Potential of Florbetapir F 18 PET to Inform Clinical Diagnosis and Management of Patients With Progressive Cognitive Decline

Inclusion Criteria: * Are one of the following: 1. Group A: Recently completed (within the past 18 months) a comprehensive clinical evaluation for progressive cognitive decline. 2. Group B: Currently being evaluated for progressive cognitive decline with further clinical or laboratory testing still planned. * Have a site enrolling physician who has 1. less than high confidence in their diagnosis for the subject related to the cognitive decline at the time of enrollment. The level of confidence in the diagnosis should be rated by the physician as less than 85%, and should be interpreted as the physician estimating that their diagnosis will be correct in less than 85% of patients with the same presentation as the subject; and 2. suspicion that the subject's cognitive decline is caused, at least in part, by Alzheimer's disease. The level of suspicion should be rated by the physician as there being at least 15% of patients with the same presentation as the subject would have Alzheimer's disease; * Can tolerate a 10 minute PET scan. The Principal Investigator will carefully assess each subject and use sound medical judgment to determine whether the subject can tolerate the PET scan procedure; * Have the ability to cooperate and comply with all study procedures; * Have a study partner willing to accompany the subject on all of the study visits; and * Give informed consent for study procedures (If the subject is incapable of giving informed consent, the subject's designated decision maker may consent on behalf of the subject but the subject must still confirm assent. This person may serve as the study partner as well). Exclusion Criteria: * Subject or site enrolling physician knows the result of a previous amyloid imaging scan. * Are considered medically unstable; * Require additional laboratory tests or workup between enrollment and completion of the florbetapir F 18 PET scan; * Have a clinically significant infectious disease, including Acquired Immunodeficiency Syndrome (AIDS) or Human Immunodeficiency Virus (HIV) infection; * Are receiving any investigational medications, or have participated in a trial with investigational medications within the last 30 days; * Have ever participated in an experimental study with an amyloid targeting agent unless it can be documented that the subject received only placebo during the course of the trial; * Have had a radiopharmaceutical imaging or treatment procedure within 7 days prior to the study imaging session; or * Are females of childbearing potential who are not surgically sterile, not refraining from sexual activity or not using reliable methods of contraception. Females of childbearing potential must not be pregnant (negative serum β-hCG at the time of screening and negative urine β-hCG on the day of imaging) or breast feeding at screening. Females must avoid becoming pregnant, and must agree to refrain from sexual activity or to use reliable contraceptive methods such as prescribed birth control or intrauterine device (IUD) for 24 hours following administration of florbetapir F 18.