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Hybrid medical imaging technology may shed new light on cancer

The image at the bottom is a composite of the first two taken of a rabbit esophagus in vivo. (Image/Courtesy of Qifa Zhou)

Scientists from USC and Washington University in St. Louis have developed a new type of medical imaging that gives doctors a fresh look at live internal organs.

The technology combines two existing forms of medical imaging — photoacoustic and ultrasound — and uses them to generate a high-contrast, high-resolution combined image that could help doctors spot tumors more quickly.

“Photoacoustic endoscopy provides deeper penetration than optical endoscopy and more functional contrast than ultrasonic endoscopy,” said Lihong Wang, principal investigator and corresponding author of a study on the technology that appeared in Nature Medicine on July 15, and professor of biomedical engineering at Washington University.

Wang collaborated with Qifa Zhou, Ruimin Chen and Kirk Shung of USC, as well as Joon-Mo Yang, Christopher Favazza, Junjie Yao, Xin Cai and Konstantin Maslov from Washington University.

“This is the first time that we have had small endoscopy with two imaging modalities,” said Qifa Zhou, one of the principal investigators and corresponding authors of the study, and professor at the NIH Resource Center for Medical Ultrasonic Transducer Technology in the USC Department of Biomedical Engineering.

Currently, doctors routinely employ ultrasound endoscopy to study internal organs. This technique places an ultrasound camera, similar to ones used to create images of fetuses, on a flexible scope that can be inserted internally.

Though these images are typically high-resolution, they are also low-contrast — making a dim image, like a photograph shot in a poorly lit room.

To address the problem, Wang, Zhou and their teams added a photoacoustic-imaging device to the ultrasound endoscope. The resulting camera zaps organ tissue with a light. When the light is absorbed by tissue, the tissue gets slightly hotter and expands. That expansion produces a sound pressure wave that the ultrasound device on the endoscope picks up.

“This technology combines the best of both worlds,” said Shung, director of the NIH Resource Center and professor of biomedical engineering at USC.

The researchers have tested their new device inside the gastrointestinal tract, producing in vivo images detailed enough to show blood vessels, as well as the density of the tissue around them.

“This imaging has fine resolution and high contrast,” said Yang, a postdoctoral researcher in Wang’s group. With a clearer picture of what’s going on inside the gastrointestinal tract, doctors could potentially spot colon and prostate cancers earlier.

The research was funded by the National Cancer Institute at the National Institutes of Health,  grants R01 CA157277, R01 EB000712, R01 EB008085, R01 CA134539, P41-EB2182, and U54 CA136398 (Network for Translational Research).

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