The effect of wall linings and door lamination on photoneutron dose distribution around linear medical accelerators

Background:The aim of this study is to investigate the shielding effect of the internal wall linings and laminated shield door on photoneutron and capture gamma doses at the isocenter and at the maze entrance of radiotherapy treatment rooms.Material and Methods: The Monte Carlo N-Particle Transport (MCNP5) code was used to simulate the radiotherapy room within a medical linear accelerator operating at 12, 15, 18, and 25 MV.The energy spectra of neutron and secondary gamma rays, with their corresponding dose equivalents, were calculated inside the bunker and at various points along the maze.To verify the accuracy of our Monte Carlo simulation, we compared our findings with those obtained through analytical methods recommended by (IAEA) safety report No.47.Once validated, the Monte Carlo simulation was used for assessing dose reduction by the room wall linings and the laminated shield door.Results: Our results showed that the use of paraffin wax infused with boron carbide within the lining of radiotherapy room walls reduces doses of both neutron and capture gamma radiation at the isocenter by up to 13% and 35.9%, respectively.However, the laminated shield door reduced significantly both neutron and capture gamma dose equivalents near the bunker door by up to 99.75% and 38.20%, respectively.Conclusion: The obtained results show that the use of neutron shielding material in the lining of the radiotherapy wall rooms reduces neutron and capture gamma radiation doses to the patient.While, the laminated shield door presents enough effectiveness in protecting the workers and general public.