Researchers from the Perelman School of Medicine at the University of Pennsylvania (Philadelphia, PA, USA) are using a magnetic resonance imaging (MRI) technique called arterial spin labeling (ASL) to diagnose Alzheimer's disease.

The team has determined that the ASL-MRI test is a promising alternative to the current standard -- a specific positron emission tomography (PET) scan that requires exposure to small amounts of a radioactive glucose analog and costs approximately four times more than an ASL-MRI.

In brain tissue, regional blood flow is tightly coupled to regional glucose consumption. Increases or decreases in brain function are accompanied by changes in both blood flow and glucose metabolism.

ASL-MRI can be used to measure neurodegenerative changes in a similar way that fluorodeoxyglucose positron emission tomography (FDG-PET) scans are used to measure glucose metabolism in the brain. Both tests correlate with cognitive decline in patients with Alzheimer's disease.

Dr. John Detre, a professor of neurology and radiology at the university, said that the ASL-MRI test had been designed to allow cerebral blood flow to be imaged noninvasively and quantitatively using a routine MRI scanner.

When Alzheimer's disease is suspected, patients typically receive an MRI initially to look for structural changes that could indicate other medical causes, such as a stroke or brain tumor.

Adding about 10-20 minutes to the test time, ASL can be incorporated into the routine MRI and capture functional measures to detect Alzheimer's disease upfront, turning a routine clinical test (structural MRI) into both a structural and functional test.

Given that ASL-MRI is entirely noninvasive, has no radiation exposure, is widely available and easily incorporated into standard MRI routines, it is potentially more suitable for screening than FDG-PET scans.

-- By Dave Wilson, Senior Editor, Vision Systems Design