Abstract:
The present invention is directed to a seed cartridge assembly including a cartridge body, a seed drawer slideably disposed within the cartridge body, a radiation shield slideably disposed around the cartridge body and a seed retainer in the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above including a gravity lock between the seed drawer and the cartridge body. Further embodiments of the present invention include a seed cartridge assembly as described above, wherein the cartridge body includes a magnification lens positioned above the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above wherein a seed channel extends axially along the seed drawer and a plurality of vents extending from the seed channel to an exterior surface of the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above wherein the gravity lock includes a moveable locking element, a first locking recess in an interior surface of the cartridge body and a second locking recess in an exterior surface of the drawer opposite the first locking recess.

Description:
This is a Continuation of U.S. patent application Ser. No. 09/359,867 Filed Jul. 26, 1999 now U.S. Pat. No. 6,267,718. 
     This application is related to the following copending patent applications: U.S. patent application Ser. No. 09/260,705 now U.S. Pat. No. 6,221,003 which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates, in general, to a brachytherapy seed cartridge and, more particularly, to an improved brachytherapy seed cartridge including a removable seed drawer. 
     BACKGROUND OF THE INVENTION 
     Prostatic cancer has been estimated to affect as many as one in three men. In the U.S. alone, this implies an estimated fifty-million patients who are candidates for treatment of prostatic cancer. Prior methods of treatment include surgical intervention, external radiotherapy, and other brachytherapy (interstitial radiation) techniques. A general discussion of the localized use of radiation therapy is found in Bagshaw, M. A., Kaplan, I. D. and Cox, R. C., Radiation Therapy for Localized Disease, CANCER 71: 939-952, 1993. Disadvantages associated with surgical intervention include impotence and incontinence. External radiotherapy may have deleterious effects on surrounding normal tissues (e.g., the bladder, the rectum, and the urethra). In contrast, brachytherapy diminishes complications such as impotence and incontinence, and allows a higher and more concentrated radiation dose to be delivered to the prostate gland as compared to external radiotherapy. An additional advantage of brachytherapy is that treatment can be accomplished within a matter of days as compared to weeks, greatly reducing radiation exposure of the adjacent organs. 
     Prostate brachytherapy can be divided into two categories, based upon the radiation level used. The first category is temporary implantation, which uses high activity sources, and the second category is permanent implantation, which uses lower activity sources. These two techniques are described in Porter, A. T. and Forman, J. D., Prostate Brachytherapy, CANCER 71: 953-958, 1993. The predominant radioactive sources used in prostate brachytherapy include iodine-125, palladium-103, gold-198, ytterbium-169, and iridium-192. Prostate brachytherapy can also be categorized based upon the method by which the radioactive material is introduced into the prostate. For example, a open or closed procedure can be performed via a suprapubic, transperineal or retropubic approach. 
     While there are various therapies to treat this condition, one of the more successful approaches is to expose the prostate gland to radiation by implanting radioactive seeds. The seeds are implanted in rows and are carefully spaced to match the specific geometry of the patient&#39;s prostate gland and to assure adequate radiation dosages to the tissue. Current techniques to implant these seeds include loading them one at a time into the cannula of a needle-like insertion device, which may be referred to as a brachytherapy needle. Between each seed may be placed a spacer, which may be made of catgut. In this procedure, a separate brachytherapy needle is loaded for each row of seeds to be implanted. 
     In brachytherapy procedures, large amounts of time are currently consumed loading radio active seeds and spacers into the brachytherapy needles. Further, once the needles are loaded, it becomes difficult to verify the dosage (i.e. number of seeds) or to check the level of radioactivity in any individual seed or seeds. Thus, it is preferable to load the appropriate number of seeds and spacers into a cartridge which may then be used to visually verify the number of seeds or to conveniently extract one or more seeds to verify the radio activity of the seeds prior to loading the seeds into a brachytherapy needle. It is also preferable, in certain circumstances, to sterilize the seeds prior to loading them into the brachytherapy needles, allowing the surgeon to review the dosage after sterilization and immediately prior to implantation. 
     It would, therefore, be advantageous to design a brachytherapy seed cartridge which decreases the time required to check dosage and radioactivity. It would further be advantageous to design a brachytherapy seed cartridge which facilitates loading of brachytherapy needles prior to the brachytherapy procedure. In particular, it would be advantageous to design a brachytherapy seed cartridge which is adapted to organize, view and conveniently add or remove seeds and spacers. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a seed cartridge assembly including a cartridge body, a seed drawer slideably disposed within the cartridge body, a radiation shield slideably disposed around the cartridge body and a seed retainer in the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above including a gravity lock between the seed drawer and the cartridge body. Further embodiments of the present invention include a seed cartridge assembly as described above, wherein the cartridge body includes a magnification lens positioned above the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above wherein a seed channel extends axially along the seed drawer and a plurality of vents extending from the seed channel to an exterior surface of the seed drawer. Further embodiments of the present invention include a seed cartridge assembly as described above wherein the gravity lock includes a moveable locking element, a first locking recess in an interior surface of the cartridge body and a second locking recess in an exterior surface of the drawer opposite the first locking recess. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to organization and methods of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a of a seed cartridge assembly according to the present invention, wherein the seed cartridge assembly contains radioactive seeds employed in the treatment of cancer. 
     FIG. 2 is an exploded perspective view of the elements of the seed cartridge assembly illustrated in FIG.  1 . 
     FIG. 3 is a plan view of the body of a seed cartridge according to the present invention. 
     FIG. 4 is a side elevation view of the seed cartridge body illustrated in FIG.  3 . 
     FIG. 5 is a bottom view of the seed cartridge body illustrated in FIG.  3 . 
     FIG. 6 is an enlarged distal end view of the seed cartridge body taken along line  6 — 6  of FIG.  4 . 
     FIG. 7 is an enlarged proximal end view of the seed cartridge body taken along line  7 — 7  of FIG.  4 . 
     FIG. 8 is an enlarged view in upright section of the seed cartridge body taken along line  8 — 8  of FIG.  4 . 
     FIG. 9 is an enlarged view in upright section of the seed cartridge body taken along line  9 — 9  of FIG.  4 . 
     FIG. 10 is an upright section view of the seed cartridge body taken along line  10 — 10  of FIG.  3 . 
     FIG. 11 is a plan view of the seed drawer of the seed cartridge illustrated in FIG.  2 . 
     FIG. 12 is a side elevation view of the seed drawer illustrated in FIG.  11 . 
     FIG. 13 is a bottom view of the seed drawer illustrated in FIG.  11 . 
     FIG. 14 is an enlarged proximal end view taken along line  14 — 14  of FIG.  12 . 
     FIG. 15 is an enlarged view in upright section taken along line  15 — 15  of FIG.  12 . 
     FIG. 16 is an upright section view taken along line  16 — 16  of FIG.  11 . 
     FIG. 17 is a plan view of a seed cartridge radiation shield according to the present invention. 
     FIG. 18 is an enlarged distal end view in upright disposition of the radiation shield illustrated in FIG.  17 . 
     FIG. 19 is a centerline section view of the radiation shield taken along line  19 — 19  of FIG.  16 . 
     FIG. 20 is a plan view of a seed cartridge assembly seed retainer according to the present invention. 
     FIG. 21 is a side elevational view of the seed retainer illustrated in FIG.  20 . 
     FIG. 22 is an enlarged plan view of a seed cartridge assembly locking cylinder according to the present invention. 
     FIG. 23 is an enlarged upright section view through the locking cylinder, seed cartridge body and seed drawer in assembly. 
     FIG. 24 is an enlarged inverted view of the section view of FIG. 23 illustrating the position of the locking cylinder when the seed cartridge assembly is inverted. 
     FIG. 25 is a plan view of a seed drawer according to the present invention including a retainer, seeds and spacers. 
     FIG. 26 is an isometric view of a seed cartridge according to the present invention wherein seeds and spacers are positioned for loading into the seed cartridge drawer. 
     FIG. 27 is an isometric view of a body and drawer of a loaded seed cartridge according to the present invention wherein the seed cartridge drawer has been closed. 
     FIG. 28 is an isometric view of a loaded seed cartridge assembly according to the present invention wherein the radiation shield is closed. 
     FIG. 29 is an isometric view of a loaded seed cartridge assembly with the seed cartridge drawer opened for the removal of one or more seeds. 
     FIG. 30 is a schematic view of a seed cartridge according to the present invention positioned in an assay device. 
     FIG. 31 is an isometric view of a seed cartridge assembly according to the present invention with its radiation shield in an open position. 
     FIG. 32 is an exploded isometric view of a brachytherapy needle and a stylet rod in combination with a seed cartridge assembly according to the present invention. 
     FIG. 33 is an isometric view of a loaded brachytherapy needle in combination with its stylet. 
     FIG. 34 is an enlarged view in upright section of the seed cartridge body taken along line  34 — 34  of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a perspective view of one embodiment of a seed cartridge assembly  11  according to the present invention. In the embodiment illustrated in FIG. 1, seed cartridge assembly  11  is adapted to hold and dispense radioactive seeds which may be employed in the treatment of, for example, cancerous prostates. As illustrated in FIG. 1, seed cartridge assembly  11  is fully assembled and includes a seed cartridge  15  and a radiation shield  10 . Seed cartridge  15  includes a cartridge body  14  and a seed drawer  16 . FIG. 2 is an exploded perspective view of the elements of the cartridge assembly FIG. 1, including seed cartridge  15  and radiation shield  10 . Cartridge body  14  of seed cartridge  15  includes a cartridge hub  28  and a cartridge shaft  29 . Cartridge hub  28  includes an upper needle guide  26 , cartridge hub grips  32 , hub locking flanges  44 , a luer opening  78  and an orientation indicator  90 . Cartridge shaft  29  includes a viewing lens  30 , a distal shield locking rib  46 , an intermediate shield locking rib  50  and a proximal shield locking rib  52 . Viewing lens  30  may be, for example, a prism. Seed drawer  16  of seed cartridge  15  includes locking cylinder  22 , vents  24 , lower needle guide  54 , lower locking recess  56 , locking spring  58 , rear handle  60 , seed channel  64 , locking nib  66  and seed retainer  74 . In FIG. 2, brachytherapy seeds  20  are interspersed with spacers  18 . Spacers  18  may be, for example, absorbable spacers made from an autoclaveable material such as, for example a polyglectin  910 . With seed drawer  16  positioned in its closed position, upper needle guide  26  and lower needle guide  54  combine to form needle guide  27 . Radiation shield  10  of seed cartridge assembly  11  includes a locking tab  12 . 
     FIGS. 3-5 illustrate one embodiment of cartridge body  14 . FIG. 3 is a plan view of cartridge body  14 . FIG. 4 is a side elevation view of cartridge body  14 . FIG. 5 is a bottom view of cartridge body  14 . As illustrated in FIG. 5, cartridge body  14  further includes lower drawer support  34 , drawer locking spring seat  36 , lower drawer support  38 , distal retention tab  40 , proximal retention tab  42  and an upper locking recess  72 . 
     FIGS. 6-10 are cut away views of one embodiment of the present invention. FIG. 6 is an enlarged end view of cartridge body  14  taken along line  6 — 6  looking into cartridge hub  28  as illustrated in FIG.  4 . FIG. 7 is an enlarged end view of cartridge body  14  taken along line  7 — 7  looking into cartridge shaft  29  as illustrated in FIG.  4 . FIG. 8 is an enlarged view in upright section of cartridge body  14  taken along line  8 — 8  through cartridge hub  28  as illustrated in FIG.  4 . FIG. 9 is an enlarged view in upright section of cartridge body  14  taken along line  9 — 9  through cartridge hub  28  as illustrated in FIG.  4 . FIG. 10 is an upright section view of cartridge body  14  taken along line  10 — 10  as illustrated in FIG.  3 . 
     FIGS. 11-13 are a series of views of seed drawer  16  according to one embodiment of the present invention. FIG. 11 is a plan view of seed drawer  16 . In FIG. 11 seed drawer  16  includes retainer seat nibs  62  and butt plate  92  while locking spring  58  of seed drawer  16  includes locking nib  59 . FIG. 12 is a side elevation view of seed drawer  16  including support rib  70 . FIG. 13 is a bottom view of seed drawer  16 . 
     FIGS. 14-16 are a series of views, including cutaway views, of one embodiment of the present invention. FIG. 14 is an enlarged proximal end view of seed drawer  16  looking from the proximal to the distal end of seed drawer  16  taken along line  14 — 14  as illustrated in FIG.  12 . FIG. 15 is an enlarged view in upright section looking toward the distal end of seed drawer  16  taken along line  15 — 15  as illustrated in FIG.  12 . FIG. 16 is an upright section view of seed drawer  16  taken along line  16 — 16  as illustrated in FIG.  11 . 
     FIGS. 17-19 are a series of views, including a cutaway view of a tubular radiation shield  10  according to the present invention. FIG. 17 is a plan view of radiation shield  10 . FIG. 18 is an enlarged distal end view in upright disposition looking into the distal end of radiation shield  10  along line  18 — 18  as illustrated in FIG.  17 . FIG. 19 is a centerline section view of radiation shield  10  taken along line  19 — 19  as illustrated in FIG.  17 . 
     FIGS. 20 and 21 are side and top views of seed retainer  74  according to the present invention. FIG. 20 is a plan view of seed retainer  74 . FIG. 21 is a side elevational view of seed retainer  74 . FIG. 22 is an enlarged plan view of a locking cylinder  22  according to one embodiment of the present invention. 
     FIGS. 23 and 24 illustrate the interaction of locking cylinder  22  with lower locking recess  56  and upper locking recess  72 . FIG. 23 is an enlarged upright section view through locking cylinder  22 , cartridge hub  28  and seed drawer  16  of seed cartridge assembly  11  along line  23 — 23  as illustrated in FIG.  1 . FIG. 24 is an enlarged view of the section view of FIG. 23 illustrating the position of locking cylinder  22  in lower locking recess  56  and upper locking recess  72  with cartridge assembly  11  inverted. 
     FIGS. 25-28 illustrate a procedure according to the present invention for loading radioactive seeds into a seed cartridge assembly  11  according to the present invention. FIG. 25 is a plan view of the seed drawer  16  including, spacers  18 , brachytherapy seeds  20  and seed retainer  74  in assembly. FIG. 26 is an isometric view of seed cartridge  15  with seed drawer  16  open to receive spacers  18  and brachytherapy seeds  20 . Seeds and spacers may be loaded into seed drawer  16  by, for example, hand wearing leaded gloves or using tweezers. FIG. 27 is an isometric view of a loaded seed cartridge  15  according to the present invention after spacers  18  and brachytherapy seeds  20  have been loaded into seed drawer  16  and seed drawer  16  has been closed. The number of seeds  20  and spacers  18  placed in seed drawer  16  will, of course, depend upon the procedure. Viewing lens  30 , which may be, for example, a window having a convex outer surface, provides magnification of seeds  20  for easier counting and classification after they are loaded, seed drawer  16  is closed and radiation shield  10  is moved back to expose viewing lens  30 . FIG. 28 is an isometric view of a loaded cartridge assembly  11  wherein radiation shield  10  has been added to seed cartridge  15  to substantially reduce radiation emitted to the surrounding environment by brachytherapy seeds  20 . FIG. 29 is an isometric view of a cartridge assembly opened by a hospital physicist for the removal of a 10% seed sample for assay purposes. In this assay procedure, radiation shield  10  stays in place and calibration is accomplished one seed at a time. In an alternate procedure, illustrated in FIG. 30, a seed cartridge  15  is inserted in an assay device, since seed cartridge  15  does not include radiation shield  10 , the resulting calibration would yield the total count for the contents of seed cartridge  15 . FIG. 31 is an isometric view of a cartridge assembly  11  with its radiation shield  10  withdrawn for a visual count of the contents. Radiation shield  10  is retained on the proximal end of seed cartridge  15  by locking tab  12  and locking rib  50 . 
     FIGS. 32 and 33 illustrate how seeds  20  are incorporated into a brachytherapy needle  82 . FIG. 32 is an exploded isometric view of a cartridge assembly  11 , brachytherapy needle  82 , and a stylet  84 . In the embodiment illustrated, brachytherapy needle  82  is particularly adapted for use in brachytherapy procedures involving treatment of cancer of the prostate. Suitable brachytherapy needles are available from Indigo Medical, Incorporated as Model BPN18. In the embodiment of the invention illustrated, needle hub  88  of brachytherapy needle  82  may be attached to cartridge hub  28  with a sixty degree turn, locking the proximal end of brachytherapy needle  82  to the distal end of seed cartridge  11 . Stylet  84  may then be used to move spacers  18  and seeds  20  from seed cartridge  11  to needle cannula  86 . Once spacers  18  and seeds  20  are positioned in needle cannula  86 , stylet  84  may be removed. FIG. 33 is an isometric view of a loaded brachytherapy needle  82  with seed cartridge  11  removed and stylet  84  inserted into needle hub  88 . Once brachytherapy needle  82  is properly positioned within the patient, stylet  84  may be used to force spacers  18  and seeds  20  out of needle cannula  86  and into the portion of the patient to be treated, such as, for example, the prostate. 
     FIG. 34 is an enlarged view in upright section of cartridge body  14  taken along line  8 — 8  through cartridge shaft  29  as illustrated in FIG.  4 . In the embodiment of the invention illustrated in FIG. 34, viewing lens  30  includes a convex upper surface  49  and a flat lower surface  48 . In the embodiment illustrated, lower surface  48  of viewing lens  30  acts as a channel cover for seed channel  64 , holding spacers  18  and seeds  20  in channel  64  when seed drawer  16  is closed. Upper surface  49  of viewing lens  30 , being convex magnifies images of elements placed under lower surface  48 , thus, viewing the contents of seed channel  64  from the top of seed cartridge  15  through viewing lens  30  makes the contents appear larger and makes it easier for a technician to count the number of seeds and spacers in seed channel  64  and to ensure that the seeds and spacers in seed channel  64  are properly arranged. 
     Referring now to FIGS. 1-25, there is illustrated one embodiment of the present invention. In FIGS. 1-25, a seeding needle cartridge assembly  11  useful for storing and dispensing radioactive seeds  20  such as those used in low dose brachytherapy procedures is shown. In the embodiment shown and described herein, cartridge assembly  11  includes radiation shield  10 , cartridge body  14 , and seed drawer  16 . Within seed drawer  16  is nestled seed retainer  74  which is adapted to passively enclose the brachytherapy seeds  20  and spacers  18  in seed channel  64  until seeds  20  and spacers  18  are propelled through seed channel  64  and out needle guide  27  by, for example, stylet  84 . Seed cartridge  11  further includes luer opening  78  which is adapted to mate with a conventional brachytherapy needle  82  having a conventional luer mating element  94 . 
     As best illustrated in FIGS. 23 and 24 seed cartridge assembly  11  includes a gravity lock which prevents seed drawer  16  from opening when seed cartridge assembly  11  is inverted. Thus, the gravity lock prevents seed drawer  16  from being opened with seed cartridge assembly  11  in a position where seeds  20  would fall out of seed channel  64 . In the embodiment of the invention illustrated in FIGS. 23 and 24, the gravity lock includes cylinder  22 , lower locking recess  56  and upper locking recess  72  wherein the depth of lower locking recess is greater than the cross-sectional diameter of locking cylinder  22  while the depth of upper locking recess is less than the diameter of locking cylinder  22 . Thus, with seed cartridge assembly in an upright position, as illustrated in FIG. 23, the force of gravity displaces locking cylinder  22  toward seed drawer  16  and locking cylinder  22  sits in lower locking recess  56 , leaving seed drawer  16  free to slide in and out of cartridge body  14 . However, with seed cartridge assembly  11  in an inverted position, as illustrated in FIG. 24, the force of gravity displaces locking cylinder  22  toward cartridge body  14  such that a portion of locking cylinder  22  rests in upper locking recess  72  and a portion of locking cylinder  22  extends into lower locking recess  56 . In the inverted position, as illustrated in FIG. 24, cartridge drawer  16  will not freely slide in and out of cartridge body  14  because locking cylinder  22  obstructs the movement of cartridge drawer  16  with respect to cartridge body  14 . In particular, when seed cartridge assembly  11  is inverted, as illustrated in FIG. 24, and force is applied to attempt to move seed drawer  16  proximally with respect to seed cartridge body  14  (i.e. to open seed drawer  16 ) the proximal end of locking cylinder  22  is forced against the proximal end of upper locking recess  72  while the distal end of locking cylinder  22  is forced against the distal end of lower locking recess  56 , preventing seed drawer  16  from moving proximally with respect to cartridge body  14 . 
     Referring now to FIGS. 3-10, the cartridge body  14  is constructed to have a transparent or translucent viewing lens  30 , which is designed to be of a convex structure so as to magnify contents beneath viewing lens  30 . Lower drawer support  34 , lower drawer support  38  and retention tabs  40  and  42  provide a flat base on which seed drawer  16  can slide and rest. Drawer locking spring seat  36  is adapted to engage locking nib  59  with seed drawer  16  closed. Retention tab  42  is adapted to engage locking nib  66  with seed drawer  16  closed and to engage locking nib  59  with seed drawer  16  fully open. Locking tab  96  is adapted to stop against lower drawer support  38  and so inhibit the movement of locking nib  59  past proximal retention tab  42  when seed drawer  16  is opened. Locking spring  58  and locking nib  59  also provide lateral support for seed drawer  16 , limiting side to side movement of seed drawer  16  in cartridge body  14 . 
     Cartridge body  14  also includes the cartridge hub  28  which is attached to brachytherapy needle  82  when seeds  20  are to be loaded into needle cannula  86 . Cartridge hub grips  32  facilitate gripping cartridge hub  28  for attachment to a needle hub  88 . Cartridge hub  28  further includes hub locking flanges  44  which prevent over-rotation of needle hub  88  during attachment. Hub locking flanges  44  may also provide tactile feedback, indicating a fully locked position. 
     Distal shield locking rib  46 , intermediate shield locking rib  50 , and proximal shield locking rib  52  are designed to facilitate the positioning, removal and replacement of radiation shield  10  on seed cartridge  15 . Distal shield locking rib  46 , intermediate shield locking rib  50 , and proximal shield locking rib  52  define three different detent positions with which locking tab  12  of radiation shield  10  can rest, with each position revealing different portions of seed cartridge  15 . 
     Referring now to FIGS. 11-16, seed drawer  16  is more explicitly illustrated and labeled. Locking spring  58  along with locking nib  59  mates with drawer locking spring seat  36  in the cartridge body  14  to provide a locking mechanism for the seed drawer  16  within the cartridge body  14 . Locking nib  66  also provides resistance which prevents seed drawer  16  from opening accidentally. A sufficiently large force is thus required to overcome the spring and thus deflect the locking spring  58  and locking nib  66 , promoting motion of drawer  16  with respect to body  14 . 
     Vents  24  allow steam to enter and leave seed channel  64  in order to sterilize seeds and spacers positioned in seed channel  64  using, for example, an autoclave. Multiple vents  24  are used to ensure that steam can flow freely around spacers  18  and seeds  20  positioned in seed channel  64 . Thus, both the seed cartridge assembly  11  and the contents of seed drawer  16  may be sterilized together, after seed drawer  16  has been filled with seeds and spacers. Generally retainer gates  76  of seed retainer  74  prevent spacers  18  and seeds  20  positioned in seed channel  64  from sliding out the proximal or distal ends of seed cartridge assembly. Retainer seat nibs  62  hold seed retainer  74  in place through the application of a three point bending force, limiting proximal-distal motion and lateral motion of seed retainer  74  when stylet  84  is inserted into seed channel  64  to force spacers  18  and seeds  20  out the distal end of needle guide  27 . As stylet  84  is inserted into seed channel  64 , it forces the retainer gate  76  at the proximal end of seed retainer  74  aside and, as it continues to move toward the distal end of seed channel  64 , it pushes spacers  18  and seeds  20  past the retainer gate  76  at the distal end of seed retainer  74  and out the distal end of needle guide  27 . 
     Rear handle  60  may be used to open and close seed drawer  16  or to hold seed drawer  16  when it is removed from cartridge body  14 . Support rib  70  provides support for the seed drawer  16  in addition to facilitating manufacture and assembly of seed drawer  16  and cartridge body  14 . Butt plate  92  provides a stopping point where seed drawer  16  cannot further travel distally relative to cartridge body  14 . Rear funnel  68  facilitates insertion of stylet  84  into seed channel  64  in seed cartridge assembly  11 . 
     FIG. 25 demonstrates a typical setup of the seed drawer  16 , with brachytherapy seeds  20  and spacers  18  within the retainer gates  76  in seed channel  64 . FIGS. 26-33 then demonstrate a typical mode of use. FIG. 26 demonstrates the loading of the brachytherapy seeds  20  and spacers  18  into the seed drawer  16  (specifically in the seed channel  64 ). Following loading, the seed drawer  16  is inserted into the cartridge body  14 . This cartridge is then covered by radiation shield  10  and delivered to the customer, such as, for example, a hospital. Upon receipt, technicians at the hospital may withdraw seed drawer  16  and remove a number of brachytherapy seeds  20  for assay (typically they will remove 10% of all seeds in a batch to calibrate radioactivity). An alternate method of assay is shown in FIG. 30, which illustrates a seed cartridge  15  suspended within an ion chamber  80  (where the method of suspension can be any method of the like where seed cartridge  15  is exposed inside the ion chamber  80 ). After determining the radioactivity of the brachytherapy seeds  20  and verifying the correct values, radiation shield  10  is repositioned on seed cartridge  15  and seed cartridge assembly  11  is autoclaved alone or with other seed cartridge assemblies. 
     After the seed cartridge assembly  11  is autoclaved, a number of seed cartridge assemblies  11  (typically  20 - 25 ) are matched with the brachytherapy procedure plan and the seeds  20  and spacers  18  are transferred to needle cannulas  86  of brachytherapy needles  82 . In particular, for each autoclaved seed cartridge assembly, radiation shield  10  is moved proximally to allow a technician to view the contents of seed channel  64  through the cartridge body  14  in order to identify the order and number of brachytherapy seeds  20  and spacers  18  as shown in FIG.  31 . In one embodiment of the present invention, this process is particularly facilitated by the presence of viewing lens  30  above seed drawer  16 . The technician then compares the contents of the seed cartridge assembly  11  with a predetermined plan. If the contents of seed drawer  16  do not correspond to the plan, seed drawer  16  may opened as illustrated in FIG.  29  and seeds  20  removed or added to seed drawer  16 . If the contents of the seed cartridge assembly match the predetermined plan the seed cartridge assembly  11  is attached to a brachytherapy needle  82 . More particularly, luer mating element  94  at the proximal end of needle hub  88  is inserted into luer opening  78  at the distal end of cartridge hub  28 . Following attachment, a stylet  84  is used to propel the contents of the seed cartridge assembly  11  through the seed channel  64  into needle cannula  86 . Seed cartridge assembly  11  is then disconnected from brachytherapy needle  82  and stylet  84  is positioned in brachytherapy needle  82  to be used intraoperatively as in a normal brachytherapy procedure utilizing preloaded needles. 
     It will be recognized that equivalent structures may be substituted for the structures illustrated and described herein and that the described embodiment of the invention is not the only structure which may be employed to implement the claimed invention. As one example of an equivalent structure which may be used to implement the present invention, seed channel  64  may be built into cartridge body  14  and accessed using, for example, a living hinge built into seed body  14 . 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.