US 20040220444 A1
Methods and apparatus are provided for improved brachytherapy treatment of prostate disease. The apparatus provides for angular reorientation of a needle template with respect to an ultrasound probe during brachytherapy administration. Angular reorientation is expected to beneficially overcome anatomical constraints, such as skeletal structures, that may limit a medical practitioner's ability to deliver radioactive brachytherapy seeds into a prostate in proper alignment.
1. Apparatus for improved positional control during administration of brachytherapy, the apparatus comprising:
a needle guide body having a needle guide channel sized to slidably receive a standard brachytherapy needle;
a support for securing the needle guide body to a brachytherapy apparatus; and
means for disposing the needle guide body at a selected angular and positional orientation relative to the brachytherapy apparatus.
2. The apparatus of
3. The apparatus of
4. The apparatus of
5. Apparatus for improved positional control during administration of brachytherapy, the apparatus comprising:
a needle guide body having a plurality of needle guide channels, each one of the needle guide channels sized to slidably receive a standard brachytherapy needle; and
a support for securing the needle guide body to a brachytherapy apparatus, wherein the needle guide body is configured for angular and positional orientation relative to the brachytherapy apparatus having an ultrasound probe.
6. The apparatus of
7. The apparatus of
8. The apparatus of
9. The apparatus of
10. The apparatus of
11. The apparatus of
12. The apparatus of
13. The apparatus of
14. The apparatus of
15. The apparatus of
16. A method for administering brachytherapy, the method comprising:
providing an apparatus comprising an ultrasound probe, a frame rigidly disposed in relation to the ultrasound probe, a needle guide body comprising at least one needle guide channel, the needle guide body affixed to the frame such that the needle guide channel may be angularly orientated with respect to the probe;
longitudinally positioning the ultrasound probe through the patient's rectum to facilitate imaging of the patient's prostrate and reference plane; and
angularly orienting the needle guide channel at a desired angle in real-time with respect to the ultrasound probe.
17. The method of
18. The method of
 This application is a continuation-in-part of U.S. patent application Ser. No. 10/128,616, filed on Apr. 23, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 09/648,091, filed on Aug. 25, 2000, now U.S. Pat. No. 6,398,711.
 This invention relates to improved apparatus and methods for the treatment of prostate cancer. More particularly, the present invention provides an apparatus and method that provides for multi-angle positioning for more effective administration of brachytherapy.
 Excluding non-melanoma skin cancers, prostate cancer is the most common cancer afflicting American men. The American Cancer Society estimates that over 189,000 new cases will be diagnosed in the U.S. in the year 2002 alone, and that nearly 30,200 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%.
 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 aggressiveness and differentiation, 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 beyond the prostate with no distant metastasis. By Stage D, cancer has spread to the regional lymph nodes.
 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.
 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 7-10 days. Possible complications include impotence and urinary incontinence.
 Internal radiation therapy or brachytherapy has recently been developed and holds great promise for the treatment of early stage prostate cancer. Radioactive pellets or seeds of, for example, iodine-125, palladium-103, or iridium-192, are deposited directly and permanently into the prostate through a small incision. Imaging techniques, such as transrectal ultrasound, CT scans, or MRI, are used to accurately guide placement of the radioactive material. Advantageously, radiation from the brachytherapy seeds is administered directly to the prostate with less damage to surrounding tissues, delivering a substantially higher radiation dosage to the prostate than to the surrounding tissues, as compared to external beam radiation therapy. The procedure need only be performed once, and impotence and urinary incontinence complications are significantly reduced, as compared to prostate removal procedures.
 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 delivers the seeds in a line within the prostate.
 The seeds, which are permanently implanted, give off radiation for weeks or months. Their presence causes little discomfort, and they remain in the prostate after decay of the radioactivity. For several weeks following needle insertion, patients may experience pain in the perineal area, and urine may have a red-brown discoloration.
 Although, when performed correctly, radioactive seed implantation may provide several benefits as compared to prostate removal and other techniques, current surgical apparatuses and methods for delivering the seeds to target locations within the prostate are somewhat crude and are subject to practitioner error. U.S. Pat. No. 5,871,448 to Ellard, for example, describes apparatus similar to that currently in widespread use. The apparatus includes a needle template with a template holder. The template may be moved longitudinally along a track to alter the distance between the template and a patient's perineum. The template holder is then rigidly affixed to the track, and brachytherapy needles are passed through the needle template to stabilize the needles prior to insertion through the patient's perineum. A drawback of the Ellard device is that, apart from longitudinal adjustment, a medical practitioner is not able to alter the orientation of the template.
 U.S. Pat. No. 5,957,935 to Brown et al. describes a disposable needle template that need not be painstakingly sterilized. It further discloses a mount for the template that may be oriented in multiple planes. Specifically, the template may be positioned longitudinally, horizontally, and vertically. Although Brown's apparatus may provide improved needle template orientation capabilities as compared to Ellard's apparatus, it permits constrained movement, and does not allow simultaneous reorientation in multiple planes, as is necessary to change the angle of attack between the template and the patient.
 A preferred angular orientation of the needle template may vary from needle to needle during a procedure due to anatomical constraints, including skeletal structures. Thus, a template that allows only one angular orientation is not optimal and may lead to incorrect placement of radioactive seeds within a patient's prostate.
 U.S. Pat. No. 5,626,829 to Koutrouvelis provides a stereotactic assembly for orienting a template vertically, horizontally, rotatably, and angularly. While the assembly may be effective for the transgluteal brachytherapy procedure described by Koutrouvelis, it is not tailored for the more commonly used transperineal approach. For example, it does not provide for longitudinal adjustment of the needle template. Furthermore, the assembly is large and may prove cumbersome in the smaller surgical field of transperineal procedures.
 European Patent Application EP 0 995 406 A1 by Yanof et al. provides a multi-apertured grid lattice positionable by a stereotactic arm assembly. While the assembly may be effective for a brachytherapy procedure after volumetric imaging of the patient as described therein, it is not suitable when used in conjunction with a transrectal ultrasound probe. Performing brachytherapy with a transrectal probe requires exact positioning and orientation of the needle and needle guide relative to the probe. The stereotactic assembly described by Yanof et al. provides too many degrees of freedom, and as a consequence requires “position resolvers” to indicate its spatial position relative to a reference frame. Furthermore, the device does not allow angular reorientation in real-time in conjunction with a detection device.
 In view of the drawbacks associated with orienting previously-known needle templates, it would be desirable to provide methods and apparatus that overcome such drawbacks.
 It further would be desirable to provide methods and apparatus with improved orientation capabilities, sized to permit use in the surgical field of standard, transperineal brachytherapy procedures in conjunction with a transrectal ultrasound probe.
 In view of the foregoing, it is an object of the present invention to provide apparatus and methods for orientating a needle guide that overcome drawbacks associated with previously-known methods and apparatus.
 It is also an object of the present invention to provide methods and apparatus with improved orientation capabilities, sized to permit use in the surgical field of standard, transperineal brachytherapy procedures.
 It is a further object of the present invention to provide methods and apparatus for orienting a needle guide in a manner to access the broadest range of available orientations, thereby providing a more precise and accurate brachytherapy procedure.
 It is a still further object of the present invention to provide methods and apparatus for orienting a needle guide in real-time in conjunction with a transrectal ultrasound probe.
 These and other objects of the present invention are accomplished by providing methods and apparatus for angular repositioning of the needle guide with respect to an ultrasound probe. When used in conjunction with previously-known apparatus for longitudinal, horizontal, and vertical orientation of the template, the present invention provides enhanced control over needle template orientation, so that brachytherapy needles may be inserted in a manner that avoids skeletal structures.
 Methods of using the present invention also are provided.
 The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:
FIG. 1 is a schematic view of a prior art method of performing brachytherapy;
FIGS. 2A-2G are schematic views detailing the prior art method in greater detail;
FIGS. 3A and 3B are, respectively, a proximal view and a side view of an apparatus constructed in accordance with an embodiment of the present invention and installed on a brachytherapy device;
FIGS. 4A and 4B are, respectively, an exploded isometric view and an exploded cross-sectional view of the guide body and the socket of the present invention, illustrating axes of rotation and means for securing the guide body to the socket;
FIGS. 4C and 4D are isometric views of the guide body of the present invention depicting means for rotation about, respectively, the horizontal axis and the vertical axis;
FIGS. 5A and 5B are, respectively, a proximal view and an isometric view of an embodiment of the present invention detailing means for, respectively, vertical and horizontal repositioning;
FIGS. 6A-6D depict proximal and isometric views of alternative methods for affixing the needle guide of the present invention to a standard brachytherapy apparatus, detailing means for horizontal and vertical repositioning;
FIG. 7 is an isometric view of a linear array embodiment of the present invention;
FIGS. 8A and 8B are, respectively, an isometric view and a side cross-sectional view of an alternative embodiment of the present invention;
FIGS. 9A and 9B are, respectively, an isometric view and a top view of another embodiment of the present invention, with FIG. 9B depicting angular reorientation of the apparatus;
FIGS. 10A and 10B are, respectively, an isometric view and a top cross-sectional view of still another embodiment of the present invention;
FIGS. 11A-11C are views of another embodiment of the present invention, in which FIG. 11A depicts an isometric view and FIGS. 11B and 11C are top cross-sectional views of different angular configurations; and
FIGS. 12A-12D are views of still another embodiment of the present invention, in which FIG. 12A depicts an isometric view, FIG. 12B details means for attachment of the guide channels to the planes, and FIGS. 12C and 12D depict side views of different angular orientations of the apparatus.
 The present invention provides methods and apparatus for improved administration of brachytherapy. More particularly, the present invention provides an apparatus comprising a needle guide that allows angular repositioning of the guide to the ultrasound device, thereby providing improved orientation capabilities for implantation of radioactive seeds.
 Referring now to FIGS. 1 and 2A-2G, the prior art method of performing brachytherapy is described. The method and apparatus as described here are 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, needle template 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 needle template 54, through the patient's perineum Pe, and into prostate P, where needle 56 is retracted and seeds 60 are delivered to the patient.
 Needle template 54 is attached to template mount 55, which is slidably received on track 53 and may be longitudinally repositioned with respect to ultrasound probe 52. Alternatively, mount 55 may be rigidly attached to track 53, in which case the track may be longitudinally repositioned with respect to ultrasound probe 52.
 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 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.
 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.
 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 needle template 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.
 Once needle 56 is aligned with base plane BP, a distance D2 between the proximal face of needle template 54 and the proximal face of hub 66 is established, as shown in FIG. 2E. D2 may be altered via template mount 55 by longitudinally repositioning template 54 relative to ultrasound probe 52. 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 bone wax used to plug the tip.
 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.
 While the previously known apparatus used to position ultrasound probe 52 and needle template 54 may allow longitudinal, vertical, and/or horizontal orientation of needle template 54, the apparatus does not allow angular reorientation of the template during a brachytherapy procedure. Angular reorientation is expected to beneficially overcome anatomical constraints, such as skeletal structures, that may limit the medical practitioner's ability to deliver radioactive brachytherapy seeds into the prostate in proper alignment.
 With reference now to FIGS. 3A and 3B, apparatus constructed in accordance with a first embodiment of the present invention is described. Needle guide apparatus 100 is installed upon frame 80 of brachytherapy apparatus 50. Frame 80 provides a stable platform that allows for longitudinal repositioning of ultrasound probe 52. Accordingly, the proximity of frame 80 and apparatus 100 to ultrasound probe 52 provides for a more accurate angular reorientation relative to the longitudinal axis of the ultrasound probe.
 Needle guide apparatus 100 comprises needle guide body 110, socket 120, support 130 and needle guide channel 150. Socket 120 is configured to retain guide body 110, while allowing angular reorientation of the guide body and guide channel 150 therein. The apparatus is secured onto frame 80 by means of support 130.
 Referring now to FIGS. 3B and 4A, guide channel 150 forms a substantially linear passage through guide body 110 that communicates with proximal aperture 160 and distal aperture 165. The angular orientation of guide channel 150 is determined by the angular orientation of guide body 110. Guide channel 150 and its proximal and distal apertures are sized for slidably receiving a standard brachytherapy needle. A needle slidably received within guide channel 150 in the foregoing manner adopts an angular orientation substantially the same as that of the guide channel. The guide channels in the other embodiments described herein are sized accordingly to provide substantially the same needle guidance functions as that of guide channel 150.
 Referring now to FIGS. 4A and 4B, socket 120 is configured to retain guide body 110 while enabling angular reorientation of guide body 110 and needle guide channel 150. For example, guide body 110 may independently rotate about vertical axis 190 and horizontal axis 195. Enabling rotation about these two axes allows guide channel 150 to access a full range of angular orientations with respect to the longitudinal axis of the brachytherapy apparatus.
 Referring again to FIGS. 4A and 4B, an embodiment to enable rotation of guide body 110 within socket 120 is illustrated. Guide body 110 further comprises recessed slot 175 that is disposed along meridian 115, the meridian passing through both proximal and distal apertures. Socket 120 comprises retaining knob 170 that is centrally disposed on the interfacial surface of the socket. Referring now to FIGS. 4C and 4D, knob 170 and slot 175 are configured such that knob 170 is retained securely within slot 175, thereby attaching guide body 110 to socket 120. Knob 170 and slot 175 are further configured to allow the knob to slidably translate along the length of slot 175 while following meridian 115.
 Referring again to FIG. 4C, a mechanism for rotating guide body 110 about horizontal axis 195 is provided. Rotating the guide body about horizontal axis 195 is accomodated by knob 170 following meridian 115 while slidably moving within slot 175. In this manner, the rotation may be accomplished while guide body 110 remains secured by the socket. Referring again to FIG. 4D, knob 170 is further configured so as not to impede rotation of guide body 110 about vertical axis 190 while the guide body is retained within the socket. Rotation about both axes in the foregoing manner allows guide body 110 to access substantially all angular orientations bounded by the limits of each rotational means.
 With reference to FIGS. 5A and 5B, means for horizontal and vertical repositioning of apparatus 100 with respect to ultrasound probe are illustrated. Support 130 may further comprise, for example, telescoping member 136 that allows for vertical repositioning of guide channel 150, thereby modifying height D3. Referring now to FIG. 5B, frame 80 may further comprise slot 138 disposed thereon, which is configured to receive support 130 of apparatus 100. Support 130 is slidably movable along the length of slot 138, thereby allowing horizontal repositioning of apparatus 100 with respect to the brachytherapy apparatus and the ultrasound probe.
 With reference to FIGS. 6A-6D, alternative embodiments for mounting the needle guide apparatus on frame 80 are depicted. Referring now to FIGS. 6A and 6B, mount 132 comprises frame 134 to which socket 120 and guide body 110 are affixed. In this embodiment, mount 132 may further comprise mechanisms that allow vertical or horizontal repositioning of the needle guide apparatus relative to frame 80 and ultrasound probe 52. For example, frame 134 may comprise telescoping member 136 that allows repositioning of height D3. Horizontal repositioning may be accomplished by, for example, means of slot 138 disposed on frame 80 with frame 134 received therein. Slidable repositioning of frame 134 within slot 138 provides for horizontal repositioning of the needle guide apparatus.
 In still another embodiment as illustrated in FIGS. 6C and 6D, support 140 comprises vertical segment 142 and cantilevered horizontal arm 144, to which is affixed socket 120 and guide body 110. Segment 142 may comprise telescoping mechanism 146 that allows vertical repositioning of the guide apparatus, thereby adjusting height D4. To adjust distance D5, cantilevered arm 144 is slidably movable with respect to vertical segment 142, thereby providing a means for horizontal repositioning of guide channel 150. Horizontal, vertical and angular repositioning of the needle guide in foregoing manners may be controlled by automated means, such as are known in the art.
 With respect to FIG. 7, an alternative embodiment of the present invention is described. In this embodiment, guide apparatus 200 comprises a plurality of guide bodies 210 conjoined linearly following common axis 250, each guide body 210 comprising a guide channel 220. Guide channels 220 are arranged substantially perpendicular to common axis 250. Guide apparatus 200 is installed on frame 80 of the brachytherapy device via shaft 230 that allows rotation about axis 250, thereby enabling angular reorientation of guide channels 220 with respect to the longitudinal axis of the ultrasound probe. Apparatus 200 allows independent rotation of each guide body 210 with respect to the other guide bodies.
 In another embodiment of the present invention, guide apparatus 300 comprises guide body 310 as depicted in FIGS. 8A and 8B. Guide body 310 comprises proximal plane 360 and distal plane 365 directed towards the practitioner and the patient, respectively. Guide body 310 further comprises orthogonal arrays of distal apertures 370 and proximal apertures 375 disposed on the distal and proximal planes, respectively. Each proximal aperture 370 communicates with its corresponding distal aperture 375 by guide channel 320, the guide channels substantially the same as those described hereinabove. Guide apparatus 300 may be installed on a standard brachytherapy device by shaft 330, which provides vertical axis 360 about which the guide apparatus may rotate for angular reorientation. Handle 390 may be disposed on guide body 310 to provide a mechanical advantage for guide body rotation.
 Referring now to FIGS. 9A and 9B, guide apparatus 300 further comprises guide posts 340 instead of aforementioned shaft 330. Guide posts 340 are received within curved guide tracks 390 disposed on the surface of frame 80. When installed in this manner, guide apparatus 300 may be angularly reoriented by slidably moving guide posts 340 within their respective guide tracks, as depicted in FIG. 9B.
 In still another embodiment as depicted in FIGS. 10A and 10B, curved guide body 410 of needle guide apparatus 400 comprises proximal convex surface 460 and distal concave surface 465. Proximal apertures 470 and distal apertures 475 are disposed on, respectively, the proximal and distal surfaces. Needle guide channels 420 communicate between corresponding apertures such that the longitudinal axis of each guide channel 420 is substantially normal to both surfaces. Therefore, the guide channels disposed within curved guide body 410 in the foregoing manner provide a spectrum of angular orientations relative to the longitudinal axis of ultrasound probe 52. Guide body 410 may be composed of a malleable material, such as plastic, metal, synthetic polymer, natural polymer or a metal frame embedded within or supporting a plastic or polymer body, thereby allowing the medical practitioner to modify its curvature, hence adjusting the angular orientations of the guide channels therein.
 With reference to FIGS. 11A-11C, another embodiment of the guide apparatus is illustrated. Guide apparatus 500 comprises two or more guide body sections 570 that are joined by hinges 540, thereby forming a single articulated guide body 510. These hinges are configured to allow the guide body sections to be oriented at different angles with respect to each other as illustrated in FIGS. 11B and 11C. Guide channels 520 are disposed in orthogonal arrays on each section 570, the guide channels being substantially the same as those described hereinabove. Guide channels 520 communicate through each section 570, each guide channel having a longitudinal axis substantially normal to its respective section.
 Referring now to FIG. 12A, guide apparatus 600 comprises proximal plane 660 and distal plane 665 positioned in parallel with respect to each other. Disposed therebetween are a plurality of rigid guide channels 620 that connect distal plane 660 to proximal plane 665. As in the other embodiments described herein, the guide channels are in communication with their respective proximal apertures 670 and distal apertures 675. Disposed at the ends of the guide channels are flexible junctions 680. Flexible junctions 680, which may be ball joints 690 as illustrated in FIG. 12B, allow guide channels 620 to rotate with respect to the distal and proximal planes while remaining in communication with their respective proximal and distal apertures. In this manner, proximal plane 660 may be repositioned horizontally, vertically, or a combination thereof with respect to distal plane 665 while remaining parallel and connected thereto.
 In the configuration depicted in FIG. 12C, distal plane 665 and proximal plane 660 are positioned such that the longitudinal axis of each guide channel 620 is substantially normal to the planes. Hence, a needle slidably received by a guide channel in this configuration is oriented also substantially perpendicular to the planes. Angular reorientation of the guide channels is accomplished by repositioning proximal plane 660 vertically, horizontally, or a combination thereof with respect to distal plane 665. As in the example depicted in FIG. 12D, vertical repositioning of the planes in the foregoing manner causes the guide channels connected therebetween to rotate with respect to both planes in order to remain in communication with their respective apertures. Rotation in this manner results in angular reorientation of the guide channels.
 With reference to FIGS. 3-12, it is understood that the features described in the embodiments depicted therein may be combined, thereby providing their respective advantages to a single apparatus.
 Referring now to FIGS. 3A-5B, as well as FIGS. 1-2G, a method of using apparatus 100 is described.
 With seeds 60 loaded into needle 56 and distance D1 verified; the needle, seeds, and plunger 58 are inserted through needle guide channel 120 of needle guide apparatus 100 and into the patient. The longitudinal axis of the guide channel may initially be aligned with the longitudinal axis of ultrasound probe 52, or it may be oriented at an angle. The distance D2 is established and may be altered by longitudinally repositioning frame 80 relative to ultrasound probe 52. As will of course be understood, longitudinal repositioning of needle guide apparatus 100 may also require angular repositioning to ensure proper alignment with prostate P.
 The first medical practitioner holds needle 56 stationary while the second medical practitioner advances the first seed 60 to the distal tip of the needle with plunger 58. The second medical practitioner then holds plunger 58 stationary while the first practitioner rotates and proximally retracts needle 56 to sow the seeds in a line within prostate P. The needle and plunger are removed from the patient.
 The seed delivery procedure is repeated at other locations as necessary. In accordance with the present invention, needle guide body 110 and needle guide channel 120 may be angularly reoriented with respect to ultrasound probe 52 between seed delivery procedures, in the manner illustrated in FIGS. 4C and 4D. Angular reorientation may, for example, be used when anatomical constraints, such as skeletal structures, for example, the pelvis and pubic bone, are expected to limit the medical practitioner's ability to deliver radioactive brachytherapy seeds into the prostate in proper alignment. The procedure outlined hereinabove is then repeated as necessary.
 With respect to the embodiments depicted in FIGS. 7-12 and described herein, the needle guide apparatus of those embodiments are used in conjunction with the foregoing method for performing brachytherapy in substantially the same manner. The needle guide apparatus depicted in FIGS. 7-12 may be angularly reoriented with respect to ultrasound probe 52 in preparation for and during brachytherapy. Reorientation of these embodiments are accomplished in the manners provided in their respective descriptions hereinabove.
 Although preferred illustrative embodiments of the present invention are described hereinabove, it will be evident to one skilled in the art that various changes and modifications may be made without departing from the invention. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.