MAZE DESIGN OF A GANTRY ROOM FOR PROTON THERAPY

Monte Carlo simulations with the LCS code were performed for the desig n of the access maze of an isocentric gantry room for proton therapy. The double distributions of secondary neutrons, produced by 250 MeV pr otons in the gantry structural materials and in the patient, were dete rmined at the treatment room access for different irradiation directio ns. Neutron transport was simulated in a three-leg maze of various len gths. The secondary photons produced by neutrons in the maze walls wer e taken into account. The simulation results were fitted by analytical expressions based on the solution of the Hubbell integral for a recta ngular radiation source. Some simulations were also performed with the FLUKA code for comparison.