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Can PET Scans Detect Alzheimer’s Disease?

Medically reviewed by Abhay Sanan, MD, Susan Kerrigan, MD and Marianne Madsen on January 15, 2022

A PET scan is a type of imaging test used to diagnose tumors, brain disorders, and heart problems. The scan is very accurate and is able to detect small changes in the body at the cellular level. Research shows that PET scans may even be able to detect early signs of Alzheimer’s disease.


PET scans and diagnosing Alzheimer’s


Alzheimer’s disease is a complicated condition to diagnose. There is no laboratory analysis or blood test that can determine if an individual has the disease. Instead, a diagnosis is confirmed via a number of methods, including evaluating past medical history, performing cognitive tests, and carrying out brain scans. 


One type of brain scan for Alzheimer’s disease is the aforementioned PET scan. However, PET scans are not always accurate in diagnosing the condition, because the type of PET scan typically used for Alzheimer’s relies on a key marker: the presence of amyloid plaques in the brain.


What are amyloid plaques and how do they relate to Alzheimer’s?


Amyloid plaques are clumps of cells commonly found in the brains of people with Alzheimer’s disease. These plaques damage nerve cells in areas of the brain associated with memory. As Alzheimer’s disease progresses, amyloid plaques build up, causing the condition to gradually worsen.


A PET scan uses a radioactive material to highlight abnormalities in the brain. This material is called a tracer, and when injected, it gives a doctor a clear, accurate image of the brain, enabling him or her to diagnose tumors or brain problems. Amyloid plaques are highlighted in the resulting brain image as well. 


If no plaques are found in your brain, the chances that you have Alzheimer’s disease are low. But if plaques are present, it doesn’t necessarily mean that you have Alzheimer’s, or even that you’re at risk for the disease. So how can PET scans be used correctly to diagnose the condition?


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Alzheimer's - Diagnosis

Alzheimer's - Diagnosis

When should a PET scan be used for Alzheimer’s?


A PET scan can only assist in diagnosing Alzheimer’s if results of other medical exams come back inconclusive. For instance, if you’ve been experiencing key symptoms of Alzheimer’s and you’ve done all the required tests, but your doctor still can’t make a diagnosis, a PET scan may be of help. 


What are the downsides of a PET scan?


A PET scan, while useful in some cases, is not for everyone. 


  • It’s expensive. A PET scan, when combined with a CT scan, costs over $5,000. Many insurance plans do not cover PET scans.
  • It can lead to a false diagnosis. As mentioned above, if you undergo a PET scan before completing all of the available tests for Alzheimer’s, you can be diagnosed with the condition even if you don’t have it.
  • It uses radiation. PET scans involve small amounts of radiation, which are normally considered safe. But PET scans are often done in conjunction with CT scans, which further raises your exposure to radiation. 


PET scans can, in fact, help diagnose Alzheimer’s disease, but only if you’ve eliminated all other possible factors that could be causing your symptoms. If you think a PET scan may be right for you or a loved one, consult with your doctor before making a decision.


Written by Natan Rosenfeld

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