Can MRI scans predict dementia risk?

New research from the Washington University School of Medicine in St. Louis suggests doctors may one day be able to study MRI scans to determine a patient's risk of developing dementia, which today affects more than 50 million people around the globe. The number of cases of dementia is slated to nearly triple by 2050, according to the World Health Organization.

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While PET scans are known to be good at detecting early signs for Alzheimer’s disease, the scans cost upwards of thousands of dollars and require specific radioactive materials, thus few and far between. MRI scans, on the other hand, are widely available.

For the new, small study of just 20 individuals, researchers used MRI scans and predicted with 89 percent accuracy who would go on to develop dementia within three years.

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Lead author Cyrus Raji, an assistant professor of radiology at Washington University's Mallinckrodt Institute of Radiology, and his colleagues identified 10 people with declining cognitive skills and matched them by age and sex with 10 others with steady cognitive skills.

They then used a technique called diffusion tension imaging to study the individuals’ brains, specifically the white matter in their brains.

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This MRI technique tracks the movement of water molecules in the brain, a measurement known as fractional anisotropy (FA). When someone has healthy white matter in the brain, water molecule movement is “fairly uniform.” Healthy white matter measures high in FA.

"If water molecules are not moving normally it suggests underlying damage to white tracts that can underlie problems with cognition," Raji said in a university article.

Raji and his team found that the people who experienced significant cognitive decline showed more signs of white matter damage.

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Even after repeating the analysis in 61 other individuals using “a more refined measure of white matter integrity,” the scientists were able to predict cognitive decline with 89 percent accuracy when studying the entire brain. Accuracy jumped to 95 percent when they narrowed their focus to specific parts of the brain most likely to reveal damage. A single MRI scan was able to predict dementia about 2.6 years before memory loss is typically clinically detectable.

“We could tell that the individuals who went on to develop dementia have these differences on diffusion MRI, compared with scans of cognitively normal people whose memory and thinking skills remained intact,” Raji said. But before diffusion MRIs can be part of a clinical routine, more research is needed.

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Scientists need to “get more control subjects and develop computerized tools that can more reliably compare individual patients’ scans to a baseline normal standard,” Raji added. “With that, doctors might soon be able to tell people whether they are likely to have Alzheimer’s develop in the next few years.”

He and his fellow researchers presented their new findings on Sunday at the Radiological Society of North America meeting in Chicago.

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