Brain imaging

Brain imaging, such as MRI or CT scanning, can be important in evaluating memory problems. Brain imaging can help identify certain potentially treatable brain conditions, such as a tumor or excess fluid buildup, which may be the cause of a person’s memory problems. Imaging can also detect vascular disease in the brain, such as small blood vessel disease that can lead to dementia.

The most common types of brain imaging used in the Memory & Aging Program are CT (computer tomography, also known as CAT – computer assisted tomography) and MRI (magnetic resonance imaging) scans. In CT, x-rays are used to take pictures of the brain; whereas in MRI, a powerful magnet is used. MRI is often preferred to CT because the images are clearer and show greater anatomic detail. MRI is also more flexible than CT in that different types of MRI pictures can be taken to look for different kinds of abnormalities. In certain situations, however, CT is more useful. CT is generally quicker than MRI and less expensive. It is more useful than MRI for detecting a new stroke. Also, CT can be safely performed on individuals who cannot have an MRI because they have a pacemaker, metal fragments in their eyes, or other safety concerns. CT can be performed safely in these individuals.

Figure 1 shows the MRI and CT scans.

CT and MRI provide information about brain anatomy or structure. Other types of brain imaging provide information about how the brain is functioning. These imaging techniques include SPECT (single photon emission computed tomography), PET (positron emission tomography), and fMRI (functional MRI). These techniques are used less commonly for clinical care but are important research tools.

At the present time, it is not possible to diagnose Alzheimer’s disease or other types of dementia from an MRI or CT scan alone. However, certain patterns of changes seen on MRI or CT images, when combined with a patient’s history of memory problems and other symptoms, can help a doctor be more confident in diagnosing someone with Alzheimer’s disease (or other types of dementia).

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