title: RBE-LET relationships for cell inactivation and mutation induced by low energy protons in V79 cells: further results at the LNL facility.
abstract: OBJECTIVE
  RBE-LET relationships for cell inactivation and hprt mutation in V79 cells have been studied with mono-energetic low-energy proton beams at the radiobiological facility of the INFN-Laboratori Nazionali di Legnaro (LNL), Padova, Italy.
  
  
  METHODS
  V79 cells were irradiated in mono-layer on mylar coated stainless steel petri dishes, in air. Inactivation data were obtained at 7.7, 34.6 and 37.8 keV/microm and hprt mutation was studied at 7 7 and 37.8 keV/microm. Additional data were also collected for both the end points with the proton LET already considered in our previous publications, namely 11.0, 20.0 and 30.5 keV/microm.
  
  
  RESULTS
  A maximum in the RBE-LET relationship for cell inactivation was found at around 31 keV/microm, while the RBE for mutation induction increased continuously with LET.
  
  
  CONCLUSIONS
  The proton RBE-LET relationship for cell inactivation is shifted to lower LET values compared with that for heavier ions. For mutation induction, protons of LET equal to 7.7keV/microm gave an RBE value comparable with that obtained by helium ions of about 20 keV/microm. Mutagenicity and lethality caused by protons at low doses in the LET range 7.7-31 keV/microm were proportional, while the data at 37.8 keV/microm suggest that this may not hold at higher LET values.
authors.affiliation: Laboratorio di Fisica, Istituto Superiore di Sanità, INFN-Sezione Sanità, Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Belli
authors.forename: F
authors.initials: F
authors.lastname: Cera
authors.forename: R
authors.initials: R
authors.lastname: Cherubini
authors.forename: M
authors.initials: M
authors.lastname: Dalla Vecchia
authors.forename: A M
authors.initials: AM
authors.lastname: Haque
authors.forename: F
authors.initials: F
authors.lastname: Ianzini
authors.forename: G
authors.initials: G
authors.lastname: Moschini
authors.forename: O
authors.initials: O
authors.lastname: Sapora
authors.forename: G
authors.initials: G
authors.lastname: Simone
authors.forename: M A
authors.initials: MA
authors.lastname: Tabocchini
authors.forename: P
authors.initials: P
authors.lastname: Tiveron
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D018499:Linear Energy Transfer; D016296:Mutagenesis / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011522:Protons / Q000009:adverse effects*; D012062:Relative Biological Effectiveness
chemical_list: D011522:Protons; D007041:Hypoxanthine Phosphoribosyltransferase