To develop a method to detect dendritic cell recruitment in Alzheimer's disease (DC RAD), this study is designed in 2 parts.~The first part assesses the safety and efficacy of indocyanine green (ICG) in labeling peripheral immune phagocytic cells in healthy adult subjects.~The second part is designed to determine the presence of ICG in the brain of adult subjects diagnosed with Alzheimer's disease (AD). In the first part of the study, ICG will be delivered by intravenous infusion to healthy subjects to verify that peripheral immune phagocytic cells, of which DCs are a subset, can be labeled with ICG. If ICG labeling of phagocytic cells is confirmed, then in the second part of the study the presence of ICG in brain of AD patients, putatively carried in by ICG-labeled cells, will be investigated by NIRS using the INVOS 7000 cerebral oximeter.
This is a proof-of-concept study designed to confirm that human phagocytic cells can be labeled with the near-infrared dye indocyanine green (ICG) and the presence of the labeled cells 48 hours later in cerebral cortex can be inferred using near infrared spectroscopy (NIRS).