Patent Publication Number: US-2006015132-A1

Title: Probe introducer with valve assembly to minimize air entry

Description:
FIELD OF INVENTION  
      The present invention relates generally to devices for introducing medical probes into the body, e.g., for performing a tissue biopsy or a radio frequency (RF) ablation procedures.  
     BACKGROUND OF THE INVENTION  
      Medical probes are slender, flexible instruments designed for introduction into a organ, cavity, or solid tissue in the body for purposes of exploration or treatment. The use of a probe allows for minimally invasive procedures to be completed with (typically) fewer complications than procedures using open surgery. While probes may also be used in open surgery, one of the advantages of using a probe is its adaptability for percutaneous procedures.  
      For example, medical probes are particularly suited for procedures in the lungs. In order to introduce a working medical probe into a lung, a solid core stylet is positioned in an inner lumen of an introducer cannula, which is then passed percutaneously through the patient&#39;s chest wall, until the distal tip of the stylet and distal cannula opening are positioned at a target location in the lung. The stylet is then withdrawn from, and the working probe inserted into, the cannula lumen. As the stylet and cannula pass through the pleural cavity, it is possible for air to enter into the cavity from between the outside diameter of the stylet and the inside diameter of the cannula. Similarly, during removal of the stylet and introduction of a working probe in the cannula lumen, the same possibility of air passage into the pleural cavity from between the outer diameter of the probe and the inner diameter of the cannula exists. Once air enters the pleural cavity, pressure in the pleura can become greater than the pressure in the lung, causing the lung to partially or completely collapse.  
      Thus, it is desirable to provide an apparatus for introducing a medical probe into a lung, or other body organ or cavity, while minimizing the unwanted and/or dangerous ancillary entry of air into the body.  
     SUMMARY OF THE INVENTION  
      In accordance with the present inventions, an introducer for accessing an internal body region is provided. The introducer comprises a cannula having an axial lumen configured to receive a medical probe and a distal port from which the medical probe can be deployed. In one embodiment, the cannula is rigid, although in some cases, the cannula may be semi-rigid or even flexible. The introducer further comprises a valve assembly located on cannula in communication with the distal cannula port. The valve assembly is preferably located at the proximal end of the cannula in order to minimize the design constraints on the valve assembly, although the valve assembly can be located anywhere along the cannula without straying from the principles taught by this invention.  
      In accordance with one aspect of the inventive introducer, the valve assembly is configured to allow passage of the medical probe, while substantially sealing the distal cannula port from an external environment during passage of the medical probe. In accordance with another separate aspect of the inventive introducer, the valve assembly comprises a slit valve in communication with the cannula lumen. The slit valve is configured to allow passage of the medical probe. In accordance with still another separate aspect of the inventive introducer, the valve assembly is a multi-stage valve assembly to further ensure that the distal cannula port is sealed. The multi-stage valve assembly comprises a first valve configured to allow passage of the medical probe, while substantially sealing the distal cannula port from an external environment during passage of the medical probe, and a manually adjustable second valve, such as a rotary valve, configured to seal around the medical probe. In one embodiment, the first valve also seals the cannula lumen from the external environment when the medical probe does not reside within the valve assembly.  
      In accordance with the present inventions, a medical kit comprising any one of the previous introducers is provided. The medical kit further comprises a medical probe, such as a stylet probe, therapeutic probe (e.g., a radio frequency ablation probe), or a diagnostic probe (e.g., a biopsy probe). Optionally, the medical kit comprises two or more medical probes that can be exchanged within the introducer.  
      In accordance with the present inventions, a method of accessing an internal region (e.g., a lung) within a body is provided. The method comprises introducing a cannula into the body (e.g., using a percutaneous procedure), wherein a distal port of the cannula is adjacent the internal region (e.g., in the pleural cavity if the internal region is the lung), and introducing a medical probe (such as a stylet probe, diagnostic probe, or therapeutic probe) through the cannula to deploy the medical probe from the distal cannula port. The cannula may be introduced into the body while the medical probe is deployed from the distal cannula port, in which case, the medical probe will be used to pierce tissue. The method may optionally comprise using the medical probe to perform a medical procedure (e.g., a therapeutic or diagnostic procedure) on the internal region.  
      In accordance with one aspect, the inventive method further comprises substantially sealing the distal cannula port from an external environment while the medical probe is introduced through the cannula. The distal cannula port can be sealed at a location proximal to the cannula, although it can be sealed anywhere along the cannula as well without straying from the principles taught by this invention. The distal cannula port can optionally also be substantially sealed prior to introducing the medical probe through the cannula. The inventive method may also comprise removing the medical probe from the cannula, in which case, the method will further comprise substantially sealing the distal cannula port from the external environment while the medical probe is removed from the cannula.  
      In accordance with another aspect, the method further comprises removing the medical probe from the cannula, and introducing another medical probe to deploy the other medical probe from distal cannula port. In this case, the distal cannula port is substantially sealed from the external environment while both medical probes are introduced into the cannula and while the first medical probe is removed from the cannula.  
      Other aspects and features of the invention will be evident from the following detailed description of the illustrated embodiments, which are provided to illustrate, and not to limit, the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The drawings illustrate the design and utility of preferred embodiment(s) of the invention, in which similar elements are referred to by common reference numerals. In order to better appreciate the advantages and objects of the invention, reference should be made to the accompanying drawings that illustrate the preferred embodiment(s). The drawings, however, are not drawn to scale and depict only some embodiment(s) of the invention, and therefore, should not be taken as limiting its scope. With this caveat, the embodiment(s) of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
       FIG. 1  is a side view of an exemplary medical probe introducer constructed in accordance with one embodiment of the invention, wherein a stylet probe is particularly shown received within the introducer;  
       FIG. 2  is a side view of the introducer of  FIG. 1 , wherein a radio frequency (RF) ablation probe is particularly shown received within the introducer;  
       FIG. 3  is a side view of the introducer of  FIG. 1 , wherein a biopsy probe is particularly shown received within the introducer;  
       FIG. 4  is a partially cutaway perspective view of a valve assembly used in the introducer of  FIG. 1 ;  
       FIG. 5  is a partially cutaway perspective view of the valve assembly of  FIG. 4 , particularly showing a stylet probe introduced through the valve assembly;  
       FIG. 6  is a partially cutaway-perspective view of a modification of the valve assembly of  FIG. 4 ;  
       FIG. 7  is a partially cutaway perspective view of a dual-stage valve assembly that can alternatively be used in the introducer of  FIG. 1 ;  
       FIG. 8  is a partially cutaway perspective view of a modification of the dual-stage valve assembly of  FIG. 7 ;  
       FIG. 9  is a partially cutaway perspective view of the dual-stage valve assembly of  FIG. 7 , particularly showing a stylet probe introduced through the valve assembly;  
       FIG. 10  is a partially cutaway perspective view of another dual-stage valve assembly that can alternatively be used in the introducer of  FIG. 1 ;  
       FIG. 11  is a partially cutaway perspective view of a modification of the dual-stage valve assembly of  FIG. 10 ;  
       FIG. 12  is a partially cutaway perspective view of the dual-stage valve assembly of  FIG. 10 , particularly showing a stylet probe introduced through the valve assembly; and  
       FIGS. 13A-13D  are side views illustrating a method of using the introducer, stylet probe, RF ablation probe, and biopsy probe of  FIGS. 1-3  to percutaneously treat a tumor within a lung of a patient. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS  
       FIGS. 1-3  illustrate an exemplary introducer  100  that can be used with a variety of medical probes, including a solid core stylet probe  102  ( FIG. 1 ), a radio frequency (RF) ablation probe  104  ( FIG. 2 ), and a biopsy probe  106  ( FIG. 3 ). Together, the introducer  100 , stylet probe  102 , ablation probe  104 , and biopsy probe  106  can be packaged and sold as a kit to a medical care provider, such as hospital. As will be described in further detail below, a physician may advance the introducer  100  into a patient&#39;s body, and place the stylet probe  102 , ablation probe  104 , and biopsy probe  106  into contact with an internal region within the patient&#39;s body. These medical probes can be exchanged in and out of the introducer  100  without exposing the internal body region to the environment external to the patient&#39;s body.  
      To this end, the introducer  100  generally comprises a cannula  110  configured to be percutaneously introduced into a patient&#39;s body, and a valve assembly  112  configured to provide a seal that prevents the internal body region from being exposed to the external environment during introduction of the cannula  110  and subsequent exchange of the stylet probe  102 , ablation probe  104 , and biopsy probe  106 . In this embodiment, the valve assembly  112  is conveniently located at the proximal end of the cannula  110 , so that it resides outside of the patient&#39;s body when the cannula  110  is inserted into the patient&#39;s body. Alternatively, however, the valve assembly  112  can be located anywhere along the cannula  110 —although such placement will not be as convenient, since additional design constraints would need to be imposed on the valve assembly  112 , and in particular, the profile of the valve assembly  112  would have to match that of the cannula  110 .  
      The cannula  110  comprises a cannula shaft  114  that is preferably rigid or semi-rigid, and constructed from medical grade metal or plastic. The cannula shaft  114  is generally a hollow tube having an axial lumen  116  (shown in phantom) extending from a proximal end opening  118  to a distal end opening  120 . The lumen  116  is sized to allow the probes (i.e., the stylet probe  102 , ablation probe  104 , and biopsy probe  106 ) to be alternately positioned therein, e.g., with the diameter of the lumen  116  preferably being 0.001 inch to 0.020 inch greater than the outer diameter of the shafts of the probes. The cannula  110  further comprises a proximal connector  122  mounted on the proximal end of the cannula shaft  114  for mating with the valve assembly  112 , as will be described in further detail below.  
      As illustrated in  FIG. 1 , the stylet probe  102  comprises a shaft  124  that is preferably rigid or semi-rigid, and constructed from medical grade metal or plastic. The stylet probe  102  has a tissue piercing tip  126  located at the distal end of the shaft  124  for penetrating through a patient&#39;s skin and underlying tissue and/or organ(s), while minimizing tissue trauma. That is, the stylet tip  124  prevents the cannula  110  from coring tissue when introduced through the tissue. The length of the stylet shaft  124  is selected, such that the stylet tip  126  deploys from the distal cannula opening  120  a predetermined distance when the stylet probe  102  is fully engaged with the cannula  110 , as illustrated in  FIG. 1 . The stylet probe  102  further comprises a proximal connector  128  mounted on the proximal end of the stylet shaft  124  for mating with the valve assembly  112 , as will be described in further detail below. The proximal connector  128  is shaped to act as a handle for grasping by a physician when advancing the stylet probe  102  through the introducer  100 .  
      As illustrated in  FIG. 2 , the RF ablation probe  104  comprises a shaft  130  that is preferably rigid or semi-rigid, and constructed from medical grade metal or plastic. The ablation probe  104  comprises an electrode element  132  (shown here as an electrode array) mounted to the distal end of the probe shaft  130  for therapeutically ablating targeted tissue. The length of the ablation probe shaft  130  is selected, such that the electrode element  132  deploys from the distal cannula opening  120  a predetermined distance when the ablation probe  104  is fully engaged with the cannula  110 , as illustrated in  FIG. 2 . The ablation probe  104  further comprises a proximal connector  134  mounted on the proximal end of the probe shaft  130  for mating with the valve assembly  112 , as will be described in further detail below. The proximal connector  134  is shaped to act as a handle for grasping by a physician when advancing the ablation probe  104  through the introducer  100 . The proximal connector  134  also comprises a RF electrical connector (not shown) that allows the ablation probe  104  to be mated within an RF generator via a RF cable  136 .  
      In alternative embodiments, the ablation probe  104  may have a solid core shaft with a sharpened tip or may otherwise be designed to be self-penetrating and prevent tissue coring. In this case, the use of the stylet probe  102  may not be needed, and the cannula  110  can be introduced through tissue with the ablation probe  104  in place.  
      As illustrated in  FIG. 3 , the biopsy probe  106  comprises a shaft  138  that is preferably rigid or semi-rigid, and constructed from medical grade metal or plastic. The biopsy probe  106  further comprises a biopsy element  140  (shown here as a slicing mechanism) mounted to the distal end of the probe shaft  138  for removing tissue for diagnostic purposes. The length of the probe shaft  138  is selected, such that the biopsy element  140  deploys from the distal cannula opening  120  a predetermined distance when the biopsy probe  106  is fully engaged with the cannula  110 , as illustrated in  FIG. 3 . The biopsy probe  106  further comprises a proximal connector  142  mounted on the proximal end of the probe shaft  138  for mating with the valve assembly  112 , as will be described in further detail below. The proximal connector  142  is shaped to act as a handle for grasping by a physician when advancing the biopsy probe  106  through the introducer  100 .  
      Referring additionally to  FIG. 4 , the valve assembly  112  of the cannula  110  comprises a valve housing  144  having a generally annular wall  146 . The housing wall  146  has a uniform thickness and has a cylindrical exterior surface and an interior surface, which defines a lumen  148  that extends the length of the valve housing  144 . When the valve assembly  112  is mated with the cannula  110 , as is shown in  FIGS. 1-3 , the housing lumen  146  is axially aligned and in communication with the cannula lumen  116  to allow passage of the probes through the respective valve assembly  112  and into the cannula  110 .  
      The valve housing  144  of the valve assembly  112  comprises a proximal connector  150  that defines a proximal opening  154  into which a probe can be inserted and passed into the valve lumen  148 , and a distal connector  150  that forms a distal opening  154  from which the probe can exit into the cannula lumen  116 . The proximal connector  150  is configured to mate with the respective connectors  128 ,  134 , and  142  of the stylet probe  102 , ablation probe  104 , and biopsy probe  106 , and the distal connector  152  is configured to mate with the cannula connector  122 . In the illustrated embodiment, the stylet, ablation probe, and biopsy probe connectors  128 / 134 / 142  and the cannula connector  122  are female luer connectors, in which case, the proximal and distal valve connectors  150 / 152  are male luer connectors. Alternatively, any or all of the stylet, ablation probe, and biopsy probe connectors  128 / 134 / 142  and the cannula connector  122  can be male luer connectors, in which case, the respective proximal valve connector  150  and/or distal valve connector  152  will accordingly be female luer connectors. It should be appreciated that any mating set of connectors capable of joining with a complementary fitting and providing an integral fit between the probe and valve housing  144 , as well as creating an air tight seal between the distal valve opening  152  and the cannula lumen  116 , is suitable for use.  
      The valve housing  144  can be constructed of any material that provides durability and rigidity, such as a molded medical grade synthetic resinous material or plastic. In the illustrated embodiment, the valve housing  144  is formed of a unibody structure, but may be constructed as separately formed components that are subsequently integrated with each other, e.g., by bonding. For example, the proximal and distal valve connectors  150 / 152  can be separately formed, and then bonded to the respective ends of the valve housing  144 .  
      The valve assembly  112  may comprise any one of a variety of sealing mechanisms that allow passage of the selected probe through the valve lumen  148  and into the cannula lumen  116 , while sealing the cannula lumen  116 , and thus the distal cannula opening  120 , from the external environment. In particular, the sealing mechanism prevents air from entering the valve lumen  148 , and being conveyed through the cannula lumen  116  where it can escape out of the distal cannula opening  120  into the patient&#39;s body.  
      For example, as shown in  FIG. 4 , the valve assembly  112  comprises a slit valve  158  having a thin membrane  160  and a slit  162  formed within the center of the membrane  160 . The membrane  160  is preferably made from silicone or other medical grade material that has flexibility, resilience, and tensile strength over a wide temperature range. The membrane  160  is contained within the proximal end of the valve housing  144  and extends transversely across the valve lumen  148  to seal it from the external environment. The edges of the membrane  160  may be retained within an annular recess (not shown) formed within the valve housing  144 . Due to the resilient nature of the slit  162 , it is designed to sealingly close when a probe does not reside within the valve lumen  148 . The size of the slit  162  is designed to accommodate the shafts of the probes. For example, as illustrated in  FIG. 5 , the slit  162  transforms into a circular opening that conforms to the outer circumference of a probe shaft (in this case, the stylet shaft  124 ) to seal it as the probe shaft is introduced therethrough. Thus, it can be appreciated that the slit valve  158  seals the cannula lumen  116 , and thus, the distal cannula opening  120 , from the external environment when a probe is both inserted into the valve lumen  148  and not inserted into the valve lumen  148 . Further details regarding the manufacture and use of slit valves are disclosed in U.S. Pat. No. 5,843,044, which is expressly incorporated herein by reference.  
      In the embodiment illustrated in  FIG. 4 , the slit valve  158  has a single slit  162  that is formed through the membrane  160 . Alternatively, as shown in  FIG. 6 , a pair of intersecting slits  164  are provided to allow for a greater variety of probe sizes to be used with the valve assembly  112 . In particular, the slit pair  164  provides for greater flexibility by allowing the opening in the membrane  160  to vary in size over a greater range, while still surrounding a probe along its outer circumference. While this embodiment illustrates slits  164  as being orthogonal to each other to form a cross, this is not intended to be a limitation on the design of the valve assembly  112 . The angle between the two slits  164  may vary and the lengths of the slits may vary as well, depending on the size of the probes that are intended to fit through the valve assembly  112 . In addition, a greater number of slits can be used to provide the valve assembly  112  with more flexibility.  
       FIG. 7  illustrates another embodiment of a valve assembly  212  that can alternatively be used in the introducer  100  of  FIG. 1 . The valve assembly  212  is similar to the previously described valve assembly  112 , with the exception that it is a two-stage valve assembly that additionally comprises a flexible ring  258 , such as a grommet. The flexible ring  258  may be composed of rubber, plastic or any other nonporous flexible material suitable for medical applications that is capable of acting as a seal with a probe. The flexible ring  258  is positioned within the valve housing  144  distal to the slit valve  158  and extends transversely across the valve lumen  148 . The edges of the flexible ring  258  may be retained within an annular recess (not shown) formed within the valve housing  144 . Alternatively, as shown in  FIG. 8 , the flexible ring  258  can be positioned within the distal connector  152 . In either embodiment, the flexible ring  258  comprises a permanent opening  260  designed to tightly receive and seal a probe shaft (in this case, the stylet shaft  124 ) when placed through valve lumen  148 , as shown in  FIG. 9 , thereby providing an additional mechanism for sealing the cannula lumen  116 , and thus distal cannula opening  120 , from the external environment. As previously discussed, when a probe is not inserted through the valve lumen  148 , the slit valve  158  will seal the cannula lumen  116  and distal cannula opening  120  from the external environment. Alternatively, one or more slits (not shown) can radially extend outward from the opening  260  to facilitate insertion of the probe shaft through the valve lumen  148 .  
       FIG. 10  illustrates another embodiment of a valve assembly  312  that can alternatively be used in the introducer  100  of  FIG. 1 . The valve assembly  312  is similar to the previously described valve assembly  112 , with the exception that it is a two-stage valve assembly that additionally comprises a manually adjustable valve  358  associated with the valve housing  144 . In the embodiment illustrated in  FIG. 10 , the adjustable valve  358  is a rotary valve, and in particular, a Touhy-Borst valve, that comprises a flexible washer  360  with an opening  362  (shown in phantom). The flexible washer  360  may be composed of rubber, plastic or any other nonporous flexible material suitable for medical applications that is capable of acting as a seal with a probe. The flexible washer  258  is positioned within the valve housing  144  distal to the slit valve  158  and extends transversely across the valve lumen  148 . The edges of the flexible ring  258  may be retained within an annular recess (not shown) formed within the valve housing  144 . Alternatively, as shown in  FIG. 11 , the flexible washer  360  (shown in phantom) is located within the lumen of the distal connector  152 .  
      The adjustable valve  358  further comprises a compression nut  362  coupled to the outside of the valve housing  144  (in the case of the  FIG. 10  embodiment) or the distal connector  152  (in the case of the  FIG. 11  embodiment). The nut  362  can be rotated to compress the washer  360 , thereby modifying the size of the opening  362 . As a result, the opening  362  of the flexible washer  360  can be adjusted to tightly receive any one of a variety of differently sized probe shafts, as illustrated in  FIG. 12 . Thus, the adjustable valve  358  provides an additional mechanism for sealing the cannula lumen  116 , and thus distal cannula opening  120 , from the external environment. As previously discussed, when a probe is not inserted through the valve lumen  148 , the slit valve  158  will seal the cannula lumen  116  and distal cannula opening  120  from the external environment.  
      It should be noted that the valve combinations disclosed in these embodiments are intended to be exemplary only and are not intended to be a limitation on the design of any particular valve or valve assembly for use in embodiments of the invention. Any combination of valves that work cooperatively to prevent fluid or air flow in the cannula lumen  104  when a device is inserted or removed could be incorporated into this design. In addition, the aforementioned valve assemblies have been described as being separate units that can be mounted to the cannula  110  to form the introducer  100 . Alternatively, these valve assemblies can be fabricated with the cannula  110  to form a unibody introducer  100 .  
      Having described the detailed structure of the various embodiments of the invention, a kit including the introducer  100 , stylet probe  102 , ablation probe  104 , and biopsy probe  106 , will now be described in performing a medical procedure on a tissue region within a patient&#39;s body. The tissue region may be located anywhere in the body where hyperthermic exposure may be beneficial. Most commonly, the tissue region will comprise a solid tumor within an organ of the body, such as the lung, liver, kidney, pancreas, breast, prostrate (not accessed via the urethra), and the like. The use of the kit lends itself particularly well in the treatment of lung tumors where the threat of Pneumothorax is great. The volume to be treated will depend on the size of the tumor or other lesion, typically having a total volume from 1 cm 3  to 150 cm 3 , and often from 2 cm 3  to 35 cm 3 . The peripheral dimensions of the tissue region may be regular, e.g., spherical or ellipsoidal, but will more usually be irregular. The tissue region may be identified using conventional imaging techniques capable of elucidating a target tissue, e.g., tumor tissue, such as ultrasonic scanning, magnetic resonance imaging (MRI), computer-assisted tomography (CAT), fluoroscopy, nuclear scanning (using radiolabeled tumor-specific probes), and the like. Preferred is the use of high resolution ultrasound of the tumor or other lesion being treated, either intraoperatively or externally.  
      Referring now to  FIGS. 13A-13D , the treatment of a tissue region TR located beneath the skin S of a patient will now be described. In this method, the tissue region TR is a tumor that has formed on the lung of the patient. First, the introducer  100  is assembled by connecting the valve assembly  112  to the cannula  110 , and specifically, by mating the distal valve connector  152  to the proximal cannula connector  112 . Optionally, the valve assembly  112  may be part of a preassembled co-access cannula set or the valve assembly  112  may form an integral portion of the cannula  110 , in which case, the valve assembly  112  need not be separately connected to the cannula  110 .  
      Once the introducer  100  is assembled, the stylet probe  102  is inserted through the valve assembly  112  into the cannula lumen  116  until the distal stylet tip  126  deploys from the distal cannula opening  120  and the stylet connector  128  mates with the proximal valve connector  150 , as illustrated in  FIG. 1 . At this point, the valve mechanism of the valve assembly  112 , and in particular, the slit valve  158 , seals around the stylet shaft  124 , thereby sealing the cannula lumen  116  and distal cannula opening  120  from the external environment. If the dual-stage valve assembly  212  is alternatively used, the additional valve mechanism, and in particular, the flexible ring  258 , will also seal around the stylet shaft  124 . If the dual-stage valve assembly  312  is alternatively used, the compression nut  364  on the valve  358  can be adjusted to tightened the flexible washer  360  onto the stylet shaft  124  after the stylet probe  102  has been inserted into the introducer  100 .  
      Next, the introducer  100 , with the stylet probe  102 , is positioned at the region of the patient where access will be provided to the tissue region. In this method, the tissue region is in the lung, and therefore the access point will be in the chest region of the patient. The introducer  100 , facilitated by the stylet tip  126 , is then percutaneously advanced through the patients skin S and chest wall until the distal cannula opening  120  is adjacent the tissue region TR within the pleural space PS of the patient ( FIG. 13A ). Alternatively, if the introducer  100  has a non-coring tip and is rigid enough, it can be percutaneously advanced into the patient without the use of the stylet probe  102 . In either case, because the valve assembly  112  seals the distal cannula opening  120  from the external environment, no air will leak from the external environment through the cannula lumen  116  and into the pleural space PC, thereby preventing the onset of pneumothorax.  
      Once the introducer  100  is in place, the stylet probe  102  is removed from the introducer  100  ( FIG. 13B ). Because the slit valve  158  of the valve assembly  112  continuously seals around the stylet shaft  124  while it is being removed from the introducer  100 , the distal cannula opening  120  remains sealed from the external environment, thereby preventing air from leaking through the cannula lumen  116  and into the pleural space PS. If the dual-stage valve assembly  212  is alternatively used, the flexible ring  258 , will also seal around the stylet shaft  124  as it is removed from the introducer. If the dual-stage valve assembly  312  is alternatively used, the compression nut  364  on the valve  358  will be adjusted to loosen the flexible washer  360  on the stylet shaft  124  prior to its removal from the introducer  100 .  
      The biopsy probe  106  is then inserted through the valve assembly  112  into the cannula lumen  116  until the biopsy mechanism  140  deploys from the distal cannula opening  120  into the tissue region TR and the probe connector  142  mates with the proximal valve connector  150  ( FIG. 13C ). Because the slit valve  158  of the valve assembly  112  continuously seals around the probe shaft  138  while it is being advanced into the introducer  100 , the distal cannula opening  120  remains sealed from the external environment, thereby preventing air from leaking through the cannula lumen  116  and into the pleural space PS. If the dual-stage valve assembly  212  is alternatively used, the flexible ring  258 , will also seal around the probe shaft  138  as it is advanced into the introducer  100 . If the dual-stage valve assembly  312  is alternatively used, the compression nut  364  on the valve  358  will be adjusted to tighten the flexible washer  360  on the probe shaft  138  after it has been fully advanced into the introducer  100 .  
      With a sample tissue region captured by the biopsy mechanism  140 , the biopsy probe  106  is removed from the introducer  100 . Again, the distal cannula opening  120  is sealed from the environment during removal of the biopsy probe  106  in the same manner that it was sealed during removal of the stylet probe  102 . The ablation probe  106  is then inserted through the valve assembly  112  into the cannula lumen  116  until the electrode element  132  deploys from the distal cannula opening  120  into the tissue region TR and the probe connector  134  mates with the proximal valve connector  150  ( FIG. 13D ). The distal cannula opening  120  is sealed from the environment during introduction of the ablation probe  104  in the same manner that it was sealed during introduction of the biopsy probe  106 . The ablation probe  104  is then connected to an RF generator (not shown) and operated to therapeutically ablate the tissue region TR, after which the introducer  100 , with the ablation probe  104 , is removed from the patient.  
      Optionally, prior to removing the introducer  100  from the patient, the ablation probe  104  can be removed from the introducer  100  while the distal cannula opening  120  is sealed by the valve mechanism  112 , so that a biocompatible sealing agent can be delivered through the valve assembly  112 , through the cannula lumen  116 , and out of the distal cannula opening  120  as the introducer  100  is being removed from the patient. In this manner, the access channel previously created by the introducer  100  can be sealed to prevent the entry of air into the pleural cavity PS when the introducer  100  is removed from the channel.  
      Although particular embodiments of the present inventions 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. Thus, 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.