Processing of projections containing phase contrast in laboratory micro-computerized tomography imaging

• Published in: Journal of applied crystallography 2013-08, Vol.46 (4), p.933-938
• Main Authors: Zaprazny, Zdenko, Korytar, Dusan, Mikulik, Petr, Ac, Vladimir
• Format: Article
• Language: English
• Subjects: Beams (radiation); Coherence; computed radiography; computerized tomography; Crystallography; digital radiography; Imaging; Phase contrast; phase-contrast imaging; Projection; Synchrotrons; Tomography; X-Ray Diffraction and Imaging; X-ray imaging; X-ray radiography; X-rays
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S002188981300558X

Free‐space‐propagation‐based imaging belongs to several techniques for achieving phase contrast in the hard X‐ray range. The basic precondition is to use an X‐ray beam with a high degree of coherence. Although the best sources of coherent X‐rays are synchrotrons, spatially coherent X‐rays emitted from a sufficiently small spot of laboratory microfocus or sub‐microfocus sources allow the transfer of some of the modern imaging techniques from synchrotrons to laboratories. Spatially coherent X‐rays traverse a sample leading to a phase shift. Beam deflection induced by the local change of refractive index may be expressed as a dark–bright contrast on the edges of the object in an X‐ray projection. This phenomenon of edge enhancement leads to an increase in spatial resolution of X‐ray projections but may also lead to unpleasant artefacts in computerized tomography unless phase and absorption contributions are separated. The possibilities of processing X‐ray images of lightweight objects containing phase contrast using phase‐retrieval methods in laboratory conditions are tested and the results obtained are presented. For this purpose, simulated and recorded X‐ray projections taken from a laboratory imaging system with a microfocus X‐ray source and a high‐resolution CCD camera were processed and a qualitative comparison of results was made.