MIT engineers are developing ultrasonic stickers that can see inside the body

Newer postage-stamp-size ultrasound glues provide clearer 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 imaging for a safe and non-invasive look at how the body works. To capture these revealing images, trained technicians manipulate ultrasound wands and probes to direct sound waves into the body. These waves are reflected back and used to create high-resolution images of the patient’s heart, lungs and other deep organs.

Ultrasound imaging requires bulky and specialized equipment that is currently only available in hospitals and doctor’s 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.

a sticky problem

For ultrasound imaging, a technician first applies a liquid gel to the patient’s skin, which transmits the ultrasound waves. A probe or transducer is then pressed against the gel and sends sound waves into the body, which resonate with internal structures and travel back to the probe, where the resonance signals are translated into visual images.

For patients who need long-term imaging, some hospitals offer probes attached to robotic arms that can hold a transducer without fatigue, but the liquid ultrasound gel tends to ooze and dry out over time, hindering long-term imaging becomes.

In recent years, scientists have been exploring designs for stretchable ultrasound probes that would allow for portable, flat imaging of internal organs. These designs resulted in a flexible array of tiny ultrasound transducers, the idea being that such a device would stretch and conform to the patient’s body.

However, these experimental designs have produced low-resolution images due to their stretchability: moving with the body, the transducers shift their position relative to each other, resulting in a distorted image.

“Wearable ultrasound imaging tools will have great potential in the future of clinical diagnosis. However, the resolution and imaging time of existing ultrasound patches are relatively short, and they cannot image deep organs,” says Chonghe Wang, an MIT graduate student.

inside view

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

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

“The elastomer keeps the hydrogel from drying out,” says Chen, a postdoc at MIT. “Only when the hydrogel is highly hydrated can sound waves penetrate effectively and enable high-resolution imaging of internal organs.”

The bottom layer of elastomer is designed to stick to the skin, while the top layer sticks to a rigid array of transducers that the team also designed and manufactured. The entire ultrasonic sticker measures about 2 square centimeters and 3 millimeters thick, about the area of ​​a postage stamp.

Researchers put ultrasound stickers through a series of tests on healthy volunteers who wore stickers on different parts of their bodies, including their necks, chests, abdomens and arms. The stickers stuck to her skin, providing clear images of underlying structures for 48 hours. Meanwhile, the volunteers did a variety of activities, from sitting and standing in the lab to jogging, cycling and weightlifting.

Using the images of the stickers, the team was able to observe the changing diameter of the major blood vessels when sitting versus standing. The stickers also captured details of the deeper organs, such as how the heart changes shape during exercise. The researchers were also able to watch the stomach shrink and then shrink back as the volunteers drank and later flushed the juices from their systems. And as some of the volunteers lifted weights, the team could see bright patterns in the underlying muscles that indicated temporary microscopic damage.

“With imaging, we may be able to capture the moment in a workout prior to overuse and stop before muscle soreness occurs,” says Chen. “We don’t know when that moment might come, but we can now provide imagery that experts can interpret.”

The engineering team is working to make the stickers work wirelessly. They are also developing artificial intelligence-based software algorithms that can better interpret and diagnose sticker images. Then, Zhao believes that ultrasound stickers can be packaged and purchased by patients and consumers, and can be used not only to monitor various internal organs, but also the progression of tumors, as well as the fetus in the womb. also used for development of

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

Reference: “Bioadhesive Ultrasound for Long-Term Continuous Imaging of Various Organs” by Chonghe Wang, Xiaoyu Chen, Liu Wang, Mitsutoshi Makihata, Hsiao-Chuan Liu, Tao Zhou and Xuanhe Zhao, July 28, 2022, Science,
DOI: 10.1126/science.abo2542

The research was funded by MIT, the Defense Advanced Research Projects Agency, the National Science Foundation, the National Institutes of Health, and the US Army Research Office through MIT’s Institute for Soldier Nanotechnologies.