Fractionated irradiation of carbon beam and the isoeffect dose on acute reaction of skin

Materials and methods: Mice: C3H/HeMsNrsf female mice aged 4 months old were used for this study. The animals were produced and maintained in specific pathogen-free (SPF) facilities. Irradiation: The mice right hind legs received daily fractionated irradiation ranged from single to six fractions. Carbon ions (C) were accelerated by the HIMAC synchrotron to 290 MeV/u. Irradiation was conducted using horizontal carbon-ion beams with a dose rate of ~3 Gy/min. We chose the LETs at entrance of plateau (20keV/μm) and the SOBP (proximal: 40 keV/μm, middle: 45 keV/μm, distal: 60 keV/μm, distal-end: 80 keV/μm). The reference beam was Cs gamma rays with a dose rate of 1.2 Gy/min. Skin reaction: Skin reaction of the irradiated legs was scored every other day, between the14th and 35th post-irradiation days. Our scoring scale consisted of seven steps, ranging from 0.5 to 3.5 [1]. The skin score analyzed a result by the method that described by Ando et al. [2]. The Fe-plot proposed by Douglas and Fowler was used as a multifraction linear quadratic model. A plot between the reciprocal of the isoeffect dose and the dose per fraction resulted in a straight line.