To save others googling - [11C]PBR28 is a TSPO radiotracer TSPO is translocator protein, a marker of activated glial cells expressed on mitochondrial membranes TSPO is a commonly used marker used to investigate neuroinflammation Elevated levels have been associated with migraine, and with poor short-term memory performance in set of twins discordant for memory performance, and with post-stroke patients and multiple sclerosis. There looks to be a flurry of studies using this technique. It's not without its difficulties though:
Expanding on @Hutan's comments on the difficulties with TPSO — from Integrated MRI and [11C]-PBR28 PET Imaging in Amyotrophic Lateral sclerosis There's probably a baseline expression of TSPO also, e.g. in vascular endothelium, but this sounds to be sparse. See Cellular Sources and Regional Variations in the Expression of the Neuroinflammatory Marker Translocator Protein (TSPO) in the Normal Brain. An endothelitis or BBB disruption might also contribute to increased avidity. See Impact of Endothelial 18-kDa Translocator Protein on the Quantification of 18F-DPA-714 (which is discussing a different tracer). See also [1] and [2] for more papers on TPSO.
Related to the imaging of neuroinflammation that might overcome some of the limitations of PET-CT with TPSO — Mapping microglia and astrocyte activation in vivo using diffusion MRI, 2022
