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Quick, easy imaging of brain function.

For medical diagnosis, magnetic resonance imaging (MRI) quickly took a place next to computerized tomography (CT) as a sophisticated imaging technology. Now, a variant of this technique is poised to join a different imaging tool, positron emission tomography (PET), as a means of monitoring brain function. Called functional MRI, this 3-year-old technology follows the flow of blood in the brain by detecting changes in the relative proportion of oxygenated and deoxygenated red cells. PET, too, tracks blood flow, but unlike PET, functional MRI works quickly and does not require the administration of a radioactive tracer, says Stephen M. Rao of the Medical College of Wisconsin in Milwaukee.

"It's an extremely easy-to-use technology to probe brain function," adds Kenneth Kwong, who is helping develop MRI at Massachusetts General Hospital in Boston.

Just a few research centers can carry out PET studies, but many hospitals and diagnostic centers routinely use MRI machines that, if modified with a special coil that generates a different pattern of magnetic pulses, can provide blood-flow data like those obtained from PET scans. Already, Rao has used functional MRI to observe how the brain plans and carries out movements.

For these experiments, volunteers tapped their fingers in unison, repeated a specific sequence of finger taps, or simply imagined they were doing this sequence. With each task, "we find a very large change in brain activity," Rao reports.

As a previous PET study had noted, the repetitive taps activated the primary motor cortex, while the sequences demanded that the motor cortex, a supplementary motor area, and two other regions become active. The imagined movements required activity primarily by the supplementary area, Rao notes. In addition, the MRI studies revealed details not seen with PET.

Studies like this are just the first step for the new technology, "You can do experiments so quickly that there will be literally an explosion of knowledge about the brain," Rao predicts.

However, he and his colleagues also note that they need to improve their ability to judge the sizes of blood vessels in the MRI image and their statistical techniques for analyzing the data obtained.
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Title Annotation:reports from American Association for the Advancement of Science meeting
Author:Pennisi, Elizabeth
Publication:Science News
Date:Mar 5, 1994
Words:351
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