Investigation of Medical Neutron Radiation Doses Using Two types of bubble Detectors

This study measured the amount of pollution of fast and slow neutrons generated from a Elekta Synergy linear accelerator, using various photons and electrons and two bubble detectors, BDT and BD-PND. The BDT bubble detector is preferentially sensitive to thermal neutrons. The BDPND is the recommended detector for personal neutron dosimetry.First, 10-MV photon radiation fields of 40×40 cm, 30×30 cm, 20×20 cm, 10×10 cm, 5×5 cm, and 0.4×0.4 cm were measured electron energies of 6, 9, 12, 15, and 18 MeV, irradiated by 10 cm electronic-cone, to probe for the equivalent dose of fast neutrons and thermal neutrons in the center during quality examination. After measuring the equivalent dose of fast and slow neutrons, the equivalent dose of neutrons changed depending on the irradiated field and energy in 10-MV photon. The equivalent doses at 40×40 cm and 0.4×0.4 cm were 1125 ± 34 and 390 ± 20 μSv per Gy X-ray, respectively. Using 12, 15, and 18 MeV electrons, the equivalent doses were 2.2 ± 1.5, 9.9 ± 3.2 and 19.8 ± 4.5 μSv per Gy-electron, respectively. When electron energy was below 9 MeV, the amount of neutron pollution was lower than its detection limit.Neutron equivalent doses decreased as the irradiated field became smaller, and increased as the electron energy increased. The result of this study can be regarded as a reference for estimating neutron pollution for dose quality assurance.