Yale University researchers have developed a new way of seeing inside solid objects. The technique, a novel kind of magnetic resonance imaging (MRI), creates 3D images of hard and soft solids based on signals emitted by their phosphorus content. The image here shows the interior spongy bone of a rabbit femoral head, or the “ball” of the rabbit’s hip bone. Image: Yale University
Researchers at Yale University
have developed a new way of seeing inside solid objects, including animal bones
and tissues, potentially opening a vast array of dense materials to a new type
of detailed internal inspection.
The technique, a novel kind of magnetic
resonance imaging (MRI), creates 3D images of hard and soft solids based on
signals emitted by their phosphorus content.
“We are extending the reach of MRI
technology,” said Sean Barrett, a professor of physics and applied physics at
Yale and the principal investigator of research published in the journal PNAS. Merideth A. Frey, a doctoral
student in physics at Yale, is the paper’s lead author.
Traditional MRI produces an image by
manipulating an object’s hydrogen atoms with powerful magnets and bursts of
radio waves. The atoms absorb, then emit the radio wave energy, revealing their
precise location. A computer translates the radio wave signals into images.
Standard MRI is a powerful tool for examining water-rich materials, such as
anatomical organs, because they contain a lot of hydrogen. But it is hard to
use on comparatively water-poor solids, such as bone.
The Yale team’s method targets phosphorus
atoms rather than hydrogen atoms, and applies a more complicated sequence of
radio wave pulses. These extra pulses are the key innovation that allow for
high-spatial-resolution imaging of elements like phosphorus, which is a
relatively abundant element in many biological samples.
So far, the new MRI method, which the researchers
call “quadratic echo MRI of solids,” can only be applied to non-living objects.
It generates too much heat, among other things, according to Barrett. The new
Yale method could also be applied to archaeological artifacts and oil- or
gas-bearing rocks, for example.
In the experiments reported in PNAS, the Yale team generated
high-resolution 3D MRIs of phosphorus in a variety of ex vivo animal bone and soft tissue
samples, including cow bone and mouse liver, heart, and brains.
The researchers say this new type of MRI would
complement traditional MRI, not supplant it. MRI of solids should also be
possible with elements other than phosphorus, they say.
Barrett’s project began about 10 years ago
with a different aim—the study of silicon powders, part of a broader effort to
advance quantum computing.
“This shows how basic research in one area
can have an unexpected impact on very different areas of science,” he said.
Additional authors of the paper are Michael
Michaud, Joshua N. VanHouten, Karl L. Insogna, and Joseph A. Madri, all of the
Yale School of Medicine.
study represents a critical advance because it describes a way to ‘see’
phosphorus in bone with sufficient resolution to compliment what we can determine
about bone structure using X-rays,” said Insogna, a professor at Yale School of
Medicine and director of the Yale
Bone Center. “It opens up an entirely new approach to assessing bone quality.”