title: Biological intercomparison using gut crypt survivals for proton and carbon-ion beams.
abstract: Charged particle therapy depends on biological information for the dose prescription. Relative biological effectiveness or RBE for this requirement could basically be provided by experimental data. As RBE values of protons and carbon ions depend on several factors such as cell/tissue type, biological endpoint, dose and fractionation schedule, a single RBE value could not deal with all different radiosensitivities. However, any biological model with accurate reproducibility is useful for comparing biological effectiveness between different facilities. We used mouse gut crypt survivals as endpoint, and compared the cell killing efficiency of proton beams at three Japanese facilities. Three Linac X-ray machines with 4 and 6 MeV were used as reference beams, and there was only a small variation (coefficient of variance < 2%) in biological effectiveness among them. The RBE values of protons relative to Linac X-rays ranged from 1.0 to 1.11 at the middle of a 6-cm SOBP (spread-out Bragg peak) and from 0.96 to 1.01 at the entrance plateau. The coefficient of variance for protons ranged between 4.0 and 5.1%. The biological comparison of carbon ions showed fairly good agreement in that the difference in biological effectiveness between NIRS/HIMAC and GSI/SIS was 1% for three positions within the 6-cm SOBP. The coefficient of variance was < 1.7, < 0.6 and < 1.6% for proximal, middle and distal SOBP, respectively. We conclude that the inter-institutional variation of biological effectiveness is smaller for carbon ions than protons, and that beam-spreading methods of carbon ions do not critically influence gut crypt survival.
authors.affiliation: Heavy-Ion Radiobiology Research Group, National Institute of Radiological Sciences.
authors.forename: Akiko
authors.initials: A
authors.lastname: Uzawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Ando
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Furusawa
authors.forename: Go
authors.initials: G
authors.lastname: Kagiya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fuji
authors.forename: Masaharu
authors.initials: M
authors.lastname: Hata
authors.forename: Takeji
authors.initials: T
authors.lastname: Sakae
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Terunuma
authors.forename: Michael
authors.initials: M
authors.lastname: Scholz
authors.forename: Sylvia
authors.initials: S
authors.lastname: Ritter
authors.forename: Peter
authors.initials: P
authors.lastname: Peschke
mesh_terms: D000818:Animals; D002244:Carbon; D002470:Cell Survival; D011522:Protons; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D014965:X-Rays
chemical_list: D011522:Protons; D002244:Carbon