Abstract:
An implantable port for accessing internal body structures, the port comprises a proximal housing including an opening providing access to an interior of the port and a distal housing adapted for assembly with the proximal housing, the distal housing including a reservoir which, when the distal housing is mated with the proximal housing is in fluid communication with the opening of the proximal housing in combination with a radiopaque element in one of the proximal and distal housings, a shape of the radiopaque element identifying, when imaged, a structural characteristic of the port not otherwise identifiable visually.

Description:
BACKGROUND  
       [0001]    Implantable ports are designed for patients who require long term access to the central venous system or other internal structures for the administration and/or withdrawal of fluids, including hydration fluids, antibiotics, chemotherapy, analgesics, nutritional therapy and blood products. A catheter is typically inserted to form a path to the vascular system by advancing a distal end of the catheter into a blood vessel while a proximal end is connected to the port that is implanted subcutaneously. The port is generally placed under the skin on the upper part of the chest wall or the upper arm, and allows patients to access the desired body lumen while avoiding repeated needlesticks to the target structure. Power injectable implantable ports offer the additional advantage of providing access for the power injection of contrast agents to enhance imaging, such as Contrast-Enhanced Computer Tomography (CECT) scans, which rely on intravenously administered contrast agents to enhance the visibility of internal structures. The contrast agent is power injected into the blood stream to highlight features that would otherwise be difficult to distinguish from nearby tissues. Thus, power injectable ports provide access for the standard injection and withdrawal of fluids (e.g., for therapeutic purposes) and for power injection of contrast agents to enhance imaging. 
         [0002]    Although, it is desirable to use ports which are also suitable for power injection, users must be able to positively identify such ports to ensure they are not accessing a port which is not useable for power injection. The industry has established a “CT” mark, which when viewed under a CT scan, is a standard indication of power injectability. Some existing “CT” identifying technologies known in the field today include a cut-through “CT” design through the port body. The limitation of this design is the space available on the port that would allow for adequate size and visibility of the “CT” lettering. Another disadvantage of cut-through design is that the space could promote tissue ingrowth, which may make it more difficult to remove the port later. 
         [0003]    Pad printing the “CT” letters onto the port using radiopaque ink is another existing technology. Radiopaque ink prevents X-rays or similar radiation waves to pass therethrough so that they may be identified in scans. However, the radiopaque ink in these ports is often located on an outer surface of the port, which can be susceptible to damage such as smearing, cracking and fragmenting in the subcutaneous environment, making the marking unreadable. In addition, fragments of ink may migrate, leading to ink integrity issues. 
         [0004]    Another CT identifying technology is used in the POWERPORT®, manufactured by Bard Access Systems Inc., Salt Lake City, Utah. The POWERPORT® includes an external metal component with “CT” lettering at the base. However, the “CT” lettering occupies a space on the base of the port where the device labeling is typically placed. Device labeling may include manufacturer and/or lot numbers, which may be helpful in identifying the port. In addition, there is a risk of the external component becoming separated from the device. 
       SUMMARY OF THE INVENTION  
       [0005]    The present invention is directed to an implantable port for accessing internal body structures, the port comprises a proximal housing including an opening providing access to an interior of the port and a distal housing adapted for assembly with the proximal housing, the distal housing including a reservoir which, when the distal housing is mated with the proximal housing is in fluid communication with the opening of the proximal housing in combination with a radiopaque element in one of the proximal and distal housings, a shape of the radiopaque element identifying, when imaged, a structural characteristic of the port not otherwise identifiable visually. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  shows a port according to an exemplary embodiment the invention; 
           [0007]      FIG. 2  shows a cross-sectional view of a distal housing of the port of  FIG. 1 ; 
           [0008]      FIG. 3  shows a cross-sectional view of a port according to another embodiment of the invention; 
           [0009]      FIG. 4  shows an exploded view of the port of  FIG. 3 ; 
           [0010]      FIG. 5  shows an exploded bottom view of a port according to another embodiment of the invention; and 
           [0011]      FIG. 6  shows an exploded view of a port according to yet another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0012]    The present invention may be further understood with reference to the following description of exemplary embodiments and the related appended drawings, wherein like elements are provided with the same reference numerals. The present invention relates to devices for accessing the vascular system via a catheter and, more specifically, relates to a power-injectable port that may be identified as such after implantation. Those skilled in the art will understand that the ports described herein are generally implanted with an opening through which fluids are to be introduced or withdrawn facing the skin. As used in this application, the term proximal refers to a direction toward the skin while distal refers to a distance deeper into the body. 
         [0013]    As shown in  FIGS. 1 and 2 , a port  10  according to an exemplary embodiment the invention comprises a distal housing  12  and a proximal housing  14  which are mated together to seal an internal reservoir  16  coupled to a fluid outlet  18  which is coupled to a body structure to which fluids are to be supplied and/or from which fluids are to be withdrawn. A proximal surface of the proximal housing  14  includes an opening  20  via which fluids are supplied and/or withdrawn from the reservoir  16 . The opening  20  is sealed by a self-sealing septum  22 . Thus, the reservoir and the body structure to which the outlet  18  is coupled may be accessed by passing a needle through the septum  22  with the septum  22  resealing itself as soon as the needle is withdrawn, as would be understood by those skilled in the art. 
         [0014]    As shown in  FIG. 2 , a radiopaque insert  24  is embedded in a base  26  of the distal housing  12 . The radiopaque insert  24  incorporates an identifying mark  28  (e.g., a CT mark or other indication of characteristics of the port) visible through the use of one or more types of electromagnetic scan such as X-rays, etc. As would be understood by those skilled in the art, the radiopaque insert  24  may be formed of any material having the desired radiopaque properties (e.g., titanium). The identifying mark  28  may, for example, be cut-through the radiopaque insert  24  allowing the scanning radiation to pass therethrough in a pattern indicative of a characteristic (e.g., suitability for power injection) of the port  10 . Those skilled in the art will understand that, as the insert  24  is embedded in the distal housing  12 , the cut-through design of the identifying mark  28  will be clearly visible without increasing the likelihood of tissue ingrowth. The CT mark shown in  FIG. 2  is for illustrative purposes only, and it will be understood by those of skill in the art that a CT mark on the radiopaque insert  24  may be a mirror image of the marking shown so that the CT may be legible when viewed under the electromagnetic scan. 
         [0015]    As would be understood by those skilled in the art, the radiopaque insert  24  may be embedded within distal housing  12  via an insert molding process in which the radiopaque insert  24  is robotically or hand loaded into a mold cavity between shots. The insert  24  is supported in position in the mold by a series of needle-like core pins and, during injection, these pins are retracted into the mold base as the plastic fills the cavity and encapsulates the insert. Once the insert  24  has been embedded in the distal housing  12 , the distal housing  12  is ready to be assembled with the other port components in the same manner for a port without such a radiopaque insert  24 . Standard assembly techniques such as ultrasonic welding, snap fit or solvent bond may be utilized as would be understood by those skilled in the art. 
         [0016]    As shown in  FIGS. 3 and 4 , a port  30  according to another embodiment of the invention comprises a distal housing  32 , a proximal housing  34  and a radiopaque insert  36 . The distal housing  32  includes a distal flange  38  extending radially outward from a wall of  40  of the distal housing forming a reservoir of the port  30  with a corresponding proximal flange  42  of the proximal housing  34  extending thereover when assembled with the distal housing  32 . The proximal housing  34  is preferably formed so that, when mated with the distal housing  32 , a recess  44  is formed between the distal and proximal flanges  38 ,  42 , respectively. The radiopaque insert  36  is received in the recess  44  between the distal and proximal flanges  38 ,  42 , respectively. The distal housing  32  and the proximal housing  34  may then be joined via any standard plastic joining process, such as ultrasonic welding, snap-fit, and solvent bond, to hold the radiopaque insert  36  in place as would be understood by those skilled in the art. 
         [0017]    As described above, the radiopaque insert  36  may be made of any radiopaque material with an identifying mark  46  (e.g., CT) cut-out so that the mark  46  is clearly visible when imaged using any of the known scanning techniques. As the insert  36  is housed between the proximal and distal flanges  38 ,  42 , respectively, the cut-out poses no risk of tissue ingrowth and the risk of the insert  36  becoming detached from the port  30  is also minimized. 
         [0018]    In a further embodiment of the present invention, the radiopaque insert  36  may be embedded in either of the proximal and distal flanges  38 ,  42 , respectively using an insert molding process. As described above, the radiopaque insert  36  may be placed into a mold cavity between shots and held in place by a series of needle-like core pins. During injection, these pins are retracted into the mold base as plastic fills the cavity and encapsulates the insert  36 . Once the insert  36  has been embedded, the distal housing  32  is ready to be assembled with the other port components including the proximal housing  34  as described above. 
         [0019]    In another embodiment of the present invention, as shown in  FIG. 5 , a port  50  comprises a distal housing  52  and a radiopaque insert  54  having a periphery shaped to define an identifying mark  56 . Those skilled in the art will understand that, when the identifying mark consists of more than one element (e.g., multiple letters) a minimal amount of radiopaque material may extend between these elements to maintain a desired alignment during the molding process. The insert  54  may be overmolded into the distal housing  52  by inserting it into the cavity before injection. The plastic would form around the insert, leaving the surface of the CT mark visible on the underside of the base. The distal housing  52  with overmolded radiopaque insert  54  may be assembled with the rest of the port components using any standard assembly techniques as described above. 
         [0020]    In a further embodiment, the overmolded insert  54  may be mechanically combined with a port stem and inserted into the mold. Overmolding would then encapsulate and seal the insert  54  into the distal housing  52  while simultaneously binding the stem to the distal housing  52 . Such an embodiment provides a radiopaque marker for power injectability while eliminating a separate stem/port assembly step. 
         [0021]    In another embodiment of the present invention, shown in  FIG. 6 , a port  60  comprises a proximal housing  62  that may be molded using plastic loaded with radiopaque fillers such as barium, bismuth, and tungsten. The proximal housing  62  includes a proximal flange  64  extending radially outward therefrom with a corresponding distal flange  68  extending radially outward from a distal housing  70  in the same manner described above in regard to the port  30  of  FIGS. 3 and 4 . The proximal flange  64  includes an identifying mark  72  mark cut through a thickness thereof (e.g., during a molding process). The distal housing  70 , or at least the distal flange  68 , is formed of standard plastic with no radiopaque fillers so that the mark  72  creates a “negative” of the mark  72  when imaged (e.g., under CT or other body scan). In order to prevent tissue ingrowth, a silicone boot or skirt may be incorporated such that the boot or skirt covers the cut-through lettering. It will be understood by those of skill in the art that the boot or skirt may additionally be composed of any suitable non-radiopaque material. Furthermore, those skilled in the art will understand that the distal housing  70  may, alternatively, be formed of a material incorporating radiopaque fillers with the mark  72  cut out of the distal flange  68  while the proximal housing  64  is formed of a material free of radiopaque fillers. 
         [0022]    It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and the methodology of the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents.