Patent Publication Number: US-2021177502-A1

Title: Devices and methods for radiofrequency neurotomy

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/933,811, filed Jul. 20, 2020, titled NEEDLES AND SYSTEMS FOR RADIOFREQUENCY NEUROTOMY, which is a continuation of U.S. patent application Ser. No. 15/092,945, filed Apr. 7, 2016, titled SYSTEMS AND METHODS FOR TISSUE ABLATION, issued as U.S. Pat. No. 10,716,618 on Jul. 21, 2020, which is a continuation of U.S. patent application Ser. No. 13/101,009, filed May 4, 2011, titled SYSTEMS AND METHODS FOR TISSUE ABLATION, which claims priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 61/347,351, filed May 21, 2010, titled METHODS AND SYSTEMS FOR SPINAL RADIO FREQUENCY NEUROTOMY, U.S. Provisional Patent Application No. 61/357,886, filed Jun. 23, 2010, titled INTERVERTEBRAL DISC HEATING, and U.S. Provisional Patent Application No. 61/357,894, filed Jun. 23, 2010, titled LARGE FIELD DIRECTIONAL RADIOFREQUENCY NEUROABLATION, each of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     The present application generally relates to thermal ablation systems and methods, and more particularly to systems and methods for radio frequency (RF) neurotomy, such as spinal RF neurotomy. 
     Description of the Related Art 
     Thermal ablation involves the creation of temperature changes sufficient to produce necrosis in a specific volume of tissue within a patient. The target volume may be, for example, a nerve or a tumor. A significant challenge in ablation therapy is to provide adequate treatment to the targeted tissue while sparing the surrounding structures from injury. 
     RF ablation uses electrical energy transmitted into a target volume through an electrode to generate heat in the area of the electrode tip. The radio waves emanate from a non-insulated distal portion of the electrode tip. The introduced radiofrequency energy causes molecular strain, or ionic agitation, in the area surrounding the electrode as the current flows from the electrode tip to ground. The resulting strain causes the temperature in the area surrounding the electrode tip to rise. RF neurotomy uses RF energy to cauterize a target nerve to disrupt the ability of the nerve to transmit pain signals to the brain. 
     SUMMARY 
     This application describes example embodiments of devices and methods for tissue ablation, such as spinal radio frequency neurotomy. Systems include needles with deployable filaments capable of producing asymmetrical offset lesions at target volumes, which may include a target nerve. Ablation of at least a portion of the target nerve may inhibit the ability of the nerve to transmit signals, such as pain signals, to the central nervous system. The offset lesion may facilitate procedures by directing energy towards the target nerve and away from collateral structures. Example anatomical structures include lumbar, thoracic, and cervical medial branch nerves and rami and the sacroiliac joint. 
     In some embodiments, a needle comprises an elongate member having a distal end, a tip coupled to the distal end of the elongate member, and a plurality of filaments. The tip comprises a bevel to a point. The plurality of filaments is movable between a first position at least partially in the elongate member and a second position at least partially out of the elongate member. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. 
     In some embodiments, a needle comprises an elongate member having a distal end, a tip coupled to the distal end of the elongate member, and a plurality of filaments. The tip comprises a bevel portion comprising a point on a side of the elongate member. The plurality of filaments is movable between a first position at least partially in the elongate member and a second position at least partially out of and proximate to the side of the elongate member. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. 
     In some embodiments, a needle comprises an elongate member having a proximal end and a distal end, a tip coupled to the distal end of the elongate member, a plurality of filaments, and a filament deployment mechanism coupled to the proximal end of the elongate member. The tip comprises a bevel portion comprising a point. The plurality of filaments is movable between a first position at least partially in the elongate member and a second position at least partially out of the elongate member. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. The filament deployment mechanism comprises an advancing hub, a spin collar, and a main hub. The advancing hub includes a stem coupled to the plurality of filaments. The spin collar includes a helical track. The stem of the advancing hub is at least partially inside the spin collar. The main hub comprises a stem comprising a helical thread configured to cooperate with the helical track. The stem of the main hub is at least partially inside the spin collar. The stem of the advancing hub is at least partially inside the main hub. Upon rotation of the spin collar, the filaments are configured to move between the first position and the second position. 
     In some embodiments, a needle comprises an elongate member having a distal end, a tip coupled to the distal end of the elongate member, and a plurality of filaments. The tip comprises a point. The plurality of filaments is movable between a first position at least partially in the elongate member and a second position at least partially out of the elongate member. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. A single wire comprises the plurality of filaments. 
     In some embodiments, a needle comprises an elongate member having a distal end, a tip coupled to the distal end of the elongate member, and a plurality of filaments. The tip comprises a bevel to a point. The plurality of filaments is movable between a first position at least partially in the elongate member and a second position at least partially out of the elongate member. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. The tip comprises a stem at least partially in the elongate member. The stem includes a first filament lumen, a second filament lumen, and a third lumen. The bevel portion comprises a fluid port in fluid communication with the third lumen. 
     In some embodiments, a needle comprises an elongate member having a proximal end and a distal end, a tip coupled to the distal end of the elongate member, a plurality of filaments, and a rotational deployment mechanism coupled to the proximal end of the elongate member. The tip comprises a bevel to a point. The plurality of filaments is movable between a plurality of positions between at least partially in the elongate member and at least partially out of the elongate member. The deployment mechanism comprises indicia of fractional deployment of the plurality of filaments relative to the tip. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. 
     In some embodiments, a needle comprises an elongate member having a distal end, a tip, and a plurality of filaments. The tip comprises a first body portion and a second body portion. The first body portion includes a tapered portion and a point. The tapered portion includes a plurality of filament ports. The second body portion is coupled to the distal end of the tip. The second body portion is at an angle with respect to the first body portion. The plurality of filaments is movable between a first position at least partially in at least one of the tip and the elongate member and a second position at least partially out of the filament ports. The plurality of filaments and the tip are configured to transmit radio frequency energy from a probe to operate as a monopolar electrode. 
     In some embodiments, a method of heating a vertebral disc comprises: positioning a distal end of a needle in a posterior annulus; deploying a filament out of the needle; traversing the posterior annulus from lateral to medial; applying radio frequency energy to the tip and to the filament; and ablating pain fibers in the posterior annulus. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member, an actuator interconnected to the plurality of filaments, and a lumen in the elongate member. The tip is shaped to pierce tissue of the patient. Movement of the actuator relative to the hub moves the plurality of filaments relative to the tip. The lumen and the tip are configured to accept an RF probe such that an electrode of an inserted RF probe, the tip, and the first and second filaments are operable to form a single monopolar RF electrode. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a fully deployed position. In the fully deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the fully deployed position. Each point is distal to the distal end of the needle. The average of all the points is offset from a central longitudinal axis of the elongate member. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. Each point is on a common side of a plane that contains a central longitudinal axis of the elongate member. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The plurality of filaments consists of a first filament and a second filament, and the needle contains no filaments other than the first and second filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. In the deployed position, a midpoint between the distal end of the first filament and the distal end of the second filament is offset from a central longitudinal axis of the needle. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The plurality of filaments consists of a first filament and a second filament, and the needle contains no filaments other than the first and second filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. In their respective deployed positions, each distal end defines a vertex of a polygon. A centroid of the polygon is offset from a central longitudinal axis of the needle. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The plurality of filaments consists of a first filament and a second filament, and the needle contains no filaments other than the first and second filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. In their respective deployed positions, each of the plurality of filaments points in an at least partially distal direction. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The plurality of filaments consists of a first filament and a second filament, and the needle contains no filaments other than the first and second filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. When the plurality of filaments are in the deployed position, portions of each filament extend outwardly away from the tip. Each portion of each filament extending outwardly away from the tip is straight. 
     In some embodiments, a needle for insertion into a patient during an RF ablation procedure comprises a hub, an elongate member fixed to the hub, a tip fixed to the elongate member at a distal end of the needle, a plurality of filaments in at least a portion of the elongate member in a retracted position, and an actuator interconnected to the plurality of filaments. The plurality of filaments consists of a first filament and a second filament, and the needle contains no filaments other than the first and second filaments. The actuator is operable to move the plurality of filaments relative to the hub, the elongate member, and the tip between the retracted position and a deployed position. In the deployed position, the plurality of filaments extends outwardly and away from the tip. Each filament comprises a distal end that defines a point in the deployed position. Each point is distal to the distal end of the needle. When the plurality of filaments is in the deployed position, the tip comprises an angle of at least 200° about the central longitudinal axis of the elongate member that is free of filaments. 
     In some embodiments, a method of performing spinal RF neurotomy in a patient comprises moving a tip of a needle to a first position proximate to a target nerve along the spine of the patient, after achieving the first position, advancing a plurality of filaments relative to the tip to a deployed position, and after the advancing step, applying RF energy to the tip and plurality of filaments, wherein said applying generates heat that ablates a portion of the target nerve. 
     In some embodiments, a method of performing lumbar RF neurotomy on a medial branch nerve in a patient comprises: moving a tip of a needle to a first position between the transverse and superior articular processes of a lumbar vertebra such that an end point of the tip is proximate to a surface of the vertebra; after achieving the first position, advancing a plurality of filaments relative to the tip to a deployed position; and after advancing the plurality of filaments, applying RF energy to the tip and the plurality of filaments. Said applying generates heat that ablates a portion of the medial branch nerve. 
     In some embodiments, a method of performing sacroiliac joint RF neurotomy in a patient comprises: a. moving a tip of a needle to a first position proximate to a sacrum of the patient; b. advancing a plurality of filaments relative to the tip to a first deployed position; c. applying RF energy to the tip and plurality of filaments, wherein the applying generates heat that ablates a first volume; d. retracting the plurality of filaments; e. with the tip in the first position, rotating the needle about a central longitudinal axis of the needle to re-orient the plurality of filaments; f re-advancing the plurality of filaments relative to the tip; and g. re-applying RF energy to the tip and plurality of filaments, wherein the re-applying comprises ablating a second volume proximate to the tip, wherein a center of the first volume is offset from a center of the second volume. 
     In some embodiments, a method of performing thoracic RF neurotomy on a medial branch nerve in a patient comprises: moving a tip of a needle to a first position proximate a superior surface of a transverse process of a thoracic vertebra such that an end point of the tip is proximate to the superior surface; after achieving the first position, advancing a plurality of filaments relative to the tip toward a vertebra immediately superior to the thoracic vertebra to a deployed position; and after advancing the plurality of filaments, applying RF energy to the tip and the plurality of filaments, wherein said applying generates heat that ablates a portion of the medial branch nerve between the thoracic vertebra and the vertebra immediately superior to the thoracic vertebra. 
     In some embodiments, a method of performing cervical medial branch RF neurotomy on a third occipital nerve of a patient comprises: a. positioning the patient in a prone position; b. targeting a side of the C2/3 Z-joint; c. rotating the head of the patient away from the targeted side; d. locating the lateral aspect of the C2/3 Z-joint; e. moving, after steps a, b, c and d, a tip of a needle over the most lateral aspect of bone of the articular pillar at the juncture of the C2/3 z-joint to a first position contacting bone proximate to the most posterior and lateral aspect of the z-joint complex; f. retracting, after step e, the tip of the needle a predetermined distance from the first position; g. extending, after step f, a plurality of filaments outwardly from the tip and towards the lateral aspect of the C2/3 z-joint such that the plurality of filaments are positioned straddling the lateral joint lucency and posterior to the C2/3 neural foramen; h. verifying, after step g, the position of the tip and filaments by imaging the tip and a surrounding volume; and i. applying, after step h, RF energy to the tip and the plurality of filaments, wherein the applying generates heat that ablates a portion of the third occipital nerve. 
     For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention are described herein. Of course, it is to be understood that not necessarily all such objects or advantages need to be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein. 
     All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description having reference to the attached figures, the invention not being limited to any particular disclosed embodiment(s). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure are described with reference to the drawings of certain embodiments, which are intended to illustrate certain embodiments and not to limit the invention. 
         FIG. 1  is a schematic diagram of an RF neurotomy system being used to perform RF neurotomy on a patient. 
         FIG. 2A  is a perspective view of an example embodiment of a needle that may be used in an RF neurotomy procedure. 
         FIG. 2B  is a cut away perspective view of a portion of the needle of  FIG. 2A . 
         FIG. 2C  is a partial cut away and partial cross-sectional view of a portion of another example embodiment of a needle that may be used in an RF neurotomy procedure. 
         FIG. 2D  is a perspective view of another example embodiment of a needle that may be used in an RF neurotomy procedure. 
         FIG. 2E  is a perspective view of an example embodiment of filaments formed from a single wire. 
         FIG. 3A  is a detailed view of an example embodiment of a needle tip with filaments in a fully deployed position. 
         FIG. 3B  is a detailed view of the needle tip of  FIG. 3A  with filaments in a retracted position. 
         FIG. 3C  is a detailed view of another example embodiment of a needle tip with filaments in a deployed position. 
         FIG. 3D  is a detailed view of another example embodiment of a needle tip with filaments in a fully deployed position. 
         FIG. 3E  is a detailed view of the needle tip of  FIG. 3D  with filaments in a retracted position. 
         FIG. 3F  is a cross-sectional view of the needle tip of  FIG. 3D  with filaments in a retracted position. 
         FIG. 3G  is a detailed view of yet another example embodiment of a needle tip with filaments in a deployed position. 
         FIGS. 3H and 3I  are detailed views of still other example embodiments of a needle tip with filaments in a deployed position. 
         FIG. 4  is a schematic diagram of an example embodiment of an RF probe assembly. 
         FIG. 5  is a proximal-facing end view of an example embodiment of a needle tip. 
         FIG. 6  is a side view of an example embodiment of a needle tip. 
         FIG. 7  is a proximal-facing end view of another example embodiment of a needle tip. 
         FIG. 8  is a proximal-facing end view of yet another example embodiment of a needle tip. 
         FIG. 9  is a proximal-facing end view of still another example embodiment of a needle tip. 
         FIG. 10  is a side view of another example embodiment of a needle tip. 
         FIG. 11A  is an illustration of an example set of isotherms that may be created with the needle of  FIG. 2A . 
         FIG. 11B  is an illustration of an example lesion that may be created with the needle of  FIG. 2A . 
         FIG. 11C  is an illustration of an example lesion that may be created with a single-filament needle. 
         FIG. 12  is a perspective view of the needle of  FIG. 2A  positioned relative to a lumbar vertebra for performing RF neurotomy. 
         FIG. 13  is an illustration of a sacrum including target lesion volumes for performing Sacroiliac Joint (SIJ) RF neurotomy. 
         FIG. 14  is a perspective view of the needle of  FIG. 2A  positioned relative to a thoracic vertebra for performing RF neurotomy. 
         FIG. 15  is a perspective view of the needle of  FIG. 2A  positioned relative to the C2/3 cervical zygapophyseal joint (z-joint) for performing cervical medial branch RF neurotomy on the third occipital nerve. 
         FIG. 16A  is a perspective view of an example embodiment of a needle tip. 
         FIG. 16B  is a back elevational view of the needle tip of  FIG. 16A . 
         FIG. 16C  is a front elevational view of the needle tip of  FIG. 16A . 
         FIG. 16D  is a perspective view of an example embodiment of an elongate member. 
         FIG. 16E  is a perspective view of the needle tip of  FIG. 16A  and the elongate member of  FIG. 16D . 
         FIG. 16F  is a cross-sectional view of the needle tip and elongate member of  FIG. 16E  along the line  16 F- 16 F of  FIG. 16E  and example embodiments of a filament and an RF probe. 
         FIG. 16G  is a cross-sectional view of another example embodiment of a needle tip and elongate member and example embodiments of a filament and an RF probe. 
         FIG. 17A  is an exploded view of components of the deployment mechanism of  FIG. 2D . 
         FIG. 17B  is a cross-sectional view of components of the deployment mechanism of  FIG. 2D . 
         FIG. 17C  is a perspective view of an example embodiment of an advancing hub and the wire of  FIG. 2E . 
         FIG. 17D  is a cross-sectional view of an example embodiment of a spin collar. 
         FIG. 17E  is a cross-sectional view of an example embodiment of a main hub, taken along the line  17 E- 17 E of  FIG. 17B , in exploded view with an example embodiment of an elongate member. 
         FIG. 18A  is an axial view of posterior oblique needle entry. 
         FIG. 18B  is a saggital view of posterior oblique needle entry. 
     
    
    
     DETAILED DESCRIPTION 
     Although certain embodiments and examples are described below, those of skill in the art will appreciate that the invention extends beyond the specifically disclosed embodiments and/or uses and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention herein disclosed should not be limited by any particular embodiments described below. 
     In the following description, the invention is set forth in the context of apparatuses and methods for performing RF ablation. More particularly, the systems and methods may be used to perform RF neurotomy to ablate portions of target nerves. Even more particularly, the systems and methods may be used to perform spinal RF neurotomy to ablate portions of target nerves along the spine of a patient to relieve pain. For example, embodiments of methods and apparatuses described herein relate to lumbar RF neurotomy to denervate a facet joint between the L4 and L5 lumbar vertebrae. Denervation may be achieved by application of RF energy to a portion of a medial branch nerve to ablate or cauterize a portion of the nerve, thus interrupting the ability of the nerve to transmit signals to the central nervous system. In another example, embodiments described herein relate to sacroiliac joint RF neurotomy. 
       FIG. 1  illustrates an example embodiment of a system  100  for performing RF neurotomy on a patient  101 . The patient  101  may be positioned face down on a table or surface  109  to allow access along the spine of the patient  101 . Other patient orientations are also possible depending on the procedure. The table  109  may comprise radiolucent materials substantially transparent to x-rays, such as carbon fiber. 
     The system  100  may include an RF generator  102  capable of generating an RF energy signal sufficient to ablate target tissue (e.g.: cause lesions in targeted volumes; cauterize targeted portions of target nerves). The RF generator  102  may, for example, be capable of delivering RF energy between about 1 W and about 200 W and between about 460,000 Hz and about 500,000 Hz. A needle  103  capable of conducting (e.g., transmitting or directing) RF energy may be interconnected to the RF generator  102  and may be used to deliver an RF energy signal to a specific site within the patient  101 . In some embodiments in which the needle  103  is a monopolar device, a return electrode pad  104  may be attached to the patient  101  to complete a circuit from the RF generator  102 , through the needle  103 , through a portion of the patient  101 , through the return electrode pad  104 , and back to the RF generator  102 . In some embodiments comprising a bipolar arrangement, the needle  103  may comprise at least one supply electrode and at least one return electrode to define the circuit. 
     The RF generator  102  may be operable to control the RF energy emanating from the needle  103  in a closed-loop fashion. For example, the needle  103  and/or an RF probe in the needle  103  may include a temperature measurement device, such as a thermocouple, configured to measure temperature at the target tissue. Data may also be available from the RF generator  102 , such as power level and/or impedance, which may also be used for closed-loop control of the needle  103 . For example, upon detection of a temperature, a parameter (e.g., frequency, wattage, application duration) of the RF generator  102  may be automatically adjusted. 
       FIG. 4  illustrates an example RF probe assembly  400  compatible with the needle  103 . The RF probe assembly  400  includes an RF probe  401  that may be inserted into a patient (e.g., through the needle  103 ) and may direct RF energy to the target tissue. In some embodiments, the RF probe  401  may be in electrical communication with the needle  103  to direct RF energy to the target tissue, but is not inserted into the patient. The RF probe  401  may include a thermocouple operable to measure temperature at a distal end  402  of the RF probe  401 . The RF probe assembly  400  may include a connector  403  and a cable  404  configured to connect the RF probe  401  to an RF generator (e.g., the RF generator  102 ). 
     Returning to  FIG. 1 , the system  100  optionally includes an imaging system  105  capable of producing internal images of the patient  101  and the needle  103 , for example to facilitate navigation of the needle  103  during a procedure. The system  100  may further include a display device for displaying the generated images to a user performing the procedure. In some embodiments, the imaging system  105  comprises a fluoroscope capable of generating real-time two dimensional images of the needle  103  and internal structures of the patient  101 . In certain such embodiments, the imaging system includes an X-ray source  106 , an X-ray detector  107 , and a controller  108  in electrical communication with the X-ray source  106  and/or the X-ray detector  107 . The X-ray source  106  and X-ray detector  107  may be mounted on a movable structure (e.g., a C-arm), to facilitate capturing a variety of images of the patient  101  (e.g., at various angles or projection views). Other imaging systems  105  are also possible (e.g., a computed tomography (CT) scanner). 
       FIG. 2A  illustrates an example embodiment of a needle  103  that may be used in the system  100  for performing RF neurotomy. The needle  103  includes a tip  201  that tapers to a point  301  capable of piercing the skin of a patient. In some embodiments, the tip point tapers to a point substantially at the center of the tip  201  (e.g., a “pencil-point” tip). In some embodiments, the tip point tapers to a point substantially at one side of the tip  201  (e.g., a “cutting” or “beveled” or “lancet” or “Quincke” tip). The needle  103  further includes an elongate member  203  connected to the tip  201  at a distal end  202  of the needle  103  and connected to a hub  204  at a proximal end  205  of the needle  103 . The needle  103  includes a longitudinal axis  223  along the center of the elongate member  203 . 
       FIG. 2D  illustrates another example embodiment of a needle  103  that may be used in the system  100  for performing RF neurotomy. The needle  103  includes a tip  211  that tapers to a point  301  capable of piercing the skin of a patient. In some embodiments, the tip point tapers to a point substantially at the center of the tip  211  (e.g., a “pencil-point” tip). In some embodiments, the tip point tapers to a point substantially at one side of the tip  211  (e.g., a “cutting” or “beveled” or “lancet” or “Quincke” tip). The needle  103  further includes an elongate member  203  connected to the tip  211  at a distal end  202  of the needle  103  and connected to a hub  204  at a proximal end  205  of the needle  103 . The needle  103  includes a longitudinal axis  223  along the center of the elongate member  203 . 
     The needle  103  may include a self-contained mechanical mechanism, in the form of deployable filaments  206   a ,  206   b , operable to expand the volume of effective RF energy delivery as compared to known single-electrode RF probes. The filaments  206   a ,  206   b  may be at least partially in the elongate member  203  and may be operable to emerge through one or more apertures of the needle  103  proximate to the distal end  202  of the needle  103 . In some embodiments, the needle  103  includes a single filament or three or more filaments. The filaments  206   a ,  206   b  allow contraction/expansion, offsetting, and/or contouring of the effective RF energy delivery over a selected area of anatomy to adjust lesion geometry produced using the needle  103  to match a desired target volume (e.g., spherical, hemispherical, planar, spheroid, kidney-shaped, catcher&#39;s mitt-shaped, oblong, snowman-shaped, etc.). The filaments  206   a ,  206   b  may be deployable and/or retractable by moving (e.g., rotating) an actuator  216  relative to the hub  204 . 
     As will be further described, the needle  103  may further include a tube  207  that includes a lumen  222  therethrough. The lumen  222  may be used to transport fluids to and/or from the target volume. The lumen  222  may also accept the RF probe  401  for delivery of RF energy to the target volume. The lumen  222  may also accept a dummy or temporary probe, for example to occlude the fluid port  210  during insertion. In some embodiments, the RF probe  401  is integrated with the needle  103 . In certain such embodiments, the tube  207  need not be present for RF energy delivery, although it may be included to facilitate fluid delivery. In some embodiments, the filaments  206   a ,  206   b  include lumens therethrough for the transportation of fluid to and/or from the target volume. In some embodiments, the filaments  206   a ,  206   b  do not include lumens therethrough (e.g., being solid). The filaments  206   a ,  206   b  may function as thermocouples. 
     As RF energy penetrates biological tissue, protein and water molecules oscillate in response to the RF current and the tissue adjacent to the RF electrode is heated. As the tissue heats and coagulates, the biophysical properties of the tissue change. These tissue changes limit penetration of the RF energy beyond a leading edge defined by the shape and size of an active needle tip. Accordingly, the size of a radiofrequency lesion using conventional single needle technology is practically limited after achievement of a certain temperature delivered for a certain time. 
     A needle  103  with deployable filaments  206   a ,  206   b  can overcome this obstacle and expand the effective area of RF energy delivery by providing multiple locations (e.g., the tip  201 ,  211  the filament  206   a , and/or the filament  206   b ) from which the RF energy emanates. The use of multiple filaments  206   a ,  206   b  provides additional conduits for RF energy, creating a multiple electrode RF field effect. The size, shape, and location of a lesion created with the needle  103  may be at least partially determined by, for example, the quantity, angle, length, location, and/or orientation of the filaments and RF energy parameters such as wattage, frequency, and/or application duration, one or all of which may be beneficially modified to suit a specific anatomical application by changing various aspects of the filaments as discussed below. 
     Where it is desired to create a lesion offset from the central longitudinal axis  223 , the lesion may be offset in a desired direction from the central longitudinal axis  223  by rotationally orienting the needle  103 . The needle  103  may be used to create a lesion offset from the central longitudinal axis  223  in a first direction. The filaments  206   a ,  206   b  may be retracted (e.g., after creating a first lesion), the needle  103  rotated, and the filaments  206   a ,  206   b  re-deployed to create a lesion offset from the central longitudinal axis  223  in a second direction (e.g., to create a second lesion). 
       FIGS. 3A and 3B  are detailed views of an example embodiment of a distal end  202  of a needle  103  that includes a tip  201 . The tip  201  may include a sharpened point  301  (e.g., tapering to a point substantially at the center of the tip  201 , a pencil-point tip) for piercing the skin of a patient and facilitating advancement through tissue. The tip  201  may include a tapered portion  302  that transitions the tip  201  from the point  301  to a body portion  303 . The body portion  303  is the portion of the tip  201  that is proximal to the tapered portion  302 . The body portion  303  may be cylindrical as illustrated, or may be other appropriate shapes. The body portion  303  may have a cross-section that coincides with (e.g., is coaxial with) the cross section of the elongate member  203 . 
       FIGS. 3D and 3E  are detailed views of another example embodiment of a distal end  202  of a needle  103  that includes a tip  211 . The tip  211  may include a sharpened point  301  (e.g., tapering to a point substantially at one side of the tip  201 , a cutting or beveled or lancet or Quincke tip) for piercing the skin of a patient and facilitating advancement through tissue. The tip  211  may include a tapered portion  302  that transitions the tip  211  from the point  301  to a body portion  303 . The body portion  303  is the portion of the tip  201  that is proximal to the tapered portion  302 . The body portion  303  may be cylindrical as illustrated, or may be other appropriate shapes (e.g., as illustrated in  FIG. 16A ). The body portion  303  may have a cross-section that coincides with (e.g., is coaxial with) the cross section of the elongate member  203 . In some embodiments, the tip  211  has a bevel angle between about 10° and about 45°, between about 15° and about 35°, between about 20° and about 30° (e.g., about 25°), combinations thereof, and the like. Other bevel angles are also possible. In some embodiments, the point  301  has an angle between about 40° and about 120°, between about 70° and about 90°, between about 75° and about 85° (e.g., about 79°), combinations thereof, and the like. Other angles are also possible. 
     The tip  201 ,  211 , or a non-insulated portion thereof, may act as an RF energy delivery element. The tip  201 ,  211  may comprise (e.g., be made from) a conductive material such as, for example, stainless steel (e.g., 300 Series Stainless Steel). The tip  201 ,  211  may be at least partially coated (e.g., with an insulator). The material of the tip  201 ,  211  and the material of the optional coating may be selected, for example, to act as an insulator, improve radiopacity, improve and/or alter RF energy conduction, improve lubricity, and/or reduce tissue adhesion. 
     The tip  201 ,  211  includes a first filament port or slot  304   a  (not visible in the views of  FIGS. 3A, 3B, 3D, and 3E ) and a second filament port or slot  304   b . The geometry of the filament slots  304   a ,  304   b  may be selected to allow filaments  206   a ,  206   b  to be adequately retracted (e.g., such that the filaments  206   a ,  206   b  are in a cross-sectional envelope of the body portion  303  of the tip  201 ,  211 , as shown in  FIG. 3F ) while the needle  103  is inserted into the body, so that the filaments  206   a ,  206   b  do not cause any unintended damage to the patient. Such positioning of the filament slots  304   a ,  304   b  avoids having filament exit features on the tapered portion  302  and thus avoids potential coring that could be caused by such positioning. 
     The internal geometry of the filament slots  304   a ,  304   b  may be designed such that the filaments  206   a ,  206   b  may be easily retracted and advanced. For example, the internal geometry of the filament slots  304   a ,  304   b  may include a transition region  305  that meets the outer surface of the body portion  303  at an angle of about 30°. The transition region  305  may, for example, be curved and/or planar. Advancement of filaments  206   a ,  206   b  without a pre-set bias (e.g., substantially straight) relative to the filament slots  304   a ,  304   b  can causes the filaments  206   a ,  206   b  to be deflected outwardly as the filaments  206   a ,  206   b  move distally along the transition region  305 . Depending on the positioning of the transition region  305  relative to where the filaments  206   a ,  206   b  are confined (e.g., in the needle  103  of  FIG. 3A , the filaments  206   a ,  206   b  are confined to only longitudinal movement where they enter into the elongate member  203 ) and on the mechanical properties of the filaments  206   a ,  206   b , various deployment angles of the filaments  206   a ,  206   b  relative to the central longitudinal axis  223  may be achieved. Generally, the portions of the filaments  206   a ,  206   b  that extend outwardly away from the filament slots  304   a ,  304   b  may be unrestrained and thus may take any appropriate form. For example, where there is no pre-set bias, the portions of the filaments that extend outwardly away from the filament slots  304   a ,  304   b  (and therefore from the tip) may be substantially straight, such as shown in  FIGS. 2A, 3A, 3C, 3D, 6, 11A-11C, and 14 . For another example, when there is a pre-set bias, the portions of the filaments that extend outwardly away from the filament slots may take any appropriate shape, such as, for example, curved as shown in  FIG. 10 . 
     The radial orientation of the filament slots  304   a ,  304   b  may be selected such that a center point between the filament slots  304   a ,  304   b  does not coincide (e.g., is not coaxial with) with the central longitudinal axis  223 . For example, as shown in  FIGS. 2A, 3A, 3B, 3D, and 3E , the filament slots  304   a ,  304   b  may be positioned such that they are about 120° apart about the circumference of the tip  201 ,  211 . Other filament slot configurations may be configured to achieve the filament placements discussed below. For example, the filament slots  304   a ,  304   b  may be between about 45° and about 180° apart about the circumference of the tip  201 ,  211 , between about 90° and about 180° apart about the circumference of the tip  201 ,  211 , between about 90° and about 150° apart about the circumference of the tip  201 ,  211 , combinations thereof, and the like. Other angles are also possible. These configurations may be achieved by varying, for example, the quantity of filament slots, the placement of filament slots about the circumference of the tip  201 ,  211 , and/or the placement of filament slots along the center longitudinal axis  223  to achieve the filament placements discussed below. 
     As noted herein, and illustrated in  FIGS. 3A and 3B , the needle  103  may comprise a tube  207  that includes a lumen  222  therethrough. The lumen  222  may be employed to accept the RF probe  401  for delivery of RF energy, for the transport of fluids, and/or for occluding a fluid port  210 . The tip  201 ,  211  may include a fluid port  210  that may be in fluid communication with the lumen  222  via a channel through the tip  201 ,  211 . In certain embodiments, the lumen  222  is a dual-purpose lumen that can allow injection of fluids and that can receive the distal end  402  of the RF probe  401  to deliver RF energy to the tip  201 ,  211 , the filament  206   a , and/or the filament  206   b . In some embodiments, the fluid port  210  is longitudinally spaced from the tip  301  (e.g., by between about 1 mm and about 3 mm). The fluid port  210  may be centrally located (e.g., as illustrated in  FIG. 3D ) or it may be located offset from the center longitudinal axis  223  (e.g., as shown in  FIGS. 2A and 3A ). The fluid port  210  may be used to transfer fluid between the region of the tip  201 ,  211  and the proximal end  205  of the needle  103 . For example, during an RF neurotomy procedure, an anesthetic and/or an image enhancing dye may be introduced into the region of tissue around the tip  201 ,  211  through the fluid port  210 . In some embodiments, the fluid port  210  is located along the tapered portion  302  of the tip  201 ,  211  (e.g., as illustrated in  FIGS. 3A and 3D ). In some embodiments, the fluid port  210  is located along the body portion  303  of the tip  201 ,  211 . 
       FIG. 16A  is a perspective view of an example embodiment of the needle tip  211 . In some embodiments, the needle  103  does not comprise a tube  207 , but the elongate member  203  comprises a lumen  308  therethrough and the tip  211  comprises a lumen  306   c  therethrough. The lumen  308  and the lumen  306   c  may be employed to accept the RF probe  401  for delivery of RF energy, for the transport of fluids, and or for occluding the fluid port  210 . In certain embodiments, the lumen  308  and the lumen  306   c  are dual-purpose lumens that can allow injection of fluids and that can receive the distal end  402  of the RF probe  401  to deliver RF energy to the tip  211 , the filament  206   a , and/or the filament  206   b . The filament lumens  306   a ,  306   b  may also allow liquid transfer from a proximal end of the needle to the filament ports  304   a ,  304   b.    
     In some embodiments, the filament lumens  306   a ,  306   b  are sized to inhibit buckling and/or bending of the filaments in the tip  211 . In some embodiments, the elongate member  203  may also include filament lumens (e.g., comprising tubes in the elongate member  203 ). In some embodiments, filament lumens in the elongate member  203  may be formed by an inner member (not shown) extending at least part of the length of the elongate member  203 . For example, a transverse cross-section of the inner member may have the same cross-section as the portion of the tip  211  illustrated in  FIG. 3F , including channels in which the filaments may lie and a lumen for passing fluid, an RF probe  401 , and/or a dummy probe. 
       FIG. 16B  is a back elevational view of the needle tip  211  of  FIG. 16A .  FIG. 16C  is a front elevational view of the needle tip  211  of  FIG. 16A . The needle tip  211  comprises a filament lumen  306   a  in fluid communication with and terminating at the filament slot  304   a , a filament lumen  306   b  in fluid communication with and terminating at the filament slot  304   b , and the lumen  306   c . In some embodiments, the lumens  306   a ,  306   b  are spaced by about 120° along the circumference of the tip  211 . Other angles are also possible. In some embodiments, the lumen  306   c  is spaced from each of the lumens  306   a ,  306   b  by about 120° along the circumference of the tip  211 . Other angles are also possible. Referring again to  FIG. 3F , the filament  206   a  may be in the filament lumen  306   a  and the filament  206   b  may be in the filament lumen  306   b . The lumen  306   c  is in fluid communication with the fluid port  210 . In some embodiments, the proximal end of the tip  211  includes a tapered surface, as shown in  FIG. 16A . When filaments  206   a ,  206   b  are in the filament lumens  306   a ,  306   b , the tapered surface may help to guide insertion of an RF probe  401  into the lumen  306   c . In some embodiments, the tapered surface has an angle normal to the tip  211  between about 15° and about 75°, between about 30° and about 60°, between about 40° and about 50° (e.g., about 45°), combinations thereof, and the like. Other angles are also possible. 
       FIG. 16D  is a perspective view of an example embodiment of an elongate member  203 . The elongate member  203  includes the lumen  308 , the filament slot  304   a , and the filament slot  304   b . In some embodiments, the filament slots  304   a ,  304   b  are spaced by about 120° along the circumference of the elongate member  203 .  FIG. 16E  is a perspective view of the needle tip  211  of  FIG. 16A  and the elongate member  203  of  FIG. 16D . As described herein, the elongate member  203  may be coupled to the tip  211  by adhering with conductive epoxy, welding, soldering, combinations thereof, and the like. A proximal portion of the tip  211  can be inserted into the lumen  308  of the elongate member  203 . The filament slot  304   b  of the elongate member  203  is substantially aligned with the lumen  306   b  of the tip  211 , allowing the filament  206   b  to be deployed out of the lumen  306   b . Although not illustrated, the filament slot  304   a  of the elongate member  203  is substantially aligned with the lumen  306   a  of the tip  211 , allowing the filament  206   a  to be deployed out of the lumen  306   a . In some embodiments, each of the filament slots  304   a ,  304   b  has a length between about 0.025 inches and about 0.2 inches (approx. between about 0.6 mm and about 3 mm), between about 0.05 inches and about 0.15 inches (approx. between about 1.3 mm and about 3.8 mm), between about 0.075 inches and about 0.125 inches (approx. between about 1.9 mm and about 3.2 mm) (e.g., about 0.105 inches (approx. about 2.7 mm)), combinations thereof, and the like. Other lengths are also possible. In some embodiments, each of the filament slots  304   a ,  304   b  has a width between about 0.01 inches and about 0.4 inches (approx. between about 0.25 mm and about 10 mm), between about 0.02 inches and about 0.03 inches (approx. between about 0.5 mm and about 0.76 mm), between about 0.015 inches and about 0.025 inches (approx. between about 0.38 mm and about 0.64 mm) (e.g., about 0.02 inches (approx. about 0.5 mm)), combinations thereof, and the like. Other widths are also possible. In some embodiments, the each of the transition regions  305  has a length between about 0.02 inches and about 0.2 inches (approx. between about 0.5 mm and about 5 mm), between about 0.05 inches and about 0.15 inches (approx. between about 1.3 mm and about 3.8 mm), between about 0.075 inches and about 0.125 inches (approx. between about 1.9 mm and about 3.2 mm) (e.g., about 0.104 inches (approx. about 2.6 mm)), combinations thereof, and the like. Other lengths are also possible. In some embodiments in which the transition regions include curved surfaces, the each of the transition regions  305  has a radius of curvature between about 0.01 inches and about 0.4 inches (approx. between about 0.25 mm and about 10 mm), between about 0.15 inches and about 0.35 inches (approx. between about 3.8 mm and about 8.9 mm), between about 0.2 inches and about 0.3 inches (approx. between about 5 mm and about 7.6 mm) (e.g., about 0.25 inches (approx. about 6.4 mm)), combinations thereof, and the like. Other radii of curvature are also possible. Certain combinations of dimensions of the transition regions  305  and filaments slots  304   a ,  304   b  described herein may cause deployment of the filaments  206   a ,  206   b  at desired angles (e.g., about 30°). 
     The lumen  308  is not visible in  FIG. 16E  because the elongate member  203  covers the lumen  308 . Covering the lumen  308  causes fluid inserted into the lumen  308  to exit the fluid port  210 , and possibly the filament slots  304   a ,  304   b . In some embodiments, for example as illustrated in  FIGS. 3A and 3B , the elongate member  203  may also include a slot proximate to the tube  207 . In certain such embodiments, the tube  207  may extend distal to the slot and substantially all fluid inserted into the lumen  222  exits the fluid port  210 . 
     In the embodiment illustrated in  FIG. 16E , the body portion  303  of the tip  211  and the elongate member  203 , excluding the sleeve  307 , have substantially equal diameters, for example to provide a smooth transition between the tip  211  and the elongate member  203 . In some embodiments, the elongate member  203  has an inner diameter between about 0.01 inches and about 0.04 inches (approx. between about 0.25 mm and about 1 mm), between about 0.015 inches and about 0.035 inches (approx. between about 0.38 mm and about 0.89 mm), between about 0.02 inches and about 0.03 inches (approx. between about 0.5 mm and about 0.76 mm) (e.g., about 0.025 inches (approx. about 0.64 mm)), combinations thereof, and the like. Other diameters are also possible. In some embodiments, the elongate member  203  has an outer diameter between about 0.01 inches and about 0.05 inches (approx. between about 0.25 mm and about 1.3 mm), between about 0.02 inches and about 0.04 inches (approx. between about 0.5 mm and about 1 mm), between about 0.025 inches and about 0.035 inches (approx. between about 0.64 mm and about 0.89 mm) (e.g., about 0.029 inches (approx. about 0.74 mm)), combinations thereof, and the like. Other diameters are also possible. In some embodiments, the proximal portion of the tip has an outer diameter between about 0.01 inches and about 0.04 inches (approx. between about 0.25 mm and about 1 mm), between about 0.015 inches and about 0.035 inches (approx. between about 0.38 mm and about 0.89 mm), between about 0.02 inches and about 0.03 inches (approx. between about 0.5 mm and about 0.76 mm) (e.g., about 0.025 inches (approx. about 0.64 mm)), combinations thereof, and the like. Other diameters are also possible. In some embodiments, the tip  211  has an outer diameter between about 0.01 inches and about 0.05 inches (approx. between about 0.25 mm and about 1.3 mm), between about 0.02 inches and about 0.04 inches (approx. between about 0.5 mm and about 1 mm), between about 0.025 inches and about 0.035 inches (approx. between about 0.64 mm and about 0.89 mm) (e.g., about 0.029 inches (approx. about 0.74 mm)), combinations thereof, and the like. Other diameters are also possible. 
       FIG. 16F  is a cross-sectional view of the needle tip  211  and the elongate member  203  along the line  16 F- 16 F of  FIG. 16E .  FIG. 16F  also illustrates an example embodiment of a filament  206   a  in the lumen  308  and the lumen  306   a , then exiting via the filament slot  304   a , and an RF probe  401  in the lumen  308 . In some embodiments, the elongate member  203  and the tip each  211  comprise (e.g., are each made from) a conductive material (e.g., 300 Series Stainless Steel), and can conduct electrical signals from the RF probe  401  to the tip  211  and the filaments  206   a ,  206   b  (e.g., due to physical contact of conductive components) to form a monopolar electrode. In some embodiments, the RF probe  401 , the filaments  206   a ,  206   b , the tip  211 , and/or the elongate member  203  may include features configured to increase physical contact between the components. The cross-sectional view shows the lumen  308  in fluid communication with the lumen  306   c  and the fluid port  210 . 
       FIG. 16G  is another cross-sectional view of an example embodiment of a needle tip  211  and the elongate member  203  along a line similar to the line  16 F- 16 F in  FIG. 16E . The tip  211  in  FIG. 16G  does not include a fluid port  210 , but fluid can permeate out of the filament slots  304   a ,  304   b  because the filament slots are in fluid communication with the lumen  308 . In some embodiments, the tip  211  includes a lumen  306   c , for example to assure placement of or contact with the probe  401  (e.g., as illustrated in  FIG. 16G ). In some embodiments, the tip  211  does not include a lumen  306   c , for example to reduce manufacturing costs if the lumen  306   c  is cut from a solid tip stem. 
     As may be appreciated, the channel through the tip  201 ,  211  may be sized to accommodate a tip of the RF probe  401  that may be inserted into the needle  103 . The channel may be sized such that RF energy from the inserted RF probe  401  is satisfactorily communicated from the RF probe  401  to the tip  201 ,  211 , the filament  206   a , and/or the filament  206   b.    
       FIGS. 3C and 3G  are each a detailed view of the distal end  310  of a needle  309  that is an alternate embodiment of the needle  103 . The distal end  310  includes a tip  311 ,  321  that may include a sharpened point  312  for piercing the skin of a patient and facilitating advancement through tissue. The tip  311 ,  321  may include a tapered portion  313  that transitions the tip  311 ,  321  from the point  312  to a first body portion  314 . The first body portion  314  may be connected to a second body portion  315  at an angle  316 . In some embodiments, the angle  316  is about 15°. Other angles  316  are also possible. For example, the angle  316  may be between about 5° and about 90°, between about 10° and about 60°, between about 10° and about 45°, between about 10° and about 20°, combinations thereof, and the like. Other angles are also possible. The second body portion  315  may be aligned with an elongate member  317 . The elongate member  317  may be similarly configured as the elongate member  203  of  FIGS. 3A, 3B, 3C, and 3D . The angle  316  between the first body portion  314  and the second body portion  315  may aid the user in navigating the needle  309  to a desired position. For example, by rotating the needle  309  such that the first body portion  314  is pointing in a desired direction, subsequent advancement of the needle  309  may result in the needle  309  following a non-straight path biased toward the desired direction. 
     The first and second body portions  314 ,  315  may be cylindrical as illustrated, or they may be of any other appropriate shape. The first and second body portions  314 ,  315  may have cross-sections that coincide with (e.g., is coaxial with) the cross section of the elongate member  317 . 
     The tip  311 ,  321 , or a non-insulated portion thereof, may act as an RF energy delivery element. The tip  311 ,  321  may comprise (e.g., be made from) a conductive material such as, for example, stainless steel (e.g., 300 Series Stainless Steel). The tip  311 ,  321  may be coated (e.g., with an insulator). The material of the tip  311 ,  321  and the material of the optional coating may be selected, for example, to act as an insulator, improve radiopacity, improve and/or alter RF energy conduction, improve lubricity, and/or reduce tissue adhesion. 
     The filaments  319   a ,  319   b  may also act as RF energy delivery elements. The filaments  319   a ,  319   b  may be constructed in a manner similar to as described with respect to the filaments  206   a ,  206   b.    
     The tip  311  of  FIG. 3C  includes a filament slot  318   a  and a filament slot  318   b . The geometry of the filament slots  318   a ,  318   b  may be selected to allow filaments  319   a ,  319   b  to be adequately retracted (e.g., such that they are in a cross-sectional envelope of the second body portion  315 ) while the needle  309  is inserted into the body, so that the filaments  319   a ,  319   b  do not cause any unintended damage to the patient (e.g., by being along the second body portion  315 ). Such positioning of the filament slots  318   a ,  318   b  may avoid having filament exit features on the tapered portion  313  and on the first body portion  314 , which may avoid potential coring. The internal geometry of the filament slots  318   a ,  318   b  may include a transition region that meets the outer surface of the second body portion  315  at an angle, and advancement of filaments  319   a ,  319   b  without a pre-set bias (e.g., substantially straight) relative to the filament slots  318   a ,  318   b  can causes the filaments  319   a ,  319   b  to be deflected outwardly as the filaments  319   a ,  319   b  move distally along the transition region. 
     The configuration and orientation of the filament slots  318   a ,  318   b  may be selected such that deployed filaments  319   a ,  319   b  may achieve the positioning illustrated in  FIG. 3C . In  FIG. 3C , the filaments  319   a ,  319   b  are generally positioned in a plane that is perpendicular to a plane that includes the angle  316  between the first and second body portions  314 ,  315 . As illustrated, the filaments  319   a ,  319   b  may be positioned such that they extend at an angle (e.g., about 15°, between about 10° and about 90°, between about 10° and about 60°, between about 10° and about 45°, between about 10° and about 20°, combinations thereof, and the like) relative to the plane that includes the angle  316 . Other angles are also possible. Other filament slot  318   a ,  318   b  configurations may be configured to achieve other desired filament  319   a ,  319   b  placements. These configurations may be achieved, for example, by varying the quantity of filament slots and filaments, the placement of filament slots about the circumference of the tip  311 , the angle at which the filaments extend away from the first and second body portions  314 ,  315 , and/or the placement of filament slots along the first and second body portions  314 ,  315 . 
       FIG. 3G  illustrates an example embodiment of a tip  321  that includes a filament slot  318   a  and a filament slot  318   b  along the first body portion  314 . The geometry of the filament slots  318   a ,  318   b  may be selected to allow filaments  319   a ,  319   b  to be adequately retracted (e.g., such that they are in a cross-sectional envelope of the second body portion  315 ) while the needle  309  is inserted into the body, so that the filaments  319   a ,  319   b  do not cause any unintended damage to the patient. Positioning of the filament slots  318   a ,  318   b  along the first body portion  314  may potentially cause coring, so the filaments  319   a ,  319   b  may be configured to substantially occlude the filament slots  318   a ,  318   b , which may avoid potential coring. The internal geometry of the filament slots  318   a ,  319   b  may lack a transition region and, due to being positioned on the first body portion  314 , advancement of the filaments  319   a ,  319   b  without a pre-set bias (e.g., substantially straight) can cause the filaments  319   a ,  319   b  to continue to advance substantially straight (e.g., along the longitudinal axis of the elongate member  317  and/or the second body portion  315 ) as the filaments move distally out of the filament slots  318   a ,  318   b . Although not illustrated, placement of filament slots along the tapered portion  313  is also possible (e.g., the filaments continuing to advance along the longitudinal axis of the first body portion  314 ). Although not illustrated, the embodiments depicted in  FIGS. 3A and 3D  may be adapted so the filaments  206   a ,  206   b  exit along the tapered portion  302 . 
     The needle  309  may comprise a tube that includes a lumen therethrough, for example as described herein with respect to  FIGS. 3A, 3B, 3D, and 3E . The lumen may be employed to accept an RF probe for delivery of RF energy and/or for the transport of fluids. In this regard, the tip  311  may further include a fluid port  320  that may be in fluid communication via a channel through the tip  311  with the lumen. The fluid port  320  may be used to transfer fluid between the region of the tip  311  and a proximal end of the needle  309 . 
     In the deployed position as shown in  FIG. 3C , the distal ends of the filaments  319   a ,  319   b  are disposed away from the point  312 . In the deployed position as shown in  FIG. 3G , the distal ends of the filaments  319   a ,  319   b  are disposed away from the point  312 . In a retracted position (not shown, but similar to as shown in  FIGS. 3B and 3E ), the distal ends of the filaments  319   a ,  319   b  are entirely within an outer perimeter (e.g., circumference where the second body portion  315  of the tip  311 ,  321  is round) of the tip  311 ,  321 . In the deployed position, the filaments  319   a ,  319   b  act as broadcast antennae for an RF probe inserted into the needle  309 . The tip  311  or  321 , the filament  319   a , and/or the filament  319   b  may form a monopolar electrode for application of RF energy to the target volume. The filaments  319   a ,  319   b  may allow the RF energy from the RF probe to be dispersed over a larger volume than would be possible with the tip  311 ,  321  alone. 
     In general, any or all of the herein variables may be incorporated into a particular embodiment of a needle to yield a needle capable of producing a lesion with a particular size, position and shape relative to the tip of the needle. Such custom sizes, positions and shapes may be designed for specific procedures. For example, a particular lesion size, position and shape may be selected to enable a user to navigate the needle to a particular landmark (e.g., proximate to or touching a bone visible using fluoroscopy) and then orient the needle such that deployed filaments will be operable to produce a lesion at a particular location relative to the landmark. By navigating to a particular internal landmark, as opposed to attempting to visualize a relative position of a needle offset from a landmark, a more accurate and/or consistent positioning of the needle may be achieved. In this regard, the skill level required to accurately position the needle for a particular procedure may be reduced. 
     The lesion shapes achievable through selection of the herein variables may include, for example, generally spherical, oblong, conical, and pyramidal shapes. The orientation relative to, and the amount of offset from, the tip of such shapes may be selectable. In an embodiment, the tips of the deployed filaments may be positioned distally relative to the point of the tip to provide for a facile positioning of the lesion relative to the tip. Such capability may allow for the needle to be inserted directly toward a target volume. In other embodiments, the tips of the deployed filaments may be positioned at the same axial position along the central longitudinal axis as the point of the tip or the tips of the deployed filaments may be positioned proximally relative to the point of the tip. In other embodiments, some filament endpoints may be located distal to the point of the tip while others are proximal to the point of the tip. 
     The elongate member  203  may be in the form of a hollow tube (e.g., sheath, cannula) interconnecting the tip  201 ,  211  with the hub  204 . The elongate member  203  may be configured with adequate strength to allow the needle  103  to pierce a patient&#39;s skin and advance to a target area through various tissue types, including, for example, fat and muscle tissue. The elongate member  203  may also be capable of resisting kinking as it is advanced. In some embodiments, the elongate member  203  comprises a rod with a plurality of lumens along its length to accommodate the filaments  206   a ,  206   b , the RF probe  401 , and/or a fluid passage. 
     The elongate member  203  houses portions of the filaments  206   a ,  206   b  and the tube  207 , and allows for relative movement of the filaments  206   a ,  206   b . The elongate member  203  may be of any appropriate size and internal configuration to allow insertion into a patient and to house componentry therein. In some embodiments, the elongate member  203  is a 16 gauge round tube or smaller. For example, the elongate member  203  may be 18 gauge or 20 gauge. In some embodiments, the elongate member  203  has a maximum cross-sectional dimension of about 1.7 mm. In some embodiments, the elongate member  203  has a maximum cross-sectional dimension of about 1 mm. The elongate member  203  may have a length selected for performing a specific spinal RF neurotomy procedure on a particular patient. In some embodiments, the elongate member  203  has a length of about 10 cm. 
     In certain embodiments, the elongate member  203  comprises (e.g., is constructed from) an insulative material to reduce (e.g., eliminate) the amount of RF energy emitted along the length of the elongate member  203  when the RF probe  401  is disposed therein. For example, the elongate member  203  may comprise (e.g., be constructed from) polymeric, ceramic, and/or other insulative material. In certain embodiments, the elongate member  203  includes an insulating coating or sleeve  307  ( FIGS. 2D and 16D ). In some embodiments, the elongate member is insulated (e.g., constructed from insulative material and/or having an insulating coating  307 ) except for a distal part having a length between about 5 mm and about 10 mm.  FIG. 3H  illustrates an example embodiment of a needle  309  comprising an insulating coating  330  covering a proximal portion of the tip  321  and coatings  332   a ,  332   b  covering a proximal portion of the filaments  319   a ,  319   b . The coating  330  insulates, inter alia, the bent area between the first body portion  314  and the second body portion  315  if the tip  321 . 
     In some embodiments, the elongate member is insulated (e.g., constructed from insulative material and/or having an insulating coating) except for a proximal part.  FIG. 3I  illustrates an example embodiment of a needle  309  comprising an insulating coating  330  covering a distal portion of the tip  321  and coatings  332   a ,  332   b  covering a distal portion of the filaments  319   a ,  319   b . In some embodiments in which the distal portion of the tip  321  is, the needle  309  may create a kidney or catcher&#39;s mitt shaped lesion, which may be useful, for example, for ablating tissue where the active tip is pressed against the wall of a structure with the device staying in the lumen of a structure. For example, when ablating endocardial lesions in which the device accesses the target through a cardiac chamber, insulating the distal portion of the tip  321 , which stays in the chamber, can make the biophysics of the lesion (e.g., impedance, power, heat) more precise because the insulated distal portion of the tip  321  that is surrounded by blood in the chamber will not be part of the field. 
       FIGS. 3H and 3I  illustrate example embodiments of insulation of parts of the tip  321  and the filaments  319   a ,  319   b  illustrated in  FIG. 3G . Parts of components of the distal ends of other needle tips described herein may also be insulated (e.g., those illustrated in  FIGS. 3A, 3C, and 3D ). In some embodiments, only parts of the tip  321 , and not parts of the filaments  319   a ,  319   b , are insulated. In some embodiments, only parts of the filaments  319   a ,  319   b , and not parts of the tip  321 , are insulated. In some embodiments, a distal portion of the tip  321  is insulated (e.g., as illustrated in  FIG. 3I ) and proximal portions of the filaments  319   a ,  319   b  are insulated (e.g., as illustrated in  FIG. 3H ). In some embodiments, a distal portion of the filaments  319   a ,  319   b  are insulated (e.g., as illustrated in  FIG. 3I ) and a proximal portion of the tip  321  is insulated (e.g., as illustrated in  FIG. 3H ). In some embodiments, the insulative coating or sleeve  330 ,  332   a ,  332   b  may be adjustable. For example, one or all of the sleeves  330 ,  332   a ,  332   b  may be advanced or retracted relative to the tip  321 , the filament  319   a , and the filament  319   b , respectively, to increase or decrease the amount of exposed conductive area. 
     The elongate member  203  may include a coating that may improve radiopacity to aid in visualization of the position of the needle  103  using fluoroscopy. The elongate member  203  may include a lubricious coating to improve its ability to be inserted and positioned in the patient and/or to reduce tissue adhesion. The elongate member  203  may include markers  224  along its length to assist in determining the depth to which the needle  103  has entered into the anatomy. The markers  224  may be radiopaque so that they may be viewed under fluoroscopy. A collar (not shown) may be disposed about the elongate member  203  to assist in placement of the tip  201 ,  211  of the needle  103 . For example, the tip  201 ,  211  may be positioned in a first position, the collar may then be placed against the patient&#39;s skin, and then the needle  103  may be advanced and/or withdrawn a certain distance. Such a distance may be indicated, for example, by the distance between the collar and a patient&#39;s skin or other anatomy. 
     The elongate member  203  may be fixedly interconnected to the tip  201 ,  211  and the hub  204  in any appropriate manner. For example, the tip  201 ,  211  may be press fit into the elongate member  203  and the elongate member  203  may be press fit into the hub  204 . Other example methods of attachment include adhesive bonding and welding. In some embodiments, the elongate member  203  and the tip  201 ,  211  are a single unitary structure. The elongate member  203  may be steerable and incorporate controlling mechanisms allowing the elongate member  203  to be deflected or steered after insertion into the anatomy. 
     The tube  207  containing the lumen  222  may comprise (e.g., be constructed from) any appropriate material. For example, the tube  207  comprise a conductive material, such as stainless steel (e.g., 300 Series Stainless Steel), such that when the RF probe  401  is inserted in the tube  207 , the RF energy emitted by the RF probe  401  may be conducted through the tube  207  and into and through the tip  201 ,  211 , the filament  206   a , and/or the filament  206   b . The tube  207  may be interconnected to the tip  201 ,  211  such that the lumen  222  is in sealed, fluid communication with the channel through the tip  201 ,  211 . This may be accomplished by a press fit, weld, or any other appropriate method. 
     As noted, the lumen  222  may be in fluid communication with the tip  201 ,  211  at the distal end  202 . A proximal end of the lumen  222  may be disposed at the proximal end  205  of the needle  103 . In this regard, the lumen  222  may extend from the distal end  202  to the proximal end  205 , with the only access being at the distal and proximal ends  202 ,  205 . In some embodiments, the lumen  222  is the only lumen of the needle  103  disposed along the elongate member  203 . 
     The RF probe  401  inserted into the lumen  222  may be positioned such that an end of the RF probe  401  is proximate to the tip  201 ,  211 . For example, the RF probe  401  may be positioned such that the distal end  402  of the RF probe  401  is in the lumen  222  near the tip  201 ,  211  or in the channel through the tip  201 ,  211 . RF energy transmitted through the RF probe  401  may then be conducted by the tip  201 ,  211 , the filament  206   a , and/or the filament  206   b . The size of the lumen  222  may be selected to accommodate a particular size of RF probe  401 . For example, the lumen  222  may be configured to accommodate at least a 22 gauge RF probe  401 , at least a 21 gauge RF probe  401 , or a larger or smaller RF probe  401 . For another example, the lumen  222  may have a maximum cross-sectional dimension of less than about 0.85 mm. 
     The proximal end of the tube  207  may be operable to receive the RF probe  401 . The proximal end of the tube  207  and the actuator  216  may be configured to accept a connector, such as a Luer fitting, such that a fluid source may be connected to the tube  207  (e.g., to deliver fluid through the lumen  222  and out the fluid port  210 ). 
     The needle  103  includes two filaments  206   a ,  206   b  in and along elongate member  203 . Distal ends of the filaments  206   a ,  206   b  are proximate to the tip  201 ,  211 , and proximal ends of the filaments  206   a ,  206   b  are fixed to a filament hub  221  discussed below. The filaments  206   a ,  206   b  are movable along the central longitudinal axis  223  between a fully deployed position as illustrated in  FIGS. 3A, 3C, 3D, and 3F  and a retracted position illustrated in  FIGS. 3B and 3E . Moving the filaments  206   a ,  206   b  distally from the retracted position moves the filaments  206   a ,  206   b  toward the fully deployed position, while moving the filaments  206   a ,  206   b  proximally from the deployed position moves the filaments  206   a ,  206   b  toward the retracted position. The filaments  206   a ,  206   b  may be deployed in intermediate positions between the fully deployed positions and the retracted positions. For example, a mechanism for advancement and/or retraction of the filaments  206   a ,  206   b  may include detents indicating partial deployment and/or retraction and a stop indicating full deployment and/or retraction. 
     In the fully deployed position, the distal ends of the filaments  206   a ,  206   b ,  319   a ,  319   b  are disposed away from the tip  201 ,  211 ,  311 ,  321 . In the retracted position, the distal ends of the filaments  206   a ,  206   b ,  319   a ,  319   b  are entirely within an outer perimeter (e.g., circumference where the body portion  303  of the tip  201 ,  211 ,  311 ,  321  is round) of the tip  201 ,  211 ,  311 ,  321 . In the deployed position, the filaments  206   a ,  206   b ,  319   a ,  319   b  can act as broadcast antennae for the RF probe  401  (e.g., RF energy passes from the RF probe  401  to the tip  201 ,  211 ,  311 ,  321  and to the filaments  206   a ,  206   b ,  319   a ,  319   b , and into a target volume within a patient). In this regard, together, the RF probe  401  inserted into the lumen  222 , the tip  201 ,  211 ,  311 ,  321 , and the filaments  206   a ,  206   b ,  319   a ,  319   b , may form a monopolar electrode for application of RF energy to the target volume. The filaments  206   a ,  206   b ,  319   a ,  319   b  allow the RF energy from the RF probe  401  to be dispersed over a larger volume than would be possible with the tip  201 ,  211 ,  311 ,  321  alone. 
     The filaments  206   a ,  206   b ,  319   a ,  319   b  may be constructed from a material operable to conduct RF energy, e.g., a metal such as stainless steel (e.g., 303 Stainless Steel), Nitinol, or shape memory alloy. The filaments  206   a ,  206   b  may be coated, for example to enhance and/or inhibit their ability to conduct RF energy. The filaments  206   a ,  206   b  may include a lubricious coating to aid in insertion and/or reduce tissue adhesion. 
       FIG. 2E  illustrates an embodiment in which the filaments  206   a ,  206   b  are formed from a single wire  206  that is bent at the proximal end. The distal ends of the filaments  206   a ,  206   b  are shown as bent, which can be the result of deflection upon exit from a tip  201 ,  211 , shape memory, combinations thereof, and the like. Forming the filaments  206   a ,  206   b  from a single wire  206  may provide advantages such as, for example, coherent activation of the filaments  206   a ,  206   b , simultaneous deployment of the filaments  206   a ,  206   b , and/or simultaneous retraction of the filaments  206   a ,  206   b . It will be appreciated that the wire  206  may be a single wire or a plurality of wire segments joined together (e.g., via adhering with conductive epoxy, welding, soldering, combinations thereof, and the like). Other filaments described herein may also be coupled or bent at the proximal end. The filaments  206   a ,  206   b  illustrated in  FIG. 2E  are substantially parallel, and taper outwards before being bent at the proximal end. In some embodiments, the filaments  206   a ,  206   b  are substantially parallel and do not taper out before being bent at the proximal end. In certain such embodiments, the proximal end of the wire  206  is a semi-circle, for example having a radius between about 0.03 inches and about 0.07 inches (approx. between about 0.76 mm and about 1.8 mm), between about 0.04 inches and about 0.06 inches (approx. between about 1 mm and about 1.5 mm), between about 0.05 inches and about 0.055 inches (approx. between about 1.3 mm and about 1.4 mm) (e.g., about 0.052 inches (approx. about 1.32 mm)), combinations thereof, and the like. In some embodiments, the filaments  206   a ,  206   b  are parallel and spaced by a distance between about 0.025 inches and about 0.125 inches (approx. between about 0.64 mm and about 3.2 mm), between about 0.05 inches and about 0.1 inches (approx. between about 1.3 mm and about 2.5 mm) (e.g., about 0.075 inches (approx. about 1.9 mm)), combinations thereof, and the like. In some embodiments, the filaments  206   a ,  206   b  in the elongate member  203  may be braided, wrapped, or twisted together. Such embodiments may increase column strength, providing resistance to buckling and/or bending in the elongate member  203 . In some embodiments, the wire  206  has a diameter between about 0.0025 inches and about 0.04 inches (approx. between about 0.06 mm and about 1 mm), between about 0.005 inches and about 0.025 inches (approx. between about 0.13 mm and about 0.64 mm), between about 0.01 inches and about 0.02 inches (approx. between about 0.25 mm and about 0.5 mm) (e.g., about 0.014 inches (approx. about 0.36 mm)), combinations thereof, and the like. Other diameters are also possible. In some embodiments, the filaments  206   a ,  206   b  each have a diameter between about 0.0025 inches and about 0.04 inches (approx. between about 0.06 mm and about 1 mm), between about 0.005 inches and about 0.025 inches (approx. between about 0.13 mm and about 0.64 mm), between about 0.01 inches and about 0.02 inches (approx. between about 0.25 mm and about 0.5 mm) (e.g., about 0.014 inches (approx. about 0.36 mm)), combinations thereof, and the like. Other diameters are also possible. In some embodiments, the filaments  206   a ,  206  have different diameters (e.g., by being formed from different wires, by being formed from portions of wires with different diameters that are coupled to form the wire  206 , etc.). 
     The distal ends of the filaments may be shaped (e.g., pointed) to improve their ability to move through tissue. For example, the tips of the filaments  206   a ,  206   b  in  FIG. 3A  have an outward-facing bevel. In some embodiments, the bevel is at an angle between about 15° and about 45°, between about 20° and about 40°, between about 25° and about 35° (e.g., about 30°), combinations thereof, and the like. In embodiments in which the filaments  206   a ,  206   b  each have a diameter of about 0.014 inches (approx. about 0.36 mm) and a bevel of about 30°, the length of the bevel is about 0.024 inches (approx. about 0.61 mm). The tips of the filaments  206   a ,  206   b  may have the same shape (e.g., beveled) or different shapes. For another example, the tips of the filaments  206   a ,  206   b  in  FIG. 3D  have an inward-facing bevel. In certain embodiments, bevels (e.g., inward-facing bevels) can help to induce splay between the tips of the filaments  206   a ,  206   b  (e.g., splay of between about 15° and about 20°) by tracking to one side (e.g., away from the beveled side) upon deployment, which can improve placement of the filaments  206   a ,  206   b . For yet another example, the tips of the filaments  319   a ,  319   b  in  FIG. 3G  have a pencil-point. In certain embodiments, a pencil-point tip can help to reduce splay between the tips of the filaments  206   a ,  206   b  by substantially straight tracking deployment, which can improve placement of the filaments  206   a ,  206   b . In some embodiments, the filaments  206   a ,  206   b  comprise materials with different tensile strength and/or rigidity, and the filaments  206   a ,  206   b , which can affect their ability to flex due to contact with tissue and thus the amount of splay, if any. In certain embodiments in which the filaments  206   a ,  206   b  comprise a shape memory material, the deflection to an unconfined state may work with or against the shapes of the tips. In some embodiments, certain filament tips may help to occlude filaments slots, improve interaction with a transition region, etc. Although certain combinations of filament tips are illustrated with respect to certain embodiments herein, the various shapes of the filament tips described herein and otherwise may be selected for any of these embodiments (e.g., the filaments  206   a ,  206   b  of  FIG. 3A  may have inwardly-facing bevels or pencil-point tips, the filaments  206   a ,  206   b  of  FIG. 3D  may have outwardly-facing bevels or pencil-point tips, the filaments  319   a ,  319   b  of  FIG. 3C  may have inwardly-facing bevels or pencil-point tips, the filaments  319   a ,  319   b  of  FIG. 3G  may have inwardly-facing bevels or outwardly-facing bevels, etc.). 
     The positioning of the filaments  206   a ,  206   b  of the embodiments illustrated in  FIGS. 3A and 3D  will now be described in relation to  FIG. 5 .  FIG. 5  is an end view of the tip  201  and deployed filaments  206   a ,  206   b  of the embodiment illustrated in  FIGS. 2A and 3A . The filaments  206   a ,  206   b  are positioned at a filament angle  503  of about 120° apart from each other about the central longitudinal axis  223 . This coincides with the positions of the filament slots  304   a ,  304   b  discussed herein since the filaments  206   a ,  206   b  emerge from the filament slots  304   a ,  304   b . Other filament angles  503  are also possible. For example, the filament angle  503  may be between about 90° and about 180°, between about 90° and about 150°, between about 100° and about 140°, between about 110° and about 130°, combinations thereof, and the like. A filament-free angle  504  of about 240° is defined as the largest angle about the circumference of the tip  201 ,  211  that is free of filaments. In an embodiment consisting of two filaments  206   a ,  206   b , the filament angle  503  may be less than 180° and the filament-free angle  504  may be correspondingly greater than 180° (e.g., greater than 200° or greater than 240°). 
     In  FIG. 5 , the central longitudinal axis  223  is perpendicular to the plane of the illustration. A midpoint  502  is defined between distal ends  501   a ,  501   b  of the filaments  206   a ,  206   b , respectively. The midpoint  502  is offset from the central longitudinal axis  223 . For example, in some embodiments, the midpoint  502  is offset from the central longitudinal axis  223  by about 2 mm. Other offset values are also possible. For example, the offset may be between about 0.5 mm and about 5 mm, between about 1 mm and about 4 mm, between about 1 mm and about 3 mm, greater than about 0.5 mm, less than about 5 mm, combinations thereof, and the like. When RF energy is transmitted from the tip  201  and both of the filaments  206   a ,  206   b , the RF energy will be transmitted asymmetrically with respect to the central longitudinal axis  223  the cause the RF energy will be emitted from the tip  201  and the filaments  206   a ,  206   b . As oriented in  FIG. 5 , the energy will be biased in an upward direction in the direction from the point  301  toward the midpoint  502 . Thus, when RF energy is transmitted during an RF neurotomy procedure, a lesion will be created that is correspondingly offset from the central longitudinal axis  223  in the direction from the point  301  toward the midpoint  502 . 
     Referring again to the asymmetric nature of the lesion, the lesion may be substantially a three-dimensional polygon (e.g., with rounded edges) of known dimensions and volume that is offset from the central cannula in a known and predictable way. Different embodiments may have different three-dimensional polygonal structures adapted to the intended ablation target. By contrast, needles without deployable filaments may be used to create asymmetric planar lesions by varying needle insertion during the ablation procedure, and may require substantial ablation volume overlap. 
       FIG. 6  is a side view of the tip  201  and the filaments  206   a ,  206   b , oriented such that the deployed filament  206   b  is entirely within the plane of the figure. The filaments  206   a ,  206   b  extend from the tip  201  at a common distance, or location, along the central longitudinal axis  223 . In some embodiments, the filaments  206   a ,  206   b  may extend different distances. The filament  206   b  is deflected radially outwardly from the central longitudinal axis  223 . The filament  206   b  emerges from the tip  201  at an angle  601  of about 30° from the central longitudinal axis  223 , which is parallel to the longitudinal axis of the elongate member  203 . The angle  601  may vary, for example, based at least partially on positioning of a transition region  305 , mechanical properties of the filament  206   b  (e.g., shape-memory properties or lack thereof), and the like. In some embodiments, the angle  601  is between about 5° and about 85°, between about 10° and about 60°, between about 20° and about 40°, greater than about 5°, less than about 85°, combinations thereof, and the like. In some embodiments, the angle  601  is related to the angle  503 . For example, the angle  601  may be a fraction of the angle  503 , such as about ¼. In some embodiments, the angle  601  is unrelated to the angle  503 , for example both being independently chosen to produce a certain lesion size or shape. In some embodiments, the distal tips  501   a ,  501   b  are positioned distally beyond the point  301  by a distance  602 , are disposed at a distance  603  from the central longitudinal axis  223 , and/or are disposed at a distance  604  from each other. In some embodiments, the distance  602  is about 3.5 mm, the distance  603  is about 3 mm, and/or the distance  604  is about 4.5 mm. Other distances are also possible. For example, in some embodiments, the distance  602  is between about 0.5 mm and about 6 mm, between about 1 mm and about 5 mm, between about 3 mm and about 4 mm, combinations thereof, and the like. Other distances are also possible. For another example, in some embodiments, the distance  603  is between about 0.5 mm and about 6 mm, between about 1 mm and about 5 mm, between about 2 mm and about 4 mm, combinations thereof, and the like. Other distances are also possible. For yet another example, in some embodiments, the distance  604  is between about 2 mm and about 7 mm, between about 3 mm and about 6 mm, between about 4 mm and about 5 mm, combinations thereof, and the like. Other distances are also possible. 
     The angles described herein (e.g., the angles  503 ,  601 ) may be measured with respect to a needle  103  in a deployed state outside of a patient&#39;s body, and that the angles may when the needle is inside a patient&#39;s body, for example based at least in part on splay of filaments due to beveling. 
     The tip  211  and deployed filaments  206   a ,  206   b  of the embodiment illustrated in  FIG. 3D  may also have a filament angle  503 , a filament-free angle  504 , a midpoint  502 , an angle  601 , distances  602 ,  603 ,  604 , and other features described herein, for example with respect to  FIGS. 5 and 6 . In some embodiments, the portion of the lesion based at least partially on RF energy emitted by the tip  211 , and thus the shape of the lesion, may vary based on the position of the point  301  (e.g., in  FIG. 3 d   , the point  301  is on the side of the tip  211  that comprises the filaments  206   a ,  206   b ). 
     The configuration of the filaments  206   a ,  206   b  illustrated in  FIGS. 2A, 3A, 3D, 5, and 6  may be operable to produce lesions that are radially offset from the central longitudinal axis  223  and distally offset from the point  301  as compared to a lesion created by the tip  201 ,  211  without the filaments or a lesion created with the needle  103  with the filaments  206   a ,  206   b  in the retracted position. 
     Variations in the relative shapes, positions, and sizes of lesions created with the needle may be achieved by repositioning the filaments. For example, as noted herein, the lesion produced by the needle will be in different positions depending on whether the filaments are in the deployed or retracted positions. Lesions having intermediate shapes, positions, and/or sizes may be achieved by positioning the filaments in intermediate positions between the fully deployed (e.g., as illustrated in  FIGS. 3A, 3C, 3D, and 3G ) and fully retracted positions (e.g., as illustrated in  FIGS. 3B and 3E ). As noted herein, the needle with deployed filaments is operable to produce larger lesion volumes than the needle with retracted filaments. For example, the needle with fully deployed filaments may be operable to produce lesion volumes of about 500 mm 3 . Other lesion volumes are also possible. For example, the needle with fully deployed filaments may be operable to produce lesion volumes between about 100 mm 3  and about 2,000 mm 3 , between about 200 mm 3  and about 1,000 mm 3 , between about 250 mm 3  and about 750 mm 3 , between about 400 mm 3  and about 600 mm 3 , combinations thereof, and the like. 
     Further variation in the shape, position, and/or size of lesions created by needles with deployable filaments may be achieved by different configurations of filaments. Variations may include, for example, variations in materials, the number of filaments, the radial positioning of the filaments, the axial positioning of the filaments, the length of the filaments, the angle at which the filaments exit the tip, the shape of the filaments, etc. By varying these parameters, the needle may be configured to produce lesions of various sizes and shapes that are positioned at various locations relative to the tip. Such variations may be specifically tailored to be used in specific procedures, such as RF neurotomy procedures of particular nerves adjacent to particular vertebrae. 
     Variations of the materials used for the tip and/or the filaments may be selected to achieve particular lesion sizes, positions, and/or shapes. For example, the tip may comprise (e.g., be made form) a material that does not conduct RF energy, in which case RF energy from the RF probe  401  may be conducted by substantially only the deployed filaments. In certain such embodiments, emitting RF energy from the filaments may provide for a lesion with a larger offset from the central longitudinal axis  223  than would be produced if the tip conducts RF energy and acts as an electrode along with the filaments. 
     Another material-related variation that may affect lesion shape, size, and/or position is the addition and placement of insulation over the tip and/or over the filaments. For example, by placing a layer of insulation over a proximal part of the portions of the filaments that extend from the tip when in the deployed position, the shape of the lesion may be altered since RF energy may primarily emanate from the distal, non-insulated part of the filaments. For another example, by placing a layer of insulation over a proximal part of the tip, the shape of the lesion may be altered since RF energy may primarily emanate from the distal, non-insulated part of the tip. Other parts of the filaments and/or tip may also be covered by an insulating material, for example a distal part of the filaments and/or tip, an intermediate part of the filaments and/or tip, combinations thereof, and the like, for example as described with respect to  FIGS. 3H and 3I . 
     Moreover, the materials used in making the filaments and tip may be selected based on RF conductivity. For example, by using a material for the tip that is less conductive of RF energy, the proportion of RF energy emanating from the tip as compared to that emanating from the filaments may be altered resulting in a corresponding change in lesion size, position and/or shape. 
     The RF needles and RF probes discussed herein may be constructed from materials that are Magnetic Resonance Imaging (MRI) compatible (e.g., titanium, aluminum, copper, platinum, non-magnetic 300 Series Stainless Steel, etc.). In certain such embodiments, MRI equipment may be used to verify the positioning of the needles and/or portions thereof and/or monitor the progress of an ablation procedure (e.g., RF neurotomy). 
     Variations of the number of filaments used for needle may be selected to achieve particular lesion sizes, positions and/or shapes. For example, as illustrated in  FIG. 7 , a third filament  701  may extend from the tip  201 ′ (or other tips described herein such as the tip  211 ) in a position between filaments  206   a ,  206   b . The tips  501   a ,  501   b  of the filaments  206   a ,  206   b  and a tip  702  of filament  701  may form a polygon  703  that has a centroid  704 . The centroid  704  is offset from the central longitudinal axis  223 . Such an arrangement may produce a lesion that is offset from the central longitudinal axis  223  to a different degree than, and shaped differently than, a lesion created by the needle of  FIG. 5 . In general, where a centroid of a polygon formed by the tips of filaments (or, in the case where there are two filaments, the midpoint between them) is offset from the central longitudinal axis  223 , a lesion created by such a configuration will be correspondingly offset from the central longitudinal axis  223 . The filaments  206   a ,  206   b ,  702  are positioned at the same filament angle  503  of about 120° as in the embodiment of  FIG. 5 . Other filament angles  503 , in either  FIG. 5  or  FIG. 7 , are also possible. The embodiment illustrated in  FIG. 7  has a filament-free angle  504  of about 240°, also the same as in the embodiment of  FIG. 5 . Other filament-free angles  504 , in either  FIG. 5  or  FIG. 7 , are also possible. In general, in embodiments in which the filaments are positioned in a filament angle  503  that is less than about 180°, resultant lesions will be offset from the central longitudinal axis  223  in the direction of the filaments. In embodiments in which the filaments are positioned in a filament angle  503  that is less than about 180°, the filament-free angle is correspondingly greater than about 180° (e.g., greater than about 200° or greater than about 240°). 
     For another example, as illustrated in  FIG. 8 , four filaments  801   a - 801   d  are positioned about a tip  201 ″ (or other tips described herein such as the tip  211 ). The tips of the filaments  801   a - 801   d  may form a polygon  802  that has a centroid  803 . The centroid  803  is offset from the central longitudinal axis  223 . Such an arrangement may produce a lesion that is offset from the central longitudinal axis  223  in the direction of the centroid  803 . The filaments  801   a - 801   d  are positioned at a filament angle  804  of about 200°. Other filament angles  804  are also possible. The embodiment illustrated in  FIG. 8  has a filament-free angle  805  of about 160°. Other filament-free angles  805  are also possible.  FIG. 8  illustrates an embodiment in which the filament-free angle  805  is less than about 180°, but which is capable of producing a lesion offset from the central longitudinal axis  223 . 
     In the herein-described embodiment of  FIGS. 2A, 3A, 3B, 5, and 6  with two filaments, a midpoint  502  between the filaments was discussed. In embodiments with more than two filaments, a centroid of a polygon formed by the distal ends of the filaments was discussed. Both the midpoints and the centroids may be considered to be “average” points of the filaments for their particular configurations. In such embodiments, the midpoint between filaments in two-filament embodiments and the centroid of the polygon in embodiments with more than two filaments may be offset from the central longitudinal axis of the elongate member. For example, the midpoint or centroid may be offset from the central longitudinal axis by 1 mm or more. In embodiments, the polygon may lie in a plane perpendicular to the central longitudinal axis. 
     As illustrated in, for example,  FIGS. 2A, 2D, 3A, 3C, 3D, 3G-3I, 5, 7, 8, 9, and 10 , the distal ends of the filaments when fully deployed may be in a common plane. In some embodiments, the common plane is perpendicular or transverse to the central longitudinal axis. In some embodiments, the common plane is distal to the point  301 ,  312 . 
     As illustrated in, for example,  FIGS. 2A, 2D, 3A, 3C, 3D, 3G-3I, 5, 7 , and  10 , the filaments of the needle may all be deployed on a common side of a central plane of the needle (where the central longitudinal axis is entirely within the central plane). In certain such embodiments, the distal ends of the filaments are all on a common side of the central plane. Such a configuration may enable the needle to be used to create a lesion that is offset from the tip of the needle to the same side of the central plane as the deployed filament ends. 
     As illustrated, for example, in  FIGS. 2A, 2D, 3A, 3C, 3D, 3G-3I, and 10 , the filaments when fully deployed may point in an at least partially distal direction. In this regard, a vector extending longitudinally from the distal end of a filament and coinciding with a central axis of the portion of the filament out of the tip  211  has at least some distal component. The fully deployed filaments in the embodiments illustrated in  FIGS. 2A, 2D, 3A, 3C, 3D, 3G-3I, and 10  all point in an at least partially distal direction. 
       FIG. 9  illustrates an embodiment in which the filaments are uniformly distributed about the circumference of the tip  201 ″″. The needle of  FIG. 9  includes three filaments  901   a ,  901   b ,  901   c  distributed substantially equally about the circumference of the tip  201 ″″, the angles  902   a ,  902   b ,  902   c  between the filaments  901   a ,  901   b ,  901   c  each being about 120°. Such a needle may be operable to produce a lesion that is generally centered along the central longitudinal axis  223 . However, the position of the produced lesion longitudinally along the central longitudinal axis  223  may be determined by the configuration (e.g., length, deployment angle, etc.) of the filaments. For example, relatively longer filaments may be operable to produce lesions that are positioned distal to lesions produced by configurations with relatively shorter filaments. For another example, in an embodiment in which the filament  901   b  is longer than the filaments  901   a ,  901   c , the needle may be operable to create a lesion that is offset from the tip of the needle towards the filament  901   b . For yet another example, in an embodiment in which the filaments  901   a ,  901   b  are longer than the filament  901   c , the needle may be operable to create a lesion that is offset from the tip of the needle towards the filaments  901   a ,  901   b.    
     Referring again to  FIG. 7 , if the filament  701  was distal to the filaments  206   a ,  206   b , the resultant lesion may be longer along the central longitudinal axis  223  than lesions resulting from an embodiment in which the filaments  206   a ,  206   b ,  701  are each positioned along substantially the same plane perpendicular or transverse to the central longitudinal axis  223 . In another variation, as deployed, two or more filaments may be at the same radial position and at different axial positions. Such embodiments may include multiple rows of filaments. 
     Referring again to  FIGS. 5 and 6 , if the lengths of the deployed portions of the filaments  206   a ,  206   b  were increased, the needle may be capable of producing lesions that are more distally positioned than lesions created by the embodiment as shown in FIGS.  5  and  6 . The effects of lengthening or shortening the deployed length of the filaments may be similar to those discussed herein with respect to partially deploying filaments. 
     In some embodiments, the needle includes filaments having deployed portions with different lengths. In certain embodiments in which all of the filaments are deployed and/or retracted by a common actuator and/or are part of the same wire, variations in filament lengths may be achieved by varying the overall length of the filaments. For example, the distal end of a shorter filament may be retracted further into the tip or elongate member than the distal end of a longer filament. The effects of lengthening or shortening the length of the deployed portions of the filaments may be similar to those discussed herein with respect to variations in the axial positioning of filaments emergence from the tip of the needle and/or with respect to partially deploying filaments. 
     The angle at which a filament exits a tip (e.g., the angle  601  of  FIG. 6 ) may be varied to achieve particular lesion sizes, positions, and/or shapes. For example, if the angle  601  in  FIG. 6  was about 60°, the needle may be operable to produce a lesion that has a larger maximum cross-sectional dimension in a plane perpendicular to the central longitudinal axis  223  than if the angle  601  was about 30°, for example because the filaments can emanate RF energy at a distance further away from the central longitudinal axis. In some embodiments, the filaments can be deployed at different angles  601  relative to the central longitudinal axis  223 . 
     Referring again to  FIG. 10 , the deployed portions of the filaments  1001   a ,  1001   b  may be curved. As described herein, the term “curved” may mean a continuous curve, a curve in combination with a straight section, a plurality of curves in different directions, combinations thereof, and the like. Such curvatures may be achieved, for example, by filaments  1001   a ,  1001   b  comprising shape memory material (e.g., Nitinol) or spring material. When the filaments  1001   a ,  1001   b  are retracted, the shape of the tip  201  and/or the elongate member  203  may cause the filaments  1001   a ,  1001   b  to be in constrained straightened configurations. As the filaments  1001   a ,  1001   b  are advanced toward the fully deployed position, they become unconstrained and return to their curved shapes as shown in  FIG. 10 . The deployed shape of the filaments  1001   a ,  1001   b  may be predetermined, or the filaments  1001   a ,  1001   b  may comprise (e.g., be made from) a material that may be shaped by a user prior to insertion. The filaments of other embodiments described herein (e.g., FIGS.  3 A,  3 C,  3 D, and  3 G- 3 I) may also be curved. In some embodiments, one filament is curved and one filament is straight. 
     The curved filaments  1001   a ,  1001   b  of  FIG. 10  are positioned in planes that include the central longitudinal axis  223 . In other embodiments, the filaments  1001   a ,  1001   b  may be curved in other directions, such as in a corkscrew arrangement. This may be beneficial to assist the filaments in remaining anchored to the tissue during delivery of RF energy. The curved filaments  1001   a ,  1001   b  of  FIG. 10  may be operable to produce a lesion that is flatter in a plane perpendicular to the central longitudinal axis  223  than, for example, the straight filaments  206   a ,  206   b  of  FIG. 6 . 
     In the embodiment illustrated in  FIGS. 2A and 2B , the filaments  206   a ,  206   b  are illustrated as running the entire length of the elongate member  203  from the filament hub  221  to the tip  201 . In some embodiments, a single member may run along at least part of the elongate member  203  and the filaments  206   a ,  206   b  may be interconnected to the single member at a point proximal to the tip  201 . 
     The illustrated embodiments show all of the filaments of a given embodiment as commonly deployed or retracted. In some embodiments, one or more filaments may be individually deployed and/or retracted. In some embodiments, a plurality of filaments may exit from the tip at a common location and form a fan-like arrangement as they are deployed. 
     Deployment of filaments discussed herein has been described as movement of the filaments relative to a stationary tip. In some embodiments, the filaments may be deployed by pulling the tip back relative to the filaments (e.g., movement of the tip relative to stationary filaments). Movement of the tip rather than the filaments may be advantageous, for example, in embodiments in which the needle is initially advanced until in contact with bone to ensure proper positioning relative to target tissue, and then the tip may be retracted, leaving the filaments (e.g., curved shape memory filaments) in a precise, known position. In some embodiments, the filaments may be deployed by advancing the filaments and retracting the tip. 
     Referring again to  FIGS. 2A and 2B , the hub  204  may be fixedly attached to the elongate member  203 . The hub  204  may be the primary portion of the needle  103  gripped by the user during insertion and manipulation of the needle  103 . The hub  204  may include an asymmetric feature, such as an indicator  225 , that is in a known orientation relative to the asymmetry of the tip  201 . In this regard, the indicator  225  may be used to communicate to the user the orientation of the tip  201  within a patient. For example, in the embodiment illustrated in  FIG. 2A , the indicator  225  is fixed at an orientation circumferentially opposite to the filament slots  304   a ,  304   b . Internally, the hub  204  may include a cavity  213  sized to house a longitudinal protrusion  218  of the actuator  216 . The hub  204  may include a hole through which a projection  215  may project into the interior of the cavity  213  to control the motion of the actuator  216  relative to the hub  204  and to secure the actuator  216  to the hub  204 . The hub  204  may comprise (e.g., be made from) any appropriate material (e.g., a thermoset plastic, Makrolon® 2548, available from Bayer). 
     The actuator  216  may be used to control the motion to deploy and/or retract the filaments  206   a ,  206   b . The actuator  216  is operable to move relative to the hub  204 , the elongate member  203 , and the tip  201  (e.g., parallel to the central longitudinal axis  223 ). The actuator  216  includes the longitudinal protrusion  218  extending into the cavity  213  of the hub  204 . The outer surface of the longitudinal protrusion  218  includes a helical track  219  sized to accommodate the projection  215 . In this regard, as the actuator is rotated relative to the hub  204  (e.g., by a user to deploy the filaments  206   a ,  206   b ), the helical track  219  and the projection  215  combine to cause the actuator  216  to move longitudinally (e.g., parallel to the central longitudinal axis  223 ). The actuator  216  comprises an interface portion  217  that may be gripped by a user when rotating the actuator  216 . The interface portion  217  may be knurled or otherwise textured to enhance the user&#39;s ability to rotate the actuator  216 . The hub  204  may also include a textured or shaped feature (e.g., the indicator  225 ) configured to enhance the user&#39;s ability to rotate the actuator  216  relative to the hub  204 . The longitudinal protrusion  218  of the actuator  216  may include an inner cavity  226  sized to accept a filament hub  221  and to allow the filament hub  221  to rotate freely relative to the actuator  216 . In this regard, the linear motion of the actuator  216  may be transmitted to the filament hub  221  while the rotational motion of the actuator  216  may not be transmitted to the filament hub  221 . 
     The actuator  216  may include a Luer fitting  220  or any other appropriate fitting type on a proximal end thereof. The Luer fitting  220  may be in fluid communication with the lumen  222  and provide a connection such that fluid may be delivered into the lumen  222  and to the fluid port  210  of the tip  201 ,  211 . The Luer fitting  220  may also be configured to allow for the insertion of the RF probe  401  into the lumen  222 . The actuator  216  may comprise any appropriate material (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). 
     The filaments  206   a ,  206   b  may be fixedly interconnected to the filament hub  221 . In this regard, the longitudinal movement of the filament hub  221  due to the actuator  216  may be communicated to the filaments  206   a ,  206   b  to deploy and retract the filaments  206   a ,  206   b  upon rotation of the actuator  216 . The filament hub  221  may comprise any appropriate material (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). 
     The user can deploy or retract the filaments  206   a ,  206   b  by twisting or rotating the actuator  216 . For example, as illustrated, a counterclockwise (as seen from the viewpoint of  FIG. 5 ) rotation of the actuator  216  relative to the hub  204  will result in the deployment (extension) of the filaments  206   a ,  206   b , while a clockwise rotation of the actuator  216  relative to the hub  204  will result in the retraction of the filaments  206   a ,  206   b.    
     The filaments  206   a ,  206   b  may be partially deployed or retracted by partially rotating the actuator  216  relative to the hub  204 . The actuator  216  and/or the hub  204  may include markings to indicate the position of the filaments  206   a ,  206   b  (e.g., the depth or extent of deployment). The actuator  216  and/or the hub  204  may include detents to provide audible and/or tactile feedback of the position of the filaments  206   a ,  206   b.    
     In some embodiments, the filaments may be deployed at the user&#39;s discretion to a deployed position proximal to, at, or distal to a plane perpendicular or transverse to the central longitudinal axis  223  at the point  301 ,  312 . For example, in some embodiments, full (e.g., 3/3) rotation of the actuator  216  may deploy the filaments in a fully deployed position that is distal to a plane perpendicular or transverse to the central longitudinal axis  223  at the point  301 ,  312 , partial (e.g., ⅔) rotation of the actuator  216  may deploy the filaments in a partially deployed position that is at a plane perpendicular or transverse to the central longitudinal axis  223  at the point  301 ,  312 , and partial (e.g., ⅓) rotation of the actuator  216  may deploy the filaments in a partially deployed position that is proximal to a plane perpendicular or transverse to the central longitudinal axis  223  at the point  301 ,  312 . The actuator  216  and/or the hub  204  may include features such as stops or detents to provide audible and/or tactile feedback regarding the extent of deployment (e.g., at 0/3, ⅓, ⅔, and 3/3) and/or the position of the filaments  206   a ,  206   b  (e.g., fully retracted, ⅓ deployed, ⅔ deployed, and fully deployed). Other fractions are also possible, including fractions at uneven intervals (e.g., a combination of ⅓, ½, and ⅘). In certain embodiments, selectable controlled partial deployment allows for controlled adaptation of the lesion to any particular shape and/or conformance of the filaments to a specific anatomy (e.g., boney anatomy). 
       FIGS. 17A-17E  illustrate components of the mechanism at the proximal end  205  of the needle  103  of  FIG. 2D . The mechanism may also be used, for example, with the needle  103  of  FIG. 2A  and other needles described herein. The components described with respect to  FIGS. 17A-17E  may include features described herein with respect to  FIGS. 2B and 2C , and the components described herein, for example with respect to  FIGS. 2B and 2C  may include features described herein with respect to  FIGS. 17A-17E . Combinations of components are also possible. 
       FIG. 17A  is an exploded view of components of the deployment mechanism of  FIG. 2D . The mechanism comprises an advancing hub or slide member  1710 , a spin collar or actuator  1720 , and a main hub  1730 .  FIG. 17B  is a cross-sectional view of the advancing hub  1710 , the spin collar  1720 , and the main hub  1730  assembled together, as well as half of the wire  206  illustrated in  FIG. 2E . The advancing hub  1710  includes a stem or longitudinal protrusion  1712 . The spin collar  1720  includes a lumen  1721  extending from the proximal end to the distal end. The main hub  1730  includes a lumen  1731  extending from the proximal end to the distal end. When assembled, the stem  1712  of the advancing hub  1710  is in the lumen  1721  of the spin collar  1720  and in the lumen  1731  of the main hub  1730 . The advancing hub  1710  may include an annular protrusion  1714  that may interact with an annular protrusion of the spin collar  1720  (e.g., the annular protrusion  1714  having a larger diameter than the annular protrusion  1724 ) to inhibit the stem  1712  from exiting the proximal end of the lumen  1721 . In some embodiments, the annular protrusions  1714 ,  1724  include tapered surfaces that may interact to allow insertion of the stem  1712  and the annular protrusion  1714  into the lumen  1721  and perpendicular surfaces to inhibit the annular protrusion  1714  and the stem  1712  from exiting the proximal end of the lumen  1721 . The main hub  1730  includes a stem or longitudinal protrusion  1734 . When assembled, the stem  1734  of the main hub  1730  is in the lumen  1721  of the spin collar  1720 . Other interactions between the advancing hub  1710 , the spin collar  1720 , and the main hub  1730  are described herein, for example with respect to  FIGS. 17C-17E . 
       FIG. 17C  is a perspective view of an example embodiment of the advancing hub  1710  and the wire  206  of  FIG. 2E . The stem  1712  of the advancing hub  1710  comprises a U-shaped recess  1713  configured to interact with the bent proximal portion of the wire  206 . Other shapes of the recess  1713  are also possible (e.g., V-shaped). The recess  1713  may complement the shape of the proximal end of the wire  206 . In some embodiments, the width of the recess  1713  is slightly smaller (e.g., about 0.001 inches (approx. about 0.025 mm) smaller) than the diameter of the wire  206  such that after being press-fit, the wire  206  is fixedly interconnected to the advancing hub  1710 . 
     In some embodiments, the stem  1712  is shaped as illustrated in  FIG. 17C , including a perpendicular or transverse cross-section that includes flat surfaces (e.g., the surface comprising the top of the recess  1713 ) and arcuate surfaces, for example an ellipse with squared ends. The lumen  1731  of the main hub  1730  may comprise complementary surfaces, for example in a wider proximal portion, such that when the stem  1712  is in the lumen  1731 , the advancing hub  1710  is in a fixed rotational position relative to the main hub  1710 . Other shapes and rotational fixation configurations are also possible. 
     The proximal end of the advancing hub  1710  comprises a fitting  220  (e.g., a Luer fitting or any other appropriate fitting). When assembled, the fitting  220  is proximal to the spin collar  1720 . The advancing hub  1710  comprises a lumen  1711  extending from the proximal end to the distal end. A fluid delivery device such as a syringe may be attached to the fitting  220  to deliver fluid through the lumen  1711  and then through the lumen  1731  of the main hub, the lumen  308  of the elongate member  203 , the lumen  306   c  of the tip  211 , and out the fluid port  210  of the tip  211 . The RF probe  401  may be inserted into the lumen  1711 , then into the lumen  1731  of the main hub, then into the lumen  308  of the elongate member  203 , then into the lumen  306   c  of the tip  211 . The RF probe  401  may include a fitting configured to interact with the fitting  220 . The lumen  1711  may include a wide diameter portion in the area of the fitting  220  and a narrow diameter portion in the area of the stem  1712 , and a tapered surface  1715  transitioning from the wide diameter portion to the narrow diameter portion. The tapered surface  1715  may help direct fluid and/or an RF probe  401  into the narrow diameter portion. In some embodiments, the narrow diameter portion of the lumen  1711  has a diameter between about 0.005 inches and about 0.05 inches (approx. between about 0.13 mm and about 1.3 mm), between about 0.01 inches and about 0.03 inches (approx. between about 0.25 mm and about 0.76 mm), between about 0.015 inches and about 0.025 inches (approx. between about 0.38 mm and about 0.64 mm) (e.g., about 0.02 inches (approx. about 0.5 mm)), combinations thereof, and the like. In some embodiments, the narrow diameter portion of the lumen  1711  has a diameter that is no larger than the diameter of any other lumen of the needle  103  such that fluid pressure will default to the distal end of the needle  103 . For example, the narrow diameter portion of the lumen  1711  may have a diameter of about 0.02 inches (approx. about 0.5 mm), the narrow diameter portion of the lumen  1731  may have a diameter of about 0.05 inches (approx. about 1.3 mm), the lumen  308  of the elongate member  203  may have a diameter of about 0.05 inches (approx. about 1.3 mm), and the lumen  306   c  may have a width of about 0.02 inches (approx. about 0.5 mm). In some embodiments, the lumen  306   c  may be slightly smaller than the narrow diameter portion of the lumen  1711  and have the same effect, for example due to small losses of fluid through the lumens  306   a ,  306   b  and out the filament ports  304   a ,  304   b , which may be acceptable because anesthesia and dye, for example, may permeate through fluid and proximate to the filament ports  304   a ,  304   b  even if substantially only dispensed from the fluid port  210 . In some embodiments, the advancing hub  1710  comprises a polymer (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). 
       FIG. 17D  is a cross-sectional view of an example embodiment of a spin collar  1720 . The cross-section is along the same line as in  FIG. 17B , but further features are visible because not blocked by the advancing hub  1710  or the main hub  1730 . As illustrated in  FIG. 17B , the lumen  1721  is configured to at least partially contain the stem  1712  and the stem  1734 , and not to contact fluid or an RF probe  401 . The lumen  1721  comprises a helical track  1722  sized to interact with a corresponding helical thread  1735  ( FIG. 17A ) on the stem  1734  of the main hub  1730 . As the spin collar  1720  is rotated relative to the main hub  1730  (e.g., by a user stabilizing the needle and gripping the main hub  1730  with the non-dominant hand and manipulating the spin collar  1720  with the dominant hand), for example, to deploy the filaments  206   a ,  206   b , the helical track  1722  and the helical thread  1735  interact to cause the spin collar  1720  and the advancing hub  1710  to move longitudinally parallel to the central longitudinal axis  223 . In this regard, a linear motion of the advancing hub  1710  relative to the main hub  1730  may be created while the rotational motion of the spin collar  1720  may not be transmitted to the advancing hub  1710  and the main hub  1730 . In some embodiments, between about 1.25 turns and about 1.5 turns of the spin collar  1720  fully deploys the filaments  206   a ,  206   b . In some embodiments, between about 0.75 turns and about 1.25 turns (e.g., one 360° rotation) of the spin collar  1720  fully deploys the filaments  206   a ,  206   b . The configuration of the helical track  1722  and the helical thread  1735  may be adjusted to provide varying levels of filament deployment with varying levels of rotation of the spin collar  1720 . An outer surface of the spin collar  1720  may be textured or include features  1723  to assist the user in gripping and twisting or rotating the spin collar  1720  relative to the main hub  1730 . In some embodiments, the spin collar comprises the helical thread  1735  and the main hub  1730  comprises the helical track  1722 . In some embodiments, the spin collar  1720  comprises a polymer (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). 
       FIG. 17E  is a cross-sectional view of an example embodiment of the main hub  1730 , taken along the line  17 E- 17 E of  FIG. 17B , in exploded view with an example embodiment of an elongate member  203 . The proximal end of the elongate member  203 , to the right in  FIG. 17E , includes a partial circumferential portion  1736 . The distal end lumen  1731  of the main hub  1730  includes a complementary partial circumferential portion  1737 . The partial circumferential portions  1736 ,  1737  can cause the elongate member  203  to be in a fixed and known rotational orientation with the main hub  1730 , for example after assembly because the relative position of the indicator  1733  and the partial circumferential portion  1737  is known. For example, the distal end of the elongate member  203 , to the left in  FIG. 17E , includes the filament ports  304   a ,  304   b  on the same side as the partial circumferential portion  1736 . Other partial circumferential portions and other complementary shapes are also possible. For example, the partial circumferential portions may comprise interlocking teeth. In some embodiments, the thickness of the partial circumferential portion  1737  is substantially the same as the thickness of the walls of the elongate member  1736  to provide a smooth transition between the lumen  1731  and the lumen  308 . In some embodiments, the main hub  1730  comprises clear polycarbonate (e.g., thermoset plastic such as Makrolon® 2548, available from Bayer). In some embodiments, the elongate member comprises a hypotube (e.g., comprising 300 Series Stainless Steel) with features such as the filament ports  304   a ,  304   b  and the partial circumferential portion  1736  cut out (e.g., by laser, mechanical, chemical, or other cutting methods). 
     Other types of mechanisms may be used to control deployment and retraction of the filaments. For example, in some embodiments, the mechanism includes a spring configured to bias the filaments  206   a ,  206   b  toward a predetermined position (e.g., fully deployed, fully retracted), analogous to a spring loaded mechanism used in retractable ballpoint pens. For another example, the mechanism may include a roller wheel, for example incorporated into the hub  204 , that would advance or retract the filaments  206   a ,  206   b  upon rotation, for example with a user&#39;s thumb. For yet another example, the hub  204  and the actuator  216  may interact via complimentary threaded features. As the actuator  216  is threaded into the hub  204 , the filaments  206   a ,  206   b  would advance, and as the actuator  216  is threaded out of the hub  204 , the filaments  206   a ,  206   b  would retract. For still another example, a Touhy-Borst type mechanism could be incorporated to control the deployment and retraction of the filaments  206   a ,  206   b . Any other appropriate mechanism for controlling linear motion of the filaments  206   a ,  206   b  may be incorporated into the needle  103 . Any of the mechanisms described herein may be used for controlling deployment and retraction of the filaments of any of the embodiments described herein. For example, the mechanisms illustrated in  FIGS. 2A-2D and 17A-17E  may be used to deploy and retract the filaments in  FIGS. 3A, 3C, 3D, 3G-3I, and 5-10 . 
       FIG. 2C  is a partial cut away and partial cross-sectional view of a portion of an alternate embodiment of a mechanism  230  comprising a hub  231  and actuator  232  that may be part of a needle  103  used in an RF neurotomy procedure. The hub  231  may be fixedly attached to the elongate member  203 . The hub  231  may be the primary portion of the needle  103  gripped by the user during insertion and manipulation of the needle  103 . The hub  231  may include an asymmetric feature, such as an indicator  233 , that is in an known orientation relative to the asymmetry of the tip  201 . In this regard, the indicator  233  may be used to communicate to the user the orientation of the tip  201  within a patient. Internally, the hub  231  may include a cavity  234  sized to house a longitudinal protrusion  235  of a slide member  236 . The longitudinal protrusion  235  may include a keyway or key slot  237  that may run along a longitudinal direction of the longitudinal protrusion  235 . The internal surface of the hub  231  through which the longitudinal protrusion  235  moves may include a mating key (not shown) configured to fit and slide in the key slot  237 . Together, the key slot  237  and mating key of the hub  231  may limit the slide member  236  to a linear motion parallel to the central longitudinal axis  223 . 
     The filaments  206   a ,  206   b  may be fixedly connected to the longitudinal protrusion  235  of the slide member  236  for longitudinal movement therewith. In this regard, distal movement (e.g., movement to the right as shown in  FIG. 2C ) of the longitudinal protrusion  235  relative to the hub  231  may cause extension of the filaments  206   a ,  206   b  relative to the hub  231 , the elongate member  203 , and the tip  201 . For example, distal movement of the longitudinal protrusion  235  may move the filaments  206   a ,  206   b  from a retracted position to a deployed position. For another example, proximal movement (e.g., movement to the left as shown in  FIG. 2C ) of the longitudinal protrusion  235  relative to the hub  231  may result in retraction of the filaments  206   a ,  206   b  relative to the hub  231 , the elongate member  203 , and the tip  201 . 
     The hub  231  may be made from any appropriate material (e.g., a thermoset plastic, Makrolon® 2548, available from Bayer). The hub  231  may be at least partially transparent such that the position of the longitudinal protrusion  235  and/or other components of the hub  231  may be observable by a user. The hub  231  may further include demarcations (e.g., molded or printed marks) such that the amount of extension of the filaments  206   a ,  206   b  may be determined from the position of the longitudinal protrusion  235  and/or other components relative to the demarcations. 
     An actuator  232  may be used to control the motion to deploy and/or retract the filaments  206   a ,  206   b  fixedly connected to the longitudinal protrusion  235 . The actuator  232  may be generally tubular such that it fits around a longitudinal hub projection  238  projecting from the proximal end of the hub  231 . At least a portion of the cavity  234  may be in the longitudinal hub projection  238 . The actuator  232  may also include an annular feature  239  configured to fit in an annular slot  240  in the slide member  236 . The annular feature  239  may be sized relative to the annular slot  240  such that the actuator  232  may rotate relative to the slide member  236  about the central longitudinal axis  223  or an axis parallel thereto while the position of the actuator  232  relative to the slide member  236  along the central longitudinal axis  223  remains fixed. In this regard, the actuator  232  and the slide member  236  may be configured to move in tandem relation along the central longitudinal axis  223 . The annular feature  239  and annular slot  240  may be configured such that, during assembly, the actuator  232  may be pressed onto the slide member  236  and the annular feature  239  may snap into the annular slot  240 . 
     The inner surface of the actuator  232  may include a helical track  241  sized to accommodate a corresponding mating helical thread  242  on the longitudinal hub projection  238 . In this regard, as the actuator  232  is rotated relative to the slide member  236  and the hub  231  (e.g., by a user to deploy the filaments  206   a ,  206   b ), the helical track  241  and the helical thread  242  interact to cause the actuator  232  and the slide member  236  to move longitudinally along the central longitudinal axis  223 . In this regard, a linear motion of the slide member  236  relative to the hub  231  may be created while the rotational motion of the actuator  232  may not be transmitted to the slide member  236  and the hub  231 . An outer surface of the actuator  232  may be textured or include features to assist the user in gripping and twisting or rotating the actuator  232  relative to the hub  231 . In some embodiments, the longitudinal hub projection  238  comprises the helical track  241  and the inner surface of the actuator  232  comprises the helical thread  242 . 
     The proximal end of the slide member  236  may include a Luer fitting  243  or any other appropriate fitting type. The Luer fitting  243  may be in fluid communication with a lumen passing through the slide member  236  and may provide a connection such that fluid may be delivered through the Luer fitting  243  and into the lumen of the slide member  236 . In turn, the lumen of the slide member  236  may be in fluid communication with the cavity  234  of the hub  231 , which may in turn be in fluid communication with a lumen in the elongate member  223  (e.g., the lumen  222 ). The lumen in the elongate member  223  may be in fluid communication with the tip  201  (e.g., the fluid port  210 ). In this regard, fluid may flow into the Luer fitting  243 , into and through the lumen in the slide member  236 , into and through the cavity  234  of the hub  231 , into and through the elongate member  223 , and out from fluid portion  210  of the tip  201 . The Luer fitting  243 , the lumen in the slide member  236 , the cavity  234  of the hub  231 , and the lumen of the elongate member  223  may all also be configured to allow for the insertion of the RF probe  401  therethrough. The protrusion  235  and the cavity  234  of the longitudinal hub projection  238  may be sized and/or configured to form a fluid seal therebetween, allowing fluid delivered under pressure through the Luer fitting  220  to flow through the cavity  238  and into the elongate member  203  substantially without leaking past the interface between the protrusion  235  and the cavity  234  of the longitudinal hub projection  238 . 
     As described herein, the filaments  206   a ,  206   b  may be fixedly interconnected to the slide member  236 . Axial movement of the slide member  236  due to the actuator  232  may be thereby communicated to the filaments  206   a ,  206   b  to deploy and retract the filaments  206   a ,  206   b  upon rotation of the actuator  232 . The slide member  236  may be made from any appropriate material (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). The actuator  232  may be made from any appropriate material (e.g., Pro-fax  6523  polypropylene homopolymer, available from LyondellBasell Industries). 
     The user can deploy or retract the filaments  206   a ,  206   b  by twisting or rotating the actuator  232 . By partially rotating the actuator  232  relative to the hub  231 , the filaments  206   a ,  206   b  may be partially deployed or retracted. The actuator  232  and/or hub  231  may include detents to provide audible and/or tactile feedback of the position of the filaments  206   a ,  206   b . The detents may be configured such that audible and/or tactile feedback associated with engagement of a detent coincides with a predetermined amount of deployment or retraction of the filaments  206   a ,  206   b , as described herein. In this regard, such audible and/or tactile feedback may be used in determining filament position. 
     In some embodiments, the needle  103  is a multipolar (e.g., bipolar) device in contrast to the monopolar devices described herein. In certain such embodiments, the filaments are isolated from each other and/or from the tip to enable bipolar operation (e.g., the filaments having one polarity and the tip having a second polarity, one filament having one polarity and one filament and the tip having a second polarity, one filament having one polarity and one filament having a second polarity, etc.). In embodiments in which the needle  103  comprises more than two filaments, elements may be included to allow for selection of the polarity of the certain filaments to aid in lesion shape, size, and/or position control. In some embodiments, the needle  103  may be used in either a monopolar mode or in a bipolar mode as selected by the user. For example, RF probes  401  may include shapes, insulating features, etc. configured to produce monopolarity or bipolarity. 
     The herein-described embodiments of needles may be used in spinal RF neurotomy procedures, which will now be described. In general, for an RF neurotomy procedure, the patient may lie face down on a table so that the spine of the patient is accessible to the user. At any appropriate time before, during, and/or after the procedure, the user may use imaging equipment, such a fluoroscope, to visualize the patient&#39;s anatomy and/or to visualize the positioning of equipment (e.g., the needle relative to a target volume). 
     The patient may be administered sedatives and/or intravenous fluids as appropriate. The skin of the patient surrounding the procedure location may be prepared and maintained using an appropriate sterile technique. In embodiments in which the needle is monopolar, a return electrode pad  104  may be attached to the patient. A local anesthetic may be injected subcutaneously where the needle will be inserted or along the approximate path of the needle, for example through the needle itself or through a different needle. 
     With the filaments in the retracted position, the needle may be introduced into the patient and moved to a target position relative to a target portion of a target nerve or to a target position relative to a target volume in which the target nerve is likely situated (all of which are generally referred to herein as the target nerve or portion of the target nerve). The target nerve may be an afferent nociceptive nerve such as, for example, a medial branch nerve proximate a lumbar facet joint. Introduction of the needle into the patient may include percutaneously using the tip of the needle to pierce the skin of the patient. The moving of the needle may include navigating toward the target position using fluoroscopic guidance. Furthermore, the moving of the needle may include advancing the needle to an intermediate position and then repositioning the needle to the target position. For example, the needle may be advanced until it contacts a bone or other structure to achieve the intermediate position. This may be followed by retracting the needle a predetermined distance to achieve the target position. Such a procedure may be facilitated by the markers  224  or collar discussed herein. 
     During the moving of the needle or after the target position has been achieved, the needle may be used to inject an anesthetic and/or a dye proximate to the target nerve. The dye may increase contrast in fluoroscopic images to assist in visualizing the patient&#39;s anatomy, which may aid the user in guiding and/or verifying the position of the needle. 
     The needle may be rotated about the central longitudinal axis of the elongate member of the needle to achieve a desired orientation relative to the target nerve. For example, the needle may be rotated such that a lesion created with the needle with the filaments deployed will be offset from the central longitudinal axis toward the target nerve. Such rotation of the needle may be performed prior to insertion of the needle into the patient and/or after insertion into the patient. For example, the user may rotate the needle prior to insertion such that the needle is generally in the desired rotational orientation. Then, after achieving the target position, the user may fine tune the rotational orientation of the needle by rotating the needle to a more precise orientation. As described herein, the hub or another portion of the needle outside the patient&#39;s body may indicate the rotational orientation of the needle. 
     Once the target position and desired rotational orientation have been achieved, the next step may be to advance one or more filaments of the needle relative to the tip of the needle. The particular needle used for a procedure may have been selected to enable the creation of a particular sized and shaped lesion at a particular position relative to the needle. The particular needle used may be of any appropriate configuration discussed herein (e.g., any appropriate number of filaments, any appropriate filament positioning, monopolar or bipolar, any appropriate deployment and retraction mechanism, etc.). 
     In embodiments in which the needle is configured as illustrated in  FIGS. 5 and 6  (e.g., about 120° apart), the advancement of filaments may include advancing the filaments such that when the filaments are in their respective deployed positions, a midpoint between a distal end of the first filament and a distal end of the second filament is offset from the central longitudinal axis of the needle, and the filament endpoints are distal to the tip of the needle. Such deployment may enable the needle to be used to create a lesion that is offset from the tip of the needle toward the midpoint between the deployed filament ends. The lesion created may also be positioned at least partially distal to the tip of the needle. 
       FIG. 11A  is an illustration of an example set of isotherms  1010   a - 1010   c  that may be created with the needle  103  of  FIG. 2A . As illustrated by the set of isotherms  1010   a - 1010   c , RF energy emanating from the tip  201  and from the filaments  206   a ,  206   b , may produce a region of elevated temperature about the tip  201  and the filaments  206   a ,  206   b . The isotherms  1010   a - 1010   c  may be offset from the central longitudinal axis  223  such that a centroid of the isotherms as viewed in  FIG. 11A  is offset from the central longitudinal axis  223  in the direction of the filaments  206   a ,  206   b . The centroid of the isotherms  1010   a - 1010   c  as viewed in  FIG. 11A  may also be distal relative to the tip  201  and between the tip  201  and the distal ends of the deployed filaments  206   a ,  206   b . The isotherms  1010   a - 1010   c  may also be shaped such that, as viewed in  FIG. 11A , the isotherms  1010   a - 1010   c  have a maximum cross-sectional dimension along the central longitudinal axis  223  that is greater than a maximum cross dimension in the plane of  FIG. 11A  perpendicular to the central longitudinal axis  223 . As visible in the illustrated orientation of  FIG. 11B , the isotherms  1010   a - 1010   c  may have a maximum cross-sectional dimension along the central longitudinal axis  223  that is greater than a maximum cross-sectional dimension perpendicular to the plane of  FIG. 11A  and perpendicular to the central longitudinal axis  223 . 
     The offset of the centroid of the isotherms  1010   a - 1010   c  from the central longitudinal axis  223  may result in greater lesion width in a plane perpendicular to the central longitudinal axis  223 , as compared to a similarly-sized straight needle with no filaments. The offset of the centroid of the isotherms  1010   a - 1010   c  may also allow for projection of the centroid of a corresponding lesion volume in a direction away from the central longitudinal axis  223 . By way of example, such offsets may advantageously enable the execution of the example procedures described herein. Such offsets may advantageously enable the creation of lesion volumes distal (relative to the needle  103 ) to potentially interfering structures (e.g., an ossified process). Such offsets may advantageously enable the needle  103  to be inserted into a patient at a more desirable angle (e.g., closer to perpendicular to the surface of the patient such as within 30° of perpendicular to the surface of the patient), at a more desirable piercing location, and/or through more desirable tissue than may be attempted using a needle without offset lesion capabilities. 
       FIG. 11B  is an illustration of an example lesion  1011  that may be created with the needle  103  of  FIG. 2A . In  FIG. 11B , the needle  103  has been placed perpendicular to a surface  1012 . The surface  1012  may, for example, be the surface of a bone, such as a lumbar vertebra. As illustrated, the filaments  206   a ,  206   b  are deployed such they are proximate to the surface  1012 . In some embodiments, contact with the surface  1012  might undesirably deform the filaments  206   a ,  206   b , but such contact may be avoided, for example by the needle advancement and retraction procedures described herein. The lesion  1011  has a width along the surface  1012  that is wider than would be created by the needle  103  if the filaments  206   a ,  206   b  were not deployed. Such capabilities may, for example, be advantageous where a target structure (e.g., a nerve) is known to be positioned along the surface  1012 , but its exact position is unknown. In such a case, the needle  103  may be positioned generally perpendicular to the surface  1012  to achieve the illustrated lesion width along the surface  1012 , whereas achieve the same lesion width along the surface  1012  using a the needle  103  without the filaments  206   a ,  206   b  deployed would require either multiple repositioning steps or placement of the needle  103  generally parallel to the surface  1012 . 
       FIG. 11C  is an illustration of an example lesion  1022  that may be created with a single-filament needle  1020 . The single-filament needle  1020  may be similar to the needle  103 , although the single-filament needle  1020  includes only a single filament  1021 . The filament  1021  may be configured similarly to the filaments  206   a ,  206   b . The single-filament needle  1020  with the filament  1021  deployed may be operable to produce a lesion  1022  that is a flattened version (e.g., thinner in a direction perpendicular to the central longitudinal axis  223 , which is the left to right direction as illustrated in  FIG. 11C ) of a lesion that may be produced by the needle  103  with two filaments  206   a ,  206   b  deployed. The capability to produce such a lesion shape may be beneficial when it is desirable to have a relatively large lesion in a particular direction (e.g., to compensate for the variability of location of a target nerve) and a relatively small lesion width in another direction (e.g., to avoid a structure such as viscera or a patient&#39;s skin). As described herein, certain embodiments of the needle  103  may allow differential or selective deployment and/or activation of the filaments  206   a ,  206   b  such that the needle  103  may imitate the single-filament needle  1020 . 
     In embodiments in which the needle is configured such that all of the filaments of the needle are deployed on a common side of a central plane of the needle (in which the central longitudinal axis is entirely within the central plane), the advancement of filaments may include advancing the filaments such that when the filaments are in their respective deployed positions, the distal ends of all of the filaments are on a common side of the central plane. Such deployment may enable the needle to be used to create a lesion that is offset from the tip of the needle to the same side of the central plane as the deployed filament ends. The lesion created may also be positioned at least partially distal to the tip of the needle. 
     In embodiments in which the needle is configured as illustrated in  FIG. 7 or 8 , the advancement of filaments may include advancing the filaments such that when the filaments are in their respective deployed positions, each filament distal end defines a vertex of a polygon whose centroid is offset from a central longitudinal axis of the needle. Such deployment may enable the needle to be used to create a lesion that is offset from the tip of the needle toward the centroid. The lesion created may also be positioned at least partially distal to the tip of the needle. 
     The advancement of the filaments may be achieved using any of the mechanisms discussed herein. For example, in the embodiment of  FIG. 2A , rotating the actuator  216  relative to the hub  204  may cause the filaments to advance to the deployed position. The advancement of the filaments may be performed such that each of the plurality of filaments passes through a surface of the needle that is parallel to the central longitudinal axis of the needle. In some embodiments, the filaments of the needle may be advanced to a position that is an intermediate position between the retracted position and the fully deployed position. The degree of deployment may be based on the desired lesion size and/or the accuracy of the placement of needle. For example, the same needle may be used in two different procedures where the variability of the location of a target nerve is greater in the first procedure than it is in the second procedure. In such situation, the greater deployment of the filaments may be used in the first procedure, whereas in the second procedure, a smaller degree of deployment may be used since a smaller lesion may suffice to ensure that the target nerve has been ablated. For another example, after placement of the needle during a procedure, the position of the needle may be determined to be slightly offset from a target position. In such a case, the filaments may be deployed to a greater degree than would have been required if the needle were placed exactly on target. In such a case, the greater degree of deployment may be used to compensate for the needle positioning inaccuracy. In such a case, needle repositioning and possible associated trauma may be avoided. 
     During and/or after advancing the filaments to the deployed position, their positions may be confirmed using an imaging system (e.g., using a fluoroscope). Proper filament positioning may also be verified by using the needle to stimulate the target nerve. For example, an electrical signal (e.g., up to about 2 volts applied at about 2 Hz) may be applied to the needle and the user may observe any related patient movement (e.g., muscle fasciculation in the territory supplied by the nerve). For another example, an electrical signal (e.g., up to about 1 volt applied at about 50 Hz) may be applied to the needle and the patient may indicate if they feel any associated sensations and their locations to assist in verifying correct needle positioning. Such stimulation (user-observed and/or patient reported) may be used to stimulate a targeted nerve to determine if the deployed position is adequate to achieve denervation of the targeted nerve. In this regard, it is desirable for the stimulation to affect the targeted nerve. Upon determination that the target nerve is stimulated, increased energy may be applied to ablate a volume comprising the target nerve. 
     Such stimulation may also be used to attempt to stimulate a nerve that is not targeted for denervation (e.g., a nerve where no denervation is desired) to determine the position of the needle relative to such a non-targeted nerve. In this regard, if the stimulation signal does not stimulate the non-targeted nerve, the user may determine that the position of the needle relative to the non-targeted nerve is such that the application of ablation energy to the needle will not result in significant damage to (e.g., ablation of) the non-targeted nerve. If the stimulation stimulates the non-targeted nerve (e.g., as determined by user observation and/or patient reporting), the needle may be repositioned to avoid damaging the non-targeted nerve. In this regard, it is desirable for the stimulation not to affect the non-targeted nerve. 
     After correct needle positioning has been verified (e.g., by imaging and/or stimulation), an anesthetic may be injected through the needle, for example out of at least one of the fluid port  210 ,  320 , the filament ports  304   a ,  304   b ,  318   a ,  318   b , the lumen  306   c , etc. 
     After the filaments have been advanced to the desired position, the next step may be to apply RF energy to the needle using the interconnected RF generator. In embodiments that use a separate RF probe to deliver RF energy, the RF probe may be inserted into a lumen of the needle prior to application of the RF energy. When using such a configuration, the application of RF energy may include applying RF energy to the RF probe and conducting the RF energy away from the probe by the tip and/or filaments. 
     The resultant RF energy emanating from the tip and/or the filaments may generate heat that ablates the target nerve. Such ablation may be achieved by creating a lesion volume that includes the target nerve. It is desired that the target nerve be completely ablated to prevent incomplete neurotomy which may result in dysesthesia and/or patient discomfort. For example, a lesion with a maximum cross-sectional dimension between about 8 mm and about 10 mm may be created. Larger or smaller lesions may be created by varying filament characteristics (e.g., filament advancement distance) and/or RF energy levels. The created lesion may be offset from the central longitudinal axis of the needle. The center of the lesion may be distal to the tip of the needle. Of note, since the RF energy is emanating from the tip and filaments, a particularly sized lesion may be created with a lower peak temperature (the maximum temperature experienced in the patient) than would be possible if a needle without filaments or without deployed filaments were to be used to create the same-sized lesion. For example, a particular lesion may be achieved with the needle with deployed filaments where the peak temperature is between about 55° C. and about 60° C. or less than about 70° C., whereas creation of the same lesion using a needle without filaments or without deployed filaments could require a peak temperature of about 80° C. Such lower temperature lesions achievable by a needle with deployed filaments may result in greater patient safety and/or procedure tolerance. 
     Before, during, and/or after the application of RF energy, a temperature sensor (e.g., thermocouple) at or near the tip of the needle may be used to monitor the temperature at or near the tip. Such readings may be used as control signals (e.g., a feedback loop) to control the application of RF energy to the needle. For example, control signals and/or temperature data may be used for closed-loop control of the needle  103  by automatic adjustment of a parameter (e.g., frequency, wattage, and/or application duration of the RF energy, and/or filament deployment length, needle position, etc.) upon detection of a temperature. Feedback loops involving the user are also possible. If it is desired to ablate additional target nerves or to ablate an additional volume to ensure ablation of the original target nerve, the spinal RF neurotomy procedure may continue. In some embodiments, the distal end  402  of the RF probe  401  is a dual-purpose wire that can deliver RF energy to the tip and/or the filaments and that can act as a thermocouple (e.g., having thermosensing properties). 
     In embodiments in which the needle is configured to create lesions offset from the central longitudinal axis, and an additional target nerve or target volume is within a volume that may be ablated using the needle in its current position but in a different rotational orientation, the procedure may continue as follows. First, after the initial RF energy application, the filaments may be retracted into the needle. Once retracted, the needle may be rotated, and the filaments redeployed. The redeployment may have the same characteristics (e.g., length of the deployed portions of the filaments) as the original deployment or different characteristics. Next, the reoriented needle may be used to at least partially ablate the additional target nerve or target volume. Such retargeting of ablation volumes without repositioning (e.g., without withdrawing the needle from the patient and reinserting), may result in reduced patient trauma as compared to known spinal RF neurotomy procedures, which may require removal and reinsertion of a needle to achieve lesioning of the second target volume. Moreover, such retargeting of ablation volumes without repositioning (e.g., with only rotation of the needle, without additional tissue piercing) may result in the ability to create uniquely shaped lesions from a single insertion position. Such shaped lesions may include, for example, lesions that are in the shape of two or more intersecting spheres or oblong spheroids. The steps of retracting the filaments, rotating the needle, redeploying the filaments, and applying RF energy may be repeated a plurality of times. In some embodiments, an second ablation volume may be defined without rotating the needle, but by different deployment characteristics (e.g., lengths, RF energy parameters, etc.) of the filaments. 
     In embodiments in which the additional target nerve or target volume is not within a volume that may be ablated by rotating the needle, the needle may be repositioned. Such repositioning may include partially or fully removing the needle from the patient and then repositioning the needle and repeating the herein-described steps. In some embodiments, the second ablation is performed using a different needle (e.g., a needle with different properties (e.g., longer filaments)) than the original needle. 
     When no additional ablation is desired, the filaments of the needle may be retracted, and the needle may be removed from the patient. After removal of the needle, a sterile bandage may be placed over the needle insertion site or sites. The patient may then be held for observation and recovery from the effects of any sedative that may have been administered. 
     Examples of specific spinal RF neurotomy procedures will now be described. Generally, steps unique to each procedure will be discussed while steps common to any spinal RF neurotomy procedure (e.g., site preparation such as infiltrating the skin and subcutaneous tissues with 1.5% lidocaine to achieve skin anesthesia, nicking the skin to facilitate needle insertion, insertion monitoring with fluoroscopy, stimulation, etc., filament deployment mechanics, needle removal, and the like) will not be further discussed. Each of the procedures is described as being performed with a needle comprising two filaments offset from the central longitudinal axis, for example as described herein. It will be appreciated that the variations in needle configuration discussed herein may be used in these procedures. For example, to increase the offset of the created lesion relative to the central longitudinal axis, curved filaments (e.g., as illustrated in  FIG. 10 ) and/or partially insulated filaments (e.g., as illustrated in  FIGS. 3H and 3I ) may be used to create a lesion different properties (e.g., greater offset from the central longitudinal axis). 
     1. Lumbar RF Neurotomy of a Medial Branch Nerve Proximate a Lumbar Facet Joint. 
     This process may include using a needle that enables the creation of lesions that are offset from the central longitudinal axis. The procedure will be described as being performed on the L5 vertebra  1101  of  FIG. 12  and the needle  103  of  FIG. 2A . It should be understood that other embodiments of needles described herein and/or other lumbar vertebra may be used in the described procedure or variations thereof. 
     The lumbar RF neurotomy process may include positioning the tip  201  of the needle  103  (e.g., using fluoroscopic navigation) such that the tip  201  is in contact with, or proximate to, the groove  1102  between the transverse process  1103  and the superior articular process  1104  of the targeted lumbar vertebra  1101 . Such positioning is shown in  FIG. 12 . By contacting the lumbar vertebra  1101 , a positive determination of the position of the needle  103  may be made. By way of example, such positioning may be performed such that the needle  103  is within 30° of being perpendicular to the lumber vertebra  1101  at the point of contact with the lumbar vertebra  1101 , or at the point of the lumbar vertebra  1101  closest to the tip  201  of the needle  103 . Optionally, from such a position, the needle  103  may be retracted a predetermined amount (e.g., between about 3 mm and about 5 mm), for example as measured by markers  224  on the needle  103 , as determined using the collar about the elongated member  203  discussed herein, and/or by fluoroscopic navigation. 
     The process may include rotating the needle  103  such that the midpoint  502  is oriented toward the superior articular process  1104  and a medial branch nerve  1105  that is positioned along a lateral face  1106  of the superior articular process  1104 . Next, the filaments  206   a ,  206   b  may be advanced to the deployed position, as shown in  FIG. 12 . The positions of the needle  103  and the deployed filaments  206   a ,  206   b  may be verified using fluoroscopy and/or patient stimulation (e.g., motor and/or sensory). The RF probe  401  may then be inserted into the lumen  222  such that RF energy emanating from the probe  103  will be conducted by the tip  201  and filaments  206   a ,  206   b  to the target medial branch nerve  1105  and away from the intermediate branch of the posterior primary ramus. 
     Next, RF energy may be applied to the RF probe  401 . The RF energy emanating from the needle  103  may be preferentially biased toward the target medial branch nerve  1105 . The lesion created by such a procedure may, for example, have a maximum cross-sectional dimension of between about 8 mm and about 10 mm, and may ablate a corresponding portion of the medial branch nerve  1105 , thus denervating the facet joint. 
     In some embodiments, the needle may be operable to create a generally symmetric lesion relative to its central longitudinal axis (e.g., as illustrated in  FIG. 9 ). In certain such embodiments, the sequence of steps may include insert needle, deploy filaments, and apply RF energy. 
     In some embodiments, the needle may be inserted to be along the length of a portion of the nerve (as illustrated by needle  103 ′ outlined by broken lines). Such positioning may be similar to known methods of RF neurotomy performed using needles without filaments. After positioning the needle, the filaments may be deployed and a lesion may be created. As noted herein, a needle with deployable filaments that is capable of producing a lesion equivalent to that of a needle without deployable filaments may be smaller in diameter than the needle without deployable filaments. Although positioning of the needle  103 ′ may be similar to known processes, the process utilizing the needle  103 ′ with deployable filaments may cause less trauma and be safer than procedures using a needle without deployable filaments due to the smaller size of the needle with deployable filaments. As discussed herein, the peak temperatures capable of producing the desired lesion volume may be less when using the needle  103 ′ with deployable filaments as compared to a needle without deployable filaments, further contributing to patient safety. The filaments of the needle  103 ′ may be partially or fully deployed to achieve a desired lesion location, shape, and/or size. 
     It is noted that the illustrated deployment of needle  103  with the filaments  206   a ,  206   b  deployed may be used to create a lesion that approximates a lesion that would be created with the needle without filaments that is placed in the position of needle  103 ′ (e.g., parallel to the target nerve  1105 ). The placement of needle  103  generally perpendicular to the surface of the L5 vertebra  1101  may be less difficult to achieve than the parallel placement of the needle  103 ′. 
     2. Sacroiliac Joint (SIJ) RF Neurotomy of the Posterior Rami. 
     This process may include using a needle that enables the creation of lesions which are offset from the central longitudinal axis. The procedure will be described as being performed on the posterior rami  1201  of the SIJ of  FIG. 12  and using the needle  103  of  FIG. 2A . It should be understood that other embodiments of needles described herein and/or other portions of the SIJ may be used in the described procedure or variations thereof. 
     As part of the SIJ RF neurotomy process, it may be desirable to create a series of lesions in a series of lesion target volumes  1203   a - 1203   h  lateral to the sacral foramina  1211 ,  1212 ,  1213  of a side of the sacrum  1200  to ablate posterior rami  1201  that are responsible for relaying nociceptive signals from the SIJ. Since the exact positions of the rami  1201  may not be known, ablating such a series of target volumes  1203   a - 1203   h  may accommodate the variations in rami  1201  positions. The series of target volumes  1203   a - 1203   h  may be in the form of one or more interconnected individual target volumes, such as the target volumes  1203   a ,  1203   b . In some embodiments, the process further comprises forming a lesion  1208  between the L5 vertebra  1209  and the sacrum  1200  to ablate the L5 dorsal ramus. 
     The SIJ RF neurotomy process may include positioning the tip  201  of the needle  103  (e.g., using fluoroscopic navigation) such that it is in contact with, or proximate to, and in lateral relation to the S1 posterior sacral foraminal aperture (PSFA)  1211  at a first point  1204  that is at the intersection of the two target volumes  1203   a ,  1203   b . Such positioning may be performed such that the needle  103  is oriented within 30° of being perpendicular to the sacrum  1200  at the point of contact (or at the point of the sacrum  1200  closest to the tip  201  of the needle  103 ). By contacting the sacrum  1200 , a positive determination of the position of the needle  103  may be made. Optionally, from such a position, the needle  103  may be retracted a predetermined amount (e.g., between about 3 mm and about 5 mm) as measured, for example, by markers  224  on the needle  103 , as determined using the collar about the elongated member  203  discussed herein, and/or by fluoroscopic navigation. For example, a contralateral posterior oblique view may be obtained to ascertain that the tip  201  has not entered the spinal canal. For example, a fluoroscopic view may be obtained looking down the length of the needle  103  to verify that the needle  103  is properly offset from the S1 PSFA  1211  and/or a fluoroscopic view may be obtained looking perpendicular to the central longitudinal axis  223  to verify that the needle  103  is not below the surface of the sacrum (e.g., in the S1 PSFA  1211 ). An electrical signal may be applied to the needle  103  to stimulate nerves proximate to the tip  201  to verify correct needle  103  placement. 
     The SIJ RF neurotomy process may include rotating the needle  103  such that the midpoint  502  is oriented toward the first target volume  1203   a  in the direction of arrow  1205   a . Next, the filaments  206   a ,  206   b  may be advanced to the deployed position. The position of the needle  103  and the deployed filaments  206   a ,  206   b  may be verified using fluoroscopy and/or stimulation (e.g., motor and/or sensory). The RF probe  401  may be inserted into the lumen  222  before, during, and/or after filament deployment such that RF energy emanating from the needle  103  will be conducted by the tip  201  and the filaments  206   a ,  206   b  to the first target volume  1203   a . Next, RF energy may be applied to the RF probe  401 . The RF energy emanating from the needle  103  may be preferentially biased toward the first target volume  1203   a . The lesion created by such an application of RF energy may, for example, have a maximum cross-sectional dimension of between about 8 mm and about 10 mm, and may ablate a corresponding portion of the rami  1201 . 
     Next, the filaments  206   a ,  206   b  may be retracted and the needle  103  may be rotated approximately 180° such that the midpoint  502  is oriented toward the second target volume  1203   b  in the direction of arrow  1205   b . Optionally, some lateral repositioning of the needle may performed (e.g., without any needle pull back or with a small amount of needle pull back and reinsertion). Next, the filaments  206   a ,  206   b  may be advanced to the deployed position. The position of the needle  103  and the deployed filaments  206   a ,  206   b  may be verified using fluoroscopy and/or stimulation (e.g., motor and/or sensory). The RF probe  401  may remain in the lumen  222  during the repositioning, or may be removed and then reinserted. Next, RF energy may be applied to the RF probe  401  to create a lesion corresponding to the second target volume  1203   b.    
     In this regard, with a single insertion of the needle  103 , two interconnected lesions (which may also be considered to be a single oblong lesion) may be created. Compared to methods in which an RF probe must be repositioned prior to each application of RF energy, the number of probe repositioning steps may be greatly reduced, reducing patient trauma and procedure duration. In this regard, a continuous region of lesioning may be achieved about the S1 PSFA  1211  such that the lesion occupies a volume surrounding the S1 PSFA  1211  from about the 2:30 clock position to about the 5:30 clock position (as viewed in  FIG. 13 ). Such lesioning may help to achieve denervation of the posterior rami proximate to the S1 PSFA  1211 . 
     The herein procedure may be repeated as appropriate to create lesions corresponding to the entire series of target volumes  1203   a - 1203   h , thus denervating the SIJ. For example, a first insertion may ablate the volumes  1203   a ,  1203   b , a second insertion may ablate the volumes  1203   c ,  1203   d , a third insertion may ablate the volumes  1203   e ,  1203   f , and a fourth insertion may ablate the volumes  1203   g ,  1203   h . In this regard, a similar continuous region of lesioning may be achieved about the S2 PSFA  1212  and a region of lesioning from about the 12:00 clock position to about the 3:00 clock position (as viewed in  FIG. 13 ) relative to the S3 PSFA may be achieved about the S3 PSFA  1213 . A lesion  1208  may also be created at the base of the superior articular process of the L5  1209  dorsal ramus in the grove between the superior articular process and the body of the sacrum. The needle  103  may be inserted generally perpendicular to the plane of  FIG. 13  to produce the lesion  1208 . 
     In some embodiments, three or more lesions may be created with a needle in a single position. For example, a needle positioned at a point  1206  proximate to three target volumes  1203   c ,  1203   d ,  1203   e , may be operable to create lesions at each of the three target volumes  1203   c ,  1203   d ,  1203   e , thus further reducing the number of needle repositionings. 
     In some embodiments, each individual lesion corresponding to the series of target volumes  1203  may be created using a needle with deployable filaments in which the needle is repositioned prior to each application of RF energy. In certain such embodiments, the sequence of steps may be insert needle, deploy filaments, apply RF energy, retract filaments, reposition needle, and repeat as appropriate to create each desired lesion. Such a procedure may be conducted, for example, using a needle capable of producing a lesion symmetric to a central longitudinal axis of the needle (e.g., the needle of  FIG. 9 ). 
     3. Thoracic RF Neurotomy of a Medial Branch Nerve. 
     This process may include using a needle that enables the creation of lesions which are offset from the central longitudinal axis of the needle. Successful treatment of thoracic z-joint pain using radiofrequency ablation of relevant medial branch nerves can be challenging owing to the inconsistent medial branch location in the intertransverse space, especially levels T5-T8. A needle without filaments is generally positioned at multiple locations in the intertransverse space to achieve sufficient tissue ablation for successful medial branch neurotomy. The procedure will be described as being performed on an intertransverse space between adjacent vertebrae  1301 ,  1302  of the T5 to T8 thoracic vertebrae using  FIG. 14  and the needle  103  of  FIG. 2A . It should be understood that other embodiments of needles described herein and/or other vertebrae may be used in the described procedure or variations thereof. 
     The process may include obtaining a segmental anteroposterior image at target level defined by counting from T1 and T12. This may be followed by obtaining an image that is ipsalateral oblique about 8° to about 15° off-sagittal plane of the spine to visualize costotransverse joint lucency clearly. This can allow improved visualization of the superior-lateral transverse process, especially in osteopenic patients. The angle can aid in directing the probe to a thoracic anatomic safe zone medial to the lung, reducing risk of pneumothorax. 
     The skin entry site for the needle  103  may be over the most inferior aspect of transverse process slightly medial to costotransverse joint. Inserting the needle  103  may include navigating the device over the transverse process over the bone to touch the superior transverse process slightly medial to the costotransverse joint. The process may include checking anteroposterior imaging to demonstrate that the tip  201  of the needle  103  is at the superolateral corner of the transverse process. The process may also include checking a contralateral oblique image view (e.g., at ±15°) to demonstrate, for example in “Pinnochio” view, the target transverse process in an elongate fashion. This view can be useful for showing the tip  201  of the needle  103  in relationship to the superolateral margin of the transverse process subadjacent to the targeted medial branch nerve. The process may include retracting the tip  201  slightly (e.g., about 1 mm to about 3 mm). In some embodiments, retracting the tip  201  positions the ports at the superior edge of the process (e.g., visible with a radiopaque marker). 
     In some embodiments, medial to lateral placement may be performed entering the skin beneath the segmental spinous process, and navigating the needle  103  over the transverse process to contact a point just proximal to the superolateral corner of the transverse process. The tip  201  may then be advanced to approximate the exit port  304   a ,  304   b  of the filaments  206   a ,  206   b  with the superior margin of the transverse process, and the filaments  206   a ,  206   b  are deployed. 
     The process may include rotating the needle  103  such that the midpoint  502  is oriented toward the intertransverse space between the vertebrae  1301 ,  1302  and the medial branch nerve  1303  that is positioned therein. Next, the filaments  206   a ,  206   b  may be advanced ventral into the intertransverse space between the vertebrae  1301 ,  1302  to the deployed position. The position of the needle  103  and deployed filaments  206   a ,  206   b  may be verified using fluoroscopy (e.g., using lateral imaging) and/or stimulation (e.g., motor and/or sensory), for example to rule out proximity to ventral ramus. In some embodiments, the filaments  206   a ,  206   b  are deployed in a ventral direction in the intratransverse space, which may be confirmed by obtaining lateral. The RF probe  401  may be inserted into the lumen  222  such that RF energy emanating from the probe  103  will be conducted by the tip  201  and the filaments  206   a ,  206   b  to the target medial branch nerve  1303 . Next, RF energy may be applied to the RF probe  401 . The RF energy emanating from the needle  103  may be preferentially biased toward the volume between the vertebrae  1301 ,  1302 . The lesion created by such a procedure may, for example, have a maximum cross-sectional dimension of between about 8 mm and about 10 mm, and may ablate a corresponding portion of the medial branch nerve  1303 . This method can treat the medial branch as it curves out of the intratransverse space emerging into the posterior compartment of the back. The directional bias of the lesion may advantageously heat towards the target and away from the skin. 
     It is noted that thoracic RF neurotomy performed on other thoracic vertebrae may call for different sizes of lesions. For example, thoracic RF neurotomy performed on the T3-T4 vertebrae may require a smaller lesion volume than the herein-described procedure, and thoracic RF neurotomy performed on the T1-T2 vertebrae may require a still smaller lesion volume. As described herein, the deployment of the filaments of the needle  103  may be varied to achieve such desired target lesion volumes, or different needles may be used (e.g., having shorter filaments in the fully deployed position). 
     4. Cervical Medial Branch RF Neurotomy. 
     Embodiments of needles described herein (e.g., the needle  103  of  FIG. 2A ) are capable of creating a volume of tissue ablation necessary for complete denervation of the cervical zygapophyseal joints, including the C2/3 cervical zygapophyseal joint (z-joint). Tissue ablation for cervical z-joint using embodiments of needles described herein may be accomplished using a single placement and single heating cycle. Such single placement and single heating cycle may avoid unnecessary tissue damage from multiple placements of a filament-free needle, and unintended injury to collateral tissue caused by excessive lesioning. The zone of ablation can be designed to provide sufficient and necessary tissue coagulation for a successful procedure, and thus may be expected to improve the outcomes of patients undergoing spinal radiofrequency neurotomy. 
     A cervical medial branch RF neurotomy procedure will be described as being performed on the third occipital nerve at the C2/3 z-joint using the needle  103  as shown in  FIG. 15 . In  FIG. 15 , the needle  103  is positioned between the C2 vertebra  1401  and the C3 vertebra  1402 . 
     In a first step, the patient may be placed in a prone position on a radiolucent table suited to performing fluoroscopically guided spinal procedures. Sedation may be administered. The patient&#39;s head may be rotated away from the targeted side. Sterile skin prep and draping may be performed using standard well-described surgical techniques. 
     For Third Occipital Nerve (TON) ablation (C2/3 joint innervation) the lateral aspect of the C2/3 Z-joint is located under either parasagittal or, alternatively, ipsilateral oblique rotation of less than or equal to about 30° (e.g., between about 20° and about 30°) of obliquity relative to the true sagittal plane of the cervical spine. The skin entry point may be infiltrated with local anesthetic. Then, the tip  201  of the needle  103  is moved over the most lateral aspect of bone of the articular pillar at the juncture of the C2/3 z-joint to a first position contacting bone proximate to the most posterior and lateral aspect of the z-joint complex, for example using a “gun-barrel” technique to touch the most lateral and posterior aspect of the articular pillar at the point of maximal concavity for level below C2/3 or at the point of maximal convexity at the C2/3 level when targeting the TON. 
     Once boney contact is made, the needle  103  may be retracted a predetermined distance (e.g., between about 1 mm and about 3 mm) and the filaments are deployed towards the lateral aspect of the C2/3 z-joint. The filaments will spread to encompass anticipated rostrocaudal variation in the target nerve location. The angle of the filaments with respect to the tip may effectively cover the ventral aspect of the articular pillar up to the border of the superior articular process, thus incorporating benefits of a 30° oblique pass. The needle  103  may be rotated about a central longitudinal axis prior to filament deployment to ensure that deployment will occur in the desired direction. 
     Multiplanar fluoroscopic imaging may then be employed to verify that the tip and the filaments are positioned as desired. For example, it may be verified that the filaments are positioned straddling the lateral joint lucency, and posterior to the C2/3 neural foramen. Useful imaging angles include anterior-posterior (AP), lateral, and contralateral oblique (Sluijter) views. To further verify adequate positioning of the needle  103 , motor stimulation may be performed by delivering a voltage (e.g., up to about 2 volts) at about 2 Hz to the tip  201  and filaments and/or sensory stimulation may be performed at appropriate voltage (e.g., between about 0.4 volts and about 1 volt) and frequency (e.g., about 50 Hz). 
     After position verification, RF energy may be applied to the tip and the plurality of filaments to generate heat that ablates a portion of the third occipital nerve. The cross-sectional dimensions of the lesion (e.g., between about 8 mm and about 10 mm) can incorporate all medial branches as well as the TON, which has a nerve diameter of about 1.5 mm. The directional nature of the lesion, offset towards the filaments, provides a beneficial measure of safety regarding undesired thermal damage to the skin and to collateral structures. Safety concerns may be further satisfied by fluoroscopic observation of the filaments dorsal to the intervertebral foramen and/or lack of ventral ramus activation during stimulation (e.g., with 2 Hz and 2 volts). After lesioning, the device may be removed. For levels below the C2/3 z-joint, the procedure may be similar than as described herein with respect to the third occipital nerve, with the exception that the initial boney contact target is at the waist of inflection point of the articular pillar. 
     Other spinal RF procedures may also benefit from the asymmetrical application of RF energy from embodiments of the needles described herein. Such asymmetry may, for example, be used to project RF energy in a desired direction and/or limit the projection of RF energy in undesired directions. The configuration of the filaments may be selected for a particular application to produce a desired size, shape, and/or location (relative to the needle tip) of a lesion within the patient. The location of the lesion may be offset distally and/or laterally from the tip of the needle as desired for a particular application. 
     It will be appreciated that the delivery of RF energy to tissue in the anatomy can be practiced for a multitude of reasons, and embodiments of the needles described herein may be adapted (e.g., modified or scaled) for use in other medical procedures. For example, embodiments of needles described herein could be used to deliver RF energy as a means to cauterize “feeder vessels,” such as in bleeding ulcers and/or in orthopedic applications. For another example, embodiments of the needles described herein could be adapted for use in procedures such as cardiac ablation, in which cardiac tissue is destroyed in an effort to restore a normal electrical rhythm in the heart. Certain such uses could further benefit from the ability of embodiments of needles described herein to deliver fluid through a lumen since, for example, emerging procedures in cardiac therapy may require the ability to deliver stem cells, vascular endothelial growth factor (VEGF), or other growth factors to cardiac tissue. The ability to steer embodiments of the needle described herein may provide significant benefit in the field of cardiovascular drug delivery. 
     For example, a needle may be adapted for use in vertebral disc heating. A primary longer needle (e.g., having a length of about 15 cm and a tip with an uninsulated active portion having a length of about 2 mm, although other dimensions are also possible), is placed into the post posterolateral margin of a painful intervertebral disc, for example as described elsewhere for provocation discography and/or therapeutic disc access procedures such as Dekompressor® discectomy and disc biacuplasty. Once positioned in the posterior annulus, as confirmed with fluororscopy, tactile feedback, and/or characteristic impedance readings, a single filament is deployed to traverse the posterior annulus in a lateral to medial fashion in the lamella of the annulus fibrosis, for example as illustrated in  FIG. 18A , which is an axial view of posterior oblique needle entry with the main axial tip in the posterior annulus and deployed a filament moving lateral to medial in the lamella of the posterior annulus, and  FIG. 18B , which is a saggital view with a filament moving across the posterior annulus from lateral to medial. 
     In some embodiments, the filament may act as a thermocouple (e.g., comprising a material having thermosensing properties as described herein) to allow precise measurement of actual temperatures of the annulus. In some embodiments, the filament includes a lumen configured to allow injection of therapeutic substances (e.g., methylene-blue) upon withdrawal for substantially simultaneous chemo-thermo-neurolysis and/or to allow injection of contrast agent for confirmation of intraannular placement that is definite, for example as opposed to potentially dangerous placement in the spinal canal or futile placement in the nucleus pulposus. In some embodiments, the filament has an exit angle greater than about 30°. In some embodiments, the filament includes a beveled Quincke tip oriented to bias away from the spinal canal upon advancement, as needles in tissue track away from bevel angles. In some embodiments, the deployed filament has a length between about 10 mm and about 12 mm. In some embodiments, the needle does not include a lumen for injection of liquid. In certain such embodiments, the area not occupied by a lumen may be used for the filament, which may be more complicated due to use as a thermocouple and/or including a lumen. 
     Bipolar or monopolar RF energy is applied to the tip and to the filament, creating a zone of therapeutic heating across the posterior disc annulus and resulting in destruction of the pain fibers in approximately the outer third of the annulus. The procedure may be repeated on the opposite side. In some embodiments, the needle includes a plurality of deployable filaments, and gap between the filaments (e.g., the distance  604  in  FIG. 6 ) is between about 2 mm and about 10 mm, between about 4 mm and about 8 mm, between about 5 mm and about 7 mm (e.g., about 6 mm), combinations thereof, and the like. 
     Example 1 
     Sections of raw muscle tissue were allowed to equilibrate to 37° C. in a distilled water bath. A needle with tines deployed was positioned to contact the tissue surface in 10 trials and was inserted into tissue in 10 trials. A Radionics RFG 3C RF generator energy source was set at 75° C. for 80 seconds. Propagation of tissue coagulation was documented with video and a calibrated Flir T-400 thermal camera. Tissue samples were sectioned and coagulation zones measured. Infrared observation demonstrated symmetric and homogenous lesion progression without hot spots or focal over-impeding. Calculated volume averaged 467±71 mm 3 /lesion. Topography was elongate spheroid offset from the central axis toward the filaments. Thus, the needle reliably produced lesions that are potentially useful in spinal applications. 
     Example 2 
     A 47 year-old male with recalcitrant right-sided lumbar zygapophysial joint pain presented for radiofrequency medial branch neurotomy. The diagnosis had been made by greater than 80% relief documented following both intraarticular z-joint injection and confirmatory medial branch blocks. 
     The patient was placed in a prone position on the fluoroscopy table and standard monitors were applied. No sedation was administered. The lumbar region was extensively prepped with chlorhexidine-alcohol and draped in routine sterile surgical fashion. The C-arm was adjusted to visualize a true AP of the L4/5 intervertebral disc space with vertebral end plates squared-off, and spinous process positioned between the pedicle shadows. The C-arm was rotated 30°-40° ipsilateral to the target joint until the base of the SAP of the L4 and L5 were clearly visualized. A target point was identified at the midpoint of the base of the SAP, and the overlying skin and subcutaneous tissues were infiltrated with 1.5% lidocaine. A small skin nick was made with an 18-gauge needle to facilitate placement of an embodiment of the needles described herein. Once skin anesthesia was established, the needle, with filaments in the retracted position, was advanced using a gun-barrel approach until boney contact was made with the base of the SAP. The needle was then retracted off the bone slightly, and using the indentation on the hub for orientation, the actuator was rotated 360° to fully deploy the filaments. Filaments were felt to touch bone at the base of the SAP. AP, oblique, and lateral images were obtained to document the placement and to confirm that the filaments were directed toward the SAP. In this position, the lesion was biased to cover any variant medial branch situated higher up the SAP. If the filaments were not directed in an ideal fashion, they were retracted, the device was rotated as necessary, and the filaments were redeployed. Motor stimulation at a frequency of 2 Hz up to 2 volts was incrementally administered with brisk activation of the multifidus, but with no activation of any ventral root inenervated musculature. Sensory stimulation at 50 Hz at 0.6 volts elicited a concordant aching in the distribution of the patient&#39;s pain. A 22-gauge, 10 cm, 10 mm active tip RFK connected to an independently grounded second RF generator was placed sequentially at the following targets for in vivo thermometry: (1) Most inferior and dorsal location in the supra-segmental neural foramen evaluating the potential for thermal injury of spinal nerve; (2) At a point lateral on the transverse process approximating the location of intermediate/lateral branches of the posterior primary rami; (3) At or near the central axis of the needle during stable heating; (4) On the SAP at the base and successively higher on mammillary process to evaluate heating on the region of potential MB variation (up the SAP). The process was then repeated for denervation of the L5. 
     Following the confirmation of safe and optimal placement by fluoroscopy and stimulation, the heating protocol was initiated based on previous branch testing in egg white and chicken meat. The protocol included: 45° C. for 15-30 seconds, await rapid temperature increase signaling primary consolidation of heating and biophysical changes around core axis; 50° C. for 15 seconds; 60° C. for 15 seconds; 70° C. for 10 seconds to record foraminal temperatures only. 
     Generator parameters during ablation were appropriate and within the tolerance range for a generically programmed RF generator. The lower starting impedance, relative to a monopolar needle, may be explained by greatly increased conductive surface of the needle. Brief temperature fluctuation was noted as the lesion propagated to encompass the central axis housing the thermocouple. It is anticipated that changes in the generator software may be useful to support various embodiments of the described device. Impedance readings were 75 ohms to 250 ohms. Power ranges were 2 watts to 11 watts, typically 3 watts to 4 watts after 10 seconds into the procedure. 
     The thermal mapping results were as follows: (1) Perineural temperatures (neurogram obtained via TC2) at the supra-adjacent spinal nerve did not increase from a 38° C. baseline; (2) Temperature readings from the TC2 placed near the central axis of the needle reflected delivered temperature from the generator; (3) Temperature readings from the base of the SAP to relatively dorsal position on the SAP exceed the neuroablative threshold of 45° C. 
     The patient experienced minimal discomfort following the procedure. For the sake of full disclosure, it is noted that the patient is an inventor of the present application. No postoperative analgesics were required. The patient reported near complete relieve of his right-sided low back pain within 10 days of the procedure. Bilateral paraspinal EMG at L3, L4, and L5 was performed 20 days after the RF procedure, as documented in Table 1: 
                     TABLE 1                  Paraspinal EMG                                         Side   Muscle   Nerve   Root   Ins Act   Fibs   Psw               Left   L3 Parasp   Rami   L3   Nml   Nml   Nml       Left   L4 Parasp   Rami   L4   Nml   Nml   Nml       Left   L5 Parasp   Rami   L5   Nml   Nml   Nml       Right   L3 Parasp   Rami   L3   Nml   Nml   Nml       Right   L4 Parasp   Rami   L4   *Incr   *1+   *1+       Right   L5 Parasp   Rami   L5   *Incr   *1+   *1+               *Needle evaluation of the right L4 paraspinal and the right L5 paraspinal muscles showed increased insertional activity and slightly increased spontaneous activity.       *All remaining muscles showed no evidence of electrical instability.            
There was electrodiagnostic evidence of active and acute denervation of the right lumbar paraspinals at the L4 and L5 levels. The contralateral left-sided paraspinals appeared normal. These findings are consistent with the clinical history of recent right lumbar radiofrequency rhizotomy.
 
     Thus, the needle was safely and effectively used to accomplish lumbar medial branch neurotomy. Thermal mapping demonstrated a safe and effective isotherm consistent with bench predictions, and EMG of the lumbar paraspinals demonstrated objective evidence of medial branch coagulation. The needle appears to extend beneficially on existing techniques and technology. For a first example, facilitated placement for lumbar medial branch neurotomy using “down-the-beam” technique akin to diagnostic medial branch block. This approach can be applied to other spinal targets such as cervical z-joint neurotomy, thoracic z-joint neurotomy, sacroiliac joint denervation, central innercation of the lateral C1-2 joint, RF neurotomy thoracic sympathetic chain, RF neurotomy sphlancnic chain at T10, 11, 12, RF neurotomy lumbar sympathetic pain, and RF neurotomy superior hypogastric plexus. For a second example, lab testing and in vivo thermal data demonstrates a large volume suited for efficiently dealing with common variations in afferent sensory pathways. The lesion can be directed relative to the central longitudinal axis of the needle toward targets and away from sensitive collateral structures. For a third example, the needle can deliver meaningful motor and/or sensory stimulation for documentation of safe placement. For a fourth example, lesion topography is driven by needle design, and does not require high temperatures (e.g., greater than 80° C.) for extended times. It is believed that 60° C. for 60 seconds is adequate for most targets. Reduced procedural time and/or lower temperatures should translate to fewer complications, expedited recovery, and/or diminished incidence of postoperative pain syndromes/dysesthesias. For a fifth example, relative to other large field lesion technology, the needle is of a uncomplicated and robust design, does not require additional support equipment, and is economical to manufacture. 
     Although this invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while several variations of the embodiments of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the embodiments of the disclosed invention. Thus, it is intended that the scope of the invention herein disclosed should not be limited by the particular embodiments described herein.