X-ray phase-contrast CO2angiography for sub-10 μm vessel imaging
Physics in Medicine and Biology
X-ray in-line phase contrast has recently been combined with CO 2 angiography for high-resolution small-animal vascular imaging at low radiation dose. In this paper we further investigate the potential and limitations of this method and demonstrate observation of vessels down to 8 μm in diameter, considerably smaller than the 60 μm previously reported. Our in-line phase-contrast imaging system is based on a liquid-metal-jet-anode x-ray source and utilizes free-space propagation to convert phase
... on to convert phase shifts, caused by refractive index variations, into intensity differences. Enhanced refractive index variations are obtained through injection of CO 2 gas into the vascular system to replace the blood. We show rat-kidney images with blood vessels down to 27 μm in diameter and mouseear images with vessels down to 8 μm. The minimum size of observable blood vessels is found to be limited by the penetration of gas into the vascular system and the signal-to-noise ratio, i.e. the allowed dose. The diameters of vessels being gas-filled depend on the gas pressure and follow a simple model based on surface tension. A theoretical signal-to-noise comparison shows that this method requires 1000 times less radiation dose than conventional iodine-based absorption contrast for observing sub-50 μm vessels.