A new type of brain scan may help to detect Alzheimer's early, using no radiation and at less cost than other techniques, researchers report. Doctors at the University of Pennsylvania's Perelman School of Medicine have developed a form of magnetic resonance imaging, or MRI, that detects brain changes that signal Alzheimer's disease. The doctors have developed a modification to the technique called arterial spin labeling, or ASL-MRI. Small studies show, this may be a useful way to diagnose probable early dementia.
MRI scans are routinely used in hospitals to check for tumors and other issues, and seniors with memory problems may undergo the procedure to rule out brain tumors, strokes or other problems that may be causing the deficits. If Alzheimer's is suspected, they may then undergo another scanning procedure, such as a PET scan.
The advantage of the new ASL-MRI technique is that someone could undergo brain scanning in a single session to help determine whether Alzheimer's may be present. The technique looks for changes in blood flow and the uptake of blood sugar, or glucose, in the memory centers of the brain. It requires about an additional 20 minutes compared to standard MRI scans.
"Increases or decreases in brain function are accompanied by changes in both blood flow and glucose metabolism," explained Dr. John Detre, professor of Neurology and Radiology at Penn, who has worked on ASL-MRI for the past 20 years. "We designed ASL-MRI to allow cerebral blood flow to be imaged noninvasively and quantitatively using a routine MRI scanner."
Studies show that the MRI method is similar in effectiveness to current PET scans that inject a radioactive dye to measure these brain changes. However, the ASL-MRI method uses no radiation and costs one-fourth as much.
"If ASL-MRI were included in the initial diagnostic work-up routinely, it would save the time for obtaining an additional PET scan, which we often will order when there is diagnostic uncertainty, and would potentially speed up diagnosis," said Dr. David Wolk, Assistant Director of the Penn Memory Center and a collaborator on the research.
The studies compared the MRI technique and the specialized PET scan results using flurodeoxyglucose, or FDG, a radioactive tracer. In one, published in the journal Alzheimer's and Dementia, doctors compared images from 13 patients diagnosed with Alzheimer's and 18 age-matched controls. Both methods proved equally effective in detecting signs of early Alzheimer's. In the second study, published in the journal Neurology, data from 15 AD patients were compared to 19 age-matched healthy adults. The patterns of reduction in cerebral blood flow were nearly identical to the patterns of reduced glucose metabolism by the PET scan and showed reductions in brain gray matter typical of Alzheimer's disease.
"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 and longitudinal disease tracking than FDG-PET," said the Neurology study authors.
Early diagnosis of Alzheimer's in the doctor's office has long been a goal for those who treat dementia. Increasingly, experts believe that Alzheimer's is a disease that begins many years before symptoms like memory loss and personality changes become apparent. Treatment of the disease may be most effective in these early stages, before damage to the brain has become extensive. In addition, a simple test to measure brain function would be useful for researchers to test and monitor new treatments.
Additional studies of this new MRI technique will focus on larger sample sizes, including patients with mild cognitive impairment and other kinds of brain problems.
Source: American Academy of Neurology. Musiek ES, Chen Y, Korczykowski M, et al: "Direct Comparison of Flurodeoxyglucose Positron Emission Tomography and Arterial Spin Labeling Magentic Resonance Imaging in Alzheimer's Disease." Alzheimer's and Dementia, Oct. 20, 2011, epub ahead of print.