MRI Technique Promises Easier Way to Diagnose Alzheimer’s Disease

Researchers just found what they said is a cheaper and safer way to diagnose and track Alzheimer’s disease, using arterial spin labeling (ASL), a magnetic resonance imaging (MRI) technique. University of Pennsylvania’s Perelman School of Medicine researchers published twice on the technique this month, in Neurology, the American Academy of Neurology’s journal, and Alzheimer’s Disease and Dementia: the Journal of the Alzheimer’s Association.

ASL-MRI can measure the same kind of cerebral blood flow and neurodegenerative changes in brain function as the currently used fluorodeoxyglucose Positron Emission Tomography (FDG-PET) technique, which measures the brain’s glucose metabolism. One way to confirm diagnosis of Alzheimer’s disease is by looking at brain function changes, which are accompanied by changes in glucose metabolism and blood flow.

John A. Detre, MD, professor of Neurology and Radiology at Penn and the papers’ senior author, said that the small pilot study is basically a proof of concept study. The study compared ASL-MRI to FDG-PET scans in 19 Alzheimer’s patients and in 15 age-matched controlled group subjects, measuring cerebral blood flow and glucose metabolism after injecting FDG during the MRI. They then analyzed the data two ways.

In the paper published in Alzheimer’s Disease and Dementia: the Journal of the Alzheimer’s Association, nuclear medicine experts visually analyzed images obtained from ASL-MRI and FDG-PET. They found no difference in specificity or sensitivity of the two tests.

In the Neurology study, computer analysis compared images statistically by each location in the brain. The comparison found that the patterns of reduction in cerebral blood flow were almost identical to the FDG-PET reduced glucose metabolism. They were both different from the patterns of reduction in grey matter found in patients with Alzheimer’s disease.

Detre said that they expected the ASL-MRI and FDG-PET findings to be similar, but were surprised that they were more than that. “They patterns look the same,” he said.
In addition to exposing patients to ionizing radiation, the Penn team found that the current PET technique costs four times more than ASL-MRI. “The ASL (technique) is less invasive, with no radioactivity, and is much cheaper - or free - if you’re already getting an MRI,” said Detre. “This MRI procedure could give you the same information more cheaply and more easily.”

ASL-MRI can be used to speed up the diagnosis time. Researchers note that when looking into Alzheimer’s disease, patients usually undergo an MRI to rule out other medical causes like brain tumor or stroke. By using the ASL technique, the arterial blood water is magnetically labeled before obtaining the MRI image, so the radiologist can look at the perfusion. This adds a functional level to an otherwise structural-only MRI scan.

As for further investigation, Detre would like to confirm the findings with a larger number of subjects and include those with milder disease. He stated that while there is no treatment yet for Alzheimer’s disease, the most obvious application for this is to use ASL-MRI as a screening method on patients with memory complaints. He added that drug companies would probably be the most excited about the technology, because the technique could be used to follow a patient’s progression with biomarkers.