title: Relative biological effectiveness of 50-MV X rays on jejunal crypt survival in vivo.
abstract: Earlier in vitro studies of relative biological effectiveness (RBE) of 50-MV X rays show an RBE of approximately 1.1 compared to 4 MV. No difference in RBE has been found for 20-MV X rays or 50-MeV electrons. The higher RBE for 50 MV can be explained to some extent by the small high linear energy transfer contribution from photonuclear reactions at high X-ray energies. To investigate the validity of the results in vitro, a study of the RBE of 50-MV X rays has been performed in vivo using the jejunal crypt microcolony assay in mice. The reference radiation used in this case was 20-MV X rays. The results confirm the earlier in vitro studies. The RBE for 50-MV X rays was estimated to be 1.06, calculated as the ratio between the slopes of the response curves.
authors.affiliation: Department of Oncology, University of Umeå, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Zackrisson
authors.forename: M
authors.initials: M
authors.lastname: Karlsson
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D007583:Jejunum / Q000166:cytology / Q000528:radiation effects*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D012062:Relative Biological Effectiveness; D013047:Specific Pathogen-Free Organisms; D014916:Whole-Body Irradiation