New imaging test aids Alzheimer's diagnosis

August 23, 2012
The image on the left is a PET scan of a normal brain. The image on the right is heavily blackened throughout the cerebral cortex due to the the presence of amyloid plaques. Amyloid is found in the brains of patients with dementia due to Alzheimer’s disease

In research studies, scientists regularly use positron emission tomography (PET) scans to detect signs of Alzheimer's disease. Now, Washington University physicians at Barnes-Jewish Hospital are the first in Missouri to offer a new type of PET scan for patients with memory disorders and other forms of cognitive impairment who are not involved in research studies.

This new imaging test is now available to patients being evaluated for Alzheimer's disease because the U.S. (FDA) recently approved the use of a radioactive diagnostic agent, Amyvid™ (Florbetapir F 18 Injection), for use in a clinical setting.

The agent detects neuritic plaques, a hallmark of Alzheimer's disease, by binding to abnormal deposits of the protein beta-amyloid that develop in the brains of patients with the disorder. This makes the plaques "light up" during a PET scan.

The video will load shortly

"We're using the scans in patients whose cognitive function is impaired," says Farrokh Dehdashti, MD, professor of radiology in the Division of Nuclear Medicine at the Mallinckrodt Institute of Radiology. "First, the patient sees a neurologist, or other specialist in cognitive disorders, to confirm that a test like this would be appropriate, and then we conduct the to learn whether are present. In that way, the test allows both doctors and patients to have a better idea of whether the patient's is related to Alzheimer's disease or some other illness."

With , nuclear medicine specialists like Dehdashti can now use the diagnostic agent, which has a longer half-life than the compound used in research studies, making it better suited for clinical use. As a single test, PET scans can't confirm Alzheimer's disease, but a negative test that finds no evidence of elevated beta-amyloid can help rule out the disease as the cause for the patient's cognitive impairment.

"What complicates the results of a scan is that although Alzheimer's disease is very common, it's not the only reason that we might detect amyloid," according to Jonathan McConathy, MD, PhD, assistant professor of radiology. "A positive scan could mean that a person has Alzheimer's disease, or it could be related to some other neurologic disorder. It's also possible to find amyloid in the brain of a person who has no symptoms of Alzheimer's disease or other cognitive problems, so a positive test doesn't confirm that someone has the disease."

He says a positive scan indicates only that elevated levels of amyloid are present. But amyloid plaques can accumulate in the brains of people with other types of neurologic problems, such as dementia with Lewy bodies or cerebral amyloid angiopathy. Plaques also can occur in some older adults who are cognitively normal.

"The test should be used in conjunction with other diagnostic evaluations from a neurologist," Dehdashti says. "But when a scan is negative, it's highly unlikely that the cognitive impairment is due to Alzheimer's disease."

"These PET scans have the potential to be really useful as treatments for Alzheimer's are developed," McConathy says. "Once we have treatments to significantly slow down or stop the progression of Alzheimer's , then I think this kind of imaging will become very important in deciding who should be treated and, potentially, whether a treatment is working."

Explore further: Mount Sinai is first in New York state to perform new Alzheimer's imaging test in clinical setting

Related Stories

Mount Sinai is first in New York state to perform new Alzheimer's imaging test in clinical setting

June 20, 2012
The Mount Sinai Medical Center is the first institution in New York State to use in the clinical setting a newly approved imaging technique to detect Alzheimer's disease (AD) in people who are cognitively impaired. Until ...

Alzheimer's plaques in PET brain scans identify future cognitive decline

July 11, 2012
Among patients with mild or no cognitive impairment, brain scans using a new radioactive dye can detect early evidence of Alzheimer's disease that may predict future decline, according to a multi-center study led by researchers ...

Is it Alzheimer's disease or another dementia? Marker may give more accurate diagnosis

November 30, 2011
New research finds a marker used to detect plaque in the brain may help doctors make a more accurate diagnosis between two common types of dementia – Alzheimer's disease and frontotemporal lobar degeneration (FTLD). ...

Recommended for you

Lifestyle changes to stave off Alzheimer's? Hints, no proof

July 20, 2017
There are no proven ways to stave off Alzheimer's, but a new report raises the prospect that avoiding nine key risks starting in childhood just might delay or even prevent about a third of dementia cases around the world.

Blood test identifies key Alzheimer's marker

July 19, 2017
A new study led by researchers at Washington University School of Medicine in St. Louis suggests that measures of amyloid beta in the blood have the potential to help identify people with altered levels of amyloid in their ...

Steering an enzyme's 'scissors' shows potential for stopping Alzheimer's disease

July 19, 2017
The old real estate adage about "location, location, location" might also apply to the biochemical genesis of Alzheimer's disease, according to new research from the University of British Columbia.

Brain scans may change care for some people with memory loss

July 19, 2017
Does it really take an expensive brain scan to diagnose Alzheimer's? Not everybody needs one but new research suggests that for a surprising number of patients whose memory problems are hard to pin down, PET scans may lead ...

Can poor sleep boost odds for Alzheimer's?

July 18, 2017
(HealthDay)— Breathing problems during sleep may signal an increased risk for Alzheimer's disease, a trio of studies suggests.

Hearing is believing: Speech may be a clue to mental decline

July 17, 2017
Your speech may, um, help reveal if you're uh ... developing thinking problems. More pauses, filler words and other verbal changes might be an early sign of mental decline, which can lead to Alzheimer's disease, a study suggests.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.