Participants will undergo approximately 30 minutes of static PET scanning of the brain and body starting approximately 45 minutes post injection of [18F]PI-2620. All images will be corrected for scatter and measured photon attenuation and reconstructed using standard reconstruction techniques. Standardized uptake value ratio (SUVr), the ratio of regional to reference uptake, will be calculated with cerebellum as reference, where NFTs are generally not present in neurodegenerative disorders, hence likely not in OUD.~Subjects in all three groups undergo a brain MRI including a structural MRI functional reactivity to an episodic memory task, and undergo a comprehensive neurocognitive battery.~The investigators will draw up to 20 mL of venous blood prior to injection that will be used to measure peripheral blood markers of phosphorylated tau, inflammation, and ApoE genotyping. The results of these research tests will not be given to the subject, will not be included in the medical record and will not be used in the subject's clinical management.~Additional measures will be collected: measures of substance use and related behaviors, psychological and subjective measures, neurocognitive measures and OUD-related health outcomes for correlation with the imaging results.
The investigators plan to enroll up to 60 adult subjects in this study. There will be three groups of up to 20 subjects each in this study.~Group 1: individuals with OUD and a history of at least one opioid-related OD in the past year that required naloxone treatment reversal: OUD/OD+ Group 2: individuals with OUD without a lifetime history of opioid-related OD OUD/OD- Group 3: Healthy controls without a lifetime OUD: HCs PET/CT imaging will be used to evaluate the uptake of tau in the brain using the investigational radiotracer [18F]PI-2620. Each subject will have one [18F]PI-2620 positron emission tomography/computed tomography (PET/CT) scan performed.