P4‐164: Mapping neuroinflammation in vivo in healthy aging and Alzheimer's disease: A PET study using a novel translocator protein 18kDA (TSPO) radioligand, [18F]‐FEPPA

Increased density of activated microglia is one of the cellular markers of neuroinflammation. Microglia activation is characterized by the overexpression of the 18kDA Translocator Protein (TSPO), which can be quantified in-vivo using a TSPO PET targeting radioligand. The overexpression of TSPO has been reported in many age-related disorders including the Alzheimer's disease (AD), however studies of neuroinflammation in healthy aging are limited. The aim of the present study is to examine neuroinflammation by quantifying TSPO expression using a novel TSPO PET radioligand, [18 F]-FEPPA in both healthy and AD individuals. We hypothesized that (1) neuroinflammation is related to healthy aging, and (2) neuroinflammation is elevated in AD patients. So far, 2 AD patients (age= 54 + 9 years) and 19 healthy volunteers (mean age 51 + 16 years) were included in the study. To assess the effect of age on neuroinflammation, the healthy volunteers were divided into two groups: young (n = 10, age <55 years) and old (n = 9, age > 55 years). Dynamical [18 F]-FEPPA-PET scan with full arterial sampling was acquired on HRRT-PET camera and analyzed using the 2-tissue compartment model as previously described (Rusjan 2011). A repeated measure ANOVA analysis was performed to compare [18 F]-FEPPA total volumes of distribution (V T) in the hippocampus (HC), temporal (TC), prefrontal cortex (PFC) between the (1) young (n = 10) and old group (n = 9), and (2) the AD patients (n = 2) and healthy controls (n = 19). We found no significant difference in regional [18 F]-FEPPA V T between the young and old healthy groups (F (1,17)= 0.953; P = 0.343. The AD patients showed a significantly greater [18 F]-FEPPA V T in the HC, TC, and PFC (F (1,19)= 10.761, P = 0.004). Post-hoc analysis revealed the greatest difference in the mean [18 F]-FEPPA V T was found in the TC (F (1,19) = 14.37, P = 0.001), followed by the HC (F(1,19)= 8.72, P = 0.008) and PFC (F (1,19)= 7.33, P = 0.014).