Regarding to the widespread applications of X and gamma rays in the various
branches of sciences such as radiotherapy and radiography, our knowledge
about the reduction of single and multiple scattering photons as a main factor
in the creation of the flux and dose of buildup factors, is very important. In this
study, the purpose is to calculate the gamma-rays flux buildup factor in
peripheral tissues of the liver tumor and in this regard was used from the
MCNP code. The used sources for therapy are Cs-137, Co-60 and N-16 and the
used phantom is ORNL for adults. Primarily organs nearing to soft tumor
tissues receive the highest dose. With getting away from tumor, density of
tissues is main factor in receiving of dose. The chemical composition of human
organs and tissues is seen to influence the energy absorption buildup factors.
According to the results of simulation, the buildup factor changes significantly
with the change of incident photon energy and effective atomic number. These
changes are due to the dominance of different photon interaction processes in
different energy regions and different chemical compositions of human organs
and tissues. With the proper knowledge of buildup factors of human organs
and tissues, energy absorption in the human body can be carefully controlled.
The present results will help in estimating safe dose levels for radiotherapy
patients and also useful in diagnostics and dosimetry.