The underlying goal of this study is to assess [18F] PBR06 PET imaging as a tool to detect microglial activation in the brain of Alzheimer Disease (AD), Parkinson Disease (PD) and Multiple Sclerosis (MS) research participants.

Inclusion Criteria:

• 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]-PBR06 injection.

• 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]-PBR06 injection.

• 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]-PBR06 injection

• The following criteria will be met for inclusion of healthy control subjects in this study:

  • The participant is 18 years or older.
  • Written informed consent is obtained.
  • Negative history of neurological or psychiatric illness based on evaluation by a research physician.
  • Clinical Dementia Rating score = 0.
  • For females, non-child bearing potential a negative urine or blood pregnancy test on day of [18F]-PBR06 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

• 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

• 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

• 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 evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease.
  • Pregnancy