Brain-imaging tests

Alzheimer's dementia results from the progressive loss (degeneration) of brain cells. This degeneration may show up 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 the condition because there is overlap in what doctors consider normal age-related change in the brain and abnormal change.

However, brain imaging can help:

• Rule out other causes, such as hemorrhages, 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, which 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 (plaques), which are associated with Alzheimer's dementia, but this type of PET scan is typically used in the research setting.