Brachytherapy cartridge including absorbable and autoclaveable spacers

Abstract: The present invention is directed to a brachytherapy seed delivery system which includes a seed cartridge including a central channel, a plurality of brachytherapy seeds disposed within the central channel and a plurality of absorbable, dimensionally stable spacers disposed within the central channel, wherein the absorbable, dimensionally stable spacers are interspersed between the brachytherapy seeds. The present invention is further directed to a method of loading a brachytherapy seed delivery system including the steps of: providing a seed cartridge including a central channel; placing at least two brachytherapy seeds into the central channel of the seed cartridge; placing at least one absorbable, dimensionally stable spacer in the central channel between the brachytherapy seeds; connecting the brachytherapy seed cartridge to a brachytherapy needle including a cannula; and forcing the seeds out of the brachytherapy seed cartridge into the cannula.

Description: Field of the Invention The present invention relates, in general, to a brachytherapy seed delivery system and method and, more particularly, to a brachytherapy seed delivery system and method utilizing dimensionally stable spacers between brachytherapy seeds. 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 or a perineal retropubic approach. Prostate cancer is a common cancer for men. 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'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. Typically, if a material such as catgut is used as a spacing material the autoclaving process may make the spacer soft and it may not retain its physical characteristics when exposed to autoclaving. It may become soft, change dimensions and becomes difficult to work with, potentially compromising accurate placement of the seeds. Alternatively, the seeds may be loaded into the center of a suture material such as a Coated VICRYL (Polyglactin 910) suture with its core removed. In this procedure, brachytherapy seeds are carefully placed into the empty suture core and loaded into a needle-like delivery device. Although Coated VICRYL suture is able to withstand autoclaving, the nature of its braided construction can make the exact spacing between material less than desirable. US 4,402,308 describes an injector for implanting radioactive seeds wherein the seeds are retained in place by slots cut in a needle assembly. The needle assembly may be arranged to position the radioactive seeds and then be retracted or may be of absorbable material. The arrangements described are for an injector which does not incorporate absorbable spacers between seeds. US-A-5 242 373 also describes an instrument for implentation of radioactive seeds in a body, the instrument including an elongated support rod end an elongated stylet rod spaced apart from, end parallel to the support rod, and being held in that relationship by a stop block and a slide block spaced apart from each other and longitudinally slidable with respect to both the support rod and the stylet rod. It would, therefore, be advantageous to design a seed delivery system utilizing a plurality of spacers which are absorbable and which do not degrade significantly when subjected to typical autoclave conditions. It would further be advantageous to design a method of loading a brachytherapy seed delivery system utilizing a plurality of spacers which are absorbable and which do not degrade significantly when subjected to typical autoclave conditions. It would further be advantageous to design an improved brachytherapy method utilizing a plurality of spacers which are absorbable and which do not degrade significantly when subjected to typical autoclave conditions. Summary of the Invention The present invention is directed to a brachytherapy seed delivery system which includes a seed cartridge including a central channel, a plurality of brachytherapy seeds disposed within the central channel and a plurality of absorbable, dimensionally stable spacers disposed within the central channel, wherein the absorbable, dimensionally stable spacers are interspersed between the brachytherapy seeds. Further embodiments of the present invention include a brachytherapy seed delivery system as described above wherein the spacers are cylindrical in shape, having a diameter of approximately 0,89 mm (0.035 inches). Further embodiments of the seed delivery system described above include a brachytherapy seed delivery system wherein the spacer is manufactured from dimensionally stable Polyglactin 910, a dimensionally stable compound of 95% polylactic acid and 5% polyglycolic acid or dimensionally stable polylactic acid. The present invention is further directed to a method of loading a brachytherapy seed delivery system including the steps of: providing a seed cartridge including a central channel; placing at least two brachytherapy seeds into the central channel of the seed cartridge; placing at least one absorbable, dimensionally stable spacer in the central channel between the brachytherapy seeds; connecting the brachytherapy seed cartridge to a brachytherapy needle including a cannula; and forcing the seeds out of the brachytherapy seed cartridge into the cannula. Further embodiments of the present invention include a method of loading a brachytherapy seed delivery system as described above, wherein the absorbable, dimensionally stable spacer comprises dimensionally stable Polyglactin 910, a dimensionally stable compound of 95% polylactic acid and 5% polyglycolic acid or dimensionally stable polylactic acid. The present invention is further directed to an improved brachytherapy method including the steps of: providing a seed cartridge including a central channel; placing at least two brachytherapy seeds into the central channel of the seed cartridge; placing at least one absorbable, dimensionally stable spacer in the central channel between the brachytherapy seeds; connecting the brachytherapy seed cartridge to a brachytherapy needle including a cannula; forcing the seeds out of the brachytherapy seed cartridge into the cannula; inserting the brachytherapy needle into a human organ; and forcing the seeds and the spacer through the cannula and into the human organ. Further embodiments of the present invention include an improved brachytherapy method as described above wherein the absorbable, dimensionally stable spacer comprises dimensionally stable Polyglactin 910, a dimensionally stable compound of 95% polylactic acid and 5% polyglycolic acid or dimensionally stable polylactic acid. 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: Figure 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. Figure 2 is an exploded perspective view of the elements of the seed cartridge assembly illustrated in Figure 1. Figure 3 is a plan view of the body of a seed cartridge according to the present invention. Figure 4 is a side elevation view of the seed cartridge body illustrated in Figure 3. Figure 5 is a bottom view of the seed cartridge body illustrated in Figure 3. Figure 6 is an enlarged distal end view of the seed cartridge body taken along line 6-6 of Figure 4. Figure 7 is an enlarged proximal end view of the seed cartridge body taken along line 7-7 of Figure 4. Figure 8 is an enlarged view in upright section of the seed cartridge body taken along line 8-8 of Figure 4. Figure 9 is an enlarged view in upright section of the seed cartridge body taken along line 9-9 of Figure 4. Figure 10 is an upright section view of the seed cartridge body taken along line 10-10 of Figure 3. Figure 11 is a plan view of the seed drawer of the seed cartridge illustrated in Figure 2. Figure 12 is a side elevation view of the seed drawer illustrated in Figure 11. Figure 13 is a bottom view of the seed drawer illustrated in Figure 11. Figure 14 is an enlarged proximal end view taken along line 14-14 of Figure 12. Figure 15 is an enlarged view in upright section taken along line 15-15 of Figure 12. Figure 16 is an upright section view taken along line 16-16 of Figure 11. Figure 17 is a plan view of a seed cartridge radiation shield according to the present invention. Figure 18 is an enlarged distal end view in upright disposition of the radiation shield illustrated in Figure 17. Figure 19 is a centerline section view of the radiation shield taken along line 19-19 of Figure 16. Figure 20 is a plan view of a seed cartridge assembly seed retainer according to the present invention. Figure 21 is a side elevational view of the seed retainer illustrated in Figure 20. Figure 22 is an enlarged plan view of a seed cartridge assembly locking cylinder according to the present invention. Figure 23 is an enlarged upright section view through the locking cylinder, seed cartridge body and seed drawer in assembly. Figure 24 is an enlarged inverted view of the section view of Figure 23 illustrating the position of the locking cylinder when the seed cartridge assembly is inverted. Figure 25 is a plan view of a seed drawer according to the present invention including a retainer, seeds and spacers. Figure 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. Figure 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. Figure 28 is an isometric view of a loaded seed cartridge assembly according to the present invention wherein the radiation shield is closed. Figure 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. Figure 30 is a schematic view of a seed cartridge according to the present invention positioned in an assay device. Figure 31 is an isometric view of a seed cartridge assembly according to the present invention with its radiation shield in an open position. Figure 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. Figure 33 is an isometric view of a loaded brachytherapy needle in combination with its stylet. Figure 34 is an enlarged view in upright section of the seed cartridge body taken along line 34-34 of Figure 4. Detailed Description of the Invention Figure 1 is a perspective view of one embodiment of a seed cartridge assembly 11 according to the present invention. In the embodiment illustrated in Figure 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 Figure 1, seed cartridge assembly 11 is fully assembled and includes a seed cartridge 15 and a radiation shield. Seed cartridge 15 includes a cartridge body 14 and a seed drawer 16. Figure 2 is an exploded perspective view of the elements of the cartridge assembly Figure 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 Figure 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. Figures 3-5 illustrate one embodiment of cartridge body 14. Figure 3 is a plan view of cartridge body 14. Figure 4 is a side elevation view of cartridge body 14. Figure 5 is a bottom view of cartridge body 14. As illustrated in Figure 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. Figures 6-10 are cut away views of one embodiment of the present invention. Figure 6 is an enlarged end view of cartridge body 14 taken along line 6-6 looking into cartridge hub 28 as illustrated in Figure 4. Figure 7 is an enlarged end view of cartridge body 14 taken along line 7-7 looking into cartridge shaft 29 as illustrated in Figure 4. Figure 8 is an enlarged view in upright section of cartridge body 14 taken along line 8-8 through cartridge hub 28 as illustrated in Figure 4. Figure 9 is an enlarged view in upright section of cartridge body 14 taken along line 9-9 through cartridge hub 28 as illustrated in Figure 4. Figure 10 is an upright section view of cartridge body 14 taken along line 10-10 as illustrated in Figure 3. Figures 11-13 are a series of views of seed drawer 16 according to one embodiment of the present invention. Figure I 1 is a plan view of seed drawer 16. In Figure 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. Figure 12 is a side elevation view of seed drawer 16 including support rib 70. Figure 13 is a bottom view of seed drawer 16. Figures 14-16 are a series of views, including cutaway views, of one embodiment of the present invention. Figure 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 Figure 12. Figure 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 Figure 12. Figure 16 is an upright section view of seed drawer 16 taken along line 16-16 as illustrated in Figure 11. Figures 17-19 are a series of views, including a cutaway view of a tubular radiation shield 10 according to the present invention. Figure 17 is a plan view of radiation shield 10. Figure 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 Figure 17. Figure 19 is a centerline section view of radiation shield 10 taken along line 19-19 as illustrated in Figure 17. Figures 20 and 21 are side and top views of seed retainer 74 according to the present invention. Figure 20 is a plan view of seed retainer 74. Figure 21 is a side elevational view of seed retainer 74. Figure 22 is an enlarged plan view of a locking cylinder 22 according to one embodiment of the present invention. Figures 23 and 24 illustrate the interaction of locking cylinder 22 with lower locking recess 56 and upper locking recess 72. Figure 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 Figure 1. Figure 24 is an enlarged view of the section view of Figure 23 illustrating the position of locking cylinder 22 in lower locking recess 56 and upper locking recess 72 with cartridge assembly 11 inverted. Figures 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. Figure 25 is a plan view of the seed drawer 16 including, spacers 18, brachytherapy seeds 20 and seed retainer 74 in assembly. Figure 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. Figure 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. Figure 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. Figure 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 Figure 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. Figure 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. Figures 32 and 33 illustrate how seeds 20 are incorporated into a brachytherapy needle 82. Figure 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. Figure 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. Figure 34 is an enlarged view in upright section of cartridge body 14 taken along line 8-8 through cartridge shaft 29 as illustrated in Figure 4. In the embodiment of the invention illustrated in Figure 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 Figures 1-25, there is illustrated one embodiment of the present invention. In Figures 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 Figures 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 Figures 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 Figure 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 Figure 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 Figure 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 Figure 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 Figures 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 inhibit the movement of locking nib 59 past proximal retention tab 42 when seed drawer 16 is opened. Locking spring 58 is further adapted to 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 griping 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 Figures 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 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. Figure 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. Figures 26-33 then demonstrate a typical mode of use. Figure 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 the seeds in the drawer, to calibrate radioactivity). An alternate method of assay is shown in Figure 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 Figure 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 Figure 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. The distal end of brachytherapy needle 18 may be dipped into, for example bone wax to prevent brachytherapy seeds 20 and spacers 18 from falling out the distal end of brachytherapy needle 18. In one embodiment of the present invention, spacer 18 is a material which is absorbed by the human body in addition to being dimensionally stable during a predetermined steam sterilization cycle. A material which is dimensionally stable during a predetermined steam sterilization cycle may be said to be autoclaveable. A predetermined steam sterilization or autoclave cycle consists of placing an instrument in steam at one hundred thirty five degrees centigrade for 15 minutes. A cylindrical spacer 18 according to the present invention is said to be dimensionally stable if it substantially retains its original shape during a predetermined steam sterilization cycle. More particularly a cylindrical spacer 18 according to the present invention is said to be dimensionally stable if its diameter shrinks by no more than fourteen percent and its length shrinks by no more than seven percent when subjected to the predetermined steam sterilization cycle described herein. Thus, in a spacer 18 according to the present invention, the spacer would retain its original cylindrical shape and at least 90 percent of its original diameter and length after a predetermined steam sterilization cycle. Spacers 18 which increased in size (either lengthwise or across their diameter) or frayed at either end would not be said to be dimensionally stable according to the present invention. One such dimensionally stable absorbable spacer 18 may be manufactured utilizing Polyglactin 910 (PG910). A dimensionally stable absorbable spacer 18 according to the present invention may be manufactured by extruding a rod of PG910 and orienting the rod to approximately five times its original length. In one embodiment of the present invention, the extruded rod would have a diameter of approximately 0.035 inches. The extrusion process orients the polymer molecules in the extruded rod and, by orienting the rod to approximately five times its original length, the extruded rod may be described as being highly oriented. Once the PG910 material is extruded and oriented to an appropriate length, resulting, highly oriented, structure prevents water molecules from penetrating into the interior of the extruded rod or, in the case of the present invention, into spacers 18 cut from the extruded rod. In particular, the highly oriented structure of the extruded rod prevents water molecules from penetrating into the interior of the structure and, during a predetermined steam sterilization cycle, hydrolysis of the spacer 18 must proceed from the outer surface and not throughout the interstices of the polymer system. In order to lock the crystalline structure of the extruded rod in place, it may be necessary to anneal the extruded rod. In particular, it may be necessary to anneal the extruded rod at temperatures of approximately one hundred forty five degrees centigrade or higher. Once the extruded rod has been annealed, it may be cut into seed spacers 18. One method of manufacturing a dimensionally stable absorbable spacer according to the present invention includes the following steps: Using a typical horizontal extruder, such as a one inch extruder which is available from Killion, the PG910 polymer pellets are melted and then forced through a die to form filaments. The filaments are then quenched in a heated water bath. More particularly, the horizontal extruder includes three initial zones which may all be set at a temperature of between two hundred twenty five and two hundred fifty degrees centigrade. As the PG910 polymer pellets are passed through the three zones, they melt and the melted polymer is forced through a flange which is heated to a temperature of between two hundred thirty and two hundred fifty five degrees centigrade. After passing through the heated flange, the melted polymer enters a pump which has a temperature of between two hundred thirty two and two hundred fifty five degrees centigrade. Finally, the melted polymer is forced through a die having a predetermined diameter of, for example 5,59 mm (0.22 inch). The polymer then forms a long rod which is suspended in air for approximately two to four inches and quenched in a tank of water having a temperature of approximately thirty to forty degrees centigrade, thus completing the extrusion process. Immediately following extrusion, the filaments may be oriented to about 5:1 ratio by stretching them between heated rolls. In particular, the extruded rod may be oriented by winding it around a first roller which is turning at a rate of approximately four to six meters per minute which pulls the extruded rod out of the bath. The extruded rod may then be wound around a second roll which turns at a rate of four to six meters per minute. After passing around the second roll, the extruded rod may be passed through a first oven which is set at a temperature of approximately fifty to fifty five degrees centigrade. After passing through the first oven, the extruded rod may be passed around a third roll which is turning at a rate of between seventeen and twenty-one meters per minute. After passing around the third roll, the extruded rod is passed through a second oven which is set at a temperature of between fifty and fifty-five degrees centigrade. After passing through the second oven, the extruded rod is wound around a fourth roll which is turning at a rate of between twenty four and thirty one point five meters per minute. Prior to cutting and sterilizing the rod must be annealed at a suitable temperature. An annealing temperature of approximatly 145 degrees centigrade or higher will yield acceptable crystalline properties and "lock" the structure in place. By then cutting the rod like material to suitable lengths it is possible to make an absorbable polymer spacer that can be used to properly place radioactive seeds. While spacers 18 according to the present invention have been described as being PG910, other absorbable polymers may be suitable as substitutes. In particular, polymers which are particularly well suited for the purpose of this invention may include aliphatic polyesters which include but are not limited to homopolymers of lactide (which includes lactic acid d-,1- and meso lactide) or glycolide (including glycolic acid), and copolymers of lactide (which includes lactic acid d-,1- and meso lactide), glycolide (including glycolic acid), ε-caprolactone, p-dioxanone (1,4-dioxan-2-one), trimethylene carbonate (1,3-dioxan-2-one), alkyl derivatives of trimethylene carbonate, δ-valerolactone, β-butyrolactone, γ-butyrolactone, ε-decalactone, hydroxybutyrate, hydroxyvalerate, 1,4-dioxepan-2-one (including its dimer 1,5,8,12-tetraoxacyclotetradecane-7,14-dione), 1,5-dioxepan-2-one, 6,6-dimethyl-1,4-dioxan-2-one and polymer blends thereof. 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, spacer 18 may be constructed of a dimensionally stable compound of 95% polylactic acid and 5% polyglycolic acid or of dimensionally stable polylactic acid. It will further be recognized that an absorbable, dimensionally stable spacer according to the present invention may be modified to include certain types of medication which are absorbed as the spacer is absorbed, such medications might include, for example, anti-inflammatory, anticancer or certain sustained release drugs. An absorbable, dimensionally stable spacer according to the present invention may further include markers or other materials adapted to make the spacer visible to ultrasound or x-ray. 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.

Claims: A brachytherapy seed delivery system comprising: a seed cartridge (15) including a central channel (64); a plurality of brachytherapy seeds (20) disposed within said central channel (64); a plurality of absorbable, dimensionally stable spacers (18) disposed within said central channel, wherein said absorbable, dimensionally stable spacers (18) are interspersed between said brachytherapy seeds (20), characterized in that the absorbable spacers (18) are dimensionally stable during a predetermined steam sterilization cycle. The system of claim 1 wherein said absorbable, dimensionally stable spacers (18) are cylindrical in shape, having a diameter of approximately 0.89 mm. The system of claim 1 or claim 2 wherein said absorbable, dimensionally stable spacer (18) comprises: a homopolymer of lactide (which includes lactic acid, d-, 1-and meso- lactide) or of glycolide (which includes glycolic acid); or a copolymer of at least two of lactide (which includes lactic acid, d-, 1- and meso- lactide), glycolide (which includes glycolic acid), epsilon -caprolactone, p-dioxanone, trimethylcarbonate, an alkyl derivative of trimethylenecarbonate, delta -valerolactone, beta -butyrolactone, gamma -butyrolactone, epsilon -decalactone, hydroxybutyrate, hydroxyvalerate, 1, 4-dioxepan-2-one (including its dimer 1, 5, 8, 12-tetraoxacyclotetradecane -7, 14-dione), 1,5-dioxepan-2-one, 6, 6-dimethyl-1, 4-dioxan-2-one; or a polymer blend of at least two of the above homopolymers or copolymers. The system of claim 3 wherein said absorbable, dimensionally stable spacer (18) comprises: a polymer of polyglycolic acid, such as polyglactin 910: a compound of 95% polylactic acid and 5% polyglycolic acid; polylactic acid; or a copolymer of polyglycolic acid and polylactic acid. The system of any one of claims 1 to 4, wherein said system further comprises a seed cover (30) removably attached to said channel. A method of loading a brachytherapy seed delivery system according to claims 1-4 wherein said method comprises the steps of: providing a seed cartridge (15) including a central channel; placing at least two brachytherapy seeds (20) into said central channel of said seed cartridge ( 15); placing at least one absorbable, dimensionally stable spacer (18) in said central channel between said brachytherapy seeds (20), wherein said spacer is dimensionally stable during a predetermined steam sterilization cycle; connecting said brachytherapy seed cartridge (15) to a brachytherapy needle (82) including a cannula; and forcing said seeds out of said brachytherapy seed cartridge into said cannula. A method of loading a brachytherapy seed delivery system according to claim 5 wherein said method comprises the steps of: providing a seed cartridge (15) including a central channel and a removable seed cover (30) attached to said central channel; uncovering said central channel; placing at least two brachytherapy seeds (20) into said central channel of said seed cartridge ( 15); placing at least one absorbable, dimensionally stable spacer (18) in said central channel between said brachytherapy seeds (20), wherein said spacer is dimensionally stable during a predetermined steam sterilization cycle; covering said central channel connecting said brachytherapy seed cartridge (15) to a brachytherapy needle (82) including a cannula; and forcing said seeds out of said brachytherapy seed cartridge into said cannula.

Inventors: HUXEL SHAWN T, KARL JOHN J, POPADIUK NICHOLAS M, SIEROCUK THOMAS J, HUXEL, SHAWN T., KARL, JOHN J., POPADIUK, NICHOLAS M., SIEROCUK, THOMAS J.
Applicants: BARD INC C R, C. R. BARD, INC.
Application year: 2000
Main classification: A61N5
IPC codes: A61M36, A61N5