Tech Briefs Magazine - June 2024 - 38

Shape-Shifting Ultrasound Stickers to Monitor
Post-Surgical Complications
When attached to an organ, the sticker changes in shape in response to the body's changing pH
levels, which can serve as an early warning sign for complications such as anastomotic leaks.
Northwestern University, Cook County, IL
R
esearchers led by Northwestern University
and Washington University
School of Medicine in St. Louis have developed
a first-of-its-kind sticker that enables
clinicians to monitor the health of
patients' organs and deep tissues with a
simple ultrasound device.
When attached to an organ, the soft,
tiny sticker changes in shape in response
to the body's changing pH levels, which
can serve as an early warning sign for
post-surgery complications such as anastomotic
leaks. Clinicians then can view
these shape changes in real time through
ultrasound imaging.
Currently, no existing methods can reliably
and non-invasively detect anastomotic
leaks - a life-threatening condition
that occurs when gastrointestinal
fluids escape the digestive system. By revealing
the leakage of these fluids with
high sensitivity and high specificity, the
non-invasive sticker can enable earlier interventions
than previously possible.
Then, when the patient has fully recovered,
the biocompatible, bioresorbable
sticker simply dissolves away - bypassing
the need for surgical extraction.
The study was published in the journal
Science. The paper outlines evaluations
across small and large animal models to
validate three different types of stickers
made of hydrogel materials tailored for
the ability to detect anastomotic leaks
from the stomach, the small intestine
and the pancreas.
" These leaks can arise from subtle perforations
in the tissue, often as imperceptible
gaps between two sides of a surgical
incision, " said Northwestern's John A.
Rogers, who led device development with
postdoctoral fellow Jiaqi Liu. " These
types of defects cannot be seen directly
with ultrasound imaging tools. They also
escape detection by even the most sophisticated
CT and MRI scans. We developed
an engineering approach and a set of advanced
materials to address this unmet
need in patient monitoring. The technology
has the potential to eliminate risks,
reduce costs and expand accessibility to
rapid, non-invasive assessments for improved
patient outcomes. "
38
Three variations of the ultrasound sticker displayed on a fingertip for scale. (Image: Northwestern
University)
Rogers' team devised an approach to
use tiny sensor devices designed to be
readable by ultrasound imaging. Specifically,
they created a small, tissue-adhesive
sticker out of a flexible, chemically
responsive, soft hydrogel material.
Then, they embedded tiny, paper-thin
metal disks into the thin layers of this
hydrogel. When the sticker encounters
acidic fluids, such as stomach acid, it
swells. When the sticker encounters
caustic fluids, such as pancreatic fluids,
it contracts. As the hydrogel swells or
shrinks in response to changing pH,
the metal disks either move apart or
closer together, respectively. Then, the
ultrasound can view these subtle changes
in placement.
Rogers team constructed stickers of
varying sizes. The largest sticker measures
12 mm in diameter, while the
smallest is just 4 mm in diameter. Considering
that the metal disks are each 1
mm or smaller, Rogers realized that it
might be difficult for radiologists to assess
the images manually. To overcome
this challenge, his team also developed
software that can automatically analyze
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the images to detect with high accuracy
any relative movement of the disks.
" Right now, there is no good way
whatsoever to detect these kinds of
leaks, " said gastrointestinal surgeon Dr.
Chet Hammill, who led the clinical evaluation
and animal model studies at
Washington University with collaborator
Dr. Matthew MacEwan, an Assistant Professor
of Neurosurgery. " The majority of
operations in the abdomen - when you
have to remove something and sew it
back together - carry a risk of leaking.
We can't fully prevent those complications,
but maybe we can catch them earlier
to minimize harm. Even if we could
detect a leak 24- or 48-hours earlier, we
could catch complications before the
patient becomes really sick. This new
technology has potential to completely
change the way we monitor patients after
surgery. "
Rogers and Hammill imagine that the
device could be implanted at the end of a
surgical procedure. Or, because it's small
and flexible, the device also fits (rolled
up) inside a syringe, which clinicians can
use to inject the tag into the body.
Tech Briefs, June 2024

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Tech Briefs Magazine - June 2024

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