Relatively new imaging technology is helping neuroradiologists at Spokane-based Inland Imaging LLC more definitively identify Alzheimer's disease.
Called volumetric MRI, the tool can be used when a patient first starts experiencing memory impairment and help to distinguish between clinically diagnosed mild cognitive impairment and Alzheimer's disease, says Jennifer Brown, coordinator of MRI services at Inland Imaging.
"Basically," Brown says, "what it does is measures the memory centers and compares them to an expected size. It's effective in predicting progression of mild cognitive impairment to Alzheimer's disease by measuring brain atrophy or brain shrinkage."
Specifically, says Inland Imaging neurologist Dr. Justin Frederick, volumetric MRI measures the size of a part of the brain called the hippocampus, which largely is responsible for both long-term and short-term memory. As a person ages, Frederick says, the hippocampus shrinks gradually. In people who develop Alzheimer's disease, however, it gets smaller faster.
Researchers at the University of California San Diego developed the volumetric MRI, Frederick says, and tested it for a number of years as one part of the National Institute of Health's Alzheimer's Disease Neuroimaging Initiative. Through the volumetric MRI research, which concluded in 2010, researchers gathered enough data from patients to determine a typical size of a hippocampus. If a patient's hippocampus is substantially smaller than the average for people of the same gender and age, it's likely they are developingor have developedAlzheimer's disease.
A patient's first scan can be compared with average sizes, but it also can serve as a baseline for future scans, Frederick says. For example, he says, a patient can have a second scan six months after the first, and the results can be compared to determine whether the hippocampus has atrophied.
Brown says, "The beauty of volumetric MRI is being able to detect more subtle changes earlier."
Inland Imaging has been using the volumetric MRI for just over a year and currently sees about 20 people a month who receive the test.
"As the population ages, I think that probably is going to grow," she says.
Frederick says the test has been used on patients as young as in their 40s and as old as in their 90s. The bulk of the patients, however, are in their 70s. Memory impairment appears to occur equally in men and women, he says, so they don't see more of one gender compared with another.
While the test is looking for shrinkage in the hippocampus, that sort of atrophy doesn't necessarily come from lack of usage, as is the case with muscle atrophy. Frederick says studies have tried to link Alzheimer's disease to diet, exercise, and intellectual stimulation. In his opinion, he says, those studies have been inconclusive thus far.
Frederick says volumetric MRI allows neuroradiologists to play a larger role in the diagnosis of memory impairment.
Prior to using the technology, which essentially is a software application the company installed on an existing MRI machine, Frederick says he typically was called upon to rule out other causes of memory impairment, such as vascular disease or small strokes that had gone undetected.
Because neuroradiologists review so many images of the brain, he says he could look at a regular MRI image of a patient's hippocampus and determine whether it was smaller than normal. However, he says, that's a subjective evaluation that a neurologist might or might not take into account when diagnosing a patient.
"Our role in that clinical care team was much smaller, because we could only rule out other major problems in the brain," he says.
Frederick is one of 13 Inland Imaging radiologists who subspecialize in neuroradiology.
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