title: Measurement of neutron ambient dose equivalent in carbon-ion radiotherapy with an active scanned delivery system.
abstract: In ion beam radiotherapy, secondary neutrons contribute to an undesired dose outside the target volume, and consequently the increase of secondary cancer risk is a growing concern. In this study, neutron ambient dose equivalents in carbon-ion radiotherapy (CIRT) with an active beam delivery system were measured with a rem meter, WENDI-II, at National Institute of Radiological Sciences. When the same irradiation target was assumed, the measured neutron dose with an active beam was at most ∼15 % of that with a passive beam. This percentage became smaller as larger distances from the iso-centre. Also, when using an active beam delivery system, the neutron dose per treatment dose in CIRT was comparable with that in proton radiotherapy. Finally, it was experimentally demonstrated that the use of an active scanned beam in CIRT can greatly reduce the secondary neutron dose.
authors.affiliation: National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Japan yonai@nirs.go.jp.
authors.forename: S
authors.initials: S
authors.lastname: Yonai
authors.affiliation: National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Furukawa
authors.affiliation: National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Inaniwa
mesh_terms: D002244:Carbon; D004867:Equipment Design; D063193:Heavy Ion Radiotherapy / Q000295:instrumentation* / Q000379:methods*; D007477:Ions; D015233:Models, Statistical; D009010:Monte Carlo Method; D009502:Neutrons; D019047:Phantoms, Imaging; D011522:Protons; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D014867:Water
chemical_list: D007477:Ions; D011522:Protons; D014867:Water; D002244:Carbon