New Imaging Technique Provides Unprecedented View of Capillaries

A group of researchers from Northwestern University has recently created a tool that provides unprecedented images of blood flow through capillaries. With this technology scientists have the potential to observe the 40 billion plus capillaries in the human body, bolstering cardiovascular care.

The technique utilizes spectral contrast optical coherence tomography angiography (SC-OCTA) to provide 3D images of the blood vessels. Through this system, subtle changes in capillary organization can be detected to diagnose disease earlier.

“There has been a progressive push to image smaller and smaller blood vessels and provide more comprehensive, functional information,” said study leader Vadim Backman. “Now we can see even the smallest capillaries and measure blood flow, oxygenation and metabolic rate.”

These findings were published last week in Light: Science and Applications. Backman is also the Walter Dill Scott Professor of Biomedical Engineering at the McCormick School of Engineering at Northwestern.

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Professionals have long been using Doppler ultrasound to visualize major veins and arteries, however this method does not provide in depth images of the whole circulatory system. Capillaries, unlike arteries and veins, play an active role in oxygen exchange in the circulatory system. Issues with gas exchange at these sites can lead to low blood oxygen, giving rise to a wide range of symptoms from headaches to heart failure. Now with this new imaging technology, doctors will have a better view of potential pathologies at these capillaries.

“You can have great blood flow through arteries and still have absolutely no blood sending oxygen to tissues if you don’t have the right microvasculature,” said Backman. “Oxygen exchange is important to everything the body does. But many questions about what happens in microvasculature have gone unanswered because there was no tool to study them. Now we can tackle that.”

SC-OCTA is a technique that combines spectroscopy, an analysis using visible light wavelengths, with optical coherence tomography (OCT), a process similar to ultrasound but with light waves rather than sound. OCT targets tissues of interest in a manner similar to radar, then analyzes these regions with spectroscopy.

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The technique has many advantages over conventional imaging methods, being that it does not rely on dye injections for contrast or any radiation. Several imaging techniques, such as ultrasound, are limited to moving entities (blood flow) for imaging, but the SC-OCTA is capable of imaging moving or still aspects. In other words, the technique can image both stationary fluids as well as moving organs, such as the heart.

“SC-OCTA is a valuable diagnostic tool,” added James Winkelmann, one of the graduate students in Backman’s laboratory and the study’s first author. “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.”

A shortcoming with the SC-OCTA imaging is that its maximum depth of imaging is 1 millimeter, much shallower than ultrasound’s range. Backman notes that this can be remedied by adhering the imaging tool to an endoscopic probe, inserting it into the body, and taking up-close images. His lab is currently working to develop this feature.

Source: EurekAlert