Patent Publication Number: US-2017367757-A1

Title: Systems and methods for treating tissue regions of the body

Description:
Related Applications 
     This application is a divisional of copending patent application Ser. No. 12/231,924 filed 8 Sep. 2008, which is a divisional of patent application Ser. No. 11/114,592 filed 26 Apr. 2005, which is a continuation of patent application Ser. No. 10/857,632, filed May 28, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 09/955,915, filed Sep. 19, 2001, now U.S. Pat. No. 6,699,243, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to devices, systems and methods for treating tissue regions of the body. 
     BACKGROUND OF THE INVENTION 
     Catheter-based devices that deploy expandable structures into interior body regions are well known. These structures are typically introduced through a body lumen or vessel in a collapsed, low profile condition. Once at or near the targeted body region, the structures are expanded in situ into an enlarged condition to make contact with tissue. The structures can carry operative elements that, when in contact with tissue, perform a therapeutic or diagnostic function. They can, for example, deliver energy to ablate targeted tissue in the region. 
     Some of these structures can be expanded by inflation by delivery of fluid into the interior of the structure. It is desirable to control the amount of inflation, so as not to over-inflate the structures. Over-inflation can lead to damage of the structure, or unintended trauma or damage to nearby tissue. 
     With structures that are expanded in situ, it is also desirable to ascertain whether the structure actually is in contact with the targeted tissue region. Absent such contact, the desired therapeutic or diagnostic outcome may not be achieved. 
     SUMMARY OF THE INVENTION 
     The invention provides improved systems and methods for treating a tissue region. 
     One aspect of the invention provides systems and methods for sensing the position of a therapeutic or diagnostic element with respect to a targeted tissue region. The systems and methods comprise a fluid path having an outlet located at or near the therapeutic or diagnostic element. The location of the outlet places the outlet into a position with respect to the targeted tissue region concurrently with the therapeutic or diagnostic element. The systems and methods also include a source of fluid under pressure. The source is in communication with the fluid path to convey fluid under pressure through the fluid path. The systems and methods include a fluid pressure sensor, which communicates with the fluid path to sense prevailing fluid pressure in the path. The systems and methods also include an output to indicate the sensed prevailing fluid pressure or changes in the sensed prevailing fluid pressure over time. The sensed pressure conditions correlate with the position of the therapeutic or diagnostic element relative to the targeted tissue region. In one embodiment, the source of fluid conveys air under pressure, and the fluid pressure sensor comprises a manometer. 
     According to this aspect of the invention, changes in tissue pressure at or near the path outlet governs fluid flow in the path and gives rise to changes in fluid pressure within the path. Changes in the prevailing fluid pressure can be correlated to the position of the path outlet relative to a targeted tissue region. This aspect of the invention makes possible the sensing of the position of a remote structure with respect to a targeted tissue region without direct or indirect visualization, or without other complicated electrical or mechanical paraphernalia. 
     Another aspect of the invention provides systems and methods for inflating an inflatable structure that carries a therapeutic or diagnostic element. The systems and methods comprise a source of fluid under pressure. A supply line communicates with the inflatable structure and the source to convey fluid into the inflatable structure to inflate the inflatable structure for use. The systems and methods include a pressure relief valve. The pressure relief valve communicates with the supply line. The pressure relief valve opens and vents fluid from the supply line when a predetermined pressure condition exists in the supply line. This pressure condition is indicative that a desired interior pressure exists within the inflatable structure. This aspect of the invention assures that the inflatable structure is not subject to over-inflation during use. 
     Another aspect of the invention provides systems and methods for dynamically monitoring pressure conditions within an inflatable structure that carries a therapeutic or diagnostic element. The systems and methods include a pressure sensing element that dynamically senses interior pressure within the inflatable structure and generates an output. The sensing can be accomplished in real time, with an appropriate output generated to provide visual or audible feedback to the operator, and/or provide automated process control feedback based upon the sensed pressure information. The use of a dynamic pressure sensing element makes possible the automated inflation of an inflatable body in a straightforward and reliable manner. The use of dynamic pressure monitoring and control also facilitates the use of a porous balloon structure. The porous balloon structure is inflated to a desired pressure condition by the delivery of a liquid, while a portion of the inflation liquid is discharged through pores in the balloon, to provide a desired flow of irrigation fluid to the tissue region concurrent with inflation. 
     Other features and advantages of the inventions are set forth in the following Description and drawings, as well as in the appended claims 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a system for treating tissue. 
         FIG. 2  is an enlarged view of the treatment device, with parts broken away and in section, that is associated with the system shown in  FIG. 1 , the treatment device comprising basket structure that carries selectively deployable electrode elements and that expands in response to inflation of an interior balloon structure,  FIG. 2  showing the basket in a collapsed condition with the electrode elements retracted. 
         FIG. 3  is an enlarged view of the treatment device shown in  FIG. 2 , with the basket expanded due to inflation of interior balloon structure and the electrode elements still retracted. 
         FIG. 4  is an enlarged view of the treatment device shown in  FIG. 2 , with the basket expanded due to inflation of interior balloon structure and the electrode elements extended for use,  FIG. 4  also showing the passage of irrigation fluid from the basket to cool the surface tissue while radio-frequency energy is applied by the electrode elements to subsurface tissue. 
         FIGS. 5 to 7  are simplified anatomic views showing the use of the treatment device shown in  FIGS. 2 to 4  deployed in the region of the lower esophageal sphincter to form an array of lesions. 
         FIGS. 8 and 9  show, in simplified anatomic and schematic views, a system and method for sensing the position of the treatment device shown  FIGS. 2 to 4  with respect to a targeted tissue region, by sensing fluid pressure in a fluid path having an outlet located at or near the electrode elements. 
         FIGS. 10 to 13  show, in perspective views, a system and method for manually inflating the balloon structure in the treatment device shown in  FIGS. 2 to 4  while tactilely monitoring the magnitude of the inflation pressure to avoid over-inflation of the balloon structure. 
         FIGS. 14 and 15  show, in perspective views, a system and method for manually inflating the balloon structure in the treatment device shown in  FIGS. 2 to 4  while using a pressure relief valve to avoid over-inflation of the balloon structure. 
         FIG. 16  shows, in a perspective view, a system and method that inflate the balloon structure in the treatment device shown in  FIGS. 2 to 4 , while dynamically monitoring pressure conditions within the balloon structure in real time, with an appropriate output generated to provide visual or audible feedback to the operator, and/or provide automated process control feedback based upon the sensed pressure information. 
         FIG. 17  shows, in a perspective view, a system and method that automatically inflate the balloon structure in the treatment device shown in  FIGS. 2 to 4  by dynamically monitoring pressure conditions within the balloon structure. 
         FIG. 18  is a perspective view of a treatment device comprising basket structure that carries selectively deployable electrode elements and that expands in response to inflation of an interior balloon structure with a liquid under the control of the system shown in  FIG. 17 ,  FIG. 18  showing the basket in an inflated condition with the electrode elements extended and the inflation liquid also serving as irrigation fluid discharged through an array of openings formed in the balloon structure. 
     
    
    
     The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This Specification discloses various catheter-based systems and methods for treating dysfunction in various locations in an animal body. For example, the various aspects of the invention have application in procedures requiring treatment of sphincters and adjoining tissue regions in the body, or hemorrhoids, or incontinence, or obesity, or restoring compliance to or otherwise tightening interior tissue or muscle regions. The systems and methods that embody features of the invention are also adaptable for use with systems and surgical techniques that are not necessarily catheter-based. 
     The systems and methods are particularly well suited for treating dysfunctions in the upper gastrointestinal tract, e.g., in the lower esophageal sphincter and adjacent cardia of the stomach. For this reason, the systems and methods will be described in this context. Still, it should be appreciated that the disclosed systems and methods are applicable for use in treating other dysfunctions elsewhere in the body, which are not necessarily sphincter-related. 
     I. Overview 
     A tissue treatment device  10  and associated system  36  are shown in  FIG. 1 . 
     The device  10  includes a handle  12  made, e.g., from molded plastic. The handle  12  carries a flexible catheter tube  14  constructed, for example, by extrusion using standard flexible, medical grade plastic materials, like Pebax™ plastic material, vinyl, nylon, poly(ethylene), ionomer, poly(urethane), poly(amide), and poly(ethylene terephthalate). The handle  12  is sized to be conveniently held by a physician, to introduce the catheter tube  14  into the tissue region targeted for treatment. The catheter tube  14  may be deployed with or without the use of a guide wire. 
     The catheter tube  14  carries on its distal end an operative element  16 . The operative element  16  can take different forms and can be used for either therapeutic purposes, or diagnostic purposes, or both. The operative element  16  can support, for example, a device for imaging body tissue, such as an endoscope, or an ultrasound transducer. The operative element  16  can also support a device to deliver a drug or therapeutic material to body tissue. The operative element  16  can also support a device for sensing a physiological characteristic in tissue, such as electrical activity, or for transmitting energy to stimulate tissue or to form lesions in tissue. 
     In the embodiment shown in  FIGS. 2 to 4 , the operative element  16  comprises a three-dimensional basket  18 . The basket  18  includes an array of arms  20 . The arms  20  are desirably made from extruded or molded plastic, but they could also be formed from stainless steel or nickel titanium alloy. As shown in  FIG. 2 , the arms  20  are assembled together between a distal tip  22  and a proximal base element  24 . 
     As  FIGS. 3 and 4  show, an expandable structure  26  comprising, e.g., a balloon, is located within the basket  18 . The expandable balloon structure  26  can be made, e.g., from a Polyethylene Terephthalate (PET) material, or a polyamide (non-compliant) material, or a radiation cross-linked polyethylene (semi-compliant) material, or a latex material, or a silicone material, or a C-Flex (highly compliant) material. Non-compliant materials offer the advantages of a predictable size and pressure feedback when inflated in contact with tissue. Compliant materials offer the advantages of variable sizes and shape conformance to adjacent tissue geometries. 
     The balloon structure  26  presents a normally, generally collapsed condition, as  FIG. 2  shows. In this condition, the basket  18  is also normally collapsed about the balloon structure  26 , presenting a low profile for deployment into the targeted tissue region. 
     Expansion of the balloon structure  26 , e.g., by the introduction of air through a syringe  32  coupled to a one-way check valve fitting  42  on the handle  12  (see  FIG. 3 ), urges the arms  20  of the basket  18  to open and expand, as  FIG. 3  shows. The force exerted by the balloon structure  26  upon the basket arms  20 , when expanded, is sufficient to exert an opening force upon the tissue surrounding the basket  18 . 
     For the purpose of illustration (see  FIGS. 5 and 6 ), the targeted tissue region comprises the lower esophageal sphincter (LES) and cardia of the stomach. When deployed in this or any sphincter region, the opening force exerted by the balloon structure  26  serves to dilate the sphincter region, as  FIG. 6  shows. 
     Each basket arm  20  carries an electrode element  28 . A push-pull lever  30  on the handle (see  FIG. 4 ) is mechanically coupled through the catheter tube  14  to the electrode elements  28 . In use, pushing and pulling on the lever  30  causes the electrode elements  28  to slide within the lumens in the basket arms  20  between a retracted position (shown in the  FIG. 3 ) and an extended position (shown in  FIG. 4 ). As  FIG. 4  shows, the electrode element  28 , when extended, projects through an opening  56  in the basket arm. When deployed in the tissue region (see  FIG. 6 ), the extended electrode element  28  pierces tissue. As  FIG. 4  shows, temperature sensing elements  82  (e.g., thermocouples) are desirably carried by the arms  20  near the electrode elements  28  to sense tissue temperature conditions. 
     In a desired arrangement, the electrode elements  28  deliver radio frequency energy, e.g., energy having a frequency in the range of about 400 kHz to about 10 mHz. A return path is established, e.g., by an external patch electrode, also called an indifferent electrode. In this arrangement, the application of radio frequency energy serves to ohmically heat tissue in the vicinity of the electrode elements  28 , to thermally injure the tissue and form the localized sub-surface lesions  164 , which are shown in  FIG. 6 . Of course, tissue heating can be accomplished by other means, e.g., by coherent or incoherent light; heated or cooled fluid; resistive heating; microwave; ultrasound; a tissue heating fluid; or cryogenic fluid. 
     In this arrangement, the natural healing of subsurface lesions or pattern of subsurface lesions created by the applied energy leads to a physical tightening of the sphincter and/or adjoining cardia and/or a reduction in the compliance of these tissues. The subsurface lesions can also result in the interruption of aberrant electrical pathways that may cause spontaneous sphincter relaxation. In any event, the treatment can restore normal closure function to the sphincter. 
     The electrode elements  28  can be formed from various energy transmitting materials. For deployment in the esophagus or cardia of the stomach, the electrode elements  28  are formed, e.g., from nickel titanium. The electrode elements  28  can also be formed from stainless steel, e.g., 304 stainless steel, or a combination of nickel titanium and stainless steel. 
     In this arrangement, the electrode element  28  may comprise a hybrid of materials comprising stainless steel for the proximal portion and nickel titanium alloy for the distal portion. 
     The exterior surface of each electrode element  28  can carry an electrical insulating material, except at its distal region, where the radio frequency energy is applied to tissue. The presence of the insulating material serves to preserve and protect the mucosal tissue surface from exposure to the radio frequency energy, and, thus, from thermal damage. The insulating material can comprise, e.g., a Polyethylene Terephthalate (PET) material, or a polyimide or polyamide material. 
     As  FIG. 1  shows, the treatment device  10  desirably operates as part of a system  36 . The system  36  includes a generator  38  to supply the treatment energy to the operative element  16 . In the illustrated embodiment, the generator  38  supplies radio frequency energy to the electrodes  28 . A cable  40  plugged into the handle  12  electrically couples the electrode elements  28  to the generator  38 . Electrode supply wires pass through the catheter tube  14  from the handle to the electrode elements  28 . 
     The system  36  can also include certain auxiliary processing equipment. In the illustrated embodiment, the processing equipment comprises an external fluid delivery or irrigation apparatus  44 . In the illustrated embodiment, the fluid delivery apparatus  44  comprises an integrated, self priming peristaltic pump rotor that is carried on a side panel of the generator  38 . Other types of non-invasive pumping mechanisms can be used, e.g., a syringe pump, a shuttle pump, or a diaphragm pump. 
     A luer fitting  48  on the handle  12  couples to tubing  34  to connect the treatment device  10  to the fluid delivery apparatus  44 . Irrigation supply tubing in the catheter tube  14  conveys irrigation fluid through a lumen in each basket arm  20  for discharge through irrigation openings  56  (see  FIG. 4 ) by or near the electrode elements  28 . This provides localized cooling of surface tissue. In the illustrated embodiment, the irrigation fluid (designated F in  FIG. 4 ) is discharged directly at the base of each electrode element  28 . In this arrangement, the irrigation fluid is conveyed through the same basket arm lumen and is discharged through the same basket arm opening  56  as the electrode element  28 . Of course, other irrigation paths can be used. 
     In this arrangement, the processing equipment desirably includes an aspiration source  46 . Another luer fitting  50  on the handle  12  couples tubing to connect the treatment device  10  to the aspiration source  46 . The aspiration source  46  draws irrigation fluid discharged by or near the electrodes  28  away from the tissue region. The aspiration source  46  can comprise, for example, a vacuum source, which is typically present in a physician&#39;s suite. 
     The system  36  also desirably includes a controller  52 . The controller  52  is linked to the generator  38  and the fluid delivery apparatus  44 . The controller  52 , which preferably includes an onboard central processing unit, governs the power levels, cycles, and duration that the radio frequency energy is distributed to the electrodes  28 , to achieve and maintain temperature levels appropriate to achieve the desired treatment objectives. In tandem, the controller  52  also desirably governs the delivery of irrigation fluid. 
     The controller  52  desirably includes an input/output (I/O) device  54 . The I/O device  54 , which can employ a graphical user interface, allows the physician to input control and processing variables, to enable the controller to generate appropriate command signals. 
     In use (see  FIGS. 5 to 7 ), the operative element  16  can be deployed at or near the lower esophageal sphincter (LES) for the purpose of treating GERD. A physician can use the visualization functions of, e.g., an endoscope to obtain proper position and alignment of the operative element  16  with the LES. 
     Once proper position and alignment are achieved (see  FIG. 6 ), the physician can expand the balloon structure  16  and extend the electrode elements  16  into piercing contact with tissue at or near the LES. Application of ablation energy forms the lesions  164 . Retraction of the electrode elements  28  and collapsing of the balloon structure  16  allows the physician to reposition the operative element  16  and perform one or more additional ablation sequences (see  FIG. 7 ). In this way, the physician forms a desired pattern of circumferentially and axially spaced lesions  164  at or near the LES and cardia. 
     II. Positioning Based Upon Fluid Pressure Sensing 
     It is desirable to be able to confirm that the basket arms  20  are positioned at or near the targeted tissue region. Direct visualization can be used for this purpose. In addition, or alternatively, electrode impedance can also be electrically sensed by the controller  52 . A reduction in electrode impedance reflects that the electrode element  28  rests in tissue, compared to when the electrode element  28  is not in contact with tissue. 
     Alternatively, or in combination, the system  36  can include means  58  for assessing position based upon sensed changes in tissue pressure in and surrounding a targeted tissue region. The changes in tissue pressure are sensed based upon changes in pressure of a fluid (e.g., air or liquid) that is conveyed at or near the surface of the operative element  16  where tissue contact is intended. The means  58  includes means for causing a fluid subject to a pressure to flow in a path that has an outlet located at or near a surface of the operative element  16  intended to make tissue contact. Tissue pressure encountered at or near the path outlet affects pressure exerted on the path outlet and governs fluid flow in the path to varying degrees. The correlation between increases in tissue pressure encountered at or near the path outlet and fluid flow through the path gives rise to increases in fluid pressure within the path. The means  58  includes means for sensing a fluid pressure in the path. An increase in the prevailing fluid pressure sensed over time correlates with the presence of higher tissue pressures at or near the path outlet. The means  58  makes possible the sensing of the location of a remote structure relative to a targeted tissue region without direct or indirect visualization, or without other complicated electrical or mechanical paraphernalia. 
     In the illustrated embodiment, the high pressure zone created by the lower esophageal sphincter is a marker for the targeted tissue region. By sensing the pressure at which fluid is delivered at a slow rate through ports on the basket arms  20  while moving the basket structure  18  through the esophagus, the increased tissue pressure in the high pressure zone can be detected as the ports move through the zone. 
     In the illustrated embodiment (see  FIG. 1 ) the means  58  includes a pressurized source  60  of air and a manometer  62 . The air source  60  and manometer  62  can be part of the controller  52 , or separate components coupled to the system  36 , as  FIG. 1  shows. Of course, the source  60  can provide a fluid other than air, in which case the manometer  62  would comprise a device that would sense the prevailing pressure of the selected fluid. 
     As shown in  FIG. 1 , the air source  60  and manometer  62  are coupled by tubing  64  to the irrigation supply tubing  34 , which leads to the device  10 . An inline valve  66  controls communication between the air source  60  and the tubing  34 . When the valve  66  is opened, pressurized air from the source  60  is conveyed through the irrigation lumens in the basket arms  20 , where they exit through the outlets  56 . The flow of pressurized air through this path does not occur when the valve  66  is closed. In this way, pressurized air can be selectively conveyed through the lumen or lumens when it is desired to assess the location of the basket structure  18  relative to the high pressure zone of the lower esophageal sphincter. The manometer  62  senses the air pressure prevailing in the air path  64  and provides an output reflecting the magnitude of the sensed pressure. 
     In use (see  FIG. 8 ), the basket structure  18  is advanced while in a collapsed condition to a location beyond the targeted high tissue pressure zone, which in the illustrated embodiment, is the LES. While the basket structure  18  remains in a collapsed condition, the valve  66  is opened to place the pressurized air source  60  into communication with the irrigation lumens in the basket arms  20 . Pressurized air is conveyed through the lumens, exiting through the openings  56 . The manometer  62  will register a prevailing line pressure. 
     With the flow of air established, and with the basket structure  18  still collapsed, the physician draws the basket structure  18  back (see  FIG. 9 ). The region of the basket structure  18  where the electrodes  28  are carried will eventually be brought into the high pressure zone. The increased tissue pressure in this region will impede air flow through the outlet openings  56  and generating a backpressure in the air path  64 . As  FIG. 9  shows, the manometer  62  will register an increase in sensed pressure. As the physician continues to draw the basket structure  18  back, above the high pressure zone, the sensed pressure will decrease accordingly. The localized increase in sensed pressure can thus be pin-pointed, which indicates that the electrode region of basket structure  18  is in the high tissue pressure zone and thereby positioned for use. The physician turns the valve  66  off. 
     Using reference marks on the catheter tube  14 , the high pressure zone can be marked relative to an external anatomic reference, such as a bite block worn by the patient. Since the outlet ports  56  are coincident with the needle electrode locations, the exact location for delivery of radiofrequency energy is located in this way, without the need for endoscopy (or as an adjunct to endoscopy). The physician expands the basket structure  18  and proceeds with the lesion formation sequence. 
     The controller  52  can communicate with the manometer  62  (as shown in phantom lines in  FIG. 1 ). In this arrangement, the controller  52  can be pre-programmed, e.g., to dynamically display the sensed pressure on the GUI  54  and/or to generate a visual and/or audible output when a threshold pressure indicative of tissue contact is sensed. 
     It should be appreciated that the manometer  62  and air pressure source  60  could, alternatively, be coupled to the aspiration supply line. Still alternatively, the manometer  62  can be carried on board the treatment device  10  itself, e.g., in the handle  20 . 
     III. Controlling Pressure in the Balloon Structure 
     It is desirable to establish some control mechanism to assure that the balloon structure  26  is not over-inflated or otherwise subject to over-pressure conditions. This avoids damage to the balloon structure  26 , as well as potential injury or trauma to tissue near or in contact with the balloon structure  26 . 
     A. Tactile Control 
     In one embodiment (see  FIGS. 10 to 13 ), tactile feedback can be used. In this arrangement, a syringe  32  pre-filled with a pre-established volume of air (e.g., 25 cc) (see  FIG. 10 ) is coupled to the one way check valve  42  on the handle. The physician depresses the plunger  50  of the syringe  32  to introduce air from the syringe  32  onto the balloon structure  26 . The pre-filled volume of air in the syringe  32  is empirically selected based upon the size and physical properties of the balloon structure  26 . As the balloon structure  26  approaches its desired interior pressure, the physician will tactilely feel progressive resistance to advancement of the plunger  50 . When the balloon structure  26  is at the desired interior pressure, releasing the plunger will allow a finite back flow volume of air from the balloon structure  26  into the syringe  32  (e.g., 3-4 cc) (see  FIG. 11 ). As  FIG. 11  shows, the push back volume displaces the plunger  50  by a finite amount, providing the physician with direct visual and tactile feedback that the balloon structure  26  has been properly inflated. When plunger push back is observed, the physician responds by advancing the plunger  50  to replace the push back volume (as  FIG. 12  shows), placing the balloon structure  26  at its desired inflation pressure. The physician disconnects the syringe  32  from the one-way check valve  42  (as  FIG. 13  shows), which thereafter maintains the desired interior pressure in the balloon structure  26 . 
     B. Pressure Relief Valve 
     In another embodiment (see  FIG. 14 ), a pressure relief valve  68  may be coupled in line with the syringe  32  to the one-way valve fitting  42 . The valve  68  is condition to open and vent the inflation fluid (in this case, air) at a predetermined pressure, which is selected to be the desired interior pressure of the balloon structure  26 . 
     In this arrangement, the relief valve  68  remains closed as the syringe  32 —pre-filled with a pre-established volume of air as already described—is manipulated to convey air into the balloon structure  26 , until the balloon structure  26  reaches the predetermined desired interior pressure. At this time (see  FIG. 15 ), the relief valve  68  will open, releasing excess air and venting additional air delivery by the syringe  32 . In this way, further increase in interior pressure within the balloon structure  26  is actively prevented. 
     The relief valve  68  can be located within the handle  12  or otherwise carried by the device  10 . Alternatively, the relief valve  68  can be located in or on the supply line, as  FIG. 14  shows. Still alternatively, the relief valve can be an integrated part of the controller  52 , coupled by a sensing line to the device  10 . 
     C. Real Time Pressure Monitoring 
     It may be desirable to dynamically monitor the magnitude of pressure within the balloon structure  26 . For example, different pressure magnitudes may be desired at different locations in the tissue region where the pattern of lesions  164  is formed. In this embodiment, the system  36  includes means  70  for dynamically sensing the magnitude of pressure within the balloon structure  26 . 
     In the illustrated embodiment (see  FIG. 16 ), the means  70  comprises a pressure transducer  70 . The pressure transducer  70  can be carried in the handle  20  of the treatment device  10  (as  FIG. 16  shows), or it can be integrated into the controller  38 . 
     As  FIG. 16  shows, a pressure gauge coupled to the transducer (or a virtual gauge on the GUI  54 , which  FIG. 16  shows) can be used to display the sensed pressure in real time. The controller  52  can be programmed to impose maximum pressure limits and generate visual or audible alarm conditions based upon the sensed pressure. 
     With dynamic monitoring of pressure, the inflation of the balloon structure  26  can be placed under the control of the controller  52 , and thereby automated. As  FIG. 17  shows, the system includes a source  72  of fluid pressure, which can be air or a liquid like saline. The source  72  is coupled to the controller  52  and can be commanded to selectively supply inflation fluid under either positive or negative pressure. The source  72  is coupled via a supply line  74  to a supply fitting  80  on the handle  12 . This arrangement replaces the use of a manual syringe and the one-way check valve  42 . 
     The supply line  74  includes a control valve  78 , which is coupled to the controller  52 . The supply line  74  also includes a pressure relief valve  76 , which is likewise coupled to the controller  52 . 
     In use, upon positioning of the balloon structure  26  in a collapsed condition at or near the targeted tissue site, the controller  52  (e.g., in response to a foot switch operated by the physician) commands opening of the control valve  78 . The controller  52  also commands the supply of the inflation fluid from the source  72  under positive pressure. The balloon structure  26  undergoes inflation. 
     The transducer  70  dynamically monitors the interior pressure as the balloon structure  26  inflates. The controller  52  compares the sensed pressure to a maximum threshold, which can be either preprogrammed in the controller  52  or based upon a selected input by the physician. The controller  52  can also be programmed to select the threshold pressure according to the current location of the balloon structure  26 , which can be provided by input from the physician. When the sensed pressure reaches the selected maximum threshold, the controller  52  opens the pressure relief valve  76 . Thereafter, the controller  52  toggles the pressure relief valve  76  open and closed to automatically maintain the desired interior inflation pressure at the threshold. 
     When it is desired to change the location of the balloon structure  26 , or to withdraw the balloon structure  26 , the controller  52  (e.g., in response to a foot switch operated by the physician) commands drawing negative pressure through the supply line  74  (while also closing the relief valve  76 ), to deflate the balloon structure  26 . If, after repositioning, subsequent lesion formation is desired, the controller  52  (e.g., in response to a foot switch operated by the physician) can again command the supply of inflation fluid under positive pressure from the source  72 , to again inflate the balloon structure  26  under the control of the transducer  70 , as just described. 
     In this way, the system  36  serves to automatically control the inflation and deflation of the balloon structure  26 , while keeping the balloon pressure within the prescribed limits. 
     The system  36  is particularly well suited for use in association with an operative element  18  as shown in  FIG. 18 . In this embodiment, the inflation fluid is a liquid that also serves as an irrigation fluid F. The irrigation fluid F is discharged in the vicinity of each electrode element  28  through an array of openings  90  formed in the balloon structure  18  itself. The openings  90  can be formed, e.g., by laser drilling, mechanical drilling, or poking with a hot needle. This arrangement eliminates the need for a dedicated irrigation passage and through openings in the basket arms  20 . The inflation fluid thereby serves a dual purpose. First, the inflation fluid expands the basket structure  26  carrying the electrode elements  28 , enabling their use. Second, the inflation fluid also serves as an irrigation fluid to cool the targeted tissue region. In this arrangement, the system  36  provides dynamic pressure monitoring and control of the inflation fluid and irrigation fluid, so that the requirements of simultaneous inflation of the balloon structure  18  and irrigation fluid delivery can be balanced, in order to inflate the balloon structure  18  to the desired pressure while achieving a desired irrigation fluid flow rate. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.