Patient description: The patient is a 20 year old Caucasian female presents to the clinic with one-sided vision lost and facial weakness, dysarthria and numbness lasting for 1 day. She visited her PCP and underwent brain MRI which revealed a single plaque in the brainstem. After few months, she experienced lower extremities weakness led to balance problem. The second MRI revealed another lesion in the left cerebral hemisphere. The diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) is confirmed after the second MRI. Her past surgical history is significant for a C-section 2 years ago and she has a one child. She is divorced and is not currently in any sexual relationship. She smokes 10 cigarettes per day and drinks alcohol occasionally. She is working as an editor in a publisher company and she is happy that she can keep working from home most of the time. She is under the treatment of RRMS from 7 months ago.

Clinical trial eligibility criteria: eligible ages (years): 18.0-75.0,  Parkinson Disease Healthy Volunteer Participants will be 18-75 years of age 2. Participants must be informed of the investigational nature of this study and be willing to provide written informed consent and participate in this study in accordance with institutional and federal guidelines prior to study-specific procedures. 3. Subjects with known neuropsychiatric disorder may be eligible if, in the opinion of an investigator, the psychiatric condition would not compromise subject safety or successful participation in the study. (PD cohort only) 4. History of diagnosis of probable idiopathic PD derived from UK Brain Bank Diagnostic criteria(1) per neurologist review. 5. Diagnosed with Parkinson's Disease at least 3 year prior to enrollment. 6. Subjects will be selected who have the capacity to give their  (HC and PD cohorts): 1. Females who are pregnant or breast feeding at the time of screening will not be eligible for this study; a urine pregnancy test will be performed in women of child-bearing potential within one day of the PET/CT scan. 2. At screening, the participant's weight is > 350 lb. 3. Subject reported claustrophobia that in the opinion of an investigator would interfere with acquisition of the structural MRI required for PET co-registration, and/or the PET scan itself. 4. History of epilepsy or seizure disorder as assessed by medical record review and/or self-report 5. History of head trauma that in the opinion of an investigator may interfere with the uptake of applicable radiotracer as assessed by medical record review and/or self-report 6. Current tobacco or nicotine dependence. History of greater than 5 pack years of smoking and less than 2 years since smoking cessation. 7. Self-reported current alcohol consumption of greater than or equal to 25 drinks per week 8. Inability to tolerate imaging procedures in the opinion of an investigator or treating physician 9. Any current medical condition, illness, or disorder as assessed by medical record review and/or self-reported that is considered by a physician or investigator to be a condition that could compromise participant safety or successful participation in the study (HC cohort only) 10. History of first degree relative with Parkinson's Disease 11. Use of a CNS drug (prescription, over-the counter or recreational) within 30 days of screening, as assessed by review of medical history and concomitant medication review at screening (from medical record and/or self-report) that are deemed by a physician or investigator to have a potential influence on the binding of the applicable radiotracer