Palladium-103 versus iodine-125 for ophthalmic plaque radiotherapy

Int J Radiat Oncol Biol Phys. 1993 Nov 15;27(4):849-54. doi: 10.1016/0360-3016(93)90459-9.


Purpose: A dosimetry study comparing the use of I-125 vs. Pd-103 radioactive seeds for ophthalmic plaque brachytherapy.

Methods and materials: Palladium-103 (Pd-103) seeds in ophthalmic plaques were used to treat 15 patients with intraocular malignant melanoma. Computer-aided simulations were performed to evaluate the intraocular dose distribution of I-125 versus Pd-103 ophthalmic plaques (delivering equivalent apex doses). Seven target points were selected. Starting at the outer scleral surface, four were located along the central axis of the plaque: the 1 mm point (the inner sclera), the 6 mm point, the tumors apex, and the opposite eye wall. We also evaluated the fovea, optic nerve, and the lens because they were considered to be critical structures.

Results: These studies demonstrated that the lower energy photons generated by Pd-103 seeds (average 21 KeV) in ophthalmic plaques were more rapidly absorbed in tissue than photons generated by I-125 (average 28 KeV). Therefore, during ophthalmic plaque radiotherapy, Pd-103 photons were found to be more rapidly absorbed within the tumor and less likely to reach most normal ocular structures. On average, the use of Pd-103 decreased the dose to the fovea by 5.7%, to the optic nerve by 8.4%, to the lens by 26%, and to the opposite eye wall by 38.4%.

Conclusion: Palladium-103 ophthalmic plaque brachytherapy resulted in slightly more irradiation of the tumor and less radiation to most normal ocular structures.

Publication types

  • Clinical Trial
  • Clinical Trial, Phase I
  • Comparative Study
  • Controlled Clinical Trial

MeSH terms

  • Brachytherapy*
  • Choroid Neoplasms / radiotherapy*
  • Computer Simulation
  • Humans
  • Iodine Radioisotopes / therapeutic use*
  • Melanoma / radiotherapy*
  • Palladium / therapeutic use*
  • Radioisotopes / therapeutic use*
  • Radiotherapy Dosage


  • Iodine Radioisotopes
  • Radioisotopes
  • Palladium