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Alzheimer's Disease Health Center

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PET Scans Spot Early Alzheimer's

Brain Scans Using Special Imaging Agent May Offer Diagnosis in Early Stages of Disease
WebMD Health News
Reviewed by Louise Chang, MD

Aug. 11, 2008 -- A special type of positron emission tomography (PET) scan appears to detect abnormal brain proteins associated with Alzheimer's disease.

Spotting early brain changes related to Alzheimer's can be a daunting task. Abnormal proteins called beta-amyloid plaques are a hallmark of the disease, but the only surefire way to examine such changes is to perform a brain biopsy.

A growing body of evidence suggests that PET scanning using a novel brain-imaging agent called Pittsburgh Compound B (PiB) may help offer a definitive diagnose of Alzheimer's disease in living patients. PET scans reveal functional information about the body, such as blood flow, metabolic problems, and chemical activity. PiB attaches to Alzheimer's-related brain deposits; it is injected into a vein before the scan.

For the current study, researchers in Finland compared PiB PET scan results to brain tissue samples taken from 10 patients with severe dementia. Each patient's brain biopsy was deemed medically necessary because they showed signs of abnormal fluid buildup in the brain -- suspicious indications of a condition called normal-pressure hydrocephalus (NPH). NPH also causes mind and memory problems, and some patients with symptoms of the condition have brain lesions characteristic of Alzheimer's disease.

Analysis of the brain tissue showed that six patients had beta-amyloid plaques, a telltale sign of Alzheimer's disease. Each patient received an injection of PiB through a vein and then underwent a 90-minute PET scan. All patients with the Alzheimer's-related plaques had a higher uptake of the imaging compound than those without the abnormal proteins. In other words, the brain areas afflicted by Alzheimer's disease-related changes brightly lit up.

"This study supports the use of ... PiB PET in the evaluation of beta-amyloid [deposits] in, for example, mild cognitive impairment, Alzheimer's disease or normal-pressure hydrocephalus," Ville Leinonen, MD, PhD, of the University of Kuopio, Finland, and colleagues say in a news release.

Leinonen's team believes PET scanning using Pittsburgh Compound B could potentially be used to help doctors monitor a patient's response to Alzheimer's drug treatment. More studies are needed to determine if PET scanning can be used to diagnose Alzheimer's disease.

The findings appear online today and will be published in the October 2008 print issue of Archives of Neurology.

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