Inclusion Criteria:  Enrolled in PPMI Clinical protocol Able to provide informed consent  Male or Female (Females must meet additional criteria specified below, as applicable)  Females must be of non-childbearing potential or using a highly effective method of birth control 14 days prior to until at least 24 hours after injection of [18F]PI-2620. Non-childbearing potential is defined as a female that must be either postmenopausal (no menses for at least 12 months prior to PET scan) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy). Highly effective method of birth control is defined as practicing at least one of the following: A birth control method that results in a less than 1% per year failure rate when used consistently and correctly, such as oral contraceptives for at least 3 months prior to injection, an intrauterine device (IUD) for at least 2 months prior to injection, or barrier methods, e.g., diaphragm or combination condom and spermicide. Periodic abstinence (e.g. calendar, ovulation, symptothermal, post-ovulation methods) is not acceptable. Females of childbearing potential must not be pregnant, breastfeeding or lactating. Females of childbearing potential have a negative urine pregnancy test prior to [18F]PI-2620 injection on day of PET scan.  Exclusion Criteria:  Exposure to an effective radiation dose of 50 mSv, which would be above the acceptable annual limit established by the US Federal Guidelines during the past year. Any other medical or psychiatric condition or lab abnormality, which in the opinion of the Site Investigator might preclude participation.