[Imaging of brain microgliosis by PET]

Abstract

Microglia in the brain are no longer quiescent but active by extending their dendrite and villi to their vicinity, so that microglia play roles in immune surveillance in a similar way as macrophages in the periphery. Changing their shapes from ramified to ameboid forms is a sign of neuroinflammation triggered by damaged neurons or astrocytes. This microgliosis is caused not only by direct brain injury or vascular damage but neurodegeneration, the latter of which was first shown in Alzheimer's disease in vivo by PET with widely-used peripheral benzodiazepine receptor (PBR) tracer [11C] (R)-PK11195. The number of the PRB is reportedly increased on the surface of mitochondrial adventitia of the activated microglia, but the affinity to the tracer is shown stable. Using this tracer is advantageous to depict the level of neuroinflammation in vivo in many neurodegenerative diseases. However, the weak point of the tracer is no capacity to differentiate protective microglia from proinflammatory ones. So, a new tracer with its segregation capacity would be expected to come in the near future. This talk is going to cover the application of the PBR tracer to image the neuroinflammation in vivo in neurological and psychiatric diseases.