Abstract:
A thermal ablation system, comprises a device housing and an elongated probe extending distally from the device housing, the probe including an outflow fluid passage extending between proximal and distal outflow openings and a return fluid passage extending between proximal and distal return openings, the probe being shaped and sized for insertion into a body lumen so that, when the distal outflow and return openings are located at a desired position within the body, the proximal outflow and return openings remain outside the body in combination with a pump disposed in the device housing in fluid communication with the outflow and return fluid passages of the probe for circulating a fluid through the outflow lumen into a target area of the body and back through the return lumen to the device housing and a heating element in the device housing for heating the fluid. Fluid connectors place the pump and the heating element in fluid communication with a supply of fluid and a fluid drain.

Description:
PRIORITY CLAIM 
       [0001]    This application claims the priority to the U.S. Provisional Application Ser. No. 60/973,907, entitled “Hand-Held Thermal Ablation Device,” filed Sep. 20, 2007. The specification of the above-identified application is incorporated herewith by reference. 
     
    
     BACKGROUND 
       [0002]    Conventional treatments for uterine fibroids include drug therapies that are generally better suited for less advanced cases and hysterectomies for more advanced cases. However, less invasive alternative procedures are often preferable to the hysterectomy as they typically reduce side effects, hospital stays, and discomfort. 
         [0003]    These less invasive procedures have employed electrical energy (e.g., RF energy), heat and cryogenic treatments, as well occlusion of the blood supply to the fibroids. Alternatively, the entire inner lining of the uterus may be treated by, for example, conduction uterine ablation—i.e., circulating a heated fluid within the uterus. 
         [0004]    The Hydro-Therm Ablator (HTA)™ system marketed by the Boston Scientific Corporation ablates the uterine lining by circulating saline heated to between approximately 41.5° and 99.9° C. for about 10 minutes. The system incorporates a hand-held probe for insertion into the uterus connected by tubing extending to an external device containing heating elements and a pump. In other similar systems, the heated fluid may be contained within a balloon while circulating within the uterus. 
       SUMMARY OF THE INVENTION 
       [0005]    In one aspect, the present invention is directed to a thermal ablation system, comprising an elongated probe extending distally from a device housing, the probe including an outflow fluid passage extending between proximal and distal outflow openings and a return fluid passage extending between proximal and distal return openings, the probe being shaped and sized for insertion into a body lumen so that, when the distal outflow and return openings are located at a desired position within the body, the proximal outflow and return openings remain outside the body and a pump disposed in the device housing in fluid communication with the outflow and return fluid passages of the probe for circulating a fluid through the outflow lumen into a target area of the body and back through the return lumen to the device housing in combination with a heating element in the device housing for heating the fluid and fluid connectors placing the pump and the heating element in fluid communication with a supply of fluid and a fluid drain. 
         [0006]    In another aspect, the present invention is directed to a hand-held thermal ablation device, comprising an elongated probe extending between a proximal end coupled to a handle and a distal end which, when in an operative position, is received within a body lumen and a pump within the handle in fluid connection with fluid passages in the elongated probe in combination with a fluid column within the handle containing a heating element, serially connected with the pump and an external fluid supply in fluid connection with the pump. 
         [0007]    In a still further aspect, the present invention is directed to a method of ablating target tissue, comprising advancing a distal end of an elongated probe of a hand-held device into a body lumen and heating a fluid with a heating element disposed in a housing of the hand-held device in combination with the steps of motivating the fluid with a pump disposed in the housing, to inject the fluid into the body lumen via an outflow passage of the elongated probe to ablate target tissue therein and withdrawing the fluid from the body lumen via a return passage of the elongated probe. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  is a drawing of an embodiment of a hand-held thermal ablation apparatus according to the invention; 
           [0009]      FIG. 2  is a detail view of a handle of the thermal ablation apparatus shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a drawing of a second embodiment of a hand-held thermal ablation system according to the invention; 
           [0011]      FIG. 4  is a diagram showing fluid flow through the thermal ablation system of  FIG. 3 ; 
           [0012]      FIG. 5  is an exploded view showing a reservoir and impeller of the embodiment of  FIG. 3 ; 
           [0013]      FIG. 6  is an exploded view showing a reservoir assembly and a motor housing of the embodiment of  FIG. 3 ; 
           [0014]      FIG. 7  is a photograph of a detail of the fluid reservoir and electrode of the embodiment of  FIG. 3 ; 
           [0015]      FIG. 8  is a detail view of a cap with a heating element of the embodiment shown in  FIG. 3 . 
           [0016]      FIG. 9  is a diagram showing the reservoir, upper pump and outlet port of the embodiment shown in  FIG. 3 ; 
           [0017]      FIG. 10  is a photograph of the impeller of the thermal ablation system shown in  FIG. 3 ; 
           [0018]      FIG. 11  is a detail view showing the handle inlet and outlet of the embodiment shown in  FIG. 3 ; 
           [0019]      FIG. 12  is a photograph of a further embodiment of a heating and pump unit of a hand-held thermal ablation apparatus according to the invention; and 
           [0020]      FIG. 13  is a cutaway diagram showing an integrated hand-held thermal ablation device according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The present invention may be further understood with reference to the following description and to the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to devices for treating fibroids or other target tissue in a hollow organ. In particular, the present invention relates to devices for ablating the lining of the uterus. 
         [0022]    The embodiments of the present invention provide a compact, hand-held device for ablation of the lining of a hollow organ, such as the uterus. The system according to the invention comprises a hand-held probe connected to a fluid supply with a pump and heater contained within the hand-held housing for motivating and heating the fluid as necessary. 
         [0023]    The exemplary uterine probe is inserted through the vaginal canal and the cervix to place a distal tip thereof within the uterus. During the therapy, the distal tip of the probe which contains inflow and outflow orifices is located within the uterus just distal to the internal cervical os. In one embodiment, the probe uses a coaxial design for the inflow and outflow passages. The fluid passages are connected to a pump that provides aspiration of return fluid and which imparts energy to force fluid through the probe out of the outflow orifice and into the uterus. 
         [0024]    The exemplary device also comprises a fluid channel or reservoir and a fluid heater, in line with the pump. In this embodiment, the heater is selected to provide a supply of fluid heated to, for example, approximately 90° C. for about 10 minutes. However, those skilled in the art will understand that other temperatures and/or durations may be selected to adapt the system to the requirements of particular procedures through simple adjustment and/or replacement of components such as heating elements and power supplies. For example, ablation may be carried out using any fluid temperature between approximately 41.5° and 99.9° C. with the time required to achieve a desired degree of ablation increasing as the fluid temperature decreases. As would be understood by those skilled in the art, as tissue is ablated, it becomes an insulator so that the duration of heat must be increased necrose deeply (e.g., to shut down blood flow through vessels supplying fibroids). According to the invention, the exemplary fluid circuit may also comprise a temperature probe to monitor fluid temperature and a feed back loop to shut down the pump and/or the heater when the fluid temperature exceeds a preset level. The feed back loop is an important safety feature designed to prevent injury from excessive heating of the fluid. 
         [0025]    A fluid flow sensor and/or indicator may also be included in the exemplary flow path, and may be associated to a sensor feedback loop to the pump motor to control the outflow of the pump (e.g., when an amount of fluid input to the uterus exceeds an amount withdrawn by more than a predetermined level). The pump may also be manually controlled via an on/off switch and a circulation adjustment controller for user controlled fluid circulation. As will be described in greater detail below, the flow passages may comprise a fluid fill port, a fluid drain port, an air vent port and a compliance chamber to enable reserve fluid to maintain the uterus full of fluid. The compliance chamber may be located within the handle or between the handle and the fluid feed from the priming bag. 
         [0026]    Saline may be advantageously circulated through the system according to the invention. However, it will be understood by those of skill in the art that a variety of other fluids such as glycerine, may be used without departing from the teachings of the invention. Preferably, the fluid is osmotically safe so that it will not change the electrolyte balance of the blood as it is absorbed into tissue over time. If an RF electrode is to be included in the heating element, an electrically conductive fluid (e.g., saline) is preferably selected. In addition to an RF heating element or as an alternative thereto, a cartridge and/or resistance heater may be used to bring the circulating fluid to the desired temperature even for fluids such as glycerine which are not electrically conductive. 
         [0027]    A more detailed description of exemplary embodiments of the invention is presented below. The exemplary device utilizes coaxial conduits to circulate fluid into and out of the uterus providing single point access to the uterus via the cervix. The device is manually positioned and held in place by the user during the length of the therapy, typically about 10 minutes. The hand-held probe passes through the cervix with outer surfaces of an insertion section of the probe sealing the internal cervical os as well as the external cervical os. Inlet and outlet fluid ports are located at the distal end of the probe to circulate the heated fluid into the uterus and to withdraw fluid therefrom. 
         [0028]      FIGS. 1 and 2  show an exemplary embodiment of a hand-held thermal ablation (HTA) system  100  including an elongated probe body  102  extending from a distal tip  104  to a proximal end  105  which is coupled to a handle  106 . The handle  106  which extends substantially perpendicular to an axis of the probe body  102  includes an inlet port  107  for coupling to a source of ablation fluid such as an IV bag  108  and an outlet port  109  for coupling to a drainage reservoir such as a drainage bag  112 . The handle  106  also includes a pump  116  (e.g., an oscillating pump) which circulates fluid from the bag  108 , through the probe body  102  into the uterus and back through the probe body  102  to the drainage bag  112  via the outlet port  109 . As would be understood by those skilled in the art, the pump  116  may be powered by a DC power supply  113  connected thereto by conventional means or, alternatively, by a battery or other power source contained within the handle  106 . 
         [0029]    The handle  106  also includes a heating column  114  including a pair of electrodes  118  which receive power from an RF generator  120  to heat fluid passing through the heating column  114 . As would be understood by those skilled in the art, a single bipolar electrode may be substituted for the pair of electrodes  118 . In applications where cooling of the fluid is required, a cooling rod or other cryogenic element using conventional cooling methods may be substituted for the heating elements. As the conductive fluid (e.g., saline) completes the circuit between the electrodes  118 , the current flowing therebetween heats the fluid to a desired temperature (e.g., approximately 90° C.). A prime port  115  for initializing fluid into the system  100  is formed at lower end of the heating column  114  and the heating column  114  is fluidly coupled to an inlet  117  of the pump  116 . Fluid passes through the pump  116  to an outlet  119  which is fluidly coupled to a supply lumen of the probe body  102  to pass therethough into the uterus  110 . For example, the probe body  102  may include an annular supply lumen surrounding by a central return lumen. Fluid is withdrawn from the uterus  110  into the return lumen of the probe body  102  to pass to a fluid return port  122  at an upper end of the heating column  114 . The fluid returned from the uterus  110  via the return port  122  passes through the heating column  114  back to the inlet  117  of the pump  116  to return to the uterus  110 . The fluid is circulated through this circuit with additional fluid from the bag  108  replacing any fluids lost (e.g., through absorption, etc.) until the procedure has been completed. Once the procedure is complete, the outlet port  109  is opened to permit the fluid to flow into the drainage bag  112 . 
         [0030]    In addition, the system  100  according to this embodiment includes an air venting port  160  which may be used to purge air from the system  100 . The venting port  160  may include a hydrophobic filter  158  to prevent fluids from being vented therethrough. 
         [0031]    A hand-held thermal ablation device  200  according to a second embodiment of the invention is shown in  FIG. 3 . The hand-held thermal ablation device  200  utilizes a non-displacement centrifugal pump to circulate the fluid through the uterus. Using a centrifugal pump rather than a positive displacement pump allows the selection of a dedhead pressure lower than a threshold pressure which risks forcing the fallopian tubes open reducing the risk of damage to non-targeted tissue. In addition, a centrifugal pump may be less affected by debris in the flow (e.g., tissue debris) and less susceptible to over-pressurization of the outflow due to blockage in the pump. 
         [0032]    As with the previous embodiment, the device  200  includes an elongated probe  204  adapted for insertion through the cervix into the uterus extending from a handle  202 . As would be understood by those skilled in the art, a fluid supply bag  224  may be connected to the inlet  234  via tubing, to provide a supply of fluid which fills a fluid reservoir  212  from which solid debris is filtered out. The handle  202  comprises a DC motor  206 , which is preferably a brushless motor, electrically connected to a controller such as a DC power supply  208  for driving a pump  222 . As would be understood by those skilled in the art, a temperature probe (e.g., an electronic temperature probe) may be provided in the flow path (e.g., within the pump  222 ) to monitor fluid temperature. In addition, a fluid reservoir  212  with a debris trap  214  may be incorporated into the pump housing  222  to remove particulate matter (e.g., tissue) to clean fluid returning to the pump  222  from the uterus. A heater column  216  is incorporated into the pump  222  as shown in more detail in  FIG. 11 . 
         [0033]    The pump housing  222  is shown in greater detail in  FIGS. 4-12 . The fluid column  226  extends generally through the center of the housing  222 , and contains a heating element which in this embodiment is formed as a heating column  216 . A centrifugal pump impeller  218  disposed at the lower part of the pump housing  222  is connected to the electric motor  206  via a coupling  232  which, in this embodiment, comprises a drive shaft with a seal assembly  230 . Alternatively, as would be understood by those skilled in the art, a magnetic coupling may be used as the coupling  232  obviating the need for a seal as no shaft would need to pass through the walls of the housing  222  in this case. 
         [0034]    As shown by the arrows in  FIG. 4 , fluid enters the pump housing  222  via a fluid inlet  234  formed in a top cover  240  of the housing  222 . The fluid enters a top of the fluid column  226  via an inlet  248 , is heated by the heating column  216  and enters the impeller  218  where it is accelerated, pressurized and discharged through a fluid outlet  236  connected to the elongated probe  204  via tubing. 
         [0035]    As shown in  FIG. 12 , an exemplary suite of sensors which may be used in a hand-held device according to the invention includes a flow sensor  302  disposed, for example, adjacent to the return port  234  of a pump  300  and a pressure sensor  304  may measuring the pressure of fluid leaving the pump  300  to the elongated probe. The temperature of the fluid may be measured at the exit from the pump by a temperature sensor  306 , and at the return to the pump with a temperature sensor  308 . Furthermore, the pump  300  may include air venting ports  314  which may be used to purge air from the pump  300 . Additional electrical connections may be used to provide power to the device. For example, electrical leads  310  and  312  may be used to power respectively the heating elements and the pump of the device. 
         [0036]      FIG. 5  shows an exploded view of the pump housing  222  with the reservoir  212 . In an exemplary embodiment, the pump housing  222  may be constructed of high temperature polycarbonate or polysulfone. The cap or cover  240  includes the inlet port  234  and the inlet  248  to the fluid column  226 . The exemplary bipolar RF electrode  244  forms the heating element of the heating column  216 , and is disposed concentrically to the reservoir  212  that is designed to separate bubbles and debris from the fluid. Those skilled in the art will understand that this heating element is only one exemplary embodiment and that any suitable mechanism for heating the fluid may be included in the devices according to the invention. A macro filter  246  is provided to remove from the liquid pieces of biological tissue and blood clots that may be aspired by the pump. 
         [0037]    The fluid is motivated by the impeller  218  that is mounted on a lower housing cap  250  with a bearing  242  and sealing elements. A shaft may pass through the opening of the bearing  242 , however the lower housing may be sealed in a different embodiment using a magnetic coupling. A fluid outflow port  236  is located in the high pressure side of the pump, to provide pressurized fluid to the elongated probe  204  and to the patient. 
         [0038]    The reservoir  212  and the motor housing  252  are shown in greater detail in  FIG. 6 . The motor housing  252  interfaces with the fluid reservoir  212  at the top, and with the exemplary brushless DC motor  206  at the bottom. The impeller shaft  254  extends through the bearing  242  of the lower cover  250 , such that in this exemplary embodiment the impeller  218  is mechanically coupled to the motor  206 . Alternatively, a drive shaft of the motor may be directly coupled to the impeller with appropriate seals therearound as would be understood by those skilled in the art. A magnetic coupling may be used in a different embodiment, for example comprising a magnet or magnetic disk on or about the impeller  218  and opposite coupling means on or about the motor  206 . 
         [0039]      FIG. 7  shows a close up of the fluid reservoir system according to an embodiment of the invention. The exemplary bipolar electrode  244  is electrically coupled to an RF power supply via the RF power conductor  264 . The fluid entering the fluid reservoir  212  passes through the macro filter  246 , as described above, that is disposed on the outside of the fluid column  226 . Fluid thus fills the reservoir  212  until it overflows and starts spilling into the center column  226  through inlet drain holes  248 . Within the center column  226 , the fluid is directed along the RF electrode  244 , where it is heated. 
         [0040]    As the fluid passes along the center column  226 , the ions in the saline (or other suitable fluid) carry the current and are excited, thus heating the fluid.  FIG. 8  shows a detailed view of the fluid heating column  216  integrated into the cap  240  and the fluid column  226 . The fluid path directs the heated fluid through the centrifugal pump inlet  266  into the low pressure side of the impeller  218 . 
         [0041]      FIG. 9  shows a detailed diagram of the reservoir  212  and its components. The relationship between the pump inlet  266 , pump outlet  236  and fluid column attachment point  268  can be seen within the reservoir  212 . In addition, the reservoir may include an impeller section  270  for housing the impeller  218 .  FIG. 10  shows a detailed view of the centrifugal pump impeller. The impeller  218  is connected to the coupling  232 , that in this exemplary case may be a magnetic coupling. The shaft  274  connects the impeller  218  to a magnetic disk  272 , which is magnetically coupled to a similar apparatus attached to the motor. 
         [0042]    In a different embodiment, the hand-held thermal ablation device of the invention may use a single pass flow path rather than recirculating the fluid from the uterus of the patient. For example, the saline bag used to start the system in the embodiment described above may be fluidly connected to the heater column that is in turn connected to the pump. The fluid from the pump is then routed to the uterus where it performs the therapeutic function. Instead of returning to the device, fluid from the uterus is discharged into a collection bag for disposal. Without fluid recirculation, the filter and debris catch described above are not necessary. The fluid reservoir may also be smaller or completely removed. 
         [0043]    According to embodiments of the invention, the fluid circulated by the hand-held thermal ablation device may contain therapeutic compounds as necessary. For example, drugs and medications may be added to the ablation fluid or may be circulated separately from the ablation fluid. The saline, glycerin or other fluid used for the thermal therapy may be used as a carrier for the drugs during the ablation procedure, or alternatively may be used without heating to transport the drugs. As would be understood by those skilled in the art, for applications requiring heated fluid and utilizing RF energy for the heating, the fluid used must be electrically conductive. 
         [0044]    Those of skill in the art will understand that the thermal ablation system according to the invention is not limited to use within the uterus. Other hollow organs and structures within the body may be treated by liquid hyperthermia and/or hypothermia. For example, the bladder, kidneys, intestines etc. can be flushed with circulating hot or cold fluids provided by the hand-held device according to the invention. In particular, a heated fluid may improve the absorption of medications contained therein by the walls of the vessel being treated, increasing the therapeutic benefit. 
         [0045]    Application of a heated fluid to a target tissue may be used to destroy the lining of the vessel, for example to stop bleeding, or to control the absorption of drugs by the tissue. Hypothermia treatment using a cooling rod in the device may be beneficial for the control of bleeding, to reduce blood flow to target tissue, or for temperature controlled drug activation, for example. 
         [0046]    When the hand-held thermal ablation system according to the invention is used for certain tubular organs such as the intestine, leakage from the organ may be a problem. For example, devices to occlude the organ and prevent the fluid from escaping may be incorporated in the elongated probe introduced into the organ. In one embodiment, a pair of occluding compliant balloons may be used to close off the portions of the organ being treated. 
         [0047]      FIG. 13  shows an exemplary embodiment of the components of the heat treatment device according to the invention, integrated into a handle usable during surgical procedures. The exemplary hand-held thermal ablation device  300  comprises a housing  307  connected to a fluid sheath or elongated probe  303  adapted for insertion into the patient. The housing  307  has a handle portion  305  that the physician can grasp to maneuver and operate the device. An electronic module  324  may be provided, containing a display for the pressure, temperature and any other desired parameters, as well as electrical circuits to control the device. 
         [0048]    An electric motor  309  is disposed within the housing  307 , and is coupled to an impeller  311 . In this exemplary embodiment, the preferred pump  311  is a centrifugal pump. However a displacement pump may also be used in the device if controls are incorporated preventing the pump from over-pressurizing the uterus. After exiting the pump  311  the fluid is heated by a heating element  313 . As described above, the heating element  313  may comprise monopole or dipole electrodes or other heating devices. The fluid enters the device  300  via prime ports  316 , and after heating circulates to the patient via a fluid sheath  303 . Furthermore, as would be understood by those skilled in the art, additional fluid may be added as needed via the prime ports  316  to compensate for uterine distension and any fluid absorption in the uterus. An RF cable  320  provides RF power supply to the heating element  312  while a DC motor power cable  322  provides DC current to the pump  310 . The system has a temperature sensing system  318  including two temperature sensors—“thermistors” that monitor fluid temperature. As seen in  FIG. 13 , the temperature sensing system  318  includes a top sensor measuring the temperature of fluid flowing out to the patient while the bottom sensor measures the temperature of fluid returning from the patient to the device. In addition, a drain unit  326  is coupled to the fluid sheath  303  to bleed fluid therefrom if desired. 
         [0049]    The present invention was described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. For example, the invention is not limited to methods and devices for the thermal ablation of the uterine lining. Accordingly, various modifications and changes may be made to the embodiments. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.