Abstract:
A method of ablating a uterine fibroid using a particular trocar is disclosed. The trocar comprises a plurality of ablation stylets. The trocar is adjustable to assume a plurality of configurations, each of the configurations having the stylets extended to a different extent from the trocar. A region to he ablated is imaged. The size of the region to be ablated is noted. The size of the region to be ablated is compared to a matrix of known ablation regions, each of the known ablation regions being associated with one of the configurations of the particular trocar. The region to be ablated is associated with a most nearly matching known ablation region by comparison of the region to be ablated to the known ablation regions. A trocar is inserted into the uterine fibroid at a position, which more closely matches the position of the particular trocar with respect to the known ablation region. The stylets are deployed from the trocar to an extent corresponding to the configuration.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of U.S. patent application Ser. No. 11/429,921, filed May 8, 2006, and entitled Anchored RF ablation device for the destruction of tissue masses, which in turn is a continuation in part of U.S. patent application Ser. No. 11/173,928, entitled Radio Frequency Ablation Device for the Destruction of Tissue Masses filed on Jul. 1, 2005, the disclosures of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to apparatus and methods for uterine fibroid ablation, and, in particular, to structures and methods for achieving fibroid tissue destruction in volumes with largely predictable orientations, dimensions and configurations. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0003]    (Not applicable) 
       BACKGROUND OF THE INVENTION 
       [0004]    Every year in the United States, approximately 230,000 women undergo hysterectomies for removal of uterine fibroids. In addition, it has been estimated that likely another six million women in the United States with uterine fibroid symptoms prefer to suffer, rather than taking on the risks and inconveniences associated with hysterectomy, the standard treatment and a major surgery that always results in infertility. This situation is much the same in the other parts of the world where women are in need of a safe alternative to hysterectomy. 
         [0005]    Alternatives to hysterectomy such as uterine artery embolization (in which the blood supplies to the arteries that feed the fibroids are cut off), and Myomectomy (which involves a surgical removal of the fibroid) do exist, but both these methods involve complicated surgical procedures followed by a high rate of complications and a long recovery time. 
         [0006]    In order to address these issues, an RF ablation probe that has been used to treat tumors in the human liver by hyperthermia has been demonstrated to substantially shrink or eliminate uterine fibroids. 
         [0007]    One such device has been disclosed in U.S. Pat. No. 6,840,935 to Lee. According to the disclosure in that patent, an ablation apparatus with multiple needles or deployable arms is inserted and positioned either proximate to or into a pelvic tumor, the location of which is further confirmed by using a laparoscope and an ultrasound machine. Either electromagnetic energy (and, potentially, other forms of energy) may be delivered through the ablation apparatus to the pelvic tumor to induce hyperthermia and ablate the tumor. 
         [0008]    A typical device for ablating pelvic tumors is sold by Rita Medical Systems, Inc. This device consists of a plurality of resilient springy pre-curved RF ablation antennae or stylets housed in a straight lumen. The stylets are ejected in a curved configuration defined by their preformed springy shapes as they exit a sharp-tipped catheter. The deployed antennae with their particular preformed shapes thus can define variously shaped volumes by varying the configuration of the curves which are preformed into the various springy antennae. 
       SUMMARY OF THE INVENTION 
       [0009]    In accordance with the invention, a method and apparatus are provided for the ablation of uterine tissue. According to the present invention, a plurality of conductors are housed within the walls of a cannula, each of which has a proximal end proximate to the proximal end of the cannula and a distal end proximate to the distal end of the cannula. 
         [0010]    A plurality of ablation stylets are coupled with each of these conductors such that the distal end of each conductor is connected to the proximal end of a stylet. The conductors and their respective stylets are mounted within the cannula for axial movement and a trocar point defines the distal end of the cannula. A deflection surface can be defined by the metal element defining the trocar point between the trocar point and the proximal end of the cannula. In response to forward axial movement of the stylets, at least some of them are deflected laterally and outwardly, with respect to the cannula axis in different directions along substantially straight paths with the paths defining an ablation volume. The trocar point and the stylets are provided with radio frequency energy, and together form an ablation zone. 
         [0011]    In accordance with the invention a uterine fibroid is ablated using a trocar of known dimensional characteristics. The trocar comprises a plurality of ablation stylets mounted for movement from within the trocar to positions extending from the trocar. The trocar is adjustable to assume a plurality of configurations, each of the configurations having the stylets extended to a different extent from the trocar. A region to be ablated is imaged. The region may correspond to all or a portion of a uterine fibroid. The size of the region to be ablated is noted. The size of the region to be ablated is compared to a matrix of known ablation regions, each of the known ablation regions being associated with one of the configurations of the particular trocar of known dimensions, and each of the known ablation regions being associated with a position of the trocar relative to the known ablation region. The region to be ablated is associated with a most nearly matching known ablation region by comparison of the region to be ablated to the known ablation regions. A trocar of the design of the particular trocar is inserted into the uterine fibroid at a position, with respect to the region to be ablated, which more closely matches the position of the particular trocar with respect to the known ablation region. The stylets are deployed from the trocar to an extent corresponding to the configuration associated with the most nearly matching known ablation region. 
     
    
     
       BRIEF DESCRIPTION THE DRAWINGS 
         [0012]    The operation of the invention will become apparent from the following description taken in conjunction with the drawings, in which: 
           [0013]      FIG. 1   a  is a perspective view of a multiple antennae or stylet ablation instrument  1  useful in practicing the inventive method; 
           [0014]      FIG. 1   b  is a detailed view of a multiple antennae or stylet ablation instrument useful in practicing the inventive method; 
           [0015]      FIG. 2  is a diagram illustrating an embodiment of the method as implemented according to the present invention; 
           [0016]      FIG. 3  illustrates another embodiment of the present invention in the context of achieving a larger ablation zone; 
           [0017]      FIG. 4  is a diagram illustrating a method to achieve a still larger ablation zone with the deployment of the stylets at a distance of 5 mm into a volume of uterine fibroid tissue; 
           [0018]      FIG. 5  illustrates an embodiment of the present invention where the stylets are deployed to 10 mm resulting in a generally egg-shaped volume; 
           [0019]      FIG. 6  illustrates the inventive method in the context of achieving an even larger ablation zone; 
           [0020]      FIG. 7  illustrates the inventive method in the context of achieving still an even larger ablation zone; 
           [0021]      FIG. 8  illustrates the inventive method with the stylets deployed 25 mm into a volume of uterine fibroid tissue; 
           [0022]      FIG. 9  illustrates the inventive method with the stylets deployed to 35 mm into the uterine fibroid tissue; 
           [0023]      FIG. 10  illustrates the inventive with the stylets at 45 mm; and 
           [0024]      FIG. 11  illustrates the inventive method with the stylets deployed to 50 mm, yielding a generally pear-shaped volume. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    In accordance with the invention, it has been discovered that trocar point configuration, stylet length and ablation power level may be used to create ablation zones of relatively predictable size and shape. 
         [0026]      FIG. 1   a  is a perspective view of an ablation instrument  1  with multiple antennae or stylets useful in practicing the inventive method. Ablation instrument  1  with a head end comprising a trocar  1   a  comprises a cannula  2  which houses a plurality of stylets  3 , and, optionally, a plurality of anchors  4 . A trocar point  5  is provided at the distal end of cannula  2 . At least one conductor  6  is provided within cannula  2 . Conductor  6  is electrically coupled to stylets  3  and trocar point  4  and accordingly provides RF energy to stylets  3  and trocar point  5 . 
         [0027]    In accordance with the invention, stylets  3  and trocar point  5  are electrically coupled to each other and electrically isolated from other exposed portions of ablation instrument  1 , such as cannula  2 . Each of the stylets are made of thin wire-like tubular members and during the procedure are initially housed entirely within the cannula  2 . Stylets  3  are deployed for ablation by being advanced in the forward direction toward the distal end of ablation instrument  1  out from ablation instrument  1  through openings  7 . As stylets  3  are advanced through openings  7 , they bear against deflection surfaces  8  and move into the positions illustrated in  FIG. 1 . Deflection surfaces  8  are defined in the metal body which defines trocar point  5  at the distal end of the cannula  2 . 
         [0028]    During the inventive method, trocar point  5  at the distal end of cannula  2  is used to initially pierce the tissue of the fibroid tumor during use of the inventive ablation device  1 . Optionally, a plurality of anchors  9 , also housed within ablation instrument  1 , may be deployed rearwardly toward the proximal end of ablation instrument  1 . During deployment, anchors  4  are deflected by deflection surfaces  11  to move into the positions illustrated in  FIG. 1   a.  After deployment anchors  4  act to prevent rearward movement of trocar point  5  during deployment of stylets  3  out from ablation instrument  1 . 
         [0029]    Stylets  3  are deployed through the use of a slideably mounted operator member  13  housed within cannula  2  and coupled to an operating handle at its proximal end. Anchors  4  may also be deployed through the use of a slideably mounted operator member (not illustrated) housed within cannula  2  and coupled to an operating handle at its proximal end. The distal end of operator member  13  is coupled to stylets  3  which may thus be advanced an identical distance in unison. 
         [0030]    In accordance with the invention, it has been found that by varying the extension of stylets  3  from the trocar point and by varying the power applied to stylets  3  and ablation point  5 , the size and shape of the ablation zone may be predictably controlled. For a trocar point of particular dimension, predetermined and relatively uniformly dimensioned and shaped ablation zones may be controllably created. 
         [0031]    In accordance with the invention it is contemplated that three facets cut into a right circular cylindrical metal body with a diameter of 3.5 mm define the shape and size of the trocar point. In accordance with the invention, or a trocar with a diameter of approximately 3.5 mm a height 12 of 8.2 mm has been found to yield excellent results. As shown in  FIG. 1   b,  large facet  19  has a height  15  of approximately 6 mm. Large facet  19  overlies the center of the trocar which defines a cylindrical passage  17  ( FIG. 1   a - b ), through which stylet  3 ′ extends. Large facet  19  has an oblique length  15   a  of about 7 mm. 
         [0032]    Flat facets  21  have a height  23  of approximately 4.5 mm. Facet  19  is accordingly somewhat larger in area as compared to the other two facets  21 . In accordance with a preferred embodiment, large flat facet  19  has a length at its widest girth of approximately 3 mm. Facets  21  are approximately 2.6 mm at their widest girth, but are not symmetrical, each having a straight edge which, together with facet  19 , forms the point of the trocar. As compared to facets  21 , facet  19  extends about 1.5 mm further (along the axis of cannula  2 ) from point  5  of the trocar toward the proximal end of ablation instrument  1 . Facets  21  are symmetrical with respect to each other. The angle between facet  19  and each of the facets  21  is approximately 90°. 
         [0033]    While the above-described trocar with the above dimensions as provided excellent results, it is believed that similarly dimensioned pointed trocars, of similar base diameter and length will provide good results. 
         [0034]    In accordance with the invention, it is contemplated that the dimensions of the trocar point may vary from the preferred embodiment detailed above. More particularly, it is contemplated that, for the application of the device to fibrous growths (such as uterine fibroids), using materials available today, the diameter of trocar point  5  may vary between 1.5 and 7 mm, although with existing materials, a diameter between 2.75 and 4 mm is preferred and a diameter between 3.2 and 3.7 mm is most preferred. However, to the extent that stronger materials may come to be known, smaller diameter trocars are more desirable, as they cause less trauma to the patient due to the wound created by the introduction of the trocar and cannula into the body of the patient. Conversely, I larger dimensions may be tolerated in some applications than the structure of the present invention can advantageously be used with a larger diameter cannula and trocar. 
         [0035]    In accordance with a preferred embodiment, trocar point  5  is made of stainless steel. Stylets  3  are made of tubular nickel titanium alloy having an outer diameter of approximately 0.4 mm. The transducer allows the surgeon to monitor the ablation procedure, and control the extent to which RF energy raises the temperature of the surrounding tissue, and thus control the size of the ablation zone in which substantial or complete cellular necrosis is induced. 
       EXAMPLE 1 
       [0036]    As shown in  FIG. 2 , when trocar point  5 , having the dimensions specified above, is advanced into a volume of uterine fibroid tissue and rf energy applied, an ablation zone  10  having a generally oval-shaped volume may be produced. In accordance with this example of the invention, radio frequency power at a frequency of 460 kilohertz is output into ablation instrument  1 , which is deployed without externally extending stylets as illustrated in  FIG. 2 . The radio frequency power output to trocar point  5  is 15 watts. Radio frequency power output is produced for a period of 15 seconds. The ablation zone  10  which is produced has an axial length  12  of 1 cm and a diameter or width  14  of 0.8 cm. The tip of trocar  1   a  is located approximately 0.1 cm from the distal edge of ablation volume  10 . It is noted that in this configuration, stylets  3  are wholly contained within cannula  2 . 
         [0037]    As illustrated in  FIG. 2 , it has accordingly been found that even without extending the stylets, the trocar may be used to create relatively small ablation zones. In accordance with the invention, a trocar having the particular configuration described above yielded excellent results. 
       EXAMPLE 2 
       [0038]    If a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a  with trocar point  5 , and having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  20  having a generally global-shaped volume, as illustrated in  FIG. 3 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into ablation instrument  1  and in particular trocar  1   a.  The radio frequency power output to trocar  1   a  is 15 watts. Radio frequency power output is produced for a period of 60 seconds. The ablation zone  20  which is produced has a length  22  of 1.5 cm and a width  24  of 1.2 cm. The tip  5  of trocar  1   a  is located approximately 0.5 cm from the distal edge of ablation volume  10 . Ablation zone  20  extends 1.2 centimeters behind trocar point  5 . It is noted that in this configuration, stylets  3  are still wholly contained within cannula  2 . 
       EXAMPLE 3 
       [0039]    In accordance with the invention, it is also possible to maintain the temperature surrounding ablation stylets  3  for a period of time, as opposed to applying a fixed amount of power to trocar  1   a.  For example, if a still a larger ablation zone is desired as compared to the ablation zone created in Example 2, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  30 , having a generally egg-shaped volume, as illustrated in  FIG. 4 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into ablation instrument  1 . Stylets  3  are deployed a distance of 5 mm from the surface of trocar  1   a,  thus resulting in exposing 5 mm of their length to the uterine fibroid tissue to be ablated. 
         [0040]    The radio frequency power output to stylets  3  and trocar  1   a  may be varied in analog fashion to maintain a temperature of 100° centigrade for a period of 60 seconds. Feedback from the temperature transducers contained within stylets  3  is used to adjust the power output of the RF generator to achieve the desired temperature. 
         [0041]    Alternatively, the duty cycle of, for example, a 15 watt radio frequency output coupled to trocar  1   a  may be varied, for example by turning the output on to begin the heating cycle and reach the desired temperature, shutting it off when a desired temperature of 100° C. is achieved, and turning it on again when the temperature drops below 99.5° C. 
         [0042]    The ablation zone  30  which is produced has a length  32  of 2 cm and a width  34  of 1.6 cm. The tip of stylet  3 ′ is located at a distance  36  approximately 0.8 cm from the distal edge of ablation volume  30 . Ablation zone  30  extends 1.2 centimeters behind trocar point  5 . 
         [0043]    It is further noted that in accordance with the present invention, suitable, but smaller ablation zones may be obtained by maintaining temperatures at various points within a range of, for example, 90 to 100° C. In addition, it may be desirable to use higher temperatures or higher powers toward the end of the ablation procedure, depending upon whether there is temperature maintenance as in this example or power maintenance as in Examples 1 and 2. 
       EXAMPLE 4 
       [0044]    If still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  40 , having a generally egg-shaped volume, as illustrated in  FIG. 5 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into trocar  1   a.  Stylets  3  are deployed a distance of 10 mm from the surface of trocar  1   a  on ablation device  1 , thus resulting in exposing 10 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 30 seconds. The ablation zone  40  which is produced has a length  42  of 25 mm and a width  44  of 23 mm. The tip of stylet  3 ′ is located at a distance  46  approximately 11 mm from the distal edge of ablation volume  40 . Similarly, ablation zone  40  extends about 14 mm behind trocar point  5 . 
       EXAMPLE 5 
       [0045]    If still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  50 , having a generally pear-shaped volume, as illustrated in  FIG. 6 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into ablation instrument  1 . Stylets  3  are deployed a distance of 15 mm from the surface of ablation device  1 , thus resulting in exposing 15 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  is maintained at about 100° using either of the methods detailed above. 
         [0046]    Temperature is maintained for a period of 120 seconds. The ablation zone  50  which is produced has a length  52  of 30 mm and a width  54  of 26 mm. The tip of stylet  3 ′ is located at a distance  56  approximately 11 mm from the distal edge of ablation volume  50 . Similarly, ablation zone  50  extends about 12 mm behind trocar point  5 . 
       EXAMPLE 6 
       [0047]    If an even larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a  into a fibroid to be ablated. Trocar  1   a  has the dimensions specified above and is positioned in a volume of uterine fibroid tissue to be ablated. Trocar  1   a  may be driven with RF energy to create an ablation zone  60 , having a generally pear-shaped volume, as illustrated in  FIG. 7 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into trocar  1   a  on ablation instrument  1 . Stylets  3  are deployed a distance of 20 mm from the surface of ablation device  1 , thus resulting in exposing 20 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  is maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 180 seconds. The ablation zone  60  which is produced has a length  62  of 36 mm and a width  64  of 31 mm. The tip of stylet  3 ′ is located at a distance  66  approximately 11 mm from the distal edge of ablation volume  60  thus produced. Ablation zone  60  extends about 12 mm behind trocar point  5 . 
       EXAMPLE 7 
       [0048]    If still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  70 , having a generally pear-shaped volume, as illustrated in  FIG. 8 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output into trocar  1   a  on ablation instrument  1 . Stylets  3  are deployed a distance of 25 mm from the surface of trocar  1   a,  thus resulting in exposing 25 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  is maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 240 seconds. The ablation zone  70  which is produced has a length  72  of 38 mm and a width  74  of 31 mm. The tip of stylet  3 ′ is located at a distance  76  approximately 10 mm from the distal edge of ablation volume  70 . Similarly, ablation zone  70  extends about 12 mm behind trocar point  5 . 
       EXAMPLE 8 
       [0049]    If still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  80 , having a generally pear-shaped volume, as illustrated in  FIG. 9 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output trocar  1   a.  Stylets  3  are deployed a distance of 35 mm from the surface of trocar  1   a,  thus resulting in exposing 35 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 420 seconds. The ablation zone  80  which is produced has a length  82  of 49 mm and a width  84  of 41 mm. The tip of stylet  3 ′ is located at a distance  86  approximately 12 mm from the distal edge of ablation volume  80 . Similarly, ablation zone  80  extends about 12 mm. behind trocar point  5 . 
       EXAMPLE 9 
       [0050]    If yet a still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  90 , having a generally pear-shaped volume, as illustrated in  FIG. 10 . In accordance with the invention, radio frequency power at a frequency of  460  kHz is output to trocar  1   a.  Stylets  3  are deployed a distance of 45 mm from the surface of trocar  1   a,  thus resulting in exposing 45 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 480 seconds. The ablation zone  90  which is produced has a length  92  of 59 mm and a width  94  of 46 mm. The tip of stylet  3 ′ is located at a distance  96  approximately 11 mm from the distal edge of ablation volume  90 . Ablation zone  90  extends 11 mm behind trocar point  5 . 
       EXAMPLE 10 
       [0051]    If still a larger ablation zone is desired, in accordance with the invention, one may deploy trocar  1   a,  having the dimensions specified above, into a volume of uterine fibroid tissue, to create an ablation zone  100 , having a generally pear-shaped volume, as illustrated in  FIG. 11 . In accordance with the invention, radio frequency power at a frequency of 460 kHz is output to trocar  1   a.  Stylets  3  are deployed a distance of 50 mm from the surface of ablation device  1 , thus resulting in exposing 50 mm of their length to the uterine fibroid tissue to be ablated. The temperature of the tissue surrounding stylets  3  and trocar  1   a  is maintained at about 100° using either of the methods detailed above. Temperature is maintained for a period of 720 seconds. The ablation zone  100  which is produced has a length  102  of 67 mm and a width  104  of 59 mm. The tip of stylet  3 ′ is located at a distance  96  approximately 14 mm from the distal edge of ablation volume  90 . Similarly, ablation zone  90  extends about 11 mm behind trocar point  5 . 
         [0052]    In accordance with the invention, in the power mode typified by the embodiments of  FIGS. 2 and 3 , the RF generator delivers substantially constant RF power at 460 kHz to all electrodes and the mandrel tip. 
         [0053]    In accordance with a preferred embodiment of the invention, a thermocouple is provided at the distal end of each stylet electrode. While all the strategies may be used, in a temperature-controlled ablation, such as Example 3, the system may use the average temperature of the seven thermocouples to control the power output. Alternatively, high and/or low readings may be removed from the calculation. 
         [0054]    Optionally, one may employ a power control algorithm which operates differently while it is ramping up to a target temperature, as compared to its operation when it is at or near the target temperature. In accordance with a preferred embodiment of the invention, in ramping mode, a ramping mode power control algorithm applies the full power of the system, reduced by an amount, if any, which causes the system to implement a maximum temperature increase rate of 2° C./second. In accordance with the invention, this ramp rate may be reduced as average temperature measured by the temperature transducers in the probe&#39;s ablation stylets approach the target temperature. 
         [0055]    When the probe average temperature is below, and within, for example, 0.5° C. of the target temperature, the power control algorithm switches to target power control mode where power is moderated and adjusted to maintain the desired temperature. Target power control delivers power in proportion to the small differences between the thermocouple average and the target temperature. 
         [0056]    After the algorithm has switched from ramping to target power control mode, the system may be set to never switch back to ramping mode until the RF power is turned off. That means once target temperature is achieved the amount of RF Power delivered is only to maintain target temperature, in the embodiment of Example 3 and other temperature controlled procedures. 
         [0057]    As alluded to above, manual (or power) control mode simply delivers the amount of power to the electrode array and tip that has been set as the target power. 
         [0058]    In both temperature and manual modes, the amount of ablation time is controlled by a foot pedal that is used to start and stop the RF delivery. 
         [0059]    While illustrative embodiments of the invention have been described, it is noted that various modifications will be apparent to those of ordinary skill in the art in view of the above description and drawings. Such modifications are within the scope of the invention which is limited and defined only by the following claims.