(R)-[(11)C]PK11195 is a tracer for activated microglia. The purpose of this study was to assess the validity of the simplified reference tissue model for analyzing (R)-[(11)C]PK11195 studies in traumatic brain injury (TBI), where blood-brain barrier disruptions are likely.
Methods: Dynamic (R)-[(11)C]PK11195 scans were acquired at 3 time points after TBI. Plasma input-derived binding potential (BP(ND)(PI)), volume of distribution (V(T)) and K(1)/k(2), and simplified reference tissue model-derived binding potential (BP(ND)(SRTM)) were obtained. Simulations were performed to assess the effect of varying K(1)/k(2).
Results: Early after TBI, an increase in V(T), but not in BP(ND)(PI), was found. Early K(1)/k(2) correlated with V(T) and BP(ND)(SRTM) but not with BP(ND)(PI). One and 6 mo after TBI, BP(ND)(SRTM) correlated with BP(ND)(PI).
Conclusion: Early after TBI, (R)-[(11)C]PK11195 studies should be analyzed using plasma input models.