MIT engineers develop ultrasound labels that can see inside the body

A sticky patch that produces ultrasound images of the body

MIT engineers have designed a sticky patch that produces ultrasound images of the body. The seal-size device sticks to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours. Credit: Phyllis Frankel

New seal-size ultrasound adhesives provide clear images of the heart, lungs and other internal organs.

When doctors need live images of a patient’s internal organs, they often turn to ultrasound to get a safe, non-invasive window into the body’s functioning. In order to capture these insightful images, trained technicians manipulate ultrasound sticks and probes to direct sound waves into the body. These waves are reflected back and used to produce high-resolution images of the patient’s heart, lungs, and other deep organs.

Ultrasound imaging currently requires bulky, specialized equipment that is only available in hospitals and physicians’ offices. However, a new design was developed by[{” attribute=””>MIT engineers might make the technology as wearable and accessible as buying Band-Aids at the drugstore.

The engineers presented the design for the new ultrasound sticker in a paper published on July 28 in the journal Science. The stamp-sized device sticks to skin and can provide continuous ultrasound imaging of internal organs for 48 hours.

To demonstrate the invention, the researchers applied the stickers to volunteers. They showed the devices produced live, high-resolution images of major blood vessels and deeper organs such as the heart, lungs, and stomach. As the volunteers performed various activities, including sitting, standing, jogging, and biking, the stickers maintained a strong adhesion and continued to capture changes in underlying organs.

In the current design, the stickers must be connected to instruments that translate the reflected sound waves into images. According to the researchers, the stickers could have immediate applications even in their current form. For example, the devices could be applied to patients in the hospital, similar to heart-monitoring EKG stickers, and could continuously image internal organs without requiring a technician to hold a probe in place for long periods of time.

Making the devices work wirelessly is a goal the team is currently working toward. If they are successful, the ultrasound stickers could be made into wearable imaging products that patients could take home from a doctor’s office or even buy at a pharmacy.

“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 the study’s senior author, Xuanhe Zhao, professor of mechanical engineering and civil and environmental engineering at MIT. “We believe we’ve opened a new era of wearable imaging: With a few patches on your body, you could see your internal organs.”

The study also includes lead authors Chonghe Wang and Xiaoyu Chen, and co-authors Liu Wang, Mitsutoshi Makihata, and Tao Zhao at MIT, along with Hsiao-Chuan Liu of the Mayo Clinic in Rochester, Minnesota.

sticky issue

For ultrasound imaging, the technician first applies a liquid gel to the patient’s skin, which serves to transmit ultrasound waves. Then a probe, or transducer, is pressed against the gel, and it sends sound waves into the body that resonate with internal structures and back to the probe, where the outgoing signals are translated into visible images.

For patients who require extended periods of imaging, some hospitals offer sensors mounted on robotic arms that can hold the transducer in place without tiring, but the liquid fluid flows and dries up over time, interrupting long-term imaging.

In recent years, scientists have discovered designs for stretchable ultrasound probes that would provide portable, unobtrusive 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 to the patient’s body.

But these experimental designs produced low-resolution images, in part because of their stretch: In moving with the object, the transducers change position relative to each other, distorting the resulting image.

“A wearable ultrasound imaging tool will have huge potential in the future of clinical diagnosis. However, the accuracy and imaging duration of ultrasound spots are relatively low, and they cannot image deep organs,” says Chung Wang, a graduate student at the Massachusetts Institute of Technology.

look inside

By pairing a stretchable adhesive layer with a rigid array of transducers, the MIT team’s new ultrasound label produces high-resolution images over a longer period. “This combination allows the device to conform to the skin while maintaining the relative position of the transducers to produce sharper, more accurate images.” Wang says.

The device’s adhesive layer consists of two thin layers of elastomer that encase a middle layer of a solid hydrogel, a water-based material that easily transmits sound waves. Unlike conventional gels that use ultrasound, the MIT team’s hydrogel is flexible and stretchable.

“The elastomer prevents the hydrogel from drying out,” says Chen, a postdoctoral researcher at the Massachusetts Institute of Technology. “Only when the hydrogel is highly hydrated can sound waves effectively penetrate and give high-resolution imaging of internal organs.”

The bottom rubber layer is designed to adhere to the skin, while the top layer adheres to a solid set of adapters that the team also designed and built. The entire ultrasound label measures about 2 square centimeters, and 3 millimeters thick – about the space of a postage stamp.

The researchers conducted an ultrasound sticker through a combination of tests with healthy volunteers, who wore the stickers on different parts of their bodies, including the neck, chest, abdomen and arms. The stickers remained attached to her skin, and produced clear images of the underlying structures for up to 48 hours. During this time, volunteers performed a variety of activities in the lab, from sitting and standing to jogging, cycling, and weightlifting.

From the poster images, the team was able to note the changing diameter of the major blood vessels when sitting versus standing. The posters also captured details of the deeper organs, such as how the shape of the heart changes during exercise. The researchers were also able to watch the stomachs swell, then shrink again when the volunteers drank and later flushed the juice out of their system. While some of the volunteers were lifting weights, the team was able to detect bright patterns in the core muscles, indicating small, temporary damage.

“By imaging, we may be able to capture the moment in exercise before overuse, and stop before muscle becomes afternoon,” says Chen. “We don’t know when that moment might be yet, but now we can provide imaging data that experts can interpret.”

The engineering team is working to make the stickers work wirelessly. They are also developing AI-based software algorithms that can better interpret and diagnose poster images. Next, Zhao envisions ultrasound labels that can be packaged and purchased by patients and consumers, and used not only to monitor various internal organs, but also for the development of tumors, as well as the growth of fetuses in the womb.

“We imagine we could have a box of stickers, each designed to depict a different location of the body,” Zhao says. “We think this represents a breakthrough in wearables and medical imaging.”

Reference: “Bio-adhesive ultrasound for long-term continuous imaging of diverse organs” by Chonghe Wang, Xiaoyu Chen, Liu Wang, Mitsutoshi Makihata, Hsiao-Chuan Liu, Tao Zhou, and Xuanhe Zhao, July 28, 2022, Sciences.
DOI: 10.1126 / science.abo2542

This research was funded in part by the Massachusetts Institute of Technology, the Defense Advanced Research Projects Agency, the National Science Foundation, the National Institutes of Health, and the US Army Research Office through the Soldier Nanotechnology Institute at MIT.

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