A team of researchers has learned how to distinguish between brain tissue with and without Alzheimer’s disease (AD) by evaluating the near-infrared optical properties of the gray matter.
A team of Massachusetts researchers has learned how to distinguish between brain tissue with and without Alzheimer’s disease (AD) by evaluating the near-infrared optical properties of the gray matter (Opt. Lett. 33, 624). Although the researchers used slices of postmortem human brain tissue, they predict that the spectroscopic technique might be extended to living patients.
Biomedical researchers who study Alzheimer’s disease are continually searching for ways to diagnose the disease while patients are still alive. Currently, the only method they have for definitively identifying the disease is to conduct postmortem examinations of patients’ brains. Early detection would help scientists to develop drugs to slow the progression of the disorder and to evaluate the efficacy of pharmaceuticals in clinical trials.
The Massachusetts research team, led by Eugene B. Hanlon of the U.S. Department of Veterans Affairs’ geriatric research center in Bedford, Mass., used samples of autopsied brain tissue from five patients who had been confirmed after death as having had AD and four patients who did not have AD.
Hanlon and colleagues from Boston University and Harvard Medical School built on their previous studies of 1-mm-thick slices of brain matter, from which they learned that AD and non-AD tissues have significantly different scattering coefficients.
In the recent experiments, the researchers performed spectroscopy on intact postmortem chunks of a region of the brain known as the temporal pole, a part of the temporal lobe that seems to be involved in the early stages of AD. Diffuse reflectance spectroscopy, particularly in the range of 670 to 970 nm, showed a clear difference between the AD and non-AD brain samples, while absorption spectroscopy was less effective.
The near-infrared is the spectral region that easily penetrates several centimeters into the human body. To make the technique applicable to living patients, researchers would have to
subtract out the background signals from the skin, skull, dura mater and other layers of tissue.
“We’re trying to detect the same sort of thing that the neuropathologist is detecting during microscopic evaluations,” Hanlon said.
The Massachusetts team is beginning clinical studies to see if their methods are translatable to living subjects. They also hope to develop a clearer understanding of the cellular basis for the observed spectral differences between the diseased and healthy brain tissues.