"One of the challenges of trying to diagnose Alzheimer's disease is that it doesn't cause big changes that are visible on MRI and CT scans," says Foster. "So PET imaging has a great advantage because it shows a specific pattern that differs whether a person is experiencing normal aging, Alzheimer's disease or other kinds of dementias. It helps us determine which of these diseases is present, and gives doctors a good idea about how they should be treated."
PET studies at the U-M; the University of California, Davis; the University of Pennsylvania; and the University of Washington have been performed with funding from the National Alzheimer Coordinating Center, part of the National Institute on Aging.
In one study, Foster and his colleagues showed how they were able to tell Alzheimer's disease from a disorder called frontotemporal dementia, using PET scans from 45 patients, software to analyze the scans, and autopsy results from the same patients that gave a definitive diagnosis.
They also showed that using the software package, they could compare PET scans from different patients at different medical centers, and even compare scans taken on different PET scanners of various levels of sophistication. This will allow more studies to be done at PET scanning centers around the country to gather more evidence about how useful PET could be.
"PET imaging has great potential to aid diagnosis of patients with memory problems," Foster explains. "We've been able to identify changes that occur before patients themselves may recognize those problems. And we understand from PET scans what parts of the brain are most damaged in different disorders, and how these changes relate to patients' symptoms."
About PET scans
To the untrained eye, PET scans look irregular spots of rainbow colors on a black background. But for physicians, the scans hold crucial information about the level of chemical activity going on in different regions of the brain -- areas that control or contribute to all the functions of life.
The scans are made by injecting the patient with a form of sugar that has been altered to carry a weak, short-lived radioactive element. The sugar hits the bloodstream and flows to the brain, which needs huge amounts of energy to keep all its nerve cells running.
The most active areas of the brain need the most sugar -- while damaged and less active areas need much less. By detecting the weak radiation signal from the sugar molecules as they travel throughout the brain, PET scanners can make a picture of brain cell activity. The resulting scans show the level of activity using a scale of colors; red and orange for high activity, and blue and purple for low.
Doctors can compare a patient's own PET scan, showing areas of high and low activity, with maps of the structure and function of the different areas of the human brain, and knowledge about which brain regions Alzheimer's usually strikes earliest and hardest. Taken together, this analysis can tell them the extent of the damage, and the specific disease a patient has.
For example, areas of the brain involved in thinking and understanding the world around oneself are often damaged in Alzheimer's disease, resulting in memory loss and confusion. But areas involved in movement and the senses are not usually affected, so if a PET scan shows damage in those areas, a different disorder may be to blame.
Foster hopes that as evidence from research builds, PET scanning will become a part of the standard procedure for diagnosing patients with suspected Alzheimer's disease, and that insurance companies will begin to pay for their members to have PET scans for this purpose. He also foresees that the number of hospitals with PET scanners will continue to grow, as the usefulness of the scanners in diagnosing many diseases is proven.
In the long run, Foster also hopes that scientists will use the information from PET scans of Alzheimer's brain chemistry to develop new medications. "Once we can identify what kinds of chemicals are lost or changed in the brains of people with Alzheimer's disease, then we can design drugs to return the brain chemistry to normal," he explains.
- University of Michigan
Articles in The Science of Mental Health are written by the originating institution. This article was originally posted to Newswise . Newswise maintains a comprehensive database of news releases from top institutions.
