Magnetic Attractions

Most of the researchers in the Center for Cognitive Neuroscience were attracted to Duke by high magnetic fields—more accurately, the powerful, precise, functional Magnetic Resonance Imaging (fMRI) machines of the new Brain Imaging and Analysis Center. 
  The analytical technique of fMRI works by using magnetic pulses that produce telltale changes in the molecules within brain tissues that are already under a powerful-but-harmless static magnetic field. Since even subtle differences in brain tissues cause them to react distinctively under the magnetic fields, the technique allows high-resolution mapping of the brain’s regions. Specifically, fMRI can map increased blood flow to a brain region, which is triggered by increased activity of the brain cells, called neurons, in that region.
  Duke’s cognitive neuroscientists, as well as other brain researchers in the BIAC and throughout Duke Medical Center, use the technique of “event-related fMRI,” in which they ask subjects to perform a mental task and map their brains using “magnetic snapshots” every second or so. This fMRI mapping technique has evolved only very recently, says BIAC director Gregory McCarthy.
  “I got started in it in about 1992,” he says, “and what’s happened between now and then is tremendous improvement in the instrumentation. While you can get a decent fMRI signal from practically any high-quality clinical MRI scanner, the kind of equipment we have here at Duke far surpasses that.”
  Duke’s two research fMRI machines can generate fields of 1.5 Tesla or 4 Tesla, a Tesla being 10,000 times the strength of Earth’s magnetic field. The former machine, which generates fields comparable to a commercial MRI scanner, allows researchers to “see” the blood flow through the brain’s vessels, like a satellite image that can see the freeways of a city.
  Using the more powerful 4 Tesla machine, McCarthy and his colleagues are pushing the limits of fMRI. By achieving highly stable magnetic fields and inventing new techniques for producing the pulses and analyzing the resulting signals, they hope to map blood flow changes around groups of neurons, like an aerial photograph that can see an individual neighborhood. This finer resolution will reveal even greater details of the living brain at work.
  “Up until now all of the tremendous progress in neurobiology has taken place in animal models with invasive staining techniques,” says McCarthy. “But what we want to do now is observe in detail what happens in the living human brain, both the normal and the abnormal.”
  Thus, he says, not only are the BIAC machines used in basic research but also clinically by Duke neurosurgeons to map their patients’ brains—for example, to plan surgeries to remove tumors and avoid damaging critical adjacent brain structures. Still other neuroscientists are using fMRI to map the brains of sufferers of Alzheimer’s disease, schizophrenia, autism, and elderly depression, both to understand those disorders better and even to assess the effectiveness of drug treatments.
  “However, such achievements are possible only because the BIAC is a multidisciplinary center that includes not only people with expertise in the neurosciences, but also in engineering, physics, biophysics, and statistics,” emphasizes McCarthy. “The center couldn’t have fit into a single department and still draw on all these different strengths of the university.”

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