Brain imaging tests

Alzheimer's dementia results from the loss of brain cells over time. This is known as degeneration. Degeneration may appear in a variety of ways in brain scans.

However, these scans alone aren't enough to make a diagnosis. Scans aren't used to diagnose Alzheimer's dementia because there is overlap in what is considered typical age-related change in the brain and change related to Alzheimer's.

However, brain imaging can help:

• Rule out other causes, such as heavy bleeding, brain tumors or strokes.
• Distinguish between different types of degenerative brain disease.
• Establish a baseline about the degree of degeneration.

The brain-imaging technologies most often used are:

• Magnetic resonance imaging (MRI). An MRI uses powerful radio waves and magnets to create a detailed view of your brain.
• Computerized tomography (CT). A CT scan uses X-rays to obtain cross-sectional images of your brain.

• Positron emission tomography (PET). A PET scan uses a radioactive substance known as a tracer to detect substances in the body. There are different types of PET scans. The most commonly used PET scan is a fluorodeoxyglucose (FDG) PET scan. This scan can identify brain regions with decreased glucose metabolism. The pattern of metabolism change can distinguish between different types of degenerative brain disease.

  PET scans have recently been developed that detect clusters of amyloid proteins, known as plaques, or tau, known as neurofibrillary tangles. Both are associated with Alzheimer's dementia. These types of PET scans are typically used in the research setting.