Diffusion MRI acquisition

The diffusion weighted images (DWIs) were acquired in a horizontal bore 9.4 Biospec pre-clinical MRI system (Bruker BioSpin MRI GmbH, Germany) equipped with shielded gradients (maximum gradient strength = 660 mT/m, rise time = 4570 T/m/s) and ¹H cryogenic surface coil (Cryoprobe, Bruker, BioSpin). A 2D multi-shell diffusion acquisition scheme was used. DWIs were acquired using a multi-shot dual-spin-echo echo planar imaging (EPI) sequence using the following parameters: TE/TR = 35.84/3000 ms, δ/Δ = 3/15 ms, matrix size = 128 × 125, voxel size = 130 × 130x130 µm³, number of slices = 40, slice thickness = 130 µm, 2 b-value shells (1000 and 2000) s/mm², 10 b0 (5 for each shell), 32 diffusion encoding direction for b = 1000 and 56 for b = 2000 s/mm². For MRI scan, initially mice were anesthetized under 3% isoflurane in an induction chamber. The anesthetized mice were transferred to an MR compatible cradle and positioned in an MRI compatible head holder to minimize head motion. Anesthesia was then maintained at 1.5% isoflurane in 100% oxygen throughout imaging. Respiration rate was monitored using a pressure pad placed under the animal abdomen and animal body temperature was maintained by a warming pad (37 °C) placed under the animal.