Patent Publication Number: US-2021162114-A1

Title: Energy delivery device and methods of use

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of, and priority to, U.S. Provisional Application Ser. No. 61/624,206 filed on Apr. 13, 2012, the entire contents of which are incorporated herein by reference. This application is also related to and incorporates by reference herein the complete disclosures of the following patent applications: U.S. Provisional Pat. App. No. 61/113,228, filed Dec. 11, 2008; U.S. Provisional Pat. App. No. 61/160,204, filed Mar. 13, 2009; U.S. Provisional Pat. App. No. 61/179,654, filed May 19, 2009; U.S. Pat. App. Pub. No. 2010/0204560, filed Nov. 11, 2009; U.S. Provisional Pat. App. No. 61/334,154, filed May 12, 2010; U.S. Pat. App. No. 13/106,658, filed May 12, 2011; U.S. Provisional Application Ser. No. 61/541,756, filed on Sep. 30, 2011; U.S. Provisional Application Ser. No. 61/593,147, filed on Jan. 31, 2012; and PCT Application No. PCT/US12/57967, filed on Sep. 28, 2012. 
    
    
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates generally to medical devices and methods and more particularly to devices and methods for applying radiofrequency energy to tissue. 
     BACKGROUND 
     Some medical treatment procedures involve the disruption of a region of tissue. For example, medical treatment procedures include the delivery of energy to disrupt a region of tissue. Radiofrequency (“RF”) energy devices are an example of devices that can be used to perform such medical treatments. 
     Some RF energy devices have a single RF energy element or a plurality of discrete RF energy elements that have to be repeatedly moved within the subject in order to apply sufficient RF energy to the entire region of the tissue. Such RF energy devices may need to be moved within a patient during a given procedure, which can increase the complexity, time, and energy required to perform a given procedure. 
     SUMMARY 
     Accordingly, an energy delivery system for delivering electrical energy to tissue, includes an elongate catheter member defining a longitudinal axis and dimensioned for passage within a body vessel, and an expandable treatment member mounted to the catheter member. The treatment member includes an inflatable element adapted to transition between an initial condition and an at least partially expanded condition upon introduction of an anesthetic solution within the inflatable element, an electrode for delivering electrical energy to at least nerve tissue associated with the body vessel to cause at least partial denervation thereof and at least one aperture dimensioned to permit passage of the anesthetic solution from the inflatable element to contact the body vessel whereby the solution enters a wall of the body vessel to at least partially anesthetize the nerve tissue there within. The electrode may be mounted to the inflatable element of the treatment member and may be generally helical. 
     In embodiments, the at least one aperture is dimensioned to deliver the anesthetic solution at a pressure sufficient to facilitate passage of the anesthetic solution at least within the wall of the body vessel. At least one of the inflatable element and the electrode may include a plurality of apertures dimensioned to deliver the anesthetic solution at the pressure sufficient to cause at least passage of the anesthetic solution within the wall of the body vessel. The apertures may be each dimensioned to deliver the anesthetic solution at a pressure ranging from about 1 atm to about 4 atm and, in embodiments, over a flow range of about 1 to about 20 mL/min. Each aperture may define a pore size ranging from about 0.5 mil to about 10 mil. 
     In certain embodiments, the catheter member defines a fluid lumen for delivering the anesthetic solution to the inflatable element of the treatment member. A source of anesthetic solution may be in fluid communication with the fluid lumen of the catheter member and the inflatable element of the treatment member. The system further may include a pump couplable to the fluid lumen of the catheter member. The pump may be dimensioned to deliver the anesthetic solution from the source to the fluid lumen of the catheter member at a pressure sufficient to convey the anesthetic lumen through the fluid lumen and out the apertures causing passage of the anesthetic solution at least within the wall of the body vessel. A sensor may be in fluid communication with at least the fluid lumen of the catheter member. The sensor may be a pressure sensor or transducer adapted to sense pressure corresponding to pressure within the inflatable element. In the alternative, the sensor may be a flow rate sensor adapted to detect flow rate associated with passage of the anesthetic solution through the fluid lumen. 
     In embodiments, the system includes a controller for controlling operation of the pump. The controller may include logic responsive to a parameter detected by the sensor to vary operation of the pump. 
     In some embodiments, the system includes a source of irrigation fluid in fluid communication with the inflatable element of the treatment member for passage through the apertures for, e.g., cooling the electrode and/or the tissue. The system may further include a valve in fluid communication with the source of anesthetic solution and the source of irrigation fluid. The valve may be actuable between an anesthetic mode to permit the delivery of the anesthetic solution to the fluid lumen of the catheter member and an irrigation mode to permit the delivery of the irrigation fluid to the fluid lumen of the catheter member. 
     In certain embodiments, the at least one aperture of the treatment member is dimensioned to permit passage of the anesthetic solution at a relatively pressure whereby the anesthetic solution slowly diffuses at least within the body vessel and migrates to the nerve tissue associated with the body vessel. In instances, the inflatable element of the treatment member is dimensioned to establish a reservoir between the inflatable element and a wall of the body vessel when in the at least partially expanded condition thereof. The reservoir receives the anesthetic solution for diffusion through the wall of the body vessel. 
     The treatment member may include at least one occluding element. The at least one occluding element may define a dimension greater than a corresponding dimension of the inflatable element when the at least one inflatable element is in an at least partially expanded condition thereof. The at least one occluding element may be dimensioned to at least partially occlude the body vessel to at least partially enclose the reservoir. 
     In some embodiments, the inflatable element is a balloon member. The balloon member includes first and second axially spaced occluding segments and a central segment between the first and second occluding segments. Each of the first and second occluding segments has a transverse dimension greater thas a corresponding transverse dimension of the central segment when the balloon member is in a first inflated condition, and dimensioned to substantially occlude the body vessel to enclose the reservoir. The balloon member may be adapted to transition between the first inflated condition and a second inflated condition where the central segment defines a greater transverse dimension to position the electrode in opposition to the body vessel to deliver electrical energy to the nerve tissue associated with and/or surrounding the body vessel. The catheter member may define a fluid lumen for delivering the anesthetic solution to the balloon member. 
     In other embodiments, the catheter member includes first and second occluding elements mounted adjacent opposed ends of the inflation element. The first and second occluding elements may be adapted to expand to occlude the body vessel and enclose the reservoir established between the inflatable element and the wall of the body vessel. The first and second occluding elements may be adapted for expansion independent of expansion of the inflatable element. The first and second occluding elements may be first and second occluding balloon members and the inflation element may be a treatment balloon member having the electrode mounted thereto. The catheter member may define a second fluid lumen for delivering fluid to the first and second occluding balloon members. As an alternative, the first and second occluding balloon members may be inflatable independent of each other. 
     In some embodiments, the treatment member includes a first balloon member and a second balloon member coaxially mounted about the first balloon member. The first and second balloon members are dimensioned to establish a reservoir between the first and second balloon members when in the at least partially inflated condition thereof. The reservoir receives the anesthetic solution and the second balloon member may include the at least one aperture dimensioned to permit passage of the anesthetic solution. The first and second balloon members may be inflatable independent of each other. The elongate member may define a second lumen for supplying fluids to the first balloon member to inflate the first balloon member. 
     In accordance with an aspect of the disclosure, a method for treating hypertension, includes positioning a treatment member including an inflatable segment and an electrode segment within a renal artery; delivering an anesthetic solution into the inflatable segment such that the anesthetic solution is released from at least one aperture of the treatment member to contact a wall of the renal artery whereby the anesthetic solution enters the wall of the renal artery and migrates to renal nerve tissue associated with the renal artery; and emitting RF energy from the electrode segment to disrupt renal nerve transmission to treat hypertension. 
     In some embodiments, delivering the anesthetic solution includes directing the anesthetic solution to target nerve tissue for alleviating pain during renal denervation. The targeted nerve tissue may include nerve tissue in the intima, media, adventitia, and/or surrounding tissue of a renal artery. The delivery of the anesthetic solution is at a pressure sufficient to enter and/or pass through the wall of the renal artery and contact the desired renal nerve tissue, and may further include directing the anesthetic solution through a plurality of apertures in the treatment member at, e.g., a pressure ranging from about 1 atm to about 4 atm. 
     In certain embodiments, delivering the anesthetic solution includes permitting passage of the anesthetic solution at a pressure whereby the anesthetic solution slowly diffuses through the wall of the renal artery and possibly migrates to the renal nerve tissue surrounding the renal artery. Delivering the anesthetic solution may include distributing the anesthetic solution within a reservoir defined between the inflatable segment and the wall of the renal artery. In one aspect, the treatment member may include occluding segments adjacent each end of the inflation segment. The occluding segments may be expanded to contact the wall of the renal artery to occlude the artery and substantially enclose the reservoir. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A, 1B, and 2  illustrate a portion of an energy delivery device comprising a helical electrode on an expandable element according to an embodiment of the present disclosure; 
         FIGS. 3A and 3B  show a portion of an elongate device according to an embodiment of the present disclosure; 
         FIG. 4  shows a portion of an energy delivery device comprising a temperature sensor according to an embodiment of the present disclosure; 
         FIG. 5  illustrates a portion of an energy delivery device wherein portions of a helical electrode are covered with an insulation material according to an embodiment of the present disclosure; 
         FIG. 6  illustrates an system for delivering energy to tissue according to an embodiment of the present disclosure; 
         FIG. 7  illustrates a cross section of an energy delivery device with a helical electrode in use within a renal artery according to an embodiment of the present disclosure; 
         FIGS. 8 and 9  illustrate a portion of an energy delivery device wherein energy is delivered to renal nerves through conductive fluid to the tissue according to an embodiment of the present disclosure; 
         FIG. 10  is a photograph showing tissue ablation in a general helical pattern caused by an energy delivery device with a helical electrode according to an embodiment of the present disclosure; 
         FIGS. 11A-11H  illustrate a method of manufacturing an energy delivery device with a helical electrode on an expandable element according to an embodiment of the present disclosure; 
         FIG. 12  represents an embodiment of a system similar to that of  FIG. 6  represented by the resistances of the various elements according to an embodiment of the present disclosure; 
         FIG. 13  illustrates an alternative configuration in which a capacitor, inductor, or both may be incorporated in the circuit from  FIG. 12 ; 
         FIGS. 14 and 15  illustrate an embodiment of a pressure sensor according to an embodiment of the present disclosure; 
         FIG. 16  illustrates a portion of an energy delivery device including a helical electrode pair on an expandable element according to another embodiment of the present disclosure; 
         FIG. 17  is view of a system including an energy delivery device capable of delivering an anesthetic solution to tissue according to an embodiment of the present disclosure; 
         FIG. 18  is a cross-sectional view illustrating the expandable treatment member of the energy delivery device of  FIG. 17  delivering an anesthetic solution through a wall of a renal artery and into the surrounding renal nerve tissue; 
         FIG. 19  is a view illustrating an expandable treatment member of an energy delivery device adapted to deliver anesthetic solution through the wall of the renal artery to the surrounding renal nerve tissue according to an embodiment of the present disclosure; 
         FIG. 20  is a perspective view of an expandable treatment member of an energy delivery device adapted to deliver anesthetic solstion according to an embodiment of the present disclosure; 
         FIGS. 21-22  are views illustrating an expandable treatment member of an energy delivery device for delivering anesthetic aohtrion through the wall of the renal artery to the surrounding renal nerve tissue according to an embodiment of the present disclosure; 
         FIGS. 23-25  are views of an expandable treatment member including proximal and distal occluding elements and a central inflatable clement for delivering anesthetic solution according to an embodiment of the present disclosure; 
         FIG. 26  is a view of an expandable treatment member for delivering anesthetic solution according to an embodiment of the present disclosure; and 
         FIG. 27  is a view of an expandable element including coaxially mounted inflatable elements for delivering anesthetic solution according to an embodiment of the present disclosure. 
     
    
    
     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 and may be embodied in various forms. Like reference numerals may refer to similar or identical elements throughout the description of the figures. 
     This description may use the phrases “in an embodiment,” “in embodiments,” “in some embodiments,” or “in other embodiments,” which may each refer to one or more of the same or different embodiments in accordance with the present disclosure. For the purposes of this description, a phrase in the form “A/B” means A or B. For the purposes of the description, a phrase in the form “A and/or B” means “(A), (B), or (A and B)”. For the purposes of this description, a phrase in the form “at least one of A, B, or C” means “(A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C)”. 
     As used herein, the terms proximal and distal refer to a direction or a position along a longitudinal axis of a catheter or medical instrument. The term “proximal” refers to the end of the catheter or medical instrument closer to the operator, while the term “distal” refers to the end of the catheter or medical instrument closer to the patient. For example, a first point is proximal to a second point if it is closer to the operator end of the catheter or medical instrument than the second point. The measurement term “French”, abbreviated Fr or F, is defined as three times the diameter of a device as measured in mm. Thus, a 3 mm diameter catheter is 9 French in diameter. The term “clinician” refers to any medical professional (i.e., doctor, surgeon, nurse, or the like) performing a medical procedure. 
     One aspect of the disclosure is a RF delivery device that is adapted to deliver RF energy to tissue.  FIG. 1A  illustrates a side view of a distal region of RF delivery device  10 . Device  10  has proximal region  2 , intermediate region  4 , and distal region  6 . Device  10  includes an elongate portion  12  and expandable portion  14  (shown in an expanded configuration) disposed on a distal region of elongate portion  12 . Expandable portion  14  includes inflatable element  16  on which conductive material  18  is disposed. 
       FIG. 1B  illustrates a perspective view of the portion of the device shown in  FIG. 1A , with a rectangular section of inflatable element  16  removed to illustrate elongate portion  12  disposed inside inflatable element  16 . 
       FIG. 2  shows a sectional view of the portion of the device shown in  FIG. 1A . Expandable portion  14  includes a proximal transition section  20 , intermediate section  22 , and distal transition section  24 . Proximal transition section  20  and distal transition section  24  are shown with conical configurations extending towards elongate portion  12  but are not limited to this configuration. Intermediate section  22  is substantially cylindrically-shaped when inflatable element  16  is in the expanded configuration shown in  FIGS. 1A, 1B, and 2 . The proximal end of inflatable element  16  and the distal end of inflatable element  16  are secured to catheter  26 , which is part of elongate portion  12 . 
     Conductive material  18  is disposed on catheter  26  proximal to the expandable portion  14 , and it is also disposed on the cylindrical section of inflatable element  16  in a helical pattern forming a helical electrode  19  as shown. In proximal region  2  and in proximal section  20  of the expandable portion, insulation material  34  is disposed on the layer of conductive material  18 . In the cylindrical intermediate section  22  of expandable portion  14 , insulation material  34  is not disposed on the helical electrode, allowing energy to be delivered to tissue through conductive material  18 . In the proximal region  2  of the device, and in proximal section  20  of expandable portion  14 , conductive material  18  is covered with a layer of insulation, and thus energy is not applied to tissue in those areas. The conductive material that is not covered by dielectric material on the distal portion of the system is considered an electrode. The conductive material and the electrode are in this embodiment the same material. 
     The conductive material  18  is disposed on substantially the entire catheter  26  in proximal region  2  of the device. “Substantially the entire,” or “substantially all,” or derivatives thereof as used herein include the entire surface of catheter  26 , but also includes most of the surface of the catheter. For example, if a few inches of the proximal end of catheter  26  are not covered with conductive material, conductive material is still considered to be disposed on substantially all of the catheter. The conductive material  18  and insulation material  34  extend 360 degrees around the catheter shaft, as opposed to only covering discrete lateral sections of the catheter. Alternatively, in some embodiments the conductor covers only a portion of the lateral surface of the catheter shaft. The conductive material and insulation material may cover the entirety or only a portion of the proximal transition section of the expandable portion. The insulation will typically cover the entirety of the conductive material in this region. The conductive material and insulation material could, however, also be disposed on the distal section  24  of expandable portion  14 . 
     In some embodiments the helical electrode makes about 0.5 revolutions to about 1.5 revolutions around the inflatable element. The number of revolutions is measured over the length of the helical electrode. The electrode may extend from the proximal transition section to the distal transition section (as shown in  FIG. 2 ), but the electrode may extend over any section of the inflatable element. For example, the proximal end of the electrode may be disposed distal to the proximal transition section, and the distal end of the electrode may be proximal to the distal transition section. 
     One revolution traverses 360 degrees around the longitudinal axis of the expandable element. One revolution of the electrode, along an end-view of inflatable device, forms a circle, although depending on the cross sectional shape of the expandable element, the electrode can form any variety of shapes in an end-view. An electrode making 0.5 revolutions therefore traverses one half of 360 degrees, or 180 degrees. An electrode making 0.5 revolutions has distal and proximal ends that are on opposite sides of the balloon. In an end-view of the inflatable element with a circular cross section, an electrode making 0.5 revolutions has a semi-circular, or C, shape. 
     The proximal end of the electrode can be disposed anywhere on the expandable element and the distal end of the electrode can be anywhere on the expandable element, as long as the proximal end is proximal to the distal end. In some embodiments, the proximal end of the electrode is at the boundary between the proximal transition section and the cylindrical intermediate section of the expandable element, and the distal end of the electrode is at the boundary between the distal transition section and the cylindrical intermediate section. In other embodiments the proximal end of the electrode is disposed distal to the boundary between the proximal intermediate section and the cylindrical intermediate section of the expandable element, and the distal end is proximal to the boundary between the distal transition section and the central intermediate section of the expandable element. In these other embodiments the electrode is considered to extend along a subset of the length of the central intermediate section of the expandable element. In the embodiment shown in  FIG. 1B , the electrode makes about 1 revolution around the inflatable element. In some embodiments the electrode makes about 0.5 revolutions around the inflatable element. In some embodiments the electrode makes about 0.75 revolutions around the inflatable element. In some embodiments the electrode makes about 1 revolution around the inflatable element. In some embodiments the electrode makes about 1.25 revolutions around the inflatable element. In some embodiments the electrode makes about 1.5 revolutions around the inflatable element. 
     The device is adapted to be coupled to an RF generator, which supplies RF current through the conductive material  18  on catheter  26  and inflatable element  16 . In this manner RF current can be delivered to the desired tissue. Energy is thus applied to tissue in the configuration of the conductive material on the intermediate section  22  of the expandable portion  14 , which in this embodiment is a helical, or spiral, configuration. 
     Within the expandable portion, catheter  26  is not covered with conductive material or insulation material. Catheter  26  includes guide element lumen  36  and inflation lumen  28 , also referred to herein as irrigation lumen, extending therethrough. Guide element lumen  36  extends from the proximal end of the device (not shown) to the distal end. Irrigation lumen  28  extends from the proximal end of catheter  26  (not shown) to a location within inflatable element  16 . Irrigation port  30  is located inside inflatable element  16  and is in between proximal and distal ends of irrigation lumen  28 . Irrigation lumen  28  and irrigation port  30  provide for fluid communication between the irrigation lumen and the interior of inflatable element  16 .  FIGS. 3A and 3B  illustrate additional views of guide element lumen  36 , irrigation lumen  28 , and irrigation port  30 . In some embodiments catheter  26  ranges in size from 2 to 8 French, and in some embodiments is 4 Fr. In some embodiments the guide wire lumen is between 1 and 4 Fr and in some embodiments is 2.5 Fr. 
     Expandable portion  14  includes one or more irrigation apertures  38  to allow irrigation fluid to pass from inside inflatable element  16  to outside inflatable element  16 . The irrigation apertures can be formed only in the electrode section of expandable portion  14  (see, for example,  FIG. 1A ), only in the non-elcotrode section of inflatable portion  14 , or in both the electrode section and in the non-electrode section. The irrigation fluid is adapted to cool the conductive material  18  and/or tissue. The apertures allow for fluid to flow out of the balloon, allowing either a continuous or non-continuous supply of fluid from a fluid reservoir, through the lumen, and into the balloon. The irrigation fluid is in some embodiments cooled prior to delivery. 
       FIG. 4  illustrates a portion of an embodiment of a RF delivery device. Delivery device  110  is similar to the RF delivery device shown in  FIGS. 1-3 . Device  110  includes catheter shaft  126  covered with conductive material  118 , upon which insulation material  134  is disposed. Insulation material  134  is also disposed on the proximal transition section of the expandable portion  114 , similar to the embodiment shown in  FIGS. 1-3 . The inflatable element also has conductive material  118  disposed on the inflatable element in the form of a helical electrode. Catheter  126  has guiding element lumen  136  and irrigation lumen  128  therein. Device  110  also includes at least one marker  127  disposed on catheter  126  such that the marker is within expandable portion  114  (shown as a balloon). Device  110  also includes irrigation port  130  in fluid communication with irrigation lumen  134 . Device  110  also includes temperature sensor  129 , such as a thermocouple, a resistance temperature detector, or a thermistor, that is electrically coupled from the proximal end of the device (not shown) through irrigation lumen  128 , out of irrigation port  130 , and is secured at its distal region to catheter  126 . The temperature sensor could alternatively be disposed on the inner or outer surface of inflatable element  116 . In some embodiments marker  127  is a radio opaque marker comprised of Pt, PtIr, or other suitable radio opaque material. In some embodiments the marker may also comprise features viewable under fluoroscopy that allow for the visualization of the rotational orientation of the marker, and therefore the expandable section. This allows the physician to note the location of and/or realign the expandable element and helical electrode as necessary within the renal artery. 
     The irrigation fluid is adapted to cool the electrode on the inflatable element. The irrigation fluid cools the RF electrode as it flows within the inflatable element and after it passes through the apertures as it flows across the outer surface of the inflatable element. Temperature sensor  129  is adapted to sense the temperature of the fluid within inflatable element  116 . The signal from the temperature sensor may be used in a feedback control mechanism to control the flow of fluid from a fluid reservoir (now shown) into the inflatable element. Alternatively, the irrigation fluid may be delivered at a substantially constant rate and the signal from the temperature sensor used as signal to automatically shut off the RF generator if the sensed fluid temperature is above a threshold limit, thereby terminating that portion of the procedure. Such a condition is considered a fault and after identification and resolution of a fault, a procedure may be restarted.  FIG. 5  illustrates a delivery device in which portions of the helical conductor have been covered by insulation material  734 , forming a plurality of discrete circularly-shaped windows surrounding apertures  717  on electrical conductor  718 . In this fashion a single conductor can be used to create a number of discrete burn zones following a helical path along and around a vessel wall. 
     In some embodiments, an anesthetic (such us lidocaine) may be added to the irrigation fluid, in order to reduce patient discomfort. In some such embodiments, it might be desirable to deliver the irrigation fluid and anesthetic at a higher pressure in order to achieve better tissue passage. The anesthetic may be introduced as a bolus in the initial part of the balloon inflation and electrode irrigation procedure. Alternatively, the balloon may be inflated with an anesthetic solution prior to RF energy delivery, then deflated to remove the anesthetic solution followed by reinflation with a saline solution to serve as the irrigation for the RF procedure. Delivery of the anesthetic solution may be preceded by inflation of the balloon (such as, e.g., with a contrast agent in the balloon or with saline in the balloon and contrast agent injected proximally to the balloon) to confirm positioning. Additional embodiments of energy delivery devices incorporating systems for delivery of anesthetic solution will be discussed hereinbelow. 
     One aspect of the disclosure is a system to delivery RF energy to treatment tissue.  FIG. 6  illustrates a system  300  adapted to deliver RF energy to treatment tissue. System  300  includes RF energy delivery device  302 , which can comprise any of the RF energy delivery devices described herein. Delivery device  302  is shown including inflatable element  316 , helical energy delivery element  319 , irrigation apertures  330 , guidewire  310 , and elongate member  312 . System  300  also includes external housing  320 , which includes display  322  and controller  324 . Housing includes connector  336 , which is adapted to connect to instrument interface cable  314 . System  300  also includes fluid reservoir  326 , which is in fluid communication with delivery device  302  via irrigation line  328 . The system also includes fluid pump  331 , optional pressure sensor  332 , and optional bubble sensor  334 . System  300  also includes a grounding plate or set of grounding plates  340  interfaced to controller  324  via connector  346 . 
     An embodiment of pressure sensor  332  from the system in  FIG. 6  is shown in  FIGS. 14 and 15 . Pressure sensor  332  includes a housing, which comprises capture portion  335  and a force sensor  333 . Capture portion  335  is configured to substantially surround irrigation tube  328 . Additionally, capture portion  335  captures tubing  328  such that a portion of the wall of irrigation tube  328  is compressed against force sensor  333 . The force experienced by the force sensor is then a function of the force associated by the compression of the irrigation tube and the pressure within the irrigation tube. In operation, a measurement is made under a no flow condition that describes the offset associated with the compression of the irrigation tube. This offset measurement is made prior to the initiation of a procedure and may be repeated at the beginning of each power cycle. This value is then used as an offset for subsequent measurements made under flow conditions. A force/pressure calibration per tubing type or per tube is then used to convert the force signal to a pressure value. 
     The disclosure includes methods of using any of the RF delivery devices and systems herein. In some embodiments the devices and/or systems are used to treat hypertension by disrupting the transmission within renal nerves adjacent one or both renal arteries. 
     The present methods control renal neuromodulation via thermal heating mechanisms. Many embodiments of such methods and systems may reduce renal sympathetic nerve activity. Thermally-induced neuromodulation may be achieved by heating structures associated with renal neural activity via an apparatus positioned proximate to target neural fibers. Thermally-induced neuromodulation can be achieved by applying thermal stress to neural structures through heating for influencing or altering these structures. Additionally or alternatively, the thermal neuromodulation can be due to, at least in part, alteration of vascular structures such as arteries, arterioles, capillaries, or veins that perfuse the target neural fibers or surrounding tissue. 
     Thermal heating mechanisms for neuromodulation include both thermal ablation and non-ablative thermal alteration or damage (e.g., via sustained heating or resistive heating). Thermal heating mechanisms may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature can be above body temperature (e.g., approximately 37 degrees C) but less than about 45 degrees C for non-ablative thermal alteration, or the target temperature can be about 45 degrees C or higher for the ablative thermal alteration. 
     The length of exposure to thermal stimuli may be specified to affect an extent or degree of efficacy of the thermal neuromodulation. For example, the duration of exposure can be as short as about 5, about 10, about 15, about 20, about 25, or about 30 seconds, or could be longer, such as about 1 minute, or even longer, such as about 2 minutes. In other embodiments, the exposure can be intermittent or continuous to achieve the desired result. 
     In some embodiments, thermally-induced renal neuromodulation may be achieved via generation and/or application of thermal energy to the target neural fibers, such as through application of a “thermal” energy field, including, electromagnetic energy, radiofrequency, ultrasound (including high-intensity focused ultrasound), microwave, light energy (including laser, infrared and near-infrared) etc., to the target neural fibers. For example, thermally-induced renal neuromodulation may be achieved via delivery of a pulsed or continuous thermal energy field to the target neural fibers. The energy field can be sufficient magnitude and/or duration to thermally induce the neuromodulation in the target fibers (e.g., to heat or thermally ablate or necrose the fibers). As described herein, additional and/or alternative methods and systems can also be used for thermally-induced renal neuromodulation. 
     The energy field thermally modulates the activity along neural fibers that contribute to renal function via heating. In several embodiments, the thermal modulation at least partially denervates the kidney innervated by the neural fibers via tearing. This may be achieved, for example, via thermal ablation or non-ablative alteration of the target neural fibers. 
     In some uses in which RF energy is used to ablate the renal nerve, the RF delivery device is first positioned within one or more renal arteries and RF energy is delivered into renal nerves to disrupt the nerve transmission sufficiently to treat hypertension. The disruption pattern within the artery preferably extends substantially 360 degrees around the artery. Electrodes that treat tissue falling diametrically in a single plane normal or oblique to the longitudinal axis of the vessel have been shown to increase the risk of stenosing a vessel treated with RF energy. Spiral, or helical, patterns as described herein create patterns of treated tissue for which the projection along the longitudinal axis is circular and therefore have a high probability of treating any renal nerve passing along the periphery of the renal arery. The patterns, however, have minimal risk of creating a stenosis. Previous attempts have used a point electrode at a distal end or distal region of a device. In these attempts, the electrode is disposed in the renal artery followed by RF energy delivery. To disrupt renal nerve tissue in a non circumferential pattern using a point electrode, the device is first positioned within the renal artery adjacent arterial tissue. RF energy is then delivered to disrupt a region of renal nerve. The device must then be moved axially (distally or proximally) and rotated, followed by additional RF delivery. The movement and RF delivery is repeated in a pattern until the renal nerves have been sufficiently disrupted. The repeated movements are time consuming and increase the complexity of the overall process for the physician. During an emergency situation the physician may lose track of the position and sequence of previous burns thereby jeopardizing the likelihood of creating a pattern sufficient to treat the neural tissue or be forced to increase the number of burns thereby over-treating the patient. 
     Utilizing a single helical electrode as described herein provides procedural improvements over previous attempts. By using an electrode with the configuration of the desired treatment region, the device need not be moved to disrupt tissue in a desired treatment configuration. In particular the device need not be moved axially or rotated to treat an entire renal nerve treatment region. This reduces the overall time of the treatment. Additionally, this allows energy to be delivered to a desired treatment region in a variety of patients with much greater predictability. Additionally, if markers are used that allow for rotational alignment, the device may be moved and/or removed and then replaced and realigned, allowing the procedure to be restarted at a later time. 
     A method of using an RF delivery device to treat hypertension is shown in  FIG. 7 , and will be described using the device in  FIG. 4  and the system shown in  FIG. 6 . The methods described herein can be carried out by other systems and by other RF delivery devices, such as the RF devices described herein. 
     The RF delivery device is positioned in a renal artery using a percutaneous access through a femoral artery. The expandable portion is delivered into the renal artery in a collapsed configuration (not shown). Once the expandable portion is in position, fluid from fluid reservoir  326  is pumped in an open loop control configuration, under constant flow, through irrigation line  328  and into inflatable element  116  by pump  330 . Fluid flow into inflatable element  116  causes inflatable element  116  to expand. Device  110  in  FIG. 7  is in a delivered, or expanded, configuration within renal artery  1000 . The tunica intima  1001  is surrounded by the tunica media  1002 , which is in turn surrounded by adventitial tissue  1003 . Tissue renal nerves  1004  are shown within the adventitial, and some renal nerves not shown will be found within the tunica media. 
     The fluid continually passes through apertures  138  in the expandable portion as it is replaced with new fluid from fluid reservoir  326 . Once fully expanded, the conductive material  118  on the inflatable element fully assumes the helical configuration, as shown in  FIGS. 4 and 7 . RF energy is then delivered to the helical electrode on the inflatable element. Control unit  324  controls the parameters of the RF alternating current being delivered through the conductive material on the catheter and the helical electrode on the inflatable element. 
     In general, the RF signal characteristics are chosen to apply energy to depths at which the renal nerves are disposed to effectively ablate the renal nerves. In general, the power is selected to ablate a majority of the renal nerves adjacent to where the device is positioned within the renal nerve. In some embodiments the tissue is ablated to a depth of between about 3 mm to about 7 mm from the tissue closest to the device in the renal artery. 
     The RF signal can have the following characteristics, but these are not intended to be limiting: the frequency is between about 400 KHz to about 500 KHz and is a sine wave; the power is between about 30 W to about 80 W, the voltage is between about 40v and about 80v; and the signal is an intermittent signal. 
     Tissue treated by the RF energy via the helical electrode comprised is shown as regions  1005 , delineated by a dashed line. As illustrated, a region of treated tissue  1005  adjacent to the cut away section of conductor  118  includes nerve  1004 . The device is shown being used in monopolar mode with a return electrode  340  positioned somewhere on the patient&#39;s skin. 
     Control unit  324  controls the operation of pump  330  and therefore controls the flow rate of the fluid from reservoir into the inflatable element. In some embodiments the pump is continuously pumping at constant flow rate such that the flow is continuous from the reservoir, as is illustrated in  FIG. 7 . In some embodiments the pump is operated in an open loop constant flow configuration where pump rate is not adjusted as a function of any control parameter other than an over-pressure condition sensed by pressure sensor  332 , in which case RF power delivery is terminated, the pump is turned off, and an over-pressure condition reported to the operator. The pump is typically operated for a period of time which encompasses the delivery of the RF energy and turned off shortly after the conclusion of the procedure or if the pressure sensor senses an undesirable condition, discussed herein. 
     The irrigation fluid is delivered from the pump through irrigation line  328  to irrigation lumen  128  to irrigation port  130  into the inflatable element  116 , and then out of the inflatable element through irrigation apertures  138 . The pressure measured at the pressure sensor is driven by flow rate and the series sum of the fluid resistance of all of the elements in the fluid path. The choice of fluid flow rate is driven by the required cooling rate and limited by the amount of irrigant fluid that can be tolerated by the patient which is delivered during the sum of treatments cycles. The system is designed such that at the desired fluid flow there is a defined operating pressure within the inflatable element. An optimal inflatable element inflation pressure is a pressure that is sufficient to completely inflate the inflatable element such that the RF electrode engages the treatment tissue. The operating pressure within the inflatable element will be driven by the fluid flow, the number of apertures, and their cross sections. The distribution, number, and cross section of the irrigation apertures will be driven by the flow rate, the configuration of the electrode, the intended operating pressure, and the maximum desired exit velocity for the irrigation fluid. If the number of apertures is too small and the distribution too sparse some areas of the surface will not receive appropriate irrigation and thereby be subject to overheating and possible charring of tissue. For a set of circular apertures and a given flow rate, the mean exit velocity for the irrigation fluid will drop as the number of apertures is increased while decreasing the cross sectional area of each aperture such that the fluid resistance of the sum of apertures is appropriate to maintain the desired inflation pressure. Minimizing the irrigation fluid exit velocity minimizes or precludes the possibility that lesions will be eroded through the treatment tissue. 
     A set of operating conditions and design parameters is now provided, and is not meant to be limiting. An inflation pressure between about 0.5 atm and less than about 4 atm used with a noncompliant inflatable element of approximately 0.75 mil (˜19 um) thick ensures tissue engagement in a renal artery. In some particular embodiments the inflation pressure is about 2 atm +/−0.5 atm. The irrigation fluid delivery rate is between about 1 mL/min and about 20 ml/min. In some particular embodiments the delivery rate is about 10 mL/min +/−2 mL/min. The expandable portion includes eight irrigation apertures about 2.6 mil (0.0026 inches) in diameter distributed on either side of the helical electrode and equally spaced along the edge of the electrode. In such a configuration the mean exit velocity is about 6 m/sec. In some embodiments the maximum mean fiuid exit velocity is between about 1 m/sec and about 20 m/sec. 
     The above operating parameters are not intended to be limiting. For example, the inflation pressure can be between about 0.5 atm (or less) and about 10 atm, the flow rate can be between about 1 mL/min to about 50 mL/min, and any suitable number of apertures with any suitable size can be incorporated into the device. Apertures may be of the same size or of different sizes and may also be uniformly or non-uniformly distributed through and/or about the electrode. The apertures are sized such that the total resistance of the set of apertures is appropriate to maintain the pressures defined herein internal to the inflatable element at the desired flows described herein. Alternatively, the total resistance is such that the desired flows described herein are maintained at the desired pressures described herein. The total resistance for the parallel combination of apertures is calculated as the inverse of the sum of the inverses of the individual aperture resistances. 
     The system shown also includes pressure sensor  332 , which is adapted to determine if the pressure rises above or below threshold limits. If the fluid pressure rises above an established limit, the controller shuts off the RF energy, and fluid pump  330  is automatically shut off. The pressure can elevate if one or more of the apertures become blocked, preventing fluid from passing out of the balloon, which can prevent the electrode from being cooled sufficiently. Controller  324  therefore runs fluid pump  330  in a binary manner, either open-flow or off. 
     The system as shown also includes a temperature sensor  129  secured to the catheter within the inflatable element. If the seared temperature of the fluid is above a threshold limit, the fluid will not properly cool the electrode. If the sensed fluid temperature is above a threshold limit, control unit  324  is adapted to cease RF current delivery. The fluid temperature in the balloon can rise if one or more apertures are blocked, preventing the electrode from being properly cooled and also increasing the risk of charring. The fluid pressure generally will rise above a threshold limit if this occurs as well. In some embodiments the system has only one of the temperature sensor and pressure sensor. 
     The system may also include bubble sensor  334 , which is adapted to sense bubbles in the fluid line and communicates with control unit  324  to shut off pump  330  if bubbles of sufficient volume are detected. 
     The system can also include a flow sensor to determine if the flow rate has gone below or above threshold limits. RF energy delivery is automatically stopped and the pump is automatically shut down if the flow rate goes above or below the threshold limits. 
     In an alternate embodiment to that of  FIG. 6  the constant flow control of the system may be replaced by constant pressure control. In such a system the reservoir  326  may be maintained at a pressure within the prescribed pressure range using, for example without limitation, an IV bag pressure cuff or other suitable means, and the pump replaced by a flow sensor or flow controller. In such a system pressure is maintained at a substantially constant level within the prescribed range and flow rate monitored. When flow rate falls outside of the proscribed range the RF power delivery is terminated. 
     In general, using a greater number of smaller holes provides substantially the same resistance as a fewer number of larger holes, but mean fluid exit velocity is diminished. 
       FIG. 8  illustrates a portion of an embodiment of an RF delivery device wherein the expandable portion has a general dumbbell configuration, and energy is delivered through the conductive fluid to the tissue. RF delivery device  210  includes expandable portion  222  that comprises inflatable element  216  on which is disposed conduction material  218  with a helical configuration. The catheter has guiding element lumen  236  and irrigation lumen  228 . A conductive layer and an insulation layer are disposed on the catheter as in the embodiment in  FIGS. 1-5 . The proximal and distal portions of inflatable element  216  have diameters that are greater than the intermediate section, such that the expandable portion has a general dumbbell shape. When inflated, larger diameter proximal and distal ends of the expandable portion  214  contact the vessel wall, while space is left between the cylindrical section  222  of the expandable element and the vessel wall as illustrated in  FIG. 8 . The irrigation fluid flowing through irrigation apertures  238  fills the space between the cylindrical section  222  and tissue, and current from the helical electrode is carried through the conductive irrigation fluid and into the adjacent tissue. In this configuration the helical electrode does not contact tissue directly, therefore the uniformity of heating is improved and the risk of charring or overheating the tissue is reduced. 
     Device  210  is also adapted to query the nervous tissues adjacent to the device, but need not include this functionality. Device  210  includes nerve conduction electrodes  215  located on the outer surface of the dumbbell shaped proximal and distal ends of the expandable portion  214 . In use, an electrical signal, typically a low current pulse or group of pulses is transmitted to one of the conduction electrodes. This triggers a response in adjacent renal nerves, which then travels along the nerves and at some time “t” later is sensed by the opposite electrode when the signal is traveling in the appropriate direction. By alternating which electrode is used as the exciter and which the sensor, both changes in efferent and afferent nerve conduction in the renal nerves may be monitored as a function of RF treatments induced by the RF electrode. The conduction electrodes are wired to the sensing circuits in the controller via wires traveling within the catheter shaft, as in the irrigation lumen, or additional lumens (not shown), or multiple conductors may be applied to the outer surface of the shaft (not shown). 
       FIG. 9  illustrates the delivery device  210  in a delivered, or expanded, configuration within a renal artery. Areas  1005  indicate tissue treated by the application of RF energy delivered via the helical electrode. An area  1005  adjacent to conductor  218  surrounds a renal nerve  1004 . Irrigation fluid movement is shown by the arrows. The fluid enters the inflatable element  210  at irrigation port  230  as shown by arrows  1006 . The fluid then flows out of inflatable element  216  at irrigation apertures  238 , shown by arrows  1007 . The fluid then flows past conduction electrodes  215  into the blood stream, shown by arrows  1008 . 
     In use, the dumbbell configuration creates a small space between the helical electrode and the arterial wall. The irrigation fluid, such as saline, can be used to act as a conductor and transfer energy from the electrode to the tissue. In such a system, the impedance variations, at the interface between the tissue and the electrode, associated with surface irregularities and variations in contact between the electrode and tissue will be minimized. In this manner the fluid can act both to cool the electrode and to transfer energy to tissue. The thin layer of fluid between the electrode and tissue can also prevent sticking and add lubrication. 
     Unless specifically stated to the contrary, the embodiment of  FIG. 7  includes features associated with the embodiment from  FIG. 4 . 
     The configuration of RF delivery device  210  is less dependent on considerations listed above with respect to the embodiment in  FIG. 4  as the irrigation fluid does not directly impinge on the treatment tissue and is allowed circulate in the space between the vessel wall and the cylindrical central section  222 . Such a configuration additionally requires less irrigation fluid to prevent charring as the electrode  129  does not contact the tissue directly. 
     In use, the embodiment from  FIG. 5  is used to create a discontinuous helical burn pattern formed of a plurality of discrete burn areas in the tissue. Ihe helical burn pattern is formed during a single treatment session and does not require the device be moved to create the plurality of discrete burn areas. 
       FIG. 10  is a photograph of an RF delivery device  410  on top of a piece of heart tissue  500  which has been ablated with RF energy delivered by a device similar to that in  FIG. 4  and a system similar to that of  FIG. 6 . The heart tissue was originally cut as a cylinder into the core of which the distal end  406  of the RF delivery device  410  was deployed. RF energy comprising a signal of 400 KHz at 40 volts and 40 watts was then delivered to the tissue. The cylinder of tissue was then cut along its length so that the inner surface of the tissue cylinder could be visualized. Helical burn zone  501  was created by helical electrode  419 . The burn zone has the same configuration as the helical electrode. 
     One aspect of the disclosure is a method of manufacturing RP delivery devices.  FIGS. 11A-11H  illustrate a method of manufacturing a portion of the RF delivery device  110  from  FIG. 4 . In  FIG. 11A , catheter  126  is provided and can be any suitable catheter or other elongate device, such as a sheath. For example, catheter  126  can be an extruded material, and optionally can have a stiffening element therein such as a braided material. In this embodiment catheter  126  is extruded with a guide element lumen and an irrigation lumen formed therein (not shown), and the irrigation port is formed therein (not shown). The irrigation lumen is closed off at the distal end of the catheter to prevent fluid from escaping the distal end of catheter, but the irrigation lumen can stop at the irrigation port raher than continuing further towards the distal end. 
     Inflatable element  116 , which can be an inflatable balloon, is then secured to the exterior of catheter  126  using any suitable technique such that irrigation port  130  is disposed within inflatable element  116 . Next, mask  60  is applied or slid over inflatable element  116 . The mask is configured such that it covers areas where the conductive material is not to be deposited and is open where conductive material is to be applied. In  FIG. 11C , mask  60  is configured with open area  61  to allow for the deposition of a conductive element  118  in a helical configuration. Inflatable element  116  is then inflated with a suitable inflation fluid (e.g., liquid or gas) delivered through the irrigation lumen and out port  130  to expand, or inflate, inflatable element  116 , as shown in  FIG. 11C . Additionally, mask  60  is typically configured to mask the distal transition section of the expandable portion and the catheter distal to the expandable portion. After mask  60  is applied, conductive material  118  is then deposited, in a single deposition step, onto substantially all of catheter  126 , portions of inflatable element  116 , and mask  60 . This forms a conductive material layer on substantially all of catheter  26 , proximal portion of inflatable element  116 , and in the helical pattern on inflatable element  116 . After the conduction material  118  is deposited in the single step and allowed to dry sufficiently and or cure, inflatable element  116  is deflated and the mask  60  is removed. As shown in  FIG. 11F , a second mask  70  is then applied over those areas of conductive material  118  which are intended to deliver energy directly to the tissue in the energy delivery pattern, which is the helical pattern. The inflatable element  216  is then re-inflated and insulation material  34  is applied to substantially the entire device in a single depositing step as shown in  FIG. 11G . This forms an insulation layer on substantially the entire conductive material already deposited on catheter  126 , the proximal portion of the inflatable element, and the intermediate portion of the inflatable element where mask  70  is not disposed. Next, after appropriate drying and or curing the inflatable element is deflated and the mask  70  removed as shown in  FIG. 11H . After mask  70  is removed, shaft  126 , and proximal transition section of inflatable element is encapsulated by conductor  118  which are in turn encapsulated by dielectric  134 , while helical conductive electrode  118  on the inflatable element is not covered with dielectric. The irrigation apertures are then formed, such as by laser drilling. 
     In some embodiments of manufacturing the device, the layers of conductive material and insulation material are between about 0.0001 and about 0.001 inches thick. In some embodiments the conductive layer is about 0.0003 inches thick. In some embodiments the insulation layer is about 0.0005 inches thick. 
     Alternate methods for deposition of the conductor and/or the dielectric layers which that can be used and do not require masking include ink jet and or pad printing techniques. 
     These methods of manufacturing form a unitary conductor. A “unitary conductor” as described herein is a single conductive material comprising both a conduction element and an electrode element wherein the conductive element communicates energy between the controller and the electrode element. 
     The conductive and insulation materials can each be deposited on substantially all of elongate portion  112  (excluding the portion within expandable portion  114 ) and expandable portion  114  in a single step, reducing the time necessary to form the conductive and insulation layers, respectively. This can also simplify the manufacturing process. To deposit the conductive and insulation material, the device can be secured to a mandrel and spun while the material is deposited, or the device can be secured in place while the device used to deposit the material is moved relative to the device, or a combination of the two steps. “Single step” as used herein includes a step that applies the material without stopping the deposition of material. For example, the conductive material can be deposited on substantially all of the catheter proximal to the inflatable element and to the inflatable element in a single step. “Single step” as used herein also includes applying a second or more coats to the elongate portion and the expandable portion after initially ceasing the deposition of material. For example, a process that applies a first coat of conductive material to substantially all of the catheter proximal to the inflatable element and to the inflatable element, followed by a ceasing of the deposition, but followed by application of a second coat to substantially the entire portion of the catheter proximal to the inflatable element and to the inflatable element, would be considered a “single step” as used herein. Some previous attempts to form a conductive material on an elongate device formed one or more discrete conductive elements on the elongate device, thus complicating the deposition process. These and other attempts failed to appreciate being able to form a single layer of conductive material on substantially all of the catheter or other elongate device. These attempts failed to appreciate being able to form single layer of conductive material on the catheter and an electrode element on an expandable element in a single step. 
     By disposing the conductive material on the external surfaces of the catheter and inflatable element in a single step, the creation of electrical junctions is avoided. For example, a junction need not be formed between the conductive material on the catheter and the conductive material on the inflatable element. As used herein, electrical junction refers to a connection created between two conductive materials, either the same or different materials, that allows an electrical signal to be conducted from one material to the other. 
     The inflatable element is, in some embodiments, an inflatable balloon that is adapted to be inflated upon the delivery of a fluid through the irrigation lumen and out of the irrigation port. In the embodiment in  FIGS. 1-11 , the inflatable element is a balloon made of non-elastic, or non-compliant, material, but it can be a compliant, or elastic, material as well. Materials for a non-compliant balloon include, without limitation, polyethylene, polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyurethane, and polyimide. Materials for a compliant balloon include, without limitation, nylon, silicon, latex, and polyurethane. 
     In some embodiments of the embodiment in  FIG. 4 , the length of the cylindrical intermediate portion of the inflatable element is between about 1 cm and about 4 cm. In some embodiments the inflatable element has a diameter between about 4 mm and about 10 mm. In some particular embodiments the length of the intermediate portion of the inflatable element is about 20 mm and the diameter is about 5 mm to about 7 mm. 
     The conductive material can be deposited onto the catheter and/or expandable portion. Methods of depositing include, without limitation, pad printing, screen printing, spraying, ink jet, vapor deposition, ion beam assisted deposition, electroplating, electroless plating, or other printed circuit manufacturing processes. 
     In some embodiments the conductive material deposited is an elastomeric ink and the dielectric material is an elastomeric ink. They can be sprayed on the respective components. In some embodiments the elastomeric ink is diluted with an appropriate diluent to an appropriate viscosity then sprayed in a number of coats while the delivery device is rotated beneath a linearly translating spray head. 
     Conductive materials that can be deposited on the device to form one or more conductive layers of the device include conductive inks (e.g., electrically conductive silver ink, electrically conductive carbon ink, an electrical conductive gold ink), conductive powders, conductive pastes, conductive epoxies, conductive adhesives, conductive polymers or polymeric materials such as elastomers, or other conductive materials. 
     In some embodiments the conductive material comprises an elastomeric matrix filled with conductive particles. Elastomeric components include silicones and polyurethanes. Conductive materials are conductive metals such as gold or silver. Conductive inks that can be used are conductive ink CI-1065 and CI-1036 manufactured by ECM of Delaware Ohio. This ink is an extremely abrasion resistant, flexible, and highly conductive elastomeric ink. The ink has the following properties: 65% solids in the form of silver flakes; 0.015 ohms/square (1 mil (0.001 inches) thick); and a 10 minute cure time at 248 F. 
     The electrodes described herein can also be used as a temperature sensor. Ablative electrodes are routinely used in wide variety of surgical procedures. Many of these procedures are performed percutaneously, and a subset are performed endovascularly. In many of these procedures it is customary to incorporate provisions to monitor the temperature of the ablative electrodes. This temperature information is then used in some fashion as an input in a control scheme to limit the maximum temperature the electrode is allowed to attain. In this fashion a number of mechanisms, that may be deleterious to the desired outcome, may be controlled and or limited. Some of these effects, which in some circumstances are considered deleterious are, tissue charring, creation of steam, and the resultant uncontrolled, rapid, or large changes in interface impedance. 
     The temperature monitoring is typically carried out by incorporating and mounting some form of a temperature sensor such as a thermocouple, an rdt, or a thermistor in proximity to, or on, the electrode. 
     The electrodes are typically comprised of metals or metal alloys which are either deposited as metals directly through various metal deposition procedures such as, but not limited to physical or chemical metal vapor deposition, or applied as a component in a matrix such as but not limited to organic polymers in the form of an ink. Such inks are deposited in many ways, a few of which are, screening, spraying, ink jetting. 
     Metals, metal alloys, and other metal compound have resistance characteristics which are dependent on temperature, typically called the temperature coefficient of resistance or “tempco.” The magnitude and characteristics of these effects varies and is often used in devices such as a resistance temperature detector “RTD”, such as a platinum rtd&#39;s, or in positive temperature coefficient “PTC” or negative temperature coefficient “NTC” thermistors. 
     The systems herein can therefore altentatively monitor temperature by using the inherent tempco of the electrode itself as a way of monitoring its temperature and or controlling its impedance and thereby self-limiting its power output and thereby its temperature. 
       FIG. 12  represents an embodiment of a system similar to that of  FIG. 6  represented by the resistances of the various elements. The delivery RF lead which runs down catheter is represented as resistance  626  and the electrode is represented by resistance  619 . In this embodiment there is an additional conductive element running along the catheter shaft which is a return line represented by resistance  650 . In use the leads whose resistances are represented by  626  and  650  may be sourced in parallel when RF is delivered to electrode  619  and addressed separately when used to characterize the resistance and hence temperature of the electrode  619 . Alternatively one of them may be used solely for the purpose of monitoring temperature and therefore left open circuited when RF is being delivered. The design of the delivery system and electrode will be such that the impedance  640  of the patient will be orders of magnitude greater then the impedances for the delivery leads  626 ,  650 , and the electrode  619 . In one embodiment impedance  619  will be considerably greater than  626  or  650 , or in some cases the parallel combination of  626  and  650 . 
     In one embodiment the electrode is comprised of a layer of platinum and the temperature of the electrode may be characterized by monitoring the voltage drop across the series resistances  626 ,  619 ,  650 . This may be done intermittently, interspersed in the delivery of the RF energy. As the electrode heats, its resistance will increase in a well-known and repeatable fashion. As the leads  626  and  650  have lower resistance and will not self-heat appreciable, the change in resistance will by primarily due to the heating of electrode  619  and variation in its resistance. Many other scenarios will be understood to those skilled in the art. 
     An alternate arrangement which relies on the use of a PTC for the electrode relies on the rapid change in resistance of the electrode past a particular set point which is a function of the composition of the electrode. In this configuration the tempco of the electrode is relatively small, for example, below about 40 C but above about 40 C. In this temperature range the tempco rapidly increases thereby limiting delivered power in a voltage-limited RF configuration. Many alternate embodiments will be understood by those skilled in the art. 
       FIG. 13  illustrates an alternative configuration in which a capacitor  648 , inductor (not shown), or both may be incorporated in the circuit. In one embodiment the circuit may incorporate only one source lead  621  and the inherent resonance of the circuit which will depend on the varying impedance of the electrode resistance  623 . 
     In yet another alternative the tempco associated with a conductive ink such as the ECM CI-1036 may be used. Experimentally the ECM CI-1036 demonstrated a 0.1% increase in impedance per degree over the range of 30 C to 60 C. 
     As described above, devices capable of ablating renal nerves surrounding the renal arteries are useful in treating hypertension. The device disclosed in  FIG. 16  is another embodiment of a device adapted for such purpose. The device described herein comprises a bipolar electrode pair disposed on the outer surface of an expandable structure comprised of an inflatable balloon. A bipolar electrode pair provides for both a more controlled burn and a shallower burn than a comparable monopolar electrode. The device is configured for endovascular delivery to a renal artery. Each of the individual electrodes comprising the bipolar set is in turn comprised of a unitary electrode/conductor. 
     Referring to  FIG. 16 , detailed description of the distal features of an embodiment of the device is as follows. The distal portion of a bipolar RF delivery device  810  includes an expandable section  850  including a balloon, and a catheter shaft section  820  including an inner shaft  830  and an outer shaft  840 . The inner lumen of the inner shaft  830  includes a guidewire lumen  822 . The annular gap between the inner and outer shafts includes an irrigation lumen  821 . The outer shaft  840  also includes an irrigation outflow  812  (e.g., an irrigation port) located near its distal end such that it is disposed within the balloon. A temperature sensor  811  may be located within the balloon  850  and interconnecting leads of the temperature sensor  811  may be routed through the irrigation lumen outflow  812  and irrigation lumen  821 . 
     Prior to assembly, a conductive material is deposited on substantially the entire inner shaft  830 . A dielectric material is then deposited on the conductive material except at the distal most end of the inner shaft  830 . The inner shaft  830  is then lilted within the outer shaft  840  and the two are affixed to one another such that the inner shaft  830  extends beyond the most distal portion of the outer shaft  840  and the balloon  850 . The dielectric on the inner shaft  830  is deposited on at least the portions of the surface of the conductor on the inner shaft  830  that would contact irrigation fluid, thus preventing the conductive material on the inner shaft  830  from coming into contact with irrigation fluid. The distal end of the inner shaft  830 , which extends distal to the outer shaft  840 , is not coated with dielectric. This allows the inner shaft  830  to be in electrical communication with the inner sourced electrode as described below. 
     Next, the outer shaft  840  and balloon  850  are coated with an elastomeric ink, and then, subsequently, by a dielectric as described above. The conductive coating is deposited on the outer shaft  840 , all or a portion of the proximal cone  843  of the balloon  850 , and on the balloon  850 , forming a conductive material that includes an outer sourced spiral electrode  842 . This conductive material can be deposited in a uritary manner, as is described above and in the materials incorporated by reference herein. Conductive material is also deposited on the most distal section of the shaft assembly, the distal cone portion  833  of the balloon  850 , and the balloon  850 , forming a conductive material that includes an inner sourced electrode  832 . This conductor can also be formed in a unitary manner. The conductive material that forms the inner sourced electrode can be the same material that is used for the outer sourced electrode. When the distal conductor (which includes the inner sourced electrode  832 ) is formed, it interfaces electrically with the conductor on the inner shaft  830  that extends distal to the balloon  850 . The conductive materials can be selected such that when the conductive materials are deposited, the interface is a single layer of the same material rather than two distinct layers. The conductor and dielectric structures can be fabricated as described above. When used in bipolar mode, energy passes from one spiral electrode  832  or  842 , through renal nerve tissue, to the other electrode. The electrodes  832 ,  842  can be used in a bipolar manner, or each electrode can be used in monopolar mode. Bipolar mode can be used if the tissue burn need not be in deep as may be needed if using a monopolar mode. Bipolar mode generally allows more control in the tissue burn. Additionally or alternatively, the electrodes  832 ,  842  can be used together as a single monopolar electrode (e.g., by feeding both electrodes with the same frequency and RF energy such that the electrodes appear to be one electrode). 
     In an alternative embodiment, the inner shaft is not coated with a conductor (or dielectric) and, instead, a wire extends through the irrigation lumen, and interfaces the conductor that includes the inner sourced electrode. 
     Although not shown in  FIG. 16 , irrigation ports as described above can be situated such that they pass through the electrode structures, sit adjacent to the electrode structures such as in the space between them or exterior to the pair, or both. 
     One or more radio opaque markers  813  may be affixed to the outer shaft. 
     In embodiments, an anesthetic solution may be introduced in conjunction with, or independent of, the irrigation fluid, to potentially reduce pain or discomfort associated with renal denervation treatment. Suitable anesthetics include lidocaine, articaine, bupivacaine, cinchocaine/dibucaine, etidocaine, levobupivacaine, lidocaine/lignocaine, mepivacaine, prilocaine, ropivacaine, trimecaine. Other possibilities include, but are not limited to drugs which target neuropathic pain such as: butyl-para-aminobensoate (Butamben ), an ester local anesthetic, bupivacaine microspheres, SNX-111 (a selective calcium channel blocker), nicotinic acetylcholine receptor agonists such as ABT-594, and adrenergic blocking agents such as guanethidine or reserpine. Lidocaine is particularly suitable because it is approved for arterial use and the systemic limits are understood. In addition, lidocaine is a small molecule, which may result in faster diffusion through the artery wall. A contrast agent may be incorporated in the solution to enable visualization of the delivery of the anesthetic solution and confirmation that the targeted nerve structure has been engulfed by the solution. The contrast agent can be mixed with the anesthetic solution before the mixture is conveyed through the catheter. Examples of suitable contrast agents include those traditionally used for angiographic imaging such as the non-ionic fluoroscopic contrast agents that are iodate based (e.g., UltraVist 300). 
     Several factors for consideration in the delivery of an anesthetic solution as part of a renal denervation procedure include the ability to control the total dose or volume delivered and the ability to control the residence time or period the anesthetic solution remains at the treatment site while considering parameters relating to mobility, tissue density, etc. to ensure the anesthetic solution reaches the target renal nerves. The total volume delivered may vary depending on the targeted tissue and the anesthetic used. For lidocaine, the volume may be about 10 ml for a 1% solution. 
     Various approaches for delivery of the anesthetic solution to target nerve tissue for alleviating pain during renal denervation include, e.g., a high pressure delivery approach and/or a dwell time approach. The targeted nerve tissue may include nerve tissue in the intima, media, adventitia, and/or surrounding tissue of a renal artery. Generally, a high pressure delivery approach involves delivering anesthetic solution under relatively high pressure against the renal artery wall to cause passing within and/or through the wall via the vaso vasorum and infiltrate the targeted nerve tissue. With the dwell time approach, the anesthetic solution is maintained within the renal artery for a period of time to eventually diffuse or otherwise migrate through the vessel wall to at least partially engulf the targeted nerve tissue. Any of the aforedescribed embodiments of the energy delivery devices may be modified to deliver the anesthetic solution via the high pressure or dwell time approaches. 
     Referring now to  FIGS. 17-18 , there is illustrated an energy delivery system  2000  for delivering an anesthetic solution under high pressure to the renal vasculature (e.g., the renal artery or a renal vein), such that the solution enters the vessel wall and potentially migrate to the renal nerve structure surrounding the artery or vein. The energy delivery system  2000  includes a catheter  2002  having a catheter hub  2004 , an elongate catheter member  2006  extending distally from the hub  2004  and an expandable treatment member  2008  mounted to the catheter member  2006 . The elongate catheter member  2006  and the treatment member  2008  may be substantially similar to the elongate portion  12  and the expandable portion  14 , respectively, of the energy delivery device  10  disclosed in connection with  FIGS. 1A-2 . The hub  2004  may include one or more ports for reception of a guidewire, introduction of fluids or the like. In embodiments, the catheter hub  2004  includes a guidewire port  2010  and a fluid port  2012 . The guidewire port  2010  is in communication with a guidewire lumen  2014  extending through the catheter member  2006 . The fluid port  2012  is in fluid communication with a fluid lumen  2015  extending through the catheter member  2006  and communicating with the treatment member  2008  through a fluid opening  2016 . The fluid opening  2016  extends through the wall of the catheter member  2006  and communicates with an interior portion of the treatment member  2008 . 
     The energy delivery system  2000  further includes an irrigation or inflation source  2018  and associated irrigation fluid line  2020 . The irrigation source  2018  includes fluids for expanding the treatment member  2008  and/or for cooling tissue and/or for cooling the conductive material on the treatment member  2008 . Any of the aforementioned irrigation fluids may be utilized. 
     The energy delivery device  2000  further includes a source of anesthetic solution  2022  and associated anesthetic fluid line  2024 . The anesthetic source  2022  may include any of the anesthetic solutions mentioned hereinabove or other anesthetic solutions. 
     The energy delivery system  2000  may further include a valve  2026  which is in line with the irrigation fluid line  2020  and the anesthetic fluid line  2024  to permit selective infusion of either the irrigation fluid or the anesthetic solution. The valve  2026  may be manually operated or may be controlled via automation (e.g., programmable) to switch between an irrigation mode for supplying irrigation fluids from the irrigation source  2018  and an anesthetic mode for supplying the anesthetic solution from the anesthetic source  2022 . A pump  2028  may be in fluid communication with the valve  2026  to deliver the irrigation fluid or the anesthetic solution under pressure to the fluid lumen  2012  via a supply line  2030 . 
     The energy delivery system  2000  may also include a controller, identified schematically as reference numeral  2032 , with associated logic, software or circuitry for controlling operation of the pump  2028  and/or the valve  2026 . The software may contain at least one program for automated operation of the pump  2028  and/or the valve  2026  and/or may operate in response to various parameters detected during operation. For example, a sensor  2034  may be in communication with the feed line  2030  extending from the pump  2028  to the fluid port  2012  of the catheter hub  2004  to detect flow rate (e.g., a flow rate sensor) or pressure associated (e.g., a pressure sensor or transducer) with the irrigation fluid or anesthetic solution delivered to the expandable treatment member  2008 . The activity of the pump  2028  (e.g., an increase or decrease in pump speed, output or flow rate) may be controlled by the controller  2032  based at least in part on parameters detected by the sensor  2034 . Signals transmitted between the controller  2032  and the valve  2026 , the pump  2028  and the sensor  2034  are represented as signals “v 1 ”, “v 2 ”, “v 3 ”, respectively. 
     The expandable treatment member  2008  may be any of the expandable portions described hereinabove. In embodiments, the treatment member  2008  includes a balloon or inflatable element  2036 , a helical electrode  2038  on the outer surface of the inflatable element  2036  for delivering energy to the renal nerve tissue and non-conductive segment or material  2040  surrounding the helical electrode  2038 . The treatment member  2008  further includes a plurality of apertures  2042  defined in the inflatable element  2036  and/or the helical electrode  2038 . In  FIGS. 17 and 18 , the apertures  2042  are present in both the helical electrode  2038  and the non-conductive segment  2040  of the inflatable element  2036  for illustrative purposes. The apertures  2042  may have pore sizes ranging front about 0.5 mil to about 10 mil. The pore size, pore density and the thickness of the inflatable element  2036  may be selected to deliver the anesthetic solution at a pressure sufficient to pass through the renal artery wall for dispersion into the renal artery wall and possibly to surrounding renal nerves. The pressure of the anesthetic solution may vary, but in embodiments, a range of pressure within the inflatable element  2036  is between about 1 atm to about 4 atm. When desired, a relatively high pressure may be used to deliver anesthetic solution at a velocity sufficient to cause the solution to enter the renal artery and ultimately migrate to targeted nerves, including those in the media, adventitia, or surrounding tissue. 
     In operation, with reference to  FIG. 18 , the treatment member  2008  is positioned at the targeted location within the renal artery “a” or other renal vasculature. The anesthetic solution is then delivered by positioning the valve  2026  either manually or automatically via the controller  2032 , to the anesthetic mode. The pump  2028  is activated to deliver the anesthetic solution to the fluid port  2012  through the inflation lumen  2015  and within the interior of the inflatable element  2036  for delivery through the apertures  2042  under high pressure. The anesthetic solution “s” delivered within the pressure range identified hereinabove will enter and pass within and/or through the renal artery wall “a” and migrate to the renal nerve fibers or tissue “t” via the vasculature in the vessel wall. During application of the anesthetic solution “s”, the pressure within the inflatable element  2036  or inflation lumen  2015  may be monitored with the sensor  2034 , which sends a signal back to the controller  2032 . For instance, in the event the sensed pressure is below a threshold value potentially indicating that the anesthetic solution “s” is being delivered from the apertures  2042  at a relatively low pressure where diffusion is the primary manner in which it passes within and/or through the vessel wall, the pump or flow rate may be increased to increase the flow rate through the vessel to enhance the passage of the anesthetic within and/or through the blood vessels in the vessel wall. Similarly, if the sensed pressure is above a threshold value, flow rate delivered by the pump  2028  may be decreased to an acceptable range. 
     Once the renal nerves are desensitized by the anesthetic solution “s”, the valve  2026  can be switched to the irrigation mode and the controller  2032  activated to introduce irrigation and/or inflation fluids through the inflation lumen  2015  and within the inflatable element  2036 . In the irrigation mode, the flow rate and pressure may be reduced relative to the anesthetic mode to a pressure, e.g., below 1 atm. The inflatable element  2036  expands to position the helical electrode  2038  in apposition with the wall of the renal artery “a”. The system is energized and energy is delivered through the helical electrode  2038  to treat and/or denervate the renal nerves. The irrigation fluid cools the electrode  2038  and surrounding tissue as described hereinabove. 
     If during treatment, it is determined that another injection of anesthetic solution “s” is warranted, the irrigation fluid within the irflatable element  2036  may be drained either passively or actively from the inflatable element  2036 , and the anesthetic fluid delivered directly to the uninflated inflatable element  2036  for delivery to the nerve tissues through the apertures  2042 . In some embodiments, the anesthetic solution may be prefilled within the inflatable element  2036 , and used to purge the system  2000  prior to use. This may present a more efficient and faster method for delivery of the anesthetic solution “s’. 
     In embodiments, the helical electrode  2042  may be used to enhance the delivery of the anesthetic solution “s” through electrophoresis. For example, the helical electrode  2042  can be used to deliver a low current high voltage creating a charge gradient across the tissue, which increases the infusion rate of ionic anesthetic solutions “s” through the wall and into the nerves. In some embodiments, the generator associated with the controller  2032  can have two settings. The first setting can be for the delivery of a high voltage low current signal to the electrode  2038  during delivery of the anesthetic solution “s” to establish the electrophoretic environment. The second setting can be for the delivery of RF energy for nerve ablation. The use of electrophoresis to improve infusion of anesthesia into the tissue can be used with any of die single electrode helical electrode configurations described in  FIGS. 1-15 and 17-18  and/or the double electrode configuration of  FIG. 16 . In embodiments, the first setting of the generator also may be utilized to deliver non-RF voltage to excite the surrounding renal nerves. When the patient indicates to the clinician that the patient no longer feels the excited nerves, the clinician is apprised that the nerve tissue may be sufficiently anesthetized for the denervation treatment. 
     In embodiments, the source of anesthetic solution  2022  and the pump  2028  may be replaced with a syringe  2100  containing the anesthetic solution “s” ( FIG. 17 ). The syringe  2100  may be introducible within or coupled to the fluid port  2012  of the catheter hub  2004  and delivered to the inflation lumen  2015  and the inflatable element  2036  of the treatment member  2008  for dispensing through the apertures  2042 . The syringe  2100  may be manually activated. The flow of the anesthetic solution “s” may be moderated by the clinician via monitoring of the pressure via the sensor  2034  to provide delivery of the anesthetic solution “s” at the desired flow rate and high pressure sufficient to pass within and/or through the wall of the renal artery “a” and migrate to the targeted renal nerve tissue “t”. The syringe  2100  may have gradations to assist the clinician in determining the volume of anesthetic solution “s” delivered to the inflatable member  2036 . Additionally or in the alternative, the syringe  2100  may be filled with a predetermined volume of anesthetic solution “s” corresponding to a maximum volume intended for use during the treatment. Other fluid displacement mechanisms both manual and automated for delivering the anesthetic solution “s” are also within the scope of this disclosure. 
     As indicated hereinabove, in certain embodiments, instead of, or in addition to, the high pressure delivery of anesthetic solution to the renal nerves, a dwell-time approach may be utilized for delivery of anesthetic solution to the renal nerves. In accordance with this approach, the anesthetic solution is caused to dwell for a sufficient period of time at the treatment site such that the anesthesia solution has time to passively diffuse or otherwise move through the wall of the renal vasculature, e.g., the renal artery “a” or a renal vein. Increasing the dwell time of anesthetic solution at the treatment site can effectively increase the volume of delivered anesthesia that passes within and/or through the wall of the renal artery. This can, for example, result in delivery of an effective amount of anesthetic while using only a small portion of the overall systemic dose of the anesthetic solution. 
     In embodiments, the anesthetic solution may incorporate or be infused with microbeads. For example, microbeads can be saturated in an anesthetic such as lidocaine. The saturated microbeads can be mixed with saline to form the anesthetic solution and the solution can be delivered to the inflatable member  2036 . The anesthetic solution will leave the microbeads as the microbeads migrate through the vessel wall of the renal artery “a” acting as a localized drug source delivering the anesthetic for a predetermined period of time during their migration and when at rest. This may increase the amount of time the anesthetic or drug is active in the area. This can facilitate the use of less anesthetic solution and allow for the anesthetic to be active for a longer period of time as compared to an injected drug, which gets removed by the lymphatics. 
     In the alternative, the dwell time of anesthesia delivery may be increased by altering the rate of delivery of the anesthetic solution into the inflatable element of the treatment member thereby slowing the infusion rate into the renal artery. One procedure using an anesthetic solution containing lidocaine for treating renal arteries prior to an RF ablation for the treatment of hypertension includes a slow infusion of 2-4 ml of a 1% lidocaine solution (20-40 mg lidocaine) with an upper limit of a bolus 10 ml (100 mg lidocaine). Referring now to  FIG. 19 , one embodiment of an energy delivery system  2200  adapted for delivering an anesthetic solution through a dwell-time approach in conjunction with energy delivery is illustrated. The configuration of the catheter  2202  of the system  2200  is substantially similar to the embodiment of  FIGS. 8 and 9 , and reference is made thereto for particulars of the catheter member  2202  and the expandable treatment member  2204 . The system  2200  may incorporate features of the system  2000  discussed in connection with  FIGS. 17 and 18  for providing automated control of infusion rate, pressure and/or delivery volume. The treatment member  2204  includes an inflatable element  2206  having enlarged proximal and distal occluding end segments  2208 ,  2210  and an intermediate or central segment  2212  disposed between the proximal and distal end segments  2208 ,  2210 . In embodiments, the inflatable element  2206  is a single balloon member. The enlarged end segments  2208 ,  2210  define a greater cross-sectional dimension or diameter than the intermediate segment  2212  when in an at least partially expanded condition as shown in  FIG. 19 , thereby defining a general dumbbell shape to the expanded inflatable element  2206 . In accordance with this embodiment, the spacing defined between the intermediate segment  2212  of the inflatable element  2206  and the vessel wall of the renal artery “a” provides a reservoir “r” for receiving the anesthetic solution “s”. Thus, upon expansion of the inflatable element  2206 , the end segments  2208 ,  2210  engage the interior wall surface of the renal artery “a” while the intermediate segment  2212  is in a spaced relation from the interior wall surface. The end segments  2208 ,  2210  are dimensioned to substantially occlude the interior of the renal artery “a” thereby enclosing the reservoir “r”. Anesthetic solution “s” is introduced within the irrigation lumen  2214  of the catheter member  2202  and delivered through the irrigation port  2216  under relatively low pressure, e.g., less than about 2 atm or less than about 1 atm. The anesthetic solution “s” passes through the apertures  2218  within the inflatable element  2200  and/or in the helical electrode  2220 . Due to the reservoir holding capacity, the anesthetic solution “s” remains in contact with the vessel wall of the rural artery “a”. Over time, the anesthetic solution “s” diffuses through the wall and into the surrounding renal nerve tissue “t” so that the solution has its desired anesthetic effect. In some implementations, the anesthetic solution “s” delivered to the reservoir “r” can be removed after a predetermined treatment period via aspiration through the irrigation port  2216  to minimize the amount, of anesthetic remaining in the patient&#39;s system. Irrigation fluid may then be delivered to the inflatable element  2206  and the system energized such that the electrode  2220  delivers energy to denervate the nerve fibers. The irrigation fluid cools the electrode  2220  and/or the surrounding tissue. 
       FIG. 20  illustrates a variation of the treatment member of  FIG. 19  where the inflatable element  2300  includes an enlarged distal end region  2302  while the main section  2304  of the inflatable element  2300  is of a constant smaller cross-sectional dimension or diameter when in the at least partially expanded condition of the inflatable element  2300 . With this arrangement, a more distal region of the renal artery “a” is occluded and anesthetic solution “s” is delivered through apertures  2306  in the main section  2304  to the renal artery and the renal nerves. Although the reservoir is open adjacent ihe proximal end  2308  of the inflatable element  2300 , the flow rate of the anesthetic solution “s” may be controlled to ensure a sufficient dwell time or period is achieved for the anesthetic solution “s” to pass from the reservoir to the renal nerves. In an alternative use, the proximal end  2308  of the inflatable element  2300  may occlude a vessel wall due to the geometry of the vasculature in which it is positioned to substantially enclose the reservoir. For example, the proximal end  2306  maybe positioned within a more narrow area of the renal vasculature, which, upon expansion will engage and at least partially occlude the wall to enclose the reservoir. In another approach, the proximal end  2306  may be positioned adjacent a curve or bend in the renal vasculature whereby the proximal end  2306  engages the curve to assist in enclosing the reservoir. As a further alternative, the proximal end  2306  of the inflatable element  2300  may be enlarged while the rest of the main section  2304  of the inflatable element  2300  including the distal end region is of constant dimension or diameter. Although the apertures  2306  are shown in the non-conductive segment  2312  of the inflatable element  2300 , the apertures  2306  may extend through the helical electrode  2310  or through both the electrode  2310  and the non-conductive segment  2312  of the main section  2304 . 
       FIGS. 21-22  illustrate an alternate embodiment of the expandable treatment member of  FIGS. 8, 9 and 19 . In accordance with this embodiment, an inflatable element  2400  is dimensioned to transition between at least two conditions depending on the fluid operational pressure within the interior of the inflatable element  2400 . At a first operational state or pressure depicted in  FIG. 21 , the inflatable element  2400  assumes the general “dumbbell” orientation with the proximal and distal occluding end segments  2402 ,  2404  defining a greater cross-sectional dimension or diameter than the intermediate segment  2406 . At a second operational state or pressure greater than the first operational state depicted in  FIG. 22 , the intermediate segment  2406  expands to generally approximate the dimension or diameter of the proximal and distal end segments  2402 ,  2404 . The proximal and distal end segments  2402 ,  2404  maintain substantially the same dimension or diameter exhibited in the first operational state. In embodiments, the inflation element  2400  is a single balloon member where the intermediate segment  2406  may be fabricated from a more conformable material than the end segments  2402 ,  2404  to permit greater expansion of the intermediate segment  2406  when subjected to the increase pressure of the second operational state. In other embodiments, the end segments  2402 ,  2404  could incorporate stiffening material or elements, such as polymeric strands, braids, woven materials, splines, or the like. The stiffening elements would be fabricated from a material which will not interfere with the functioning of the helical electrode  2408 . 
     In operation, a catheter member  2410  is advanced to position the inflatable element  2400  within the renal vasculature at the targeted site. The inflatable element  2400  is inflated to assume the first state or condition with the proximal and distal end segments  2402 ,  2404  engaging and at least partially occluding the vessel wall with the intermediate segment  2406  spaced from the wall to define the annular reservoir “r” discussed hereinabove and shown in  FIG. 21 . The anesthetic solution “s” is introduced within the interior of the inflatable element  2400  and communicates through the fluid port  2410  in fluid communication with the fluid lumen  2412  and out the apertures  2414  to at least partially fill the reservoir “r”. The anesthetic solution ‘s” will eventually diffuse through the wall of the renal artery “a’ distributing within the renal nerves “t” in the tunica intima, tunica media, and adventitia to anesthetize the tissue. Thereafter, the inflatable element  2400  may be expanded to its second operational state through the introduction of the irrigation fluid at, e.g., a greater pressure and/or flow rate, whereby the intermediate segment  2406  expands to contact the vessel wall as depicted in  FIG. 22 . In the second state, the helical electrode  2408  is in apposition with the vessel wall. Energy can be delivered to the helical electrode  2408  to provide the desired treatment. 
       FIGS. 23-25  illustrate an embodiment of the energy delivery system where the treatment member  2500  includes proximal and distal occluding balloon elements  2502 ,  2504  with an intermediate or central balloon or inflation element  2506  disposed therebetween. The central balloon element  2506  is a treatment balloon and incorporates the helical electrode  2508  to treat the tissue in the aforementioned manner. The proximal and distal balloon dements  2502 ,  2504  may be expandable independent of the central balloon element  2506  to occlude the renal vessel and form the reservoir “r” for accommodating the anesthetic solution “s” as shown in  FIG. 24 . In embodiments, the catheter member  2509  may include a first lumen  2510  (shown schematically) in fluid communication with each of the balloon elements  2502 ,  2504  through fluid ports  2512 ,  2514 , respectively. With this arrangement, the proximal and distal inflation elements  2502 ,  2504  are simultaneously inflated or deflated. In the alternative, proximal and distal balloon elements  2502 ,  2504  may be isolated from one another and inflated independent from each other by provision of an additional lumen (not shown). The catheter member  2509  may include a second lumen  2516  (shown schematically) in fluid communication with the central balloon element  2506  through fluid opening  2518 . In embodiments, the catheter member may include a third lumen  2519  for receiving the guidewire. The central balloon element  2506  includes a plurality of apertures  2520  extending through its wall for delivering the anesthetic solution or the irrigation fluid. The apertures  2520  may also extend through the helical electrode  2508 . 
     In operation, the expandable treatment member  2500  is positioned at the desired location within the renal artery “a”. The proximal and distal occluding balloon elements  2502 ,  2504  are simultaneously inflated with the irrigation fluid to occlude the renal artery at upstream and downstream locations as shown in  FIG. 24 . The anesthetic solution “s” may be delivered through the second lumen  2516  at a first pressure and into the central balloon element  2506  via the fluid opening  2518 . The central balloon element  2506  may be at least partially inflated while the anesthetic solution “s” flows through the apertures  2520  within the central balloon element  2506  and into the reservoir “r”. For example, infusion of the anesthetic solution “s” through the central balloon element  2506  can be controlled to limit expansion of the central balloon element  2506  such that the annular space of the reservoir “r” is maintained to accommodate the anesthetic solution “s”. After diffusion of the anesthetic solution “s” through the renal artery “a” and the renal nerve tissue “t”, the proximal and distal balloon elements  2502 ,  2504  may be deflated and the central balloon element  2506  further expanded via introduction of irrigation fluid to position the helical electrode  2508  in apposition with the wall of the renal artery “a” as depicted in  FIG. 25 . The helical electrode  2508  is activated to transmit energy to denervate the targeted nerve tissue “t”. In the alternative, the proximal and distal balloon elements  2502 ,  2504  may remain in their expanded state during treatment with the electrode  2508 . 
       FIG. 26  illustrates an alternate arrangement of the treatment member of  FIGS. 23-25 . In this embodiment, the treatment member  2600  includes central or main inflation element  2602  of generally cylindrical configuration and proximal and distal axially spaced inflation elements  2604 ,  2606 . In embodiments, the inflation elements  2602 ,  2604 ,  2606  are individual balloon members. The proximal and distal axially spaced inflation elements  2604 ,  2606  may be toroidal or generally donut shaped and mounted about, or directly to, the proximal and distal ends of the main inflation element  2602 , i.e., about the outer surface of the main inflation element. The first and second axial inflation elements  2604 ,  2606  may be in fluid communication with the irrigation fluid via tubing, identified schematically as reference numeral  2608 , which may at least partially extend along the exterior of the main inflation element  2602 . The proximal and distal axially spaced inflation elements  2604 ,  2606  are expandable to occlude the renal artery “a” and enclose the reservoir “r” defined between the at least partially inflated main inflation element  2602  and the wall of the renal artery “a”. Anesthetic solution “s” is passed through the apertures  2610  of the main inflation element  2602  for diffusion through the wall of the renal artery “a” to engulf the targeted renal nerve tissue. Subsequent to the anesthetic treatment, the proximal and distal axially spaced inflation elements  2604 ,  2606  may be deflated and the main inflation element  2602  inflated to position the electrode  2612  in apposition with the renal artery “a” for treatment of the renal nerve tissue “t”. 
       FIG. 27  illustrates another embodiment of the energy delivery device. In accordance with this embodiment, elongate member  2700  includes first inner balloon or inflation element  2702  mounted adjacent the distal end thereof and second outer balloon or inflation element  2704  coaxially mounted about the first inner inflation element  2702 . The elongate member  2700  includes a first lumen  2706  in fluid communication with the first inner inflation element  2702  through a first port  2708  within the wall of the elongate member  2700 . The elongate member  2700  includes a second lumen  2710  in fluid communication with the second outer inflation element  2704  through a second port  2712  within the wall of the elongate member  2700  external of the first inflation element  2702 . The second outer inflation element  2704  includes the helical electrode  2714  for treatment of tissue and incorporates the apertures  2716  through its wall for delivery of anesthetic solution. The first inner inflation element  2702  is devoid of apertures to define a fully enclosed volume. 
     In use, the first inflation element  2702  is at least partially inflated or fully inflated through introduction of irrigation fluids through the first lumen  2706  and out the first port  2708 . The second inflation element  2704  is inflated with, e.g., the anesthetic solution “s” through introduction of the solution through the second lumen  2710  and the second port  2712 . The anesthetic solution “s” fills the space or reservoir defined between the inner wall of the second inflation element  2704  and the outer wall of the first inflation element  2702 . The anesthetic solution “s” passes through the apertures  2716  for delivery within and/or through the wall of the renal artery “a” into the nerve structure “t”. In embodiments, the first inflation element  2702  may be fully expanded to the position depicted in  FIG. 27  with only a small gap or space defined between the first inflation element  2702  and the second inflation element  2704 . The gap receives the anesthetic solution “s” or the irrigation fluid. In this condition of the first inflation element  2702 , the second inflation element  2704  may be pressed against the wall of the renal artery “a” by the first inflation element  2702  thereby causing contact of the helical electrode  2714  with the wall. In embodiments, a volume of anesthetic solution “s” is disposed between the small gap between the first and second inflation elements  2702 ,  2704  for dispersion through the apertures  2716  as depicted in  FIG. 27 . In some embodiments, the first inflation element  2702  may be only partially expanded and the second inflation element  2704  is maintained at full expansion via the introduction of the anesthetic solution “s” to position the electrode  2714  adjacent the renal artery during the anesthetic delivery. 
     Subsequent to the treatment with the anesthetic solution “s”, the irrigation fluid is introduced through the second lumen  2710  and into the interior volume of the second inflation element  2704 . The irrigation fluids pass through the apertures  2716  to cool the electrode  2714  and/or surrounding tissue. The first inner inflation element  2702  maybe inflated/deflated to any predetermined inflation state during introduction of the anesthetic solution “s” or the irrigation fluid within the second inflation element  2704 . The independent inflation of the first inflation element  2702  to maintain apposition of the electrode  2714  against the vessel wall allows the flow rate of anesthetic and/or the irrigation fluid to be independent of maintenance of the apposition of the electrode  2714  against wall. Additionally, full inflation of the first inner inflation element  2702  may reduce the volume and/or flow rate of anesthetic solution “s” or irrigation fluid required to be delivered while maintaining the electrode(s)  2714  in contact with the vessel wall. 
     While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.