Abstract:
A method of printing radiopaque indicia on a medical device. The method includes applying radiopaque marking fluid to a surface of a plate comprising one or more etchings having a depth of at least 0.0001 inches, exposing the radiopaque marking fluid on the surface of the plate to air to allow the radiopaque marking fluid to achieve a sufficient level of tackiness, and transferring the radiopaque marking fluid to a medical device. The radiopaque marking fluid comprises a clear ink and tungsten particulates having a particulate size of more than one micron.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/331,671, entitled “Method and Apparatus for Printing Radiopaque Indicia” and filed May 5, 2010, the contents of which application are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a method and apparatus for printing radiopaque indicia on a medical device and, more specifically, to a method and apparatus for printing radiopaque marking fluid onto a venous access port. 
       BACKGROUND 
       [0003]    Venous access ports for the infusion and/or withdrawal of fluids from a patient are known in the art. Such ports generally comprise a needle-penetrable septum, a cap, and a port housing comprising a fluid reservoir. The needle-penetrable septum is disposed on the port housing to seal the fluid reservoir. The cap secures the septum to the port housing. Such ports additionally include a discharge port comprising a fluid passageway that communicates with the fluid reservoir and a catheter secured to the discharge port. 
         [0004]    It is desired to provide a venous access port assembly that provides a medical practitioner with capability to discern an important property of the port assembly after the port assembly has been implanted into a patient. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with an exemplary aspect of the present invention, there is provided a method of printing radiopaque indicia on a medical device. The method includes applying radiopaque marking fluid to a surface of a plate comprising one or more etchings having a depth of at least 0.0001 inches, exposing the radiopaque marking fluid on the surface of the plate to air to allow the radiopaque marking fluid to achieve a sufficient level of tackiness, and transferring the radiopaque marking fluid to a medical device. The radiopaque marking fluid comprises a clear ink and tungsten particulates having a particulate size of more than one micron. 
         [0006]    In accordance with a further exemplary aspect of the present invention, there is provided a printing apparatus for printing radiopaque indicia on a medical device. The printing apparatus includes a plate comprising one or more etchings having a depth of at least 0.0001 inches, a cup containing a radiopaque marking fluid, a jig for holding a medical device, and a pad for transferring radiopaque marking fluid deposited within the one or more etchings to the medical device. The radiopaque marking fluid comprises a clear ink and tungsten particulates having a particulate size of more than one micron. The cup is configured to be inverted and pressed against the plate to effect a fluid seal of the radiopaque marking fluid against the plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    For the purpose of illustration, there are shown in the drawings certain exemplary embodiments of the present invention. In the drawings, like numerals indicate like elements throughout. It should be understood, however, that the invention is not limited to the precise arrangements, dimensions, and instruments shown. In the drawings are included the following figures: 
           [0008]      FIG. 1A  illustrates an exemplary printing apparatus comprising a cup, a plate, and a pad, wherein the printing apparatus in an idle state (first position) in which the cup is disposed over etchings in the plate, in accordance with an exemplary embodiment of the present invention; 
           [0009]      FIG. 1B  illustrates the exemplary printing apparatus in a second position in which the cup has been translated off the etchings in the plate, in accordance with an exemplary embodiment of the present invention; 
           [0010]      FIG. 2  illustrates the plate of the exemplary printing apparatus, in accordance with an exemplary embodiment of the present invention; 
           [0011]      FIG. 3  illustrates the cup of the exemplary printing apparatus, in accordance with an exemplary embodiment of the present invention; 
           [0012]      FIG. 4  illustrates an exemplary venous access port assembly, in accordance with an exemplary embodiment of the present invention; 
           [0013]      FIG. 5A  is a planar view of the bottom of an exemplary venous access port assembly onto which radiopaque indicia have been printed using the exemplary printing apparatus illustrated in  FIG. 1 , in accordance with an exemplary embodiment of the present invention; and 
           [0014]      FIG. 5B  is an isometric view of the exemplary venous access port assembly of  FIG. 5A , in accordance with an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIG. 1A , there is illustrated an exemplary printing apparatus, generally designated as  100 , in accordance with an exemplary embodiment of the present invention. The printing apparatus  100  comprises a bed  110  for supporting a plate  200  and a bed  130  for supporting a jig  140  that holds a medical device (not illustrated in  FIG. 1A ) onto which the exemplary printing apparatus  100  prints indicia. 
         [0016]    Mounted onto the bed  110  is a metal plate  115  onto which the plate  200  is secured. In an exemplary embodiment, the metal plate  115  is pinned to the bed  110 , and the plate  200  is held in place with dowel pins on the metal plate  115 . 
         [0017]    The jig  140  includes bolt holes  143  and  144  through which bolts secure the jig  140  to the bed  130 . The jig  140  also includes recess  141  and  142  into which medical devices are disposed. The recesses  141  and  142  hold the medical devices in place while the printing apparatus  100  prints indicia onto the medical devices. In an exemplary embodiment, a venous access port assembly is disposed into each of the recesses  141  and  142 , with a bottom surface of each access port assembly facing upwards away from the top face of the jig  140 . 
         [0018]    The printing apparatus  100  additionally comprises a cup  300  attached to an arm  120 . Attached to the bottom of the cup  300  is a ring  350 . The cup  300  contains ink that is applied to a top surface  210  of the plate  200 . The printing apparatus  100  also comprises a pad  150  for transferring the ink on the top surface  210  of the plate  200  to the medical devices in the jig  140 . 
         [0019]      FIG. 1A  illustrates an idle state of the printing apparatus  100  in which the cup  300  is in a first position atop the plate  200 . Referring now to  FIG. 1B , there is illustrated a second position of the cup  300 , in accordance with an exemplary embodiment of the present invention. As is illustrated in  FIG. 1B , in the second position, the cup  300  is disposed at an end of the plate  200  away from the jig  140 . In the second position of the cup  300 , etchings  220  and  230  on the top surface  210  of the plate  200  are exposed. 
         [0020]    Referring now to  FIG. 2 , there is illustrated a closer view of the top surface  210  of the plate  200 , in accordance with an exemplary embodiment of the present invention. As can be seen in  FIG. 2 , the etchings  220  and  230  in the top surface  210  of the plate  200  comprise the letters “CT.” The exemplary plate  200  is used to print “CT” onto the medical devices, e.g., venous access port assemblies, held by the jig  140 . 
         [0021]    In an exemplary embodiment, the exemplary printing apparatus  100  prints a radiopaque marking fluid onto the medical devices held in the jig  140 . An exemplary radiopaque marking fluid comprises a mixture of a clear ink and tungsten particulates in a defined ratio. Generally, the ratio depends upon the substrate, i.e., the material of the medical devices in the jig  140 , on which the radiopaque marking fluid is to be applied. Thus, the ratio depends on the substrate material, the durometer of the substrate, the chemical makeup (compound) of the substrate or the material (substrate) receiving the indicia, and/or processing of the material receiving the indicia. In an exemplary embodiment, the ratio of the mixture is suitable for application to a polysulfone substrate, such as a venous access port assembly formed from polysulfone. Flexible substrates use a radiopaque marking fluid having a clear ink/tungsten ratio that results in the indicia printed onto the medical devices being flexible also to prevent cracking Stiff substrates allow a clear ink/tungsten ratio that results in stiff indicia printed onto the medical device. 
         [0022]    Each of the etchings  220  and  230  have respective depths to accommodate ink applied by the cup  300 . In the embodiment in which the exemplary printing apparatus  100  applies radiopaque marking fluid to a medical device, the depths of the etchings  220  and  230  may be between 0.0001 inch (0.000254 cm) and 0.003 inch (0.00762 cm). The depths depend upon the size of the tungsten particulates in the radiopaque marking fluid. Generally speaking, the depths of the etchings  220  and  230  must be increased to accommodate larger tungsten particulates in the radiopaque marking fluid. 
         [0023]    Radiopacity of the radiopaque marking fluid varies inversely with the size of the tungsten particulates in the radiopaque marking fluid. Smaller particulates have a lower radiopacity than larger particulates. Thus, when using a radiopaque marking fluid having relatively smaller tungsten particulates, the exemplary printing apparatus  100  desirably performs more hits (applications of radiopaque marking fluid) on the subject medical device to transfer the shape or letters defined by the etchings  220  and  230  onto the medical device, as compared to a lower number of hits required for a radiopaque marking fluid having relatively larger tungsten particulates. Desirable sizes of the tungsten particulates are on the order of one to several microns. In an exemplary embodiment, the size of the tungsten particulates is from one to five microns. 
         [0024]    To ensure proper adhesion of the radiopaque marking fluid to the medical devices within the recesses  141  and  142 , the medical devices should be cleaned using a suitable cleaning means. Examples of suitable cleaning means include plasma, solvent, aqueous, etc. The cleaning means are not limited to any one technology. 
         [0025]    Other specifications of the printing apparatus  100  include the material forming the pad  150 , the time for which the radiopaque marking fluid applied in the etchings  220  and  230  are exposed to air before being transferred by the pad  150  to the medical devices, and flash-off time for the radiopaque marking fluid. The firmness of the pad  150  is selected in order to facilitate the transfer of as much radiopaque marking fluid within the etchings  220  and  230  to the medical devices that will adhere to the devices. In a further exemplary embodiment of the printing apparatus  100 , the pad  150  is formed from silicone. 
         [0026]    The flash-off time of the radiopaque marking fluid is selected so that the radiopaque marking fluid achieves a desired level of tackiness while it is exposed to air before being transferred to the medical devices. Such exposure to air may include blowing chilled air, heated air, or air at room temperature onto the radiopaque marking fluid within the etchings  220  and  230 . The temperature and humidity of the air applied to the radiopaque marking fluid within the etchings  220  and  230  is selected to achieve the desired level of tackiness of the radiopaque marking fluid before being transferred to the medical devices. 
         [0027]    Referring now to  FIG. 3 , there is illustrated a view of the underside of the cup  300  and the ring  350 , in accordance with an exemplary embodiment of the present invention. The cup  300  comprises an outer rim  305  and an inner riser  310 . Together, the outer rim  305  and inner riser  310  define an interior cavity  330  which contains the ink or radiopaque marking fluid used in the printing process. The ring  350  is secured to the rim  305  of the cup  300 . The ring  350  performs several duties. It seals the ink within the cup  300 , specifically within the interior cavity  330  of the cup  300 , when the cup  300  is disposed on the plate  200 . Further, it acts as a squeegee to wipe ink off the top surface  210  of the plate  200  during the printing process. 
         [0028]    Disposed on the riser  310  is a plurality of magnets  320 . The magnets  320  are attracted to the plate  200  to allow the ring  350  to perform its sealing and wiping functions. Because the magnets  320  are attracted to the plate  200 , the cup  300  compresses the ring  350  against the plate  200  and presses the plate  200  against the metal plate  115 . 
         [0029]    An exemplary method of printing radiopaque marking fluid onto a bottom surface of venous access port assemblies is now described with reference to  FIGS. 1A ,  1 B,  2 , and  3 . A technician places venous access port assemblies into the recesses  141  and  142  of the jig  140  and attaches the plate  200  to the metal plate  115 . The technician fills the cavity  330  of the cup with a radiopaque marking fluid that will be applied to the venous access port assemblies within the recesses  141  and  142  and subsequent venous access port assemblies that will be placed within the recesses  141  and  142  in subsequent printing operations. The technician then places the printing apparatus  100  in the idle state in which the cup  300  is disposed on the top surface  210  of the plate  200  over the etchings  220  and  230 . 
         [0030]    In the idle state, the radiopaque marking fluid within the cup  300  covers and fills the etchings  220  and  230  and covers the portion of the top surface  210  over which the cup  300  is disposed. The technician then commands the printing apparatus  100  to transfer the radiopaque marking fluid from the etchings  220  and  230  to the medical devices, i.e., to perform a “hit.” The printing apparatus  100  translates the cup  300  away from the etchings  220  and  230 . In the process of such translation, the ring  350  secured to the bottom of the cup  300  acts as a squeegee to wipe any radiopaque marking fluid on the top surface  210  of the plate  200  outside of the etchings  220  and  230 . The cup  300  moves to the second position, and radiopaque marking fluid remains within the etchings  220  and  230 . 
         [0031]    The radiopaque marking fluid within the etchings  220  and  230  is then exposed to air to achieve a desired tackiness. Such air may be at room temperature or heated or chilled. When the radiopaque marking fluid achieves the desired level of tackiness, the pad  150  hits the etchings  220  and  230  and picks up some or all of the radiopaque marking fluid within the etchings  220  and  230 . The pad  150  then hits the medical devices within the recesses  141  and  142  to transfer the radiopaque marking fluid to the medical devices. The printing apparatus  100  returns to its idle state. 
         [0032]    The printing apparatus  100  repeats the process described above to perform additional hits on the medical devices to layer the radiopaque marking fluid on the medical devices to achieve a desired level of radiopacity of the printed indicia. When the desired level of radiopacity is achieved, the medical devices are removed from the jig, and new medical devices are inserted to be printed using the process described above. The deposited radiopaque marking fluid may be allowed to air dry, or the printed medical devices may be placed into an oven to speed the drying process. 
         [0033]    Referring now to  FIG. 4 , there is illustrated an exemplary embodiment of a venous access port assembly, generally designated as  400 , in accordance with an exemplary embodiment of the present invention. The venous access port assembly  400  comprises a septum  410  and a housing  420  that includes an interior fluid reservoir (not illustrated). The septum  410  is disposed on the port housing  420  to seal the interior fluid reservoir. 
         [0034]    The venous access port assembly  400  additionally comprises a discharge port  430  extending from a distal end  440  of the port assembly  400 . The discharge port  430  is attached securely and sealingly to the proximal end of a catheter (not illustrated). A passageway (not illustrated) extends from the interior reservoir to a distal tip opening  450  of discharge port  430 . The port assembly further comprises a cap  460  which secures the septum  410  to the port housing  420  to maintain the fluid seal within the interior fluid reservoir. 
         [0035]    In an exemplary embodiment of the printing apparatus  100 , the recesses  141  and  142  formed within the jig  140  are shaped to hold the access port assembly  400  during the printing process. In such an embodiment, an access port assembly  400  is disposed within each of the recesses  141  and  142  such that the septum  410  of each port assembly  400  faces down and a bottom surface of each port assembly  400  face up toward the pad  150 . The printing apparatus  100  applies ink to the bottom surface of each port assembly  400 . In an exemplary embodiment, the printing apparatus  100  applies radiopaque marking fluid to the bottom surface of each port assembly  400 . 
         [0036]    The venous access port assembly  400  is further described in U.S. patent application Ser. No. 11/801,050 filed May 7, 2007 and claiming priority from U.S. Provisional Patent Application Ser. No. 60/801,523 filed May 18, 2006 and in U.S. patent application Ser. No. 12/143,377 filed Jun. 20, 2008 and claiming priority from U.S. Provisional Patent Application Ser. No. 60/936,491 filed Jun. 20, 2007, the contents of all of which applications are hereby incorporated by reference in their entirety for all purposes. 
         [0037]      FIG. 5A  illustrates a planar view of a port assembly  500  onto which indicia have been printed, in accordance with an exemplary embodiment of the present invention.  FIG. 5B  illustrates an isometric view of the port assembly  500 , in accordance with an exemplary embodiment of the present invention. 
         [0038]    Referring now to  FIGS. 5A and 5B  together, the port assembly  500  comprises a base  510  having a bottom surface  520  onto which indicia have been printed. The indicia include indicia  530  centered on the bottom surface  520  of the port assembly  500 . In the example shown, indicia  530  comprise the letters “CT” representing the term “computed tomography.” The meaning of this term is described in further detail below. 
         [0039]    The indicia on the bottom surface  520  further include a smaller inner circle  540  and a larger outer circle  550  provided on the outermost periphery of bottom surface  520 . The outer circle  550  includes a gap  560  where the port assembly  500  includes a recess to accommodate a stem  570 . 
         [0040]    In an exemplary embodiment of the printing apparatus  100  described above, the printing apparatus  100  applies radiopaque marking fluid to print radiopaque indicia onto the medical devices disposed within the recesses  141  and  142  of the jig. In such embodiment, the medical devices may be formed from radiotransparent material. In a further exemplary embodiment, the printing apparatus  100  prints radiopaque indicia on venous access port assemblies, such as the port assemblies  400  or  500 . In such embodiment, the port assemblies  400  and  500  are formed from a plastic material, such as a silicone elastomer or polysulfone. Thus, in an exemplary embodiment, the indicia  530 , the inner circle  540 , and the outer circle  550  are printed with radiopaque marking fluid. 
         [0041]    A wide variety of medical procedures require infusion of a fluid into a patient. For example, vascular imaging technologies may require use of a contrast media that is injected into the patient. More specifically, computed tomography (CT) is an imaging technology that utilizes a contrast media and may be employed for the noninvasive evaluation and assessment of a vascular system (i.e., CT angiography or CTA). Multidetector computed tomography (MDCT) is one specific type of CT that may be utilized for CTA. For proper imaging of a vascular system via CT, intravenous contrast media injection protocols are coordinated and selected for the anatomic area of interest. 
         [0042]    More particularly, conventionally, a so-called “power injector” system may be employed for injecting contrast media at a high pressure into a peripherally inserted intravenous (IV) line. Because CT procedures are often defined in terms of a desired flow rate of contrast media, such power injection systems are, in general, controllable by selecting a desired flow rate. Accordingly, such power injection systems may develop pressure (within the maximum pressure capability of the power injection system) as is necessary to maintain the selected flow rate. 
         [0043]    The pressure required for contrast injection depends on many factors, including flow rate, contrast viscosity, configuration of infusion tubing, such as tube diameter and length, and any obstruction or restriction to flow (e.g., kinks, curves, fittings, compression). As mentioned above, to maintain the flow rate required for a CT or MRI study, a power injector may generate high pressures. Ruptures can occur when the injection pressure exceeds the tolerance of the vascular access devices, such as venous access ports. Other problems may occur due to timing errors between the scan and the contrast. In order to maximize the rapid scanning capacity of the newer vascular imaging devices, the starting of the scanning process can be delayed a predetermined amount of time after injection of the contrast media has begun. If the scan starts too early, just as the contrast is arriving at the heart, arteries can appear smaller than they really are when the image is post-processed. On the other hand, if scanning is delayed too long, image artifacts can arise from diluted contrast in the cardiac veins. The window of opportunity for optimal scans may be very small, because contrast media circulates quickly through cardiac arteries and into cardiac veins. 
         [0044]    The term “high pressure injection” is understood to mean injections in which pressures within the port assembly  400  or  500  reach pressures generated by power injections having fluid flow rates between about 1 milliliter per second and about 5 milliliters per second. Such pressures may be between about 37 psi (255 kPa) to about 65 psi (448 kPa) within the reservoir of such port assemblies. 
         [0045]    Thus, in an exemplary embodiment, the radiopaque indicia, such as the indicia  530 ,  540 , and  550 , indicate that the medical device, e.g., the port assembly  500 , on which such indicia are printed by the printing apparatus  100 , is rated for high pressure injection such as is necessary for infusion into a patient of contrast medium that is used in computed tomography. Hence, in an exemplary embodiment, the indicia  530  comprise the letters “CT.” Other indicia may be used that indicate some other attribute or characteristic of the venous access port assembly. 
         [0046]    By printing radiopaque indicia onto a venous access port assembly rated for high pressure injections, a clinician is able to verify that such venous access port assembly is rated for high pressure injections after being implanted into a patient. Specifically, such clinician may X-ray the implanted port assembly and be able to verify that such port assembly is rated for high pressure injection if “CT” is discernable on the port assembly in the X-ray image. Further, because the radiopaque marking fluid is applied to an exterior surface of the venous access port assembly, the indicia (e.g., “CT”) are viewable to the naked eye prior to implantation. Thus, the surgeon implanting the port assembly is able to verify that such port assembly is rated for high pressure injection by visual inspection of the port assembly prior to implantation. In an exemplary embodiment, the CT indicia appear to be black to the naked eye. 
         [0047]    These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention.