TSPO and Stroke: Ligands to the 18 kDa translocator protein TSPO, an outer membrane molecule highly upregulated in microglia, have been widely used to monitor neuroinflammation in, e.g., stroke [51] or neurodegeneration [52], but other sources of TSPO accumulation, e.g., increased neuronal activity [53], reactive astrocytes [54], or endothelial cells [55], have been debated to contribute to the PET signal.