What happens to the brain in space?
May 14, 2003
Scientists at the U.S. Department of Energy's Brookhaven National
Laboratory, in collaboration with researchers at Rush Medical College, have
demonstrated the effectiveness of a novel x-ray imaging technology to
visualize soft tissues of the human foot that are not visible with
conventional x-rays. The technique, called Diffraction Enhanced Imaging
(DEI), provides all of the information imparted by conventional x-rays as
well as detailed information on soft tissues previously accessible only with
additional scanning methods such as ultrasound or magnetic resonance imaging
(MRI). This study appears in the May 2003 issue of the Journal of Anatomy.
"We've previously shown that this technique can visualize tumors in
breast tissue and cartilage in human knee and ankle joints, but this is the
first time we have shown it to be effective at visualizing a variety of soft
tissues, such as skin, cartilage, ligaments, tendons, adipose pads, and even
collagen and large blood vessels," said physicist Zhong Zhong, who works at
the National Synchrotron Light Source (NSLS) at Brookhaven Lab, where the
current work was done. "The ability to visualize such a range of soft
tissues as well as bone and other hard tissues with just one technique has
many potential applications in diagnosis," Zhong said.
The technique makes use of the intense beams of x-rays available at
synchrotron sources such as the NSLS. These beams are thousands of times
brighter than those produced by conventional x-ray tubes, and provide enough
monochromatic x-ray flux for imaging even after selection of a single
wavelength.
In conventional x-ray images, the various shades of gray are produced
because different tissues absorb different amounts of x-ray energy. "This
works great in imaging bones and other calcified tissues," said Zhong, "but
less satisfactorily in imaging soft-tissues that have similar and low x-ray
absorption."
In DEI, the scientists are more interested in the x-rays that pass
through the tissue and how they bend and scatter as they do, because these
properties vary more subtly between different types of tissue.
To analyze a specimen with DEI, the scientists place a perfect silicon
crystal between the sample and the image detector. As x-rays from the
synchrotron go through the sample, they bend, or refract, and scatter
different amounts depending on the composition and microscopic structure of
the tissue in the sample. Then, when the variously bent rays exit the sample
and strike the silicon crystal, they are diffracted by different amounts
according to their angular spread. So the silicon crystal helps convert the
subtle differences in scattering angles produced by the different tissues
into intensity differences, which can then be readily detected by a
conventional x-ray detector. This results in extremely detailed images that
are sensitive to soft tissue types.
For example, in the current study, a conventional radiograph of a human
toe shows bones and a calcified blood vessel; except for the faint "shadow"
of the surrounding soft tissues and calcification within a tendon, no other
structures are visible. The DEI scan of the same specimen in the same
position clearly shows skin, the fat pads beneath the bones, the blood
vessel, the nail plate, and some tendons, which are clearly distinguishable
from the surrounding connective tissue. Within one of the fat pads, even the
organizational architecture of the collagen framework is visible. Moreover,
the bones take on a three dimensional appearance because of the detail
available in the scans.
In the current study, the DEI images were produced with a lower x-ray
dose than that used for diagnostic x-rays and no contrast agent was needed,
making the technique viable as a potential screening tool, said Zhong.
The scientists are still working on how to scale down the DEI design so
that it can be used in a clinical setting. But they say this should be
feasible and that the technique may eventually greatly enhance mammography
and become increasingly important in the detection of other soft tissue
pathologies such as osteoarthritis, breast cancer, and lung cancer.
Collaborators at Rush Medical College include Carol Muehleman, Jun Li,
and Klaus Kuettner. This research was funded by the National Institutes of
Health, GlaxoSmithKline, Inc., and the U.S. Department of Energy, which
supports basic research in a variety of scientific fields.
The U.S. Department of Energy's Brookhaven National Laboratory
(http://www.bnl.gov) conducts research in the physical, biomedical, and
environmental sciences, as well as in energy technologies. Brookhaven also
builds and operates major facilities available to university, industrial,
and government scientists. The Laboratory is managed by Brookhaven Science
Associates, a limited liability company founded by Stony Brook University
and Battelle, a nonprofit applied science and technology organization. Visit
Brookhaven Lab1s electronic newsroom for links, news archives, graphics, and
more: http://www.bnl.gov/newsroom
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