The emergence of phase contrast with sample-detector distance

This animation is a cartoon of a phase-contrast tomography experiment conducted on a zebrafish embryo. The embryo is less than 0.5 mm wide and only approximately 2 mm long. It was irradiated with 21-keV radiation, for which the transmission of the embryo is approximately 98% or greater. Absorption contrast is therefore very low (except for the two dark features, known as ‘otoliths’, which thus act as visual anchors). The experiment moves the scintillator screen from being immediately behind the sample (at 5 mm) to over 50 mm. One sees the increase in phase contrast as edge enhancement occurs at the boundary between distinct organs in the embryo.

I  thank Jörg Huwyler and Emre Cörek of the Institute of Pharmaceutical Sciences, University of Basel for providing the sample, and Christian Schlepütz of the TOMCAT beamline at SLS for recording the data.