PPMI Tau PET Imaging

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.