Imaging of microglia activation in stroke.

Activated microglia is one of the most important cellular components of poststroke neuroinflammation, which occurs early in the area of the infarct but also in remote regions with fiber tract connections to the site of the primary lesion. The development of different radioligands for the translocator protein, a mitochondrial membrane protein expressed in microglial cells when they transform from the resting to the activated state, allows to study the temporal dynamics of this cellular neuroinflammatory component in vivo in animal models and human stroke using positron emission tomography. In this article, we review the advantage and limitations of current and future methods for microglia imaging as well as new results of multimodal imaging approaches in clinical stroke, which try to combine microglia imaging with diffusion tensor imaging to investigate the clinical relevance of remote microglia activation along fiber tracts for poststroke recovery.