Methods and apparatus for brachytherapy treatment of prostate disease

[0002] The present application is a continuation-in-part of U.S. patent application Ser. No. 09/522,282, filed Mar. 9, 2000.

[0003] This invention relates to improved apparatus and methods for the treatment of prostate cancer. More particularly, the present invention provides improved methods and apparatus for administering brachytherapy.

[0004] Excluding non-melanoma skin cancers, prostate cancer is the most common cancer afflicting American men. The American Cancer Society estimates that over 180,00 new cases will be diagnosed in the U.S. in the year 2000 alone, and that nearly 32,000 people will die from the disease. Prostate cancer is second only to lung cancer as the leading cause of cancer death in men, accounting for roughly 11%.

[0005] Prostate cancer is defined as malignant tumor growth within the prostate gland. Its cause is unknown, although high dietary fat intake and increased testosterone levels are believed to be contributory factors. A letter scale (“A” through “D”), which accounts for the location of the cancer, is commonly used to classify the stage of disease. In Stage A, the tumor is not palpable, but is detectable in microscopic biopsy. Stage B is characterized by a palpable tumor confined to the prostate. By Stage C, the tumor extends locally beyond the prostate with no distant metastasis. By Stage D, cancer has spread to the regional lymph nodes or has produced distant metastasis.

[0006] In the early stages, prostate cancer is most commonly treated by prostate removal or by brachytherapy. More advanced cases are treated by hormonal manipulation or orchiectomy to reduce testosterone levels and curb spreading of the disease, by chemotherapy, or by external beam radiation therapy.

[0007] With regard to treatment of early stage prostate cancer, the state of the art has several drawbacks. Radical prostatectomy is often recommended for treatment of localized stage A and B prostate cancers. Under general or spinal anesthesia, an incision is made through a patient's abdomen or perineal area, and the diseased prostate is removed. The procedure is lengthy, especially if a lymph node dissection is simultaneously performed, and requires a hospital stay of 2-5 days. Possible complications include impotence and urinary incontinence.

[0008] Internal radiation therapy or brachytherapy has recently been modified and holds great promise for the treatment of early stage prostate cancer. Radioactive pellets or seeds of, for example, iodine-125, gold-198, palladium-103, ytterbium-169, or iridium-192, are deposited directly into the prostate through needle placement. Imaging tests, such as transrectal ultrasound, CT scans, or MRI, are used to accurately guide placement of the radioactive material. Advantageously, radiation is administered directly to the prostate with less damage to surrounding tissues, requiring a significantly smaller radiation dosage as compared to external beam radiation therapy. Furthermore, the procedure need only be performed once. Complications include a lower, yet still significant, incidence of impotence and urinary incontinence, compared to prostate removal procedures.

[0009] The radioactive seeds are placed inside thin needles, which are inserted through the skin of the perineum (area between the scrotum and anus) into the prostate. U.S. Pat. No. 5,928,130 to Schmidt provides a slightly modified example of such a needle device. Each needle is slowly retracted with a spinning motion by a first practitioner while a plunger within the needle, and proximal of the radioactive seeds, is held stationary by a second practitioner. The plunger keeps the seeds in place during retraction of the needle, while rotation of the needle during retraction prevents jamming of the seeds while delivering the seeds in a line within the prostate.

[0010] The seeds, which are permanently implanted, give off radiation for weeks or months. Their presence causes little discomfort, and they are left in the prostate after decay of the radioactivity. For about a week following needle insertion, patients may experience pain in the perineal area, and urine may have a red-brown discoloration.

[0011] Although, when performed correctly, radioactive seed implantation may provide several benefits, compared to prostate removal and other techniques, current surgical apparatus and methods for delivering the seeds to target locations within the prostate are somewhat crude and are subject to practitioner error. The procedure requires two practitioners working cooperatively to deliver the seeds. The depth to which the plunger is inserted into the needle, in the loaded and advanced states, is critical but crudely measured. The plunger and needle may accidentally move relative to one another during needle insertion or seed delivery, causing improper positioning of deposited seeds. The needle is somewhat flexible and should be inserted quickly to minimize bending at its distal tip, but this is often not done due to inexperience or technical ability of the practitioners, or to avoid potential relative movement between the plunger and the needle.

[0012] Attempts have been made to address various aspects of these concerns. For example, U.S. Pat. No. 4,815,449 to Horowitz describes an absorbable member with seeds spaced within the member to facilitate proper spacing during delivery. U.S. Pat. No. 4,700,692 to Baumgartner describes apparatus for delivering all of the seeds simultaneously. PCT document WO 99/20337 to Rydell describes a gun-like apparatus for delivering seeds once the needle has been inserted into the prostate.

[0013] While each of these devices may provide some benefit over the prior art, none satisfactorily addresses the shortcomings of current techniques. In view of the drawbacks associated with previously-known methods and apparatus for brachytherapy, it would be desirable to provide methods and apparatus that overcome such drawbacks.

[0014] It further would be desirable to provide methods and apparatus that allow efficient preparation of the apparatus for therapeutic administration.

[0015] It still further would be desirable to provide methods and apparatus for administering brachytherapy that require only one medical practitioner.

[0016] It further would be desirable to provide methods and apparatus that yield easy measurement and maintenance of plunger depth within the needle.

[0017] It would also be desirable to provide methods and apparatus for brachytherapy that allow rapid insertion of the needle while maintaining the distance between the needle and plunger.

[0018] In view of the foregoing, it is an object of the present invention to provide methods and apparatus for brachytherapy that overcome drawbacks associated with previously-known methods and apparatus.

[0019] It is also an object of the present invention to provide methods and apparatus that allow efficient preparation of the apparatus for therapeutic administration.

[0020] It is another object to provide methods and apparatus for brachytherapy that require only one medical practitioner.

[0021] It is yet another object to provide methods and apparatus that yield easy measurement and maintenance of plunger depth within the needle.

[0022] It still further is an object of the present invention to provide methods and apparatus for brachytherapy that allow rapid insertion of the needle while maintaining the distance between the needle and plunger.

[0023] These and other objects of the present invention are accomplished by providing methods and apparatus for brachytherapy treatment of prostate cancer comprising a specialized housing that maintains needle/plunger spacing, provides easy measurement of plunger depth within the needle, requires only one practitioner to operate, and enables rapid needle insertion. The plunger is either permanently or selectively fixed with respect to the housing, while the needle is removably coupled to the housing. Either the plunger or the housing wall is threaded to receive the needle. Measurement indicia on the apparatus simplify determination of plunger depth within the needle. Optionally, a locking mechanism may be used to maintain plunger depth during needle insertion. To deliver seeds, the needle is rotated while the housing is held stationary, causing the needle to retract along the screw thread.

[0024] In a preferred embodiment, the needle is rotated manually, and includes a mechanism for first ejecting a seed-retaining plug disposed in a distal end of the needle. Alternatively, the needle may attach to a swivel that rotates the needle by pulling it proximally along the screw thread. In a still further embodiment, a pull tab may be used to rotate the needle.

[0025] Methods of using the present invention are also provided.

[0026] Additional objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims, in which:

[0027] FIG. 1 is a schematic view of a prior art method of performing brachytherapy;

[0028] FIGS. 2A-2G are schematic views detailing the prior art method in greater detail;

[0029] FIG. 3 is an isometric exploded view of a first embodiment of apparatus constructed in accordance with the present invention;

[0030] FIG. 4 is a cross-sectional view of the apparatus of FIG. 3;

[0031] FIG. 5 is a cross-sectional view of an alternative embodiment of apparatus of the present invention;

[0032] FIG. 6 is an isometric exploded view of a further alternative embodiment of the present invention comprising a swivel;

[0033] FIG. 7 is a cross-sectional view of the apparatus of FIG. 6;

[0034] FIG. 8 is an isometric exploded view of a still further alternative embodiment with a syringe swivel;

[0035] FIG. 9 is a cross-sectional view of the apparatus of FIG. 8;

[0036] FIG. 10 is an isometric exploded view of yet another alternative embodiment of apparatus of the present invention comprising a pull tab;

[0037] FIG. 11 is a cross-sectional view of the apparatus of FIG. 10;

[0038] FIG. 12 is a detail view of the cross-section of FIG. 11;

[0039] FIG. 13 is a plan view of a preferred embodiment of the apparatus of the present invention;

[0040] FIGS. 14A and 14B are, respectively, side sectional and exploded perspective views of the internal structure of the apparatus of FIG. 13; and

[0041] FIGS. 15A and 15B are, respectively, side sectional and exploded perspective views of another illustrative embodiment of the apparatus of the present invention.

[0042] The present invention provides methods and apparatus for improved administration of brachytherapy. More particularly, the present invention provides a threaded housing with that maintains the position of the plunger with respect to the needle and provides controlled retraction of the needle.

[0043] Referring now to FIGS. 1 and 2A-2G, the prior art method of performing brachytherapy is described. The method and apparatus are as taught by Peter Grimm, DO, in a pamphlet entitled, “Ultrasound Guided Implantation of the Prostate: A Practical Review Course.” As seen in FIG. 1, brachytherapy apparatus 50 comprises transrectal ultrasound probe 52, guide block 54, needle 56, plunger 58, and radioactive seeds 60. Ultrasound probe 52 is advanced through a patient's rectum R to facilitate imaging of the patient's prostate P. Prostate P surrounds the urethra U and is just proximal of the bladder B. Needle 56, loaded with seeds 60 and plunger 58, is advanced through the patient's perineum Pe into prostate P, where needle 56 is retracted and seeds 60 are delivered to the patient.

[0044] With reference to FIG. 2, a previously known seed delivery method is described in greater detail. Needle 56 has proximal end 62, sharpened distal end 64, and a lumen extending therebetween. Proximal end 62 comprises hub 66 for easy grasping of the needle. The opening at the distal tip of needle 56 is initially filled with a material that prevents seeds 60 from falling out of the needle, and may comprise, for example, bone wax that melts when placed inside the body. The needle lumen typically is filled in an alternating pattern of seeds 60 and spacers 68.

[0045] Once a required number of seeds have been loaded, plunger 58 is inserted into proximal end 62 of needle 56 and is advanced distally until it abuts the proximal-most seed. Plunger 58 comprises grip 70 at its proximal end. The distance from the distal end of grip 70 to the distal end of the plunger is equal to the length of needle 56. Thus, since seeds 60 and spacers 68 are of known length, measurement of D1, the distance plunger 58 extends proximally of needle 56 in the loaded configuration, provides verification of the number of seeds 60 located within the needle lumen, as seen in FIG. 2A.

[0046] Ultrasound probe 52 provides signals that are converted by a previously known ultrasound system to display ultrasonic image 72 of base plane BP, which is located at a tangent to the distal surface of prostate P. All positions within the prostate are determined relative to base plane BP. With seeds 60 loaded into needle 56 and the distance D1 verified; the needle, seeds, and plunger 58 are inserted through guide block 54 and into the patient until needle 56 appears as target T on ultrasonic image 72 and extends about a centimeter distal of base plane BP, as depicted in FIG. 2B. The apparatus is then retracted until target T disappears (FIG. 2C) and is once again advanced until target T just reappears (FIG. 2D). All the while, distance D1 is maintained.

[0047] Once needle 56 is aligned with base plane BP, a distance D2 between the proximal face of guide block 54 and the proximal face of hub 66 is established, as shown in FIG. 2E. D2 serves as the reference distance for determining insertion depth for all subsequent needle insertions. A first medical practitioner then holds needle 56 stationary while a second medical practitioner advances the first seed 60 to the distal tip of the needle with plunger 58, as depicted in FIG. 2F. The advancement distance equals the length BW of the plug in the distal tip of the needle.

[0048] Finally, the second medical practitioner holds plunger 58 stationary while the first practitioner rotates and proximally retracts needle 56 to sew the seeds in a line within prostate P, as shown in FIG. 2G. The needle and plunger are then removed from the patient, and the procedure is repeated at other locations as necessary.

[0049] With reference now to FIGS. 3 and 4, a first embodiment of apparatus constructed in accordance with the present invention is described. Apparatus 100 comprises housing 102, plunger 104, needle 106, and optional lock 108. Lock 108 is configured to be received in slot 110 of needle 106. Needle 106 further comprises lumen 107, an actuator comprising male screw thread 112, and measurement indicia 113. Housing 102 comprises lumen 114, in which plunger 104 is rigidly fixed, threaded bore 116 with female screw thread 118, and standard bore 120. When assembled, male thread 112 of needle 106 engages female thread 118 of housing 102, and plunger 104 extends into lumen 107 of needle 106.

[0050] A method of using apparatus 100 in accordance with the principles of the present invention is now described. Needle 106, loaded with seeds 60 and spacers 68 in lumen 107, is inserted through bore 120 until male thread 112 of needle 106 just mates with female thread 118 of bore 116.

[0051] At this point, plunger 104 extends partially within lumen 107 of needle 106, so that plunger 104 just contacts the proximal-most seed 60. Also, slot 110 of needle 106 is just distal of the opening to bore 120. Lock 108 is removably received within slot 110 and ensures that plunger 104 is not advanced distally with respect to needle 106 until the needle is inserted within a patient's prostate. Lock 108 ensures that distance D1 between the proximal end of needle 106 and proximal base 122 of bore 116 (which is roughly equal to the length of bore 116) is maintained during insertion. Since D1 is positively maintained during insertion, the apparatus of the present invention should advantageously cause medical practitioners to be less reticent about rapid insertion of the needle into a patient.

[0052] Measurement indicia 113 of needle 106 permit easy determination of distance D1, and, thus, verification of the number of seeds 60 contained within lumen 107 of needle 106. As an illustrative example, D1 is such that the proximal-most indicator mark 113 extends beyond the distal end of housing 102. If this marking is ‘0’, the proximal end of needle 106 is in contact with proximal base 122 of bore 116. If it is ‘1’, there is one centimeter of separation, etc.

[0053] After insertion of the needle into the patient, lock 108 is removed, thereby allowing relative movement between plunger 104 and needle 106. Initially, needle 106 is held stationary while housing 102 is rotated to advance the distal-most seed 60 to the tip of needle 106. Then, housing 102 is held stationary while needle 106 is rotated. This causes needle 106 to retract proximally along thread 118 while plunger 104 remains stationary, thereby controllably sewing seeds 60 in a row in the prostate. Since the sewing motion is simplified, compared to prior art apparatus 50, only one practitioner is required to perform the procedure.

[0054] The distance D1 may be altered as needed by altering the length of bore 116 and, thus, the length of housing 102. Alternatively, bore 116 may be of a standard length in excess of that required for D1. Needle 106 then may comprise multiple slots 110 along its length to receive lock 108. The distance D1 then may be fixed at a variety of lengths.

[0055] Referring now to FIG. 5, an alternative embodiment of the present invention is disclosed. Apparatus 130 comprises housing 132, plunger 134, needle 136, and lock 138. Lock 138 is configured to be received in slot 140 of needle 136. Needle 136 further comprises lumen 137, female screw thread 142 along the walls of the proximal portion of its lumen, and measurement indicia (not shown). Plunger 134 comprises male screw thread 144 along its proximal end. Housing 132 comprises lumen 146, in which plunger 134 is rigidly fixed, and bore 148.

[0056] Needle 136, loaded with seeds 60 and spacers 68, is inserted through bore 148 until female thread 142 of needle 136 just mates with male thread 144 of plunger 134. Thus, apparatus 130 is similar to apparatus 100, except that needle 136 threadingly engages plunger 134, rather than the housing.

[0057] With reference to FIGS. 6 and 7, a further alternative embodiment of the present invention is detailed. Apparatus 150 comprises housing 152, plunger 154, needle 156, and lock 158. Lock 158 is configured to be received in slot 160 of needle 156. Needle 156 further comprises lumen 157, male screw thread 162, measurement indicia 163, and swivel 164 including cord 166. Housing 152 comprises lumen 168, in which plunger 154 is rigidly fixed; threaded bore 170 with female screw thread 172; and a standard bore (not shown) similar to bore 120 of apparatus 100. Housing 152 further comprises cord bore 174 through which cord 166 passes out of housing 152.

[0058] In use, cord 166 is threaded through cord bore 174 and the male and female screw threads are engaged as described hereinabove with reference to apparatus 100. Needle 156 then may be retracted proximally with respect to housing 152 by holding the housing stationary and pulling cord 166 proximally. The needle rotates and retracts within the screw thread, while swivel 164 moves proximally in bore 168, but does not rotate.

[0059] Referring now to FIGS. 8 and 9, a still further alternative embodiment of the present invention is described. Apparatus 180 comprises housing 182, plunger 184, needle 186, syringe swivel 188, and lock 190. Lock 190 is configured to be removably received in slot 192 of needle 186. Housing 182 comprises lumen 194, in which plunger 184 is rigidly fixed; threaded bore 196 with female screw thread 198; and a standard bore (not shown) similar to bore 120 of apparatus 100. Housing 182 is formed in two halves 200 and 202 joined at hinge 204. Hinge 204 preferably is a ‘living hinge’ as may be constructed using polymers, such as polypropylene, and previously known manufacturing techniques. Needle 186 further comprises lumen 187, male screw thread 206, measurement indicia 207, and swivel attachment 208. Syringe swivel 188 comprises swivel attachment 210, bore 212, and enlarged proximal end 214, and is formed in two halves 216 and 218 joined at hinge 220. As with hinge 204, hinge 220 preferably comprises a living hinge.

[0060] Housing 182 and syringe swivel 188 are opened at hinges 204 and 220, respectively, so that swivel attachments 208 and 210, and the male and female screw threads, engage each other. The housing and syringe swivel are then closed. After insertion into a patient, needle 186 may be retracted proximally with respect to housing 182 by holding the housing stationary and retracting enlarged end 214 of syringe swivel 188 proximally. Needle 186 rotates and retracts within the screw thread while syringe swivel 188 moves proximally but does not rotate.

[0061] With reference to FIGS. 10-12, yet another alternative embodiment of the present invention is described. Apparatus 230 comprises housing 232, plunger 234, needle 236, pull tab 238, and lock 240. Lock 240 is configured to be received in slot 242 of needle 236. Needle 236 further comprises lumen 237, male screw thread 244, and measurement indicia 245. Housing 232 comprises lumen 246, in which plunger 234 is rigidly fixed, threaded bore 248 with female screw thread 250, standard bore 252, and slot lumen 254 configured to receive pull tab 238. Slot lumen 254 is preferably located just off center of the radial axis of housing 232 and communicates with bore 252. Pull tab 238 comprises grip 256 and female threads 258.

[0062] Needle 236, loaded with seeds 60 and spacers 68, is inserted through bore 252 into threaded bore 248 until male thread 244 of needle 236 mates with both female screw thread 250 of housing 232 and female threads 258 of pull tab 238. As most clearly illustrated in FIG. 11, needle 236 then may move relative to housing 232 simply by holding housing 232 stationary and pulling or pushing pull tab 238. Pulling tab 238 causes needle 236 to rotate and proximally retract in a controlled fashion along screw thread 250 of housing 232, and along threads 258 of pull tab 238, thereby sewing the seeds along the needle track.

[0063] Whereas the preceding embodiments contemplate that the needle include a thread that acts as an actuator in conjunction with a thread in the housing to retract the needle, it would be preferable to provide embodiments adapted to accept commercially, available brachytherapy needles. Two such embodiments, which work in accordance with the principles of the present invention set forth hereinabove, are not described.

[0064] Referring now to FIGS. 13 and 14, a preferred embodiment of the present invention suitable for commercial manufacture is described. Apparatus 260 includes housing 261 having spiral groove 262 on its interior surface, knob 263 rigidly coupled to actuator 264, needle coupling 265 and stop mechanism 266 coupled to plunger 267. Plunger 267 is disposed within the lumen of seed-laden needle 275 when needle 275 is coupled to needle coupling 265. In this embodiment, plunger 267 is selectively set to a predetermined seed length using stop mechanism 266, before needle 275 is attached to needle coupling 265.

[0065] Needle coupling 265 is disposed for sliding translation and rotation in central bore 268 of actuator 264, and includes pin 269 that extends through elongated slot 270 of actuator 264 and extends into spiral groove 262. Actuator 264 is rotatably disposed in housing 261. Rotation of knob 263 causes rotation of actuator 264, thereby driving pin 269 along spiral groove 262 and elongated slot 270. This is turn causes needle coupling to be rotated and advanced or retracted through central bore 268 of actuator 264. When a seed-laden needle is coupled to needle coupling 265, rotation of knob 263 causes the needle to be rotated and retracted into housing 261. Plunger 267, which remains stationary during needle retraction, causes the seeds to be ejected from the distal tip of the needle.

[0066] Stop mechanism 266 permits the number of seeds to be varied from needle to needle during a particular procedure, and includes a coarse adjustment for the number of seeds used in a given needle, and a fine adjustment feature that permits the plug at the distal end of the needle to be ejected without changing the position of the distal tip of the needle. Stop mechanism includes stop body 271 having ratchet 272 slidably disposed in lumen 273, wherein the travel is limited by pin 274 that extends into elongated slot 276 (this subassembly is shown in exploded view in the upper right hand portion of FIG. 14B). Stop body 271 includes a series of partial circumference through-wall slits 277 arranged along its length at predetermined distances (e.g., 1 cm apart), and includes fiducial markings F on the upper surface of the stop body (see FIG. 13) aligned with slits 277.

[0067] Distal end 278 of stop body 271 extends through rear cover 279 of housing 261 and window 280 of lock 281, and is affixed to collar 282. Rear cover 279 includes notch 283 that accepts tab 284 of lock 281 and spring 285. Tab 284 includes button 286 and is biased upward by spring 285. Button 286 permits lock 281 to be depressed to permit stop body 271 to be advanced distally through window 280. Spring 285 causes the lower edge of window 280 to engage one of slits 277 and a corresponding one of teeth 287 of ratchet 272 when button 286 is released.

[0068] Stop body knob 288 is affixed to proximal end 289 of stop body 271. Distal end 290 of ratchet 272 extends through spring 291 and is rigidly coupled to ratchet knob 292. Spring 291 biases ratchet knob 292 in a proximal direction. Teeth 287 of ratchet 272 include sloped proximal edges 293. The sloped proximal edges of teeth 287 permit ratchet 272 to be advanced through window 280 of lock 281 in the distal direction by urging ratchet knob 292 in the distal direction, while simultaneously maintaining engagement between a selected slit 278 in stop body 271 and lock 281. This in turn permits plunger 267 to be advanced one unit in the distal direction, e.g., to eject the needle plug, while maintaining the position of the distal tip of stationary.

[0069] Operation of apparatus 260 is now described. To use apparatus 260, the clinician rotates knob 263 to advance needle coupling 265 to its distal-most position, and depresses button 286 to ensure that lock 281 is disengaged from ratchet 272 and ratchet knob 292 is biased in the proximal direction by spring 291. The clinician then sets the seed length by depressing button 286 and advancing or retracting stop body 271 using stop body knob 288 until the desired fiducial mark F is aligned with the endface of rear cover 279. Button 286 then is released to capture the corresponding slit in stop body 271.

[0070] A seed-laden needle is then slid proximal-end first over plunger 267 and the luer of the needle affixed to needle coupling 265, for example, using luer threads (not shown) disposed in distal end of needle coupling 265. The needle and apparatus of the present invention then is inserted into the patient's prostrate using a needle guide and an rapid insertion technique. Once the needle position is confirmed, e.g., using ultrasound, the clinician urges ratchet knob 292 in the distal direction to eject the plug from the distal tip of the needle. In particular, when ratchet knob 292 is advanced, window 280 of lock 281 rides along the sloped edge of tooth 288 and locks into the next proximal-most tooth 288 of ratchet 272, while stop-body 271 remains engaged with lock 281. This step is similar to that illustrated in FIG. 2F.

[0071] Once the plug is ejected from the distal end of the needle, housing 261 is held stationary by the clinician in one hand while knob 263 is rotated by the other. Rotation of knob 263 causes actuator 264 to rotate within housing 261, thereby causing pin 269 to be retracted along spiral groove 262 in housing 261. This in turn causes needle coupling 265 to be retracted into central bore 268 of actuator 264, thereby also rotating the needle attached to needle coupling. Because plunger 267 remains fixed at the depth selected on stop body relative to the housing, rotation and retraction of the needle causes the seeds to be ejected into the prostrate. Accordingly, a single clinician can implant seeds faster and more accurately than the conventional method using two clinicians.

[0072] When all the seeds in the needle have been implanted, the needle is removed from the patient and knob 263 is rotated in the reverse direction to fully expose needle coupling 265. The spent needle is removed from needle coupling 265, and then the process described above is repeated for subsequent needles, until the procedure is completed. Apparatus 260 preferable can be manufactured from low-cost plastic components with few machined or stamped metal components, and is therefore disposable after use for a single patient.

[0073] Referring now to FIGS. 15A and 15B, an alternative embodiment of the apparatus suitable for commercial manufacture is described. Apparatus 300 is less preferred than the embodiment of FIGS. 13 and 14, and employs several machined components. Accordingly, the embodiment of FIG. 15 may be more suitable for manufacture from metallic alloys, and therefore autoclavable for repeated use.

[0074] Apparatus 300 comprises many of the components employed in the embodiment of FIGS. 13 and 14, including housing 301 having spiral groove 302 on its interior surface, knob 303 rigidly coupled to actuator 304, needle coupling 305 and stop mechanism 306 coupled to plunger 307. Plunger 307 is disposed within the lumen of a seed-laden needle when such a needle is coupled to needle coupling 305. As in the previous embodiment, plunger 307 is selectively set to a predetermined seed length using stop mechanism 306, before the needle is attached to needle coupling 305.

[0075] Needle coupling 305 is disposed for sliding translation and rotation in central bore 308 of actuator 304, and includes pin 309 that extends through elongated slot 310 of actuator 304 and extends into spiral groove 302. Actuator 304 is rotatably disposed in housing 301, so that rotation of knob 303 causes rotation of actuator 304, thereby driving pin 309 along spiral groove 302 and elongated slot 310. This is turn causes needle coupling to be rotated and advanced or retracted through central bore 308 of actuator 304. When a seed-laden needle is coupled to needle coupling 305, rotation of knob 303 causes the needle to be rotated and retracted into housing 301. Plunger 307, which remains stationary during needle retraction, causes the seeds to be ejected from the distal tip of the needle.

[0076] Stop mechanism 306 performs the same function as stop mechanism of 266 of the embodiment of FIGS. 13 and 14 by permitting the number of seeds to be varied from needle to needle during a particular procedure. This embodiment also includes a coarse adjustment for the number of seeds used in a given needle, and a fine adjustment feature that permits the plug at the distal end of the needle to be ejected without changing the position of the distal tip of the needle.

[0077] Stop mechanism 306 includes stop body 311 having threaded rod 312 extending therethrough. Stop body 311 includes a series of partial circumference through-wall slits 313 arranged along its length at predetermined distances (e.g., 1 cm apart), and includes fiducial markings F on the upper surface of the stop body aligned with slits 313. Stop body also includes a longitudinally-oriented slot that permits threaded pawl 314 to engage the threads of threaded rod 312.

[0078] Distal end 315 of stop body 311 extends through rear cover 319 of housing 301 and window 320 of lock 321, and is affixed to collar 322. Rear cover 319 includes notch 323 that accepts upper and lower tabs 324 and 325 of lock 321, spring 326, and pawl 314. Upper tab 324 serves as a button and is biased upward by spring 326. Upper tab 324 permits lock 321 to be depressed to permit stop body 311 to be advanced distally through window 320. Spring 326 causes the lower edge of window 320 to engage one of slits 313, and for pawl 314 to engage threaded rod 312, when the upper tab is released.

[0079] Distal end 328 of threaded rod 312 is affixed to sleeve 329. Sleeve 329 is coupled to cap 330, which is disposed in bore 331 in stop knob 332. Cap 330 is keyed to the shape of bore 331, so that rotation of stop knob 332 causes rotation of cap 330, sleeve 329 and threaded rod 312. Collar 334 is affixed to proximal end 335 of stop body 311, and includes circumferential groove 336. Stop knob 332 includes pin 337 that extends into groove 336, thereby permitting rotation of stop knob 332, but not translation. Spring 338 is captured on sleeve 329 between collar 334 and cap 330, and biases cap 330 in a proximal direction.

[0080] Rotation of stop knob 332 causes rotation of cap 332, sleeve 329 and threaded rod 312. Because threaded rod 312 is threadedly engaged with pawl 314 by the biasing action of spring 326, rotation of stop knob 332 causes threaded rod 312 to advance distally, thereby causing plunger 307 to advance in the distal direction. Accordingly, after the needle has been inserted into the patient, stop knob 332 may be rotated to eject the plug at the distal end, while maintaining the position of the distal tip of stationary.

[0081] Operation of apparatus 300 is similar to that of the embodiment of FIGS. 13 and 14, and is now described. To use apparatus 300, the clinician rotates knob 303 to advance needle coupling 305 to its distal-most position, and depresses upper tab 324 to ensure that lock 321 is disengaged from slit 313 and pawl 314 is disengaged from threaded rod 312, whereby cap 330 is biased in the proximal direction by spring 338. The clinician then sets the seed length by depressing upper tab 324 of lock 321 and advancing or retracting stop body 311 using stop knob 332 until the desired fiducial mark F is aligned with the endface of rear cover 319. Upper tab 324 then is released to capture the corresponding slit in stop body 311, and so that pawl 314 engages threaded rod 312.

[0082] A seed-laden needle is then slid proximal-end first over plunger 307 and the luer of the needle affixed to needle coupling 305, for example, using luer threads (not shown) disposed in distal end of needle coupling 305. The needle and apparatus of the present invention then is inserted into the patient's prostrate using a needle guide and an rapid insertion technique. Once the needle position is confirmed, e.g., using ultrasound, the clinician rotated stop knob 332 to advance threaded rod 312 and plunger 307 to eject the plug from the distal tip of the needle.

[0083] Once the plug is ejected from the distal end of the needle, housing 301 is held stationary by the clinician in one hand while knob 303 is rotated by the other. Rotation of knob 303 causes actuator 304 to rotate within housing 301, thereby causing pin 309 to be retracted along spiral groove 302 in housing 301. This in turn causes needle coupling 305 to be retracted into central bore 308 of actuator 304, thereby also rotating the needle attached to needle coupling. Because plunger 307 remains fixed at the depth selected on stop body relative to the housing, rotation and retraction of the needle causes the seeds to be ejected into the prostrate.

[0084] When all the seeds in the needle have been implanted, the needle is removed from the patient and knob 303 is rotated in the reverse direction to fully expose needle coupling 305. The spent needle is removed from needle coupling 305, and then the process described above is repeated for subsequent needles, until the procedure is completed.

[0085] Although particular embodiments of the present invention have been described above in detail, it will be understood that this description is merely for purposes of illustration. Specific features of the invention are shown in some drawings and not in others; this is for convenience only, and any feature may be combined with another in accordance with the invention. Further variations will be apparent to one skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.