TSPO PET and MRI Biomarkers in Alzheimer's Disease

[¹⁸F]-FEPPA was synthesized as previously described.^{15 (link)} All subjects underwent one [¹⁸F]-FEPPA PET scan and one MRI scan. The MRI scans of 14 healthy control subjects were acquired with a General Electric (Milwaukee, WI, USA) Signa 1.5 Tesla MRI scanner. The other 7 control subjects and all participants with AD had the T₁ weighted images acquired on a 3-Tesla General Electric MR750 scanner. MRI acquisition parameters for both scanners have been described in detail elsewhere.^{45 (link)} The PD-weighted and T₂ FLAIR scans were visually inspected for evidence of focal and vascular lesions including the presence of white matter hyperintensities, which was determined by following established criteria.^{46 (link)}The PET images were obtained for 125 min following the injection of [¹⁸F]-FEPPA using a 3D high-resolution research tomograph brain tomograph (CS/Siemens, Knoxville, TN, USA) as previously described.^{16 (link)} A dose of 181±15 mBq of intravenous [¹⁸F]-FEPPA was administered as a bolus for the PET scan. Blood samples were collected for genotyping of TSPO rs6971 polymorphism and for obtaining the arterial input function used for the kinetic analysis of [¹⁸F]FEPPA, as previously described.^{16 (link)}