investigating the possibility of using metamaterial as neutron shield in bnct treatment to reduce the dose of secondary particles and radioactive elements produced in brain tumor

Purpose: in this research, using the geant4 software toolbox and metamaterials as a neutron shield, it was tried to introduce the proper metamaterial for this matter.materials and methods: boron neutron capture therapy )bnct( treatment is one of the most significant approaches used to treat brain tumors. the neutron source that is the main part of the bnct method is produced by protons irradiation of 7li converter. the brain tumor tissue, which contains a high concentration of 10b, is exposed to thermal neutron energy that is moderated by shield material. the dose of alpha particles that produced by the neutron decay of 10b in tumor tissue can be calculated by changing the metamaterial thickness. the best thickness of metamaterial for minimizing the radioactive elements production in brain tumor is calculated using the geant4 toolkit.results: waveguide core (wc( metamaterial with 10 cm thickness is suitable for neutron moderation. the secondary elements produced in brain tumors is less than other thickness that is calculated by taking into account the alpha spectrum in tumor tissue. the alpha spectrum was calculated by the interaction of neutron spectrum released by the wc metamaterial.conclusion: the dose of alpha and secondary particles was obtained by the calculation of numbers and energy of these particles in brain tumors. the number of radioactive elements produced in the tumor tissue, as well as the most effective thickness of proper metamaterial to reduce the dose of secondary particles indicated that the wc metamaterial with a thickness of 17 cm is the best material for reducing radiation of neutron source that is produced by 35 mev proton irradiation of 7li neutron converter.