Recently, scientists at the Massachusetts Institute of Technology (MIT) and the University of Southern California (USC) made a remarkable breakthrough by developing a small ultrasound patch that can be attached to ** to monitor the stiffness of organs deep in the body for early detection of signs of disease, such as liver and kidney failure or the progression of solid tumors. The technology, known as wearable bioadhesion ultrasound elastography (BAUS-E), is the size of a postage stamp and contains a thin array of transducers that transmit sound waves into the body through **, and the waves are reflected back to the sensor through internal organs. The pattern of the reflected waves can be interpreted as a sign of organ stiffness, and this patch can measure and track this stiffness.
In a study published in the journal Science Advances, the team demonstrated the ability of the BAUS-E patch to continuously monitor organ stiffness for up to 48 hours and detect subtle changes that could predict the development of the disease. In preliminary experiments, the researchers found that this viscous sensor was able to detect early signs of acute liver failure induced in rats.
Dr. Xuanhe Zhao, a professor of mechanical engineering at MIT and a senior author, said: "When some organs are diseased, they may harden over time. With this wearable patch, we can continuously monitor changes in stiffness, which is essential for early diagnosis of internal organ failure. ”
Dr. Xiaochuan Liu, an assistant professor at the University of Southern California and first author of the study, who was a visiting scientist at MIT at the time of the study, added, "We envision that after a liver or kidney transplant, we can attach this patch to the patient and observe how the stiffness of the organs changes over a period of days." If there is any early diagnosis of acute liver failure, doctors can take immediate action instead of waiting for the condition to become severe. ”
Currently, engineers are working to adapt the design to fit human use. They envision that the patch could be applied to the intensive care unit, with low-profile sensors that could continuously monitor patients after organ transplants. In **, Zhao, Liu, et al. conclude: "BAUS-E has potential for clinical application, especially after organ transplantation or postoperative care in intensive care units....”
Like our muscles, the tissues and organs in our body become stiffer as we age. In some diseases, organs become more hardened and may indicate an underlying decline in health. Clinicians currently have the means to measure organ stiffness using techniques such as ultrasound tangential wave elastography (SWE), a rapid and non-invasive technique similar to ultrasound imaging. Existing ultrasound elastography probes measure the stiffness of an organ by measuring tangential waves, or the vibration of the organ in response to sound wave pulses. The faster the tangential wave travels through the organ, the harder the organ is interpreted to be (similar to the ** of water polo and football).
This technique is often used in intensive care units to monitor patients who have just undergone organ transplant surgery. The technician does this by operating a hand-held probe or probe on the **. The probe emits sound waves through the body, causing the internal organs to vibrate slightly and send the waves back. The probe senses the vibrations evoked by the organ, and the pattern of the vibration can be converted into the oscillation or stiffness of the organ.
Technicians use this technique at regular intervals to quickly probe new organs and look for signs of sclerosis and potential acute failure or rejection. "Previous studies have reported a reliable biomarker of liver stiffness measured using conventional ultrasound SWE, with a significant increase in critically ill patients with acute liver failure compared to healthy controls," the researchers noted. However, they continue, "The inherent limitation of traditional ultrasound elastography is that it requires the clinician to hold an ultrasound probe in hand for examination, and it is not possible to continuously monitor changes in organ stiffness during the rapidly changing disease process....To the best of our knowledge, there is currently no ultrasound elastography technology capable of providing a continuous measurement of the stiffness of internal organs in just a few hours. ”
Professor Dr. Qifa Zhou, co-author and professor at the University of Southern California, added: "The first 72 hours after an organ transplant are critical in the intensive care unit. With traditional ultrasound, the probe is placed on the body. But you can't do it for a long time. Doctors may miss a crucial moment until organ failure and realize it's too late. ”
The researchers realized that they might be able to offer a more continuous, wearable alternative. This new technology is an extension of their previously developed ultrasound patches for imaging deep tissues and organs. "Our imaging patches capture longitudinal waves, and this time we want to capture shear waves, which will tell you the hardness of the organ," Zhao explains.
The team worked to shrink ultrasound elastography to a postage stamp-sized patch. They are also designed to maintain the same sensitivity as commercial handheld probes, which typically contain about 128 piezoelectric transducers, each of which converts an incoming electric field into an output sound wave.
To create the BAUS-E technology, the researchers precisely fabricated 128 microtransducers, integrating them onto a 25-millimeter square chip. "Thin transducer arrays can generate acoustic radiation as an excitation source, generating shear waves for elastography measurements," they noted. The bottom of the chip is covered with a hydrogel adhesive made from a mixture of water and polymer, allowing sound waves to travel to and from the device with little to no loss. "We use advanced manufacturing techniques to cut small transducers from high-quality piezoelectric materials, which allows us to design miniaturized ultrasound patches," Dr. Zhou said. ”
In a preliminary experiment, the team tested the patch, which senses hardness, in rats. They found that the patches were able to continuously measure liver stiffness over a 48-hour period. "BAUS-E was used to continuously monitor changes in liver stiffness during acute liver failure in rats with a monitoring interval of 6 h for a total of 48 h," they wrote. From the data collected from the patches, the researchers observed clear and early signs of stiffness changes in rats at different stages of progression of acute liver failure, which were later confirmed by tissue samples. "We demonstrated that the wearable BAUS-E is able to provide a living modulus that is continuously measured over time and can effectively distinguish the changes in liver stiffness in different stages of acute liver failure progression compared to normal livers. This is expected to help in the early stages** of acute liver failure and in assessing graft status after liver transplantation in the intensive care unit. ”
Liu Xiaochuan pointed out: "Once the liver fails, the stiffness of the organ will increase several times. Zhao added: "You can go from a healthy liver that is rocking like a soft-boiled egg to a diseased liver that is more like a hard-boiled egg." And this patch is able to capture these differences deep in the body and provide an alert when organ failure occurs. ”
Researchers are working with clinicians to adapt the patch to patients after organ transplants in the intensive care unit. In this case, they do not expect much change in the current design of the patch, as it can be attached to the patient's **, and any sound waves it emits and receives can be transmitted and collected through an electronic device connected to the patch, similar to electrodes and ECG machines in a doctor's office.
The researchers also wanted to design the patch as a more portable, self-enclosed version, with all the included electronics and processors miniaturized to fit a slightly larger patch. "In the near future, we plan to integrate an external power supply and data processing into the chip in order to make an all-rounder BAUSE-E in a portable format for clinical applications," they said. The researchers also envision that the patches could be worn by patients at home to continuously monitor conditions such as the progression of solid tumors, which are known to become harder as the disease worsens.
We believe this is a life-saving technology platform," Zhao said. "In the future, we think people can stick several patches on their bodies to measure many important signals, as well as image and track health status of the body's major organs. ”
As the authors summarize in **: "BAUS-E has great potential to expand the practical applications of ultrasound wearable devices, such as in patients undergoing organ transplants in intensive care units, cancer research, and acute decompensated heart failure in clinical settings....”
Reference: Wearable bioadhesive ultrasound shear w**e elastography
Editor: Wang Hong.
Typesetting: Li Li.