Magnetic resonance imaging (MRI)
For each subject, an anatomic MRI scan of the brain (T1, T2, FLAIR) was performed before the PET imaging session for subsequent image preprocessing and exclusion of any brain anomalies. MRI scans were obtained with a Philips Ingenuity PET-MR 3T scanner (Philips Medical Systems) with the following scan parameters: TR = 25 ms, TE = 4.6 ms, flip angle 30°, scan time 376 s. A trained neuroradiologist (MN) evaluated the anatomic images for any pathologic findings.