Quick, easy imaging of brain function.For medical diagnosis, magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures. (MRI 1. (application) MRI - Magnetic Resonance Imaging. 2. MRI - Measurement Requirements and Interface. ) 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 positron emission tomography: see PET scan. positron emission tomography (PET) Imaging technique used in diagnosis and biomedical research. (PET), as a means of monitoring brain function. Called functional MRI functional MRI Fast MRI Imaging A brain imaging technique that measures ↑ blood flow–BF which, like PET, relies on changes in BF and oxygenation due to brain activity; aerobic metabolism in some neurons creates a local ↑ in deoxyHb, which triggers , 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 Massachusetts General Hospital Health care The major teaching hospital for Harvard Medical School, widely regarded as one of the best health care centers in the world 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 The primary motor cortex (or M1) works in association with pre-motor areas to plan and execute movements. M1 contains large neurons known as Betz cells which send long axons down the spinal cord to synapse onto alpha motor neurons which connect to the muscles. , while the sequences demanded that the motor cortex, a supplementary motor area The supplementary motor area (SMA) is a part of the sensorimotor cerebral cortex (perirolandic, i.e. on each side of the Rolando or central sulcus). It was included, on purely cytoarchitectonic arguments, in area 6 of Brodmann and the Vogts. , 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. |
|
||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion