OPTICAL COHERENCE TOMOGRAPHY/FUNCTIONAL IMAGING: New OCT approach reveals functional information by collecting spectral data

A new technique—a modified approach to optical coherence tomography (OCT) able to provide cross-sectional images of biomolecules—promises significant implications for both clinical and research applications. While conventional OCT reveals structures such as blood vessels and even capillaries, it does not provide functional information such as absorption. The Duke University (Durham, NC) development team’s novel method for collecting and interpreting OCT information enables simultaneous collection of data describing the wavelengths of light. This data enables creation of 3-D images and also contains important spectral information that allows, for instance, visualization of the hemoglobin being carried by even the narrowest blood vessels, as well as molecules such as medical dyes.¹ Hemoglobin, which carries oxygen, acts as a “natural” contrast agent because of its absorption properties. Many disorders can be characterized by the levels of blood oxygen, a characteristic that the new technique can detect in shades of red.

The approach has several important applications, such as visualizing tumor development processes like angiogenesis and oxygen deprivation. It also could help in detecting disease of the eye, especially those that impact the tiny vessels of the eye, as well as monitoring drug delivery and effectiveness, according to Adam Wax, Theodore Kennedy associate professor of biomedical engineering. The team tested the new system in living mice. Conventional OCT enabled them to see certain structures, such as muscle and vessels, in black and white, but offered no information about the tissue function. “With the new system, we observed a wealth of information we couldn’t before,” says Francisco Robles, a graduate student at Duke’s Pratt School of Engineering. Although the muscle layer at the surface was relatively colorless, “as the light continued through the blood vessels below, a red shift in color was clear. To our knowledge, these are the first micron-scale cross-sectional images of living tissue in true color.”

1. F. Robles et al., Nat. Phot., 5, 744–747 (2011).