Abstract:
A flexible steerable device comprising a plurality of interconnected segments configured to pivot relative to each other, each of the plurality of segments having a cavity disposed therein. The device also includes a flexible tube disposed within the cavities of the plurality of segments. The flexible tube includes at least one rigidizing chamber having fusible material disposed therein, wherein upon varying temperature of the fusible material, the fusible material shifts between a first state in which the flexible steerable device is flexible and a second state in which the flexible steerable device is rigidized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 60/987,453, filed Nov. 13, 2007, the entire disclosure of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to flexible steerable instruments, such as steerable catheters and/or probes which are remotely operated in endoscopic, endoluminal and laparoscopic surgical procedures. In particular, the present disclosure is directed to a system and method for rigidizing a flexible steerable instrument. 
     2. Background of Related Art 
     Various minimally invasive surgical procedures utilize endoscopic, endoluminal and laparoscopic surgical techniques. These techniques generally involve insertion of surgical instruments through small incisions. One example of such surgical instruments is a flexible steerable instrument which may have a tool assembly (e.g., grasping jaws, cutting tool, camera, suction attachment, etc.) attached at a distal end of the instrument. These instruments can be navigated and steered inside the patient&#39;s body due to their flexibility. Once in position, it is often desired for the flexible steerable instruments to be held in a particular position to perform the desired tissue manipulation using the tool assembly. 
     Conventional flexible steerable instruments include two or more segments which are configured to pivot and/or swivel relative to each other by using one or more tensile elements running therethrough. The tensile elements are coupled to the distal segment and when the elements are tightened (e.g., pulled in the proximal direction) the segments are drawn together preventing the segments from sliding and/or pivoting due to friction forces between the segments thereby rigidizing the flexible instrument. One drawback of the conventional flexible steerable instruments utilizing tensile elements is that if an insufficient amount of tension is provided in the tensile elements, the steerable instrument may continue to swivel and/or pivot upon application of a force to the instrument. Therefore there is a need for a novel flexible steerable instrument configured to maintain its rigidity. 
     SUMMARY 
     According to one aspect of the present disclosure a flexible steerable device is disclosed. The flexible steerable device can include a plurality of interconnected segments configured to pivot relative to each other, each of the plurality of segments having a cavity disposed therein. The device can also include a flexible tube disposed within the cavities of the plurality of segments. In one embodiment, the flexible tube includes at least one rigidizing chamber having fusible material disposed therein, wherein upon varying the temperature of the fusible material, the fusible material shifts between a first state in which the flexible steerable device is flexible and a second state in which the flexible steerable device is rigidized. 
     According to another aspect of the present disclosure a flexible steerable device is disclosed. The flexible steerable device includes a plurality of interconnected segments configured to pivot relative to each other, each of the plurality of segments having a cavity disposed therein. The device also includes a plurality of fittings disposed between each of the plurality of interconnected segments, each of the plurality of fittings including a flexible membrane and fusible material disposed therein. The device further includes a flexible tube disposed within the cavities of the plurality of segments. The flexible tube includes at least one rigidizing chamber having a heating element, wherein the heating element is configured to vary heat applied to the fusible material in response to which the fusible material shifts between a liquid state in which the flexible steerable device is flexible and a solid state in which the flexible steerable device is rigidized. 
     A method for rigidizing a flexible steerable device is also contemplated by the present disclosure. The method includes the steps of providing a flexible steerable device having a plurality of interconnected segments configured to pivot relative to each other, each of the plurality of segments having a cavity disposed therein and a flexible tube disposed within the cavities of the plurality of segments. The flexible tube includes at least one rigidizing chamber having a heating element and fusible material disposed therein. The method also includes the steps of increasing heat applied to the fusible material thereby liquefying the fusible material and decreasing heat applied to the fusible material thereby solidifying the fusible material and rigidizing the flexible tube and the plurality of interconnected segments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a flexible steerable instrument according to one embodiment of the present disclosure; 
         FIG. 2  is a side cross-sectional view of a segment of the flexible steerable instrument according to one embodiment of the present disclosure; 
         FIG. 3  is a perspective view of a section of a flexible tube of the flexible steerable instrument according to one embodiment of the present disclosure; 
         FIG. 4  is a side cross-sectional view of the flexible steerable instrument according to one embodiment of the present disclosure; 
         FIG. 5  is a perspective view with parts separated of the flexible steerable instrument according to one embodiment of the present disclosure; 
         FIGS. 6 and 7  are side cross-sectional view of the flexible steerable instrument according to one embodiment of the present disclosure; 
         FIG. 8  is a perspective view with parts separated of the flexible steerable instrument according to another embodiment of the present disclosure; 
         FIG. 9  is a side cross-sectional view of a membrane of the flexible steerable instrument according to another embodiment of the present disclosure; 
         FIG. 10  is a perspective view of a section of a flexible tube of the flexible steerable instrument according to another embodiment of the present disclosure; 
         FIGS. 11 and 12  are side cross-sectional view of the flexible steerable instrument according to another embodiment of the present disclosure; 
         FIG. 13  is a side view of the flexible steerable instrument according to another embodiment of the present disclosure; and 
         FIG. 14  is a side view of the flexible steerable instrument according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
     Referring to  FIG. 1 , a flexible steerable instrument  10  is shown. The instrument  10  includes an elongated flexible body  12  and a tool assembly  13  disposed at the distal end of the body  12 . In embodiments, the tool assembly  13  may be a pair of opposing jaws as shown, e.g., graspers, pliers, etc., or other surgical tools, such as a cutting tool, e.g., scissors, dissectors, etc., and the like. Although not shown, it is envisioned that the presently disclosed instrument could be easily adapted for RF or electrical dissection or sealing. The body  12  includes a plurality of interconnected segments  14  which enclose a flexible tube  16  as shown in more detail in  FIGS. 2 and 3 . 
       FIG. 2  shows a side cross-sectional view of the segment  14  taken along the line  2 . The segment  14  has a generally spherical shape as seen in  FIG. 5  and includes a cavity  18 , which can be substantially cylindrical, for enclosing the tube  16 . Alternately, other cavity configurations are envisioned. With reference to  FIGS. 4 and 5 , each of the segments  14  includes a circular depression  20  ( FIG. 5 ) and two or more openings  22 . The circular depression  20  allows the segments  14  to mechanically interface with each other by mating the proximal end of one segment  14  with the depression  20  of the immediately distal segment  14 . This allows the segments  14  to pivot relative with respect to each other in a ball-joint fashion. In embodiments, the segments  14  may have a cylindrical shape with the distal and proximal ends retaining semi-spherical form to allow for ball-joint type mating between the segments  14 . The segments may be formed from medical grade materials, such as stainless steel, thermoplastics, titanium, or the like. 
     A tensile element  24  (e.g., tinel, multi-wire cable, etc.) passes through the openings  22  and interconnects the plurality of segments  14  due to predetermined tension in the tensile element  24 . The tension in the tensile element  24  is sufficient to maintain the segments  14  in physical contact with each other (e.g., proximal end of one segment  14  with depression  20  of another segment  14 ). Increasing tension in one of the tensile elements  24  allows for pivoting of the segments  14  in the direction in which tension is being applied. In embodiments, three or more tensile elements  24  may be used to allow for more steering control. 
     The tube  16  is disposed within the cavity  18  of the segments  14 . With reference to  FIG. 3 , the tube  16  can be formed from a flexible material such as rubber, silicone rubber, and other elastomers. The tube  16  includes an endoscope port  26 , one or more auxiliary ports  28  and one or more rigidizing chambers  30  formed therein. The endoscope port  26  may include cables and other actuation mechanisms for manipulating the tool assembly  13 . The auxiliary port  28  may be used as a suction port or may include additional instruments, such as lights and a video camera. 
     The chamber  30  includes a heating element  32  and is filled with fusible material  34 . The heating element  32  may be an electrical heating coil, non-electrical heat sources (e.g., heated fluid passage tube, etc.) which heats the material  34 . The heating coil may be operable by any type of electrical power source, either a direct or alternating current source. In one embodiment, the chamber  30  may only be filled with the fusible material  34  and does not include the heating element  32 , such that the fusible material  34  melts and solidifies in response to external temperatures (e.g., the instrument  10  being inserted into the patient). 
     The fusible material  34  may be any material which has a melting point at or about a predetermined threshold, such that when the material is heated above the threshold the material  34  is liquefied. In embodiments, the melting point can be any temperature above the body temperature, 37° C., allowing the material  34  to be solid when the material  34  (e.g., instrument  10 ) is located within the patient. The material  34  may be wax, fusible metal, fats, and the like. Thus, when the material  34  is not heated, the material  34  is solid and the instrument  10  is in rigid form since the solid material  34  prevents pivoting of the segments  14 . When the material  34  is heated, the material is liquefied and the instrument  10  becomes flexible allowing for the segments  14  to pivot in the desired direction. 
     The fusible material  34  may be a fusible alloy containing one or more of the following metals and/or metal alloys, such as bismuth, lead, tin, antimony, indium or cadmium. During transition between liquid and solid phases, these alloys have a relatively small expansion volume allowing for their use within enclosed spaces, such as the chamber  30 . When bismuth is alloyed with other metals, such as lead, tin, and cadmium, expansion of the resulting alloy is modified according to the relative percentages of bismuth and other components. Thus, bismuth alloys containing approximately 50 percent of bismuth exhibit little change of volume during solidification. Alloys containing more than this tend to expand during solidification and those containing less tend to shrink during solidification. Exemplary embodiments of the fusible alloys and their melting points are illustrated in Table (1). 
     
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE (1) 
               
               
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Melting 
               
               
                   
                 Bismuth 
                 Lead 
                 Tin 
                 Antimony 
                 Indium 
                 Cadmium 
                 Point 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Alloy 1 
                 44.7%   
                 22.6% 
                  8.3% 
                 — 
                 19.1% 
                 5.3% 
                 47° 
                 C. 
               
               
                 Alloy 2 
                 49% 
                   18% 
                   12% 
                 — 
                   21% 
                 — 
                 58° 
                 C. 
               
               
                 Alloy 3 
                 50% 
                 26.7% 
                 13.3% 
                 — 
                 — 
                  10% 
                 70° 
                 C. 
               
               
                 Alloy 4 
                 42.5%   
                 37.7% 
                 11.3% 
                 — 
                 — 
                 8.5% 
                 70-88° 
                 C. 
               
               
                 Alloy 5 
                 52.5%   
                   32% 
                 15.5% 
                 — 
                 — 
                 — 
                 95° 
                 C. 
               
               
                 Alloy 6 
                 48% 
                 28.5% 
                 — 
                 9% 
                 — 
                 14.5%  
                 103-227° 
                 C. 
               
               
                 Alloy 7 
                 55.5%   
                 44.5% 
                 — 
                 — 
                 — 
                 — 
                 124° 
                 C. 
               
               
                 Alloy 8 
                 58% 
                   42% 
                 — 
                 — 
                 — 
                 — 
                 138° 
                 C. 
               
               
                 Alloy 9 
                 40% 
                 — 
                   60% 
                 — 
                 — 
                 — 
                 138-170° 
                 C. 
               
               
                   
               
             
          
         
       
     
     The chamber  30  also includes one or more coolant tubes  33  disposed therein and surrounded by the fusible material  34 . The coolant tubes  33  may be formed from any type of flexible heat-resistant polymer (e.g., polyemide). The coolant tubes  33  of each chamber  30  may be interconnected at the distal end of the instrument  10  so that the coolant tubes  33  are in continuous fluid communication with each other. The coolant tubes  33  are coupled to a source of coolant fluid and a pump (not explicitly shown) which circulate the coolant fluid  35  through the coolant tubes  33 . The coolant fluid  35  is supplied to the coolant tubes  33  to cool the material  34  so that the material  34  cools down and rigidizes the instrument  10 . 
     Prior to inserting the instrument  10  into a body lumen, the material  34  inside the chambers  30  is heated above the melting point via the heating elements  32 . The heating element  32  is connected to a power source which is controlled by the operator when it is desired to make the instrument  10  flexible. It is envisioned that the power source may include a battery or battery pack positioned near or supported by instrument  10 . Once the material  34  is heated so that the material is liquefied, the instrument  10  becomes flexible allowing for the pivoting of the segments  14  and the instrument  10  is guided to the surgical site. Guiding is accomplished by keeping the instrument  10  flexible and steering the instrument  10  by tensioning desired tensile elements  24 . Once the instrument  10  is positioned at the site, the instrument  10  is rigidized by decreasing and/or shutting off the heat supplied by the heating element  32  and allowing the material  34  to cool and solidify. In one embodiment, the coolant fluid  35  is supplied to the coolant tubes  33  thereby cooling the material  34  and rigidizing the device  10 . The instrument  10  can be rigidized in any desired position, either straight configuration as shown in  FIG. 6  or curved configuration as shown in  FIG. 7  or in any intermediate configuration. When the instrument  10  needs to be removed or relocated, heat is increased once again to make the instrument  10  flexible and the instrument  10  is guided out of the patient&#39;s body. 
       FIGS. 8-12  illustrate another embodiment of the flexible steerable instrument  100  which includes a plurality of fittings  136  disposed in between the segments  114 . The instrument  100  includes a flexible tube  116  having one or more rigidizing chambers  130  and one or more auxiliary ports  128 . The tube  116  is disposed within the segments  114 . The fittings  136  include an outer membrane  138  and are filled with the material  134  ( FIG. 9 ). The membrane  138  is formed from a flexible elastomer such that when the material  134  is in liquid form, the fitting  136  can be deformed as shown in  FIGS. 11 and 12 . The fittings  136  include openings  137  which allow for the tensile element  124  to pass therethrough. When assembled, the fittings  136  fit into the depression  122  and are squeezed between the depression  122  and the distal end of the preceding segment  114  when the tensile elements  124  are made taut. 
     Since the material  134  is in the fittings  136 , the chamber  130  includes the heating element  132 . The chamber  130  and/or the auxiliary ports  128  may include a coolant tube  133  for supplying coolant fluid  135  through the tube  116 . During operation, the instrument  100  is made flexible by increasing the temperature within the chamber  130  which then liquefies the material  134  within the fittings  136 . This makes the fittings  136  deformable allowing the segments  114  to pivot and/or swivel relative to each other. The instrument  100  is then guided to the surgical site in flexible form. After the instrument  100  is in the desired position the instrument  100  is rigidized by lowering and/or terminating the heat supplied by the heating elements  132  thereby cooling the material  134  within the fittings  136 . This may be accomplished by pumping coolant fluid  135  through the coolant tubes  133 . Once the material  134  cools, the fittings  136  become rigid and lock the segments  114  in the desired configuration as shown in  FIGS. 11 and 12 .  FIG. 11  shows the instrument  100  rigidized in a straight configuration whereas  FIG. 12  shows the instrument  100  in a curved configuration. 
     The chamber  130  may extend the entire length of the tube  116  or at least one portion thereof. Similarly, the fittings  136  may be disposed between only some of the segments  114  e.g., the distal-most segments, such that only a selected portion or portions of instrument  100  can be rigidized. These arrangements allow for certain portions of the instrument  100  to be rigidized, e.g., tip, while the rest of the instrument  100  can remain flexible. 
       FIG. 13  illustrates another embodiment of the flexible steerable instrument  200 . The instrument  200  includes a plurality of pivoting segments namely vertically pivoting segments  202  and horizontally pivoting segments  204 . The segments  202  and  204  include one or more hinges  206  which couple the vertically pivoting segments  202  to the horizontally pivoting segments  204 . The hinge  206  may include two shafts coupling the segments  202  and  204 , each of the shafts connecting a tab  207  to the proximal end of the preceding segment at two points defining a single rotational axis. It is also envisioned that other types of hinges may be used, such as so-called “living hinges.” 
     More specifically, the distal end of the vertically pivoting segment  202  is coupled to the proximal end of the horizontally pivoting segment  204  and the vertically pivoting segment  202  is adapted to hinge in a lateral direction about the hinge  206  thereof with respect to the horizontally pivoting segment  204 . The distal end of the horizontally pivoting segment  204  is coupled to the proximal end of the vertically pivoting segment  202  and the horizontally pivoting segment  204  is adapted to hinge in a vertical direction about the hinge  206  thereof with respect to the vertically pivoting segment  202 . This configuration provides for interspersing two types of segments having orthogonal hinges such that the consecutive segment rotates in a different direction than the previous segment thereby providing for a flexible steerable instrument  200 . 
       FIG. 14  illustrates a further embodiment of the flexible steerable instrument  300 . The instrument  300  includes a plurality of rotational segments  302  separated by pivoting segments  304 . Each of the rotational segments  302  is coupled to a pivoting segment  304 . The pivoting segments  304  include a hinge  306  and a tab  307  which allows for pivotally coupling the pivoting segments  304  to the proximal end of the rotational segments  302 . The pivoting segments  304  also include a circular depression  308  adapted to interface with a hemispherical joint  309  of the rotational segment  302  thereby mechanically interfacing the distal end of the rotational segment  302  with the proximal end of the preceding pivoting segment  304 . Consequently, the instrument  300  can be flexed in any desirable direction limited only by the angle of rotation of each of the segments  302  and  304 . 
     The flexible steering instruments  300  and  400  of  FIGS. 13-14  also include one or more rigidizing chambers having heating elements disposed therein and/or coolant tubes. It is also envisioned that the instruments  300  and  400  may include the rigidizing material either directly within the rigidizing chambers or within the plurality of fittings disposed between the segments as discussed above with respect to  FIGS. 1-12 . In addition, the steering instruments  300  and  400  also include two or more tensile elements for guiding and steering the instruments to the desired location. 
     The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law. For example, with respect to instrument  10 , chamber  30  need not extend the entire length of tube  16  but may be provided in one or more portions of tube  16 , e.g., the distal and central portions of tube  16  or just the distal portion of tube  16 .