Abstract:
A method of treating abnormal tissue within a patient includes positioning a delivery cannula within the patient, the delivery cannula having a first electrode disposed on its distal end; introducing an ablation probe through the cannula and out an open distal end thereof, so that a second ablation electrode carried on the ablation probe contacts abnormal tissue within the patient; conveying ablation energy between the first and second ablation electrodes to ablate the abnormal tissue; and introducing a separate medical element, whether a device or a therapeutic agent, through the cannula before or after the ablation process.

Description:
RELATED APPLICATION DATA 
       [0001]    The present application is a continuation of pending U.S. patent application Ser. No. 10/828,032, filed Apr. 20, 2004, the priority of which is claimed under 35 U.S.C. §120, and the contents of which is incorporated herein by reference in its entirety, as though set forth in full. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention relates generally to the structure and use of radio frequency (RF) ablation probes for the treatment of tissue. 
       BACKGROUND OF THE INVENTION 
       [0003]    The delivery of radio frequency (RF) energy to target regions within solid tissue is known for a variety of purposes of particular interest to the present invention. In one particular application, RF energy may be delivered to diseased regions (e.g., tumors) for the purpose of ablating predictable volumes of tissue with minimal patient trauma. 
         [0004]    In a typical procedure, tissue suspected of containing an abnormality is imaged using a high definition imaging modality, such as Magnetic Resonance Imaging (MRI). If an abnormality, such as a tumor, is discovered, a sample of the abnormal tissue is retrieved. This is typically accomplished by percutaneously introducing a biopsy needle through healthy tissue into contact with the abnormal tissue. Proper guidance and placement of the biopsy needle is facilitated by the use of a standard imaging modality, such as fluoroscopy. The biopsy needle, with the tissue sample, is then removed from the patient&#39;s body, and the tissue sample is placed into a container and sent to a laboratory to examine whether it is malignant or benign. In the interim, the physician and/or patient may decide to treat the tumor, whether or not the tumor is actually malignant or benign. In this case, the abnormal tissue would typically be treated immediately after performing the biopsy. Alternatively, the physician and/or patient may decide to treat the tumor only if it is indeed malignant, in which case, such malignancy would be treated after receiving the laboratory results. 
         [0005]    In either case, the tumor can be treated by percutaneously introducing an RF ablation probe through the patient&#39;s body into contact with the tumor in a similar manner that the biopsy needle was described above. The ablation probe can then be operated to ablate the tumor. The interstitial space left by the removal of the tumor can then be treated with a therapeutic agent, such as a drug. Typically, this is accomplished by introducing a separate drug delivery device into the patient&#39;s body in the same manner as the biopsy needle and ablation probe was, and delivering the drug into the interstitial space. RF ablation of tumors is currently performed using one of two core technologies. 
         [0006]    The first technology uses a single needle electrode, which when attached to a RF generator, emits RF energy from the exposed, uninsulated portion of the electrode. This energy translates into ion agitation, which is converted into heat and induces cellular death via coagulation necrosis. The second technology utilizes multiple needle electrodes, which have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. U.S. Pat. No. 6,379,353 discloses such a probe, which comprises a delivery cannula and an electrode deployment member reciprocatably mounted within the delivery cannula to alternately deploy an electrode array from the delivery cannula and retract electrode array within the delivery cannula. The individual electrodes within the array have spring memory, so that they assume a radially outward, arcuate configuration as they are deployed from the delivery cannula. In general, a multiple electrode array creates a larger lesion than that created by a single needle electrode. 
         [0007]    When creating lesions using ablation electrode element (whether a single needle electrode or needle electrode array, deployable or otherwise) RF energy is commonly delivered to the tissue in one of several ways. In one arrangement, RF current may be delivered to an ablation electrode element in a monopolar fashion, which means that current will pass from the ablation electrode element to a dispersive electrode attached externally to the patient, e.g., using a contact pad placed on the patient&#39;s flank. In another arrangement, the RF current is delivered to two electrodes in a bipolar fashion, which means that current will pass between “positive” and “negative” electrodes in close proximity to each other, e.g., two electrodes on the same probe or array. Bipolar arrangements, which require the RF energy to traverse through a relatively small amount of tissue between the tightly spaced electrodes, are more efficient than monopolar arrangements, which require the RF energy to traverse through the thickness of the patient&#39;s body. As a result, bipolar electrode arrays generally create larger and/or more efficient lesions than monopolar electrode arrays. Additionally, bipolar arrangements are generally safer for the physician and patient, since there is an ever-present danger that the physician and patient may become a ground in the monopolar arrangement, resulting in painful burns. 
         [0008]    Although the current treatment of tumors is generally successful, there is still room for improvement. For example, even though such treatments can be considered minimally invasive in that open surgery is not required, they still require multiple instrument insertions during the biopsy, ablation, and drug delivery steps—causing tissue trauma with each insertion. Notably, even if the biopsy needle, ablation probe, and drug delivery device are introduced through the same opening in the skin, they will tend to take different tissue paths to the tumor. In addition, the patient must be imaged each time an instrument is guided through the patient&#39;s body into contact with the tumor. As such, the patient may have to be imaged several times during biopsy, ablative treatment, and drug delivery. Also, even though tumors come in all shapes and sizes, lesions resulting from a particular bipolar arrangement will typically have the same geometry, since the electrodes that make up a typical bipolar arrangement are fixed relative to each other. As such, some tumors may not be efficiently ablated using a standard bipolar ablation probe. 
         [0009]    Thus, there is a need for a tumor treatment kit and method that minimizes the number of instruments that must be inserted into the patient&#39;s body and provides for a more efficient bipolar ablation of the tumor. 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with a first aspect of the present invention, a medical probe kit is provided. The kit comprises a cannula having a shaft, a lumen extending through the cannula shaft, and a first ablation electrode disposed on the distal end of the cannula shaft. The cannula may have a handle mounted to the proximal end of the cannula shaft, and an optional fluid delivery port on the handle in fluid communication with the cannula lumen. 
         [0011]    The kit further comprises an ablation probe configured to be removably disposed within the delivery cannula lumen. The ablation probe has a shaft and a second ablation electrode disposed on a distal end of the probe shaft, wherein the first and second ablation electrodes are arranged in a bipolar configuration. Preferably, the ablation probe is slidable relative to the delivery cannula, whereby the distance between the first and second ablation electrodes can be adjusted. The ablation electrodes can be variously formed on the cannula shaft and probe shaft. For example, the shafts can be electrically conductive, and at least portions of the shafts can have an insulative coating, leaving the remaining portions of the shafts to form the electrodes. 
         [0012]    In the preferred embodiment, the probe shaft is rigid, but may also be flexible if desired. In the preferred embodiment, the probe shaft has a tissue-penetrating tip, so as to facilitate introduction of the cannula through tissue. Depending on the manner in which the cannula is to be introduced through tissue, the probe shaft may have a closed tip or an open tip. In the former case, the closed tip minimizes tissue trauma if desired. In the latter case, the ablation probe can be used to core tissue, e.g., in order to retrieve a tissue sample. The probe shaft may alternatively have a blunted tip, e.g., if the cannula can be introduced through tissue by itself, or with the aid of another device, such as an obturator or trocar. The kit optionally includes a biopsy stylet configured to be removably disposed within the cannula lumen. 
         [0013]    In one alternative embodiment, the kit comprises a plurality of ablation probe configured to be removably disposed in the cannula lumen. Alternatively, the cannula may have a plurality of lumens extending through the cannula lumen, in which case, the ablation probes can be configured to be removably disposed in the respective cannula lumens. Each of the ablation probes comprises a shaft and an ablation electrode disposed on the distal end of the shaft, wherein the first ablation electrode is arranged in a bipolar configuration with the plurality of ablation electrodes. 
         [0014]    In accordance with a second aspect of the present invention, a method of treating abnormal tissue within a patient is provided. The method comprises introducing a delivery cannula within the patient, e.g., percutaneously through the patient&#39;s skin, and introducing an ablation probe through a lumen within the cannula into contact with the abnormal tissue. In the preferred method, the ablation probe can be used to penetrate the tissue. Alternatively, the ablation probe can be used to core the tissue, e.g., in order to retrieve a tissue sample. 
         [0015]    The method further comprises conveying ablation energy between the first and second electrodes located on the respective cannula and ablation probe to ablate the abnormal tissue. In the preferred method, the distance between the first and second electrodes is adjusted by sliding the ablation probe relative to the delivery cannula. In this case, the ablation energy is conveyed between the first and second electrodes while the first and second electrodes are maintained from each other at the adjusted distance. Optionally, the abnormal tissue is cooled during the tissue ablation to provide for a more efficient ablation process. 
         [0016]    The method further comprises introducing a medical element through the cannula lumen into contact with the abnormal tissue. The medical element can be, e.g., a biopsy stylet, a chemotherapeutic agent, or an obturator, such as a trocar. Thus, it can be appreciated that both the ablation probe and medical element can be interchangeably used in the cannula. For example, the medical element can be removed prior to introducing the ablation probe through the cannula lumen, or the ablation probe can be removed from the cannula lumen prior to introducing the ablation probe through the cannula lumen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The drawings illustrate the design and utility of preferred embodiments of the present invention, in which similar elements are referred to by common reference numerals. In order to better appreciate how the above-recited and other advantages and objects of the present inventions are obtained, a more particular description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0018]      FIG. 1  is a plan view of a tissue treatment kit arranged in accordance with one preferred embodiment of the present inventions, wherein a delivery cannula, biopsy stylet, and ablation probe are particularly shown; 
           [0019]      FIG. 2  is a plan view of alternative ablation probe and trocar that can be used in the kit of  FIG. 1 ; 
           [0020]      FIG. 3  is a side view of the combination of the delivery cannula and stylet used in the kit of  FIG. 1 ; 
           [0021]      FIG. 4  is a side view of the combination of the delivery cannula and ablation probe used in the kit of  FIG. 1 ; 
           [0022]      FIG. 5  is a side view of an alternative embodiment of an ablation probe that can be used in the kit of  FIG. 1 ; 
           [0023]      FIG. 6  is a side view of an alternative embodiment of a delivery cannula that can be used in the kit of  FIG. 1 ; 
           [0024]      FIG. 7  is a cross-sectional view of the ablation probe illustrated in  FIG. 1 , taken along the line  7 - 7 ; 
           [0025]      FIGS. 8A-8E  illustrate cross-sectional views of one preferred method of using the tissue ablation kit of  FIG. 1  to treat tissue; and 
           [0026]      FIG. 9  is a plan view of another tissue treatment kit arranged in accordance with an alternative embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]      FIG. 1  illustrates a tissue treatment kit  100  arranged in accordance with a preferred embodiment of the present invention. The tissue treatment kit  100  generally comprises a delivery cannula  102  that can be percutaneously introduced within a patient, a biopsy stylet  104  configured for removing a tissue sample from the patient, and an ablation probe  106  configured for therapeutically ablating tissue. The biopsy stylet  104  and ablation probe  106  are configured to be alternately introduced through the delivery cannula  102  in contact with the tissue to be treated. 
         [0028]    The delivery cannula  102  comprises a cannula shaft  108  having a proximal end  110  and a distal end  112 , and a delivery lumen  114  extending through the cannula shaft  108 . As will be described in further detail below, the cannula shaft  108  may be rigid, semi-rigid, or flexible, depending upon the designed means for introducing the delivery cannula  102  to the target tissue. The distal end  112  of the cannula shaft  108  preferably carries a visualization marker  116  to allow the physician to identify the orientation of the cannula  102 . The visualization marker  116  may be an ultrasound, MRI or other visualization marker known to those of skill in the art. 
         [0029]    In the preferred embodiment, the cannula shaft  108  is composed of an electrically conductive material, such as stainless steel. In this case, the exterior surface of the cannula shaft  108 , with the exception of the tip of the distal end  112 , is preferably composed of an electrically insulative material  118 . Alternatively, the cannula shaft  108  may be composed of an electrically insulative material, such as a medical grade plastic, in which case, a separate insulative coating is not needed. The cannula shaft  108  has a suitable length, typically in the range from 5 cm to 30 cm, preferably from 10 cm to 20 cm, an outside diameter consistent with its intended use, typically being from 1 mm to 5 mm, usually from 1.3 mm to 4 mm, and an inner diameter typically being from 0.7 mm to 4 mm, preferably from 1 mm to 3.5 mm. 
         [0030]    The cannula  102  further comprises a handle  120  mounted to the proximal end  110  of the cannula shaft  108 . The handle  120  is preferably composed of a durable and rigid material, such as medical grade plastic, and is ergonomically molded to allow a physician to more easily manipulate the cannula  102 . The handle  120  comprises an electrical connector  122  with which an RF cable (not shown) mates. The handle  120  also comprises a fluid delivery port  124 , which is in communication with the delivery lumen  114 . As will be described in further detail below, the biopsy stylet  104 , ablation probe  106 , and chemotherapeutic agents can be interchangeably introduced into the delivery lumen  114  via the delivery port  124 . 
         [0031]    The cannula  102  further comprises an RF ablation electrode  126  carried by the distal end  112  of the cannula shaft  108 . In the preferred embodiment, the electrode  126  is formed by the exposed distal tip portion of the cannula shaft  108 , in which case, the electrical connector  122  is electrically coupled to the electrode  126  via the electrically conductive cannula shaft  108 . Alternatively, if the cannula shaft  108  is composed of an electrically insulative material, the distal cannula tip can be coated with an electrically conductive material to form the electrode thereon, or a discrete ring electrode can be interference fit on the distal cannula case. In this alternative case, a separate RF wire (not shown) will need to be routed from the electrode back through the cannula shaft  108  to the electrical connector  122 , preferably through the wall of the cannula shaft  108  so as to not hinder the delivery of the ablation probe  106  and biopsy stylet  104  through the delivery lumen  114 . 
         [0032]    The biopsy stylet  104  comprises a solid elongated shaft  128  with a tissue-penetrating distal tip  130  and a proximal handle  132 . The biopsy stylet  104  may operated in a standard manner to obtain a tissue sample. For example, in the illustrated embodiment, the biopsy stylet  104  comprises a grooved notch  134  just proximal to the distal tip  130 . Referring to  FIG. 3 , when the stylet  104  is advanced from the cannula  102  to expose the notch  134 , the tissue prolapses into the notch  134 , and then the cannula  102  can be advanced, thereby shearing the tissue to sever the sample. The sample is held protected inside the notch  134 . The stylet  104  can then be removed from the delivery lumen  114  in order to retrieve the tissue sample. Further details regarding the structure and use of biopsy stylets in association with cannulae are disclosed in U.S. Pat. No. 5,989,196, which is expressly incorporated herein by reference. 
         [0033]    The ablation probe  106  comprises an elongated shaft  136  having a proximal end  138  and a distal end  140 . The probe shaft  136  is preferably composed of a rigid or semi-rigid material, such that the probe shaft  136  can be introduced through solid tissue to the target tissue site when deployed from the cannula  102 . The distal end  140  of the probe shaft  136  comprises a closed tissue-penetrating tip  142 , which allows the cannula  102 , in combination with the ablation probe  106  (combination shown in  FIG. 4 ), to be more easily introduced through tissue, while preventing tissue coring and minimizing tissue trauma. 
         [0034]    As illustrated in  FIG. 2 , an obturator, e.g., a conventional trocar  144 , can be used to introduce the cannula  102  through the tissue, in which case, an alternative ablation probe  106 ′ with a tapered open tissue-penetrating tip  146  can be used in place of the biopsy needle  104  to obtain a tissue sample via tissue coring. Even more alternatively, the use of a separate trocar allows the probe shaft  136  to be composed of a flexible material and/or the distal end  112  of the probe shaft  136  to be blunted. 
         [0035]    Referring back to  FIG. 1 , the probe shaft  136 , in the preferred embodiment, is composed of an electrically conductive material, such as stainless steel. In this case, the exterior surface of the probe shaft  136 , with the exception of the distal tip  142 , is preferably composed of an electrically insulative material  148 . Alternatively, the probe shaft  136  may be composed of an electrically insulative material, such as a medical grade plastic, in which case, a separate insulative coating is not needed. As best shown in  FIG. 4 , the probe shaft  136  has a suitable length that is slightly longer than the length of the cannula shaft  108 , so that the distal tip  142  of the probe shaft  136  extends from the distal end  112  of the cannula shaft  108  when the ablation probe  106  is completely introduced into the delivery lumen  114 . The probe shaft  136  has an outer diameter that conforms with the inner diameter of the cannula  102 . Preferably, the outer diameter of the probe shaft  136  and the inner diameter of the cannula shaft  108  are closely toleranced to prevent tissue-coring during the introduction of the cannula  102  and ablation probe  106 . 
         [0036]    The ablation probe  106  further comprises an RF ablation electrode  150  carried by the distal end  140  of the probe shaft  136 . In the preferred embodiment, the electrode  150  is formed by the exposed portion of the shaft distal tip  142 . As illustrated, the electrode  150  encompasses the entire distal tip  142  and a cylindrical portion  152  just proximal to the distal tip  142 . Alternatively, to increase the tissue-penetrating function of the ablation probe  106 , the distal tip  142  can be composed of a relatively hard material, such as ceramic. In this case, the ablation electrode  150  is only formed by the cylindrical distal portion  152  of the probe shaft  136 , as illustrated in  FIG. 5 . Alternatively, if the probe shaft  136  is composed of an electrically insulative material, the distal tip  142  can be coated with an electrically conductive material to form the electrode thereon, or a discrete ring electrode can be interference fit at the base of the distal tip  142 . In this alternative case, a separate RF wire (not shown) will need to be routed from the electrode back through a lumen (not shown) with the probe shaft  136 . Thus, as shown in  FIG. 4 , it can be appreciated that the RF electrodes  126  and  150  of the respective cannula  102  and ablation probe  106  can be located a distance from each other to establish a bipolar relationship. This distance can be varied simply by displacing the ablation probe  106  within the delivery lumen  114 , thereby providing a means for modifying the size of the resulting ablation lesion. 
         [0037]    It should be noted that the ablation electrodes  126  and  150  need not be located at the distal-most portions of the cannula shaft  108  and probe shaft  136 . For example,  FIG. 6  illustrates an alternatively embodiment of a cannula  102 ′, wherein the distal-most portion of the cannula shaft  108  is coated with an insulative material, and a cylindrical portion just proximal to this insulated portion is exposed to form an ablation electrode  150 . 
         [0038]    Referring back to  FIG. 1 , the ablation probe  102  further comprises a handle  154  with an electrical connector  156  with which an RF cable (not shown) mates. The respective RF cables leading to the electrical connectors  122  and  156  of the cannula  102  and ablation probe  106  are connected to the positive and negative poles (or vice versa) of an RF generator (not shown), such that RF energy is delivered from the RF generator to the RF electrodes  126  and  150  on the respective cannula  102  and ablation probe  106  in a bipolar fashion. 
         [0039]    The RF generator (not shown) may be a conventional RF power supply that operates at a frequency in the range from  200  KHz to  1 . 25  MHz, with a conventional sinusoidal or non-sinusoidal wave form. Such power supplies are available from many commercial suppliers, such as Valleylab, Aspen, and Bovie. Most general purpose electrosurgical power supplies, however, operate at higher voltages and powers than would normally be necessary or suitable for vessel occlusion. Thus, such power supplies would usually be operated at the lower ends of their voltage and power capabilities. More suitable power supplies will be capable of supplying an ablation current at a relatively low voltage, typically below 150V (peak-to-peak), usually being from 50V to 100V. The power will usually be from 20 W to 200 W, usually having a sine wave form, although other wave forms would also be acceptable. Power supplies capable of operating within these ranges are available from commercial vendors, such as Boston Scientific Corporation of San Jose, Calif., who markets these power supplies under the trademarks RF2000™ (100 W) and RF3000™ (200 W). 
         [0040]    Referring still to  FIG. 1 , the ablation electrode  150  can be optionally cooled to provide for a more efficient tissue ablation and prevent tissue charring. To this end, the ablation probe  106  comprises a heat sink  156  composed of a thermally conductive material, such as aluminum. The heat sink  156  comprises a rod  158  that extends through the lumen  114  of the probe shaft  136  and out from the handle  154 , and cooling fins (not shown) formed at the proximal end of the heat sink rod  158  and exposed to the ambient air. As shown in  FIG. 7 , the distal end of the heat sink rod  158  is disposed within the electrode  150 . 
         [0041]    The ablation probe  106  further comprises a number of thermoelectric devices  160  (in this case, five) circumferentially arranged and mounted to the external distal surface of the heat sink rod  158 . Each thermoelectric device  160  comprises a cold side  162 , which is in thermal communication with the cylindrical portion of the electrode  150 , and a hot side  164 , which is in thermal communication with the heat sink rod  158 . When a DC signal with the proper polarity is applied to the thermoelectric devices  160  via wires (not shown), the cold and hot sides  162  and  164  of the thermoelectric devices  160  become cold and hot, respectively. As a result, thermal energy from the electrode  150  is absorbed by the cold sides  162  of the thermoelectric devices  160 , which is then conducted to the hot sides  164  of the thermoelectric devices  160 . The thermal energy emitted from the hot sides  164  of the thermoelectric devices  160  is then conducted through the heat sink rod  158  to the heat sink fins, where it dissipates into the ambient air. Further details on the structure and function of thermoelectric devices in ablation probes are disclosed in U.S. patent application Ser. No. 10/802,092, now U.S. Pat. No. 7,238,184, which is expressly incorporated herein by reference. 
         [0042]    It should be noted that means other than using thermoelectric devices can be used to cool the ablation probe  106 . For example, a cooling medium, such as saline, can be delivered through the delivery lumen  114  of the cannula  102  via the delivery port  124 , or the cooling medium can be delivered through the ablation probe  106  in a closed-loop or open-loop manner. If done in an open-loop manner, the ablation probe  106  can have a tissue-coring tip from which the cooling medium will be perfused. 
         [0043]    Having described the structure of the tissue ablation system  100 , its operation in treating targeted tissue will now be described. The treatment region may be located anywhere in the body where hyperthermic exposure may be beneficial. Most commonly, the treatment region will comprise a solid tumor within an organ of the body, such as the liver, kidney, pancreas, breast, prostrate (not accessed via the urethra), and the like. The volume to be treated will depend on the size of the tumor or other lesion, typically having a total volume from 1 cm 3  to 150 cm 3 , and often from 2 cm 3  to 35 cm 3 . The peripheral dimensions of the treatment region may be regular, e.g., spherical or ellipsoidal, but will more usually be irregular. The treatment region may be identified using conventional imaging techniques capable of elucidating a target tissue, e.g., tumor tissue, such as ultrasonic scanning, magnetic resonance imaging (MRI), computer-assisted tomography (CAT), fluoroscopy, nuclear scanning (using radiolabeled tumor-specific probes), and the like. Preferred is the use of high resolution ultrasound of the tumor or other lesion being treated, either intraoperatively or externally. 
         [0044]    Referring now to  FIGS. 8A-8E , the operation of the tissue ablation kit  100  is described in treating a treatment region TR within tissue T located beneath the skin or an organ surface S of a patient. The delivery cannula  102  is first introduced through the tissue T, so that the distal end  112  of the delivery cannula  102  is located at the treatment region TR, as shown in  FIG. 8A . This can be accomplished using any one of a variety of techniques. In the preferred method, the biopsy stylet  104  is introduced into the delivery lumen  114  of the cannula  102 , and then the cannula  102  with the stylet  104 , is introduced to the treatment region TR percutaneously directly through the patient&#39;s skin or through an open surgical incision. In this case, the sharpened tip  130  of the stylet  104  facilitates introduction to the treatment region TR. Alternatively, the ablation probe  106  or trocar  144  can be introduced into the delivery lumen  114  of the cannula  102 , in which case, the cannula  102  with the ablation probe  106  or trocar  144 , can be introduced to the treatment region TR. The sharpened distal tip  142  of the ablation probe or sharpened distal tip of the trocar  144  facilitates introduction to the treatment region TR in this case. Because the stylet  104 , ablation probe  106  or trocar  144  are sufficiently rigid, i.e., have a sufficient column strength, the cannula  102  need not be rigid, but instead can be flexible if desired. In any event, delivery cannula  102  can be properly positioned relative to the treatment region TR under ultrasonic or other conventional imaging. 
         [0045]    If the ablation probe  106  or trocar  144 , instead of the stylet  104 , is used to introduce the delivery cannula  102  to the treatment region TR, the stylet  104  can be exchanged for the ablation probe  106  or trocar  144 . In particular, the ablation probe  104  or trocar  144  are removed from the delivery lumen  114 , and then the stylet  104  can be introduced into the delivery lumen  114 . After the delivery cannula  102  is properly placed with the distal tip  130  of the biopsy stylet  104  deployed, a sample of the treatment region TR is obtained by distally advancing the delivery cannula  102  over the stylet  104  in order to shear off tissue within the notch  134  ( FIG. 8B ). The stylet  104  is then removed from the delivery lumen  114  in order to retrieve the tissue sample for analysis in a laboratory. Of course this is just one exemplary method of taking a tissue sample, and other conventional biopsy devices can be introduced through the delivery lumen  114  of the cannula  102  in order to obtain a tissue sample. 
         [0046]    The ablation probe  104  is then introduced through the delivery lumen  114  until the distal tip  142  of the probe shaft  136  is placed into contact with the treatment region TR ( FIG. 8C ). The RF generator (not shown) is then connected to the electrical connectors  122  and  156  of the respective cannula  102  and ablation probe  106 , thereby connecting the respective ablation electrodes  126  and  150  in a bipolar arrangement. The RF generator is then operated to ablate the treatment region TR. The thermoelectric devices  160  within the ablation probe  106  are preferably operated to cool the ablation electrode  150 , thereby cooling the adjacent treatment region TR and providing for a more efficient ablation. As a result of the ablation process, a lesion L will be created, which will eventually expand to include the entire treatment region TR ( FIG. 8D ). 
         [0047]    Preferably, prior to and/or during the ablation process, the distance between the ablation electrodes  126  and  150  are adjusted by moving the ablation probe  106  relative to the cannula  102 . In this manner, the bipolar arrangement of the electrodes  126  and  150  can be customized to the particular treatment region TR. For example, if the treatment region TR is particularly large, the distance between the ablation electrodes  126  and  150  can be selected to be relatively great. In this manner, the number of times that the ablation probe  104  is moved may be minimized. On the other hand, if the treatment region TR is particularly small, the distance between the ablation electrodes  126  and  150  can be selected to be relatively small. In this manner, the risk of ablating healthy tissue and the ablation time is minimized. Alternatively, the treatment region TR can be iteratively ablated by gradually increasing the distance between the electrodes  126  and  150  (by moving the ablation electrode  150  deeper into the treatment region TR) between tissue ablations. 
         [0048]    After the treatment region TR has been ablated, the ablation probe  106  is removed from the delivery lumen  114  of the cannula  102 , and one or more chemotherapeutic agents are introduced into the delivery port  124 , through the delivery lumen  114 , and out the distal end  112  of the cannula  102 , where it is perfused into the treatment region TR ( FIG. 8E ). 
         [0049]    Useful chemotherapeutic agents can include, for example, paclitaxel, docetaxel, alkylating agents including mechlorethamine, chlorambucil, cyclophosphamide, melphalan and ifosfamide; antimetabolites including methotrexate, 6-mercaptopurine, 5-fluorouracil and cytarabine; plant alkaloids including vinblastine, vincristine and etoposide; antibiotics including doxorubicin, daunomycin, bleomycin, and mitomycin; nitrosureas including carmustine and lomustine; inorganic ions including cisplatin; biological response modifiers including interferon; enzymes including asparaginase; and hormones including tamoxifen and flutamide; their homologs, analogs, fragments, derivatives, pharmaceutical salts and mixtures thereof. 
         [0050]    Thus, it can be appreciated that multiple medical elements, such as the biopsy stylet, ablation probe, and chemotherapeutic agents can be introduced through the delivery cannula using only one tissue path (i.e., the tissue path created by the initial introduction of the cannula  102  through the tissue), thereby substantially minimizing tissue trauma and imaging time. 
         [0051]    Although the previously described embodiment was illustrated and described with only one ablation probe, it should be noted that multiple ablation probes can be used. For example,  FIG. 9  illustrates another tissue treatment kit  200  arranged in accordance with a preferred embodiment of the present invention. The tissue treatment kit  200  generally comprises the previously described delivery cannula  102  and an array of ablation probes  206  configured to be independently introduced through the delivery cannula  102  in contact with the tissue to be treated. The tissue treatment kit  200  can optionally include the biopsy stylet  104  and/or trocar  144  previously described above. 
         [0052]    Like the ablation probe  106 , each of the ablation probe  206  comprises an elongated shaft  236  having a proximal end  238  and a distal end  240 . The probe shaft  236  is preferably composed of a rigid or semi-rigid material, such that the probe shaft  236 , but can be composed of a flexible material. The distal end  240  of the probe shaft  136  comprises a closed tissue-penetrating tip  242 , which allows the cannula  102 , in combination with the ablation probe  206  to be more easily introduced through tissue, while preventing tissue coring and minimizing tissue trauma. Preferably, a conventional trocar can be used to introduce the cannula  102  through the tissue. 
         [0053]    Each ablation probe  206  further comprises an RF ablation electrode  250  carried by the distal end  212  of the respective probe shaft  236 . Like the previously described electrode  150 , the electrode  250  is formed by an exposed portion of the shaft distal tip  242 . That is, each probe shaft  236  is composed of an electrically conductive material that is coated with an insulative material, with the exception of the distal tip  242 . Each ablation probe  202  comprises an electrical connector  256  with which an RF cable (not shown) mates. Thus, the RF cable leading to the electrical connector  122  of the cannula  102  can be connected to the positive pole of an RF generator (not shown), and the respective RF cables leading to the electrical connectors  256  of the ablation probes  206  can be connected to the negative poles of the RF generator (or vice versa), such that RF energy is delivered from the RF generator to the RF electrodes  126  and  250  on the respective cannula  102  and ablation probes  206  in a bipolar fashion. 
         [0054]    Use of the treatment kit  200  may be similar to that of the treatment kit  100 , with the exception that multiple ablation probes  206 , instead of a single ablation probe  106 , will now be introduced through the delivery lumen  114  of the cannula  202 . 
         [0055]    Alternatively, a delivery cannula similar to the delivery cannula  202  can have a number of delivery lumens equal to the number of ablation probes  206 . In this case, the ablation probes  206  can be introduced through the respective delivery lumens of the cannula  202 . The delivery port  124  can be in fluid communication with any or all of the delivery lumens, and the biopsy stylet  104  can be selectively introduced through one of the delivery lumens. 
         [0056]    Although particular embodiments of the present inventions have been shown and described, it will be understood that it is not intended to limit the present inventions to the preferred embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventions. Thus, the present inventions are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present inventions as defined by the claims.