March 7, 2008

Powerful magnet pulls in support for imaging study

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Powerful magnet pulls in support for imaging study

Researchers at Vanderbilt University Medical Center have received a five-year, $5.7 million federal grant to study the human brain using one of the world's most powerful magnets.

The grant, from the National Institute of Biomedical Imaging and Bioengineering, renews a $4 million Bioengineering Research Partnership grant awarded in 2002 to study “integrated functional imaging of the human brain.”

But “it's a complete change of direction,” said John Gore, Ph.D., the grant's principal investigator and director of the Vanderbilt University Institute of Imaging Science. “We want to focus on the challenges of the highest field in human imaging.”

The grant will support development of “high field” magnetic resonance imaging and spectroscopy using the institute's 7 Tesla scanner, one of only 13 in the world being used in human studies.

One Tesla is roughly 20,000 times the strength of the magnetic field of the earth. Encased in 400 metric tons of steel, the 7 Tesla scanner can generate brain images down to the molecular level.

The magnet interacts with atoms in body tissues, such as hydrogen, so that they will absorb energy from particular frequencies of radio waves, causing them to resonate. By measuring these magnetic effects, scanners can construct detailed images of structures in the body, as well as determine the levels of key compounds, including molecules that are involved in signaling in the brain.

More powerful magnets require the use of higher frequency radio waves, and generate bigger signals that can be used to increase the resolution — the detail — of the images. The 7 Tesla scanner, for example, can reveal tiny blood vessels in the brain that are beyond the resolving power of conventional scanners, and can bring the focus down to single columns of neurons.

The images also can be generated more quickly, and they are more sensitive to subtle changes. “We can see smaller effects caused by brain activity in gray matter,” the cortex of the brain that contains nerve cell bodies, said Gore.

High-frequency radio waves — in the range of 300 megahertz — also create technical challenges, however. “The ability to get 300 megahertz radio waves to penetrate into the body in a uniform way is more difficult than with a lower field,” Gore said. “We have to develop engineering or scientific solutions.”

Ultimately, said Gore, high-field magnetic resonance and spectroscopy may enable researchers to study the effects of drugs in a wide range of brain disorders, from chronic pain to Alzheimer's disease, and to help develop new drugs.

In addition to the institute, the grant will involve researchers from the Vanderbilt School of Engineering and Department of Psychology, and corporate partners Philips Healthcare (which built the scanner), Invivo and Resonance Research Inc.

Gore is Chancellor's University Professor of Radiology and Radiological Sciences, Biomedical Engineering, Molecular Physiology & Biophysics and Physics.