Engineers develop stickers that can see inside the body

Clinical staff can view a patient's internal organs in real time thanks to ultrasound imaging, a safe and non-invasive window into the workings of the human body. Trained technicians use ultrasound wands and probes to manipulate sound waves into the body in order to obtain these images. The heart, lungs, and other deep organs of the patient can be seen in high resolution because to the reflection of these waves.

At the moment, ultrasound imaging requires heavy, specialized equipment that is only found in medical facilities and clinics. The technology may soon be as wearable and accessible as buying Band-Aids at the drugstore thanks to a new design by MIT engineers.

The engineers describe their innovative ultrasound sticker design in a study that will be published in Science today. The ultrasound sticker is a stamp-sized gadget that adheres to the skin and can continuously image inside organs for 48 hours.

The devices yielded real-time, high-resolution photos of the deeper organs, including the heart, lungs, and stomach, when the researchers put the stickers to volunteers. The volunteers engaged in a variety of activities, such as sitting, standing, jogging, and biking, and the stickers remained firmly adhered and documented changes in the underlying organs.

The stickers must currently be connected to devices that convert the reflected sound waves into visuals. The researchers note that the stickers might be used right away even in their current form: To continually photograph internal organs without requiring a technician to hold a probe in place for extended periods of time, the devices could, for example, be affixed to hospital patients in a manner similar to heart-monitoring EKG stickers.

The ultrasound stickers might be turned into wearable imaging items that patients could take home from a doctor's office or even buy at a drugstore if the gadgets can be made to operate wirelessly, a goal the team is now working toward.

Xuanhe Zhao, professor of mechanical engineering and civil and environmental engineering at MIT, is the study's senior author. "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," he says. "We think we've ushered in a new era of wearable imaging: you could observe your internal organs with a few patches on your body."

An ultrasound technician will first apply a liquid gel to the skin of the patient in order to transmit ultrasonic waves. Then, by pressing a probe into the gel, sound waves are sent into the body, resonating off of interior structures, and returning to the probe, where the echoed signals are converted into visual images.

Some hospitals have probes attached to robotic arms that can hold a transducer in place without tiring for patients who need prolonged imaging, but the liquid ultrasound gel eventually runs away and dries out, cutting off long-term imaging.

Stretchable ultrasonic probe designs have been studied recently in order to enable internal organ imaging that is portable and low-profile. These designs provided a stretchable array of tiny ultrasonic transducers with the intention that they would adapt to the shape of a patient's body.

But because of their stretch, these experimental designs have created low-resolution images: Transducers move relative to one another as the body does, causing an image distortion.

"Future clinical diagnostics could greatly benefit from wearable ultrasound imaging tools. However, current ultrasound patches have relatively poor resolution and imaging duration, and they cannot image deep organs "says Chonghe Wang, a graduate student at MIT.

The novel ultrasound sticker developed by the MIT team combines a stiff array of transducers with a stretchable adhesive layer to provide greater resolution images over a longer period of time. In order to provide sharper and more accurate images, the device can mold to the skin while maintaining the relative placement of the transducers. Wang opined.

The sticky layer of the device is constructed from two thin layers of elastomer that enclose a middle layer of solid hydrogel, a substance that is primarily water-based and effectively transmits sound waves. The hydrogel developed by the MIT team is elastic and stretchable, unlike conventional ultrasonic gels.

The hydrogel is not allowed to become dehydrated, according to Chen, an MIT postdoc. Acoustic waves can only successfully penetrate hydrogel that is highly hydrated and provide high-resolution imaging of inside organs.

The top layer attaches to a stiff array of transducers that the researchers also designed and made, while the bottom elastomer layer is intended to stick to skin. The complete ultrasound sticker is about the size of a postage stamp: 2 square centimeters wide and 3 millimeters thick.

With healthy participants wearing the stickers on various body areas, such as the neck, chest, belly, and arms, the researchers put the ultrasound sticker through a series of tests. For up to 48 hours, the stickers remained affixed to their skin and produced sharp photos of the underlying structures. Volunteers engaged in a range of activities in the lab during this period, including sitting and standing, jogging, biking, and lifting weights.

e team was able to see how the diameter of the main blood vessels changed between standing and sitting thanks to the images on the stickers. The stickers also recorded information about deeper organs, such as the way that exercise causes the heart to change shape. As subjects drank juice and then subsequently passed it out of their systems, the researchers were also able to observe the stomach expanding and then contracting. Additionally, the team could see colorful patterns in the muscles beneath some participants as they lifted weights, indicating transitory microdamage.

With imaging, Chen speculates, "we might be able to halt a workout before muscles become sore and catch the moment just before overuse." Although we do not yet know when it might occur, we can now offer imaging data that professionals can decipher.

The group is attempting to make the stickers wirelessly functional. They are also creating artificial intelligence-based software algorithms that can more accurately decipher and diagnose the images of the stickers. Zhao then imagines that ultrasound stickers may be packed and bought by patients and customers, and used to not only monitor different internal organs but also the growth of malignancies and fetuses inside the womb.

Zhao explains, "We envision having a box of stickers, each picturing a distinct part of the body. "We think this is a breakthrough in medical imaging and wearable technology."

Through MIT's Institute for Soldier Nanotechnologies, this research was supported in part by MIT, the Defense Advanced Research Projects Agency, the National Science Foundation, the National Institutes of Health, and the U.S. Army Research Office.

Massachusetts Institute of Technology