Tech Briefs Magazine - March 2022 - PIT-25

this problem, the Argonne researchers
proposed leveraging tools built to train
deep neural networks, a form of AI.
Neural networks are essentially a series
of algorithms designed to mimic
the human brain and nervous system.
When given a series of inputs and outputs,
these algorithms seek to map out
the relationship between the two. But to
do this accurately, neural networks have
to be trained. That's where training algorithms
come into play.
" Tech companies like Google and
Facebook have developed packages of
software that are designed to train neural
networks. What we've essentially done is
taken those and applied them to the scientific
challenge of phase retrieval, " said
group leader Mathew Cherukara.
Using these training algorithms, the
research team demonstrated a way to recover
phase information. But what makes
their approach unique is that it also enables
scientists to retrieve essential information
about their electron microscope.
" Normally when you're trying to retrieve
the phase, you presume you know
your microscope parameters perfectly.
However, that knowledge might not
be accurate, " said Professor Tao Zhou.
" With our method, you don't have to rely
on this assumption. Instead, you actually
get the conditions of your microscope -
that's something other phase retrieval
methods can't do. "
Their method also improves the resolution
and sensitivity of existing equipment.
This means that researchers will
be able to recover tiny shifts in phase,
and in turn, get information about small
changes in magnetization and electrostatic
potential, all without requiring
costly hardware upgrades.
For more information, contact media@
anl.gov.
An Innovative Imaging Technique for Dynamic Optical
Nanothermometry
Institut National de la Recherche Scientifique, Laval, Quebec, Canada
A
new imaging tech nique, developed
by the teams of Professors
Jinyang Liang and Fiorenzo Vetrone at
the Institut National de la Recherche
Scientifique (INRS), can measure
temperature in 2D, without contact.
This accurate real-time temp erature detection
could one day improve photothermal
therapy and help in the early
diagnosis of skin cancers.
This technology, known as single-shot
photoluminescence lifetime imaging
ther mometry (SPLIT), is based on the luminescence
of nanoparticles doped with
rare earth ions. " These nanoparticles
are considered as nanothermometers
because their luminescent properties
change with the temperature of the environment.
They are also biocompatible, "
said Professor Vetrone.
Instead of imaging the luminescence
point by point, which is time consuming,
SPLIT uses a novel ultra-high-speed
camera to track how quickly the luminescence
of these nanoparticles decays
in every spatial point. The temperature
can then be sensed by checking how fast
the emitted light fades out. Since it is in
real time, SPLIT can follow the phenomenon
as it happens.
For the first time, it enables luminescence
thermometry using the nanoparticle's
lifetime with a moving sample. " Compared
to existing thermometry techniques,
SPLIT is faster and has higher resolution.
This allows a more accurate temperature
sensing with both an advanced and economical
solution, " said Professor Liang.
Photonics & Imaging Technology, March 2022
20 °C
27 °C
33 °C
39 °C
46 °C
40 µm
20 °C
27 °C
33 °C
39 °C
46 °C
40 µm
1
395
Lifetime (µs)
495
Normalized
intensity
Lifetime images of green (top row) and red (bottom row) upconversion emission bands under different
temperatures captured by SPLIT. (Image: Jinyang Liang)
Professors Liang and Vetrone believe
that SPLIT technology could, among
other things, increase the ability to detect
and treat skin cancers. At present,
the capacity to detect melanomas, and
more specifically micro-melanomas,
is still limited. Existing diagnostic approaches
are restricted by their invasiveness,
resolution, and accuracy, which
leads to a large number of unnecessary
biopsies.
Optical thermometry could thus be
used to detect cancer cells, whose rapid
metabolism leads to a higher temperature
than that of normal tissue, making
them more visible with SPLIT.
To detect melanoma, clinics can use
a thermal camera, but the resolution is
low. " SPLIT marks an important step in
the technical development. With high
resolution, the technology could be used
to precisely locate the cancerous mole, "
said Professor Liang.
Beyond detection, this technology
could also be used to monitor the light
dose during certain types of treatment.
For example, photothermal therapy
attacks cancer cells through the heat
generated by exposure to near-infrared
light. " We want to eradicate the
cancer, but not the surrounding tissue,
so if the temperature is too high,
the treatment could be decreased or
stopped for a while. If it's too low, we
could increase the light to get the right
dose, " said Vetrone.
For more information, contact Professor
Jinyang Liang at jinyang.liang@inrs.ca.
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Tech Briefs Magazine - March 2022

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