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 were modeled
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.