A new fluorescence imaging technique developed by Stanford scientists offers the ability to view the pulsing blood vessels of living animals with, as described in a news release, "unprecedented clarity." The release contains more details on the technique, which is called near infrared-II imaging or NIR-II:
Compared with conventional imaging techniques, the increase in sharpness is akin to wiping fog off your glasses... [It] involves first injecting water-soluble carbon nanotubes into the living subject's bloodstream.
The researchers then shine a laser (its light is in the near-infrared range, a wavelength of about 0.8 micron) over the subject; in this case, a mouse.
The light causes the specially designed nanotubes to fluoresce at a longer wavelength of 1-1.4 microns, which is then detected to determine the blood vessels' structure.
That the nanotubes fluoresce at substantially longer wavelengths than conventional imaging techniques is critical in achieving the stunningly clear images of the tiny blood vessels: longer wavelength light scatters less, and thus creates sharper images of the vessels. Another benefit of detecting such long wavelength light is that the detector registers less background noise since the body does not does not produce autofluorescence in this wavelength range.
Researchers said the ability to obtain both blood flow information and blood vessel clarity, which was not previously possible, will be particularly useful in studying vasculature diseases in small animals and how such conditions respond to therapies as well as devising new treatments. In the future, researchers intend to alternative fluorescent molecules in an effort to make the technology more easily accepted for use in humans.