Patent Abstract:
An energy delivering probe is used for thermally coagulating and/or constricting hollow anatomical structures (HAS) including, but not limited to, blood vessels such as perforator veins. The probe includes a shaft and an energy source.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation of U.S. application Ser. No. 12/626,569, filed Nov. 25, 2009, now U.S. Pat. No. 8,361,061, which is a continuation of U.S. application Ser. No. 11/197,849, filed Aug. 5, 2005, now U.S. Pat. No. 7,625,372, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 60/656,036 filed on Feb. 23, 2005, the entire disclosures of which are hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates generally to medical methods and apparatus. More particularly, the disclosure relates to the design and use of energy delivering probes for thermally coagulating and/or constricting hollow anatomical structures (HAS) including blood vessels such as the perforator veins which connect the superficial veins to the deep veins in the leg, truncal superficial veins of the leg (e.g., great saphenous vein, short saphenous vein, and the like), superficial tributary veins of the leg, internal spermatic veins (varicoceles), ovarian veins, gonadal veins, hemorrhoidal vessels, fallopian tubes, a-v malformations, a-v fistula side branches, esophageal varices, and the like. Additionally, the probes may be used for thermally coagulating tissue, such as cancerous breast or liver tissue. For purposes of illustration, apparatus and methods for use in treating perforator veins will typically be described. 
     2. Description of the Related Art 
     Perforator veins connect the deep venous system of a leg to the surface veins which lie closer to the skin. Normal or healthy perforator veins pass blood from the surface veins to the deep veins as part of the normal blood circulation. Incompetent perforator veins allow blood flow from the deep venous system to the surface veins, causing or contributing to problems, such as varicose veins, edema, skin and soft tissue changes, lipodermatosclerosis, chronic cellulites, venous ulcers, and the like. 
     Several procedures have been proposed for interruption of incompetent perforator veins. The “Linton” procedure requires a very long incision (knee to ankle) on the medial calf to expose the perforator veins. Individual veins may then be surgically dissected, ligated, and cut to prevent blood flow between the superficial and deep venous systems. A less invasive alternative has been developed by DePalma where individual incompetent perforator veins are identified along “Linton&#39;s Line” using ultrasound. Small incisions are then used to access the individual perforators for ligation and dissection. More recently, individual ligation and dissection of perforator veins has been performed using an endoscope inserted in the proximal calf. 
     Although generally effective, each of the above-described procedures requires surgical incisions followed by ligation and cutting of the veins. Thus, even at best, the procedures are traumatic to the patient and require significant surgical time. Moreover, the procedures are complex and often require a second surgeon to assist in the procedure. 
     For these reasons, it would be desirable to provide additional and improved techniques for disrupting incompetent perforator veins for the treatment of varicose veins, edema, skin and soft tissue changes, lipodermatosclerosis, chronic cellulites, venous ulcers, venous ulcers, and other conditions. Such procedures should preferably be minimally invasive, e.g., relying on an introducer sheath, cannula, catheter, trocar, or needle for gaining access to the perforator veins at the deep fascial plane. In particular, it would be desirable if the methods required few or no incisions, could be performed under a local anesthetic, would reduce post-operative healing time, as well as morbidity and complication rates, and would require only a single surgeon. In addition, it would be desirable to provide apparatus and methods which are useful for performing procedures on other tissues and hollow anatomical structures in addition to perforator veins. At least some of these objectives will be met by the disclosure described herein below. 
     SUMMARY 
     The present disclosure provides both apparatus and methods for coagulating and/or constricting a hollow anatomical structure (HAS) in order to inhibit or stop fluid flow therethrough. By “constricting,” it is meant that a portion of the lumen of the treated HAS is reduced in size so that fluid flow therethrough is either reduced or stopped entirely. Usually, constriction will result from endothelial denudation, a combination of edema and swelling associated with cellular thermal injury, and denaturation and contraction of the collagenous tissues, leading to a fibrotic occlusion of the HAS so that fluid flow is reduced or stopped entirely. In other cases, constriction could result from direct fusion or welding of the walls together, typically when pressure and/or energy are applied externally to the HAS. In either case, some portions of the lumen may remain open allowing fluid flow at a greatly reduced rate. The constriction may thus occur as a result of contraction of the collagenous tissue in the HAS, or may alternately occur as a result of direct fusion or welding of the walls together induced by heating of that tissue and/or surrounding tissue. Such heating may occur as a result of the application of energy directly to the walls of the HAS and/or to the tissue surrounding the HAS. Although the disclosure will describe delivering RF energy from the electrode(s) it is understood that other forms of energy such as microwave, ultrasound, lower frequency electrical energy, direct current, circulating heated fluid, fiber optics with radiant light, and lasers, as well as thermal energy generated from a resistive coil or curie point element may be used as well. In the case of RF energy, the energy will typically be applied at a power level in the range from 0.1 W to 300 W, typically at a frequency in the range from 100 KHz to 1 MHz and for a time in the range from 1 second to 5 minutes, although for longer regions, the treatment time could be 10 minutes or longer. 
     While the apparatus and methods of the disclosure will be particularly suitable for constricting incompetent perforator veins for the treatment of varicose veins, venous ulcers, or the like, they will also be suitable for treating other venous structures, such as the saphenous veins for the treatment of venous reflux, and other conditions. In other cases, the apparatus and methods may be suitable for treatment of arterial and other hollow anatomical structures as well. In other cases, the apparatus and methods may be suitable for treatment of tissues such as cancerous breast or liver tissue. 
     The methods of the present disclosure may be performed with a wide variety of apparatus which are adapted to position electrode structures adjacent to or within the HAS to be constricted, typically a perforator vein at a location beneath the fascial layer. The apparatus will generally include a shaft having the electrode structure at or near its distal end. The electrode structure may comprise one or more electrode(s) energized at a common polarity for use in “monopolar” protocols. Alternatively the electrode structure may comprise at least two electrically isolated electrodes for performing bipolar protocols. The electrode shaft may be rigid, flexible, or have regions of varying rigidity and/or flexibility. Often, the apparatus shaft will be used in combination with an introducer sheath, cannula, or catheter where the shaft will be introduced through a lumen thereof. For example, the apparatus may be introduced through the working channel of an endoscope which acts as a delivery sheath or cannula. Alternatively or additionally, the shaft itself may comprise one or more lumens, and such lumen(s) may be adapted to receive a needle or trocar to facilitate direct or “self-penetrating” introduction of the shaft or to advance the shaft over a guidewire through tissue to the target treatment site. As a third alternative, the shaft may have an integral or fixed sharpened distal tip in order to allow direct or “self-penetrating” introduction of the shaft through tissue to the target treatment site. The latter two approaches will generally require that at least a portion of the shaft be rigid in order to allow for pushability, but it would also be possible to provide for temporary placement of a rod or other stiffening element within or around an otherwise flexible shaft while it is being forwardly advanced through tissue to the target treatment site. 
     Thus, the apparatus of the present disclosure may be introduced to the target treatment site in a variety of ways, including direct or “self-penetrating” introduction where the shaft has a sharpened distal tip, either permanently affixed or removably placed in a lumen of the shaft, e.g. using a needle or trocar. Alternatively, the shaft carrying the electrodes may be introduced through the lumen of a separate introducer sheath, cannula, or catheter which has been previously introduced using conventional techniques. Third, the shaft can be introduced over a guidewire which has been previously introduced, typically using a needle for conventional guidewire placement. Other introduction protocols, including combinations of the three just described, may also be used. Furthermore, endoscopic introduction as well as endoscopically guided introduction of the apparatus may also be used. 
     The treatment protocols of the present disclosure may rely on endovascular treatment, extravascular treatment, or combinations thereof. By “endovascular,” it is meant that one or more of the treatment electrodes will be introduced into the lumen of the HAS being constricted. The electrodes may be introduced and left at a treatment location immediately adjacent to the entry penetration through the HAS wall. Alternatively, particularly when using flexible shafts and guidewires, the electrodes may be advanced intraluminally to a treatment location spaced some distance from the entry penetration through the HAS wall. By “extravascular,” it is meant that the treatment electrodes are placed adjacent or near to the outside wall of the HAS being treated. More simply, the electrode structure may be introduced to such a location outside of the HAS wall, and the treatment initiated by delivering the treatment energy. Alternatively, the electrodes may be pinned on the side of the HAS wall using a sharpened tip or trocar associated with the apparatus shaft. The combinations of these approaches may also be used, for example where a first electrode is passed to a posterior side of the HAS while a second electrode remains on the anterior side. 
     In one aspect, a bipolar electrode probe comprises a shaft having a proximal end and a distal end, a generally spherical or toroidal first electrode disposed near the distal end of the shaft, a second electrode spaced axially from the first electrode, and an electrical connector near the proximal end of the shaft for connecting the first and second electrodes to opposite poles of an electrosurgical power supply. By generally “spherical or toroidal,” it is meant that the electrode will have an outer, exposed surface which protrudes radially from a cylindrical wall or section of the shaft. The outer surface will usually be axially symmetrical and will be curved in a plane passing axially through the shaft. The curve will preferably be smooth, but will not necessarily have a constant radius. The radius will usually vary with a range from 0.5 to 10 times the shaft diameter. 
     In the preferred embodiments, the bipolar electrode probes will include only first and second electrodes. There will be no additional electrodes spaced axially from the first and second electrodes. In some cases, however, it may be desirable to form either the first or second electrodes in multiple segments arranged either axially or circumferentially, but such segments will always be commonly connected to a pole of the power supply and will be intended to act together as a single electrode surface. 
     In other specific embodiments, the second electrode structure will also be a generally spherical or toroidal electrode. In cases where both the first and second electrodes are spherical or toroidal, the more proximal of the two electrodes may have a less curved surface than the more distal of the electrodes. In some cases, the more proximal electrode may have a generally tapered, curved surface which becomes smaller in the distal direction. In other cases, the more distal electrode may have a taper in the distal direction providing an entry angle and transition to the electrode to ease advancing of the probe through tissue and/or through the wall of a hollow anatomical structure. 
     The spherical or toroidal electrodes will have a diameter in a range from 1 mm to 5 mm, preferably from 1 mm to 3 mm, typically being about 2 mm. The particular diameter chosen will depend on the selected method of access, where smaller diameter electrodes will require smaller access holes or incisions. The electrodes will be spaced-apart axially by a distance in the range from about 1 mm to 5 mm, preferably by about 1.5 mm (measured axially from inner edge to inner edge). 
     The shaft may be flexible or rigid and will preferably have at least a single central lumen extending from the proximal end to the distal end. The bipolar electrode structure may further comprise a trocar having a sharpened distal end disposed in one of the central or other lumens of the shaft so that the sharpened end extends distally beyond the shaft, typically by distance in the range from 1 mm to 10 mm. The trocar will preferably be removable, although in other embodiments described below, a trocar may be fixed to the shaft and define a distal-most electrode surface. In all cases, the trocar can be solid or flexible, but will preferably have an axial lumen to optionally permit introduction over a guidewire or delivery of fluid to the treatment site. 
     The trocar lumen can also provide for blood “flashback” indicating when the trocar has entered the HAS being treated. 
     In embodiments intended for direct introduction through tissue with a trocar or other sharpened distal tip, the shaft and/or the trocar will preferably be rigid to facilitate advancement. In other cases, where the electrode probe is intended for introduction over a guidewire, the shaft will usually be flexible. In the case of such flexible shafts, a sliding external sheath or cannula may be provided over the exterior in order to enhance stiffness to assist in insertion. Alternatively, in the case of flexible shaft devices, an internal stiffening member may be provided. Said stiffening member may be comprised of polymeric materials including PEEK, metals including stainless steel, composite structures including braided polyimide, and the like. 
     In a specific embodiment, the bipolar probe has a sharpened distal end that extends distally from the first electrode. The sharpened distal end may be formed as a trocar received within a central lumen of the shaft, usually being fixed in the shaft but optionally being removable and replaceable. Alternatively, the sharpened distal tip may be formed as a separate component and attached at the distal end of the shaft. The sharpened distal end is preferably electrically active and defines at least a portion of the electrode, preferably being formed as a cylindrical tube having a diameter in the range from about 0.5 mm to about 1 mm, and a length in the range from about 1.5 mm to 5 mm. The proximal end of the sharpened distal electrode and the distal end of the first electrode will preferably be spaced-apart by a distance in the range from 1 mm to 5 mm, preferably by about 1.5 mm. In some cases, the space between the electrode may be tapered in the distal direction providing an entry angle and transition to the electrode to ease advancing of the probe through tissue and/or through the wall of a hallow anatomical structure. The shaft will preferably have a lumen therethrough, including through the sharpened distal end, in order to permit the detection of flashback upon HAS entry, optional introduction over a guidewire and/or the delivery of saline or other fluids during a procedure. 
     In all of the above embodiments, at least one temperature sensor may be disposed on the probe, typically being on or near one or more of the electrodes. In the specific examples, at least one temperature sensor may be placed on a spherical or toroidal electrode. The temperature sensors will be suitable for connection to the external power supply to allow for monitoring and optional control of the temperature during the treatment. 
     In another aspect, a method for constricting a target HAS comprises percutaneously introducing a distal end of a probe to a location near the HAS and delivering energy into the target HAS to constrict the target region of the HAS. The probe may be introduced by advancing a sharpened distal end thereof through tissue directly to the target region, by positioning a sheath through tissue to the target region and advancing the probe through the sheath, or by positioning a guidewire through a needle, removing the needle, and advancing the probe over the guidewire to the location near the target HAS. Other combinations of these approaches may also be possible. 
     In some cases, it will be preferable to image the target location, such as the HAS and surrounding tissue while the probe is being introduced. Usually, color duplex or other ultrasonic imaging will be sufficient, although other imaging, such as fluoroscopic, would be possible. As a third alternative, the target location may be endoscopically viewed while the probe is being introduced, e.g., through a working channel of an endoscope. 
     The electrodes may be positioned in a variety of relationships to the HAS being treated. For example, the electrodes may be positioned extravascularly, typically on one side of the HAS, usually within 4 mm and preferably directly adjacent to the exterior of the HAS wall, while energy is being delivered. Alternatively, one or both electrodes may be positioned endovascularly where the electrode(s) are located within a lumen of the HAS when energy is delivered. 
     In a specific embodiment, an electrode having a sharpened end is penetrated through the HAS while an exterior surface of the HAS is engaged by a spherical or toroidal electrode on the probe. The HAS may be collapsed by pressure from the spherical or toroidal electrode so that the simultaneous application of pressure and heat will cause constriction of the HAS. 
     In other alternative protocols, either or both of the electrodes, preferably spherical or toroidal electrodes, may be passed entirely through the target HAS and thereafter drawn backwardly against the HAS wall and optionally through the HAS wall while applying energy. 
     In some preferred aspects, the temperature will be monitored near at least one of the electrodes, allowing monitoring and/or control of the HAS constriction. For example, the radiofrequency energy may be delivered at from 0.1 W to 300 W to obtain a monitored temperature in the range from 70° C. to 100° C. for a time sufficient to achieve HAS constriction. 
     In further preferred aspects of some methods, saline or other physiologically acceptable fluid will be delivered to the region being treated while the radiofrequency energy is being delivered. Preferably, the fluid will be delivered through a lumen in the probe itself. 
     In another aspect, a method for constricting a perforator vein comprises introducing at least one electrode to a location adjacent to or within the perforator vein and delivering energy through the electrode to constrict the lumen of the perforator vein. 
     In yet another aspect, an electrode probe comprises a shaft having a proximal end and a distal end, a generally spherical or toroidal first electrode disposed near the distal end of the shaft, and a second electrode spaced axially from the first electrode. 
     Another aspect is a probe with a proximal end and distal end for use in treating a hollow anatomical structure. Preferably, the probe has at least one energy emitting element located near its distal end, and the perimeter of this element increases as the element extends proximally. The probe may also have a sharp tip at its distal end that is configured to puncture body tissue as it is urged against the tissue. 
     Another aspect is an energy-emitting probe for use in treating a hollow anatomical structure comprising a shaft having a proximal end and distal end. Preferably, there is at least one energy emitting element located near the distal end of the shaft. The element may have an outer surface tapering outward as the element extends proximally, or a portion of the element may be cylindrical. Preferably, the probe also comprises a sharp tip at its distal end that is configured to puncture body tissue as it is urged against the tissue. 
     In another aspect, a method for treating body tissue with an energy-emitting probe comprises puncturing the body tissue with a sharp distal end of the probe and advancing the shaft of the probe distally into the tissue. Preferably, the method further comprises inserting an energy emitting element having tapered edges into the body tissue, the tapered edges easing insertion of the element into the tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a system constructed in accordance with principles of the disclosure including a probe and a radiofrequency electrosurgical power supply. 
         FIG. 2  illustrates a first exemplary distal tip of a probe constructed in accordance with principles of the disclosure. 
         FIG. 3  illustrates the probe tip of  FIG. 2 , shown with an introducer trocar removed. 
         FIG. 4  illustrates a second exemplary probe constructed in accordance with principles of the disclosure, comprising a flexible shaft. 
         FIGS. 5 and 5A  are schematic illustrations illustrating the dimensions of a first probe-tip construction according to the principles of the disclosure. 
         FIG. 6  illustrates a third exemplary probe constructed in accordance with principles of the disclosure. 
         FIGS. 7 ,  7 A, and  7 B are schematic illustrations of alternate embodiments of the tip of the probe of  FIG. 6  marked to show dimensions. 
         FIGS. 8A-8D  illustrate use of the probe illustrated in  FIG. 1  in performing a procedure according to a method. 
         FIGS. 9A-9C  illustrate the probe of  FIG. 1  in performing a second exemplary procedure in accordance with principles of the disclosure. 
         FIGS. 10A-10E  illustrate the use of the probe of  FIG. 1  for performing a third exemplary procedure according to the principles of the disclosure. 
         FIGS. 11A-11B  illustrate the use of the probe of  FIG. 6  for performing a fourth exemplary procedure according to principles of the disclosure. 
         FIGS. 12A-12D  illustrate the use of a trocar with a rigid probe having a pair of spaced-apart electrodes for endovascular treatment of a HAS in order to constrict the HAS in accordance with the principles of the disclosure. 
         FIGS. 13A-13C  illustrate the use of a rigid probe having a single electrode for penetrating and pinning a HAS in order to constrict the HAS in accordance with principles of the disclosure. 
         FIGS. 14A-14D  illustrate the use of a flexible probe introduced through a percutaneous sheath performing an endovascular treatment of a HAS in order to constrict the HAS in accordance with principles of the disclosure. 
         FIGS. 15A-15F  illustrate the use of a small gage needle for placement of a guidewire and introduction of a two electrode probe with sliding external sheath over the guidewire in order to constrict the HAS in accordance with principles of the disclosure. 
         FIGS. 16A and 16B  illustrate a particular method for introducing a two electrode probe to the fascial layer and moving the probe until the defect in the fascial layer is detected and the probe is introduced through the defect to a location adjacent to a HAS in order to constrict the HAS in accordance with principles of the disclosure. 
         FIGS. 17 and 18  illustrate an electrode configuration suitable for use with various embodiments of the electrode probe disclosed herein. 
         FIGS. 19 and 20  illustrate another electrode configuration suitable for use with various embodiments of the electrode probe disclosed herein. 
         FIGS. 21 and 22  illustrate another electrode configuration suitable for use with various embodiments of the electrode probe disclosed herein. 
         FIG. 23  illustrates another electrode configuration suitable for use with various embodiments of the electrode probe disclosed herein. 
         FIG. 24  illustrates a resistive-heater tip usable in place of, or in addition to, the electrode(s) of any of the various probes disclosed herein. 
         FIGS. 17 through 23  are drawn to scale. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , a first exemplary system  10  constructed in accordance with principles of the disclosure comprises a bipolar electrode probe  12  and a radiofrequency (RF) electrosurgical power supply  14 . A bipolar electrode probe  12  comprises a flexible shaft  16  having a distal end  18  and a proximal end  20  having a Y-shaped connector hub  22  attached thereto. A first electrode  24  and second electrode  26  are mounted on the shaft  16  near the distal end  18 . The shaft  16  has a central lumen which extends over its entire length (from the proximal end to the distal tip), and the lumen may be connected, typically via a luer connector (now shown) through a flexible line  30  having a luer or other connector hub  32  at its other end which can be connected to a source of infusion fluid, typically saline. The electrodes  24  and  26  may be connected to the radiofrequency electrosurgical power supply  14  through a cable  34  and connector  36 . The connections to the electrodes  24  and  26  are isolated so that the two electrodes may be connected to opposite poles of the power supply  14 , in the case of a bipolar configuration. 
     Optionally, an external sheath  38 , typically in the form of a rigid metal or other cannula, is slidably received over the exterior of the flexible shaft  16 . The sheath provides external stiffening of the flexible shaft  16  when desired. The sheath may include a handle or grip  40  near a proximal end thereof to facilitate its manipulation. Additionally, the sheath  38  may be sharpened at its distal end to allow for improved tissue penetration. 
     The external sheath  38  may allow selective stiffening of an otherwise flexible shaft  16 . Typically, during access, the sheath  38  will be placed in a forwardly advanced position to provide a rigid structure which is more controllable during subcutaneous manipulation and advancement over a guidewire or through a cannula where flexibility is not required and can even be a disadvantage. After positioning a distal end  18  of the shaft  16  at the desired treatment location, the external sheath  38  can be partially or fully withdrawn to expose a distal length of the flexible shaft  16  to allow further advancement into the HAS or to simply remove the rigid structure during treatment or while external compression is used to manipulate the device tip into contact with the HAS wall. 
     The first and second electrodes  24  and  26  are illustrated as generally spherical or toroidal electrodes, as defined above. The flexible body  16 , which is typically formed from a polymer or other electrically insulating material, acts to isolate the electrodes and provide the desired axial spacing, also as discussed above. While the electrodes are illustrated as spherical or toroidal, a variety of other specific designs may used under different circumstances, as will be discussed below. 
     Referring now to  FIGS. 2 and 3 , a first specific electrode design comprising a first electrode  44  in the form of a ring which is typically toroidal with a very flat surface and a second electrode  46  which is generally spherical or toroidal, as defined above. The first and second electrodes are disposed at the distal end of a polymeric shaft or body  48 , in a variety of ways. For the flexible shaft embodiment of  FIGS. 1 through 3 , as well as  4  discussed below, they can be attached through the center lumen of the shaft. Preferably, in embodiments that include spherical or toroidal electrodes, the opening formed in the center of the elements is approximately centered on the longitudinal axis of the shaft. Other embodiments are described below. 
     A trocar or needle  50  is received in the central lumen of the body  48 . The trocar  50  has a sharpened distal end or tip  52  so that it may be introduced directly into solid tissue, for example for accessing a HAS in the procedures described below. Electrodes  44  and  46  are spaced-apart by a spacer  54  located therebetween and isolated by a polymeric tube (not shown) insulating the entire length under the proximal electrode  44 . The trocar is preferably removable, leaving the structure illustrated in  FIG. 3 . At least one temperature sensor, typically a thermocouple or a thermistor  56 , will be provided on or near either of the electrodes. As illustrated, it is at the proximal end of the first electrode  44 . The temperature sensor is connected to the power supply through wires  58 . The first and second electrodes are connected to a power supply through isolated wires  60  and  62 . In other embodiments, the electrode(s) may run the entire length of the device, thus eliminating the need for separate connecting wires. 
     Usually, at least one of the probe body or shaft  48  and the trocar  50  will be rigid to facilitate advancement of the sharpened tip of trocar  50  through tissue. Usually, at least the trocar will be rigid since it will most often be composed of stainless steel or another metal. Often, the probe body  48  will also be rigid or stiffened by reinforcing elements. 
     The trocar  50  may have an internal lumen and a port or opening  64  at its distal end, typically to permit the detection of flashback upon HAS entry, optional introduction over a guidewire and/or the delivery of saline or other physiologically acceptable fluid to the treatment region during a procedure. 
     Construction of a particular embodiment of the electrosurgical probe  12  of  FIG. 1  is shown in more detail in  FIG. 4 . The flexible body or shaft  16  has lumen  70  shown in a broken-away portion thereof. The lumen  70  carries a tube  72  which is connected to the second electrode  26 . An insulating region  74  is provided between the second electrode  26  and the first electrode  24 , and a wire  78  is connected to the second electrode and runs proximally through the probe and to the electrical connector  36 . A second wire (not shown) is connected to the first electrode  24  and also runs proximally to the connector  36 . Similarly, temperature sensor wires are connected to the thermocouple, thermistor, or other thermosensor  80  and run through the flexible body  16  to the connector  36 . The inner shaft  72  is preferably formed from a structurally reinforced material such as braided polyimide, while the outer shaft may be formed from a polymeric extrusion such as thermoplastic polyester elastomers, polyimide, nylons, PEEK, polyether-block co-polyamide polymers, and the like. The connecting tube  30  may be formed from polyvinylchloride (PVC) or other suitable polymer and have a luer fitting  32  at both free ends. Tube  30  may be connected to the hub  22  by a luer  31 . 
     Referring now to  FIG. 5 , exemplary dimensions for embodiments which employ pairs of spherical or toroidal electrodes will be described. These spherical or toroidal electrodes will typically have a diameter D in a plane which is transversed to the axis of the catheter body in the range from 1 mm to 3 mm. The flexible probe body will have a diameter d which is smaller than that of the electrodes, typically being in the range from 0.5 mm to 2.5 mm. The distance l between the inner edges of the spherical electrodes will be in the range from 1 mm to 5 mm. As shown in  FIG. 5A , the distal electrode may have a taper in the distal direction providing an entry angle β to the electrode improving the ability to advance the probe through tissue and/or through the wall of an HAS. The entry angle β of the spherical or toroidal electrode will be in the range from 0° to 90°, typically being in the range from 0° to 60°. 
     Referring now to  FIG. 6 , a third embodiment of a bipolar electrode probe  90  constructed in accordance with principles of the disclosure is illustrated. Proximal portions of probe body  92  will be the same as for previously described embodiments. Probe body  92  may be rigid or flexible and will, as with prior embodiments, have a lumen therethrough. Within the lumen, a trocar  94  having a sharpened tip  96  will be removably received within the lumen. A first spherical or toroidal electrode  98  is integral or attached to the distal end of the probe body  92 . The trocar  94  acts as the second electrode, and is insulated from the remaining components by a sleeve  100 . The sleeve  100  may run the entire length of the device to provide insulation. The first electrode  98  may also run the entire length over the sleeve  100  and within the probe body  92  to provide for electrical connection back to a proximal hub (not shown). A thermocouple  104  or other temperature sensor may be connected through wires (not shown) which run the length of the probe. The apparatus of  FIG. 6  can provide for the introduction of saline or other physiologically acceptable fluid through a multi-arm hub (not shown). The fluid can be delivered through the lumen running through the trocar  94  and/or through an annular space between the outer surface of sleeve  100  and the inner surface of the electrode  98 . 
     Typical dimensions for the distal probe end of  FIG. 6  are shown in  FIG. 7 . The exposed portion of trocar  94  has a length l 1  in the range from 1 mm to 10 mm, and a diameter d in the range from 0.5 mm to 1 mm. The proximal most end of the exposed trocar  94  is spaced apart from a spherical or toroidal electrode  108  by a distance l 2  in the range from 1 mm to 5 mm. The diameter D of the spherical or toroidal electrode is generally the same as described above, typically being in the range from 1 mm to 3 mm. As shown in  FIG. 7A , the generally spherical or toroidal electrode may have a taper in the distal direction providing an entry angle β to the electrode improving the ability to advance the probe through tissue and/or through the wall of an HAS. The entry angle β is generally the same as described above being in the range from 0° to 90°, typically being in the range from 0° to 60°. Optionally, as shown in  FIG. 7B , the space between the electrodes may be tapered in the distal direction providing an entry angle β and transition element  95  improving the ability to advance the probe through tissue and/or through the wall of an HAS. The entry angle β is generally the same as described above being in the range from 0° to 90°, typically being in the range from 0° to 60°. 
     Referring now to  FIGS. 8A-8D , use of the probe for performing constriction of a perforator vein P or other HAS is illustrated. While the use is described in connection with the rigid bipolar electrode probe  12 , the method will generally apply to the other embodiments described herein. The perforator vein connects the deep venous system DV to the superficial venous system SV, as generally shown in each of the figures. Access to the perforator vein P or other HAS may be achieved with a conventional needle and cannula assembly  110 , as illustrated. Alternatively, direct access may be achieved relying on the exposed trocar tip  52  or  96  ( FIG. 2  or  6 ). As illustrated in  FIGS. 8A-8D , cannula  110  is introduced through the skin to the target site, and a needle removed from the cannula, as shown in  FIG. 8B . At this point, access to the interior of the perforator vein P or other HAS is provided. The probe  12  may be introduced through the cannula to a site within the perforator vein P or other HAS, as shown in  FIG. 8C . Energy may then be applied through the electrodes  24  and  26  until a desired degree of constriction has been achieved. In the exemplary embodiments, bipolar RF energy will heat the tissue and/or HAS, the temperature will be monitored with a thermocouple on the probe, and the radiofrequency generator will modulate power to maintain the desired temperature. After a desired amount of treatment time, the treatment can be terminated and the probe and cannula removed, leaving a constricted region CON in the perforator vein PV as shown in  FIG. 8D . 
     The treatment protocol illustrated in  FIGS. 8A-8D , is generally referred to herein as endovascular, i.e., within the HAS. While the use is described in connection with the rigid bipolar electrode probe  12 , the method will generally apply to the other embodiments described herein. Radiofrequency probe  12  may also be used to perform extravascular treatment, as illustrated in  FIGS. 9A-9C . Access with the assembly  110  may be achieved as generally described before, except that the perforator vein P or other HAS is not necessarily penetrated. Alternatively, direct access may be achieved relying on the exposed trocar tip  52  or  96  ( FIG. 2  or  6 ). As illustrated, the bipolar electrode probe  12  is introduced through the cannula  110  and the electrodes  24  and  26  are positioned adjacent the exterior of the vein or other HAS. The electrodes are energized and the tissue heated sufficiently to constrict the walls of the vein or other HAS, without any penetration, with the resulting constriction shown in  FIG. 9C . 
     Referring now to  FIGS. 10A-10E , a third protocol using the bipolar electrode probe  12  for constricting the perforator vein P or other HAS is illustrated. The needle and cannula  110  is introduced to fully penetrate the perforator vein P or other HAS so that the tip passes through the far side. The needle is removed and bipolar electric probe  12  introduced through a cannula, as shown generally in  FIG. 10B . As illustrated, the probe  12  is rigid but it could also have a flexible shaft. While the use is described in connection with passing the probe through a cannula, this method could alternatively be performed by “directly” penetrating the vein with a probe having a needle or trocar in a central lumen thereof as in  FIG. 2  or having a sharpened distal electrode being rigidly fixed to the probe as in  FIG. 6 . The electrodes on the probe  12  are then energized as the probe is drawn back to contact the far side of the vein or other HAS, as shown in  FIG. 10C . The vein or other HAS is heated and collapsed as the probe  12  is continued to be drawn back through the HAS, as shown in  FIG. 10D . Optionally, the cannula is completely removed by this point. As probe  12  is withdrawn, the perforator vein P or other HAS is constricted, as shown in  FIG. 10E . 
     Referring now to  FIGS. 11A and 11B , a fourth protocol of the bipolar electrode probe  90  of  FIG. 6  for treating a perforator vein P or other HAS will be described. The probe  90  is introduced directly through tissue under ultrasonic guidance until the sharpened tip  96  contacts the exterior of the vein or other HAS. The surgeon then advances the sharpened tip  96  through the vein or other HAS so that the spherical or toroidal electrode  98  engages and collapses the vein or other HAS, as shown in  FIG. 11B . The electrodes  94  and  98  are then energized to heat and constrict the walls of the vein or other HAS. As with all previous embodiments, the area may optionally be infused with saline or other physiologically acceptable fluid in order to enhance current flow, tissue heating, and HAS constriction. Hollow anatomical structure access may be confirmed by observation of flashback through a lumen of the system. 
     To this point, several devices and protocols for introducing rigid and non-rigid probes through an introducer sheath, cannula, or catheter have been described. As shown in  FIGS. 12A-12D , however, it is also possible to introduce electrode structures on the exterior of a rigid or non-rigid probe “directly”. Direct access is achieved using probe  120  having a needle or trocar  122  in a central lumen thereof or having a sharpened distal electrode being rigidly fixed to the probe as in  FIG. 6 . The needle or trocar  122  has a sharpened distal tip  124  which allows direct penetration through the tissue until the sharpened tip  124  reaches the perforator vein P or other HAS. The sharpened tip  124  is then used to penetrate the HAS, as shown in  FIG. 12B . The needle or trocar  122  may then be retracted to within the probe  120 , and radiofrequency energy delivered through the electrodes  126 , as shown in  FIG. 12C . The energy causes constriction CON of the perforator vein P or other HAS as shown in  FIG. 12D . After the treatment is complete, the probe  120  may be withdrawn. The protocol illustrated in  FIGS. 12A-12D  could also be performed using a single polarity and/or electrode device. Additionally, the protocol illustrated could also be used in performing an extravascular procedure. 
     Referring now to  FIGS. 13A-13C , a rigid probe  140  having a sharpened distal tip  142  and a single electrode  144  may be introduced to directly access the perforator vein P or other HAS, as shown in  FIG. 13A , and to penetrate and pin the vein, as shown in  FIG. 13B . Sufficient manual force is maintained on the probe  140  to collapse the perforator vein P or other HAS while energy is being delivered, as shown in  FIG. 13B . The result is a constriction CON in perforator vein P or other HAS when the procedure is terminated, as shown in  FIG. 13C . While the use is described in connection with the rigid single polarity and/or electrode probe  140 , the method will generally apply to the other embodiments described herein. 
     Referring now to  FIGS. 14A-14D , use of a flexible instrument introduced through an introducer sheath, cannula, or catheter will be described. A conventional needle and cannula assembly  160  having a removable needle  162  may be introduced to a perforator vein P or other HAS under ultrasound guidance. The cannula  160  may be introduced into the perforator vein P or other HAS using the needle  162 , and the needle withdrawn, as shown in  FIG. 14B . It is contemplated that the needle may be hollow in some embodiments. A flexible probe  170  having a pair of electrodes  172  at its distal end may then be introduced through the cannula  160 . The probe  170 , with flexible and atraumatic tip, will align itself with the interior of the perforator vein P or other HAS lumen, as shown in  FIG. 14C . The length of the flexible probe allows for distal advancement into the lumen after insertion. Energy is then delivered through the electrodes  172  to constrict CON the vein or other HAS as shown in  FIG. 14D . The probe  170  is then withdrawn into the cannula  160 , and the assembly withdrawn. 
     Endovascular procedures may also be performed over a guidewire GW introduced through an introducer sheath, cannula, or catheter  180  which may be introduced over a needle (not shown) in a conventional manner. Optionally, the guidewire GW may be introduced directly through the needle. While the use is described in connection with a bipolar electrode probe, the method will generally apply to the other embodiments described herein. Referring now to  FIGS. 15A-15F , the needle  180  is introduced so that its distal end  182  enters the lumen of the perforator vein P or other HAS, as shown in  FIG. 15B . The guidewire GW is then introduced through the needle  180 , and the needle withdrawn, as shown in  FIG. 15C , leaving the guidewire GW in place through the tissue, as shown in  FIG. 15D . A combination flexible probe with rigid sliding external sheath  186  is then introduced over the guidewire GW, as shown in  FIG. 15E . The sliding external sheath may be partially or fully retracted to expose a distal length of the flexible probe to allow for further advancement into the HAS or to simply remove the rigid structure during treatment (not shown). Radiofrequency energy is delivered through the electrodes  188  to constrict the perforator vein P or other HAS, as shown in  FIG. 15F . The sheath and probe  186  may then be withdrawn. As illustrated, the probe  186  has a flexible shaft, but it could also be rigid. 
     To this point, the access protocols have all involved penetrating the tissue using a needle, cannula, trocar, or other penetrating instrument. Such penetration generally requires ultrasonic or other image guidance in order to properly locate the perforator vein or other HAS and initiate treatment. As an alternative to this approach, as illustrated in  FIGS. 16A and 16B , a probe  200  may be introduced through overlying tissue until its distal tip  202  encounters the fascial layer F, as shown in  FIG. 16A . Initially, as shown in broken line, the probe  200  will almost certainly encounter a region of the fascia remote from the defect D through which the perforator vein P or other HAS passes. By properly moving or “dottering” the tip  202  of the probe over the fascial layer, as shown in  FIG. 16A , eventually the probe will encounter the defect and pass therethrough. Once the distal end of the probe has passed through the defect, the electrodes  204  will be properly positioned adjacent the extravascular wall of the perforator vein P or other HAS, as shown in  FIG. 16B . Additional manipulation, such as conical rotation of the probe  200 , may allow the perforator vein P or other HAS to become wrapped around the electrode portion of the probe  200 . Another form of manipulation may include using the probe  200  as a lever to press the perforator vein P or other HAS against the fascial layer from below. Radiofrequency energy can then be delivered to constrict the HAS. As with all previous protocols, the probe  200  may then be withdrawn after the treatment is complete. As illustrated, the probe  200  has a rigid shaft, but it could also be a flexible or combination flexible probe with sliding external rigid sheath. Additionally, while the use is described in connection with a bipolar electrode probe, the method will generally apply to the other embodiments described herein. 
       FIGS. 17-18  depict another electrode configuration  300  which can be used in any of the embodiments of the electrode probes  12 ,  120 ,  140 , etc. disclosed herein, or in any suitable electrode probe, or in any of the embodiments of the system  10  disclosed herein. An electrode probe employing the electrode configuration  300  can be used in practicing any of the embodiments of the protocols disclosed herein, e.g., in practicing any of the treatment methods disclosed herein, and/or any one or more of the protocols depicted in  FIGS. 8A-8D ;  9 A- 9 C;  10 A- 10 E;  11 A- 11 B;  12 A- 12 D;  13 A- 13 C; and/or  14 A- 14 D. Except as otherwise disclosed herein, the electrode configuration  300  of  FIGS. 17-18  can be generally similar to any of the electrode designs or configurations disclosed herein. 
     The electrode configuration  300  comprises a proximal electrode  302  and a distal electrode  304  which are separated by an electrically insulative spacer  306 . An electrically insulative layer  308  extends proximally from the proximal electrode  302 . A trocar or needle  350  is removably received within a lumen of the probe on which the electrodes  302 ,  304  are mounted. The distal electrode  304  has a distal taper  320  to ease insertion of the electrode  304  and probe through the patient&#39;s tissues. In one embodiment, the taper  320  comprises a truncated cone with a taper angle of 70 degrees referenced from a plane located distal of the electrodes and normal to the electrodes&#39; center axis; however, in other embodiments the taper angle may be between 45 and 85 degrees. Proximal of the taper  320  is a curved electrode surface  322  of the distal electrode  304 . In one embodiment, the radius of the curved electrode surface  322  is about 0.063 inches (in the sectional plane depicted in  FIGS. 17-18 ); however, in other embodiments this radius may be between 0.040 and 0.080 inches. In one embodiment, the proximal electrode  302  also forms a curved electrode surface  330 . The radius of this curved electrode surface  330  can be, in various embodiments, about 0.063 inches (in the sectional plane depicted in  FIGS. 17-18 ), or between 0.040 and 0.080 inches. 
     In one embodiment, the electrode configuration  300  may take on the following dimensions: exposed axial length (i.e., the length measured along a direction parallel to the longitudinal axis of the electrode configuration  300 ) of the distal electrode  304 =0.070 inches; maximum diameter of the distal electrode  304  and proximal electrode  302 =0.077 inches; inner lumen diameter of the distal electrode  304 =0.0370 inches; exposed axial length of the proximal electrode  302 =0.035 inches. 
       FIGS. 19-20  depict another electrode configuration  400  which can be used in any of the embodiments of the electrode probes  12 ,  120 ,  140 , etc. disclosed herein, or in any suitable electrode probe, or in any of the embodiments of the system  10  disclosed herein. An electrode probe employing the electrode configuration  400  can be used in practicing any of the embodiments of the protocols disclosed herein, e.g., in practicing any one or more of the protocols depicted in  FIGS. 8A-8D ;  9 A- 9 C;  10 A- 100 E;  11 A- 11 B;  12 A- 12 D;  13 A- 13 C; and/or  14 A- 14 D. Except as otherwise disclosed herein, the electrode configuration  400  of  FIGS. 19-20  can be generally similar to any of the electrode designs or configurations disclosed herein. 
     The electrode configuration  400  comprises a proximal electrode  402  and a distal electrode  404  which are separated by an electrically insulative spacer  406 . An electrically insulative layer  408  extends proximally from the proximal electrode  402 . A trocar or needle  450  is removably received within a lumen of the probe on which the electrodes  402 ,  404  are mounted. Each of the electrodes  402 ,  404  has a corresponding curved, tapered outer surface  422 ,  424  to ease insertion of the electrodes  402 ,  404  and probe through the patient&#39;s tissues. Each of the outer surfaces of the electrodes  402 ,  404  is tapered in that the diameter of each outer surface  422 ,  424  is greater at the proximal end than at the distal end thereof. 
     In one embodiment, the outer surface  422  of the proximal electrode  402  tapers from a diameter of 0.075 inches at its proximal end to a diameter of 0.068 inches at its distal end, over an exposed axial length of 0.035 inches, while the outer surface  422  has a maximum diameter of 0.077 inches between the distal and proximal ends. These dimensions may vary as needed in other embodiments. In one embodiment, the outer surface  424  of the distal electrode  404  tapers from a diameter of 0.0552 inches at its proximal end to a diameter of 0.045 inches at its distal end, over an exposed axial length of 0.047 inches, while the outer surface  424  has a maximum diameter of 0.0565 inches between the distal and proximal ends. These dimensions may vary as needed in other embodiments. 
     In one embodiment, the radius of the outer surface  422  of the proximal electrode  402  is 0.063 inches in the sectional plane depicted in  FIGS. 19-20 , and the radius of the outer surface  424  of the distal electrode  404  is 0.113 inches in the sectional plane depicted in  FIGS. 19-20 . 
     In one embodiment, the electrically insulative spacer  406  is tapered to provide a smooth graduation between the proximal electrode  402  and the distal electrode  404 . 
     In one embodiment, the inner lumen diameter of the distal electrode  404  is 0.0370 inches. 
     In one embodiment, the exposed surface area of the outer surface  422  of the proximal electrode  402  is approximately equal to the exposed surface area of the outer surface  424  of the distal electrode  404 . 
       FIGS. 21-22  depict another electrode configuration  500  which can be used in any of the embodiments of the electrode probes  12 ,  120 ,  140 , etc. disclosed herein, or in any suitable electrode probe, or in any of the embodiments of the system  10  disclosed herein. An electrode probe employing the electrode configuration  500  can be used in practicing any of the embodiments of the protocols disclosed herein, e.g., in practicing any one or more of the protocols depicted in  FIGS. 8A-8D ;  9 A- 9 C;  10 A- 10 E;  11 A- 11 B;  12 A- 12 D;  13 A- 13 C; and/or  14 A- 14 D. Except as otherwise disclosed herein, the electrode configuration  500  of  FIGS. 21-22  can be generally similar to any of the electrode designs or configurations disclosed herein. 
     The electrode configuration  500  comprises a proximal electrode  502  and a distal electrode  504  which are separated by an electrically insulative spacer  506 . An electrically insulative layer  508  extends proximally from the proximal electrode  502 . A trocar or needle  550  is removably received within a lumen of the probe on which the electrodes  502 ,  504  are mounted. 
     Each of the electrodes  502 ,  504  has a corresponding tapered outer surface  522 ,  524  to ease insertion of the electrodes  502 ,  504  and probe through the patient&#39;s tissues. Each of the outer surfaces of electrodes  502 ,  504  is tapered in that the diameter of each outer surface  522 ,  524  is greater at the proximal end than at the distal end thereof. 
     The outer surfaces  522 ,  524  are “flat tapered” in that each defines a truncated cone or frustum with a taper angle of 84 degrees referenced from a plane located distal of the electrodes and normal to the electrodes&#39; center axis. In other embodiments, this taper angle can vary between 70 and 88 degrees. 
     In one embodiment, the outer surface  522  of the proximal electrode  502  tapers from a diameter of 0.075 inches at its proximal end to a diameter of 0.068 inches at its distal end, over an exposed axial length of 0.035 inches. These dimensions may vary as needed in other embodiments. In one embodiment, the outer surface  524  of the distal electrode  504  tapers from a diameter of 0.0552 inches at its proximal end to a diameter of 0.045 inches at its distal end, over an exposed axial length of 0.047 inches. These dimensions may vary as needed in other embodiments. 
     In one embodiment, the electrically insulative spacer  506  is tapered to provide a smooth graduation between the proximal electrode  502  and the distal electrode  504 . 
     In one embodiment, the inner lumen diameter of the distal electrode  504  is 0.0370 inches. 
     In one embodiment, the exposed surface area of the outer surface  522  of the proximal electrode  502  is approximately equal to the exposed surface area of the outer surface  524  of the distal electrode  504 . 
       FIG. 23  depicts another electrode configuration  600  which can be used in any of the embodiments of the electrode probes  12 ,  120 ,  140 , etc. disclosed herein, or in any suitable electrode probe, or in any of the embodiments of the system  10  disclosed herein. An electrode probe employing the electrode configuration  600  can be used in practicing any of the embodiments of the protocols disclosed herein, e.g., in practicing any one or more of the protocols depicted in  FIGS. 8A-8D ;  9 A- 9 C;  10 A- 100 E;  11 A- 1 B;  12 A- 12 D;  13 A- 13 C; and/or  14 A- 14 D. Except as otherwise disclosed herein, the electrode configuration  600  of  FIG. 23  can be generally similar to any of the electrode designs or configurations disclosed herein. 
     The electrode configuration  600  comprises a proximal electrode  602  and a distal electrode  604  which are separated by an electrically insulative spacer  606 . An electrically insulative layer  608  extends proximally from the proximal electrode  602 . 
     The distal electrode  604  is integrally formed with a sharp entry tip  660  which extends distally from the distal end of the distal electrode  604 . The entry tip  660  is appropriately tapered and sharpened to facilitate passage of the electrodes  602 ,  604  and probe through the tissues of the patient. The outer surface  662  of the entry tip may be electrically insulated to isolate the function of the distal electrode  604  to the desired region. 
     Each of the electrodes  602 ,  604  preferably has a corresponding exposed, curved, tapered outer surface  622 ,  624  to further ease insertion of the electrodes  602 ,  604  and probe through the patient&#39;s tissues. Each of the outer surfaces of electrodes  602 ,  604  is tapered in that the diameter of each outer surface  622 ,  624  is greater at the proximal end than at the distal end thereof. 
     In the depicted embodiment, the electrodes  602 ,  604  and outer surfaces  622 ,  624  thereof have shapes and dimensions which are similar to those of the electrodes  402 ,  404  (and the outer surfaces  422 ,  424  thereof) of the configuration  400  shown in  FIGS. 19-20 . However, in other embodiments, the electrodes  602 ,  604  and outer surfaces  622 ,  624  thereof can take on other suitable shapes and dimensions. For example, the shapes and dimensions of the electrodes  502 ,  504  (and the outer surfaces  522 ,  524  thereof) of the configuration  500  shown in  FIGS. 21-22  may be employed as an alternative. 
     In one embodiment, the electrically insulative spacer  606  is tapered to provide a smooth graduation between the proximal electrode  602  and the distal electrode  604 . 
     In one embodiment, the inner lumen diameter of the distal electrode  604  is 0.0370 inches. 
     In one embodiment, the exposed surface area of the outer surface  622  of the proximal electrode  602  is approximately equal to the exposed surface area of the outer surface  624  of the distal electrode  604 . 
       FIG. 24  depicts a resistive-element tip  700  which can be used in any of the embodiments of the electrode probes  12 ,  120 ,  140 , etc. disclosed herein, in place of (or in addition to) the electrodes. The tip  700  comprises a resistive-element heater  702  mounted on a distal section  704  of the probe. The distal section  704  with heating element  702  may be tapered or cylindrical or tapered distally and cylindrical proximally. In use, the heater  702  is heated by passing electrical current therethrough and the hot heater  702  can be used to heat the inner lumen of a vein to close the vein. Thus, a probe employing the resistive-element tip  700  can be used in practicing any of the embodiments of the protocols disclosed herein, e.g., in practicing any one or more of the protocols depicted in  FIGS. 8A-8D ;  9 A- 9 C;  10 A- 10 E;  11 A- 11 B;  12 A- 12 D;  13 A- 13 C; and/or  14 A- 14 D, with the exception that thermal energy is applied via the resistive-element tip  700  instead of RF power applied via electrodes. 
     The resistive-element heater  702  can comprise a simple coil of resistive-heating material or wire, or a series of axially adjacent, separately operable coils. Such separate coils can be operated sequentially or in overlapping sequential groups, or in a fixed subset to vary the treatment length and/or minimize the power requirements of the heater. Each coil can have a separate temperature sensor to facilitate such separate operation and control. In other embodiments, the structure and/or operation of the heater  702  can be similar to any of the various embodiments of resistive elements or heaters, and/or modes of operation thereof, disclosed in U.S. Provisional Application No. 60/613,415, filed Sep. 27, 2004, titled RESISTIVE ELEMENT SYSTEM. The entire disclosure of the above-mentioned provisional application is hereby incorporated by reference herein and made a part of this specification. 
     A trocar or needle  750  is removably received (or, alternatively, fixedly received) within a lumen of the probe on which the heater  702  is mounted. 
     While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.

Technology Classification (CPC): 0