PET Scans May Assist in Early Detection of Alzheimer’s

According to a group of Finnish researchers, PET (positron emission tomography) scans may detect abnormal brain plaques that are associated with Alzheimer's, providing doctors with a non-invasive method of detecting the disease in its early stages. Until now, the only reliable way to detect the abnormal proteins, called beta-amyloid plaques, known to be a characteristic of the disease has been through the analysis of brain tissue samples obtained by performing a brain biopsy when a patient is alive or after death. However, evidence now suggests that PET scans that use a brain-imaging agent called Pittsburgh Compound B (PiB) may assist in making a definitive diagnose of Alzheimer's disease in living patients.

Doctors currently use PET scans to detect cancer, cardiac problems and other conditions. PET scans show information about the body's functions, such as blood flow, metabolic issues, and chemical activity. But, with PiB injected into a patient's vein prior to the scan, the PiB will attach to those brain deposits related to Alzheimer's.

The study shows PET scans may become a useful tool to diagnose Alzheimer's disease, a fatal and incurable mind-robbing ailment that is the most common form of dementia in the elderly, according to Ville Leinonen, MD, Ph.D., of the University of Kuopio, Finland, an author of the study.

The researchers compared PiB PET scan results to brain tissue samples taken from 10 patients with severe dementia. These patients brain biopsies had all been deemed medically necessary due to signs of an abnormal fluid buildup in the brain which is an indication of a condition called normal-pressure hydrocephalus (NPH) that causes Cognitive impairment. 22 to 42 percent of patients with symptoms of NPH also have brain lesions, which are a trait of Alzheimer's disease.

During the analysis of the brain tissue, it was found that six patients had beta-amyloid plaques, indicating a strong possibility of having Alzheimer's disease. These six patients were injected with PiB and underwent a 90-minute PET scan. All of the six patients had a higher uptake of the imaging compound in the brain areas containing the Alzheimer's disease-related changes, which simply means that they brightly lit up during the scan.

In a news release, Leinonen and colleagues said, "This study supports the use of PiB PET in the evaluation of beta-amyloid in, for example, mild cognitive impairment, Alzheimer's disease or normal-pressure hydrocephalus." The researchers also believe that PET scans using PiB has the potential to be used in helping doctors monitor patient response to Alzheimer's drug treatment. There will be more studies needed in determining whether or not PET scanning can be used to diagnose Alzheimer's disease.

There are an estimated 26 million people suffering from Alzheimer's worldwide and experts predict the number will grow to 106 million by the year 2050.

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