Wearable ultrasound patch images the heart in real time

Roughly the size of a postage stamp, worn for up to 24 hours and working during exercise, a wearable cardiac ultrasound imager could help doctors spot heart problems that may be missed by current medical technology. A new study finds that the day may come.

Cardiovascular disease is the leading cause of death among the elderly and is becoming an increasing problem among the younger generations due to factors such as unhealthy diets. Because the signs of heart disease are often unpredictable in the short term, long-term cardiac imaging may help detect heart abnormalities that might otherwise go undetected.

For example, a heart failure patient may appear well at rest. “Because the heart sacrifices its efficiency to maintain the same cardiac output,” said the study’s co-lead author. hong jae hooNano-engineer at the University of California, San Diego. “Pushing your heart to its limit while exercising can reveal inefficiencies.”

Additionally, the heart is able to recover quickly from problems that may occur during exercise. That’s because cardiac imaging is traditionally done after exercise, not during exercise, Hu says.

However, cardiac imaging techniques are often limited in their ability to analyze the heart. This is primarily due to the bulkiness of the device.For example, a conventional heart ultrasound imaging “Evaluate cardiac images immediately before and after intense exercise. During this process, it is impossible to hold the ultrasound probe manually over the chest and maintain a stable position,” Hu said. says. Earlier wearable heart sensors could only pick up signals on the skin.

Scientists are now wearableultrasound A device that enables safe, continuous, real-time, longitudinal, and highly detailed cardiac imaging.they detailed their discovery Online 25 January Journal Nature.

“Potential applications include continuous monitoring of the heart in everyday life, during exercise and during surgery,” said the study’s co-authors. Ray WuNano-engineer at the University of California, San Diego. “This opens up the possibility of detecting previously undetectable disease symptoms, identifying symptoms at a very early stage and significantly improving patient outcomes.”

The new device is a patch 1.9 centimeters long, 2.2 centimeters wide and just 0.9 millimeters thick.use an array of piezoelectric A transducer that transmits and receives ultrasound waves to produce a continuous stream of images of the structure and function of the heart. The researchers were able to acquire such images even while exercising on a stationary bike. After 24 hours of continuous use, no skin irritation or allergies were observed.

“The most exciting result is that the patch works well when the individual is in motion,” Fu says. “Our patch allows us to assess cardiac performance during exercise and provides valuable information about the heart under high stress.”

The new patch is almost as flexible as human skin. It can also stretch up to 110% of its size. This means it can withstand far greater strains than human skin normally experiences. These features aid in close contact with the body, which is not possible with rigid instruments commonly used for cardiac imaging.

“Wearable imagers remove the bulk of traditional imagers and adhere naturally to the body,” says Wu. “This will allow the heart to be imaged in ways and scenarios that were not possible before, eliminating the need for physicians to continuously operate traditional ultrasound probes.”

The wearable ultrasonic sensor is roughly the size of a postage stamp, can be worn for up to 24 hours, and works even during strenuous exercise.Xu Lab/University of California San Diego Jacobs School of Engineering

In the new study, researchers focused on imaging the left ventricle, the largest of the four chambers of the heart. says Wu. Cardiac imaging is usually focused on the left ventricle, but because new devices can image all four ventricles of the heart simultaneously, “future studies may focus on other ventricles or multiple ventricles.” could be possible,” he adds. Furthermore, “this imager can also be applied to imaging a variety of other organs, such as the stomach, kidney, and liver.”

In conventional cardiac ultrasound imaging, the ultrasound probe is constantly rotated to analyze the heart in multiple dimensions. To eliminate the need for this rotation, the array of ultrasonic sensors and emitters in the new device are cruciform so that the ultrasonic waves travel at right angles to each other.

Scientists have developed a habit deep learning An AI model that analyzes data from patches and can automatically and continuously estimate important details such as the percentage of blood pumped out of the left ventricle with each beat and the amount of blood the heart pumps with each beat and every minute . Researchers point out that the root of most heart problems is that the heart isn’t pumping enough blood, a problem that often only appears when the body is in motion.

Scientists didn’t start investigating cardiac imaging until they developed a wearable ultrasound device.

“After learning in casual conversation that one of our colleague’s relatives died of a sudden heart attack, we realized that our technology could have a real impact on people’s lives. says Hao Huang, a nanoengineer at the University of California and co-lead author of the study. in San Diego. “I did not expect the image quality of the imager to be so good. However, after careful engineering, it turned out that we could achieve quality comparable to commercially available probes. As a result, when we saw the detailed images, we knew we had reached something big and thought we should continue to pursue this path so as not to waste imager capabilities. .”

In the beginning, “we were always struggling with focusing the ultrasound beam,” recalls Huang. “Debugging required intensive trial and error based on measurements. After many failures, an automated alignment strategy was used to create transducer arrays with high uniformity and perfect alignment, resulting in beam guaranteed the convergence of

Another problem involved noise in the signal. “We went through a lot of trial and error to identify all the noise sources and separate the imager from them all, but we were still left with the most important thing: the human body,” says Huang. They eventually developed a stretchable electromagnetic shield made of the same liquid metal used in the device’s electrodes. The optimized shielding layer worked really well and finally we were able to remove the noise from the image. “

Researchers now note that devices are connected to computers via cables. They are developing a wireless version of the patch, the details of which are in ongoing research, Hu said.

Senior author of the study, Shen ShuThe University of California, San Diego professor plans to commercialize the technology through SoftSonics, a company he co-founded with Shu Xiang, one of the study’s co-authors. Further work is needed to develop the device into a fully integrated wearable system with a built-in power source, Hu said.