MIT engineers have developed stickers that can see inside the body MIT News

Ultrasound is a safe and non-invasive window into the workings of the body, providing clinicians with vivid images of a patient’s internal organs. To take these images, trained technicians manipulate ultrasound wands and probes to direct sound waves into the body. These waves are reflected back to produce high-resolution images of the patient’s heart, lungs, and other deep organs.

Currently, large and specialized ultrasound equipment is required only in hospitals and doctors’ offices. But a new design by MIT engineers could make the technology as wearable and accessible as buying Band-Aids at the drugstore.

In today’s newspaper scienceengineers have unveiled the design of a new ultrasound sticker — a stamp-sized device that sticks to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours.

The researchers applied the stickers to volunteers, and the devices displayed vivid, high-resolution images of major blood vessels and deeper organs such as the heart, lungs and stomach. As the volunteers performed a variety of activities, including sitting, standing, running, and cycling, the stickers maintained strong adhesion and tracked changes in the lower organs.

The current design calls for connecting the stickers to devices that translate reflected sound waves into images. The researchers note that the stickers in their current form could be used immediately: For example, the devices could be used on hospitalized patients, similar to EKG stickers used to monitor the heart, and could continuously take pictures of internal organs without the need for a technician. holding the probe for a long time.

If the devices could work wirelessly—a goal the team is currently working toward—we could create wearable imaging products with ultrasound stickers that patients could take home from the doctor’s office or buy at the pharmacy.

“We envision multiple patches attached to different parts of the body, and the patches communicate with your cell phone, where AI algorithms analyze the images on demand,” said senior study author Xuanhe Zhao, professor of mechanical engineering and civil and construction. in environmental engineering at MIT. “We believe we have ushered in a new era of wearable imaging: with just a few spots on your body, you can 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 of MIT and Xiao-Chuan Liu of the Mayo Clinic in Rochester, Minnesota.

A sticky issue

To take an ultrasound image, the technician first applies a liquid gel to the patient’s skin, which conducts the ultrasound waves. A probe or transducer is then pressed onto the gel, sending sound waves into the body, which travel through internal structures and back to the probe, where the updated signals are translated into visual images.

For patients requiring long-term imaging, some hospitals offer probes mounted on robotic arms that can hold the transducer without tiring, but the liquid ultrasound gel leaks and dries over time, disrupting long-term imaging.

In recent years, researchers have explored designs for stretchable ultrasound probes that can provide portable, low-profile imaging of internal organs. These designs yielded flexible arrays of tiny ultrasound transducers, the idea being that the device would stretch and conform to the patient’s body.

But these experimental designs produced lower-resolution images, in part because of their stretch: when moving with the body, the transducers moved relative to each other, distorting the resulting image.

“A wearable ultrasound device would have great potential in clinical diagnostics in the future. However, current ultrasound patches have relatively low resolution and imaging duration, and they cannot image deep organs,” said MIT graduate student Chonghe Wang.

Interior view

The MIT team’s new ultrasound sticker produces long-lasting high-resolution images by pairing a stretchable adhesive layer with solid-array transducers. “This combination allows the device to conform to the skin while maintaining the relative location of the transducers to produce clear and precise images.” Van says.

The adhesive layer of the device is made of two thin layers of elastomer that encapsulate a middle layer of hard hydrogel, which is basically a water-based material that easily transmits sound waves. Unlike traditional ultrasound gels, the MIT team’s hydrogel is flexible and stretchable.

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

The bottom elastomeric layer is designed to adhere to the skin, while the top layer adheres to a rigid transducer array designed and manufactured by the team. All ultrasound stickers are approximately 2 square centimeters wide and 3 millimeters thick – about the size of a postage stamp.

The researchers put the ultrasound patch through a battery of tests on healthy volunteers who wore it on different parts of their body, including the neck, chest, abdomen and arms. The stickers stuck to their skin, creating precise images of the underlying structures for up to 48 hours. During this time, the volunteers performed a variety of activities in the lab, including sitting and standing, running, cycling, and lifting weights.

From the images of the stickers, the team was able to observe changes in the diameter of major blood vessels while sitting and standing. The stickers also showed deeper organ details, such as how the heart changed shape during exercise. The researchers were also able to observe that the stomachs of the volunteers who drank it would expand, then shrink again, and then expel the juice from their system. And when some volunteers lifted weights, the team observed bright patterns in the underlying muscles, indicating temporary microdamage.

“By taking pictures, we can capture the moment during exercise before we overuse it and stop before the muscles hurt,” says Chen. “We don’t know when that moment will be, but now we can provide imaging data that experts can interpret.”

The team is working on making the stickers work wirelessly. They are also developing software algorithms that better interpret and diagnose sticker images based on artificial intelligence. After that, Zhao thinks that ultrasound stickers can be packaged and bought by patients and consumers, and can be used not only to monitor various internal organs, but also to monitor the progression of tumors, as well as the development of the fetus inside the uterus.

“We think we’ll have a box of stickers, each designed to represent a different location on the body,” says Zhao. “We believe this is a breakthrough in wearables and medical imaging.”

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

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