New Medical Imaging Promises Whole-Body Scanning in Real Time

By combining light and ultrasound, Duke and Caltech researchers want to help doctors see what's happening, as it happens, in the human body.

Ever since the time of Hippocrates, physicians have had a fundamental problem with internal injuries and disease — they can't directly see inside the human body. Well, they can, but it involves scalpels and bone saws and a whole other set of headaches.

Happily, modern medical professionals have some nice hands-off options — x-ray and ultrasound, to name two. But all medical imaging technologies have their limitations. The good news is that biomedical engineers are overcoming these limitations by combining different imaging techniques.

Case in point, researchers at Duke and Caltech have developed a new hybrid imaging technology that can track internal systems with unprecedented speed and resolution. By way of the new technique, doctors can observe various internal processes — blood flowing, medicine circulating, neurons firing — in a single, real-time, whole-body scan.

Dubbed SIP-PACT (single-impulse photoacoustic computed tomograph), the technology uses light and sound together to create a more thorough and accurate image. The SIP-PACT technique works by sending a short but powerful light burst that causes internal cells to emit ultrasound waves — like ringing a million tiny organic bells. Because ultrasound waves can pass safely through tissue, external sensors can collect the echoing sound and transpose it back into visual information. No scalpels required.

Alas, even this new space-age technique has its limitations, and they're pretty significant — from an anthropocentric point of view, anyway. As of now, the whole-body imaging aspect only works on small animals since the initial light burst can only peer about five centimeters into typical biological tissue. In other words, we humans are just too big for whole-body imaging. But if you've got a sick mouse, you're in business.

Still, that could change quite soon, according to researcher Junjie Yao, assistant professor of biomedical engineering at Duke University.

“We are actively working at Duke and Caltech to develop the next generation technology for human imaging, especially for breast cancer screening, functional brain mapping, and skin disease diagnosis,” Yao said in an email. “Photoacoustic is a highly scalable technology, which can be readily transferred from labs to clinics.”

Yao said that development of the SIP-PACT system, led by Lihong Wang at Caltech, has advanced to the point where doctors can now get a “panoramic” view of the entire inner workings of a small animal in real time. The team's circular ultrasonic detector is plugged into an extremely fast computer system that translates sound into image instantly.

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The upgraded device can image the full cross-section of an adult rat 50 times per second, providing detailed video with 120-micrometer resolution.

"You can see the dynamics of the body in action — the pumping of the heart, the dilation of arteries, the functioning of various tissues,” Yao said in materials issued with the new research paper.  "With this advance, researchers can easily watch as drugs are distributed throughout an animal and track how different organs respond."

Yao said the SIP-PACT system has another major advantage over other imaging techniques. Thanks to some arcane mathematics involving wavelengths of light, the scan can essentially see in color.

“This technology is very sensitive to any tiny color changes deep inside the biological tissue, induced either by normal physiological processes, like elevated brain activity, or by abnormal pathological conditions,” Yao said. “This color sensitivity in deep tissues cannot be achieved by other imaging methods.”

If you and your ailing mouse are up for a little light reading, the research paper has been published in the journal Nature Biomedical Engineering.

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