Implants for use in brachytherapy and other radiation therapy that resist migration and rotation

1. A therapeutic strand implant for use in brachytherapy and deliverable to an implant site by way of a needle, comprising:

a plurality of radioactive sources arranged along a longitudinal axis of the implant;

a polymeric material molded to encapsulate said plurality of radioactive sources; and

a space defined by said polymeric material between each adjacent pair of said radioactive sources; and

a separate plurality of protrusions, defined by an outer surface of said encapsulating polymeric material, associated with each of said radioactive sources; and

wherein the separate plurality of protrusions includes a plurality of rectangular knobs having sidewalls substantially perpendicular to the longitudinal axis.

2. The therapeutic strand of claim 1 , wherein, for each said space defined by said polymeric material, at least a portion of said outer surface of said encapsulating polymeric material that surrounds said space does not include any protrusions.

3. The therapeutic strand of claim 1 , wherein for each said radioactive source, said plurality of protrusions associated with said radioactive source extends from a portion of said outer surface that surrounds said radioactive source.

4. The therapeutic strand of claim 3 , wherein a thickness of portions of said polymeric material encapsulating each said radioactive source varies such that said thickness is greater where there is one of said protrusions than where there is not one of said protrusions.

5. The therapeutic strand implant of claim 1 , wherein portions of said outer surface of said polymeric material that define said protrusions have a greater circumference than portions of said outer surface of said polymeric material that define said spaces between adjacent pairs of said radioactive sources.

6. The therapeutic strand implant of claim 1 , wherein said molded polymeric material comprises a single solid monofilament of a polymer within which said plurality of radioactive sources are spaced apart from one another and encapsulated.

7. The therapeutic strand implant of claim 1 , wherein each of said plurality of radioactive sources comprises a radioactive seed that includes radioactive material contained within a metallic housing that has a substantially smooth outer surface without any protrusions.

8. A therapeutic strand implant for use in brachytherapy and deliverable to an implant site by way of a needle, comprising:

a plurality of radioactive sources;

a polymeric material molded to encapsulate said plurality of radioactive sources; and

a space defined by said polymeric material between each adjacent pair of said radioactive sources; and

a separate plurality of protrusions, defined by an outer surface of said encapsulating polymeric material, associated with each of said radioactive sources;

said plurality of protrusions, associated with one of said radioactive sources, comprises a first protrusion and a second protrusion that each includes

a pair of sidewalls that are substantially parallel to one another and substantially perpendicular to a longitudinal axis of the implant, and

an outermost surface that extends between said pair of sidewalls, meets said pair of sidewalls at substantially right angles, and is substantially parallel to the longitudinal axis of the implant; and

one of said sidewalls of said first protrusion and one of said sidewalls of said second protrusion face one another, are substantially parallel to one another, and form a gap therebetween adapted to receive surrounding patient tissue upon implantation of the implant into a patient, to thereby reduce a tendency for the implant to migrate and rotate after implantation.

9. A therapeutic strand implant for use in brachytherapy and deliverable to an implant site by way of a needle, comprising:

a plurality of radioactive sources;

a polymeric material molded to encapsulate said plurality of radioactive sources; and

a plurality of protrusions defined by an outer surface of said encapsulating polymeric material;

wherein said plurality of protrusions comprise a first protrusion and a second protrusion that each includes

a pair of sidewalls that are substantially parallel to one another and substantially perpendicular to a longitudinal axis of the implant, and

an outermost surface that extends between said pair of sidewalls, meets said pair of sidewalls at substantially right angles, and is substantially parallel to the longitudinal axis of the implant; and

wherein one of said sidewalls of said first protrusion and one of said sidewalls of said second protrusion face one another, are substantially parallel to one another, and form a gap therebetween adapted to receive surrounding patient tissue upon implantation of the implant into a patient, to thereby reduce a tendency for the implant to migrate and rotate after implantation.

10. The therapeutic strand implant of claim 9 , wherein a space is defined by said polymeric material between each adjacent pair of said radioactive sources.

11. The therapeutic strand of claim 10 , wherein, for each said space defined by said polymeric material, at least a portion of said outer surface of said encapsulating polymeric material that surrounds said space does not include any protrusions.

12. The therapeutic strand implant of claim 9 , wherein portions of said outer surface of said polymeric material that define one of said protrusions have a greater circumference than portions of said outer surface of said polymeric material that do not define one of said protrusions.

13. The therapeutic strand implant of claim 9 , wherein said first and second protrusions comprise first and second ribs.

14. The therapeutic strand implant of claim 9 , wherein each of said plurality of radioactive sources comprises a radioactive seed that includes radioactive material contained within a metallic housing that has a substantially smooth outer surface without any protrusions.

15. The therapeutic strand implant of claim 9 , wherein said molded polymeric material comprises a single solid monofilament of a polymer within which said plurality of radioactive sources are spaced apart from one another and encapsulated.

16. The therapeutic strand of claim 9 , wherein a separate subset of said plurality of protrusions is associated with each of said radioactive sources.

17. A therapeutic implant for use in brachytherapy and deliverable to an implant site by way of a needle, comprising:

at least one radioactive source;

a polymeric material molded to encapsulate said at least one radioactive source; and

a plurality of protrusions defined by an outer surface of said encapsulating polymeric material;

wherein said plurality of protrusions comprise a first protrusion and a second protrusion that each includes

a pair of sidewalls that are substantially parallel to one another and substantially perpendicular to a longitudinal axis of the implant, and

an outermost surface that extends between said pair of sidewalls, meets said pair of sidewalls at substantially right angles, and is substantially parallel to the longitudinal axis of the implant; and

wherein one of said sidewalls of said first protrusion and one of said sidewalls of said second protrusion face one another, are substantially parallel to one another, and form a gap therebetween adapted to receive surrounding patient tissue upon implantation of the implant into a patient, to thereby reduce a tendency for the implant to migrate and rotate after implantation.

18. The therapeutic implant of claim 17 , wherein said first and second protrusions comprise first and second ribs.

19. The therapeutic implant of claim 18 , wherein:

said at least one radioactive source comprises a radioactive seed that includes radioactive material contained within a metallic housing that has a substantially smooth outer surface without any protrusions; and

said first and second ribs encircle said radioactive seed.