Abstract:
An infusion array ablation apparatus includes an elongated delivery device having a lumen and an infusion array positionable in the lumen. The infusion array includes an RF electrode and at least a first and a second infusion member. Each infusion member has a tissue piercing distal portion and an infusion lumen. At least one of the first or second infusion members is positionable in the elongated delivery device in a compacted state and deployable from the elongated delivery device with curvature in a deployed state. Also, at least one of the first or second infusion members exhibits a changing direction of travel when advanced from the elongated delivery device to a selected tissue site. At least one infusion port is coupled to one of the elongated delivery device, the infusion array, the first infusion member or the second infusion member.

Description:
This application is a continuation of U.S. patent application Ser. No. 09/513,725, filed Feb. 24, 2000, now U.S. Pat. No. 6,641,580, which is a continuation-in-part of U.S. patent application Ser. No. 09/383,166, filed Aug. 25, 1999, now U.S. Pat. No. 6,471,698, which is a continuation of U.S. patent application Ser. No. 08/802,195, filed Feb. 14, 1997, now U.S. Pat. No. 6,071,280, which is a continuation-in-part of U.S. patent application Ser. No. 08/515,379, filed Aug. 15, 1995, now U.S. Pat. No. 5,683,384, which is a continuation-in-part of U.S. patent application Ser. No. 08/290,031, filed Aug. 12, 1994, now U.S. Pat. No. 5,536,267, which is a continuation-in-part of U.S. patent application Ser. No. 08/148,439, filed Nov. 8, 1993, now U.S. Pat. No. 5,458,597, all of which are incorporated herein by reference. 
     The Ser. No. 09/513,725 application is also a continuation-in-part of U.S. patent application Ser. No. 09/364,203, filed Jul. 30, 1999, now U.S. Pat. No. 6,663,624, which is a continuation of U.S. patent application Ser. No. 08/623,652, filed Mar. 29, 1996, now U.S. Pat. No. 5,935,123, which is a divisional of U.S. patent application Ser. No. 08/295,166, filed Aug. 24, 1994, now U.S. Pat. No. 5,599,345, which is a continuation-in-part of U.S. patent application Ser. No. 08/148,439, filed Nov. 8, 1993, now U.S. Pat. No. 5,458,597, all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to an apparatus for the treatment and ablation of body masses, such as tumors, and more particularly, to an RF treatment system suitable for multi-modality treatment with an infusion delivery and a retractable multiple needle electrode apparatus that surrounds an exterior of a tumor with a plurality of needle electrodes and defines an ablative volume. The system maintains a selected power at an electrode that is independent of changes in current or voltage. 
     2. Description of Related Art 
     Current open procedures for treatment of tumors are extremely disruptive and cause a great deal of damage to healthy tissue. During the surgical procedure, the physician must exercise care in not cutting the tumor in a manner that creates seeding of the tumor, resulting in metastasis. In recent years development of products has been directed with an emphasis on minimizing the traumatic nature of traditional surgical procedures. 
     There has been a relatively significant amount of activity in the area of hyperthermia as a tool for treatment of tumors. It is known that elevating the temperature of tumors is helpful in the treatment and management of cancerous tissues. The mechanisms of selective cancer cell eradication by hyperthermia are not completely understood. However, four cellular effects of hyperthermia on cancerous tissue have been proposed, (i) changes in cell or nuclear membrane permeability or fluidity, (ii) cytoplasmic lysomal disintegration, causing release of digestive enzymes, (iii) protein thermal damage affecting cell respiration and the synthesis of DNA or RNA and (iv) potential excitation of immunologic systems. Treatment methods for applying heat to tumors include the use of direct contact radio-frequency (RF) applicators, microwave radiation, inductively coupled RF fields, ultrasound, and a variety of simple thermal conduction techniques. 
     Among the problems associated with all of these procedures is the requirement that highly localized heat be produced at depths of several centimeters beneath the surface of the body. Certain techniques have been developed with microwave radiation and ultrasound to focus energy at various desired depths. RF applications may be used at depth during surgery. However, the extent of localization is generally poor, with the result that healthy tissue may be harmed. Induction heating gives rise to poor localization of the incident energy as well. Although induction heating may be achieved by placing an antenna on the surface of the body, superficial eddy currents are generated in the immediate vicinity of the antenna. When it is driven using RF current unwanted surface heating occurs diminishing heating to the underlying tissue. 
     Thus, non-invasive procedures for providing heat to internal tumors have had difficulties in achieving substantial specific and selective treatment. 
     Hyperthermia, which can be produced from an RF or microwave source, applies heat to tissue but does not exceed 45 degrees C. so that normal cells survive. In thermotherapy, heat energy of greater than 45 degrees C. is applied, resulting in histological damage, desiccation and the denaturization of proteins. Hyperthermia has been applied more recently for therapy of malignant tumors. In hyperthermia, it is desirable to induce a state of hyperthermia that is localized by interstitial current heating to a specific area while concurrently insuring minimum thermal damage to healthy surrounding tissue. Often, the tumor is located subcutaneously and addressing the tumor requires either surgery, endoscopic procedures or external radiation. It is difficult to externally induce hyperthermia in deep body tissue because current density is diluted due to its absorption by healthy tissue. Additionally, a portion of the RF energy is reflected at the muscle/fat and bone interfaces which adds to the problem of depositing a known quantity of energy directly on a small tumor. 
     Attempts to use interstitial local hyperthermia have not proven to be very successful. Results have often produced nonuniform temperatures throughout the tumor. It is believed that tumor mass reduction by hyperthermia is related the thermal dose. Thermal dose is the minimum effective temperature applied throughout the tumor mass for a defined period of time. Because blood flow is the major mechanism of heat loss for tumors being heated, and blood flow varies throughout the tumor, more even heating of tumor tissue is needed to ensure more effective treatment. 
     The same is true for ablation of the tumor itself through the use of RF energy. Different methods have been utilized for the RF ablation of masses such as tumors. Instead of heating the tumor it is ablated through the application of energy. This process has been difficult to achieve due to a variety of factors including, (i) positioning of the RF ablation electrodes to effectively ablate all of the mass, (ii) introduction of the RF ablation electrodes to the tumor site and (iii) controlled delivery and monitoring of RF energy to achieve successful ablation without damage to non-tumor tissue. 
     There have been a number of different treatment methods and devices for minimally invasively treating tumors. One such example is an endoscope that produces RF hyperthermia in tumors, as disclosed in U.S. Pat. No. 4,920,978. A microwave endoscope device is described in U.S. Pat. No. 4,409,993. In U.S. Pat. No. 4,920,978, an endoscope for RF hyperthermia is disclosed. 
     In U.S. Pat. No. 4,763,671, a minimally invasive procedure utilizes two catheters that are inserted interstitially into the tumor. The catheters are placed within the tumor volume and each is connect to a high frequency power source. 
     In U.S. Pat. No. 4,565,200, an electrode system is described in which a single entrance tract cannula is used to introduce an electrode into a selected body site. 
     However, as an effective treatment device, electrodes must be properly positioned relative to the tumor. After the electrodes are positioned, it is then desirable to have controlled application and deposition of RF energy to ablate the tumor. This reduces destruction of healthy tissue. 
     There is a need for a RF tumor treatment apparatus that is useful for minimally invasive procedures. It would be desirable for such a device to surround the exterior of the tumor with treatment electrodes, defining a controlled ablation volume, and subsequently the electrodes deliver a controlled amount of RF energy. Additionally, there is a need for a device with infusion capabilities during a pre-ablation step, and after ablation the surrounding tissue can be preconditioned with electromagnetic (“EM”) energy at hyperthermia temperatures less than 45 degrees. This would provide for the synergistic affects of chemotherapy and the instillation of a variety of fluids at the tumor site after local ablation and hyperthermia. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the invention, an infusion array ablation apparatus includes an elongated delivery device having a lumen and an infusion array positionable in the lumen. The infusion array includes an RF electrode and at least a first and a second infusion member. Each infusion member has a tissue piercing distal portion and an infusion lumen. At least one of the first or second infusion members is positionable in the elongated delivery device in a compacted state and deployable from the elongated delivery device with curvature in a deployed state. Also, at least one of the first or second infusion members exhibits a changing direction of travel when advanced from the elongated delivery device to a selected tissue site. At least one infusion port is coupled to one of the elongated delivery device, the infusion array, the first infusion member or the second infusion member. 
     In another embodiment, a tissue ablation apparatus includes a delivery catheter, with distal and proximal ends. A handle is attached to the proximal end of the delivery catheter. An electrode deployment apparatus is positioned at least partially in the delivery catheter. It includes a plurality of electrodes that are retractable in and out of the catheter&#39;s distal end. The electrodes are in a non-deployed state when they are positioned within the delivery catheter. As they are advanced out the distal end of the catheter they become deployed, and define an ablation volume. Each electrode has a first section with a first radius of curvature, and a second section, extending beyond the first section, having a second radius of curvature or a substantially linear geometry. Alternatively, each deployed electrode has at least two radii of curvature that are formed when the needle is advanced through the delivery catheter&#39;s distal end and becomes positioned at a selected tissue site. Also each deployed electrode can have at least one radius of curvature in two or more planes. Further, the electrode deployment apparatus can include at least one deployed electrode having at least radii of curvature, and at least one deployed electrode with at least one radius of curvature in two or more planes. 
     In a further embodiment, the electrode deployment apparatus has at least one deployed electrode with at least one curved section that is located near the distal end of the delivery catheter, and a non-curved section which extends beyond the curved section of the deployed electrode. The electrode deployment apparatus also has at least one deployed electrode with at least two radii of curvature. 
     In another embodiment of the invention, each deployed electrode has at least one curved section located near the distal end of the delivery catheter, and a non-curved section that extends beyond the curved section of the deployed electrode. 
     An electrode template can be positioned at the distal end of the delivery catheter. It assists in guiding the deployment of the electrodes to a surrounding relationship at an exterior of a selected mass in a tissue. The electrodes can be hollow. An adjustable electrode insulator can be positioned in an adjacent, surrounding relationship to all or some of the electrodes. The electrode insulator is adjustable, and capable of being advanced and retracted along the electrodes in order to define an electrode conductive surface. 
     The electrode deployment apparatus can include a cam which advances and retracts the electrodes in and out of the delivery catheter&#39;s distal end. Optionally included in the delivery catheter are one or more guide tubes associated with one or more electrodes. The guide tubes are positioned at the delivery catheter&#39;s distal end. 
     Sources of infusing mediums, including but not limited to electrolytic and chemotherapeutic solutions, can be associated with the hollow electrodes. Electrodes can have sharpened, tapered ends in order to assist their introduction through tissue, and advancement to the selected tissue site. 
     The electrode deployment apparatus is removable from the delivery catheter. An obturator is initially positioned within the delivery catheter. It can have a sharpened distal end. The delivery catheter can be advanced percutaneously to an internal body organ, or site, with the obturator positioned in the delivery catheter. Once positioned, the obturator is removed, and the electrode deployment apparatus is inserted into the delivery catheter. The electrodes are in non-deployed states, and preferably compacted or spring-loaded, while positioned within the delivery catheter. They are made of a material with sufficient strength so that as the electrodes emerge from the delivery catheter&#39;s distal end they are deployed three dimensionally, in a lateral direction away from the periphery of the delivery catheter&#39;s distal end. The electrodes continue their lateral movement until the force applied by the tissue causes the needles to change their direction of travel. 
     Each electrode now has either, (i) a first section with a first radius of curvature, and a second section, extending beyond the first section, having a second radius of curvature or a substantially linear section, (ii) two radii of curvature, (iii) one radius of curvature in two or more planes, or (iv) a combination of two radii of curvature with one of them in two or more planes. Additionally, the electrode deployment apparatus can include one or more of these deployed geometries for the different electrodes in the plurality. It is not necessary that every electrode have the same deployed geometry. 
     After the electrodes are positioned around a mass, such as a tumor, a variety of solutions, including but not limited to electrolytic fluids, can be introduced through the electrodes to the mass in a pre-ablation step. RF energy is applied, and the mass is desiccated. In a post-ablation procedure, a chemotherapeutic agent can then be introduced to the site, and the electrodes are then retracted back into the introducing catheter. The entire ablative apparatus can be removed, or additional ablative treatments be conducted. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of the tissue ablation apparatus of the invention, including a delivery catheter, handle, and deployed electrodes. 
         FIG. 2  is a cross-sectional view of the tissue ablation apparatus of the invention illustrated in  FIG. 1 . 
         FIG. 3  is a perspective view of an electrode of the invention with two radii of curvature. 
         FIG. 4  is a perspective view of an electrode of the invention with one radius of curvature in three planes. 
         FIG. 5  is a perspective view of an electrode of the invention with one curved section, positioned close to the distal end of the delivery catheter, and a linear section. 
         FIG. 6  is a perspective view of an electrode of the invention with one curved section, positioned close to the distal end of the delivery catheter, a generally first linear section, and then a second linear section that continues laterally with regard to the first linear section. 
         FIG. 7  is a cross-section view of a delivery catheter associated with the invention, with guide tubes positioned at the distal end of the delivery catheter. 
         FIG. 8  is a cross-sectional view of an electrode of the invention. 
         FIG. 9  is a perspective view of the tissue ablation apparatus of the invention shown in  FIG. 1 , with the delivery catheter being introduced percutaneously through the body and positioned at the exterior, or slightly piercing, a liver with a tumor to be ablated. 
         FIG. 10  is a perspective view of the tissue ablation apparatus of the invention with an obturator positioned in the delivery catheter. 
         FIG. 11  is a perspective view of the tissue ablation apparatus of the invention shown in  FIG. 10 , positioned in the body adjacent to the liver, with the obturator removed. 
         FIG. 12  is a perspective view of the tissue ablation apparatus of the invention shown in  FIG. 10 , positioned in the body adjacent to the liver, and the electrode deployment apparatus, with an electrode template, is positioned in the delivery catheter in place of the obturator. 
         FIG. 13  is a perspective view of the ablation apparatus of the invention, with deployed electrodes surrounding a tumor and defining an ablation volume. 
         FIG. 14  is a perspective view of the tissue ablation apparatus of the invention shown in  FIG. 10 , positioned in the body adjacent to the liver, with deployed electrodes surrounding a tumor and infusing a solution to the tumor site during a pre-ablation procedure. 
         FIG. 15  is a perspective view of the tissue ablation apparatus of the invention shown in  FIG. 10 , illustrating application of RF energy to the tumor. 
         FIG. 16  is a perspective view of the tissue ablation apparatus of the invention, illustrating the electro-desiccation of the tumor. 
         FIG. 17  is a perspective view of the tissue ablation apparatus of the invention, illustrating the instillation of solutions to the tumor site during a post-ablation procedure. 
         FIG. 18  illustrates bipolar ablation between electrodes of the invention. 
         FIG. 19  illustrates monopolar ablation between electrodes of the invention. 
         FIG. 20  is a perspective view of an ablation system of the invention, including RF and ultrasound modules, and a monitor. 
         FIG. 21  is a block diagram of the ablation system of the invention. 
         FIG. 22(   a ) is a cross-sectional view of an RF treatment apparatus of the invention. 
         FIG. 22(   b ) is a close up cross-sectional view of the distal end of the RF treatment apparatus of  FIG. 22(   a ). 
         FIG. 22(   c ) is a close up cross-sectional view of the RF treatment apparatus of  FIG. 22(   a ), illustrating the proximal end of the insulation sleeve and a thermocouple associated with the insulation sleeve. 
         FIG. 22(   d ) is a close up cross-sectional view of the RF treatment apparatus of  FIG. 22(   a ), illustrating the proximal end of the RF treatment apparatus of  FIG. 22  ( a ). 
         FIG. 23  is an exploded view of an RF treatment apparatus of the invention. 
         FIG. 24  is a cross-sectional view of the RF treatment apparatus of the invention illustrating the electrode, insulation sleeve and the associated thermal sensors. 
         FIG. 25(   a ) is a perspective view of the RF treatment apparatus of the invention with the infusion device mounted at the distal end of the catheter. 
         FIG. 25   b  is a perspective view of the RF treatment apparatus of  FIG. 25(   a ) illustrating the removal of the catheter, and electrode attached to the distal end of the electrode, from the infusion device which is left remaining in the body. 
         FIG. 26(   a ) is a perspective view of the RF treatment apparatus of the invention with the electrode mounted at the distal end of the catheter. 
         FIG. 26(   b ) is a perspective view of the RF treatment apparatus of  FIG. 26(   a ) illustrating the removal of the introducer from the lumen of the electrode. 
         FIG. 27(   a ) is a perspective view of the RF treatment apparatus of the invention with the introducer removed from the lumen of the electrode. 
         FIG. 27(   b ) is a perspective view of the apparatus of  FIG. 27(   a ) illustrating the removal of the electrode from the catheter, leaving behind the insulation sleeve. 
         FIG. 28(   a ) is a perspective view of the RF ablation apparatus of the invention with the insulation sleeve positioned in a surrounding relationship to the electrode which is mounted to the distal end of the catheter. 
         FIG. 28(   b ) is a perspective view of the RF ablation apparatus of  FIG. 28(   a ) illustrating the removal of the insulation sleeve from the electrode. 
         FIG. 28(   c ) is a perspective view of the insulation sleeve after it is removed from the electrode. 
         FIG. 29(   a ) is a perspective view illustrating the attachment of a syringe to the device of  FIG. 27(   a ). 
         FIG. 29(   b ) is a perspective view of a syringe, containing a fluid medium such as a chemotherapeutic agent, attached to the RF ablation apparatus of  FIG. 27(   a ). 
         FIG. 30  is a block diagram of an RF treatment system of the invention. 
         FIG. 31(   a ) is a schematic diagram, consisting of panels  31 A- 1  and  31 A- 2 , of a power supply suitable for use with the invention. 
         FIG. 31(   b ) is a schematic diagram of a voltage sensor suitable useful with the invention. 
         FIG. 31(   c ) is a schematic diagram of a current sensor suitable useful with the invention. 
         FIG. 31(   d ) is a schematic diagram of power computing circuits suitable useful with the invention. 
         FIG. 31(   e ) is a schematic diagram of an impedance computing circuit suitable useful with the invention. 
         FIG. 31(   f ) is a schematic diagram of a power control device suitable useful with the invention. 
         FIG. 31(   g ) is a schematic diagram, consisting of panels  31 G- 1  through  31 G- 4 , of an eight channel temperature measurement suitable for use with the invention. 
         FIG. 31(   h ) is a schematic diagram, consisting of panels  31 H- 1  and  31 H- 2 , of a power and temperature control circuit useful with the invention. 
         FIG. 32  is a block diagram of an embodiment of the invention which includes a microprocessor. 
         FIG. 33  illustrates the use of two RF treatment apparatus, such as the one illustrated in  FIG. 22(   a ), that are used in a bipolar mode. 
     
    
    
     DETAILED DESCRIPTION 
     A tissue ablation apparatus  10  of the invention is illustrated in  FIG. 1 . Ablation apparatus  10  includes a delivery catheter  12 , well known to those skilled in the art, with a proximal end  14  and a distal end  16 . Delivery catheter  12  can be of the size of about 5 to 16 F. A handle  18  is removably attached to proximal end  14 . An electrode deployment device is at least partially positioned within delivery catheter  12 , and includes a plurality of electrodes  20  that are retractable in and out of distal end  16 . Electrodes  20  can be of different sizes, shapes and configurations. In one embodiment, they are needle electrodes, with sizes in the range of 27 to 14 gauge. Electrodes  20  are in non-deployed positions while retained in delivery catheter. In the non-deployed positions, electrodes  20  may be in a compacted state, spring loaded, generally confined or substantially straight if made of a suitable memory metal such as nitinol. As electrodes  20  are advanced out of distal end  16  they become distended in a deployed state, which defines an ablative volume, from which tissue is ablated as illustrated more fully in  FIG. 2 . Electrodes  20  operate either in the bipolar or monopolar modes. When the electrodes are used in the bipolar mode, the ablative volume is substantially defined by the peripheries of the plurality of electrodes  20 . In one embodiment, the cross-sectional width of the ablative volume is about 4 cm. However, it will be appreciated that different ablative volumes can be achieved with tissue ablation apparatus  10 . 
     The ablative volume is first determined to define a mass, such as a tumor, to be ablated. Electrodes  20  are placed in a surrounding relationship to a mass or tumor in a predetermined pattern for volumetric ablation. An imaging system is used to first define the volume of the tumor or selected mass. Suitable imaging systems include but are not limited to, ultrasound, computerized tomography (CT) scanning, X-ray film, X-ray fluoroscopy, magnetic resonance imaging, electromagnetic imaging, and the like. The use of such devices to define a volume of a tissue mass or a tumor is well known to those skilled in the art. 
     With regard to the use of ultrasound, an ultrasound transducer transmits ultrasound energy into a region of interest in a patient&#39;s body. The ultrasound energy is reflected by different organs and different tissue types. Reflected energy is sensed by the transducer, and the resulting electrical signal is processed to provide an image of the region of interest. In this way, the ablation volume is then ascertained, and the appropriate electrode deployment device is inserted into delivery catheter  12 . 
     The ablative volume is substantially defined before ablation apparatus  10  is introduced to an ablative treatment position. This assists in the appropriate positioning of ablation apparatus  10 . In this manner, the volume of ablated tissue is reduced and substantially limited to a defined mass or tumor, including a certain area surrounding such a tumor, that is well controlled and defined. A small area around the tumor is ablated in order to ensure that all of the tumor is ablated. 
     With reference again to  FIG. 2 , electrode sections  20 ( a ) are in deployed states when they are introduced out of distal end  16 . Although electrodes  20  are generally in a non-distended configuration in the non-deployed state while positioned in delivery catheter  12 , they can also be distended. Generally, electrode sections  20 ( b ) are in retained positions while they are non-deployed. This is achieved by a variety of methods including but not limited to, (i) the electrodes are pre-sprung, confined in delivery catheter  12 , and only become sprung (expanded) as they are released from delivery catheter  12 , (ii) the electrodes are made of a memory metal, as explained in further detail below, (iii) the electrodes are made of a selectable electrode material which gives them an expanded shape outside of delivery catheter  12 , or (iv) delivery catheter  12  includes guide tubes which serve to confine electrodes  12  within delivery catheter  12  and guide their direction of travel outside of the catheter to form the desired, expanded ablation volume. As shown in  FIG. 2 , electrodes  20  are pre-sprung while retained in delivery catheter  12 . This is the non-deployed position. As they are advanced out of delivery catheter  12  and into tissue, electrodes  20  become deployed and begin to “fan” out from distal end  16 , moving in a lateral direction relative to a longitudinal axis of delivery catheter  12 . As deployed electrodes  20  continue their advancement, the area of the fan increases and extends beyond the diameter of distal end  16 . 
     Significantly, each electrode  20  is distended in a deployed position, and collectively, the deployed electrodes  20  define a volume of tissue that will be ablated. As previously mentioned, when it is desired to ablate a tumor, either benign or malignant, it is preferable to ablate an area that is slightly in excess to that defined by the exterior surface of the tumor. This improves the chances that all of the tumor is eradicated. 
     Deployed electrodes  20  can have a variety of different deployed geometries including but not limited to, (i) a first section with a first radius of curvature, and a second section, extending beyond the first section, having a second radius of curvature or a substantially linear geometry, (ii) at least two radii of curvature, (iii) at least one radius of curvature in two or more planes, (iv) a curved section, with an elbow, that is located near distal end  16  of delivery catheter, and a non-curved section that extends beyond the curved section, or (v) a curved section near distal end  16 , a first linear section, and then another curved section or a second linear section that is angled with regard to the first linear section. Deployed electrodes  20  need not be parallel with respect to each other. The plurality of deployed electrodes  20 , which define a portion of the needle electrode deployment device, can all have the same deployed geometries, i.e., all with at least two radii of curvature, or a variety of geometries, i.e., one with two radii of curvature, a second one with one radius of curvature in two planes, and the rest a curved section near distal end  16  of delivery catheter  12  and a non-curved section beyond the curved section. 
     A cam  22 , or other actuating device, can be positioned within delivery catheter and used to advance and retract electrodes  20  in and out of delivery catheter  12 . The actual movement of cam can be controlled at handle  18 . Suitable cams are of conventional design, well known to those skilled in the art. 
     The different geometric configurations of electrodes  20  are illustrated in  FIGS. 3 through 6 . In  FIG. 3 , electrode  20  has a first radius of curvature  20 ( c ) and a second radius of curvature  20 ( d ). It can include more than two radii of curvature. As shown in  FIG. 4 , electrode  20  has at least one radius of curvature which extends to three planes. In  FIG. 5 , each electrode has a first curved section  20 ( e ) which is near distal end  16  of delivery catheter  12 . A first generally linear section  20 ( f ) extends beyond curved section  20 ( e ), and the two meet at an elbow  20 ( g ). The electrodes  20  can serve as anodes and cathodes. The plurality of electrodes  20  can have linear sections  20 ( f ) that are generally parallel to each other, or they can be non-parallel.  FIG. 6  illustrates an electrode  20  that includes a first curved section  20 ( e ) positioned near distal end  16  of delivery catheter  12 , a first linear section  20 ( f ), and a second linear section  20 ( h ) which extends beyond first linear section  20 ( f ). Section  20 ( h ) can be linear, curved, or a combination of the two. The plurality of electrodes  20  illustrated in  FIG. 6  can have parallel or non-parallel first linear sections  20 ( f ). 
     In one embodiment of the invention, electrodes  20  are spring-loaded, and compacted in their non-deployed positions. As electrodes  20  are advanced out of distal end  16  of delivery catheter  12 , they become deployed and fan out. Electrodes  20  continue this fanning out direction until the resistance of the tissue overcomes the strength of the material forming electrode  20 . This causes electrode  20  to bend and move in a direction inward relative to its initial outward fanning direction. The bending creates curved sections  20 ( c ) and  20 ( d ) of  FIG. 3 , and can also result in the formation of the other electrode  20  geometries of  FIGS. 4 ,  5  and  6 . The extent of electrode  20  fan like travel is dependent on the strength of the material from which it is made. Suitable electrode materials include stainless steel, platinum, gold, silver, copper and other electromagnetic conducting materials including conductive polymers. Preferably, electrode  20  is made of stainless steel or nickel titanium and has dimensions of about 27 to 14 gauge. 
     In one embodiment, electrode  20  is made of a memory metal, such as nickel titanium, commercially available from Raychem Corporation, Menlo Park, Calif. Additionally, a resistive heating element can be positioned in an interior lumen of electrode  20 . Resistive heating element can be made of a suitable metal that transfers heat to electrode  20 , causing deployed electrode  20  to become deflected when the temperature of electrode  20  reaches a level that causes the electrode material, such as a memory metal, to deflect, as is well known in the art. Not all of electrode  20  need be made of a memory metal. It is possible that only that distal end portion of electrode  20 , which is introduced into tissue, be made of the memory metal in order to effect the desired deployed geometrical configuration. Additionally, mechanical devices, including but not limited to steering wires, can be attached to the distal end of electrode  20  to cause it to become directed, deflected and move about in a desired direction about the tissue, until it reaches its final resting position to ablate a tissue mass. 
     Optionally included in the delivery catheter are one or more guide tubes  24 ,  FIG. 7 , which serve to direct the expansion of electrodes  20  in the fan pattern as they are advanced out of distal end  16  of the delivery catheter  12 . Guide tubes  24  can be made of stainless steel, spring steel and thermal plastics including but not limited to nylon and polyesters, and are of sufficient size and length to accommodate the electrodes to a specific site in the body. 
       FIG. 8  illustrates one embodiment of electrode  20  with a sharpened distal end  24 . By including a tapered, or piercing end  24 , the advancement of electrode  20  through tissue is easier. Electrode  20  can be segmented, and include a plurality of fluid distribution ports  26 , which can be evenly formed around all or only a portion of electrode  20 . Fluid distribution ports  26  are formed in electrode  20  when it is hollow and permit the introduction and flow of a variety of fluidic mediums through electrode  20  to a desired tissue site. Such fluidic mediums include, but are not limited to, electrolytic solutions, pastes or gels, as well as chemotherapeutic agents. Examples of suitable conductive gels are carboxymethyl cellulose gels made from aqueous electrolyte solutions such as physiological saline solutions, and the like. 
     The size of fluid distribution ports  26  can vary, depending on the size and shape of electrode  20 . Also associated with electrode  20  is an adjustable insulator sleeve  28  that is slidable along an exterior surface of electrode  20 . Insulator sleeve  28  is advanced and retracted along electrode  20  in order to define the size of a conductive surface of electrode  20 . Insulator sleeve  28  is actuated at handle  18  by the physician, and its position along electrode  20  is controlled. When electrode  20  moves out of delivery catheter  12  and into tissue, insulator sleeve  28  can be positioned around electrode  20  as it moves its way through the tissue. Alternatively, insulator sleeve  28  can be advanced along a desired length of electrode  20  after electrode  20  has been positioned around a targeted mass to be ablated. Insulator sleeve is thus capable of advancing through tissue along with electrode  20 , or it can move through tissue without electrode  20  providing the source of movement. Thus, the desired ablation volume is defined by deployed electrodes  20 , as well as the positioning of insulator sleeve  28  on each electrode. In this manner, a very precise ablation volume is created. Suitable materials that form insulator sleeve include but are not limited to nylon, polyimides, other thermoplastics, and the like. 
       FIG. 9  illustrates a percutaneous application of tissue ablation apparatus  10 . Tissue ablation apparatus  10  can be used percutaneously to introduce electrodes  20  to the selected tissue mass or tumor. Electrodes  20  can remain in their non-deployed positions while being introduced percutaneously into the body, and delivered to a selected organ which contains the selected mass to be ablated. Delivery catheter  12  is removable from handle  18 . When it is removed, electrode deployment device (the plurality of electrodes  20 ) can be inserted and removed from delivery catheter  12 . An obturator  30  is inserted into delivery catheter  12  initially if a percutaneous procedure is to be performed. As shown in  FIG. 10 , obturator  30  can have a sharpened distal end  32  that pierces tissue and assists the introduction of delivery catheter  12  to a selected tissue site. The selected tissue site can be a body organ with a tumor or other mass, or the actual tumor itself. 
     Obturator  30  is then removed from delivery catheter  12  ( FIG. 11 ). Electrode deployment device is then inserted into delivery catheter  12 , and the catheter is then reattached to handle  18  ( FIG. 12 ). As illustrated in  FIG. 12 , electrode deployment device can optionally include an electrode template  34  to guide the deployment of electrodes  20  to a surrounding relationship at an exterior of a selected mass in the tissue. 
     Electrodes  20  are then advanced out of distal end  16  of delivery catheter  12 , and become deployed to form a desired ablative volume which surrounds the mass. In  FIG. 13 , delivery catheter  12  is positioned adjacent to the liver. Electrode deployment device is introduced into delivery catheter  12  with electrode template  34 . Electrode deployment device now pierces the liver, and cam  22  advances electrodes  20  out of delivery catheter  12  into deployed positions. Each individual electrode  20  pierces the liver and travels through it until it is positioned in a surrounding relationship to the tumor. The ablative volume is selectable, and determined first by imaging the area to be ablated. The ablative volume is defined by the peripheries of all of the deployed electrodes  20  that surround the exterior of the tumor. Once the volume of ablation is determined, then an electrode set is selected which will become deployed to define the ablation volume. A variety of different factors are important in creating an ablation volume. Primarily, different electrodes  20  will have various degrees of deployment, based on type of electrode material, the level of pre-springing of the electrodes and the geometric configuration of the electrodes in their deployed states. Tissue ablation apparatus  10  permits different electrode  20  sets to be inserted into delivery catheter  12 , in order to define a variety of ablation volumes. 
     Prior to ablation of the tumor, a pre-ablation step can be performed. A variety of different solutions, including electrolytic solutions such as saline, can be introduced to the tumor site, as shown in  FIG. 14 .  FIG. 15  illustrates the application of RF energy to the tumor. Electrode insulator  28  is positioned on portions of electrodes  20  where there will be no ablation. This further defines the ablation volume. The actual electro-desiccation of the tumor, or other targeted masses or tissues, is shown in  FIG. 16 . Again, deployed electrodes  20 , with their electrode insulators  28  positioned along sections of the electrodes, define the ablation volume, and the resulting amount of mass that is desiccated. 
     Optionally following desiccation, electrodes  20  can introduce a variety of solutions in a post-ablation process. This step is illustrated in  FIG. 17 . Suitable solutions include but are not limited to chemotherapeutic agents. 
       FIG. 8  illustrates tissue ablation apparatus  10  operated in a bipolar mode. Its monopolar operation is shown in  FIG. 19 . Each of the plurality of electrodes  20  can play different roles in the ablation process. There can be polarity shifting between the different electrodes. 
     A tissue ablation system  36 , which can be modular, is shown in  FIG. 20  and can include a display  38 . Tissue ablation system  36  can also include an RF energy source, microwave source, ultrasound source, visualization devices such as cameras and VCR&#39;s, electrolytic and chemotherapeutic solution sources, and a controller which can be used to monitor temperature or impedance. One of the deployed electrodes  20  can be a microwave antenna coupled to a microwave source. This electrode can initially be coupled to RF power source  42  and is then switched to the microwave source 
     Referring now to  FIG. 21 , a power supply  40  delivers energy into RF power generator (source)  42  and then to electrodes  20  of tissue ablation apparatus  10 . A multiplexer  46  measures current, voltage and temperature (at numerous temperature sensors which can be positioned on electrodes  20 ). Multiplexer  46  is driven by a controller  48 , which can be a digital or analog controller, or a computer with software. When controller  48  is a computer, it can include a CPU coupled through a system bus. This system can include a keyboard, disk drive, or other non-volatile memory systems, a display, and other peripherals, as known in the art. Also coupled to the bus are a program memory and a data memory. 
     An operator interface  50  includes operator controls  52  and display  38 . Controller  48  is coupled to imaging systems, including ultrasound transducers, temperature sensors, and viewing optics and optical fibers, if included. 
     Current and voltage are used to calculate impedance. Diagnostics are done through ultrasound, CT scanning, or other methods known in the art. Imaging can be performed before, during and after treatment. 
     Temperature sensors measure voltage and current that is delivered. The output of these sensors is used by controller  48  to control the delivery of RF power. Controller  48  can also control temperature and power. The amount of RF energy delivered controls the amount of power. A profile of power delivered can be incorporated in controller  38 , as well as a pre-set amount of energy to be delivered can also be profiled. 
     Feedback can be the measurement of impedance or temperature, and occurs either at controller  48  or at electromagnetic energy source  42 , e.g., RF or microwave, if it incorporates a controller. For impedance measurement, this can be achieved by supplying a small amount of non-ablation RF energy. Voltage and current are then measured. 
     Circuitry, software and feedback to controller  48  result in process control and are used to change, (i) power, including RF, ultrasound, and the like, (ii) the duty cycle (on-off and wattage), (iii) monopolar or bipolar energy delivery, (iv) and electrolytic solution delivery, flow rate and pressure and (v) determine when ablation is completed through time, temperature and/or impedance. These process variables can be controlled and varied based on temperature monitored at multiple sites, and impedance to current flow that is monitored, indicating changes in current carrying capability of the tissue during the ablative process. 
     Referring now to  FIGS. 22(   a ),  22 ( b ),  22 ( c ),  22  and  24  an RF treatment apparatus  110  is illustrated which can be used to ablate a selected tissue mass, including but not limited to a tumor, or treat the mass by hyperthermia. Treatment apparatus  110  includes a catheter  112  with a catheter lumen in which different devices are introduced and removed. An insert  114  is removably positioned in the catheter lumen. Insert  114  can be an introducer, a needle electrode, and the like. 
     When insert  114  is an introducer, including but not limited to a guiding or delivery catheter, it is used as a means for puncturing the skin of the body, and advancing catheter  112  to a desired site. Alternatively, insert  114  can be both an introducer and an electrode adapted to receive RF current for tissue ablation and hyperthermia. 
     If insert  114  is not an electrode, then a removable electrode  116  is positioned in insert  114  either during or after treatment apparatus  110  has been introduced percutaneously to the desired tissue site. Electrode  116  has an electrode distal end that advances out of an insert distal end. In this deployed position, RF energy is introduced to the tissue site along a conductive surface of electrode  116 . 
     Electrode  116  can be included in treatment apparatus  110 , and positioned within insert  114 , while treatment apparatus  110  is being introduced to the desired tissue site. The distal end of electrode  116  can have substantially the same geometry as the distal end of insert  114  so that the two ends are essentially flush. Distal end of electrode  116 , when positioned in insert  114  as it is introduced through the body, serves to block material from entering the lumen of insert  114 . The distal end of electrode  116  essentially can provide a plug type of function. 
     Electrode  116  is then advanced out of a distal end of insert  114 , and the length of an electrode conductive surface is defined, as explained further in this specification. Electrode  116  can advance straight, laterally or in a curved manner out of distal end of insert  114 . Ablative or hyperthermia treatment begins when two electrodes  116  are positioned closely enough to effect bipolar treatment of the desired tissue site or tumor. A return electrode attaches to the patients skin. Operating in a bipolar mode, selective ablation of the tumor is achieved. However, it will be appreciated that the present invention is suitable for treating, through hyperthermia or ablation, different sizes of tumors or masses. The delivery of RF energy is controlled and the power at each electrode is maintained, independent of changes in voltage or current. Energy is delivered slowly at low power. This minimizes desiccation of the tissue adjacent to the electrodes  116 , permitting a wider area of even ablation. In one embodiment, 8 to 14 W of RE energy is applied in a bipolar mode for 10 to 25 minutes. An ablation area between electrodes 116 of about 2 to 6 cm is achieved. 
     Treatment apparatus  110  can also include a removable introducer  118  which is positioned in the insert lumen instead of electrode  116 . Introducer  118  has an introducer distal end that also serves as a plug, to minimize the entrance of material into the insert distal end as it advances through a body structure. Introducer  118  is initially included in treatment apparatus, and is housed in the lumen of insert  114 , to assist the introduction of treatment apparatus  110  to the desired tissue site. Once treatment apparatus  110  is at the desired tissue site, then introducer  118  is removed from the insert lumen, and electrode  116  is substituted in its place. In this regard, introducer  118  and electrode  116  are removable to and from insert  114 . 
     Also included is an insulator sleeve  120  coupled to an insulator slide  122 . Insulator sleeve  120  is positioned in a surrounding relationship to electrode  116 . Insulator slide  122  imparts a slidable movement of the insulator sleeve along a longitudinal axis of electrode  116  in order to define an electrode conductive surface that begins at an insulator sleeve distal end. 
     A thermal sensor  124  can be positioned in or on electrode  116  or introducer  118 . A thermal sensor  126  is positioned on insulator sleeve  120 . In one embodiment, thermal sensor  124  is located at the distal end of introducer  118 , and thermal sensor  126  is located at the distal end of insulator sleeve  120 , at an interior wall which defines a lumen of insulator sleeve  120 . Suitable thermal sensors include a T type thermocouple with copper constantene, J type, E type, K type, thermistors, fiber optics, resistive wires, thermocouples IR detectors, and the like. It will be appreciated that sensors  124  and  126  need not be thermal sensors. 
     Catheter  112 , insert  114 , electrode  116  and introducer  118  can be made of a variety of materials. In one embodiment, catheter  112  is black anodized aluminum, 0.5 inch, electrode  116  is made of stainless steel, preferably 18 gauge, introducer  118  is made of stainless steel, preferably 21 gauge, and insulator sleeve  120  is made of polyimide. 
     By monitoring temperature, RF power delivery can be accelerated to a predetermined or desired level. Impedance is used to monitor voltage and current. The readings of thermal sensors  124  and  126  are used to regulate voltage and current that is delivered to the tissue site. The output for these sensors is used by a controller, described further in this specification, to control the delivery of RF energy to the tissue site. Resources, which can be hardware and/or software, are associated with an RF power source, coupled to electrode  116  and the return electrode. The resources are associated with thermal sensors  124  and  125 , the return electrode as well as the RF power source for maintaining a selected power at electrode  116  independent of changes in voltage or current. Thermal sensors  124  and  126  are of conventional design, including but not limited to thermistors, thermocouples, resistive wires, and the like. 
     Electrode  116  is preferably hollow and includes a plurality of fluid distribution ports  128  from which a variety of fluids can be introduced, including electrolytic solutions, chemotherapeutic agents, and infusion media. 
     A specific embodiment of the RF treatment device  110  is illustrated in  FIG. 23 . Included is an electrode locking cap  128 , an RF coupler  310 , an introducer locking cap  312 , insulator slide  122 , catheter body  112 , insulator retainer cap  134 , insulator locking sleeve  136 , a luer connector  138 , an insulator elbow connector  140 , an insulator adjustment screw  142 , a thermocouple cable  144  for thermal sensor  126 , a thermocouple cable  46  for thermal sensor  124  and a luer retainer  148  for an infusion device  150 . 
     In another embodiment of RF treatment apparatus  110 , electrode  116  is directly attached to catheter  112  without insert  114 . Introducer  118  is slidably positioned in the lumen of electrode  116 . Insulator sleeve  120  is again positioned in a surrounding relationship to electrode  116  and is slidably moveable along its surface in order to define the conductive surface. Thermal sensors  124  and  126  are positioned at the distal ends of introducer  118  and insulator sleeve  120 . Alternatively, thermal sensor  124  can be positioned on electrode  116 , such as at its distal end. The distal ends of electrode  116  and introducer  118  can be sharpened and tapered. This assists in the introduction of RE treatment apparatus to the desired tissue site. Each of the two distal ends can have geometries that essentially match. Additionally, distal end of introducer  118  can be an essentially solid end in order to prevent the introduction of material into the lumen of catheter  116 . 
     In yet another embodiment of RF treatment apparatus  110 , infusion device  150  remains implanted in the body after catheter  112 , electrode  116  and introducer  118  are all removed. This permits a chemotherapeutic agent, or other infusion medium, to be easily introduced to the tissue site over an extended period of time without the other devices of RF treatment apparatus  110  present. These other devices, such as electrode  116 , can be inserted through infusion device  150  to the tissue site at a later time for hyperthermia or ablation purposes. Infusion device  150  has an infusion device lumen and catheter  112  is at least partially positioned in the infusion device lumen. Electrode  116  is positioned in the catheter lumen, in a fixed relationship to catheter  112 , but is removable from the lumen. Insulator sleeve  120  is slidably positioned along a longitudinal axis of electrode  116 . Introducer  118  is positioned in a lumen of electrode  116  and is removable therefrom. A power source is coupled to electrode  116 . Resources are associated with thermal sensors  124  and  126 , voltage and current sensors that are coupled to the RF power source for maintaining a selected power at electrode  116 . 
     The distal end of RF treatment apparatus  110  is shown in  FIG. 22(   b ). Introducer  118  is positioned in the lumen of electrode  116 , which can be surrounded by insulator sleeve  120 , all of which are essentially placed in the lumen of infusion device  150 . It will be appreciated, however, that in  FIG. 22(   b ) insert  114  can take the place of electrode  116 , and electrode  116  can be substituted for introducer  118 . 
     The distal end of insulator sleeve  120  is illustrated in  FIG. 22(   c ). Thermal sensor  126  is shown as being in the form of a thermocouple. In  FIG. 22(   d ), thermal sensor  124  is also illustrated as a thermocouple that extends beyond a distal end of introducer  118 , or alternative a distal end of electrode  116 . 
     Referring now to  FIGS. 25(   a ) and  25 ( b ), infusion device  150  is attached to the distal end of catheter  112  and retained by a collar. The collar is rotated, causing catheter  112  to become disengaged from infusion device  150 . Electrode  116  is attached to the distal end of catheter  112 . Catheter  112  is pulled away from infusion device  150 , which also removes electrode  116  from infusion device  150 . Thereafter, only infusion device  150  is retained in the body. While it remains placed, chemotherapeutic agents can be introduced through infusion device  150  to treat the tumor site. Additionally, by leaving infusion device  150  in place, catheter  112  with electrode  116  can be reintroduced back into the lumen of infusion device  150  at a later time for additional RF treatment in the form of ablation or hyperthermia. 
     In  FIG. 26(   a ), electrode  116  is shown as attached to the distal end of catheter  112 . Introducer  118  is attached to introducer locking cap  132  which is rotated and pulled away from catheter  112 . As shown in  FIG. 26(   b ) this removes introducer  118  from the lumen of electrode  116 . 
     Referring now to  FIG. 27(   a ), electrode  116  is at least partially positioned in the lumen of catheter  112 . Electrode locking cap  128  is mounted at the proximal end of catheter  112 , with the proximal end of electrode  116  attaching to electrode locking cap  128 . Electrode locking cap  128  is rotated and unlocks from catheter  112 . In  FIG. 27(   b ), electrode locking cap  128  is then pulled away from the proximal end of catheter  112 , pulling with it electrode  116  which is then removed from the lumen of catheter  112 . After electrode  116  is removed from catheter  112 , insulator sleeve  120  is locked on catheter  112  by insulator retainer cap  134 . 
     In  FIG. 28(   a ), insulator retainer cap  134  is unlocked and removed from catheter  112 . As shown in  FIG. 28(   b ), insulator sleeve  120  is then slid off of electrode  116 .  FIG. 28(   c ) illustrates insulator sleeve  120  completely removed from catheter  112  and electrode  116 . 
     Referring now to  FIGS. 29(   a ) and  29 ( b ), after introducer  118  is removed from catheter  112 , a fluid source, such as syringe  151 , delivering a suitable fluid, including but not limited to a chemotherapeutic agent, attaches to luer connector  138  at the proximal end of catheter  112 . Chemotherapeutic agents are then delivered from syringe  151  through electrode  116  to the tumor site. Syringe  151  is then removed from catheter  112  by imparting a rotational movement of syringe  151  and pulling it away from catheter  112 . Thereafter, electrode  116  can deliver further RF power to the tumor site. Additionally, electrode  116  and catheter  112  can be removed, leaving only infusion device  150  in the body. Syringe  151  can then be attached directly to infusion device  150  to introduce a chemotherapeutic agent to the tumor site. Alternatively, other fluid delivery devices can be coupled to infusion device  150  in order to have a more sustained supply of chemotherapeutic agents to the tumor site. 
     Once chemotherapy is completed, electrode  116  and catheter  112  can be introduced through infusion device  150 . RE power is then delivered to the tumor site. The process begins again with the subsequent removal of catheter  112  and electrode  116  from infusion device  150 . Chemotherapy can then begin again. Once it is complete, further RE power can be delivered to the tumor site. This process can be repeated any number of times for an effective multi-modality treatment of the tumor site. 
     Referring now to  FIG. 30 , a block diagram of power source  152  is illustrated. Power source  152  includes a power supply  154 , power circuits  156 , a controller  158 , a power and impedance calculation device  160 , a current sensor  162 , a voltage sensor  164 , a temperature measurement device  166  and a user interface and display  168 . 
       FIGS. 31(   a ) through  31 ( g ) are schematic diagrams of power supply  154 , voltage sensor  164 , current sensor  162 , power computing circuit associated with power and impedance calculation device  160 , impedance computing circuit associated with power and impedance calculation device  160 , power control circuit of controller  158  and an eight channel temperature measurement circuit of temperature measure device  166 , respectively. 
     Current delivered through each electrode  116  is measured by current sensor  162 . Voltage between the electrodes  116  is measured by voltage sensor  164 . Impedance and power are then calculated at power and impedance calculation device  160 . These values can then be displayed at user interface  168 . Signals representative of power and impedance values are received by controller  158 . 
     A control signal is generated by controller  158  that is proportional to the difference between an actual measured value, and a desired value. The control signal is used by power circuits  156  to adjust the power output in an appropriate amount in order to maintain the desired power delivered at the respective electrode  116 . 
     In a similar manner, temperatures detected at thermal sensors  124  and  126  provide feedback for maintaining a selected power. The actual temperatures are measured at temperature measurement device  166 , and the temperatures are displayed at user interface  168 . Referring now to  FIG. 31(   h ), a control signal is generated by controller  159  that is proportional to the difference between an actual measured temperature, and a desired temperature. The control signal is used by power circuits  157  to adjust the power output in an appropriate amount in order to maintain the desired temperature delivered at the respective sensor  124  or  126 . 
     Controller  158  can be a digital or analog controller, or a computer with software. When controller  158  is a computer it can include a CPU coupled through a system bus. On this system can be a keyboard, a disk drive, or other non-volatile memory systems, a display, and other peripherals, as are known in the art. Also coupled to the bus are a program memory and a data memory. 
     User interface  168  includes operator controls and a display. Controller  158  can be coupled to imaging systems, including but not limited to ultrasound, CT scanners and the like. 
     Current and voltage are used to calculate impedance. Diagnostics can be performed optically, with ultrasound, CT scanning, and the like. Diagnostics are performed either before, during and after treatment. 
     The output of current sensor  162  and voltage sensor  164  is used by controller  158  to maintain the selected power level at electrodes  116 . The amount of RF energy delivered controls the amount of power. A profile of power delivered can be incorporated in controller  158 , and a pre-set amount of energy to be delivered can also be profiled. 
     Circuitry, software and feedback to controller  158  result in process control, and the maintenance of the selected power that is independent of changes in voltage or current, and are used to change, (i) the selected power, including RF, ultrasound and the like, (ii) the duty cycle (on-off and wattage), (iii) bipolar energy delivery and (iv) fluid delivery, including chemotherapeutic agents, flow rate and pressure.. These process variables are controlled and varied, while maintaining the desired delivery of power independent of changes in voltage or current, based on temperatures monitored at thermal sensors  124  and  126  at multiple sites. 
     Controller  158  can be microprocessor controlled. Referring now to  FIG. 32 , current sensor  162  and voltage sensor  164  are connected to the input of an analog amplifier  170 . Analog amplifier  170  can be a conventional differential amplifier circuit for use with thermal sensors  124  and  126 . The output of analog amplifier  170  is sequentially connected by an analog multiplexer  172  to the input of analog-to-digital converter  174 . The output of analog amplifier  170  is a voltage which represents the respective sensed temperatures. Digitized amplifier output voltages are supplied by analog-to-digital converter  174  to a microprocessor  176 . Microprocessor  176  may be a type 68HCII available from Motorola. However, it will be appreciated that any suitable microprocessor or general purpose digital or analog computer can be used to calculate impedance or temperature. 
     Microprocessor  176  sequentially receives and stores digital representations of impedance and temperature. Each digital value received by microprocessor  176  corresponds to different temperatures and impedances. 
     Calculated power and impedance values can be indicated on user interface  168 . Alternatively, or in addition to the numerical indication of power or impedance, calculated impedance and power values can be compared by microprocessor  176  with power and impedance limits. When the values exceed predetermined power or impedance values, a warning can be given on interface  168 , and additionally, the delivery of RF energy can be reduced, modified or interrupted. A control signal from microprocessor  176  can modify the power level supplied by power supply  154 . 
     An imaging system can be used to first define the volume of the tumor or selected mass. Suitable imaging systems include but are not limited to, ultrasound, CT scanning, X-ray film, X-ray fluoroscope, magnetic resonance imaging, electromagnetic imaging and the like. The use of such devices to define a volume of a tissue mass or a tumor is well known to those skilled in the art. 
     Specifically with ultrasound, an ultrasound transducer transmits ultrasound energy into a region of interest in a patient&#39;s body. The ultrasound energy is reflected by different organs and different tissue types. Reflected energy is sensed by the transducer, and the resulting electrical signal is processed to provide an image of the region of interest. In this way, the volume to be ablated is ascertained. 
     Ultrasound is employed to image the selected mass or tumor. This image is then imported to user interface  168 . The placement of electrodes  116  can be marked, and RF energy delivered to the selected site with prior treatment planning. Ultrasound can be used for real time imaging. Tissue characterization of the imaging can be utilized to determine how much of the tissue is heated. This process can be monitored. The amount of RF power delivered is low, and the ablation or hyperthermia of the tissue is slow. Desiccation of tissue between the tissue and each needle  116  is minimized by operating at low power. 
     The following examples illustrate the use of the invention with two RF treatment apparatus with two electrodes shown in  FIG. 33 , or a pair of two electrodes, that are used in a bipolar mode to ablate tissue. 
     EXAMPLE 1 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 1.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 1.5 
                 cm 
               
               
                   
                 Power setting: 
                 5 
                 W 
               
               
                   
                 Ablation time: 
                 10 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 2 
                 cm 
               
               
                   
                 length: 
                 1.7 
                 cm 
               
               
                   
                 depth: 
                 1.5 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 2 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 1.5 
                   
               
               
                   
                 Distance between electrodes: 
                 2.0 
                   
               
               
                   
                 Power setting: 
                 7.0 
                   
               
               
                   
                 Ablation time: 
                 10 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 2.8 
                 cm 
               
               
                   
                 length: 
                 2.5 
                 cm 
               
               
                   
                 depth: 
                 2.2 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 3 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.0 
                 cm 
               
               
                   
                 Power setting: 
                 10 
                 W 
               
               
                   
                 Ablation time: 
                 10 
                 min 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.0 
                 cm 
               
               
                   
                 length: 
                 2.7 
                 cm 
               
               
                   
                 depth: 
                 1.7 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 4 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 8 
                 W 
               
               
                   
                 Ablation time: 
                 10 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 2.8 
                 cm 
               
               
                   
                 length: 
                 2.7 
                 cm 
               
               
                   
                 depth: 
                 3.0 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 5 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 8 
                 W 
               
               
                   
                 Ablation time: 
                 12 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 2.8 
                 cm 
               
               
                   
                 length: 
                 2.8 
                 cm 
               
               
                   
                 depth: 
                 2.5 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 6 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 1.5 
                 cm 
               
               
                   
                 Power setting: 
                 8 
                 W 
               
               
                   
                 Ablation time: 
                 14 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.0 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 2.0 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 7 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 With return electrode at 
                 1.5 
                 cm 
               
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 8 
                 W 
               
               
                   
                 Ablation time: 
                 10 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.0 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 3.0 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 8 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 10 
                 W 
               
               
                   
                 Ablation time: 
                 12 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.5 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 2.3 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 9 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 11 
                 W 
               
               
                   
                 Ablation time: 
                 11 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.5 
                 cm 
               
               
                   
                 length: 
                 3.5 
                 cm 
               
               
                   
                 depth: 
                 2.5 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 10 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 3.0 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 3.0 
                 cm 
               
               
                   
                 Power setting: 
                 11 
                 W 
               
               
                   
                 Ablation time: 
                 15 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 4.3 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 2.2 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 11 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 3.0 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 11 
                 W 
               
               
                   
                 Ablation time: 
                 11 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 4.0 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 2.2 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 12 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Exposed electrode length: 
                 4.0 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 11 
                 W 
               
               
                   
                 Ablation time: 
                 16 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.5 
                 cm 
               
               
                   
                 length: 
                 4.0 
                 cm 
               
               
                   
                 depth: 
                 2.8 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 13 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 Two pairs of electrodes (Four electrodes) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 12 
                 W 
               
               
                   
                 Ablation time: 
                 16 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 3.5 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 4.5 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 14 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 Two pairs of electrodes (Four electrodes) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Exposed electrode length: 
                 2.5 
                 cm 
               
               
                   
                 Distance between electrodes: 
                 2.5 
                 cm 
               
               
                   
                 Power setting: 
                 15 
                 W 
               
               
                   
                 Ablation time: 
                 14 
                 min. 
               
               
                   
                 Lesion size: 
               
               
                   
                 width: 
                 4.0 
                 cm 
               
               
                   
                 length: 
                 3.0 
                 cm 
               
               
                   
                 depth: 
                 5.0 
                 cm 
               
               
                   
                   
               
             
          
         
       
     
     The foregoing description of preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications, variations and different combinations of embodiments will be apparent to practitioners skilled in this art. Also, it will be apparent to the skilled practitioner that elements from one embodiment can be recombined with one or more other embodiments. It is intended that the scope of the invention be defined by the following claims and their equivalents.