Evaluation of [123I] MNI-330 and SPECT as a Marker of Beta-amyloid Protein Deposition

Inclusion Criteria: Alzheimer's Subject Selection. Subjects who have a clinical diagnosis of mild to moderate Alzheimer's disease will be recruited for this study. The following criteria will be met for inclusion of AD subjects in this study: * The participant is 50 years or older. * Written informed consent is obtained. * Participants have a clinical diagnosis of Alzheimer's disease based on National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS/ADRDA) criteria. * Mini-Mental Status Exam score \< 25. * Modified Hachinski Ischemia Scale score of ≤ 4. * Geriatric Depression Scales (GDS) ≤ 10. * For females, non-child bearing potential or negative urine and blood pregnancy test on day of 123-I MNI-330 injection. Healthy Control Subject Selection. Healthy control subjects who have no neurological disease will be recruited for this study. The following criteria will be met for inclusion of healthy control subjects in this study: * The participant is 50 years or older. * Written informed consent is obtained. * Negative history of neurological or psychiatric illness based on evaluation by a research physician. * Mini-Mental Status Exam score ≥28. * For females, non-child bearing potential or negative urine and blood pregnancy test on day of 123-I MNI-330 injection. Exclusion Criteria: Alzheimer's subjects will be excluded from participation for the following reasons: * The subject has signs or symptoms of another neurodegenerative disease including Parkinson's disease, diffuse Lewy body dementia, or history of significant cerebrovascular disease. * The subject has a clinically significant abnormal laboratory value and/or clinically significant unstable medical or psychiatric illness * The subject has any disorder that may interfere with drug absorption distribution, metabolism, or excretion (including gastrointestinal surgery). * The subject has evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease. * Pregnancy Healthy control subjects will be excluded from participation for the following reasons: * The subject has a clinically significant abnormal laboratory value and/or clinically significant unstable medical or psychiatric illness. * The subject has any disorder that may interfere with drug absorption distribution, metabolism, or excretion (including gastrointestinal surgery). * The subject has evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease. * Pregnancy