A micro-tomography method based on X-ray diffraction enhanced imaging for the visualization of micro-organs and soft tissues.

Diffraction enhanced imaging (DEI) is one of the phase contrast imaging methods using the monochromatic X-ray from synchrotron, which provides information on the out-of-plane angular deviation of X-ray. DEI allows the investigation of micro-structures inside weakly absorbing samples at high spatial resolution without serious radiation exposure. Tomographic techniques can be applied readily to phase contrast images. The combination of DEI and tomography allows for a reconstruction of refractive index gradient distribution inside weakly absorbing samples with micrometer resolution, particularly suited for the 3D observation of micro-organisms and tissues. The existing phase contrast tomography methods based on DEI use phase contrast images as projections, such images contain not only the phase information, but also the absorption information. A novel method (DEI in the tomography mode) was developed to greatly increase the proportion of refraction information in phase contrast images by computing the difference between the two sets of images acquired at different angles of the rocking curve to adopt the projections with a complete set (2pi) for reconstruction. The reconstructed images of cochlea of a guinea pig showed the spatial structures and the micro-features inside the samples. The new method reveals higher spatial resolution compared to the conventional phase contrast tomography methods and is more suitable to the investigation of micro-structures of micro-organisms and tissue materials.