Ultrasound ‘sticker’ could let pregnant women watch their babies grow — on a smartphone

CAMBRIDGE, Mass. — Mothers-to-be could soon be watching their babies grow in the womb on a digital device! MIT engineers have developed a stamp-sized sticking plaster that can produce high-resolution images of the heart, lungs, and other organs.

The technology would create a continuous ultrasound image for 48 hours. Along with pregnant women keeping an eye on their fetuses, the “sticker” could also improve monitoring of cancerous tumors. Researchers add the stickers have a host of potential applications, speeding up disease diagnosis and treatment.

“We envision a few patches adhered to different locations on the body, and the patches would communicate with your cellphone, where AI algorithms would analyze the images on demand,” says study senior author Xuanhe Zhao, a professor of mechanical engineering and civil and environmental engineering at MIT, in a media release.

“We believe we’ve opened a new era of wearable imaging: With a few patches on your body, you could see your internal organs.”

What can the stickers see?

The MIT team ran a battery of tests with healthy volunteers, who wore the stickers on various parts of their bodies, including the neck, chest, stomach, and arms. They stayed attached to their skin and took detailed snaps of underlying structures for up to two days.

During this time, participants performed a variety of activities in the lab, from sitting and standing, to jogging, biking, and lifting weights. The images revealed the changing diameter of major blood vessels when seated versus standing up.

They also captured details of deeper organs, such as how the heart changes shape as it exerts itself during exercise. Moreover, the researchers were able to watch the stomach distend, then shrink back as volunteers drank and later passed juice out of their system.

While some participants lifted weights, Prof. Zhao and the team could detect bright patterns in underlying muscles, signaling temporary microdamage.

“With imaging, we might be able to capture the moment in a workout before overuse, and stop before muscles become sore,” says study author Dr. Xiaoyu Chen. “We do not know when that moment might be yet, but now we can provide imaging data that experts can interpret.”

What exactly is an ultrasound?

Ultrasound is a safe and non-invasive window into the body’s inner workings, providing clinicians with live images of a patient’s organs. Trained technicians manipulate wands and probes to direct sound waves into the body. They reflect back out to produce high-resolution images.

Currently, the technique requires bulky and specialized equipment available only in hospitals and doctor’s offices. The new design could revolutionize medicine, making the system as wearable and accessible as buying bandages at the pharmacy.

Currently, it requires connecting the stickers to instruments that translate the reflected sound waves into images. Even in this form, they have potential immediate applications for hospital patients, similar to heart-monitoring EKG stickers.

They could also continuously image internal organs without requiring a technician to hold a probe in place for long periods of time. If the devices can be made to operate wirelessly, they could become wearable imaging products that patients could take home from a doctor’s office or even buy at the pharmacy.

To image with ultrasound, a technician first applies a liquid gel to a patient’s skin, which acts to transmit ultrasound waves. A probe, or transducer, is then pressed against the gel, sending sound waves into the body that echo off internal structures and back to the probe, where the echoed signals are translated into visual images.

For patients who require long periods of imaging, some hospitals offer probes affixed to robotic arms that can hold a transducer in place without tiring, but the liquid ultrasound gel flows away and dries out over time, interrupting long-term imaging.

How can the stickers improve medical imaging?

In recent years, researchers have explored designs for stretchable ultrasound probes that would provide portable, low-profile imaging of internal organs. These designs gave a flexible array of tiny ultrasound transducers, the idea being that such a device would stretch and conform with a patient’s body. However, these experimental designs have produced low-resolution images, in part due to their stretch. In moving with the body, transducers shift location relative to each other, distorting the resulting image.

Wearable ultrasound imaging tool would have huge potential in the future of clinical diagnosis. However, the resolution and imaging duration of existing ultrasound patches is relatively low, and they cannot image deep organs,” says Chonghe Wang, an MIT graduate student.

The ultrasound sticker produces higher resolution images over a longer duration by pairing a stretchy adhesive layer with a rigid array of transducers.

“This combination enables the device to conform to the skin while maintaining the relative location of transducers to generate clearer and more precise images.” Wang adds.

The adhesive surface is made from two thin layers of elastomer that encapsulate a middle layer of solid hydrogel, a mostly water-based material that easily transmits sound waves. Unlike traditional ultrasound gels, it is elastic and stretchy.

“The elastomer prevents dehydration of hydrogel,” says Chen. “Only when hydrogel is highly hydrated can acoustic waves penetrate effectively and give high-resolution imaging of internal organs.”

The bottom elastomer layer is designed to stick to skin, while the top layer adheres to a rigid array of transducers that the team also designed and fabricated. The sticker, described in the journal Science, measures about two square centimeters across, and is three millimeters thick.

Using AI to improve portable imaging

The team is also developing software algorithms based on artificial intelligence that can better interpret and diagnose the stickers’ images. Prof. Zhao says ultrasound stickers could be packaged and purchased by patients and consumers. They could be used not only to monitor various internal organs but also the progression of tumors – as well as the development of fetuses in the womb.

“We imagine we could have a box of stickers, each designed to image a different location of the body,” Prof. Zhao concludes. “We believe this represents a breakthrough in wearable devices and medical imaging.”

South West News Service writer Mark Waghorn contributed to this report.

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