**4. Monte Carlo calculations**

For this work, we use the MCNPX version: 2.70 (license: C00810MNYCP) originally developed in the Los Alamos laboratory (Radiation Safety Information Computer Center, US). With the visual Editor VisedX\_24E, this edition includes the package MCNP6.1/MCNP5–1.60/MCNPX-2.7.0. In addition, different tools were used for geometry modeling, particles transport, and 3D viewing of the defined geometry for the source and detectors with a dynamic model of simulation. To define the dosimetric parameters, MCNPX has different tallies to estimate each type of calculation. We consider the 60Co source used this study composed of two gamma energies: 1.173 MeV and 1.332 MeV. The radiation spectrum of the 192Ir source used was obtained from the database of (National Nuclear Data Center) neglecting the β spectrum for both of the simulated sources, since its contribution to the dose rate distribution is negligible due to the encapsulation [6, 16]. The Monte Carlo code fulfills all the recommendations of the report, "Dosimetric prerequisites for routine clinical use of photons emitting brachytherapy sources with average energy higher than 50 keV" of the AAPM and ESTRO. The following compilation options were used: CHEAP, DEC, PLOT, MCPLOT, GKSSIM, XS64, CEM, INCL, HISTP, MESHTAL, RADIOG, and SPABI. The physic models of MCNPX used in this study operating the new updated photons and electrons, the photons cross sections libraries mcplib02 and mcplib84 updated from mcplib04 photon Compton broadening data for MCNP5 [17], and the el03 for electrons.
