Mri compatible system

Eight-week male FGF21KO mice and WT littermates fed with HFD for 8 weeks were replenished with rmFGF21 or vehicle for 4 weeks. MRI measurements of mice were performed utilizing a 7 T MRI scanner (70/16 PharmaScan, Bruker) by a radiologist who was blinded to group allocation. The mice were anesthetized with 3% isoflurane. During MRI, the animals were placed on a plastic cradle with the head fixed with a tooth bar and plastic screws in the ear canals. Continuous physiological monitoring was performed using an MRI-compatible system (SA Instruments). Spin echo sequences: TR/TE = 150/5.8 ms, FOV = 31.50 × 20.25 mm², matrix size = 210 × 135. The whole abdomen of each mouse were covered with axial slices (thickness 1 mm, no spacing). Acquired images underwent measurement of SAT and VAT using a semiautomated segmentation method. According to the signal intensity of adipose tissue, SFA and VFA outline was manually traced with a graphic user interface. The area inside the outline was automatically labeled and calculated.

Following the complete normothermic or hypothermic procedure (~6 h after TBI or sham injury operation), contrast-infusion catheter placement was performed after rats were anesthetized with 3% isoflurane. The animal was positioned in a stereotaxic frame with the head flexed to 50°. A small incision was made to expose the dura mater following the atlantooccipital membrane exposure. A PE-10 catheter filled with normal saline was advanced 1 mm into the intrathecal space through the dura mater incision. The incision was sealed with cyanoacrylate glue around the catheter. The intrathecal catheter was connected to the long PE-10 line filed with paramagnetic MR contrast diluted in 0.9% NaCl when rats were transferred to the MRI instrument. A microinfusion pump with a 1-cc syringe (Baxter Model AS50 Infusion Pump, Baxter Healthcare Corporation, Shanghai, China) was attached to the PE-10 line. During image acquisition, anesthesia was maintained with a 1.5–2.0% isoflurane mixture delivered by a nose cone. The animal body temperature was monitored and kept within a range of 36.5–37.5°C using a feedback-controlled water bath. The respiratory and heart rate were continuously monitored using an MRI-compatible system (SA Instruments, Stony Brook, NY, USA).