Abstract
Purpose: :
To develop a methodology of intraocular implantation of radioactive applicator in Chinchilla rabbit model.
Methods: :
Newly developed radioactive ophthalmo–applicator (Tomsk, Russia) allows for the intraocular topical radiation of eye tissues. As a source of the radiation an isotope Yttrium–90, obtained as a result of neuronal radiation of Yttrium Oxide, was used. Surgical implantation of the radioactive applicator was performed in 10 Chinchilla rabbits, 1 year of age, weighing 2300–2500g. The applicator was implanted via sclerotomy made at the level of pars plana of ciliary body and subsequently fixed on the sides. The applicator was removed via idem sclerotomy on the fourth day. Animals were sacrificed on 4 days, 3 months and 6 months after the implantation. The implanted eyes were enucleated and examined. To estimate the results of the procedure the following tests were used: indirect ophthalmoscopy with simultaneous digital video recording, biomicroscopy of the anterior segment of the eye, full–field electroretinography, radial dosimetry of the animals’ blood, and histology of the eyes at the conclusion of the experiment.
Results: :
Summary radiation dose of the eye tissues at the distance of 4 mm from the radiation source, with maximal neutron energy of 1 MeV, varied from 83 to 123 Gy, which depended on the primary activity of the applicator. A month later, a choriodystrophy lesion appeared at the site of performed radiation. Tissue immediately surrounding the lesion looked normal. Areas at the far distance from the lesion also looked normal. The radial dosimetry of the blood always stayed unremarkable. Electroretinography revealed significant decrease of retinal photoreceptor electric activity.
Conclusions: :
We developed a new method of intraocular brachitherapy in Chinchilla rabbit model. Suggested ophthalmo–applicator allows for targeted local intraocular radiation of eye tissues, does not cause undesirable radiation of unaffected eye tissues or other side effects.
Keywords: oncology • radiation therapy • tumors