Small ultrasound sticker can monitor the stiffness of inner organs

MIT engineers have developed a small ultrasound sticker that may monitor the stiffness of organs deep contained in the physique. The sticker, concerning the dimension of a postage stamp, will be worn on the pores and skin and is designed to select up on indicators of illness, reminiscent of liver and kidney failure and the development of strong tumors. 

In an open-access examine that may seem in Science Advances, the group studies that the sensor can ship sound waves by way of the pores and skin and into the physique, the place the waves replicate off inner organs and again out to the sticker. The sample of the mirrored waves will be learn as a signature of organ rigidity, which the sticker can measure and monitor. 

When some organs endure illness, they will stiffen over time. With this wearable sticker, we will repeatedly monitor modifications in rigidity over lengthy durations of time, which is crucially essential for early prognosis of inner organ failure.”

Xuanhe Zhao, senior writer of the paper, professor of mechanical engineering at MIT

The group has demonstrated that the sticker can repeatedly monitor the stiffness of organs over 48 hours and detect refined modifications that might sign the development of illness. In preliminary experiments, the researchers discovered that the sticky sensor can detect early indicators of acute liver failure in rats. 

The engineers are working to adapt the design to be used in people. They envision that the sticker may very well be utilized in intensive care items (ICUs), the place the low-profile sensors may repeatedly monitor sufferers who’re recovering from organ transplants. 

“We think about that, simply after a liver or kidney transplant, we may adhere this sticker to a affected person and observe how the rigidity of the organ modifications over days,” lead writer Hsiao-Chuan Liu says. “If there may be any early prognosis of acute liver failure, medical doctors can instantly take motion as an alternative of ready till the situation turns into extreme.” Liu was a visiting scientist at MIT on the time of the examine and is at the moment an assistant professor on the University of Southern California.

The examine’s MIT co-authors embody Xiaoyu Chen and Chonghe Wang, together with collaborators at USC. 

Sensing wobbles

Like our muscle groups, the tissues and organs in our physique stiffen as we age. With sure ailments, stiffening organs can turn out to be extra pronounced, signaling a doubtlessly precipitous well being decline. Clinicians at the moment have methods to measure the stiffness of organs such because the kidneys and liver utilizing ultrasound elastography -; a method much like ultrasound imaging, wherein a technician manipulates a handheld probe or wand over the pores and skin. The probe sends sound waves by way of the physique, which trigger inner organs to vibrate barely and ship waves out in return. The probe senses an organ’s induced vibrations, and the sample of the vibrations will be translated into how wobbly or stiff the organ have to be. 

Ultrasound elastography is often used within the ICU to watch sufferers who’ve lately undergone an organ transplant. Technicians periodically verify in on a affected person shortly after surgical procedure to shortly probe the brand new organ and search for indicators of stiffening and potential acute failure or rejection. 

“After organ transplantation, the primary 72 hours is most vital within the ICU,” says one other senior writer, Qifa Zhou, a professor at USC. “With conventional ultrasound, you might want to maintain a probe to the physique. But you possibly can’t do that repeatedly over the long run. Doctors may miss a vital second and notice too late that the organ is failing.”

The group realized that they could be capable to present a extra steady, wearable different. Their answer expands on an ultrasound sticker they beforehand developed to picture deep tissues and organs. 

“Our imaging sticker picked up on longitudinal waves, whereas this time we needed to select up shear waves, which is able to inform you the rigidity of the organ,” Zhao explains.

Existing ultrasound elastrography probes measure shear waves, or an organ’s vibration in response to sonic impulses. The quicker a shear wave travels within the organ, the stiffer the organ is interpreted to be. (Think of the bounce-back of a water balloon in comparison with a soccer ball.) 

The group regarded to miniaturize ultrasound elastography to suit on a stamp-sized sticker. They additionally aimed to retain the identical sensitivity of economic hand-held probes, which usually incorporate about 128 piezoelectric transducers, every of which transforms an incoming electrical area into outgoing sound waves. 

“We used superior fabrication strategies to chop small transducers from high-quality piezoelectric supplies that allowed us to design miniaturized ultrasound stickers,” Zhou says. 

The researchers exactly fabricated 128 miniature transducers that they integrated onto a 25-millimeter-square chip.They lined the chip’s underside with an adhesive made out of hydrogel -; a sticky and stretchy materials that may be a combination of water and polymer, which permits sound waves to journey into and out of the machine nearly with out loss.

In preliminary experiments, the group examined the stiffness-sensing sticker in rats. They discovered that the stickers had been in a position to take steady measurements of liver stiffness over 48 hours. From the sticker’s collected knowledge, the researchers noticed clear and early indicators of acute liver failure, which they later confirmed with tissue samples. 

“Once liver goes into failure, the organ will enhance in rigidity by a number of occasions,” Liu notes. 

“You can go from a wholesome liver as wobbly as a soft-boiled egg, to a diseased liver that’s extra like a hard-boiled egg,” Zhao provides. “And this sticker can decide up on these variations deep contained in the physique and supply an alert when organ failure happens.” 

The group is working with clinicians to adapt the sticker to be used in sufferers recovering from organ transplants within the ICU. In that situation, they do not anticipate a lot change to the sticker’s present design, as it may be caught to a affected person’s pores and skin, and any sound waves that it sends and receives will be delivered and picked up by electronics that hook up with the sticker, much like electrodes and EKG machines in a physician’s workplace. 

The researchers are additionally hoping to work the sticker right into a extra transportable, self-enclosed model, the place all its accompanying electronics and processing is miniaturized to suit right into a barely bigger patch. Then, they envision that the sticker may very well be worn by sufferers at house, to repeatedly monitor situations over longer durations, such because the development of strong tumors, that are identified to harden with severity. 

“We imagine it is a life-saving expertise platform,” Zhao says. “In the longer term, we predict that folks can adhere just a few stickers to their physique to measure many very important indicators, and picture and monitor the well being of main organs within the physique.”

This work was supported, partially, by the National Institutes of Health.