Abstract:
A probe includes a shaft and an applicator head designed to treat irregularly-shaped hollow cavities, such as a cavity in breast tissue created by a lumpectomy procedure. The applicator head has a fixed geometry, and a plurality of electrodes can be advanced from an exterior surface of the applicator head in an omnidirectional pattern. The electrodes are used to deliver radiofrequency current or other energy to ablate the marginal tissue.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application No. PCT/US2015/020596 (Attorney Docket No. 47690-704.601), filed Mar. 13, 2015, which claims the benefit of provisional application no. 61/953,837 (Attorney Docket No. 47690-704.101), filed on Mar. 15, 2014, the full disclosures of which are incorporated herein by reference 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to medical devices and methods. More particularly, the present invention relates to the structure and use of probes intended to marginally ablate tissue surrounding a tissue cavity. 
         [0004]    Treatment of early stage breast cancer typically involves a combination of lumpectomy and whole breast irradiation (WBI). WBI typically utilizes ionizing radiation and can result in short and long-term complications affecting the skin, lungs, and heart. Such risks, when combined with the burden of weeks of daily WBI, drive some women to choose mastectomy instead of lumpectomy and cause up to thirty percent (30%) of women who undergo lumpectomy to stop therapy before completing the full treatment. 
         [0005]    One promising alternative to treatment with ionizing radiation is the use of a needle array to deliver radiofrequency energy to the marginal tissue surrounding the cavity left following a lumpectomy. Treatments have been performed with needle arrays intended for treating liver and other solid tissue tumors, and more recently, specialized needle arrays have been proposed for such post-lumpectomy treatments. None of the arrays used or proposed for use thus far have proven to meet all needs and circumstances encountered in when performing marginal cavity tissue ablation. 
         [0006]    As such, there remains a need for alternative and improved devices and methods for delivering non-ionizing radiation, such as radiofrequency energy, to deliver precise levels and depths of energy to the tissue immediately surrounding the site of a surgically removed tumor in order to minimize recurrence of the tumor. At least some of these objectives will be met by the inventions described below. 
         [0007]      2 . Description of the Background Art 
         [0008]    US Patent Publication No. 2014/0031810, having common inventors with the present application, describes a probe having an expandable applicator head for radiofrequency ablation of marginal tissue in a tissue cavity. 
         [0009]    U.S. Pat. No. 6,978,788 describes methods for labeling and ablating a marginal tissue region surrounding a tumor excision site in breast tissue. U.S. Pat. No. 7,942,873 describes an ablation device comprising a needle array and a surrounding sleeve for radiofrequency ablation of marginal tissue in a tissue cavity. Other patents of interest include U.S. Pat. Nos. 4,979,948; 5,562,720; 5,713,942; 5,871,483; 6,123,718; 6,142,993; 6,258,087; 6,491,710; 6,551,310; 7,150,745; 7,344,535; 7,371,231; 7,556,628; 7,632,268; 7,769,432; 7,828,793; and 7,959,631. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a probe having a radiofrequency applicator head specifically designed to treat hollow body cavities, such as irregularly-shaped cavities in breast tissue created by a lumpectomy procedure. The probe structure may be specially adapted and configured to facilitate electrode deployment in a breast or other tissue cavity to allow surgeons to deliver precise, measured doses of radiofrequency energy at controlled depths to the tissue margin surrounding the cavity. Use of the devices and methods of the present invention, however, is not limited to such post-surgical treatments and, as used herein, the phrase “body cavity” includes not surgically created cavities such as this formed by removal of tumors and other tissue lesions but also natural body cavities and passages, such as the ureter (e.g. for prostate treatment), the uterus (e.g. for uterine ablation or fibroid treatment), fallopian tubes (e.g. for sterilization), and the like. 
         [0011]    In a first aspect of the present invention, apparatus and systems include probes for ablating a marginal tissue region surrounding a body cavity, such as a cavity in breast tissue following a lumpectomy procedure. The probe comprises a shaft having a distal end. An applicator head is attached at or near the distal end of the shaft and has an outer surface which is fixedly configured to occupy a volume of the body cavity. A plurality of electrodes is disposed within the applicator head and may be reciprocated between a retracted configuration within the applicator head and an advanced configuration where a distal portion of each electrode extends beyond the outer surface of the applicator head. The applicator head may be introduced into the body cavity following a surgery, such as a surgical removal of a malignant tumor, and the electrodes may then be advanced into a marginal region of tissue surrounding the cavity. Energy, typically radiofrequency energy but optionally microwave or other energy that may be delivered by electrodes or electrode-like antennas, is then delivered into the tissue, typically at controlled depths and intensities. By properly spacing and distributing the electrodes over the fixed outer surface of the application head, the energy can be evenly applied throughout the tissue margin and a complete and uniform ablation of the marginal tissue can be achieved, reducing the risk that cancerous cells remain in the marginal tissue after the procedure is complete. 
         [0012]    In specific embodiments of the apparatus and systems of the present invention, the shaft is configured as a handle adapted for manual manipulation. In other instances the shaft may be configured for connection to and/or interface with a surgical robot, such as the Da Vinci® surgical robot available from Intuitive Surgical, Inc., Sunnyvale, Calif. In all cases, the shaft may be configured to be held in place by a shape lock or other deployment and suspension system of the type that is anchored to the patient bed and which holds the probe in place while the ablation or other procedure takes place, eliminating the need to a user to manually hold the device for the duration of the treatment. Typically, the applicator head has a plurality of channels, and at least some of the channels reciprocatably receive individual ones of the plurality of electrodes. The applicator head may comprise a solid body having the plurality of channels formed therein. Alternatively, the applicator head may have an open interior and may further comprise a plurality of shaped tubes which define the plurality of channels in the applicator head. Further alternatively, the applicator head may have an open interior and may further comprise a radially expandable support (typically an inflatable bladder) which reciprocatably carries the plurality of electrodes. Still further alternatively, the applicator head may have an open interior where at least some of the individual electrodes are configured to evert around a guide post within the open interior. Aspects of each of these embodiments may be incorporated and combined into a single applicator head. 
         [0013]    The electrodes of the probes of the present invention will preferably be configured to advance from the applicator head in an omnidirectional pattern. By “omnidirectional pattern,” it is meant that the electrodes will project or radiate radially outwardly from the applicator head, typically from a virtual center of the applicator head, in all directions. It is important that tissue on all sides of the applicator head be treated and ablated, so the electrodes are preferably distributed substantially uniformly over the outer surface of the applicator head. The distances between adjacent electrodes should be substantially equal, preferably varying by no more than 50%, preferably by no more than 25%, and preferably by 10% or less. In the illustrated embodiments, the electrodes usually advance along ray lines from the virtual center, but such orientations are not essential, and individual electrodes may lie along other (non-ray) lines and orientations so long as they are able to penetrate the marginal tissue and are distributed to provide uniform energy delivery over the entire inner surface of the tissue cavity. 
         [0014]    In further specific embodiments, the electrodes will be carried within and deflected by channels formed or provided in the applicator head. The channels will typically be arranged to deflect the individual electrodes in the omnidirectional pattern just described, and will typically provide a plurality of paths within the applicator head which radiate radically outwardly from a virtual center point therein. The channels will usually terminate in exit ports distributed substantially over the outer or exterior surface of the applicator head. 
         [0015]    In the illustrated embodiments, the electrodes may be configured to advance from the applicator head so that at least some of the electrodes advance in a distally diverging pattern and at least some of the electrodes advance in a proximally diverging pattern. Typically, the electrodes are straight and configured to be advanced in parallel in a distal direction through at least a portion of the shaft. In many embodiments, the electrodes are elastic and configured to be deflected within the applicator head so that some distally diverging electrodes continue to advance distally while said proximally diverging electrodes are everted at an angle between 90° and 180°. 
         [0016]    The number and arrangement of electrodes on the applicator head may vary widely. Usually, there will be at least six electrodes, but often there will be 10, 11, 12, 16, 20, 24, or even more. Representative ranges include two to 60, four to 50, six to 36, six to 24, six to 20, and six to 16 electrodes. The electrodes will usually be elongated and will be sufficiently elastic so that they can be bent at angles approaching 180° so that they may de everted to exit the applicator head in a generally proximal direction after being advanced distally through the shaft. Such elastic electrodes will typically be formed from a superelastic metal, such as Nitinol® or a spring stainless steel. Optionally, the elastic electrodes may include coiled or other enhanced elasticity regions to help the electrodes conform the tight bends that may be required. In other embodiments, though, the electrodes may be deployed in alternative fashions that do not require bending, as described below, and may be relatively stiff. 
         [0017]    The probes of the present invention may be configured to operate in a monopolar, bipolar, multipolar or other energy delivery protocol. For bipolar or multipolar current delivery, at least some of the electrodes may be configured to be connected to different poles of an associated radiofrequency or other power supply and/or individual electrodes may have two or more isolated electrically conductive regions, where said regions are connectable to different polarities of an associated radiofrequency or other power supply. Often, the plurality of electrodes will comprise at least a first polarity group and a second polarity group. In addition to the electrodes, the probes may have one or more electrodes formed on the shaft and/or disposed on the outer surface of the applicator head. 
         [0018]    The applicator head will have a geometry selected to treat the target tissue cavity. For lumpectomy cavities, the applicator head will usually have a spherical, spheroidal or ovoidal outer surface. The number of electrodes advanced from the outer surface will typically be within the ranges set forth above, and the electrodes will preferably be advanced from the applicator head into the marginal tissue region in an omnidirectional pattern, also as described above. The applicator head will typically have diameters or widths in the range from 5 mm to 90 mm, usually from 30 mm to 50 mm for the treatment of lumpectomy cavities. The distal portions of the electrodes will typically extendable beyond the exterior surface of the applicator head by a distance in the range from 0.5 mm to 20 mm, usually from 5 mm to 12 mm for the treatment of lumpectomy cavities. While the electrodes will usually be extendable, the electrodes need not be extended beyond the external surface for use in all circumstances. For example, the electrodes may be energized while still retracted within the interior of the applicator head in order to energize saline or other electrically conductive media which has been released into the body cavity. This may be particularly useful for cauterizing exposed tissue in the cavity before penetration of the electrodes in the tissue for an ablative treatment. 
         [0019]    In a second aspect of the present invention, a method for ablating a marginal tissue region surrounding a body cavity comprises introducing an applicator head into the body cavity. The applicator head has a fixed configuration which substantially occupies a volume of the body cavity. A plurality of electrodes are advanced from an outer surface of the applicator head into the marginal tissue region of the body cavity, and energy is delivered through the electrodes to ablate the marginal tissue region. The methods will typically but not necessarily use the ablation probes described above and in the detailed description below. 
         [0020]    The methods of the present invention will find their most immediate use in treating tissue at the margins of a tissue cavity remaining after removal of a tumor, such as treating the tissue cavity remaining after a lumpectomy to remove a breast tumor. The methods will be useful for treating other tumors and certain non-malignant conditions, such as lesions and other tissue anamolies in the liver, esophagus, lung, soft tissue (sarcoma), kidney, pancreas, open wounds, and endometrium. 
         [0021]    The methods of the present invention may combine other steps and procedure which will enhance or enable the desired marginal ablation. For example, a conductive irrigation fluid may be delivered to a region between the applicator head and the marginal tissue region prior to or concurrently with delivering energy to ablate the tissue region. Delivering the electrically conductive irrigation fluid may comprise infusing the irrigation fluid from the applicator head, for example by infusing the irrigation fluid from a location of at least some of the electrodes, typically through an open interior of the applicator head or through the electrode channels in the applicator head. As a second example, a surface of the marginal tissue region may be cauterized prior to ablating the marginal tissue region, typically by delivering a cauterizing current from the applicator head and/or the electrodes, such as in  FIG. 10-12 . As a third example, a vacuum may be drawn between the outer surface of the applicator head and a surrounding wall of the body cavity, conveniently be drawing the vacuum is through ports in the outer surface of the applicator head, which may be the electrode delivery ports. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a perspective view of a first embodiment of a tissue ablation probe constructed in accordance with the principles of the present invention. 
           [0023]      FIG. 2  is an enlarged, detailed view of a distal end of the tissue ablation probe of  FIG. 1  shown with a plurality of electrodes extended from an applicator head. 
           [0024]      FIG. 3  is view similar to  FIG. 2  shown with the electrodes retracted within the applicator head. 
           [0025]      FIG. 4  illustrates an alternative construction of an applicator head useful for the ablation probes of the present invention. 
           [0026]      FIG. 5  illustrates a second alternative construction of an applicator head useful for the ablation probes of the present invention. 
           [0027]      FIG. 6  illustrates a distal end of a single electrode having a penetration-limiting collar. 
           [0028]      FIG. 7  illustrates the electrode of  FIG. 6  with the penetration-limiting collar radially collapsed when constrained in a delivery channel of an applicator head. 
           [0029]      FIG. 8  illustrates use of an applicator head similar to that illustrated in  FIG. 4  having the electrodes of  FIGS. 6 and 7  for ablating a tissue cavity. 
           [0030]      FIG. 8A  illustrates how the penetration-limiting collar limits tissue penetration to control the ablation depth in a tissue margin. 
           [0031]      FIG. 8B  illustrates a distal end of a single electrode having an electrically conductive disc or flange element dsisposed to engage a surface electrode on the applicator head. 
           [0032]      FIG. 8C  illustrates a distal end of a single electrode having both a penetration-limiting collar and an electrically conductive disc or flange element disposed to engage a surface electrode on the applicator head. 
           [0033]      FIG. 9  illustrates a hollow core or open interior embodiment of an applicator head having a plurality of curved tubes for deflecting individual electrodes and optionally delivering irrigation or other fluids in accordance with the principles of the present invention. 
           [0034]      FIGS. 10 and 11  illustrate alternative constructions of applicator heads in accordance with the principles of the present invention having solid cores with electrode-deflecting channels formed therein. The channels can also be configured for irrigation. 
           [0035]      FIG. 12  illustrates a further embodiment of an applicator head constructed in accordance with the principles of the present invention which utilizes an expandable support for deploying a plurality of relatively rigid electrodes in a radially outward direction. 
           [0036]      FIG. 13  illustrates a still further embodiment of an applicator head constructed in accordance with the principles of the present invention which deploys a plurality of elongate straight electrodes, some of which are routed around guide posts in order to effect a reversal of direction. 
           [0037]      FIG. 14  illustrates yet another embodiment of the applicator head of the present invention which employs push- and pull-mechanisms for deploying the electrodes in distal and proximal directions, respectively. 
           [0038]      FIG. 15  illustrates an electrode having a spring-like region to enhance bendability. 
           [0039]      FIG. 16  illustrates the electrode of  FIG. 15  being deployed through a tight curve in a deployment tube. 
           [0040]      FIG. 17  shows an electrode having a sensor thereon. 
           [0041]      FIG. 18  illustrates an exemplary handle for manual manipulation of the probe of the present invention, where the handle has a single deployment slide which is coupled to the plurality of electrodes. 
           [0042]      FIG. 19  illustrates an alternative handle embodiment having a plurality of slides for deploying individual ones of the plurality of electrodes in the probe. 
           [0043]      FIGS. 20 and 21  illustrate an exemplary electrode having isolated polarity regions and optionally including a base electrode. 
           [0044]      FIG. 22  illustrates a plurality of electrodes which may be arranged in various bipolar patterns. 
           [0045]      FIG. 23  is a flowchart illustrating an exemplary protocol for electrode insertion detection. 
           [0046]      FIG. 24  is a flowchart illustrating an exemplary protocol for determining electrode over-insertion. 
           [0047]      FIG. 25  is a flowchart illustrating an exemplary protocol for determining ablation index. 
           [0048]      FIG. 26  is a flowchart illustrating an exemplary protocol for ablation mapping. 
           [0049]      FIG. 27  is a flowchart illustrating an exemplary protocol for an exemplary ablation procedure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    An exemplary ablation probe  10  constructed in accordance with the principles of the present invention is illustrated in  FIG. 1 . The probe  10  includes an applicator head  12  attached or formed at a distal end of a shaft  14  which is typically formed as a handle intended to be manually manipulated by a physician or other user. A plurality of individual electrodes  16  are configured so that they may be extended radially outwardly from the applicator head  10 , as shown in  FIGS. 1 and 2 , or be retracted within the applicator head, as shown in  FIG. 3 . Usually, the electrodes will be retracted when the applicator head  16  is being introduced into a tissue cavity to be treated, and the electrodes will then be radially advanced when applicator head is properly positioned in order to penetrate the distal ends of the electrodes into the tissue, as illustrated for example in a  FIG. 8  discussed below. Each electrode will usually have a tissue-penetrating distal tip, usually being sharpened but optionally relying on the application of a “cutting” current through the electrode as the electrode is advanced into the tissue. Each individual electrodes  16  will typically be reciprocated through a port  18  formed in the applicator head  12 , as best seen in  FIG. 3 . The various internal structures for the applicator head  12  will be described in more detail below with respect to other figures herein. 
         [0051]    For the manually manipulated probe embodiments, as shown in  FIGS. 1-3 , the applicator head  12  will typically be joined to the handle/shaft  14  by a narrow diameter neck region  20 . The applicator head  12  will have an enlarged diameter or width, typically being spherical, spheroid, or ovoid or the like, where the enlarged portion is intended to enter and occupy at least a substantial portion of the tissue cavity to be treated. The neck region  20  will usually be disposed within an incision or other entry route through the tissue, thus allowing the tissue to conform around the outer or exterior surface of the applicator head  12 , thus helping to assure that the electrodes  16  will be able to penetrate the marginal tissue and uniformly cover all or at least most of the surface area of marginal tissue within the tissue cavity. The tissue probe  10  will usually include a mechanism for advancing and retracting the electrodes  16 , such as a slide  22  received in a slot  24  on the handle. The user may advance the slide  22  in order to advance the electrodes. Conversely, the user may retract the slide  22  in a proximal direction in order to retract the electrodes. Specific mechanisms for advancing and retracting the electrodes are described in more detail below. 
         [0052]    As illustrated in  FIGS. 1-3 , the applicator head  12  may be fabricated from polymers and/or other non-electrically conductive materials, such as ceramics, glasses and the like. In this way, only the electrodes  16  will be electrically active. In such cases, the individual electrodes may be powered at a common polarity and the energy applied in a “monopolar” manner, typically using a counter electrode placed on the patient&#39;s back or other skin region. Alternatively, individual ones of the electrodes  16  may be powered at different polarities and the energy delivery effected in a bipolar or multi-polar manner Still further, alternatively, the individual electrodes may themselves have isolated electrically conductive regions allowing each electrode to deliver bipolar or multi-polar electrical energy. Specific combinations are illustrated in  FIGS. 20-22  below. In alternative embodiments, all or a portion of the applicator head may be fabricated from one or more metals or other electrically conductive materials. In such cases, the head may be electrically coupled to at least some of the electrodes, allowing the head and those electrodes to be powered at a common polarity. In other cases, at least some of the electrodes may be electrically isolated from the electrically conductive applicator head or portions thereof. In those cases, the head and individual electrodes may be powered at different polarities. 
         [0053]    Referring now to  FIG. 4 , an alternative applicator head  26  is illustrated. Applicator head  26  includes a plurality of surface electrodes  28  formed on an exterior surface of the head. The electrode surfaces  28  are shown to be generally circular, and the electrodes  16  emerged through ports  29  which may be located generally at the center of each circular electrode. The individual surface electrode  28  may be operated at a common polarity or alternatively may be electrically isolated so that they may be powered at difference polarities. Optionally, a ring electrode  30  may be provided on the shaft, typically in the neck region  20  of the shaft. The ring electrode  30  may be powered to extend the ablation region into the incision or tissue path between the cavity and the skin overlying the cavity. The ring electrode  30  may be powered at a common polarity with all other electrodes, or may be powered at a different polarity than at least some of the electrodes in order to effect a bipolar or multi-polar ablation. 
         [0054]      FIG. 5  illustrates a further embodiment of an applicator head  32  having a polarity of surface electrodes  34 . Individual electrodes  16  emerge through ports  35  located near the centers of the hexagonal surface electrodes  34 . Use of the hexagonal electrode allows the electrodes to be “closely packed” over the spherical surface of the applicator head  32  so that there are no gaps. The individual surface electrodes  34  may be connected to a common pole of the power supply or to different poles. The surface electrodes  34  may also be powered at the same or different polarities than the individual electrodes  16 . 
         [0055]    Referring now  FIGS. 6 and 7 , the individual electrodes may take a variety of forms. Most simply, the electrodes may be elongate, elastic electrically conductive metal elements or rods which can be advanced through the shaft to emerge radially outwardly from the applicator head, as shown in the figures thus far. A number of alternative constructions will be described herein below. For all these electrodes structure, however, it will sometimes be desirable to provide a penetration limit so that the electrodes may be advanced into the marginal tissue at a desired depth, typically within the ranges set forth above. As shown in  FIGS. 6 and 7 , an exemplary electrode  36  having a tissue-penetrating tip  37  includes a collar  38  spaced at a distance d from tissue-penetrating tip  37 . The collar  38  will usually be collapsible, for example being formed from a flexible or elastomeric material, so that it may be collapsed within a deployment channel  40  within an applicator head, for example applicator head  26  as shown in  FIG. 4 . When the needle  36  is advanced from the applicator head  26 , as shown in  FIG. 8 , the collars  38  will deploy radially outwardly and will serve to limit the penetration of the distal portion of the electrode into the tissue T. When the applicator head  26  is within a body cavity BC, the electrodes  36  may be advanced by different distances from the surface of the applicator head  26 , but the distal penetration of each electrode  36  will limited to a similar or equal depth as al other electrode tips. Thus, even though the applicator head has not fully conformed to the inner surface of the body cavity BC, the electrodes may be advanced by different distances from the exterior surface of the applicator head yet still achieve equal penetration depths. Such embodiments are particularly useful when treating irregularly shaped body cavities. The engagement of the collar  38  against the inner wall of the body cavity BC is best illustrated in  FIG. 8A  where the penetration depth into the tissue margin TM is shown. 
         [0056]      FIG. 8B  illustrates an electrode  136  having an electrically conductive disc or flange  137  spaced proximally from a tissue-penetrating tip. The disc or flange  137 , when advanced radially outwardly, both limits the travel of the electrode and engages an inner side of surface electrode  138  to provide a conductive path to that electrode so that energizing the electrode will simultaneously energize the surface electrode into tissue T.  FIG. 8C  illustrates an electrode  236  having both a collar  238  spaced proximally from a tissue-penetrating tip and electrically conductive disc or flange  237  spaced between the tissue-penetrating tip and the disc  237 . The disc or flange  237 , when advanced radially outwardly, both limits the travel of the electrode and engages an inner side of surface electrode  238  to provide a conductive path to that electrode so that energizing the electrode will simultaneously energize the surface electrode. The collar  237  further limit the penetration of the electrode into the tissue T. 
         [0057]    Referring now to  FIG. 9 , a specific example of an applicator head  44  having an open interior  46  with a plurality of electrode-electrode deployment tubes  48  therein is illustrated. The tubes  48  are shaped to receive and deflect individual electrodes  16  so that the deployment directions of each electrodes  16  may be individually selected and, in particular, so that the electrodes may be deployed in an omnidirectional pattern, as described above. Thus, some of the individual electrodes  16  will be directed distally from the applicator head  44  while others will be everted and directed proximally from the application head. Usually, the tubes  48  will extend through at least a portion of the length of the shaft  52 , and a mechanism in the shaft (not shown) will be provided for advancing the electrodes through each of these tubes  48 . An applicator head  54  having a further alternative construction is illustrated in  FIG. 10 . The applicator head  54  has a generally solid body which includes a distal segment  56 , a middle segment  58  and a proximal segment  60 . Adjacent surfaces of the segments will have channels  62  formed therein for receiving and deflecting individual electrodes (not shown) in distally and proximally oriented patterns. The channels  62  will be contiguous with a central passage  64  which will receive the individual electrodes that are advanced and retracted using any of the shaft or handle mechanisms described herein. 
         [0058]      FIG. 11  illustrates a similar solid core applicator head  70  which includes five individual segments  72 , each having channels  74  formed therein for deploying individual electrodes (not shown). The channels  74  are contiguous with a central passage  76  to allow the electrodes to be advanced and retracted. The use of additional segments allows an increased number of electrodes with improved axial distribution of the individual electrodes compared with the use of three segments as shown in  FIG. 10 . 
         [0059]    Applicator head  80  illustrated in  FIG. 12  comprises an alternative mechanism for advancing electrodes from the applicator head. Electrodes  82  are mounted on an expandable support  84 , typically and inflatable support such as a balloon which may be inflated through inflation line  88 . The electrodes  82  are usually short, rigid electrodes aligned with ports  86  formed through a shell of the applicator head  80 . The interior of the applicator head is generally open and free from structure so that the expandable support  84  may be expanded from a contracted configuration, as shown in full line, to an expanded configuration, shown in broken line. As the support expands, the individual electrodes  82  are advanced through the ports  86  to penetrate the surrounding tissue. 
         [0060]    A still further electrode advancement mechanism is shown in  FIG. 13  where applicator head  100  comprises a shell having a plurality of ports  104  formed therein. Elongate, flexible electrodes  106  are advanced through a neck or shaft  102  of the probe. Only two individual electrodes  106  are illustrated, but it will be appreciated that typically at least one electrode will be provided to be advanced through each of the illustrated ports. Usually, additional ports will be provided, but only those ports shown on the sectional plane of the drawing are illustrated for convenience. Many of the individual electrodes  106  may be advanced through an associated port without the need to provide for additional guidance. Others of the electrodes, however, will need to be everted so that they may be deployed in a proximal direction. In such cases, the electrodes  106  may be advanced around a guide post  110  which can at least partially reverse the direction of travel of the electrode. 
         [0061]    Yet another electrode deployment mechanism is illustrated in  FIG. 14  where applicator head  114  has an outer shell with a plurality of ports  116  formed therein. Electrodes  120  and  122  which are advanced in a generally distal direction are connected in “push” assembly  118  so that they may be advanced in the direction of arrow  128  by pushing on a proximal portion of the central electrode  120 . Other electrodes  127 , in contrast, are intended to be deployed in a proximal direction and will be incorporated into a “pull” assembly  124  including a yoke  126  which may be pulled in the direction of arrow  130  in order to deploy these electrodes. All the electrodes may be simultaneously deployed by pushing and pulling on the rods attached to these assemblies simultaneously as shown by arrows  128  and  130 . 
         [0062]    As some of the electrodes in the applicator head embodiments of the present invention will be subjected to very tight turns, typically for those being deployed proximally from the applicator head, it can sometimes be useful to provide elastic regions  136  in electrodes  134 , as illustrated in  FIG. 15 . The elastic regions may be a short coiled section or may have other modifications in order to decrease pending stiffness. For example, the surfaces of the electrodes could have small notches or wedges formed therein to allow easier deformation. As shown in  FIG. 16 , the elastic regions  136  may be disposed so that they lie at a location where the tightest bend will be found, for example in a deployment tube  138 . 
         [0063]    Referring now to  FIG. 17 , individual electrodes  142  may include one or more sensors  44  formed near their distal tips  145 . Sensors can be configured to measure temperature, impedance, or the like. In some instances the sensors may be configured to determined depths of penetration, for example using a capacitance measurement protocol. 
         [0064]    Referring now to  FIG. 18 , an exemplary handle  150  which can provide all or a portion of a shaft structure is illustrated. Then handle  150  comprises a shell or enclosure  151  having an open interior and a slot  153 . Slider  152  is received within the slot so that it may be manually advanced and retracted by a user. Slider  152  is connected to a cable  156  or other element which is connected to the plurality of electrodes in the probe, where the electrodes can have many of the embodiments described previously. A displacement sensor  154  is provided within the interior of the handle  150  and measures the distal advancement and proximal retraction of the cable as the slider  152  is advanced and retracted. In this way, the net displacement of the electrodes and their penetration into the tissue can be monitored. 
         [0065]    The construction of an alternative handle  160  is illustrated in  FIG. 19 . The principal difference between handle  160  and handle  150  is that a plurality of sliders  162  is provided in handle  160 . Each slider  162  is attached to an individual electrode  166  and a plurality of individual displacement sensors  168  are provided, one for each of the sliders and electrode pairs. In this way, each individual electrode can be advanced by a different distance and the handle can monitor the displacement distances individually. Each of the individual electrodes  166  will be connected to the radio frequency power supply by individual connection leads  170 . Handle  150  included a single connection lead  158 . 
         [0066]    Referring now to  FIGS. 20-22 , exemplary multi-polar electrodes  174  may include individual electrically conductive and electrically insulating regions. As illustrated, the multi-polar electrodes  174  include a top conductor region  176  and middle conductor region  178 . The conductor regions  176  and  178  are separated by an insulating region  180 . A further insulating region  180  may be provided between the middle conductor region  178  and a base region  182 . The base region  182  will usually be a portion of the applicator head so that the electrode  174  will be able to pass the through the base. The electrically conductive regions  176  and  178  as well as the base region  182  may be powered at a common polarity or with different polarities. As shown in  FIG. 21 , the top conductor region  176  may have a positive polarity while the middle and base may have negative polarities. Other combinations will be available. Shown in  FIG. 22 , assuming that each individual electrode  174  is powered at a common polarity, the adjacent electrodes may themselves be powered at difference polarities in order to achieve a bipolar configuration. 
         [0067]    Referring now to  FIGS. 23-27 , the probes of the present invention will typically be powered by radiofrequency power supplies having microprocessors which may be configured to provide a numbers specific operational protocols. For example, as shown in  FIG. 23 , the power supplies may have protocols which detect when electrodes having collars, as shown in  FIGS. 6-8 , are fully inserted. The flowcharts are self-explanatory. Briefly, these protocols rely on using electrodes having different regions of electrical conductivity, where those regions are electrically isolated. These regions are subsections which are energized with low-power current, and the various regions on individual electrodes may be monitored to see when that region or subsection has entered tissue in order to detect a flow of power which is present only when that subsection is within tissue. When the electrode region or subsection at the desired depth is detected to have been inserted into tissue, the system can confirm that the proper depth of penetration has been achieved. 
         [0068]    Referring now to  FIG. 24 , a protocol for detecting on the electrodes have been over-inserted is set forth. Again, the protocols are self-explanatory but generally rely on using electrodes having multiple, isolated electrically active regions so that a low power signal passing through those regions will be detected by the power supply when that region has entered tissue. If a region which is beyond the desired penetration depth enters the tissue, the system will detect that the electrode has been over-penetrated into the tissue. 
         [0069]      FIG. 25  illustrates a specific protocol for operating the power supplies to deliver energy through the probes of the present invention. Using electrodes that contain sensors, such as illustrated in  FIG. 17 , allows temperature and other data to be collected. In addition, the electrically-isolated regions of a specific electrode can be used to transmit a low-power signal and determine the conductivity of the tissue through which the signal has passed. The aggregation of the measured data is used in the protocol described in  FIG. 25  to determine when an ablation protocol has been completed. 
         [0070]      FIG. 26  illustrates a protocol for ablation mapping where a geometric representation of the current state of the ablation volume is created. The same data as collected in the protocol in  FIG. 25  are mapped to the geometric location of the sensors or regions of specific electrodes, thus linking the ablation index to a specific region of tissue. The series of these ablation index and tissue region pairs form a three-dimensional map of the current three-dimensional ablation volume, relative to the orientation of the applicator shaft. This allows either an external microprocessor-based system to automatically control the polarities and potentials on the different electrodes and their regions or for the user to manually adjust the electrical supply through the device to effect the desired ablation shape and volume. 
         [0071]      FIG. 27  illustrates a protocol for a typical ablation procedure, which includes shaping of the cavity to prepare the cavity for consistent, optimal ablation. By following the steps in the protocol, the cavity can be matched to the shape of the applicator head.