More sensitive X-ray imaging
Improvements in the material that converts X-rays into light, for medical
or industrial images, could allow a tenfold signal enhancement.

Date:
February 24, 2022
Source:
Massachusetts Institute of Technology
Summary:
Making nanoscale patterns in 'scintillator' materials that convert
X-rays into light could allow a tenfold signal enhancement for
medical or industrial imaging, researchers report. This method might
lead to improvements in medical X-rays or CT scans, to reduce dose
exposure and improve image quality.



FULL STORY ========================================================================== Scintillators are materials that emit light when bombarded with
high-energy particles or X-rays. In medical or dental X-ray systems,
they convert incoming X-ray radiation into visible light that can then be captured using film or photosensors. They're also used for night-vision
systems and for research, such as in particle detectors or electron microscopes.


========================================================================== Researchers at MIT have now shown how one could improve the efficiency
of scintillators by at least tenfold, and perhaps even a hundredfold,
by changing the material's surface to create certain nanoscale
configurations, such as arrays of wave-like ridges. While past attempts
to develop more efficient scintillators have focused on finding new
materials, the new approach could in principle work with any of the
existing materials.

Though it will require more time and effort to integrate their
scintillators into existing X-ray machines, the team believes that
this method might lead to improvements in medical diagnostic X-rays or
CT scans, to reduce dose exposure and improve image quality. In other applications, such as X-ray inspection of manufactured parts for quality control, the new scintillators could enable inspections with higher
accuracy or at faster speeds.

The findings are described in the journal Science, in a paper by
MIT doctoral students Charles Roques-Carmes and Nicholas Rivera; MIT
professors Marin Soljacic, Steven Johnson, and John Joannopoulos; and
10 others.

While scintillators have been in use for some 70 years, much of the
research in the field has focused on developing new materials that
produce brighter or faster light emissions. The new approach instead
applies advances in nanotechnology to existing materials. By creating
patterns in scintillator materials at a length scale comparable to
the wavelengths of the light being emitted, the team found that it was
possible to dramatically change the material's optical properties.

To make what they coined "nanophotonic scintillators," Roques-Carmes
says, "you can directly make patterns inside the scintillators, or you
can glue on another material that would have holes on the nanoscale. The specifics depend on the exact structure and material." For this research,
the team took a scintillator and made holes spaced apart by roughly one
optical wavelength, or about 500 nanometers (billionths of a meter).



==========================================================================
"The key to what we're doing is a general theory and framework we have developed," Rivera says. This allows the researchers to calculate the scintillation levels that would be produced by any arbitrary configuration
of nanophotonic structures. The scintillation process itself involves
a series of steps, making it complicated to unravel. The framework the
team developed involves integrating three different types of physics, Roques-Carmes says.

Using this system they have found a good match between their predictions
and the results of their subsequent experiments.

The experiments showed a tenfold improvement in emission from the
treated scintillator. "So, this is something that might translate into applications for medical imaging, which are optical photon-starved,
meaning the conversion of X- rays to optical light limits the image
quality. [In medical imaging,] you do not want to irradiate your
patients with too much of the X-rays, especially for routine screening,
and especially for young patients as well," Roques-Carmes says.

"We believe that this will open a new field of research in nanophotonics,"
he adds. "You can use a lot of the existing work and research that has
been done in the field of nanophotonics to improve significantly on
existing materials that scintillate." Soljacic says that while their experiments proved a tenfold improvement in emission could be achieved,
by further fine-tuning the design of the nanoscale patterning, "we also
show that you can get up to 100 times [improvement], and we believe we
also have a path toward making it even better," he says.

Soljacic points out that in other areas of nanophotonics, a field that
deals with how light interacts with materials that are structured at the nanometer scale, the development of computational simulations has enabled rapid, substantial improvements, for example in the development of solar
cells and LEDs. The new models this team developed for scintillating
materials could facilitate similar leaps in this technology, he says.

Nanophotonics techniques "give you the ultimate power of tailoring
and enhancing the behavior of light," Soljacic says. "But until now,
this promise, this ability to do this with scintillation was unreachable because modeling the scintillation was very challenging. Now, this work
for the first time opens up this field of scintillation, fully opens it,
for the application of nanophotonics techniques." More generally, the
team believes that the combination of nanophotonic and scintillators
might ultimately enable higher resolution, reduced X-ray dose, and energy-resolved X-ray imaging.

Yablonovitch adds that while the concept still needs to be proven in
a practical device, he says that, "After years of research on photonic
crystals in optical communication and other fields, it's long overdue
that photonic crystals should be applied to scintillators, which are of
great practical importance yet have been overlooked" until this work.

The research team included Ali Ghorashi, Steven Kooi, Yi Yang, Zin
Lin, Justin Beroz, Aviram Massuda, Jamison Sloan, and Nicolas Romeo
at MIT; Yang Yu at Raith America, Inc.; and Ido Kaminer at Technion
in Israel. The work was supported, in part, by the U.S. Army Research
Office and the U.S. Army Research Laboratory through the Institute for
Soldier Nanotechnologies, by the Air Force Office of Scientific Research,
and by a Mathworks Engineering Fellowship.

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


========================================================================== Related Multimedia:
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Improving_the_efficiency_of_scintillators_by_at_least_tenfold_by_changing
the_material's_surface.

========================================================================== Journal Reference:
1. Charles Roques-Carmes, Nicholas Rivera, Ali Ghorashi, Steven
E. Kooi, Yi
Yang, Zin Lin, Justin Beroz, Aviram Massuda, Jamison Sloan,
Nicolas Romeo, Yang Yu, John D. Joannopoulos, Ido Kaminer, Steven
G. Johnson, Marin Soljačić. A framework for scintillation
in nanophotonics.

Science, 2022; 375 (6583) DOI: 10.1126/science.abm9293 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220224140851.htm

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