MRI on Verge of Imaging Revolution
A commonplace medical instrument is beginning to open some uncommon new avenues for researchers at the University of Arizona who study the human brain and how it works.
Magnetic resonance imaging, or MRI, has been around for about a decade as a clinical tool, helping physicians diagnose an array of ailments and injuries. Now, MRI is on the verge of an imaging revolution that could help unlock secrets of scourges as daunting as stroke and Alzheimer's disease. It may well also give scientists outside of medicine insights into more routine tasks as how the brain behaves when it learns a new language, dredges up old memories or works out a business deal.
Studying a working brain is no simple task. X-rays, CT scans and PET scans can provide a snapshot, but the radiation that makes them possible also makes them dangerous for long term studies. MRI instead uses a combination of electromagnetic fields and radio waves.
"Very benign stuff," says Lee Ryan, an assistant professor of psychology who runs the Cognition and Neural Imaging Laboratory at the UA. The lab includes an eclectic group of researchers from departments spread out from psychology to neurology, speech and hearing science and economics. The group is currently funded with a $350,000 annual matching grant from the Arizona Health Services Department, and is one of seven research groups statewide that form the Arizona Alzheimer's Disease Research Center.
"MRI allows us to look at individuals to scan their brain function. We can put them in the scanner many, many times to do longitudinal studies with very few issues about safety," Ryan says.
Pregnant women are among those excluded as test subjects because the impact of MRI radiation on developing fetuses is not yet clear. So are people with pacemakers and automatic defibrillators because magnetic fields will shut them down. Those who wear metal braces and welders (who may unknowingly carry bits of metal imbedded under their skin from their jobs) are also excluded.
Otherwise there are plenty of volunteers: students, faculty and folks from the community who have responded in droves to a public service television spot that has aired in Tucson.
Interesting but inconvenient
MRI measures blood flow associated with neural activity in the brain. By measuring changes in flow while a subject is engaged in some cognitive task, researchers can map those specific regions of the brain that are active and relevant during the test.
A big downside is that MRI scanners are notoriously claustrophobic. This can be irksome for many subjects, especially older adults and children, who must remain inside the machines for as long as an hour-and-a-half for a series of scans that require them to remain absolutely motionless for up to 15 minutes at a time.
The other unpleasantry that both subjects and researchers must deal with are the hours. Ryan and her group have access to a clinical MRI scanner at University Medical Center, which is only available on weekends and after 10 p.m. on weekdays when medical personnel have finished using it on patients.
"This is why the neighbors never see us at home," Ryan laments.
The hoped for solution is a scanner the group can use for their very own. The UMC scanner is a 1.5T (for tesla, an international measure of magnetic flux density) that is a standard throughout the medical industry.
"What we would REALLY like to get is a 3T, which has a much stronger magnet," says Ryan.
"It will allow us to do the same kind of imaging research now, except at higher power and with a greater signal-to-noise ratio. They are also faster, so we could do the same amount of research in a much shorter period of time. That's a very important concern for us with older people, children and patients."
Highly technical scientific experimentation often revolves around access to equipment that is frequently over-booked. Ryan says a dedicated, more powerful scanner would free researchers to pursue new questions about their research.
"Last time I counted," says Ryan, "we had 12 labs from various departments using the UMC scanner. Everything from motor learning to navigating through space, language, dysfunctional children, a whole raft of things.
"What we want to do is bring this tool to UA researchers, so people who are already experts in a particular area of research can then apply functional imaging to what they're already doing."
Ryan herself studies the neural basis of memory, including a project that compares memory tasks that older adults (age 65 to 85, and beyond) do as well as young adults (mid 20s) with those that they find more difficult.
"Memory is probably the largest and most frequent complaint older adults have about their cognitive function. We're trying to compare the regions of activation that we see in them during these tasks that they can and cannot do, so we can better understand what brain regions are changing across the life span that actually have an impact on memory function."
Ryan and Lynn Nadel, who heads the UA psychology department, are looking at the hippocampus region of the brain and its role accessing decades-old autobiographical memories. Ryan and Nadel scan subjects, adults over the age of 55, about recent events and events that happened during their 20s to see how the hippocampus behaves when people recall very distant memories from their lives.
Stroke victims may also benefit from MRI. Knowing the kind of stroke a person is experiencing can be crucial for emergency personnel trying to decide what kind of medicine to administer.
Ryan also sees MRI as a valuable tool for longitudinal studies necessary for drug testing.
"If you have someone at risk for Alzheimer's and you know what to watch for and the patterns of brain function as the disease progresses, you could scan them before the onset of symptoms and then give prophylactic drugs to stop or slow its progression," Ryan notes.
Imaging technology is only scratching the surface of its potential. In another 10 years, Ryan predicts scientists will look back and laugh at the quality of images now being produced.
"We're really excited at images of activation, but this is nothing compared to what it is going to be like in 15 to 20 years. It has enormous possibility."
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