Abstract:
A stranded brachytherapy product and methods of forming a stranded brachytherapy product. The methods includes the step of applying an adhesive to a carrier containing at least one brachytherapy seed so as to, upon curing of the adhesive, impart substantial rigidity to the carrier. Alternatively, the adhesive may be selectively applied so as to provide a deflectable brachytherapy product.

Description:
This application is a filing under 35 U.S.C. 371 of international application number PCT/US2008/068965, filed Jul. 2, 2008, which claims priority to application No. 60/947,586 filed Jul. 2, 2007, in the United States the entire disclosure of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of brachytherapy devices. More specifically, the present invention is directed to a stiffened brachytherapy strand and a method for making the same. 
     BACKGROUND OF THE INVENTION 
     Brachytherapy strands are cancer therapy devices in which radioactive brachytherapy seeds are provided in an elongate carrier. One such device marketed by the assignee of the present invention is RAPID Strand®, available from its Arlington Heights, Ill. facility. RAPID Strand® is manufactured using a Polyglactin braided carrier. Polyglactin is a mixture of polyglocolide and poly l-lactide and is commonly used as a biologically absorbable material.  FIG. 1  depicts a RAPID Strand® product  10  as presently manufactured and sold by GE Healthcare of North Arlington Heights, Ill. The braided carrier  12 , clearly seen in  FIG. 1 , contains radioactive seeds and non-radioactive spacers. The locations of the seeds and spacers are noted by the reference numbers  14  and  16 , respectively. The seeds are the cancer therapy components. The spacers are used for optimum seed separation and long axis rigidity of the assembled RAPID Strand®. The seeds and spacers are inserted into the braided carrier, and then the assembled unit is heated in an oven. The oven cycle causes the braided carrier, and seeds and spacers contained within it, to gain enormous strength long axis. This is accomplished by a thermo-induced change in the structure of the Polyglactin material. This heat stiffening process takes considerable time and energy to perform, but is required for finished device assembly functionality. 
     During implant preparation it is common to cut the standard RAPID Strand® segments into smaller segments for optimum clinical value to the patient. One such method is described in U.S. Pat. No. 5,460,592 assigned to the assignee of the present invention and the contents of which are hereby incorporated by reference as if fully stated herein. When cutting the segments it is not uncommon for the inner components to become somewhat separate from the outer braid. Heating the end, after cutting the segment, can help in retaining the components in the braided carrier material. It should be noted that the seed components themselves are made of titanium and have no physical connection to the braided carrier or the spacers. The seeds are contained within the heat-stiffened suture and between the spacers. Long axis rigidity is accomplished by having components (seeds and spacers) stacked end to end within a very tight braided material. 
     There is therefore a need for an alternative method for imparting long-axis stiffness, and end spacer retention when cut, to a brachytherapy strand. There is also a need for an elongate brachytherapy strand having regions of longitudinal stiffness adjacent regions of considerably reduced longitudinal stiffness to facilitate deflection of the strand when used for applications in which it is desired for the strand to more closely conform to deflectable tissue, such as lung tissue during the process of inhalation and exhalation. 
     SUMMARY OF THE INVENTION 
     The present invention utilizes chemical adhesion instead of the current thermal process. The new method will be used to stiffen the RAPID Strand assembled unit during manufacturing using an adhesive, such as cyanoacrylate. The new method will similarly allow a technician to end-seal the cut RAPID Strand segments during implant preparation using an adhesive, such as cyanoacrylate. In one embodiment, the present invention provides an elongate strand having distinct regions about the seeds where the carrier is adhered to either the seeds themselves, to spacers extending within the carrier between the seeds, or where the carrier closes off the carrier adjacent to each seed so as to fix the seed in place within the carrier. In an another embodiment, the present invention provides an elongate strand having relatively stiff regions where the seeds are fixed into place adjacent to relatively deflectable regions where the carrier may be deflected so as to give an ability to shape the strand to non-linear or non-planar tissue applications. 
     During the manufacturing process, the assembled strand is passed through an adhesive vapor chamber where the hydroscopic Polyglactin will absorb the adhesive vapor creating chemical adhesion between the braided carrier, the seeds and any spacers employed within the carrier. This process can also be done by dipping, spraying or any other means of applying an extremely small and controlled amount of adhesive to the assembly. In one embodiment of the present invention, the adhesive so applied is cyanoacrylate. 
     Additionally, during the segmentation of strand, the exposed ends of the cut strand segment is dipped, sprayed, or by any other means of applying an extremely small and controlled amount of adhesive to the cut ends of the segment so as to seal the segment ends. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a close-up view of a section of a brachytherapy product of the prior art. 
         FIG. 2  depicts a section of a brachytherapy product of the present invention. 
         FIG. 3  depicts a close-up view of a section of the brachytherapy product of  FIG. 2 . 
         FIG. 4  depicts a further brachytherapy product of the present invention. 
         FIG. 5  illustrates alternative methods for affixing a seed within a carrier so as to provide a brachytherapy product of  FIG. 4 . 
         FIG. 6  depicts a brachytherapy patch of the present invention. 
         FIG. 7  depicts a first method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
         FIG. 8  depicts a second method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
         FIG. 9  depicts a third method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
         FIG. 10  depicts a fourth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
         FIG. 11  depicts a fifth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
         FIG. 12  depicts a sixth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The initial loading of the brachytherapy strand may be performed by the current method, such as seeds and spacers loaded into a hollow suture material manually or by using an automated or semi-automated manufacturing process. As is known in the art, the spacers may be of uniform length or of varying lengths as dictated by a particular dosimetry plan. 
     The carrier assembly (i.e., the carrier loaded with seeds and, optionally, spacers) will be exposed to an adhesive by either exposing the assembled unit to a spray type coating, exposing the assembled unit to a vapor stream, dipping the assembled unit in a bath, or using the hydroscopic polyglactin material of the carrier to induce adhesive transfer. Desirably the adhesive used will be a medical grade cyanoacrylate or any other suitable adhesive. 
     Alternatively, the carrier material may only be loaded with seeds spaced apart as desired by a particular dosimetry plan. The adhesive will stiffen the carrier between the seed components (in the void areas), resulting in a medical device with less bio-absorbable material (there would be no spacers). Without spacers the device may be assembled with considerably less time and cost. 
     The devices and methods of the present invention can eliminate or reduce the possibility of seeds becoming dislodged from the strand as a result of cutting the strand. Similarly, the devices and methods of the present invention can also eliminate or reduce the possibility of spacers becoming dislodged from the stand as a result of cutting. Additionally, it may not be necessary to even use spacers in a strand of the present invention. The devices and methods of the present invention provide a strand having the desired long-axis stiffness. The present invention also allows the elimination of using an oven in the manufacturing process with its attendant validation requirements. The rigidity of devices of the present invention will be maintained even in moist conditions. 
       FIG. 2  depicts a brachytherapy strand  110  of the present invention. Strand  110  includes an elongate carrier material  112  loaded with radioactive seeds  114  and inert spacers  116 . Carrier  112  is a hollow polyglactin braid. The lead lines from reference numbers  112  and  114  indicate the respective location of the seeds and spacers within the hollow interior of carrier  112 . A medical grade cyanoacrylate adhesive material has been applied to carrier  112  so as to affix the seeds  114  and spacers  116  therein and to impart long-axis stiffness to strand  110 .  FIG. 2  shows that the applied adhesive may form localized protrusions  120  on the surface of carrier  112 . The protrusions  120  can serve as anchors for strand  110  once implanted in tissue. The protrusions  120  thus help prevent migration of strand  110  after implantation. 
       FIG. 3  depicts an alternate brachytherapy strand  210  of the present invention. Strand  210  includes an elongate carrier material  212  loaded with radioactive seeds  214 . Carrier  212  is also a hollow polyglactin braid. The lead lines from reference numbers  212  indicate the location of the seeds within the hollow interior of carrier  212 . A medical grade cyanoacrylate adhesive material has been applied to carrier  212  so as to affix seeds  214  therein and to impart long-axis stiffness to strand  210 . 
       FIGS. 4 and 5  depict a further brachytherapy strand  310  of the present invention. Strand  310  includes a carrier material  312  loaded with a number of radioactive seeds  314 . Carrier material  312  may be hollow polyglactin braid or suture. Strand  310  is characterized by its regions  325  between adjacent seeds  314  where the carrier material  312  is able to deflect so as to allow the strand to conform to non-linear or non-planar applications or tissue. For example, as shown in  FIG. 6 , strand  312  may be incorporated into or onto a planar surgical mesh  350  so as to provide an implantable and deflectable brachytherapy mesh patch  360 . Patch  360  is suitable for implantation, for example, along the abdominal wall or over lung tissue. The deflectability of the strands  310  used in the construction of patch  360  will allow the patch to more easily deflect with the tissue, reducing patient strain while also reducing tension between patch  360  and the tissue it is implanted on as the tissue deflects during movement. Additionally, by allowing a technician to attach or otherwise affix pre-formed brachytherapy strands to mesh  350 , patch  360  may be constructed quickly so as to reduce operator exposure to the radioactive seeds during construction. 
       FIG. 5  illustrates alternative methods for affixing a seed  314  within carrier  312  so as to provide a brachytherapy product such as strand  310  of  FIG. 4 . While  FIG. 5  depicts different methods for affixing the seeds  314  within the same carrier  312 , it is generally contemplated that any particular strand  310  will employ only a single one of such methods such that each adjacent seed will be affixed in the same manner. Thus, for illustrative purposes, all of the methods are shown in a single strand. Seed  314   a  is shown affixed to carrier  312  by adhesive  318  applied through carrier  312  so as to contact the elongate outer surface  322  of seed  314 . Alternatively, seed  314   b  is shown affixed to carrier  312  by adhesive  318  applied through carrier  312  so as to contact the opposed ends  324  and  326  of seed  314 . Where each of these methods seek to apply the adhesive so as to directly contact the seed, the present invention also contemplates, as shown for seed  314   c , that adhesive  318  may be applied through carrier  312  so as to seal-off the internal passageway  340  of carrier  312  to either side of seed  314   c . Note that seed  314   c  is not adhered to carrier  312  as much as it is affixed within it between successive adhesive blockages. Each of these methods result in a region  340  between each adjacent seeds  314  where there is no adhesive applied so that the carrier  312  is free to deflect in that region so as to allow greater flexibility to strand  310 . 
     The present invention contemplates several methods for applying an adhesive, desirably cyanoacrylate, onto a carrier assembly (a carrier loaded with seeds and, optionally, spacers).  FIG. 7  depicts a first method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method, an open-top tank  400  holds a volume of liquid adhesive  402 , desirably cyanoacrylate. A carrier assembly  404  is dipped into the liquid adhesive  402  so that the carrier about the loaded seeds is coated with the adhesive. The coated carrier assembly is then removed from the adhesive pool and held in tension until the adhesive thereon cures. Excess lengths of carrier material may be cut-away and, if necessary, the exposed ends of the carrier may be sealed by adhesive. 
       FIG. 8  depicts a second method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method, an open-top container  500  holds a volume of liquid adhesive  502 . Container  500  is placed in a sealed chamber  504  which defines a chamber cavity  506 . A carrier assembly  508  held in tension by frame  510  is placed in chamber cavity  506 . Either a vacuum is drawn in cavity  506  or cavity  506  is filled with an inert gas so as to cause vapors from adhesive  502  to coat carrier assembly  508 . The coating applied to carrier assembly  508  need not be a continuous layer of adhesive. After sufficient time to coat as desired, frame  510  and carrier assembly  508  are placed in a normal atmosphere so that the applied adhesive cures. 
       FIG. 9  depicts a third method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method a nozzle  600  is connected to a source of liquid adhesive, desirably cyanoacrylate, under pressure. A carrier assembly  602  is held in tension adjacent to nozzle  600  and a sprayed or atomized adhesive  604  is applied to the carrier assembly. Once again, it not necessary to completely coat the outside of the carrier assembly with the adhesive. The adhesive is allowed to cure. 
       FIG. 10  depicts a fourth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method a nozzle  700  is connected to a source of liquid adhesive, desirably cyanoacrylate. A carrier assembly  702  is drawn, under tension, below the nozzle so that the adhesive  704  is either sprayed or dripped onto the moving carrier assembly. It is not necessary to fully coat the outside of the carrier assembly. As the carrier assembly continues past the nozzle, the applied adhesive cures and the desired brachytherapy strands are cut to length. 
       FIG. 11  depicts a fifth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method, a container  800  is provided having transverse holes  802  and  804  formed in opposing upstanding walls  806  and  808 , respectively. Container  800  defines a container cavity  810 . Carrier assembly  812  is drawn, under tension through holes  802  and  804  so as to traverse cavity  810 . While carrier assembly  812  is drawn through cavity  810 , a liquid adhesive  814 , desirably cyanoacrylate, is provided to cavity  810  so as to coat carrier assembly  812 . Hole  804 , being the exit hole from cavity  810 , is desirably sized to provide a sliding contact with carrier assembly  812  so as to remove any excess adhesive applied thereto. Upon curing of the adhesive applied to assembly  812 , strands may be cut to length. 
       FIG. 12  depicts a sixth method of applying an adhesive to the carrier material of a stranded brachytherapy product of the present invention. In this method, a container  900  holding liquid adhesive  902 , desirably cyanoacrylate, is provided. Container  900  defines a flow port  904  through which adhesive  902  may flow. A carrier assembly  906 , under tension, is drawn through stream of the falling adhesive. Once the adhesive applied to the carrier assembly  906  cures, brachytherapy strands may be cut to length. 
     While the particular embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the teachings of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.