Alzheimer‘s disease is neuropathologically characterized by neuronal loss, gliosis, and the deposition of misfolded proteins such as amyloid plaques and tau tangles. Reactive astrocytes and activated microglia are observed surrounding amyloid plaques and tau tangles in postmortem AD brains. These activated glial cells secrete pro-inflammatory cytokines and reactive oxygen species, which may contribute to neurodegeneration. Therefore, in vivo imaging of glial response by positron emission tomography (PET) combined would provide new insights to monitoring glial response disease-specific therapeutics, as well as aid in the differential diagnosis, and better understand the disease process. Recently, we developed a novel PET tracer, [¹⁸F]SMBT-1 for imaging monoamine oxidase-B (MAO-B), which is predominantly expressed in the mitochondrial membranes of astrocytes and upregulated in not only AD but also various neurodegenerative conditions. Here, we introduce the development of [¹⁸F]SMBT-1 and its applications.