MIT engineers develop ultrasound patches that can see inside the body

MIT engineers develop ultrasound patches that can see inside the body

MIT engineers designed a patch that produces ultrasound images of the body. The postage stamp-sized device adheres to the skin and can provide continuous ultrasound images of internal organs for 48 hours. Credit: Felice Frankel

New postage stamp-sized ultrasound patches 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 imaging for a safe, non-invasive window into the body’s functioning. To capture these insightful images, trained technicians manipulate wands and ultrasound probes to direct sound waves into the body. These waves reflect back and are used to produce high-resolution images of a patient’s heart, lungs, and other deep organs.

Ultrasound imaging currently requires bulky, specialized equipment available only in hospitals and doctors’ offices. However, a new design developed by

MIT
MIT is an acronym for the Massachusetts Institute of Technology. It is a prestigious private research university in Cambridge, Massachusetts, founded in 1861. It is organized into five schools: architecture and planning; Engineering; humanities, arts and social sciences; management; and science. MIT’s impact includes many scientific advances and technological advances. Its stated aim is to make a better world through education, research and innovation.

” data-gt-translate-attributes=”[{” 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

To image with ultrasound, a technician first applies a liquid gel to the 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 return 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 liquid ultrasound gel flows and dries over time, disrupting long-term imaging.

In recent years, scientists have explored extendable ultrasound probe designs that would provide portable, low-profile images of internal organs. These designs gave a flexible set of tiny ultrasound transducers, with the idea that this device would stretch and adapt to the patient’s body.

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

“The wearable ultrasound imaging tool would have enormous potential in the future of clinical diagnostics. However, the resolution and imaging duration of existing ultrasound patches are relatively low, and they cannot visualize deep organs,” says Chonghe Wang, a graduate student at MIT.

a look inside

By combining an elastic adhesive layer with a rigid array of transducers, the MIT team’s new ultrasound adhesive produces high-resolution images for a longer period of time. “This combination allows the device to adapt to the skin while maintaining the relative location of the transducers to generate clearer and more accurate images.” says Wang.

The device’s adhesive layer is made of two thin layers of elastomer that encapsulate an intermediate 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 elastic.

“The elastomer prevents dehydration of the hydrogel,” says Chen, a postdoctoral fellow at MIT. “Only when the hydrogel is highly hydrated can acoustic waves effectively penetrate and provide high resolution images of internal organs.”

The bottom elastomer layer is designed to adhere to the skin, while the top layer adheres to a rigid array of transducers that the team also designed and manufactured. The entire ultrasound sticker measures about 2 square centimeters in diameter and 3 millimeters thick – approximately the area of ​​a postage stamp.

The researchers ran the ultrasound patch on a battery of tests with healthy volunteers, who used the patches on various parts of the body, including the neck, chest, abdomen and arms. The patches remained attached to the skin and produced clear images of underlying structures for up to 48 hours. During this time, the volunteers performed a variety of activities in the lab, from sitting and standing, to running, cycling and lifting weights.

From the images of the patches, the team was able to observe the change in the diameter of major blood vessels when sitting versus standing. The patches also captured details of deeper organs, such as how the heart changes shape as you exercise during exercise. The researchers were also able to watch the stomach distend, then shrink as the volunteers drank, and then expel juice from their system. And as some volunteers lifted weights, the team could detect bright patterns in the underlying muscles, signaling temporary microdamage.

“With imaging, we can capture the moment in a workout before overuse and stop before the muscles get sore,” says Chen. “We don’t yet know when that moment might be, but we can now provide imaging data that experts can interpret.”

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

“We imagined we could have a box of stickers, each designed to depict a different location on the body,” says Zhao. “We believe this represents a breakthrough in wearables 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

This research was funded, in part, 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.


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