Soft skin patch could provide early warning for strokes, heart attacks


Date:
July 22, 2021
Source:
University of California - San Diego
Summary:
Engineers developed a soft, stretchy ultrasound patch that can be
worn on the skin to monitor blood flow through vessels deep inside
the body. Such a device can make it easier to detect cardiovascular
problems, like blockages in the arteries that could lead to strokes
or heart attacks.



FULL STORY ========================================================================== Engineers at the University of California San Diego developed a soft
and stretchy ultrasound patch that can be worn on the skin to monitor
blood flow through major arteries and veins deep inside a person's body.


========================================================================== Knowing how fast and how much blood flows through a patient's blood
vessels is important because it can help clinicians diagnose various cardiovascular conditions, including blood clots; heart valve problems;
poor circulation in the limbs; or blockages in the arteries that could
lead to strokes or heart attacks.

The new ultrasound patch developed at UC San Diego can continuously
monitor blood flow -- as well as blood pressure and heart function --
in real time.

Wearing such a device could make it easier to identify cardiovascular
problems early on.

A team led by Sheng Xu, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering, reported the patch in a paper published
July 16 in Nature Biomedical Engineering.

The patch can be worn on the neck or chest. What's special about the
patch is that it can sense and measure cardiovascular signals as deep
as 14 centimeters inside the body in a non-invasive manner. And it can
do so with high accuracy.

"This type of wearable device can give you a more comprehensive, more
accurate picture of what's going on in deep tissues and critical organs
like the heart and the brain, all from the surface of the skin," said Xu.



========================================================================== "Sensing signals at such depths is extremely challenging for wearable electronics. Yet, this is where the body's most critical signals and the central organs are buried," said Chonghe Wang, a former nanoengineering graduate student in Xu's lab and co-first author of the study. "We
engineered a wearable device that can penetrate such deep tissue depths
and sense those vital signals far beneath the skin. This technology can
provide new insights for the field of healthcare." Another innovative
feature of the patch is that the ultrasound beam can be tilted at
different angles and steered to areas in the body that are not directly underneath the patch.

This is a first in the field of wearables, explained Xu, because existing wearable sensors typically only monitor areas right below them. "If you
want to sense signals at a different position, you have to move the sensor
to that location. With this patch, we can probe areas that are wider
than the device's footprint. This can open up a lot of opportunities."
How it works The patch is made up of a thin sheet of flexible, stretchable polymer that adheres to the skin. Embedded on the patch is an array of millimeter-sized ultrasound transducers. Each is individually controlled
by a computer -- this type of array is known as an ultrasound phased
array. It is a key part of the technology because it gives the patch
the ability to go deeper and wider.



==========================================================================
The phased array offers two main modes of operation. In one mode,
all the transducers can be synchronized to transmit ultrasound waves
together, which produces a high-intensity ultrasound beam that focuses
on one spot as deep as 14 centimeters in the body. In the other mode,
the transducers can be programmed to transmit out of sync, which produces ultrasound beams that can be steered to different angles.

"With the phased array technology, we can manipulate the ultrasound beam
in the way that we want," said Muyang Lin, a nanoengineering Ph.D. student
at UC San Diego who is also a co-first author of the study. "This gives
our device multiple capabilities: monitoring central organs as well
as blood flow, with high resolution. This would not be possible using
just one transducer." The phased array consists of a 12 by 12 grid of ultrasound transducers. When electricity flows through the transducers,
they vibrate and emit ultrasound waves that travel through the skin
and deep into the body. When the ultrasound waves penetrate through a
major blood vessel, they encounter movement from red blood cells flowing inside. This movement changes or shifts how the ultrasound waves echo
back to the patch -- an effect known as Doppler frequency shift.

This shift in the reflected signals gets picked up by the patch and is
used to create a visual recording of the blood flow. This same mechanism
can also be used to create moving images of the heart's walls.

A potential game changer in the clinic For many people, blood flow is not something that is measured during a regular visit to the physician. It
is usually assessed after a patient shows some signs of cardiovascular problems, or if a patient is at high risk.

The standard blood flow exam itself can be time consuming and labor
intensive.

A trained technician presses a handheld ultrasound probe against a
patient's skin and moves it from one area to another until it's directly
above a major blood vessel. This may sound straightforward, but results
can vary between tests and technicians.

Since the patch is simple to use, it could solve these problems, said
Sai Zhou, a materials science and engineering Ph.D. student at UC San
Diego and co-author of the study. "Just stick it on the skin, then read
the signals. It's not operator dependent, and it poses no extra work
or burden to the technicians, clinicians or patients," he said. "In the
future, patients could wear something like this to do point of care or continuous at-home monitoring." In tests, the patch performed as well as
a commercial ultrasound probe used in the clinic. It accurately recorded
blood flow in major blood vessels such as the carotid artery, which is an artery in the neck that supplies blood to the brain. Having the ability
to monitor changes in this flow could, for example, help identify if a
person is at risk for stroke well before the onset of symptoms.

The researchers point out that the patch still has a long way to go before
it is ready for the clinic. Currently, it needs to be connected to a
power source and benchtop machine in order to work. Xu's team is working
on integrating all the electronics on the patch to make it wireless.

Paper: "Continuous monitoring of deep-tissue haemodynamics with
stretchable ultrasonic phased arrays." Co-authors include Baiyan Qi*,
Zhuorui Zhang*, Mitsutoshi Makihata, Boyu Liu, Yi-hsi Huang, Hongjie
Hu, Yue Gu, Yimu Chen, Yusheng Lei, Shu Chien and Erik Kistler, UC San
Diego; Taeyoon Lee, Yonsei University and Korea Institute of Science
and Technology; and Kyung-In Jang, Daegu Gyeonbuk Institute of Science
and Technology, Republic of Korea.

*These authors contributed equally This work was supported by the National Institutes of Health (grant 1R21EB027303-01A1) and the Center for Wearable Sensors at the UC San Diego Jacobs School of Engineering.

========================================================================== Story Source: Materials provided by
University_of_California_-_San_Diego. Original written by Liezel
Labios. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Chonghe Wang, Baiyan Qi, Muyang Lin, Zhuorui Zhang, Mitsutoshi
Makihata,
Boyu Liu, Sai Zhou, Yi-hsi Huang, Hongjie Hu, Yue Gu, Yimu Chen,
Yusheng Lei, Taeyoon Lee, Shu Chien, Kyung-In Jang, Erik B. Kistler,
Sheng Xu.

Continuous monitoring of deep-tissue haemodynamics with stretchable
ultrasonic phased arrays. Nature Biomedical Engineering, 2021; 5
(7): 749 DOI: 10.1038/s41551-021-00763-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210722145217.htm

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