PET scans can detect amyloid plaques and tau tangles in the brain, which are often early signs of Alzheimer’s disease. But they’re not enough on their own to make a diagnosis.
One of the characteristic signs of Alzheimer’s is the irregular buildup of proteins in the brain called plaques and tangles. PET scans are under investigation for their potential to help identify these proteins.
Doctors can’t use PET scan results to diagnose Alzheimer’s, but the scans may provide supportive evidence along with other tests.
Keep reading to learn more about the role PET scans play in diagnosing Alzheimer’s.
Three types of PET scans can potentially help detect Alzheimer’s disease:
- Amyloid PET scans: These scans can potentially
help diagnoseAlzheimer’s by measuring levels of a protein called beta-amyloid that makes up plaques.
- Tau PET scans: These scans detect the buildup of tau protein, which forms tangles characteristic of Alzheimer’s and other dementias. Tau PET scans can potentially allow doctors to monitor Alzheimer’s progression, but they’re most often
used in research.
- Fluorodeoxyglucose (FDG) PET scans: These scans measure your brain’s metabolism of glucose. They can help your doctor distinguish Alzheimer’s from other types of dementia, such as frontotemporal dementia (FTD).
The proposed draft 2023 guidelines from the National Institute on Aging and the Alzheimer’s Association suggest that doctors can diagnose Alzheimer’s with any core biomarker, such as:
- beta-amyloid levels measured with a spinal tap
- amyloid PET scan results
- tau PET levels
PET scans may show reductions in brain activity in certain regions as well as the buildup of plaques and tangles in the brain.
FDG PET scans can reveal atypical glucose consumption by certain parts of your brain.
Doctors can use other types of brain imaging to help in diagnosing Alzheimer’s, but mainly to exclude other causes of dementia.
CT scans were the
- blood tests such as complete blood count and metabolic panel to rule out other conditions
- spinal fluid analysis
- electroencephalogram (EEG)
- neuropsychological testing
- genetic testing in some families with rare early-onset Alzheimer’s
- asking close friends and family members about symptoms they observe
- psychiatric evaluation to screen for mental health conditions such as depression
PET scans may also help diagnose other types of dementia by identifying changes in your brain.
For example, fluorodeoxyglucose PET scans may help identify atypical patterns of glucose use in certain parts of your brain associated with FTD, which makes up about
You may be told not to eat for about 6 hours before a PET scan and to avoid exercise for about 24 hours. During your procedure:
- A healthcare professional will inject a radiotracer into a vein in your arm roughly 1 hour before your scan. This tracer will bind with plaques in your brain.
- During the scan, you’ll lie on a bed that will move through a large cylindrical scanner.
- You’ll need to lie still for about 30–60 minutes during the scan.
Here are some frequently asked questions people have about PET scans and Alzheimer’s disease:
How accurate is a PET scan for detecting Alzheimer’s?
PET scans seem to correctly identify Alzheimer’s in about
What is the best scan to detect Alzheimer’s?
Amyloid PET scans are one of the best types of imaging for identifying changes in the brain associated with Alzheimer’s. Amyloid scans are more accurate than FDG PET scans. MRI and CT scans may help rule out other conditions.
How much does an amyloid PET scan cost?
According to the Alzheimer’s Association, the out-of-pocket cost for an amyloid PET scan averages $3,000 or more. Medicare and private insurance do not typically cover the cost of amyloid PET scans.
PET scans may help doctors identify changes in your brain associated with Alzheimer’s. They may also help identify other types of dementia, such as FTD.
Researchers are examining how best to use PET scans to diagnose Alzheimer’s. Doctors sometimes use imaging to provide supportive evidence alongside other tests, such as neuropsychological tests, blood tests, and spinal taps.