title: Accelerated reoxygenation of a murine fibrosarcoma after carbon-ion radiation.
abstract: OBJECTIVE
  Reoxygenation of a murine tumour after irradiation with carbon ions was investigated and compared to that after gamma-rays.
  
  
  METHODS
  NFSa fibrosarcoma cells were transplanted into the right hind legs of syngeneic C3H male mice. Conditioning irradiation with either 290 MeV/u carbon ions or 137-Cs gamma-rays was delivered to the tumours at 8 mm diameter. At given times after irradiation the leg tumours, either clamped or not, received test doses of photons. Differences in tumour growth delay between the clamped and non-clamped tumours were interpreted in terms of reoxygenation. A lung-colony assay was used to obtain cell-survival curves.
  
  
  RESULTS
  The oxygen enhancement ratio in the NFSa tumour for 74 keV microm(-1) carbon ions was 1.6 while that for gamma-rays was 3.4. The NFSa tumours reoxygenated 4 days after 30 Gy of gamma-ray irradiation, but reoxygenated as early as 1 day after 16 Gy of carbon ions. Reoxygenation after gamma-rays shortened to 1 day when the tumours were initially clamped for the conditioning irradiation.
  
  
  CONCLUSIONS
  The fraction of surviving oxic cells in the NFSa tumours is larger after irradiation with carbon ions than with gamma-rays, resulting in accelerated reoxygenation.
authors.affiliation: Space and Particle Radiation Science Research Group, National Institute of Radiological Sciences, Chiba, Japan. ando@nirs.go.jp
authors.forename: K
authors.initials: K
authors.lastname: Ando
authors.forename: S
authors.initials: S
authors.lastname: Koike
authors.forename: C
authors.initials: C
authors.lastname: Ohira
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chen
authors.forename: K
authors.initials: K
authors.lastname: Nojima
authors.forename: S
authors.initials: S
authors.lastname: Ando
authors.forename: T
authors.initials: T
authors.lastname: Ohbuchi
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
authors.forename: W
authors.initials: W
authors.lastname: Shimizu
authors.forename: M
authors.initials: M
authors.lastname: Urano
mesh_terms: D000818:Animals; D002244:Carbon; D015687:Cell Hypoxia; D004307:Dose-Response Relationship, Radiation; D005354:Fibrosarcoma / Q000098:blood supply / Q000378:metabolism* / Q000532:radiotherapy*; D005720:Gamma Rays; D020450:Heavy Ions; D007700:Kinetics; D018499:Linear Energy Transfer; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D010100:Oxygen / Q000097:blood / Q000378:metabolism*
chemical_list: D002244:Carbon; D010100:Oxygen