Phase 1 Test-retest Evaluation of [18F]MNI-958 PET

Inclusion Criteria (for all subjects): * Written informed consent must be obtained before any assessment is performed. * Female subjects must be documented by medical records or physician's note to be either surgically sterile (by means of hysterectomy, bilateral oophorectomy, or tubal ligation) or post-menopausal for at least 1 year or, if they are of childbearing potential, must commit to use a barrier contraception method for the duration of the study. * Male subjects and their partners of childbearing potential must commit to the use of two methods of contraception, one of which is a barrier method for male subjects for the study duration. * Male subjects must not donate sperm for the study duration. * Willing and able to cooperate with study procedures Inclusion criteria for healthy volunteer subjects * Males and females aged ≥50 years. Healthy with no clinically relevant finding on physical examination at screening and upon reporting for the \[18F\]MNI-958 imaging visit. * No cognitive impairment from neuropsychological battery as judged by the investigator * Have screening or prior (in the last 90 days) amyloid PET imaging demonstrating no significant amyloid binding based on qualitative (visual read). * No family history of Alzheimer's disease or neurological disease associated with dementia * Have a CDR global score=0 * Have an MMSE score ≥28 * Willing and able to cooperate with study procedures Inclusion criteria for subjects with a diagnosis of probable Alzhei…