Abstract:
In one embodiment an after-loader for providing an implant to a hollow needle, the after-loader comprising a body having a distal end including a bevel for receiving a hub of a seed lock needle, and a bore therethrough for receiving a hub of a MICK® needle; a proximal end having a funnel shaped opening; a shield adapted to be provided over the body; and wherein the distal end further includes a taper along a portion of a distance from the distal end to the proximal end for providing a friction fit to a shield. This abstract is not intended to be a complete description of the invention.

Description:
CLAIM OF PRIORITY 
     This application claims priority to the following U.S. Provisional Applications, which are incorporated herein by reference. 
     U.S. Provisional Application Ser. No. 60/799,161, entitled “After-loader for Positioning Implants for Needle Delivery in Brachytherapy and Other Radiation Therapy,” by Gary Lamoureux et al., filed May 9, 2006; 
     U.S. Provisional Application Ser. No. 60/847,834, by Gary Lamoureux et al., entitled “After-loader for Positioning Implants for Needle Delivery in Brachytherapy and Other Radiation Therapy,” filed Sep. 28, 2006. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to radiotherapy. More particularly, it relates to applicators for positioning implants e.g., for use in brachytherapy. 
     BACKGROUND 
     Brachytherapy is a general term covering medical treatment which involves placement of radioactive sources near a diseased tissue and can involve the temporary or permanent implantation or insertion of radioactive sources into the body of a patient. The radioactive sources are located in proximity to the area of the body which is being treated. A high dose of radiation can thereby be delivered to the treatment site with relatively low doses of radiation to surrounding or intervening healthy tissue. Exemplary radioactive sources include radioactive seeds, radioactive rods and radioactive coils. 
     Brachytherapy has been used or proposed for use in the treatment of a variety of conditions, including arthritis and cancer. Exemplary cancers that can be treated using brachytherapy include breast, brain, liver and ovarian cancer and especially prostate cancer in men. For a specific example, treatment for prostate cancer can involve the temporary implantation of radioactive sources (e.g., rods) for a calculated period, followed by the subsequent removal of the radioactive sources. Alternatively, radioactive sources (e.g., seeds) can be permanently implanted in the patient and left to decay to an inert state over a predictable time. The use of temporary or permanent implantation depends on the isotope selected and the duration and intensity of treatment required. 
     Permanent implants for prostate treatment include radioisotopes with relatively short half lives and lower energies relative to temporary seeds. Exemplary permanently implantable sources include iodine-125, palladium-103 or cesium-131 as the radioisotope. The radioisotope can be encapsulated in a biocompatible casing (e.g., a titanium casing) to form a “seed” which is then implanted. Temporary implants for the treatment of prostate cancer may involve iridium-192 as the radioisotope. For temporary implants, radioactive rods are often used. 
     Conventional radioactive seeds are typically smooth sealed containers or capsules of a biocompatible material, e.g., titanium or stainless steel, containing a radioisotope within the sealed chamber that permits radiation to exit through the container/chamber walls. Other types of implantable radioactive sources for use in radiotherapy are radioactive rods and radioactive coils, as mentioned above. 
     Preferably, the implantation of radioactive sources for brachytherapy is carried out using minimally-invasive techniques such as, e.g., techniques involving needles and/or catheters. It is possible to calculate a desired location for each radioactive source which will give the desired radiation dose profile. This can be done using knowledge of the radioisotope content of each source, the dimensions of the source, accurate knowledge of the dimensions of the tissue or tissues in relation to which the source is to be placed, plus knowledge of the position of the tissue relative to a reference point. The dimensions of tissues and organs within the body for use in such dosage calculations can be obtained prior to or during placement of the radioactive sources by using conventional diagnostic imaging techniques including X-ray imaging, magnetic resonance imaging (MRI), computed tomography (CT) imaging, fluoroscopy and ultrasound imaging. 
     During the placement of the radioactive sources into position, a surgeon can monitor the position of tissues such as the prostate gland using, e.g., ultrasound imaging or fluoroscopy techniques which offer the advantage of low risk and convenience to both patient and surgeon. The surgeon can also monitor the position of the relatively large needle used in implantation procedures using ultrasound or other imaging. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a hub of a seed lock needle. 
         FIG. 2  is a side view of an embodiment of an after-loader in accordance with the present invention. 
         FIG. 3  is a perspective view of the after-loader of  FIG. 2 . 
         FIG. 4A  is an embodiment of a distal end plug for use with the after-loader of  FIG. 2 ;  FIG. 4B  is an embodiment of a proximal end plug for use with the after-loader of  FIG. 2 ;  FIG. 4C  is an alternative embodiment of a distal end plug for use with the after-loader of  FIG. 2 ;  FIG. 4D  is an alternative embodiment of a proximal end plug for use with the after-loader of  FIG. 2 . 
         FIG. 5  is a side view of the after-loader of  FIG. 2  with the distal end plug and proximal end plug in place. 
         FIG. 6  is a side view of the after-loader of  FIG. 2  with shielding arranged over a portion of the after-loader. 
         FIG. 7A  is a cross-sectional side view of the after-loader of  FIG. 1  mated with a needle, and having a stylet disposed within the after-loader and needle;  FIG. 7B  is a cross-sectional side view of the after-loader of  FIG. 2  mated with a needle, and having a stylet disposed within the after-loader and needle. 
         FIG. 8  is a flowchart of an embodiment of a method of using an after-loader in accordance with the present invention. 
         FIG. 9  is a flowchart of an alternative embodiment of a method of using an after-loader in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Brachytherapy typically employs a hollow needle that is insertable through a template and into a patient&#39;s body. A typical template used to guide and/or inform the positioning of hollow needles at the surgical site can provide access to more than one hundred locations. The number of locations can be so numerous that a typical pitch between needle access points can include a pitch of 5 mm. 
     One or more implants are provided to the hollow needle for delivery at a surgical site. A distal end of the hollow needle is typically inserted to the desired depth, thus at least one of the implant is typically urged to approximately the proximal end of the hollow needle. The implants can include a radioactive source. The radioactive source can be a radioactive seed, a radioactive rod, or a radioactive coil, but is not limited thereto. The radioactive source can further be an anchor seed, which is a seed having an outer shape and/or outer coating adapted to resist movement once implanted at a desired location within the patient, for example, as disclosed in U.S. patent application Ser. No. 11/187,411, entitled “Implants for Use in Brachtherapy and Other Radiation Therapy That Resist Migration and Rotation,” filed Jul. 22, 2005, which is incorporated herein by reference. Alternatively, the implant can be some other object and need not be radioactive, e.g. the implant can be a spacer, or a marker. For reasons of convenience, embodiments will be described with reference to a “seed,” however it will be understood that embodiments can additionally or alternatively be used with any implant. 
     A hollow needle for use in Brachytherapy can include a MICK® needle or alternatively some other hollow needle, such as a seed lock needle. It has become a relatively common practice for physicians to employ needles other than MICK® needles; however, MICK® needles continue to be in popular use. A MICK® needle includes a hub positioned at a proximal end, the hub being a generally simple cylinder in shape. Referring to  FIG. 1 , a seed lock needle  4  differs from a MICK® needle in that the hollow needle  2  is coupled to a hub  6  having an enlarged diameter with a funneled proximal end  8  that typically screws onto a syringe. The funneled proximal end  8  allows a more forgiving tolerance for inserting implants into the hollow needle  2 . However, tools for expediting and/or simplifying the loading process of the implant within the hollow needle are typically compatible with only one of multiple types of needles. 
     Referring to  FIGS. 2 ,  3  and  5  through  7 B, embodiments of after-loaders  100  in accordance with the present invention can simplify and/or expedite loading of implants into a needle. The after-loader  100  can accommodate a MICK® needle  160  (shown in  FIG. 7B ) within a bore  120  of a distal end  110  of the after-loader  100 , or alternatively a seed lock needle  4  (shown in  FIG. 7A ), providing flexibility in hollow needle choice. The distal end  110  can include an enlarged diameter tapering at an angle θ from its largest diameter toward the proximal end of the after-loader  100  at some small angle. In accordance with an embodiment, the maximum diameter of the after-loader  100  near the distal end  110  is 3/16″ necking down at a 5 degree angle. The purpose of this taper is to accept a shield  150  (shown in  FIG. 6 ) over the outside of the after-loader  100 , and to further provide a friction fit to lock the shield over the after-loader  100 , the friction fit being attributable to the increase in diameter toward the distal end  110 . The shield  150  is positioned around the after-loader  100  to reduce or minify an amount of radiation that escapes from the after-loader  100  where the implants placed in the after-loader  100  are radioactive. The after-loader  100  itself can be formed using a transparent plastic, for example by molding, but is not limited thereto. Where the after-loader  100  is formed of a plastic, the after-loader  100  does not sufficiently restrict radiation from escaping the after-loader  100 ; therefore, shielding is employed to prevent leakage. The shield  150  can be formed of some material that sufficiently restricts the amount of radiation that escapes the shield  150 , such as stainless steel. In other embodiments, after-loaders  100  of the present invention can be formed from a different material more opaque to radiation, such as stainless steel. In such embodiments a separate shield is not necessary. 
     Referring to  FIG. 7A , the nose  118  of the after-loader  100  is tapered at an angle α generally corresponding to an angle of the funneled proximal end  8  of a seed lock needle  4 . Thus, an external angle of the nose end  118  can be approximately 15 degrees in angle, in an embodiment wherein a typical seed lock needle  4  is to be accommodated. The nose  118  of the after-loader  100  is positioned within the funneled proximal end  8  so that the after-loader  100  is removably mated with the hub  6  of the seed lock needle  4 . 
     Still further, the distal end  110  of the after-loader  100  includes an enlarged diameter relative to the body  112  of the after-loader  100 , which roughly corresponds to a diameter of a hollow needle. As further shown  FIG. 7B , the distal end  110  is such that the enlarged diameter can accommodate the hub  162  of a MICK® needle  160 , and in an embodiment the distal end  110  has a length generally sufficient to receive the hub  162  of the MICK® needle  160 . Thus, the after-loader  100  can be removably mated with a MICK® needle or a seed lock needle, at the option of the physician. The funneled shape of the distal end  110  also accommodates a distal end plug  180  (shown in  FIGS. 4A and 5 ) inserted into the distal end  110 , the distal end plug  180  functioning to hold implants positioned within the after-loader  100  in place. The distal end plug  180  prevents implants from falling out of the after-loader  100 , and further can be employed to block radiation from emitting from the end of the after-loader  100 . It should be noted that the distal end plug  180  need not be shaped as shown in  FIGS. 4A and 5 . The distal end plug  180  need only be shaped so as to function to accommodate the implant within the after-loader  100 . For example, where radiation emission from the longitudinal ends of implant is not a concern, the end plug need not function to block radiation. Thus, in some embodiments, for example, a distal end plug  280  as shown in  FIG. 4C  can be employed to resist undesired movement within the after-loader  100  and provide for removal, which as shown is accomplished by way of a textured surface  281 . 
     An opening at the proximal end  130  of the after-loader  100  can be funneled having an angle β to simplify insertion into a bore  114  of the body  112  of the after-loader  100  an implant, or a stylet (also referred to herein as a push-rod). For example, the funnel can cause an increase in diameter at a 10 degree angle. The funneled shape of the opening at the proximal end  130  also accommodates a proximal end plug  182  (shown in  FIGS. 4B and 5 ) inserted into the proximal end  130 , the proximal end plug  182  functioning to hold implants positioned within the after-loader  100  in place. The proximal end plug  182  prevents implants from falling out of the after-loader  100 , and further can be employed to block radiation from emitting from the end of the after-loader  100 . The distal end plug  180  and proximal end plug  182  shown in  FIGS. 4A-5  are merely embodiments of plugs for use with after-loaders in accordance with the present invention. In other embodiments, some other style of plug can be employed to retain an implant with an after-loader. In still other embodiments, plugs for use with the after-loader of the present invention can be integrally formed with an implant housed within the after-loader. The proximal end plug  182  need only be shaped so as to function to accommodate the implant within the after-loader  100 . For example, where radiation emission from the longitudinal ends of the implant is not a concern, the end plug need not function to block radiation. Thus, in some embodiments, a distal end plug  282  as shown in  FIG. 4D  can be employed to resist undesired movement within the after-loader  100  and provide for removal, which as shown is accomplished by way of a textured surface  283 . 
     Referring to  FIG. 8 , the distal end of a hollow needle is positioned at the desired location within a patient&#39;s body (e.g. by way of a template) prior to use of the after-loader  100  (Step  100 ). The hub of the hollow needle is mated with the distal end  110  of the after-loader  100  (Step  102 ), either by way of the tapered nose  118  or the bore  120  of the distal end  110 . With the implant positioned within the after-loader  100  a stylet  170  (shown in  FIGS. 7A and 7B ) is inserted into the proximal end  130  of the after-loader  100  (Step  104 ) and is urged toward the distal end of the needle until the implant is positioned at the desired location (Step  106 ). The stylet  170  for use with the after-loader  100  can be sufficient in length to accommodate both the needle and the after-loader  100 , which are retracted while the stylet  170  is held in position so that the implant is deposited at a desired location (Step  108 ). Referring to  FIG. 9 , alternatively, a stylet of less than sufficient length to accommodate both the needle and the after-loader  100  can be employed. When such a stylet is used, the stylet can urge the implant from the after-loader  100  to the hollow needle (Step  206 ). The stylet can then be removed, and the after-loader  100  disconnected (Step  208 ). The stylet  170  can then be reinserted into the hub of the needle to urge the implant to the desired location (Step  210 ). The needle can then be retracted with the stylet held in position so that the implant is deposited at a desired location (Step  212 ). 
     As mentioned, the after-loader  100  can be employed for use with a single seed, an anchor seed, multiple seeds with or without spacers between adjacent seeds, strands, a radioactive rod, or a radioactive coil, a marker, or some other implantable device. A strand can include a plurality of radioactive sources spaced apart from one another, e.g. in accordance with a treatment plan. 
     In further embodiments of after-loaders in accordance with the present invention, the after-loaders  100  can be pre-loaded with strands, loose seeds and spacers, or other implants so that the after-loader can be selected by the physician and used without loading by the physicians. Pre-configured strands, and other implants can be loaded into the after-loader  100  off-site and fitted with plugs at the proximal end  130  and the plugs to hold the ends in, and then shipped to the user and assigned to certain patients. Thus, the proper treatment can be determined as part of a pre-plan. In such embodiments, the after-loader would include shielding securely fitted to the outside surface of the after-loader  100 . Such pre-loaded after-loaders can simplify and expedite the implantation process. Further, such pre-loaded after-loaders  100  offer benefits to hospitals or clinics that strive to minify the amount of handling of the implants performed by staff. It is also possible for a physician to load seeds, strands, or other implants into the after-loaders  100  before needles are inserted into a patient. As will be appreciated, and which can be extrapolated from the embodiments described, the after-loaders  100  can be longer or shorter in length as needed. For example, where an implant appropriate for a treatment plan is an anchor seed, the after-loaders  100  can have a length appropriate to the implant. 
     The after-loader  100  can include a diameter that, at a maximum, is at least 5 mm in size to generally match the pitch of a typical template. However, in other embodiments, the after-loader  100  can be larger or smaller in diameter. 
     The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the embodiments of the present invention. While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.