Retrospective comparasion of retro-orbital radiotherapy plans obtained by using three different radiotherapy techniques of graves ophthalmopthy diagnosed cases

In this study, we aimed to compare the doses of target volume and critical organs by using the methods of lateral Three Dimensional Conformal Radiotherapy (3DCRT), 7 field Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) in the treatment of Graves Ophthalmopthy (GO) patients with radiotherapy (RT). The study included 15 patients with orbital RT between 2013 and 2017. 3DCRT, IMRT and VMAT treatment plans were created with fractions dose of 2 Gy, a total dose of 20 Gy. 3DCRT plans were created by the opposed lateral angles that the gantry angles of 80o-90o and 270o-280o degrees to be able to avoid from the dose of the lens, IMRT treatment plans were generated depending or the location of the tumor that the angles of 0o, 40o, 80o, 110o, 250o, 280o, 320o, VMAT treatment plans were created by the angles of clockwise (CW) 180o-225o, CW 35o-145o two partial arcs and 90o of couch angles CW 340o-45o that VMAT and IMRT plans were created by 6 MV photon energies at Monaco 5.1. Treatment Planning System (TPS). In the planned techniques, the dose values of planned treatment volume (PTV), lacrimal gland, lens, eye, brain stem, pituitary gland and optic chiasm were compared. Homogenity index (HI), conformity index (CI) values were calculated and Monitor Unit (MU) values were evaluated. In terms of PTV dose covarage and dose homogeneity, IMRT and VMAT techniques were superior to 3DCRT and for dose conformation and MU values, 3DCRT technique was superior. In terms of critical organs, the superiority of 3DCRT technique is seen in all other organs except the lacrimal gland and the orbitals. As a result, although there are statistically significant differences between treatment plans in GO RT, all techniques are within acceptable limits and can be used in treatment. Key Words: Graves Ophthalmopthy, Intensity Modulated Radiation Therapy, Three Dimensional Conformal Radiotherapy, Volumetric Modulated Arc Therapy