Systems capable of performing phase-contrast X-ray micro-CT currently represent only a fraction of all installed micro- CT devices. Institutions without dedicated phase-contrast research therefore often lack the necessary equipment and expertise to apply these techniques. Until this gap is closed, X-ray contrast agent-enhanced absorption-contrast micro-CT remains the primary means for soft tissue imaging where enhanced sensitivity, but not quantitative imaging is required. Commercial contrast agents for in vivo applications are, however, typically small molecular compounds that can easily diffuse across the blood vessel walls, which makes them unsuitable for ex vivo high resolution X-ray micro-CT imaging. We evaluated the suitability for kidney capillary imaging of the nanoparticle-based blood pool contrast agents Aurovist 15 nm and ExiTron nano 12000, along with the vascular casting resin μAngiofil, by post mortem imaging of whole mouse kidneys with 4-5 μm voxel size using the laboratory source micro-CT system Nanotom m. Based on the results, we identified specific obstacles to reliable capillary filling in the kidney, which will aid in the development of next generation X-ray contrast agents and protocols.
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