Dedicated small animal 7 t mri system

After administration of targeting or nontargeting siRNAs, BBB integrity was assessed using a dedicated small-animal 7-T MRI system (Bruker BioSpec) at TCD. Mice were anesthetized with 5% isoflurane and placed on an MRI-compatible support cradle. This cradle has an in-built system for maintaining the animal’s body temperature at 37°C, and a probe underneath the animal allows it to be physiologically monitored (electrocardiogram, respiration, and temperature). To ensure accurate positioning of the animal, an initial rapid pilot image was recorded and used to ensure correct geometry for all subsequent scans. The scale of BBB integrity was then visualized in high-resolution T1-weighted MR images [resolution, 0.156 × 0.156 × 5 mm³; field of view, 20 × 20 × 17.9 mm³; matrix, 128 × 128 × 30; TR (repetition time)/TE (echo time), 500/2.7 ms; flip angle, 30°; number of averages, 3; acquisition time, 2 min, 24 s; repetitions, 8] before and after tail-vein administration of 100 μl of a 1:3 dilution of Gd-DTPA (0.5 M stock solution, Bayer), which was monitored over a period of 20 min after injection. MRI analysis was performed using ImageJ and MIPAV software, and all data were analyzed blind to treatment.