Dortmund 2021 – wissenschaftliches Programm

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ST: Fachverband Strahlen- und Medizinphysik

ST 5: Medical Imaging

ST 5.7: Vortrag

Dienstag, 16. März 2021, 17:30–17:45, STa

Geometry optimization in X-ray propagation based phase contrast imaging — •Hanna Dierks and Jesper Wallentin — Division of Synchrotron Radiation Research, Lund, Sweden

X-ray microscopy and tomography using propagation-based phase contrast (PB-PC) is a powerful technique to study low absorption samples on the micrometer scale. The main benefit of the technique is an increased contrast given by edge enhancement, that is, by near-field interference fringes around sharp edges. In setups with a divergent source, a trade-off between the distance dependent flux and the source coherence must be made. We present a systematical experimental and theoretical investigation of this trade-off, based on experiments with two different setups with high-resolution detectors: a custom-built system with a Cu microfocus source and a commercial system (Zeiss Xradia) with a W source. The fringe contrast, CNR and fringe separation for a low-absorption test sample were measured for 130 different combinations of magnification and overall distances. We find that these figures-of-merit are sensitive to the magnification and that a theoretical optimum can be found that is independent of the overall source-detector distance. In general, we show that the developed theoretical models show excellent agreement with the measurements, if the X-ray source spectrum and the energy dependence of the detector sensitivity are considered. These results can be used for optimizing an imaging system, especially concerning the used magnification.