The innate neuroimmune response is characterized, in part, by proliferation and morphological changes of microglia and astrocytes. Over-activation of microglia results in the production of a number of pro-inflammatory markers and the release of reactive oxygen and nitrogen species that cause neuronal damage. The aims of this thesis were to investigate if there is a significant difference in the tracer plasma concentrations between healthy controls (HC) and MA users and to identify an alternative to arterial Ifs by generating a population-based input functions (PBIF).