title: Designing a ridge filter based on a mouse foot skin reaction to spread out Bragg-peaks for carbon-ion radiotherapy.
abstract: OBJECTIVE
  Carbon-ion radiotherapy uses spread-out Bragg peaks (SOBP) to produce uniform biological effects within a target volume. The relative biological effectiveness is determined by the in vitro cell kill after a single dose is employed to design the SOBP. A question remains as to whether biological effects for in vivo tissues after fractionated doses are also uniform within the SOBP.
  
  
  METHODS
  Mouse foot skin was irradiated with fractionated doses of carbon ions at various linear energy transfer (LET) values. A new ridge filter was designed based on alpha and beta values for each LET to cause moderate skin reaction, and was studied concerning its uniformity.
  
  
  RESULTS
  The reciprocal total doses of intermediate-LET carbon ions and of reference gamma rays linearly increased with an increase of a dose per fraction in Fe-plots. As the single total dose of higher LET run off linearity, data obtained from 2 to 6 fractions were used to design a new ridge filter. The physical dose distribution of the new ridge filter was almost identical to, and indistinguishable from, the ridge filter designed based on the in vitro cell kill.
  
  
  CONCLUSIONS
  The LET dependence of alpha is a principle of the biological factor to be used for designing spread-out Bragg peaks of carbon-ion radiotherapy.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Uzawa
authors.affiliation: Heavy Ion Medical Center, Gunma University, Japan. Electronic address: kando3@air.email.ne.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Ando
authors.affiliation: Proton Therapy Division, Shizuoka Cancer Center Research Institute, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kase
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Hirayama
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan.
authors.forename: Naruhiro
authors.initials: N
authors.lastname: Matsufuji
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Koike
authors.affiliation: Department of Planning and Management, National Institute of Radiological Sciences, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Kobashi
mesh_terms: D000818:Animals; D019583:Dose Fractionation, Radiation; D005121:Extremities / Q000528:radiation effects; D005260:Female; D005374:Filtration; D005720:Gamma Rays; D063193:Heavy Ion Radiotherapy; D018499:Linear Energy Transfer; D051379:Mice; D008809:Mice, Inbred C3H; D012062:Relative Biological Effectiveness; D012867:Skin / Q000528:radiation effects*
keywords: Fe-plot; LET; RBE; Spread-out Bragg peak; Survival parameters