g., mesh elements spaced less than 1/10λ apart). In some embodiments the window region of themesh1772 includes a non-conductive material or any material that is transparent to microwave energy. In other embodiments, the windows1773a-1773eformed inconductive mesh structure1772 are open and do not include any material what so ever.
• During use, the flexible microwave catheter may be positioned adjacent to targeted tissue, theconductive mesh structure1772 is then expanded, and an application of denervation energy is applied to tissue exposed to the windows1773a-1773e.
• FIG. 17B illustrates a renal artery RA after the application of denervation energy by the device illustrated inFIG. 17A. The denervation energy applied to the renal artery RA through each of the windows1773a-1773egenerates a corresponding denervation zone1774a-1774e.
• For illustrative purposes, the renal artery RA inFIG. 17B is provided with a plurality of renal nerves RN extending longitudinally along the renal artery RA. The denervation zones1774a-1774e(and the corresponding windows1773a-1773e) are longitudinally spaced from each other while providing circumferential overlap such that each of the individual renal nerves RN pass through at least one of the denervation zones1774a-1774d. By this arrangement, denervation energy is applied to each of the renal nerves through at least one of the plurality of windows1773a-1773ealong the length of the renal artery RA.
• Embodiments that provide circumferential overlap and/or circumferential delivery of energy may require a single treatment to obtain a desirable outcome.
• As illustrated inFIG. 18A, aconductive mesh structure1872 includes awindow1873 defined in at least a portion of the lengthwise section thereof. Theconductive mesh structure1872 is configured to enable the delivery of denervation energy to tissue through thewindow1873, while attenuating or eliminating the delivery of denervation energy to tissue from the remainder of themesh structure1872. Proximal and distal mesh end-caps1872a,1872bmay be configured to substantially limit the resonant structure to the confines of themesh structure1872.
• In some embodiments, thewindow1873 may include a mesh which includes a mesh density greater than about 1/10λ. The non-window region of theconductive mesh1872 may have a mesh density of less than about 1/10λ.
• A method of applying denervation energy, utilizing theconductive mesh structure1872 illustrated inFIG. 18A, is illustrated inFIGS. 18B-18H. As illustrated inFIG. 18B, the distal end of the flexible microwave catheter1820 is positioned in a target artery (e.g., renal artery RA). As illustrated inFIG. 18C theouter sheath1835 is retracted to remove theconductive mesh structure1872 and theconductive mesh structure1872 is expanded. Thewindow1873 is directed to afirst target portion1874aof the renal artery RA and a first application of denervation energy is applied to renal artery RA as first targetedtissue1874ais exposed to thewindow1873. After the initial application of denervation energy, theconductive mesh structure1872 is repositioned, as illustrated inFIG. 18D, thereby exposing a different region (e.g., second targetedtissue1874b) of the renal artery RA to thewindow1873. Theconductive mesh structure1872 may be fully or partially collapsed during repositioning and subsequently re-expanded as illustrated inFIG. 18E. After repositioning the flexible microwave catheter1820, a second application of denervation energy is applied to thesecond target tissue1874b. As illustrated inFIGS. 18F-18G, subsequent repositions of theflexible microwave catheter1830 and applications of denervation energy may be delivered in this manner as needed, thereby applying energy to a first, second, and third target tissue1874a-1874c, and so forth.
• Theconductive mesh structure1872 is initially positioned at a distal-most position within a body vessel, and drawn proximally for each subsequent repositioning. In some embodiments, the conductive mesh structure1872 (and hence, the window1873) is independently rotatable about the longitudinal axis of theflexible microwave catheter1830. A rotatingactuator15g(seeFIG. 7), such as without limitation, a knob or a lever, may be provided on the catheter hub18 (seeFIG. 7) to enable a surgeon to rotate and/or manipulate theconductive mesh structure1872 in situ without the need to withdraw and re-insert the flexible microwave catheter, and/or without needing to rotate the entireflexible microwave catheter1830.
• Theflexible microwave catheter30 inFIGS. 18A-18H may include atemperature sensor1834 at a distal end of the radiatingportion100.Temperature sensor1834 may be used to measure the temperature of fluid circulating through the renal artery and passing through the proximal and distal end-cap mesh1872a. The fluid temperature measured by thetemperature sensor1834 may be indicative of the energy delivered by the radiatingportion100. The fluid temperature measured by thetemperature sensor1834 may be indicative of the flow rate of fluid through the proximal and distal end-cap mesh1872a. A low flow rate may be characterized by an unexpected rise in temperature, a change in the rate of temperature change, and/or the failure of a temperature decrease when energy delivery is terminated. Low flow rate may indicate the presence of a clot, emboli, or other blockage proximal theconductive mesh structure1872.
• Sensor leads1834aare routed along the outer surface of theconductive mesh structure1872. Theconductive mesh structure1872 at least partially isolates the sensor leads1834afrom the electromagnetic field generated by the radiatingportion100.
• One or more indicia may be provided in association with the rotatingactuator15gto apprise a surgeon of the position of theconductive mesh structure1872. In some embodiments, theconductive mesh structure1872, or a portion thereof, is formed from material detectable by imaging techniques, thereby enabling a surgeon to determine the position thereof by fluoroscopic and other medical imaging devices, e.g., MRI and/or angiography.
• In some embodiments, the radiatingportion100 includes an antenna structure in accordance with the present disclosure that includes a plurality offeed gaps1950a,1950b,1950c(e.g., energy feedpoints).FIG. 19A illustrates aflexible microwave catheter1930 including a flexiblecoaxial cable1932 connected to a radiatingportion100 on the distal end thereof with a plurality of radiating feed gaps1950a-1950c. Radiatingportion100 includes a firstradiating feed gap1950a, a secondradiating feed gap1950bdistal to the firstradiating feed gap1950a, and a thirdradiating feed gap1950cdistal to the first and secondradiating feed gaps1950a,1950b. In these embodiments, the total power delivered to tissue is divided among the plurality of radiating feed gaps1950a-1950c. A dimension of each feed gap1950a-1950c, e.g., the longitudinal length of the exposed inner conductor, may be tailored to determine which fraction of the energy total is delivered by each respective feed gap1950-1950c.
• FIG. 19A illustrates just one non-limiting example having a radiatingportion100 with three radiating feed gaps1950a-1950c. Since the energy arriving from the generator initially reaches the firstradiating feed gap1950a, thefeed gap1950amay be dimensioned to deliver one-third of the arriving energy. Moving to the secondradiating feed gap1950b, since one-third of the total energy was propagated by the firstradiating feed gap1950a, a remainder of two-thirds of the total energy arrives at the secondradiating feed gap1950b. Accordingly, the secondradiating feed gap1950bmust propagate one-half the arriving energy to deliver one-third of the total energy to tissue. Finally, one-third of the total energy arrives at the thirdradiating feed gap1950c, therefore, the thirdradiating feed gap1950cmust propagate one-hundred percent of the arriving energy to deliver one-third of the total energy to tissue.
• InFIG. 19A, the radiatingportion100, with a plurality of radiating slots1973a-1973c, includes aconductive mesh structure1972 that centers the radiating portion within theconductive mesh structure1972 and includes a plurality of windows1973a-1973dfor delivering denervation energy to tissue through the windows1973a-1973d. In some embodiment, each window1973a-1973dis configured to deliver denervation energy to 90 degrees of the circumference of theconductive mesh structure1972. In some embodiments, the radial section of each window is related to the total number of windows.
• In some embodiments, the dielectric constant of the coaxial insulation D0-D7 is selected to match a particular structure of the radiatingportion100. For example, the dielectric constant of the proximal coaxial insulation D0 may be related to the dielectric constant of the flexible coaxial cable1832, and the dielectric constant of the remaining coaxial insulation D0-D7 is related to the specific section of the radiatingportion100.
• In some embodiments, the width of each feed gap1950a-1950cvaries to promote even energy delivery to each slot, as discussed in detail hereinbelow (seeFIGS. 51 and 53).
• In some embodiments, theproximal mesh structure1972aand thedistal mesh structure1972bare configured to provide minimal restriction of fluid flow therethrough. A sufficient flow of fluid through theproximal mesh structure1972aand thedistal mesh structure1972bprovides a cooling effect and may prevent clotting. In some embodiments, the microwave energy delivery system halts the delivery of the microwave energy power signal if the blood temp approaches and/or rises above clotting levels.
• As illustrated inFIG. 19B, each window1973a-1973ddelivers denervation energy to a corresponding target tissue1974a-1974don the renal artery RA wherein at least a portion of tissue along the entire circumference of the renal artery RA is targeted along the longitudinal length thereof.
• In some embodiments having a plurality of feed gaps, a plurality of corresponding conductive mesh structures2072a-2072cis provided, as illustrated inFIG. 20. Each feed gap2050a-2050cis operatively associated with an individual conductive mesh structure2072a-2072c. Each individual conductive mesh structure2072a-2072cmay include a variable mesh density construction and/or one or more windows2073a-2073c, as described herein. As illustrated inFIG. 20, the orientation of the windows2073a-2073cmay be arranged to radiate in differing directions (e.g. distributed radially). In some embodiments, the windows2073a-2073cmay be arranged to radiate in a similar direction (e.g., indexed radially).
• One or more of the conductive mesh structures2072a-2072cmay be independently rotatable around a longitudinal axis of theflexible microwave catheter2030, either individually or in tandem. One or morecorresponding actuators15g(seeFIG. 7) may be provided, e.g., on the catheter hub18 (seeFIG. 7), and may enable remote positioning and/or monitoring of the conductive mesh structures2072a-2072c.
• An individual actuator may be selectively associated to one or more conductive mesh structures2073a-2073c, thereby enabling the surgeon to manipulate/rotate arbitrary combinations of the conductive mesh structures2072a-2072cas desired. For example, and without limitation, each conductive mesh structure2072a-2072cmay be associated with a switch that, when thrown, operatively couples the respective mesh structure to a dial actuator. One or more conductive mesh structures2072a-2072cmay be selected in this manner such that, as the dial actuator is turned, the chosen conductive mesh structures2072a-2072crotate accordingly. Other actuator control schemes and coupling arrangements may additionally or alternatively be included in a catheter or system in accordance with the present disclosure, including electromechanical or mechanical, utilizing, without limitation, a clutch, a pawl, a hydraulic coupling, a magnetorheological coupling, a motor, a stepper, one or more gears, one or more rollers, one or more pulleys, and so forth.
• As illustrated inFIG. 21, aflexible microwave catheter2130 in accordance with the present disclosure may include one ormore mesh structures2172a-2172darranged between, or adjacent to, one or more feed gaps2150a-2150c. Themesh structures2172a-2172dmay be individually or collectively expandable and/or collapsible. The flexible microwave catheter may include anouter sheath2135 that may be drawn distally to selectively deploy one or more of themesh structures2172a-2172dto vary the region of energy delivery. The dimensions of the feed gaps2150a-2150ce.g., the length L1-L3 of each feed gap2150a-2150c, may be tailored to distribute the denervation energy (e.g., the microwave energy) around the feed gaps2150a-2150cas described herein. A length of transitional dielectric2126a-2126chaving a generally tubular shape may be coaxially disposed about the exposedinner conductor2120 in one or more of the feed gaps2150a-2150c, which may load each section, improve impedance matching, reduce reflections and/or standing waves, improve efficiently, and reduce the risk of embolism (e.g., clotting).
• Themesh structures2172a-2172dare configured to center the radiatingportion100 within the tubular body structure or body portion (e.g., renal artery RA). In some embodiments, the tubular body structure may not be uniformly shaped and the diameter of each of the mesh structures may vary to accommodate the non-uniform shape of the tubular body structure thereby centering the radiatingportion100 within the tubular body structure or body portion. Each of themesh structures2172a-2172dmay be formed from different materials. In some embodiments, one or more of themesh structures2172a-2172dmay be configured to function as a choke or balun thereby preventing at least a portion of the microwave energy signal from propagating longitudinally beyond themesh structure2172a-2172d. For example, in one embodiment theproximal mesh structure2172aanddistal mesh structure2172dinclude a conductive material and configured to function as a choke or balun thereby preventing at least a portion of the microwave energy signal from propagating proximally from theproximal mesh structure2172aand distally from thedistal mesh structure2172d(e.g., reduces propagation of microwave energy from the radiating portion in an axial direction).
• In some embodiments, theproximal mesh structure2172aand/or thedistal mesh structure2172dhave a higher density to act as an effective electrical wall at the operational frequency of the radiatingportion100
• In some embodiments, each of themesh structures2172a-2172dform a choke or balun thereby limiting the propagation of energy generated by each of thefeed gaps2150a. As illustrated inFIG. 21A, the distal portion of the flexible microwave catheter2150 may be defined by zones D0-D7. Energy radiated in zone D0 is limited by theproximal mesh structure2172a. Eachmesh structure2172a-2172dlimits microwave energy in zones D1, D3, D5 and D7, respectively. The energy inzone2 is limited to the energy radiated byfirst feed gap2150a, the energy inzone4 is limited to energy radiated bysecond feed gap2150b, and the energy inzone6 is limited to energy radiated bythird feed gap2150c.
• In some embodiments, the proximal and/or distal surfaces may be selectively coated on a proximal and/or a distal surface with a conductive film, foil, and/or ink to enhance energy directionality.
• As illustrated inFIGS. 22A-23B, aflexible microwave catheter2230 in accordance with the present disclosure includes a distalmesh basket structure2278a,2278bhaving a basket-like and/or an umbrella-like shape. Distal mesh basket structure includes a distal apex and a proximal open (expandable) end. The apex of the distal mesh basket structure is anchored to, or adjacent to, adistal cap2233 of theflexible microwave catheter2230. By this arrangement, the distal mesh basket structure may capture any embolic material that may form during use, e.g., to prevent clots and other biomaterials from entering the bloodstream.
• InFIG. 22A, the distalmesh basket structure2278aand themesh structure2272aare configured to center thefeed gap2250 of the radiatingportion100 in the tubular body structure (e.g., renal artery RA) and/or improve the delivery of denervation energy by preventing or reducing the distal propagation of energy, as described herein.
• InFIG. 22B, radiatingportion100 includes distal and proximal mesh structures for centering thefeed gap2250 of the radiatingportion100 in the natural body lumen (e.g., renal artery RA). The distalmesh basket structure2278bis connected to thecap2233 via atether2278c.Tether2278cmay be released by the rotatingactuator15gin the catheter hub18 (seeFIG. 7) ortether2278cmay be incorporated into a guide wire system.
• As illustrated inFIG. 23, a steppedflexible microwave catheter2330 in accordance with the present disclosure includes a stepped configuration wherein aproximal portion2330ahas a first, larger diameter and adistal portion2330bhas a second, smaller diameter. Generally, the amount of power deliverable by a system is determined, at least in part, by the size of the conductors therein. Largerproximal portion2330acan accommodate a larger diameter flexiblecoaxial cable2332awith conductors can handle more power than smaller conductors. Larger conductors tend to be less flexible than thinner conductors. Advantageously, the thinner, more flexible distal flexiblecoaxial cable2332cof the disclosed steppedflexible microwave catheter2330 enables facile feeding of thedistal portion2330bof the steppedflexible microwave catheter2330 within the circuitous confines of a tubular body structure (e.g., the renal artery) or other body portion, while the larger,proximal portion2330aof the steppedflexible microwave catheter2330 is well suited for the larger, straighter tubular body structure (e.g., the femoral artery). The amount of energy deliverable to the targeted site may be increased, since the losses are reduced in theproximal portion2330aof the steppedflexible microwave catheter2330.
• The flexiblecoaxial cable2332a,2332bin the respective proximal anddistal portions2330a,2330bof the steppedflexible microwave catheter2330 are coupled by atapered matching network2332c. Thetapered matching network2332cmay include a linear tapered portion and/or an exponential tapered portion. Additionally or alternatively, different dielectric layers may be utilized within the flexible coaxial cable2332 in theproximal section2330a, the taperedsection2332c, and/or thedistal section2332cto improve matching, reduce reflections/standing waves (VSWR), and reduce losses.
• As illustrated inFIG. 24, in some embodiments in accordance with the present disclosure, the radiating portion of aflexible microwave catheter2430 for natural lumens includes aninflatable balloon2479 formed from biocompatible elastomeric material. Theinflatable balloon2479 may be inflated with any suitable media, including without limitation a dielectric fluid (e.g., saline or deionized water) and/or a gas (e.g., air, CO₂, etc.) In some embodiments, thefeed gap2450 may be included within theinflatable balloon2479 and the dielectric fluid and/or a portion of the inflatable balloon may form part of an anatomical resonant structure as discussed herein. Theinflatable balloon2479 may include one or more conduits or channels disposed in a generally longitudinal orientation that are arranged to facilitate the flow of vascular fluid (e.g., bloodflow) past the balloon while in use (seeFIGS. 25A-25B and26A-26C). One or more fluid ports may be provided in a proximal portion of the catheter and/or the tip of the catheter that are in fluid communication with the one or more balloon conduits to enhance the flow of vascular fluid therethrough. At least a part of the balloon may include a conductive layer disposed thereon (seeFIGS. 58A-58D). The conductive layer may be disposed on an outer surface, or preferably, an inner surface of the balloon. The conductive layer may be formed by any suitable manner of coating or deposition, including without limitation, thin film deposition, plating, application of conductive ink, foil, and the like. In some embodiments, the conductive layer is formed from conductive silver ink. The conductive layer may be formed in a pattern, e.g., a spiral pattern, a lattice pattern, a halftone pattern, a gradient pattern, or any pattern that facilitates the elastic inflation and deflation of the balloon while maintaining conductivity among and between the elements of the conductive layer pattern. In some embodiment, spiral regions of transparent (e.g., no ink coverage) may have a width of about 3-5 mils (0.003″-0.005″). By this arrangement, a Faraday cage may be formed by the conductive layer, which may improve the radiation pattern and hence delivery of denervation energy. For example, and without limitation, a balloon in accordance with this disclosure may include a spiral conductive pattern disposed at the proximal and distal ends thereof, while having little, or no, conductive material along the middle portion. In embodiments, the balloon structure may include conductive patterns arranged in accordance with the heretofore described configuration(s) of a mesh structure, e.g., a windowed balloon (having conductive coating on all but a windowed portion of the balloon), multiple balloons, a single balloon with multiple windows, rotatable balloon(s), and so forth.
• FIG. 25A illustrates a microwaveenergy delivery system2512 according to some embodiments of the present disclosure that includes acatheter hub2518 connected to aflexible microwave catheter2530 with a distal radiating portion within aninflatable balloon2579 on the distal end thereof.System2512 only illustrates aspects related to theinflatable balloon2579 although it is understood that any aspect or embodiment described herein may be incorporated into thesystem2512.
• Balloon catheter hub2518 includes aballoon fluid coupler2545 for inflating and/or deflating theinflatable balloon2579.Balloon catheter hub2518 may also include any other aspects of thecatheter hubs18 andcoupler45 or adjustablefluid coupler845 described herein (seeFIGS. 7-9C).Balloon fluid coupler2545 forms inflow andoutflow ports2542a,2543athat are in fluid communication with inflow andoutflow plenums2542b,2543b, respectively. Inflow andoutflow plenums2542b,2543bare in fluid communication with respective inflow andoutflow fluid passageways2544a,2544bformed between a fluid flow lumen, the flexiblecoaxial cable2532 and theouter sheath2535.
• As illustrated inFIGS. 25A-25B,inflatable balloon2579 includes aninflatable material2579athat forms the outer surface of aballoon cavity2579b.Balloon cavity2579bmay include one or more chambers formed by eachballoon lobe2579b-2579d. In some embodiments,inflatable balloon2579 includes threelobes2579b-2579dwherein the cavities formed by eachballoon lobe2579b-2579care inflated by fluid provided from theinflow fluid passageway2544a.
• Balloon lobes2579b-2579dare configured to center the radiatingportion100 in a body lumen or body portion.Balloon lobes2579b-2579dprovide a passageway for fluid to pass between eachballoon lobe2579b-2579dand the body lumen wherein fluid flow provides cooling to theballoon lobes2579b-2579dand the body lumen.
• Maintaining sufficient blood flow past the radiating portion is critical in cases, such as balloon centering devices, where the device would otherwise block critical blood flow to distal tissues. As such, any of theinflatable balloons2579 described herein, in addition to any of the other centering devices andflexible microwave catheters30, may be made to have multiple invaginations (e.g., pleats, channels or interfolding parts), about its circumference such that fluid (blood) may continue to pass over the structure while it is placed.
• Fluid from theinflow fluid passageway2544ais delivered to the distal-most portion of theballoon cavity2579b, adjacent thecap2533. Fluid exits theballoon cavity2579bthrough theoutflow fluid passageway2544bconnected to the proximal-most portion of theballoon cavity2579b. As such, fluid travels proximally through theballoon cavity2579bthereby proving an additional cooling source to the radiatingportion100. In some embodiments, fluid flow is needed to dissipate heat generated by the radiatingportion100 and to maintain a dielectric buffer.
• Inflatable balloon2579 may be pre-formed to include theballoon lobes2579b-2579. In some embodiments, theinflatable material2579ais joined to the radiatingportion100 between eachlobe2579b-2579d.
• System2512 may include pressure regulation to maintain pressure in theinflatable balloon2579. Maintaining pressure may be required to maintain antenna position and to maintain the passageway between the inflatable balloon and the body lumen. Pressure regulation may be accomplished by regulating the pressure at theoutflow port2542ausing a pressure sensor as feedback to the pump or mechanical regulator in the fluid cooling system40 (SeeFIG. 7). Pressure regulation may be achieved by maintaining a differential pressure between the inflow port2542 and theoutflow port2543awith adifferential pressure regulator2534din theballoon fluid coupler2545.
• In some embodiments, fluid in the inflatable balloon is expelled into the tubular lumen and/or body structure.Inflatable balloon2579 receives fluid from aninflow fluid passageway2544a. To maintain pressure in theinflatable balloon2579 and/or to maintain the shape ofinflatable balloon2579, fluid in theinflatable balloon2579 escapes through an orifice formed in theinflatable material2579a. The amount of fluid expelled into the tubular lumen and/or body structure may depend on the length of the procedure and the size of the orifice.
• The pressure may also be regulated by performing an anatomical measurement. For example, if used in a vascular system, the pressure in theinflatable balloon2579 may also be regulated using a pressure sensor2542eto detect the systolic blood pressure pulses inside theinflatable balloon2579. Pressure pulses measured inside of theinflatable balloon2579 would increase as the vascular structure became more occluded by inflation of theinflatable balloon2579 and decreasing pressure pulses would indicate a lessinflated balloon2579.
• FIGS. 26A-26C illustrate another embodiment of aninflatable balloon2679 for centering a radiating portion in a body lumen (e.g., renal artery RA).Inflatable balloon2679 includes first, second, andthird lobes2679b-2679dthat are joined to an inflatable balloon housing2679e. Inflatable balloon housing2679eforms an internal chamber that houses cooling fluid. Cooling fluid from the inflatable balloon housing2679eflows to the first, second, andthird lobes2679b-2679dvia a plurality ofinflow fluid passageways2644a.
• FIGS. 27A-41B illustrate various centering devices that may be used to position a radiating portion according to the present disclosure within a body lumen or body structure. One or more centering device may be connected to any portion of the flexible microwave catheter. In some embodiments the centering devices are connected to a deployable portion wherein in a first undeployed position, the centering device is in a constrained condition, and in a second deployed position, the centering device is in an unconstrained condition, e.g., expanded and configured to center the radiating portion in the body lumen.
• FIGS. 27A-27D illustrate centeringfins2790 for centering a radiatingportion100 in a body lumen BL. Centeringfins2790 include first, second, andthird fins2790a-2790cthat connect to a portion of aflexible microwave catheter2730.FIG. 27A illustrates the centeringfins2790 restrained within theouter sheath2735. Centeringfins2790 are illustrated distal to the radiatingportion100 however centeringfins2790 may be positioned adjacent or proximal the radiatingportion100.FIG. 27B is a transverse cross-section ofFIG. 27A that illustrates each of thefins2790a-2790crestrained by theouter sheath2735 and offset by about 120 degrees with respect to each other.
• InFIGS. 27C-27D the centeringfins2790 and radiatingportion100 are deployed from theouter sheath2735.Fins2790a-2790c, when released from the constraints of theouter sheath2735, center the radiatingportion100 about the center of the body lumen BL. After use, the centeringfins2790 and radiatingportion100 are retracted to a constrained position (seeFIG. 27A) within theouter sheath2735.
• As illustrated inFIG. 27C, centeringfins2790 may center the radiatingportion100 by contacting with the body lumen BL. In some embodiments, centeringfins2790 self center the radiatingportion100 via fluid/hydrodynamic, and/or mechanical forces within the body lumen BL thereby ensuring even energy delivery.
• In some embodiments,cap2733 extends distally from theflexible microwave catheter2730 and longitudinally positions theradiating section100 adjacent a targeted tissue in a body lumen. For example,cap2733 may be dimensioned to enter, and/or become lodged in, a branch of the renal artery at the hilum of the kidneys. The distance between thecap2733 and the radiatingportion100 is dimensioned such that the radiatingportion100 is positioned adjacent a target tissue in the renal artery.
• FIG. 28 illustrates a four-prong centering device2891 that includes fourprongs2891a-2891dthat connect to adistal receiver2891eand form aproximal receiver2891f.Distal receiver2891eandproximal receiver2891fare each configured to receive a portion of a flexible coaxial cable (not shown) therethrough.
• FIGS. 29-32 illustrate a centeringbasket2992 for centering a radiatingportion100 in a body lumen BL. Each centeringbasket2992 include first, second, third, andfourth bands2992a-2992dthat connect toproximal receiver2992eanddistal receiver2992f. In some embodiments, at least one of theproximal receiver2992eand thedistal receiver2992fis fastened to a portion of the flexible microwave catheter while the other slides freely of the flexible microwave catheter. As such, in a deployed condition the centeringbasket2992 is expanded, as illustrated inFIG. 29. In an undeployed condition (e.g., constrained with an outer sheath or similar device) thebands2992a-29992dare compressed thereby elongating the centeringbasket2992.
• InFIG. 29, theproximal receiver2992eis distal to the radiatingportion100 and connected to theelongated cap2933.Distal receiver2992fis unrestrained and extends distally from theelongated cap2933. In some embodiments, distal end ofelongated cap2933 includes a rounded surface to facilitate insertion and/or navigation of theflexible microwave catheter2930 to a targeted tissue.
• InFIG. 30, the centeringbasket3092 is positioned proximal the radiatingportion100. The distal receiver3092eis fastened to theflexible microwave catheter3030.Proximal receiver3092fslides freely over theflexible microwave catheter3030 thereby allowing the centeringbasket3092 to be compressed and elongated when constrained within an outer sheath or similar device (not explicitly shown).
• InFIG. 31, the centeringbasket3192 is centered about the radiatingportion100 wherein the distal receiver3192eis fastened to theflexible microwave catheter3130 between the radiatingportion100 and the cap3122. The proximal receiver3192fslides freely over theflexible microwave catheter3030 proximal the radiatingportion100, thereby allowing the centeringbasket3192 to be compressed and elongated when constrained within an outer sheath or similar device.
• InFIGS. 32A and 32B, a proximal centeringbasket3292aand a distal centeringbasket3292bare connected to theflexible microwave catheter3230. The proximal centeringbasket3292aand the distal centeringbasket3292bare configured to center the radiatingportion100 that includes aproximal feed gap3250aand adistal feed gap3250binFIG. 32A and aproximal feed gap3250ainFIG. 32B. The proximal centeringbasket3292ais positioned proximal to theproximal feed gap3250aand the distal receiver3292aeis fastened to theflexible microwave catheter3230. Proximal receiver3292afof the proximal centeringbasket3292aslides freely over theflexible microwave catheter3230, thereby allowing the proximal centeringbasket3292ato be compressed and elongated when constrained within an outer sheath or similar device (not explicitly shown).
• InFIG. 32B, the distal centeringbasket3292bis centered on thedistal feed gap3250bwherein the distal receiver3292beis fastened to theflexible microwave catheter3130 between the distal feed gap3250 and thecap3233. The proximal receiver3292bfof the distal centeringbasket3292bslides freely over theflexible microwave catheter3230 proximal thedistal feed gap3250b, thereby allowing the distal centeringbasket3292bto be compressed and elongated when constrained with an outer sheath or similar device.
• InFIG. 32B, theproximal feed gap3250ais centered between the proximal centeringbasket3292aand the distal centeringbasket3292b. In some embodiments, the proximal centeringbasket3292ais positioned proximal to theproximal feed gap3250aand the distal receiver3292aeis fastened to theflexible microwave catheter3230 such that the proximal receiver3292afof the proximal centeringbasket3292aslides freely over theflexible microwave catheter3230. The distal centeringbasket3292bis positioned distal to theproximal feed gap3250aand the distal receiver3292beis fastened to theflexible microwave catheter3130 proximal thecap3233 such that the proximal receiver3292bfslides freely over theflexible microwave catheter3230. As such, the proximal and distal centeringbaskets3292a,3292bmay be compressed and elongated when constrained with an outer sheath or similar device.
• InFIG. 33, a dual-band centering device3393 is centered about the feed gap3250 of the radiatingportion100. Dual-band centering device3393 includes aproximal receiver3393fthat is fastened to theflexible microwave catheter3333, and adistal receiver3393bthat slides freely over thecap3333 of theflexible microwave catheter3330.
• Dual-band centering device3393 includes a first andsecond bands3393a,3393b, respectively, that are offset 180 degrees from each other. As such, the dual-band centering device3393, when expanded in a body lumen BL, elongates the body lumen BL with respect to the first andsecond bands3393a,3393bwhile drawing the body lumen BL toward thefeed gap3350 of the radiating portion100 (e.g., along each of the side of the dual-band centering device3393). In this manner, the dual-band centering device3393 shapes the body lumen into an oblong shape wherein the portion drawn toward thefeed gap3350 will generate hot spots due to the oblong coaxial arrangement.
• InFIG. 34, a clover-leaf centering device3494 is connected to thecap3433 distal to thefeed gap3450 of the radiatingportion100. Clover-leaf centering device3494 includes a plurality ofpetals3494a-3494dequally spaced about the circumference of theflexible microwave catheter3430.Petals3494a-3494dmay be formed from a shape-memory material, such as nitonal, such that thepetals3494a-3493dexpand outward to form the clover-leaf shape after being deployed from theouter sheath3435.
• In some embodiments, a clover-leaf centering device3494 is electrically isolated from the radiatingportion100. Clover-leaf centering device3494 may be joined by a dielectric having adhesive properties (e.g., dielectric glue) thereby preventing metal-to-metal contact between thepetals3494a-3494dof the clover-leaf centering device3494 and/or any metallic portion of the in the radiatingportion100.
• InFIG. 35, aflexible microwave catheter3530 includes a clover-leaf centering device3594 and a centeringbasket3592. Clover-leaf centering device3594 is joined to thedistal cap3533 and positioned distal thefeed gap3550 of the radiatingportion100. Centeringbasket3592 is positioned on a portion of theflexible microwave catheter3530 proximal to thefeed gap3550.
• FIGS. 36A and 36B illustrate apaddle centering device3695 according to some embodiments of the present disclosure.Paddle centering device3695 includes first, second, andthird paddles3695a-3695cfixed to a portion of theflexible microwave catheter3650.Paddles3695a-3695cmay be fixed by a hinge-like attachment3695dthat pivotally attaches and/or hingedly attachments eachpaddle3695a-3695cto the flexiblecoaxial cable3632.
• InFIG. 36A, thepaddles3695a-3695cof thepaddle centering device3695 are constrained within theouter sheath3635 of theflexible microwave catheter3630. In the constrained condition, thepaddles3695a-3695care folded inward and positioned adjacent the flexiblecoaxial cable3632.
• InFIG. 36B, the flexiblecoaxial cable3632 andpaddles3695a-3695care shown deployed from theouter sheath3635 of theflexible microwave catheter3630.Paddles3695a-3695care opened by moving each paddle about the hinge-like attachment. In the open position, paddles3695a-3695care prevented from over-extending by a paddle stop3695e, and/or motion is limited by the hinge-like connection3695d. In some embodiments, the paddle stop3695eis a choke or balun formed on the flexible coaxial cable3532.
• Paddles3695a-3695cmay articulate between a closed condition, as illustrated inFIG. 36A, and an open condition, as illustrated inFIG. 36B. In some embodiments, articulation may be affected by an actuator on the catheter hub18 (seeFIG. 7). In some embodiments, articulation may be affected by the deployment of the flexiblecoaxial cable3632 from theouter sheath3635.
• Paddle centering device3695 may include any number ofpaddles3695a-3695csymmetrically positioned (e.g., regularly distributed) about theflexible microwave catheter3730. In some embodiments, thepaddles3695a-3695care substantially identical in length and width, although in some embodiments,paddles3695a-3695cmay vary in length and/or width thereof.
• FIGS. 37A and 37B illustrate a dualpaddle centering device3795 according to some embodiments of the present disclosure. Dualpaddle centering device3795 includes a proximalpaddle centering device3795aand a distalpaddle centering device3795b. Proximalpaddle centering device3795ais positioned on theflexible microwave catheter3730 between thefirst feed gap3750aand thesecond feed gap3750b. Distalpaddle centering device3795bis positioned on theflexible microwave catheter3730 between thesecond feed gap3750band the third feed gap3750c. Proximalpaddle centering device3795aand a distalpaddle centering device3795bcenter thefirst feed gap3750a,second feed gap3750b, and third feed gap3750cin the body lumen BL.
• FIGS. 38A and 38B illustrate apaddle centering device3896 according to some embodiments of the present disclosure.Paddle centering device3896 includes first, second, andthird paddles3896a-3896cfixed to a portion of theflexible microwave catheter3830.Paddles3896a-3896cmay be fixed by a hinge-like attachment3996dthat pivotally attaches and/or hingedly attaches eachpaddle3896a-3896cto the flexible microwave catheter3850.
• InFIG. 38A, thepaddles3896a-3696cof thepaddle centering device3896 are constrained within theouter sheath3835 of theflexible microwave catheter3830. In the constrained condition, thepaddles3896a-3896care folded inward and positioned adjacent the flexiblecoaxial cable3832.
• InFIG. 38B, the flexiblecoaxial cable3832 andpaddles3896a-3896care shown deployed from theouter sheath3835 of theflexible microwave catheter3830.Paddles3896a-3896care opened by moving each paddle about the hinge-like attachment. In theopen position paddles3896a-3896care prevented from over-extending by a paddle stop (e.g., outer sheath3835) and/or motion is limited by the hinge-like connection3896d.
• Paddles3896a-3896cmay articulate between a closed condition, as illustrated inFIG. 38A, and an open condition, as illustrated inFIG. 38B. In some embodiments, articulation may be affected by an actuator on the catheter hub18 (seeFIG. 7). In some embodiments, articulation may be affected by the deployment of the flexiblecoaxial cable3832 from theouter sheath3835.
• Paddles3896a-3696cmay open in a direction opposite the fluid flow FF, as illustrated inFIG. 38B orpaddles3695a-3695c(seeFIGS. 36A-36B) may open in the same direction as the fluid flow FF.
• FIGS. 39A and 39B illustrate a dualpaddle centering device3996 according to some embodiments of the present disclosure. Dualpaddle centering device3996 includes a proximalpaddle centering device3996aand a distalpaddle centering device3996b. Proximalpaddle centering device3996ais positioned on theflexible microwave catheter3930 proximal thefirst feed gap3950a. Distalpaddle centering device3996bis positioned on theflexible microwave catheter3930 between thefirst feed gap3950aand the second feed gap3950b. Proximalpaddle centering device3996aand a distalpaddle centering device3996bcenter thefirst feed gap3950aand second feed gap3950bin the body lumen BL.
• FIGS. 40A and 40B illustrate a deployable centering device that centers thedistal radiating portion100 of aflexible microwave catheter4030 with a plurality oftines4097. In an undeployed condition, as illustrated inFIG. 40A, the tines are restrained within theouter sheath4035 of theflexible microwave catheter4030.Outer sheath4035 may retract proximally thereby deploying the radiatingportion100 andtines4097 from theouter sheath4035. Alternatively, radiatingportion100 andtines4097 may deploy distally from theouter sheath4035. In a deployed condition, as illustrated inFIG. 40B, the tines are attached to, and extend radially outward from, the flexible microwave catheter thereby centering the radiating portion in the renal artery RA.
• FIG. 41A illustrates a helical centeringdevice4198 that may be used to center thedistal radiating portion100 of aflexible microwave catheter4030. Helical centeringdevice4198 includes a plurality ofhelical ribs4198a-4198cthat each connect to the outer surface of a distal end of the flexible microwave catheter4130a. In some embodiments, thehelical ribs4198a-4198care attached to the outer surface of the flexiblecoaxial cable4032a. In an undeployed condition, thehelical ribs4198a-4198care compressed between the flexiblecoaxial cable4032aand the inner surface of theouter sheath4035. As the helical centering devices are deployed from the outer sheath4025, each of thehelical ribs4198a-4198cextends radially from the flexiblecoaxial cable4032athereby centering the radiatingportion100 within a body lumen.
• FIG. 41B illustrates a helical centeringdevice4199 configured to insert over the distal portion of a flexible microwave catheter according to embodiments of the present disclosure.Helical ribs4199a-4199cattach to the outer surface of ahelical sleeve4199dand the helical sleeve is configured to slidably engage the distal portion of a flexible microwave catheter.
• FIGS. 42-44 illustrate aflexible microwave catheter30 including anouter sheath135 that forms the outer layer of theflexible microwave catheter30 and a flexiblecoaxial cable32 that slidably engages the inner surface of theouter sheath135. The proximal portion of theouter sheath135 includes a first inner diameter D1 that accommodates the outer diameter of theouter conductor124. A distal-most portion of theouter sheath135 forms a slidinghub135athat accommodates the radiatingportion100 of the flexiblecoaxial cable32. Slidinghub135aincludes a second inner diameter D2 that accommodates the outer diameter of the outer dielectric insulatinglayer128, wherein the first inner diameter D1 of theouter sheath135 is less than the second inner diameter D2 of the slidinghub135a. As such, amechanical stop129 is formed by the transition of theouter sheath135 between the first inner diameter D1 and the second inner diameter D2.
• In some embodiments, slidinghub135ais less flexible than the proximal portion of theflexible microwave catheter30. In some embodiments, slidinghub135ais rigid.Flexible microwave catheter30 may also include a guidance system (not explicitly shown) for manipulating the angle between a proximal, more flexible portion of theflexible microwave catheter30 and a distal, less-flexible and/or rigid, portion of the flexible microwave catheter (e.g., slidinghub135a).
• An outer surface of theouter sheath135 may include a dielectric coating. In one embodiment, the dielectric coating is a chemically vapor deposited polymer such as the coating sold and manufactured by Parylene Coating Services of Katy, Tex., under the tradename Parylene™. In another embodiment, the dielectric coating includes one or more blood clot reducing properties or components.
• FIGS. 42,43 and44 illustrate the flexiblecoaxial cable32 and the radiatingportion100 on the distal end thereof positioned in various positions, e.g., positioned in a fully retracted position (seeFIG. 42), in a partially deployed position (seeFIG. 43), and in a fully deployed position (seeFIG. 44).
• Turning now toFIG. 42, the radiatingportion100 is fully retracted within the slidinghub135aof theouter sheath135. In a fully retracted condition the proximal end of the outer dielectric insulatinglayer128 abuts themechanical stop129 of theouter sheath135 thereby preventing further retraction of the flexiblecoaxial cable32 within theouter sheath135. The proximal end of outer dielectric insulatinglayer128 may engage themechanical stop129 wherein the engaging surface further prevents retraction of the flexiblecoaxial cable32 within theouter sheath135.
• Cap133 abuts the distal end of theouter sheath135 and forms a smooth transition between the outer surface of theouter sheath135 and the outer surface of thecap133.Cap133 andouter sheath135 may be joined together by mechanical engagement, an interference fit, or by soldering, brazing, adhesive and/or laser welding, thereby preventing unintended separation (e.g. deployment) between thecap133 andouter sheath135.Cap133 may prevent further retraction of the flexiblecoaxial cable32 within theouter sheath135. While the embodiments illustrated herein illustrate a blunt distal end that enables theflexible microwave catheter30 to benignly follow a guiding lumen, in other embodiments, the cap may include a sharpened tip configured for percutaneous insertion into tissue.
• In use, a clinician inserts the flexible microwave catheter30 (e.g., radiating portion100) into a patient through a channel and maneuvers theflexible microwave catheter30 to a desired position with the patient. The channel may be a naturally formed body channel and/or lumen (e.g. artery vein, esophagus, bronchial, anus, vagina, urethra, and so forth), a lumen inserted in a naturally formed body channel, a cannula, a shaft or any other suitable insertion needle, device, guide, or system.
• During an insertion step, the radiatingportion100 is housed in the slidinghub135aof theouter sheath135. Slidinghub135aengagesouter conductor124 and prevents any unintended release of energy to patient tissue.
• Cap133 may electrically engageouter sheath135 thereby forming an electrical pathway (e.g., electrical short) between theinner conductor120 and theouter conductor124 via a portion of theouter sheath135. In a fully retracted position, as illustrated inFIG. 42, theentire radiating portion100 is contained within the outer sheath andcap133 thereby minimizing or eliminating, discharge of electrosurgical energy therefrom.
• Turning now toFIG. 43, distally advancing the flexiblecoaxial cable32 within theouter sheath135 of theflexible microwave catheter30 deploys the radiatingportion100 from the slidinghub135a. The length of the radiatingportion100 deployed from the slidinghub135ais selectable by the clinician.
• With reference toFIGS. 7,8C and42-44, at least a portion of the flexiblecoaxial cable32 connects to theactuator15,815 in thecatheter hub18. Actuation of theactuator15,815 moves the flexiblecoaxial cable32 and advances and retracts the flexiblecoaxial cable32 within theouter sheath35.Actuator15,815 may be actuated to any desirable position along theactuator slot15a. The position of theactuator15,815 in theactuator slot15ais related to the position of the radiatingportion100 in the slidinghub135aand related to the section of the radiatingportion100 that deploys from the slidinghub135a.
• Lock mechanism817 may be integrated into thebody845a,854bof theadjustable fluid coupler845. In some embodiments, the most-proximal position of the lock mechanism817 includes a lock position that locks theactuator15,815 in position to prevent accidental deployment of the radiatingportion100 while positioning theflexible microwave catheter30 in a guiding lumen. In some embodiments, the lock mechanism817 and/or theactuator15,815 includes a tensioning mechanism, such as a spring (not explicitly shown) that provides a proximal bias on the flexiblecoaxial cable32 when theactuator15,815 is in the lock position. In some embodiments, the lock position of theactuator15,815 includes a take-up mechanism that compensates for any length changes between the flexiblecoaxial cable32 and the outer sheath due35 to bending and/or turning of theouter sheath35 and flexiblecoaxial cable32 while positioning theflexible microwave catheter30 in a guiding lumen. In some embodiments,actuator15,815 includes a lock mechanism817, a tensioning mechanism, a take-up mechanism or any combination thereof. For example,actuator15,815 may include a raisedportion817athat mates with areceiver portion817bformed on thefluid coupler body845aand thereceiver portion817bprovides a plurality of longitudinal positions to receive the raisedportion817aalong its length.Actuator15,815 may further include a biasing mechanism, such as a spring or elastic member, or any other suitable tensioning mechanism and/or take-up mechanism.
• FIG. 44 illustrates a cross-sectional view of the distal portion of theflexible microwave catheter30 with the radiating portion fully deployed from the slidinghub135a.Proximal portion128aof the outer dielectric insulatinglayer128 remains housed within the slidinghub135ain the fully deployed position.Proximal portion128aof the outerdielectric insulation layer128 maintains engagement with the slidinghub135athereby facilitating the subsequent retraction of the radiatingportion100 within the slidinghub135a(seeFIGS. 42 and 43).Proximal portion128amay form a fluid-tight seal121awith the slidinghub135a. Fluid-tight seal121amay prevent body fluid from entering the slidinghub135aand filling the void135bwithin the slidinghub135aformed by deploying the radiatingportion100.
• Thetransitional dielectric126 may have dielectric properties related to the dielectric properties of the outer dielectric insulatinglayer128. In some embodiments, a dielectric gradient is formed between thetransitional dielectric126, the outer dielectric insulatinglayer128 and the anatomical structures with which the radiatingportion100 may be used, e.g., the renal artery or other body lumen/body structure).
• The outer surface of the outer dielectric insulatinglayer128 and the inner surface of the slidinghub135amay include interfacingsurfaces117a,117bthat provide a mechanical stop thus preventing theproximal portion128aof the outer dielectric insulatinglayer128 from advancing from the slidinghub135a. For example, in one embodiment, the inner surface of the slidinghub135aincludes a radially inward protrudingtab117a. At a fully deployed position the radially inward protrudingtab117aengages amechanical stop117bformed in the dielectric insulatinglayer128 thereby preventing further distal deployment of the radiatingportion100 from slidinghub135a.
• In some embodiments, a choke or balun short (not explicitly shown) is positioned longitudinally proximal to the formation of thehelical feed gap50 and may be fixed to theouter conductor124 and/or theouter sheath135. The balun may be formed from a short conductive (e.g., metallic) ring having an inner diameter dimensioned to accept the outer conductor124 (or the outer sheath135). Alternatively, the balun may be formed on the inner surface of theouter sheath135. The balun is electrically bonded (e.g., soldered and/or electrically connected by a suitable conductor) to theouter conductor124. This balun affects a radiofrequency short which, in turn, may optimize, control, focus, and/or direct the general proximal radiating pattern of the radiating portion antenna, e.g., reduce the propagation of denervation energy beyond the proximal end of the antenna radiating portion and/or the balun.
• The balun assembly may include a balun dielectric sleeve, which may be formed from extruded polytetrafluoroethylene (PTFE, e.g., Teflon®). The balun dielectric may be positioned over the radiatingportion100 of theflexible microwave catheter30 and mated to the balun ring. A length of heat shrink tubing (not explicitly shown), having a conductive material on a surface thereof, preferably an inner surface, may be positioned over the PTFE sleeve to improve the performance of the balun and thus, improve the radiating pattern of denervation energy.
• In some embodiments, as discussed in detail hereinbelow and illustrated inFIGS. 42-57, a flexible microwave catheter in accordance with the present disclosure includes a radiating portion having a spiral configuration, wherein the outer conductor of the radiating portion is exposed in a spiral pattern. The width of the spiral opening may optionally be tapered, increasing in width as the spiral winds distally along the radiating portion, in order to radiate energy evenly along the length thereof (seeFIGS. 42-49 and54-57). A spiral sensor lumen or conductor may be interspersed within the spiral feedpoint to operatively couple a sensor disposed at or near the distal region of the probe to a generator or other apparatus located proximally of the probe.
• Any number of baskets, centering devices or expandable members, as discussed hereinabove, may be utilized with this spiral structure to selectively ablate tissue in a radial direction away from the centralized structure. This would allow for a procedure which normally requires multiple placements of an ablation device to be simplified by necessitating only one placement providing multiple selectively directed radiating elements. The user may choose to deploy any number of the baskets, centering devices or expandable members, while leaving others collapsed and thus deactivated due to the conductive sheath covering the feed gap.
• The deployable structure illustrated inFIGS. 42-44 and described herein, may also be utilized to deploy any of the structures and radiatingportion100 described herein.
• As discussed hereinabove with respect toFIGS. 42-44, the radiatingportion100 includes a shieldingouter conductor124athat exposes theinner conductor120 thereby forming a helical feed gap50 (e.g., feed point). In one embodiment, the shieldingouter conductor124ais formed by removing a portion of theouter conductor124 at thehelical feed gap50. The shieldingouter conductor124athat remains on theinner conductor120 is wrapped helically around the longitudinal axis of theinner conductor120. A helical and/or spiral feed gap provides uniform distribution of energy along the axial length of the radiation section as well as an ideal impedance match to the coaxial waveguide impedance thereby reducing unwanted heating along the flexiblecoaxial feedline32.
• In some embodiments, prior to use (e.g., during manufacturing) theouter conductor124 and inner dielectric insulator are removed from theinner conductor120 in the radiatingportion100 and a shieldingouter conductor124aand shielding dielectric (not explicitly shown) are positioned on the exposed inner conductor. The shieldingouter conductor124ais wrapped helically around the longitudinal axis of theinner conductor120. The proximal portion of the shieldingouter conductor124ais electrically connected to the distal portion of theouter conductor124. The distal portion of the shieldingouter conductor124ais electrically connected to thecap133. The cap shorts the shieldingouter conductor124ato theinner conductor120.
• Cooling fluid from the fluid cooling system40 (seeFIG. 7) may flow through fluid lumens formed in the shieldingouter conductor124aand connected to theinflow fluid passageway44aandoutflow fluid passageway44bin theflexible microwave catheter30 thereby proving fluid pathways for cooling fluid to flow to and from the distal end of the radiatingportion100.
• As discussed hereinabove, atransitional dielectric126 may be disposed in thehelical feed gap150 and may generally and/or geometrically correspond to the dimensions of thehelical feed gap150. Thetransitional dielectric126 and the shielding dielectric (not explicitly shown) may be formed from similar materials with similar dielectric properties. In some embodiments, thetransitional dielectric126 and the shielding dielectric may have different dielectric properties. In some embodiments, a single dielectric layer includes thetransitional dielectric126 and the shielding dielectric includes a first geometrical portion having dielectric properties corresponding to thetransitional dielectric126 and a second geometrical portion having dielectric properties corresponding to the shielding dielectric.
• As discussed hereinabove, thefeed gap150 is defined by the void formed from the removal of a portion of theouter conductor124. Similarly, thehelical feed gap150 is defined by the void formed between adjacent windings of the helically wrapped shieldingouter conductor124a(e.g., helically wrapped about the longitudinal axis of the inner conductor120). The dimensions of thehelical feed gap150 are related to properties and the position of the shieldingouter conductor124a. Thehelical feed gap150 may also be defined by the portion of the inner conductor not helically wrapped by the shieldingouter conductor124a. As such, defining the dimensional properties and position of the shielding outer conductor124cnecessarily defines thehelical feed gap150 that varies along the longitudinal length of the radiatingportion100. In one embodiment, the position of thehelical feed gap150 changes circumferentially along the length thereof. In some embodiments, the pitch of the helix (e.g., the width of one complete helix turn, measured parallel to the axis of the helix) varies along the longitudinal length of the radiatingportion100. In some embodiments, the pitch may vary due to a change in the helix angle (e.g., the angle between any helix and an axial line formed perpendicular to the inner conductor). In some embodiments, the pitch may vary due to a change in the width of the helical feed gap150 (e.g., a varying thickness of thehelical feed gap150 along the longitudinal length thereof). In some embodiments, the pitch may vary due to a change in the helix angle and a change in the width of thehelical feed gap150.
• In use, the energy transmitted to tissue by the radiatingportion100 is related to the area and position of thehelical feed gap150. As illustrated inFIGS. 42-44, the area of thehelical feed gap150 increases as the helix winds distally, transitioning from a narrowhelical feed gap150 on the proximal end to a widehelical feed gap150 on the distal end of the radiatingportion100. The change in area (e.g., increase in area as the helix distally winds) translates in a low coupling factor on the proximal end and a high coupling factor on the distal end. On the proximal end of the radiatingportion100 the coupling factor is 1% and the coupling factor increases in an exponential manner to 100% at the distal end.
• FIGS. 45 and 46 illustrate another embodiment of a non-linear wrap pattern that forms a radiatingportion200 that may be incorporated into anyflexible microwave catheter30 according to some embodiments of the present disclosure. The area of thehelical feed gap250 increases as the helix winds distally with the proximal end providing anarrow feed gap250 and the distal portion being more substantially exposed. The non-linear change in the area of thehelical feed gap250 at the proximal end of the radiatingportion200 and the area of thehelical feed gap250 at the distal end of the radiatingportion200 is due to the geometry of the shieldingouter conductor224a.
• As illustrated inFIG. 46, the shieldingouter conductor224aincludes a proximal firstnon-linear edge224b, a second distalnon-linear edge224cwherein the firstnon-linear edge224band the secondnon-linear edge224cterminate on thedistal end224dthereby forming a substantially pointeddistal end224d.
• FIGS. 47 and 48 illustrate yet another embodiment of a non-linear wrap pattern that forms a radiatingportion300 that may be incorporated into anyflexible microwave catheter30 of the present disclosure. The area of thehelical feed gap350 increases as the helix travels distally with the proximal end providing a narrow feed gap and the distal portion being substantially exposed. The non-linear change in the area of thehelical feed gap350 at the proximal end of the radiatingportion300 and the area of thehelical feed gap350 at the distal end of the radiatingportion300 is due to the geometry of the shieldingouter conductor324a.
• As illustrated inFIG. 48, the shieldingouter conductor324aincludes a proximal firstnon-linear edge324b, and a second distallinear edge324cthat terminates on the distal end thereof. The distal end forms a flatdistal edge324dconfigured to align with the distal end of the inner conductor (not explicitly shown).
• One measure of the varyinghelical feed gap150 is the feed gap ratio, defined herein as the ratio between the cross-sectional circumference of thehelical feed gap150 and the cross-sectional circumference of the shieldingouter conductor124a.FIG. 49 is a graph illustrating the feed gap ratio along the longitudinal length of theradiation portion1000,200,300 of the respective embodiments illustrated inFIGS. 44,45 and47. The feed gap ratio of radiatingportion1000 inFIG. 44 varies between 0% and 50% and varies linearly along the longitudinal length between the proximal end and the distal end of the radiatingportion1000. The feed gap ratio ofradiation portion200 inFIG. 45 varies between 0% and 100% and varies non-linearly along the longitudinal length between the proximal end and the distal end of the radiatingportion300. The feed gap ratio ofradiation portion300 inFIG. 47 varies between 0% and 100% and varies non-linearly along the longitudinal length between the proximal end and the distal end of the radiatingportion300. Other geometries that may be used include an exponential taper, a triangular taper and a Klopfenstein logarithmic taper from a stepped Chebyshev transformer where the sections increase to infinite (e.g., analogous to a Taylor distribution).
• As discussed hereinabove with respect toFIGS. 6A-6B and8A-8C, theflexible microwave catheter30 may include atubular inflow lumen37 positioned coaxially between the inner flexiblecoaxial cable32 and theouter sheath135. A clearance between the outer diameter of the flexiblecoaxial cable32 and the inner diameter of theinflow lumen37 defines aninflow fluid passageway44a. A clearance between the outer diameter of theinflow lumen37 and an inner diameter of theouter sheath135 defines anoutflow fluid passageway44b. During use, a coolant, e.g., carbon dioxide, air, saline, water, or other coolant media may be supplied to the radiatingportion100 by theinflow fluid passageway44aand evacuated from the radiatingportion100 by theoutflow fluid passageway44b.
• In some embodiments, theinflow fluid passageway44athat supplies coolant and is the inner-most fluid conduit and theoutflow fluid passageway44bthat evacuates coolant is the outer-most fluid conduit. In other embodiments, the direction of fluid flow may be opposite. One or more longitudinally-oriented fins or struts (not explicitly shown) may be positioned within the inflow fluid pathway and/or the outflow fluid pathway to support and control the position of the inflow lumen with respect to theouter sheath135 and to support and control the position of the flexiblecoaxial cable32 with respect to theinflow lumen37.
• FIG. 50 is an electrical circuit diagram of a leaky waveguide according to another embodiment of the present disclosure. The leaky waveguide includes a network with an impedance of Z_Owherein all energy is radiated or dissipated in the leaky waveguide. Each Z_Lis composed of a radiation resistance, reactive impedance and loss resistance wherein:
• 
  Z_L=R_R−iR_i+R₁  (1)
• Although represented by a lumped element, the Z_Lcomponents may be a distributed network. As illustrated inFIG. 51, each Z_Lcomponent may represent one of the five slots S1-S5 in a coaxial cable.
• Another waveguide according to the present disclosure may include any number of slots.FIG. 52 illustrates an embodiment having a radiatingportion200 utilizing ten (10) slots. To provide a uniform radiating pattern along the length of the radiating portion, each of the ten (10) slots must radiate approximately 10% of the total available energy provided to the waveguide Z_O. Since each slot radiates a portion of the total available energy, the remaining energy available to each subsequent slot is less than the energy provided to the previous slot. As such, a uniform radiating pattern requires each distally positioned slot to radiate a higher percentage of the remaining available energy than each proximally positioned (e.g., prior) slot.
• In the example embodiment illustrated inFIG. 52, 100 Watts of energy is provided to theleaky waveguide200, therefore,slot1 must transmit about 10% of the total energy provided thereto (e.g., 10% of 100 Watts=10 Watts).Slot2 is provided with about 90 Watts (100 Watts minus the 10 Watts transmitted by slot1), therefore,slot2 must transmit about 11% of the total energy provided thereto (e.g., 11% of 90 Watts=10 Watts).Slot3 is provided with about 80 Watts (100 W minus the 20 Watts transmitted by slots1-2), therefore,slot3 must transmit about 12.5% of the total energy provided thereto (e.g., 12.5% of 80 Watts=10 Watts).Slot4 is provided with about 70 Watts (100 Watts minus 30 Watts transmitted by slots1-3), therefore,slot4 must transmit about 14.3% of the total energy provided thereto (e.g., 14.3% of 70 Watts=10 Watts).Slot4 is provided with about 70 Watts (100 Watts minus 30 Watts transmitted by slots1-3), therefore,slot4 must transmit about 14.3% of the total energy provided thereto (e.g., 14.3% of 70 Watts=10 Watts).Slot5 is provided with about 60 Watts (100 Watts minus 40 Watts transmitted by slots1-4), therefore,slot5 must transmit about 16.7% of the total energy provided thereto (e.g., 16.7% of 60 Watts=10 Watts).Slot6 is provided with about 50 Watts (100 Watts minus 50 Watts transmitted by slots1-5), therefore,slot6 must transmit about 20% of the total energy provided thereto (e.g., 20% of 50 Watts=10 Watts).Slot7 is provided with about 40 Watts (100 Watts minus 60 Watts transmitted by slots1-6), therefore,slot7 must transmit about 25% of the total energy provided thereto (e.g., 25% of 40 Watts=10 Watts).Slot8 is provided with about 30 Watts (100 Watts minus 70 Watts transmitted by slots1-7), therefore,slot8 must transmit about 33% of the total energy provided thereto (e.g., 33% of 30 Watts=10 Watts).Slot9 is provided with about 20 Watts (100 Watts minus 80 Watts transmitted by slots1-8), therefore,slot9 must transmit about 50% of the total energy provided thereto (e.g., 50% of 20 Watts=10 Watts).Slot10 is provided with about 10 Watts (100 Watts minus 90 Watts transmitted by slots1-9), therefore, slot10 must transmit about 100% of the total energy provided thereto (e.g., 100% of 10 Watts=10 Watts).
• Moving distally along the waveguide, each slot must progressively transmit a higher percentage of energy available to the individual slot. One method of progressively increasing the percentage of energy transmitted from each slot is to vary the width of each slot as the waveguide progresses distally (increasing the width of each slot moving distally).FIG. 53 illustrates a waveguide wherein each slot progressively increases in width. In some embodiments the increase in width provides an improvement in efficiency thereby resulting in an increase in the percentage of energy transmitted therefrom. The distal-most slot may be regarded as highly efficient slot capable of radiating the total remaining power therefrom (e.g., radiating 100% of the power provided thereto).
• The energy radiated from each of the slots is related to the desired efficiency of the slot, the width of the slot and/or the wavelength of the energy provided to waveguide (e.g., each slot). In some embodiments, the width of each slot is related the desired efficiency of the slot. For example, if the desired efficiency of a slot is 20% of the energy provided thereto, the width may be calculated by the microwave signal wavelength and desired efficiency.
• In another embodiment, the effective length of the distal-most slot is equal to ½ of the wavelength of microwave signal, and the width of the slots proximal the distal-most slot is related to the desired efficiency of the slots wherein the efficiency of each slot is determined by the energy provided to each individual slot and the desired power output of each slot.
• Due to losses in the coaxial waveguide, the amount of energy provided to each slot is equal to the energy provided to the waveguide minus the amount of energy transmitted by the proximal slots and minus any losses in the coaxial cable. As such, the percentage for each progressive slot may be increased and/or the number of slots may be decreased to compensate for the energy losses in the coaxial waveguide.
• Usingslot4 inFIG. 52 as an example, and assuming the losses in slots1-3 to equal 5 Watts, the actual energy provided toslot4 is 65 Watts (100 Watts minus 30 Watts transmitted by slots1-3 and less the losses of 5 Watts). Therefore,slot4 must transmit about 15.4% of the 65 Watts provided to slot4 (e.g., 15.4% of 65 Watts). As such, losses in the proximal slots may result a reduction in the number of slots in order to provide an even and equal pattern of energy radiation from each slot.
• A more distributed approach, as opposed to the segmented approach of individual slots, provides an even and uniform energy distribution pattern.FIG. 54 shows a waveguide wherein the progressively increasing width of each slot, as illustrated in the waveguide ofFIG. 53, is arranged as a continuoushelical slot450. In one embodiment, the geometry of the slot (e.g., the helix angle, pitch and slot width) is related to the required efficiency of each section of the helix. In some embodiments, the efficiency of each section of the helix is determined by the energy provided to each section of the helix and the desired power output of each section of the helix. Geometric parameters that may vary include the axial ratio, the number of turns and the width of the feed gap. The helix, which eliminates the individual slots, may also reduce losses generated as a result of having each individual slot.
• As the opening widens (e.g., in a proximal to distal direction), due to the change in pitch and/or the change in the helix angle, the slot progressively radiates more energy thereby promoting a uniform energy pattern and resulting in less return loss.
• FIGS. 55 and 56 illustrateflexible microwave catheters530 and630 withwaveguides500 and600 related to the waveguides ofFIGS. 53 and 54, respectively. InFIG. 55, thewaveguide500 includes a plurality of progressively spacedslots550 wherein the width of each distally spaced slot increases to provide the desired power output. InFIG. 56, thewaveguide600 includes ahelical feed slot650 with a varying pitch, slot width and helix angle wherein the progressively increasing slot width, and exposed portion of the radiatinginner conductor520,620, provides the desired power output along the length of thewaveguide600. Theflexible microwave catheters530 and630 may include a cooling fluid arrangement as discussed hereinabove.
• FIG. 57 illustrateswaveguides700 and800, wherein slottedwaveguide700 includes five (5) slots andhelix waveguide800 includes five turns of a helix.Waveguides700 and800 are arranged to provide a comparison/correlation between the slots S1-S5 of the slottedwaveguide700 and the respective helix turns HT1-HT5 of the helix waveguide. Each helix turn HT1-HT5 includes a corresponding position on the helix wherein the width of the helix is related to the width of the corresponding slot S1-S5 and the exposedinner conductor720. As discussed hereinabove, the shape and position of the helix slot HS is related to, and defined by, the void between the individual wraps of the shieldingouter conductor824aon theinner conductor820.
• As further illustrated inFIG. 57, the slottedwaveguide700 includes five radiation slots S1-S5 with each slot S1-S5 exposing a portion of theinner conductor720. Slots S1-S5 generate a corresponding electromagnetic field F1-F5, respectively. The electromagnetic fields F1-F5 are distinct and independently generated, although at least a portion of one or more of the electromagnetic fields F1-F5 may overlap and/or combine with an adjacent electromagnetic field F1-F5.
• Thehelix waveguide800 generates a helical-electromagnetic field HF that extends along the longitudinal length of thehelix waveguide800. The shape of the helical-electromagnetic field HF is related to the shape of the helix slot HS and related to the varying void formed between the individual wraps of the shielding outer conductor.
• The shape of the helical-electromagnetic field HF may be represented as a plurality of inter-connected, helically-shaped electromagnetic fields HF1-HF5 with each of the inter-connected helically-shaped electromagnetic field being related to a corresponding slot S1-S5 on the slottedwaveguide700. The helical-electromagnetic field HF may include a plurality of minimum nodes and a plurality of maximum nodes wherein the magnitude of the helical-electromagnetic field at a minimum node is a relative minimum and the magnitude of the helical-electromagnetic field at a maximum node is a relative maximum. In one embodiment, the number of minimum nodes is related to the number of helix turns. The overall shape of the helical-electromagnetic field HF may dynamically change about the helix. In some embodiments, the number of maximum nodes is related to the number of helix turns.
• FIG. 58A is a perspective view of a deflatedballoon centering device5872 having aspiral window5899 formed therein according to some embodiments of the present disclosure.Balloon centering device5872 includes aballoon membrane5872acoated with aconductive layer5872b. As illustrated in the cut-out portion ofFIG. 58A,conductive layer5872bmay be formed on the inner surface of balloon membrane5772a. Alternatively, in some embodiments, theconductive layer5872bis formed on the outer surface of theballoon membrane5872a.
• Theconductive layer5872bmay be formed by any suitable manner of coating or deposition, including without limitation, thin film deposition, plating, application of conductive ink, foil, and the like. In some embodiments, theconductive layer5872bis formed from conductive silver ink. Theconductive layer5872bmay be formed in a pattern, e.g., a spiral pattern, a lattice pattern, a halftone pattern, a gradient pattern, or any pattern that facilitates the elastic inflation and deflation of theballoon centering device5872 while maintaining conductivity among and between the elements that form the pattern of theconductive layer5872b.
• Spiral window5899 includes theballoon membrane5872aand does not include aconductive layer5872b.Balloon membrane5872ain thespiral window5899 area is formed of a material that is transparent to microwave energy thereby exposing the tissue adjacent thespiral window5899 to an application of denervation energy. Thespiral window5899 may have a maximum width of about 3-5 mils (0.003″-0.005″). By this arrangement, theconductive layer5872bforms a Faraday cage structure that improves the radiation pattern and facilitates the delivery of denervation energy to the tissue adjacent thespiral window5899. In some embodiments, theballoon membrane5872 may be formed from a non-compliant material to ensure the correct geometer is achieved.
• In some embodiments, aballoon centering device5872 in accordance with the present disclosure may include aconductive layer5872bdisposed at the proximal and distal ends thereof, while having little, or no, conductive material in aconductive layer5872balong the middle portion, thereby forming a conductive gradient between the proximal end and distal ends, and the middle portion. Theballoon centering device5872 may include conductive patterns arranged in accordance with the heretofore described configuration(s) of mesh structures, wherein theconductive layer5872 is coated on all but awindowed portion5899 of theballoon centering device5872. Some embodiments may include multiple balloon centering devices, a single balloon centering device with multiple windows, a rotatable balloon(s) centering device, and so forth.
• Fluid ports5872cform a plurality of lumens through theballoon centering device5872. The radial position of thefluid ports5872cmay be positioned radially outward to provide cooling for the anatomical structure. In embodiments,fluid ports5872cmay be positioned radially inward to provide cooling to the radiating portion of theflexible microwave catheter5830.
• FIG. 58B is a perspective view of the balloon centering device ofFIG. 58A shown fully inflated and positioned within a renal artery RA. Thewindow5899 extends around about the entire circumference along the longitudinal length of theballoon centering device5872. When placed in a body lumen, such as the renal artery RA, the energy applied through thewindow5899 results in a heating pattern consistent with the shape of thewindow5899.
• Fully inflated, thespiral window5899 may radiate energy over 360 degrees along a longitudinal span of about 2 to 3 cm. In other body lumens, thespiral window5899 may radiate energy over 360 degrees along a longitudinal span of about 3 to 5 cm. In yet other body lumens, thespiral window5899 may radiate energy over 360 degrees along a longitudinal span of about 5 to 7 cm. In yet other body lumens, thespiral window5899 may radiate energy over 360 degrees along a longitudinal span of over 7 cm.
• FIG. 58C illustrates a renal artery RA after the application of denervation energy by the device illustrated inFIG. 58A-B. The denervation energy applied to the renal artery RA through thewindows5899 generates a correspondingdenervation zone5874. The 360 degree heating pattern is applied across a portion of the renal artery to derivate the kidney without causing morbidity resulting from vessel wall damage. Other treatment angles that may be utilized include 90 degree heating patterns, 180 degree heating patterns, 180 degree heating patterns and 450 degree heating patterns.
• A method for using the embodiments described herein includes the steps of accessing the femoral artery; placing a long sheath for renal artery access into the femoral artery, abdominal aorta and renal artery; placing aflexible microwave catheter30 according to one embodiment of the present disclosure into the long sheath, and into a portion of the renal artery, delivering microwave energy to the anatomical radiating structure via a flexible coaxial cable, continuing the energy delivery until a sufficient amount of energy has been delivered to damage targeted nerve structures while preserving the critical structure of the renal artery by cooling (e.g. by circulation of blood), and removing the microwave catheter, removing the long sheath, and closing access to the femoral artery. Another step in the method may include the step of monitoring fluid temperature for dangerous temperature elevation via a distally positioned temperature sensor.
• Another method for using the embodiments described herein includes the steps of placing a flexible microwave catheter, including one or more embodiments described herein, into the renal artery via an intravascular approach; utilizing a retractable sheath to deploy an electrically conductive mesh (according to an embodiment described herein) about a radiating portion (e.g., feed gap) wherein the conductive mesh enhances microwave energy delivery to the renal nerves (e.g., sympathetic nerves surrounding the renal artery) by generating an anatomical waveguide that resonates microwave signals through tissue. Another step in the method includes providing a location in the electrically conductive mesh having a window characterized by the lack of material thereby generating an ablation region related to the window. Another step in the method may include providing a fluid cooling structure to enhance energy delivery and reduce cable heating of tissues surrounding the access path. Another step may include providing a catheter hub that allows for the flexible coaxial structure to slide longitudinally therethrough.
• 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 herein and/or in the following claims both literally and in equivalents recognized in law.

Claims (20)

What is claimed is:

1. A method for implementing a microwave ablation waveguide, comprising:

selecting a lumen adapted to convey a fluid and formed from living biological tissue;

introducing an elongate inner conductor into the lumen;

positioning at least a portion of the elongate inner conductor within the lumen such that a longitudinal axis of the elongate inner conductor is positioned substantially parallel to and at a desired distance from a longitudinal axis of the lumen and proximate an anatomical feature of interest; and

transferring microwave energy along the elongate inner conductor such that the lumen shields the inner conductor and allows a predetermined amount of microwave energy to propagate through the anatomical feature of interest.

2. The method in accordance withclaim 1, wherein the lumen in selected in accordance with a dielectric property of the fluid conveyed therein.

3. The method in accordance withclaim 1, wherein positioning step includes providing a centering member which facilitates the flow of the conveyed fluid therethrough.

4. The method in accordance withclaim 1, further comprising altering a dielectric property of the conveyed fluid.

5. The method in accordance withclaim 1, further comprising introducing a fluid amendment into the conveyed fluid.

6. The method in accordance withclaim 5, wherein the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter.

7. The method in accordance withclaim 6, wherein the sensed electrical parameter is selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance.

8. The method in accordance withclaim 5, wherein the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter.

9. The method in accordance withclaim 8, wherein the sensed biological parameter is selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response.

10. The method in accordance withclaim 5, wherein the fluid amendment is introduced into the conveyed fluid at continuous rate.

11. The method in accordance withclaim 5, wherein the fluid amendment is introduced into the conveyed fluid at variable rate.

12. The method in accordance withclaim 5, wherein the fluid amendment is introduced into the conveyed fluid at rate selected in response to a sensed electrical parameter and/or a sensed biological parameter.

13. A method of using a microwave ablation instrument, comprising:

selecting a lumen adapted to convey a fluid and formed from living biological tissue;

introducing a microwave antenna into the lumen, the microwave antenna having an outer conductor with a structure capable of producing a predefined radiation pattern;

positioning the microwave antenna at a location proximate an anatomical feature of interest; and

energizing the microwave antenna with microwave energy such that as the microwave energy emanates from the microwave antenna in the predetermined radiation pattern, the lumen controls the amount of microwave energy allowed to propagate therethrough.

14. The method in accordance withclaim 13, wherein the lumen in selected in accordance with a dielectric property of the fluid conveyed therein.

15. The method in accordance withclaim 13, further comprising altering a dielectric property of the conveyed fluid.

16. The method in accordance withclaim 13, further comprising introducing a fluid amendment into the conveyed fluid.

17. The method in accordance withclaim 16, wherein the fluid amendment is introduced into the conveyed fluid in response to a sensed electrical parameter.

18. The method in accordance withclaim 17, wherein the sensed electrical parameter is selected from the group consisting of a VSWR, a power factor, an impedance, a capacitance, an inductance, and a resistance.

19. The method in accordance withclaim 16, wherein the fluid amendment is introduced into the conveyed fluid in response to a sensed biological parameter.

20. The method in accordance withclaim 19, wherein the sensed biological parameter is selected from the group consisting of a tissue temperature, a blood pressure, a heart rate, a respiratory rate, a tissue impedance, a blood oxygenation, and a neural response.

Images