For the first time, a comparison of two programs, the European program FOTELP and the American program MCNP, are presented in this research. For this purpose, a numerical experiment with concentric spheres filled with water and a selected electron source of 10 MeV was performed. The deposited energy in concentric spheres was determined, with the radius of the first 0.5 cm and the last 15 cm. The deposited energy was determined, with the discrepancy between these two programs ranging from 0.4 to 17%. The increasing of application Monte Carlo's technique in medicine relies on voxelized geometric shapes that are obtained by voxelization or from CT data. These programs could be used as general-purpose software packages in dosimetry and radiology. Melanoma of the eye was used as an example to illustrate the use of CT data and voxelized geometry in radiotherapy. Domestic program FOTELP (R. Ilić) and derived versions from it, including the package for brachytherapy, is already being applied at the Institute for Nuclear Research, Russian Academy of Sciences, Laboratory for Medical Physics.

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