title: Comprehensive track-structure based evaluation of DNA damage by light ions from radiotherapy-relevant energies down to stopping.
abstract: Track structures and resulting DNA damage in human cells have been simulated for hydrogen, helium, carbon, nitrogen, oxygen and neon ions with 0.25-256 MeV/u energy. The needed ion interaction cross sections have been scaled from those of hydrogen; Barkas scaling formula has been refined, extending its applicability down to about 10 keV/u, and validated against established stopping power data. Linear energy transfer (LET) has been scored from energy deposits in a cell nucleus; for very low-energy ions, it has been defined locally within thin slabs. The simulations show that protons and helium ions induce more DNA damage than heavier ions do at the same LET. With increasing LET, less DNA strand breaks are formed per unit dose, but due to their clustering the yields of double-strand breaks (DSB) increase, up to saturation around 300 keV/μm. Also individual DSB tend to cluster; DSB clusters peak around 500 keV/μm, while DSB multiplicities per cluster steadily increase with LET. Remarkably similar to patterns known from cell survival studies, LET-dependencies with pronounced maxima around 100-200 keV/μm occur on nanometre scale for sites that contain one or more DSB, and on micrometre scale for megabasepair-sized DNA fragments.
authors.affiliation: Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Friedland
authors.affiliation: Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schmitt
authors.affiliation: Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Kundrát
authors.affiliation: Department of Physics, East Carolina University, Greenville, NC, USA.
authors.forename: M
authors.initials: M
authors.lastname: Dingfelder
authors.affiliation: Department of Physics, University of Pavia, Pavia, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Baiocco
authors.affiliation: Department of Physics, University of Pavia, Pavia, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Barbieri
authors.affiliation: Department of Physics, University of Pavia, Pavia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Ottolenghi
mesh_terms: D002244:Carbon / Q000737:chemistry / Q000494:pharmacology; D003198:Computer Simulation; D004247:DNA / Q000528:radiation effects*; D053903:DNA Breaks, Double-Stranded; D006371:Helium / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008027:Light; D018499:Linear Energy Transfer; D009356:Neon / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry / Q000494:pharmacology; D010789:Phototherapy / Q000009:adverse effects*; D011522:Protons; D011878:Radiotherapy / Q000009:adverse effects*
chemical_list: D011522:Protons; D006371:Helium; D009356:Neon; D002244:Carbon; D004247:DNA; D010100:Oxygen