RBE-LET relationships for cell inactivation and mutation induced by low energy protons in V79 cells: further results at the LNL facility.
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.
Belli
M
M
Laboratorio di Fisica, Istituto Superiore di Sanità, INFN-Sezione Sanità, Rome, Italy.
Cera
F
F
Cherubini
R
R
Dalla Vecchia
M
M
Haque
A M
AM
Ianzini
F
F
Moschini
G
G
Sapora
O
O
Simone
G
G
Tabocchini
M A
MA
Tiveron
P
P
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
D011522:Protons; D007041:Hypoxanthine Phosphoribosyltransferase