Modern simulations could improve MRIs
Engineers find more efficient models to analyze contrast agents that find disease

Date:
September 20, 2021
Source:
Rice University
Summary:
Rice University engineers improve simulations that analyze
gadolinium- based contrast agents used in clinical magnetic
resonance imaging. More efficient simulations could help make
better compounds for imaging technologies.



FULL STORY ========================================================================== Gadolinium-based contrast agents, the gold standard in magnetic resonance imaging(MRI) to determine the health of a patient, can be improved,
according to Rice University engineers who are refining models they
first used to enhance oil and gas recovery.


==========================================================================
The team led by Dilip Asthagiri and Philip Singer of the George R. Brown
School of Engineering had studied how nuclear magnetic resonance tools, commonly used in the oil industry to characterize deposits underground,
could be optimized through molecular dynamics simulations.

"We addressed a lot of fundamental scientific questions there, and
we wondered if there were other ways we could use these simulations,"
Asthagiri said.

"There are roughly 100 million MRIs taken worldwide every year, and
about 40% of them use gadolinium-based contrast agents, but the way they
model MRI response to these agents hasn't changed significantly since
the 1980s," Singer said. "We thought it would be a good test bed for
our ideas." The results of their research appear in the Royal Society
of Chemistry journal Physical Chemistry Chemical Physics.

Their paper demonstrates how limiting the number of parameters in
simulations has the potential to improve the analysis of gadolinium-based contrast agents and how effective they are at imaging for clinical
diagnosis. Their goal is to make better and more customizable contrast
agents.



========================================================================== Doctors use MRI devices to "see" the state of soft tissues inside the
body, including the brain, by inducing magnetic moments in the hydrogen
nuclei of ever-present water molecules to align along the magnetic
field. The device detects bright spots when the aligned nuclei "relax"
back to thermal equilibrium following an excitation, and the faster they
relax, the brighter the contrast.

That's where paramagnetic gadolinium-based contrast agents come
in. "Gadolinium ions increase sensitivity and make the signal brighter
by decreasing the T1 relaxation time of hydrogen nuclei," Asthagiri
said. "Our ultimate goal is to help the optimization and design of these agents." Typically, gadolinium is "chelated" -- surrounded by metal
ions -- to make it less toxic. "The body doesn't remove gadolinium by
itself and needs to be chelated so the kidneys can get rid of it after
a scan," Singer said. "But chelation also slows the molecular rotation,
and that creates better contrast in the MRI image." The researchers
noted "chelate" comes from the Greek word for claw. "In this case, these
claws grip the gadolinium to make it stable," he said. "We hope our
models help us design a stronger grip, which will make them safer while maximizing their ability to increase contrast." They acknowledged that gadolinium chelates, which revolutionized MRI testing when introduced in
the late 1980s, have been controversial lately since it was discovered
that patients with kidney impairment were unable to eliminate all of the toxins. "They've since worked out that if you have good kidney function,
the benefits outweigh the potential risks," Singer said.

The team is also adapting its models beyond interactions with water. "In biological systems, cells have other constituents like osmolytes and denaturants like urea, so we're modeling gadolinium with these different environments to build toward a variety of applications," Asthagiri said.

Co-authors of the paper are Rice graduate students Arjun Valiya
Parambathu, Thiago Pinheiro dos Santos and Yunke Liu; senior research
scientist Lawrence Alemany; George Hirasaki, the A.J. Hartsook Professor Emeritus and a research professor; and Walter Chapman, the William
W. Akers Professor of Chemical and Biomolecular Engineering.

Vinegar Technologies LLC, Chevron Energy Technology, the Rice University Consortium on Processes in Porous Media, the Department of Energy Office
of Science and the Texas Advanced Computing Center at the University of
Texas at Austin supported the research.

========================================================================== Story Source: Materials provided by Rice_University. Original written
by Mike Williams. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Philip M. Singer, Arjun Valiya Parambathu, Thiago J. Pinheiro
dos Santos,
Yunke Liu, Lawrence B. Alemany, George J. Hirasaki, Walter
G. Chapman, Dilip Asthagiri. Predicting 1H NMR relaxation in Gd3
-aqua using molecular dynamics simulations. Physical Chemistry
Chemical Physics, 2021; DOI: 10.1039/D1CP03356E ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210920113018.htm

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