Pivoting needle template apparatus for brachytherapy treatment of prostate disease and methods of use

Abstract

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.

Description

REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/648,091, filed Aug. 25, 2000.

FIELD OF THE INVENTION

[0002] 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 angular reorientation of a needl e template for more effective administration of brachytherapy.

BACKGROUND OF THE INVENTION

[0003] Excluding nonmelanoma 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%.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

SUMMARY OF THE INVENTION

[0016] In view of the foregoing, it is an object of the present invention to provide methods and apparatus for orienting a needle guide that overcome drawbacks associated with previously-known methods and apparatus.

[0017] 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.

[0018] These and other objects of the present invention are accomplished by providing methods and apparatus for angular repositioning of the needle template 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 superior control over needle template orientation, so that brachytherapy needles may be inserted in a manner that avoids skeletal structures. A guide tube is also provided to ensure “straight” insertion of the brachytherapy needles.

[0019] Methods of using the present invention are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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:

[0021] FIG. 1 is a schematic view of a prior art method of performing brachytherapy;

[0022] FIGS. 2A-2G are schematic views detailing the prior art method in greater detail;

[0023] FIGS. 3A-3E are views of apparatus constructed in accordance with an embodiment of the present invention shown, respectively, in isometric view, in isometric view with needle template removed, in top view with needle template removed, in sectional view along section line A′-A of FIG. 3B with needle template removed, and in top view coupled to standard brachytherapy apparatus and illustrating a method of use;

[0024] FIGS. 4A-4F are views of an alternative embodiment of apparatus constructed in accordance with the present invention, in which

[0025] FIGS. 4A and 4B show the apparatus coupled to standard brachytherapy apparatus, and

[0026] FIGS. 4C-4F are partial views showing details of the apparatus;

[0027] FIG. 5 is a schematic view detailing an additional disadvantage of the prior art method of FIGS. 2A-2G;

[0028] FIG. 6 is an isometric view of guide tube apparatus in accordance with the present invention that addresses the disadvantage of FIG. 5 and ensures “straight” insertion of brachytherapy needles; and

[0029] FIG. 7 is a schematic view of a method of performing brachytherapy with the apparatus of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention provides methods and apparatus for improved administration of brachytherapy. More particularly, the present invention provides an apparatus comprising needle template that allows angular repositioning of the template to the ultrasound device, thereby providing improved orientation capabilities for implantation of radioactive seeds.

[0031] 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.

[0032] 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.

[0033] With reference to FIGS. 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] With reference now to FIGS. 3A-3D, apparatus constructed in accordance with an embodiment of the present invention is described. Apparatus 100 comprises needle template mount 102. Mount 102 illustratively comprises upper half 103 and lower half 104, but it should be understood that mount 102 may alternatively be formed as a single piece. Upper half 103 and lower half 104 combine to form ultrasound bore 106, in which ultrasound probe 52 is slidably received. Lower half 104 further comprises track bores 108, which slidably receive track 53. Upper half 103 further comprises arc slot 110, which provides for angular reorientation of needle template 54 during a brachytherapy procedure. Template 54 comprises stem 112 that is translatably received in slot 110; by translating stem 112 within slot 110, the longitudinal axis of template 54 may be oriented at an angle to the longitudinal axis of ultrasound probe 52. Upper half 103 optionally may still further comprise markings 114, which allow a medical practitioner to determine and set that angle.

[0040] With reference to FIG. 4A, apparatus in accordance with an alternative embodiment of the current invention is described. Brachytherapy apparatus 120 comprises needle template 54, needle template mount 130, frame 60 and ultrasound probe 52. Frame 60 provides a stable platform for longitudinal repositioning of ultrasound probe 52. Mount 130 is installed on and rigidly attached to frame 60, and is configured to facilitate angular reorientation of template 54 relative to frame 60 and ultrasound probe 52 as shown in FIG. 4B, where the dotted lines represent possible orientations of needle template 54.

[0041] In addition to allowing longitudinal repositioning of probe 52, frame 60 is slidably received on track 53 and may be longitudinally repositioned with respect to ultrasound probe 52. Alternatively, frame 60 may be rigidly attached to track 53, in which case the track and frame may be longitudinally repositioned with respect to ultrasound probe 52.

[0042] Mount 130 is attached to frame 60 by means of feet 131 with posts 132 attached thereon. Posts 132 are slidably received in holes 133 disposed in frame 60. Because the actual distance D3 between holes 133 may depend on the design or manufacturer of frame 60, it is desirable to provide means for adjusting distance D4 by repositioning feet 131 relative to mount 130. Such repositioning may be accomplished by configuring feet 131 to be slidably movable relative to mount 130. In a preferred embodiment, mount 130 comprises guide pins 134 that are engaged by guide slots 135 disposed on feet 131, thereby guiding and limiting the slidable movement of the feet. Alternatively, feet 131 and mount 130 may be separable, thereby allowing feet 131 to attach to mount 130 such that the posts are separated by a desired distance D4. Posts 132 preferably comprise radially expandable clips that engage holes 133 to prevent relative movement between frame 60 and mount 130.

[0043] Mount 130 includes telescoping legs 136 that slidably extend or retract relative to mount 130 to permit adjustment of distance D5 between template 54 and ultrasound probe 52. Telescoping legs 136 may be secured at a desired height by insertion of locking pins 137 through mount 130 and legs 136 via holes 138. The positions of holes 138 may be predetermined to correspond to heights suitable for adaptation to commercially available frames.

[0044] Needle template holder 140 is disposed to rotate relative to mount 130 on shaft 141 and carries template 54 secured therein. Needle template 54 may be rotated to adopt a desired angular orientation relative to the longitudinal axis of ultrasound probe 52 by manipulation of knob 142 disposed on shaft 141. Knob 142 may be configured to rotate freely, allowing the template to adopt any angular orientation within its range.

[0045] Alternatively, as illustrated in FIGS. 4C and 4D, knob 142 may be configured to rotate incrementally between predetermined angular positions, illustratively by moving locking pin 145 to a selected one of locking holes 146 disposed in mount 130. A plurality of these locking holes may be arranged circumferentially around shaft 141, with each hole corresponding to a predetermined angular orientation. To rotate needle template 54 to a desired angular position, locking pin 145 is disengaged from a hole 146 by pulling knob 142 upward, knob 142 is rotated to a desired predetermined angular orientation, and then locking pin 145 is reengaged with a new hole 146. This engagement also prevents accidental angular repositioning of needle template 54 during brachytherapy. Knob 142 and mount 130 further may comprise indicia 147 and 148, respectively, that indicate the angular orientation of knob 142 and needle template 54 with respect to the longitudinal axis of probe 52.

[0046] With reference to FIGS. 4E and 4F, needle template holder 140 comprises interior surface 150 suitable for engaging exterior surface 151 of needle template 54. Holder 140 may further comprise embossed or recessed features disposed on surface 150, such as guide rails 152, that are configured to engage complementary features disposed on exterior surface 151, such as slots 153. Features 152 and 153 allow holder 140 more securely to engage template 54, as well as providing for precise alignment and positioning of template 54 within holder 140.

[0047] Template holder 140 may further comprise guide stop 154 disposed at one end. Guide stop 154 abuts against the edge of needle template 54 when the latter is inserted within template holder 140. Needle template 54 may further comprise notch 155 that is suitable for accommodating the guide stop. Template holder 140 preferably further comprises latch 156 that, when closed, prevents accidental movement or removal of needle template 54 in template holder 140.

[0048] Referring now to FIGS. 3E and 4B, as well as FIGS. 1-3D and FIG. 4A, a method of using apparatus 100 or apparatus 120 is described. The dotted lines of FIG. 3E and FIG. 4B represent angular reorientation of the longitudinal axis of needle template 54 with respect to the longitudinal axis of ultrasound probe 52.

[0049] 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. The longitudinal axis of needle template 54 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 template mount 102 in FIG. 3A or frame 60 in FIG. 4A, both with template 54 attached thereon, relative to ultrasound probe 52. As will of course be understood, longitudinal repositioning of template 54 may also require angular repositioning when the template is aligned at an angle, to ensure proper alignment with prostate P.

[0050] 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 sew the seeds in a line within prostate P. The needle and plunger are removed from the patient.

[0051] The seed delivery procedure is repeated at other locations as necessary. In accordance with the present invention, needle template 54 may be angularly reoriented with respect to ultrasound probe 52 between seed delivery procedures, as seen in FIGS. 3E and 4B. 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. In FIG. 3A, stem 112 of template 54 translates within arc slot 110 to angularly reorient the template. The medical practitioner optionally may use markings 114 to orient template 54 at a specific angle to ultrasound probe 52. In FIG. 4A, knob 142 is rotated to angularly reorient needle template 54 at a specific angle to ultrasound probe 52. The medical practitioner optionally may use indicia 147 and 148 to orient template 54 at a specific angle to ultrasound probe 52. The procedure outlined hereinabove is then repeated as necessary.

[0052] Referring now to FIG. 5, an additional shortcoming of the prior art method of brachytherapy delivery is described. If needle 56 is not “straight” when advanced through needle template 54, the needle may be misaligned when advanced into prostate P, as illustrated by dotted lines in FIG. 5. This may lead to improper delivery positioning of brachytherapy seeds, and, thus, potentially harmful improper distribution of radiation exposure within the patient. In the context of the present invention, “straight” advancement comprises advancing a brachytherapy needle through a needle template such that the needle is disposed at substantially no angle with respect to the longitudinal axis of the template.

[0053] With reference to FIG. 6, apparatus in accordance with the present invention is provided that ensures straight advancement of a brachytherapy needle. Guide tube 160 comprises posts 162 configured for insertion within template holes 54a of needle template 54. Guide tube 160 further comprises elongated member 164 having proximal end 166, distal end 168, and lumen 170 extending therebetween. Proximal end 166 is configured for insertion within template holes 54a, and lumen 170 is configured to slidably receive needle 56. Mount 172 connects posts 162 to elongated member 164.

[0054] Guide tube 160 is preferably fabricated from a substantially rigid material to mitigate angular deflection of elongated member 164 with respect to mount 162, and may be disposable or reusable. Guide tube 160 further may comprise measurement indicia, scales, or stops in order to regulate needle insertion depth. Although, in FIG. 6, the guide tube is illustratively provided with two posts 162, it will be apparent to one of skill in the art that guide tube 160 may alternatively be provided with any other number of posts, or no posts.

[0055] Referring now to FIG. 7, a method of using guide tube 160 with the apparatus of FIG. 1 is described. As seen in FIG. 7, guide tube 160 is coupled to needle template 54, and needle 56 is advanced through lumen 170 of guide tube 160. The guide tube ensures that needle 56 is advanced straight and is properly positioned within the patient's prostate P. Guide tube 160 may then be repositioned in other template holes 54a, and needle 56 may be reinserted through lumen 170 into the patient at another target location.

[0056] As will of course be understood, guide tube 160 may also be used in conjunction with apparatus 100 of FIGS. 3 or with apparatus 120 of FIG. 4A. When used in conjunction with apparatus 100 or 120, guide tube 160 provides superior control over positioning of needle 56, as compared to current apparatus and methods.

[0057] 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. For example, guide tube 160 may be coupled to the opposite side of needle template 54 such that elongated member 164 extends away from the patient, thereby facilitating rapid repositioning of guide tube 160 in other template holes 54a of needle template 54. 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.

Claims

1. Apparatus for improved positional control during administration of brachytherapy, the apparatus comprising:

a needle template mount; and

a needle template coupled to the needle template mount to permit angular and spatial reorientation of the needle template relative to the needle template mount.

2. The apparatus of claim 1 wherein said needle template is adapted to be disposable.

3. The apparatus of claim 1 wherein the needle template mount is adapted to be coupled to a system comprising an ultrasound probe with a longitudinal axis.

4. The apparatus of claim 1 wherein the needle template mount comprises a slot adapted to slidably receive the needle template.

5. The apparatus of claim 4 wherein the needle template is positionable within the slot.

6. The apparatus of claim 1 wherein the needle template mount comprises indicia indicating the angular orientation of the needle template relative to the needle template mount.

7. The apparatus of claim 1 further comprising a needle template holder disposed between the needle template and the needle template mount.

8. The apparatus of claim 7 wherein the needle template holder is rotatably affixed to the needle template mount by a shaft.

9. The apparatus of claim 8 further comprising a knob coupled to the shaft for controlling angular orientation of the needle template holder.

10. The apparatus of claim 7 wherein the needle template is adapted to rotate between predetermined angles.

11. The apparatus of claim 8 wherein the needle template holder has an interior surface adapted to engage a complimentary feature of the needle template.

12. The apparatus of claim 11 wherein the interior surface feature comprises an embossed or recessed feature.

13. The apparatus of claim 12 wherein the interior surface comprises a guide rail and the complimentary feature comprises a guide slot.

14. The apparatus of claim 8 wherein the needle template holder further comprises means for preventing movement or removal of the needle template.

15. A method for administering brachytherapy, the method comprising:

providing apparatus comprising an ultrasound probe, a mount rigidly disposed in relation to the ultrasound probe, a needle template attached to the mount such that the needle template may be angularly oriented with respect to the probe;

longitudinally positioning the ultrasound probe through the patient's rectum to facilitate imaging of the patient's prostate and reference plane; and

angularly orienting the needle template at a desired angle with respect to the ultrasound probe.

16. The method of claim 15 further comprising guiding the sharpened distal tip of a needle containing brachytherapy seeds through the needle template and into a target location within the patient's prostate until it is aligned with the reference plane.

17. The method of claim 16 further comprising retracting the needle in a manner that delivers the brachytherapy seeds into the prostate.

18. The method of claim 15 wherein said apparatus further comprises indicia indicating the angular orientation of the needle template.

19. The method of claim 18 wherein angularly orienting the needle template at a desired angle with respect to the ultrasound probe comprises using the indicia as a guide.

20. The method of claim 15 further providing a guide tube, wherein said guide tube facilitates straight insertion of the needle into the target location.