In this paper, the effect of additional adipose and muscle layers was investigated on the effective dose and the organ absorbed dose. Calculations were performed using the Monte Carlo N-Particle Transport Code (MCNP) and the ORNL mathematical phantom for external photon and neutron beams. Variations in adipose and muscle tissue thickness weremodeled by adding layers of adipose and soft tissues around the torso of the phantom. The effective dose decreased by about 7%–40% when the thickness of the extra layer increased from 0.5 to 5 cm considering all photon energies (10 keV–10 MeV) and neutron energies (10–9–20 MeV) for anterior- posterior, posterior-anterior, left-lateral, right-lateral, rotation and isotropic irradiation geometries. The results calculated here were compared with those reported in previous studies such as those of the VIPMAN, NORMAN05, MASH-3 and ICRP reference voxel phantoms. Our data shows that adding proper adipose or muscle layers to two very different phantoms can cause similar effective dose values, and also more than half of the organ absorbed doses have satisfactory agreement.

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