French
English
Abstract :
X-ray phase contrast imaging is an imaging technique with great potential due to its improved contrast compared to conventional radiography. Unlike the attenuation which is directly measurable, at X-ray wavelengths the phase is not a directly measurable quantity. Therefore, in order to measure the phase, specific techniques are used, all of which require free space propagation between the sample and detector. Originally, these techniques were confined to synchrotron sources due to the high spatial coherence provided, though more recently they have been demonstrated with conventional sources. One of the drawbacks of these techniques is that to perform quantitative phase retrieval, several images with different experimental parameters are required, as opposed to the single exposure needed conventionally, increasing the dose delivered and the time required for imaging. With the advent of spectral X-ray detectors, it is possible in a single acquisition to obtain images in several wavelength bands simultaneously. The work presented combines one such phase retrieval method with images acquired at multiple energies with the intention of improving the phase retrieval compared to the monochromatic case. The phase retrieval method investigated is speckle based imaging which involves tracking the sample induced modifications to a spatially random pattern. In combining this method with spectral imaging, several algorithms have been adapted and developed to account for the polychromatic data, whilst several improvements to the existing monochromatic algorithms have also been made.