MRI system offers potential for imaging of brain
Researchers move to human experiments
With initial safety trials of the world's most powerful MRI system completed, clinicians are one step closer to accessing real-time images of biological processes in the brain.
The device, which was constructed by investigators at the University of Illinois in Chicago (UIC), is the only human-sized MRI machine that has a 9.4 tesla magnetic field. The hope is that it eventually will provide clinicians with new insight into the workings of the brain so that diseases can be detected even before symptoms appear and targeted therapies can be developed for stroke, cancer, and many other illnesses.
Most MR devices in clinical use have magnetic fields in the 1.5 to 3 tesla range, and they visualize water molecules so that biochemical processes can be tracked. What more powerful magnets can do is enable researchers to view different types of molecules such as sodium and oxygen, thereby providing a window to a new dimension of activity, according to Keith Thulborn, MD, PhD, director of UIC's Center for Magnetic Resonance Research. Thulborn worked with researchers at Wauwatosa, WI, based-GE Healthcare, Americas, to develop the 9.4 tesla system, which has been in operation now for about three years.
In the safety trials, 12 men and 13 women were exposed to sodium imaging in a static magnetic field and to a mock scanner that simulated the sound of a scanning device. There were no significant changes in vital signs recorded in the participants as a result of the scanner or the mock scanner, or in cognitive testing that was conducted on all the participants before and after each procedure. However, some of the participants did report some discomfort as a result of entering into the 9.4 tesla magnetic field.
"At least 25% of the people that went into the protocol experienced nothing, and around 60% experienced a slight spinning sensation," explains Ian Atkinson, PhD, a research specialist at UIC. In addition, Atkinson indicates that some of the participants reported having a metallic taste in their mouths when they were in the magnetic field, although he emphasizes that all the symptoms ceased when the participants stopped moving within the field. "There was nothing new that was unique to the 9.4 tesla that hadn't been seen at other fields," he says.
Human experimentation is next
As a result of the successful safety trials, researchers are submitting paperwork to the Food and Drug Administration (FDA) so that they can move on to human experimentation involving sodium imaging. This experimentation could lead to potential new treatments for stroke and the ability to monitor a tumor's response to treatment in real time. At the same time as this work is going on, researchers plan to begin safety trials involving other molecules such as phosphorus and oxygen. "If you do a timed series of oxygen [images] while a person is performing a task…you can get the metabolic rate of oxygen consumption, so you can basically [see] what is happening on a metabolic level in the brain," says Atkinson.
Ultimately, researchers have two chief goals in mind, according to Atkinson. "The first would be to take everything we have learned from high-field imaging and try to trickle it down to what is currently used in the clinical field, so everything we do with the 9.4 tesla, we will attempt to roll down to a 3 tesla scanner so it can be used clinically now and in the next couple of years," he says. The other goal, which is probably five years away at this point, according to Atkinson, is to be able to use the 9.4 tesla for patient care. "The FDA may raise its guidelines [from the current limit of 8 tesla to 9.4 tesla], at which point we could do more routine types of clinical imaging with the new protocols that we have developed."
With initial safety trials of the world's most powerful MRI system completed, clinicians are one step closer to accessing real-time images of biological processes in the brain.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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