Abstract:
The present invention relates to surgical instruments and more specifically to surgical instruments for removing polyps and growths from within a patient&#39;s body. The surgical instrument of the present invention comprises an electrically conductive probe and a shape memory alloy filament attached to the working end of the electrically conductive probe. The shape memory alloy has a first working position and a second working position and is capable of acquiring the second working position in response to the passage of electrical current flowing through, and elevating the temperature of the filament.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of surgical tools and more specifically, to surgical tools that use strands or filaments of shape memory alloy to remove polyps and growths from within a patient&#39;s body.  
         BACKGROUND OF THE INVENTION  
         [0002]    Surgical tools for removing polyps and growths from the colon and other areas of the human body are well known in the art. Examples of such surgical tools are described in U.S. Pat. No. 6,015,415, U.S. Pat. No. 5,908,429, and Russian Patent 5004687.  
           [0003]    Specifically, U.S. Pat. No. 6,015,415 describes a surgical snare tool for removing polyps that comprises a handle assembly, a tubular sheath, a flexible probe and a closed snare-loop that is located at the working end of the flexible probe. In operation, the handle assembly is used to maneuver the snare-loop within a patient&#39;s body in order to loop the snare-loop around a designated polyp. The snare-loop is built so that as it exits the tubular sheath and extends parallel to the tubular sheath but non-axially, thereby allowing the snare-loop to get closer to the base of the polyp than if it were aligned axially with the sheath.  
           [0004]    Once the snare-loop has been looped around the designated polyp, the user operates the hand assembly in such a way as to tighten the snare-loop securely around the designated polyp. Once the loop is securely tightened, a cautery current is transmitted through the flexible probe to the snare-loop, so that the snare-loop can burn through the designated polyp.  
           [0005]    The drawback of the surgical snare tool described in U.S. Pat. No. 6,015,415 is that the snare-loop is a noose shaped device that needs to be located around the polyp to be removed. During surgery it is not always possible to place the loop around the polyp. Polyps may be very long, or positioned in such a way that it is difficult if not impossible to position the loop around them. In these cases more invasive surgery, and an excessive amount of time, is required in order to remove the polyp.  
           [0006]    Against this background it is clear that there is a need in the industry for a wider range of improved surgical polypectomy tools that are capable of easily and efficiently capturing and removing polyps from within a patient&#39;s body.  
         SUMMARY OF THE INVENTION  
         [0007]    As embodied and broadly described herein, the present invention provides a surgical tool for removing growths from within a patient&#39;s body. The surgical tool comprises an electrically conductive probe that has a working end that is adapted to be inserted into a patient&#39;s body and a shape memory alloy filament that is attached to the working end of the electrically conductive probe. The shape memory alloy filament has a first working position and a second working position. In the first working position, the shape memory alloy filament is in a position that enables it to be inserted into a patient&#39;s body and placed next to a growth designated for removal. In the second working position, the shape memory alloy filament forms a bend around a polyp or other growth.  
           [0008]    The shape memory alloy filament is capable of transitioning from the first working position to the second working position in response to the passage of electrical current therethrough that elevates the temperature of the filament. As the electrical current passes through the filament, the filament becomes hot, which allows the filament to excise the polyp or other growth.  
           [0009]    As further embodied and broadly described herein, the present invention provides a process for removing a growth from within a patient&#39;s body. The process comprises providing a shape memory alloy filament that has a first working position and a second working position. In the first working position the shape memory alloy filament is in a condition that enables it to be inserted into a patient&#39;s body and placed next to a growth. In the second working position, the shape memory alloy filament forms a bend around the growth. The shape memory alloy filament is able to transition from the first working position to the second working position in response to the passage of electrical current therethrough that elevates the temperature of the shape memory alloy filament. As the electrical current passes through the filament, the filament becomes hot, which allows the filament to excise the polyp or other growth.  
           [0010]    The process further comprises inserting the shape memory alloy filament into the patient&#39;s body while the shape memory alloy filament is in the first working position, positioning the shape memory alloy filament while it is in the first working position next to the growth and applying an electrical current through the shape memory alloy filament for transitioning the shape memory alloy filament into the second working position wherein the shape memory alloy filament forms a bend around the growth. Finally, the process comprises excising the growth with the shape memory alloy filament.  
           [0011]    As still further embodied and broadly described herein, the present invention provides a method for setting at least one working position of a shape memory alloy filament for use in excising a growth from within a patient&#39;s body. The method comprises forming the shape memory alloy filament into a bend, heating the shaped memory alloy while in the formed bend, and quenching the shape memory alloy filament while in the formed bend. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is top plan view of the surgical tool according to a specific embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is an enlarged view of the working end of the surgical tool of FIG. 1 shown in the straight position, which the curved position indicated by dotted lines;  
         [0014]    [0014]FIG. 3 is the working end of the surgical tool of FIG. 2 positioned next to a polyp;  
         [0015]    [0015]FIG. 4 is the working end of the surgical tool shown in FIG. 3 around the polyp;  
         [0016]    [0016]FIG. 5 is an expanded view of the working end of the surgical tool according to an alternative embodiment of the invention;  
         [0017]    [0017]FIG. 6 is an expanded view of the working end of the surgical tool according to a further alternative embodiment of the invention;  
         [0018]    [0018]FIG. 7 is an expanded view of the working end of the surgical tool according to a still further alternative embodiment of the invention.  
     
    
     DETAILED DESCRIPTION  
       [0019]    Shown in FIG. 1 is a shape memory surgical tool  100  in accordance with a specific embodiment of the invention that is able to excise growths and polyps from within a patient&#39;s body. Surgical tool  100  has a handle assembly  10 , a long flexible electrically insulating sheath  20  and an electrically conductive flexible and extendable probe  22 . Handle assembly  10  includes a frame section  12  and a finger section  14 . Frame section  12  contains a thumb hold  24  and a track  26 . Finger section  14  includes two finger holds  28  and  30 , and is adapted to slide from one end of frame section  12  to the other, along track  26 . Handle assembly  10  further includes a terminal  18  for attachment to an electrical power supply unit. The electrical power supply unit allows the electrical current supplied to terminal  18  to be varied. The lower portion of handle assembly  10  comprises an irrigation port  16  and a tubular section  17 , both of which are axially rotatable in relation to frame  12 , thereby permitting rotation of sheath  20 .  
         [0020]    Flexible sheath  20  is connected to the bottom of frame section  12 . A shorter more rigid sheath  19  is also connected to the bottom of frame section  12  and is positioned over sheath  20 , thereby protecting sheath  20  from bending too sharply at its connection to frame section  12 . Probe  22  is made of an electrically conductive material, and fits slidably within sheath  20 . Probe  22  is attached to movable finger section  14  of hand assembly  10 , such that as finger section  14  moves up and down along track  26  of frame section  12 , probe  22  moves in and out of sheath  20  at working end  32 . When movable finger section  14  is at the base of frame  12 , probe  22  is at its most extended position outside sheath  20 . When movable finger section  12  is at the position closest to thumb hold  24 , then probe  22  is retracted as far inside sheath  20  as possible. Although flexible sheath  20  has been described as being connected to frame section  12 , and probe  22  has been described as being connected to finger section  14 , it is within the scope of the invention for flexible sheath  20  to be connected to finger section  14 , and probe  22  to be connected to frame section  12 .  
         [0021]    At working end  32 , a filament or strand of shape memory alloy is welded, or attached mechanically by any suitable means to the working end of probe  22 . As examples of non-limiting means of attachment, filament  34  can be welded, brazed, silver soldered or swaged in place. In a preferred embodiment, filament  34  of shape memory alloy is nickel titanium(Ni—Ti) with heat activated shape memory properties. As can be seen in FIG. 2, filament  34  of Ni—Ti has two working positions, namely, a straight working position  36 , and a curved working position  38 . In the curved working position  38 , filament  34  is able to encircle a polyp to be excised. As a non-limiting example of a curved working position, filament  34  is bent into a continuous circular loop. However, in alternate embodiments of a curved working position, filament  34  forms a series of straight segments joined by bends having angles of less than  180  degrees. In such positions, filament  34  can be in the form of a triangle, square, etc.  
         [0022]    In a very specific and non-limiting example, filament  34  is a Ni—Ti wire with a diameter of 0.015 inches and a phase transition temperature of approximately 70 degrees Celsius. Alternatively, filament  34  may be of a thicker diameter, which will provide more strength, however filaments having a thicker diameters will not form as tight a curved working position as a filament having a thinner diameter.  
         [0023]    In order to achieve the heat-activated curved working position  38 , filament  34  is pre-treated. The pre-treatment process includes forming filament  34  such that it includes at least one bend, heating filament  34 , and quenching filament  34  in cold water. After pre-treatment, filament  34  is straightened back into its straight working position  36  in preparation for surgery. In order to return to the curved working position  38 , filament  34  is heated. It should be expressly understood that other manufacturing techniques are possible and are within the scope of the present invention.  
         [0024]    In use, a surgeon places the working end  32  of the probe into the patient&#39;s body with the assistance of an endoscope. The endoscope allows the surgeon to locate the polyp or growth designated for removal, and allows the user to view the movement of the working end  32  of surgical tool  100  inside the patient&#39;s body. As can be seen in FIG. 3, once the polyp or growth designated for removal has been located, the surgeon maneuvers filament  34 , while in its straight working position  36 , next to the base of polyp  40 .  
         [0025]    Once shape memory filament  34  has been positioned next to polyp  40 , the surgeon applies an electric current to filament  34  through probe  22  (from the power supply connected to terminal  18 ). The electric current heats filament  34  and activates its pretreated shape memory position so that it transitions to curved working position  38 . As can be seen in FIG. 4, when the shape memory properties of filament  34  are activated by heat, filament  34  reverts to its pretreated state, thereby encircling the base of polyp  40 . In a non-limiting example of implementation, at this point the electrical current can be turned off until the surgeon is ready to excise the polyp. Alternatively, the polyp can be excised directly after filament  34  encircles polyp  40  by maintaining the electrical current at the applied level, or by increasing the applied electrical current, depending on the heat required to excise the polyp or growth.  
         [0026]    If the surgeon wishes to reposition filament  34  around the polyp, filament  34  can be retracted back into sheath  20  in order to re-straighten filament  34 . The mechanical force generated by sheath  20  is sufficient to at least partially straighten filament  34  for a second try. In a non-limiting example of implementation, filament  34  can be designed to return to its initial straight position when the electrical current is stopped.  
         [0027]    Once the surgeon is ready to excise the polyp, the electric current is re-established up to the desired intensity. The user then moves finger portion  14  of hand assembly  10  towards thumb hold  24  so that a force is applied to filament  34  that combined with the electric current, cuts through the base of polyp  40  and cauterizes the tissue.  
         [0028]    It should be understood that it is within the scope of the invention for filament  34  to have a straight working position and a plurality of curved working positions. For example, in a non-limiting example of implementation, filament  34  has a first curved working position that is a large continuous loop, and a second curved working position that is a small tight loop. When a first level of electrical current is applied through filament  34  such that the temperature of filament  34  elevates to a first temperature, filament  34  forms into the first working position. When the level of electrical current applied to filament  34  is increased such that the temperature of filament  34  elevates to a second temperature that is higher than the first temperature, filament  34  forms the second working position.  
         [0029]    It will be appreciated that several variations of the configuration of filament  34  can be envisioned. In an alternate embodiment shown in FIG. 5, filament  34  includes a blob of a bio-compatible substance  42  on its tip, that rounds out the potentially sharp tip of filament  34 . Thereby making the tip blunt. Therefore, the blob of bio-compatible substance  42  prevents filament  34  from inadvertently spearing the tissue during insertion, thereby making it easier to maneuver during surgery.  
         [0030]    In a further specific embodiment, as seen in FIG. 6, filament  34  can be pre-formed to have a hook  44  at its tip. In this embodiment hook  44  can latch onto the lower portion of filament  34  upon formation of its curved working position, thereby preventing filament  34  from unwinding as the surgeon pulls on probe  22 .  
         [0031]    In yet another embodiment, as seen in FIG. 7, filament  34  may be in the shape of a flattened loop with a rounded loop shape memory position. In this configuration, when an electric current is applied, filament  34  opens up to form a loop of a pre-formed shape, which in this case is a rounded loop as shown by the dotted lines. A loop formed into the shape of a square, triangle, rectangle, or any other shape is also within the scope of the present invention. In addition, a kit which would allow a surgeon or technician to “train” filament  34  into a particular shape prior to surgery may be provided. Such a kit would allow a user to form filament  34  into any unique shape that would best suit the needs of a particular patient.  
         [0032]    In yet another embodiment of surgical tool  100 , two filaments of shape memory alloy are attached to probe  22  so that the two filaments wrap around polyp  44  simultaneously upon being heated by an electric current. This embodiment provides increased strength to surgical tool  100 , for removing larger and thicker polyps. Alternatively, additional strength can be added to surgical tool  100  by using a flat piece of shape memory alloy wire that has a width and a thickness, wherein the width is greater than the thickness.  
         [0033]    The above description of preferred embodiments should not be interpreted in a limiting manner since other variations, modifications and refinements are possible within the spirit and scope of the present invention. The scope of the invention is defined in the appended claims and their equivalents.