Calculation-experimental modeling of 125I brachytherapy for orbital tumors

    Purpose. To develop schemes of interstitial irradiation with seed 125I for orbital tumor on the basis of computer calculation and experimental modeling.

    Material and methods. Modeling of provisional brachytherapy was carried out for irradiation of orbit after removal of adenocarcinoma of lacrimal gland, incision biopsy of basal cell carcinoma of eyelid with orbital extension, enucleation for choroidal melanoma with extraocular extension of tumor. Calculation-experimental modeling of brachytherapy included creation of human orbital phantom with main structures, dummy source and models of carries, preimplantation planning, implantation of dummy source in orbital model in carries, postimplantation planning.

    Results. Dosimetric planning of 125I brachytherapy enabled to get dose on the ocular and orbital structures for each case. Parameters of irradiation schemes of pre- and post-implantation planning are produced.

    Conclusions. Using the calculation-experimental modeling schemes of contact irradiation of orbit are developed for particular cases of malignant orbital tumors. The suggested schemes of irradiation with 125I source of residual orbital tumors are realizable in practice using distribution of analogous radiation dose loads on the orbital structures in pre- and post-implantation planning. Brachytherapy of orbital tumors with 125I is an alternative method to external beam radiation therapy. The performed modeling of brachytherapy of orbital tumors is a necessary stage for subsequent clinical studies.

    Key words: brachytherapy, 125I, orbit, modeling.