Brachytherapy devices and related methods providing bioabsorbability and/or asymmetric irradiation

1. A method of forming a low-dose (LDR) brachytherapy device, the method comprising:

forming a plurality of substrates having a water-insoluble form of a radioactive material thereon; and

positioning the plurality of substrates on a carrier core; and

forming a medical device from the carrier core and the plurality of substrates, wherein forming the plurality of substrates having the water-insoluble form of the radioactive material thereon comprises:

depositing a solution comprising a soluble form of a radioactive material on a substrate; and

converting the soluble form of the radioactive material to a water-insoluble form of the radioactive material on the substrate, and

wherein converting the soluble form of the radioactive material to a water insoluble form of the radioactive material comprises exposing the substrate and the water-soluble form of the radioactive material to plasma thereby decomposing the soluble form of the radioactive material to a water-insoluble form of the radioactive material.

2. The method of claim 1 , wherein the plasma comprises hydrogen plasma and/or an oxygen plasma.

3. The method of claim 2 , wherein the hydrogen or oxygen plasma is at atmospheric pressure or in a partial vacuum.

4. The method of claim 2 , wherein the soluble form the radioactive material comprises a salt of Pd-103.

5. The method of claim 4 , wherein the salt of Pd-103 comprises tetraaminopalladium chloride.

6. The method of claim 1 , wherein the substrate comprises a polymer substrate.

7. The method of claim 1 , wherein forming a medical device comprises enclosing the substrates, the carrier core and the water-insoluble form of the radioactive material with a biocompatible material.

8. The method of claim 1 , wherein depositing a solution comprising a soluble form of a radioactive material on a substrate comprises depositing an array of spaced-apart globules of the soluble form of the radioactive material on the substrate.

9. The method of claim 8 , wherein the substrate comprises micro-wells, and the array of spaced-apart globules are deposited in at least some of the micro-wells on the substrate.

10. The method of claim 8 , wherein the substrate is substantially planar.

11. The method of claim 8 , wherein forming a medical device from the carrier core and the plurality of substrates comprises:

adhering a polymer sheet on the substrate and the water-insoluble form of the radioactive material; and

sizing elongated portions of the carrier core to thereby form a brachytherapy strand.

12. The method of claim 11 , wherein forming a medical device from the substrate and the water-insoluble form of the radioactive material comprises:

positioning the brachytherapy strand in a biocompatible tube;

filling the tube with a curable thermoplastic resin; and

curing the thermoplastic resin such that the radioactive material is sealed.

13. The method of claim 1 , wherein the solution comprises a soluble form of Pd-103 comprising [Pd(NH 3 ) 4 ]Cl 2 and/or PdCl 2 .

14. The method of claim 13 , wherein the solution comprises [Pd(NH 3 ) 4 ]Cl 2 dissolved in ammonium hydroxide (NH 4 OH) and/or PdCl 2 dissolved in HCl.

15. The method of claim 1 , wherein the radioactive material comprises I-125.

16. The method of claim 1 , further comprising coating the plurality of substrates with a biocompatible coating.

17. The method of claim 16 , wherein the biocompatible coating comprises a polyurethane sleeve.

18. The method of claim 17 , wherein the polyurethane sleeve has a thickness greater than 150 micrometers.

19. The method of claim 1 , wherein depositing the solution comprises depositing discrete, spaced-apart globules of the solution using a solenoid dispensing system having a controlled pressurized fluid source, a micro-syringe pump and/or micropipette.

20. The method of claim 19 , wherein a volume for each of the globules is between 5 and 500 nanoliters.

21. The method of claim 19 , further comprising depositing the respective volumes of the globules to an accuracy of 10% of an intended volume.

22. The method of claim 19 , wherein the globules are spaced apart by about 500-1000 μm.

23. The method of claim 1 , wherein each of the substrates is an elongated body.

24. The method of claim 1 , wherein depositing a solution comprising a soluble form of a radioactive material on a substrate comprises depositing spaced-apart globules of the soluble form of the radioactive material, wherein the globules have a volume of about 30-200 nanoliters.