Knight Ridder/Tribune
Jon Van , Chicago Tribune
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Mar. 25--Just as jogging sends your lungs and heart into high gear, infusing more blood with oxygen and pumping it to replenish your leg muscles, there's a similar--if barely noticeable--response to nourish your brain when you think.
New technology using ultra-high magnetic fields and radio waves can trace the movement of oxygenated blood as it flows through the brain, providing a window on the parts that are most active.
Indeed, using the newest technology, physicians may soon peer inside a brain to watch how it's working, with only a bit more effort than they expend now to take an X-ray to examine a broken bone. This should help them to better diagnose pathology such as Alzheimer's and Parkinson's diseases and to monitor the progress stroke patients make using different therapies.
Technology to monitor blood flow has been used for several years by academic researchers to study the brain, and a new generation of magnetic resonance imaging equipment soon will bring this capability to clinical medicine.
The key to this development is the increasing field strength of magnets that power new imaging machines. The newest machines operate at strengths of 3 Tesla, which is roughly 30,000 times greater than the Earth's natural magnetic field and twice the strength of most magnetic resonance imaging machines in use.
A 3 Tesla machine has been in place since last summer at the University of Illinois at Chicago's West Side campus, and work is under way to build an experimental 9.4 Tesla machine on the Illinois campus to explore new frontiers in brain research.
Dr. Keith Thulborn, director of the university's magnetic resonance research, said that magnetic field strength is important because the brain physiology under scrutiny is so subtle.
Magnetic resonance uses the magnetic field to line up atomic nuclei within the brain in a uniform way and to bombard them with radio signals that cause them to send back signals that can be converted into images. Boosting the magnetic field increases signal strength and the speed of information gathering. This is especially important when researchers look at brain function, which is more difficult to envision than brain anatomy.
"The signal changes are small, only about 1 or 2 percent, in a 1.5 Tesla machine," Thulborn said. "But when you go to 3 Tesla, you get a 4 to 8 percent difference, which produces signals that are much easier to read."
MRI machines are used widely by physicians today, mostly to spot anatomical abnormalities like brain tumors. Thulborn and his colleagues use their 3 Tesla machine to look at brain function.
They note which parts of an individual patient's brain are getting more blood--and are, therefore, more active--when the subject engages in speech, motor skills, vision and the like. This information can be especially useful to a surgeon who is planning to cut through part of the brain to excise an abnormality.
By mapping precisely the brain tissue that's essential for functions such as speech and hearing, the surgeon may find a path through the brain that does the patient little or no harm.
Thulborn also has used 3 Tesla technology to gain new insights into how patients recover from damage inflicted by strokes.
For example, he has shown that when a part of the brain that handles language skills is damaged, patients can regain those skills by recruiting new parts of the brain to do jobs once performed by the damaged tissue.
"We can think of gray matter as the central process units of the brain," said Thulborn, "while white matter is like the connecting cables. If gray matter is damaged, you may still regain function if the cables are intact to recruit other gray matter. But if the cables are damaged, that's another story."
Gaining deeper understanding of the condition of an individual patient's brain should enable physicians to prescribe tailored therapies that will be more effective, Thulborn said. But using magnetic resonance equipment to study brain function is more difficult than acquiring anatomical images to locate tumors.
Patients placed in the magnetic apparatus are asked to do certain tasks, such as repeatedly touching fingers together or watching a white dot appear at different spots on a screen. The tasks must be matched to a patient's abilities, Thulborn said, and the routine should be arranged so that physicians are assured that the information acquired by the equipment is truly caused by the prescribed stimulus and not something random.
Several vendors market 3 Tesla magnetic scanners, but most physicians haven't been trained in how to use the machines to gather accurate brain function information, Thulborn said.
Working with General Electric Medical Systems, a magnetic scanner-maker based in Milwaukee, Thulborn leads training courses for physicians in functional magnetic resonance. Illinois researchers also are working to package their expertise in the form of software that can be used by others to help interpret functional magnetic resonance information.
Using knowledgeable magnetic resonance researchers such as Thulborn to train other physicians is an important part of GE's strategy for promoting 3 Tesla scanners in clinical medicine, said David Weber, GE's manager for magnetic resonance growth.
GE has been making those machines for about six years, Weber said, but they mostly have been sold to research centers, and much of the research has focused on brain function in healthy volunteers rather than on aiding people with illness.
"Our strategy has been to take this at the right pace, and that pace has been very gradual so far," Weber said. "The rate of interest in these machines has been significantly increasing, and many clinical centers will soon be using them."
Among other local centers getting 3 Tesla machines, which can cost about $3 million, are the University of Chicago and Northwestern University.
Dr. Steven Small, co-director of the brain imaging center at the University of Chicago, said the new machine "is a whole new enterprise that is bringing the physical and social sciences together."
The machine is dedicated purely to research, said Small, and is providing linguists, psychologists and other social scientists with a new tool to explore the links between brain function and behavior.
At Northwestern, about 80 percent of functional magnetic resonance work has focused on basic research and 20 percent has been clinical, looking at such things as helping to plan brain surgery, said Todd Parrish, assistant professor of radiology.
"The academic centers will have these more powerful machines first, but they will trickle down to the rest of the community," Parrish said. "Right now it's a big open field, and the radiologists need to acquire the skills to do functional analysis.
"Very few centers have pioneers like Keith Thulborn who go to extreme magnetic fields to keep pushing the research envelope. But many centers will benefit from the research."
Once the new 9.4 Tesla machine begins operating at Illinois next year, Thulborn will be able to explore more subtle aspects of brain function. Instead of looking primarily at blood flow to determine brain function, he expects to look at the flow of some chemicals in and out of cells.
Such information should provide new insights into how the brain works and suggest new therapies, he said.
For now, the 9.4 Tesla machine will be strictly an advanced research tool, used only to further knowledge about how brains work. But it's possible that someday a new generation of 9.4 Tesla equipment could become commercially available for widespread clinical application.
"When you look at the history of MRI, you never rule out anything," said Weber, whose company is working with Thulborn to build the 9.4 Tesla machine in Chicago. "There was a time when the 1.5 Tesla machine was strictly a lab machine for research, and people said it would never become a clinical field strength. Yet today, 1.5 is standard, and we're moving to 3 Tesla."