3D-imaging tool first to provide inside view of capillaries

Researchers at Northwestern University have developed new technology that provides images of the tiny, hair-like blood vessels in the human body.

Called spectral contrast optical coherence tomography angiography (SC-OCTA), the non-invasive 3D-imaging tool can measure blood flow and oxygen exchange in microscopic capillaries, providing early diagnosis of diseases.

“There has been a progressive push to image smaller and smaller blood vessels and provide more comprehensive, functional information,” says Vadim Backman, Walter Dill Scott Professor of Biomedical Engineering in Northwestern University’s McCormick School of Engineering. “Now we can see even the smallest capillaries and measure blood flow, oxygenation and metabolic rate.”

SC-OCTA combines spectroscopy—which looks at the various visible light wavelengths or color spectra—with conventional optical coherence tomography, which is similar to ultrasound except uses light waves instead of sound waves.

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“SC-OCTA is a valuable diagnostic tool,” says James Winkelmann, a graduate student in Backman’s laboratory and the first author of a paper published in the journal Light: Science and Applications. “We can now detect alterations to capillary organization, which is evident in a variety of conditions ranging from cancer to cardiovascular disease. Detecting these diseases earlier has the potential to save lives.”

Unlike traditional imaging, SC-OCTA does not rely on injected dyes for contrast or harmful radiation. And, while many types of imaging only work if the area of interest is moving—such as ultrasound which can only image blood when it is flowing or completely still—SC-OCTA can take a clear picture of both.

“It can measure blood flowing regardless of how fast it goes, so motion is not a problem,” added Backman.

Winkelmann notes that SC-OCTA’s “unique ability to image non-flowing blood could also become a valuable tool for the booming field of organoids, which studies how organs develop and respond to disease.”

At the same time, the 3D-imaging technique does have one limitation—it cannot image deeper than 1 millimeter. However, Backman contends this shortfall can be fixed by attaching the tool on the end of an endoscopic probe, a capability his laboratory is currently developing.

“Future plans will aim to further optimize SC-OCTA algorithms and implement visible OCT endoscopy for minimally invasive in vivo imaging with molecular sensitivity,” states the paper.