| Zugriffsnummer | 43340 |
| Dokumenttyp | Konferenzartikel |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | Correcting the lack of secondary particle equilibrium in simulations of nanoparticle-induced dose enhancement |
| Autor(in); Institution |
Rabus, Hans; 6.5, Strahlenwirkung, PTB-Braunschweig
Gargioni, Elisabetta; University Medical Center Hamburg-Eppendorf, Hamburg, GERMANY
Nettelbeck, Heidi; 6.5, Strahlenwirkung, PTB-Braunschweig
Villagrasa, Carmen; Institut de Radioprotection et Sûreté nucléaire, Fontenay-aux-Roses, FRANCE
|
| Quelle/Jahr | Strahlenschutz und Medizin, Patienten - Beschäftigte - Gesellschaft:(2019), 191 - 196 |
| ISBN | 978-3-7406-0446-2 |
| Verlag | Köln: TÜV Media GmbH |
| Konferenzangaben | 51. Jahrestagung des Fachverbandes Strahlenschutz e.V., Würzburg, 9-12, September, 2019, Deutschland |
| Freie Schlagworte | Nanodosimetry ; track structure ; nanoparticles |
| Zusammenfassung | Introduction: Nanoparticles (NP) of high-Z elements are known to enhance the biological effectiveness of photon radiation, which is believed to be due to the local dose enhancement around NPs. While this can only be assessed by Monte Carlo (MC) simulations, such setups often fail to assure secondary particle equilibrium, thus resulting in an overestimation of dose enhancement. This work presents a method for correcting such a bias in results. Methods: The irradiation of a spherical gold NP in water by orthovoltage x-rays was simulated for a parallel photon beam of diameter comparable to that of the NP. The simulations were performed for two different NP diameters and three different x-ray spectra. Using photon interaction data from literature, the absorbed dose under secondary electron equilibrium (SEE) was calculated analytically and used to correct the simulation results based on two assumptions: i) a comparable lack of energy deposition by electrons with and without a NP, and ii) a negligible influence of the biased photon energy spectrum on the energy spectrum of emitted of secondary electrons from the NP. Results: For all six combinations of NP dimensions and photon spectra, the dose enhancement factors after correction for lack of SPE were about an order of magnitude smaller than those obtained for the narrow-beam MC simulation. Furthermore, if SEE is ensured, significant dose enhancement is only observed within the first 100 nm to 200 nm around the NP rather than extending to several micrometers. Taking into account the influence of secondary (scattered) photons interacting with the NP does not significantly change these observations. Conclusions: A realistic assessment of dose enhancement factors by high-Z NPs requires a proper determination of absorbed dose under SEE conditions. Such an approach results in an absorbed dose to water (in the absence of the NP) that is constant over microscopic dimensions. This dose value can be determined by an analytical approach using known photon interaction data. Biased, narrow-beam MC simulations can thus be corrected to obtain realistic dose enhancement factors, which otherwise could only be obtained with full broad-beam simulations requiring several orders of magnitude longer computing time. |
| Themenbereich der Metrologie | Ionisierende Strahlung |
Zitierung
Rabus, H., Gargioni, E., Nettelbeck, H., & Villagrasa, C. (2019). Correcting the lack of secondary particle equilibrium in simulations of nanoparticle-induced dose enhancement. 51. Jahrestagung des Fachverbandes Strahlenschutz e.V., Würzburg, 9-12, September, 2019, Deutschland.