S2E4 - Understanding Amyloid PET Scans and Alzheimer’s Disease

In this episode of Minding Dementia, we explore one of the most common questions families ask during the diagnostic journey: How accurate is a PET scan for Alzheimer’s disease?
We break down what an amyloid PET scan is, what it can and cannot tell you, and how it fits into the broader process of identifying Alzheimer’s disease and other forms of dementia. This episode is designed to reduce fear, clarify confusion, and help families better understand the tools used in modern dementia care.

What Is an Amyloid PET Scan?
An amyloid PET scan is a specialized imaging test that looks for amyloid plaques in the brain. These plaques are associated with Alzheimer’s disease. During the scan, a tracer is administered that binds to amyloid, allowing doctors to see where and how much plaque is present.
While amyloid plaques are strongly linked to Alzheimer’s disease, their presence alone does not confirm a diagnosis.

How Accurate Is an Amyloid PET Scan?
Amyloid PET scans are estimated to be 58% to 90% accurate in detecting the presence and location of amyloid plaques in the brain. They are highly useful for ruling out Alzheimer’s disease when plaques are not present and for helping narrow diagnostic possibilities when they are found.

Why PET Scans Are Not Used Alone
A PET scan is only one piece of the diagnostic puzzle. Healthcare providers also rely on:
Cognitive and memory testing

Medical history

MRI or CT scans
Blood or spinal fluid biomarkers
Together, these tools help create a clearer and more accurate picture of what is happening in the brain.
PET Scans, MRI, and CT: How They Work Together
While amyloid PET scans detect plaque buildup, MRI and CT scans show brain structure and health. These scans can reveal:
Brain atrophy
Vascular changes
Tumors or bleeding
Other conditions that may mimic dementia symptoms
Using multiple imaging tools helps providers better understand the root cause of cognitive changes.

Early Detection and Mild Cognitive Impairment
Amyloid PET scans can sometimes detect plaque buildup before noticeable symptoms appear, a stage known as preclinical Alzheimer’s disease. They are also helpful in cases of mild cognitive impairment (MCI), helping providers determine whether Alzheimer’s disease may be the underlying cause or if other factors should be explored.

A Final Important Reminder
The presence of amyloid plaques does not automatically mean a person has Alzheimer’s disease. Likewise, the absence of plaques can be just as informative, guiding providers toward other explanations and care plans.
Definitive confirmation of Alzheimer’s disease can only be made through a brain autopsy after death. However, today’s diagnostic tools allow clinicians to make highly accurate, informed diagnoses during life, helping families plan, understand, and access appropriate care.

Who This Episode Is For
Individuals experiencing memory or thinking changes
Family members and caregivers seeking clarity
Anyone navigating dementia testing and diagnosis
Those wanting to better understand medical imaging and brain health
Sources & References

The Lancet – Research on Alzheimer’s disease biomarkers and diagnostic imaging

National Institute on Aging (NIA) – Dementia biomarkers, PET scans, MRI, and diagnostic tools

Psychology Today – Dr. Barry Rovner on Alzheimer’s diagnosis and diagnostic accuracy

Northwestern Medicine – Clinical diagnosis and causes of Alzheimer’s disease

UPMC Neuropathology – Brain autopsy as the gold standard for definitive diagnosis

UC Davis Health – Advances in Alzheimer’s testing, including PET scans and biomarkers

Mayo Clinic (2025) – FDA-approved blood testing for Alzheimer’s disease