Background—Phase-contrast x-ray imaging using an x-ray interferometer has great potential to reveal the structures inside soft tissues, because the sensitivity of this method to hydrogen, carbon, nitrogen, and oxygen is 1000 times higher than that of the absorption-contrast x-ray method. Imaging of vessels is very important to understand the vascular distribution of organs and tumors, so the possibility of selective angiography based on phase contrast is examined with a physiological material composed of low-atomic-number elements.

Methods and Results—Phase-contrast x-ray imaging was performed with a synchrotron x-ray source. Differences in refractive index, d, of physiological saline, lactated Ringer's solution, 5% glucose, artificial blood such as pyridoxylated hemoglobin--polyoxyethylene conjugate, and perfluorotributylamine were measured. Because the d of physiological saline has highest contrast, it was used for the phase-contrast x-ray imaging of vessel, and this was compared with absorption-contrast x-ray images. Vessels >0.03 mm in diameter of excised liver from rats and a rabbit were revealed clearly in phase-contrast x-ray imaging, whereas the vessel could not be revealed at all by the absorption-contrast x-ray image. Absorption-contrast x-ray images with iodine microspheres depicted only portal veins >0.1 mm in diameter with nearly the same x-ray dose as the present phase-contrast x-ray imaging.

Conclusions—Phase-contrast x-ray imaging explored clear depiction of the vessels using physiological saline with small doses of x-rays.