On contrast of biological X-ray nanomicroscopy

We analyse the absorption contrast of histological and cytological preparations, which can be achieved in nanomicroscopic studies using monochromatic radiation in the spectral range of 90–600 eV (14–2 nm). Two types of unstained biological objects are considered: untreated and fixed in paraffin, and optimum wavelengths are determined for the study of samples with a thickness of 0.5–10 μm with a spatial resolution of 100–20 nm. Taking into account the efficiency of X-ray optics, the number of source photons required to produce a single image is estimated. It is shown that the greatest interest for the study of fixed objects represents the spectral region of 7–14 nm, for which, on the basis of rapidly developing compact sources of incoherent and coherent radiation and effective optics, microscopes for scientific and clinical research can be designed.