Alzheimer’s disease is really tough to diagnose. More specifically, it is tough to diagnose at an early stage, when something can still be done to slow it down. Currently, MRI is employed to detect early forms of dementia, such as mild cognitive impairment (MCI), but we have been unable to effectively distinguish them from Alzheimer’s disease until after brain tissue has suffered irreversible damage. That could change now that researchers in The Netherlands have coupled machine learning methods with a special MRI technique that measures the perfusion, or tissue absorption rate, of blood throughout the brain.
“With standard diagnostic MRI, we can see advanced Alzheimer’s disease, such as atrophy of the hippocampus,” said principal investigator Alle Meije Wink, Ph.D., from the VU University Medical Centre in Amsterdam. “But at that point, the brain tissue is gone and there’s no way to restore it. It would be helpful to detect and diagnose the disease before it’s too late.”
For the new study, the researchers applied machine learning methods to special type of MRI called arterial spin labeling (ASL) imaging. ASL MRI is used to create images called perfusion maps, which show how much blood is delivered to various regions of the brain.
The automated machine learning program is taught to recognize patterns in these maps to distinguish among patients with varying levels of cognitive impairment and predict the stage of Alzheimer’s disease in new (unseen) cases.
The study included 100 patients diagnosed with probable Alzheimer’s disease, 60 patients with mild cognitive impairment (MCI) and 100 patients with subjective cognitive decline (SCD), and 26 healthy controls. SCD and MCI are considered to be early stages of the dementia process and are diagnosed based on the severity of cognitive symptoms, including memory loss and thought- and decision-making problems.
The automated system was able to distinguish effectively among participants with Alzheimer’s disease, MCI and SCD. Using classifiers based on the automated machine learning training, the researchers were then able to predict the Alzheimer’s diagnosis or progression of single patients with a high degree of accuracy, ranging from 82 percent to 90 percent.
“ASL MRI can identify brain changes that appear early in disease process, when there’s a window of opportunity for intervention,” Dr. Meije Wink said. “If the disease process from SCD to MCI to Alzheimer’s disease could be intercepted or slowed, this technique could play a role in screening.”