Hollow bioabsorbable elements for positioning material in living tissue

#The invention relates to positioning material in living tissue. More particularly, the invention relates to positioning medical material, such as radioactive seeds or therapeutic drugs, in living tissue using hollow, bioabsorbable elements that are formed unitarily from synthetic material.

#Some medical treatments rely on implanting a medical material, such as a time-released drug or a radiation source, at a target site within a patient to direct localized action. For example, brachytherapy is a form of internal radiation therapy in which radioactive materials are introduced near or within a tumor of a cancer patient. Such radioactive materials may provide a high dose rate (HDR) treatment during transient implantation, and then may be removed. Alternatively, low dose-rate (LDR) materials may be implanted more permanently in the cancer patient and allowed to decay radioactively over a longer time period.

#LDR brachytherapy is used commonly for treating prostrate cancer. In such LDR treatment, radioactive “seeds” act as radiation sources implanted at predefined regions within (or near) a prostate tumor, directing a sustained, localized dose of radiation to the tumor, with reduced radiation exposure to surrounding healthy tissue.

#FIG. 1 is a side elevation view of an embodiment of a synthetic bioabsorbable tube from the prior art, with the tube formed from multiple solid fibers braided around a central core.

#FIG. 2 is an embodiment of a system for introducing material into living tissue using a cannula and a stylet, with the cannula holding an array of radioactive seeds enclosed by a carrier and separated by spacers.

#FIG. 3 is a fragmentary sectional view of the seed array, carrier, and spacers of FIG. 2.

#The invention provides a system, including apparatus and methods, for positioning medical material in living tissue using hollow elements that are formed unitarily from a synthetic bioabsorbable material. In some embodiments, the hollow elements may be used as bioabsorbable carriers and/or spacers for implanting radioactive seeds. A carrier and/or one or more spacers may be combined with one or more seeds to form a seed assembly for delivering the seed(s) into tissue. Each seed carrier may provide an elongate sleeve within which one or more radioactive seeds (or other medical materials) are retained. The seed spacers may separate the seeds so that the seeds are disposed in a spaced array, for example, within a carrier. In some embodiments, the seed assembly includes a hollow carrier and hollow spacers, each formed unitarily from the same synthetic bioabsorbable material.

#The methods may include processes for unitarily forming hollow bioabsorbable monofilaments from which the positioning elements can be fabricated. In some embodiments, the processes may produce each monofilament as a coating of synthetic bioabsorbable material on an elongate core. Removal of the core creates the hollow monofilament, which may be segmented into positioning elements of any suitable length.

#FIG. 2 shows an embodiment of a system 30 for positioning medical material in living tissue. System 30 may include a cannula or needle 32, a stylet 34, and a seed assembly 36. Cannula 32 may include a pointed distal end 38 at which the cannula can be directed into tissue. Both stylet 34 and seed assembly 36 may be configured to be received by, and slidable within, bore 40 of the cannula. The stylet may be configured as a rod that is movable reciprocally within the bore of the cannula. Accordingly, relative advancement of the stylet from the proximal end of the cannula toward distal end 38 may be used to deliver pre-loaded seed assembly 36 as a unit from the distal end into tissue. As used herein, “positioning in tissue” means facilitating establishment and/or maintenance of position within an organism in tissue or near tissue, for example, in a cavity adjacent to tissue.