[18F]NOS

The purpose of this research is to measure the extent of inflammation in the brain between different groups of participants using a radioactive tracer called [18F]NOS. A radioactive tracer is a type of imaging drug that is labeled with a radioactive tag and injected into the body. This study will see how the tracer is taken up in the brain using an imaging scan called Positron Emission Tomography / Computed Tomography (PET/CT).
Participants will undergo approximately 60 minutes of dynamic scanning of the brain starting at approximately the time of injection of [18F]NOS.
Participants are required to have a brain MRI performed within 1 year prior to study enrollment, or if the subject has not had a brain MRI that is deemed acceptable for use for this study they will be asked to undergo a research brain MRI after they have consented for this study.

This research study is being done to learn more about inflammation in the brain using Positron Emission Tomography/Computed Tomography (PET/CT) imaging in people with Alzheimer's Disease/Mild Cognitive Impairment or healthy controls.
If the subject agrees to be in this study, she/ he will have a PET/CT scan using the investigational radiotracer [18F]NOS. A subject with a specific genetic polymorphism may also agree to be in the sub-study in which she/he will have another PET/CT scan using the investigational tracer [11C]PBR28 for comparison with the FNOS [18F]NOS scan. For subjects who agree to this sub-study they may undergo the brain PET/CT scan with [11C]PBR28 either on the same day as the [18F]NOS PET/CT or on another day. The subject may have a screening visit before the PET/CT scan visit if the investigator needs to confirm the subject is able to be in the study.
A blood sample will be taken before the scans. Additional blood samples will be taken during the PET scans. Subjects must also agree to have an MRI scan for this research study if she/he has not had a recent scan that the study doctor decides can be used for this study.