KentuckyFC writes "The early symptoms of many diseases show up first in the smallest blood vessels, but imaging the fine structure of these vessels is a tricky problem for medics. The most common way is to inject them with a contrast agent and use x-ray tomography to create a 3D image of their structure. This shows problems in the large vessels but not smaller ones. The problem is the lack of contrast. Conventional contrast agents are based on iodine, which has a high electron density and so better absorbs x-rays than other atoms. But a better solution would be to use a higher density fluid, such as a liquid metal. The obvious fears associated with toxicity and so forth mean this has never been tried. Until now. A team of Chinese biomedical engineers have created the world's first images of a pig's heart injected with gallium. This has a melting point of 29 degrees C, so it's a liquid at body temperature. And the results show the detailed structure of the tiniest blood vessels, revealing capillaries just 0.07 mm in diameter. That's significantly more detailed than is possible with iodine-based contrast agents. An important question is whether this technique will ever be possible in humans. The Chinese team seems optimistic. They say gallium is chemically inert, non-toxic to humans and can be injected and sucked out without leaving a residue. 'It suggests the possibility for localized in vivo vascular-enhanced radiological imaging in the near future.'"