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Alzheimer's detection using near-infrared light

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March 25, 2008

MRI of a brain with A.D. (left) and a normally aged brain
 Image credit: NASA

MRI of a brain with A.D. (left) and a normally aged brain Image credit: NASA

March 26, 2008 It is estimated that around 4.5 million people in the US are currently living with Alzheimer's and the disease is one of the leading causes of death, accounting for tens of thousands each year. There has been no definitive way of diagnosing the disease on living patients so doctors have had to rely on medical histories, administering physical exams, and neuropsychological assessments. Now a team of researchers in Massachusetts has developed a way of examining brain tissue with near-infrared light to detect signs of Alzheimer's disease.

After someone with Alzheimer's dies, pathologists can perform an autopsy and examine slices of the brain under the microscope, looking for the same signs that Alois Alzheimer first recognized when he identified the disease more than a century ago. Finding accumulations of amyloid plaques in the brain substance and tangle-like proteins in nerve cells is the only way to confirm with certainty that someone had Alzheimer's while they were alive. This type of examination can not be carried out on living patients so doctors have relied on less exact methods to diagnose the disease. The breakthrough from the team at Harvard Medical School/Beth Israel Deaconess Medical Center and Boston University, led by Eugene Hanlon, used optical technology to examine tissue samples taken from different autopsies and correctly identified which samples came from people who had Alzheimer's disease. The new technique can detect alterations to the optical properties of the brain that occur as the tissue undergoes microscopic changes due to Alzheimer's—sometimes far in advance of clinical symptoms. The technique is now being tested for its effectiveness at diagnosing Alzheimer's disease in living people.

The team’s research was recently published in the Optical Society of America’s journal, Optics Letters. The full article, “Scattering Differentiates Alzheimer Disease In Vitro", is available to read online. Accurate, early detection of Alzheimer's could save many lives. While there is no cure for the disease, clinically proven treatments can slow its progress—especially if they are administered early on. Moreover, being able to follow the disease progression over time would greatly enhance the ability of researchers and pharmaceutical companies to find new and improved drugs and treatment strategies for people at all stages of the disease.

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