Estimation of gamma- and X-ray photons buildup factor in soft tissue with Monte Carlo method.

Buildup factor of gamma- and X-ray photons in the energy range 0.2-2MeV in water and soft tissue is computed using Monte Carlo method. The results are compared with the existing buildup factor data of pure water. The difference between soft tissue and water buildup factor is studied. Soft tissue is assumed to have a composition as H(63)C(6)O(28)N. The importance of such work arises from the fact that in medical applications of X- and gamma-ray, soft tissue is usually approximated by water. It is shown that the difference between water and soft tissue buildup factor is usually more than 10%. On the other hand, buildup factor in water resulted from Monte Carlo method is compared with the experimental data appearing in references. It seems there is around 10% error in the reference data as well.