Calculation of Neutron Dose Ratio of Heart, Lung and Liver due to breast cancer Proton Therapy using MCNPX code

Introduction: The proton beam produced in particle accelerators has an appropriate therapeutic potential. In this research, proton therapy of breast cancer is simulated using the MCNPX code in a MIRD phantom, also the contribution of scattered neutron dose during the proton therapy were calculated for the Heart, Lung and Liver.   Materials and Methods: For simulation of the proton therapy, the code based on the Monte Carlo method is used. Many investigations on the proton therapy planning simulations have been carried out using MCNPX and the other codes. In this study, a spherical tumor with the same elemental composition of breast is located at its tissue with 1 cm in radius. Bragg peak is created in tumor of the breast, for the proton beam energy of 70 MeV. Bragg peak of the 70 MeV proton beam energy is precisely placed at the end of the tumor.   Results: The results show that the scattered neutron dose ratio in the tissues close to the breast such as heart (1.25E-3), lung (1.2E-3) and liver (9E-5) are negligible.   Conclusion: The MCNPX (a Monte carlo simulation code) is a multi-purpose code which can be used for calculation of absorbed doses in radiation therapy. As the results of the code show, the contribution of scattered neutron dose is negligible in breast proton therapy.