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Imaging Procedures Used in the Diagnosis of Alzheimer's Disease

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Updated June 14, 2008

Imaging procedures produce detailed pictures of the brain or other parts of the body that show abnormalities. Imaging procedures are used in the diagnosis of Alzheimer's to detect changes in brain structure or size that are common among those with the disease. Imaging is also used to look for brain tumors, blood clots, strokes or other problems that might account for Alzheimer's-like symptoms.

Imaging procedures are used in conjunction with other diagnostic procedures, such as a mental status exam, physical exam, and blood tests. Here are the most common imaging procedures used in the diagnosis of Alzheimer's.

CT Scan

Photo © National Institutes of Health
Photo © National Institutes of Health
A CT scan produces a clear, two-dimensional image of the brain that shows abnormalities such as brain tumors, blood clots, strokes, or damage due to head injury. CT scans are painless and noninvasive (nothing is inserted into the head in order to get the image), but they might be difficult if you're claustrophobic. The 20-minute procedure is usually done at a hospital or clinic that specializes in imaging. It involves lying on a table that's inserted into a chamber where the pictures are taken. You will be able to communicate with the technician during the procedure.

MRI

Photo © National Institutes of Health
Photo © National Institutes of Health
An MRI uses computer-generated radio waves and a strong magnetic field to produce a detailed image of the brain. MRIs are helpful in the diagnosis of tumors, eye diseases, infections, inflammation, and damage due to head injury. Similar to the CT scan, an MRI requires you to lie on a table that slides into a tube that contains the imaging equipment. If you're uncomfortable in small and enclosed spaces, or if you are obese, you might be uneasy with this procedure. Also, because of the strong magnetic field involved in the procedure, those with medical implants like pacemakers should avoid this test. MRIs take up to an hour to complete and produce both two-dimensional and three-dimensional images.

PET Scans

Photo © National Institute on Aging
Photo © National Institute on Aging
A PET scan provides both two- and three-dimensional pictures of brain activity by measuring radioactive isotopes (elements that attach to chemicals that flow to the brain) injected into the bloodstream. PET scans are used to detect tumors and damaged tissue, measure metabolism, and view how blood flows in the brain. PET scans are often ordered as follow-ups to CT scans or MRIs. PET scans are performed in a hospital or outpatient imaging clinic. After the isotope is injected into your bloodstream, you'll lie still while overhead sensors detect the isotope's activity. The information is processed by a computer and displayed on a monitor or film. The length of time to complete a PET scan varies depending on the reason for the test.

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Sources:

Brain imaging. Alzheimer's Association. November 26, 2007. http://www.alz.org/alzheimers_disease_steps_to_diagnosis.asp#imaging

Neurological diagnostic tests and procedures. National Institute of Neurological Disorders and Stroke. 2008. http://www.ninds.nih.gov/disorders/misc/diagnostic_tests.htm

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