The chemical marker essentially seeks out and temporarily attaches itself to the abnormal amyloid, thus providing a clear PET scan signal in the areas of the brain where Alzheimer's strikes. In healthy people without Alzheimer's, these brain regions produce little or no signal. However, in people with the disease, the signal is so strong and accurate that it actually correlates with each individual's degree of memory impairment. The UCLA group has also found that people who are at risk for Alzheimer's disease (mild cognitive impairment) have an amyloid-PET pattern intermediate between normal people and patients with Alzheimer's and that [F-18]FDDNP binding is influenced by APOE-4 status (9,10). Therefore, this technology will likely assist in early detection of the disease so that prevention treatments might be used prior to significant cognitive decline. It will also be useful in detecting and developing treatments for other conditions. Patients with dementias that have different treatment approaches (e.g., frontotemporal) have an an [F-18]FDDNP-PET pattern distinct from Alzheimer's, as do patients with cognitive impairment associated with prion disease(11).