saeideh ali akbari

Lead has been widely used for internal shielding. It is recognized as a toxic material that pollutes the environment and does not fit well the patient's body because of its inflexibility. In this study, a specific combination (70% W, 18.61% Ni, and 11.39% C) of lead-free and flexible putty metal was introduced and validated for internal shielding by Monte Carlo study. To evaluate the putty metal for internal shielding by Monte Carlo study, Varian 2100 C/D was validated within measurements. Then, using the given energy spectrum of Varian 2100 C/D, the shield thickness and backscatter factors were calculated by Monte Carlo study and compared with those of lead. The results showed that this putty metal shield required a comparable thickness compared to lead for providing protection. In addition, it is nontoxic and flexible and can be easily cut. Internal shielding with high atomic number materials causes dose enhancement that is not taken into account in treatment planning systems. This study showed that this composition as an internal shield causes 5% - 7% reduction in electron backscatter factor compared to lead. It can be concluded that lead can be replaced by putty metal with a specific combination (70% W, 18.61% Ni, and 11.39% C). It is lead-free and flexible and its required thickness for protection is acceptable under clinical condition. It causes a 5% - 7% reduction in electron backscattering.

In the recent decades the Monte Carlo simulation in the field of radiation therapy has been used a lot. In this study photon contamination of Lead free and flexible internal shield was investigated in the electron field.
Subjects and To evaluate photon contaminationthat caused by this new material in the electron field by Mont Carlo study. Varian 2100 C/D was validated within measurement and then by given energy spectrum shield thickness and photon contamination were obtained and compared to those of lead.
The results show that this material required 1.2 times thickness of those leadfor providing protection. In addition, it causes photon contamination approximately equal those of lead for energy 6 and 9 MeV.
It can be concluded that thickness of specific combination (70% W, 18.61% Ni, 11/39% c) which has equal transmission same as lead caused photon contamination equal those of Lead that it can be acceptable under clinical condition.