Abstract:
A method of treating a tissue region includes inserting a flexible sheath within a vessel, the vessel leading to a tissue region, placing a distal end of the sheath through a wall of the vessel to thereby position the distal end is at or adjacent the tissue region, deploying a plurality of electrodes from the distal end of the sheath such that tips of the deployed electrodes approximately face towards a proximal end, and delivering energy to the tissue region using the deployed electrodes.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The field of the invention relates to medical devices, and more particularly, to medical devices and methods of their use for treating tumors or other targeted bodily tissue using electrical energy. 
         [0003]    2. Background 
         [0004]    Tissue may be destroyed, ablated, or otherwise treated using thermal energy during various therapeutic procedures. Many forms of thermal energy may be imparted to tissue, such as radio frequency electrical energy, microwave electromagnetic energy, laser energy, acoustic energy, or thermal conduction. 
         [0005]    In particular, radio frequency ablation (RFA) may be used to treat patients with tissue anomalies, such as liver anomalies and many primary cancers, such as cancers of the stomach, bowel, pancreas, kidney and lung. RFA treatment involves the destroying undesirable cells by generating heat through agitation caused by the application of alternating electrical current (radio frequency energy) through the tissue. 
         [0006]    Various RF ablation devices have been suggested for this purpose. For example, U.S. Pat. No. 5,855,576 describes an ablation apparatus that includes a plurality of wire electrodes. Each of the wires includes a proximal end that is coupled to a generator; and a distal end that may project from a distal end of a cannula. The wires are arranged in an array with the distal ends located generally radially and uniformly spaced apart from the catheter distal end. The wires may be energized in a monopolar or bipolar configuration to heat and necrose tissue within a precisely defined volumetric region of target tissue. The current may flow between closely spaced wire electrodes (bipolar mode) or between one or more wire electrodes and a larger, common electrode (monopolar mode) located remotely from the tissue to be heated. To assure that the target tissue is adequately treated and/or to limit damaging adjacent healthy tissues, the array of wires may be arranged uniformly, e.g., substantially evenly and symmetrically spaced-apart so that heat is generated uniformly within the desired target tissue volume. Such devices may be used either in open surgical settings, in laparoscopic procedures, and/or in percutaneous interventions. 
         [0007]    Currently, tumor near a vessel may be difficult to ablate. This is because the vessel continuously provide blood to the tumor during an ablation procedure, thereby carrying heat away from a targeted region. As a result, it may be difficult to achieve a complete burn for the tumor near the vessel. 
       SUMMARY 
       [0008]    In accordance with some embodiments, a method of treating a tissue region includes inserting a flexible sheath within a vessel, the vessel leading to a tissue region, placing a distal end of the sheath through a wall of the vessel to thereby position the distal end at or adjacent the tissue region, deploying a plurality of electrodes from the distal end of the sheath such that tips of the deployed electrodes approximately face towards a proximal end, and delivering energy to at least a portion of the tissue region using the deployed electrodes. 
         [0009]    In accordance with other embodiments, a system for treating tissue within a tissue region using electrical energy includes a flexible sheath having a proximal end, a distal end, and a body extending between the proximal and the distal ends, wherein the body is sized such that it can be placed within a blood vessel, and has a length such that when placed within the blood vessel, the proximal end is outside a patient&#39;s body and the distal end is adjacent the tissue region, and an array of electrodes slidably disposed within a lumen of the sheath, wherein the sheath further has a sharp distal tip for puncturing a vessel. 
         [0010]    In other embodiments, a system for treating tissue within a tissue region using electrical energy includes a flexible sheath having a proximal end, a distal end, and a body extending between the proximal and the distal ends, wherein the body is sized such that it can be placed within a blood vessel, and has a length such that when placed within the blood vessel, the proximal end is outside a patient&#39;s body and the distal end is adjacent the tissue region, a shaft having a body, the body having a wall and a plurality of openings through the wall, and an array of electrodes coupled to the shaft, and slidably disposed within a lumen of the sheath. 
         [0011]    Other aspects and features will be evident from reading the following detailed description of the embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The drawings illustrate the design and utility of the illustrated embodiments, in which similar elements are referred to by common reference numerals. In order to better appreciate how advantages and objects of the embodiments are obtained, a more particular description of the embodiments is illustrated in the accompanying drawings. 
           [0013]      FIG. 1  illustrates a system for delivering electrical energy to tissue in accordance with some embodiments. 
           [0014]      FIG. 2  is a cross-sectional side view of an embodiment of an ablation device, showing electrode tines constrained within a sheath. 
           [0015]      FIG. 3  is a cross-sectional side view of the ablation device of  FIG. 2 , showing the electrode tines deployed from the sheath. 
           [0016]      FIG. 4  illustrates a system for delivering electrical energy to tissue in accordance with other embodiments. 
           [0017]      FIGS. 5A-5D  are cross-sectional views, showing a method for treating tissue, in accordance with some embodiments. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]      FIG. 1  shows an ablation system  10 , in accordance with some embodiments. The ablation system  10  includes a source of energy  12 , e.g., a radio frequency (RF) generator, and an ablation device  18  configured to be coupled to the generator  12  via a cable  20  during use. 
         [0019]    The generator  12  is preferably capable of operating with a fixed or controlled voltage or current so that power and current diminish as impedance of the tissue being ablated increases. Exemplary generators are described in U.S. Pat. No. 6,080,149, the disclosure of which is expressly incorporated by reference herein. The preferred generator  12  may operate at relatively low fixed voltages, typically below one hundred fifty volts (150 V) peak-to-peak, and preferably between about fifty and one hundred volts (50-100 V). Such radio frequency generators are available from Boston Scientific Corporation, assignee of the present application, as well as from other commercial suppliers. It should be noted that the generator  12  is not limited to those that operate at the range of voltages discussed previously, and that generators capable of operating at other ranges of voltages may also be used. 
         [0020]    Turning to  FIGS. 2 and 3 , in the illustrated embodiments, the ablation device  18  of  FIG. 1  is a ablation assembly  50  that includes a sheath  52  having a lumen  54 , a shaft  56  having a proximal end  58  and a distal end  60 , and a plurality of electrode tines (or wires)  62  secured to the distal end  60  of the shaft  56 . The proximal end  58  of the shaft  56  may include a connector (not shown) for coupling to the generator  12 . Alternatively, the ablation assembly  50  may itself include a cable (not shown) on the proximal end  58  of the shaft  56 , and a connector may be provided on the proximal end of the cable (not shown). 
         [0021]    In the illustrated embodiments, the sheath  52  has a length between about forty and one hundred and thirty centimeters (40-130 cm), and more preferably, between sixty and eighty (60-80 cm). Also, the sheath  52  has an outer diameter or cross sectional dimension between about one and five millimeters (1-5 mm), and more preferably, between two and four millimeters (2-4 mm). In one implementation, the sheath  52  is configured (e.g., sized and shaped) such that it can be inserted within a vessel (e.g., a jugular vein), and that a body of the cannula  52  can extend between a proximal end  72  located outside a patient&#39;s body and a distal end  70  located at or adjacent a target region, e.g., a liver, when the sheath  52  is inserted into a jugular vein. In other embodiments, the sheath  52  may also have other lengths and outer cross sectional dimensions, depending upon the application. The sheath  52  may be formed from a polymer, and the like, as long as it is sufficiently flexible for allowing the sheath  52  to be steered through a vessel. The sheath  52  may be electrically active or inactive, depending upon the manner in which electrical energy is to be applied. The sheath  52  coaxially surrounds the shaft  56  such that the shaft  56  may be advanced axially from or retracted axially into the lumen  54  of the sheath  52 . The shaft  56  can be made from any of a variety of elastic materials, such as a polymer, or a metal, as long as it is sufficiently elastic to be steered through a vessel. For example, the shaft  56  can be a Nitinol tube having a plurality of openings for providing a desired flexibility for the tube, which is available at Boston Scientific Corporation, the Precision Vascular Division. In other cases, instead of being a tube, the shaft  56  can have a solid cross-section. Optionally, a handle  64  may be provided on the proximal end  58  of the shaft  56  to facilitate manipulating the shaft  56 . The electrode tines  62  is compressed into a low profile when disposed within the lumen  54  of the sheath  52 , as shown in  FIG. 2 . As shown in  FIG. 3 , the proximal end  58  of the shaft  56  or the handle  64  (if one is provided) can be advanced to deploy the wires  62  from the lumen  54  of the sheath  52 . When the electrode tines  62  are unconfined outside the lumen  54  of the sheath  52 , they assume a relaxed expanded configuration.  FIG. 3  shows an exemplary two-wire array including electrode tines  62  biased towards a generally “U” shape and substantially uniformly separated from one another about a longitudinal axis of the shaft  56 . Alternatively, each electrode tine  62  may have other shapes, such as a “J” shape, a flare shape, a bent shape, a parabolic shape, and/or the array may have one electrode tine  62  or more than two electrode tines  62 . The array may also have non-uniform spacing to produce an asymmetrical lesion. In some embodiments, the electrode tines  62  are formed from spring wire, superelastic material, or other material, such as Nitinol, that may retain a shape memory. During use of the ablation assembly  50 , the electrode tines  62  are deployed into a target tissue region to deliver energy to the tissue to create a lesion. Ablation devices having a spreading array of electrode tines have been described in U.S. Pat. No. 5,855,576, the disclosure of which is expressly incorporated by reference herein. 
         [0022]    Optionally, a marker (not shown) may be placed on the handle  64  and/or on the proximal end  58  of the shaft  56  for indicating a rotational orientation of the shaft  56  during use. In other embodiments, the ablation assembly  50  may also carry one or more radio-opaque markers (not shown) to assist positioning the ablation assembly  50  during a procedure, as is known in the art. For example, in some embodiments, the ablation assembly  50  may further include a radio opaque marker located at a distal end  70  of the sheath  52  or the shaft  56 . Alternatively or additionally, one or more of the electrode tines  62  may each carry a radio opaque element (e.g., a marker). Optionally, the ablation assembly  50  may also include a sensor, e.g., a temperature sensor and/or an impedance sensor (not shown), carried by the distal end of the shaft  56  and/or one or more of the electrode tines  62 . In such cases, the energy source  12  may be configured to control an amount of energy delivered to the electrode tines  62  based at least in part on a signal provided by the sensor. 
         [0023]    In the illustrated embodiments, the ablation assembly  50  further include a steering mechanism  80  secured to the proximal end  72  of the sheath  52  for steering a distal end  70  of the sheath  52 . The steering mechanism  80  includes a rotatable cam and one or more steering wires (not shown) connected between the cam and the distal end  70  of the sheath  52 . During use, the cam can be rotated to apply tension to a steering wire, thereby causing the distal end  70  of the sheath  52  to bend. Further details regarding the steering mechanism  80  are described in U.S. Pat. No. 5,273,535, the entire disclosure of which is herein incorporated by reference. Steering devices that can be used with the ablation assembly  50  have also been described in U.S. Pat. Nos. 5,254,088, 5,336,182, 5,358,478, 5,364,351, 5,395,327, 5,456,664, 5,531,686, 6,033,378, and 6,485,455, the entire disclosures of which are expressly incorporated by reference herein. 
         [0024]    In other embodiments, the ablation assembly  50  does not include the steering mechanism  80 . In such cases, a separate introducer sheath or introducer catheter may be used to gain access through a vessel. The introducer sheath may have a pre-bent distal end for assisting steering through a vessel. Alternatively, the introducer sheath may be steered using a guidewire in a conventional manner, or may include a steering mechanism, such as the steering mechanism  80  discussed previously, for steering its distal end. In some embodiments, the introducer sheath/catheter can have a sharp distal tip for piercing tissue. 
         [0025]    In other embodiments, the ablation assembly  50  can include a guidewire (not shown) to assist placement of the distal end  70  of the sheath  52  in a conventional manner. The guidewire may be located within the lumen  54  of the sheath  52 , or alternatively, located within another lumen (not shown) in the sheath  52  that is parallel to the lumen  54 . 
         [0026]    It should be noted that the ablation device  18  is not necessarily limited to the ablation assembly  50  shown in  FIGS. 2 and 3 , and that the ablation device  18  may be selected from a variety of devices that are capable of delivering ablation or therapeutic energy. For example, medical devices may also be used that are configured for delivering ultrasound energy, microwave energy, and/or other forms of energy for the purpose of ablation, which are well known in the art. In the illustrated embodiments, the ablation assembly  50  also includes an electrode  90  secured to the sheath  52 . A wire (not shown) may be disposed within the wall of the sheath  52  to electrically couple the electrode  90  to the generator  12  during use. The electrode  90  and the array of electrodes  62  are connected to opposite terminals of the generator  12  for delivering energy to target tissue in a bipolar mode. In other embodiments, the ablation assembly  50  does not include the electrode  90  ( FIG. 4 ). In such cases, the system  10  further includes an electrode pad  92  electrically coupled to the generator  12 . The electrode pad  92  functions as a return electrode, and operates in conjunction with the ablation assembly  50  to deliver energy to target tissue in a monopolar mode. 
         [0027]    Referring now to  FIGS. 5A-5D , the ablation system  10  may be used to treat at least a portion, e.g., a target tissue TS, within a treatment region TR within tissue T located beneath skin or an organ surface S of a patient. First, if an introducer sheath/catheter  100  is provided, the introducer sheath  100  can be inserted through a patient&#39;s skin and into a vessel V. The introducer sheath  100  is then steered through the vessel V in a conventional manner (e.g., using a guidewire or a steering mechanism) until its distal end  102  is at or adjacent to the treatment region TR. As shown in  FIG. 5A , the sharp distal tip of the introducer sheath  100  can then be used to puncture the vessel V to gain access to the treatment region TR. Next, the ablation assembly  50  is inserted into the introducer sheath  100 , and is advanced until the distal end  70  of the sheath  52  of the ablation assembly  50  reaches the treatment region TR ( FIG. 5B ). In other embodiments, instead of using an introducer sheath/catheter  100 , if the ablation assembly  50  includes the steering mechanism  80 , the ablation assembly  50  can be inserted through a patient&#39;s skin and into the vessel V, and be steered to a desired location at or adjacent to the target region TR. In one implementation, a transjugular approach may be used, in which the distal end  70  is inserted through a jugular vein in the patient&#39;s neck. After the distal end  70  of the sheath  52  has been inserted through the patient&#39;s skin, the distal end  70  is then steered to the tissue T, such as a liver tissue, through the vessel V. The sheath  52  may be steered by using the guidewire in a conventional manner, or by applying tension to steering wire(s) (if the steering mechanism  80  is provided). If the sheath  52  has a sharp distal tip, it can be used to puncture the vessel V to allow the distal end  70  of the sheath  52  to gain access to the target region TR. In other embodiments, a separate puncturing device, such as a wire or a needle, can be inserted through the sheath  52  to puncture the vessel V. 
         [0028]    Turning to  FIG. 5C , after the sheath  52  is properly placed, the shaft  56  of the ablation assembly  50  is then advanced distally, thereby deploying the array of electrode tines  62  from the distal end  70  of the sheath  52  into the target tissue TS at the target region TR. As illustrated, delivering the electrode tines  62  via the vessel V that leads to the target region TR is advantageous in that, if any bleeding occurs at the target region TR, it will do so back into the vessel V. In the illustrated embodiments, the electrode tines  62  are deployed such the electrode tines  62  are located in close proximity (e.g., within 0.1 millimeter (mm) to 10 mm) to the vessel V. In such arrangement, the distal ends of the electrode tines  62  are positioned among or around sub-branches (not shown) of the vessel V, thereby allowing ablation energy to be effectively delivered to the target tissue TS while minimizing, or at least reducing, the effect of the heat sink due to blood delivered to or from the target region TR. As shown in the figure, the distal ends  63  of the deployed electrode tines  62  are distal to the distal end of the vessel V. Alternatively, the distal ends  63  of the deployed electrode tines  62  may be proximal to the distal end of the vessel V such that the deployed electrode tines  62  at least partially circumscribe a portion of the vessel V. Preferably, the electrode tines  62  are biased to curve radially outwardly as they are deployed from the sheath  52 . The shaft  56  of the ablation device  18  may be advanced sufficiently such that the electrode tines  62  fully deploy to circumscribe substantially tissue within the target tissue TS of treatment region TR, as shown in  FIG. 5D . Alternatively, the electrode tines  62  may be only partially deployed or deployed incrementally in stages during a procedure. 
         [0029]    Next, energy, preferably RF electrical energy, may be delivered from the generator  12  to the wires  62  of the ablation device  18 , thereby substantially creating a lesion at the target tissue TS of the treatment region TR. If the system of  FIG. 1  is used, the electrode  90  and the electrodes  62  will operate to deliver ablation energy in a bipolar mode. In such cases, ablation energy will flow between the electrode  90  and the array of electrodes  62 . Alternatively, if the system of  FIG. 4  is used, the electrode pad  92  may be coupled to the opposite terminal (not shown) of the generator  12 , and is placed on the patient&#39;s skin in a conventional manner. In such cases, ablation energy will flow between the electrode pad  92  and the electrodes  62 , thereby delivering ablation energy in a monopolar manner. As shown in the figure, the deployed electrodes  62  have distal ends  63  that point at least partially towards a proximal end (e.g., a component of the vector representing the direction in which the distal ends  63  point is towards a proximal end—e.g., towards the vessel V). Such configuration allows the ablation energy to be effectively delivered to the target tissue TS while minimizing, or at least reducing, the heat sink effect resulted from blood flowing to or from the vessel V. 
         [0030]    When a desired lesion at the target tissue TS of the treatment region TR has been created, the electrode tines  62  of the ablation device  18  may be retracted into the lumen  54  of the sheath  52 , and the ablation device  18  may be removed from the treatment region TR. In some cases, the entire treatment region TR may be ablated in a single pass. In other cases, if it is desired to perform further ablation to increase the lesion size or to create lesions at different site(s), e.g., at other target tissue TS, within the treatment region TR or elsewhere, the electrode tines  62  of the ablation device  18  may be introduced and deployed at different target site(s), and the same steps discussed previously may be repeated. 
         [0031]    Although particular embodiments have been shown and described, it will be understood that it is not intended to limit the present inventions to the preferred embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventions. For example, the electrode tines  62  may be a single electrode made from a plurality of conductive components, or a plurality of electrodes. As such, the term, “a plurality of electrodes” should not be limited to more than one electrode, and may include a single electrode having a plurality of conductive components/parts. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The present inventions are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present inventions as defined by the claims.