Abstract:
A system for use in tumor ablation. The tumor ablation system includes a microwave antenna which has a channel along the length thereof. There are two ports proximate the proximal end of the microwave antenna. The first port is an energy port configured to connect the antenna to an energy source. The second port is a fluid port configured to connect the channel to a fluid delivery mechanism. The system also includes an inflatable balloon configured to be attached to a distal end of the antenna. The channel permits fluid access from the fluid port to an interior of the balloon for inflation thereof.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to a tumor ablation system. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    Spinal metastases are the most common cause of severe pain among patients with cancer. Spinal metastases are also often accompanied by vertebral compression fractures. 
         [0003]    Balloon kyphoplasty is a minimally invasive procedure designed to repair vertebral compression fractures by reducing and stabilizing the fractures. Reduction is accomplished by inserting at least one compliant balloon into the central portion of the fractured vertebral body. The balloon(s) are carefully inflated such that the cancellous bone is pushed out toward the cortical was until the vertebral body returns to the correct height. After reduction, the balloons are deflated and removed. Stabilization is accomplished by filling the resulting cavities with bone cement. The bone cement hardens, forming an internal cast, stabilizing the fracture. 
         [0004]    Radiofrequency ablation is used for the destruction of unwanted tissue, including tumors. During radiofrequency ablation, a probe is inserted into the unwanted tissue. A plurality of small electrodes are deployed from the end of the probe to encompass the unwanted tissue. The opposite end of the probe is connected to a radiofrequency generator which sends radiofrequency energy through the electrodes causing the immediately adjacent tissue to heat up. Once the unwanted tissue reaches a sufficient temperature for a specific period of time, the tissue dies. Radiofrequency ablation of a tumor takes about 20-30 minutes. 
         [0005]    Microwave ablation is also used for the destruction of unwanted tissue, including tumors. During microwave ablation, a probe is inserted into the unwanted tissue. The other end of the probe is connected to a microwave generator which sends microwave energy through the end of the probe and causes the nearby tissue to heat up. Once the unwanted tissue reaches a sufficient temperature for a specific period of time, the tissue dies. Microwave ablation of a tumor takes about 10-15 minutes. However, the direct heating caused by the emitted microwave energy creates a risk of heating, and therefore damaging, the sensitive neural pathways adjacent the vertebral body. 
         [0006]    Therefore, there is a need for an apparatus and method for quickly repairing vertebral compression fractures while ablating a tumor without causing damage to nearby neural pathways or other vital organs. 
       SUMMARY OF THE INVENTION 
       [0007]    A microwave antenna, in accordance with the present invention, includes an inner conductor and an outer conductor separated by a dielectric. The outer conductor is surrounded by a shield. The dielectric includes a channel that extends along the length of the antenna and connects a fluid port at a proximal end of the antenna to an inflatable balloon attached to a distal end of the antenna. The fluid port is attached via tubing to a high pressure syringe filled with a mixture of saline and contrast material or simply with sterile water. 
         [0008]    The proximal end of the antenna also includes a microwave port that facilitates the attachment of a microwave generator to the inner and outer conductors of the microwave antenna to enable the transmission of microwave energy from the microwave generator to the fluid in the balloon attached to the proximal end of the antenna and the adjacent tissue. 
         [0009]    The method includes placing the patient in the prone position and making an incision in the skin. The surgeon inserts a cannula through the incision into contact with the bone that has a tumor. The surgeon introduces a drill through the cannula and creates an opening in the bone and into the tumor. Next, the surgeon inserts the antenna through the cannula to position the balloon in the opening. With the balloon in the opening, the surgeon depresses the plunger on the high pressure syringe, which forces saline and contrast material into the balloon. The saline inflates the balloon and presses against the tumor. With the balloon pressing against the tumor, the surgeon turns on the microwave generator. The microwave energy heats the mixture in the balloon, which conducts the heat into the tumor. Once the heat destroys the tumor, the microwave generator is turned off. 
         [0010]    After the tumor is destroyed, the balloon is further inflated until the fracture is reduced. After reduction is achieved, the balloon is deflated and the resulting cavity is filled with bone cement for stabilization. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages, and principles of the invention. In the drawings: 
           [0012]      FIG. 1  is a partially cross-sectional elevational view of a system for use in tumor ablation and vertebral compression fracture repair in accordance with an embodiment of the present invention showing a microwave antenna with a balloon attached to the distal end thereof inserted into a fractured vertebral body and a high pressure syringe and microwave generator connected to the proximal end of the microwave antenna; 
           [0013]      FIG. 2  is a partially cross-sectional plan view of the microwave antenna of the system shown in  FIG. 1  for use in tumor ablation and vertebral compression fracture repair showing the balloon partially inflated inside the fractured vertebral body; 
           [0014]      FIG. 3A  is a cross-sectional view of the distal end of the microwave antenna for use in tumor ablation and vertebral compression fracture repair showing saline inflating the balloon; 
           [0015]      FIG. 3B  is an enlarged cross-sectional view of the antenna show in  FIG. 3A . 
           [0016]      FIG. 3C  is a cross-sectional view of an alternative embodiment of the antenna show in  FIGS. 3A and 3B . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the embodiments described below be considered as exemplary only, with a true scope and spirit of the invention being indicated by the appended claims. 
         [0018]    The detailed description of the invention below is described for, and shown in the figures for, use in a fractured vertebral body V. However, it should be understood that the invention could be used for tumor ablation as well as reduction in any bone. 
         [0019]    As shown in  FIGS. 1-3A , a system  10  for use in tumor ablation includes a microwave antenna  20  and a balloon  50  configured to be attached to the distal end of antenna  20 . Balloon  50  and the majority of the length of microwave antenna  20  is sized and configured to be inserted through a cannula  60  into an opening prepared in fractured vertebral body V. 
         [0020]    As shown in  FIGS. 3A and 3B , antenna  20  includes an inner conductor  21  which extends along a length of antenna  20 . Inner conductor  21  may be constructed of copper or any other conductive material suitable for transmission of microwave energy. Antenna  20  further includes a dielectric layer  22  surrounding inner conductor  21 . Dielectric layer  22  may be constructed of Teflon or any other material suitable for use as a dielectric. Dielectric layer  22  is surrounded by an outer conductor  24  constructed of copper or any other suitable conductive material. Outer conductor  24  is surrounded by a shield  25  to electrically and thermally insulate outer conductor  24 . Outer conductor  24 , inner conductor  21 , and dielectric  22  form a coaxial structure. Antenna  20  may further include a handle  26  ( FIGS. 1 and 2 ) at the proximal end thereof to control the movement of antenna  20 . 
         [0021]    As shown in  FIG. 3A , inner conductor  21  extends beyond the distal ends of dielectric layer  22 , outer conductor  24 , and shield  25 , such that inner conductor  21  extends into balloon  50  when balloon  50  is attached to the distal end of antenna  20 . Balloon  50  may include a flexible member  52  attached to the distal end of balloon  50 . Alternatively, the distal end of flexible member  52  may be free floating. A further alternative may include inner conductor  21  attached to the distal end of balloon  50 . Proximal end of flexible member  52  is configured to attach to distal end of inner conductor  21  through a bonding process. 
         [0022]    As shown in  FIGS. 1 and 2 , antenna  20  includes a fluid port  30  proximate the proximal end of antenna  20 . Fluid port  30  facilitates attachment of a high pressure syringe  34  via tubing  32 . High pressure syringe  34  includes a barrel  35  and a plunger  36 . Fluid port  30  is in communication with a channel  23  ( FIGS. 3A and 3B ), or alternatively, multiple channels  23  (FIG. C). Channel  23  runs the length of antenna  20  through dielectric layer  22  and communicates with the interior of balloon  50 . As such, pressing plunger  36  forces saline  38  and contrast material out of barrel  35  through tubing  32 , fluid port  30 , and channel  23 , and into balloon  50 . The increase of volume of saline  38  and contrast material in balloon  50  causes balloon  50  to inflate. The inflation of balloon  50  causes balloon  50  to apply pressure to the tumor, ensuring a good contact between balloon  50  and vertebral body V. Continued inflation of balloon  50  causes the cancellous bone to be pressed outward toward the cortical layer of fractured vertebral body V. Balloon  50  is inflated until fractured vertebral body V achieves the desired corrected height. 
         [0023]    As shown in  FIGS. 1 and 2 , antenna  20  includes an energy port  40  proximate the proximal end of antenna  20 . Energy port  40  facilitates attachment of a microwave generator  44  via a coaxial cable  42 . Energy port  40  facilitates the transmission of microwave energy from coaxial cable  42  to inner and outer conductors  21  and  24 . The microwave energy exits the distal end of antenna  20 . The microwave energy exiting the distal end of antenna  20  heats the saline  38  within balloon  50 . The heated saline  38  conducts heat to the tumor. The conducted heat is used to destroy the tumor. The microwave energy preferentially heats the saline and contrast mixture and therefore reduces the negative impact of microwave energy to adjacent vital structures. The direct heating effect of microwave ablation is replaced by indirect heating through conduction. As such, since most of the microwave energy is used to heat the saline and contrast mixture, the present invention will reduce harmful effects of microwave energy on the adjacent structures. In addition, performing the balloon inflation simultaneously with the ablation will reduce the duration of the procedure and may help the balloon kyphoplasty procedure as the bone softens. The temperature of the heated saline  38  may be monitored via a temperature probe (not shown) located at the distal end of the microwave antenna or at the distal end of outer conductor  24 . The temperature inside balloon  50  may be monitored with a temperature sensing element such as RTD, TC, fiber optic thermometer or radiometry. 
         [0024]    In a preferred embodiment of the present invention, system  10  is utilized in the following manner. The preferred method includes placing the patient in the prone position and making a small incision in the skin over fractured vertebral body V. The surgeon then inserts a cannula  60  through the incision into contact with fractured vertebral body V. The surgeon may manipulate the position of the cannula  60  by grasping a handle  62  located at the proximal end of cannula  60 . When the cannula  60  is properly aligned, the surgeon introduces a drill (not shown) through cannula  60  and creates an opening in fractured vertebral body V and into the tumor. The surgeon withdrawals the drill and inserts antenna  20  through cannula  60  until balloon  50  is positioned within the opening created in fractured vertebral body V. With balloon  50  in the opening, the surgeon depresses plunger  36  on high pressure syringe  34 , forcing saline  38  and the contrast material into balloon  50 . The saline  38  inflates balloon  50 , causing balloon  50  to press against the tumor. With balloon  50  pressing against the tumor, the surgeon turns on microwave generator  44 . The microwave energy heats saline  38  in balloon  50 . Saline  38  conducts the heat into the tumor. After the heat destroys the tumor, microwave generator  44  is turned off. At this point, the surgeon further depresses plunger  36 , causing further inflation of balloon  50  until the correct height of fractured vertebral body V is achieved. When the correct height is achieved, balloon  50  is deflated and removed from fractured vertebral body V, leaving a larger cavity in fractured vertebral body V. The cavity in fractured vertebral body V is then filled with polymethyl methacrylate (“PMMA”) bone cement. 
         [0025]    Alternatively, the surgeon may continue reduction of fractured vertebral body V during the application of microwave energy. In addition, part or all of the procedure may be performed on both sides of fractured vertebral body V at the same time. 
         [0026]    There is disclosed in the above description and the drawings, tumor ablation systems, which fully and effectively accomplish the objectives of this invention. It will be apparent, however, that variations and modifications of the disclosed embodiments may be made without departing from the principles of the invention or the scope of the appended claims.