Abstract
Refraction-contrast X-ray computed tomography (RCT) can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, RCT requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. We propose a RCT reconstruction algorithm by which these non-linear effects can be overcome and excellent soft-tissue contrast of RCT can be preserved in the vicinity of such artefact-producing structures.
