| Zugriffsnummer | 37086 |
| Dokumenttyp | Konferenzartikel |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | Double differential electron-emission cross sections of DNA constituents induced by protons at Bragg peak energies |
| Autor(in); Institution |
Rudek, Benedikt; 6.5, Strahlenwirkung, PTB-Braunschweig
Bennett, Daniel; 6.5, Strahlenwirkung, PTB-Braunschweig
Bug, Marion U.; 6.5, Strahlenwirkung, PTB-Braunschweig
Wang, Mingjie; 6.5, Strahlenwirkung, PTB-Braunschweig
Baek, Woon Yong; 6.5, Strahlenwirkung, PTB-Braunschweig
Buhr, Ticia; 6.5, Strahlenwirkung, PTB-Braunschweig
|
| Quelle/Jahr | ECAMP 12, 12th European Conference on Atoms, Molecules and Photons: Extended abstracts:(2016), 342 |
| Availability | [Online only] |
| URL | |
| Konferenzangaben | 12th European Conference on Atoms, Molecules and Photons, Frankfurt am Main, 05-09, September, 2016, Germany |
| Freie Schlagworte | interactions of photons with charged particles ; photoionization ; synchrotron radiation |
| Zusammenfassung | Radiation damage in human tissue can be attributed to either direct damage by the ionizing particle or to indirect effects following the emission of secondary electrons. Indirect effects are estimated to contribute two thirds of the overall damage. The vast majority of secondary electrons carry kinetic energies of only few electron volts and thus their inelastic mean free path amounts to only a few nanometers. To simulate damage in the DNA, which is considered to be the most radiosensitive target within the cell, it is therefore necessary to consider secondary electron emission not only from the surrounding water molecules but also from the DNA constituents themselves. In proton beam therapy, the highest probability for electron emission occurs at the end of the proton trajectory, the so called Bragg peak, when the proton beam has been decelerated from kinetic energies of initially several MeV to about 100 keV. Our incentive was to quantify the electron emission from DNA constituents in this energy range and implement the data into the MC trajectory simulation toolkit Geant4 DNA, which should eventually lead to a better estimation of the relative biological effectiveness (RBE) of proton beams. In detail, double differential cross sections were measured for the electron emission from vapor-phase pyrimidine, tetrahydrofuran and trimethyl phosphate that are structural analogues to the base, the sugar and the phosphate residue of the DNA, respectively. The range of proton energies was from 75 keV to 135 keV, the angles ranged from 15° to 135°, and the electron energies were measured from 10 eV to 200 eV. Single differential and total electron emission cross sections are derived by integration over angle and electron energy and compared to a semi-empirical and a quantum mechanical calculation, both within the first Born approximation. The CB1 calculation provides the best prediction of double and single differential cross section for electron energies larger than 60 eV. The total emission cross sections of the three samples are proportional to their total number of valence electrons. The measurements were part of the EMRP Joint Research Project BioQuaRT which aimed to determine the physical properties of ionizing particle track structure on molecular and nanoscopic scales, and to correlate these track structure properties at the cellular level with the biological effects of radiation. While proton beam therapy has the advantage of a superior localization of dose compared to the standard use of therapeutic x-rays, it still involves a significant dose to healthy tissue. In an attempt to improve the therapeutic index, high-Z contrast agents have been introduced into tumor cells as effective electron emitters in cell experiments. The experimental dose enhancement factors have not yet been verified by simulations due to the lack of experimental input data. At our presentation, we would like to discuss ideas, challenges and first results for measuring the electron emission spectra of gold nanoparticles. References [1] M. U. Bug, Nanodosimetric particle track simulations in water and DNA media, Dissertation, University of Wollongong, Australia (2014), URL http://ro.uow.edu.au/theses/4150/. [2] S. Incerti, G. Baldacchino, M. Bernal, R. Capra, C. Champion, Z. Francis, P. Guèye, A. Mantero, B. Mascialino, P. Moretto, P. Nieminen, C. Villagrasa, and C. Zacharatou, The GEANT4-DNA project, International Journal of Modeling, Simulation, and Scientific Computing, 01, 157-178 (2010). [3] H. Rabus, H. Palmans, G. Hilgers, P. Sharpe, M. Pinto, C. Villagrasa, H. Nettelbeck, D. Moro, A. Pola, S. Pszona, and P. Teles, Biologically weighted quantitiesin radiotherapy: an EMRP joint research project, EPJ Web of Conferences, 77, 00021 (2014). [4] H. Palmans, H. Rabus, A. L. Belchior, M. U. Bug, S. Galer, U. Giesen, G. Gonon, G. Gruel, G. Hilgers, D. Moro, H. Nettelbeck, M. Pinto, A. Pola, S. Pszona, G. Schettino, P. H. G. Sharpe, P. Teles, C. Villagrasa, and J. J. Wilkens, Future development of biologically relevant dosimetry, The British Journal of Radiology, 88, 1045 (2015). |
Zitierung
Rudek, B., Bennett, D., Bug, M. U., Wang, M., Baek, W. Y., & Buhr, T. (2016). Double differential electron-emission cross sections of DNA constituents induced by protons at Bragg peak energies. 12th European Conference on Atoms, Molecules and Photons, Frankfurt am Main, 05-09, September, 2016, Germany.