K. Fukutsu et al., RESPONSE OF MOUSE INTESTINE AFTER SINGLE AND FRACTIONATED-IRRADIATIONWITH ACCELERATED CARBON-IONS WITH A SPREAD-OUT BRAGG PEAK, Radiation research, 148(2), 1997, pp. 168-174
The responses of mouse intestine were examined after irradiation with
accelerated carbon ions with a spread-out Bragg peak. The carbon-ion b
eam (135 MeV/nucleon), accelerated by the RIKEN ring cyclotron facilit
y, was modulated to have a spread-out Bragg peak (SOBP)3 cm wide. In t
he SOBP the biological dose (relative physical dose x RBE) was designe
d in earlier studies to be flat at the 10% survival level of Chinese h
amster V79 cells. The numbers of surviving crypt clonogenic cells afte
r single and fractionated irradiation with the carbon-ion beam were ob
tained by a microcolony assay method. The composite single-dose surviv
al curves for the crypt clonogenic cells were calculated and fitted by
a linear-quadratic (LQ) model. An analysis with the LQ model for cryp
t clonogenic cells showed that the alpha coefficient increased along w
ith increasing LET, and that the beta coefficient was relatively const
ant, even for high-LET radiations. The biological dose distributions f
or the crypt clonogenic cells at the 10% survival level were flat in t
he SOBP. The isoeffective design of the SOBP for the 135 MeV/nucleon c
arbon-ion beam, based on biological data from a mammalian in vitro cel
l system, appears to be applicable to the response of murine intestina
l tissue in vivo. (C) 1997 by Radiation Raearch Society.