Blood vessels: depiction at phase-contrast X-ray imaging without contrast agents in the mouse and rat-feasibility study.

The ability of phase-contrast x-ray imaging to depict blood vessels without contrast agents was tested by observing livers of a mouse and a rat with synchrotron x rays. Livers were excised by tying arteries and veins to prevent blood from flowing out of the liver. An x-ray interferometer was used to obtain x-ray phase contrast. With the technique of phase-shifting x-ray interferometry, the image mapping x-ray phase shift caused by a liver was measured. The x-ray phase shift caused by blood was substantially different from that caused by other soft tissues; consequently, trees of blood vessels were revealed on the image. Vessels with diameter smaller than 0.1 mm were recognized. This result allows new possibilities for investigation of the vascular system.