Abstract:
A series of medical instruments can be made with the use of shape memory tube with a transformation temperature that is above or below the ambient temperature. In the first case, the material behaves with the shape memory effect and in the second case the behavior is superelastic. The wall of the tube has been provided with a plurality of slots in specific places, often near or at the distal end of the instrument, and in specific arrangements which allow local variations in diameter, shape, and/or length. These variations can either be caused by the memory effect during temperature change or by superelastic behavior during change of the mechanical influences on the memory metal by the surrounding material.

Description:
The present application is a continuation of U.S. Ser. No. 11/381,217, filed May 2, 2006, now issued as U.S. Pat. No. 8,052,670, which is a continuation of U.S. Ser. No, 10/923,918, filed Aug. 23, 2004, now issued as U.S. Pat. No. 7,037,321, which is a continuation of U.S. Ser. No. 09/156,276, filed Sep. 17, 1998, now issued as U.S. Pat. No. 6,780,175, which is a continuation of U.S. Ser. No. 08/804,018, filed Feb. 21, 1997, now issued as U.S. Pat. No. 5,885,258, which claims the filing benefit of U.S. Provisional Application No. 60/012,220, filed Feb. 23, 1996, each disclosure of which is expressly incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to an instrument which uses a slotted memory metal tube to perform or assist in various medical procedures. 
     BACKGROUND INFORMATION 
     Surgical and other medical procedures are often performed at sites within a patient&#39;s body. In the past, the only way to perform such medical procedures was to cut a large enough incision in the patient&#39;s body to expose the operating site sufficiently to permit direct access by a physician. Such operations, however, typically caused a great deal of trauma to the affected tissue requiring lengthy periods for recovery and causing the patient substantial pain and suffering. With technological advances in the medical profession, more and more of these procedures are being performed using less invasive endoscopic and similar procedures. In general, endoscopic procedures include using an instrument having a delivery tube with an inner bore through which a tool can be inserted. With such an instrument, the delivery tube is usually inserted into the patient&#39;s body by way of either a comparatively small incision or a body orifice and through a body cavity or hollow organ to the site desired. In this way, any trauma to the patient&#39;s body can be generally limited to surrounding tissue along the insertion path of the delivery tube. 
     Many procedures have been limited to traditional direct access methods due to the size and method of operation of the tools used to perform the procedures. As a result, there is a need for tools which are more adaptable to use with endoscopic and similar procedures. 
     OBJECTS OF THE INVENTION 
     One object of the invention is a medical instrument with slotted memory metal tube. 
     Another object of the invention is a retrieval basket for small particles. 
     A further object of the invention is a tool for dilating vessels and other tubular structures. 
     Yet another object of the invention is a device for reaming vascular, other tubular structures, or different shaped cavities. 
     Still a further object of the invention is a pump for injection of a defined quantity of fluid. 
     Yet a further object of the invention is an optical system with an expanding section which allows inspection of the expanded area. 
     Another object of the invention is an internal gripper for holding soft tissue such as skin, nerves, arteries, or the like or for holding clips. 
     Yet a further object of the invention is an external gripper for attaching to stems, tissue, or skin. 
     Still a further object of the invention is a tool for expanding cavities for inspection. 
     A further object of the invention is an expandable plug for closing a cavity or tubular structure. 
     Yet another object of the invention is a device for measuring the diameter of tubular structures. 
     Another object of the invention is a steerable catheter tip. 
     Still another object of the invention is a reinforced stent. 
     Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description. 
     SUMMARY OF THE INVENTION 
     According to the present invention, the foregoing and other objects are attained by a medical instrument with slotted memory metal tube. A series of medical instruments can be made with the use of a shape memory tube with a transformation temperature that is above or below the ambient temperature. In the first case, the material behaves with the shape memory effect, and in the second case, the behavior is superelastic. Thus, the memory metal tube of the medical instrument is programmed for an effect selected from the group of effects consisting of memory effect and superelasticity. 
     In all of the disclosed types of instruments, the wall of the tube has been provided with a plurality of slots in specific places, often near or at the distal end of the instrument, and in specific arrangements, which allow local variations in diameter, shape, and/or length. These variations can either be caused by the memory effect during temperature change or by superelastic behavior during change of the mechanical influences on the memory metal by the surrounding material. One possibility to activate the superelastic shape change can be the use of a second tube, surrounding the memory metal tube, sliding more or less over the area where the slots in the memory metal tube are placed. The second tube is used to control the final shape and it prevents shape changes at undesired moments, such as during the procedure of insertion into the human body. The delivery tube can be pulled backward over the central memory metal tube. As soon as the memory metal tube comes free, it can regain its preprogrammed shape whether by superelasticity or by temperature change. 
     Dependent on the intended function of the device, the amount and pattern of slots in the wall of the memory metal tube can be chosen. The slots can be made by a variety of methods, such as, but not limited to, etching, spark erosion, water jet cutting, abrasive water jet cutting, laser cutting, or any mechanical means. An expansion of the slotted part of the desired programmed shape can be achieved by some internal or external mechanical means and, when the final heat treatment has been applied, the prestrained shape will be the new programmed shape. After removing the internal or external shaping tool, the memory metal tube is ready for use. 
     It is possible to make memory metal tubes which are deformed to a small diameter and which will return to a larger diameter in the slotted section by superelasticity or by shape memory effect. The reverse is also possible when the slotted section is opened to a larger diameter than the programmed diameter by some internal restraining means. It will return to a smaller diameter when it is released. The slotted section can be made in several places along the length of the memory metal tube and the programmed shapes can vary over the length of the tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are pictorial views of a retrieval basket of the present invention. 
         FIGS. 1C and 1D  are cross-sectional views taken along lines  1 C- 1 C and  1 D- 1 D of  FIGS. 1A and 1B , respectively. 
         FIG. 2  is a partial sectional pictorial view of a dilation tool of the present invention. 
         FIG. 3  is a pictorial view of a reamer of the present invention. 
         FIG. 4  is a pictorial view of a micropump of the present invention. 
         FIG. 5  is a partial sectional pictorial view of an optical system with expander of the present invention. 
         FIGS. 6A and 6B  are partial sectional pictorial views of an internal gripper of the present invention. 
         FIGS. 7A through 7D  are partial sectional pictorial views of an external gripper of the present invention. 
         FIG. 8  is a partial sectional pictorial view of an expander of the present invention. 
         FIGS. 9A through 9C  are partial sectional pictorial views of an expandable plug of the present invention. 
         FIGS. 10A through 10C  are partial sectional pictorial views of a measuring tip of the present invention. 
         FIG. 11  is a pictorial view of a steerable tip of the present invention. 
         FIGS. 12A and 12B  are cross-sectional views of a reinforced stent of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A series of examples will describe certain preferred embodiments of the present invention. 
     Retrieval Basket 
       FIGS. 1A and 1B  show a memory metal tube  11  with four slots  12  near the distal end. The slots  12  create a balloon-shaped structure which can be used as a retrieval basket for small particles  14 , with a closure around the caught particle due to the concave shape of the inner wall of the memory metal tube  11 . As shown in  FIGS. 1A to 1D , particle  14  is a solid particle. Dependent on the application, either the delivery tube  13  or the memory metal tube is moved, but in both cases the relative axial movement enables the expansion or the contraction of the memory metal tube. The single piece construction is far more simple than with conventional baskets made of several pieces that have to be connected. The advantage of the concave surface can be seen in the top views  1 C and  1 D. In the case of activation by heat, the use of a delivery tool is not necessarily required. With a warm liquid pumped into the memory metal tube, it can be activated (expanded) and with cold fluid it can be brought into the martensitic, deformed state again (contracted). 
     Dilation Tool 
       FIG. 2  shows a tool for dilation of tubular structures such as vessels  24  where the wall thickness of the capillary memory metal tube  21  and the geometry of the segments  22  determine the dilation force F. The delivery tube  23  can be kept in place and the memory metal dilator with the desired dilation force can be inserted. Several dilators with increasing force can be inserted to gradually increase the inner diameter of the artery or cavity. The memory metal tube can either be heated to increase the force and/or diameter, or it can be used superelastically where the well defined plateau stresses give a predetermined and known force. Conventional dilation techniques use a series of tools with increasing diameters, which work less efficiently in many cases. 
     Reamer 
       FIG. 3  shows a reamer where the edges  32  of the slotted section have been sharpened. By relative axial movement of the memory metal tube  31  and delivery tube  33 , the diameter of the reamer is continuously variable. By relative tangential movement (rotation) of the reamer in the delivery tube, the sharp edges of the expanded section cut particles of the inner wall of the artery or any other tubular or other shaped cavity. 
     Micropump 
       FIG. 4  shows a small micropump for the local injection of a well defined quantity of fluid. An example of such a fluid would be a dissolution fluid for obstructions in arteries or kidney stones. The slotted section  42  of the metal tube  41  creates a balloon shaped room  45  with a specific volume. The slotted section  42  is expandable and either surrounds or is surrounded by an elastic material in the shape of a balloon. Two one way valves  46  and  47  above and below the balloon section and connected to its distal and proximal ends, respectively, enable a pumping action in the distal direction by advancing the delivery tube  43  over the slotted section  42  of metal tube  41 . This decreases the volume. Both valves are opening in the same direction and by moving in and out (as shown by the arrows) the balloon pump and deliver one shot of liquid repeatedly. 
     Optical System with Expander 
       FIG. 5  shows a memory metal tube  51  with an expanding section  52  that can contain an optical fiber  56  in the center, with the free end of the fiber in the center of the expanding section  52 , thus enabling an inspection of this expanded area and adjacent areas. The ratio between constrained and expanded diameter can be very large (e.g., a factor of 10), which makes it possible to inspect cavities that are more or less collapsed or deformed. The inner wall of the expanded cavity can be observed as well as the area in front of the tip as shown by the multidirectional arrows. This tool can be used for gynealogics, urethra, ear, nose, arteries, biliaric, esophageal inspections in cavities and/or cylindrical rooms, etc. Another feature of this device is the exact fixation of the inspection fiber(s) in the center of the cavity. A delivery tube  53  can also be utilized to control the expansion of the expanding section  52 . 
     Internal Gripper 
       FIG. 6A  shows a memory metal tube  61  with slots  65  that proceed to the distal end of the tube. The tube end has been programmed into a gripper shape for holding soft tissue like skin, nerves, arteries, clips, etc. When the delivery tube  63  is pushed forward the curved tube segments  62  close toward the center axis of the instrument. In the case of use with clips, a double hook such as that shown in  FIG. 6B  is used to hold a surgical memory metal clip  67 , bring it over the artery  68 , fallopian tube, oviduct, or nerve that has to be held by the clip, heat the clip to close it over the artery by means of a warm fluid inserted through the memory metal tube. After closing of the clip, the delivery tube  63  is moved back to open the hooks again, leaving the clip where it is. Then the gripper is closed again and the tool is pulled back. 
     External Gripper 
     Similar to the previous example of an internal gripper,  FIGS. 7A and 7B  show an external gripper in which the slots  77  proceed to the free end of the memory metal tube  71 . Now the curved segments  72  have been programmed to curve into an outward direction.  FIG. 7A  shows a gripper that can catch a lost or migrated stent from the inside to move it in a longitudinal direction.  FIG. 7B  shows a gripper with segments  72  that are programmed to make a closed loop against the outside wall of the delivery tube  73 . When the tip of each section is sharpened, these sections can cut themselves a path through soft tissue. This enables the use as a connector, that holds itself tightly to the soft tissue, because of its geometry. Such a connector can be the tip of a pacemaker lead or an electrode for measuring or electrical stimulation, e.g., for potential measurements in the inner wall of the stomach.  FIG. 7C  gives an example of a conventional skin hook that holds a wound open during surgery. Sometimes these skin hooks fall off. Superelastic skin hooks using a closed loop  72  do not fall off so quickly, because they lock the skin completely in their closed loop. In this construction, as seen in  FIG. 7D , the delivery tube  73  can have the shape of a hollow needle with a sharp point. Eventually a weight  78  is attached to the opposite end from the loop  72  to keep the skin  79  open. 
     Expander 
     An expansion tool, shown in  FIG. 8 , is used for difficult accessible cavities where optical information is needed or where a place is required for working with instruments. As contrasted with the expander shown in  FIGS. 2 and 5 , here the expanding area is at the distal tip  82  of the memory metal tube  81 . The expander has a working canal  84  with diameter D 1 , to enable bringing instruments into the narrow cavity, which now has an expanded area  87 . The cavity wall  89  is expanded by the tool from its normal diameter C 1  to an expanded diameter C 2  to create the expanded area  87 . 
     Expandable Plug 
       FIGS. 9A and 9B  show a short length of memory metal tube  91  with a slotted section  92  that can be brought into a fallopian tube or oviduct  97  in case of sterilization or any other cavity that is to be closed, either temporarily or permanently. This is done via a delivery catheter  93 . When the plug  94  (or sterilization device) is pushed from the delivery catheter  93  into the cavity (such as fallopian tube  97 ), it will expand and seal the cavity. This is achieved by the combination of the expanded slotted section  92  of plug  94  with an elastic polymer  95  that fills the slotted section  92  in the plug  94 . This elastic material has to be able to completely follow the deformation of the plug  94  from collapsed to final size. Eventually, the plug  94  can be filled with a UV-curing material to make it solid by means of a light from a core fiber. At the proximal end of the plug  94 , an extraction wire  96  (or hook or eyelet) is provided for withdrawal into delivery tube  93  in case the plug has to be removed again.  FIG. 9C  shows a chalice-shaped variant of a sterilization device  94  with a slotted tube  150  that has slots at both ends to make a device that can be put into a cavity that has a shape with a smaller diameter in the center area and bigger diameters above and below (i.e., a cavity with a constricted portion). This is the case in the exit side of the oviduct, near the uterus. The center area of the hollow memory metal tube  150  is sealed with a plug  99  having an attached extraction wire  96 . The expanded sections  151  and  152  of tube  150  can be combined with an elastic polymer (not shown) that finishes the chalice shape to result in less irritation of the adjacent tissue and to get a better sealing against the wall of the oviduct  97 . 
     Measuring Tip 
     The reamer of  FIG. 3  or the expander of  FIGS. 2 and 5  can also be combined with an optical or mechanical means to measure the diameter of the cavity at any position near the distal end of the tube, such as an artery wall  10 . This can be achieved in several ways.  FIG. 10A  shows a memory metal tube  101  with an expanding section  102  and a delivery tube  103 . The memory metal tube  101  itself acts as a delivery tube for a third tube  107  that contains an optical system  106  that looks forward from the distal tip  109  for visual inspection (as represented generally by the arrows), and provides a light image. 
     An alternative embodiment is shown in  FIG. 10B  where the memory metal tube  101  holds a delivery tube  107  with a superelastic measuring wire  108  in the center thereof, that has been programmed to make a curvature at the tip when it leaves the restraining tube  107 . With a scale readout at the proximal side of the catheter/endoscope, the radius of the cavity at the measuring spot can be seen by determining the moment that the bending tip touches the inner wall. 
     In  FIG. 10C , a third variant is shown with a hollow superelastic wire  108  that has been programmed in the same way as described above with respect to  FIG. 10B . In this embodiment, the hollow wire  108  contains an optical system  111 , thus combining the optical readout with a bending tip. This improves the accuracy, because the light emitter/sensor  109  comes closer to the wall than in the situation described under  FIG. 10A . 
     Steerable Tip 
     A steerable catheter tip can be made by means of a slotted memory metal tube, where the slots are made in such a way that a contraction or expansion of a part of the wall can be achieved by local temperature changes. There are many options for the shape of expanding or contracting sections. Pure bending of one or more segments of the wall can also be used to make the tip steerable. In  FIG. 11 , one example is given of a memory metal tube  201  with slots  202  in a zigzag pattern to enlarge the possible contraction per segment  203 , when it is heated to give an angular deviation of the top portion  204  compared to the central axis of the lower portion of the memory metal tube  201 . Heating can also be achieved in several ways, such as local light from a light source or resistance heating. The latter can either be indirect by heating a resistance film that is attached to the memory segment  202 , or by direct resistance heating of the memory metal. In the latter case, the segment  202  must at least at one end be electrically isolated from the rest of the memory metal tube. This can be done by letting the zigzag slots run to the free end of the distal tip (not shown), where the electrical leads can be connected to the end of any single segment  202 . 
     Reinforced Stent 
     A UV-curing polymer is used to make a stent very flexible during insertion and then let it solidify by light emission. A double-walled balloon with the UV curing polymer in-between is already on the market. However, in some cases, it would be an improvement to reinforce this type of stent with an integrated memory metal stent based on the principle of a slotted memory metal tube to make the construction more stable.  FIGS. 12A and 12B  give a view of the cross section through a combined stent in collapsed and expanded shape, respectively. The UV-curing balloon stent  303  is reinforced with segments  302  of a memory metal tube. The slots in the memory metal tube are made in such a pattern that the stent is expandable. 
     Although several embodiments of the present invention have been illustrated in the accompanying drawings and described in the foregoing Description of the Preferred Embodiments, it will be understood that the invention is not limited to the embodiments disclosed but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit and scope of the invention. In some cases the tube can exist from several segments that run through the entire length from proximal to distal. This can be necessary if there has to be an electrical isolation between the expandable segments, like in the application of an electrode for measuring potential and/or electrical stimulation of body parts. 
     The direction of the slots has been parallel to the longitudinal axis of the memory metal tube in the embodiments described above, but they can also be cut into the wall in alternative directions to achieve better performance. An example would be a retrieval basket with helical shaped segments. Further, it can be necessary to use more than one concentric tube with varying functions. Non-concentric tubes, which can be placed beside one another, parallel in the delivery tube, are also embodiments of the present invention.