[18F] THK-5351 PET imaging acquisition

All PET images were acquired using Discovery 690, 710, and 690 Elite PET/CT scanners (GE Healthcare; Milwaukee, WI, USA) at Asan Medical Center and a Discovery STE PET/CT scanner (GE Healthcare) at Samsung Medical Center. The identical imaging and reconstruction protocol was used in both centers. [18F] THK-5351 PET images were obtained for 20 min, starting 50 min after injection of 185 ± 18.5 MBq of [18F] THK-5351, which binds to the aggregated tau in paired helical filaments^36,37. Prior to the PET scan, a head holder was applied to minimize head motion and brain CT images were obtained for attenuation correction. Using the ordered-subsets expectation maximization algorithm (iteration = 4, subset = 16), 3D PET images were reconstructed with a voxel size of 2.0 × 2.0 × 3.27 mm³. To increase data uniformity between different PET scanners, a 3D Hoffman phantom-based PET harmonization method was applied based on the results of correction factors obtained from phantom studies using 3D Hoffman brain phantom^38,39.