Evaluation of [11C]CB184 for imaging and quantification of TSPO overexpression in a rat model of herpes encephalitis

Purpose Evaluation of translocator protein (TSPO) overexpression is considered an attractive research tool for monitoring neuroinflammation in several neurological and psychiatric disorders. [ 11 C]PK11195 PET imaging has been widely used for this purpose. However, it has a low sensitivity and a poor signal-to-noise ratio. For these reasons, [ 11 C]CB184 was evaluated as a potentially more sensitive PET tracer. Methods A model of herpes simplex encephalitis (HSE) was induced in male Wistar rats. On day 6 or 7 after virus inoculation, [ 11 C]CB184 PET scans were acquired followed by ex vivo evaluation of biodistribution. In addition, [ 11 C]CB184 and [ 11 C]PK11195 PET scans with arterial blood sampling were acquired to generate input for pharmacokinetic modelling. Differences between the saline-treated control group and the virus-treated HSE group were explored using volumes of interest and voxel-based analysis. Results The biodistribution study showed significantly higher [ 11 C]CB184 uptake in the amygdala, olfactory bulb, medulla, pons and striatum ( p