The evaluation of change in attenuation coefficient of cerrobend block used for radiation protection of healthy tissues in megavoltage photon radiation therapy after multiple melting

Introduction: Protecting the vital organs in radiation therapy is one of the most important issues. Cerrobend alloy, the most common material used as the shield, is melted several times and used for different patients. In this study changes in attenuation coefficient of cerrobend due to melting was investigated.   Materials and Methods: In melting furnace, cerrobend was melted up to nine times and irradiated by Varian accelerator at radiotherapy department of Golestan hospital and the dose was measured by CC-13 ionization chamber with and without cerrobend blocks. The attenuation coefficients of cerrobend blocks were measured for irradiation fields of 6 × 6 cm2 and 10×10 cm2 at the photon energies of 6 mv and 18mv and analyzed by statistical methods.   Results: Results of regression analysis with P<0.05, indicated that there was a significant relationship between the attenuation coefficient and frequencies of cerrobend melting: the attenuation coefficient increases with the increasing frequency of cerrobend melting.   Conclusion: Continuous increasing in the frequency of cerrobend melting leads to increase in the attenuation coefficient of cerrobend block, thus cerrobend blocks can be used for patients, safely.