Abstract:
Disclosed is a brachytherapy seed deployment system, for use in any of a variety of medical procedures such as radiation treatment of the prostate gland. The system includes a number of brachytherapy seed deployment needles, each preloaded with brachytherapy seeds in patterns and activities predetermined for a unique patient. The seeds are contained in transparent tubular sleeves, thereby allowing direct visualization of the brachytherapy seeds and spacers, so that the seed pattern may be inspected at the clinical site. A releasable retainer prevents accidental brachytherapy seed loss. The system additionally includes shipping containers, separately accessible calibration seeds and a display stand for use at the clinical site. Methods are also disclosed.

Description:
RELATED APPLICATION  
       [0001]    This is a continuation application of U.S. patent application Ser. No. 09/694,107, filed Oct. 20, 2000, the disclosure of which is incorporated in its entirety herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to the field of brachytherapy and the manufacture and handling of small radioactive seeds. Brachytherapy involves the implantation of small radioactive seed, or pellets into tumors to eradicate cancerous cells, and is an alternative to external radiation therapy such as electron beam irradiation.  
           [0003]    Brachytherapy has been used in the treatment of numerous types of cancer, including cervical, breast, lung, head and neck, and prostate. As an example of the procedure the treatment of prostate cancer will be used. This is in no way intended to limit the scope of this application, as the use of the invention disclosed herein has general application in the handling of the radioactive pellets, or seeds, as will be obvious to those skilled in the art.  
           [0004]    The treatment of prostate cancer using radioactive seed implantation has been known for some time. Currently either Palladium-103 or Iodine-125 seeds are used, with apparent activities ranging from about 0.25 mcuries to 1.2 mcuries, depending on the prostate size and aggressiveness of the cancer. Recent advances in ultrasound imaging and other technological advancements have enabled this procedure to become a very viable alternative to other treatments such as external beam irradiation and radical prostatectomy. The procedure involves ultrasound mapping of the prostate gland and size of tumor using a transrectal ultrasound probe. A radiation oncologist will then decide on the number and positioning of the radioactive seeds needed to deliver a sufficient amount of radiation to kill the cancerous cells. The requisite number of radioactive seeds are typically loaded into 18 gauge brachytherapy needles. Needles may contain anywhere from one to seven seeds, usually separated by bio-absorbable spacers of catgut or other suitable suture material. To prevent the seeds and/or the spacers from falling out of the needle accidentally, the distal end of the needle, the tip, is plugged with a small amount of bone-wax. Bone-wax is a medical grade beeswax material. The seeds are prevented from falling out of the proximal or hub end of the needle by a blunt obturator, which is ultimately used to force the seeds from the 18 gauge needle once in position in the prostate. The needles are inserted into the prostate transperineally.  
           [0005]    In a typical procedure the needles loaded with seeds are inserted into the prostate gland under the guidance of the ultrasound rectal probe. A metal grid, abutting the peritoneum, having X-Y coordinates is matched to a grid overlaid on the real-time ultrasound picture, so that the requisite number of seeds can be placed at each location in accordance with the mapping planes used by the radiation oncologist to optimize dose delivery. Once the tip of the needle is visualized in the correct location on the ultrasound screen, the needle is withdrawn over the obturator whilst maintaining the position of the obturator, such that a pattern of seeds and spacers is laid down as required. Typically about 85 seeds are placed during the procedure, but the number can be as high as about 140 or as low as about 40. Thus a typical procedure uses about 30 needles per patient.  
           [0006]    Currently the seeds and the spacers are loaded into the needles by the radiation oncologist or radiation physicist by hand. This is a laborious task, and can take up to an hour to complete. This can tie-up Operating Room time, and at a minimum is wasting radiation oncologist or physicist time. Furthermore, during this time the person doing the loading is exposed to undesirable levels of radiation, and the loading task is extremely fatiguing. Some mechanical assist devices exist, but they are either unreliable, and can jam or, even worse, break or crush a seed allowing radioactive material to escape. In addition, verification of seed loading per needle is generally not readily accomplished. A system marketed by Northwest Radiation Therapy Products organizes the seeds, spacers, and needles on a stand. This lessens operator movement, but the process is still time consuming.  
           [0007]    An alternate approach for delivering the seeds to the patient is typified by instruments called the Mick Applicator and the Quick Seeder Applicator sold by Mick Radio-Nuclear Instruments, Inc. In this system the empty needles are first inserted into the patient at the predetermined locations. Then using the Mick Applicator one seed at a time is delivered from a pre-loaded cartridge, indexing back a pre-determined distance after delivering each individual seed. In the case of the Quick Seeder Applicator, a cartridge pre-loaded with seeds and spacers is attached to the needle. This device transfers a column of seeds and spacers by indexing back a pre-determined distance to accomplish the delivery. Again the cartridges are loaded ether by hand or by using a device that consists of a chamber in which the seeds and spacers are lined up before being pushed into the cartridge. This is time consuming because seeds and spacers still have to be hand loaded into the transfer chamber, thus offering little benefit over straight hand loading. The invention described herein overcomes the deficincies in the prior art and provides an improved means for loading needles. No supplier provides pre-loaded needles for brachytherapy.  
           [0008]    U.S. Pat. No. 5,928,130 by Schmidt describes a tool for implanting radioactive seeds that includes a needle, spacers and seeds loaded into a transparent or translucent sleeve, and an obturator to facilitate the displacement of spacers and seeds and deposit them into tissue.  
           [0009]    Notwithstanding the various efforts in the prior art, there remains a need for a preloded brachytherapy seed system as described in detail below.  
         SUMMARY OF THE INVENTION  
         [0010]    One aspect of the present invention is to enable brachytherapy needles to be per-loaded with radioactive seeds and spacers, organized, packaged and shipped sterile in quantites perscribed on a per order basis. Another aspect of the invention is to provide one presciption in one shipper. Another aspect of the invention is to provide a system that allows for at least about 10% of the seeds to be assayed for activity without affecting the sterility of the pre-loaded seeds for implantation. Yet another aspect of the invention is to provide a system that allows for the addition of about two extra needles for insertion of extra seeds in order to accommodate unforeseen adjustments in the procedure.  
           [0011]    Another aspect of the invention is to eliminate the preparation time at the clinical site of loading and sterilizing the seeds as required in the past. Yet another aspect is to reduce operator exposure to radiation to a minimum and to reduce Operating Room use, thus reducing costs. Another aspect of the present invention is to reduce the amount of paper work required by the hospital by reducing the invoicing, ordering and stocking from four individual products to one.  
           [0012]    Another aspect of the invention is to provide a system that optimizes the needle by arranging the needles in order by needle number previously prescribed in the treatment plan. Yet another aspect of the invention is to provide a system that allows the user to remove any one of the needles at any time during the procedure and does not require that the needles be unloaded sequentially thus providing the physician with flexibility during the procedure without adding concern about potentially damaging the pre-loaded needles. Another aspect of the invention is to provide pre-loaded sleeves having a marker corresponding to the number of seeds in the sleeve. Another aspect of the invention is to provide pre-loaded sleeves identified with their corresponding needle numbers according to the pre-planned prescription information.  
           [0013]    Another aspect of the invention is to provide a system that allows the loading pattern of each needle to be confirmed at any time up to and including the time of implant. The loading pattern is confirmed by removing the sleeve from the needle and viewing the seeds and spacers through the sleeve.  
           [0014]    Yet another aspect of the invention is to provide a sterile system that eliminates the time and processing equipment needed to sterilize the components on site, thus reducing the cost. Another aspect of the invention is to provide a system that allows for double aseptic transfer of the injected components into the sterile field of the operating room.  
           [0015]    Another aspect of the invention is to provide a system that allows the physician to implant seeds and spacers using their current method. Yet another aspect of the invention is to provide the physician with a tactile feedback of the dispensing of spacers and seeds, thus providing the user with a confirmation that spacers and seeds are being implanted.  
           [0016]    The invention comprises a system of components that enable brachytherapy needles to be pre-loaded with radioactive seeds and spacers, organized, packaged and shipped sterile from the manufacturing facility to the clinical site in quantities prescribed on a per patient per order basis. In a preferred embodiment the seeds required for assay of the activity of the shipment are provided in a manner that does not compromise the sterility of the seeds for implantation. In a preferred embodiment additional extra empty needles are provided to accommodate unforeseen adjustments in the procedure that require insertion of extra seeds.  
           [0017]    In a preferred embodiment, the seeds and spacers are loaded in transparent or translucent sleeves that allow visual confirmation of the loading pattern of seeds and spacers up to and including the time of implant. In a preferred embodiment the seeds and spacers are retained in the sleeve by a retaining element. In a preferred embodiment the system provides the physician with confirmation in the form of tactile feedback of the dispensing of each seed and each spacer.  
           [0018]    In a preferred embodiment, the pre-loaded sleeves are marked with an indication of the number of seeds inside. In a preferred embodiment the pre-loaded sleeve is marked with an identifier indicating which corresponding needle it should be used with according to the pre-planned prescription information and treatment plan.  
           [0019]    In a preferred embodiment the system allows for double aseptic transfer of the injected components into the sterile field of the operation room.  
           [0020]    Thus, there is provided in accordance with one aspect of the present invention a brachytherapy seed and spacer deployment system, which includes a deployment device. The deployment device comprises an elongate tubular sleeve, having a proximal end and a distal end. An elongate obturator is axially movable through the tubular sleeve. At least one retention structure is provided on the tubular sleeve, for retaining brachytherapy seeds and spacers therein. The retention structure is movable between a first position in which it will retain a seed and spacer within the sleeve, and a second position in which it will release the seed and spacer separately from the sleeve.  
           [0021]    Preferably, the retention structure is biased in the direction of the first position. The sleeve is also preferably visually transparent.  
           [0022]    In one embodiment, the system further comprises a lock on the obturator, for resisting distal advancement of the obturator through the sleeve. The obturator lock may comprise a tubular wall, having an axially extending slot therein. The tubular wall surrounds a proximal portion of the obturator, which extends proximally from the tubular sleeve and prevents distal advancement of the obturator into the sleeve.  
           [0023]    In accordance with another aspect of the present invention, there is provided a method of controllably deploying a plurality of seeds and spacers from a brachytherapy seed deployment device. The method comprises the steps of providing a brachytherapy seed deployment device, having a tubular body, a plurality of seeds and spacers therein, a deployment control, and a releasable retainer for preventing inadvertent release of seeds and spacers from the device. The device is positioned at a treatment site, and the control is manipulated to deploy a first seed past the retainer and from the device. The retainer is permitted to retain at least a spacer within the device. In one embodiment, the manipulating the control step comprises distally advancing an obturator. Preferably, the method further comprises the step of deploying at least a spacer past the retainer and from the device. In many applications, at least a second and often at least a third seed are controllably sequentially deployed.  
           [0024]    In accordance with a further aspect of the present invention, there is provided a brachytherapy system. The system comprises an elongate tubular needle, and an elongate tubular sleeve positioned within the needle. The sleeve has a proximal end and a distal end. At least one brachytherapy seed is positioned in the sleeve, and an obturator extends into the proximal end of the sleeve. The needle is carried by a flexible drape. Preferably, a plurality of brachytherapy seeds and spacers are positioned within the sleeve. In addition, a plurality of needles are preferably carried by the drape.  
           [0025]    The foregoing drape carrying a plurality of needles may be positioned within a needle pig. The system preferably additionally comprises one or more calibration seeds. The calibration seeds are preferably carried by a calibration seed pig, or carried in a calibration seed cavity on the needle pig, such that the calibration seeds can be accessed without exposing the needles.  
           [0026]    In accordance with another aspect of the present invention, there is a provided a brachytherapy system. The brachytherapy system comprises a shipping container, having a needle pig carried therein. A calibration seed pig is also provided in the shipping container. A plurality of brachytherapy needles are positioned in the needle pig, the brachytherapy needles preloaded with brachytherapy seeds and spacers. At least one, and in some embodiments a plurality of calibration seeds are provided in the calibration pig, such that the calibration seed or seeds can be accessed without opening the needle pig.  
           [0027]    Preferably, the brachytherapy needles are carried by a flexible drape. The system preferably additionally comprises a needle loading report, for identifying the contents of each needle and the target position for each needle in the patient.  
           [0028]    In accordance with another aspect of the present invention, there is provided a nonuniform dosing profile brachytherapy needle set. The needle set comprises a flexible drape, and a plurality of needles, each containing at least one brachytherapy seed, the needles carried by the drape. At least a first seed in a first needle is provided with a first activity, and at least a second seed in a second is provided with a second, different activity. In one embodiment, at least a third seed having a third activity is positioned in the first needle.  
           [0029]    In accordance with another aspect of the present invention, there is provided a nonuniform dosing profile brachytherapy seed deployment device. The device comprises a brachytherapy needle, and a tubular sleeve within the needle. A plurality of brachytherapy seeds and spacers are positioned within the sleeve, such that the device exhibits a first activity in a first zone and a second activity in a second zone.  
           [0030]    In accordance with further aspects of the present invention, there are provided methods for customizing a dosing profile to the three-dimensional target tissue with in a patient. The method comprises the steps of identifying the three-dimensional shape of the target tissue within a patient, and preloading a plurality of brachytherapy seeds having two or more activities into a plurality of brachytherapy needles in a pattern which corresponds to the three-dimensional profile of the target tissue. The brachytherapy needles are labeled and delivered to the clinical site. Each needle is thereafter inserted into its predetermined location within the target tissue, to reconstruct the predetermined three-demensional dosing profile for that patient.  
           [0031]    Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    The novel features, advantages, and aspects of the present invention will be more readily understood upon reading the following detailed description taken in connection with the accompanying drawings in which:  
         [0033]    [0033]FIG. 1 is a partially exploded perspective view of components of the invention;  
         [0034]    [0034]FIG. 2A is a schematic exploded view of components of the invention;  
         [0035]    [0035]FIG. 2B is a side elevational view of an assembled, loaded deployment dance with the present invention;  
         [0036]    [0036]FIG. 2C are schematic views of an obturator lock in accordance with the present invention;  
         [0037]    [0037]FIG. 2D is a side elevational view as in FIG. 2B, without brachytherapy seeds and with the obturator fully distally advanced;  
         [0038]    [0038]FIG. 3 is a front perspective view of a sleeve assembly pre-loaded with seeds and spacers;  
         [0039]    [0039]FIGS. 4A, 4B,  4 C and  4 D are views of seed and spacer retaining elements;  
         [0040]    [0040]FIG. 5A is a cross-sectional view of a sleeve hub;  
         [0041]    [0041]FIG. 5B is a cross-sectional view of an alternate sleeve hub;  
         [0042]    [0042]FIG. 5C is an end view of the sleeve hub of FIG. 5B.  
         [0043]    [0043]FIG. 6 is a schematic view of needles, pre-loaded sleeves, and obturators organized on a needle drape;  
         [0044]    [0044]FIGS. 7A and 7B are a needle loading report;  
         [0045]    [0045]FIG. 8 is an exploded perspective view of a folded needle drape, and an outer pouch;  
         [0046]    [0046]FIG. 9 is a partially exploded perspective view of a needle drape, pouch, needle canister lid and needle canister base;  
         [0047]    [0047]FIG. 10 is an exploded perspective view of a shipping assembly;  
         [0048]    [0048]FIG. 11 is an exploded perspective view of a calibration seed pig;  
         [0049]    [0049]FIG. 12 is a front elevational perspective view of a closed needle drape attached to a needle stand; and  
         [0050]    [0050]FIG. 13 is a view of a needle drape attached to a needle stand as in FIG. 11, with the needle drape open. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0051]    Referring to FIGS. 1 through 3, there is illustrated a brachytherapy seed deployment device  20  in accordance with one aspect of the present invention. The deployment device  20  is adapted to controllably deploy a plurality of radioactive seeds and spacers along a linear path in a target tissue site. Radioactive seeds and spacers may be individually deployed, with tactile feedback to the operator as each seed and spacer leaves the device. The risk of inadvertent deployment or loss of radioactive seeds or spacers is minimized or reduced by the distal tip design as will be discussed below.  
         [0052]    The deployment device  20  comprises an elongate needle  22  for penetrating tissue to reach the target site as is known in the art. Needle  22  comprises an elongate tubular body  24  exending between a proximal end  26  and a sharpened distal tip  28  for puncturing tissue see FIG. 2A. Proximal end  26  is provided with a Hub  30  as is understood in the art. In general, needle  22  has an axial length which is sufficient to reach the target tissue, from a predetermined access point. Thus, depending upon the target and access point, various needle lengths may be utilized. Axial lengths within the range from about 6 inches to about 12 inches and, in one embodiment, about 7.9 inches, are utilized in a system intended to treat the prostate gland.  
         [0053]    Needles of various diameters may also be utilized, with an optimum diameter for any particular application selected to be sufficient to carry an appropriate seed while minimizing the cross-section of the puncture. In a system intended for treating the prostate gland, needles within the range from about 26 gauge to about 12 gauge, and, in one embodment, 18 gauge, will normally be used. Needles made from any of a variety of materials including stainless steel, nitinol, or others may be utilized as will be understood in the art.  
         [0054]    Tubular sleeve  32  is dimensioned to be axially slidably positioned within the needle  22 . Sleeve  32  comprises an elongate tubular body  34 , extending between a proximal end  36  and a distal end  38 . Proximal end  36  is provided with a Hub  40 . The distal end  38  of sleece  32  is preferably provided with one or more brachytherapy seed retention structure, which will be disclosed in greater detail below.  
         [0055]    Sleeve  32  is adapted to slidably receive one or more radioactive seeds for deployment at a tissue site. Generally, from one to about seven seeds, usually separated by bioabsorbable spacers of cat gut or other suitable material will be preloaded into the sleeve depending upon the particular clinical needs of the patient. The preloading process prefrebly occurs at the point of manufacture or at a loading station which is remote from the clinical site.  
         [0056]    Tubular body  34  is preferably manufactured from a material which permits visual observation of the contents, so that the physician or other clinical staff may observe the number and location of seeds and spacers within the sleeve  32 . Materials having sufficient structural integrity and transparency for this purpose can be readily determined through routine experimentation by those of skill in the art in view of the objectives recited herein. In one embodiment, intended for use with 18 gauge needle, tubular body  34  comprises a polyimide extrusion having an outside diameter of about 0.039 inches, an inside diameter of about 0.036 inches and a wall thickness of about 0.0015 inches. The specific dimensions of the sleeve  32  will be determined to cooperate with the Needle  22  as will be apparent to those of skill in the art in view of the disclosure herein.  
         [0057]    An obturator  42  is adapted to be axially slidably received within the sleeve  32 . Obturator  42  comprises an elongate body  44  having a proximal end  46  and a distal end  48 . A Hub or control  50  is provided at the proximal end  46 . The body  44  may comprise either a solid rod or a tubular element. Solid rods or tubes of stainless steel or other medically acceptable metals may be utilized. Alternatively, extruded rod or tubing of a polymeric material may also be utilized. In one embodiment, the body  44  comprises ABS plastic. The outside diameter of the body  44  is adapted to be slidably received within the sleeve  32 . Thus, in a system adapted for use with an  
         [0058]    needle, and a sleeve  32  having an inside diameter of about 0.036 inches, the outside diameter of body  44  of Obturator  42  is about 0.032 inches.  
         [0059]    The role of the obturator  42  is to distally advance the seeds  70  and spacers  72  from the distal end  38  of the sleeve  32 . As a consequence, distal end  48  of obturator  42  is preferably blunt, and provided with as large a cross-sectional area as will be slidably accommodated within the sleeve  32 . slideability may be optimized by providing the distal end  48  with a slight chamfer or break to reduce snagging. The axial length of the obturator  42  is preferably sufficient that the distal end  48  will reach the distal end  38  of the sleeve  32  at or about the time the Hub  50  engages Hub  40 . In this manner, the entire contents of the sleeve  32  may be deployed into the patient.  
         [0060]    Referring to FIG. 2B, the foregoing elements are illustrated in a loaded and locked orientation, such as for shipping and handling. The sleeve  32  carries a deployable load  60  such as a plurality of radioactive seeds  70  and spacers  72 . Sleeve  32  is positioned within Needle  22 , and obturator  42  is advanced distally through the central lumen  76  of sleeve  32  to about the point of contact with the proximal end of the deployable load  60 .  
         [0061]    The loaded needle and sleeve assembly is coaxially positioned within an outer needle shield  52 . Needle shield  52  preferably extends between a proximal end  54  and a distal end  56 . The axial length of the needle shield  52  is preferably longer than the axial length of the Needle  22 , to minimize the risk of needle sticks during handling. The proximal end  54  of needle shield  52  is preferably frictionally engaged with the Hub  30 , such as at a distal tapered engagement surface  58 . Needle shield  52  may be removed at the clinical site, to expose the distal tip  28  of the Needle  22  for insertion at the treatment site.  
         [0062]    In one embodiment in which needle  22  extends approximately 7.9 inches distally of the hub  30 , needle shield  52  has an axial length of about 8.25 inches. The inside diameter of the needle shield  52  is sufficient to slidably receive needle  22  axially therethrough. In one embodiment intended for use with an 18 gauge needle, the needle shield  52  has an inside diameter of about 0.16 inches and an outside diameter of about 0.20 inches. Needle shield  52  may be manufactured by any of a variety of techniques well known in the art, such as extrusion of any of a variety of polymers well known in the medical device arts.  
         [0063]    The deployment device  20  is further illustrated with an obturator lock  62 . See FIG. 2B. In the loaded configuration, the proximal end  46  of the obturator  42  is positioned proximally of the hub  40  of sleeve  32  by a distance which corresponds to the axial length of the deployable load  60 . Distal advancement of the obturator hub  50  will deploy the deployable load  60  out of the distal end  38  of the sleeve and distal tip  28  of the needle  22 . Premature advancement of the hub  50 , such as during handling or positioning of the needle  22 , may accidentally deploy a portion or all of the deployable load  60  prior to the time that the needle  22  is appropriately positioned at the treatment site. In many radiation treatments, particularly in the prostate gland, a large number of needles  22  will be loaded with unique patterns or numbers of radioactive seeds. As a consequence, inadvertent loss of radioactive seeds from the sleeve  32  can significantly complicate and delay the procedure while the unique pattern of seeds and spacers for that needle is reconstructed. In addition, the possibility of accidental deployment of radioactive seeds in the operating room is disadvantageous to the clinical staff.  
         [0064]    The present invention thus provides a lock for resisting distal advancement of the obturator  42  until the desired deployment time. Lock  62  thus axially fixes the position of the obturator  42  with respect to the hub  30 , until the lock is released. This lock may be accomplished using any of a variety of structures, such as Toohey-Borst type hubs, clamps, cams or other friction generating structures at about the hub  30 . Alternatively, as illustrated in FIG. 2B, the obturator lock  62  comprises an elongate axial support, such as a tubular body  64 , which is dimensioned to extend coaxially around the obturator  42 , but not around the hub  30  or hub  50 . In this manner, hub  50  cannot be advanced distally towards hub  30  until the obturator lock  62  has been removed. Obturator lock  62  in the illustrated embodiment comprises a tubular body  64  having an axially extending longitudinal slit  66  to allow the obturator lock  62  to be advanced laterally onto and removed from the obturator  42 . A pull tab  68  may be provided on the tubular body  64 , preferably centered approximately 180° apart from the longitudinal slit  66 . The pull tab  68  may be pulled away from the obturator  42 , thereby causing the tubular body  64  to be peeled away from the obturator  42 . This low profile, low cost locking structure enables the positioning of the brachytherapy seed deployment device  20  at the treatment site, and then rapid removal of the obturator lock  62  by pulling pull tab  68  when the time is appropriate to deploy the deployable load  60 .  
         [0065]    Although the present invention is described primarily herein in the context of the radiation delivery device, it will be understood by those of skill in the art that the deployable load  60  may comprise any of a variety of devices, structures, or materials that may desirably be implanted within the body. For example, any of a wide variety of medications may be included within the sleeve  32 . Drugs in solid or liquid form, time release structures, such as microporous materials or gels, or prosthetic devices may alternatively be deployed from the system disclosed herein.  
         [0066]    Referring to FIG. 2D, the deployment system of FIG. 2B is illustrated, with the obturator lock  62  removed, and the obturator hub  50  advanced to its distal limit of travel in contact with the hub  40 .  
         [0067]    The obturator lock  62  may be manufactured in any of a variety of ways, which are known in the art. For example, obturator lock  62  may be extruded in tubular form, with the longitudinal slit  66  and tab  68  formed as a post-extrusion step. Materials such as various densities of polyethylene, polyethylene terephthalate, nylon, PEBAX, or others well known in the catheter and medical device arts may be utilized. In one embodiment, the obturator lock  62  comprises an extruded polypropylene tube having an inside diameter of about 0.06 inches, an outside diameter of about 0.09 inches, and an axial length of about 3.3 inches.  
         [0068]    Preferably, the needle  22  is provided with markings along its axial length to allow visual observation of the depth of penetration at the treatment site. In addition, a distal zone  29  is preferably provided with a textured surface or radiopaque coating to enhance visualization as will be understood in the art.  
         [0069]    Referring to FIG. 3, the tubular body  34  is illustrated with a load of seeds  70  and spacers  72 . The seeds  70  and spacers  72  together define a deployable load length  74 . The length  74  will vary depending upon the clinical needs of the patient. In general, load lengths within the range of from about 0.30 inches to about 3.31 inches are utilized in most applications where the device is utilized to deliver radioactive seeds to the prostate gland.  
         [0070]    Referring to FIG. 4A, there is disclosed an enlarged distal end  38  of sleeve  32  including a seed retention structure to prevent inadvertent loss of seeds from the sleeve  32 . Central lumen  76  within sleeve  32  is in communication with a distal opening  78 , for deploying radioactive seeds and spacers or other material. At least one retention structure  80  is provided, for resisting accidental distal loss of the radioactive seeds  70  or spacers  72 . In the illustrated embodiment, the retention structure  80  comprises one or more interference surfaces  82 . Interference surfaces  82  are movably positioned at least part way across the path of the load to retain the load within the central lumen  76 . The interference surface  82  is movable so that it can be advanced from a first position in which it obstructs the load to a second position in which the load may be distally deployed through the distal opening  78 . Preferably, the interference surface  82  is biased in the direction of the first position.  
         [0071]    In this manner, a seed may be forcibly advanced through the distal opening  78  by pushing the interference surface  82  out of the way. Once the seed has been deployed from the distal opening  78 , the interference surface  82  returns to its first position, thereby providing tactile feedback to the clinician that the seed has been deployed and resisting accidental deployment of subsequent radioactive seeds or spacers.  
         [0072]    The interference surface  82  may be provided on any of a variety of structures, such as radially inwardly extending tabs, flanges, tapered surfaces, inserts or other interference elements, as will be apparent to those of skill in the art in view of the disclosure herein. The interference surface  82  may be integrally formed with the sleeve  32 , or may be manufactured separately and attached to the tubular body  34  during the manufacture process.  
         [0073]    In the illustrated embodiment, the interference surface  82  is provided on the radially inwardly facing surface of an inclined flange  84 . The illustrate flange  84  is in the form of an annular frusto-conical tip on the tubular body  34 , inclining radially inwardly in the distal direction. Preferably, one or more axially extending slots  86  extend from the distal limit of the inclined flange  84 , in a proximal direction, to facilitate the enlargement of the distal opening  78  when the clinician puts sufficient distal pressure on the obturator hub  50  to deploy a seed or spacer.  
         [0074]    The interference surface  82 , whether carried by inclined flange  84  or other structure, can extend circumferentially either entirely around or only part way around the distal opening  78 . For example, in the embodiment illustrated in FIG. 4A, the inclined flange  84  extends substantially the entire circumference of the distal opening  78 . Alternatively, inclined flange  84  may extend no more than about 180°, no more than about 90°, or even no more than about 10° or 15° of the circumference of distal opening  78 . The foregoing circumferential lengths of inclined flange  84  may represent a single continuous flange, or the sum of a plurality of distally inclined tabs. For example, by removing portions of the flange, a plurality of spaced apart tabs may be provided such as two or four or six or more tabs, spaced apart around the circumference of distal opening  78 . The number and spacing of these tabs can be selected to achieve a desired minimum deployment force and tactile feedback as will be apparent to those of skill in the art in view of the disclosure therein.  
         [0075]    The illustrated inclined flange  84  can be manufactured in any of a variety of ways, depending in part upon the material of tubular body  34 . For example, molding, machining, or attachment of a separately formed tip such as with adhesives, thermal bonding or other technique may be used. In one embodiment, the flange  84  is formed in a polyimide tubular body  34  by advancing the tube into a frusto-conical bore with a corresponding mandrel positioned within central lumen  76 , under the application of heat.  
         [0076]    An alternate retention structure  80  is illustrated in FIG. 4B. An inclined tab  88  is created by forming a slot  90  in a generally U-shaped configuration, or by forming two parallel slots  90  at the distal end of the tubular body  34 . The resulting tab  88  may then be bent radially inwardly to provide an interference surface  82  in the path of the brachytherapy seed. One or two or more inclined tabs  88  may be provided in a common plane transverse to the longitudinal axis of the tube  34 , depending upon the desired performance characteristics of the device.  
         [0077]    A similar structure may be provided at the proximal end of the deployable load  60 , if desired, to prevent proximal loss or travel of seeds  70  or spacers  72 . The proximal stop  92  may be formed by a slot  94  in the wall of the tubular body  34 , such as in a U- or V-shape. The resulting proximal stop  92  may be bent radially inwardly to provide a ramp  98  and a stop surface  96 . As will be apparent to those of skill in the art, ramp  98  allows distal advancement of seeds through the central lumen  78  but proximal travel of seeds will be prevented by stop surface  96 .  
         [0078]    The provision of a proximal stop  92  is optional, and may be desirable in embodiments in which shipping of loaded sleeves is accomplished without an obturator  42  positioned within the tubular body  34  proximally of the deployable load  60 .  
         [0079]    Referring to FIG. 4C, there is illustrated an alternate retention structure  80  and optional proximal stop  92 . Retention structure  80  is formed by a crimp or dent  100  in the wall  34  of tubular body  32 . The crimp  100  provides an interference surface  82 , which interferes with the distal travel of a brachytherapy seed  70  or spacer  72 . Upon application of sufficient distal force on the brachytherapy seed  70 , the interference surface  82  is pushed out of the path of travel such that the seed  70  is deployed through the distal opening  78 . Crimp  100  may be in the form of an annular indentation, or one or more discrete indentations or dents around the circumference of the tubular body  34 . For example, two opposing crimps may be provided or three crimps provided with 120° spacing, or four crimps at 90° spacing around the circumference of the tubular body  34 . The precise location, depth, and number of crimps  100  may be determined through routine experimentation, depending upon the desired performance of the device.  
         [0080]    Similarly, the optimal proximal stop  92  is provided by one or more crimps or dents  102 . The resulting structure provides a ramp  98  to permit distal travel of radioactive seeds  70  under distal pressure by an obturator or other loading device. The stop surface  96  inhibits proximal travel of the seeds or spacers.  
         [0081]    The crimp  100  or  102  may be provided in any of a variety of manners depending upon the construction materials and wall thickness of the tubular body  34 . For example, certain materials may retain a crimp provided by controlled mechanical compression of the tubular body  34 . The compression may be accomplished with or without the application of heat, depending upon the material and wall thickness. In one embodiment in which the tubular body  34  comprises a polyimide extrusion, the crimp  100  and, optionally, crimp  102  is provided by compressing the wall  34  at an elevated temperature within the range of from about 600°F. to about 800°F.  
         [0082]    An alternate retention technique is schematically illustrated in FIG. 4D. In this embodiment, the distal opening  78  is obstructed by a removable plug such as a wax or gel. Suitable materials for the plug include medical grade bone-wax, available from medical goods suppliers. Care should be taken to ensure consistent needle to needle plug size, so that the seeds may be precisely placed at the treatment site.  
         [0083]    Referring to FIG. 5A, there is illustrated a cross-sectional view through a sleeve hub  40 , for connecting to the proximal end  36  of sleeve  32 . In general, sleeve hub  40  comprises a proximal connector  106  such as a standard luer connector or a simple annular flange. The distal end  108  of sleeve hub  40  is provided with a lumen or bore  104  for receiving the proximal end  36  of sleeve  32 . Sleeve  32  is preferably advanced into lumen  104  during the manufacturing process and secured in any of a variety of ways such as through the use of adhesives, solvent bonding, thermal bonding, or other techniques known in the medical device manufacturing arts.  
         [0084]    A proximally extending annular recess  110  defines a distal projection or nose  112 , which may serve as the male component of a luer connector. For this purpose, the wall of annular recess  110  may be provided with radially inwardly directed threads as are well understood in the art. In this manner, the hub  40  may be advanced distally toward and connected to the hub  30  by a partial rotation of hub  40  with respect to hub  30 . A gripping surface  114  may be provided on the hub  40 , including friction enhancing surface structures such as a plurality of axially extending ribs as is understood in the art. Preferably, the hub  40  is in the form of a male luer connector which may be securely engaged with a complementary female luer connector on hub  30  of the needle  22 . In particular, the projection  112  is provided with a tapered surface  116 , which fits within a complimentary tapered surface  118  surrounding a cavity in the proximal end of hub  30 .  
         [0085]    Brachytherapy needles  22  are currently marketed by more than one manufacturer, and complete uniformity in the design of hub  30  has not been achieved. The taper angle on interior surface  118  on the needle hub  30  is not uniform for all manufacturers. For example, some needles  22  are available having a taper on surface  118  of about 6 degrees, while other commonly available commercial needles  22  have a taper angle on surface  118  of about 2 degrees. If the taper angle on surface  118  does not correspond closely to the taper angle on surface  116 , a secure fit between the needle  22  and sleeve  32  will not be achieved.  
         [0086]    Accordingly, referring to FIG. 5B, there. is provided in accordance with another aspect of the present invention a universal hub  40  for attachment to the proximal end  36  of tubular body  34 . The projection  112  is provided with a first taper zone  120  having a first taper angle, and a second, distal taper zone  122  having a second, greater taper angle. The projection  112  on hub  40  can thus accommodate needle hubs  30  of differing internal tapers on surface  118 . In one embodiment, the tapered surface  120  extends at an angle of approximately 2 degrees with respect to the longitudinal axis of tubular body  34 , and tapered surface  122  resides at an angle of approximately 6 degrees with respect to the longitudinal axis of tubular body  34 . Alternative tapers may readily be selected, depending upon the construction of the corresponding needle hubs which are desirably accommodated. In addition, three or more distinct taper surfaces may be provided on projection  112 , if desired to accommodate a larger number of corresponding needle hubs.  
         [0087]    Referring to FIG. 6, there is illustrated a schematic plan view of a drape  124  in accordance with the present invention, adapted to carry a plurality of brachytherapy seed deployment devices  20 . The drape  124  comprises a back portion  126 , a left flap  128  and a right flap  130  for folding over the brachytherapy seed deployment devices  20 . Alternatively, a single flap may be utilized to cover the entire front surface of the drape  124 . The right flap  130  in the illustrated embodiment is provided with at least one removable attachment structure such as an adhesive patch  131 . Adhesive patch  131  may be removably attached to the back surface of left flap  128  to releasably close the drape  124 .  
         [0088]    The illustrated drape  124  is additionally provided with a bottom flap  132  and a top flap  134 . A support  136  is preferably provided with one or more attachment structures such as apertures  138 , for attaching the drape  124  to a support structure as will be described.  
         [0089]    The drape  124  is preferably additionally provided with a needle carrier  140 . In the illustrated embodiment, needle carrier  140  is secured to the back  126 , such that it will be covered by the closed right and left flaps  130  and  128 . Needle carrier  140  is provided with a plurality of pairs of opposing apertures such as  142  and  144  adapted to receive a brachytherapy seed deployment device  20  therethrough. Although  30  opposing pairs of apertures are illustrated in FIG. 6, the capacity of the needle carrier  140  may be varied as desired. Preferably, each opposing pair of apertures  142  and  144  is provided with an identifying indicium  146  such as a letter or number to allow identification of each unique deployment device  20 .  
         [0090]    The drape  124  may be manufactured in any of a variety of ways, such as by cutting a desired profile on a polymeric sheet comprising any of a variety of medical grade, sterilizable materials. Suitable materials include polypropylene. In one embodiment, the back portion  126  has a vertical dimension of about 18 inches and a horizontal dimension of about 14.5 inches. The width in the horizontal direction of each of the left flap  128  and right flap  130  from the fold to the outer edge is approximately 7.75 inches. The needle carrier  140  comprises polypropylene, and is heat sealed at the top and bottom edges to the back  126 . The back portion  126  or other portion of the drape  124  may optionally be additionally provided with a radiation attenuation layer such as a thin lead sheet to contribute to the radiation attenuation function of the needle pig  152  as will be discussed.  
         [0091]    [0091]FIGS. 7A and 7B illustrate pages 1 and 2 of a needle loading report, which will accompany the loaded drape  124 . On page 1 of the needle loading report illustrated at FIG. 7A, the spatial orientation of each needle at the treatment site is identified, as well as the number of radioactive seeds per needle. Page 2 of the needle loading report illustrated at FIG. 7B discloses the precise seed and spacer arrangement for each needle contained in the drape  124 . Additional patient information is also included. In accordance with the present invention, each of the needles is preloaded at the point of manufacture for a unique patient&#39;s needs, and delivered to the treatment site. The clinical staff receive the loaded drape  124  and corresponding needle report, which enables them to both identify the precise desired location of each needle as well as audit the contents of each needle compared to the desired needle loading report, due to the transparent wall of the tubular sleeve  32 .  
         [0092]    [0092]FIG. 8 illustrates a needle drape  124  including four brachytherapy seed deployment devices  20 , in which the left flap  128 , right flap  130 , and bottom flap  132  are folded closed. For shipping, the entire folded needle drape is positioned within a sterile pouch  148 .  
         [0093]    Referring to FIG. 9, the pouch  148  containing the needle drape  124  is rolled following the loading process and positioned within a chamber  150  in a needle pig  152 . The needle pig  152  comprises a needle canister base  154  having the chamber  150  therein, together with a corresponding needle canister lid  156 . Preferably, the needle canister base  154  and lid  156  are made from lead, or other material which helps attenuate radiation from the brachytherapy seeds.  
         [0094]    Referring to FIG. 10, a shipping assembly  158  is illustrated for shipment of the needle pig  152  to the clinical site. In the illustrated embodiment, a foam or other support  160  is provided with a needle pig cavity  162  for removably received the needle pig  152 . A calibration pig cavity  164  is also provided, for receiving a calibration seed pig  166  which will be described below. The support  160 , optionally with an additional foam base  168  is positioned within a shipping box  170 . A foam lid  172  or other cushioning or closure element is positioned on top of the calibration seed pig  166  and needle pig  152 , and placed within the box  170 . The various components of the shipping assembly  158  preferably sufficiently attenuate radiation from the brachytherapy seeds that the loaded shipping assembly  158  may be transported under ordinary shipping conditions such as via Federal Express or other commercial carrier.  
         [0095]    Referring to FIG. 11, there is illustrated an exploded view of an exemplary calibration seed pig  166 . Due to the known characteristics of radioactive decay, the activity of the brachytherapy seeds  70  is constantly declining until the radiation has dropped below a therapeutically useful range, and ultimately becomes fully dissipated. As a consequence, the activity must be assayed or calibrated at the time of the clinical procedure, to enable delivery of the desired radioactive dose. This is accomplished in the context of the present brachytherapy system by providing a calibration seed pig  166  which includes brachytherapy seeds  70  of the same activity as the seeds  70  which have been preloaded into each of the brachytherapy seed deployment devices  20 . The provision of extra calibration seeds in the separate calibration seed pig  166  enables the clinical staff to calibrate the activity of the seeds without needing to disassemble any of the preloaded deployment devices or break the sterile seal on the needle pig  152 .  
         [0096]    The calibration seed pig  166  includes a pig base  174 , constructed from a suitable radiation attenuating material such as lead. The pig base  174  is provided with a cavity  176  for receiving a glass vial  178 . Glass vial  178  includes a plurality of seeds  70  having the same activity as the corresponding seeds in the associated deploymentdevices. A lid  180  is provided for the glass vial  178 . The glass vial  178  is positioned within the cavity  176  The cavity  176  may be lined by an annular foam insert  182 , to provide additional cushioning for the glass vial  178 . The pig base  174  is closed by a correspondingpig lid  184 . preferably , a label  186  is provided on the pig base  174 , and may be held thereto by an outer layer of shrienk rap  188 .  
         [0097]    Any of a variety of alternate constructions for the calibration seed pig may be devised, in view of the disclosure herein, to achieve the advantages of the present invention. In general, the distinct calibration seed pig enables the calibration of the brachytherapy seed deployment system without needing to open the sterile drape which includes the deployment device.  
         [0098]    Referring to FIGS. 12 and 13, there is illustrated a drape stand  190  in accordance with another aspect of the brachytherapy seed delivery system of the present invention. The drape stand  190  comprises a support surface  192  for supporting a drape  124 . Preferably, The support surface  192  lies in a plane which is inclined with respect to the horizontal, such as within the range of from about 45° to about 90°. Alternatively, the support surface  192  can be parallel to horizontal, although this orientation will require a greater countertop surface area.  
         [0099]    The support surface  192  may be supported by or attached to a frame  194 , and a base  196 . Preferably, the base  196  is designed to fit on an existing surgical table, and has dimensions of approximately 9 inches by about 14 inches. The support surface  192  is preferably additionally provided with one or two or more attachment structures  198 , such as post or chips for retaining a drape  124  thereon. In the illustrated embodiment, first and second posts  198  are adapted to receive first and second apertures  138  (see FIG. 6) to retain the drape  124  hereon.  
         [0100]    As illustrated in FIG. 13, the right and left flaps  130  and  128  of the drape  124  may be opened, while the drape  124  is secured to the support surface  192 , to facilitate sequential removal of each brachytherapy seed deployment device  20  as it may be needed during the procedure.  
         [0101]    The drape stand  190  may be manufactured either as a one-time use disposable device, or as a reusable device. Preferably, the drape stand  190  is reusable, and may be manufactured, from any other variety of materials such as stainless steel, or plastics which are well known in the medical device arts.  
         [0102]    In addition to other advantages discussed previously herein, two types of customized dosing profiles are facilitated by the present invention. In the first, seed to seed activity may be varied within a single sleeve  32 , to achieve higher resolution dosing patterns compared to the standard uniform seed activity devices currently in use. For example, at least a first seed within a sleeve  32  may be provided with a first activity, and at least a second seed in the same sleeve may be provided with a second, different activity. By “different”, the inventors contemplate a measurable, intended different activity, and not merely manufacturing tolerance differences. Two or more seeds may be provided at the first activity, and two or more seeds may be provided at the second activity. Additional combinations may also be provided, based upon patient needs. In addition, more than two different activities may be provided in a single sleeve  32 . For example, at least a first seed may be provided at a first activity, at least a second seed at a second activity, and at least a third seed at a third activity within a single sleeve  32 .  
         [0103]    In this manner, the activity and resulting delivered dose can be controllably varied along the axial direction of the needle. One or more needles prepared in this manner will have a first zone which exhibits at least a first activity, and a second zone which exhibits at least a second, different activity.  
         [0104]    A second form of dose customization that can be readily accomplished in accordance with the present invention results from needle to needle variations in activity. A first sleeve  32  may be provided with one or more seeds having a first activity, and a second sleeve  32  may be provided with one or more seeds having a second, different activity. Combinations of the two forms of dose customization can also be used to optimize conformity between the three dimensional delivered dose profile and the desired treatment site.  
         [0105]    Once the three dimensional shape of the desired target tissue has been established for a particular patient, and tissue to be avoided (e.g., urethra, rectum) has been mapped, the sleeves are loaded with seeds and spacers in a pattern to most closely conform to the target tissue in both the axial dimension and the transverse (to the axis of the needles) dimension. The deployment devices are assembled and loaded into the drape and prepared for shipment to the clinical site. At the site, the drape is preferably placed on a drape stand and each needle is removed and advanced into the target tissue at its unique, predetermined site to produce the predetermined three dimensional dosing profile. Preprocedure calibration can be enabled by either providing calibration seeds at each activity level, or providing calibration seeds at a single level or two levels from which calibration values for the other levels can be extrapolated.  
         [0106]    Although exemplary embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.