Abstract:
There is disclosed a system and method for allowing use within a body of devices having material not known for its biocompatibility with the body. In one embodiment, a magnetically controlled solenoid/valve is used where portions of the valve are directly in contact with compositions that are to be delivered to a target site. Advantage is taken of an existing solenoid/valve having chromium alloy parts by coating the portions of the valve that contact the deliverable composition with a known biocompatible material having good wear resistance. In one embodiment, titanium nitride (TiN) is used as the coating material.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to Provisional Application Ser. No. 60/512,124 entitled “SYSTEM AND METHOD FOR IMPLANTATION OF DEVICES HAVING UNKNOWN BIOCOMPATIBLE MATERIALS, filed Oct. 17, 2003, the disclosure of which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to systems and methods for implantation of devices having unknown biocompatible materials and more particularly to human implantable fluid valves and more specifically to such valves in which a portion of the valve having unknown bio-compatibility is contained within the fluid flow. 
       BACKGROUND OF THE INVENTION 
       [0003]    In many situations medication, or other liquid material, is delivered internal to the human body directly to a particular target location. For example, it has become accepted practice to deliver pain medication directly to a spine using a pump implanted within the body. These pumps may operate on constant pressure preset prior to insertion into the body. Such constant pressure pumps are designed to deliver a premeasured amount of medication per unit of time. 
         [0004]    In some situations, it is desirable to control the flow of medication by, for example, controlling the flow rate of the medication. This can be accomplished by changing the opening through which the liquid must pass, thereby changing the volume of medication sent to the target site. One design for metering such delivery is to use a solenoid which magnetically controls a valve located directly in the flow stream of the liquid. 
         [0005]    Such devices suited for this task might use plungers of unknown bio-compatibility which may potentially allow traces of potentially harmful substances to be delivered to the target site, if the plunger were to be in contact with the medication. While, often, these substances have not proven to be medically significant they likewise have not been shown to be harmless. Tests to prove lack of harm are time consuming and expensive. Because of extensive testing, it has not been feasible to use “off-the-shelf” devices for implantation because of the unknown risk factors such devices might present. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    There is disclosed a system and method for allowing a user to determine which components within a device are of biocompatible concern and to isolate such components. In one embodiment, a magnetically controlled solenoid/valve is used where the valve is directly in contact with compositions that are to be delivered to a target site. Advantage is taken of an existing solenoid/valve having a chromium plunger by coating the portions of the plunger that contact the deliverable composition with a known biocompatible metallic material having good wear resistance. In one embodiment, titanium nitride (TiN) is used as the coating material. 
         [0007]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
           [0009]      FIG. 1  illustrates a valve shown in the open position; 
           [0010]      FIG. 2  is a sectional view taken along section  2 - 2  of  FIG. 1 ; 
           [0011]      FIG. 3  illustrates a typical valve and pump system used for the delivery of medication to a human spine; and 
           [0012]      FIG. 4  shows one embodiment of the distal end of the valve plunger. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  shows valve  10  in the open position where voltage is applied to solenoid  104  forcing plunger  14  to the right (proximal end). Fluid arriving at input port  102  fills chamber  106  and passes along plunger  14  via channels  12 . The fluid then passes around (or through) the ends of seal  13  (for example, via openings  13   a ) and enters chamber  107 . The fluid then passes out of the valve via opening  108  and output port  103 . 
         [0014]    Plunger  14  is longitudinally positioned within a hollow core of housing  101  through the center of solenoid  104  essentially forming a first chamber  106  at the proximal end of the plunger and a second chamber  107  at the distal end. Spring  15  is positioned within chamber  106  and exerts longitudinal force on the proximal end of plunger  14  when the valve is open (plunger  14  moved to the right toward the proximal end). The force of spring  15  acting on plunger  14  is toward the distal end, when spring  15  is compressed. 
         [0015]    When it is desired to stop or reduce the fluid flow, electrical voltage is removed from solenoid  104  allowing spring  15  to push plunger  14  to the left (toward the distal end) forcing the body of seal  13  into contact with opening  108  of output port  103  so as to prevent (or reduce) fluid from passing out of valve  10 . 
         [0016]    In operation, the voltage can be pulsed on and off so that the amount of fluid delivered at the output of port  103  is precisely controllable. The power source for valve  10  can be either internal to the body or external, and can be a battery ( 33 ,  FIG. 3 ) or other voltage source with power and control delivered via wires (or wireless)  304 . The pulsing of the solenoid can be hard wired controlled (via wires not shown) or can be wirelessly controlled. The valve can be designed to operate in the opposite manner such that when the voltage is applied the valve closes and when the voltage is removed the valve opens. However, for fail-safe purposes in most applications it would be desirable to have the valve close when power fails so that less and not more medication passes to the target site. Note that in some embodiments the seal could be designed to allow some fluid to flow even when in the “closed” position. 
         [0017]    Spring  15  can be, for example,  316  stainless steel or any other material acceptable for implantable use directly into the liquid stream being delivered to the target site. Plunger  14 , is material responsive to the magnetic fields created by solenoid  104 . In the embodiment shown, plunger  14  is a chromium alloy, for example Cr 18 . The portion of plunger  14  and interior chamber walls that contact the material to be delivered to the target site is coated in a biocompatible material, such as titanium nitride (TiN). The coating material can be metallic or non-metallic as desired. Housing  101 , which can be implantable in a human body, comprises material, such as 316 stainless steel which is known to be biocompatible for implant purposes where contact with the medication is not present. Seal  15  on the end of plunger  14  can be, for example, silicone, which is also a biocompatible material. 
         [0018]    In one embodiment, the plunger is made of non-biocompatible or unknown biocompatible material, whose biocompatible properties are not well know. While analysis of each material&#39;s biocompatible property could occur, this involves expensive and time consuming testing, which may not provide ascertainable results. Such testing would delay introduction of materials into products and might not provide the surety needed to satisfy governmental approval for use. 
         [0019]    Use of known biocompatible materials as a coating on parts having unknown biocompatiblility solves this problem. For one embodiment, titanium nitride (TiN) is used for the above mentioned properties, thereby allowing the valve to be produced at a relatively low cost without costly testing. 
         [0020]    In operation, a user desiring to implant a device in a human (or in an animal) could select an off-the-shelf device having unknown biocompatible materials and then determine which portions of the selected device would cause problems if the material of the determined portions was not biocompatible with the human (or animal) body. Once these “potential” trouble portions are identified, the user would select a material that is known to be biocompatible and also known to be compatible with the desired function within the device. The potential trouble spots are then coated by plating or otherwise with the selected material. In some situations, different portions of the device could have different requirements depending upon the function to be performed and the implanted location of the device. Thus, as discussed herein, those portions of the device that are implanted under the skin may have a different biocompatibility requirement than does those portions of the device coming into contact with medication to be delivered or coming into contact with the blood supply of the patient. 
         [0021]    In some embodiments, the liquid could flow on the outside of plunger  14  provided plunger  14  was supported within the hollow core of housing  101  and provided any surface that the liquid contacted was of a biocompatible material. This support, for example, could be a series of O-rings, each having holes therethrough so that the liquid could pass around the plunger while the plunger is supported within the O-rings. The liquid would then flow into chamber  107  and out of outlet  103  when the plunger is in the open position. When the plunger moves to the closed position, seal  13  would be forced against opening  108  thereby stopping (or reducing) the flow of liquid. 
         [0022]      FIG. 2  is a sectional view taken along section  2 - 2  of  FIG. 1 . Housing  101  is shown around solenoid  104  which in turn surrounds plunger  14  and seal  13 . Fluid channels  12  are shown around the outside of plunger  14 . Note that the fluid channels can be spiraled, as shown in  FIG. 1 , or can be longitudinal along the plunger. These channels can be on the outside surface of plunger  14  or internal thereto, or a combination thereof. 
         [0023]      FIG. 3  shows one illustrative system  30  in which catheter  302  delivers a measured amount of medication to human spine  303  within human body  32 . Catheter  302  is connected to output port  103  of valve  10 . Pump  31  is any pressure source which can deliver a measured amount of medication, under constant pressure if desired, to catheter  301  which, in turn, delivers the medication to input port  102  of valve  10 . Valve  10 , then is operational to meter the medication to the target site, or sites, within spine  303 . In this embodiment, pump  31 , valve  10  and catheters  301  and  302  are all implanted within human body  32 . Pump  31  could also be, for example, a spring driven infusion pump of the type described in U.S. Pat. No. 4,772,263. Also, instead of a pump, or in addition thereto, a positive pressure reservoir can be used. 
         [0024]    Since plunger  14  is constructed of a relatively hard material, such as chromium or a chromium alloy, the coating placed thereon should also be hard. Accordingly, the use of titanium nitride (TiN) which is a relatively brittle and hard material will work well. The thickness of the coated TiN, in one embodiment is between 3 microns and 5 microns but may vary depending on the application. The metallic coating could be deposited using well-known vapor depositing techniques or any other process. One method for depositing the coating would be to put a pin (or other holding device) through hole  401  ( FIG. 4 ) at the distal end of plunger  14  for the purpose of holding the plunger during the vapor depositing process. At the end of the coating process, the plunger is removed from the depositing bath and the pin (or other holding device) is removed. The plunger will then be coated, except possibly where the pin (or other holding device) had been positioned. 
         [0025]    As shown in  FIG. 4 , in one embodiment seal  13  then can be force fitted, or otherwise attached using adhesive or fasteners as desired, to circumferentially reduced portion  401  at the distal end of plunger  14  allowing the seal to effectively cover any portion of plunger  14  that was not fully coated. Platinum would be another know biocompatible material, however platinum does not have the durability as does titanium nitride. 
         [0026]    By using titanium nitride, a known biocompatible material, and recognizing that it has the hardness required to coat a magnetic material, such as chromium, without interfering in the magnetic solenoid operation, a metering valve can be constructed from an essentially “off-the-shelf” valve that is human implantable, even though the “off-the-shelf” valve could not be so used without proper coating of the plunger. 
         [0027]    While an in-line valve (liquid stopper) has been shown in one embodiment, any type of valve could benefit form the concepts taught herein. For example, a rotary valve could be used which rotates open and closed with the areas touching the liquid being coated with a biocompatible material. Also, while a human body has been shown, the concepts taught herein can be used for implantation in any body, including animals. 
         [0028]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.