TUESDAY, July 12 (HealthDay News) -- The use of brain scans to
diagnose Alzheimer's disease may have just taken a small step
Longer-lasting radioactive "tracers" used in the brain-scanning
process could allow wider use of the imaging technique that, to
date, has required costly equipment, according to two new studies
funded by the manufacturers of the tracers.
PET scans, or brain scans, create images using the tracers,
known as florbetapir and flutemetamol. Using the images, doctors
diagnose the existence of beta-amyloid, the protein plaques in the
brain linked to Alzheimer's disease.
Before now, PET scans (positron emission tomography) could only
be done in a facility that owned a cyclotron, a particle
accelerator used to make radioactive material, because the tracer
compound needed to do the scan did not last long enough to
The new imaging compounds last much longer, and once produced,
can be transported and used in the scanning technology.
The two new studies are published online July 11 in
Archives of Neurology.
In one study, conducted by Dr. Adam S. Fleisher at the Banner
Alzheimer's Institute in Phoenix, Ariz., researchers compared brain
images of 68 people with probable Alzheimer's disease to 60
participants with mild cognitive, or memory, problems and 82
healthy volunteers. The participants were mostly in their early to
The study found a high correlation between PET scan readings for
amyloid and both the disease, and milder symptoms. Healthy adults
showed only very low levels of amyloid.
Fleisher said, however, that not enough is known to use the
procedure for routine screenings.
"Without anti-amyloid therapy available, there are ethical questions regarding using this type of imaging as a screening tool for patients without any symptoms " because no treatment could be offered, Fleisher said.
In the other study, conducted by Dr. David Wolk at the
University of Pennsylvania in Philadelphia, researchers compared
brain tissue samples of seven patients undergoing a procedure for
hydrocephalus (a degenerative brain disease) with PET scans
performed at a later date. People with hydrocephalus often also
The Pennsylvania researchers found a high correlation between
amyloid in the brain tissue and PET scans showing the plaque. The
average age of patients in that study was 70.
A big issue for research is being able to test drugs on people
who actually have Alzheimer's, said Wolk, assistant director of the
Penn Memory Center in Philadelphia.
By helping to diagnose Alzheimer's early, PET scans using the
new tracers will improve drug testing, treatment and prevention,
Wolk's study was sponsored by GE Healthcare, which manufactures
flutemetamol. Fleisher's study was supported by funding from Avid
Radiopharmaceuticals, a subsidiary of Eli Lilly and Co., which
One expert agreed that the longer-lasting tracers could help
speed progress in treating the disease.
"There are a couple of different potential uses, both in terms of current clinical care, but more importantly for the future for testing drugs that may be able to intervene in the disease process," said Dr. Marc Gordon, a neurologist at the Feinstein Institute for Medical Research in Manhasset, N.Y.
By improving early diagnosis, the technology will be useful in
identifying the "correct population" for drug testing when patients
are "pre-symptomatic," before dementia occurs, said Gordon.
Alzheimer's disease affects about 5 million Americans, 90
percent over the age of 65, according to the National Institutes of
Health. But another form of the illness, "early onset" Alzheimer's,
can develop in the 30s, 40s or 50s, is genetically based and runs
in families, the NIH says. Genetic and lifestyle factors contribute
to the late onset of the disease.
The presence of amyloid doesn't mean someone will "necessarily
develop Alzheimer's," said Gordon, noting that about 30 percent of
elderly people have plaque, but not Alzheimer's.
There are some drugs for treating Alzheimer's, the most common
form of dementia, but they don't slow the disease. Their benefits
are "modest, they are not cures," said Gordon.
In June, a study presented at a Society of Nuclear Medicine
meeting suggested that PET scans for detecting Alzheimer's could be
commercially available this year, although experts said such scans
could be expensive. In the past, diagnosis has relied on
psychological tests and family reports.
To learn more about Alzheimer's, visit the
U.S. National Institutes of Health.
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