title: Visualization of free radical reactions in an aqueous sample irradiated by 290 MeV carbon beam.
abstract: The detection of free radical reactions in a gelatin sample irradiated by a heavy-ion beam was tested using electron paramagnetic resonance (EPR) spectroscopic and MRI methods. Geometry and the amount of free radical generation in a sample are described. A reaction mixture containing glutathione and a nitroxyl radical, TEMPOL, was caked with gelatin, and then irradiated with a 290 MeV carbon beam. The amount of free radical generation in a solid sample was almost flat from the surface to the beam end, except for a small peak, the peak radioactivation profile, and then steeply decreased approaching the beam end. Total free radical reactions obtained with carbon-beam irradiation were expected to be less than one-third of X-ray irradiation, when the same dose for a deeper target was considered. Both EPR and MRI are useful tools to visualize free radical generation in samples irradiated by a heavy-ion beam. The EPR-based method is more sensitive and quantitative than the MRI-based method; however, the MRI method can achieve high spatial resolution. This study gives the rationale for a redox regulation trial using antioxidant drugs to reduce the side effects on normal tissues in carbon-beam therapy.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Inage-ku, Chiba-shi, Chiba, Japan. matsumok@nirs.go.jp
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Katsura
authors.initials: K
authors.lastname: Nagata
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Kazutoyo
authors.initials: K
authors.lastname: Endo
authors.forename: Kazunori
authors.initials: K
authors.lastname: Anzai
authors.forename: Ichio
authors.initials: I
authors.lastname: Aoki
mesh_terms: D002244:Carbon; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D020450:Heavy Ions
chemical_list: D005609:Free Radicals; D002244:Carbon