Evaluation of [18F] FEPPA and PET Imaging as a Marker of Inflammation in Subjects With Neurological Conditions

Inclusion Criteria: * Alzheimer's disease patients 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 probable Alzheimer's disease based on National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS/ADRDA) criteria. * Clinical Dementia Rating Scale score ≤ 2. * Modified Hachinski Ischemia Scale score of ≤ 4. * For females, non-child bearing potential or a negative urine or blood pregnancy test on day of \[18F\]-FEPPA injection. Exclusion Criteria: * Alzheimer's subjects will be excluded from participation for the following reasons: * The subject has a 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 evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease. * Pregnancy Inclusion Criteria: * The following criteria will be met for inclusion of PD subjects in this study: * The participant is 30 years or older. * Written informed consent is obtained. * Participants have a clinical diagnosis of Parkinson disease (at least two of the three cardinal symptoms: resting tremor, rigidity, bradykinesia). * Hoehn and Yahr ≤4. * For females, non-child bearing potential or a negative urine or blood pregnancy test on day of \[18F\]-FEPPA injection. Exclusion Criteria: * Parkinson's 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 evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease. * Pregnancy Inclusion Criteria: * Multiple Sclerosis Subject Selection. Subjects who have a clinical diagnosis of Multiple Sclerosis (MS) will be recruited for this study. The following criteria will be met for inclusion of MS subjects in this study: * The participant is 18 years or older. * Written informed consent is obtained. * Participants have a clinical diagnosis of Multiple Sclerosis (per the 2005 Revised McDonald Criteria; Polman, et al., 2005). * Kurtzke Expanded Disability Status Scale (EDSS) ≤ 7.5. * For females, non-child bearing potential or a negative urine or blood pregnancy test on day of \[18F\]-FEPPA injection. Exclusion Criteria: * MS 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 evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease. * Pregnancy