| Zugriffsnummer | 22871 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | From macro to nanodosimetry: limits of the absorbed-dose concept and definition of new quantities |
| Autor(in); Institution |
Großwendt, Bernd; 6.6, Grundlagen der Dosimetrie, PTB-Braunschweig
|
| Quelle/Jahr | Proceedings of the International Workshop on "Uncertainty assessment in computational dosimetry" : a comparison of approaches:(2008) |
| Availability | [CD-ROM] ; file name: micro_grosswendt.pdf |
| Herausgeber(in) |
Gualdrini, Gianfranco
|
| ISBN | 978-3-9805741-9-8 |
| Verlag | Bologna: |
| Konferenzangaben | CONRAD WP4, Bologna, 08-10, October, 2007, Italy |
| Zusammenfassung | In view of the fact that radiation-induced damage to cells and genes is governed, to the greater part, by the pattern of inelastic interactions of ionizing particles in sub-cellular targets (segments of the DNA, nucleosomes, segments of the chromosome fibre), the effectiveness and the quality of ionizing radiation should be defined more in terms of quantities directly related to the particle track structure than in terms of macroscopic quantities like absorbed dose and linear energy transfer (LET). Therefore, a potential new concept for characterizing radiation quality is presented, which is based on the assumption that the initial damage to the DNA is mainly due to the number of ionizations (the ionization cluster size) produced by single ionizing particles directly within short segments of the DNA or in the near neighbourhood. In this concept, it is expected that the probabilities of cluster size one or of cluster size greater than or equal to two can be directly related to the radiation induced yields of single- or double-strand breaks of the DNA. The application of the concept in practice requires a detailed knowledge of the frequency distribution of ionization cluster size due to the interaction of single ionizing particles in target volumes of nanometric dimensions (nanodosimetry). After a short description of a potential measuring principle, radiation quality is defined in terms of quantities derived from ionization duster-size distributions which were calculated by a simulation of ionization cluster-size formation by electrons, protons, 4He-ions,7 Li-ions, 12C-ions, and 20Ne-ions in DNA-segment-like liquid water cylinders (2.3 nm in diameter, 3.4 nm in height) using the Monte Carlo method. The validity of the concept is checked by a comparison of nanodosimetric quantities derived from the calculated ionization cluster-size distributions (i) with bio-effect cross sections of SV40 viral DNA for x-rays. 4He-ions, 12C-ions, 16O, and 20Ne-ions, and (ii) with the relative biological effectiveness of protons in V79 Chinese hamster cells. |
