A wearable sensor to help ALS patients communicate

Date:
October 22, 2020
Source:
Massachusetts Institute of Technology
Summary:
Researchers have designed a skin-like device that can be attached
to the face and measure small movements such as a twitch or a
smile. With this approach, patients with amyotrophic lateral
sclerosis (ALS) could communicate a variety of sentiments with
small movements that are measured and interpreted by the device.



FULL STORY ========================================================================== People with amyotrophic lateral sclerosis (ALS) suffer from a gradual
decline in their ability to control their muscles. As a result, they often
lose the ability to speak, making it difficult to communicate with others.


==========================================================================
A team of MIT researchers has now designed a stretchable, skin-like
device that can be attached to a patient's face and can measure small
movements such as a twitch or a smile. Using this approach, patients could communicate a variety of sentiments, such as "I love you" or "I'm hungry,"
with small movements that are measured and interpreted by the device.

The researchers hope that their new device would allow patients to
communicate in a more natural way, without having to deal with bulky
equipment. The wearable sensor is thin and can be camouflaged with makeup
to match any skin tone, making it unobtrusive.

"Not only are our devices malleable, soft, disposable, and light, they're
also visually invisible," says Canan Dagdeviren, the LG Electronics Career Development Assistant Professor of Media Arts and Sciences at MIT and
the leader of the research team. "You can camouflage it and nobody would
think that you have something on your skin." The researchers tested the initial version of their device in two ALS patients (one female and one
male, for gender balance) and showed that it could accurately distinguish
three different facial expressions -- smile, open mouth, and pursed lips.

MIT graduate student Farita Tasnim and former research scientist Tao
Sun are the lead authors of the study, which appears today in Nature
Biomedical Engineering. Other MIT authors are undergraduate Rachel
McIntosh, postdoc Dana Solav, and research scientist Lin Zhang. Yuandong
Gu of the A*STAR Institute of Microelectronics in Singapore and Nikta
Amiri, Mostafa Tavakkoli Anbarani, and M. Amin Karami of the University
of Buffalo are also authors.



==========================================================================
A skin-like sensor Dagdeviren's lab, the Conformable Decoders group, specializes in developing conformable (flexible and stretchable)
electronic devices that can adhere to the body for a variety of medical applications. She became interested in working on ways to help patients
with neuromuscular disorders communicate after meeting Stephen Hawking
in 2016, when the world-renowned physicist visited Harvard University
and Dagdeviren was a junior fellow in Harvard's Society of Fellows.

Hawking, who passed away in 2018, suffered from a slow-progressing form
of ALS.

He was able to communicate using an infrared sensor that could detect
twitches of his cheek, which moved a cursor across rows and columns
of letters. While effective, this process could be time-consuming and
required bulky equipment.

Other ALS patients use similar devices that measure the electrical
activity of the nerves that control the facial muscles. However, this
approach also requires cumbersome equipment, and it is not always
accurate.

"These devices are very hard, planar, and boxy, and reliability is a
big issue.

You may not get consistent results, even from the same patients within
the same day," Dagdeviren says.



==========================================================================
Most ALS patients also eventually lose the ability to control their limbs,
so typing is not a viable strategy to help them communicate. The MIT
team set out to design a wearable interface that patients could use to communicate in a more natural way, without the bulky equipment required
by current technologies.

The device they created consists of four piezoelectric sensors embedded
in a thin silicone film. The sensors, which are made of aluminum nitride,
can detect mechanical deformation of the skin and convert it into an
electric voltage that can be easily measured. All of these components
are easy to mass-produce, so the researchers estimate that each device
would cost around $10.

The researchers used a process called digital imaging correlation on
healthy volunteers to help them select the most useful locations to
place the sensor.

They painted a random black-and-white speckle pattern on the face and
then took many images of the area with multiple cameras as the subjects performed facial motions such as smiling, twitching the cheek, or mouthing
the shape of certain letters. The images were processed by software that analyzes how the small dots move in relation to each other, to determine
the amount of strain experienced in a single area.

"We had subjects doing different motions, and we created strain maps of
each part of the face," McIntosh says. "Then we looked at our strain maps
and determined where on the face we were seeing a correct strain level for
our device, and determined that that was an appropriate place to put the
device for our trials." The researchers also used the measurements of
skin deformations to train a machine-learning algorithm to distinguish
between a smile, open mouth, and pursed lips. Using this algorithm,
they tested the devices with two ALS patients, and were able to achieve
about 75 percent accuracy in distinguishing between these different
movements. The accuracy rate in healthy subjects was 87 percent.

Enhanced communication Based on these detectable facial movements, a
library of phrases or words could be created to correspond to different combinations of movements, the researchers say.

"We can create customizable messages based on the movements that you can
do," Dagdeviren says. "You can technically create thousands of messages
that right now no other technology is available to do. It all depends
on your library configuration, which can be designed for a particular
patient or group of patients." The information from the sensor is sent
to a handheld processing unit, which analyzes it using the algorithm that
the researchers trained to distinguish between facial movements. In the
current prototype, this unit is wired to the sensor, but the connection
could also be made wireless for easier use, the researchers say.

The researchers have filed for a patent on this technology and they now
plan to test it with additional patients. In addition to helping patients communicate, the device could also be used to track the progression of
a patient's disease, or to measure whether treatments they are receiving
are having any effect, the researchers say.

"There are a lot of clinical trials that are testing whether or
not a particular treatment is effective for reversing ALS," Tasnim
says. "Instead of just relying on the patients to report that they feel
better or they feel stronger, this device could give a quantitative
measure to track the effectiveness." The research was funded by the MIT
Media Lab Consortium, the National Science Foundation, and the National Institute of Biomedical Imaging and Bioengineering.


========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Anne
Trafton. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sun, T., Tasnim, F., McIntosh, R.T. et al. Decoding of facial
strains via
conformable piezoelectric interfaces. Nat Biomed Eng, 2020 DOI:
10.1038/ s41551-020-00612-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201022112609.htm

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