Patent Publication Number: US-2011054459-A1

Title: Ecogenic Cooled Microwave Ablation Antenna

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to medical/surgical ablation assemblies and methods of their use. More particularly, the present disclosure relates to an ecogenic cooled microwave ablation system and antenna assemblies configured for direct insertion into tissue for diagnosis and treatment of the tissue and methods of using the same. 
     2. Background of Related Art 
     In the treatment of diseases such as cancer, certain types of cancer cells have been found to denature at elevated temperatures (which are slightly lower than temperatures normally injurious to healthy cells). These types of treatments, known generally as hyperthermia therapy, typically utilize electromagnetic radiation to heat diseased cells to temperatures above 41° C. while maintaining adjacent healthy cells at lower temperatures where irreversible cell destruction will not occur. Other procedures utilizing electromagnetic radiation to heat tissue also include ablation and coagulation of the tissue. Such microwave ablation procedures, e.g., such as those performed for menorrhagia, are typically done to ablate and coagulate the targeted tissue to denature or kill it. Many procedures and types of devices utilizing electromagnetic radiation therapy are known in the art. Such microwave therapy is typically used in the treatment of tissue and organs such as the prostate, heart, and liver. 
     One procedure generally involves the treatment of tissue (e.g., a tumor) underlying the skin via the use of a percutaneously inserted microwave energy delivery device. The microwave energy delivery device penetrates the skin and is positioned relative to the target tissue, however, the effectiveness of such a procedure is often determined by the precision in which the microwave energy delivery device is positioned. Thus, the placement of the microwave energy delivery device requires a great deal of control. 
     SUMMARY 
     The present disclosure describes an electrosurgical positioning and energy delivery system for direct insertion into tissue. The electrosurgical positioning and energy delivery system includes a positioning introducer, a microwave energy delivery device and a jacket configured to slideably receive one of the positioning introducer and the microwave energy delivery device. The positioning introducer and the jacket form a positioning assembly and are configured for percutaneous insertion in patient tissue. The positioning assembly is visible percutaneously to an imaging system. The microwave energy delivery device and the jacket form a microwave energy delivery assembly. The microwave energy delivery assembly is configured to circulate cooling fluid therethrough during delivery of microwave energy to the patient tissue. 
     In one embodiment the positioning introducer is hyperechoic. In another embodiment, the positioning introducer is visible to an ultrasonic imaging system and/or an MRI imaging system. The positioning introducer may include a treatment configured to improve visibility of the positioning introducer by an ultrasonic imaging system. The treatment may include a surface dispersion treatment, a dimpled surface and a surface of imbedded particles. The positioning introducer may include a resonant material that resonates when exposed to energy transmitted from the ultrasonic imaging system. One resonate material is a crystalline polymer. 
     In yet another embodiment, the positioning introducer includes a geometry that resonates at the frequency of the energy transmitted from the ultrasonic imaging system. The geometry is defined by at least one of wall thickness of the positioning introducer, a gap defined in a periphery of the positioning introducer, a series of grooves defined in a periphery of the positioning introducer and a fin extending from a periphery of the positioning introducer. 
     In yet another embodiment, the positioning introducer includes a non-ferromagnetic material that is percutaneously visible to an MRI imaging system. The non-ferromagnetic material may include one of a ceramic, titanium and plastic. 
     In yet another embodiment, the jacket, assembled with the positioning introducer, includes a geometry at a distal end thereof to facilitate tissue penetration. 
     In still yet another embodiment the microwave energy delivery assembly is adapted to connect to a microwave energy source that supplies a microwave energy signal. The microwave energy delivery may also be adapted to connect to a cooling fluid source that supplies cooling fluid. 
     A method for deploying an electrosurgical energy apparatus includes the steps of: providing an electrosurgical positioning and energy delivery system including a positioning introducer, a microwave energy delivery device and a jacket configured to slideably receive one of the positioning introducer and the microwave energy delivery device; forming a positioning assembly by slideably receiving the positioning introducer within the jacket; advancing the positioning assembly to target tissue whereby the advancement of the positioning assembly is percutaneously observed on a image system, the positioning assembly defining a pathway during tissue penetration; withdrawing the positioning introducer from the jacket, with the jacket remaining in situ; forming a microwave energy delivery assembly by slideably receiving the microwave energy delivery device within the jacket; treating target tissue with electrosurgical microwave energy; and withdrawing the microwave energy delivery assembly from the pathway. 
     The method may further include the steps of: connecting a fluid supply to the microwave energy delivery device and a cooling fluid return to the jacket and circulating the cooling fluid through at least a portion of the microwave energy delivery assembly to absorb thermal energy therefrom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  are perspective views of the positioning assembly according to an embodiment of the present disclosure including a positioning introducer and an outer jacket; 
         FIG. 2A  is an illustration of the positioning assembly of  FIG. 1B  partially inserted into tissue; 
         FIG. 2B  is an illustration of the positioning introducer removed from the jacket after the jacket is positioned in a target tissue. 
         FIG. 3A  is a perspective view of a microwave energy delivery assembly according to another embodiment of the present disclosure including a microwave energy delivery device and an outer jacket; 
         FIG. 3B  is a cross sectional view of the assembled microwave energy delivery assembly of  FIG. 3A ; 
         FIG. 4A  is an illustration of the microwave energy delivery device being inserted into the jacket positioned in a tissue pathway; 
         FIG. 4B  is an illustration of the energy delivery device assembly positioned in a tissue pathway; and 
         FIGS. 5A-5D  are prospective views of various jacket configurations according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed assemblies, systems and methods are described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. As used herein and as is traditional, the term “distal” refers to the portion which is furthest from the user and the term “proximal” refers to the portion that is closest to the user. In addition, terms such as “above”, “below”, “forward”, “rearward”, etc. refer to the orientation of the figures or the direction of components and are simply used for convenience of description. 
     During invasive treatment of diseased areas of tissue in a patient, the insertion and placement of an electrosurgical energy delivery apparatus, such as a microwave antenna assembly, relative to the diseased area of tissue is important for successful treatment. Generally, assemblies described herein allow for placement of a microwave antenna in a target tissue in a two step process. In a first step, a positioning assembly is directly inserted and positioned into target tissue and in a second step the positioning introducer is removed from a positioning jacket and replaced with a microwave energy delivery device, the jacket and microwave energy delivery device thereby forming an energy delivery device assembly in the target tissue. 
     Referring now to  FIGS. 1A-1B , a positioning assembly, according to an embodiment of the present disclosure, is shown as  10 . The positioning assembly  10  includes a positioning introducer  16  and a jacket  20 . The positioning introducer  16  includes a handle  14  that connects to an elongated shaft  12 . The elongated shaft  12  includes a tip  13  at a distal end thereof. Jacket  20  includes a receiver portion  20   a,  a sheath portion  20   b,  a receptacle tip portion  20   c  and a fluid outlet  204 . Sharpened tip  21  (on the distal end of the receiver portion  20   a ) is configured to be percutaneously inserted into tissue to define a pathway therethrough. 
     As illustrated in  FIG. 2B , the positioning introducer  16  is configured to slideably engage the jacket  20  and forms a percutaneously insertable positioning assembly  10 . Receiver portion  20   a  of the jacket  20  is configured to receive at least a portion of the handle  14  of the positioning introducer  16  thereby forming an assembly handle  15 . Assembly handle  15 , when grasped by a clinician, enables the clinician to control the positioning assembly  10  during insertion. Sheath portion  20   b  is configured to slideably engage the elongated shaft  12 . 
     Receptacle tip portion  20   c  is configured to receive and engage at least a portion of tip  13  thereby forming a structurally rigid tip assembly  22  with the sharpened tip  21  on the distal end of the positioning assembly  10 . 
     Elongated shaft  12  and tip  13  of positioning introducer  16  are configured to produce a highly identifiable image on a suitable imaging system used to aid in the positioning of an ablation device in target tissue. The elongated shaft  12  and tip  13  may be highly identifiable due to one or more materials used in their construction and/or one or more identifiable features incorporated into the design and/or the materials of the positioning introducer  16 . 
     In one embodiment, the elongated shaft  12  and tip  13  of the positioning introducer  16  are readily identifiable by an ultrasonic imaging system  40 , as illustrated in  FIG. 2A . Ultrasonic imaging system  40  includes an imaging device  40   a,  such as, for example, a suitable ultrasonic transducer, a display  40   b  and one or more suitable input devices such as, for example, a keypad  40   c,  keyboard  40   e,  a pointing device  40   d  and/or an external display (not explicitly shown). 
     As illustrated in  FIG. 2A , the positioning assembly  100  is percutaneously inserted into patient tissue  60 . During insertion, the disposition of the positioning assembly  100  with respect to the target tissue is percutaneously observed on the display  40   b  of the imaging device  40 . The hyperechoic positioning introducer  116  of the positioning assembly  100  is easily identifiable on display  40   b.  The positioning assembly  100  is guided by a clinician into a desirable position within a portion of the target tissue  60   a  while the clinician percutaneously observes the advancement of the positioning assembly  100  on the display  40   b  forming a pathway in tissue. 
     Various echogenic treatments may be applied to the positioning introducer  116  to enhance the ability of the ultrasonic imaging device  40  to replicate the positioning introducer on the display  40   b.  In one embodiment, the positioning introducer  116  includes a surface dispersion treatment. The surface dispersion treatment may include a dimpled surface or a surface imbedded with particles wherein the surface dispersion treatment creates wide angles of dispersion of the energy transmitted from the imaging device  40   a.  In another embodiment, the positioning introducer  116  is formed from a composite material that includes particles or fibers bonded within the structure wherein the orientation of the particles or fibers create a wider angle of dispersion of the energy transmitted from the imaging device  40   a.    
     In yet another embodiment, the positioning introducer  116  includes resonant materials or structures configured to resonate when exposed to energy transmitted from the imagine device  40   a.  The positioning introducer  116  may include materials, such as crystalline polymers, that absorb energy and resonate when exposed to the energy transmitted from the imaging device  40   a.  Alternatively, the surface of the positioning introducer  116  may include specific geometries, such as, for example, wall thickness of the positioning introducer  116 , gaps defined in a periphery of the positioning introducer  116 , a groove or a series of groves defined in a periphery of the positioning introducer  116  and/or fins extending from a periphery of the positioning introducer  116 , wherein the specific geometry is configured to resonate at the frequency of the energy transmitted from the imagine device  40   a.    
     In yet another embodiment, a clinician may utilize a Magnetic Resonance Imaging (MRI) device to observe the positioning introducer  116  during the positioning step. The positioning introducer  116 , when used with an MRI device, may include one or more non-ferromagnetic materials with very low electrical conductivity, such as, for example, ceramic, titanium and plastic. 
     As illustrated in  FIG. 2B , after positioning, where the positioning assembly  100  is properly positioned in the target tissue  60   a,  the positioning introducer  116  is removed from the jacket  120   b  leaving at least a portion of the jacket  120  in the tissue pathway created during the positioning step. The jacket  120  is further configured to receive a microwave energy delivery device  370  as further described hereinbelow and illustrated in  FIGS. 3A-3B . 
     In one embodiment, at least a portion of the jacket  120  lacks sufficient structural strength to maintain a form and/or a structure in the patient tissue  60  or in the target tissue  60   a  after the positioning introducer  116  is removed from the jacket  120 . For example, during or after removal of the positioning introducer  116  a portion of the jacket  120  may collapse inward and/or upon itself. Collapsing of a portion of the jacket  120 , such as the sheath  120   b,  as illustrated in  FIG. 2B , may reduce or relieve vacuum created during the removal of the sheath  120   b.    
     In another embodiment the cooling jacket is radiually flexible, (e.g. expandable in the radial direction). As such, the positioning introducer  116  of  FIGS. 1A-1B  may be formed as a smaller gage than the microwave energy delivery device  370  illustrated in  FIGS. 3A-3B . During insertion, the positioning assembly  100  forms a smaller initial puncture site in patient tissue  60  that will typically stretch to accommodate the larger microwave energy delivery device  370  without enlarging or creating a further incision. 
     Elongated shaft  112  of positioning introducer  116  may provide a passageway for fluids to flow between the distal and proximal ends of the elongated shaft  112 . For example, the elongated shaft  112  may form a tip vent hole  112   b  and a handle vent hole  112   c  fluidly connected by a lumen  112   a.  Lumen  112   a  provides a passageway for fluid (e.g., air, water, saline and/or blood) to flow through the positioning introducer  16  and in or out of the jacket  20  to relieve vacuum or pressure that may be created when the positioning introducer  16  is moved within the jacket  120 . 
     In another embodiment, the outer surface of the elongated shaft  112  may form one or more channels (not explicitly shown) that extend longitudinally between the distal end and the proximal end of the elongated shaft  112 . In yet another embodiment, the elongated shaft  112  of the positioning introducer  116  may be formed of a porous material that includes a structure that facilitates the flow of fluid longitudinally between the distal end and the proximal end of the elongated shaft  112 . 
     The sharpened tip  121  may be configured to maintain a form and/or a structure after the removal of the positioning introducer  116  as illustrated in  FIG. 2B . 
       FIG. 3A  is a perspective view of the disassembled microwave energy delivery assembly  300  according to an embodiment of the present disclosure. Microwave energy delivery assembly  300  includes a microwave energy delivery device  370  and the jacket  320  of the positioning assembly  10  of  FIGS. 1A-1B . The microwave energy delivery device  370  is configured to slideably engage jacket  320  and form a fluid-cooled microwave energy delivery assembly  300  as illustrated in  FIG. 3B  and described hereinbelow. 
     Microwave energy delivery device  370  includes an input section  378 , a sealing section  380   a  and an antenna section  372 . Input section  378  includes a fluid input port  378   a  and a power connector  378   b.  Fluid input port  378   a  connects to a suitable cooling fluid supply (not explicitly shown) configured to provide cooling fluid to an electrosurgical energy delivery device. A power connector  378   b  is configured to connect to a microwave energy source such as a microwave generator. Sealing section  380   a  of the microwave energy delivery device  370  interfaces with the sealing section  380   b  of the jacket  320  and is configured to form a fluid-tight seal therebetween. Antenna section  372  includes a microwave antenna  371  configured to radiate energy when provided with a microwave energy power signal. A cooling fluid exit port  374  resides in fluid communication with fluid input port  378   a.  More particularly, fluid supplied to the fluid input port  378   a  flows through one or more lumens formed within the microwave energy delivery device  370  and exits though the cooling fluid exit port  374 . Tip  376  of the microwave energy delivery device  370  is configured to engage receptacle tip  320   c  of jacket  320 . 
       FIG. 3B  is a cross sectional view of the assembled microwave energy delivery assembly of  FIG. 3A  according to an embodiment of the present disclosure. Microwave energy delivery device  370  slideably engages jacket  320  such that the sealing section  380   a  and tip  376  of the microwave energy delivery device  370  engage the jacket sealing section  380   b  and receptacle tip  320   c  of the jacket  320 , respectively, and form a fluid-tight seal therebetween. 
     In use, the energy delivery device assembly  300  is configured as a fluid-cooled microwave energy delivery device. As illustrated by the flow arrows  375  in  FIG. 3B , fluid enters the fluid input port  378   a  and travels distally through the microwave energy delivery device  370  to the cooling fluid exit port  374 . A fluid-tight engagement between the tip  376  and the receptacle tip  320   c  limits the flow of fluid distally relative to the cooling fluid exit port  374 . Fluid that exits the cooling fluid exit port  374  flows proximally through a lumen  376  formed between the outer surface of the microwave energy delivery device  370  and the inner surface of the jacket  320  thereby cooling at least a portion of the sheath portion  320   b  of the jacket  320 . Fluid exits the energy delivery device assembly  300  through the fluid outlet  320   d.    
     The tip  376  of the microwave energy delivery device  370  and the receptacle tip  320   c  may be any suitable shape provided that tip  376  and receptacle tip  320   c  mutually engage one another. 
     As illustrated in  FIGS. 4A and 4B , an energy delivery assembly  400  includes the microwave energy delivery device  470  described similarly hereinabove and illustrated in  FIGS. 3A and 3B  and the jacket  420  described similarly hereinabove and illustrated in  FIGS. 1A-1B  and  FIGS. 3A-3B  and shown as  20  and  320 , respectively. The jacket  420  in  FIG. 4A and 4B  is similar to jacket  320  of the positioning assembly  100  of  FIGS. 2A-2B  positioned in the pathway in tissue  460  and in the target tissue  460   a .) The microwave energy delivery assembly  400  is assembled by inserting the microwave energy delivery device  470  into the jacket  420  as indicated by the arrow “A”. 
     After assembling the microwave energy delivery assembly  400  in the tissue pathway, a fluid supply (not shown) connects to the fluid input port  478   a,  a fluid drain connects to the fluid outlet  420   d  and a suitable microwave energy signal source connects to the power connector  478   b.  Fluid is circulated through the microwave energy delivery assembly  400  in a similar fashion as described above and energy is delivered to the target tissue  460   a  through the antenna  472  of the microwave energy delivery device  470 . 
     After a suitable amount of energy is delivered to the target tissue  460   a,  the microwave energy delivery assembly  400  is removed from the tissue pathway. In one embodiment, the assembly  400  is removed by grasping the receiver portion  420   a  of the jacket  420  and the input section  478  of the microwave energy delivery device  470  and withdrawing the assembly from the patient. 
       FIGS. 5A-5D  are each cross-sectional views of the distal portion of a jacket  520   a - 520   d  according to various embodiments of the present disclosure. In  FIG. 5A , jacket  520   a  includes a semi-rigid sheath  580   a  and a semi-rigid receptacle tip  582   a.  The semi-rigid receptacle tip  582   a  forms a sharpened tip  521   a  at the distal end that is sufficiently rigid to pierce tissue. In  FIG. 5B , jacket  520   b  includes a flexible sheath  580   b  and a semi-rigid receptacle tip  582   b.  Flexible sheath  580   b  may stretch in diameter and/or length to accommodate the positioning introducer and/or the microwave energy delivery device when inserted into the jacket  520   b  as described hereinabove. In one embodiment, at least a portion of the receptacle tip  582   b  forms a portion of the microwave antenna  571   b  and radiates energy to tissue. In yet another embodiment at least a portion of the sheath  580   b  includes a microwave energy choke  573  capable of preventing energy from traveling proximally from the antenna. 
     In  FIG. 5C , jacket  520   c  includes a flexible sheath  580   c  and a rigid receptacle tip  582   c.  Jacket  520   c  is configured to receive a sharpened or pointed tip. In  FIG. 5D , jacket  520   d  includes a flexible sheath  582   d  and a flexible receptacle tip  582   d.  A distal tip  521   d  is configured to receive a positioning introducer and microwave energy delivery device with a sharpened tip. The receptacle tip  582   d  is configured to form a watertight seal between the jacket  520   d  and the introducer (e.g., introducer  16 , see  FIG. 1 ) and/or the delivery device (e.g., delivery device  370 , see  FIG. 3A ) inserted therewithin. 
     The assemblies and methods of using the assemblies discussed above are not limited to microwave antennas used for hyperthermic, ablation, and coagulation treatments but may include any number of further microwave antenna applications. Modification of the above-described assemblies and methods for using the same, and variations of aspects of the disclosure that are obvious to those of skill in the art are intended to be within the scope of the claims.