|Titel:||Experimental and Numerical Studies for Synchrotron-based X-ray Fluorescence Imaging in Medium Sized Objects||Sonstige Titel:||Experimentale und Numerische Studien zu Synchrotron gestützer Röntgenfluoreszenzbildgebung in mittelgroßen Objekten||Sprache:||Englisch||Autor*in:||Schmutzler, Oliver||Schlagwörter:||X-ray; Fluorescence; Imaging; Synchrotron; gold; gadolinium; retention; Compton||Erscheinungsdatum:||2020||Tag der mündlichen Prüfung:||2020-11-23||Zusammenfassung:||
The increasing interest in nano materials, nano medicine and general applications of nano particles in biological systems demands imaging and analysis methods which meet the requirements of small concentrations and smallest scales without applying destructive force. Synchrotron-based X-ray fluorescence imaging (XFI) is a promising modality for such applications. This work describes hurdles and opportunities of mono energetic pencil beam synchrotron-radiation-based XFI in theory and experiment, probing various tracers in medium sized targets. With numerical studies the parameter space of incident beam energy, tracer element and phantom size was explored for best fluorescence yield. Kα1, Kβ1 and Lα1 fluorescence yield calculations of 1µg tracers in spherical water phantoms with radii of 1mm and 10mm irradiated with mono energetic photons from 10 to 100keV are shown for all stable elements, relevant background phenomena are also displayed. Potential background by scattered polarized photons is studied spatially and spectrally with GEANT4 simulations for water phantoms with radii of 1mm to 50mm covering energies from 5 to 110keV. Experimental studies on medically an biologically relevant probes were performed at the PETRAIII synchrotron. Low energy gold L-shell fluorescence was used experimentally to determine sub pg cellular uptake of PSMAi+ and MUA functionalized gold nano particles in PC3 cells with smallest irradiated sample sizes of 622 and 311 cells. Medium energy gadolinium K-shell fluorescence was applied to image gadolinium based MRI contrast agent Gadovist residuals in a rat bone. Here the XFI quality of beam size dependent spacial resolution was demonstrated with pixel size of 1x1mm2, 0.2x0.2mm2 and 0.1x0.1mm2, allowing for area scans with locally increased spatial resolution. Highly localized gadolinium concentrations of over 500µg/g(bone) thereby were found. A multi modal approach of heavy element K-shell fluorescence, using platinum, iridium, gold and bismuth, imaging of all four elements simultaneously was demonstrated and compared to sensitivities of single element imaging. Only high concentrations yielded significant sensitivity losses compared to single element usage, therefore multi mode XFI is as viable as single element tracer usage if moderate concentrations are expected.
|Enthalten in den Sammlungen:||Elektronische Dissertationen und Habilitationen|