Purpose: Melanoma at the choroid region is the most common primary cancer that affects the eye in adult patients. Concave ophthalmic applicators with 106 Ru/ 106 Rh beta sources are the more used for treatment of these eye lesions, mainly lesions with small and medium dimensions. The available treatment planning system for 106 Ru applicators is based on dose distributions on a homogeneous water sphere eye model, resulting in a lack of data in the literature of dose distributions in the eye radiosensitive structures, information that may be crucial to improve the treatment planning process, aiming the maintenance of visual acuity. Methods: The Monte Carlo code MCNPX was used to calculate the dose distribution in a complete mathematical model of the human eye containing a choroid melanoma; considering the eye actual dimensions and its various component structures, due to an ophthalmic brachytherapy treatment, using 106 Ru/ 106 Rh beta-ray sources. Two possibilities were analyzed; a simple water eye and a heterogeneous eye considering all its structures. Two concave applicators, CCA and CCB manufactured by BEBIG and a complete mathematical model of the human eye were modeled using the MCNPX code. Results and Conclusion: For both eye models, namely water model and heterogeneous model, mean dose values simulated for the same eye regions are, in general, very similar, excepting for regions very distant from the applicator, where mean dose values are very low, uncertainties are higher and relative differences may reach 20.4%. For the tumor base and the eye structures closest to the applicator, such as sclera, choroid and retina, the maximum difference observed was 4%, presenting the heterogeneous model higher mean dose values. For the other eye regions, the higher doses were obtained when the homogeneous water eye model is taken into consideration. Mean dose distributions determined for the homogeneous water eye model are similar to those obtained for the heterogeneous eye model, indicating that the homogeneous water eye model is a reasonable one. The determined isodose curves give a good visualization of dose distributions inside the eye structures, pointing out their most exposed volume.

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In recent years, there have been major changes in radiotherapy, particularly in dose delivery for treatments using the techniques of Three-Dimensional Conformal Radiation Therapy (3D-CRT), Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). However, in the literature, no workload results for radiation therapy treatments performed exclusively with the VMAT technique were found. In this study, a new workload and a new VMAT factor will be proposed. For such, patient data originating from management and planning systems were acquired, such as dose values, monitor units, numbers of arcs per patient and number of hypofractionated treatments. The average clinical workload values for conventional treatments were 328 Gy/week, resulting in a VMAT factor of 1.97; similarly, for hypofractionated treatments, the clinical workload was 33Gy/week and the VMAT factor was 1.54. The total workload has a value of 596 Gy/week, less than the value used in the facility shielding design, 1250 Gy/week, and the average value of VMAT factor for conventional and hypofractionated treatments showed that a smaller amount of C should be used at facilities that perform exclusive VMAT treatment.