Using a Bruker Pharmascan 7 Tesla MR scanner (Bruker Biospin, Billerica, MA), axial T2-weighted RARE sequences were acquired (repetition time, 4,200 ms; echo time, 36 ms; slice thickness, 1 mm; field of view, 3.2 cm; matrix size, 2566256; 20 slices). During scanning, the animals were kept under anesthesia with 1.5% isofluorane (Schering-Plough, Kenilworth, NJ) mixed with 50% air and 50% O2.