title: Evaluation of the relative biological effectiveness of spot-scanning proton irradiation in vitro.
abstract: Variations in relative biological effectiveness (RBE) from a fixed value of 1.1 are critical in proton beam therapy. To date, studies estimating RBE at multiple positions relative to the spread-out Bragg peak (SOBP) have been predominantly performed using passive scattering methods, and limited data are available for spot-scanning beams. Thus, to investigate the RBE of spot-scanning beams, Chinese hamster fibroblast V79 cells were irradiated using the beam line at the Hokkaido University Hospital Proton Therapy Center. Cells were placed at six different depths, including the entrance of the proton beam and the proximal and distal part of the SOBP. Surviving cell fractions were analyzed using colony formation assay, and cell survival curves were obtained by the curve fitted using a linear-quadratic model. RBE10 and RBE37 were 1.15 and 1.21 at the center of the SOBP, respectively. In contrast, the distal region showed higher RBE values (1.50 for RBE10 and 1.85 for RBE37). These results are in line with those of previous studies conducted using passive scattering proton beams. Taken together, these data strongly suggest that variations in RBE should be considered during treatment planning for spot-scanning beams as well as for passive scattering proton beams.
authors.affiliation: Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Maeda
authors.affiliation: Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Yasui
authors.affiliation: Department of Medical Physics, Proton Beam Therapy Center, Hokkaido University Hospital.
authors.forename: Taeko
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University.
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamamori
authors.affiliation: Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University.
authors.forename: Motofumi
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nagane
authors.affiliation: Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education, Hokkaido University.
authors.forename: Jin-Min
authors.initials: JM
authors.lastname: Nam
authors.affiliation: Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University.
authors.forename: Osamu
authors.initials: O
authors.lastname: Inanami
authors.affiliation: Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education, Hokkaido University shirato@med.hokudai.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D061766:Proton Therapy; D011522:Protons; D012062:Relative Biological Effectiveness
chemical_list: D011522:Protons
keywords: proton therapy; radiotherapy; relative biological effectiveness; spot scanning
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