Elektronenemissionsspektren von Goldnanopartikeln zur Dosisberechnung in der Strahlentherapie

authored by: Philine Antonia Hepperle
supervised by: Clemens Walther
Abstract: Radiation therapy is one of the three standard methods for cancer treatment and is based on the cell-damaging effect of ionizing radiation and secondary electrons released during the interaction of the radiation with tissue. Since radiation interactions are not cell-specific, healthy tissue is also affected. To reduce the radiation damage in healthy tissue so-called radiosensitizers such as gold nanoparticles (AuNPs) are deposited into the tumorous tissue. These particles confine the dose distribution to the tumor volume. Monte-Carlo (MC) track structure simulations play an important role in modern therapy
planning. These simulations are currently based on physical models, which are only a rough approximation, especially for electron energies below a few keV. MC simulations of different studies often show a wide range of results.
The aim of this work was to determine the electron emission spectra of AuNPs for electron, proton, and photon radiation, which will provide a valuable data set for benchmarking MC simulations. In a first step a suitable substrate and technique for the deposition of AuNPs had to be found. A self-supporting carbon foil was identified as the most suitable substrate on which the AuNPs have to be deposited. The drop-casting technique proved to be the best method for deposition. Deposition using a spin-coater also showed good results,
while the microdrop could not produce a sufficiently homogeneous sample.
The samples were then characterized by scanning electron microscopy and scanning transmission electron microscopy with respect to their size, spatial distribution and surface coverage. This showed that the AuNPs form both monolayers and clusters, which merge into multilayers. Characterization of the samples by X-ray photoelectron spectroscopy with respect to their chemical structure revealed carbon and oxygen contamination. Sputtering the sample with argon removed the contaminations but also the coating of the AuNPs so that sputtering of the sample is only possible to a limited extent. The electron emission spectra measured using an electron beam did not show a noticeable enhancement of the yield of secondary electrons by AuNPs deposited on a carbon foil due to their coating as well as surface contaminations compared to measurements of the carbon foil without AuNP. Doubly differential electron emission spectra of AuNPs as a function of energy and emission angle were measured for the first-time for proton beams. These spectra showed an increased yield of secondary electrons using AuNPs compared to the bare carbon foil. Electron emission spectra measured using photon radiation at beamline P22 at PETRA III at DESY in Hamburg also showed an enhanced yield of electrons by AuNPs compared to the carbon foil without AuNPs. They provide essential benchmark data for MC simulations for photon and electron transport processes in AuNPs in the energy range up to about 10 keV.
Type: Doctoral thesis
No. of pages: 188
Publication date: 03.06.2024
Publication status: Published
Sustainable Development Goals: SDG 3 - Good Health and Well-being
Electronic version(s): https://doi.org/Doubly differential electron emission spectra of AuNPs as a function of energy and emission angle were measured for the first-time for proton beams. These spectra showed an increased yield of secondary electrons using AuNPs compared to the bare carbon foil. Electron emission spectra measured using photon radiation at beamline P22 at PETRA III at DESY in Hamburg also showed an enhanced yield of electrons by AuNPs compared to the carbon foil without AuNPs. They provide essential benchmark data for MC simulations for photon and electron transport processes in AuNPs in the energy range up to about 10 keV. (Access: Open)
https://d-nb.info/1331812259/34 (Access: Unknown)
https://nbn-resolving.org/urn:nbn:de:101:1-2406060209083.070972214935 (Access: Unknown)
https://www.repo.uni-hannover.de/handle/123456789/17536 (Access: Unknown)
https://doi.org/10.15488/17406 (Access: Unknown)