Patent Publication Number: US-2010130815-A1

Title: Intraurethral and extraurethral apparatus

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application: 
     (a) is a continuation-in-part of PCT Patent Application PCT/IL08/00677 to Gross et al., entitled, “Prostate implant and methods for insertion and extraction thereof,” filed May 18, 2008 which claims priority from U.S. Provisional Patent Application 60/930,705 to Gross et al., entitled, “Prostate implant and methods for insertion and extraction thereof,” filed May 18, 2007; and 
     (b) claims priority from U.S. Provisional Patent Application 61/200,372 to Gross et al., entitled, “Intraurethral and extraurethral apparatus,” filed Nov. 26, 2008. 
     All of the above applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     Some applications of the present invention relate generally to implants and delivery tools therefor. Specifically, some applications of the present invention relate to an implant that is placed around or within a body lumen, such as but not limited to, a transurethrally implantable prostatic implant for treatment of benign prostatic hyperplasia (BPH). 
     BACKGROUND OF THE INVENTION 
     Benign prostatic hyperplasia (BPH) is a condition wherein a benign (non-cancerous) tumor with nodules enlarges the prostate gland. Although the growth is non-cancerous, the internal lobes of the prostate slowly enlarge and progressively occlude the urethral lumen. Severe BPH can cause serious problems over time: Urine retention and strain on the bladder can lead to urinary tract infections, bladder or kidney damage, bladder stones, and incontinence. 
     U.S. Pat. No. 7,004,965 to Gross, which is incorporated herein by reference, describes an implant system including a transurethral prostatic implant positioned in a prostate and including a lumen with an inner perimeter that surrounds an outer perimeter of a urethra at the prostate. The implant system includes a delivery tool including a shaft having a distal portion and an implant-holding portion proximal to the distal portion, the distal portion being sized for entry into a urethra, and the implant-holding portion being thicker than the distal portion, and an implant positioned on the implant-holding portion. 
     U.S. Pat. No. 5,601,591 to Edwards et al., describes a stent for introduction into a portion of a urethra in a body of a patient. The stent includes a longitudinally-extending body made from a material adapted for absorption by the body of the patient. The longitudinally-extending body has an expanded condition in which the body has a predetermined diameter greater than the diameter of the portion of the urethra extending through the prostate. The longitudinally-extending body is formed with a plurality of coils along the length thereof adapted to engage the wall of the urethra when the longitudinally-extending body is in the expanded condition. The longitudinally-extending body is provided with spaces between the coils to permit the wall of the urethra to extend therein and serve to anchor the longitudinally-extending body to the wall. 
     U.S. Pat. No. 6,517,566 to Hovland et al., describes a permanent implanted support for e.g. the urethral neck of the bladder, generally preventing urinary leakage caused by transmission of intra-abdominal pressure pulse waves. The support is implanted in a straightforward manner without the significant complexity and invasiveness associated with known surgical techniques. Pelvic trauma is dramatically reduced. The support can be used in treatment of stress incontinence, and other types of incontinence, in both males and females. 
     U.S. Pat. No. 6,991,647 to Jadhav, describes a bio-compatible and bioresorbable stent that is intended to restore or maintain patency following surgical procedures, traumatic injury or stricture formation. The stent composes a blend of at least two polymers that is either extruded as a monofilament then woven into a braid-like embodiment, or injection molded or extruded as a tube with fenestrations in the wall. Methods for manufacturing the stent are also disclosed. 
     U.S. Pat. No. 7,104,949 to Anderson et al., describes a minimally invasive surgical instrument for placing an implantable article about a tubular tissue structure. The surgical instrument is described as being useful for treating urological disorders such as incontinence. Surgical methods using the novel instrument are also described. 
     US Patent Application Publication 2004/0181287 to Gellman, describes a stent for treatment of a body lumen through which a flow is effected on either side of a sphincter, said stent comprising one or more windings and having an inner core substantially covered by an outer core and including a first segment, a second segment, and a connecting member disposed between the segments. When the stent is positioned within a patient&#39;s urinary system, the first segment and second segments are described as being located on either side of the external sphincter to inhibit migration of the stent while not interfering with the normal functioning of the sphincter. The outer coating is described as comprising an absorbable material that provides temporary structural support to the stent. After absorption of substantially all the outer coating of the stent, the remaining relatively compliant inner core facilitates removal by the patient by pulling a portion of the stent that extends outside the patient&#39;s body for this purpose. 
     US Patent Application Publication 2006/0276871 to Lamson et al., describes devices, systems and methods for compressing, cutting, incising, reconfiguring, remodeling, attaching, repositioning, supporting, dislocating or altering the composition of tissues or anatomical structures to alter their positional or force relationship to other tissues or anatomical structures. In some applications, the invention may be used to used to improve patency or fluid flow through a body lumen or cavity (e.g., to limit constriction of the urethra by an enlarged prostate gland). 
     The following patents and patent application publications, may be of interest: 
     PCT Publication WO 02/058577 to Cionta et al. 
     U.S. Pat. No. 4,978,323 to Freedman 
     U.S. Pat. No. 5,160,341 to Brenneman et al. 
     U.S. Pat. No. 5,776,142 to Gunderson 
     U.S. Pat. No. 6,119,045 to Bolmsjo 
     U.S. Pat. No. 6,231,516 to Keilman 
     U.S. Pat. No. 6,258,094 to Nicholson et al. 
     U.S. Pat. No. 6,280,465 to Cryer 
     U.S. Pat. No. 6,679,851 to Burbank et al. 
     U.S. Pat. No. 6,702,846 to Mikus et al. 
     U.S. Pat. No. 6,709,452 to Valimaa et al. 
     U.S. Pat. No. 7,175,589 to Deem et al. 
     US Patent Application Publication 2002/0177904 to Huxel et al. 
     US Patent Application Publication 2003/0144658 to Schwartz et al. 
     US Patent Application Publication 2004/0133263 to Dusbabek et al. 
     US Patent Application Publication 2004/0254520 to Porteous et al. 
     US Patent Application Publication 2005/0216074 to Sahatjian et al. 
     US Patent Application Publication 2006/0095058 to Sivan et al. 
     US Patent Application Publication 2006/0106109 to Burbank et al. 
     US Patent Application Publication 2006/0173517 to Gross 
     US Patent Application Publication 2007/0106233 to Huang et al. 
     US Patent Application Publication 2008-0039889 to Lamson et al. 
     SUMMARY OF EMBODIMENTS OF THE INVENTION 
     In some embodiments of the present invention, a system for treating urethral constriction at the prostate comprises at least one transurethrally implantable prostatic implant and a delivery tool therefor. The delivery tool is advanced into a constricted urethra of a patient. Typically, the implant is removably coupled to the delivery tool at a distal site of the tool. The delivery tool functions to advance the implant distally through the urethra of the patient. In some embodiments, the implant is advanced until the implant emerges at a distal end of the urethra and into a bladder of the patient. (In this context, in the specification and in the claims, “proximal” means closer to the orifice through which the tool is originally placed into the urinary tract, and “distal” means further from this orifice.) 
     Typically, the implant comprises a coiled implant comprising at least one coil, which is disposed in a compressed state during transurethral advancement thereof. In some embodiments, the implant comprises a radially-expandable implant configured to expand prior to implantation of the implant in the vicinity of the prostate of the patient. In some embodiments, the implant comprises a rigid material, e.g., stainless steel, and is configured for advancement through the urethra in a compressed state thereof in which the implant had a narrow diameter. Prior to implantation of the implant, the implant is expanded to assume a larger diameter using a mechanical device, e.g., a balloon, a stent, or a basket wire, that is disposed in a lumen of the compressed implant. 
     In some embodiments, the implant is shaped to define an implant lumen that is configured to surround an outer circumference of the urethra as the implant is implanted within the prostate. For embodiments in which the implant is implanted around the urethra from within the bladder, a pointed tip at a proximal end of the implant enables the implant to puncture and penetrate into the prostatic tissue surrounding the urethra of the patient. Rotation of a portion of the delivery tool about a longitudinal axis thereof moves the implant proximally while corkscrewing the implant into the prostatic tissue and thereby around the urethra in order to maintain an expanded diameter of the pathologically constricted urethra. Typically, the implant is configured to reside chronically in the prostate of the patient. 
     In some embodiments, the implant is corkscrewed around the urethra of the patient while the implant is disposed in the urethra. In such an embodiment, the implant comprises a pointed proximal tip which punctures tissue of the urethra and facilitates the proximal corkscrewing of the implant around the urethra. Alternatively, the implant comprises a pointed distal tip which punctures tissue of the urethra and facilitates the distal corkscrewing of the implant around the urethra. 
     In either embodiment, following implantation, the implant radially supports the prostatic tissue and maintains an expanded diameter of the pathologically constricted urethra. Typically, the implant is configured to reside chronically in the prostate of the patient. 
     In some embodiments of the present invention, the at least one implant comprises two or more coiled implants which, when implanted within the tissue, are configured to be disposed in a relative spatial configuration in which the implants are concentrically disposed and have opposing rotational directions, i.e., one implant is left-handed and the other is right-handed. In some embodiments, respective ends of the implants are rotationally offset by a given angle with respect to each other. The two or more implants are implanted substantially at the same time. During the implantation, each implant is rotated in a direction corresponding to the rotational direction of the implant. Additionally, in response to the rotational force of a first one of the implants in a given direction, the prostatic tissue is pulled in the given direction. By implanting two implants having opposing rotational directions, the opposing rotational force applied to the tissue by the second one of the implants balances the rotational force applied to the tissue by the first implant. Thus, the pulling of the prostatic tissue in a given direction is reduced. 
     In some embodiments of the present invention, the at least one implant comprises two or more coiled implants which, when implanted within the tissue, are configured to be disposed in a relative spatial configuration in which the implants are coaxially disposed and rotationally offset by a given angle with respect to each other. Additionally, when positioned in the relative spatial configuration, at least a portion of each of the implants overlap longitudinally. Typically, the implants longitudinally essentially entirely overlap each other. 
     In some embodiments, a plurality of distinct coiled implants are implanted around the urethra. In some embodiments, a plurality of distinct curved needles are implanted around the urethra. 
     In some embodiments, a conically-shaped coiled implant is implanted in the prostate and functions as a scaffold for advancement therethrough and support of a plurality of longitudinal rods. The rods are advanced around the urethra in a manner in which the rods are disposed circumferentially around the urethra and maintain an open state of the constricted urethra. For some applications, the rods are implanted prior to the implanting of the coiled implants with respect to the rods. In such an embodiment, the implant is not necessarily conic, and may comprise any coil-shaped implant. 
     Typically, one or more implants are disposed within a lumen of a delivery tool comprising a deflectable distal tip which is controllable by the operating physician to be steerable radially away from a longitudinal axis of the delivery tool. In response to deflecting the distal tip of the tool, the distal tip pushes the wall of the urethra which compresses tissue outside of the urethra, i.e., prostate tissue, and consequently the perimeter of the urethra at the prostate expands. The delivery tool then delivers an implant in the portion of the tissue of the prostate that has been compressed, and the implant functions to maintain the tissue in a compressed state upon withdrawal of the delivery tool from the urethra. 
     For some applications, a plurality of implants are designated for implantation in respective portions of the prostate. For example, a plurality of implants may be implanted adjacent to (e.g., around) the urethra in a single transverse sectional plane of the prostate. For some applications, a plurality of implants are sequentially disposed along parallel planes of the prostate along a longitudinal axis of the urethra. Typically, the implants comprise coiled implants which are implanted in a manner in which a longitudinal axis of the implant is disposed at a non-zero angle, e.g., 90 degrees, with respect to the longitudinal axis of the urethra. 
     For some applications, each coiled implant, which is implanted at the non-zero angle with respect to the urethra, is delivered to the prostate tissue in an expanded state thereof along a longitudinal axis of the implant. Upon implantation, the implant compresses to return to its unexpanded resting state, and thereby compresses tissue radially with respect to the longitudinal axis of the urethra. For some applications, since these coiled implants are made to pull tissue in response to a tension force, these coiled implants are typically implanted in the prostate without first pushing the tissue. 
     There is therefore provided, in accordance with an embodiment of the present invention apparatus, including: 
     an implant; and 
     a delivery tool, removably coupled to the implant, the tool configured to:
         advance the implant distally through a urethra of a patient until the implant emerges at a distal end of the urethra into a bladder of the patient, and   subsequently, facilitate expansion of the urethra by retracting the implant and by the retracting, implant the implant around the urethra in tissue of a prostate of the patient.       

     In an embodiment, the implant includes a low-friction coating. 
     In an embodiment a surface of the implant includes a polished surface configured to reduce friction of the implant during implantation. 
     In an embodiment the implant is radially-expandable, and configured to expand upon emergence into the bladder. 
     In an embodiment the implant includes a transurethrally-implantable prostatic implant configured to be positionable in the prostate of the patient, and the implant is shaped so as to define an implant lumen that surrounds an outer circumference of the urethra upon implantation. 
     In an embodiment the implant is shaped to define an implant lumen having an inner diameter of at least 2.5 mm. 
     In an embodiment the implant is shaped to define an implant lumen having an inner diameter of between 2.5 mm and 15 mm. 
     In an embodiment the implant is configured to prevent stenosis of the urethra. 
     In an embodiment the implant is configured to treat benign prostate hyperplasia. 
     In an embodiment the delivery tool is shaped to define a delivery tool lumen for passing an imaging device therethrough. 
     In an embodiment the apparatus includes an imaging device configured to guide the retraction of the implant. 
     In an embodiment the delivery tool includes a rotating element configured to corkscrew the implant into the tissue during the retracting of the implant. 
     In an embodiment the delivery tool includes a rotating element configured to corkscrew the implant into the tissue by rotation about a longitudinal axis of the delivery tool. 
     In an embodiment the implant includes a flexible, biocompatible material selected from the group consisting of: nitinol and silicone. 
     In an embodiment the apparatus includes a needle coupled to a proximal end of the implant. 
     In an embodiment the needle includes a rigid, biocompatible material configured to puncture tissue of the patient. 
     In an embodiment the needle includes stainless steel. 
     In an embodiment the implant includes at least one rod, and the delivery tool is configured to implant the rod in tissue of the prostate at an angle that is less than 90 degrees with respect to a longitudinal axis of the urethra. 
     In an embodiment the apparatus includes at least one coiled implant, and the delivery tool is configured to implant the implant in tissue of the prostate in a manner in which the at least one coiled implant is couplable to the rod at at least a portion of the coiled implant. 
     In an embodiment, the rod has a longitudinal axis that is less than 90 degrees with respect to the longitudinal axis of the urethra, and the coiled implant is implantable at a non-zero angle with respect to the longitudinal axis of the rod. 
     In an embodiment, the implant includes a coiled implant including at least one coil. 
     In an embodiment, the delivery tool is configured to corkscrew the coiled implant into the prostate while retracting the implant. 
     In an embodiment, the coiled implant is configured to corkscrew into the prostate of the patient. 
     In an embodiment, the coil includes a conically-shaped coiled implant. 
     In an embodiment, a proximal coil of the conically-shaped coiled implant has a diameter that is larger than a diameter of a distal coil of the conically-shaped coiled implant. 
     In an embodiment, the coiled implant is configured to corkscrew into tissue of the patient. 
     In an embodiment, the coiled implant is shaped to define a proximal pointed end configured to puncture the tissue. 
     In an embodiment, the delivery tool is configured to implant the implant around the urethra by corkscrewing the coiled implant into the tissue while retracting the implant. 
     In an embodiment, the implant is shaped to define at least one slit configured for engaging of the delivery tool thereto. 
     In an embodiment, the implant includes a coiled implant. 
     In an embodiment, the implant is shaped to provide a proximal slit and a distal slit. 
     In an embodiment, the delivery tool includes a proximal locking mechanism and a distal locking mechanism, the proximal locking mechanism is configured to engage the proximal slit of the implant, and the distal locking mechanism is configured to engage the distal slit of the implant. 
     In an embodiment, the proximal and distal locking mechanisms are configured to maintain the implant in a compressed state thereof during the advancement of the implant into the bladder of the patient. 
     In an embodiment, the implant is configured to expand radially following a disengagement of the proximal locking mechanism therefrom. 
     In an embodiment, the implant is shaped to define a helical implant, and the apparatus includes a sheath shaped to define a hollow lumen helically surrounding the helical implant. 
     In an embodiment the apparatus includes, an ablation tool configured to be slidably advanced through the lumen of the sheath, and the sheath is shaped to define at least one hole at a proximal end thereof configured for advancement therethrough of at least a portion of the ablation tool. 
     In an embodiment the apparatus includes, a flexible tube coupled to a portion of the sheath, the tube being configured to facilitate passage of a fluid through the lumen of the sheath, and the sheath is shaped to define one or more holes configured for passage of the fluid externally to the implant. 
     In an embodiment, the implant includes a hollow, helical implant shaped to define a helical lumen thereof. 
     In an embodiment the apparatus includes, an ablation tool configured to be slidably advanced through the lumen of the implant, and the implant is shaped to define at least one hole at a proximal end thereof configured for advancement therethrough of at least a portion of the ablation tool. 
     In an embodiment the apparatus includes, a flexible tube coupled to a portion of the helical implant, the tube being configured to facilitate passage of a fluid through the lumen of the implant, and the implant is shaped to define one or more holes configured for passage of the fluid externally to the implant. 
     In an embodiment, the implant defines a first implant, and the apparatus includes a second implant. 
     In an embodiment, the first and second implants include respective first and second helical implants. 
     In an embodiment, the at least first and second helical implants are configured to assume respective longitudinal positions and are configured to be disposed in a relative spatial configuration in which: 
     the first and second helical implants are disposed coaxially, 
     the first and second helical implants are rotationally offset, and 
     the respective longitudinal positions of the first and second helical implants overlap at least in part. 
     In an embodiment, the first and second implants have the same diameter. 
     In an embodiment, the first and second helical implants each have a first pitch, and, when disposed in the relative spatial configuration, the first and second implants define an effective second pitch which is less than half the first pitch. 
     In an embodiment, the delivery tool is configured to implant the first and second helical implants sequentially and position the first and second helical implants in the relative spatial configuration thereof. 
     In an embodiment, the first and second helical implants are configured to be coupled to the delivery tool in the relative spatial configuration. 
     In an embodiment, the first and second helical implants are configured to be simultaneously implanted around the urethra of the patient. 
     In an embodiment, the at least first and second helical implants include respective transurethrally-implantable prostatic implants configured to be positionable in the prostate of the patient, and the first and second implants are shaped to define respective implant lumens that surround an outer circumference of the urethra upon implantation. 
     In an embodiment, the first and second helical implants are shaped to define respective proximal pointed ends configured to puncture the tissue. 
     There is further provided, in accordance with an embodiment of the present invention, a method, including: 
     distally advancing an implant through a urethra of a patient until the implant emerges in a bladder of the patient; and 
     facilitating expanding of a pre-operative perimeter of a portion of the urethra to a post-operative perimeter of the portion of the urethra that is larger than the pre-operative perimeter by proximally retracting the implant and implanting the implant in prostate tissue surrounding the urethra. 
     In an embodiment, expanding the pre-operative perimeter includes treating benign prostate hyperplasia. 
     In an embodiment, advancing the implant includes advancing a coiled implant defining an inner lumen thereof, and implanting the implant includes surrounding a portion of the urethra by the inner lumen of the coiled implant. 
     In an embodiment, facilitating the expanding of the pre-operative perimeter of a portion of the urethra includes the surrounding of the portion of the urethra by the inner lumen of the coiled implant. 
     In an embodiment, advancing the implant includes advancing at least one rod through the urethra, and implanting the implant includes retracting the rod into the prostate tissue at an angle that is less than 90 degrees with respect to a longitudinal axis of the urethra. 
     In an embodiment the method further includes: 
     distally advancing at least one coiled implant through the urethra of the patient; 
     further facilitating expanding of the pre-operative perimeter of the portion of the urethra by implanting the at least one coiled implant in the prostate tissue; and 
     facilitating coupling to the rod at least a portion of the coiled implant. 
     In an embodiment, the rod has a longitudinal axis that is less than 90 degrees with respect to the longitudinal axis of the urethra, and implanting the at least one coiled implant includes implanting the at least one coiled implant at a non-zero angle with respect to the longitudinal axis of the rod. 
     In an embodiment, the implant includes a radially-expandable implant, and advancing the implant into the bladder includes facilitating the expansion of the implant within the bladder of the patient. 
     In an embodiment, the implant includes a conically-shaped coiled implant in which a diameter of a proximal coil thereof is larger than a diameter of a distal coil thereof, and implanting the implant includes implanting the conically-shaped coiled implant in the prostate tissue of the patient. 
     In an embodiment, the method includes reversibly coupling the implant to a delivery tool, and advancing the implant includes advancing the delivery tool, when it is reversibly coupled to the implant, through the urethra of the patient. 
     In an embodiment, implanting the implant includes decoupling the implant from the delivery tool. 
     In an embodiment, proximally retracting the implant includes corkscrewing the implant into the prostate tissue by rotating at least a portion of the delivery tool. 
     In an embodiment, implanting the implant includes corkscrewing the implant into the prostate tissue by rotating at least a portion of the delivery tool. 
     In an embodiment, the method includes imaging via an imaging device coupled to the delivery tool. 
     In an embodiment, imaging includes examining the bladder of the patient via the imaging device, prior to the advancing of the implant through the urethra, by imaging a vicinity of a neck of the bladder of the patient. 
     In an embodiment, imaging includes imaging the implanting of the implant in the tissue surrounding the urethra of the patient. 
     In an embodiment, distally advancing the implant includes distally advancing at least first and second implants through the urethra of the patient, and implanting the implant includes implanting the at least first and second implants in the prostate tissue. 
     In an embodiment, implanting the at least first and second implants in tissue surrounding the urethra implant includes corkscrewing the first and second implant into the prostate tissue. 
     In an embodiment the method includes: 
     reversibly coupling the first implant to a delivery tool; and 
     reversibly coupling the second implant to the delivery tool, and 
     advancing the first and second implants includes advancing the first and second implants through the urethra of the patient by the delivery tool. 
     In an embodiment, implanting the first and second implants includes decoupling the first and second implants from the delivery tool. 
     In an embodiment, proximally retracting the implant includes corkscrewing the first and second implants into the tissue by rotating at least a portion of the delivery tool. 
     In an embodiment, implanting the first and second implants includes implanting first and second implants in respective longitudinal positions thereof in a relative spatial configuration in which: 
     the first and second helical implants are disposed coaxially, 
     the first and second helical implants are rotationally offset, and 
     the respective longitudinal positions of the first and second helical implants overlap at least in part. 
     In an embodiment, reversibly coupling the first and second implants to the delivery tool includes reversibly coupling to the delivery tool the first and second implants in the relative spatial configuration thereof, and advancing the first and second implants includes simultaneously advancing the first and second implants through the urethra of the patient. 
     In an embodiment, implanting the first and second implants in the relative spatial configuration thereof includes: 
     during a first period:
         reversibly coupling the first implant to the delivery tool,   advancing the delivery tool, when it is reversibly coupled to the first implant, through the urethra of the patient, and   implanting the first implant in tissue surrounding the urethra by proximally retracting the first implant through a first opening created by the first implant, and       

     during a second period subsequent to the first period:
         reversibly coupling the second implant to the delivery tool,   advancing the delivery tool, when it is reversibly coupled to the second implant, through the urethra of the patient, and   implanting the second implant in tissue surrounding the urethra by proximally retracting the second implant through a second opening created by the second implant, and the second opening is rotationally offset from the first opening with respect to a longitudinal axis of the urethra.       

     There is additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     at a first time, implanting an implant around a lumen of a patient by: 
     advancing the implant distally through the lumen until the implant emerges at a distal end of the lumen into a cavity, and 
     subsequently, implanting the implant around the lumen by proximally retracting the implant; and 
     at a second time, extracting the implant from around the lumen by:
         moving the implant distally by rotating the implant, and   subsequently, pulling the implant proximally through the lumen.       

     In an embodiment, implanting the implant around the lumen includes rotating the implant in a first direction thereof, and extracting the implant includes rotating the implant in a reverse direction to the first direction. 
     In an embodiment, the implant includes a radially-expandable implant, and advancing the implant includes allowing the expansion of the implant within the cavity. 
     In an embodiment, extracting the implant includes:
         clamping a distal portion of the implant and moving the implant distally by rotating the implant; and   clamping a proximal portion of the implant.       

     In an embodiment, the lumen includes a urethra of the patient and pulling the implant includes pulling the implant through the urethra. 
     In an embodiment, rotating the implant includes extracting the implant from a prostate of the patient. 
     There is yet further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     at least first and second helical implants configured to assume respective longitudinal positions and to be disposed in a relative spatial configuration in which: 
     the first and second helical implants are disposed coaxially, 
     the first and second helical implants are rotationally offset, and 
     the respective longitudinal positions of the first and second helical implants overlap at least in part; and 
     a delivery tool, configured to be reversibly coupled to the at least first and second helical implants, the tool configured to: 
     advance the at least first and second implants distally through a body lumen of a patient until the first and second implants emerge at a distal end of the body lumen into a body cavity of the patient, and
         implant the at least first and second implants in the relative spatial configuration thereof around the body lumen by retracting the first and second implants.       

     In an embodiment, the first and second implants have the same diameter. 
     In an embodiment, the first and second implants include low-friction coatings. 
     In an embodiment, the first and second implants are radially expandable, and configured to expand upon emergence into the body cavity. 
     In an embodiment, the body lumen includes a urethra, and the first and second implants are configured to be implanted around the urethra. 
     In an embodiment, the first and second implants include respective transurethrally-implantable prostatic implants configured to be positionable in a prostate of the patient, and the body lumen includes a urethra of the patient, the implants being shaped to define respective implant lumens that surround an outer circumference of the urethra upon implantation. 
     In an embodiment, the first and second implants are shaped to define respective implant lumens that surround an outer circumference of the lumen upon implantation. 
     In an embodiment, the first and second implants are shaped to define respective inner diameters of at least 2.5 mm. 
     In an embodiment, the first and second implants are shaped to define respective inner diameters of between 2.5 mm and 15 mm. 
     In an embodiment, the first and second helical implants each have a first pitch, and, when disposed in the relative spatial configuration, the first and second implants define an effective second pitch which is less than half the first pitch. 
     In an embodiment, the delivery tool is configured to implant the first and second helical implants sequentially and position the first and second helical implants in the relative spatial configuration thereof. 
     In an embodiment, the first and second helical implants are shaped to define respective proximal pointed ends configured to puncture the tissue. 
     In an embodiment, the first and second helical implants are configured to be coupled to the delivery tool in the relative spatial configuration. 
     In an embodiment, the first and second helical implants are configured to be simultaneously implanted around the body lumen of the patient. 
     There is still further provided, in accordance with an embodiment of the present invention, a method, including: 
     creating a first opening in tissue of a patient by puncturing the tissue; advancing through the first opening a first helical implant to a first longitudinal position; 
     creating a second opening in tissue of the patient by puncturing the tissue, the second opening being rotationally offset from the first opening with respect to a longitudinal axis of the first helical implant when it has been advanced through the first opening; and 
     advancing through the second opening a second helical implant to a second longitudinal position, in which:
         the first and second helical implants are disposed coaxially,   the first and second helical implants are rotationally offset with respect to each other, and   respective longitudinal positions of the first and second helical implants overlap at least in part.       

     In an embodiment, advancing through the first opening the first helical implant to the first longitudinal position includes corkscrewing the first helical implant into the tissue, and advancing through the second opening the second helical implant to the second longitudinal position includes corkscrewing the second helical implant into the tissue. 
     In an embodiment, the tissue includes a prostate of the patient, and advancing the first and second helical implants includes corkscrewing the first and second helical implants into the prostate. 
     In an embodiment, the method includes: 
     distally advancing the first and second helical implants through a body lumen of a patient until the first and second implants emerge in a body cavity of the patient, and: 
     advancing through the first opening the first helical implant to the first longitudinal position includes implanting the first implant in tissue surrounding the body lumen by proximally retracting the first implant, and 
     advancing through the second opening the second helical implant to the second longitudinal position includes implanting the second implant in tissue surrounding the body lumen by proximally retracting the second implant. 
     In an embodiment, the method includes: 
     reversibly coupling the first implant to a delivery tool; and 
     reversibly coupling the second implant to the delivery tool, and 
     distally advancing the first and second implants includes distally advancing the first and second implants through the body lumen of the patient by the delivery tool. 
     In an embodiment, implanting the first and second implants includes decoupling the first and second implants from the delivery tool. 
     In an embodiment, proximally retracting the implants includes corkscrewing the first and second implants into the tissue by rotating at least a portion of the delivery tool. 
     In an embodiment, reversibly coupling the first and second implants to the delivery tool includes reversibly coupling to the delivery tool the first and second implants in the relative spatial configuration thereof, and advancing the first and second implants includes simultaneously advancing the first and second implants through the body lumen of the patient. 
     In an embodiment, implanting the first and second implants in the relative spatial configuration thereof includes: 
     during a first period:
         reversibly coupling the first implant to the delivery tool,   advancing the delivery tool, when it is reversibly coupled to the first implant, through the body lumen of the patient, and   implanting the first implant in tissue surrounding the body lumen by proximally retracting the first implant through a first opening created by the first implant, and       

     during a second period subsequent to the first period:
         reversibly coupling the second implant to the delivery tool,   advancing the delivery tool, when it is reversibly coupled to the second implant, through the body lumen of the patient, and   implanting the second implant in tissue surrounding the body lumen by proximally retracting the second implant through a second opening created by the second implant, and the second opening is rotationally offset from the first opening with respect to a longitudinal axis of the body lumen.       

     There is yet additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a helical implant; and 
     a sheath, helically surrounding the implant, the sheath shaped to define one or more holes. 
     In an embodiment, the sheath is shaped to define three or more holes. 
     In an embodiment, the helical implant is shaped to define an inner lumen having a diameter thereof that is between 2.5 mm and 15 mm. 
     In an embodiment, the sheath tightly surrounds the helical implant. 
     In an embodiment the apparatus includes: 
     a lubricant; and 
     a pressure source configured to push the lubricant (a) from within a space between the helical implant and the sheath, (b) through the one or more holes, (c) to outside of the sheath. 
     There is also provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a helical implant having a wall shaped to define a plurality of holes, the helical implant shaped to define a helical lumen thereof; 
     a lubricant, disposed within the lumen; and 
     a pressure source, configured to push the lubricant through the plurality of holes. 
     In an embodiment, the pressure source includes a syringe. 
     In an embodiment, the helical implant is shaped to define an inner lumen having a diameter thereof that is between 2.5 mm and 15 mm. 
     There is additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     first and second coiled implants, an outer diameter of the second implant being smaller than an inner diameter of the first implant, one of the coiled implants being right-handed and one of the coiled implants being left-handed; and 
     a delivery tool, reversibly couplable to the first and second coiled implants, the tool being configured to facilitate implantation of the first and second implants around a body lumen of a patient. 
     In an embodiment, the second implant is configured to be disposed concentrically with respect to the first implant. 
     In an embodiment, the first and second implants includes low-friction coatings. 
     In an embodiment, a respective surface of each of the first and second implants includes a polished surface configured to reduce friction of the implants during implantation. 
     In an embodiment, the first and second implants are radially-expandable, and are configured to expand prior to the implantation of the first and second implants around the body lumen of the patient. 
     In an embodiment, the body lumen includes a urethra, and the first and second implants are configured to be implanted around the urethra. 
     In an embodiment, the first and second implants include respective transurethrally-implantable prostatic first and second implants configured to be positionable in a prostate of the patient, and the body lumen includes a urethra of the patient, the implants each being shaped to define a respective implant lumen that is configured to surround an outer circumference of the urethra upon implantation. 
     In an embodiment, the first and second implants are shaped to define respective implant lumens that are configured to surround an outer circumference of the lumen upon implantation. 
     In an embodiment, the first and second implants are each shaped to define respective inner diameters of at least 2.5 mm. 
     In an embodiment, the first and second implants are each shaped to define respective inner diameters of between 2.5 mm and 15 mm. 
     In an embodiment, the first and second implants are each shaped to define respective proximal pointed ends configured to puncture the tissue. 
     In an embodiment, the first and second implants are each shaped to define respective distal pointed ends configured to puncture the tissue. 
     In an embodiment, the first and second implants are configured to prevent stenosis of the body lumen. 
     In an embodiment the apparatus includes, an imaging device configured to guide the implantation of the implants. 
     In an embodiment, the delivery tool is shaped to define a delivery tool lumen for passing an imaging device therethrough. 
     In an embodiment, the delivery tool includes a rotating element configured to corkscrew the implants into the tissue during the implantation thereof. 
     In an embodiment, the delivery tool includes a rotating element configured to corkscrew the implants into the tissue by rotation about a longitudinal axis of the delivery tool. 
     In an embodiment, each one of the first and second implants is shaped to define at least two conically-shaped portions. 
     In an embodiment the apparatus includes, a motor coupled to the apparatus, the motor being configured to facilitate implantation of the first and second implants around the body lumen. 
     In an embodiment, the motor is coupled to the delivery tool. 
     In an embodiment the apparatus includes, first and second motors, the first motor is coupled to the first implant and the second motor is coupled to the second implant. 
     In an embodiment, the motor includes an ultrasound transducer configured to create vibrations in the implants in response to vibrations effected by the ultrasound transducer. 
     In an embodiment, the motor includes a vibrator configured to create vibrations in the implants in response to vibrations effected by the vibrator. 
     In an embodiment, the motor is configured to control the implantation of the implants around the body lumen by cycling between: 
     (a) facilitating advancement, by a first number of degrees, of the implants in their respective first rotational directions through tissue of the body lumen, and 
     (b) facilitating retracting, by a second number of degrees, of the implants in a second rotational direction that is opposite the first direction. 
     In an embodiment: 
     the first and second implants includes first and second wires, respectively, the first and second wires being shaped to define the respective first and second implants, 
     the first wire has a width that is larger than the second wire, and 
     the first implant has a diameter that is larger than the second implant. 
     In an embodiment, the first and second wires are shaped to define a shape in a cross-section thereof, the shape being selected from the group consisting of: a triangle, a square, a diamond, a circle, and an ellipse. 
     In an embodiment, the first and second implants are configured to be coupled to the delivery tool in a configuration in which the second implant is disposed concentrically with respect to the first implant. 
     In an embodiment, the delivery tool is configured to facilitate simultaneous implantation of the first and second helical implants around the body lumen of the patient. 
     In an embodiment, the first and second helical implants are configured to be sequentially implanted around the body lumen of the patient, and following the implantation of the first and second implants, the first and second implants are configured to be disposed concentrically with respect to each other. 
     In an embodiment, the first and second helical implants are disposed at respective longitudinal positions with respect to the delivery tool. 
     In an embodiment, the first and second implants each include a flexible, biocompatible material selected from the group consisting of: nitinol and silicone. 
     In an embodiment the apparatus includes, a respective needle coupled to at least one end of each of the first and second implants, the needle being configured to puncture tissue of the patient. 
     In an embodiment, the needle includes a rigid, biocompatible material configured to puncture tissue of the patient. 
     In an embodiment, the needle includes stainless steel. 
     In an embodiment, the first and second coiled implants include respective coiled implants that are conically-shaped at least in part. 
     In an embodiment, a proximal coil near a proximal end of each one of the conically-shaped coiled implants has a diameter that is larger than a diameter of a distal coil near a distal end of each one of the conically-shaped coiled implants. 
     In an embodiment, the delivery tool is configured to facilitate implantation of the first and second implants around the body lumen by corkscrewing the first and second coiled implants into the tissue. 
     In an embodiment, the tissue includes a prostate of the patient and the body lumen includes a urethra of the patient, and the delivery tool is configured to facilitate corkscrewing of the first and second coiled implants into the prostate. 
     In an embodiment, the delivery tool is configured to facilitate the implantation of the first and second implants from within the urethra. 
     In an embodiment, the delivery tool is configured to facilitate distal advancement of the first and second implants around the urethra by facilitating corkscrewing of the first and second implants. 
     In an embodiment, the delivery tool is configured to facilitate: 
     advancement of the first and second implants distally through the body lumen of the patient until the first and second implants emerge at a distal end of the body lumen into a body cavity of the patient, and 
     implantation of the first and second implants around the body lumen by retracting the first and second implants. 
     In an embodiment, the delivery tool is configured to facilitate: 
     rotation of the first implant in a first direction, 
     rotation of the second implant in a second direction thereof, and 
     implantation of the first and second implants in a manner in which the second implant is disposed concentrically with respect to the first implant. 
     In an embodiment, the body lumen includes a urethra of the patient and the body cavity includes a bladder of the patient, and the delivery tool is configured to facilitate the implantation of the first and second implants around the urethra of the patient. 
     In an embodiment the apparatus includes, first and second sheaths having respective first and second lumens thereof, the first and second lumens configured to helically surround the first and second coiled implants, respectively. 
     In an embodiment the apparatus includes: 
     a first ablation tool configured to be slidably advanced through the first lumen, the first sheath is shaped to define at least one first hole at an end of the implant that is configured to puncture tissue of the patient, and a portion of the first ablation tool is configured for advancement through the first hole; and 
     a second ablation tool configured to be slidably advanced through the second lumen, the second sheath is shaped to define at least one second hole at an end of implant that is configured to puncture tissue of the patient, and a portion of the first ablation tool is configured for advancement through the second hole. 
     In an embodiment the apparatus includes: 
     a first flexible tube coupled to a portion of the first coiled implant, the first tube being configured to facilitate passage of a fluid through the lumen of the implant, and the first implant is shaped to define one or more holes configured for passage of the fluid externally to the first implant; and 
     a second flexible tube coupled to a portion of the second coiled implant, the second tube being configured to facilitate passage of a fluid through the lumen of the implant, and the second implant is shaped to define one or more holes configured for passage of the fluid externally to the second implant. 
     In an embodiment, the first and second implants include respective first and second hollow, coiled implants shaped to define respective first and second helical lumens thereof. 
     In an embodiment the apparatus includes: 
     a first ablation tool configured to be slidably advanced through the first lumen, and the first sheath is shaped to define at least one first hole near an end of the first implant that is configured to puncture tissue of the patient, a portion of the first ablation tool is configured for advancement through the first hole; and 
     a second ablation tool configured to be slidably advanced through the second lumen, and the second sheath is shaped to define at least one second hole near an end of the second implant that is configured to puncture tissue of the patient, and a portion of the second ablation tool is configured for advancement therethrough the second hole. 
     In an embodiment the apparatus includes: 
     a first flexible tube coupled to a portion of the first coiled implant, the first tube being configured to facilitate passage of a fluid through the first lumen of the first implant, and the first implant is shaped to define one or more first holes configured for passage of the fluid externally to the implant; and 
     a second flexible tube coupled to a portion of the second coiled implant, the second tube being configured to facilitate passage of a fluid through the second lumen of the second implant, and the second implant is shaped to define one or more second holes configured for passage of the fluid externally to the implant. 
     There is yet additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a coiled implant including:
         a proximal coil, near a proximal end of the coiled implant, the proximal coil having a diameter thereof during a resting state of the coiled implant;   a distal coil, near a distal end of the coiled implant, the distal coil having a diameter thereof during the resting state; and       

     a plurality of coils disposed between the proximal and distal coils, the coiled implant being shaped in a manner in which, during the resting state thereof, the plurality of coils have respective diameters, the respective diameters of the plurality of coils each being smaller than the diameters of the proximal and distal coils; and 
     a delivery tool, removably couplable to the coiled implant, the tool configured to facilitate implantation of the implant around a body lumen of a patient. 
     In an embodiment, the proximal coil is a proximal-most coil of the coiled implant. 
     In an embodiment, the distal coil is a distal-most coil of the coiled implant. 
     In an embodiment, the delivery tool is configured to facilitate: 
     advancement of the implant distally through the body lumen of the patient until the implant emerges at a distal end of the body lumen into a body cavity of the patient, and 
     subsequent implantation of the implant around the body lumen by retracting the implant. 
     In an embodiment, the respective diameters of the proximal and distal coils are substantially equal. 
     In an embodiment, the plurality of coils includes: 
     a first conically-shaped portion of coils disposed in series in a manner in which one coil thereof is disposed adjacently to the proximal coil, and respective diameters of the coils of the first portion of coils decrease in series from (a) the coil adjacent to the proximal coil to (b) a coil of the coils of the first portion that is furthest from the proximal coil; and 
     a second conically-shaped portion of coils disposed in series in a manner in which one coil thereof is disposed adjacently to the distal coil, and respective diameters of the coils of the second portion of coils decrease in series from (a) the coil adjacent to the distal coil to (b) a coil of the coils of the second portion that is furthest from the distal coil. 
     In an embodiment the apparatus includes, a motor coupled to the apparatus, the motor being configured to facilitate implantation of the implant around the body lumen. 
     In an embodiment, the motor is coupled to the delivery tool. 
     In an embodiment, the motor is coupled to the implant. 
     In an embodiment, the motor includes an ultrasound transducer configured to create vibrations in the implant in response to vibrations effected by the ultrasound transducer. 
     In an embodiment, the motor includes a vibrator configured to create vibrations in the implant in response to vibrations effected by the vibrator. 
     In an embodiment, the motor is configured to control the implantation of the implant around the body lumen by cycling between: 
     (a) facilitating advancement, by a first number of degrees, of the implant in a first rotational direction through tissue of the body lumen, and 
     (b) facilitating retracting, by a second number of degrees, of the implant in a second rotational direction that is opposite the first direction. 
     There is yet further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a plurality of curved needles; and 
     a delivery tool coupled to the plurality of curved needles, the delivery tool being configured to facilitate advancing of the needles through a lumen of a patient, puncturing by the needles of an inner wall of the lumen, advancing of the needles around the lumen, and decoupling of the needles from the delivery tool. 
     In an embodiment, each one of the plurality of curved needles is not coupled to one another following the decoupling of the needles from the delivery tool. 
     In an embodiment, each one of the plurality of curved needles is shaped to define between 180 and 360 degrees in a resting state thereof. 
     In an embodiment, each one of the plurality of curved needles is shaped to define between 250 and 300 degrees in the resting state thereof. 
     There is still additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a plurality of distinct coiled implants; and 
     a delivery tool configured to simultaneously hold the implants, and facilitate advancement of the implants in a lumen of a patient and implantation of the implants around the lumen. 
     In an embodiment, the implants are each shaped to define an inner lumen having a diameter that is larger than a diameter of the body lumen. 
     In an embodiment, the delivery tool is configured to facilitate implantation of the implants around the lumen from within the lumen. 
     In an embodiment, the delivery tool is configured to facilitate corkscrewing of the implants around the lumen from within the lumen. 
     In an embodiment, each implant of the plurality of distinct coiled implants is shaped to have 1-5 coils in a resting state thereof. 
     In an embodiment, the plurality of distinct coiled implants are each shaped to have 3-4 coils in a resting state thereof. 
     In an embodiment the apparatus includes a motor coupled to the apparatus, the motor being configured to facilitate implantation of the implant around the body lumen. 
     In an embodiment, the motor is coupled to the delivery tool. 
     In an embodiment the apparatus includes a plurality of motors, and a respective motor of the plurality of motors is coupled to each implant of the plurality of implants. 
     In an embodiment, the motor includes an ultrasound transducer configured to create vibrations in the implants in response to vibrations effected by the ultrasound transducer. 
     In an embodiment, the motor includes a vibrator configured to create vibrations in the implants in response to vibrations effected by the vibrator. 
     In an embodiment, the motor is configured to control the implantation of the implants around the body lumen by cycling between: 
     (a) facilitating advancement, by a first number of degrees, of the implants in a first rotational direction through tissue of the body lumen, and 
     (b) facilitating retracting, by a second number of degrees, of the implants in a second rotational direction that is opposite the first direction. 
     There is further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a conically-shaped coiled implant shaped to define a longitudinal lumen thereof, the implant including at least a proximal coil having an outer surface thereof and a distal coil having an inner surface thereof, the distal coil having a diameter that is larger than the proximal coil; 
     a plurality of rods configured to be disposed in part within the longitudinal lumen of the implant; and 
     a delivery tool, removably coupled to the implant, the tool configured to:
         facilitate advancement of the implant around a body lumen of a patient in a manner in which the longitudinal lumen of the implant surrounds the body lumen of the patient, and   subsequently, facilitate implantation of the plurality of rods substantially in parallel with and around the body lumen by facilitating advancement of the rods below the inner surface of the distal coil and above the outer surface of the proximal coil.       

     In an embodiment, the implant includes a flexible, biocompatible material selected from the group consisting of: nitinol and silicone, and the rods include a material selected from the group consisting of: nitinol, silicone, and stainless steel. 
     In an embodiment, the delivery tool is configured to facilitate implantation of the coiled implant around the body lumen from within the body lumen. 
     In an embodiment, the delivery tool is configured to facilitate corkscrewing of the coiled implant around the body lumen from within the body lumen. 
     In an embodiment, the delivery tool is configured to facilitate advancement of the rods into a body cavity at an end of the lumen, and implantation of the rods around the body lumen from within the body cavity. 
     In an embodiment, the delivery tool is configured to facilitate corkscrewing of the coiled implant around the body lumen from within the body cavity. 
     In an embodiment, the body cavity includes a bladder of the patient and the body lumen includes a urethra of the patient, and the delivery tool is configured to facilitate corkscrewing of the coiled implant around the body lumen from within the body cavity. 
     There is still further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     an elongate coiled structure having a lumen and a transverse cross-sectional shape selected from the group consisting of: a square, a diamond, and a triangle, the elongate structure being resorbable by a body lumen of a patient; and 
     a delivery tool reversibly couplable to the elongate structure and configured to facilitate advancement of the structure to a vicinity within the body lumen of the patient. 
     In an embodiment, the elongate structure includes a pro-fibrotic coating. 
     In an embodiment, the body lumen includes a urethra of the patient and the vicinity within the body lumen includes a portion of the urethra that is surrounded by a prostate of the patient, and the elongate structure is configured to be disposed in the portion of the urethra that is surrounded by the prostate of the patient. 
     In an embodiment, the elongate structure includes a radially-expandable structure configured to expand in the vicinity of the body lumen. 
     In an embodiment, the elongate structure includes a plurality of successively-disposed coils defining respective areas between the successive coils, and the coils are configured to pinch tissue into the areas between the successive coils. 
     In an embodiment, the elongate structure includes a wire defining the elongate structure, and the wire shaped to define a shape in cross-section thereof, the shape being selected from the group consisting of: a triangle, a square, a diamond, a circle, and an ellipse. 
     In an embodiment the apparatus includes, a mechanical element selected from the group consisting of: a stent, a balloon, a wire and basket, and the mechanical element is disposed within the lumen of the elongate structure between the elongate structure and the delivery tool, and the mechanical structure is configured to radially expand the elongate structure. 
     In an embodiment, the elongate structure includes stainless steel. 
     There is additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     advancing through a body lumen of a patient first and second coiled implants, an outer diameter of the second implant being smaller than an inner diameter of the first implant, one of the coiled implants being right-handed and one of the coiled implants being left-handed; and 
     implanting the first and second implants around the body lumen in a manner in which, subsequently to the implanting, the second implant is disposed concentrically with respect to the first implant. 
     In an embodiment, implanting the first and second implants includes: 
     rotating the first implant in a first direction; and 
     rotating the second implant in a second direction that is opposite the first direction. 
     In an embodiment, implanting the first and second implants includes implanting the first and second implants simultaneously. 
     In an embodiment, implanting the first and second implants includes implanting the first and second implants in sequence. 
     In an embodiment, implanting the first and second implants includes cycling between: 
     (a) advancing, by a first number of degrees, the first and second implants in their respective first rotational directions through tissue of the body lumen, and 
     (b) retracting, by a second number of degrees, the first and second implants in a second rotational direction that is opposite the first direction. 
     In an embodiment the method includes, advancing the first and second implants through the body lumen and into a body cavity of the patient prior to the implanting, and implanting the first and second implants around the lumen includes implanting the first and second implants around the body lumen by proximally corkscrewing the implants around the body lumen from within the body cavity. 
     In an embodiment: 
     the body lumen includes a urethra of the patient and the body cavity includes a bladder of the patient, 
     advancing the implants through the body lumen and into the body cavity of the patient includes advancing the implants through the urethra and into the bladder of the patient, and 
     proximally corkscrewing the implants around the body lumen from within the body cavity includes proximally corkscrewing the implants around the urethra from within the bladder. 
     In an embodiment, implanting the first and second implants around the body lumen of the patient includes implanting the implants around the body lumen of the patient from within the body lumen. 
     In an embodiment, implanting the first and second implants around the body lumen of the patient from within the body lumen includes corkscrewing the first and second implants around the lumen from within the lumen. 
     In an embodiment the method includes, vibrating the first and second implants during the implanting. 
     In an embodiment, vibrating the first and second implants includes mechanically vibrating the implants. 
     In an embodiment, vibrating the first and second implants includes vibrating the implants by applying to the implants ultrasound energy. 
     There is yet additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     advancing through a body lumen of a patient, a coiled implant including:
         a proximal coil, near a proximal end of the coiled implant, the proximal coil having a diameter thereof during a resting state of the coiled implant,   a distal coil, near a distal end of the coiled implant, the distal coil having a second diameter thereof during the resting state, and       

     a plurality of coils disposed between the proximal and distal coils, the coiled implant being shaped in a manner in which, during the resting state thereof, the plurality of coils have respective diameters, the respective diameters of the plurality of coils each being smaller than the diameters of the proximal and distal coils; and 
     implanting the implant around the body lumen of the patient. 
     In an embodiment, implanting the implant includes cycling between: 
     (a) advancing, by a first number of degrees, the implant in a first rotational direction through tissue of the body lumen, and 
     (b) retracting, by a second number of degrees, the implant in a second rotational direction that is opposite the first direction. 
     In an embodiment the method includes, advancing the implant through the body lumen and into a body cavity of the patient prior to the implanting, and implanting the implant around the lumen includes implanting the implant around the body lumen by proximally corkscrewing the implant around the body lumen from within the body cavity. 
     In an embodiment: 
     the body lumen includes a urethra of the patient and the body cavity includes a bladder of the patient, 
     advancing the implant through the body lumen and into the body cavity of the patient includes advancing the implant through the urethra and into the bladder of the patient, and 
     proximally corkscrewing the implant around the body lumen from within the body cavity includes proximally corkscrewing the implant around the urethra from within the bladder. 
     In an embodiment, implanting the implant around the body lumen of the patient includes implanting the implant around the body lumen of the patient from within the body lumen. 
     In an embodiment, implanting the implant around the body lumen of the patient from within the body lumen includes corkscrewing the implant around the body lumen from within the lumen. 
     In an embodiment the method includes, vibrating the implant during the implanting. 
     In an embodiment, vibrating the implant includes mechanically vibrating the implant. 
     In an embodiment, vibrating the implant includes vibrating the implant by applying ultrasound energy to the implant. 
     There is further provided, in accordance with an embodiment of the present invention, a method including: 
     advancing a plurality of curved needles through a body lumen of a patient; and maintaining an open state of the body lumen by implanting the plurality of curved needles around at least a part of the body lumen of the patient. 
     In an embodiment, implanting the plurality of curved needles around the body lumen includes implanting the plurality of curved needles around the body lumen from within the urethra. 
     In an embodiment, implanting the plurality of curved needles around the body lumen includes puncturing an inner wall of the body lumen by the plurality of curved needles. 
     There is additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     simultaneously advancing a plurality of distinct coiled implants through a body lumen of a patient; and 
     implanting the plurality of implants around the lumen. 
     In an embodiment, implanting the plurality of implants includes cycling between: 
     (a) advancing, by a first number of degrees, the implants in a first rotational direction through tissue of the body lumen, and 
     (b) retracting, by a second number of degrees, the implants in a second rotational direction that is opposite the first direction. 
     In an embodiment the method includes, vibrating the implants during the implanting. 
     In an embodiment, vibrating the implants includes mechanically vibrating the implants. 
     In an embodiment, vibrating the implants includes vibrating the implants by applying ultrasound energy to the implants. 
     In an embodiment, implanting the first and second implants around the body lumen of the patient includes implanting the implants around the body lumen of the patient from within the body lumen. 
     In an embodiment, implanting the first and second implants around the body lumen of the patient from within the body lumen includes corkscrewing the first and second implants around the lumen from within the lumen. 
     There is further provided, in accordance with an embodiment of the present invention, a method, including: 
     advancing, through a body lumen of a patient, a conically-shaped coiled implant shaped to define a longitudinal lumen thereof, the implant including at least a proximal coil having an outer surface thereof and a distal coil having an inner surface thereof, the distal coil having a diameter that is larger than the proximal coil; 
     implanting the implant around the body lumen of the patient; 
     advancing a plurality of rods toward the implant; and 
     implanting the rods in part within the longitudinal lumen of the implant and substantially in parallel with and around the body lumen by advancing the plurality of rods below the inner surface of the distal coil and above the outer surface of the proximal coil. 
     There is yet further provided, in accordance with an embodiment of the present invention, a method, including: 
     advancing through a body lumen of a patient an elongate coiled structure having a lumen and a transverse cross-sectional shape selected from the group consisting of: a square, a diamond, and a triangle, the elongate structure being resorbable by a body lumen of a patient; and 
     releasing the elongate structure in a vicinity within the body lumen of the patient. 
     In an embodiment, releasing the elongate structure includes facilitating expansion of the elongate structure within the body lumen. 
     There is yet additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     advancing an implant to a vicinity of soft tissue of a body lumen of the patient; 
     implanting the implant in the soft tissue by applying a jackhammer force to the implant during the implanting. 
     In an embodiment, applying the jackhammer force to the implant includes remotely applying the force to the implant. 
     There is still further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a transurethral delivery tool insertable in a urethra of a patient, the tool having a flexible distal tip that is:
         deflectable from a position that is aligned with a longitudinal axis of the tool, and   when deflected, operative to compress tissue of a prostate of the patient, by pushing a wall of the urethra; and       

     at least one implant that is deliverable to a portion of the compressed tissue and configured to maintain the tissue in a compressed state upon withdrawal of the delivery tool from the urethra. 
     In an embodiment the apparatus includes, an imaging device couplable to the delivery tool. 
     In an embodiment, the at least one implant includes a plurality of implants, and the delivery tool is configured to implant the plurality of implants by orienting the implants radially with respect to a portion of the urethra. 
     In an embodiment, the at least one implant includes a plurality of implants, and the delivery tool is configured to implant each of the plurality of implants at respective transverse planes of the urethra that are disposed along a longitudinal axis of the urethra. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the tissue and does not extend within the urethra. 
     In an embodiment, the implant includes a coiled implant defining an implant lumen having a longitudinal axis thereof, and the delivery tool is configured to orient the implant with respect to the urethra of the patient in a manner in which: 
     the implant is disposed entirely within the tissue of the prostate of the patient, and 
     the longitudinal axis of the implant lumen defined by the implant is disposed at a nonzero angle with respect to a longitudinal axis of the urethra. 
     In an embodiment, the delivery tool is configured to deliver the implant in a manner in which the longitudinal axis of the implant lumen is disposed substantially perpendicularly with respect to the longitudinal axis of the urethra. 
     In an embodiment the implant includes: 
     a body portion including a plurality of successive contiguous coils and defining a longitudinal axis of the implant, 
     a first end including a first coil that is at a first end of the body portion, the first end being configured to puncture urethral tissue of the patient; and 
     a second end including a second coil that is at a second end of the body portion, the second end being configured to be disposed within the prostate tissue. 
     In an embodiment the apparatus includes, a wire, and the at least one implant includes a plurality of implants, and the plurality of implants are coupled to each other by means of the wire. 
     In an embodiment: 
     the wire has first and second ends and a portion disposed between the first and second ends, the portion having a first-end-to-second-end length, 
     the wire has a longitudinal axis measured along the length, and 
     each of the implants is coupled to the wire at successive sites along the longitudinal axis of the wire. 
     In an embodiment, the delivery tool is configured to implant the plurality of implants such that upon implantation, each of the implants is coupled to the wire at successive sites along the longitudinal axis of the wire. 
     In an embodiment, the implant is longitudinally compressible following implantation and configured to further compress the prostate tissue. 
     In an embodiment, the implant is longitudinally compressible following implantation, in response to an application of energy thereto by an energy source. 
     In an embodiment, the implant is longitudinally compressible, in response to an increase in temperature of the implant as a result of implantation. 
     In an embodiment, the implant includes a screw implant defining an implant body having a longitudinal axis thereof, and the delivery tool is configured to orient the implant with respect to the urethra of the patient in a manner in which: 
     the implant is at least partially disposed within the tissue of the prostate of the patient, and 
     the longitudinal axis of the implant body is disposed at a nonzero angle with respect to a longitudinal axis of the urethra. 
     In an embodiment, the delivery tool is configured to deliver the implant in a manner in which the longitudinal axis of the implant body is disposed substantially perpendicularly with respect to the longitudinal axis of the urethra. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is partially embedded within the prostate tissue in a manner in which the implant (a) does not extend beyond a prostate capsule of the patient, and (b) is partially disposed within the urethra. 
     In an embodiment, the implant includes a screw implant including: a body portion having a longitudinal axis thereof, 
     a first end including a head portion that is at a first end of the body portion; and 
     a second end including a pointed tip portion that is at a second end of the body portion, the pointed tip being configured to puncture urethral tissue of the patient. 
     In an embodiment, at least a portion of the implant includes a biodegradable material. 
     In an embodiment, the portion of the implant including the biodegradable material further includes a medication. 
     In an embodiment, the medication includes a medication for treatment of benign prostatic hyperplasia. 
     In an embodiment, the implant includes at least one flexible curved implant shaped to define an arc of up to 360 degrees in an expanded state thereof. 
     In an embodiment, the flexible curved implant, in the expanded state, is shaped to define a plane having a normal thereto, and the delivery tool is configured to implant the implant in a manner in which the normal to the plane defined by the implant is substantially parallel to a longitudinal axis of the urethra. 
     In an embodiment, the flexible curved implant includes a resilient curved implant, the resilient curved implant: 
     in an expanded state thereof, is shaped to define an arc of up to 360 degrees and a plane having a normal thereto, 
     is implantable in prostate tissue surrounding the urethra of a patient and configured to move the prostate tissue away from a longitudinal axis of the urethra, 
     during implantation, has a first configuration thereof in which the implant defines a first radius of curvature, 
     following implantation, assumes a second configuration thereof in which the implant defines a second radius of curvature, and 
     while transitioning between the first and second configurations, is operative to radially push the prostate tissue. 
     In an embodiment, the first radius of curvature is smaller than the second radius of curvature. 
     In an embodiment, the at least one flexible curved implant includes a plurality of flexible curved implants, and the delivery tool is operative to implant the plurality of flexible curved implants around a portion of the urethra. 
     In an embodiment, the delivery tool is operative to implant: 
     a first one of the plurality of implants at least in part in a first lobe of the prostate of the patient, and 
     a second one of the plurality of implants at least in part in a second lobe of the prostate of the patient. 
     In an embodiment, the delivery tool is operative to implant: 
     the first one of the plurality of implants entirely within the first lobe, and 
     the second one of the plurality of implants entirely within the second lobe. 
     In an embodiment the apparatus includes, at least one inflatable element coupled to the delivery tool at a distal portion thereof, the inflatable element is configured to be inflated in a manner in which the inflatable element: 
     contacts an inner wall of the urethra and applies pressure thereto, and 
     stabilizes the delivery tool during deflection of the distal tip and implantation of the implant. 
     In an embodiment, the inflatable element has a volume in an inflated state thereof that is 1-50 cc. 
     In an embodiment, the inflatable element includes an annular inflatable element surrounding the distal portion of the delivery tool. 
     In an embodiment, the inflatable element is further operative to compress the prostate tissue and maintain the prostate tissue in a compressed state during implantation of the implant. 
     There is still additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a transurethral delivery tool insertable in a urethra of a patient, the tool being configured to compress tissue of a prostate by pushing a wall of the urethra; 
     at least first and second implants deliverable to a portion of the compressed tissue and configured to maintain the tissue in a compressed state upon withdrawal of the delivery tool from the urethra; and 
     a flexible longitudinal member coupled at a first portion thereof to the first implant and at a second portion thereof to the second implant, the longitudinal member having an extendable portion between the first and second portions thereof, 
     the delivery tool is configured to:
         implant the first implant at a first location in a first portion of the tissue of the prostate, and       

     extend the extendable portion of the wire to a second location in tissue surrounding the urethra by implanting the second implant at the second location in a second portion of the tissue of the prostate. 
     In an embodiment, the at least first and second implants are configured to compress the respective first and second portion of the tissue of the prostate, and the extendable portion is configured to provide supplemental radial compressing of the tissue of the prostate. 
     In an embodiment, each one of the first and second implants includes: 
     a body portion including a plurality of successive contiguous coils, the body portion defining a longitudinal axis of the implant; 
     a first end including a first coil that is at a first end of the body portion, the first end being configured to puncture urethral tissue of the patient; and 
     a second end including a second coil that is at a second end of the body portion, the second end being configured to be disposed within the prostate tissue. 
     In an embodiment, the at least first and second implants includes a plurality of implants, and the plurality of implants are coupled to each other by being coupled to the wire at respective locations along the wire. 
     In an embodiment: 
     the wire has first and second ends and a portion disposed between the first and second ends, the portion having a first-end-to-second-end length, 
     the wire has a longitudinal axis measured along the length of the portion, and 
     each of the plurality of implants is coupled to the wire at successive sites along the longitudinal axis of the wire. 
     In an embodiment, the delivery tool is configured to implant the plurality of implants such that upon implantation, each of the implants is coupled to successive sites along the longitudinal axis of the wire. 
     In an embodiment, each of the at least first and second implants is longitudinally compressible along the longitudinal axis thereof following implantation to further compress the tissue of the prostate. 
     There is yet additionally provided, in accordance with an embodiment of the present invention, apparatus, including: 
     a transurethral delivery tool insertable in a urethra of a patient, and configured to compress tissue of a prostate by pushing a wall of the urethra; and 
     at least one rod implantable in tissue of the prostate; and 
     at least one implant that is deliverable by the delivery tool to a portion of the compressed tissue, at least a portion of the implant being couplable to the rod to maintain the tissue in a compressed state upon withdrawal of the delivery tool from the urethra. 
     In an embodiment, the delivery tool includes a flexible distal tip that is deflectable from a position that is aligned with a longitudinal axis of the tool, and when deflected, operative to additionally compress tissue of the prostate of the patient, by pushing the wall of the urethra. 
     In an embodiment: 
     the rod has first and second ends and a portion disposed between the first and second ends, the portion having a first-end-to-second-end length, 
     the rod has a longitudinal axis measured along the length of the portion, 
     the at least one implant includes a plurality of implants, and 
     each of the plurality of implants is coupled at at least respective portions thereof to the rod at successive sites along the longitudinal axis of the rod. 
     In an embodiment: 
     the rod has first and second ends and a portion disposed between the first and second ends, the portion having a first-end-to-second-end length, 
     the rod has a longitudinal axis measured along the length of the portion, 
     the at least one implant includes a plurality of implants, and 
     the delivery tool is configured to implant the plurality of implants such that upon implantation, each of the plurality of implants is coupled at at least a portion thereof to successive sites along the longitudinal axis of the rod. 
     In an embodiment, the at least one implant is longitudinally compressible following implantation and configured to further compress the prostate tissue. 
     In an embodiment, the at least one rod includes a plurality of rods. 
     There is yet further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     at least one implant; and 
     a transurethral delivery tool insertable in a urethra of a patient, configured to deliver the implant in a manner in which:
         the implant is disposed entirely within a portion of tissue of a prostate of the patient, and   a longitudinal axis of a lumen of the implant is disposed at a nonzero angle with respect to a longitudinal axis of the urethra.       

     In an embodiment, the implant includes: 
     a body portion including a plurality of successive contiguous coils and defining an implant lumen having a longitudinal axis thereof; 
     a first end including a first coil that is at a first end of the body portion, the first end being configured to puncture urethral tissue of a patient; and 
     a second end including a second coil that is at a second end of the body portion, the second end being configured to be disposed within tissue of a prostate of the patient. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the prostate tissue and does not extend within the urethra. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the prostate tissue and does not extend beyond a prostate capsule of the prostate of the patient. 
     In an embodiment, the delivery tool is configured to deliver the implant in a manner in which the longitudinal axis of the implant lumen is disposed substantially perpendicularly with respect to the longitudinal axis of the urethra. 
     In an embodiment, the at least one implant includes a plurality of implants, and the delivery tool is configured to implant the plurality of implants by orienting the implants radially with respect to a portion of the urethra. 
     In an embodiment, the at least one implant includes a plurality of implants, and the delivery tool is configured to implant each of the plurality of implants at respective transverse planes of the urethra that are disposed along the longitudinal axis of the urethra. 
     In an embodiment: 
     the delivery tool:
         when deflected, is operative to compress the prostate tissue by pushing a wall of the urethra, and   operative to implant the implant in a portion of the compressed prostate tissue, and       

     the implant is configured to maintain the portion of the prostate tissue in a compressed state upon withdrawal of the delivery tool from the urethra. 
     In an embodiment, the implant following implantation is longitudinally compressible along the longitudinal axis of the lumen and configured to compress the portion of tissue of the prostate. 
     In an embodiment, the implant is longitudinally compressible following implantation in response to an application of energy thereto by an energy source disposed externally to the body of the patient and not in contact with the implant. 
     In an embodiment, the implant is longitudinally compressible, in response to an increase in temperature of the implant as a result of implantation. 
     In an embodiment the apparatus includes, at least one inflatable element coupled to the delivery tool at a distal portion thereof, and the inflatable element is configured to be inflated in a manner in which the inflatable element: 
     contacts an inner wall of the urethra and applies pressure thereto, and 
     stabilizes the delivery tool during implantation of the implant. 
     In an embodiment, the inflatable element is operative to compress the portion of the prostate tissue and maintain the prostate tissue in a compressed state during implantation of the implant. 
     There is still further provided, in accordance with an embodiment of the present invention, apparatus, including: 
     at least one flexible curved implant shaped to define an arc of up to 360 degrees in an expanded state thereof, the implant being implantable in prostate tissue surrounding a urethra; and 
     a transurethral delivery tool having a delivery tool lumen thereof for housing the implant in a compressed state thereof, and shaped to define an opening in a surface of the delivery tool, through which the implant passes, changing from the compressed state to the expanded state as a result of passing through the opening, 
     the implant in the expanded state being shaped to define a plane having a normal thereto, and the delivery tool being configured to implant the implant in a manner in which the normal to the plane defined by the implant is substantially parallel to a longitudinal axis of the urethra. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the prostate tissue and does not extend beyond a prostate capsule of a prostate of the patient. 
     In an embodiment, while transitioning between the compressed state and the expanded state, the implant is operative to radially push the prostate tissue. 
     In an embodiment the apparatus includes, a curved implantation-facilitating sleeve configured to surround the implant as the implant is housed in the delivery tool lumen, the implantation-facilitating sleeve being: 
     disposed in a compressed state thereof while disposed within the delivery tool lumen, 
     while surrounding the implant, advanceable though the opening in the surface of the delivery tool, 
     changeable from the compressed state thereof to an expanded state thereof as a result of passing through the opening, and 
     shaped to define a pointed tip configured to puncture the prostate tissue and create a channel therein for passage of the implant. 
     In an embodiment, following implantation of the implant in the channel of the prostate tissue, the sleeve is retractable back into the delivery tool lumen. 
     In an embodiment, while transitioning between the compressed state and the expanded state, the sleeve is operative to radially push the prostate tissue. 
     In an embodiment, the flexible curved implant includes a resilient curved implant: 
     the resilient curved implant, in an expanded state thereof, is shaped to define an arc of up to 360 degrees and a plane having a normal thereto, the implant being implantable in prostate tissue surrounding the urethra of a patient and configured to move the prostate tissue away from a longitudinal axis of the urethra, 
     during implantation, having a first configuration thereof in which the implant defines a first radius of curvature, 
     following implantation, assuming a second configuration thereof in which the implant defines a second radius of curvature, and 
     while transitioning between the first and second configurations, radially pushing the prostate tissue. 
     In an embodiment, the first radius of curvature is smaller than the second radius of curvature. 
     In an embodiment, at least one inflatable element coupled to the delivery tool at a distal portion thereof, the inflatable element is configured to be inflated in a manner in which the inflatable element: 
     contacts an inner wall of the urethra and applies pressure thereto, and 
     stabilizes the delivery tool during implantation of the implant. 
     In an embodiment, the inflatable element has a volume in an inflated state thereof that is 1-50 cc. 
     In an embodiment, the inflatable element includes an annular inflatable element surrounding the distal portion of the delivery tool. 
     In an embodiment, the inflatable element is operative to compress the portion of the prostate tissue and maintain the tissue in a compressed state during implantation of the implant. 
     In an embodiment, the inflatable element has a volume in an inflated state thereof that is 1-50 cc. 
     In an embodiment, the inflatable element includes an annular inflatable element surrounding the distal portion of the delivery tool. 
     In an embodiment, the at least one flexible curved implant includes a plurality of flexible curved implants, and the delivery tool is operative to implant the plurality of flexible curved implants by placing the implants around a portion of the urethra. 
     In an embodiment, the delivery tool is operative to implant: 
     a first one of the plurality of implants at least in part in a first lobe of a prostate of the patient, and 
     a second one of the plurality of implants at least in part in a second lobe of the prostate of the patient. 
     In an embodiment, the delivery tool is operative to implant: 
     the first one of the plurality of implants entirely within the first lobe, and 
     the second one of the plurality of implants entirely within the second lobe. 
     There is further provided, in accordance with an embodiment of the present invention, apparatus including: 
     at least one resilient curved implant, in an expanded state thereof, being shaped to define an arc of up to 360 degrees and a plane having a normal thereto, the implant being implantable in prostate tissue surrounding a urethra of a patient and configured to move the prostate tissue away from a longitudinal axis of the urethra, the implant:
         during implantation, having a first configuration thereof in which the implant defines a first radius of curvature,   following implantation, assuming a second configuration thereof in which the implant defines a second radius of curvature, and   while transitioning between the first and second configurations, radially pushing the prostate tissue; and       

     a transurethral delivery tool being configured to implant the implant in a manner in which the normal to the plane defined by the implant is substantially parallel to a longitudinal axis of the urethra. 
     In an embodiment, the first radius of curvature is smaller than the second radius of curvature. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the prostate tissue and does not extend within the urethra. 
     In an embodiment, the delivery tool is configured to implant the implant in a manner in which the implant is fully embedded within the prostate tissue and does not extend beyond a prostate capsule of a prostate of the patient. 
     In an embodiment the apparatus includes, at least one inflatable element coupled to the delivery tool at a distal portion thereof, the inflatable element is configured to be inflated in a manner in which the inflatable element: 
     contacts an inner wall of the urethra and applies pressure thereto, and 
     stabilizes the delivery tool during implantation of the implant. 
     In an embodiment, the inflatable element has a volume in an inflated state thereof that is 1-50 cc. 
     In an embodiment, the inflatable element is operative to compress the prostate tissue and maintain the tissue in a compressed state during implantation of the implant. 
     In an embodiment, the inflatable element includes an annular inflatable element surrounding the distal portion of the delivery tool. 
     In an embodiment the apparatus includes, a curved implantation-facilitating sleeve configured to surround the implant as the implant is housed in the delivery tool lumen, the implantation-facilitating sleeve being: 
     disposed in a compressed state thereof while disposed within the delivery tool lumen, 
     while surrounding the implant, advanceable though the opening in the surface of the delivery tool, 
     changeable from the compressed state thereof to an expanded state thereof as a result of passing through the opening, and 
     shaped to define a pointed tip configured to puncture the prostate tissue and create a channel therein for passage of the implant. 
     In an embodiment, following implantation of the implant in the channel of the prostate tissue, the sleeve is retractable back into the delivery tool lumen. 
     In an embodiment, while transitioning between the compressed state and the expanded state, the sleeve is operative to radially push the prostate tissue. 
     In an embodiment, the at least one flexible curved implant includes a plurality of flexible curved implants, and the delivery tool is operative to implant the plurality of flexible curved implants by placing the implants around a portion of the urethra. 
     In an embodiment, the delivery tool is operative to implant: 
     a first one of the plurality of implants at least in part in a first lobe of a prostate of the patient, and 
     a second one of the plurality of implants at least in part in a second lobe of the prostate of the patient. 
     In an embodiment, the delivery tool is operative to implant: 
     the first one of the plurality of implants entirely within the first lobe, and 
     the second one of the plurality of implants entirely within the second lobe. 
     There is additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     transurethrally advancing a flexible, distal tip of a delivery tool through a urethra of a patient; 
     deflecting the distal tip of the tool from a position that is aligned with a longitudinal axis of the tool, and, by the deflecting of the distal tip, compressing tissue of a prostate of the patient by pushing a wall of the urethra; and 
     maintaining the tissue in a compressed state by implanting at least one implant in the compressed prostate tissue. 
     In an embodiment, maintaining the tissue in the compressed state includes maintaining the tissue in the compressed state following removal of the delivery tool from the urethra. 
     In an embodiment, implanting the implant includes implanting the implant in the prostate tissue in a manner in which the implant is fully embedded within the prostate tissue and does not extend beyond a prostate capsule of the patient. 
     In an embodiment, implanting the implant includes implanting the implant in the prostate tissue in a manner in which the implant is partially embedded within the prostate tissue. 
     In an embodiment, implanting the implant includes implanting the implant in the compressed tissue in a manner in which the implant is fully embedded within the tissue and does not extend within the urethra. 
     In an embodiment, implanting the at least one implant includes implanting a plurality of implants in the prostate tissue, and implanting the plurality of implants includes implanting the plurality of implants orienting the implants radially with respect to a portion of the urethra. 
     In an embodiment, implanting the at least one implant includes implanting a plurality of implants in the prostate tissue, and implanting the plurality of implants includes implanting the plurality of implants at respective transverse planes of the urethra that are disposed along a longitudinal axis of the urethra. 
     In an embodiment the method includes, adjusting a configuration of the implant following implantation thereof by applying energy to the implant from an energy source disposed externally to a body of the patient and not in contact with the implant. 
     In an embodiment the method includes, stabilizing the delivery tool during the deflecting by inflating at least one inflatable element to 1-50 cc in a manner in which the inflatable element contacts an inner wall of the urethra. 
     In an embodiment, implanting the implant includes implanting a longitudinally-compressible implant and facilitating further compressing of the prostate tissue in response to longitudinal compressing of the longitudinally-compressible implant. 
     In an embodiment, implanting the implant includes implanting the implant at a non-zero angle with respect to a longitudinal axis of the urethra. 
     In an embodiment, implanting the implant at the non-zero angle includes implanting the implant substantially perpendicularly with respect to the longitudinal axis of the urethra. 
     In an embodiment, implanting the implant includes: 
     implanting in the prostate tissue at least one flexible curved implant shaped to define an arc of up to 360 degrees in an expanded state thereof, and 
     further compressing the prostate tissue in response to the implanting. 
     In an embodiment, implanting the flexible curved implant includes implanting the implant in a manner in which a normal to a plane defined by the implant is substantially parallel to the longitudinal axis of the urethra. 
     In an embodiment, implanting the at least one flexible curved implant includes implanting a plurality of flexible curved implants around a portion of the urethra. 
     In an embodiment, implanting the plurality of implants includes: 
     implanting a first one of the plurality of implants at least in part in a first lobe of the prostate of the patient, and 
     implanting a second one of the plurality of implants at least in part in a second lobe of the prostate of the patient. 
     In an embodiment: 
     implanting the first one of the plurality of implants at least in part in the first lobe of the prostate of the patient includes implanting the first one of the plurality of implants entirely within the first lobe, and 
     implanting the second one of the plurality of implants at least in part in the second lobe of the prostate of the patient includes implanting the second one of the plurality of implants entirely within the second lobe. 
     In an embodiment, implanting the flexible curved implant includes: 
     implanting a resilient curved implant having a first configuration thereof in which the implant defines a first radius of curvature during the implanting and, following the implanting, a second configuration thereof in which the implant defines a second radius of curvature, and 
     radially pushing the prostate tissue by the implant transitioning between the first and second configurations. 
     There is yet additionally provided, in accordance with an embodiment of the present invention, a method, including: 
     transurethrally advancing through a urethra of a patient at least one flexible curved implant shaped to define an arc of up to 360 degrees in an expanded state thereof; 
     compressing tissue of a prostate of the patient by implanting the implant in the tissue of the prostate in a manner in which:
         a normal to a plane defined by the implant is substantially parallel to a longitudinal axis of the urethra, and   the implant pushes the tissue of the prostate away from a longitudinal axis of the urethra.       

     In an embodiment, implanting the implant includes implanting the implant in the tissue of the prostate in a manner in which the implant is fully embedded within the tissue of the prostate and does not extend beyond a prostate capsule of the patient. 
     In an embodiment, implanting the at least one implant includes implanting a plurality of implants in the prostate tissue, and implanting the plurality of implants includes implanting the plurality of implants at respective transverse planes of the urethra that are disposed along a longitudinal axis of the urethra. 
     In an embodiment the method includes, adjusting a configuration of the implant following implantation thereof by applying energy to the implant from an energy source. 
     In an embodiment, implanting the flexible curved implant includes: 
     implanting a resilient curved implant having a first configuration thereof in which the implant defines a first radius of curvature during the implanting and, following the implanting, a second configuration thereof in which the implant defines a second radius of curvature, and 
     radially pushing the tissue of the prostate by the implant transitioning between the first and second configurations. 
     In an embodiment, the method further includes compressing the prostate tissue by inflating an inflatable element to 1-50 cc. 
     In an embodiment, implanting the implant includes implanting the implant such that the implant maintains the tissue in a compressed state thereof following the compressing. 
     In an embodiment, transurethrally advancing the implant includes transurethrally advancing the implant in a compressed state thereof in a lumen of a delivery tool, and implanting the implant includes: 
     advancing the implant through an opening of the delivery tool and into the tissue of the prostate, and 
     implanting the implant such that the implant maintains the tissue in a pushed state thereof following removal of the delivery tool from the urethra. 
     In an embodiment, advancing the implant through the opening includes advancing the implant surrounded by a sleeve, and creating a channel in the tissue of the prostate by the sleeve. 
     In an embodiment the method includes, stabilizing the delivery tool during the implanting by inflating at least one inflatable element to 1-50 cc in a manner in which the inflatable element contacts an inner wall of the urethra. 
     In an embodiment, implanting the at least one implant includes implanting a plurality of implants in the prostate tissue, and implanting the plurality of implants includes implanting the plurality of implants by orienting the implants radially with respect to a portion of the urethra. 
     In an embodiment, implanting the plurality of implants includes: 
     implanting a first one of the plurality of implants at least in part in a first lobe of the prostate of the patient; and 
     implanting a second one of the plurality of implants at least in part in a second lobe of the prostate of the patient. 
     In an embodiment: 
     implanting the first one of the plurality of implants at least in part in the first lobe of the prostate of the patient includes implanting the first one of the plurality of implants entirely within the first lobe, and 
     implanting the second one of the plurality of implants at least in part in the second lobe of the prostate of the patient includes implanting the second one of the plurality of implants entirely within the second lobe. 
     There is further provided, in accordance with an embodiment of the present invention, a method, including: 
     transurethrally advancing through a urethra of a patient at least one coiled implant including: 
     a plurality of successive contiguous coils and defining a lumen having a longitudinal axis in an expanded state thereof; and 
     compressing tissue of a prostate of the patient by implanting the implant in the tissue of the prostate in a manner in which the implant moves the tissue of the prostate away from a longitudinal axis of the urethra by the implant changing from an expanded to a compressed state. 
     In an embodiment, implanting the implant includes implanting the implant in the tissue of the prostate in a manner in which the implant is fully embedded within the tissue of the prostate and does not extend beyond a prostate capsule of the patient. 
     In an embodiment, implanting the at least one implant includes implanting a plurality of implants in the prostate tissue, and implanting the plurality of implants includes implanting the plurality of implants at respective transverse planes of the urethra that are disposed along a longitudinal axis of the urethra. 
     In an embodiment the method includes, adjusting a configuration of the implant following implantation thereof by applying energy to the implant from an energy source. 
     In an embodiment the method includes, adjusting a configuration of the implant by increasing a temperature of the implant as a result of the implanting. 
     In an embodiment, implanting the coiled implant includes: 
     implanting a coiled implant having a first configuration thereof in which the implant defines a larger, expanded configuration during the implanting and, following the implanting, a second configuration thereof in which the implant defines a smaller, compressed configuration; and 
     radially moving the tissue of the prostate by the implant transitioning between the first and second configurations. 
     There is yet further provided, in accordance with an embodiment of the present invention, a method including: 
     transurethrally advancing a flexible, distal tip of a delivery tool through a urethra of a patient; 
     deflecting the distal tip of the tool from a position that is aligned with a longitudinal axis of the tool, and, by the deflecting of the distal tip, compressing tissue of a prostate of the patient by pushing a wall of the urethra; and 
     treating the prostate tissue with medication by implanting an at least partially biodegradable implant including the medication, the implant maintaining the compression of the prostate. 
     The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a delivery tool being introduced within a constricted urethra of a patient, in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic illustration of an implant disposed in a compressed state at a distal end of the delivery tool of  FIG. 1 , in accordance with an embodiment of the present invention; 
         FIGS. 3 and 4  are schematic illustrations of the implant of  FIG. 2  expanding once inside a bladder of the patient, in accordance with an embodiment of the present invention; 
         FIG. 5  is a schematic illustration of the implant of  FIG. 2  being implanted around the urethra in a prostate of the patient, in accordance with an embodiment of the present invention; 
         FIG. 6  is a schematic illustration of the implant of  FIG. 2  implanted within the prostate of the patient, in accordance with an embodiment of the present invention; 
         FIG. 7  is a schematic illustration of an extraction tool being advanced into the bladder of the patient, in accordance with an embodiment of the present invention; 
         FIG. 8  is a schematic illustration of the extraction tool removing the implant from the prostate of the patient, in accordance with an embodiment of the present invention; 
         FIG. 9  is a schematic illustration of the implant being extracted from the body of the patient, in accordance with an embodiment of the present invention; 
         FIG. 10  is a schematic illustration of the delivery tool coupled to first and second coiled implants, in accordance with an embodiment of the present invention; 
         FIG. 11  is a schematic illustration of the delivery tool coupled to a conic coiled implant, in accordance with an embodiment of the present invention; 
         FIG. 12  is a schematic illustration of an implant configured to be implanted around a body lumen of the patient, in accordance with an embodiment of the present invention; 
         FIG. 13A  is a schematic illustration of the delivery tool and an implant coupled thereto, in accordance with another embodiment of the present invention; 
         FIGS. 13B-C  are schematic illustrations of a cross-section of a wire shaped to define the implant of  FIG. 13A , in accordance with respective embodiments of the present invention; 
         FIG. 13D  is a schematic illustration of the implant of  FIG. 13A  implanted around the urethra of the patient, in accordance with an embodiment of the present invention; 
         FIGS. 14A-B  are schematic illustrations of a coiled implant and a mechanical element disposed within a lumen of the implant, in accordance with an embodiment of the present invention; 
         FIG. 15  is a schematic illustration of a delivery tool comprising a motor, in accordance with an embodiment of the present invention; 
         FIG. 16  is a schematic illustration of an implant providing a scaffold for longitudinal rods, in accordance with an embodiment of the present invention; 
         FIGS. 17A-D  are schematic illustrations of a delivery tool and a plurality of implants coupled thereto, in accordance with an embodiment of the present invention; 
         FIGS. 18A-E  are schematic illustrations of a delivery tool and plurality of implants coupled thereto, in accordance with another embodiment of the present invention; 
         FIGS. 19A-B  are schematic illustrations of a resorbable implant, in accordance with an embodiment of the present invention; 
         FIGS. 20A-D  are schematic illustrations of a delivery tool coupled to two implants, in accordance with an embodiment of the present invention; 
         FIGS. 21A-F  are schematic illustrations of a deflectable delivery tool to implant a plurality of implants, in accordance with an application of the present invention; 
         FIGS. 22A-C  are schematic illustrations of a delivery tool and a curved implant being implanted in tissue surrounding the urethra, in accordance with an application of the present invention; 
         FIGS. 23A-B  are schematic illustrations of a cross-section of the prostate showing a plurality of curved implants implanted in tissue surrounding the urethra, in accordance with an application of the present invention; 
         FIGS. 24A-B  are schematic illustrations of a plurality of coiled implants implanted in the prostate, in accordance with an application of the present invention; 
         FIGS. 25A-B  are schematic illustrations of a delivery tool comprising inflatable balloons and a plurality of coiled implants being implanted in prostate tissue, in accordance with an application of the present invention; 
         FIG. 26  is a schematic illustration of a plurality of screw implants implanted in the prostate, in accordance with an application of the present invention; 
         FIGS. 27A-D  are schematic illustrations of a delivery tool and a plurality of coiled implants coupled to a wire, in accordance with an application of the present invention; and 
         FIGS. 28A-D  are schematic illustrations of a rod, a coiled implant, and a delivery tool, in accordance with an application of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference is made to  FIG. 1 , which is a schematic illustration of a system  20  comprising a delivery tool  22  being introduced into a urethra  60  of a patient, in accordance with an embodiment of the present invention. Urethra  60  is constricted due to pressure exerted thereupon by a prostate  100  of the patient. Stenosis of urethra  60  by prostate  100  defines a diameter D 1  at a bladder neck  64  of the patient and along a portion of urethra  60  surrounded by prostate  100 . Untreated stenosis of urethra  60  by prostate  100  (e.g., responsively to benign prostate hyperplasia) often engenders acute urinary retention by bladder  80  of the patient, thus causing infrequent urination and ultimately, incontinence. Systems, methods, and apparatus described herein are configured to enlarge and expand the diameter of the constricted urethra and, in some embodiments, treat benign prostate hyperplasia. 
     An outer sheath  24  is advanced distally through a proximal end  62  of urethra  60  and toward bladder neck  64  of the patient. Outer sheath  24  expands urethra  60  as sheath  24  is distally advanced toward bladder  80  of the patient. Typically, outer sheath  24  is advanced via an introducer tube (not shown) having a rounded proximal end which facilitates atraumatic advancement of outer sheath  24  through urethra  60 . Outer sheath  24  is advanced along urethra  60  prior to the advancement of delivery tool shaft  25 , thus creating an open passageway for the subsequent insertion of delivery tool  22 . Typically, outer sheath  24  is hollow and enables passage of tools through the urethra by providing a working channel of sheath  24 . An imaging device (not shown), e.g., a fiberscope or a cystoscope, is advanced through outer sheath  24  into bladder  80 . Bladder  80  and bladder neck  64  are examined prior to the introduction of delivery tool  22  into urethra  60  of the patient. The imaging device is typically flexible and bends 180 degrees in a proximal direction, facilitating visualization of a vicinity of bladder neck  64  of the patient. 
     Delivery tool  22  comprises a body  21  and a delivery tool shaft  25  which is advanced distally through outer sheath  24  toward bladder  80  of the patient. Typically, shaft  25  comprises a hollow lumen for passing substances and/or tools therethrough, such as but not limited to, medications, fiber optics, biopsy tools, optical devices (e.g., CCD) and/or other imaging devices. 
     Reference is now made to  FIG. 2 , which is a schematic illustration of system  20  comprising a transurethrally implantable prostatic implant  120 , which surrounds a distal end of shaft  25  of delivery tool  22 , in accordance with an embodiment of the present invention. Typically, implant  120  comprises a radially-expandable implant, e.g., a coil or a helical implant. Implant  120  typically comprises a flexible biocompatible material, e.g., nitinol or silicone. 
     During transurethral advancement, implant  120  is disposed in a compressed state thereof between a proximal implant holder  124  and a distal implant holder  54 . Typically, a distal end  126  and a proximal end  122  of implant  120  are each shaped to define a slit ( 134  and  132 , respectively). Each slit is configured for passage of respective fastening devices therethrough. The fastening devices maintain the compressed state of implant  120  during advancement thereof into bladder  80  of the patient. 
     Proximal implant holder  124  is shaped to provide a latitudinal groove  125  for holding and securing proximal end  122  of implant  120 . Additionally, proximal implant holder  124  is shaped to provide a longitudinal slit for advancement of a first elongate mechanical fastener  127  therethrough and subsequently through slit  132  of proximal end  122  of implant  120 . Fastener  127  is advanced (a) through the longitudinal slit within holder  124 , (b) subsequently through slit  132  of proximal end  122  of implant  120 , and (c) back into a slit at a portion of holder  124  distal to groove  125 . 
     Distal implant holder  54  comprises a similar securing mechanism as holder  124 . Distal implant holder  54  is shaped to provide a latitudinal groove  56  at a proximal end thereof which holds and secures distal end  126  of implant  120  in a compressed state during advancement thereof. Additionally, distal implant holder  54  maintains coupling of implant  120  to tool  22  during implantation of implant  120 . A second elongate mechanical fastener  129  is advanced (a) through a longitudinal slit within distal implant holder  54 , (b) subsequently through slit  134  of distal end  126  of implant  120 , and (c) back into a slit at a portion of distal implant holder  54  proximal to groove  56 . 
     The securing and releasing of fasteners  127  and  129  are controlled remotely, by body  21  of delivery tool  22 . 
       FIG. 3  shows implant  120  expanding from a compressed state thereof, in accordance with an embodiment of the present invention. The distal-most end of sheath  24  is disposed distally to bladder neck  64 , facilitating proper placement within bladder  80  of any device passed through sheath  24 , e.g., implant  120 . Typically, outer sheath  24  is shaped to define a length which is shorter than a length of delivery tool shaft  25 . Thus, once shaft  25  has been fully advanced through sheath  24 , proximal end  122  of implant  120  is disposed distally with respect to the distal-most end of sheath  24 . When proximal end  122  of implant  120  has sufficiently entered bladder  80  of the patient (e.g., as shown), proximal end  122  is released from proximal implant holder  124 , allowing implant  120  to assume an expanded configuration. 
     Reference is again made to  FIG. 1 . Delivery tool  22  comprises a rotating element  30  at a proximal end thereof which is configured to facilitate implantation of implant  120  once the implant is inside bladder  80  of the patient. During the distal advancing of delivery tool shaft  25  toward bladder  80  of the patient, rotating element  30  is disposed adjacent to body  21  of tool  22 , as shown. 
     Body  21  comprises one or more control elements  28  on a surface of tool  22  which enables a physician to control, from outside of the patient&#39;s body, one or more functional elements located at the distal end of delivery tool  22 . Typically, but not necessarily, control elements  28  comprise rings for the physician to engage her fingers therethrough and push or pull on control elements  28 . During advancement of delivery tool  22  within sheath  24 , elements  28  are disposed in a distal orientation with respect to delivery tool  22 , e.g., at the distal end of a slot  130  in delivery tool  22  (configuration not shown). 
     As shown in  FIG. 3 , once the distal end of delivery tool shaft  25  enters bladder  80 , implant  120  is further pushed distally by pushing on a switch  42  disposed at a proximal end of body  21  of tool  22 . Such pushing further facilitates that proximal end  122  of implant  120  is disposed distal to bladder neck  64  prior to implantation of implant  120  therearound. Control elements  28  are then pulled proximally with respect to delivery tool  22 . Control elements  28  are coupled to a proximal end of fastener  127 . In response to the pulling, a distal end of fastener  127  is pulled to a position that is proximal to proximal end  122  of implant  120 , thereby releasing proximal end  122  of implant  120  and effecting radial expansion thereof.  FIG. 3  shows system  20  immediately after control elements  28  have reached their proximal-most extent, decoupling fastener  127  from implant  120 , but prior to the resultant radial expansion of the implant. During expansion of implant  120 , distal end  126  of implant  120  remains coupled to distal implant holder  54 . 
     To minimize the chance of physician error, tool  22  may comprise a distal lock  32 , a proximal lock  34 , and a release  36 . Pulling and pushing of control elements  28  is restricted by locks  32  and  34 . For example, when elements  28  are disposed distally with respect to tool  22 , distal lock  32  automatically maintains the distal position of elements  28  such that elements  28  are not inadvertently pulled (resulting in premature expansion of implant  120  during advancement thereof). When proximal motion of control elements  28  is desired, the physician activates release  36 , to release lock  32 , allowing for such proximal motion of elements  28 . Once disposed proximally with respect to tool  22 , proximal lock  34  secures elements  28  in place, typically automatically. 
     Reference is now made to  FIG. 4 , which is a schematic illustration of system  20  comprising expandable guiding elements  26 , in accordance with an embodiment of the present invention. 
     Reference is now made to  FIGS. 3 and 4 . As shown in  FIG. 3 , during advancement of tool  22  through outer sheath  24 , distal implant holder  54  is disposed in a configuration such that a distal portion thereof covers a lumen of shaft  25  of delivery tool  22 . Switch  42  is oriented in a downward configuration indicative of the closed configuration of distal implant holder  54 . As shown in  FIG. 4 , manually rotating switch  42  in an upward configuration, e.g., 180 degrees, rotates distal implant holder  54 , thereby exposing the lumen of delivery tool shaft  25 . Additionally, rotation of distal implant holder  54  positions implant  120  coaxially with respect to the urethra, such that implant  120  is properly corkscrewed symmetrically around the urethra. Imaging device  70  is then advanced through the lumen of shaft  25 , and guides the subsequent implantation of implant  120 . Imaging device  70  is configured to bend 180 degrees and rotate 360 degrees in order to image the implantation procedure. 
     Reference is now made to  FIGS. 2 and 4 . As shown in  FIG. 2 , expandable guiding elements  26  surround a portion of delivery tool shaft  25  proximal to implant  120 . Distal and proximal ends of expandable elements  26  are each coupled to a first ring  27  and a second ring  29 , respectively. Typically, first ring  27  is fixed to a portion of shaft  25  while second ring  29  is configured to slide distally and proximally along shaft  25 . Alternatively, first ring  27  is configured to slide distally until a stopping element impedes continued distal motion of ring  27 . Such distal motion of ring  27  facilitates positioning of ring  27  and distal portions of guiding elements  26  within the lumen of the implant prior to expansion of elements  26 . During the advancing of delivery tool shaft  25  toward bladder  80 , guiding elements  26  are typically pressed against the outer surface of shaft  25 . 
       FIG. 4  shows deployment of expandable guiding elements  26  following expansion of implant  120 . Distal pushing of control elements  28  slides ring  29  distally toward ring  27 . The distal and proximal ends of expandable elements  26  are drawn toward one another, resulting in the radial expansion of expandable elements  26 . Expandable guiding elements  26  expand such that they align with an inner surface of implant  120 . Such alignment facilitates the guiding of implant  120  and the maintenance of a straight configuration thereof during the implantation procedure. 
     Typically, once implant  120  is fully disposed within bladder  80 , body  21  of tool  22  is disposed adjacent to a proximal-most end of sheath  24 . The implantation of implant  120  within prostate  100  begins when the physician distances body  21  from outer sheath  24 , thereby shifting tool  22  proximally. Such shifting positions proximal end  122  of implant  120  in proximity with bladder neck  64  immediately prior to implantation of implant  120 . 
     Reference is now made to  FIG. 5 , which is a schematic illustration of implant  120  of system  20  being partially implanted in prostate  100  of the patient, in accordance with an embodiment of the present invention. Upon expansion within bladder  80  of the patient, implant  120  is shaped to define an inner lumen diameter, e.g., 2.5 mm to 15 mm, typically larger than the non-constricted outer diameter of urethra  60 . 
     Proximal end  122  of implant  120  is typically pointed and is configured to puncture tissue of prostate  100 . In some embodiments, proximal end  122  is coupled to, e.g., soldered to or attached using any other applicable attachment means, a pointed needle which is configured to puncture tissue of the patient. Typically, the needle coupled to proximal end  122  comprises a rigid, biocompatible material, e.g., stainless steel, configured to configured to facilitate ongoing penetration of the implant as it is advanced through tissue of prostate  100 . It is to be noted that the needle is shaped to define any suitable shape configured for cutting/penetrating tissue. 
     Following the puncturing of the tissue by proximal end  122  or, in some embodiments, the needle coupled thereto, implant  120  is further advanced proximally in the tissue of prostate  100 , around urethra  60  of the patient. Counterclockwise rotation of rotating element  30  rotates and proximally retracts implant  120 , thus corkscrewing implant  120  within tissue of prostate  100  surrounding urethra  60 . Positioning of implant  120  within tissue of prostate  100  is typically guided by imaging element  70 . 
     In some embodiments, as proximal end  122  (or a needle coupled thereto) of implant  120  is advanced through the tissue of the patient, it is configured to ablate the tissue. In such an embodiment, implant  120  may be coated with a substance, such as but not limited to, a medication (e.g., an antibiotic) or with an electrical insulator (e.g., Teflon). A portion of proximal end  122  of implant  120 , i.e., one or more of the coils, may be energized to deliver RF energy, for example, to ablate tissue. In some embodiments, the portion of proximal end  122  of implant  120  is coupled to an electrode. Additionally or alternatively, the portion of proximal end  122  of implant  120  may be energized to provide ultrasound or thermal energy (e.g., heating or cooling). 
     In some embodiments, the implant  120  comprises a hollow, helical implant shaped to define a helical lumen and at least one hole, e.g., a plurality of holes, at the proximal end thereof. In such an embodiment, a fluid, e.g., saline, is injected at high pressure through the lumen of the hollow, helical implant and externally to the implant via the at least one hole in order to cut tissue near the proximal tip of the implant as it advances through the tissue. 
     In some embodiments, the hollow, helical implant is configured for passage through its lumen and through the hole at the proximal end thereof, of a laser fiber to ablate tissue in the path of the implant as it is advanced therethrough. In some embodiments, an insulated RF transmitting wire (i.e., having a non-insulated transmitting-tip) is advanced through the helical lumen of the hollow implant. 
     In some embodiments, the hollow, helical implant is configured for passage through its lumen of a fluid (configuration described hereinbelow with reference to  FIG. 12 ). The hollow, helical implant is shaped to define holes (e.g., typically toward the proximal end of the implant) for release of the fluid externally to the implant. In some embodiments, the fluid comprises a lubricant which passes externally to the implant via the holes defined thereby in order to reduce a frictional force between the tissue and the implant. 
     Expandable guiding elements  26  guide the initial implantation (e.g., longitudinal motion of 6 mm to 11 mm in a proximal direction) of proximal end  122  of implant  120  around urethra  60 . Control elements  28  are then pulled proximally, thereby sliding ring  29  proximally such that guiding elements  26  are pressed once again against the outer surface of shaft  25  (alignment shown in  FIG. 2 ). As shown in  FIG. 5 , control elements  28  are disposed in a proximal orientation with respect to body  21  of delivery tool  22  indicating a retracted state of guiding elements  26 . 
     Clockwise rotation of rotating element  30  retracts shaft  25 , thereby retracting distal implant holder  54  attached to distal portion  126  of implant  120 . In response to the retracting, distal implant holder  54  helps corkscrew implant  120  into tissue of prostate  100  by applying to implant  120  a force in the proximal direction. During the clockwise rotation, rotating element  30  is distanced from body  21  of delivery tool  22  by a distance L 1 . L 1  is typically smaller than a maximal distance between rotating element  30  and body  21  of tool  22 , thus indicating partial implantation of implant  120  around urethra  60  of the patient. 
     Following initial partial implantation of implant  120  and alignment of expandable guiding elements  26  along shaft  25 , implant  120  is further advanced proximally through prostate  100 , around urethra  60  of the patient. Once implant  120  is fully implanted in prostate  100 , distal end  126  is decoupled from distal implant holder  54  by retracting fastener  129  from slit  134  at distal end  126  of implant  120 . Fastener  129  is controlled by a control element  40 , which is disposed at a proximal end of body  21  of delivery tool  22 . Pulling on element  40  retracts fastener  129  from slit  134 , thereby releasing implant  120  from holder  54 . Switch  42  is then rotated in a downward direction, e.g., 180 degrees (not shown), restoring the original position of distal implant holder  54 , enabling subsequent passage thereof through sheath  24 . Imaging device  70  is then straightened and extracted from bladder  80  via sheath  24 . 
     Typically, as implant  120  is advanced through tissue of prostate  100 , tissue of prostate  100  applies a frictional force to implant  120 . In some embodiments, in order to reduce the effect of the frictional force applied to implant  120 , implant  120  is coated with a low-friction coating, e.g., PTFE (Teflon), MoST, ADLC or the like. In some embodiments, the implant surface is polished, e.g., electro-polished, mechanically polished, or other, to reduce friction as implant  120  is advanced through the tissue of the patient. 
     In some embodiments, implant  120  comprises a helical implant comprising a plurality of coils which are helically surrounded by a sheath coupled to a tube for passage therethrough of a lubricant into the sheath surrounding the implant (configuration shown hereinbelow with reference to  FIG. 12 ). Typically, a lubricant is passed through the sheath surrounding implant  120 . In such an embodiment, the sheath surrounding the implant is shaped to define holes (e.g., typically toward proximal end  122  of implant  120 ) for release of the lubricant externally to implant  120 . The lubricant reduces a frictional force between the tissue of prostate  100  and implant  120 . In some embodiments, implant  120  itself is a hollow, helical implant defining a helical lumen therein configured for passage of lubricant therethrough. The hollow, helical implant is shaped to define holes (e.g., typically toward proximal end  122  of implant  120 ) for release of the lubricant externally to implant  120 . In such an embodiment, the implant is coupled to the tube for delivering the lubricant thereto, typically without the use of a sheath. 
     Reference is now made to  FIG. 6 , which is a schematic illustration of implant  120  implanted within prostate  100  of the patient, in accordance with an embodiment of the present invention. Once implant  120  is implanted within prostate  100 , delivery tool shaft  25  and outer sheath  24  are extracted from within urethra  60 . Following implantation of implant  120  within prostate  100 , a post-operative diameter D 2  of the portion of urethra  60  at prostate  100  is larger than diameter D 1  of the portion of urethra  60  prior to implantation of implant  120 . Implant  120  is generally rigid relative to the rigidity of the prostate. The implant thus supports the urethral tissue, minimizing restenosis of urethra  60  should prostate  100  continue to enlarge. 
     Typically, implant  120  is selected to provide a length according to the needs of a given patient. A length of prostate  100  is measured prior to the implantation procedure such that an implant of a suitable length is selected. Typically, the end-to-end length of the coiled implant ranges from between 2.5 cm and 7 cm, to accommodate a prostate length of between 3 and 8.6 cm, respectively. 
     Typically, implant  120  supports prostatic tissue  100  surrounding urethra  60  without touching the urethral epithelium or other delicate tissue, and enlarges the lumen in urethra  60 . 
       FIGS. 7 and 8  show a system  400  comprising an extraction tool  300  configured to remove implant  120  from prostate  100 , in accordance with an embodiment of the present invention. An outer sheath  260  is advanced distally through proximal end  62  of urethra  60  and toward bladder neck  64  of the patient. Subsequently, a resection tool, e.g., a resectoscope (not shown), is advanced through sheath  260 . The resection tool removes tissue surrounding distal end  126  of implant  120 , thereby exposing a portion of implant  120  and enabling engaging thereof by extraction tool  300 . 
     Typically, extraction tool  300  comprises a shaft  210  which is coupled at a distal end thereof to a mechanically adjustable clamp  224  via a hinge  240 . Clamp  224  is advanced through sheath  260  into bladder  80  in an “extended” configuration with respect to hinge  240  (as shown in  FIG. 7 ), and later assumes a “flexed” configuration with respect to the hinge, which enables clamp  224  to engage implant  120  (as shown in  FIG. 8 ). An optical guide  250 , e.g., a CCD, CIS, or CMOS sensor or an optical fiber-based system, guides the engaging and subsequent extraction of implant  120 . 
     As shown in  FIG. 8 , a control element  320  is disposed along extraction tool  300  and enables a physician to control, from a location outside the body of the patient, various mechanical functions being performed at the distal end of tool  300 . By proximal pulling of element  320 , clamp  224  is flexed at hinge  240  with respect to shaft  210 . 
     Additionally, extraction tool  300  comprises a proximal rotating element  360  and a distal rotating element  340 . Proximal rotating element  360  regulates a distance between an upper jaw  222  and a lower jaw  220  of clamp  224 . Upon an indication from imaging device  250  that clamp  224  surrounds a portion of implant  120 , proximal rotating element  360  is rotated in a clockwise direction in order to reduce the distance between jaws  220  and  222  thus facilitating clamping of implant  120  by clamp  224 . 
     The extraction process begins when clamp  224  engages a distal portion of implant  122 . Distal rotating element  340  is rotated in a counterclockwise direction, i.e., in a direction opposite the direction used in the implantation procedure. Such rotation of element  340  moves implant  120  distally by rotating implant  120  about a longitudinal axis of extraction tool  300 . 
     Once implant  120  is extracted fully from within prostate  100 , jaws  220  and  222  are released from the distal portion of implant  120  by counterclockwise rotation of proximal rotating element  360 . Element  320  is pushed distally, restoring clamp  224  to an extended configuration with respect to hinge  240 . Clamp  224  is then pulled proximally, such that jaws  220  and  222  are aligned with a proximal portion of implant  120 . Element  320  is again pulled proximally, and rotating element  360  is once again rotated in a clockwise direction such that jaws  220  and  220  are drawn together and engage the proximal end of implant  120  (configuration not shown). 
       FIG. 9  is a schematic illustration of extraction tool  300  extracting implant  120 , in accordance with an embodiment of the present invention. The proximal end of the coiled implant is pulled in a proximal direction through a lumen of shaft  210 . Due to the relative flexibility and elasticity of implant  120  compared to extraction tool  300 , pulling of implant  120  through sheath  260  enables implant  120  to assume an elongated, generally straightened configuration. 
     In some embodiments, two clamps are used in order to extract the implant from the bladder of the patient. A distal clamp typically extracts the implant from the prostate. Subsequent to the extraction, a proximal clamp is advanced into the bladder of the patient and engages the proximal end of the implant. The proximal clamp is used to pull the implant through the outer sheath as the distal clamp remains at a fixed distance within the bladder of the patient. Such configuration of the distal clamp with respect to the proximal clamp enhances stability of the extraction procedure by maintaining the distal end of the implant within the bladder as the proximal end is being pulled by the proximal clamp into a straight configuration and ultimately outside the body of the patient. 
     Reference is now made to  FIG. 10 , which is a schematic illustration of a system  200  comprising first and second transurethrally implantable prostatic implants  500  and  502 , which surround the distal end of shaft  25  of delivery tool  22 , in accordance with an embodiment of the present invention. Typically, implants  500  and  502  comprise helical, radially-expandable implants, e.g., coils, each having an inner diameter of at least 2.5 mm, e.g., between 2.5 mm and 15 mm. The respective diameters of the inner lumens of implants  500  and  502  enable implants  500  and  502  to be implanted in tissue surrounding urethra  60 . Typically, the respective diameters of implants  500  and  502  are the same. Implants  500  and  502  typically comprise a flexible biocompatible material, e.g., nitinol or silicone. 
     First implant  500  comprises a pointed proximal end  510 , and second implant  502  comprises a pointed proximal end  512 . In some embodiments, proximal ends  510  and  512  are each coupled to, e.g., soldered to, a respective pointed tip, e.g., a needle. 
     Typically, the needles coupled to each proximal end  510  and  512  comprise a generally rigid, biocompatible material, e.g., stainless steel, and are configured to provide strength to implants  500  and  502 , respectively, to facilitate their puncture of and advancement through tissue of prostate  100 . 
     During transurethral advancement, implants  500  and  502  are disposed in a compressed state thereof. In some embodiments, implants  500  and  502  are compressed between respective proximal and distal implant holders  520  and  530 . Typically, distal implant holders  520  and  530  function similarly to distal implant holder  54  as described hereinabove with reference to  FIGS. 2-5 . Typically, the distal and proximal ends  510  and  512  of implants  500  and  502 , respectively, are each shaped to define a slit. Each slit is configured for passage of respective fastening devices therethrough. The fastening devices maintain the compressed state of implants  500  and  502  during advancement thereof into bladder  80  of the patient. Once delivery tool  22  positions implants  500  and  502  in bladder  80 , the fastening devices are released and implants  500  and  502  are allowed to expand to assume the configuration shown. 
     As shown, implants  500  and  502  are disposed in a relative spatial configuration in which implants  500  and  502  are coaxially disposed and rotationally offset 180 degrees with respect to each other, by way of illustration and not limitation. Additionally, a longitudinal position of implant  500  overlaps at least in part (e.g., entirely, as shown) a longitudinal position of implant  502 . Implants  500  and  502  may be rotationally offset at any given angle with respect to each other. It is to be noted that although two implants are shown, any suitable number of implants may be corkscrewed into tissue of prostate  100 . For example, three or four longitudinally-overlapping coiled implants may be coaxially disposed and rotationally offset  120  or 90 degrees with respect to each other, respectively. 
     Typically, implants  500  and  502  are corkscrewed at the same time into tissue of prostate  100 . During implantation: 
     proximal end  510  of the first implant  500  punctures the tissue of prostate  100  at a first location thereof, and 
     proximal end  512  of second implant  502  punctures the tissue of prostate  100 , at a location 180 degrees from the first location. 
     The scope of the present invention includes sequentially implanting first and second implants  500  and  502 . Delivery tool  22  is coupled to first implant  500  and delivers implant  500  to within bladder  80  and allows implant  500  to expand, as described hereinabove in  FIGS. 1-4 , with reference to the delivering and expanding of implant  120  within bladder  80 . (As appropriate, delivery tool  22  may be sold already coupled to first implant  500 .) First implant  500  punctures the tissue at a first location and is fully advanced into prostate  100  by delivery tool  22 , as described hereinabove in  FIGS. 5-6 , with reference to the implanting of implant  120  within prostate  100 . 
     Once first implant  500  is implanted, delivery tool  22  is removed from the patient, is coupled to second implant  502 , and is reintroduced within urethra  60  of the patient. (Alternatively, another delivery tool  22  coupled to implant  502  is used in the following steps.) Second implant  502  is advanced into bladder  80  of the patient, is allowed to expand within bladder  80 , as described hereinabove in  FIGS. 1-4 , with reference to the delivering and expanding of implant  120  within bladder  80 . Second implant  502  then punctures the tissue of prostate  100  at a second location which is rotationally offset 180 degrees from the first location. Second implant  502  is corkscrewed into the tissue (as described hereinabove in  FIGS. 5-6 , with reference to the implanting of implant  120  within prostate  100 ). Second implant  502  is implanted coaxially with respect to a position of the implanted first implant  500 . Second implant  502  is advanced fully through the tissue, until it is disposed coaxially and is rotationally offset by 180 degrees with respect to first implant  500 . 
     For either embodiment in which implants  500  and  502  are implanted simultaneously or sequentially, once implanted, implants  500  and  502  are configured to assume the relative spatial configuration, as shown and as described hereinabove. Typically, once implanted, implants  500  and  502  maintain substantially the same spatial relationship as shown in  FIG. 10 , i.e., coaxially disposed, longitudinally overlapping, and rotationally offset by 180 degrees with respect to each other. 
     In order to minimize the frictional force of prostate  100  on each implant  500  and  502  during implantation: 
     1) when implanted, the end-to-end respective lengths of each of the coiled implants range from between 2.5 cm and 7 cm, to accommodate a prostate length of between 3 cm and 9 cm, respectively, and 
     2) in accordance with the lengths of implants  500  and  502  in the abovementioned range, implants  500  and  502  are each shaped to define a pitch of between 8 mm and 23 mm, respectively. 
     For example, each of implants  500  and  502  may have an end-to-end length of about 4.5-5.5 cm and a pitch of about 14-16 mm. 
     The scope of the present invention includes the implantation of any suitable number of coiled implants around the urethra of the patient. For example, when one coiled implant is implanted in the tissue, the coiled implant may have a length of 4.5-5 cm and a pitch of approximately 8 mm. When first and second coiled implants (e.g., implants  500  and  502 , as shown) are configured to be coaxially disposed and rotationally offset 180 degrees with respect to each other, each coiled implant  500  and  502  has a length of 4.5-5 cm and a pitch of approximately 16 mm (i.e., twice that indicated for an embodiment in which one coiled implant is implanted). In this manner, when the respective longitudinal positions of the implants are overlapped, and the implants are rotationally offset and coaxially disposed within tissue of prostate  100 , the average effective pitch between adjacent coils of the coaxially disposed first and second coiled implants  500  and  502  is approximately 8 mm. 
     Typically, a pitch of each coiled implant is directly proportional to the number of coiled implants configured to be coaxially disposed when implanted in tissue of the patient. For example, when one coiled implant is implanted in the tissue, the coiled implant may have a length of 3-5 cm and a pitch of approximately 3-9 mm. When first and second coiled implants are configured to be coaxially disposed and rotationally offset 180 degrees with respect to each other (e.g., when implanted in tissue), each coiled implant has a length of 3-5 cm and a pitch of approximately 6-18 mm, such that when the respective longitudinal positions of the implants are overlapped, and the implants are coupled together by being coaxially disposed, the effective average pitch between adjacent coils of the coaxially disposed first and second coiled implants is approximately 3-9 mm. 
     The total frictional force of the tissue of prostate  100  on any coiled implant during implantation is generally inversely related to the pitch and the length of the coil that is being implanted. That is, a small-pitch coiled implant has an along-the-coil length, i.e., the length of the wire when the coil is straightened, that is larger than an along-the-coil length of a high-pitch coiled implant. Thus, the overall frictional force applied to a small-pitch coiled implant is larger than the overall frictional force applied to a large-pitch coiled implant, because the frictional force applied to a small-pitch coiled implant is applied along a larger coil length, i.e., a larger cumulative surface area. Thus, as each of first and second coiled implants  500  and  502  is implanted within prostate  100 , e.g., simultaneously or sequentially, the force needed in order to overcome the frictional force applied to each coiled implant  500  and  502  is smaller in comparison to the force applied to a coiled implant having a pitch similar to the average pitch of the combined first and second coiled implants  500  and  502 . By reduction of the frictional force applied by the prostate to the implant during implantation, any undesired deformation of the portion of the implant that has not yet entered the prostate is reduced. 
     Additionally, the higher-pitch implant is characterized as being stronger and more rigid in comparison to the small-pitch coiled implants. 
       FIG. 11  shows a system  1300  comprising a prostatic implant  1302 , which surrounds the distal end of shaft  25  of delivery tool  22 , in accordance with an embodiment of the present invention. Typically, implant  1302  is shaped to define a conically-shaped implant comprising a proximal coil  1320  having a larger diameter than a distal coil  1360 . Typically, the respective diameters of adjacent coils decrease from proximal coil  1320  to distal coil  1360 . 
     Prior to advancement of implant  1302  through urethra  60 , delivery tool  22  is coupled to implant  1302  in a compressed state thereof. Delivery tool  22  maintains the compressed state of implant  1302  as it is advanced through urethra  60  and into bladder  80 . Once within bladder  80 , implant  1302  is allowed to expand, as described hereinabove in  FIGS. 1-4  with reference to the delivering and expanding of implant  120  within bladder  80 . Pointed proximal end  122  of coil  1320  punctures the tissue of prostate  100  and is fully advanced into prostate  100  by delivery tool  22 , as described hereinabove in  FIGS. 5-6  with reference to the implanting of implant  120  within prostate  100 . Once implant  1302  is implanted, delivery tool  22  is removed from the patient. 
     As proximal coil  1320  of implant  1302  is advanced through the tissue of prostate  100 , the tissue applies a frictional force on the proximal coils of coiled implant  1302 . In an attempt to continue corkscrewing into the tissue, the tissue exerts an increasingly larger cumulative frictional force on the increasing number of coils that are within the prostate. In response to the frictional force applied to the intra-prostate coils as they are corkscrewed into the tissue, the distal coils have a tendency to expand radially, such that the respective diameters of the distal coils are generally similar to the respective diameters of the proximal coils. In this manner, the overall outline of the entire implant when it has finished being inserted into the prostate tends to be generally rectangular (i.e., coils of same radius), rather than conical. 
     Once implanted, the distal coils maintain their expanded diameters such that implanted implant  1302  resembles implanted implant  120  as shown in  FIG. 5 . 
       FIG. 12  shows an implant system  301  comprising a helical implant  302  helically surrounded by a sheath  304 , in accordance with an embodiment of the present invention. Typically, implant system  301  is advanced toward the bladder and is implanted around the urethra, as described hereinabove in  FIGS. 1-6  with reference to the delivering and implantation of implant  120 . Helical implant  302  is shaped to define a proximal end (not shown for clarity of illustration) comprising a pointed distal tip configured to puncture tissue of the prostate and facilitate ongoing penetration of implant system  301  within the tissue. Typically, the proximal end of helical implant  302  extends proximally from a proximal-most end of sheath  304  in order to facilitate unobstructed penetration of system  301  through tissue of the patient. 
     Typically, sheath  304  is shaped to define a plurality of holes  306  and is coupled at a distal end  308  thereof to a tube  310 . Sheath  304  is fixedly attached to implant  302  at a site distal to the proximal end of implant  302  and is shaped to provide a helical lumen surrounding helical implant  302 . Fluid is injected via tube  310  through the lumen of sheath  304 . Holes  306  are configured for release of the fluid externally to implant system  301 . In some embodiments, the fluid comprises a lubricant which passes externally to implant system  301  via holes  306  in order to reduce a frictional force between the tissue and implant system  301 . 
     In some embodiments, sheath  304  is shaped to define at least one hole at the proximal end thereof (configuration not shown for clarity of illustration). In such an embodiment, the fluid may comprise saline which is injected at high pressure through the lumen sheath  306  and externally to implant system  301  via the at least one hole in the proximal end of sheath  304  in order to cut tissue near the proximal tip of implant  302  as it advances through the tissue. It is to be noted that the scope of the present invention includes the use of the high-pressure fluid to cut tissue independently of or in combination with cutting tissue using helical implant  302 . 
     In some embodiments, implant  302  comprises a helical implant comprising a plurality of coils which are helically surrounded by a sheath (i.e., if the helical implant were to be pulled straight, the implant would be relatively-tightly enclosed within the sheath, analogously to a normal insulated wire (the implant) surrounded by a plastic insulator (the sheath)). The sheath is coupled at one end thereof to a tube for passage therethrough of a lubricant into the sheath surrounding the implant. In such an embodiment, the sheath surrounding the coils of the implant is shaped to define holes (e.g., toward the proximal end of the implant), for release of the lubricant externally to the implant. The lubricant, in turn, reduces the frictional force between the tissue and the implant. 
     In some embodiments, the hollow, helical lumen is configured for passage therethrough of a laser fiber to ablate tissue in the path of the implant as it is advanced therethrough. In some embodiments, an insulated RF transmitting wire having a non-insulated transmitting tip is advanced through the helical lumen of the hollow implant. It is to be noted that the scope of the present invention includes the use of the laser fiber and/or the RF wire independently of or in combination with helical implant  302 . 
     In some embodiments, sheath  304  is shaped to define holes  304  only at the proximal end of the implant  302 . 
     In some embodiments, helical implant  302  itself is a hollow, helical implant defining a helical lumen therein. Typically, the hollow, helical implant is functionally and structurally similar to and has the properties of sheath  304 . In such an embodiment, the hollow, helical implant is typically implanted independently of sheath  304 . In such an embodiment, the hollow, helical implant is coupled directly to tube  310 . 
     Reference is now made to  FIGS. 7-12 . It is to be noted that the scope of the present invention includes use of extraction tool  300  ( FIGS. 7-9 ) for extracting implants  500  and  502  ( FIG. 10 ),  1302  ( FIG. 11 ),  302  ( FIG. 12 ), and any other implant described herein. 
     Reference is still made to  FIGS. 7-12 . In some embodiments of the present invention, a proximal clamp and a distal clamp are used in order to extract implants  120 ,  500 ,  502 ,  1302 ,  302 , and/or any other implant described herein from prostate  100  and bladder  80  of the patient. The distal clamp typically extracts the implant from the prostate (as described hereinabove with reference to clamp  224 ). Subsequent to the extraction, the proximal clamp is advanced into bladder  80  of the patient and engages the proximal end of the implant (in a manner as described hereinabove with respect to clamp  224 ). The proximal clamp is used to guide the implant through outer sheath  230  as the distal clamp remains within bladder  80  of the patient. 
     Reference is made to  FIGS. 13A-C , which are schematic illustrations of a system  2040  comprising delivery tool  22  coupled to an implant  1200  at a distal end of delivery tool shaft  25 , in accordance with an embodiment of the present invention. Urethra  60  is constricted due to pressure exerted thereupon by a prostate  100  of the patient. Implant  1200  comprises a coiled implant comprising a proximal coil  1220  at a proximal end thereof, a distal coil  1260  at a distal end thereof, and a plurality of coils  1201  disposed between coils  1220  and  1260 . In some embodiments, implant  1200  comprises a wire  1202  having a circular cross-section (shown in  FIG. 13B ). In other embodiments, wire  1202  of implant  1200  has a triangular cross-section (shown in  FIG. 13C ). It is to be noted that wire  1202  may be shaped to define any other suitable shape, e.g., a square, a diamond, or an ellipse, in cross-section thereof. Typically, the shape of wire  1202  helps facilitate pinching of tissue of the patient between the successive coils of implant  1200 . 
       FIG. 13A  shows implant  1200  in a resting state thereof in which implant  1200  provides a longitudinal lumen having a diameter larger than a diameter of urethra  60  of the patient. For example, implant  1200  is shaped to define a lumen having a diameter of between 2.5 mm and 15 mm. In its resting state, implant coils  1220  and  1260  each have a respective diameter that is larger than the respective diameters of each of the plurality of coils  1201 . In some embodiments, the diameters of coils  1220  and  1260  are substantially equal. Alternatively, the diameter of distal coil  1260  is larger than the diameter of proximal coil  1220 . 
     Typically, implant  1200  has a proximal conic portion  1240  and a distal conic portion  1230 . Conic portions  1230  and  1240  have a slope at an angle of between 5-10 degrees, e.g., between 7 and 8 degrees, with respect to the longitudinal axis of tool  22 . Conic portion  1240  comprises a plurality of coils that are disposed in series in a manner in which: (1) a proximal-most coil thereof is disposed adjacently to proximal coil  1220 , and (2) respective diameters of the coils of portion  1240  decrease in series from (a) the coil adjacent to proximal coil  1220  to (b) a coil of portion  1240  that is furthest from proximal coil  1220 . Conically-shaped portion  1230  comprises coils disposed in series in a manner in which: (1) a distal-most coil thereof is disposed adjacently to distal coil  1260 , and (2) respective diameters of the coils of the second portion of coils decrease in series from: (a) the distal-most coil of portion  1230  to a proximal-most coil of portion  1230 . Such a configuration of implant  1200  helps overcome a force of friction of tissue of the prostate on implant  1200  (in a manner described hereinbelow), as it is implanted around urethra  60 . 
     Typically, prior to introducing delivery tool  22  into urethra  60 , outer sheath  24  is advanced distally through proximal end  62  of urethra  60  and toward bladder neck  64  of the patient. Outer sheath  24  expands urethra  60  as sheath  24  is distally advanced toward bladder  80  of the patient. Typically, outer sheath  24  is advanced via an introducer tube (not shown) having a rounded proximal end which facilitates atraumatic advancement of outer sheath  24  through urethra  60 . Outer sheath  24  is advanced along urethra  60  prior to the advancement of delivery tool shaft  25 , thus creating an open passageway for the subsequent insertion of delivery tool  22 . Typically, outer sheath  24  is hollow and enables passage of tools through the urethra by providing a working channel of sheath  24 . An imaging device (not shown), e.g., a fiber optic scope or a cystoscope, is advanced through outer sheath  24  into bladder  80 . Bladder  80  and bladder neck  64  are examined prior to the introduction of delivery tool  22  into urethra  60  of the patient. The imaging device is typically flexible, and bends 180 degrees in a proximal direction, facilitating visualization of a vicinity of bladder neck  64  of the patient. Alternatively or additionally, an optical sensor, e.g., CCD, CIS, or CMOS, is coupled to a distal portion of shaft  25  of delivery tool  22 . 
     Delivery tool  22  comprises body  21  and delivery tool shaft  25  is advanced distally through outer sheath  24  toward bladder  80  of the patient. Typically, shaft  25  comprises a hollow lumen for passing substances and/or tools therethrough, such as but not limited to, medications, fiber optics, biopsy tools, optical devices (e.g., CCD) and/or other imaging devices. 
     Typically, implant  1200  comprises a radially-expandable implant, e.g., a coil. Implant  1200  typically comprises a flexible biocompatible material, e.g., nitinol or silicone. During transurethral advancement, implant  1200  is disposed in a compressed state thereof between a proximal implant holder (shown in  FIG. 14A  as proximal implant holder  124 ) and distal implant holder  54 . In some embodiments, a distal end and a proximal end of implant  1200  are each shaped to define a slit. Each slit is configured for passage of respective fastening devices therethrough. The fastening devices maintain the compressed state of implant  1200  during advancement thereof into bladder  80  of the patient. 
     Proximal coil  1220  is shaped to define a slit  132  for advancement of a first elongate mechanical fastener  127  therethrough. Fastener  127  functions to hold implant  1200  in place with respect to tool  22  during the advancement of implant  1200  toward prostate  100  of the patient. 
     Distal implant holder  54  is shaped to provide a groove  56  at a proximal end thereof which holds and secures distal coil  1260  of implant  1200 . Together with fastener  127 , distal implant holder  54  functions to keep implant  1200  in a compressed state during advancement thereof. Additionally, distal implant holder  54  maintains coupling of implant  1200  to tool  22  during implantation of implant  1200 . A second fastener (i.e., similar to fastened  127 ) fastens distal coil  1260  to distal implant holder  54 . The securing and releasing of the fasteners are controlled remotely, by body  21  of delivery tool  22 . 
     The distal-most end of sheath  24  is disposed distally to bladder neck  64 , facilitating proper placement within bladder  80  of any device passed through sheath  24 , e.g., implant  1200 . Typically, outer sheath  24  is shaped to define a length which is shorter than a length of delivery tool shaft  25 . Thus, once shaft  25  has been fully advanced through sheath  24 , proximal coil  1220  of implant  1200  is disposed distally with respect to the distal-most end of sheath  24 . When proximal coil  1220  of implant  1200  has sufficiently entered bladder  80  of the patient (e.g., as shown), proximal end  1220  is released from delivery tool  22 , allowing implant  1200  to assume a radially-expanded configuration. 
     Delivery tool  22  comprises rotating element  30  at a proximal end thereof which is configured to facilitate implantation of implant  1200 , once the implant is inside bladder  80  of the patient. During the distal advancing of delivery tool shaft  25  toward bladder  80  of the patient, rotating element  30  is disposed adjacent to body  21  of tool  22 , as shown. 
     Body  21  comprises one or more control elements  28  on a surface of tool  22  which enables a physician to control, from outside of the patient&#39;s body, one or more functional elements located at the distal end of delivery tool  22 . Typically, but not necessarily, control elements  28  comprise rings for the physician to engage her fingers therethrough and push or pull on control elements  28 . During advancement of delivery tool  22  within sheath  24 , elements  28  are disposed in a distal orientation with respect to delivery tool  22 , e.g., at the distal end of a slot  130  in delivery tool  22  (configuration not shown). 
     Once the distal end of delivery tool shaft  25  enters bladder  80 , implant  1200  is further pushed distally by pushing on switch  42  disposed at the proximal end of tool  22 . Such pushing further ensures that proximal coil  1220  of implant  1200  is disposed distal to bladder neck  64  prior to implantation of implant  1200  around urethra  60 . Control elements  28  are then pulled proximally with respect to delivery tool  22 . Control elements  28  are coupled to a proximal end of fastener  127 . In response to the pulling, a distal end of fastener  127  is pulled to a position that is proximal to proximal end  122  of implant  120 , thereby releasing proximal coil  1220  of implant  1200  and effecting radial expansion thereof. During radial expansion of implant  1200 , distal coil  1260  of implant  1200  remains coupled to distal implant holder  54 . 
     To minimize the chance of physician error, tool  22  may comprise distal lock  32 , proximal lock  34 , and release  36 . Pulling and pushing of control elements  28  is restricted by locks  32  and  34 . For example, when elements  28  are disposed distally with respect to tool  22 , distal lock  32  automatically maintains the distal position of elements  28  such that elements  28  are not inadvertently pulled (resulting in premature expansion of implant  1200  during advancement thereof). When proximal motion of control elements  28  is desired, the physician activates release  36  to release lock  32 , allowing for such proximal motion of elements  28 . Once disposed proximally with respect to tool  22 , proximal lock  34  secures elements  28  in place, typically automatically. 
     Distal implant holder  54  is rotatable by switch  42  of tool  22 . Implant holder  54  positions implant  1200  coaxially with respect to urethra  60 , such that implant  1200  is properly corkscrewed symmetrically around the urethra. An imaging device  70  is then advanced through the lumen of shaft  25 , and guides the subsequent implantation of implant  1200 . Imaging device  70  is configured to bend 180 degrees and rotate 360 degrees in order to image the implantation procedure. 
     Delivery tool  22  typically comprises expandable guiding elements  26  which surround a portion of delivery tool shaft  25  proximal to implant  1200 . Distal and proximal ends of expandable elements  26  are each coupled to a first ring  27  and a second ring  29 , respectively. Typically, first ring  27  is fixed to a portion of shaft  25  while second ring  29  is configured to slide distally and proximally along shaft  25 . Alternatively, first ring  27  is configured to slide distally until a stopping element impedes continued distal motion of ring  27 . Such distal motion of ring  27  facilitates positioning of ring  27  and distal portions of guiding elements  26  within the lumen of the implant prior to expansion of elements  26 . During the advancing of delivery tool shaft  25  toward bladder  80 , guiding elements  26  are typically pressed against the outer surface of shaft  25 . 
     Distal pushing of control elements  28  slides ring  29  distally toward ring  27 . The distal and proximal ends of expandable elements  26  are drawn toward one another, resulting in the radial expansion of expandable elements  26 . Expandable guiding elements  26  expand such that they align with an inner surface of implant  1200 . Such alignment facilitates the guiding of implant  1200  and the maintenance of a straight configuration thereof during the implantation procedure. 
     Typically, once implant  1200  is fully disposed within bladder  80 , body  21  of tool  22  is disposed adjacent to a proximal-most end of sheath  24 . The implantation of implant  1200  within prostate  100  begins when the physician distances body  21  from outer sheath  24 , thereby shifting tool  22  proximally. Such shifting positions proximal coil  1220  of implant  1200  in proximity with bladder neck  64  immediately prior to implantation of implant  1200 . 
     Following expansion within bladder  80  of the patient, implant  1200  is shaped to define an inner lumen diameter, e.g., between 2.5 mm and 15 mm, typically larger than the non-constricted outer diameter of urethra  60 . Proximal coil  1220  of implant  1200  comprises pointed tip  122  configured to puncture tissue of prostate  100 . In some embodiments, pointed tip  122  is coupled to, e.g., soldered to or attached using any other applicable attachment means, a pointed needle which is configured to puncture tissue of the patient. Typically, the needle of tip  122  comprises a rigid, biocompatible material, e.g., stainless steel, configured to facilitate ongoing penetration of the implant as it is advanced through tissue of prostate  100 . It is to be noted that the needle is shaped to define any suitable shape configured for cutting/penetrating tissue. 
     Following the puncturing of the tissue by pointed tip  122  or, in some embodiments, the needle coupled thereto, implant  1200  is further advanced proximally in the tissue of prostate  100 , around urethra  60  of the patient. Counterclockwise rotation of rotating element  30  with respect to a longitudinal axis of tool  22 , rotates and proximally retracts implant  1200 , thus corkscrewing implant  1200  within tissue of prostate  100  surrounding urethra  60 . Positioning of implant  1200  within tissue of prostate  100  is typically guided by imaging element  70 . 
     In some embodiments, as pointed tip  122  of implant  1200  is advanced through the tissue of the patient, it is configured to ablate the tissue. In such an embodiment, implant  1200  may be coated with a substance, such as but not limited to, (a) a medication (e.g., an antibiotic) or (b) an electrical insulator (e.g., Teflon). A proximal portion of implant  1200 , i.e., one or more of the coils, may be energized to deliver RF energy, for example, to ablate tissue. In some embodiments, the proximal portion of implant  1200  is coupled to an electrode. Additionally or alternatively, the proximal portion of implant  1200  may be energized to provide ultrasound or thermal energy (e.g., heating or cooling). 
     In some embodiments, implant  1200  comprises a hollow, helical implant shaped to define a helical lumen and at least one hole, e.g., a plurality of holes, at the proximal end thereof. In such an embodiment, a fluid, e.g., saline, is injected at high pressure through the lumen of the hollow, helical implant and externally to the implant via the at least one hole, in order to cut tissue near the proximal tip of the implant as it advances through the tissue. 
     In some embodiments, a laser fiber is passed through the lumen of the hollow, helical implant  1200  and through the hole at the proximal end thereof. Typically, the laser fiber ablates tissue in the path of the implant as it is advanced therethrough. In some embodiments, an insulated RF transmitting wire (i.e., having a non-insulated transmitting-tip) is advanced through the helical lumen of the hollow implant. 
     In some embodiments, a fluid is passed through the lumen of the hollow, helical implant  1200 . The hollow, helical implant is shaped to define holes (e.g., typically toward the proximal end of the implant) for release of the fluid externally to the implant. In some embodiments, the fluid comprises a lubricant which passes externally to the implant via the holes defined thereby in order to reduce a frictional force between the tissue and the implant. 
     Expandable guiding elements  26  guide the initial implantation (e.g., longitudinal motion of  6  mm to  11  mm in a proximal direction) of the proximal portion of implant  1200  around urethra  60 . Control elements  28  are then pulled proximally, thereby sliding ring  29  proximally such that guiding elements  26  are pressed once again against the outer surface of shaft  25 . 
     Following initial partial implantation of implant  1200  and alignment of expandable guiding elements  26  along shaft  25 , implant  1200  is further advanced proximally through prostate  100 , around urethra  60  of the patient. Once implant  1200  is fully implanted in prostate  100 , distal coil  1260  is decoupled from distal implant holder  54  by retracting the fastener coupling distal coil  1260  to holder  54 . 
     Typically, as implant  1200  is advanced through tissue of prostate  100 , tissue of prostate  100  applies a frictional force to implant  1200 . In some embodiments, in order to reduce the effect of the frictional force applied to implant  1200 , implant  1200  is coated with a low-friction coating, e.g., PTFE (Teflon), MoST, ADLC or the like. In some embodiments, the implant surface is polished, e.g., electro-polished, mechanically polished, or otherwise, to reduce friction as implant  1200  is advanced through the tissue of the patient. 
     As proximal coil  1220  of implant  1200  is advanced through the tissue of prostate  100 , the tissue applies a frictional force on coils  1201  of coiled implant  1200 . In an attempt to continue corkscrewing into the tissue, the tissue exerts an increasingly larger cumulative frictional force on the increasing number of coils that are introduced within prostate  100 . In response to the frictional force applied to the intra-prostate coils as they are corkscrewed into the tissue, the coils disposed distally to coil  1220  have a tendency to expand radially, such that the respective diameters of the distal coils are generally similar to the respective diameters of the proximal coils. In such a manner, each successive distal coil of helical implant  1220  enters an opening that is defined by the larger-diameter proximal coil adjacent thereto. 
     Reference is now made to  FIG. 13D , which is a schematic illustration of implant  1200  implanted within prostate  100  of the patient, in accordance with an embodiment of the present invention. Once implant  1200  is implanted within prostate  100 , delivery tool shaft  25  and outer sheath  24  are extracted from within urethra  60 . Following implantation of implant  1200  within prostate  100 , a post-operative diameter of the portion of urethra  60  at prostate  100  is larger than the pre-operative diameter of the portion of urethra  60 . Implant  1200  is generally rigid relative to the rigidity of the prostate. The implant thus supports the urethral tissue, minimizing restenosis of urethra  60  should prostate  100  continue to enlarge. Typically, the implant improves urine flow from bladder  80 , past bladder neck  64 , and through urethra  60 . Expanding of the perimeter of urethra  60  typically treats benign prostate hyperplasia. 
     Following implantation, implant  1200  returns to its resting state thereof, as shown and as described hereinabove with reference to  FIG. 13A . Distal coiled portion  1230  increases in diameter from proximal to distal to create improved flow of urine at bladder neck  64  of bladder  80 . 
     Reference is now made to  FIGS. 13A-D . It is to be noted that the scope of the present invention includes the implantation of implant  1200  around urethra  60  from within urethra  60 , i.e., in a manner in which implant  1200  is not first introduced within bladder  80  prior to implantation of implant  1200  around urethra  60 . In such an embodiment, distal coil  1260  comprises a pointed tip, which punctures tissue of prostate  100 , and implant  1200  is advanced around the urethra in a proximal-to-distal direction. 
     Reference is now made to  FIGS. 14A-B , which are schematic illustrations of a system  1120  comprising delivery tool  22 , a coiled implant  1122  reversibly coupled to tool  22 , and a mechanical element  1124  disposed between tool  22  and implant  1122 , in accordance with an embodiment of the present invention. Typically, mechanical element  1124  comprises an expandable device, e.g., a balloon, a stent, or a wire basket. In such an embodiment, implant  1122  comprises a substantially rigid material, e.g., stainless steel, by way of illustration and not limitation. For example, implant  1122  may comprise a flexible material such as nitinol. Typically, during advancement of implant  1122  toward prostate  100 , implant  1122  is held in a compressed state between distal implant holder  56  and proximal implant holder  124 . Proximal implant holder  124  is shaped to provide a groove  125  for holding and securing a proximal end  1121  of implant  1122 . Additionally, proximal implant holder  124  is shaped to provide a longitudinal slit for advancement of a first elongate mechanical fastener  127  therethrough and subsequently through slit  132  of proximal end  1121  of implant  1122 . Fastener  127  is advanced (a) through the longitudinal slit within holder  124 , (b) subsequently through slit  132  of proximal end  1121  of implant  1122 , and (c) back into a slit at a portion of holder  124  distal to groove  125 . 
     Reference is now made to  FIG. 14B . Once implant  1122  is disposed within bladder  80  and the proximal end of implant  1122  is released from proximal implant holder  124 , mechanical element  1124  expands within the lumen defined by implant  1122  and forces the surrounding implant  1122  to expand in turn. In such an embodiment, implant  1122  is expanded to a desired diameter, e.g., between 2.5 mm and 15 mm, that is suitable to facilitate implantation of implant  1122  around urethra  60 . 
     In some embodiments, implant  1122  is expanded within urethra  60  and is not first advanced into bladder  80 . In such an embodiment, implant  1122  is implanted around urethra  60  from within urethra  60  in a proximal-to-distal direction. Alternatively, implant  1122  is expanded such that it exerts a force on an inner wall of urethra  60  and is resorbed by the urethra without puncturing urethra  60 . 
     It is to be noted that the scope of the present invention includes the expanding of implant  1122  independently of mechanical element  1124 . In such an embodiment, in order to expand implant  1122 , a first end of implant  1122  is held in place while a second end of implant  1122  is twisted to expand coils of implant  1122 . For example, a proximal end of implant  1122  may be held in place by proximal implant holder  124  while a distal end of implant  1122  is rotated by rotating distal implant holder  54  with respect to shaft  25 . 
       FIG. 15  shows a system  1030  comprising delivery tool  22  coupled to a motor  1032 , in accordance with an embodiment of the present invention. Typically, motor  1032  helps facilitate implantation of implant  120  around urethra  60  of the patient. In some embodiments, motor  1032  controls the corkscrewing of implant  120  into tissue of prostate  100  by imparting a jackhammer-like function, or force, to the implant. Motor  1032  causes implant  120  to move in fast jerks when entering tissue so as to overcome the force of friction as it is advanced into the tissue. As implant  120  is functioning as a jackhammer, the physician also rotates the handle (in the direction as indicated by the arrow) to facilitate the corkscrewing of the implant into the tissue. In some embodiments, a second motor may be coupled to tool  22  which is used to rotate implant  120  in order to facilitate corkscrewing of implant  120  around urethra  60 . 
     In some embodiments, motor  1032  is configured to facilitate oscillation of implant  120  as it is advanced within tissue of the patient. In such an embodiment, motor  120  causes implant to be rotationally advanced and retracted by given rotational distances. Typically, motor  1032  cycles between facilitating (a) advancement of implant  120  into the tissue by a first number of degrees, and (b) retraction of implant  120  by a second number of degrees. For example, motor  1032  may cause implant to be rotated 270 degrees in order to be implanted into the tissue, and subsequently, motor  1032  may cause implant to be retracted by 60 degrees. Such oscillation of implant between implanting and retracting helps overcome the friction that the tissue of prostate  100  applies to implant  120 . 
     In some embodiments, motor  1032  comprises a vibrator configured to vibrate, which causes implant  120  to agitate the tissue of prostate  100  as implant  120  is implanted therein. In some embodiments, motor  1032  comprises a source of ultrasound energy, e.g., an ultrasound transducer, which causes implant  1032  to vibrate in response to ultrasound energy created by the transducer. Such vibration helps overcome the friction applied to implant  120  as it is implanted in the tissue of prostate  100 . 
     It is to be noted that motor  1032  is coupled to tool  22  at body  21  thereof by way of illustration and not limitation, and that motor  1032  may be coupled to any portion of delivery tool  22 . In some embodiments, motor  1032  may be coupled to implant  120 . For embodiments in which motor  1032  is coupled to a portion of tool  22  that is remote from body  21 , motor  1032  may be remotely controllable. In some embodiments, motor  1032  is used to automate rotation of implant  120  in order to facilitate automated corkscrewing of implant  120 . 
     It is to be noted that implant  120  is shown in  FIG. 15  by way of illustration and not limitation, and that delivery tool  22  coupled to motor  1032  may be used to implant any one of implants described herein. 
     Reference is now made to  FIG. 16 , which is a schematic illustration of a system  1040  comprising a coiled implant  1042  having a proximal coil  1044  and a distal coil  1046 , which form a scaffold for supporting a plurality of longitudinal implant rods  1048 , in accordance with an embodiment of the present invention. Typically implant  1042  and rods  1048  comprise a biocompatible material, e.g., nitinol, silicone, and/or stainless steel. Typically, implant  1042  is shaped to provide between  1 . 5  and  2  coils, which define a conically-shaped implant. Proximal coil  1044  has a diameter that is smaller than a diameter of distal coil  1046 . The respective diameters of coils  1044  and  1046  are each larger than a diameter of urethra  60 , i.e., each coil  1044  and  1046  has a diameter of between 2.5 mm and 15 mm. 
     Implant  1042  is implanted around urethra  60  by being corkscrewed therearound. In some embodiments, implant  1042  is first advanced into bladder  80  and is corkscrewed proximally around urethra  60 . Alternatively, implant  1042  is corkscrewed, e.g., distally around urethra  60 , from within urethra  60 . 
     In either embodiment, rigid longitudinal rods  1048  are implanted in urethra  60  and are supported therein by implant  1042 , which functions as a scaffold. Each rod  1048  is first advanced into bladder  80 . Once inside bladder  80 , rod  1048  is then retracted proximally into tissue of prostate  100 . Rod  1048  is advanced with respect to implant  1042  in a manner in which rod  1048  is advanced below the inner surface of distal coil  1046  and above an outer surface of proximal coil  1044 . Typically, the plurality of rods  1048  are implanted substantially in parallel with urethra  60  of the patient. 
     It is to be noted that for some embodiments of the present invention, rods  1048  may be implanted prior to implantation of implant  1042 . In such an embodiment, rods  1048  function to support implant  1042  (as described hereinbelow with reference to  FIGS. 28A-D ). 
       FIGS. 17A-D  show a system  1050  comprising delivery tool  22  reversibly coupled to and facilitating implantation around urethra  60  of a plurality of curved needles  229 , in accordance with an embodiment of the present invention. Typically, needles  229  comprise an expandable material, e.g., nitinol. During advancement of needles  229  toward prostate  100 , needles  229  are compressed between a distal portion of delivery tool shaft  25  and a retractable sheath  225  ( FIG. 17A ). When compressed within sheath  225 , needles  229  are tightly wrapped around shaft  25 . Prior to the advancement of needles  229  through urethra  60 , urethra  60  defines a constricted, preoperative diameter D 1  at prostate  100 . As shaft  25  is advanced through urethra  60 , a distal portion of shaft  25 , needles  229 , and sheath  225  expand urethra  60  to a diameter D 2 . Following implantation of needles  229  around urethra  60 , needles  229  maintain a postoperative diameter D 2  of urethra  60  at prostate  100 . 
     Reference is now made to  FIG. 17B . Body  21  of delivery tool  22  is shaped to define one or more slots  130  which facilitate back and forth sliding of mechanical control elements  28 . Control elements  28  are pulled proximally and, responsively, control the retraction of sheath  225  proximally with respect to needles  229 . Following the retraction of sheath  225 , needles  229  are exposed within urethra  60  at prostate  100 . Once exposed, needles  229  expand and push against tissue of prostate  100  that constricts urethra  60 . Needles  229  typically expand such that an inner lumen defined by each needle  229  is larger than a diameter of urethra  60  at prostate  100 . For example, the inner lumen of each needle  229  has a diameter, e.g., between 2.5 mm and 15 mm, that is larger than diameter D 2  (diameter D 2  shown in  FIG. 17A ). 
     Typically, needles  229  comprise curved needles which are each shaped to define between 180 and 360 degrees, e.g., between 250-300 degrees in a resting state thereof (shown in  FIGS. 17B-D ). Each needle  229  is shaped to provide a pointed tip  230 . In some embodiments, tip  230  comprises stainless steel which is welded to the body of needle  229 . 
       FIG. 17C  shows partial implantation of needles  229  in tissue of prostate  100  that surrounds urethra  60 . Rotating element  30  is rotated in a counter-clockwise direction, i.e., in the direction such that the pointed ends of each needle  229  enter tissue of prostate  100 . 
     Needles  229  are coupled together during the advancement toward prostate  100  and subsequent implantation around urethra  60  ( FIG. 17C ). Following implantation of needles  229  around urethra  60  (as shown in  FIG. 17D ), needles  229  are decoupled from one another. 
     Reference is now made to  FIGS. 17C-D . Needles  229  are coupled together by a longitudinal bar  232  which is configured for slidable advancement with respect to needles  229 . As shown in  FIG. 17D , each needle  229  (at an end thereof that opposes pointed tip  230 ) is shaped to define a longitudinal slit  233  for passage therethrough of bar  232 . Each needle  229  is coupled to a respective needle holder  234  that is coupled to delivery tool shaft  25 . Needle holder  234  has a pair of arms which surround the end of needle  229 . The arms of needle holder  234  are each shaped to provide a longitudinal slit  231  that is in alignment with slit  233  of needle  229  when the end of needle  229  is disposed within holder  234 . When needles  229  are coupled together, for each needle  229  and needle holder  234 , bar  232  passes through slit  231  of a first arm of needle holder  234 , through slit  233  of needle  229 , and finally through slit  231  of a second arm of needle holder  234 . 
       FIG. 17D  shows the decoupling of bar  232  from needles  229  following implantation of needles  229  around urethra  60 . Bar  232  is controlled by a mechanical element  227 . By pulling on mechanical element  227 , in a direction as indicated by the arrow, bar  232  is retracted into sheath  24  and releases needles  229 . Typically, the ends of needles  229  that oppose pointed tips  230  remain disposed within urethra  60  following the initial implantation of needles  229 . Ultimately, the ends are resorbed into the tissue surrounding urethra  60 . 
     Reference is now made to  FIGS. 18A-E , which are schematic illustrations of a system  1060  comprising delivery tool  22  reversibly coupled to and facilitating implantation around urethra  60  of a plurality of coiled implants  1070 ,  1072 , and  1074 , in accordance with an embodiment of the present invention. Typically, coiled implants  1070 ,  1072 , and  1074  comprise a flexible material, e.g., nitinol. During advancement of needles  229  toward prostate  100 , implants  1070 ,  1072 , and  1074  are compressed between a distal portion of delivery tool shaft  25  and retractable sheath  225  ( FIG. 18A ). Implants  1070 ,  1072 , and  1074  are typically wrapped tightly around shaft  25  when compressed within sheath  225 . 
     Prior to the advancement of implants  1070 ,  1072 , and  1074  through urethra  60 , urethra  60  defines a constricted, preoperative diameter D 1  at prostate  100 . As shaft  25  is advanced through urethra  60 , a distal portion of shaft  25 , implants  1070 ,  1072 , and  1074 , and sheath  225  expand urethra  60  to a diameter D 2 . Following implantation of implants  1070 ,  1072 , and  1074  around urethra  60 , implants  1070 ,  1072 , and  1074  will maintain a postoperative diameter D 2  of urethra  60  at prostate  100 . 
     Implants  1070 ,  1072 , and  1074  are advanced through urethra  60  until they are disposed in urethra  60  in the vicinity of prostate  100 .  FIG. 18B  shows partial retraction of sheath  225  by pulling on mechanical controls  28  along slots  130  in the direction as indicated by the arrow. As sheath  225  is retracted and implants  1070 ,  1072 , and  1074  are exposed, implants  1070 ,  1072 , and  1074  expand and push against tissue of prostate  100  that constricts urethra  60 . 
       FIG. 18C  shows complete retraction of sheath  225  and expansion of implants  1070 ,  1072 , and  1074 . Once exposed and expanded, implants  1070 ,  1072 , and  1074  push against tissue of prostate  100  that constricts urethra  60 . Each implant  1070 ,  1072 , and  1074  is shaped to provide a respective pointed distal tip  1071 ,  1073 , and  1075 . In some embodiments, tips  1071 ,  1073 , and  1075  comprise stainless steel tips which are welded to implants  1070 ,  1072 , and  1074 , respectively. 
     Reference is now made to  FIGS. 18A and 18C . In a compressed state during delivery of implants  1070 ,  1072 , and  1074  through urethra  60 , implants  1070 ,  1072 , and  1074  are tightly wound around shaft  25  of delivery tool  22 , and have  2 - 5  coils (e.g.,  3 - 4  coils as shown in  FIG. 6A ). Following expansion of implants  1070 ,  1072 , and  1074 , implants  1070 ,  1072 , and  1074  are in their relaxed states in which implants  1070 ,  1072 , and  1074  have 1-5 coils (typically, 2-3 coils, as shown). Implants  1070 ,  1072 , and  1074  typically expand such that an inner lumen defined by each implant  1070 ,  1072 , and  1074  is larger than a diameter of urethra  60  at prostate  100 . For example, the inner lumen of each implant  1070 ,  1072 , and  1074  has a diameter, e.g., between 2.5 mm and 15 mm, which is larger than diameter D 2  (diameter D 2  shown in  FIG. 18A ). 
     During delivery of implants  1070 ,  1072 , and  1074  through urethra  60 , implants  1070 ,  1072 , and  1074  are coupled together by a longitudinal bar, as described hereinbelow. 
     Reference is again made to  FIG. 18C . Delivery tool  22  comprises mechanical locks  1062  and  1064  which allow for certain mechanical activity of delivery tool  22  only when locks  1062  and  1064  are released. For example, lock  1062  is released by pulling downward on a knob of lock  1062  in a direction as indicated by the arrow. Releasing lock  1062  allows for the operating physician to distally advance implants  1070 ,  1072 , and  1074  slightly within urethra  60 , without having to distally push the entire delivery tool  22 . 
       FIG. 18D  shows partial implantation of implants  1070 ,  1072 , and  1074  in response to counterclockwise rotation of rotating element  30  (i.e., in the direction such that the pointed ends of each implant  1070 ,  1072 , and  1074  enter tissue of prostate  100 ). Rotation of rotating element  30  also proximally distances element  30  from body  21  which retracts implants  1070 ,  1072 , and  1074  as they are corkscrewed around urethra  60 . 
       FIG. 18E  shows implants  1070 ,  1072 , and  1074  in their fully-implanted state around urethra  60 . Implants  1070 ,  1072 , and  1074  maintain an unconstricted state of urethra  60  at prostate  100 . Following implantation, implants  1070 ,  1072 , and  1074  are decoupled from one another. 
     Typically, implants  1070 ,  1072 , and  1074  are coupled together by a longitudinal bar  1086  which is configured for slidable advancement with respect to implants  1070 ,  1072 , and  1074 . Each implant  1070 ,  1072 , and  1074 , at respective ends  1080 ,  1083 , and  1087  thereof (i.e., at an end thereof that opposes pointed tips  1071 ,  1073 , and  1075 , respectively) is shaped to define a respective groove  1081 ,  1082 , and  1085  for passage therethrough of bar  1086 . Typically, grooves  1081 ,  1082 , and  1085  are shaped to define “T”-shaped grooves which surround respective portions of bar  1086 . The portions of bar  1086  that are disposed within grooves  1081 ,  1082 , and  1085  are shaped to define narrow portions which are configured to be slid within and displaced from within grooves  1081 ,  1082 , and  1085  in response to a force applied thereto. 
       FIG. 18E  shows the decoupling of bar  1086  from implants  1070 ,  1072 , and  1074  following implantation thereof around urethra  60 . Bar  1086  is controlled by a mechanical element  1068 . By pulling on mechanical element  1068 , bar  1086  is agitated and retracted slightly such that the portions of bar  1086  that are disposed within grooves  1081 ,  1082 , and  1085  move out of grooves  1081 ,  1082 , and  1085 , thereby releasing implants  1070 ,  1072 , and  1074 . Typically, ends  1080 ,  1083 , and  1087  of implants  1070 ,  1072 , and  1074 , respectively, remain disposed within urethra  60  following initial implantation of the implants. Ultimately, ends  1080 ,  1083 , and  1087  are resorbed into the tissue surrounding urethra  60 . 
     Reference is now made to  FIGS. 19A-B  which are schematic illustrations of an implant  2000  shaped to define vertices  2002 , in accordance with an embodiment of the present invention. Implant  2000  is typically resorbable. Typically, implant  2000  is shaped to define a prism having a triangular face when viewed in cross-section. In some embodiments, implant  2000  comprises a radially-expandable implant comprising a flexible material, e.g., nitinol. In some embodiments, implant  2000  is less flexible, e.g., comprising stainless steel, which is nevertheless expandable by a mechanical element (as described hereinabove with reference to  FIGS. 14A-B ). 
     As shown in  FIG. 19B , implant  2000  is delivered to a portion of urethra  60  that is in the vicinity of prostate  100 . Implant  2000  is either (a) allowed to expand (in embodiments in which implant  2000  comprises an expandable material such as nitinol) or (b) is made to expand using a mechanical element, such that vertices  2002  are in contact with an inner surface of urethra  60 . A respective area  2003  is defined between neighboring vertices  2002  of implant  2000 . Typically, tissue of urethra  60  is pinched into areas  2003  between neighboring vertices  2002 . Ultimately, implant  2000  is resorbed by urethra  60  and into tissue of prostate  100 . 
     In some embodiments, implant  2000  is coated with a pro-fibrotic agent which helps enhance the resorption of implant  2000  into prostate  100 . 
     In some embodiments, implant  2000  comprises a wire  2001  having a circular cross-section. In other embodiments, wire  2001  of implant  2000  has a triangular cross-section. It is to be noted that wire  2001  may be shaped to define any other suitable shape, e.g., a square or an ellipse, in cross-section thereof. Typically, the shape of wire  2001  helps facilitate pinching of tissue of the patient between the successive coils of implant  2000 . 
     It is to be noted that implant  2000  is shaped to define a prism by way of illustration and not limitation. For example, implant  2000  may be shaped to define a cylinder having a circular or elliptical face when viewed in cross-section. In other embodiments, implant  2000  may be shaped to define a rectangle having a square or diamond-shaped face when viewed in cross-section. 
       FIGS. 20A-D  show a system,  2020  comprising delivery tool  22  reversibly coupled to and facilitating implantation around urethra  60  of a plurality of a first coiled implant  2022  and a second coiled implant  2024 , in accordance with an embodiment of the present invention. Implant  2022  is shaped to define a left-handed coil, and implant  2024  is shaped to define a right-handed coil. Implant  2024  has an outer diameter that is smaller than an inner diameter of implant  2022 . Implant  2022  is shaped from a wire having a width that is larger than the width of the wire used to shape implant  2024 . Implants  2022  and  2024  are each shaped to provide an inner lumen which has a diameter that is larger than a diameter of urethra  60 . Typically, implants  2022  and  2024  are coupled to delivery tool  22  in a relative spatial configuration in which implant  2024  is disposed concentrically within implant  2022 . 
     It is to be noted that although two implants  2022  and  2024  are shown, any suitable number of implants may be reversibly coupled to delivery tool  22 . In some embodiments, a respective portion of implant  2022  and  2024  ablates tissue of the patient as it is advanced therethrough. In such an embodiment, implants  2022  and  2024  may be coated with a substance, such as but not limited to, (a) a medication (e.g., an antibiotic) or (b) an electrical insulator (e.g., Teflon). One or more of the coils of implants  2022  and  2024 , may be energized to deliver RF energy, for example, to ablate tissue. In some embodiments, a respective portion of implants  2022  and  2024  is coupled to an electrode. Additionally or alternatively, a respective portion of implants  2022  and  2024  may be energized to provide ultrasound or thermal energy (e.g., heating or cooling). 
     In some embodiments, implants  2022  and  2024  each comprise a hollow, helical implant shaped to define a helical lumen and at least one hole, e.g., a plurality of holes, at the proximal end thereof. In such an embodiment, a fluid, e.g., saline, is injected at high pressure through the respective lumens of the hollow, helical implants and externally to the implants via the at least one hole, in order to cut tissue near the puncturing tip of the implant as it advances through the tissue. 
     In some embodiments, a respective laser fiber is passed through the lumen of the each one of hollow, helical implants  2022  and  2024  and through the hole at the proximal end thereof. Typically, the laser fiber ablates tissue in the path of the implant as it is advanced therethrough. In some embodiments, an insulated RF transmitting wire (i.e., having a non-insulated transmitting-tip) is advanced through the helical lumen of the hollow implant. 
     In some embodiments, a fluid is passed through each one of the lumens of the hollow, helical implants  2022  and  2024 . Each hollow, helical implant is shaped to define holes (e.g., typically toward the proximal end of the implant) for release of the fluid externally to the implant. In some embodiments, the fluid comprises a lubricant which passes externally to the implant via the holes defined thereby in order to reduce a frictional force between the tissue and the implant. 
     Typically, as implants  2022  and  2024  are advanced through tissue of prostate  100 , tissue of prostate  100  applies a frictional force to implants  2022  and  2024 . In some embodiments, in order to reduce the effect of the frictional force applied to implants  2022  and  2024 , implants  2022  and  2024  are coated with a low-friction coating, e.g., PTFE (Teflon), MoST, ADLC or the like. In some embodiments, the implant surface is polished, e.g., electro-polished, mechanically polished, or otherwise, to reduce friction as implants  2022  and  2024  is advanced through the tissue of the patient. 
     Delivery tool  22  is reversibly couplable to implants  2022  and  2024 . Tool  22  provides (1) a first implant holder  2021  which is reversibly coupled to a distal end  2030  of implant  2022 , and (2) a second implant holder  2023  which is reversibly coupled to a distal end  2032  of implant  2024 . 
     Implants  2022  and  2024  comprise a flexible material, e.g., nitinol. Typically, during advancement of implants  2022  and  2024  through urethra  60 , implants  2022  and  2024  are compressed within a retractable sheath (not shown for clarity of illustration). Once advanced into bladder  80 , the retractable sheath is retracted to expose implants  2022  and  2024  which expand radially upon retraction of the sheath. The retractable sheath is controllable by mechanical elements disposed on body  21  of tool  22 , as described hereinabove. 
       FIG. 20A  shows implants  2022  and  2024  in their spatial configuration after they have been advanced into bladder  80  and expanded therein. Upon expansion, implants  2022  and  2024  define a lumen having a diameter, e.g., between 2.5 mm and 15 mm, that is larger than a diameter of urethra  60 . Tool  22  is retracted slightly so that the proximal ends of implants  2022  and  2024  are disposed at bladder neck  64  of bladder  80 . 
       FIG. 20B  shows partial implantation of implants  2022  and  2024  around urethra  60 . Implant  2022  is shaped to provide a pointed proximal tip  2025  which punctures tissue of prostate  100 . Implant  2024  is shaped to provide a pointed proximal tip  2027  which punctures tissue of prostate  100 . In some embodiments, tips  2025  and  2027  comprise a rigid material, e.g., stainless steel, which is welded to the proximal ends of implants  2022  and  2024 , respectively. 
     During implantation, (1) implant  2022  is rotated by holder  2021  in a counter-clockwise direction, as indicated by arrow  2 , while, substantially at the same time, (2) implant  2024  is rotated by holder  2023  in a clockwise direction, as indicated by arrow  1 . Implants  2022  and  2024  are implanted substantially at the same time around urethra  60 . Implantation of implants  2022  and  2024  in counter-clockwise and clockwise directions, respectively, helps reduce a torsion force of implants  2022  and  2024  on tissue of prostate  100 . That is, implant  2024  rotates tissue of prostate  100  clockwise (i.e., in a direction opposite the direction of implantation of implant  2022 ), and thereby balances the twisting of tissue  100  in a counter-clockwise direction in response to the implantation of implant  2022 . 
       FIG. 20C  shows continued implantation of implants  2022  and  2024  around urethra  60  in opposing rotational directions. 
       FIG. 20D  shows implants  2022  and  2024  in their implanted states in which implant  2024  is disposed concentrically within implant  2022 . Implants  2022  and  2024  support a post-operative diameter of urethra  60  in a in an unconstricted state. 
     It is to be noted that implants  2022  and  2024  are implanted in a distal-to-proximal direction from within bladder  80  by way of illustration and not limitation. For example, implants  2022  and  2024  may be implanted in a proximal-to-distal direction from within urethra  60  of the patient. In such an embodiment, implants  2022  and  2024  are coupled to tool  22  by their proximal ends, which the respective distal ends of implants  2022  and  2024  comprise pointed tips which puncture tissue of the urethra. 
     It is to be additionally noted that in some embodiments, implants  2022  and  2024  are implanted successively around urethra  60 . In such an embodiment, implants  2022  and  2024  may be advanced through urethra  60  at different times. Alternatively, implants  2022  and  2024  may be disposed at respective longitudinal positions with respect to shaft  25  of delivery tool  22 . In either embodiment, implants  2022  and  2024  are made to assume the spatial configuration (i.e., concentrically disposed) when implanted around urethra  60 . 
     It is to be further noted that coiled implants  2022  and  2024  are shown by way of illustration and not limitation and that coiled implants  2022  and  2024  may be shaped to define any implant described herein. For example, coiled implants  2022  and  2024  may each be shaped to define implant  1200  as described hereinabove with reference to  FIGS. 13A-D . 
     Reference is made to  FIGS. 21A-F , which are schematic illustrations of a system  5020  comprising a transurethral delivery tool  5021  housing at least one coiled implant  5040 , in accordance with an application of the present invention. Delivery tool  5021  comprises a handle  5022  and a delivery tool shaft  5024 , and is configured to be inserted into a urethra  60  of a penis  160  of a patient. Shaft  5024  houses a deflectable shaft  5030  having a distal end that is deflectable from a longitudinal axis of delivery tool  5021 . Delivery tool  5021  comprises a flexible, deflectable distal portion  5026  comprising a sleeve  5027  which surrounds distal portion  5026  of delectable shaft  5030 . A distal ring  5034  is coupled to and surrounds a distal end of portion  5026  of shaft  5030 . Deflection of distal portion  5026  is controllable by a pull-wire  5032  which is coupled (a) at a distal end thereof to ring  5034 , and (b) at a proximal end thereof to handle  5022  of tool  5021 . Pull-wire  5032  is manipulated by the operating physician via a tool-deflection-actuation system provided by handle  5022 . 
     A portion of urethra  60  at prostate  100  is constricted due to pressure exerted thereupon by prostate  100 . Typically, prior to introducing delivery tool  5021  into urethra  60 , an outer sheath (not shown for clarity of illustration) is advanced distally through a proximal end of urethra  60  and toward bladder neck  64  of the patient. The outer sheath expands urethra  60  at prostate  100  as it is distally advanced toward bladder  80  of the patient. Typically, the outer sheath is advanced via an introducer tube (not shown) having a rounded proximal end which facilitates atraumatic advancement of the outer sheath through urethra  60 . The outer sheath is advanced along urethra  60  prior to the advancement of delivery tool shaft  5024 , thus creating an open passageway for the subsequent insertion of delivery tool  5021 . Typically, the outer sheath is hollow and enables passage of tools through the urethra by providing a working channel. Delivery tool shaft  5024  is advanced distally through the outer sheath and toward bladder  80  of the patient. Typically, shaft  5024  comprises a hollow lumen for passing substances and/or tools therethrough, such as but not limited to, medications, fiber optics, biopsy tools, optical devices (e.g., CCD) and/or other imaging devices. 
     Delivery tool  5021  houses one or more implants  5040  within shaft  5024  of tool  5021 . For some applications, a plurality of implants  5040  are disposed within shaft  5024 . At a given time, a single implant  5040  is disposed within flexible sleeve  5027  of tool  5021  and surrounds a portion of distal portion  26  of deflectable shaft  5030 . 
     Implant  5040  comprises a coiled implant comprising a proximal coil at a proximal end thereof, a distal coil at a distal end thereof, and a plurality of successive contiguous coils disposed between the proximal and distal coils. The distal coil of implant  5040  comprises a pointed tip  5042  which punctures tissue of prostate  100  during implantation of implant  5040 . Ultimately, both the distal and proximal coils are disposed entirely within prostate tissue of the patient. That is, the distal coil does not extend beyond the prostate capsule (the capsule that surrounds the prostate), and the proximal coil does not extend into the urethra. 
     For some applications, implant  5040  comprises an expandable implant, e.g., a coil. Implant  5040  typically comprises a flexible biocompatible material, e.g., nitinol or silicone. Alternatively, implant  5040  is rigid. During transurethral advancement, implant  5040  is disposed in a compressed state thereof within tool  5021 . Implant  5040  comprises a wire having a circular cross-section, by way of illustration and not limitation. For example, the wire of implant  5040  may be shaped to define any other suitable shape, e.g., a square, a triangle, a diamond, or an ellipse, in cross-section thereof. Typically, the shape of the wire forming the coiled implant helps facilitate pinching of tissue of the patient between the successive coils of implant  5040  during implantation thereof. 
     Delivery tool  5021  houses an imaging device  5028 , e.g., a fiber optic scope or a cystoscope, which extends from handle  5022  toward sleeve  5027  of distal portion  5026  of tool  5021 . Sleeve  5027  is shaped to define a slit in which a distal portion of imaging device  5028  is positioned such that, during deflection of distal portion  5026  of deflectable shaft  5030  and sleeve  5027 , (a) sleeve  5027  is moved away from the distal portion of imaging device  5028  and (b) imaging device  5028  is freed from sleeve  5027  and remains disposed in parallel with respect to the longitudinal axis of urethra  60 . Typically, imaging device  5028  comprises a side-viewing imaging device configured for imaging urethra  60  during implantation of implant  5040 . Alternatively or additionally, an optical sensor, e.g., CCD, CIS, or CMOS, is coupled to a distal portion of shaft  5024  of delivery tool  5021 . 
       FIG. 21B  shows the deflection of sleeve  5027  and distal portion  5026  of tool  5021 . Prior to the deflection, the entire tool  5021  is rotated by the physician 180 degrees, in the direction as indicated by arrow  5011 A. The rotation prior to the deflection of distal portion  5026  and the implantation of implant  5040  is shown by way of illustration and not limitation. For example, the following steps for implanting implant  5040  may be performed without initially rotating tool  5021  by 180 degrees. 
     Handle  5022  comprises a deflection-actuation system comprising a knob  5070  coupled to a spool  5072 . As described hereinabove with reference to  FIG. 21A , pull-wire  5032  is coupled at a distal end thereof to distal portion  5026  of delectable shaft  5030  by being coupled to ring  5034  that surrounds a portion of distal portion  5026  of shaft  5030 . A proximal portion  5074  of pull-wire  5032  is coupled to spool  5072  of the deflection-actuation system of handle  5022 . Upon rotation of knob  5070  in the direction as indicated by arrow  5022 A, portion  5074  of pull-wire  5032  is wrapped around spool  5072  thereby pulling on pull-wire  5032  and effecting tension in pull-wire  5032 . Consequently, the distal portion of pull-wire  5032  pulls ring  5034  that is coupled to distal portion  5026  of deflectable shaft  5030 , which causes distal portion  5026  of shaft  5030  to be pulled proximally, as shown. 
     As distal portion  5026  of shaft  5030  is pulled by pull-wire  5032 , a flexible, distal tip of portion  5026  is deflected radially (e.g., by 90 degrees, as shown) from a position that is aligned with a longitudinal axis of tool  5021 . During the deflection, flexible distal tip of portion  5026  slides along a wall of urethra  60  and compresses prostate tissue by pushing the wall of urethra  60 . 
     Tool  5021  comprises an inflatable element  5050 , e.g., a balloon, at a site proximal to flexible distal portion  5026 . During the deflection of distal portion  5026  and subsequent implantation of implant  5040 , inflatable element  5050  is inflated to push against and apply pressure to a wall of urethra  60  in order to stabilize and maintain in place tool  5021  during the deflection of portion  5026  and the subsequent implantation of implant  5040 . Inflatable element  5050  has a volume in an inflated state thereof that is up to 50 cc, e.g., up to 5 cc. For some applications, inflatable element  5050  comprises an annular inflatable element that surrounds a distal portion of delivery tool  5021 . 
     It is to be noted that an inflation conduit (not shown for clarity of illustration) is coupled at a distal end thereof to inflatable element  5050  and extends through the lumen of shaft  5024  and toward handle  5022  of tool  5021 . When the physician desires to inflate element  5050 , pressurized fluid is delivered via the conduit toward inflatable element  5050  from a fluid source that is disposed outside the body of the patient. 
     Typically, tool  5021  is preloaded with a plurality of implants  5040 , which are disposed within shaft  5024  and surround deflectable shaft  5030 . Typically, implants  5040  are successively disposed and surround the portion of shaft  5030  which is not configured for deflection, i.e., the portion of shaft  5030  that is proximal to deflectable portion  5026 . Prior to deflection of distal portion  5026  of tool  5021 , a first one of implants  5040  is pushed by an elongate pushing tool (not shown for clarity of illustration) disposed within shaft  5024 , toward a position within the distal tip of portion  5026 . Once positioned at the distal tip of portion  5026 , the proximal coil of implant  5040  is engaged by an elongate, flexible screwdriver tool  5047  that is disposed within a lumen of shaft  5030 . Implant  5040  is thereby primed for implantation in tissue of prostate  100 . Screwdriver tool  5047  defines a distal portion that is flexible and deflectable together with distal portion  5026  of shaft  5030 . 
       FIG. 21C  shows implantation of a first implant  5040  in tissue of prostate  100  that has been compressed by the distal tip of tool  5021  in response to the deflection of distal portion  5026 . As shown, following deflection of portion  5026 , the distal tip of portion  5026  is positioned perpendicularly with respect to the wall of urethra  60  and in alignment with a vicinity of prostate  100  designated for implantation of implant  5040 . That is, prior to implantation, the deflected portion  5026  moves implant  5040  along an axis which will ultimately define the longitudinal axis of implant  5040  upon implantation of implant  5040  in tissue of prostate  100 . 
     Handle  5022  comprises an implant-actuation-system comprising a knob  5076  that is rotatable by the operating physician in order to corkscrew implant  5040  into tissue of prostate  100 . Rotation of knob  5076  controls the rotation of screwdriver tool  5047  to effect corkscrewing of implant  5040  into tissue of prostate  100 . 
     As described hereinabove with reference to  FIG. 1A , the distal coil of implant  5040  is shaped to provide a pointed tip  5042  configured to puncture tissue of prostate  100 . For some applications, pointed tip  5042  comprises a pointed needle which is coupled to (e.g., soldered to or attached using any other applicable attachment means) the distal coil of implant  5040 . Typically, the needle of tip  5042  comprises a rigid, biocompatible material, e.g., stainless steel, configured to facilitate ongoing penetration of implant  5040  as it is advanced through tissue of prostate  100 . It is to be noted that the needle is shaped to define any suitable shape configured for cutting/penetrating tissue. 
     For some applications, as pointed tip  5042  of implant  5040  is advanced through the tissue of the patient, it is configured to ablate the tissue. Implant  5040  may be coated with a substance, such as but not limited to, (a) a medication (e.g., an antibiotic) or (b) an electrical insulator (e.g., Teflon). A distal portion of implant  5040 , i.e., one or more of the coils, may be energized to deliver RF energy, for example, to ablate tissue. For some applications, the distal portion of implant  5040  is coupled to an electrode. Additionally or alternatively, the distal portion of implant  5040  may be energized to provide ultrasound or thermal energy (e.g., heating or cooling.( 
     For some applications, implant  5040  comprises a hollow, helical implant shaped to define a helical lumen and at least one hole, e.g., a plurality of holes, at the proximal end thereof. A fluid, e.g., saline, is typically injected at high pressure through the lumen of the hollow, helical implant and externally to the implant via the at least one hole, in order to cut tissue near the proximal tip of the implant as it advances through the tissue. 
     For some applications, a laser fiber is passed through the lumen of the hollow, helical implant  5040  and through the hole at the proximal end thereof. Typically, the laser fiber ablates tissue in the path of the implant as it is advanced therethrough. For some applications, an insulated RF transmitting wire (i.e., having a non-insulated transmitting-tip) is advanced through the helical lumen of the hollow implant. 
     For some applications, a fluid is passed through the lumen of the hollow, helical implant  5040 . The hollow, helical implant is shaped to define holes (e.g., typically toward the proximal end of the implant) for release of the fluid externally to the implant. For some applications, the fluid comprises a lubricant which passes externally to the implant via the holes defined thereby in order to reduce a frictional force between the tissue and the implant. 
     Deflection of tool  5021  places the distal tip of tool  5021  in a position in which screwdriver tool  5047  implants implant  5040  in tissue of prostate  100  at a non-zero angle, e.g., 90 degrees, as shown, with respect to the longitudinal axis of urethra  60 . Knob  5076  is rotated by the physician, in the direction as indicated by arrow  5033 A, in order to rotate screwdriver tool  5047  and thereby effect implantation of implant  5040 . Once implant  5040  is fully implanted in prostate  100 , it is embedded entirely within tissue of prostate  100 , i.e., a portion thereof is not disposed external to the capsule of prostate  100 . That is, both the distal and proximal coils of implant  5040  are disposed within tissue of prostate  100 . 
     Typically, as implant  5040  is advanced through tissue of prostate  100 , tissue of prostate  100  applies a frictional force to implant  5040 . For some applications, in order to reduce the effect of the frictional force applied to implant  5040 , implant  5040  is coated with a low-friction coating, e.g., PTFE (Teflon), MoST, ADLC or the like. For some applications, the implant surface is polished, e.g., electro-polished, mechanically polished, or otherwise, to reduce friction as implant  5040  is advanced through the tissue of the patient. 
     Following the corkscrewing of implant  5040  in tissue of prostate  100 , implant  5040  is decoupled from screwdriver tool  5047  and from delivery tool  5021  and maintains the tissue in a compressed state in order to enlarge the perimeter of urethra  60  in the vicinity of implant  5040 . Typically, the tensile force of coiled implant  5040  maintains the tissue in the compressed state. 
       FIG. 21D  shows deflectable portion  5026  of tool  5021  returning to a position that is parallel with respect to the longitudinal axis of tool  5021 . This is done by rotation of knob  5070  of the tool-deflection-actuation system in the direction as indicated by arrow  5022 B (i.e., in the direction opposite the direction used to pull distal portion  26  proximally, as indicated by arrow  5022 A, with reference to  FIG. 21B ). Rotating knob  5070  in the direction as indicated by arrow  5022 B unwinds portion  5074  of pull-wire  5032  from spool  5072  thereby loosening pull-wire  5032  and releasing the pulling force on the distal tip of deflectable portion  5026 . Once deflectable portion  5026  is returned to a position that is parallel with the longitudinal axis of tool  5021 , imaging device  5028  is returned within the slit defined by sleeve  5027 . As shown, even after the distal tip of deflectable portion  5026  has been moved away from the wall of urethra  60 , implant  5040  maintains the tissue of prostate  100  in a compressed state. This creates an enlarged perimeter of urethra  60  in the vicinity of implant  5040 , as shown. 
     Inflatable element  5050  is deflated so as to release the stabilizing pressure force it exerts on the wall of urethra  60  during implantation of implant  5040 . 
     Tool  5021  is then rotated 180 degrees with respect to the longitudinal axis thereof, in a direction as indicated by arrow  5011 B (i.e., in the direction opposite the direction used to initially rotate tool 180 degrees, as indicated by arrow  5011 A, with reference to FIG.  21 B.( 
     As shown in  FIG. 21E , a second implant  5040  is implanted in tissue of prostate  100  in a vicinity of prostate  100  that is opposite the site of implantation of the first implant  5040 . Prior to implantation, the second implant  5040  is advanced distally within shaft  5024  to a position at the distal tip of deflectable portion  5026  such that implant  5040  is primed for implantation. Once positioned at the distal tip of deflectable portion  5026 , screwdriver tool  5047  is coupled to implant  5040  at a distal portion thereof. Inflatable element  5050  is then inflated to stabilize and maintain the position of tool  5021  during the subsequent implantation of second implant  5040 . 
     Knob  5070  of the tool-deflection-actuation system is rotated in the direction as indicated by arrow  5022 A in order to radially deflect deflectable portion  5026  in a manner as described hereinabove with reference to  FIG. 21B . Responsively, the distal tip of deflectable portion  5026  is slid along the wall of urethra  60  while radially pushing the wall of urethra  60  and the prostate tissue. Once the wall of urethra  60  is pushed and the tissue of prostate  100  is compressed, knob  5076  of the implant-actuation-system is rotated in the direction as indicated by arrow  5033 A in order to drive screwdriver tool  5047  to corkscrew implant into tissue of prostate  100 , as described hereinabove with respect to the implantation of first implant  5040  with reference to  FIG. 21C . Second implant  5040  is also positioned in tissue of prostate  100  at a non-zero angle (e.g., 90 degrees, as shown) with respect to the longitudinal axis of urethra  60 . 
     The steps for deflection of tool  5021  and implantation of implants  5040  are repeated until all implants, e.g., four, as illustrated by way of illustration and not limitation in  FIGS. 21A-F , have been implanted in tissue of prostate  100 . It is to be noted that any suitable number of implants  5040 , e.g., between 1 and 9 implants, may be implanted in tissue of prostate  100 . Typically, delivery tool  5021  implants implants  5040  by orienting implants  5040  radially with respect to the urethra. As shown, delivery tool  5021  implants each of the plurality of implants  5040  at respective transverse planes of urethra  60  that are disposed along the longitudinal axis of urethra  60 . 
       FIG. 21F  shows four coiled implants  5040  implanted in respective implantation vicinities of the tissue of prostate  100 . Once all four implants have been implanted, delivery tool  5021  is withdrawn from within urethra  60  of the patient. For every vicinity in which implant  5040  is implanted, the respective implant  5040  maintains the tissue in the vicinity in a compressed state thereof even after delivery tool  5021  has been withdrawn. As such, the perimeter of urethra  60  at each vicinity of prostate  100  is enlarged in response to the maintaining of the tissue in its compressed state by the respective coiled implant  5040 , as shown. 
     The entirety of each implant  5040  is implanted in tissue of prostate  100 . That is, no portion of any of implants  5040  is disposed within urethra  60  or outside the capsule of prostate  100 . 
     It is to be noted that, although implants  5040  are implanted around urethra  60  symmetrically with respect to each other, as shown in  FIG. 21F , implants  5040  may be positioned at any suitable location in prostate  100  and at any desired non-zero angle with respect to the longitudinal axis of urethra  60 . 
     Following implantation of implants  5040  within prostate  100 , a post-operative perimeter of the portion of urethra  60  at each implantation vicinity of prostate  100  is larger than the preoperative perimeter of the portion of urethra  60 . Implants  5040  are generally rigid relative to the rigidity of the prostate. Implants  5040  thus support the urethral tissue, minimizing restenosis of urethra  60  should prostate  100  continue to enlarge. 
     Reference is again made to  FIGS. 21A-F . Deflectable portion  5026  of tool  5021  facilitates independent control by the operating physician of the implantation of each implant  5040  in tissue of prostate  5040 . The deflection of portion  5026  of tool  5021  enables specific targeting of a desired location of the prostate, by aligning the distal tip of deflectable portion  5026  to the portion of the wall of urethra  60  overlying the desired location of the prostate. Such alignment enables target-specific implantation of implants  5040 . That is, deflectable portion  5030  facilitates the positioning of each implant at a desired location in prostate  100  and at a desired angle with respect to the longitudinal axis of urethra  60 . As such, implants  5040  may be implanted in a manner which accommodates the dimensions and configurations of the lobes of the prostate of a given patient. 
     Reference is yet again made to  FIGS. 21A-F . Implants  5040  may passively or actively contract following implantation in tissue of the prostate. For some applications, implants are made to adjust their configuration, e.g., contract, following implantation and in response to the application of energy thereto from an energy source (e.g., RF or ultrasound) which may be disposed (1) externally to the body of the patient, (2) in contact with the implant, or (3) internally to the patient&#39;s body but not in contact with the implant. For some applications, implants  5040  passively contract following implantation to further compress and pull the prostate tissue radially with respect to the longitudinal axis of the urethra. For example, each implant  5040  may be implanted in an expanded state thereof, in which the longitudinal length thereof is longer in its expanded state than in its resting state because the coils of each implant are distanced from each other. Once released from the delivery tool and implanted in tissue of the patient, implants  5040  contract to assume their resting state length, thereby pulling tissue in response to the contracting. 
     Reference is now made to  FIGS. 22A-C , which are schematic illustrations of a system  5120  comprising a transurethral delivery tool  5124  and a curved implant  5132 , in accordance with an application of the present invention. Delivery tool  5124  has a rounded distal end  5127  which facilitates atraumatic insertion of tool  5124  through urethra  60  and toward bladder  80 . A portion of tool  5124  near distal end  5127  houses implant  5132  in a compressed state thereof, as shown in  FIG. 22A . Implant  5132  is surrounded by an implantation-facilitating sleeve  5130 , as described hereinbelow. Implant  5132  in a compressed state is shaped to define a coil in order to fit and be compressed within the lumen of delivery tool  5124 . Similarly, sleeve  5130  is disposed in a compressed state and is shaped to define a coil in order to fit and be compressed within the lumen of delivery tool  5124 . Once expanded from within the lumen of the delivery tool, implant  5132  is shaped to define an arc of up to 360 degrees, e.g., between 60 and 180 degrees. Following expansion, implant  5132  assumes its resting state, i.e., its uncompressed state. 
     Delivery tool  5124  is shaped to define an opening  5126  in a vicinity of distal end  5127  of tool  5124 . As shown in  FIG. 22B , implant  5132  surrounded by sleeve  5130 , emerges from within the lumen of tool  5124  through opening  5126  of tool  5124 . As implant  5132  and sleeve  5130  emerge from within the lumen of tool  5124 , implant  5132  and sleeve  5130  expand from their compressed states to assume an arc of up to 360 degrees in its resting state. 
     Typically, sleeve  5130  surrounds implant  5132  during the initial implantation of implant  5132  in tissue of prostate  100 . Sleeve  5130  comprises a material, e.g., stainless steel or nitinol, and by its physical construction is less flexible than implant  5132 , which typically comprises a material such as nitinol. The rigidity of sleeve  5130  helps (1) push and compress tissue and puncture the tissue in order to create a channel in tissue of prostate  100  for receiving implant  5132 , and (2) overcome the force of friction that prostate  100  applies to implant  5132  during implantation thereof. 
       FIG. 22B  shows sleeve  5130  partially retracted with respect to a free end of implant  5132  (i.e., the end exposed from within sleeve  5130 , as shown), leaving a portion of implant  5132  exposed from within sleeve  5130 . Ultimately, sleeve  5130  is fully retracted within the lumen of the delivery tool and returns to its compressed state. 
       FIG. 22C  shows implant  5132  in an implanted state within prostate  100  following implantation thereof from within urethra  60  by transurethral delivery tool  5124 . As described hereinabove, as implant  5132  emerges from its compressed state within tool  5124 , implant  5132  expands to assume its resting state. As implant  5132  expands, it pushes tissue of prostate  100  radially with respect to the longitudinal axis of urethra  60 . Responsively to the pushing, the perimeter of urethra  60  at the vicinity of implant  5132  expands to a perimeter that is larger than the constricted, preoperative perimeter of urethra  60 . 
     As shown in  FIG. 22C , implant  5132  in its expanded, implanted state is shaped to define an implant plane having a normal thereto that is substantially parallel to the longitudinal axis of urethra  60 . Although one implant  5132  is shown, it is to be noted that any number of implants may be implanted in a given transverse sectional plane of prostate  100 , e.g., 1-9 implants. Additionally, a plurality of implants  5132  may be implanted in series along the longitudinal axis of urethra  60  at respective transverse planes thereof such that the plurality of implants  5132  resemble in spatial configuration at least a portion of a coiled implant. 
     Implant  5132  maintains an enlarged perimeter at prostate  100 , as shown. A plurality of implants  5132  may be implanted within prostate  100  in the same manner as described hereinabove. The delivery tool used to implant the plurality of implants  5132  implants the plurality of implants  5132  by orienting the implants radially with respect to urethra  60  along a single transverse plane of prostate  100 , as shown by way of illustration in  FIG. 23B , which is a schematic illustration of a system  5140  for maintaining an expanded perimeter of urethra  60  at prostate  100 , in accordance with another application the present invention. Such a relative positioning of implants  5132  with respect to urethra  60  and prostate  100  helps ensure that the entirety of each implant  5132  is implanted within respective lobes of prostate  100  and that portions of each implant are not exposed within the lumen of urethra  60 . Additionally, implanting implants  5132  that are shaped to define up to 360 degrees reduces the forces of friction of prostate  100  acting upon the implants as they are implanted in tissue of prostate  100 . Each implant  5132  may be shaped differently so as to define different sized implants. For example, one implant may be shaped so as to define 270 degrees while the other may be shaped so as to define 90 degrees. The relative sizes of each implant  5132  accommodate the dimensions of a given lobe of the prostate in which at least a portion of each respective implant is implanted. That is, a first lobe may be larger at a given transverse sectional plane of prostate  100  than a second lobe. Thus, a larger implant may be implanted in the vicinity of the first lobe, while a smaller implant may be implanted in the vicinity of the second lobe. For some applications, a respective implant may be implanted entirely within a given lobe. The entirety of each implant  5132  is implanted in tissue of prostate  100 . That is, no portion of any of implants  5132  is disposed within urethra  60  or outside the capsule of prostate  100 . 
     Reference is again made to  FIGS. 22A-B . Delivery tool  5124  and opening  5126  therein facilitates target-specific delivery of implant  5132  in tissue of prostate  100 . That is, prior to implantation of implant  5132 , tool  5124  is advanced until opening  5126  is positioned in alignment with a specific lobe of prostate or with a transverse sectional plane of prostate in which implant  132  is ultimately implanted. 
     Reference is again made to  FIGS. 22A-C . It is to be noted that for some applications, tool  5124  comprises inflatable element  5050 , as described hereinabove with reference to  FIGS. 21A-F . 
     Reference is now made to  FIGS. 23A-B  which are schematic illustrations of a plurality of discrete, resilient curved implants  5141 , in accordance with an application of the present invention. Implants  5141  comprise first, second, and third implants  5142 ,  5144 , and  5146 , respectively. Each implant  5141  is shaped to define up to 360 degrees. Each implant  5141  is implanted in prostate  100  such that it defines an implant plane having a normal thereto which is substantially parallel with respect to the longitudinal axis of urethra  60 . 
       FIG. 23A  shows implants  5141  implanted in a first configuration thereof in which each implant  5141  is shaped to define around 240 degrees, as shown, and has a first radius of curvature thereof. The delivery tool implants  5141  by placing implants  5141  adjacent to (e.g., around) a constricted urethra  60  and in a transverse sectional plane of prostate  100 . 
       FIG. 23B  shows implants  5141  in their expanded, resting states following implantation. Each implant  5141  enlarges to assume a second configuration in which implant  5141  defines around 180 degrees and a second radius of curvature that is larger than the first radius of curvature (as shown in  FIG. 23A ). While transitioning between the first and second configurations thereof, implants  5141  expand, and implants  5142  remodel and compress tissue of prostate  100  along a radius with respect to the longitudinal axis of urethra  60 . The expansion of implants  5141  enlarges the perimeter of urethra  60  at the site of implantation of implant, i.e., the vicinity of the transverse plane in which implants  5141  are implanted. The perimeter of urethra  60  shown in  FIG. 23B  is larger than the perimeter of urethra  60  shown in  FIG. 23A . 
     It is to be noted that for some applications, the radius of curvature of each implant  5141  may be larger in a resting state thereof (shown in  FIG. 23B ) than in a non-resting state thereof (shown in  FIG. 23B ). 
     Implants  5141  maintain an enlarged perimeter at prostate  100 , as shown. Implants  5141  may be implanted within prostate  100  in the same manner as described hereinabove with reference to  FIGS. 22A-B . Implants  5141  are implanted such that portions of neighboring implants are implanted in a given lobe of prostate  100 . For example, a first portion of implant  5142  and a first portion of implant  5144  are implanted in a first lobe, and a second portion of implant  5144  and a first portion of implant  5146  are implanted in a second lobe of prostate  100 . The relative positioning of implants  5141  with respect to urethra  60  and prostate  100 , helps ensure that the entirety of each implant  5141  is implanted within respective lobes of prostate  100  and that portions of each implant  5141  are not exposed within the lumen of urethra  60 . Additionally, implanting implants  5141  that are shaped to define up to 360 degrees reduces the forces of friction of prostate  100  acting upon the implants as they are implanted in tissue of prostate  100 . 
     Each implant  5141  may be shaped differently so as to define different sized implants in their resting states thereof. For example, one implant may be shaped so as to define 270 degrees in a resting state thereof in awhile the other may be shaped so as to define 90 degrees in a resting state thereof. The relative sizes of each implant  5141  accommodate the dimensions of a given lobe of the prostate in which at least a portion of each respective implant is implanted. That is, a first lobe may be larger at a given transverse sectional plane of prostate  100  than a second lobe. Thus, a portion of an implant or a larger implant may be implanted in the vicinity of the first lobe, while a smaller portion of an implant or a smaller implant may be implanted in the vicinity of the second lobe. 
     For some applications, a respective implant may be implanted entirely within a given lobe and is sized in accordance with the dimensions of the lobe in which it is implanted. The entirety of each implant  5141  is implanted in tissue of prostate  100 . That is, no portion of any of implants  5141  is disposed within urethra  60  or outside the capsule of prostate  100 . In such an embodiment, each implant functions to independently remodel by compressing and maintaining in a compressed state tissue of the lobe in which the implant is implanted. 
     Although three implants  5141  are shown, it is to be noted that any number of implants may be implanted in a given transverse sectional plane of prostate  100 , e.g., 1-9 implants. Additionally, a plurality of implants  5141  may be implanted in series along the longitudinal axis of urethra  60  at respective longitudinal planes thereof such that the plurality of implants  5141  resemble in spatial configuration at least a portion of a coiled implant. 
     Reference is again made to  FIGS. 23A-B . It is to be noted that implants  5141  are shaped to define around 240 degrees in their first configuration and 180 degrees in their second configuration, by way of illustration and not limitation. For example, in the first configuration, implants  5141  may be shaped to define between 120 and 300 degrees, and, in their second configuration, between 60 and 240 degrees. 
       FIGS. 24A-B , show a system  5150  comprising coiled implants  5152  implanted at a non-zero (e.g., 90 degree) angle with respect to the longitudinal axis of urethra  60 , in accordance with an application of the present invention.  FIG. 24A  shows a stage in an implantation procedure where a first implant  5154  has been implanted in a first lobe of prostate  100  in an expanded state thereof, and prior to second and third implants  5156  and  5158  (shown in phantom) being implanted in the prostate.  FIG. 24B  shows implants  5154 ,  5156 , and  5158  in their contracted, resting states following their initial implantation. 
     For some applications, implants  5152  are made to contract following implantation and in response to the application of energy thereto from an energy source (e.g., RF or ultrasound), which may be disposed (1) externally to the body of the patient, (2) in contact with the implant, or (3) internally to the patient&#39;s body but not in contact with the implant. For such an application, following initial implantation, implants  5152  maintain the larger pitch between the successive coils (as shown in  FIG. 24A ) than the pitch of implants  5152  in their compressed state (as shown in  FIG. 24B ). This application of energy causes implants  5152  to compress and pull tissue of prostate  100  radially from the longitudinal axis of urethra  60 . 
     Alternatively or additionally, other techniques are used to cause implants  5152  to compress following implantation. For example, each implant may be coated with or otherwise coupled to a biodegradable support structure that maintains the implant in the expanded state. Upon degradation of the biodegradable support structure, implants  5152  compress and pull tissue of prostate  100  radially from the longitudinal axis of urethra  60 . 
     For some applications, implants  5152  comprise a shape memory alloy, e.g., nitinol. For such an application, implants  5152  may be cooled prior to implantation and are thereby deformed into an expanded (substantially not curved) configuration. Upon implantation, the implants reach body temperature, causing them to regain their original compressed shape, by contracting in response to the heat. This recovery of the original compressed shape causes implants  5152  to compress and pull tissue of prostate  100  radially from the longitudinal axis of urethra  60 . 
     For some applications, the following procedure is used to implant implants  5152  as shown in  FIGS. 24A-B  or to implant other implants described herein. Implants  5152  are transurethrally implanted in tissue of prostate  100  using a delivery tool which houses implants  5152  and has a deflectable tip having an open distal end. The deflectable tip is steered such that the distal end is made to contact the wall of urethra  60  at a non-zero angle, e.g., between 40 and 160 degrees, with respect to the longitudinal axis of urethra  60 . The delivery tool provides a lumen thereof which houses a corkscrewing tool having a flexible tip. In such an alignment implant  5152  may be corkscrewed by the corkscrewing tool into tissue of prostate  100  and implanted in alignment with the non-zero angle of the deflected tip of the delivery tool. The transitioning of implants  5152  from their expanded state ( FIG. 24A ) to their compressed state ( FIG. 24B ) compresses and pulls tissue of prostate  100  away from the longitudinal axis of urethra  60  in order to expand the perimeter of the wall of urethra  60 , as shown in  FIG. 24B . 
     For some applications (not as shown in  FIGS. 24A-B ), prior to implantation, the delivery tool is radially deflected to compress and push the wall of urethra  60  and the prostate tissue away from the longitudinal axis of urethra  60  (i.e., as described hereinabove with reference to  FIGS. 21A-F ). Implants  5152  maintain the expanded perimeter of urethra  60  caused by the pushing of the tissue. 
     Reference is again made to  FIGS. 24A-B . It is to be noted that each implant  5152  is typically implanted in a respective lobe of prostate  100 . (For some applications, a patient only has implant  5152  placed in one lobe, and does not have the other lobes treated with an implant.) In such a manner, the lobes of the prostate may be controlled individually and independently. In an embodiment, more than one implant  5152  may be implanted in tissue of a given lobe if appropriate. 
     Implants  5152  each comprise a coiled implant comprising a proximal coil at a proximal end thereof, a distal coil at a distal end thereof, and a plurality of successive contiguous coils disposed between the proximal and distal coils. The distal coil of each implant  5152  comprises a pointed tip which punctures tissue of prostate  100  during implantation of implant  5152 . Ultimately, both the distal and proximal coils are disposed entirely within prostate tissue of the patient, i.e., the distal coil does not extend beyond the prostate capsule and the proximal coil does not extend into the urethra. The entirety of each implant  5152  is thus implanted in tissue of prostate  100 . 
     Reference is made to  FIGS. 21A-F  and  24 A-B. It is to be noted that implants  5040  of system  5020  may be implanted in prostate  100  in a similar relative spatial configuration of implants  5152  as shown in  FIG. 24B . That is, each implant  5040  may be implanted in prostate  100  in a respective lobe of prostate  100 . 
     Reference is now made to  FIGS. 21A-F ,  22 A-C,  23 A-B, and  24 A-B. It is to be noted that delivery tool  5021  shown in  FIGS. 21A-F  may be used to implant the implants described herein. That is, deflectable portion  5026  of tool  5021  is used to first push the wall of urethra  60  and prostate tissue radially with respect to the longitudinal axis of urethra  60  prior to implantation of the implants described herein. Following implantation, the implants function to further enlarge and/or maintain the expanded perimeter of urethra  60  at the site of implantation. 
       FIGS. 25A-B  show a system  5160  for transurethrally implanting coiled implants  5162  in tissue of prostate  100  using a delivery tool  5170  comprising annular inflatable elements  5176  and  5178  at a distal portion thereof, in accordance with an application of the present invention. Delivery tool  5170  is through urethra  60  until a distal portion thereof is positioned in urethra  60  in the vicinity of prostate  100 . Once delivery tool  5170  is properly positioned, annular inflatable elements  5176  and  5178  are inflated in order to push against the wall of urethra  60 . In response to the pushing, the prostate tissue surrounding the portion of the wall being pushed is compressed and pushed radially with respect to the longitudinal axis of urethra  60 , thereby enlarging the perimeter of urethra  60  at the implantation site. 
     It is to be noted that respective inflation conduits (not shown for clarity of illustration) are coupled at a respective distal ends thereof to inflatable elements  5176  and  5178 , respectively. The conduits extend through the lumen of shaft  5024  and toward handle  5022  of tool  5021 . When the physician desires to inflate element  5050 , pressurized fluid is delivered toward inflatable element  5050  via the conduits from a fluid source that is disposed outside the body of the patient. 
     The distal portion of tool  5170  is shaped to provide a lateral opening  5172  (e.g., a hole, or a channel, as shown). Tool  5170  is shaped so as to provide a lumen which houses implants  5162  (prior to their implantation) and a screwdriver tool  5174  which has a distal deflectable portion. Once appropriately positioned in urethra  60 , and following inflation of elements  5176  and  5178 , screwdriver exits opening  5172  and corkscrews an implant  5162  in tissue of prostate  100 . Lateral opening  5172  facilitates implantation of implant  5162  at a non-zero angle (e.g., 90 degrees, as shown) with respect to the longitudinal axis of urethra  60 . The entirety of implant  5162  is implanted in tissue of prostate  100 . That is, no portion of implant  5162  is disposed within urethra  60  or outside the capsule of prostate  100 . 
     As shown in  FIG. 25B , following removal of delivery tool  5170  from within urethra  60 , implants  5162  function to maintain (a) the prostate tissue in a compressed state, and (b) the perimeter of urethra  60  that has been enlarged by annular inflatable elements  5176  and  5178 . 
     Although two implants  5162  are shown, it is to be noted that any number of implants may be implanted in a given transverse sectional plane of prostate  100 , e.g., 1-9 implants. Additionally, a plurality of implants  5162  may be implanted in series along the longitudinal axis of urethra  60 . It is to be noted that implants  5162  may comprise compressible implants, as described hereinabove with reference to  FIGS. 24A-B . Compressible implants function to further compress tissue of prostate  100  and thereby further expand the perimeter of urethra  60  that has been expanded by annular inflatable elements  5176  and  5178 . 
     Implants  5162  each comprise a coiled implant comprising a proximal coil at a proximal end thereof, a distal coil at a distal end thereof, and a plurality of successive contiguous coils disposed between the proximal and distal coils. The distal coil of each implant  5162  comprises a pointed tip which punctures tissue of prostate  100  during implantation of implant  5162 . Ultimately, both the distal and proximal coils are disposed entirely within prostate tissue of the patient, i.e., the distal coil does not extend beyond the prostate capsule and the proximal coil does not extend into the urethra. 
     It is to be noted that delivery tool  5170  may be used to implant any of the implants described herein with reference to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B, and  26 . 
     Reference is made to  FIG. 26 , which shows a system  190  comprising screw implants  6192  implanted generally perpendicularly with respect to the longitudinal axis of urethra  60 , in accordance with an embodiment of the present invention. Implants  6192  are transurethrally implanted in tissue of prostate  100  using a delivery tool (not shown), which houses a plurality of implants  6192 , e.g., four, and has a deflectable tip having an open distal end. The deflectable tip is steered such that the distal end is made to contact the wall of urethra  60  at a non-zero angle, e.g., 90 degrees, with respect to the longitudinal axis of urethra  60 . The delivery tool is then radially deflected to compress and push the wall of urethra  60  and the prostate tissue away from the longitudinal axis of urethra  60  thus expanding the perimeter of the wall of urethra  60  (i.e., as described hereinabove with reference to  FIGS. 21A-F ). While the prostate is compressed, screw implant  6192  is screwed by a screwing tool into tissue of prostate  100  and implanted in alignment with the non-zero angle, e.g., 90 degrees, of the deflected tip of the delivery tool. Once screw implants  6192  have been implanted into compressed prostate tissue, the delivery tool is withdrawn from within urethra  60  of the patient. Implants  6192  maintain tissue of prostate  100  in a compressed state such that the expanded perimeter of urethra  60  in the vicinity of implants  6192  is maintained in an enlarged state following removal of the delivery tool. 
     It is to be noted that, although screw implants  6192  are implanted around urethra  60  symmetrically with respect to each other, as shown in  FIG. 26 , implants  6192  may be positioned at any suitable locations in prostate  100  and at any desired non-zero angle with respect to the longitudinal axis of urethra  60 . 
     For some applications, implant  6192  comprises a screw implant comprising a screw head  6094  at a proximal end thereof, a pointed tip  6096  at a distal end thereof, and a screw body wrapped by a helical thread extending between the proximal and distal ends. The distal end of implant  6192  comprises a pointed tip  6096  which punctures tissue of prostate  100  during implantation of implant  6192 . During implantation of screw implant  6192 , the distal end is typically advanced into the prostate tissue until ultimately, the entire screw, excluding head portion  6094 , is disposed within prostate tissue of a patient. That is, the head  6094  of screw implant  6192  remains within the urethra, secured to the wall of urethra  60 . The distal end of implant  6192  does not extend beyond the prostate capsule (the capsule that surrounds the prostate). Alternatively, during implantation of screw implant  6192 , the distal end is advanced into the prostate tissue until ultimately the entire screw is disposed within prostate tissue of a patient. That is, the distal end of implant  6192  does not extend beyond the prostate capsule (the capsule that surrounds the prostate), and the proximal end of implant  192  does not extend into the urethra. 
     Some or all of implant  6192  is generally rigid relative to the rigidity of the prostate, and typically comprises a biodegradable material, e.g., a biodegradable polymer, such as PLA and/or PGA. Thus, following implantation in the prostate, the biodegradable portion of screw implant  6192  gradually degrades into natural metabolites that are absorbed entirely in the body or secreted from the body, thereby reducing the risk of infection. 
     Screw implant  6192  may comprise in its body, or be coated with, a substance, such as but not limited to, a medication (e.g., an antibiotic and/or an anti-inflammatory medication). For some applications, the medication is intended for the treatment of benign prostatic hypertrophy. Examples for such medications are alpha adrenergic antagonists, e.g., Alfuzosin, Doxazosin mesylate, Tamsulosin and Terazosin. Thus, following implantation, these biodegradable medication-coated implants function (a) to maintain the expanded perimeter of urethra  60  at the site of implantation, and (b) to treat the prostatic tissue by releasing medication at the site of implantation as the implant disintegrates. 
     For some applications, screw head  6094  comprises a biodegradable material, e.g., PLA and/or PGA, and is typically coated with a medication, whereas, the screw body comprises a biocompatible material, configured for chronic implantation. Typically, during implantation, the screw body is advanced into the prostate tissue until ultimately it is entirely disposed within the prostate tissue, while the screw head  6094  remains in the urethra and is fixed to the wall of urethra  60 . Following implantation of implant  6192  the screw body functions to maintain an expanded perimeter of urethra  60  at the site of implantation, by maintaining prostate tissue in a compressed state. The screw head gradually degrades, releasing medication, e.g., for treatment of benign prostatic hypertrophy. Alternatively, during implantation, the entire screw implant is disposed within prostate tissue of a patient. That is, the distal end of the implant does not extend beyond the prostate capsule, and the proximal end of the implant does not extend into the urethra. Typically, following implantation of the implant, the screw body functions to maintain an expanded perimeter of urethra  60  at the site of implantation, by maintaining prostate tissue in a compressed state. The screw head gradually degrades, releasing medication, e.g., for treatment of benign prostatic hypertrophy, directly into the prostatic tissue. 
     It is to be noted that any of the implants described herein with reference to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B, and  25 A-B may be coated with a medication, such as but not limited to, a medication for treatment of benign prostatic hypertrophy. 
     Reference is again made to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B, and  25 A-B. It is to be noted that delivery tools  5021 ,  5124 , or  5170  may be used to implant any of the implants described herein with reference to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B,  25 A-B, and  26 . 
     Reference is again made to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B,  25 A-B, and  26 . The prostatic implants described herein may be coated with any low-friction coating as described herein. For example, the implants may be coated with a substance, such as but not limited to, a medication (e.g., an antibiotic) or with an electrical insulator (e.g., Teflon). The implants may be coated with low friction coatings, e.g., PTFE (Teflon), MoST, ADLC or the like. For some applications, the surfaces of the implants are polished, e.g., electro-polished, mechanically polished, or other, to reduce friction as the implants are implanted in the tissue of the patient. For some applications, a portion of each of the implants, i.e., one or more of the coils, may be energized to deliver RF energy, for example, to ablate tissue. For some applications, a portion of each one of the implants is coupled to an electrode. Additionally or alternatively, the portion of each implant may be energized to provide ultrasound or thermal energy (e.g., heating or cooling). 
     For some applications, implants described herein are coated with a pro-fibrotic agent, which helps enhance the anchoring of the implants in prostate  100 . 
     Reference is again made to  FIGS. 21A-F ,  22 A-C,  23 A-B,  24 A-B,  25 A-B, and  26 . The number of prostatic implants described herein is selected according to the needs of a given patient. A length of prostate  100  is measured prior to the implantation procedure such that a suitable number of implants, each having a desired length, is selected. 
     Reference is now made to  FIGS. 27A-D  which are schematic illustrations of a system  7020  comprising a transurethral delivery tool  7021  housing at least two implants  7040 , typically coiled implants  7040 , coupled to a wire  7010 , in accordance with an application of the present invention. It is to be noted that wire  7010  is shown by way of illustration and not limitation, and that any suitable flexible longitudinal member (e.g., a suture, a string, or a rope comprising a metal or a fabric) may be coupled to implants  7040 . 
     Implant  7040  comprises a proximal coil at a proximal end thereof, a distal coil at a distal end thereof, and, typically, a plurality of successive contiguous coils disposed between the proximal and distal coils. The distal coil of implant  7040  comprises a pointed tip which punctures tissue of urethra  60  and prostate  100  during implantation of implant  7040 . Ultimately, both the distal and proximal coils are disposed entirely within prostate tissue of a patient. That is, the distal coil does not extend beyond the prostate capsule (the capsule that surrounds the prostate), and the proximal coil does not extend into the urethra. Optionally, the coiled implant facilitates pinching of tissue of the patient between the successive coils of implant  7040  during implantation thereof, thus supplementing compression of prostate tissue  100 . 
     As shown in  FIGS. 27A-D , implants  7040  are coupled to wire  7010  extending from one coiled implant to the next coiled implant. Typically, delivery tool  7021  houses at least one set of successive coiled implants  7040 , e.g., three coiled implants, comprising a wire  7010  extending between implants  7040 . Wire  7010  is typically flexible and comprises a biocompatible material. 
     Reference is made to  FIG. 27A . Delivery tool  7021  is inserted into urethra  60  of penis  160  of the patient and is advanced distally toward bladder  80  of the patient as described herein with reference to  FIGS. 21A-F . 
     Delivery tool  7021 , which houses at least one set of coiled implants  7040  which are coupled to wire  7010 , optionally has a deflectable tip  7026  having an open distal end. (Alternatively or additionally, delivery tool comprises one or more inflatable elements, as described hereinabove with reference to  FIGS. 25A and 25B .) When the distal end of the delivery tool reaches a portion of urethra  60  at prostate  100  that is constricted due to pressure exerted thereupon by prostate  100 , the deflectable tip is steered radially away from a longitudinal axis of the delivery tool. In response to the deflecting, the distal tip of tool  7021  pushes the wall of the urethra, which compresses tissue outside of the urethra, i.e., prostate tissue, and consequently the perimeter of the urethra at the prostate expands. Delivery tool  7021  then delivers first coiled implant  7040  into the portion of the tissue of the prostate that has been compressed, and the implant functions to maintain the tissue in a compressed state upon withdrawal of the delivery tool from the urethra. 
       FIG. 27A  shows deflectable portion  7026  of the delivery tool optionally having returned to a position that is aligned with respect to the longitudinal axis of the tool  7021 , following implantation of implant  7040 . As shown, even after the distal tip of deflectable portion  7026  has been moved away from the wall of urethra  60 , implant  7040  maintains the tissue of prostate  100  in a compressed state. This creates an enlarged perimeter of urethra  60  in the vicinity of implant  7040 , as shown. Wire  7010  is coupled to the proximal end of first implant  7040  and to the proximal end of a second implant  7040  (not shown) which is still disposed within delivery tool  7021 . 
     As shown in  FIG. 27B , second implant  7040  is implanted in tissue of prostate  100  in a vicinity of prostate  100  that is adjacent to the site of implantation of first implant  7040 . The steps for deflection of delivery tool  7021 , rotation of knob  7076  and implantation of implants  7040  are repeated as described herein with reference to  FIGS. 21A-F , and second implant  7040  is implanted in tissue of prostate  100 . As shown, wire  7010  is coupled to the proximal ends of both implants  7040  and extends between the proximal ends of the implants. 
       FIG. 27C  shows deflectable portion  7026  of the delivery tool  7021  optionally having returned to a position that is aligned with respect to the longitudinal axis of the tool, following implantation of second implant  7040 . As shown in  FIG. 27C , wire  7010  enhances the enlargement of the perimeter of urethra  60 , and subsequently helps to maintain the enlarged perimeter of urethra  60  in the area  7015  that is between the sites of implantation of the implants  7040 . Over the long term (e.g., months or years), wire  7010  reduces constriction of the urethra in areas  7015  that would otherwise occur due to pressure exerted thereupon by prostate  100 . Additionally, wire  7010  typically helps maintain implants  7040  in place. 
     Reference is made to  FIG. 27D , which shows a first set  7050  of three coiled implants  7040  (by way of illustration and not limitation), coupled to wire  7010 , implanted in prostate tissue  100 . Additionally,  FIG. 27D  shows a second set  7052  of three coiled implants  7040  coupled to wire  7010  being implanted in tissue of the prostate in a vicinity of the prostate that is opposite the site of implantation of the first set  7050  of implants  7040 . As shown, a generally even enlargement of the perimeter of urethra  60  is obtained along a longitudinal axis of the urethra, both at the vicinity of implants  7040  and in areas  7015  which are between the sites of implantation of implants  7040 . 
     It is to be noted that any suitable number of implants  7040 , e.g., between 2 and 9 implants, may be implanted in tissue of prostate  100 . Typically, delivery tool  7021  implants implants  7040  by orienting the implants radially with respect to the urethra. 
     Additionally, it is to be noted that, although coiled implants  7040  are implanted around urethra  60  symmetrically with respect to each other, as shown in  FIG. 27 , implants  7040  may be positioned at any suitable locations in prostate  100  and at any desired angle with respect to the longitudinal axis of urethra  60 . 
     Reference is made to  FIGS. 28A-D , which are schematic illustrations of a system  8020  comprising at least one implant rod  8080 , at least one coiled implant  8040 , and an implant-delivery tool  8021  for delivering the coiled implant, in accordance with an application of the present invention. A rod-delivery tool (not shown) is inserted into urethra  60  of penis  160  of a patient and is advanced distally toward bladder  80  of the patient. The rod-delivery tool, which houses a plurality of rods  8080 , e.g., two, has a deflectable tip having an open distal end. When the distal end of the rod-delivery tool is disposed inside bladder  80 , the deflectable tip is steered radially, e.g., by 90 degrees, away from a longitudinal axis of the rod-delivery tool such that the distal end is generally perpendicular to the longitudinal axis of the rod-delivery tool. The deflectable tip is then steered again until it reaches a position in which it has turned 180 degrees, such that the open distal end of the deflectable tip is in a vicinity of prostate  100  and is facing the prostate. Rod  8080  is then advanced through the bladder wall and disposed in the prostate such that the longitudinal axis of the rod is parallel to the longitudinal axis of the urethra. Rod  8080  typically is shaped to define a pointed tip which punctures tissue of the bladder wall and prostate  100  during implantation of the rod. 
     For some applications, following implantation of first rod  8080 , the distal end of the rod-delivery tool remains within bladder  80 , and a second rod  8080  is implanted in tissue of prostate  100 . Second rod  8080  is typically implanted in a vicinity of prostate  100  that is opposite the site of implantation of the first rod. (Alternatively, if for example three rods are used, then they are typically separated by about 120 degrees.) Prior to implantation, the second rod is advanced distally within the rod-delivery tool to a position at the distal tip of the deflectable portion, such that rod  8080  is primed for implantation. Once the rod is positioned at the distal tip of the deflectable portion, second rod  8080  is advanced through the bladder wall and disposed in the prostate, using the technique described hereinabove with respect to first rod  8080 , such that the longitudinal axis of the rod is parallel to the longitudinal axis of the urethra. 
     Alternatively, rods  8080  are implanted in tissue of prostate  100  by any other suitable implantation procedure, e.g., using a hollow needle. 
     Rod  8080  is flexible enough to be maneuvered through the rod-delivery tool and is generally rigid enough in order to support tissue of the prostate. Rod  8080  typically comprises a biocompatible material configured for permanent implantation in the prostate. Rod  8080  has proximal and distal ends, and an elongated cylindrical body extending between the proximal and the distal ends. Typically, as rod  8080  is advanced through tissue of prostate  100 , tissue of prostate  100  applies a frictional force to the rod. For some applications, in order to reduce the effect of the frictional force applied to rod  8080 , the rod is coated with a low-friction coating, e.g., PTFE (Teflon), MoST, ADLC or the like. For some applications, the rod surface is polished, e.g., electro-polished, mechanically polished, or otherwise, to reduce friction as rod  8080  is advanced through the tissue of the patient. 
     It is to be noted that for some embodiments, a single delivery tool is used to implant both rods  8080  and implants  8040 . 
       FIG. 28A  shows rods  8080  implanted in tissue of prostate  100 , on opposite sides of prostate  100  around urethra  60 . The rods are placed in a position in which their longitudinal axes are parallel to the longitudinal axis of urethra  60 . It is to be noted, however, that rods  8080  may be positioned at any suitable location in prostate  100  and at any desired angle with respect to the longitudinal axis of urethra  60 . Typically, the rods are configured to be disposed at an angle that is less than 90 degrees with respect to the longitudinal axis of urethra  60 , e.g., less than 30 degrees. For some embodiments, rods  8080  are implanted substantially in parallel with the longitudinal axis of the urethra. As shown in  FIG. 28A , implant-delivery tool  8021 , housing at least one coiled implant  8040  (not shown), is about to be inserted into urethra  60  of a penis  160  of a patient. Typically, tool  8021  is preloaded with a plurality of successively disposed coiled implants  8040 , which are designated for implantation at least in part around rods  8080  in tissue of prostate  100 . 
     Reference is made to  FIG. 28B-C . Implant  8040  comprises a coiled implant comprising a proximal coil at a proximal end of implant  8040 , a distal coil at a distal end of implant  8040 , and typically a plurality of successive contiguous coils disposed between the proximal and distal coils. The distal coil of implant  8040  comprises a pointed tip which punctures tissue of urethra  60  and prostate  100  during implantation of implant  8040 . The proximal coil of implant  8040  is shaped to define a hook. For some applications, during implantation of implant  8040  the proximal coil is wound around rod  8080  that is implanted in tissue of prostate  100 , as shown in  FIG. 28C . Ultimately, both the distal and proximal coils are disposed entirely within prostate tissue of a patient. That is, the distal coil does not extend beyond the prostate capsule (the capsule that surrounds the prostate), and the proximal coil does not extend into the urethra. 
     Reference is still made to  FIGS. 28B-C . As shown, delivery tool  8021  is inserted into urethra  60  of a penis  160  of the patient and is advanced distally toward bladder  80  of the patient. The steps for deflection of tool  8021  and implantation of implant  8040  are carried out as described in  FIGS. 21A-F . Ultimately, implant  8040  is implanted such that the proximal end of coiled implant  8040  is wound around rod  8080 , coupling the implant to the rod and securing it in place. For some applications, delivery tool  8021  comprises a screwdriver tool (not shown) which facilitates implantation of coiled implant  8080  in tissue of prostate  100  such that the proximal end of implant  8040  is wound around rod  8080 . As shown, knob  8076  of tool  8021  is rotated by the operating physician, in the direction as indicated by arrow  8033 A, in order to rotate the screwdriver tool and thereby effect implantation of implant  8040  around rod  8080 . Following the corkscrewing of implant  8040  in tissue of prostate  100 , implant  8040  is decoupled from the screwdriver tool and from delivery tool  8021  and maintains the tissue in a compressed state in order to enlarge the perimeter of urethra  60  in the vicinity of implant  8040 . 
       FIG. 28C  shows implantation of second coiled implant  8040  in tissue of prostate  100  in a vicinity of the prostate that is opposite the site of implantation of first implant  8040 . The steps for implantation of second implant are carried out as described with reference to implantation of first implant  8040 . As shown with reference to first implant  8040 , even after the distal tip of deflectable portion  8026  of delivery tool  8021  has been moved away from the wall of urethra  60 , implant  8040  maintains the tissue of prostate  100  in a compressed state. This creates an enlarged perimeter of urethra  60  in the vicinity of implant  8040 , as shown. Optionally, the coiled implant facilitates pinching of tissue of the patient between the successive coils of implant  8040  during implantation thereof, thus supplementing compression of prostate tissue  100 . Once implanted in place, implants  8040  pull on rods  8080  causing rods  8080 , which are positioned generally parallel to the longitudinal axis of the urethra, to shift positions such that the rods are at an angle that is typically less than 90 degrees with respect to the longitudinal axis of urethra  60 , e.g., less than 30 degrees. Optionally, the shifting in position of the rods is also due to pinching of tissue of the prostate between the successive coils of implant  8040  during implantation thereof. 
     Reference is made to  FIG. 28D , which shows 2 pairs of coiled implants  8040 , by way of illustration and not limitation, implanted in tissue of prostate  100 , on opposite sides of urethra  60 . The proximal ends of implants  8040  are wound around rods  8080  (by way of illustration and not limitation, i.e., any portion of implant  8040  any portion of may be wound around rod  8080 ). Implants  8040  maintain the tissue of prostate  100  in a compressed state. This creates an enlarged perimeter of urethra  60  in the vicinity of implant  8040 , as shown. Additionally, as shown, an enlarged perimeter of urethra  60  is also obtained in the area  8015  that is between the each pair of implants  8040 . This is due to additional pulling/tension effect of implants  8040  on tissue of prostate  100 , when implants  8040  are coupled to rods  8080 . For some application, rod  8080  may enable the use of a reduced number of implants  8040 . 
     It is to be noted that the prostatic implants described herein may be coated with any low-friction coating as described herein. For example, the implants may be coated with a substance, such as but not limited to, a medication (e.g., an antibiotic) or with an electrical insulator (e.g., Teflon). The implants may be coated with low friction coatings, e.g., PTFE (Teflon), MoST, ADLC or the like. In some embodiments, the surfaces of the implants are polished, e.g., electro-polished, mechanically polished, or other, to reduce friction as the implants are implanted in the tissue of the patient. In some embodiments, a portion of each of the implants, i.e., one or more of the coils, may be energized to deliver RF energy, for example, to ablate tissue. In some embodiments, a portion of each one of the implants is coupled to an electrode. Additionally or alternatively, the portion of each implant may be energized to provide ultrasound or thermal energy (e.g., heating or cooling). 
     It is to be further noted that the prostatic implants described herein are selected to provide a length according to the needs of a given patient. A length of prostate  100  is measured prior to the implantation procedure such that an implant of a suitable length is selected. Typically, the end-to-end length of the coiled implant ranges from between 2.5 cm and 7 cm, to accommodate a prostate length of between 3 and 8.6 cm, respectively. 
     The scope of the present invention includes application of the techniques described herein to body lumens other than the urethra, in order to treat a condition of patient. For example, the implants described herein may be sized for implantation around another body lumen of the patient, such as the esophagus or a blood vessel which is connected to a body cavity. 
     The scope of the present invention includes embodiments described in the following patents and patent applications, which are incorporated herein by reference. 
     In an embodiment, techniques and apparatus described in one or more of the following patents and patent applications are combined with techniques and apparatus described herein: 
     U.S. patent application Ser. No. 11/325,731 to Gross, entitled, “Implant and delivery tool therefor,” filed Jan. 5, 2006; 
     U.S. Provisional Patent Application 60/930,705 to Gross et al., entitled, “Prostate implant and methods for insertion and extraction thereof,” filed May 18, 2007; 
     PCT Patent Application PCT/IL08/00677 to Gross et al., entitled, “Prostate implant and methods for insertion and extraction thereof,” filed May 18, 2008; and/or 
     U.S. Provisional Patent Application 61/200,372 to Gross et al., entitled, “Intraurethral and extraurethral apparatus,” filed Nov. 26, 2008. 
     For some applications, techniques described herein are practiced in combination with techniques described in one or more of the references cited in the Background and Cross-References section of the present patent application, which are incorporated herein by reference. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.