The purpose of this study is to assess MK-9470 Positron Emission Tomography (PET) imaging as a tool to evaluate the activity of the CB-1 receptor in the brain.

The underlying goal of this study is to assess MK-9470 PET imaging as a tool to evaluate the activity of the CB-1 receptor in the brain of Parkinson's Disease (PD) research participants.

Early PD Subjects

Inclusion criteria:

• The participant is 30 years or older.
• Written informed consent is obtained.
• Participants have a diagnosis of PD (based on UK Brain Bank Criteria) within the past 2 years.
• Modified Hoehn and Yahr stages 1-2.
• No evidence of dyskinesia by history or clinical examination
• For females, non-child bearing potential or a negative urine or blood pregnancy test on day of [18F]-MK-9470 injection.

Advanced PD subjects

Inclusion criteria:

• The participant is 30 years or older.
• Written informed consent is obtained.
• Participants have a diagnosis of PD (based on UK Brain Bank Criteria) of at least 5 years duration.
• Modified Hoehn and Yahr stages 1-4.
• No evidence of dyskinesia by history or clinical examination
• For females, non-child bearing potential or a negative urine or blood pregnancy test on day of [18F]-MK-9470 injection.

Subjects who have a clinical diagnosis of advanced PD with dyskinesia will be recruited for this study.

ePD subjects

Inclusion criteria:

• The participant is 30 years or older.
• Written informed consent is obtained.
• Participants have a diagnosis of PD (based on UK Brain Bank Criteria) of at least 5 years.
• Modified Hoehn and Yahr stages 1-4.
• Evidence of dyskinesia either by history or clinical examination
• For females, non-child bearing potential or a negative urine or blood pregnancy test on day of [18F]-MK-9470 injection.

PD (all stages- e-PD, aPD, aPD-dys)Subject Selection. Subjects who have a clinical diagnosis of ePD, aPD, aPD-dys will be recruited for this study.

All PD subjects

Exclusion criteria:

• 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.
• The patient has evidence of unstable gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, pulmonary, or other disorder or disease.
• Evidence of a stroke or mass lesion in a clinically relevant area that may interfere with the imaging outcome measure
• Subjects with radiation exposure above acceptable levels
• Pregnancy

Healthy Control Subject Selection: subjects who have no neurological disease will be recruited for this study.

Healthy control subjects

Inclusion criteria:

• 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.
• For females, non-child bearing potential a negative urine or blood pregnancy test on day of [18F]-MK9470 injection.

Exclusion criteria:

• 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.
• The subject has any disorder that may interfere with drug absorption, distribution, metabolism, or excretion.
• Subjects with radiation exposure above acceptable levels
• Pregnancy